Rapid Visual Screening 

of Buildings for Potential 

Seismic Hazards: 

Supporting Documentation 

Third Edition 

FEMA P-155 / January 2015 

January 2015 

FEMA P-155
 

THIRD EDITION 

Rapid Visual Screening of Buildings for Potential 

Seismic Hazards: 

Supporting Documentation
 

Prepared by 

APPLIED TECHNOLOGY COUNCIL 

201 Redwood Shores Parkway, Suite 240 

Redwood City, California 94065 

www.ATCouncil.org 

Prepared for 

FEDERAL EMERGENCY MANAGEMENT AGENCY
 

Michael Mahoney, Project Officer
 

Mai Tong, Task Monitor
 

Erin Walsh, Task Monitor
 

John Gillengerten, Technical Monitor
 

Washington, D.C. 

ATC MANAGEMENT AND OVERSIGHT
 

Christopher Rojahn (Program Executive) 

Jon A. Heintz (Program Manager) 

Ayse Hortacsu (Project Manager) 

Thomas McLane (Project Manager) 

PROJECT REVIEW PANEL 

Charles Scawthorn (Chair) 

Timothy Brown 

Melvyn Green 

Laura Kelly
 

Stephanie King
 

John Osteraas 

Steven Sweeney 

Christine Theodoropoulos 

PROJECT TECHNICAL COMMITTEE 

Bret Lizundia (Project Technical Director) 

Michael Griffin 

William T. Holmes 

Brian Kehoe 

Keith Porter 

Barry Welliver 

PROJECT WORKING GROUP 

Sarah Durphy 

Charles A. Kircher 

Nicolas Luco 

Kenneth Rukstales 
 

 

Notice 

Any opinions, findings, conclusions, or recommendations expressed in this publication do not 

necessarily reflect the views of the Applied Technology Council (ATC), the Department of 

Homeland Security (DHS), or the Federal Emergency Management Agency (FEMA). 

Additionally, neither ATC, DHS, FEMA, nor any of their employees, makes any warranty, 

expressed or implied, nor assumes any legal liability or responsibility for the accuracy, 

completeness, or usefulness of any information, product, or process included in this publication. 

Users of information from this publication assume all liability arising from such use. 
Preface 

In 2011, the Applied Technology Council (ATC), with funding from the 

Federal Emergency Management Agency (FEMA) under Task Order 

Contract HSFEHQ-08-D-0726, commenced a series of projects (ATC-71-4, 

ATC-71-5, and ATC-71-6) to update the FEMA 154 Report, Rapid Visual 

Screening of Buildings for Potential Seismic Hazards: A Handbook (FEMA, 

2002a) and the FEMA 155 report, Rapid Visual Screening of Buildings for 

Potential Seismic Hazard: Supporting Documentation (FEMA, 2002b). The 

purpose of FEMA 154 and the accompanying FEMA 155, which were 

developed by ATC under contract to FEMA (ATC-21 Project) and published 

in 1988, was to provide a methodology to evaluate the seismic safety of a 

large inventory of buildings quickly and inexpensively, with minimum 

access to the buildings, and determine those buildings that require a more 

detailed examination. In 2002, FEMA 154 and FEMA 155 were updated to 

create a Second Edition, based on (1) experience from the widespread use of 

the original FEMA 154 by federal, state, and municipal agencies and others; 

(2) new knowledge about the performance of buildings during damaging 

earthquakes; (3) new knowledge about seismic hazards; and (4) other thennew seismic evaluation and performance prediction tools, such as the FEMA 

310 report, Handbook for the Seismic Evaluation of Buildings - A 

Prestandard (FEMA, 1998). 

Since the publication of the second edition of FEMA 154 and FEMA 155, 

there have been several initiatives that have advanced the state-of-the-art in 

rapid visual screening of buildings for seismic risk. One of these was the 

development of FEMA P-154 Rapid Observation of Vulnerability and 

Estimation of Risk (ROVER) software for use on smart phones (FEMA, 

2014), which enables users to document and transmit data gathered in the 

field. The rapid visual screening application of ROVER is based on the 

second edition of FEMA 154 and incorporates several improvements made 

possible by the electronic calculation capability of the device (e.g., sitespecific determinations of the seismic shaking hazard). In addition, users in 

Oregon and Utah have made some modifications to their application of the 

FEMA 154 screening process in the course of performing extensive seismic 

screenings of schools and other buildings. 

FEMA P-155 Preface iii 
The objective of the Third Edition remains the same as its predecessors: to 

identify, inventory, and screen buildings that are potentially hazardous. This 

third edition of the FEMA P-155 provides the technical basis for the rapid 

visual screening procedure documented in the third edition of the FEMA 

P-154 (FEMA, 2015), which includes the following enhancements: 

	 Update of the Data Collection Form, and the addition of an optional 

more detailed page to the form, 

	 Update of the Basic Scores and Score Modifiers, 

	 Update of the ground motion definitions, 

	 Preparation of additional reference guides, 

	 Inclusion of additional building types that are prevalent, 

	 Inclusion of additional considerations, such as nonstructural hazards, 

existing retrofits, building additions, and adjacency, 

	 Addition of an optional electronic scoring methodology, and 

	 Additional information on how to run an effective screening program. 

Note that per FEMA’s current report numbering system, the third editions of 

FEMA 154 and FEMA 155 are now referred to as FEMA P-154 and FEMA 

P-155, respectively. 

ATC is indebted to the leadership of Bret Lizundia, Project Technical 

Director, and to the members of the ATC-71-4, ATC-71-5, and ATC-71-6 

Project Teams for their efforts in developing this updated Supporting 

Documentation. The Project Technical Committee, consisting of Michael 

Griffin, William Holmes, Brian Kehoe, Keith Porter, and Barry Welliver, 

managed and performed the technical development efforts. Updated scores 

were developed by Charles Kircher. Sarah Durphy, as a Project Working 

Group member, provided special assistance in the development of the 

updated Handbook. Andrew Bishop, Brian Kehoe, and Scott Hiner prepared 

the illustrations for the report. Nicolas Luco and Kenneth Rukstales prepared 

the seismicity maps in the document. The Project Review Panel, consisting 

of Charles Scawthorn (chair), Timothy Brown, Melvyn Green, Laura Kelly, 

Stephanie King, John Osteraas, Steven Sweeney, and Christine 

Theodoropoulos, provided technical review, advice, and consultation at key 

stages of the work. A workshop of invited experts was convened to obtain 

feedback on the updated Handbook, and input from this group was 

instrumental in shaping the final methodology and report. The names and 

affiliations of all who contributed to this report are provided in the list of 

Project Participants. 

iv Preface FEMA P-155 
ATC also gratefully acknowledges Michael Mahoney (FEMA Project 

Officer), Mai Tong (FEMA Task Monitor), Erin Walsh (FEMA Task 

Monitor), and John Gillengerten (FEMA Technical Monitor) for their input 

and guidance in the preparation of this document. Ayse Hortacsu and 

Thomas McLane managed the project and Amber Houchen and Peter N. 

Mork provided report production services. 

Jon A. Heintz Christopher Rojahn 

ATC Director of Projects ATC Executive Director 

FEMA P-155 Preface v 

Table of Contents
 

Preface........................................................................................................... iii 

List of Figures............................................................................................... xi 

List of Tables ................................................................................................xv 

1. Introduction...................................................................................... 1-1 

1.1 Overview, Purpose, and Target Audience................................ 1-1 

1.2 Impetus for Updating the FEMA 154 Handbook ..................... 1-1 

1.3 Technical Approach ................................................................. 1-2 

1.4 Organization of this Report ...................................................... 1-3 

2.	 Revision Considerations and Conclusions ..................................... 2-1 

2.1 Introduction .............................................................................. 2-1 

2.2 Paper or Electronic Form ......................................................... 2-1 

2.3 Reorganization of the Data Collection Form ............................ 2-1 

2.4 Optional Level 2 Form ............................................................. 2-2 

2.5 Scoring Update ........................................................................ 2-2 

2.6 Ground Motions ....................................................................... 2-3 

2.7 Seismicity Regions ................................................................... 2-4 

2.8 Default Soil Type ..................................................................... 2-4 

2.9 Addressing Negative Scores ..................................................... 2-4 

2.10 Inclusion of W1A and MH Building Types ............................. 2-5 

2.11 Update of Occupancy Classes .................................................. 2-6 

2.12 Treatment of Vertical and Plan Irregularities ........................... 2-6 

2.13 Consideration of Geologic Hazards .......................................... 2-6 

2.14 Consideration of Pounding ....................................................... 2-7 

2.15 Consideration of Building Additions........................................ 2-7 

2.16 Consideration of Damage and Deterioration ............................ 2-7 

2.17 Consideration of Retrofits ........................................................ 2-7 

2.18 Screener Qualifications and Supervising Engineer .................. 2-8 

2.19 Rapid Visual Screening in Low Seismicity .............................. 2-8 

2.20 Underlying Performance Objective .......................................... 2-8 

2.21 Using FEMA P-154 on High Importance Buildings ................ 2-9 

2.22 Screening for Nonstructural Hazards ....................................... 2-9 

2.23 Update of FEMA P-154 ROVER ............................................. 2-9 

3. Building Classification ..................................................................... 3-1 

3.1 Introduction .............................................................................. 3-1 

3.2 Building Classification Systems in Previous Editions of 

FEMA 154................................................................................ 3-1 

3.3	 Third Edition Updates to the Building Classification 

System ...................................................................................... 3-3 

FEMA P-155	 Table of Contents vii 
4. 

5.

3.4 Occupancy Classes ...................................................................3-5 

3.5 Occupancy Class Mapping .......................................................3-8 

3.6 Occupancy Load Determination ...............................................3-9 

Introduction to Third Edition Scoring ............................................4-1 

4.1 Introduction...............................................................................4-1 

4.2 Review of Second Edition Scores.............................................4-1 

4.2.1 URM Scoring ...............................................................4-2 

4.2.2 Negative Scores ...........................................................4-2 

4.2.3 Beta Values ..................................................................4-2 

4.2.4 Mid-Rise and High-Rise Modifiers .............................4-3 

4.2.5 FEMA Building Types ................................................4-3 

4.3	 Scoring Enhancements for the Third Edition ...........................4-3 

4.3.1 Ground Motions ...........................................................4-3 

4.3.2 Seismicity Regions ......................................................4-4 

4.3.3 Default Soil Type.........................................................4-4 

4.3.4 Vertical and Plan Irregularity Score Modifiers ............4-4 

4.3.5 Minimum Scores ..........................................................4-5 

4.4	 Methodology for Development of Third Edition Basic Scores 

and Score Modifiers ..................................................................4-5 

4.4.1 Defining Collapse ........................................................4-5 

4.4.2 Calculating Probability of Collapse with HAZUS 

Methodology..............................................................4-12 

4.4.3	 History and Purpose of the OSHPD HAZUS 

Procedure ...................................................................4-18 

4.4.4 Calculating Collapse Probability with the OSHPD 

HAZUS Procedure.....................................................4-19 

4.4.5 Use of the OSHPD HAZUS Procedure for 

FEMA P-154..............................................................4-23 

 Development of Third Edition Basic Scores and Modifiers...........5-1 

5.1 Introduction...............................................................................5-1 

5.2 Development of Third Edition Basic Scores ............................5-1 

5.2.1 Seismicity Regions ......................................................5-1 

5.2.2 FEMA Building Types ................................................5-5 

5.2.3 Using OSHPD HAZUS Values ...................................5-6 

5.2.4 Values for Calculation of Basic Scores .......................5-8 

5.2.6 Adjustment of Betas ..................................................5-10 

5.3 Sample Calculation of a Basic Score ......................................5-10 

5.3.1 Step 1. Development of the Capacity Curve ..............5-10 

5.3.2 Step 2: Determination of Input Spectral Acceleration 

Response Values........................................................5-12 

5.3.3	 Step 3: Computation of Modified Input Spectral 

Acceleration Response Values, SMS and SM1 .............5-12 

5.3.4	 Step 4: Development of a 5%-Damped Demand 

Response Spectrum ....................................................5-12 

5.3.5	 Step 5: Development of Damped Response 

Spectrum ....................................................................5-14 

5.3.6 Step 6: Determination of Peak Response ...................5-18 

5.3.7 Step 7: Development of Fragility Curve....................5-19 

5.3.8 Step 8: Determination of Probability of Complete 

Damage......................................................................5-19 

5.3.9 Step 9: Determination of Probability of Collapse ......5-20 

viii Table of Contents FEMA P-155 
5.3.10 Step 10: Relate Probability of Collapse to an 

Associated Score ....................................................... 5-20 

5.3.11 Step 11: Determine the Basic Score .......................... 5-20 

5.4 Review of Basic Scores.......................................................... 5-21 

5.5 Development of Score Modifiers ........................................... 5-21 

5.5.1 Soil Type Modifiers................................................... 5-21 

5.5.2 Vertical and Plan Irregularities .................................. 5-22 

5.5.3 Pre-Code.................................................................... 5-23 

5.5.4 Post-Benchmark ........................................................ 5-24 

5.5.5 Minimum Score ......................................................... 5-27 

5.6 Summary of Third Edition Scores.......................................... 5-27 

5.7 Development of Level 2 Score Modifiers .............................. 5-27 

5.7.1 Vertical Irregularity Score Modifiers ........................ 5-31 

5.7.2 Plan Irregularity Score Modifiers.............................. 5-31 

5.7.3 Other Level 2 Score Modifiers .................................. 5-36 

5.8 Comparison of Second Edition and Third Edition Scores...... 5-39 

6. Pounding ........................................................................................... 6-1 

6.1 Introduction .............................................................................. 6-1 

6.2 Overview and Background Research ....................................... 6-1 

6.2.1 Previous Editions of FEMA 154 and FEMA 155 ....... 6-1 

6.2.2	 Building Pounding State of Art: Identifying Structures 

Vulnerable to Pounding Damage ................................ 6-2 

6.2.3	 Assessment and Improvement of the Structural 

Performance of Buildings in Earthquakes ................... 6-3 

6.2.4 Adjacency Issues in Soft-Story Wood Frame 

Buildings ..................................................................... 6-4 

6.2.5	 ASCE/SEI 41-13 Seismic Evaluation of Existing 

Buildings ..................................................................... 6-4 

6.2.6	 The Performance of Unreinforced Masonry Buildings 

in the 2010/2011 Canterbury Earthquake Swarm ...... 6-6 

6.3 Pounding Criteria Determination ............................................. 6-7 

6.3.1 Rationale for Pounding Separation Determination ...... 6-8 

6.3.2 Calculation of Pounding Separation ............................ 6-8 

6.3.3 Validation .................................................................. 6-13 

7. Building Additions ........................................................................... 7-1 

7.1 Introduction .............................................................................. 7-1 

7.2 Identifying Building Additions ................................................ 7-1 

7.2.1 Structural Connections ................................................ 7-2 

7.2.2 Structural Framing ....................................................... 7-3 

7.2.3 Size of Addition .......................................................... 7-4 

7.3 Implementing Irregularity Recommendations from the 

Building Additions Reference Guide on the Screening 

Forms........................................................................................ 7-4 

7.3.1 Level 1 Screening for Additions ................................. 7-5 

7.3.2 Level 2 Screening for Additions ................................. 7-6 

8.	 Risk Associated with the RVS Score .............................................. 8-1 

8.1 Introduction .............................................................................. 8-1 

8.2 Risk versus Probability ............................................................. 8-1 

8.3 Introducing the Risk Score ....................................................... 8-2 

8.4 Calculating the Risk Score ....................................................... 8-3 

FEMA P-155	 Table of Contents ix 
8.5 Relating the Risk Score to Risk ..............................................8-11 

9. Comparison of Paper-Based and Electronic Scoring 

Methodologies ...................................................................................9-1 

9.1 Introduction...............................................................................9-1 

9.2	 Development of Scores for the Electronic Scoring 

Methodology.............................................................................9-1 

9.3	 Interpolating and Extrapolating Basic Scores and Score 

Modifiers ..................................................................................9-2 

9.4	 Comparison of Scores Derived with Electronic Scoring versus 

Paper-Based Scores ..................................................................9-7 

9.5 Conclusions ............................................................................9-13 

10.	 Benchmarking Studies and Trial Runs ........................................10-1 

10.1 Purpose ...................................................................................10-1 

10.2 AOC Benchmarking Study .....................................................10-1 

10.2.1 Overview of the AOC Seismic Assessment 

Program .....................................................................10-1 

10.2.2 Selection of Buildings for Benchmarking .................10-2 

10.2.3 Calculating the RVS Score ........................................10-7 

10.2.4 Benchmarking Results ...............................................10-9 

10.2.5	 Benchmarking Conclusions and 

Recommendations ...................................................10-13 

10.3 Trial Runs .............................................................................10-14 

10.3.1 Year 1 Trial Runs ....................................................10-14 

10.3.2 Year 2 Trial Runs ....................................................10-15 

10.3.3 Year 3 Trial Runs ....................................................10-16 

10.4 Conclusions ..........................................................................10-16 

Appendix A: Third Edition Scoring Parameters..................................... A-1 

References .................................................................................................. B-1 

Project Participants...................................................................................C-1 

x Table of Contents FEMA P-155 
 

 

List of Figures
 

Figure 3-1	 Examples of flood and wind tie-down systems for 

manufactured housing ........................................................ 3-4 

Figure 3-2 Illustration of an earthquake-resistant bracing system ....... 3-5 

Figure 3-3 Photographs of a metal skirt and pony-wall perimeter 

covering systems ................................................................ 3-5 

Figure 4-1 Examples of collapse and partial collapse ......................... 4-7 

Figure 4-2 Example intersection of demand spectra and building
 

capacity curves ................................................................. 4-13 

Figure 4-3 Example building capacity curve and control points....... 4-14 

Figure 4-4 Example calculation of demand spectrum by reduction of 

5%-damped response spectrum of ground motions ......... 4-15 

Figure 4-5 Example fragility curves for Slight, Moderate, Extensive 

 and Complete structural damage ..................................... 4-17 

Figure 5-1 Building capacity curve for a one-story S2 in High
 

seismicity ......................................................................... 5-11 

Figure 5-2 5%-Damped demand spectrum for high seismicity
 

region ............................................................................... 5-14 

Figure 5-3	 βeff-Damped locus demand spectrum for one-story S2 in 

High seismicity region ..................................................... 5-18 

Figure 5-4 Fragility curve for one-story S2 in the High seismicity
 

region ............................................................................... 5-20 

Figure 5-5	 Comparison of Second Edition and Third Edition Basic 

Scores on Soil Type B ..................................................... 5-40 

Figure 5-6	 Comparison of Second Edition and Third Edition Basic 

Scores on Soil Type CD ................................................... 5-40 

Figure 5-7	 Comparison of Second Edition and Third Edition Scores 

with a Severe Vertical Irregularity on Soil Type CD ....... 5-41 

Figure 5-8	 Comparison of Second Edition and Third Edition Scores on 

Soil Type CD with Post-Benchmark Score Modifiers ..... 5-42 

FEMA P-155 List of Figures xi 
 

Figure 5-9 Comparison of Second Edition and Third Edition Scores 

on Soil Type E with more than seven stories ...................5-43 

Figure 6-1 Pounding categorization .....................................................6-2 

Figure 6-2 Critical pounding configurations ........................................6-3 

Figure 6-3 Initial Evaluation Procedure in NZSEE .............................6-5 

Figure 7-1 Row houses are not considered additions...........................7-1 

Figure 7-2 Vertical addition considered as a setback irregularity ........7-7 

Figure 7-3 Stiff original building with a flexible addition leading to 

a moderate vertical irregularity ..........................................7-8 

Figure 7-4 Plan view illustrating irregularity caused by difference in 

horizontal dimension or original building and addition .....7-9 

Figure 7-5 Addition relying on the original building for gravity 

support ..............................................................................7-10 

Figure 8-1 Sample-average hazard curves used to relate fragility to 

risk ....................................................................................8-8 

Figure 9-1 Spline fit to the example data .............................................9-6 

Figure 9-2 Distribution of the population of the United States by
 

FASS...................................................................................................................................... 9-9
 

Figure 9-3 (a) Incorrect failures and (b) incorrect-passing scores 

resulting from the use of the paper-based scoring, as a 

function of site-specific FASS............................................9-11 

Figure 9-4	 Distribution of the difference between the Final Score 

when calculated using the electronic method and the 

paper method. ...................................................................9-12 

Figure 10-1 Distribution of AOC database buildings and 

benchmarking subset by seismicity region .......................10-5 

Figure 10-2 Distribution of AOC database buildings and 

benchmarking subset by DSA rating ................................10-5 

Figure 10-3 Distribution of AOC database buildings and 

benchmarking subset by FEMA Building Type...............10-6 

Figure 10-4 Distribution of AOC database buildings and 

benchmarking subset by building height ..........................10-6 

Figure 10-5 Distribution of AOC database buildings and 

benchmarking subset by building size .............................10-7 

xii List of Figures FEMA P-155 
Figure 10-6 Distribution of AOC database buildings and benchmarking 

subset by building age...................................................... 10-7 

Figure 10-7 Second Edition Score versus DSA Rating ..................... 10-11 

Figure 10-8 Third Edition Level 1 Score versus DSA Rating ........... 10-11 

Figure 10-9 Third Edition Level 2 Score versus DSA Rating........... 10-12
 

FEMA P-155 List of Figures xiii 

 

 

 

 

 

List of Tables
 

Table 3-1 FEMA 154 (First Edition) Building Classifications .......... 3-1 

Table 3-2 FEMA 154 (Second Edition) Building Classifications ...... 3-2 

Table 3-3 FEMA P-154 (Third Edition) Building Types ................... 3-6 

Table 3-4 FEMA 154 (Second Edition) Building Occupancy
 

Classes ............................................................................... 3-7 

Table 3-5 FEMA P-154 (Third Edition) Building Occupancy
 

Classes and Occupancy Designations ................................ 3-7 

Table 3-6 FEMA P-154 Occupancy Class HAZUS Mapping ............ 3-9 

Table 3-7 FEMA P-154 Occupancy Load Determination ................ 3-10 

Table 4-1 OSHPD HAZUS Significant Structural Deficiency
 

Matrix .............................................................................. 4-20 

Table 5-1 Range and Median MCER Spectral Response Acceleration 

Values in Each Seismicity Region ..................................... 5-2 

Table 5-2 Seismicity Region for 35 Selected Cities in the United 

States.................................................................................. 5-3 

Table 5-3 Site Coefficients for Soil Types B, C, D, and E................. 5-4 

Table 5-4 Median Spectral Acceleration Values in Each Seismicity 

Region Adjusted for Soil Type CD .................................... 5-5 

Table 5-5 5%-Damped Response Spectrum for Soil Type CD in
 

High Seismicity Region ................................................... 5-14 

Table 5-6 Median MCER Response Values in Each Seismicity
 

Region Adjusted for Soil Type B and E .......................... 5-22 

Table 5-7 Performance Level Considered for Various 

Irregularities..................................................................... 5-23 

Table 5-8 Basis of Second Edition Post-Benchmark Score 

Modifiers.......................................................................... 5-24 

Table 5-9 Basis of Third Edition Post-Benchmark Score 

Modifiers.......................................................................... 5-25 

Table 5-10 Third Edition Basic Scores and Score Modifiers............. 5-28 

FEMA P-155 List of Tables xv 
Table 5-11 Basis of Level 2 Vertical Irregularity Score Modifiers....5-32 

Table 5-12 Level 2 Vertical Irregularity Score Modifiers ..................5-33 

Table 5-13 Basis of Level 2 Plan Irregularity Score Modifiers..........5-35 

Table 5-14 Level 2 Plan Irregularity Score Modifiers ........................5-35 

Table 5-15 Basis of Other Level 2 Score Modifiers...........................5-36 

Table 5-16 Other Level 2 Score Modifiers .........................................5-37 

Table 5-17 Second Edition Basic Scores and Rankings in High 

Seismicity .........................................................................5-43 

Table 5-18 Third Edition Basic Scores and Rankings in High 

Seismicity .........................................................................5-43 

Table 5-19 Second Edition and Third Edition Basic Scores and 

Minimum Scores in Low Seismicity ................................5-44 

Table 6-1 Spectral Acceleration Response Parameters SA02 and 

SA10...................................................................................6-9 

Table 6-2 Minimum Separation Distance for FEMA Building 

Types W1, W1A, W2 as a Percentage of H .....................6-12 

Table 6-3 Minimum Separation Distance for FEMA Building Type 

C1 as a Percentage of H ...................................................6-12 

Table 6-4 Minimum Separation Distance for FEMA Building Type 

S1 as a Percentage of H....................................................6-12 

Table 6-5 Minimum Separation Distance for All Other FEMA 

Building Types as a Percentage of H ...............................6-13 

Table 6-6 Recommended Minimum Separation Distance Values as 

a Percentage of H .............................................................6-13 

Table 8-1 Parameters of Fragility Functions Used to Relate Fragility 

to Risk ...............................................................................8-5 

Table 8-2 Sites with Hazard Curves that were Used to Relate 

Fragility to Risk ..................................................................8-7 

Table 8-3 Expected Value of PMFR .................................................8-11 

Table 8-4 Fatality Risk in Existing Buildings Compared with New 

Buildings ..........................................................................8-12 

Table 8-5 Relationship Between Risk Score SR and Collapse 

Probability R(t).................................................................8-13 

xvi List of Tables FEMA P-155 
 

 

   

Table 9-1 Site Coefficients for Soil Type CD ................................... .9-2 

Table 9-2 Median Spectral Acceleration Values in Each Seismicity 

Region Adjusted for Soil Type CD .................................... 9-4 

Table 9-3 Low-Rise W1 Building, FASS = 0.322g, with Severe 

Vertical Irregularity, Plan Irregularity, on Soil Type E ..... 9-7 

Table 9-4 Errors avoided Using Electronic Scoring .......................... 9-9 

Table 9-5 Low-Rise W2, FASS =0.133g, with Moderate Vertical
 

Irregularity, Plan Irregularity, on Soil Type E ................. 9-10 

Table 9-6 Incorrect Failures and Incorrect Passing Resulting from
 

the Use of Paper-Based Scoring, by FEMA Building 

Type ................................................................................. 9-11 

Table 9-7 Incorrect Failures and Incorrect Passing Resulting from 

 the Use of Paper-Based Scoring, by Seismicity 

Region.............................................................................. 9-12 

Table 10-1 Characteristics of 49 Benchmarked Buildings................. 10-3 

Table 10-2 Summary AOC Benchmarking Results ........................... 10-9 

Table 10-3 RVS Results by DSA Rating ......................................... 10-12 

Table A-1 Building Height, HR, and Elastic Period, Te ...................... A-1 

Table A-2a	 Seismic Design Coefficient, CS, for Calculating Basic 

Scores................................................................................ A-2 

Table A-2b Seismic Design Coefficient, CS, for Calculating Pre-Code 

Score Modifiers ................................................................. A-3 

Table A-2c	 Seismic Design Coefficient, CS, for Calculating PostBenchmark Score Modifiers ............................................. A-4 

Table A-3 Gamma, γ, and Lambda, λ, Factors................................... A-5 

Table A-4 Ductility Factor, μ............................................................. A-6 

Table A-5 Alpha 1, 1, and Alpha 2,  2, Factors .............................. A-7 

Table A-6 Alpha 3,  3, Modal Factors .............................................. A-8 

Table A-7 Elastic Damping, E .......................................................... A-9 

Table A-8 Degradation Factor, κ...................................................... A-10 

Table A-9 Story Drift Ratio, ΔC........................................................ A-11 

Table A-10 Lognormal Standard Deviation, βC,D .............................. A-12 

FEMA P-155 List of Tables xvii 
Table A-11 Collapse Factor (P[COL|STR5]) ...................................... A-12 

xviii List of Tables FEMA P-155
 
 

 

Chapter 1 

Introduction 

1.1 Overview, Purpose, and Target Audience 

The FEMA P-154 report, Rapid Visual Screening of Buildings for 

Potential Seismic Hazards: A Handbook, (FEMA, 2015) describes a 

rapid visual screening (RVS) procedure for identifying those buildings 

that might pose serious risk of loss of life and injury when a damaging 

earthquake occurs due to collapse. The Handbook provides detailed 

guidance on what rapid visual screening is and how to conduct it 

effectively. This report provides the technical basis for the method. 

Similar to the first and second editions of FEMA 154 and FEMA 155 

(FEMA, 1988a,b and 2002a,b), two documents have been created for 

the Third Edition, in part because it is anticipated that there will be two 

different target audiences. FEMA P-154 is written for those who will 

screen buildings and for those policy makers tasked with determining 

what type of screening program to implement. FEMA P-155, on the 

other hand, is written for those who want to understand the details and 

assumptions that underlie the methodology and how Basic Scores and 

Score Modifiers were calculated. 

A key goal in the third edition of FEMA P-155 is to provide sufficient 

information and clarity that a knowledgeable professional with some 

basic understanding of statistics, the capacity spectrum method, and 

fragility curves would be able to independently calculate the Basic 

Scores and Score Modifiers and arrive at the same answer as those 

contained in the Handbook. 

This report also provides background on issues that were considered in 

the Third Edition update, and why key choices were made. 

Comparisons of scores between the Second Edition and Third Edition 

are provided. 

1.2 Impetus for Updating the FEMA 154 Handbook

Since the publication of the second edition of FEMA 154, there have been 

several initiatives that have advanced the state-of-the-art in rapid visual 

screening of buildings for seismic risk. 

The RVS procedure utilizes a methodology 

based on a "sidewalk survey" approach 

that involves: 

 identification of the primary seismic 

force-resisting system and building 

materials, 

 assignment of a Basic Score, which 

relates to the probability of the building 

collapse for a specified earthquake 

recurrence interval, and 

 assignment of Score Modifiers that 

relate to significant seismic-related 

defects the screener may observe. 

Application of the procedure results in a 

ranking of surveyed buildings, which may 

be divided into two categories: (1) those 

acceptable as a risk to life safety, or (2) 

those that may be seismically hazardous 

and should be analyzed in more detail by 

a professional engineer experienced in 

seismic design. 

The RVS procedure was developed for a 

wide range of screeners including civil 

engineers, structural engineers, architects, 

design professionals, building officials, 

construction contractors, firefighters, 

architectural or engineering students, or 

other individuals with general familiarity 

or background in building design or 

construction. 

FEMA P-155 1: Introduction 1-1 
 

Much has been learned over the last decade about the expected seismic 

performance of existing buildings, including new knowledge gained on a 

broad range of task order projects conducted under FEMA and National 

Earthquake Hazards Reduction (NEHRP) projects. These efforts provide 

insight into how observable building characteristics, such as vertical and plan 

irregularities, as well as other conditions, such as pounding, affect the 

seismic performance of buildings. 

In addition, in the course of performing extensive seismic screenings of 

schools and other buildings in Oregon and Utah, some modifications to the 

FEMA 154 screening procedures were found desirable. These programs 

provided insight into improving the technical basis of the FEMA 154 

methodology, as well as recommendations for improving the management 

and implementation of an RVS program. Details regarding these programs 

are provided in FEMA P-154 Chapter 5. 

Finally, the development of FEMA P-154 Rapid Observation of 

Vulnerability and Estimation of Risk (ROVER) software (FEMA, 2014) for 

use on smartphones inspired the optional electronic scoring methodology 

presented in FEMA P-154. FEMA P-154 ROVER, which is based on the 

second edition of FEMA 154, enables users to document and transmit data 

gathered in the field and incorporates several tools made possible by the 

electronic calculation capability of the device (e.g., site-specific 

determinations of the seismic shaking hazard). 

Updates to FEMA 154 chosen to be implemented were limited to those that 

would not change the unique and important role of FEMA 154 in the broad 

spectrum of seismic evaluation tools. The Third Edition remains a rapid 

visual screening tool, accessible to a broad audience of engineers, architects, 

building owners, state legislatures, city councils, private companies, facility 

managers, and the general public. Any individual with a general familiarity 

or background in building design or construction (including architects, 

design professionals, building officials, construction contractors, facility 

managers, firefighters, architectural or engineering students, and others) can 

be trained to perform screenings. 

1.3 Technical Approach 

The third edition update of FEMA P-154 occurred over the course of three 

years. In the first year, the project team: 

	 performed an extensive literature and research review that focused on 

RVS programs conducted since 2002, existing RVS procedures 

1-2 1: Introduction FEMA P-155 
throughout the world, and new knowledge gained since 2002 about how 

a variety of building characteristics affect seismic performance; 

	 developed a draft rapid visual screening methodology; 

	 benchmarked the draft rapid visual screening methodology; and 

	 developed an outline for the third edition of FEMA P-154. 

In the second year, the project team: 

	 developed a draft third edition of FEMA P-154; 

	 conducted a workshop to solicit feedback on the updated Handbook; 

	 completed a 95% draft of third edition of FEMA P-154; and 

	 completed a preliminary draft of the third edition of FEMA P-155. 

In the third and final year, the project team: 

	 recalculated the Basic Scores and Score Modifiers using the most current 

information; 

	 conducted trial runs with the updated Basic Scores and Score Modifiers; 

and 

	 completed the final version of third edition of FEMA P-154 and FEMA 

P-155 reports. 

1.4 Organization of this Report 

This report documents the efforts undertaken to update the second edition of 

FEMA 154 and the technical basis for the updates. Chapter 2 describes the 

revisions that were considered and decisions reached. Chapter 3 describes 

the effort undertaken to update the building classification system. Chapter 4 

describes the impetus for updating the Second Edition scores, and describes 

the methodology used to develop the Third Edition scores. Chapter 5 

provides a comprehensive description of the steps and assumptions used to 

develop the Third Edition scores, including example calculations, and 

provides the results. Detailed information and assumptions used in the 

calculations are located in Appendix A. Chapter 6 describes the treatment of 

pounding in the Third Edition. Chapter 7 describes the treatment of building 

additions in the Third Edition. Chapter 8 discusses the risk associated with 

the RVS Score and introduces a new frequency-based risk score. Chapter 9 

provides the technical background on the electronic scoring methodology. 

Chapter 10 describes the benchmarking studies that were conducted of the 

updated RVS methodology. References cited within this report are provided 

at the end of this report. 

FEMA P-155 1: Introduction 1-3 

Chapter 2 

Revision Considerations and 

Decisions 

2.1 Introduction 

For the third edition update of FEMA P-154, the project team sought to 

incorporate technical and practical lessons learned since the publication of 

the second edition of FEMA 154 in 2002. It was found that FEMA 154 fills 

a unique and important role in the broad spectrum of seismic evaluation 

tools. Accordingly, updates were limited to those that would preserve this 

role. As such, FEMA P-154 remains a rapid visual screening tool, accessible 

to a broad audience of engineers, architects, building owners, state 

legislatures, city councils, private companies, facility managers, and the 

general public. Any individual with a general familiarity or background in 

building design or construction (including architects, design professionals, 

building officials, construction contractors, facility managers, firefighters, 

architectural or engineering students, and others) can be trained to perform 

screenings. 

The following sections provide a summary of the updates considered by the 

project team and describe those that were included in the third edition update. 

2.2 Paper or Electronic Form 

With the increasing use of computers and smartphones, the project team 

explored the option of an electronic form in lieu of the paper form used in the 

second edition of FEMA 154. However, in order to keep FEMA P-154 

accessible for everyone, the paper form is retained as the primary screening 

tool. An optional electronic scoring methodology has been developed and is 

described in the Handbook, and additional details are provided in Chapter 9 

of this document. 

2.3 Reorganization of the Data Collection Form 

The Data Collection Form used for rapid visual screening has been extended 

with an optional second page, where the first page represents a Level 1 

screening and the second page represents an optional Level 2 screening. The 

Level 1 screening is similar to the procedure used in the second edition of the 

FEMA P-155 2: Revision Considerations and Conclusions 2-1 
Handbook, with the same objectives and same general level of expertise 

required from screeners. 

The Level 1 screening form was reorganized so that data collection is 

concentrated towards the top of the page. Administrative fields, such as 

screener name and building address, are at the very top, followed by fields 

that describe attributes of the buildings, such as number of stories, year built, 

and soil type. The calculation of RVS score occurs in the middle of the page, 

and, finally, fields that document the extent of review and resulting action 

required are located at the bottom of the page. 

The elimination of the sketch field was given detailed consideration, 

particularly as it increases the time required to complete the screening and 

many screeners do not have experience drawing plan and elevation sketches. 

However, the sketch field has been retained because the act of drawing a 

sketch may help the screener to better observe the building and enable the 

screener to note important features, such as levels where pounding may 

occur. The availability of a sketch will also help in the quality control 

process. A more detailed discussion of how to use the sketch field has been 

added to Chapter 3 of FEMA P-154. 

Separating information that could be obtained during pre-field data 

collection, such as liquefaction potential, from information that can be 

determined in the field, such as falling hazards, was considered. However, it 

was found that too many items could be determined either way to make it 

practical to create such a separation. Instead, information was grouped by 

topic, allowing the screening process to flow more naturally to the final 

answer (i.e., whether Detailed Structural Evaluation and Detailed 

Nonstructural Evaluation are required.) 

2.4 Optional Level 2 Form 

The Level 2 screening is more detailed than the Level 1 screening, and the 

qualification requirements for the Level 2 screener are higher than those for 

the Level 1 screener. The Level 2 form is designed to take advantage of the 

added experience of the screener to determine a more accurate, less 

conservative score by allowing the Level 2 screener to apply more specific 

modifiers for vertical and plan irregularities, pounding, and existing retrofits. 

2.5 Scoring Update 

An important part of the Third Edition update was the development of 

updated Basic Scores and Score Modifiers. Chapters 4 and 5 describe the 

2-2 2: Revision Considerations and Conclusions FEMA P-155 
 

 

impetus for this scoring update, together with the methodology and 

assumptions, and detailed results are provided. 

2.6 Ground Motions 

The project team was faced early on with deciding what ground motions to 

consider in the Third Edition. Ground motions are continually evolving, and 

the time span between the publication of the Second Edition and the Third 

Edition was no exception. During this time, risk-targeted Maximum 

Considered Earthquake (MCER) ground motions were developed and adopted 

by ASCE/SEI 7-10, Minimum Design Loads for Buildings and Other 

Structures (ASCE, 2010), replacing the uniform hazard Maximum 

Considered Earthquake (MCE) ground motions used in earlier versions of 

ASCE/SEI 7, ASCE/SEI 41, and the second edition of FEMA 154. 

The older uniform seismic hazard maps of MCE specified shaking that had a 

2% chance of being exceeded in 50 years. The risk-targeted ground motion 

maps take into account regional differences in the shape of the seismic 

hazard curve. The distinction between the MCE and MCER is that a risktargeted design aims for a consistent probability of life-threatening damage 

during a particular period of time, as opposed to a consistent probability of 

damage given a single, particular level of shaking. MCER ground motions 

are higher than MCE in California and are generally smaller than MCE in 

other parts of the United States (Chapter 22 of ASCE/SEI 7-10). 

ASCE/SEI 41-13, Seismic Evaluation and Retrofit of Existing Buildings 

(ASCE, 2014), considers additional hazard levels, such as 5% in 50-year and 

20% in 50-year ground motions. The project team considered using these 

ground motions in the Third Edition; however, the team decided that because 

FEMA P-154 is focused on assessing risk of collapse (rather than other 

performance objectives, such as life safety), the larger MCER ground 

motions, which are more often associated with collapse assessments, are 

more appropriate. 

Within ASCE/SEI 41-13, MCER ground motions are referred to as “BSE2N.” These are the ground motions that users of Third Edition FEMA P-154 

are directed to consider when determining a building’s seismicity region, and 

they are the same as the ground motions in ASCE/SEI 7-10. 

For calculations used to develop Basic Scores and Modifiers, the Second 

Edition used 2/3 of the MCE values. In the Third Edition, the demand is 

based on the full value of MCER. Use of the full value was found to produce 

a better correlation with the Second Edition Basic Scores and Modifiers and 

permit retaining the same cut-off score of S = 2.0. Note that the current 

FEMA P-155 2: Revision Considerations and Conclusions 2-3 
 

version of FEMA P-154 Rapid Observation of Vulnerability and Estimation 

of Risk (ROVER) software, Version 2 (FEMA, 2014), is based on ground 

motions from the Second Edition. 

2.7 Seismicity Regions 

In the first and second editions of FEMA 154, the United States was divided 

into three seismicity regions (Low, Moderate, and High), with the High 

seismicity region representing a large range of seismicity. The scoring 

update provided the opportunity to subdivide the High seismicity region 

further to improve accuracy. A total of five seismicity regions are used in the 

Third Edition. This is described in more detail in Chapters 4 and 5. 

2.8 Default Soil Type 

In the second edition of FEMA 154, the Basic Scores assume Soil Type B, 

and Score Modifiers are provided for Soil Types C, D, and E. The most 

typical soil conditions, however, are Soil Type C and Soil Type D. 

Accordingly, the Third Edition Basic Scores are based on an average of Soil 

Type C and D, which is referred to as Soil Type CD. The difference between 

Soil Type C and CD or between Soil Type D and CD is small. Modifiers are 

provided to adjust from this average soil type to Soil Type B and to Soil 

Type E. This is believed to be a more accurate way than always adjusting 

from stiffer soil to softer soil as was necessary in the Second Edition. 

2.9 Addressing Negative Scores 

Feedback obtained during the literature and research review phase of the 

project included criticism that the RVS methodology can result in negative 

scores. Negative scores imply that the probability of collapse is greater than 

100%, which is not possible. The following four approaches were 

considered for addressing this issue: 

1.	 Revise the definition of the score, S, to be based on frequency of 

collapse, rather than probability of collapse. 

2.	 Keep the current definition of the score, S, permit negative scores, but 

explain how frequency of collapse can be derived from S. 

3.	 Keep current definition of the score, S, but require scores less than zero 

to be truncated at zero. 

4.	 Keep the current definition of the score, S, but perform calculations 

assuming the worst combination of building characteristics to establish a 

minimum score. This rectifies the overly conservative approach of 

2-4 2: Revision Considerations and Conclusions FEMA P-155 
linearly combining the various Score Modifiers and eliminates the 

possibility of negative scores. 

The project team decided to use the fourth approach for determination of 

Final Scores. The score calculated from the worst combination of Score 

Modifiers is called the Minimum Score, SMIN. In addition, a Risk Score, SR, 

is defined in FEMA P-155 Chapter 8 that relates to the frequency of collapse, 

which can help to inform risk-management decisions. The relationship 

between S and SR is described in detail in Chapter 8. 

2.10 Inclusion of W1A and MH Building Types 

FEMA Building Types W1A (multistory, multi-unit wood frame residential 

building) and MH (manufactured housing) have been added. 

W1A buildings are similar in construction to W1 buildings, but are larger in 

plan and multistory. Many of these buildings are constructed with open front 

garages or commercial space at the first story, creating a potential 

irregularity. It was important to include the W1A building type because of 

what has been learned about the vulnerability of W1A buildings with open 

fronts (e.g., tuckunder buildings). 

Manufactured housing is part of a larger class of prefabricated structures that 

includes modular buildings. Mobile home is an older term for a 

manufactured home, though mobile home remains in widespread use. It was 

important to include the MH building type because of its extensive use as 

housing. Approximately 7% of the housing units in the United States in 

2008 were mobile homes (United States Census Bureau, 2014). They are 

also used as relocatable classrooms. 

Typically, the RVS score is related to the risk of collapse and the related risk 

to life. The superstructure of the MH building type rarely collapses, but the 

buildings do fall off their supports, which can cause significant financial 

damage, fire following earthquake, and some risk to life. It was discussed 

whether applying an RVS score to MH is appropriate, given that the typical 

type of damage is different from other building types. It was decided to 

include the MH building type so that communities looking at large portfolios 

of buildings will be able to get a better indication of seismic risk. 

The MH scores are developed using Multi-hazard Loss Estimation 

Methodology, Earthquake Model, HAZUS-MH MR4 Technical Manual 

(FEMA, 2009a). The methodology, referred to in this document as “HAZUS 

methodology,” calculates probability of collapse using the spectral 

displacement of the roof. For MH, the primary mode of failure is falling off 

FEMA P-155 2: Revision Considerations and Conclusions 2-5 
the support, so spectral roof displacement is less relevant. It was concluded, 

however, that this mode of failure is similar to the failure of W1 cripple walls 

and that the HAZUS methodology provided the most effective means to 

determine the FEMA P-154 scores for MH. 

2.11 Update of Occupancy Classes 

Utility and warehouse categories have been added to the occupancy class 

selections on the Data Collection Form. A field has been added to note the 

number of residential units, where applicable. 

“Historic” and “Government” fields have been separated from the occupancy 

class. A “Shelter” field has been added based on user request to indicate 

when a building is intended for use as an emergency shelter. These three 

descriptors are now used as occupancy designation checkboxes. 

The entry for occupancy load has been removed, because it was burdensome 

to calculate this value in the field, and the possibility of a wide range of 

estimates resulted in limited value. Additionally, occupancy load, if desired, 

can be easily calculated at a later time using the occupancy class and building 

area. It does not need to be calculated in the field. 

2.12 Treatment of Vertical and Plan Irregularities 

Feedback on the second edition of FEMA 154 included criticism that the 

vertical irregularity modifiers were overly severe. To address this, vertical 

irregularities have been separated into “Severe” and “Moderate” 

irregularities to reduce the penalty when only moderate irregularities exist. 

Appendix B of the updated Handbook includes reference guides to help 

screeners determine vertical and plan irregularities consistently and to reduce 

ambiguity. 

2.13 Consideration of Geologic Hazards 

Geologic hazards do not affect the Final Score; however, if there is risk of 

landslide, liquefaction, or surface rupture, the building should be referred for 

a Detailed Structural Evaluation. Without a Detailed Structural Evaluation, it 

will not be possible to determine with certainty that a building subject to one 

of these geologic risks is not seismically hazardous. If the existence of such 

hazards cannot be determined during preplanning activities, the screener is 

directed to ignore them because assuming they exist would be overly 

conservative and could potentially send whole portfolios of buildings without 

geologic hazard mapping to Detailed Structural Evaluations. 

2-6 2: Revision Considerations and Conclusions FEMA P-155 
2.14 Consideration of Pounding 

Pounding potential is an observable condition that can significantly affect the 

seismic performance of a building and should be captured by the rapid visual 

screening procedure. Within the Level 1 screening, if risk of pounding (as 

defined in the Pounding Reference Guide in Appendix B of FEMA P-154) is 

observed, a Detailed Structural Evaluation is triggered. Within the Level 2 

screening, pounding is incorporated into the score with a negative modifier. 

Six pounding conditions were identified; however, these were narrowed 

down to three easily observable conditions for the RVS procedure. For 

example, adjacent buildings with different floor levels are considered, but 

adjacent buildings with different floor masses are not, as this is difficult to 

determine during a rapid visual screening. Chapter 6 describes the treatment 

of pounding in the Third Edition. 

2.15 Consideration of Building Additions 

Guidance on screening buildings with additions has been expanded. The 

recommended RVS approach is carefully described in Chapters 3 and 4 of 

FEMA P-154, in the Level 1 and Level 2 Building Additions Reference 

Guides in Appendix B of FEMA P-154, and in the detailed discussion in 

Chapter 7 of this report. 

2.16 Consideration of Damage and Deterioration 

Significant damage and deterioration affect the seismic performance of a 

building. If there is significant damage or deterioration, such as extensive 

dry rot, corrosion, or concrete spalling, the building should be referred to a 

Detailed Structural Evaluation. Specific signs of damage or deterioration 

that might be observed during a rapid visual screening are discussed in in 

Chapter 3 of FEMA P-154 and in Appendix F of FEMA P-154. 

2.17 Consideration of Retrofits 

The treatment of buildings with existing retrofits was specifically considered. 

There was concern that a screener might believe a building has been 

retrofitted, when the upgrades are either only architectural or only mitigate a 

local hazard (such as the addition of parapet bracing). For this reason, the 

issue of retrofits is not addressed on the Level 1 form. The Level 2 screener 

is given the option of applying a retrofit modifier, but only if the retrofit is 

comprehensive (i.e., the full seismic force-resisting system has been 

strengthened). 

FEMA P-155 2: Revision Considerations and Conclusions 2-7 
2.18 Screener Qualifications and Supervising Engineer 

The second edition of FEMA 154 noted that screening could be conducted by 

“informed, appropriately trained, members of the public.” In the Third 

Edition, the following definition for Level 1 screeners was developed in an 

attempt to balance the benefits of keeping the pool of potential screeners as 

wide as possible with the desire to have screeners who can, with training, 

accurately identify FEMA Building Type and building characteristics to 

obtain accurate RVS scores: 

“Structural engineer, architect, design professional, building 

official, construction contractor, facility manager, firefighter, 

architectural or engineering student, or another individual with a 

general familiarity or background in building design or 

construction.” 

The second edition of FEMA 154 noted that all RVS programs should be 

overseen by a design professional knowledgeable in seismic design for 

quality assurance purposes. In addition, knowledge gained from RVS 

programs conducted since 2002 emphasized the need for oversight by a 

“Supervising Engineer” with specific qualification requirements and 

responsibilities. In the Third Edition, the importance of the Supervising 

Engineer is emphasized, and the qualifications and responsibilities of the 

Supervising Engineer are explicitly defined. Of key importance to the 

Supervising Engineer’s responsibility is determining the code and benchmark 

years for the jurisdiction being screened. 

2.19 Rapid Visual Screening in Low Seismicity 

The project team discussed whether it is appropriate to screen buildings in 

Low Seismicity regions when even brand new buildings in these areas have 

limited seismic design requirements. It was decided to keep the Low 

seismicity form, so that FEMA P-154 screenings can be performed anywhere 

in the country. The Handbook recommends that screening in these areas 

focus on the most significant hazards, such as finding URM bearing wall 

buildings or unbraced URM parapets. The pounding criteria on the Low 

seismicity form are revised (the required separation is lower in Low 

seismicity areas). 

2.20 Underlying Performance Objective 

The project team considered updating the FEMA P-154 methodology to 

consider additional performance objectives, but decided to keep the focus of 

the previous editions of determining the probability of collapse or partial 

2-8 2: Revision Considerations and Conclusions FEMA P-155 
collapse. To understand the meaning of the Final Score, it was necessary to 

decide how the Third Edition should define the probability of collapse or 

partial collapse. HAZUS uses collapse probability differently than FEMA 

P-695 (FEMA, 2009b), and the two definitions produce significantly 

different values of the Final Score. FEMA P-154 Chapter 1 provides a 

general definition of collapse probability used. Chapter 4 of this report 

describes the issue in more technical detail. See Figure 4-1 for examples of 

collapse and partial collapse. 

2.21 Using FEMA P-154 on High Importance Buildings 

Application of the FEMA P-154 methodology to buildings of high 

importance, such as hospitals, was considered. The focus of the RVS 

procedure is collapse. Where higher performance is desired, such as 

continued functionality in a hospital, an alternate, more detailed evaluation 

should be performed. 

2.22 Screening for Nonstructural Hazards 

Additional guidance was added to the Handbook for Level 1 screening of 

nonstructural hazards. Creation of a scoring system for nonstructural hazards 

was considered, but not pursued. The Level 2 form presents nonstructural 

statements not contained on the Level 1 form. Building characteristics that 

will not be easily visible, such as pipe and duct bracing, and stair seats, were 

not included. Also, in order to limit the extent of effort and time required to 

obtain access to ceilings or mechanical rooms, questions regarding sprinkler 

bracing, unanchored life safety equipment, unbraced ceilings or heavy 

ceilings, were not included in the Level 2 form. 

2.23 Update of FEMA P-154 ROVER 

FEMA P-154 ROVER Version 2 is based on the second edition of FEMA 

154. A project to update FEMA P-154 ROVER for the changes made in the 

third edition of FEMA P-154 is not currently planned. It is recommended the 

reader check the website (www.roverready.org) for the latest version of 

FEMA P-154 ROVER software. 

RVS Programs can still use FEMA P-154 ROVER, but they will need to do 

so using the Second Edition methodology. Users will need continued access 

to the second edition of FEMA 154. 

FEMA P-155 2: Revision Considerations and Conclusions 2-9 

 

Chapter 3 

Building Classification 

3.1 Introduction 

Urban communities are made up of many different types of structures, which 

are generally designed to withstand a prescribed set of environmental loads. 

If the actual loads are greater than the prescribed set, damage can occur, to an 

extent that depends on several engineering characteristics. Among the main 

engineering characteristics affecting the extent of damage are construction 

material and seismic force-resisting system. A building classification system 

helps to identify a building’s earthquake-resistant characteristics, and thus 

the expected performance during earthquake shaking. Third Edition updates 

to the FEMA P-154 building classification system and occupancy classes 

(referring to building use) are discussed below. 

3.2 Building Classification Systems in Previous Editions 

of FEMA 154 

The first edition of the FEMA 154 Handbook (FEMA, 1988a) for rapid 

visual screening defined a building classification system that consisted of one 

type of wood structure, five types of steel structures, three types of concrete 

structures, and four other types of structures. Table 3-1 provides the building 

classification systems used in the First Edition. 

Table 3-1 FEMA 154 (First Edition) Building Classifications 

W Wood frame buildings 

S1 Steel moment-resisting frame buildings 

S2 Braced steel frame buildings 

S3 Light metal buildings 

S4 Steel frame buildings with cast-in-place concrete shear walls 

C1 Concrete moment-resisting frame buildings 

C2 Concrete shear wall buildings 

C3/S5 Concrete or steel frame buildings with unreinforced masonry infill walls 

PC1 Tilt-up buildings 

PC2 Precast concrete frame buildings 

RM Reinforced masonry 

URM Unreinforced masonry 

FEMA P-155 3: Building Classification 3-1 
 

The second edition of FEMA 154 expanded the number of building types to 

make it consistent with FEMA 178 (FEMA, 1992), its successor FEMA 310, 

Handbook for the Seismic Evaluation of Buildings – A Prestandard (FEMA, 

1998), and other FEMA documents, such as the FEMA 273, NEHRP 

Guidelines for the Seismic Rehabilitation of Existing Buildings (FEMA, 

1997), and FEMA 356, Prestandard and Commentary for the Seismic 

Rehabilitation of Buildings (FEMA, 2000). The building classification 

system adopted for the second edition of the FEMA 154 Handbook is listed 

in Table 3-2. 

Table 3-2 FEMA 154 (Second Edition) Building Classifications 

W1 Light wood frame residential and commercial buildings smaller than or 

equal to 5,000 square feet 

W2 Light wood frame buildings larger than 5,000 square feet 

S1 Steel moment-resisting frame buildings 

S2 Braced steel frame buildings 

S3 Light metal buildings 

S4 Steel frames with cast-in-place concrete shear walls 

S5 Steel frame buildings with unreinforced masonry infill walls 

C1 Concrete moment-resisting frame buildings 

C2 Concrete shear wall buildings 

C3 Concrete frame buildings with unreinforced masonry infill walls 

PC1 Tilt-up buildings 

PC2 Precast concrete frame buildings 

RM1 Reinforced masonry buildings with flexible floor and roof diaphragms 

RM2 Reinforced masonry buildings with rigid floor and roof diaphragms 

URM Unreinforced masonry bearing wall buildings 

The Second Edition building classification system: 

	 included the building types defined in the classification system from the 

first edition of FEMA 154; 

	 expanded the First Edition list to include two types of wood frame 

buildings: 

o	 W1: light wood frame, residential and commercial buildings smaller 

than or equal to 5,000 square feet; and 

o	 W2: light wood frame buildings larger than 5,000 square feet; 

	 separated C3 buildings (concrete frame buildings with unreinforced 

masonry infill walls) and S5 buildings (steel frame buildings with 

unreinforced masonry infill walls) into two separate types; and 

3-2 3: Building Classification FEMA P-155 
 

	 subdivided the RM building type (reinforced masonry) into two types, 

one with flexible diaphragms and one with rigid diaphragms (other 

building types were not subdivided into subclasses reflecting flexible or 

rigid diaphragms in the floors and roof). 

3.3	 Third Edition Updates to the Building Classification 

System 

The third edition of FEMA P-154 adopted the term “FEMA Building Type.” 

There are 17 FEMA Building Types in the Third Edition, including the 15 

used in the Second Edition, W1A (multi-unit, multi-story residential wood 

frame buildings) and MH (manufactured housing). The descriptions of 

FEMA Building Types in the Third Edition have also been updated to reflect 

the language of ASCE/SEI 31-03, Seismic Evaluation of Existing Buildings 

(ASCE, 2003), ASCE/SEI 41-06, Seismic Rehabilitation of Existing 

Buildings (ASCE, 2007), and ASCE/SEI 41-13, Seismic Evaluation and 

Retrofit of Existing Buildings (ASCE, 2014). 

W1A buildings are residential multi-story, similar in construction to W1 

buildings, but have plan areas on each floor greater than 3,000 square feet. 

Older construction often has an open front or garage at the lowest story. The 

W1A building type was included because of their higher occupancy levels 

and the observed vulnerability of W1A buildings with open fronts (e.g., 

tuckunder buildings) in the 1989 Loma Prieta and 1994 Northridge 

earthquakes. 

The manufactured housing building type is part of a larger class of 

prefabricated structures that includes modular buildings. The MH building 

type includes manufactured homes that are built in a factory on a permanent 

chassis and transported to the site. Mobile home is an older term for a 

manufactured home, though the term mobile home remains in widespread 

use. The focus for screening this building type is on buildings that are 

mobile, raised up off the ground, not anchored to the ground, and may or 

may not have an earthquake-resistant bracing system (ERBS). The MH 

building type was included because of their extensive use as housing and as 

relocatable school classrooms. 

Construction and installation requirements for manufactured housing are 

addressed by varying entities. Several of the principal organizations and 

standards include: 

	 U.S. Department of Housing and Urban Development HUD 24CFR Part 

3280; 

FEMA P-155 3: Building Classification 3-3 
 

	 2012 International Building Code Appendix G Flood Resistant 

Construction (ICC, 2012a); 

	 2012 International Residential Code Appendix E Manufactured Housing 

used as Dwellings (ICC, 2012b); and 

	 State agencies such as State of California, Department of Housing and 

Community Development (HCD) policies and construction standards. 

The first three principally address flood and wind loading; earthquake 

resistance is not treated as thoroughly. However, the State of California 

HCD does specifically address earthquake loading in their policies and 

construction standards. 

It is important to be able to differentiate between a Manufactured Housing 

ground or tie-down strap system and an earthquake-resistant bracing system. 

The former is a requirement for flood and wind loading, and is not 

specifically engineered for resisting earthquake loads. Figure 3-1 shows two 

examples of typical ground anchor strap systems used for flood and wind 

resistance. 

Figure 3-1 Examples of flood and wind tie-down systems for manufactured 

housing. 

Earthquake-resistant bracing systems are engineered to resist earthquake 

forces. These types of systems may take many forms from a complete 

foundation perimeter or pony wall system very similar to a standard wood 

frame home on an engineered cripple wall to post installed units positively 

attached directly to the carriage and foundation system. A post-installed unit 

is illustrated in Figure 3-2. ERBS generally have increased structure, 

foundation and attachment detailing over the more simple straps and minimal 

attachments used in a typical flood/wind tie-down system. 

3-4 3: Building Classification FEMA P-155 
Figure 3-2 Illustration of an earthquake-resistant bracing system. 

Identifying the type of restraint system for a manufactured housing unit can 

be difficult due to perimeter cosmetic coverings or skirts that conceal the 

underside of the carriage. Skirt construction may be corrugated metal or 

fiberglass material to match the siding, or built-up 2x4 framing and wood 

siding for pony-wall systems. Access hatches or skirt vent systems should be 

identified during the field review that may allow visual review of the undercarriage area to identify the anchoring system being used. Figure 3-3 shows 

photographs of two types of skirt construction. 

Figure 3-3 Photographs of a metal skirt and pony-wall perimeter covering 

systems. 

The 17 FEMA Building Types considered in the third edition of the FEMA 

P-154 Handbook are listed in Table 3-3. 

3.4 Occupancy Classes 

The occupancy classes defined in the second edition of FEMA 154 and listed 

on the Second Edition forms (shown in Table 3-4) were reviewed along with 

the Occupancy Groups defined in the 2012 International Building Code, and 

FEMA P-155 3: Building Classification 3-5 
Table 3-3 FEMA P-154 (Third Edition) Building Types 

W1 Light wood frame single- or multiple-family dwellings of one or more stories in 

height 

W1A Light wood frame multi-unit, multi-story residential buildings with plan areas 

on each floor of greater than 3,000 square feet 

W2 Wood frame commercial and industrial buildings with a floor area larger than 

5,000 square feet. For commercial and industrial buildings with less than 5,000 

square feet, the W2 type can be used as well. 

S1 Steel moment-resisting frame buildings 

S2 Braced steel frame buildings 

S3 Light metal buildings 

S4 Steel frame buildings with cast-in-place concrete shear walls 

S5 Steel frame buildings with unreinforced masonry infill walls 

C1 Concrete moment-resisting frame buildings 

C2 Concrete shear wall buildings 

C3 Concrete frame buildings with unreinforced masonry infill walls 

PC1 Tilt-up buildings 

PC2 Precast concrete frame buildings 

RM1 Reinforced masonry buildings with flexible floor and roof diaphragms 

RM2 Reinforced masonry buildings with rigid floor and roof diaphragms 

URM Unreinforced masonry bearing wall buildings 

MH Manufactured housing 

the Building Occupancy Classes used in FEMA’s multi-hazard loss 

estimation software, known as HAZUS (FEMA, 2009a). It was seen as 

particularly important to align the occupancy classes with those in HAZUS, 

so that results from rapid visual screenings could be more easily imported 

into HAZUS. The third edition of FEMA P-154 added the following two 

new occupancy classes to more closely reflect the building occupancy classes 

used in HAZUS: 

	 Utility. Facilities include buildings for public or private utilities for 

water, wastewater, power, gas, electric power plants, and substations. 

	 Warehouse. This class includes large warehouses used for storing 

products, and commercial warehouses where items are sold. 

Additionally, the third edition of FEMA P-154 further refines building 

occupancy into occupancy classes and occupancy designations. The new 

occupancy designation added in the Third Edition includes: 

	 Shelter. This designation includes buildings specifically identified as 

shelters for post-event occupancy. 

3-6 3: Building Classification FEMA P-155 
 

Table 3-4 FEMA 154 (Second Edition) Building Occupancy Classes 

Assembly Public assembly where 300 or more people gather. Examples include theaters, auditoriums, 

community centers, performance halls, and churches. 

Commercial Retail and wholesale businesses, financial institutions, restaurants, parking structure and light 

warehouses. 

Emergency 

Services 

Critical facilities including police, fire stations, hospitals, and communication centers. 

Government Local, state and federal non-emergency related buildings. 

Historic Many variations from community to community. 

Industrial Large facilities including factories, assembly plants, large warehouse and heavy manufacturing 

facilities. 

Office Typical office buildings that house clerical and management functions. 

Residential Houses, townhouses, dormitories, motels, hotels, apartments and condominiums, and residences 

for the aged or disabled. 

School All public and private educational facilities from nursery school to university level. 

Government, Historic and Shelter are defined as occupancy designations in 

the Third Edition. Table 3-5 presents the occupancy classes and occupancy 

designations for the Third Edition. 

Table 3-5 FEMA P-154 (Third Edition) Building Occupancy Classes and Occupancy Designations 

Occupancy Classes 

Assembly Public assembly where 300 or more people gather. Examples include theaters, auditoriums, 

community centers, performance halls, and churches. 

Commercial Retail and wholesale businesses, financial institutions, restaurants, parking structure, and light 

warehouses. 

Emergency Critical facilities including police, fire stations, hospitals, and communication centers. 

Services 

Industrial Large facilities including factories, assembly plants, and heavy manufacturing facilities. 

Office Typical office buildings that house clerical and management functions. 

Residential Houses, townhouses, dormitories, motels, hotels, apartments and condominiums, and residences 

for the aged or disabled. 

School All public and private educational facilities from nursery school to university level. 

Warehouse Large warehouses used for product and commercial warehouses. (The Second Edition “Industrial” 

class included large warehouses). 

Utility Water, wastewater, power, gas, and electric facilities. (Captured as “Industrial” class facilities in the 

Second Edition). 

Occupancy Designations 

Government Local, state, and federal non-emergency related buildings. 

Historic Many variations from community to community. 

Shelter Designated shelters or buildings specifically identified as shelters for post-event occupancy 

(Captured in “Emergency Services” of the Second Edition). 

FEMA P-155 3: Building Classification 3-7 
3.5 Occupancy Class Mapping 

Many RVS Authorities (the entity performing the rapid visual screening 

program) are interested in importing FEMA P-154 data into HAZUS in order 

to develop a more robust building data set for the HAZUS risk assessment 

estimates. However, mapping 12 general categories of occupancy classes 

and occupancy designations in the third edition of FEMA P-154 into the 

nearly 100 occupancy classes contained in HAZUS is difficult. The mapping 

algorithm RedROVER, included in FEMA P-154 Rapid Observation of 

Vulnerability and Estimation of Risk (ROVER) software (FEMA, 2014) for 

the second edition of FEMA 154, which maps the nine occupancy classes 

into HAZUS, was used. In addition, the three new occupancy classes and 

occupancy designations were also aligned with the best match to HAZUS 

occupancy classes. 

Table 3-6 presents the third edition of FEMA P-154 occupancy classes and 

occupancy designations, possible HAZUS occupancy class designations, and 

the suggested HAZUS default occupancy classes, if no further information is 

known regarding the building occupancy. 

The HAZUS definitions for the suggested default occupancy classes used 

are: 

 RES1: Single family dwelling or house 

 RES3A: Duplex, apartment/condominium 

 RES5: Group housing, college dormitories, military housing, jails 

 COM1: Commercial retail or trade 

 COM2: Wholesale trade, warehouse 

 COM4: Professional or technical service offices 

 COM9: Theaters 

 IND1: Heavy industrial, factory 

 GOV1: General services, office 

 GOV2: Emergency response, police, fire, emergency operations center 

 EDU1: Grade schools 

Tables B.3 to B.18 in Multi-hazard Loss Estimation Methodology, 

Earthquake Model, HAZUS-MH MR4 Technical Manual (FEMA, 2009a) 

provide a complete description of the occupancy classes available within 

HAZUS. 

3-8 3: Building Classification FEMA P-155 
 

Table 3-6 FEMA P-154 Occupancy Class HAZUS Mapping 

FEMA P-154 Occupancy 

Classification/Designation 

Possible HAZUS Occupancy 

Classes 

Suggested HAZUS Default 

Occupancy Class 

Second Edition 

Residential:

 - Dwellings 

- Hotels and Apartments

 - Dormitories 

RES1, RES2 

RES3A-F, RES4, RES5, RES6 

RES3A-F 

RES1 

RES3A 

RES5 

Commercial COM1, COM2, COM3, COM5, 

COM10 

COM1 

Office COM3, COM4, COM7 COM4 

Industrial IND1, IND2, IND3, IND4, 

IND5, IND6, AGR1 

IND1 

School EDU1, EDU2 EDU1 

Assembly COM8, COM9, REL1 COM9 

Emergency Services COM6, GOV2 GOV2 

Government GOV1 GOV1 

Historic Any COM1 

Third Edition 

Shelter EDU1, EDU2, REL1, GOV2 

EFSI, EFS2 

GOV2 

Utility Varies IND1 

Warehouse COM1, COM2, IND1, IND2, 

IND3, IND4, IND5, IND6, 

AGR1 

COM2 

3.6 Occupancy Load Determination 

The entry for occupancy load, reporting the number of persons in a given 

square foot of floor area was removed from the Data Collection Form in the 

third edition of FEMA P-154. Although the accurate estimation of the 

number of occupants is difficult to obtain in the field, the information is 

valuable because it can be used for prioritizing a large portfolio of 

community buildings in a mitigation planning effort. Thus, while the 

occupancy load information is not recorded on the Level 1 Data Collection 

Form, the RVS Authority may want to determine the building occupancy 

load for further prioritization efforts or for additional uses. Table 3-7 

presents the third edition of FEMA P-154 occupancy classes and occupancy 

designations with their respective typical occupancy loads, which may be 

calculated from the building floor area square footage recorded on the Level 

1 Data Collection Form. 

FEMA P-155 3: Building Classification 3-9 
Table 3-7 FEMA P-154 Occupancy Load Determination 

Occupancy Classification/Designation Occupancy Load 

Residential:

 - Dwellings 

- Hotels and Apartments

 - Dormitories 

1 Person / 300 sq ft 

1 Person / 200 sq ft 

1 Person / 100 sq ft 

Commercial 1 Person / 50 - 200 sq ft 

Office 1 Person / 100 - 200 sq ft 

Industrial 1 Person / 200 sq ft 

School 1 Person / 50 - 100 sq ft 

Assembly 1 Person / 10 sq ft 

Emergency Services 1 Person / 100 sq ft 

Government 1 Person / 100 - 200 sq ft 

Historic Varies greatly 

Shelter 1 Person / 50 sq ft 

Utility 1 Person / 500 sq ft 

Warehouse 1 Person / 100 - 500 sq ft 

3-10 3: Building Classification FEMA P-155 
Chapter 4 

 Introduction to Third Edition
 

Scoring 

 

 

 

4.1 Introduction 

An important part of the Third Edition update of FEMA P-154 is the 

development of new and improved Basic Scores and Score Modifiers. This 

chapter describes the impetus for updating the Second Edition scores, and 

describes the general methodology used to develop the Third Edition scores. 

Chapter 5 provides a comprehensive description of the steps and assumptions 

used to develop the Third Edition scores, and the resulting score values. 

4.2 Review of Second Edition Scores 

The Second Edition scores were developed using the loss estimation 

methodology documented in Earthquake Loss Estimation Methodology 

Technical Manual, HAZUS99 Service Release 2 (FEMA, 2001). The 

methodology, referred to in this document as “HAZUS methodology,” was 

first released by FEMA in 1997 and has been updated several times. The 

methodology remains current in Multi-hazard Loss Estimation Methodology, 

Earthquake Model, HAZUS-MH MR4 Technical Manual (FEMA, 2009a), 

referred to as HAZUS TM. 

The basis of the Second Edition scores is thoroughly described in the Second 

Edition of FEMA 155. Basic Scores (previously known in the Second 

Edition as “Basic Structural Hazard Scores”) and Score Modifiers were 

developed using capacity and fragility parameters provided in HAZUS99 

Service Release 2. Engineering judgment was used in some cases, such as 

for vertical irregularity modifiers. 

As part of the Third Edition update, the Second Edition scores were reviewed 

considering three criteria: 

	 Were the values of the Basic Scores and Score Modifiers provided in the 

Second Edition consistent with current engineering judgment? 

	 Was the development of the Second Edition Basic Scores and Score 

Modifiers consistent with the HAZUS methodology? 

A key goal of FEMA P-155 

is to provide all the 

information and 

assumptions needed for a 

knowledgable professional 

to calculate Basic Scores 

and Score Modifiers. 

FEMA P-155 4: Introduction to Third Edition Scoring 4-1 
 

 Are there additional Basic Scores and Score Modifiers beyond what was 

provided in the Second Edition that would be beneficial to performing 

RVS? 

Several issues were identified during the review of the Second Edition scores 

prompting the decision to update the scores for the Third Edition and 

ultimately to develop a more comprehensive, current set of scores. The 

identified issues are described in the following sections. 

4.2.1 URM Scoring 

During the development of the FEMA P-154 Rapid Observation of 

Vulnerability and Estimation of Risk (ROVER) software (FEMA, 2014) 

using the Second Edition methodology, it was observed that unreinforced 

masonry (URM) buildings in Low and Moderate seismicity regions 

sometimes scored higher than other FEMA Building Types. This is due to 

several factors. One is that the URM Basic Score is relatively close to that of 

several other FEMA Building Types and higher than a few. For example, in 

Moderate seismicity, the Basic Score for URM is 3.4 and for C3 (concrete 

frame with URM infill) it is 3.2. A second factor is that some of the negative 

Score Modifiers are smaller for URM than for other FEMA Building Types, 

particularly for vertical irregularities and soft soil. For example, in Moderate 

seismicity, the URM Vertical Irregularity Score Modifier is -1.5, while it is ­

2.0 for C3. When multiple modifiers are added linearly, the result is a lower 

score for FEMA Building Types other than URM. 

4.2.2 Negative Scores 

Negative scores occur for some combinations of modifiers, indicating a 

greater than 100% probability of collapse. Individual modifiers are calculated 

by varying one condition at a time and calculating the change in probability 

of collapse. When several conditions exist at once, summing the modifiers 

algebraically can result in a negative score, indicating a greater than 100% 

probability of collapse, which is not possible. 

4.2.3 Beta Values 

The set of lognormal standard deviation values (referred to as “beta” values) 

used in the development of the Second Edition scores were included within 

the HAZUS software at the time and were chosen because they were 

considered to be more accurate than the values provided in the Technical 

Manual (FEMA, 2001). Subsequently, concerns were identified with the 

beta values used, and they were removed from the HAZUS software. 

4-2 4: Introduction to Third Edition Scoring FEMA P-155 
 

Because the beta values were not documented in the Second Edition and are 

no longer publically available, a reader could not reproduce them. 

4.2.4 Mid-Rise and High-Rise Modifiers 

Second Edition mid-rise and high-rise modifiers are generally positive, 

indicating a benefit for taller buildings. The benefit is attributed in the 

Second Edition FEMA 155 discussion to the assumption that taller buildings 

have better designs, as reflected in the HAZUS parameters used in the 

Second Edition calculations. However, in recent earthquakes, low-rise 

buildings have often performed better than mid-rise buildings. 

In the Second Edition, soil type and building height are considered with 

separate modifiers, thus ignoring their interaction. For example, the unique 

behavior of tall buildings on soft soils and the potential for resonance is 

ignored. 

4.2.5 FEMA Building Types 

Two new FEMA Building Types are added in the Third Edition: Multistory, 

multi-unit residential wood frame buildings (W1A) and manufactured 

housing (MH). New Basic Scores and Score Modifiers are required for these 

two types. 

4.3 Scoring Enhancements for the Third Edition 

Once the decision was made to update the Basic Scores and Score Modifiers 

in the Third Edition, a host of additional revisions to the RVS scoring basis, 

including whether to keep scores as part of the RVS procedure, were 

considered. Because FEMA P-154 is primarily a screening tool (i.e., it 

separates buildings into two bins: those that require additional detailed 

evaluation and those that do not), having a system that provides each 

building with a numerical score increases FEMA P-154’s usefulness as a 

prioritization tool. Accordingly, the use of scores was kept and further, the 

definition of the score, S = ‒log10(Probability of Collapse), was not altered. 

The following revisions to the RVS scoring basis were identified as 

desirable. 

4.3.1 Ground Motions 

The Third Edition scores are based on the most current version of risktargeted Maximum Considered Earthquake (MCER) ground motions 

available from the USGS. As discussed in Chapter 2, the older uniform 

hazard Maximum Considered Earthquake (MCE) ground motions used in the 

FEMA P-155 4: Introduction to Third Edition Scoring 4-3 
Second Edition are replaced in the Third Edition with the newer risk-targeted 

MCER ground motions. 

Basic Score and Score Modifier values that appear on the Second Edition 

forms were calculated using 2/3 of the MCE values. In the Third Edition, the 

demand is based on the full value of MCER. Use of the full value of MCER 

was found to produce a better correlation with the Second Edition scores and 

permit retaining the same cut-off score of S = 2.0. See Chapter 5 for detailed 

comparisons of Second Edition and Third Edition scores. 

4.3.2 Seismicity Regions 

In the first and second editions of FEMA 154, the United States was divided 

into three seismicity regions (Low, Moderate, and High), with the High 

seismicity region representing a large range of seismicity. The Low 

seismicity region also covers a large range of seismicity, including areas of 

almost zero seismicity. In the Second Edition, the median seismicity of the 

Low region was used to develop Low seismicity scores. The median Low 

seismicity is so insignificant that probabilities of collapse are effectively 

zero. The Third Edition uses the upper part of the Low seismicity range as 

the basis, developing more meaningful scores. In addition, the High 

seismicity region was subdivided to provide further accuracy. A total of five 

seismicity regions are used in the Third Edition. 

4.3.3 Default Soil Type 

In the second edition of FEMA 154, the Basic Scores assume Soil Type B, 

and Score Modifiers are provided for Soil Types C, D, and E. The most 

typical soil conditions, however, are Soil Type C and Soil Type D. 

Accordingly, the Third Edition Basic Scores are based on an average of Soil 

Type C and D, which is referred to as Soil Type CD. The difference between 

Soil Type C and CD or between Soil Type D and CD is small. Modifiers are 

provided to adjust from this average soil type to Soil Type B and to Soil 

Type E. This is believed to be more accurate than always adjusting from 

stiffer soil to softer soil, as was necessary in the Second Edition. 

4.3.4 Vertical and Plan Irregularity Score Modifiers 

In the Second Edition, Vertical Irregularity Score Modifiers were based on 

engineering judgment. In High and Moderate seismicity regions, Vertical 

Irregularity Score Modifiers were assigned values such that, if that were the 

only modifier selected during the rapid visual screening process, the Final 

Score, S, would be less than the typical cut-off score of 2.0, thereby 

triggering a Detailed Seismic Evaluation of the building. In the Low 

4-4 4: Introduction to Third Edition Scoring FEMA P-155 
seismicity region, the values assigned were generally comparable to those 

assigned for the Moderate seismicity region. Plan Irregularity Score 

Modifiers were developed by assuming an increased seismic load to 

approximate the effect of plan irregularity. For the third edition of FEMA P154, the Score Modifiers for plan and vertical irregularity are determined 

using a procedure developed by the California Office of Statewide Health 

Planning and Development (OSHPD) that can be used to calculate the 

collapse probability of buildings considering specific types of plan and 

vertical irregularities. The details of the procedure are codified within the 

California Administrative Code, California Code of Regulations, (CAC, 

2010) Title 24, Part 1, Chapter 6. The procedure’s methodology is referred 

to in this document as the “OSHPD HAZUS methodology.” 

4.3.5 Minimum Scores 

For each FEMA Building Type in each seismicity region, the probability of 

collapse considering the worst case combination of deficiencies is calculated. 

This probability of collapse is then converted to a Minimum Score. This 

Minimum Score is used in the Third Edition to avoid negative scores. 

4.4 Methodology for Development of Third Edition Basic 

Scores and Score Modifiers 

Similar to the Second Edition, Basic Scores and Score Modifiers are 

calculated by determining the probability of collapse, and then converting 

this to a score, S: 

S = ‒log10(P[Collapse|MCER ground motions]) (4-1) 

For the Third Edition, the probability of collapse is calculated using a 

modified version of the OSHPD HAZUS methodology (which is itself a 

modified version of the HAZUS methodology that was used to develop the 

Second Edition scores). This section first defines collapse for purposes of 

FEMA P-154, and then presents the method used here to calculate the 

probability of collapse. The differences between the portfolio analysis of 

multiple buildings used by HAZUS and the single building evaluation of 

FEMA P-154 are discussed. 

4.4.1 Defining Collapse 

To understand the meaning of FEMA P-154 scores, it is first necessary to 

understand how FEMA P-154 defines collapse probability. Collapse was not 

formally defined in the first or second editions of FEMA 154. Chapter 1 of 

the Third Edition provides a general definition of collapse where, in a portion 

of the building or in the entire building, the gravity load-carrying system (its 

FEMA P-155 4: Introduction to Third Edition Scoring 4-5 
beams, columns, floors, shear walls) loses the ability to carry its own weight 

and the weight of whatever else it supports. That failure leads to severe 

structural deformation of a potentially life-threatening nature, especially 

falling of all or portions of a structure. The word collapse, however, has no 

formal uniform definition in the relevant literature. From an analytical 

perspective, structural engineers sometimes treat large displacements or 

substantial reduction in tangent stiffness estimated during structural analysis 

to indicate that dynamic instability would occur in the real structural system, 

but collapse is the instability itself, not the proxy that engineering 

practitioners and researchers use to estimate it. 

Even with the foregoing definition, collapse can reasonably be used different 

ways to mean different things, and the difference matters here. Five 

important terms—building collapse, collapsed area, collapsed portion, 

collapse factor, and collapse probability—related to collapse are discussed in 

the following sections. 

4.4.1.1 Building Collapse 

As used here, building collapse means that any part of the gravity system 

experiences dynamic instability leading to the loss of load bearing capacity. 

The dynamic instability leads to severe structural deformation of a 

potentially life-threatening nature, especially falling of all or portions of a 

structure. Note that, as used here, partial building collapse means that the 

dynamic instability occurs only in a portion of the building. The probability 

of at least partial building collapse refers to the expected value of the chance 

that partial collapse or collapse will occur, given some specified conditions. 

The conditions used here are knowledge of building features observed during 

the screening and occurrence of MCER shaking. 

Some additional detail is required to understand what collapse means for 

manufactured housing (MH) and wood frame buildings (W1 and W1A). In 

the case of manufactured housing and wood frame buildings, building 

collapse also includes the condition that the manufactured home falls off one 

or more of its supports, or the cripple walls of a wood frame building 

experience a sidesway mechanism and lose their vertical load-carrying 

capacity, even if the resulting displacement. Even though this does not 

necessarily lead to falling of the superstructure, it can pose life safety risks 

and has often led to fires due to gas line damage. Building collapse does not 

include wood frame buildings sliding relative to their foundations if there is 

no vertical drop in any part of the floor or roof. Nor is the falling of a 

parapet from a URM building or brick veneer or chimney from any FEMA 

4-6 4: Introduction to Third Edition Scoring FEMA P-155 
 

Building Type considered to constitute building collapse. See Figure 4-1 for 

examples of collapse and partial collapse. 

Figure 4-1 Examples of collapse and partial collapse. 

4.4.1.2 Collapsed Area 

The collapsed area of a collapsed building is defined here as the total square 

footage in which there a loss of load bearing capacity leading to severe 

structural deformation of a potentially life-threatening nature, especially 

falling of all or portions of a structure. It also includes the area littered with 

masonry fallen from unreinforced masonry walls or concrete fallen from 

concrete walls, even if that area is outside the pre-earthquake footprint of the 

building. It does not include the square footage of rooms or floors that fall in 

a rigid body fashion without deformation, such as the non-collapsed stories 

of a building that experiences sidesway collapse of one story. Collapsed area 

is measured in units of area, such as square feet. In the two buildings shown 

in Figure 4-1, the collapsed area includes the square footage of all the rooms 

where the floor of the room, the floor above the room, or the roof above the 

FEMA P-155 4: Introduction to Third Edition Scoring 4-7 
 

second-floor room, dropped. It also includes the area littered with heavy 

debris. 

4.4.1.3 Collapsed Portion 

The collapsed portion of the building is defined as the collapsed area divided 

by the total square footage of a building, given that the building has 

experienced partial or complete collapse. The collapsed portion is measured 

as a unitless fraction. 

4.4.1.4 Collapse Factor 

The collapse factor is the expected value of collapsed area given that the 

building is in the HAZUS Complete structural damage state. The difference 

between collapsed portion and the collapse factor is that collapsed portion is 

given that the building has experienced partial or complete collapse, and the 

latter is only given that the building is in the HAZUS Complete structural 

damage state, which might or might not include any collapse in any given 

building. The collapse factor will generally be smaller than the collapsed 

portion, because only some buildings in the HAZUS Complete structural 

damage state will have any collapse. The collapse factor includes this 

fraction and the collapsed portion does not. 

4.4.1.5 Collapse Probability 

As used in FEMA P-154 to calculate scores, collapse probability is defined 

as the probability that a building will be in the HAZUS Complete structural 

damage state when subjected to MCER shaking, times the collapse factor. 

The FEMA P-154 collapse probability also equals the probability of at least 

partial building collapse given that the building is subjected to MCER 

shaking, reduced by expected value of the collapsed portion. 

It is important to recognize that the FEMA P-154 collapse probability is 

smaller than the probability of at least partial collapse given MCER shaking 

by a factor equal to the expected value of the collapsed portion. The 

expected value of the collapsed portion cannot exceed 1.0. Since it is 

typically less than 1.0, the FEMA P-154 collapse probability is generally less 

than the probability of at least partial building collapse. 

The calculation of collapse probability is detailed later in Section 4.4.2, but 

to better understand it, consider two examples. 

Example 1 

Suppose one were examining an apartment building with tuckunder parking 

on the ground floor and two stories of living space above, and all three 

4-8 4: Introduction to Third Edition Scoring FEMA P-155 
 

 

stories have the same plan area of 10,000 square feet each. Suppose in 

MCER ground motion one would expect the following: (1) one of every 10 

such buildings to experience some collapse; and (2) the other nine not to 

collapse, but almost certainly experience complete structural damage. That 

is, the probability of the building experiencing at least partial collapse is 

10%, and the probability of HAZUS Complete structural damage is near 

100%. Suppose that if the building collapses, one would expect the ground 

story to pancake, that is, the whole area of the second floor falls and comes to 

rest on the ground, but the second and third stories remain generally intact. 

In this example, the probability of the HAZUS Complete structural damage 

state is nearly 100%, and the estimated fraction of the total area in the 

HAZUS Complete structural damage state that is likely to collapse is 3.3% 

(10% chance of at least partial collapse times 33% expected value of the 

collapsed portion). So as used here, the FEMA P-154 collapse probability is 

0.1 × 0.33 = 0.033, so the FEMA P-154 score S = ‒log10(0.033) = 1.5. 

If the FEMA P-154 collapse probability had been defined as the probability 

of at least partial collapse, imagined in the example as 10%, the score would 

have been S = ‒log10(0.1) = 1.0. 

Example 2 

Suppose there are 10 buildings all of the same size, and at the MCER shaking, 

there is a 50% probability of being in the HAZUS Complete structural 

damage state and a collapse factor of 20%, assuming the building is in the 

HAZUS Complete damage state. The collapse probability is thus estimated 

to be 0.50 × 0.20 = 0.10, and the FEMA P-154 Final Score S = ‒log10(0.1) = 

1.0. There are, however, many scenarios of how this might occur. Four 

scenarios are described below. In all of these scenarios, five of the 10 

buildings or 50% are in the HAZUS Complete structural damage state. 

	 Scenario 1: One of the 10 buildings completely collapses, but none of 

the other buildings suffer any collapse or partial collapse. The collapse 

probability is thus (1 building with some collapse / 10 total buildings) × 

100% collapsed portion in that building = 0.10 × 1.00 = 0.10. 

	 Scenario 2: Each of two buildings experiences a partial collapse with 

50% collapsed portion, and no collapsed area in the other buildings. The 

collapse probability is thus (2 buildings with some collapse / 10 total 

buildings) × 50% collapsed portion in each of those buildings = 0.20 × 

0.50 = 0.10. 

	 Scenario 3: This is the same as Scenario 2 except that there is a partial 

collapse involving 5% of the area in one of the buildings and 95% in the 

FEMA P-155 4: Introduction to Third Edition Scoring 4-9 
other. The collapse probability is thus (1 building / 10 total) × 0.05 + (1 

building / 10 total) × 0.95 = 0.10 × 0.05 + 0.10 × 0.95 = 0.10. 

 Scenario 4: All five buildings in the complete damage state suffer some 

amount of partial collapse. In one, only 1% of the area in the building 

collapses, and the collapsed portion in the others is 9%, 15%, 25%, and 

50%, respectively. The collapse probability is 0.10 × 0.01 + 0.10 × 0.09 

+ 0.10 × 0.15 + 0.10 × 0.25 + 0.10 × 0.25 = 0.10. 

There are an infinite number of scenarios in Example 2 that could actually 

occur and yield the same collapse probability of 0.10. A key difference is 

that in Scenario 1 only one building suffers any form of collapse, but in 

Scenario 4, five do. Thus, while the collapse probability as defined here is 

the same, the number of buildings that suffers some form of collapse differs 

by a factor of five. 

The probability of at least partial collapse is useful in a methodology whose 

objective is to measure the adequacy of a structural design. The FEMA 

P-154 definition of collapse probability is more appropriate to a methodology 

whose objective is to measure life safety, which is the underlying goal of 

FEMA P-154. With the assumption that the risk to life safety is proportional 

to being in the collapsed portion of the building (as HAZUS assumes), then 

the risk of dying in all four of the scenarios in Example 2 is the same, even 

though the number of buildings with some form collapse or partial collapse 

differs widely in each scenario. 

If it is not known which building a person is in, then the risk of death to a 

building occupant is the chance of being in any given building, times the 

probability of dying if one were in that building, summed over all the 

buildings. Notice that the four scenarios in Example 2 could all reflect the 

behavior of the same building type with the same features. This means that 

the FEMA P-154 methodology does not require that all the buildings of a 

given type and with given features must behave identically. 

Comparison to Portfolio Risk Analysis 

It is useful to compare portfolio risk analysis (as in HAZUS), and risk 

analysis of a single building (as in FEMA P-154). Regardless of whether one 

is evaluating one building, or 10, or 100, the expected value of the 

performance measure (here, collapse probability) is the same. The reason is 

that the expected value of a sum of uncertain variables is the sum of the 

expected values. FEMA P-154 estimates the expected value of the collapsed 

area of a building subjected to MCER shaking. A portfolio risk analysis that 

calculates the expected value of the total collapsed area of many buildings 

4-10 4: Introduction to Third Edition Scoring FEMA P-155 
 

can do so by calculating the sum of the expected values of the collapsed 

areas of individual buildings. Thus, it does not matter that HAZUS is a 

portfolio risk estimation tool and FEMA P-154 applies to single buildings. 

Portfolio risk analyses differ from analyses of single buildings in the 

estimation of other important parameter values, such as the uncertainty in 

collapsed area, but not in the estimation of the expected value of the 

collapsed area. 

For example, if one were performing a portfolio risk analysis of an apartment 

complex with 10 identical buildings exactly like the one just discussed. Each 

building has 30,000 square feet of area, for a total of 300,000 square feet in 

the portfolio. In MCER shaking, each has a 10% probability of at least partial 

collapse, so on average, one would expect one of the 10 buildings to 

collapse. In that building, one expects the ground floor to pancake. The 

other buildings are assumed to be in the HAZUS Complete structural damage 

state. The expected collapsed area is 10,000 square feet out of a total of 

300,000 square feet. The FEMA P-154 collapse probability is still 

10,000/300,000 = 0.033. Whether one is looking at one building, or 10 

identical buildings, or 100 identical buildings, the collapse probability is the 

same. 

In the same portfolio risk analysis, one could alternatively suppose that the 

10 buildings are perfectly correlated in their behavior, in which case in one 

earthquake out of 10 with MCER shaking at the apartment complex, all of the 

buildings collapse onto their parking floor and in the other nine earthquakes, 

none collapse, but in either case the buildings are almost certainly in the 

HAZUS Complete structural damage state. Even with this supposition, the 

collapse probability is the same: 10% chance that any given building 

collapses, with a collapsed portion of 33%, for a FEMA P-154 collapse 

probability of 0.033. For purposes of calculating the expected value of the 

collapsed area, it does not matter if one is performing the calculations on a 

single building or a portfolio of buildings. 

When it comes to the risk to a single person, the portfolio case (like HAZUS) 

is indistinguishable from the single-building case (like FEMA P-154). But 

this does not require that every building with a given Final Score is expected 

to behave identically to every other building with that Final Score. A 

building with a score of 1.0, for example, could be one with a 10% 

probability of 100% of its area to collapse (as in the case of a mobile home 

that either falls off its supports or does not). It could be a URM building 

with a 20% probability of the exterior bearing walls falling out-of-plane and 

leading to collapse of half the floor area. Or it could be a building with a 

100% probability that 10% of its area will collapse (as in the case of a 10­

FEMA P-155 4: Introduction to Third Edition Scoring 4-11 
story building with a weak story irregularity that is almost certain to 

experience sidesway collapse at the weak story). 

As a final point, although the portfolio-based HAZUS approach to defining 

collapse probability was used in the Second Edition and continued in the 

Third Edition, rapid visual screening in FEMA P-154 focuses on the 

individual building, rather than on a portfolio analysis. While the statistics 

and examples above mathematically imply that in theory every building in a 

HAZUS Complete structural damage state could suffer some form of partial 

collapse, this is not a likely scenario and should not be taken as a literal 

estimate of the percentage of square feet of partial collapse in an individual 

building. Rather, the S score is a helpful quantitative metric based on 

collapse potential that is useful in assessing and ranking buildings for 

potential seismic hazards. 

4.4.2	 Calculating Probability of Collapse with HAZUS 

Methodology 

This section introduces the process for calculating probability of collapse 

using the HAZUS methodology. 

The method includes three distinct parts: (1) calculation of peak response 

(i.e., peak displacement for evaluation of damage to the structure) of the 

building for a given set of ground motions (e.g., MCER response spectral 

accelerations); (2) calculation of the probability of complete damage given 

the peak response; and (3) calculation of probability of collapse given the 

probability of complete damage. 

Properties are provided for 35 different combinations of building type and 

height, known within HAZUS as “Model Building Types” or MBTs. 

4.4.2.1 Part 1: Response Calculation 

HAZUS methods are used to calculate the peak response of the building by 

finding the intersection of the building capacity curve (a plot of a building’s 

lateral load resistance as a function of a characteristic lateral displacement) 

and the demand spectrum of earthquake ground motions. This method is 

illustrated in Figure 4-2 for two capacity curves and three example demand 

spectra. In this illustration, the demand spectra represent what can be 

considered as weak, medium, and strong ground shaking, and the two 

building capacity curves represent weaker and stronger construction. 

Different colors along the capacity curves correspond to the range of 

displacements associated with each of the four discrete states of structural 

damage (slight, moderate, extensive, and complete). 

4-12	 4: Introduction to Third Edition Scoring FEMA P-155 
Figure 4-2 Example intersection of demand spectra and building capacity 

curves. 

As shown in Figure 4-2, stronger and stiffer construction displaces less than 

weaker and less stiff construction for the same level of shaking. As seen in 

the color bands of the capacity curves in Figure 4-2, for similar displacement, 

the more ductile construction (i.e., construction with long green, yellow, and 

orange bands) will be in a less severe structural damage state than the less 

ductile construction (i.e., construction with short green, yellow, and orange 

bands). Therefore, for similar levels of shaking, the stronger and more 

ductile building will have less structural damage than the weaker, less ductile 

building. 

The building capacity curve is a plot of a building’s lateral load resistance as 

a function of a characteristic lateral displacement (i.e., a force-deflection 

plot). It is derived from a plot of static-equivalent base shear versus building 

displacement at the roof, known commonly as a pushover curve. In order to 

facilitate direct comparison with spectral demand, base shear is converted to 

spectral acceleration, and the roof displacement is converted to spectral 

displacement using modal properties that represent pushover response. 

Building capacity curves are constructed from values of the design 

coefficient, Cs, and other HAZUS capacity parameters as shown in Figure 

4-3. 

The capacity curve is defined by two control points: (1) the yield capacity 

point (Dy, Ay); and (2) the ultimate capacity point (Du, Au). The yield 

capacity represents the lateral strength of the building at initial yield and 

accounts for design strength, redundancies in design, conservatism in code 

requirements and expected (rather than nominal) strength of materials. The 

structure is assumed to be fully elastic up to the yield capacity point. The 

FEMA P-155 4: Introduction to Third Edition Scoring 4-13 
 

Figure 4-3 Example building capacity curve and control points. 

ultimate capacity represents the displacement at which the full strength of the 

building is reached considering additional sources of overstrength. 

Beyond the ultimate capacity point, the HAZUS method assumes the 

capacity curve is fully plastic (i.e., constant strength). Between the yield 

point and the ultimate point, the capacity curve is assumed to have an 

elliptical shape that is tangent to the elastic segment at yield capacity point 

and tangent to the plastic segment at the ultimate capacity point, which may 

be expressed as follows: 

(D D u )

2 (A k  )

2 

2  2 1 (4-2) a b

where the values of a, b, and k are given by the following equations: 

D ( D D ) y 2 u y a  b (4-3) Ay ( A k y  ) 

b A  k u  (4-4) 

A2 

2 2 y A A   (D D ) u y y u Dy k  (4-5) A

2 A  A )  y ( ( D D ) u y y u Dy

In reality, the red portion of the capacity curve does not continue as a flat line 

indefinitely. Loss of strength and a corresponding drop in the curve is 

expected. For analysis purposes, however, the HAZUS method assumes the 

structure maintains constant strength beyond the complete damage state. 

4-14 4: Introduction to Third Edition Scoring FEMA P-155 
The demand spectrum is constructed from the 5%-damped response spectrum 

of MCER ground motions by reducing spectral response for effective 

damping greater than 5% damping. The amount of effective damping is a 

function of the inherent elastic damping of the Model Building Type of 

interest and additional energy dissipated during post-yield, inelastic response, 

considering possible degradation of the structure during repeated cycles of 

inelastic response. 

The 5%-damped response spectrum is reduced at each period by factors, RA, 

in the acceleration domain and, RV, in the velocity domain, as illustrated in 

Figure 4-4. Note that in Figure 4-4, spokes from the origin represent lines of 

constant period. As described previously, the intersection of the demand 

spectrum and the capacity curve define the point of peak building response 

(D, A). 

Figure 4-4 Example calculation of demand spectrum by reduction of 

5%-damped response spectrum of ground motions. 

The reduction factors, RA and RV, are a function of the effective damping, eff, 

due to the combined effects of elastic damping, E, and hysteretic damping, 

H, associated with the non-degraded portion of the area of the hysteresis 

loop shown in green in Figure 4-4. The values of reduction factors, RA and 

RV, are given in the following equations: 

. R  2 12 	 A (4-6) 3 21 . 0 68 ln( eff .  ) 

FEMA P-155 4: Introduction to Third Edition Scoring 4-15 
 

 

. RV  1 65 

(4-7) 2 31 0 41 ln( eff . .  ) 

where the value of effective damping, eff, is given by the following equation: 

   E   H    

Area

eff E (4-8) 2 D A

In Equation 4-8, the degradation factor, , describes the non-degraded 

fraction of the area of the hysteresis loop, and is function of the duration of 

earthquake shaking (i.e., the longer the shaking duration, the greater the 

degradation). Since the area of the hysteresis loop increases as (post-yield) 

response increases, values of reduction factors, RA and RV, are inherently 

amplitude dependent. 

In certain cases where the effects of degradation are modest (e.g., larger 

values of ), post-yield (inelastic) displacements of demand spectrum 

calculated using the HAZUS reduction factors, RA and RV, as defined by 

Equations 4-6 and 4-7, can be somewhat less than the elastic displacement, 

De, the value of capacity spectrum at the elastic period, Te. Conceptually, 

inelastic displacements should not be less than the elastic displacement (i.e., 

based on the “equal displacement” rule attributed to Newmark). For 

development of Basic Scores (and Score Modifiers), the displacement D of 

the demand spectrum is, in all cases, taken as not less than the elastic 

displacement, De. 

4.4.2.2 Part 2: Probability of Complete Damage State 

HAZUS building fragility curves are lognormal probability functions that 

describe the likelihood of reaching, or exceeding, discrete states of structural 

and nonstructural damage, given an estimate of peak building response (e.g., 

the spectral displacement calculated in Section 4.4.2.1). The fragility curves 

take into account the variability and uncertainty associated with capacity 

curve properties, damage states, and ground shaking. 

Development of Basic Scores and Score Modifiers only requires the fragility 

curve for the Complete damage state. Complete damage indicates that the 

structure is in imminent danger of collapse or has collapsed. 

Figure 4-5 provides an example of HAZUS fragility curves for Slight, 

Moderate, Extensive, and Complete structural damage states, respectively, 

and illustrates differences in damage state probabilities for three levels of 

spectral response corresponding to weak, medium, and strong earthquake 

ground shaking, respectively. The terms “weak,” “medium,” and “strong” 

4-16 4: Introduction to Third Edition Scoring FEMA P-155 
 

are used here for simplicity, but may be thought of representing different 

intensities of MCER ground motions. Probability 

1.0 

0.5 

0.0 

Extensive 

Complete 

Slight Moderate 

Weak Medium Strong Spectral Response Shaking Shaking Shaking 

Figure 4-5 Example fragility curves for Slight, Moderate, Extensive and 

Complete structural damage. 

Each fragility curve is defined by a median value of the demand parameter 

that corresponds to the threshold of that damage state and by the total 

variability associated with that damage state. The demand parameter is 

spectral displacement, Sd,ds, for the structure, and is the product of the story 

drift ratio, ds, associated with the damage state of interest, building height, 

HR (in inches), and the ratio of modal parameters, 2/ where α2 is the 

modal height factor and α3 is the modal shape factor relating maximum-story 

drift and roof drift. Median values of fragility curves are based on 

observations of damage in past earthquakes, laboratory tests of structural 

components and systems, and engineering judgment. 

The median value of spectral displacement, Sd, of the Complete structural 

damage state is given by the following equation: 

Sd C,  C R H (2 3 /  )	 (4-9)

Lognormal standard deviation values, S,ds, describe the total variability of 

fragility-curve damage states. Three primary sources contribute to the total 

variability of any given state, namely, the variability associated with the 

capacity curve, the variability associated with the demand spectrum, and the 

variability associated with threshold of the damage state. Uncertainty due to 

damage-state threshold is assumed to be independent of other sources of 

uncertainty. However, demand and capacity curve uncertainties are not 

independent for the structure and their combined effect on total damage-state 

variability is a function of response, in particular post-yield response. 

FEMA P-155 4: Introduction to Third Edition Scoring 4-17 
 

 

 

The beta values given in HAZUS TM are intended primarily for use with 

deterministic (scenario earthquake) ground motions. As such, the variability 

associated with the demand spectrum includes so-called record-to-record 

variability not included in the calculation of deterministic ground motions. 

Using the values of Sd,C and S,C provided in HAZUS TM and the peak 

response, D, determined in Section 4.4.2.1, the probability of complete 

damage is calculated as: 

 1  D 

PCompleteDamage   ln   (4-10)  

  β S  S C,  d C, 

4.4.2.3 Part 3: Probability of Collapse 

Once the probability of complete damage has been determined, the 

probability of collapse can be calculated by applying a collapse factor. 

PCOL  PCOL| Complete DamageP[ Complete Damage] (4-11)

where: 

PCOL|Complete Damage  CollapseFactor

HAZUS TM provides collapse factors for each Model Building Type. The 

collapse factor is small for light wood frame single or multiple-family 

dwellings (W1) (3%) and larger for Model Building Types more prone to 

collapse, such as unreinforced masonry bearing-wall buildings (URM) 

(15%). 

4.4.3 History and Purpose of the OSHPD HAZUS Procedure 

Tokas and Lobo (2009) summarize the history and purpose of the procedure 

developed by OSHPD for risk-based seismic evaluation of pre-1973 hospital 

building using the HAZUS methodology. The procedure was developed 

when pre-1973 hospital buildings were evaluated using conventional seismic 

evaluation procedures according to the California State Senate Bill 1953 

regulations and over 90% of them were found to not meet the minimum lifesafety standard. In response, OSHPD looked for a possible alternative to 

reclassify some of these buildings with the goal of ranking the risk of the 

failing hospitals so that, given limited resources, a “worst first” strategy 

could be applied to upgrading the hospital stock. OSHPD used HAZUS to 

determine probability of collapse (considering building type, age, and 

height), but modified the procedure so that the results also take into account a 

variety of deficiencies. The details of the procedure have since been codified 

within the California Administrative Code, California Code of Regulations, 

4-18 4: Introduction to Third Edition Scoring FEMA P-155 
Title 24, Part 1, Chapter 6. The procedure is referred to in this document as 

the “OSHPD HAZUS” procedure. 

4.4.4	 Calculating Collapse Probability with the OSHPD HAZUS 

Procedure 

As in HAZUS, probability of collapse is calculated with OSHPD HAZUS 

using the same three step process of calculating peak displacement, 

probability of complete damage, and, finally, the probability of collapse. 

Properties are provided for 16 different building types, known within 

OSHPD HAZUS as “Model Building Types” or MBTs. The significant 

difference between HAZUS and OSHPD HAZUS is that the assumed 

properties of the building (capacity, response, fragility, and collapse rate) 

vary based on the presence of deficiencies in OSHPD HAZUS, but not in 

HAZUS. 

Deficiencies can affect the probability of collapse in a number of different 

ways. The deficiency may reduce the building’s ultimate capacity; it may 

reduce the roof drift associated with the Complete damage state; it may 

increase the probability of collapse given the Complete damage state; or 

some combination of these effects may be triggered. In the case of a soft 

story, for example, a significant portion of the roof drift is assumed to be 

concentrated within a single story. The roof drift corresponding to the 

Complete damage state is reduced since it becomes more akin to the story 

drift associated with the Complete damage state. Vertical elements at that 

story experience higher drifts, leading to greater damage and a higher 

probability of collapse. Therefore, the collapse factor is increased. For 

example, a steel building with a soft story is assigned a 15% chance of 

collapsing given it reaching the complete damage state versus only an 8% 

chance of collapse for a similar building without a soft story. 

When no deficiencies are present, the probability of collapse is calculated 

assuming “Baseline” performance properties. When deficiencies are present, 

Sub-Baseline (SubBase) or Ultra-Sub-Baseline (USB) performance 

properties are used as specified in OSHPD HAZUS Table A6-1 (reproduced 

below in Table 4-1). Deficiencies that moderately degrade the building 

performance, such as the presence of a weak story, result in the use of 

SubBase performance properties. Deficiencies (or certain combinations of 

deficiencies) that seriously degrade performance, such as the combination of 

weak story with torsional irregularity, result in the use of USB performance 

properties. When SubBase properties are used, the collapse probability 

increases. When USB properties are used, the collapse probabilities are 

increased even further. 

FEMA P-155 4: Introduction to Third Edition Scoring 4-19 
 

 

 

 

 

 

 

 

 

Table 4-1 OSHPD HAZUS Significant Structural Deficiency Matrix 

Significant Structural 

Deficiency/Condition1 

Capacity Response Structural Damage - Complete Damage State Collapse 

Overstrength Duration Fragility Curve Median4 

Fragility Curve 

Variability - Beta 

Factor (βc) 

Collapse Factor 

(P[COL|STR5 γ and λ Factors ])

Degradation, κ,

Factor 

Maximum Story 

Drift Ratio, ∆c

Mode Shape, 3

Factor 

SubBase USB SubBase USB5 SubBase USB SubBase USB6 SubBase USB5 SubBase USB6 

Age (Pre-1933 buildings) X X7 

Materials Testing (None) X X 

No Redundancy X X X6 

Weak Story Irregularity X X X6 X X6 

Soft Story Irregularity X X X6 X X6 

Mass Irregularity X 

Vertical Discontinuity X X 

Torsional Irregularity X X X6 

Deflection 

Incompatibility2 X X X X6 

Short Column3 X X 

Wood Deterioration X X 

Steel Deterioration X X 

Concrete Deterioration X X 

Weak Column-Steel X X 

Weak Column- X X X 

No Cripple Wall 

Bracing X X X6 X X6 

Topping Slab X X X X X6 

Inadequate Wall 

Anchorage X X 

Load Path/Diaphragm 

Openings X X X6

 1 Sub-Baseline (SubBase) and Ultra-Sub-Baseline (USB) properties are based on one, or more, significant structural deficiencies. 2 The deflection incompatibility structural deficiency applies only to concrete systems (C1, C2, and C3). 3

 The short column structural deficiency applies only to concrete and masonry systems (C1, C2, C3, RM1, and RM2). 4

 Effects of deficiencies related to drift and mode shape are limited to a combined factor of five reduction in Complete median (of HAZUS 

default value). 

5

 Grey shading indicates USB performance is not defined/used for deficiencies related to degradation (kappa) and fragility curve (beta) 

factors. 

6

 USB performance required for systems with multiple, SubBase deficiencies related to either the mode shape () factor or the collapse 

rate. 

7

 USB performance required for pre-1933 buildings with other over-strength-related deficiencies (else use SubBase performance for pre1933 buildings). 

4-20 4: Introduction to Third Edition Scoring FEMA P-155 
 

 

 

 

 

 

 

OSHPD HAZUS provides Equations A6-2 through A6-5 (reproduced below 

as Equations 4-12 through 4-15) to define building capacity: 

Ay = Cs γ / α1	 (4-12) 

D  9.8 A T 2	 

y ye (4-13)

Au  Ay	 (4-14) 

Du  Dy	 (4-15) 

where: 

Cs = seismic design coefficient – values of CS are given in OSHPD 

HAZUS Tables A6-2a and A6-2b. OSHPD HAZUS Table 

A6-2a provides values of CS for the various Model Building 

Types and for varying number of stories considering buildings 

built post-or pre-1961 located in UBC Seismic Zone 4. OSHPD 

HAZUS Table A6-2b provides values of CS for the various 

Model Building Types and for varying number of stories 

considering post-1961 or pre-1961 buildings located in UBC 

Seismic Zone 3. 

γ = yield strength factor – values of γ are given in OSHPD HAZUS 

Table A6-5 for varying number of stories. 

α1 = modal weight factor – values of α1 are given in OSHPD HAZUS 

Table A6-4 for the various Model Building Types and for 

varying number of stories. 

Te = elastic period, in seconds – values of Te are given in OSHPD 

HAZUS Table A6-3 for the various Model Building Types and 

for varying number of stories. 

λ = overstrength factor – values of λ are given in OSHPD HAZUS 

Table A6-5 for the various Model Building Types and for 

varying number of stories. This factor varies for Baseline, 

SubBase, and USB performance. 

μ = ductility factor – values of μ are given in OSHPD HAZUS Table 

A6-6 for varying number of stories. 

FEMA P-155 4: Introduction to Third Edition Scoring 4-21 
OSHPD HAZUS then provides variables βE and κ to define building response 

where: 

βE = elastic damping – values of βE are given in OSHPD HAZUS 

Table A6-7 for the various Model Building Types. 

κ = degradation factor – values of κ are given in OSHPD HAZUS 

Table A6-8 for varying scenario earthquakes. The degradation 

factor also varies for Baseline and SubBase performance. 

Based on the building capacity and the building response defined above, the 

user calculates the peak response of the building using the methods described 

in the HAZUS discussion above. 

OSHPD HAZUS then provides equations and variables to create fragility 

curves for the building in the form: 

S d C,  CH R  2 / 3 	 (4-16)

where: 

ΔC = story drift ratio at the threshold of Complete Structural Damage - 

values of ΔC are given in OSHPD HAZUS Table A6-9 for the 

various Model Building Types considering post-1961 or pre1961. ΔC varies for Baseline, SubBase, or USB performance. 

HR = height of building at the roof level – default values of HR are 

given in OSHPD HAZUS Table A6-3 for the various Model 

Building Types and for varying number of stories. 

α2 = modal height factor – values of α2 are given in OSHPD HAZUS 

Table A6-4 for the various Model Building Types and for 

varying number of stories. 

α3 = modal shape factor relating maximum-story drift and roof drift – 

values of α3 are given in OSHPD HAZUS Table A6-10 for 

varying number of stories and for Baseline, SubBase, and USB 

performance. 

Lognormal standard deviation values for complete damage, βC, are provided 

in OSHPD HAZUS Table A6-11. These values consider post-1961 or pre1961 designations, and vary for number of stories and for Baseline or 

SubBase performance. These are referred to in HAZUS TM as βS, C. 

Appendix A presents tables that have been developed to document the values 

of all variables used to develop the Third Edition Basic Scores. These tables 

4-22	 4: Introduction to Third Edition Scoring FEMA P-155 
include values from OSHPD HAZUS, values from OSHPD HAZUS adjusted 

for use in calculation of Third Edition Score Modifiers, and values derived 

for FEMA Building Types not included in OSHPD HAZUS. Section 5.2.4 

presents a detailed list of Appendix A tables, Chapter 5 details how to use the 

tables. 

Using the peak response and the fragility parameters Sd,C and βC, the user 

determines the probability of complete damage using the methods described 

in the HAZUS discussion above. 

Finally, the OSHPD HAZUS procedure defines the probability of collapse, 

P[COL], as follows: 

P COL]  [ | 5 ]  P STR5 [ P COL STR [ ] (4-17)

where the term STR5 designates the Complete structural damage state and 

P[COL|STR5] is the collapse factor. Values of the collapse factor are given in 

OSHPD HAZUS Table A6-12 for the various Model Building Types and 

vary for Baseline, SubBase, and USB performance. 

4.4.5 Use of the OSHPD HAZUS Procedure for FEMA P-154 

Basic Scores were developed using properties that correspond to Baseline 

building performance. Score Modifiers were developed by varying 

assumptions of pre-1961 or post-1961, building height, and SubBase and 

USB performance. Specific mapping of OSHPD HAZUS tables to FEMA 

P -154 input is described in Chapter 5. 

One significant difference between the OSHPD HAZUS procedure and the 

modified procedure for FEMA P-154 is the adjustment of the beta values. 

Another difference is in calculating Post-Benchmark Score Modifiers. 

4.4.5.1 Adjustment of Beta Values 

Like HAZUS, the beta values provided in OSHPD HAZUS are deterministic. 

When used with probabilistic ground motions (e.g., MCER ground motions 

other than certain sites of very high seismicity), these so-called deterministic 

betas should be reduced to avoid double counting the variability associated 

with demand, since the calculation of probabilistic ground motions includes 

record-to-record variability. The amount of reduction is a function of the 

degree of inelastic response. Incremental dynamic analysis results (e.g., 

studies in FEMA P-695 (FEMA, 2009b) have shown that the responses of a 

highly yielded nonlinear system exhibit significant record-to-record 

variability for a set of earthquake records scaled to have no variability in 

FEMA P-155 4: Introduction to Third Edition Scoring 4-23 
 

linear elastic response (i.e., records scaled to the same spectral acceleration at 

elastic period). 

Considering the above discussion, probabilistic betas are derived from the 

deterministic betas of OSHPD HAZUS by removing a modest amount of 

demand (record-to-record) variability when the building is responding 

elastically, and by removing less demand variability when the building is 

responding inelastically, in proportion to the degree of inelastic response. 

Accordingly, values of probabilistic betas, C,P, are derived from 

deterministic betas, C,D, for the Complete damage state using the following 

equation: 

2 2 2 

2 2 

1 

                 

, , 

, , 

( ) ( ) C D CAP T C

C P CAP T C

e

D X

D

(4-18) 

Values of C,D are derived from OSHPD HAZUS values of c, which vary by 

number of stories, performance level, and age. Values of CAP (variability 

associated with the capacity curve) and T,C (variability associated with the 

threshold of the damage state) are selected from the Multi-hazard Loss 

Estimation Methodology, Earthquake Model, HAZUS-MH MR1, Advanced 

Engineering Building Module, Technical and User's Manual (FEMA, 2003). 

The HAZUS Advanced Engineering Building Module (AEBM) procedures 

are an extension of the more general methods of HAZUS. While HAZUS 

provides damage and loss functions for generic Model Building Types, the 

AEBM can be used to develop building-specific damage and loss functions. 

The elastic displacement, De, is defined as the value of demand spectrum at 

the elastic period, Te. As previously established, D is always greater than or 

equal to, De. 

The factor X in Equation 4-18 affects the amount of beta reduction. When X 

is equal to zero, the calculation is set so that the probabilistic betas come out 

the same as the deterministic betas. When X is large (e.g., 100), the 

probabilistic betas include only uncertainties associated with capacity and 

threshold of Complete damage. When X is small (e.g., around one), the 

probabilistic betas reflect reasonable amounts of ground motion uncertainty. 

4.4.5.2 Post-Benchmark Score Modifiers 

The OSHPD HAZUS procedure was designed to evaluate pre-1971 hospital 

buildings. It does not, therefore, provide parameters for newer buildings. In 

order to determine Post-Benchmark Score Modifiers, the approach used for 

4-24 4: Introduction to Third Edition Scoring FEMA P-155 
 

post-benchmark buildings in HAZUS was adapted for the FEMA P-154 

procedure. 

In the Second Edition, Basic Scores for High, Moderate, and Low seismicity 

were based on HAZUS values for Moderate-Code, Low-Code, and Pre-Code, 

respectively. Post-Benchmark Score Modifiers for High, Moderate, and Low 

seismicity were based on HAZUS values for High-Code, Moderate-Code, 

and Low-Code, respectively. 

The change from one code level to another (for example, from Low-Code to 

Moderate-Code for Post-Benchmark Score Modifiers in Moderate seismicity) 

triggered an increase in values for CS, μ, Sd.C, and κ, and a decrease in beta 

values. Values of CS typically doubled when going from Moderate-Code 

(basis of High seismicity Basic Score) to High-Code (basis of High 

seismicity Post-Benchmark Score Modifier). Other parameters had similar 

trends with varying ratios of the associated Post-Benchmark value to Basic 

Score value. 

Ratios for calculating Post-Benchmark Score Modifiers using the OSHPD 

HAZUS values are based on the ratios given in HAZUS. In order to obtain 

meaningful Post-Benchmark Score Modifier values in Very High and High 

seismicity regions, ratios based on HAZUS’s Special High-Code were used. 

FEMA P-155 4: Introduction to Third Edition Scoring 4-25 

 

Chapter 5 

 Development of Third Edition Basic 

Scores and Score Modifiers 

5.1 Introduction 

An important part of the Third Edition update of FEMA P-154 is the 

development of new and improved Basic Scores and Score Modifiers. In 

addition to discussing the impetus for updating the Second Edition scores, 

Chapter 4 describes the theory behind the calculation of Basic Scores and 

Modifiers. Specifically, Chapter 4 describes the methodology documented in 

Multi-hazard Loss Estimation Methodology, Earthquake Model, HAZUS-MH 

MR4 Technical Manual (FEMA, 2009a), referred to in this document as 

“HAZUS methodology,” as well as the procedure developed by the 

California Office of Statewide Health Planning and Development (OSHPD), 

referred to in this document as the “OSHPD HAZUS methodology” (CAC, 

2010). It introduces how the HAZUS and OSHPD HAZUS methodologies 

were combined to create a unique FEMA P-154 procedure for calculating 

Third Edition scores. This chapter provides a comprehensive description of 

the steps and assumptions used to develop the Third Edition scores, and it 

provides the results. 

5.2 Development of Third Edition Basic Scores 

Basic Scores were calculated for five unique seismicity regions and the 17 

FEMA Building Types considered in the Third Edition. All Basic Scores 

were calculated considering low-rise buildings on Soil Type CD. 

5.2.1 Seismicity Regions 

Five seismicity regions are considered: Low, Moderate, Moderately High, 

High, and Very High. These seismicity regions are demarcated by ranges of 

spectral response acceleration parameters. The ranges are defined in Table 

5-1 for Ss, spectral response acceleration parameter for 5%-damped 

maximum considered earthquake (MCER) at a period of 0.2 seconds, and S1, 

spectral response acceleration parameter for 5%-damped MCER at a period of 

1 second, assuming Soil Type B (also referred to as Site Class). The colors 

in the table correspond to the maps provided in Appendix A of FEMA P-154. 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-1 
 

 

 

Table 5-1 Range and Median MCER Spectral Response Acceleration Values in 

Each Seismicity Region 

Seismicity Region 

Range of Response Values for Each Region 

SS (g) S1 (g) 

Median Response 

Values for Each 

Region 

SS,avg (g) S1,avg (g)

 Low (L) SS < 0.250g S1 < 0.100g 0.20 0.08 

Moderate (M) 0.250g < SS < 0.500g 0.100g < S1 < 0.200g 0.40 0.16

 Moderately 

High (MH) 

0.500g < SS < 1.000g 0.200g < S1 < 0.400g 0.80 0.32 

High (H) 1.000g < SS < 1.500g 0.400g < S1 < 0.600g 1.20 0.48 

Very High (VH) SS > 1.500g S1 > 0.600g 2.25 0.90 

Table 5-1 also shows the median values of Ss and S1 for each region. These 

median values approximate the average seismicity in the region and are used 

as the basis of the scores for that region. The maximum seismicity (at the 

extreme end of the Very High seismicity region) is considered to be SS = 3.8g 

and S1 = 1.5g. 

Table 5-2 presents SS and S1 values and the resulting seismicity region for 35 

selected cities throughout the United States. The SS and S1 values were 

obtained from the U.S. Seismic Design Maps web application on the USGS 

website (http://earthquake.usgs.gov/designmaps/us/application.php) using the 

latitude and longitude shown corresponding to a point within each city. The 

point used does not necessarily correspond to the location of maximum 

ground motion within the city. Hence, some locations within some cities 

may fall within a higher seismicity region than noted. The reported values 

are for BSE-2N (i.e., MCER) ground motion criteria, as defined in ASCE/SEI 

41-13, Seismic Evaluation and Retrofit of Existing Buildings (ASCE, 2014), 

and Site Class B soil. The seismicity region designation from each city 

according to the Second Edition is also included for comparison. 

Spectral acceleration response parameters are adjusted for different soil types 

by multiplying SS by Fa and S1 by Fv, where Fa and Fv, are the short-period 

and one-second period site coefficients, respectively. Site coefficients for 

Soil Types B, C, D, and E are provided in ASCE/SEI 7-10, Minimum Design 

Loads for Buildings and Other Structures (ASCE, 2010, Tables 11.4-1 and 

11.4-2) and repeated in Table 5-3. Note that the coefficient for Soil Type B 

is equal to unity. 

5-2 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 5-2 Seismicity Region for 35 Selected Cities in the United States 

City Latitude Longitude 

MCER Response 

Values 

SS (g) S1 (g) 

Third Edition 

Seismicity Region 

Second Edition 

Seismicity Region 

Southern California 

Los Angeles 34.05 -118.25 2.402 0.843 Very High High 

Century City 34.05 -118.4 2.165 0.804 Very High High 

Northridge 34.2 -118.55 1.69 0.6 Very High High

Long Beach 33.8 -118.2 1.643 0.617 Very High High 

Irvine 33.65 -117.8 1.55 0.571 Very High High

Riverside 33.95 -117.4 1.5 0.6 Very High High

San Bernardino 34.1 -117.3 2.367 1.083 Very High High 

San Luis Obispo 35.3 -120.65 1.116 0.426 High High 

San Diego 32.7 -117.15 1.254 0.484 High High 

Santa Barbara 34.45 -119.7 2.828 0.993 Very High High 

Ventura 34.3 -119.3 2.381 0.9 

Northern California 

Very High High

Oakland 37.8 -122.25 1.861 0.747 Very High High

Concord 37.95 -122.0 2.075 0.735 Very High High

Monterey 36.6 -121.9 1.526 0.56 Very High High

Sacramento 38.6 -121.5 0.672 0.293 Moderately High High

San Francisco 37.75 -122.4 1.5 0.642 Very High High 

San Mateo 37.55 -122.3 1.849 0.86 Very High High 

San Jose 37.35 -121.9 1.5 0.6 Very High High 

Santa Cruz 36.95 -122.05 1.517 0.6 Very High High 

Vallejo 38.1 -122.25 1.5 0.6 Very High High

Santa Rosa 38.45 -122.7 2.509 1.036 

Oregon and Washington 

Very High High 

Seattle 47.6 -122.3 1.365 0.528 High High

Tacoma 47.25 -122.45 1.297 0.506 High High

Everett 48 -122.2 1.269 0.482 High High

Portland 45.5 -122.65 0.982 0.421 

Idaho, Utah, and Nevada 

High High 

Salt Lake City 40.75 -111.9 1.539 0.557 Very High High 

Boise 43.6 -116.2 0.309 0.105 Moderate Moderate

Reno 39.55 -119.8 1.5 0.517 Very High High

Las Vegas 36.2 -115.15 0.495 0.166 Moderate Moderate 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-3 
 

 

 

 

 

 

 

Table 5-2 Seismicity Region for 35 Selected Cities in the United States (Continued) 

City Latitude Longitude 

MCER Response 

Values Third Edition 

S Seismicity Region S (g) S1 (g) 

Second Edition 

Seismicity Region 

Missouri, Tennessee, South Carolina, Illinois, New York, Massachusetts 

St. Louis 38.6 -90.2 0.438 0.168 Moderate Moderate 

Memphis 35.15 -90.05 1.011 0.351 High High

Charleston 32.8 -79.95 1.149 0.366 High High

Chicago 41.85 -87.65 0.135 0.062 Low Low

New York 40.75 -74 0.28 0.072 Moderate Moderate 

Boston 42.36 -71.06 0.217 0.069 Low Low

Table 5-3 Site Coefficients for Soil Types B, C, D, and E 

Spectral Acceleration on 

Site Class B 

Site Class 

B C D E 

Short-Period, SS (g) Short-Period Amplification Factor, FA 

< 0.25 1.0 1.2 1.6 2.5

0.50 1.0 1.2 1.4 1.7

0.75 1.0 1.1 1.2 1.2

1.0 1.0 1.0 1.1 0.9

> 1.25 1.0 1.0 1.0 0.9

1-second Period, S1 (g) 1.0-second Period Amplification Factor, FV 

< 0.1 1.0 1.7 2.4 3.5

0.2 1.0 1.6 2.0 3.2

0.3 1.0 1.5 1.8 2.8

0.4 1.0 1.4 1.6 2.4

> 0.5 1.0 1.3 1.5 2.4

To calculate Basic Scores, the median spectral acceleration values for each of 

the five seismicity regions from Table 5-1 (assumed to be based on Soil Type 

B) were multiplied by site coefficients for Soil Type CD. The site

coefficients for Soil Type CD were determined by averaging the site 

coefficients for Soil Type C and Soil Type D. The resulting values, FaSS and 

FVS1, for Soil Type CD were used to develop an initial demand spectrum and 

are shown in Table 5-4. In addition to calculating Basic Scores for the 

median in each of the five seismicity regions, calculations were also 

performed at the extreme end of the Very High seismicity region (VHmax). SS 

and S1 are taken as 3.8g and 1.5g, respectively, approximating the maximum 

seismicity in the United States. The scores that were calculated at the 

maximum seismicity are not presented on any Data Collection Form. 

5-4 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

 

 

 

 

 

 

 

Table 5-4 Median Spectral Acceleration Values in Each Seismicity Region Adjusted for Soil Type CD 

Site B 5% MCER 

Site Class C 

Factors 

Site Class D 

Factors 

Site Class CD 

Factors Basis of Basic Scores 

Region SS (g) S1 (g) Fa Fv Fa Fv Fa Fv FaSS (g) FvS1 (g) 

L 0.20 0.08 1.20 1.70 1.60 2.40 1.40 2.05 0.28 0.16 

M 0.40 0.16 1.20 1.64 1.48 2.16 1.34 1.90 0.54 0.30 

MH 0.80 0.32 1.08 1.48 1.16 1.76 1.12 1.62 0.90 0.52 

H 1.20 0.48 1.00 1.32 1.02 1.52 1.01 1.42 1.21 0.68 

VH 2.25 0.90 1.00 1.30 1.00 1.50 1.00 1.40 2.25 1.26 

VHmax 3.80 1.50 1.00 1.30 1.00 1.50 1.00 1.40 3.80 2.10 

They are, however, provided to users of the electronic scoring methodology 

to allow for interpolation of scores at locations where the seismicity is 

greater than the median of Very High. See Chapter 6 for additional 

discussion of interpolating scores with electronic scoring. 

The seismicity regions of FEMA P-154 can be compared with the Seismic 

Design Categories (SDC) in ASCE/SEI 7-10 and the “levels of seismicity” 

defined in ASCE/SEI 41-13. Similar to the seismicity regions of FEMA 

P-154, the ASCE/SEI 7-10 Seismic Design Categories and the ASCE/SEI 

41-13 levels of seismicity are also used to describe the severity of earthquake 

ground motions at a given site. The ASCE/SEI 7-10 Seismic Design 

Categories range from SDC A (low seismicity) to SDC E (high seismicity). 

Seismic design requirements are less stringent for SDC A buildings and more 

stringent for SDC E buildings. ASCE/SEI 41-13 levels of seismicity include 

Very Low, Low, Moderate, and High. 

Unlike the FEMA P-154 seismicity regions, Seismic Design Category and 

level of seismicity designations take into account site-specific soil 

conditions. It should not be assumed that all buildings in FEMA P-154 Low 

seismicity correspond to SDC A or B; some may be SDC C, or even SDC D 

in limited cases. For example, a building in FEMA P-154 Low seismicity 

region on Soil Type B may correspond to SDC A according to ASCE/SEI 

7-10 and the Very Low level of seismicity according to ASCE/SEI 41-13, 

while a building in FEMA P-154 Low seismicity on Soil Type E may 

correspond to SDC C and the Moderate level of seismicity. 

5.2.2 FEMA Building Types 

The FEMA P-154 procedure considers 17 FEMA Building Types. Basic 

Scores for 15 of these (W1, W2, S1, S2, S3, S4, S5, C1, C2, C3, PC1, PC2, 

RM1, RM2, and URM) were calculated considering the W1, W2, S1, S2, S3, 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-5 
 

S4, S5, C1, C2, C3, PC1, PC2, RM1, RM2, and URM Model Building Types 

(MBTs) included in OSHPD HAZUS. OSHPD HAZUS does not include 

W1A and has limited consideration of MH. Basic Scores for W1A were 

developed using engineering judgment to equal the average of the Basic 

Scores for W1 and W2. The OSHPD HAZUS procedure was used to 

develop the Basic Score for MH using values for capacity and fragility 

parameters as defined in the HAZUS-MH MR4 Technical Manual (HAZUS 

TM). 

5.2.3 Using OSHPD HAZUS Values 

OSHPD HAZUS provides values of all the parameters needed to calculate 

probability of collapse; they are also defined in Chapter 4. Guidance was 

needed to select the appropriate values from the OSHPD HAZUS tables to 

use for the Basic Score calculations for each FEMA Building Type in each 

seismicity region. 

OSHPD HAZUS values for elastic damping, βE, vary only by building type. 

Therefore, determining the appropriate value of βE to use to calculate the 

Basic Score for any given FEMA Building Type was straightforward. 

More often, values from the OSHPD HAZUS tables vary by building type 

and number of stories. This is true for default building height, HR, elastic 

period, Te, 1,  2, γ, and μ (the last of which is constant across building types 

and varies only by number of stories). Because Te,  1,  2, and μ vary 

depending on number of stories, the probability of collapse of a given 

building type varies depending on the number of stories. The Basic Score is 

meant to represent the probability of collapse of a low-rise building (i.e., one 

that is one-story, two-story, or three-story). Therefore, calculations were run 

for a one-story building, a two-story building, and a three-story building. 

The Basic Score was then determined considering the average of the 

probability of collapse of the three different buildings. In some cases, such 

as for MH, a three-story structure does not exist and is not considered. 

Values for λ,  3, and collapse factor (P[COL|STR5]) can vary depending on 

both number of stories and performance level. As described in Chapter 4, 

OSHPD HAZUS considers three performance levels: Baseline, Sub-Baseline 

(or SubBase), and Ultra-Sub-Baseline (or USB). Buildings without 

deficiencies were evaluated considering Baseline performance. When 

deficiencies are present, select parameters were adjusted for SubBase or USB 

performance. Values of λ, 3, and P[COL|STR5] vary depending on 

performance levels and are provided for Baseline, SubBase, or USB 

5-6 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
performance. For these parameters, number of stories were varied (as 

above), and Basic Scores were determined assuming Baseline values. 

The remaining parameters vary by age (in addition to varying by number of 

stories and performance level). Values are provided for pre-1961 buildings 

and post-1961 buildings. Basic Scores were typically calculated using pre1961 values. The following guidelines were used. See Chapter 4 for a 

description of the parameters. 

	 CS: Varies by building type, age, number of stories, and Uniform 

Building Code (UBC) Seismic Zone. The UBC Seismic Zone 

categorization is relevant in the OSHPD HAZUS methodology which 

was developed to address older California buildings that were subject to 

UBC. For FEMA P-154, mapping to the various seismicity regions was 

needed. For Low and Moderate seismicity regions, Basic Scores were 

calculated using Zone 3, pre-1961 values. For High and Very High 

seismicity, Basic Scores were calculated using Zone 4, pre-1961 values. 

For Moderately High seismicity, an average of the Zone 3 and Zone 4 

pre-1961 values was used. 

	 κ: Varies by scenario earthquake, age, and performance level. The 

scenario earthquake is defined by both magnitude of the earthquake and 

distance of the building from the fault. In a Low seismicity region, the 

scenario earthquake was considered to be greater than 50km from the 

site. For all other seismicity regions, the scenario earthquake was 

considered to be 10km to 25km from the site with a magnitude greater 

than 7.0. Baseline performance and pre-1961 values were considered. 

	 ΔC: Varies by building type, age, and performance level. In Low and 

Moderate seismicity regions, Basic Scores were calculated assuming pre1961 values. In High and Very High seismicity regions, Basic Scores 

were calculated assuming post-1961 values. In Moderately High 

seismicity regions, an average of the pre- and post-1961 values was used. 

All Basic Scores were calculated assuming Baseline performance. 

	 βC,D: Values of C,D are derived from OSHPD HAZUS values of C, 

which vary by number of stories, performance level, and age. Basic 

Scores were calculated using post-1961 SubBase values. (OSHPD 

HAZUS Table A6-1 indicates that if material data are not present, 

SubBase values of βC shall be used.) 

5.2.3.1 Exceptions 

After reviewing preliminary results from the scoring update study, some 

selected revisions were made in the input parameters as follows: 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-7 
	 Based on engineering judgment, typical W1 buildings are expected to

have strength comparable to the larger CS values provided in the HAZUS

TM. Use of the OSHPD HAZUS values would underestimate the

strength of these buildings. Hence, CS values for W1 buildings were

taken from the HAZUS TM.

	 For S3 buildings, the strength, Cs, values use the W1 values from

HAZUS TM because S3 buildings are light and are designed for wind

loading, and thus are expected to have strength comparable to W1

buildings. The lambda factor, λ, for S3 was taken as 2.0 to match the

value used for W1.

	 Basic Scores for MH were calculated using values from HAZUS TM

because values for MH are not provided in OSHPD HAZUS.

	 For S5 buildings, α1 values are not provided in OSHPD HAZUS. The

values were taken from the column for “W1, W2, S2, S3, S4, C2, C3,

PC2, RM1 and RM2” in OSHPD HAZUS Table A6-4.

	 Values of elastic damping are not provided in OSHPD HAZUS for

URMs. An elastic damping of 7% was used, which matches the elastic

damping that OSHPD HAZUS provides for URM infill buildings (C3

and S5).

	 For URM, S5, and C3 buildings, CS values were using Zone 3, pre-1961

values for all seismicity regions because these buildings pre-date seismic

codes, even when located in High seismicity regions (Zone 4).

	 Values of ΔC for C1 and PC2 buildings were taken from the row for “S5,

C3 and URM” in OSHPD HAZUS Table A6-9, rather than the row for

“S3, S4, PC1, PC2, RM1 and RM2” because the FEMA P-154 project

team believed C1 and PC2 buildings have lower story drift capacities and

thus the Basic Scores for C1 and PC2 buildings should be lower to

achieve the desired ranking order of the FEMA Building Types. For S5

buildings, values of ΔC were taken from the row for “S1, C1, S2 and C2”

in OSHPD HAZUS Table A6-9, rather than the row for “S5, C3, and

URM” because the FEMA P-154 project team noted that steel frame

infill buildings have a much better history of performance than concrete

frame infill buildings and URM bearing wall buildings. By increasing

the ΔC value, the S5 Basic Score was raised and achieved the desired

ranking order for the FEMA Building Types.

5.2.4 Values for Calculation of Basic Scores 

Tables have been developed to document the values of all variables used to 

develop the Third Edition Basic Scores. These tables are presented in 

5-8	 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

Appendix A. Some of the tables include adjusted values for use in 

calculating Pre-code and Post-Benchmark Score Modifiers and Plan and 

Vertical Irregularity Score Modifiers. A discussion of how these values were 

adjusted for calculating Score Modifiers is provided in Section 5.2. 

Table A1: Default building height, HR, and elastic period, Te; values 

vary by FEMA Building Type and number of stories. 

Table A2a-c: Seismic design coefficient, CS; values vary by FEMA 

Building Type, number of stories, and seismicity region. 

Table A2a provides values for calculating Basic Scores. 

Table A2b provides values for calculating Pre-Code Score 

Modifiers. Table A2c provides values for calculating PostBenchmark Score Modifiers. 

Table A3: γ and λ, factors; values vary by FEMA Building Type and 

number of stories. (Values are also provided for calculating 

Pre-Code Score Modifiers.) 

Table A4: Ductility factor, μ; values vary by number of stories. (Values 

are also provided for calculating Post-Benchmark Score 

Modifiers.) 

Table A5: Modal factors, α1 and α2; values vary by FEMA Building 

Type and number of stories. 

Table A6: Modal factor, α3; values vary by number of stories. (Values 

are also provided for calculating Vertical Irregularity Score 

Modifiers.) 

Table A7: Elastic damping, βE; values vary by FEMA Building Type. 

Table A8: Degradation factor, κ; values vary by seismicity region. 

(Values are also provided for calculating Pre-Code and PostBenchmark Score Modifiers.) 

Table A9: Story drift ratio, ΔC; values vary by FEMA Building Type 

and seismicity region. (Values are also provided for 

calculating Plan and Vertical Irregularity Score Modifiers 

and Pre-Code and Post-Benchmark Score Modifiers.) 

Table A10: Lognormal standard deviation values, βC,D; values vary by 

number of stories. (Values are also provided for calculating 

Pre-Code and Post-Benchmark Score Modifiers.) 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-9 
 

 

 

Table A11: Collapse factor (P[COL|STR5]); values vary by FEMA 

Building Type. (Values are also provided for calculating 

Plan and Vertical Irregularity Score Modifiers.) 

5.2.5 Adjustment of Betas 

As noted in Chapter 4, the deterministic beta values provided in the OSHPD 

HAZUS procedure were reduced when calculating Basic Scores for FEMA 

P-154 to avoid “double counting” the variability associated with demand. 

Probabilistic betas, C,P, were derived from deterministic betas, C,D, using 

Equation 4-18, repeated below: 

2 2 2 

2 2 

1 

                 

, , 

, , 

( ) ( ) C D CAP T C

C P CAP T C

e

D X

D

where CAP is set equal to 0.3 and T,C is set equal to 0.4, such that the square 

root of (2  2 ) is 0.5. CAP T C,

The value of X, which determines the magnitude of beta reduction, was set 

equal to 0.75. This value of X was selected to best align the Third Edition 

scores with observed damage from past earthquakes and the Second Edition 

scores. 

5.3 Sample Calculation of a Basic Score 

This section presents a sample calculation of the Basic Score for FEMA 

Building Type S2 in the High seismicity region. 

5.3.1 Step 1: Development of the Capacity Curve 

As described in Chapter 4, the capacity curve is defined by the yield capacity 

and ultimate capacity points, (Dy, Ay) and (Du, Au): 

Ay = CS γ/α1 = 0.109 × 2.70 / 0.80 = 0.368g 

Dy = 9.8 Ay Te

2 = 9.8 × 0.368 × 0.402 = 0.577 in 

Au = λ Ay = 1.67 × 0.368 = 0.613g 

Du = λ μ Dy = 1.67 × 6.0 × 0.577 = 5.77 in 

where values of CS, γ, α1, Te, λ, and μ are obtained from Appendix A Tables 

A-1 through A-5 for a one-story S2 building in the High seismicity region. 

The building capacity curve is assumed to be linear when the spectral 

displacement is less than the yield displacement and is assumed to remain 

5-10 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

 

plastic past the ultimate point. The transition from yield point to ultimate 

point of the capacity curve is assumed to be elliptical with the following form 

(from Equation 4-2): 

(D D A k u )

2 (  )

2 

2  2 1 

a b

where a, b, and k are constants with the following values from Equations 4-3 

through 4-5: 

D ( D D ) y 2 u y a  b  5 206 . Ay ( A k y  ) 

b A  u   k 0 266 . 

2
 

2 2 Ay A A   (D D ) u y y u

k   0 347 

Dy .
 Ay 2 (A A  )  (D D ) u y y u Dy

Figure 5-1 shows the building capacity curve of a one-story S2 in the High 

seismicity region. 

Figure 5-1 Building capacity curve for a one-story S2 in High seismicity. 

This step is repeated for two- and three-story buildings, resulting in two 

additional capacity curves. 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-11 
 

 

 

 

 

 

 

 

 

5.3.2	 Step 2: Determination of Input Spectral Acceleration 

Response Values 

Per Table 5-1, the median short-period spectral acceleration response, SS, and 

the median one-second period spectral acceleration response, S1, in a High 

seismicity region are 1.20g and 0.48g, respectively. 

5.3.3	 Step 3: Computation of Modified Input Spectral 

Acceleration Response Values, SMS and SM1 

Values of SS and S1 are adjusted for Soil Type CD using site coefficients 

given in Table 5-4, SMS = FaSS = 1.21g and SM1 = FvS1 = 0.68g. 

5.3.4	 Step 4: Development of a 5%-Damped Demand Response 

Spectrum 

The demand response spectrum, formatted with spectral displacement 

response as the x-axis and spectral acceleration response as the y-axis, is 

developed through the use of the following equations, as taken from HAZUS 

TM: 

At short periods (acceleration domain), 0 < T < TS: 

SA (T) = SMS/RA 

At long periods (velocity domain), TS < T < TVD: 

SA (T) = (SM1/T)/RV 

SD (T) = 9.8 × SA × T2 

where:

 SA(T) = spectral acceleration response in g at period, T; 

SD(T) = spectral displacement response in inches at period, T; 

Ts = the transition period between the constant acceleration and 

the constant velocity regions of the response spectrum 

= (SM1/SMS) × (RA/RV); 

RA = reduction factor in acceleration domain (Equation 4-6) 

= 2.12/(3.21 - 0.68ln(βeff)); 

RV = reduction factor in velocity domain (Equation 4-7) 

= 1.65/(2.31 - 0.41ln(βeff)); 

5-12 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

 

 

 

 

βeff = effective damping (Equation 4-8), which is the sum of the 

elastic damping, βE, and hysteretic damping, βH; 

βH = hysteretic damping, which is dependent on the amplitude of 

response, and is based on the area enclosed by the hysteresis 

loop, considering the potential degradation of energyabsorption capacity of the structure during cyclic earthquake 

loading 

= κ × (Area / 2πDA) 

where: 

Area = area enclosed by the hysteresis loop, as defined by the 

symmetric building capacity curve between peak positive and 

negative displacement, +D

 D = peak displacement response

 A = peak acceleration response at the peak displacement, D. 

κ = degradation factor from Table A-8. 

Thus, the 5%-damped spectrum for the High seismicity region is developed 

as follows and summarized in Table 5-5: 

SMS = 1.21g 

SM1 = 0.68g 

βeff = 5% 

2 12 . 2.12 RA = = = 1.00 

3 21  0 68 ln( eff . .  ) 3.21 0.68 ln(5) 

1 65 . 1.65 RV = = = 1.00 

2 31 . .  0 41 ln(  2.31 0.41ln(5) eff )

F Sv R 0 68 . 1 00 . TS = 1  A =  = 0.56 

F Sa s RV 1 21 . 1 00 .

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-13 
 

 

 

 

 

Table 5-5 5%-Damped Response Spectrum for Soil Type CD in High 

Seismicity Region 

T (seconds) SA (5%) (g) SD (5%) (g) 

0 1.21 0

0.56 1.21 3.72

1 0.68 6.66

2 0.34 13.3

4 0.17 26.7

8 0.085 53.3

The 5%-damped demand spectrum is shown in Figure 5-2. 

Figure 5-2 5%-Damped demand spectrum for high seismicity region. 

5.3.5 Step 5: Development of Damped Response Spectrum 

The demand spectrum developed in the previous step assumes 5% damping. 

As the spectral displacement of the building increases, the area under the 

hysteresis loop increases, thereby increasing βH and βeff. As βeff increases, the 

demand curve decreases (via reduction factors RA and RV). Hence, the 

demand spectrum is dependent on the peak response. An iterative method is 

therefore required to determine the peak response, i.e., the intersection of the 

demand and capacity curves. Several methods exist to perform this 

calculation. 

The peak response is calculated by developing what is termed a “βeff-damped 

locus demand spectrum.” This spectrum is developed by calculating the 

period and effective damping at each possible displacement, D, and then 

5-14 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

plotting spectral displacement versus spectral acceleration for each value of 

D as effective damping and period vary. 

The process uses the following steps: 

	 Start at a displacement value, D, of Du/500. At this very small 

displacement (D is approximately zero), the period, T, is equal to the 

elastic period, Te, and the effective damping, βeff, is equal to the elastic 

damping, βE. 

	 Increment the value of D by a fraction of Du, then for each value of D: 

o	 Compute the acceleration value, A, on the capacity curve 

o	 Compute the period, T, from D and A 

o	 Compute the area enclosed by the hysteresis loop up to the given 

(D, A) point 

o	 Compute effective damping, βeff, based on the area 

o	 Compute RA and RV based on βeff 

o	 Compute the demand curve point (SD, SA) reduced according to RA 

and RV. When SD is less than the elastic displacement De associated 

with Te, use De in lieu of the calculated SD. 

	 Overlay the capacity curve on the βeff-damped locus demand spectrum 

and take the intersection as the peak response. 

For the specific case of the one-story S2 building in the High seismicity 

region, calculations were performed to determine more than 1,500 points on 

the βeff-damped locus demand spectrum. Sample calculations are presented 

here for four of those points. 

Recall, from Section 5.3.1: 

Yield point: Dy = 0.58 in, Ay = 0.37g 

Capacity point: Du = 5.77 in, Au = 0.61g 

For elliptical portion of capacity curve, k = 0.347, b = 0.266, a = 5.206 

Demand: SMS = 1.21g, SM1 = 0.68g 

Point 1: At start of capacity curve 

D = Du /500 = 5.77/500 = 0.012 in 

A = (D/Dy) × Ay = (0.012/0.58) × 0.37 = 0.007g 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-15 
 

 

 

 

 

 

 

 

T = (D/9.8A)

1/2 = (0.012/9.8/0.007)1/2 = 0.40 sec 

Area = 0 (still on elastic portion of demand curve) 

βH = 0 

βeff = 5.0%
 

RA = 2.12/(3.21 - 0.68 ln(5)) = 1.0 

RV = 1.65/(2.31 - 0.41 ln(5)) = 1.0
 

SA = SDS/RA = 1.21/1.0 = 1.21g
 

SD = 9.8 SA T2 = 9.8 × 1.21 × 0.42 = 1.90 in
 

Repeat at small increments of D until, 

Point 21: At yield point on capacity curve 

D = Dy = 0.58 in 

A = Ay = 0.37 g 

T = (D/9.8A)

1/2 = (0.58/9.8/0.37)1/2 = 0.40 sec (note that the 

period has not changed because it is still on the elastic portion 

of the capacity curve) 

Area = 0 (still on elastic portion of capacity curve) 

βH = 0 

βeff = 5.0% 

RA = 2.12/(3.21 - 0.68 ln(5)) = 1.0 

RV = 1.65/(2.31 - 0.41 ln(5)) = 1.0 

SA = SMS/RA = 1.21/1.0 = 1.21g
 

SD = 9.8 SA T2 = 9.8 × 1.21 × 0.42 = 1.90 in
 

Points 1 through 21 all occur within the elastic portion of the capacity curve. 

In this range, the period, T, is always equal to the elastic period, Te, and the 

effective damping, βeff, is always equal to the elastic damping, βE. Hence, 

these points all occur at SA = SDS = 1.21g and SD = 9.8 SA Te 

2

. Point 1 is equal 

to Point 21. While the generic 5%-damped demand spectrum shown in 

Figure 5-2 starts at a spectral displacement of zero, the building-specific 

βeff-damped locus demand spectrum begins at a point on the elastic period 

line. 

5-16 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

 

Repeat at small increments of D until, 

Point 101: At halfway point to Du; on elliptical portion of capacity curve 

D = Du/2 = 5.77/2 = 2.88 in
 

A = b[1-((D - Du)/a)

2

]

1/2 + k
 

= 0.266[1- ((2.88 - 5.77)/5.206)2

]

1/2 + 0.347 = 0.57g 

T = (D/9.8A)

1/2 = (2.88/9.8/0.57)1/2 = 0.72 sec 

Area = 4.66 (solved by numerical integration; see Tokas and Lobo 

[2009] for further details) 

βH = (Area/2πDA) = 0.4 · 4.66 / (2π × 2.88 × 0.57) = 18.1% 

βeff = βE + βH = 5% + 18.1% = 23.1% 

RA = 2.12/(3.21 - 0.68 ln(23.1)) = 1.97 

RV = 1.65/(2.31 - 0.41 ln(23.1)) = 1.61 

SA = SM1/T/RV = 0.68/0.72/1.61 = 0.59g
 

SD = 9.8 SA T2 = 9.8 × 0.59 × 0.722 = 2.97 in 

Repeat at small increments of D until, 

Point 151: At ultimate point on capacity curve 

D = Du = 5.77 in 

A = Au = 0.61g 

T = (D/9.8A)

1/2 = (5.77/9.8/0.61)1/2 = 0.98 sec 

Area = 11.6 (solved by numerical integration; see Tokas and Lobo 

[2009] for further details) 

βH =  (Area/2πDA) = 0.4 · 11.6 / (2π × 5.77 × 0.61) = 20.9% 

βeff = βE + βH = 5% + 20.9% = 25.9% 

RA = 2.12/(3.21 - 0.68 ln(25.9)) = 2.13 

RV = 1.65/(2.31 - 0.41 ln(25.9)) = 1.69 

SA = SM1/T/RV = 0.68/0.98/1.69 = 0.41 g
 

SD = 9.8 × SA × T2 = 9.8 × 0.41 × 0.982 = 3.86 in
 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-17 
 

 

Continue to repeat for small increments of D. 

The resulting βeff-damped locus demand spectrum is plotted in Figure 5-3.
 

Figure 5-3 βeff-Damped locus demand spectrum for one-story S2 in High 

seismicity region. 

5.3.6 Step 6: Determination of Peak Response 

The peak response is taken as the intersection between the capacity curve and 

the demand spectrum.
 

From the overlay of the capacity curve and demand spectrum shown in 

Figure 5-3, the peak response is taken as 3.04 in. 

This is compared to the elastic displacement, De: 

At the elastic period, Te = 0.4 sec < Ts = 0.56 sec, 

SA = SMS/RA = 1.21 / 1.0 = 1.21g 

SD = 9.8 × SA × T2 = 9.8 × 1.21 × 0.42 = 1.89 in = De 

D/De = 3.04 / 1.89 = 1.61 > 1.0; use D = 3.04 in. 

This step is repeated for the two- and three-story cases to determine the peak 

response for each case. 

5-18 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

 

5.3.7 Step 7: Development of Fragility Curve 

The median value of the Complete (C) structural damage state is (Equation 

4-9): 

S ,   H ( /  ) d C C R 2 3 

Using the Appendix A tables, values are determined for ΔC (Table A-9), HR 

(Table A-1), α2 (Table A-5), and α3 (Table A-6). The median value of the 

Complete structural damage state for a one-story S2 building in the High 

seismicity region is: 

S ,   H ( /  ) = 0.06 × (14 × 12) × 0.75 / 1.00 = 7.6 in d C C R 2 3 

The lognormal standard deviation (beta) factor is (Equation 4-18): 

2 2 2 

2 2 

1 

                 

, , 

, , 

( ) ( ) C D CAP T C

C P CAP T C

e

D X

D

βC,D is determined using Appendix A Table A-10. βCAP is taken as 0.3 and 

βT,C is taken as 0.4. D and De were calculated above. X is taken as 0.75 for 

all FEMA P-154 calculations. 

2 2 2 0.95  (0.3  0.4 ) 2 2  ,   (0.3  0.4 )  0.89 CP  3.04  0.75 1    1.89 

The resulting fragility curve for a one-story S2 in High seismicity is defined 

by the following equation (Equation 4-10) and is shown in Figure 5-4: 

  
 P Complete Damage     1 ln 



D 



  β S  C P,  d C , 

This step is repeated for the two-story and three-story cases, resulting in two 

additional fragility curves. 

5.3.8 Step 8: Determination of Probability of Complete Damage 

The probability of complete damage for a one-story S2 building in the High 

seismicity region is: 

 1   D 

PCompleteDamage   ln    

  β S  C P,  d C, 

 1  3 04 .   ln  0 1526 .    0 89 .  7 6  . 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-19 
Figure 5-4	 Fragility curve for one-story S2 in the High seismicity region. 

Note that the probability of complete damage at the mean 

spectral displacement of 7.6 inches is 50%. 

This step is repeated for the two-story and three-story cases, resulting in two 

additional probabilities of complete damage. 

5.3.9	 Step 9: Determination of Probability of Collapse 

Per Table A-11, the collapse rate P(Collapse) for S2 is 0.08. 

The probability of collapse of the one-story S2 in High seismicity is therefore 

(Equation 4-17): 

P(Collapse) = 0.08 × 0.1526 = 0.0122. 

This step is repeated for the two-story and three-story cases, resulting in two 

additional probabilities of collapse. 

5.3.10	 Step 10: Relate Probability of Collapse to an Associated 

Score 

The associated score for the one-story S2 in High seismicity is 

S = –log10(P(Collapse)) = –log10(0.0122) = 1.91 

This step is repeated for the two-story and three-story cases, resulting in two 

additional scores. The associated scores for the two-story S2 and the threestory S2 are 2.05 and 2.13, respectively. 

5.3.11	 Step 11: Determine the Basic Score 

The Basic Score for an S2 building in the High seismicity region is taken as 

the average of the one-story, two-story, and three-story results. 

5-20 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

Basic Score = (1.91 + 2.05 + 2.13) / 3 = 2.03, approximated to 2.0. 

5.4 Review of Basic Scores 

Following the calculation of all the Basic Scores (for all FEMA Building 

Types and all seismicity regions), an extensive review of all of the scores 

was conducted, including a study of whether the relative ranking of the 

various FEMA Building Types was consistent with engineering judgment. 

As a result of this review, adjustments to the methodology, corrections to 

calculations, and modifications to some input parameters were made. The 

sample calculation provided above reflects the final methodology, 

calculations, and inputs used to develop the Third Edition Basic Scores. 

Using engineering judgment and consideration of past performance, the 

Basic Scores for MH in Very High and High seismicity regions were 

adjusted from 1.4 and 1.8 to 1.1 and 1.5, respectively. 

5.5 Development of Score Modifiers 

Score Modifiers were determined by a three-step process: 

1.	 Calculate the probability of collapse given the condition (e.g., plan 

irregularity, pre-code) under consideration: P[COL|Condition] 

2.	 Convert the probability of collapse to an equivalent score: 

SCondition = –log10(P[COL|Condition] 

3.	 Calculate the modifier by subtracting the Basic Score from the equivalent 

score: Modifier = SCondition – Basic Score 

Where the condition is beneficial to the building’s seismic performance, 

there will be a decrease in the probability of collapse, SCondition will be greater 

than the Basic Score, and the modifier will be positive. Where the condition 

is detrimental, there will be an increase in the probability of collapse, SCondition 

will be less than the Basic Score, and the modifier will be negative. 

5.5.1 Soil Type Modifiers 

Modifiers for Soil Type B and Soil Type E were determined by varying the 

spectral demand. No revisions to assumptions about building properties were 

required. 

The median spectral response acceleration parameters were adjusted for Soil 

Type B or Soil Type E by multiplying SS and S1 by the appropriate site 

coefficients, Fa and Fv, as defined in Table 5-3. For Soil Type B, Fa and Fv 

are equal to 1.0. For Soil Type E, they vary based on seismicity. The 

adjusted values are as shown in Table 5-6. 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-21 
 

Table 5-6 Median MCER Response Values in Each Seismicity Region 

Adjusted for Soil Type B and E 

Seismicity 

Region 

Basis of Soil Type B 

Modifiers Site Class E Factors 

Basis of Soil Type E 

Modifiers 

FaSS (g) FVS1 (g) Fa Fv FaSS (g) FvS1 (g) 

L 0.20 0.08 2.50 3.50 0.50 0.28 

M 0.40 0.16 2.02 3.32 0.81 0.53 

MH 0.80 0.32 1.10 2.72 0.88 0.87 

H 1.20 0.48 0.90 2.40 1.08 1.15 

VH 2.25 0.90 0.90 2.40 2.03 2.16 

VHmax 3.80 1.50 0.90 2.40 3.42 3.60 

Using these adjusted spectral demands, probability of collapse was calculated 

for each FEMA Building Type and each seismicity region. 

Soil Type B Score Modifiers were calculated considering low-rise buildings; 

that is, the average Score Modifier for one-story, two-story, and three-story 

was used. Using engineering judgment and consideration of past 

performance, Soil Type B Score Modifiers for MH in Very High and High 

seismicity were adjusted from 0.2 and 0.5 to 0.1 and 0.3, respectively. 

To capture the interaction that occurs between building height and soil type, 

separate modifiers are provided for low-rise buildings on Soil Type E (one to 

three stories) and taller buildings on Soil Type E (> 3 stories). 

5.5.2 Vertical and Plan Irregularities 

Vertical and Plan irregularity Score Modifiers were calculated for each 

FEMA Building Type at each seismicity level. The Vertical and Plan 

Irregularity Score Modifier calculations assume low-rise buildings and Soil 

Type CD. 

The modifiers for severe vertical irregularities were calculated considering a 

building with both weak story plus soft story deficiencies. Per OSHPD 

HAZUS Table A6-1, the simultaneous presence of these two deficiencies 

triggers the use of USB values of α3 and the collapse factor, as well as 

SubBase performance values of ΔC. 

The modifiers for moderate vertical irregularities were calculated considering 

a building with either a weak story or a soft story. Per OSHPD HAZUS 

Table A6-1, the presence of one of these deficiencies triggers the use of 

SubBase performance values of α3, the collapse factor, and ΔC. 

5-22 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

 

The modifiers for plan irregularity were calculated considering a torsional 

irregularity. Per OSHPD HAZUS Table A6-1, the presence of a torsional 

irregularity triggers the use of USB values of ΔC and SubBase performance 

values of the collapse factor. 

Finally, modifiers were calculated considering both plan and vertical 

irregularity. For this condition, USB values were used for α3, the collapse 

factor, and ΔC. 

Table 5-7 shows how the performance level considered for α3, ΔC, and 

collapse factor vary for each irregularity, and for combined plan plus vertical 

irregularity. 

Table 5-7 Performance Level Considered for Various Irregularities 

Parameter 

Severe 

Vertical 

Irregularity 

Moderate 

Vertical 

Irregularity 

Plan 

Irregularity 

Performance Level 

Plan + 

Vertical 

Irregularity 

Notes 

α3 USB SubBase Baseline USB See Table 

A-6 

ΔC SubBase SubBase USB USB See Table 

A-9 

P[COL|STR5] USB SubBase SubBase USB See Table 

A-11 

 Weak + 

Soft Story 

Weak or 

Soft Story 

Torsional 

Irregularity 

NA OSHPD 

HAZUS 

Deficiency 

Specifically, for all of the above irregularity cases, Score Modifiers were 

calculated assuming pre-1961 values of ΔC for Low and Moderate seismicity 

and post-1961 values for High and Very High seismicity. Average values of 

ΔC were used for the Moderately High seismicity region. 

All of the adjustments described above are reflected in the Appendix A 

tables. For example, Table A-6 provides unique values of α3 depending on 

the presence of Moderate or Severe Vertical Irregularity. 

5.5.3 Pre-Code 

Pre-Code Score Modifiers were calculated for each FEMA Building Type at 

each seismicity level. The modifier calculations assume low-rise buildings 

and Soil Type CD. 

Pre-Code Score Modifiers were calculated considering USB values of λ. In 

lieu of the post-1961 SubBase values of βC,D that were used for the Basic 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-23 
 

-

 

Score, pre-1961 SubBase values were used. For all seismicity regions, Zone 

3 pre-1961 values of CS were used. 

Resulting Pre-Code Score Modifiers are provided on the Moderate, 

Moderately High, High, and Very High Data Collection Forms. In the case of 

Low seismicity, the Basic Scores were adjusted to include these modifiers 

before being reported on the Low seismicity form as Basic Scores. No PreCode Score Modifiers are provided on the Low seismicity form as it is 

expected that pre-benchmark buildings in Low seismicity were not designed 

for seismic codes. 

5.5.4 Post-Benchmark 

Post-Benchmark Score Modifiers were calculated for each FEMA Building 

Type at each seismicity level. The modifier calculations assume low-rise 

buildings and Soil Type CD. 

Because OSHPD HAZUS was specifically developed to evaluate pre-1973 

buildings, it does not provide capacity and fragility parameter values 

corresponding to the improved performance of post-benchmark buildings. 

Within HAZUS, on the other hand, changes in code level trigger changes to 

capacity and fragility parameter values (CS, μ, Sd,C, κ, and βS,C) and 

subsequently the probability of collapse for five different code levels: PreCode, Low-Code, Moderate-Code, High-Code and Special High-Code. 

Values of Te, γ, λ, 1,  2,  3, be, and P[COL|STR5] do not vary by code level. 

The mapping shown in Table 5-8 was used to develop Post-Benchmark Score 

Modifiers in the second edition of FEMA 154. Post-Benchmark Score 

Modifiers in the Low seismicity region reflected the relative difference in 

performance between Pre-Code and Low-Code. Similarly, Post-Benchmark 

Score Modifiers in the High seismicity region reflected the relative 

difference in performance between Moderate-Code and High-Code. 

Table 5-8 Basis of Second Edition Post-Benchmark Score Modifiers 

Seismicity Region 

Code Considered for 

Developing Basic Scores 

Code Considered for 

Developing Post 

Benchmark Score 

Modifiers 

Low Pre-Code Low-Code

Moderate Low-Code Moderate-Code

High Moderate-Code High-Code

A slightly altered version of this mapping was used for Third Edition scoring, 

as shown in Table 5-9. 

5-24 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
-

 

 

Table 5-9 Basis of Third Edition Post-Benchmark Score Modifiers 

Seismicity Region 

Code Considered for 

Developing Basic Scores 

Code Considered for 

Developing Post 

Benchmark Score 

Modifiers 

Low Pre-Code Low-Code 

Moderate Low-Code Moderate-Code 

Moderately High Use average of Moderate and High, Very High values 

High, Very High Moderate-Code Special High-Code1 

1

Special High-Code was used rather than High-Code because using High-Code resulted in 

Post-Benchmark Score Modifiers that the project team deemed to be too small. Special 

High-Code values are taken from HAZUS TM Chapter 6. 

To generate Third Edition Post-Benchmark modifiers, OSHPD HAZUS 

values of key parameters (CS, μ, Sd,C, κ, and βc) were multiplied by ratios that 

approximate the increases provided by HAZUS when changing code levels. 

For example, HAZUS TM Table 5.4 shows that CS for an S3 building is 0.05 

for Pre-Code and Low-Code, 0.10 for Moderate-Code, 0.20 for High-Code, 

and 0.30 for Special High-Code (as back-calculated from values of Ay 

provided in HAZUS TM Table 6.3a). The Low-Code to Pre-Code ratio for 

CS in HAZUS TM is 1.0; thus no adjustment to the value of CS was made in 

the Low seismicity region. In the Moderate seismicity region, the value of 

CS is doubled when calculating the Post-Benchmark Score Modifier because 

the Low-Code to Moderate-Code ratio in HAZUS TM is 2.0. In High and 

Very High seismicity regions, the value of CS is tripled when calculating the 

Post-Benchmark Score Modifier because the Special High-Code to 

Moderate-Code ratio in HAZUS TM is 3.0. In the Moderately High 

seismicity region, an average ratio of 2.5 was used. Note that the ratios are 

slightly different for W1 and MH building types. This reflects the unique 

ratios of CS for these building types as defined in the HAZUS TM. The 

calculated ratios are reflected in the post-benchmark values of CS provided in 

Table A-2c. 

Similar comparisons were made for parameters μ, Sd,c, κ, and βC. For most 

building types, the Low seismicity ratio (Pre-Code to Low-Code) of μ is 1.0, 

the Moderate seismicity ratio (Low-Code to Moderate-Code) is 1.2, and the 

Very High and High seismicity ratio (Moderate-Code to Special High-Code) 

is 1.33. For Post-Benchmark calculations, the baseline values of μ were 

factored for simplicity by 1.33 for all seismicity regions and all building 

types to reflect the increased ductility of post-benchmark buildings. These 

ratios are reflected in Table A-4. 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-25 
 

 

For κ the Low seismicity ratio (Pre-Code to Low-Code) is 1.5, the Moderate 

seismicity ratio (Low-Code to Moderate-Code) varies between 1.0 and 1.5, 

and the High and Very High seismicity ratio (Moderate-Code to Special 

High-Code) varies between 1.33 and 2.0, depending on the building type. 

For Post-Benchmark calculations for all building types, the baseline values of 

κ were factored by 1.5 for Low, Moderate, and Moderately High seismicity 

regions. A factor of 1.67 was used for High and Very High seismicity 

regions. These ratios are reflected in Table A-8. 

For Sd,C, the ratios vary by building type. For each seismicity region, the 

ratios were averaged across building types and were applied as follows: 1.25 

for Low and Moderate seismicity, 1.5 for Moderately High seismicity, and 

1.67 for High and Very High seismicity. Table A-9 presents the values of 

ΔC, which is a component of Sd,C, thus the ratios are evident in this table. 

For βC,D the ratios again vary by building type. The average ratios resulted in 

similar post-benchmark values of βC as using post-1961 Baseline 

performance values (per OSHPD HAZUS Table A6-11). Hence the OSHPD 

HAZUS post-1961 values were used for post-benchmark calculations as is 

reflected in Table A10. Values of βC were reduced by engineering judgment 

for S1 buildings to account for the increased reliability expected from postNorthridge steel moment frames. 

Finally, βCAP was taken as 0.25 for post-benchmark calculations (versus 0.30 

for Basic Score calculations). This reflects the HAZUS variation of βCAP by 

code level as defined in the HAZUS TM Chapter 5. 

The Post-Benchmark Score Modifier results compare favorably with 

engineering judgment. If a post-benchmark building has no other 

deficiencies, then it passes the 2.0 cut-off score for all FEMA Building Types 

in all seismicity regions except for MH buildings in Very High seismicity. 

When a post-benchmark building also has a severe vertical irregularity, the 

Post-Benchmark Score Modifier is sufficient such that the Final Score is 

above the 2.0 cut-off score for all FEMA Building Types from Low to High 

Seismicity except for MH. There are some building types in the Very High 

seismicity region that fall below the cut-off score in this case. Given the 

current value of the seismic demand in this region and the lack of use of near 

field factors for determining seismic design forces until only recently, this 

result was judged to be reasonable. MH buildings have a comparatively 

lower Post-Benchmark Score Modifier as post-benchmark status is not 

necessarily a guarantee that foundation bracing is fully addressed. 

5-26 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
5.5.5 Minimum Score 

For each FEMA Building Type and each seismicity region, a Minimum 

Score was calculated considering that all deficiencies exist simultaneously: 

Values of CS, λ, α3, and the collapse factor were selected from the tables in 

Appendix A considering a Pre-Code building with plan plus vertical 

irregularity and the worst case soil type. 

By definition, the Minimum Score should always be greater than zero, since 

the probability of complete damage can never be greater than 100%, and the 

probability of collapse is only a fraction of the probability of complete 

damage. 

For example, consider an S2 building. If the S2 building has a severe vertical 

irregularity, the collapse factor is 0.30 (per Table A-11). At very large 

demands and for capacity and fragility parameters related to Pre-Code 

properties, the probability of complete damage may approach 100%. The 

probability of collapse would then be 100% × 0.3 = 30%. The associated 

minimum score is –log10(0.30) = 0.52. Hence, the Minimum Score for S2 in 

high seismic zones is approximately 0.5. In lower seismicity zones, the 

Minimum Score increases. 

Vertical and Plan Irregularity Score Modifiers are not used on the Data 

Collection Forms for MH buildings because MH buildings typically do not 

have these deficiencies in the superstructure. Minimum Scores for MH are 

set equal to the Basic Score plus the Soil Type E Score Modifier plus the PreCode Score Modifier. 

5.6 Summary of Third Edition Scores 

The resulting Basic Scores and Score Modifiers are shown on the Data 

Collection Forms of FEMA P-154 Appendix B and are shown below in 

Table 5-10. 

5.7 Development of Level 2 Score Modifiers 

Using engineering judgment, Level 2 Score Modifiers were anchored to the 

calculated Level 1 Score Modifiers. 

On the Level 2 form, the screener is asked detailed questions about building 

characteristics that affect seismic performance. To develop the Level 2 

Score Modifiers, each condition was associated with a comparable Level 1 

condition (e.g., vertical irregularity, plan irregularity, or post-benchmark) and 

assigned a severity based on engineering judgment. For conditions that 

greatly influence seismic performance, the full Level 1 Score Modifier was 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-27 
 

 

 

 

 

 

 

 

Table 5-10 Third Edition Basic Scores and Score Modifiers 

Low Seismicity Region 

FEMA Building 

Type W1 W1A W2 S1 S2 S3 S4 S5 C1 C2 C3 PC1 PC2 RM1 RM2 URM MH 

Basic Score 6.2 5.9 5.7 3.8 3.9 4.4 4.1 4.5 3.3 4.2 3.5 3.8 3.3 3.7 3.7 3.2 4.6 

Severe Vert. 

Irreg. -1.5 -1.5 -1.5 -1.4 -1.3 -1.6 -1.2 -1.3 -1.3 -1.2 -1.1 -1.3 -1.1 -1.1 -1.1 -1.2 NA 

Moderate Vert. 

Irreg. -1.0 -0.9 -0.9 -0.9 -0.8 -1.0 -0.7 -0.7 -0.7 -0.7 -0.6 -0.8 -0.6 -0.6 -0.6 -0.7 NA 

Plan Irreg. -1.6 -1.4 -1.3 -1.2 -1.1 -1.4 -1.0 -1.1 -1.0 -1.0 -0.9 -1.2 -0.9 -0.9 -0.9 -1.0 NA 

Pre-Code NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 

Post-Benchmark 2.2 2.4 2.5 2.0 1.6 1.4 2.1 NA 2.3 2.2 NA 1.9 2.6 2.3 2.3 NA 1.8 

Soil Type B 0.9 1.1 1.3 1.0 1.2 0.8 1.3 1.4 0.9 1.2 1.2 1.3 1.3 1.4 1.4 1.3 0.9 

Soil Type E -

Low-Rise -1.2 -1.7 -2.3 -1.2 -1.4 -1.0 -1.7 -2.0 -1.4 -2.0 -1.6 -1.7 -1.6 -1.7 -1.7 -1.5 -2.1 

Soil Type E -

Mid/High-Rise -1.7 -2.0 -2.2 -1.2 -1.4 NA -1.7 -1.9 -1.3 -1.9 -1.6 NA -1.6 -1.6 -1.7 -1.4 NA 

Min. Score 2.7 2.1 1.5 0.9 0.8 1.2 0.8 0.9 0.5 0.6 0.5 0.6 0.4 0.6 0.5 0.4 2.5 

Moderate Seismicity Region 

FEMA Building 

Type W1 W1A W2 S1 S2 S3 S4 S5 C1 C2 C3 PC1 PC2 RM1 RM2 URM MH 

Basic Score 5.1 4.5 3.8 2.7 2.6 3.5 2.5 2.7 2.1 2.5 2.0 2.1 1.9 2.1 2.1 1.7 2.9 

Severe Vert. 

Irreg. -1.4 -1.4 -1.4 -1.2 -1.2 -1.4 -1.1 -1.2 -1.1 -1.2 -1.0 -1.1 -1.0 -1.1 -1.1 -1.0 NA 

Moderate Vert. 

Irreg. -0.9 -0.9 -0.9 -0.8 -0.7 -0.9 -0.7 -0.7 -0.7 -0.7 -0.6 -0.7 -0.6 -0.7 -0.7 -0.6 NA 

Plan Irreg. -1.4 -1.3 -1.2 -1.0 -0.9 -1.2 -0.9 -0.9 -0.8 -1.0 -0.8 -0.9 -0.8 -0.8 -0.8 -0.7 NA 

Pre-Code -0.3 -0.5 -0.6 -0.3 -0.2 -0.2 -0.3 -0.3 -0.3 -0.4 -0.3 -0.2 -0.2 -0.2 -0.2 -0.1 -0.5 

Post-Benchmark 1.4 2.0 2.5 1.5 1.5 0.8 2.1 NA 2.0 2.3 NA 2.1 2.5 2.3 2.3 NA 1.2 

Soil Type B 0.7 1.2 1.8 1.1 1.4 0.6 1.5 1.6 1.1 1.5 1.3 1.6 1.3 1.4 1.4 1.3 1.6 

Soil Type E -

Low-Rise -1.2 -1.3 -1.4 -0.9 -0.9 -1.0 -0.9 -0.9 -0.7 -1.0 -0.7 -0.8 -0.7 -0.8 -0.8 -0.6 -0.9 

Soil Type E -

Mid/High-Rise -1.8 -1.6 -1.3 -0.9 -0.9 NA -0.9 -1.0 -0.8 -1.0 -0.8 NA -0.7 -0.7 -0.8 -0.6 NA 

Min. Score 1.6 1.2 0.9 0.6 0.6 0.8 0.6 0.6 0.3 0.3 0.3 0.3 0.2 0.3 0.3 0.2 1.5 

5-28 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

 

 

 

 

 

 

 

Table 5-10 Third Edition Basic Scores and Score Modifiers (Continued) 

Moderately High Seismicity Region 

FEMA Building 

Type W1 W1A W2 S1 S2 S3 S4 S5 C1 C2 C3 PC1 PC2 RM1 RM2 URM MH 

Basic Score 4.1 3.7 3.2 2.3 2.2 2.9 2.2 2.0 1.7 2.1 1.4 1.8 1.5 1.8 1.8 1.2 2.2 

Severe Vert. 

Irreg. -1.3 -1.3 -1.3 -1.1 -1.0 -1.2 -1.0 -0.9 -1.0 -1.1 -0.8 -1.0 -0.9 -1.0 -1.0 -0.8 NA 

Moderate Vert. 

Irreg. -0.8 -0.8 -0.8 -0.7 -0.6 -0.8 -0.6 -0.6 -0.6 -0.6 -0.5 -0.6 -0.6 -0.6 -0.6 -0.5 NA 

Plan Irreg. -1.3 -1.2 -1.1 -0.9 -0.8 -1.0 -0.8 -0.7 -0.7 -0.9 -0.6 -0.8 -0.7 -0.7 -0.7 -0.5 NA 

Pre-Code -0.8 -0.9 -0.9 -0.5 -0.5 -0.7 -0.6 -0.2 -0.4 -0.7 -0.1 -0.4 -0.3 -0.5 -0.5 -0.1 -0.3 

Post-Benchmark 1.5 1.9 2.3 1.4 1.4 1.0 1.9 NA 1.9 2.1 NA 2.1 2.4 2.1 2.1 NA 1.2 

Soil Type B 0.3 0.6 0.9 0.6 0.9 0.3 0.9 0.9 0.6 0.8 0.7 0.9 0.7 0.8 0.8 0.6 0.9 

Soil Type E -

Low-Rise 0.0 -0.1 -0.3 -0.4 -0.5 0.0 -0.4 -0.5 -0.2 -0.2 -0.4 -0.5 -0.3 -0.4 -0.4 -0.3 -0.5 

Soil Type E -

Mid/High-Rise -0.5 -0.8 -1.2 -0.7 -0.7 NA -0.7 -0.6 -0.6 -0.8 -0.4 NA -0.5 -0.6 -0.7 -0.3 NA 

Min. Score 1.6 1.2 0.8 0.5 0.5 0.9 0.5 0.5 0.3 0.3 0.3 0.3 0.2 0.3 0.3 0.2 1.4 

High Seismicity Region 

FEMA Building 

Type W1 W1A W2 S1 S2 S3 S4 S5 C1 C2 C3 PC1 PC2 RM1 RM2 URM MH 

Basic Score 3.6 3.2 2.9 2.1 2.0 2.6 2.0 1.7 1.5 2.0 1.2 1.6 1.4 1.7 1.7 1.0 1.5 

Severe Vert. 

Irreg. -1.2 -1.2 -1.2 -1.0 -1.0 -1.1 -1.0 -0.8 -0.9 -1.0 -0.7 -1.0 -0.9 -0.9 -0.9 -0.7 NA 

Moderate Vert. 

Irreg. -0.7 -0.7 -0.7 -0.6 -0.6 -0.7 -0.6 -0.5 -0.5 -0.6 -0.4 -0.6 -0.5 -0.5 -0.5 -0.4 NA 

Plan Irreg. -1.1 -1.0 -1.0 -0.8 -0.7 -0.9 -0.7 -0.6 -0.6 -0.8 -0.5 -0.7 -0.6 -0.7 -0.7 -0.4 NA 

Pre-Code -1.1 -1.0 -0.9 -0.6 -0.6 -0.8 -0.6 -0.2 -0.4 -0.7 -0.1 -0.5 -0.3 -0.5 -0.5 0.0 -0.1 

Post-Benchmark 1.6 1.9 2.2 1.4 1.4 1.1 1.9 NA 1.9 2.1 NA 2.0 2.4 2.1 2.1 NA 1.2 

Soil Type B 0.1 0.3 0.5 0.4 0.6 0.1 0.6 0.5 0.4 0.5 0.3 0.6 0.4 0.5 0.5 0.3 0.3 

Soil Type E -

Low-Rise 0.2 0.2 0.1 -0.2 -0.4 0.2 -0.1 -0.4 0.0 0.0 -0.2 -0.3 -0.1 -0.1 -0.1 -0.2 -0.4 

Soil Type E -

Mid/High-Rise -0.3 -0.6 -0.9 -0.6 -0.6 NA -0.6 -0.4 -0.5 -0.7 -0.3 NA -0.4 -0.5 -0.6 -0.2 NA 

Min. Score 1.1 0.9 0.7 0.5 0.5 0.6 0.5 0.5 0.3 0.3 0.3 0.2 0.2 0.3 0.3 0.2 1.0 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-29 
 

 

 

 

 

 

 

 

 

 

 

 

Table 5-10 Third Edition Basic Scores and Score Modifiers (continued) 

Very High Seismicity Region 

FEMA Building 

Type W1 W1A W2 S1 S2 S3 S4 S5 C1 C2 C3 PC1 PC2 RM1 RM2 URM MH 

Basic Score 2.1 1.9 1.8 1.5 1.4 1.6 1.4 1.2 1.0 1.2 0.9 1.1 1.0 1.1 1.1 0.9 1.1 

Severe Vert. 

Irreg. -0.9 -0.9 -0.9 -0.8 -0.7 -0.8 -0.7 -0.7 -0.7 -0.8 -0.6 -0.7 -0.7 -0.7 -0.7 -0.6 NA 

Moderate Vert. 

Irreg. -0.6 -0.5 -0.5 -0.4 -0.4 -0.5 -0.4 -0.3 -0.4 -0.4 -0.3 -0.4 -0.4 -0.4 -0.4 -0.3 NA 

Plan Irreg. -0.7 -0.7 -0.6 -0.5 -0.5 -0.6 -0.4 -0.4 -0.4 -0.5 -0.3 -0.5 -0.4 -0.4 -0.4 -0.3 NA 

Pre-Code -0.3 -0.3 -0.3 -0.3 -0.2 -0.3 -0.2 -0.1 -0.1 -0.2 0.0 -0.2 -0.1 -0.2 -0.2 0.0 0.0 

Post-Benchmark 1.9 1.9 2.0 1.0 1.1 1.1 1.5 NA 1.4 1.7 NA 1.5 1.7 1.6 1.6 NA 0.5 

Soil Type B 0.5 0.5 0.4 0.3 0.3 0.4 0.3 0.2 0.2 0.3 0.1 0.3 0.2 0.3 0.3 0.1 0.1 

Soil Type E -

Low-Rise 0.0 -0.2 -0.4 -0.3 -0.2 -0.2 -0.2 -0.1 -0.1 -0.2 0.0 -0.2 -0.1 -0.2 -0.2 0.0 -0.1 

Soil Type E -

Mid/High-Rise -0.4 -0.4 -0.4 -0.3 -0.3 NA -0.3 -0.1 -0.1 -0.3 -0.1 NA -0.1 -0.2 -0.2 0.0 NA 

Min. Score 0.7 0.7 0.7 0.5 0.5 0.5 0.5 0.5 0.3 0.3 0.3 0.2 0.2 0.3 0.3 0.2 1.0 

Very High MAX (these values are used for electronic scoring only) 

FEMA Building 

Type W1 W1A W2 S1 S2 S3 S4 S5 C1 C2 C3 PC1 PC2 RM1 RM2 URM MH 

Basic Score 1.6 1.5 1.5 1.2 1.2 1.3 1.2 1.1 0.9 1.0 0.9 0.9 0.8 0.9 0.9 0.8 1.0 

Severe Vert. 

Irreg. -0.8 -0.7 -0.7 -0.6 -0.6 -0.7 -0.6 -0.6 -0.6 -0.6 -0.6 -0.6 -0.6 -0.6 -0.6 -0.6 NA 

Moderate Vert. 

Irreg. -0.4 -0.4 -0.4 -0.3 -0.3 -0.4 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 NA 

Plan Irreg. -0.5 -0.5 -0.4 -0.3 -0.3 -0.4 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 NA 

Pre-Code -0.2 -0.1 -0.1 -0.1 -0.1 -0.1 -0.1 0.0 0.0 -0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 

Post-Benchmark 1.5 1.4 1.4 0.7 0.7 0.8 0.9 NA 0.9 1.0 NA 0.8 0.8 0.8 0.8 NA 0.2 

Soil Type B 0.3 0.3 0.2 0.2 0.1 0.2 0.1 0.1 0.1 0.1 0.0 0.1 0.0 0.1 0.1 0.0 0.0 

Soil Type E -

Low-Rise -0.2 -0.2 -0.1 -0.1 -0.1 -0.1 -0.1 0.0 0.0 -0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 

Soil Type E -

Mid/High-Rise -0.2 -0.2 -0.1 -0.1 -0.1 NA -0.1 0.0 0.0 -0.1 0.0 NA 0.0 0.0 0.0 0.0 NA 

Min. Score 0.7 0.7 0.7 0.5 0.5 0.5 0.5 0.5 0.3 0.3 0.3 0.2 0.2 0.3 0.3 0.2 1.0 

5-30 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
used on Level 2. For less significant conditions, only a portion of the Level 1 

Score Modifier was used. 

5.7.1 Vertical Irregularity Score Modifiers 

On the Level 2 form, the screener is asked detailed questions about different 

types of vertical irregularities. Each vertical irregularity was assigned a 

severity based on engineering judgment. For severe vertical irregularities, 

the full Level 1 Score Modifier, VL1, was used on Level 2. For less severe 

irregularities, only a portion of VL1 was used on Level 2. The basis of the 

Level 2 Vertical Irregularity Score Modifiers is shown in Table 5-11. Based 

on the rules in Table 5-11, Score Modifiers are defined as shown in Table 5­

12. 

Where multiple vertical irregularities occur, VL2 is the sum of the applicable 

modifiers, but is subject to a cap. The cap corresponds to the maximum 

value of VL1 for the given seismicity range. These caps are noted on the 

Level 2 forms. 

5.7.2 Plan Irregularity Score Modifiers 

On the Level 2 form, the screener is asked detailed questions about different 

types of plan irregularities. Each plan irregularity was assigned a severity 

based on engineering judgment. Note that for W1A, W1A with an open front 

is excluded because the penalty has already been applied in the vertical 

irregularity section and need not be double counted. In comparison, a 

torsional irregularity was considered to have a more severe effect on the 

building’s seismic performance than a large diaphragm opening. For severe 

plan irregularities, the full Level 1 Plan Irregularity Score Modifier, PL1, is 

applied. For less severe irregularities, only a percentage of PL1 is applied. 

The basis of the Level 2 Plan Irregularity Score Modifiers is shown in Table 

5-13. Based on the rules in Table 5-13, Score Modifiers are defined as 

shown in Table 5-14. 

Where multiple plan irregularities occur, PL2 is the sum of the applicable 

modifiers, but is subject to a cap. The cap corresponds to the maximum 

value of PL1 for the given seismicity range. These caps are noted on the 

Level 2 forms. 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-31 
 

 

Table 5-11 Basis of Level 2 Vertical Irregularity Score Modifiers 

Level 2 Statement 

Relative 

Severity of 

Condition Basis of Level 2 Score Modifier 

Sloping Site W1 building: There is at least a full story 

grade change from one side of the 

building to the other. 

High 100% of Level 1 Severe Vertical 

Irregularity Score Modifier for W1 

Non-W1 building: There is at least a full 

story grade change from one side of the 

building to the other. 

Low 33% of average of Level 1 Severe 

Vertical Irregularity Score 

Modifiers for all FEMA Building 

Types except W1, W1A, and W2 

Weak and/or 

Soft Story 

W1 building cripple wall: An unbraced 

cripple wall is visible in the crawl space. 

Moderate 50% of Level 1 Severe Vertical 

Irregularity Score Modifier for W1 

W1 house over garage: Underneath an 

occupied story, there is a garage opening 

without a steel moment frame, and there 

is less than 8' of wall on the same line (for 

multiple occupied floors above, use 16' of 

wall minimum). 

High 100% of Level 1 Severe Vertical 

Irregularity Score Modifier for W1 

W1A building open front: There are 

openings at the ground story (such as for 

parking) over at least 50% of the length of 

the building. 

High 100% of Level 1 Severe Vertical 

Irregularity Score Modifier for 

W1A 

Non-W1 building: Length of lateral 

system at any story is less than 50% of that 

at story above or height of any story is 

more than 2.0 times the height of the 

story above. 

High 100% of average of Level 1 

Severe Vertical Irregularity Score 

Modifiers for all FEMA Building 

Types except W1, W1A, and W2 

Non-W1 building: Length of lateral 

system at any story is between 50% and 

75% of that at story above or height of 

any story is between 1.3 and 2.0 times 

the height of the story above. 

Moderate 50% of average of Level 1 Severe 

Vertical Irregularity Score 

Modifiers for all FEMA Building 

Types except W1, W1A, and W2 

Setback Vertical elements of the lateral system at 

an upper story are outboard of those at 

the story below causing the diaphragm to 

cantilever at the offset. 

High 100% of average of Level 1 

Severe Vertical Irregularity Score 

Modifiers for all FEMA Building 

Types 

Vertical elements of the lateral system at 

upper stories are inboard of those at 

lower stories. 

Moderate 50% of average of Level 1 Severe 

Vertical Irregularity Score 

Modifiers for all FEMA Building 

Types 

There is an in-plane offset of the lateral 

elements that is greater than the length of 

the elements. 

Low 33% of average of Level 1 Severe 

Vertical Irregularity Score 

Modifiers for all FEMA Building 

Types 

5-32 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

Table 5-11 Basis of Level 2 Vertical Irregularity Score Modifiers (Continued) 

Level 2 Statement 

Relative 

Severity 

of 

Conditio 

n Basis of Level 2 Modifier 

Short 

Column/ 

Pier 

C1,C2,C3,PC1,PC2,RM1,RM2: At least 

20% of columns (or piers) along a column 

line in the lateral system have 

height/depth ratios less than 50% of the 

nominal height/depth ratio at that level. 

Moderat 

e 

50% of average of Level 1 

Severe Vertical Irregularity Score 

Modifiers for C1, C2, C3, PC1, 

PC2, RM1, and RM2 

C1,C2,C3,PC1,PC2,RM1,RM2: The 

column depth (or pier width) is less than 

one half of the depth of the spandrel, or 

there are infill walls or adjacent floors that 

shorten the column. 

Moderat 

e 

50% of average of Level 1 

Severe Vertical Irregularity Score 

Modifiers for C1, C2, C3, PC1, 

PC2, RM1, and RM2 

Split Level There is a split level at one of the floor 

levels or at the roof. 

Moderat 

e 

50% of average of Level 1 

Severe Vertical Irregularity Score 

Modifiers for all FEMA Building 

Types 

Other 

Irregularity 

There is another observable severe 

vertical irregularity that obviously affects 

the building’s seismic performance. 

High 100% of average of Level 1 

Severe Vertical Irregularity Score 

Modifiers for all FEMA Building 

Types 

There is another observable moderate Moderat 50% of average of Level 1 

vertical irregularity that may affect the e Severe Vertical Irregularity Score 

building’s seismic performance. Modifiers for all FEMA Building 

Types 

Table 5-12 Level 2 Vertical Irregularity Score Modifiers 

Level 2 Statement VH 

Level 2 Score Modifier 

(by Seismicity Region) 

H MH M L 

Sloping 

Site 

W1 building: There is at least a full story 

grade change from one side of the 

building to the other. 

-0.9 -1.2 -1.3 -1.4 -1.5 

Non-W1 building: There is at least a full 

story grade change from one side of the 

building to the other. 

-0.2 -0.3 -0.3 -0.4 -0.4 

Weak 

and/or Soft 

Story 

W1 building cripple wall: An unbraced 

cripple wall is visible in the crawl space. -0.5 -0.6 -0.6 -0.7 -0.7 

W1 house over garage: Underneath an 

occupied story, there is a garage opening 

without a steel moment frame, and there 

is less than 8’ of wall on the same line (for 

multiple occupied floors above, use 16’ of 

wall minimum). 

-0.9 -1.2 -1.3 -1.4 -1.5 

W1A building open front: There are 

openings at the ground story (such as for 

parking) over at least 50% of the length of 

the building. 

-0.9 -1.2 -1.3 -1.4 -1.5 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-33 
Table 5-12 Level 2 Vertical Irregularity Score Modifiers (continued) 

Level 2 Statement VH 

Level 2 Score Modifier 

(by Seismicity Region) 

H MH M L 

Weak 

and/or Soft 

Story 

(continued) 

Non-W1 building: Length of lateral system at 

any story is less than 50% of that at story above 

or height of any story is more than 2.0 times the 

height of the story above. 

-0.7 -0.9 -1.0 -1.1 -1.3 

Non-W1 building: Length of lateral system at 

any story is between 50% and 75% of that at 

story above or height of any story is between 

1.3 and 2.0 times the height of the story above. 

-0.4 -0.5 -0.5 -0.6 -0.6 

Setback Vertical elements of the lateral system at an 

upper story are outboard of those at the story 

below causing the diaphragm to cantilever at 

the offset. 

-0.7 -1.0 -1.0 -1.2 -1.3 

Vertical elements of the lateral system at upper 

stories are inboard of those at lower stories. -0.4 -0.5 -0.5 -0.6 -0.6 

There is an in-plane offset of the lateral 

elements that is greater than the length of the 

elements. 

-0.2 -0.3 -0.3 -0.4 -0.4 

Short 

Column/ 

Pier 

C1,C2,C3,PC1,PC2,RM1,RM2: At least 20% of 

columns (or piers) along a column line in the 

lateral system have height/depth ratios less than 

50% of the nominal height/depth ratio at that 

level. 

-0.4 -0.5 -0.5 -0.5 -0.6 

C1,C2,C3,PC1,PC2,RM1,RM2: The column 

depth (or pier width) is less than one half of the 

depth of the spandrel, or there are infill walls or 

adjacent floors that shorten the column. 

-0.4 -0.5 -0.5 -0.5 -0.6 

Split Level There is a split level at one of the floor levels or 

at the roof. -0.4 -0.5 -0.5 -0.6 -0.6 

Other 

Irregularity 

There is another observable severe vertical 

irregularity that obviously affects the building’s 

seismic performance. 

-0.7 -1.0 -1.0 -1.2 -1.3 

There is another observable moderate vertical 

irregularity that may affect the building’s seismic 

performance. 

-0.4 -0.5 -0.5 -0.6 -0.6 

5-34 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

Table 5-13 Basis of Level 2 Plan Irregularity Score Modifiers 

Level 2 Statement 

Relative 

Severity of 

Condition Basis of Level 2 Score Modifier 

Plan 

Irregularity 

Torsional irregularity: Lateral system does 

not appear relatively well distributed in 

plan in either or both directions. (Do not 

include the W1A open front irregularity 

listed above.) 

High 100% of average of Level 1 Plan 

Irregularity Score Modifiers for all 

FEMA Building Types 

Non-parallel system: There are one or more 

major vertical elements of the lateral 

system that are not orthogonal to each 

other. 

Moderate 50% of average of Level 1 Plan 

Irregularity Score Modifiers for all 

FEMA Building Types 

Reentrant corner: Both projections from an 

interior corner exceed 50% of the overall 

plan dimension in that direction. 

Moderate 50% of average of Level 1 Plan 

Irregularity Score Modifiers for all 

FEMA Building Types 

Diaphragm opening: There is an opening 

in the diaphragm with a width over 50% of 

the total diaphragm width at that level. 

Low 33% of average of Level 1 Plan 

Irregularity Score Modifiers for all 

FEMA Building Types 

C1, C2 building out-of-plane offset: The 

exterior beams do not align with the 

columns in plan. 

Moderate 50% of average of Level 1 Plan 

Irregularity Score Modifiers for C1 

and C2 

Other irregularity: There is another 

observable plan irregularity that obviously 

affects the building's seismic performance. 

High 100% of average of Level 1 Plan 

Irregularity Score Modifiers for all 

FEMA Building Types 

Table 5-14 Level 2 Plan Irregularity Score Modifiers 

Level 2 Statement VH 

Level 2 Score Modifier 

(by Seismicity Region) 

H MH M L 

Plan 

Irregularity 

Torsional irregularity: Lateral system does 

not appear relatively well distributed in 

plan in either or both directions. (Do not 

include the W1A open front irregularity 

listed above.) 

-0.5 -0.7 -0.8 -1.0 -1.1 

Non-parallel system: There are one or more 

major vertical elements of the lateral 

system that are not orthogonal to each 

other. 

-0.2 -0.4 -0.4 -0.5 -0.6 

Reentrant corner: Both projections from an 

interior corner exceed 50% of the overall 

plan dimension in that direction. 

-0.2 -0.4 -0.4 -0.5 -0.6 

Diaphragm opening: There is an opening 

in the diaphragm with a width over 50% of 

the total diaphragm width at that level. 

-0.2 -0.2 -0.3 -0.3 -0.4 

C1, C2 building out-of-plane offset: The 

exterior beams do not align with the 

columns in plan. 

-0.2 -0.4 -0.4 -0.4 -0.5 

Other irregularity: There is another 

observable plan irregularity that obviously 

affects the building's seismic performance. 

-0.5 -0.7 -0.8 -1.0 -1.1 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-35 
 

5.7.3 Other Level 2 Score Modifiers 

Other Level 2 modifiers, such as for pounding, retrofits, and building typespecific Level 2 statements, were determined using a similar combination of 

engineering judgment and Level 1 Score Modifier values. The basis of the 

other Level 2 Score Modifiers is shown in Table 5-15. Based on the rules in 

Table 5-15, Score Modifiers are defined as shown in Table 5-16. 

Table 5-15 Basis of Other Level 2 Modifiers 

Level 2 Statement 

Relative 

Severity of 

Condition Basis of Level 2 Score Modifier 

Redundancy The building has at least two bays of 

lateral elements on each side of the 

building in each direction. 

Low (benefit) Benefit of 33% of average of Level 1 Severe 

Vertical Irregularity Score Modifiers for all 

FEMA Building Types 

Pounding Building is separated from an adjacent 

structure by less than 1.5% of the height 

of the shorter of the building and 

adjacent structure and:The floors do 

not align vertically within 2 feet. 

High 100% of average of Level 1 Severe Vertical 

Irregularity Score Modifiers for all FEMA 

Building Types 

One building is 2 or more stories taller 

than the other. 

High 100% of average of Level 1 Severe Vertical 

Irregularity Score Modifiers for all FEMA 

Building Types 

The building is at the end of the block. Moderate 50% of average of Level 1 Severe Vertical 

Irregularity Score Modifiers for all FEMA 

Building Types 

S2 Building “K” bracing geometry is visible. High 100% of Level 1 Severe Vertical Irregularity 

Score Modifier for S2 

C1 Building Flat plate serves as the beam in the 

moment frame. 

Moderate 50% of Level 1 Severe Vertical Irregularity 

Score Modifier for C1 

PC1/RM1 

Bldg 

There are roof-to-wall ties that are 

visible or known from drawings that do 

not rely on cross-grain bending. (Do not 

combine with post-benchmark or 

retrofit modifier.) 

Low (benefit) 33% of average of Level 1 Severe Vertical 

Irregularity Score Modifiers for PC1 and RM1 

PC1/RM1 

Bldg 

The building has closely spaced interior 

walls (rather than an interior space with 

no walls such as in a warehouse or box 

store). 

Low (benefit) Benefit of 33% of average of Level 1 Severe 

Vertical Irregularity Score Modifiers for PC1 

and RM1 (similar to redundancy benefit) 

URM Gable walls are present. Moderate 50% of Level 1 Severe Vertical Irregularity 

Score Modifier for URM 

MH There is a supplemental seismic bracing 

system provided between the carriage 

and the ground. 

High (benefit) 100% of Level 1 Post-Benchmark Score 

Modifier for MH 

Retrofit Comprehensive seismic retrofit is visible 

or known from drawings. 

Moderately 

High (benefit) 

Benefit of 75% of average of Level 1 PostBenchmark Score Modifiers for all FEMA 

Building Types 

5-36 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
Table 5-16 Other Level 2 Score Modifiers 

Level 2 Statement VH 

Level 2 Score Modifier 

(by Seismicity Region) 

H MH M L 

Redundancy The building has at least two bays 

of lateral elements on each side of 

the building in each direction. 

0.2 0.3 0.3 0.4 0.4 

Pounding Building is separated from an 

adjacent structure by less than 

1.5% of the height of the shorter of 

the building and adjacent structure 

and: 

The floors do not align vertically 

within 2 feet. 

-0.7 -1.0 -1.0 -1.2 -1.3 

One building is 2 or more stories 

taller than the other. -0.7 -1.0 -1.0 -1.2 -1.3 

The building is at the end of the 

block. -0.4 -0.5 -0.5 -0.6 -0.6 

S2 Building “K” bracing geometry is visible. 

-0.7 -1.0 -1.0 -1.2 -1.3 

C1 Building Flat plate serves as the beam in the 

moment frame. -0.3 -0.4 -0.5 -0.5 -0.6 

PC1/RM1 

Bldg 

There are roof-to-wall ties that are 

visible or known from drawings 

that do not rely on cross-grain 

bending. (Do not combine with 

post-benchmark or retrofit 

modifier.) 

0.2 0.3 0.3 0.4 0.4 

PC1/RM1 

Bldg 

The building has closely spaced 

interior walls (rather than an 

interior space with no walls such as 

in a warehouse or box store). 

0.2 0.3 0.3 0.4 0.4 

URM Gable walls are present. 

-0.3 -0.4 -0.4 -0.5 -0.6 

MH There is a supplemental seismic 

bracing system provided between 

the carriage and the ground. 

0.5 1.2 1.2 1.2 1.8 

Retrofit Comprehensive seismic retrofit is 

visible or known from drawings. 1.2 1.4 1.4 1.4 1.6 

Where multiple pounding conditions occur, the sum of the applicable Score 

Modifiers is used, subject to a cap. The cap for pounding is the same as the 

vertical irregularity cap. These caps are noted on the Level 2 forms. 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-37 
 

Some comments on the rationale underlying the relative severity and basis 

for the modifiers in Table 5-16 are as follows. 

	 Redundancy: Design standards such as ASCE/SEI 7-10 penalize

structural systems that do not meet certain criteria related to redundancy.

In rapid visual screening, when redundancy is observed due to multiple

bays of lateral elements on each side of the building, a benefit is

considered warranted, but the benefit is considered relatively low

compared to other structural attributes in the absence of calculations.

	 Pounding: There are a variety of pounding configurations, as discussed

in Chapter 6. The configurations where floors in adjacent buildings do

not align or there is a significant difference in the number of stories

between the two structures are considered to be somewhat similar to a

severe vertical irregularity such as a soft story as they can clearly lead to

the potential for increasing the risk of collapse. Buildings at the end of

blocks have performed worse than those in the middle of blocks, but the

increase in the risk of actual collapse is considered to be moderate.

	 S2 building with “K” bracing: “K” bracing has been prohibited for use

in resisting seismic loading in design standards such as ANSI/AISC

341-10 (AISC, 2010), due to the risk of column buckling after

compression buckling of one of the braces intersecting the column.

While the failure would be local, FEMA P-154 rapid visual screening is

intended to address partial collapse as well as full collapse. Thus, Kbracing is considered similar to the full value of a severe vertical

irregularity such as a soft story.

	 C1 building with a flat plate moment frame: When a concrete moment

frame lacks a dropped beam running through the column, the risk of a

punching shear failure at the column is increased. This is viewed as a

moderate deficiency in the absence of calculations.

	 PC1/RM1 building with roof-to-wall ties that do not rely on cross-grain

bending: Many PC1 or RM1 buildings will not have ceilings, and the

connection at the roof-to-wall intersection may be visible during an

interior visit. Historic detailing often relied on a connection with a

ledger bolted to the wall and the wood roof nailed to the top of the

ledger. The vertical eccentricity between these connection points during

out-of-plane loading places the ledger in cross-grain bending, a

particularly weak and brittle mode of behavior in wood that is no longer

permitted. If modern tension ties and hardware are observed that do not

rely on cross-grain bending, then a benefit is given. In the absence of

calculations, it is considered a relatively low benefit.

5-38 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

	 PC1/RM1 building with closely spaced walls: Typical PC1 and RM1 

buildings are assumed to be similar to warehouses and have limited if 

any interior partitions that can improve redundancy and provide 

additional damping. However, when the buildings are used for offices or 

some other uses, they may have relatively closely spaced partitions that 

can provide some redundancy for carrying gravity loads and additional 

damping. In the absence of calculations, this is considered a relatively 

low benefit. 

	 URM with gable walls: Gable walls have a poor history of performance. 

In some cases, an out-of-plane wall failure might lead to compromising 

gravity support for the roof above. This is considered a relatively 

moderate hazard as there are many buildings that have had out-of-plane 

gable failures, but have not necessarily had collapses. 

	 MH with a supplemental seismic bracing system: 100% of the postbenchmark modifier is assigned as lack of bracing under the carriage is 

the critical seismic issue with MH buildings, and a supplemental bracing 

system thus addresses the primary issue of concern. 

	 Retrofit: As noted in FEMA P-154, to qualify for the retrofit modifier, 

the retrofit needs to be known to be comprehensive. Many retrofit 

standards use 75% of current code level of forces when designing 

seismic force-resisting elements. As such, 75% of the average PostBenchmark Score Modifier was considered to be a reasonable value for 

the Level 2 retrofit modifier. 

5.8 Comparison of Second Edition and Third Edition 

Scores 

The following two plots show comparisons of the Second Edition Basic 

Scores to the updated Third Edition Basic Scores. Figure 5-5 shows a 

comparison of the Basic Scores when the buildings are on Soil Type B, 

which was the default in the Second Edition. 

Figure 5-6 shows a comparison of the Basic Scores when the buildings are on 

Soil Type CD, which is the default for the Third Edition. Data points above 

the diagonal 1:1 line indicate the Second Edition scores are higher; data 

points below the line indicate the Third Edition scores are higher. In general, 

scores fall relatively close to the 1:1 line. 

For Soil Type B, the Third Edition scores are somewhat lower in the High 

seismicity region, and a bit higher for Moderate and Low seismicity regions. 

For Soil Type CD, the scores straddle the 1:1 line more closely in all regions. 

The shaded zones represent areas where in one edition, the score is below 2.0 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-39 
Figure 5-5 Comparison of Second Edition and Third Edition Basic Scores on Soil Type B. 

Figure 5-6 Comparison of Second Edition and Third Edition Basic Scores on Soil Type CD. 

5-40 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155
 
and in the other edition it is above 2.0. For example, in Soil Type B, a 

couple of building types are in the upper shaded zone, meaning they scored 

above 2.0 in the Second Edition, but would be just below 2.0 in the Third 

Edition. Thus, rescreening would be recommended. For Soil Type CD, 

there are building types also in the Moderate seismicity region that would fall 

in this category. There are no buildings in the lower shaded zone, meaning 

they scored below 2.0 in the Second Edition, but above in the Third Edition. 

Above comparisons are only for Basic Scores. 

When Score Modifiers are considered, the results are more diverse. Figure 

5-7 shows a comparison of the scores when the building is on Soil Type CD 

and has a Vertical Irregularity in the Second Edition (or a Severe Vertical 

Irregularity in the Third Edition). 

Figure 5-7 Comparison of Second Edition and Third Edition Scores with a 

Severe Vertical Irregularity on Soil Type CD. 

As shown in Figure 5-7, in the Moderate seismicity region, the Third Edition 

score is 3.7, 2.4, and 2.1, for W1, W2, and S3 buildings, respectively, on Soil 

Type CD with a vertical irregularity. All the other buildings have scores 

below 2.0. In the High seismicity region, the W1 building has a score of 2.4, 

with the rest below 2.0. The W1 building with severe vertical irregularity 

falls in the lower shaded zone meaning that it scored below 2.0 in the Second 

Edition. If the Severe Vertical Irregularity Score Modifier in the Third 

FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-41 
5-42 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 

Edition were increased, then the points in the lower shaded zone would move 

to the left and be below the 2.0 cut-off, consistent with the Second Edition 

scores. For Soil Type B, there would be many more that would fall in this 

category, as the calculations for the Third Edition yield somewhat lower 

irregularity modifiers than those in the Second Edition. 

Figure 5-8 shows a comparison of the Second Edition and Third Edition

scores for post-benchmark buildings on Soil Type CD. The Post-Benchmark 

Score Modifier increases the scores such that nearly all FEMA Building 

Types are above the cut-off score. The Third Edition scores are somewhat 

smaller than the Second Edition scores. 

Figure 5-8 Comparison of Second Edition and Third Edition Scores on Soil Type CD 

with Post-Benchmark Score Modifiers. 

Figure 5-9 shows a comparison of the Second Edition and Third Edition

scores for high-rise buildings on Soil Type E. Because the high-rise benefit 

of the Second Edition is not provided in the Third Edition, many of the 

buildings fall in the upper shaded zone. 

With the updated Third Edition Scores, the relative ranking of the different 

building types has changed. Consider, for example, the relative rankings for 

High seismicity. Table 5-17 shows a ranking of the building types of the 

Second Edition by Basic Score. Only three of the building types, C3, S5, and 

URM, had Basic Scores less than or equal to 2.0. 
FEMA P-155 5: Development of Third Edition Basic Scores and Modifiers 5-43 

Figure 5-9 Comparison of Second Edition and Third Edition Scores on Soil Type E with 

more than seven stories.

Table 5-17 Second Edition Basic Scores and Rankings in High Seismicity (Using Soil Type B) 

Second Edition Basic Score < 2.0 Basic Score > 2.0 

Building Type C3 URM S5 PC2 C1 PC1 S1 S4 C2 RM1 RM2 S2 S3 W2 W1

Basic Score 1.6 1.8 2.0 2.4 2.5 2.6 2.8 2.8 2.8 2.8 2.8 3.0 3.2 3.8 4.4 

Third Edition Basic Scores (adjusted for Soil Type B) result in the revised 

rankings shown in Table 5-18. Five of the building types, URM, C3, PC2, 

MH, and C1, have Basic Scores less than or equal to 2.0. 

Table 5-18 Third Edition Basic Scores and Rankings in High Seismicity (Using Soil Type B) 

Third Edition Basic Score < 2.0 Basic Score > 2.0 

Building Type URM C3 PC2 MH C1 S5 RM2 RM1 PC1 C2 S1 S2 S4 S3 W2 W1A W1 

Basic Score 

(Soil Type B) 1.3 1.5 1.8 1.8 1.9 2.2 2.2 2.2 2.2 2.5 2.5 2.6 2.6 2.7 3.4 3.6 3.7 

The updated Third Edition scores for the Low seismicity region are generally 

comparable to the Second Edition values. Table 5-19 shows a comparison of 

the Third Edition Basic Scores (adjusted to Soil Type B) with the Second 

Edition Basic Scores. Also shown are the minimum possible scores with the 

Third Edition (using Third Edition calculated “Minimum Scores”) and the 
 

 

 

 

Second Edition (summing the Basic Score with the worst possible 

combination of modifiers). 

Table 5-19 Second Edition and Third Edition Basic Scores (using Soil Type B) and Minimum Scores in Low Seismicity 

Second 

Edition W1 W1A W2 S1 S2 S3 S4 S5 C1 C2 C3 PC1 PC2 RM1 RM2 URM MH 

Basic Score 7.4 NA 6.0 4.6 4.8 4.6 4.8 5.0 4.4 4.8 4.4 4.4 4.6 4.8 4.6 4.6 NA 

Min. Score 0.8 NA 0.2 -0.2 0.0 1.8 -0.2 0.2 0.1 0.0 -0.4 1.8 0.3 0.6 0.7 0.9 NA 

Third Edition 

Basic Score 

(Soil Type B) 7.0 7.0 7.0 4.8 5.0 5.2 5.4 5.9 4.2 5.4 4.7 5.1 4.6 5.1 5.1 4.6 5.5 

Min. Score 2.7 2.1 1.5 0.9 0.8 1.2 0.8 0.9 0.5 0.6 0.5 0.6 0.4 0.6 0.5 0.4 2.5 

In the Low seismicity region, two building types will never fall below the 

cut-off score in the Third Edition (W1 and W1A), whereas in the Second 

Edition, it was possible for any building type to fall below the cut-off score. 

The MH building type was not included in the Second Edition procedure; 

therefore, the Second Edition and Third Edition scores cannot be compared. 

Review of damage data to MH buildings after the 1994 Northridge 

earthquake helped confirm that the Basic Score of less than 2.0 for MH in 

High seismicity was appropriate. Considering the damage data, the Basic 

Scores and Soil Type B Score Modifiers for MH in High and Very High 

were reduced so that non-post-benchmark MH buildings on Soil Type B in 

these high seismicity regions will receive Level 1 scores less than 2.0. 

5-44 5: Development of Third Edition Basic Scores and Modifiers FEMA P-155 
 

 

Chapter 6 

6.1 Introduction 

Consideration of pounding effects between adjacent buildings has been 

added to the rapid visual screening in the Third Edition. This chapter 

summarizes the research and literature that was considered, how it was 

synthesized into the criteria used in FEMA P-154, and the basis of the 

quantitative values in the criteria. 

6.2 Overview and Background Research 

Building pounding issues can arise when structures are built in close 

proximity. This becomes a particularly important factor when considering 

older existing buildings where setback requirements may not have been in 

force at the time of construction and developments maximized the use of the 

property. 

Damage from adjacency and pounding has been observed in many different 

earthquakes and regions. Buildings have been subject to moderate to severe 

damage and collapse, causing concern that this type of effect needs to be 

better identified as a consideration during rapid visual evaluations. 

A number of resources were used to help define and develop the criteria for 

pounding in the third edition of FEMA P-154. The literature available is 

relatively new and due to the complexity of the issue sometimes 

contradictory. There are, however, some basic parameters that can be used to 

identify potential problems caused by adjacent buildings pounding together, 

such as building separation, alignment of floor and roof levels, height 

differences, and end-of-row considerations. 

The following is a brief review of selected resources used to develop the 

pounding criteria in the Level 1 and Level 2 screening forms. 

6.2.1 Previous Editions of FEMA 154 and FEMA 155 

The first edition of FEMA 155 (FEMA, 1988b) noted that certain site 

aspects, such as pounding, corner buildings, and adjacencies, had been used 

as identifying criteria in the prior survey methods, and might be useful for 

rapid visual screening procedure. 

Pounding 

FEMA P-155 6: Pounding 6-1 
 

This set of attributes was reduced to a single consideration for pounding for 

FEMA 154 (FEMA, 1988a). The effect was used as a Score Modifier (-0.5) 

for S1, S2, S4, C1, and PC2 building types for the Low, Medium, and High 

NEHRP map areas. Presumably, this recognized the flexibility of certain 

building types as a key contributing factor in building pounding. The Score 

Modifier trigger occurred where there was inadequate seismic clearance 

between buildings and when adjacent building floor heights differed so that 

one building’s floors would impact the neighboring building’s columns at 

locations away from floor levels and thus weaken the columns. 

This Score Modifier was subsequently dropped in the second edition of 

FEMA 154 (FEMA, 2002a) to facilitate the screening effort by shortening 

the effort necessary to complete the form. 

6.2.2	 Building Pounding State of Art: Identifying Structures 

Vulnerable to Pounding Damage 

Building Pounding State of the Art: Identifying Structures Vulnerable to 

Pounding Damage (Cole et al., 2012) was created to help engineers using the 

New Zealand Initial Evaluation Procedure (IEP) in Assessment and 

Improvement of the Structural Performance of Buildings in Earthquakes 

including Corrigenda Nos. 1 and 2 (NZSEE, 2012) understand the 

background and basis of pounding. It describes fundamental concepts of 

building response under earthquake forces and categorizes pounding into two 

general cases: floor-to-floor and floor-to-column, as shown in Figure 6-1. 

= potential point of im pact 

floor-to-floor	G floor-to-colum n 

Figure 6-1 Pounding categorization (NZSEE, 2012). 

Building Pounding State of the Art contains a review of the available 

literature on pounding and presents six critical building configurations 

vulnerable to pounding that could affect the likelihood of structural collapse 

taken from Jeng and Tzeng (2000). The six configurations are shown in 

Figure 6-2 and are as follows. 

1. Floor-to-column 

2. Adjacent buildings with greatly differing mass 

3. Buildings with significantly different heights 

6-2 6: Pounding FEMA P-155 
4. External (end) buildings in a row 

5. Buildings subject to horizontal plan torsion 

6. Buildings made of brittle materials 

Figure 6-2 Critical pounding configurations (Jeng and Tzeng, 2000). 

Cole, et al. (2012) observed that buildings subject to pounding, but without 

the above characteristics are less likely, to experience detrimental effects. It 

was also noted that very little consensus exists at this time regarding generic 

building performance, and criteria such as separation distances and building 

mass are difficult to assess. 

For the third edition of FEMA P-154, three of the six building configurations 

above were deemed important to capture: floor-to-column, buildings with 

significantly different heights, and external (end) buildings in a row. 

6.2.3 Assessment and Improvement of the Structural 

Performance of Buildings in Earthquakes 

Assessment and Improvement of the Structural Performance of Buildings in 

Earthquakes was prepared at the request of the New Zealand Building 

Industry Authority to provide a consistent means for Territorial Authorities 

to use in assessing the earthquake performance of pre-1976 buildings. It 

establishes a method for identifying Earthquake Prone Buildings as described 

in The Building Act of 2004 as administered by the New Zealand 

Department of Building and Housing (now part of the Ministry of Business, 

Innovation, and Employment). 

The guidelines cover a full range of topics including prioritization, initial 

evaluation, detailed assessment, and improvement measures. The Initial 

Evaluation Procedure (IEP) contains within it specific measures to identify 

and quantify the effects of building pounding. The process is similar to the 

rapid visual screening in FEMA P-154 in that a basic score is established 

and then modified by known building and site features that reduce 

seismic capacities. 

FEMA P-155 6: Pounding 6-3 
 

There are two basic configurations considered – floor alignments and 

building height differences. These conditions, when met, generate factors D1 

and D2 that are further graded according to the severity of the deficiency. 

The lesser of D1 or D2 is then used in the computation of the final grade and 

structural performance score. 

The D1 and D2 factors assume the building has a frame structure and allows 

for reduction of these values if it is a stiff, or shear wall, structure. Figure 

6-3 shows a page from the Assessment and Improvement of the Structural 

Performance of Buildings in Earthquakes IEP screening form where 

pounding is addressed. 

6.2.4 Adjacency Issues in Soft-Story Wood Frame Buildings 

Adjacency Issues in Soft-Story Wood-Framed Buildings (Maison et al., 2011) 

was prepared for the Structural Engineers Association of Northern California 

to help characterize the damage observed to multi-story wood frame 

buildings during the 1989 Loma Prieta earthquake in San Francisco. 

The study used computer modeling to simulate actual earthquake response 

and analyzed twenty-two hypothetical pounding situations for both as-built 

and retrofitted buildings. The findings revealed that for a typical pounding 

situation there was a 14% increase in the collapse rate for corner buildings at 

design earthquake intensities. 

The study revealed that there were several factors that appeared to 

significantly increase the potential collapse rate including negligible building 

separations and multiple adjacent buildings having low effective damping 

and large mass. Conditions that appeared to have no discernible effect on 

collapse rate included effective periods common to adjacent buildings in a 

row and whether the adjacent buildings were modeled as rigid or flexible 

diaphragms. 

6.2.5 ASCE/SEI 41-13 Seismic Evaluation of Existing Buildings 

ASCE/SEI 41-13, Seismic Evaluation of Existing Buildings (ASCE, 2014), 

recognizes the influence of adjacent buildings in Commentary Section 

C3.2.5.1 on Building Pounding: 

“Building pounding can alter the basic response of the building to 

ground motion and impart additional inertial loads and energy to the 

building from the adjacent structure. Of particular concern is the 

potential for extreme local damage to structural elements at the 

zones of impact, particularly where the floor and roof levels of 

adjacent building do not align in height.” 

6-4 6: Pounding FEMA P-155 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Building Name Ref. 

Location By 

Direction Considered: a) Longitudinal b) Transverse 

( Choose worse case if clear at start. Complete IEP-1 and IEP-2 for each if in doubt) Date 

Step 3 - Assessment of Performance Achievement Ratio (PAR) 

(Refer 3.4.3 - Section B3.2) 

3.1 Plan Irregularity 

Effect on Structural Performance Severe Significant Insignificant 

Factor A 0.4 max 0.7 1 

Comment 

3.2 Vertical Irregularity 

Effect on Structural Performance Severe Significant Insignificant 

Factor B 0.4 max 0.7 1 

Comment 

3.3 Short Columns 

Effect on Structural Performance Severe Significant Insignificant 

Factor C 0.4 max 0.7 1 

Comment 

3.4 Pounding Potential 

(Estimate D1 and D2 and set D = the lower of the two, or =1.0 if no potential for pounding) 

a) Factor D1: - Pounding Effect 

Select appropriate value from Table 

Note: 

Values given assume the building has a frame structure. For stiff buildings ( eg with shear walls), the effect 

of pounding may be reduced by taking the co-efficient to the right of the value applicable to frame buildings. 

Factor D1 

Table for Selection of Factor D1 Severe Significant Insignificant 

Separation 0<Sep<.005H .005<Sep<.01H Sep>.01H 

Alignment of Floors within 20% of Storey Height 0.7 0.8 1 

Alignment of Floors not within 20% of Storey Height 0.4 0.7 0.8 

b) Factor D2: - Height Difference Effect 

Select appropriate value from Table 

Factor D2 

Table for Selection of Factor D2 Severe Significant Insignificant 

0<Sep<.005H .005<Sep<.01H Sep>.01H 

Height Difference > 4 Storeys 0.4 0.7 1 

Height Difference 2 to 4 Storeys 0.7 0.9 1 

Height Difference < 2 Storeys 1 1 1 

Factor D (Set D = lesser of D1 and D2 or.. 

set D = 1.0 if no prospect of pounding) 

3.5 Site Characteristics - (Stability, landslide threat, liquefaction etc) 

Effect on Structural Performance Severe Significant Insignificant 

Factor E 0.5 max 0.7 1 

3.6 Other Factors 

Factor F 

This factor is included to enable allowance for other characteristics of the building to be taken into account. 

These may be beneficial or detrimental to the structural performance. For < 4 storeys - Maximum value 2.0. No minimu 

otherwise - M aximum value 1.5. No minimum

 Record rationale for choice of Factor F 

....................................................................................................................................................................... 

....................................................................................................................................................................... 

3.7 Performance Achievement Ratio (PAR) 

(equals A x B x C x D x E x F ) 

Critical Structural Weakness Building 

Score 

Effect on Structural Performance 

(Choose a value - Do not interpolate) 

Figure 6-3 Initial Evaluation Procedure in NZSEE (2012). 

FEMA P-155 6: Pounding 6-5 
ASCE/SEI 41-13 requires that data “be collected to permit evaluation of the 

effects of building pounding, wherever a portion of an adjacent structure is 

located within 4% of the height above grade at the location of potential 

impact.” The evaluation procedure uses the square root sum of the squares 

(SRSS) criteria allowing the drift of the adjacent building to be estimated 

using available information. The total building separation need not exceed 

4% of the height of the shorter building. 

For Structural Performance Levels of Life Safety or lower, buildings adjacent 

to structures that have diaphragms located at the same elevation and differ in 

height by less than 50% of the height of the shorter building need not meet 

the minimum separation distance. 

Additionally, ASCE/SEI 41-13 establishes certain drift limits in the 

Structural Performance Levels for vertical building elements at Collapse 

Prevention. For frame elements, the drifts vary from 2% to 4%. For wall 

elements, the drift ranges from 0.6% to 3%. 

A final consideration of note is that if a potential collapse hazard exists due 

to pounding, then there is a responsibility to report such to the neighboring 

property owner. 

6.2.6	 The Performance of Unreinforced Masonry Buildings in the 

2010/2011 Canterbury Earthquake Swarm 

The Performance of Unreinforced Masonry Buildings in the 2010/2011 

Canterbury Earthquake Swarm (Ingham and Griffith, 2011) report was 

created to be a resource document to parties planning to make submissions to 

the Royal Commission of Inquiry into Building Failure Caused by the 

Canterbury Earthquakes. It provides information regarding the 

characteristics and performance of unreinforced masonry (URM) buildings in 

the Central Business District, as well as commentary on the adequacy of 

current practice and methodologies being considered for adoption in response 

to the events in Christchurch, New Zealand. 

Pounding is among the many performance issues observed. Specifically, 

shorter stiff buildings were shown to have caused damage to columns in 

taller adjacent buildings. 

Damage levels were investigated for stand-alone and row buildings 

indicating that row buildings performed better overall. Similarly, end-of-row 

structures showed greater damage levels than mid-row buildings. 

6-6 6: Pounding FEMA P-155 
It was estimated that 12% of the 370 buildings in the Central Business 

District had some degree of damage attributed to pounding with an adjacent 

neighbor. 

6.3 Pounding Criteria Determination 

Based on the literature review including damage observed in recent 

earthquakes, the issue of pounding was determined to be of sufficient 

importance so as to re-introduce it into the third edition of FEMA P-154. 

Four defining characteristics were chosen to be part of the Third Edition 

RVS procedure. 

	 Separation gap between adjacent buildings. For Level 2 screenings, the 

separation gap is defined as a percentage of building height. For 

simplicity, round, fixed dimensions were chosen for the Level 1 

separation gap criteria. The criteria are set as follows: 

o	 Very High seismicity: 1.50% for Level 2 (or 2 inches per story for 

Level 1) 

o	 High seismicity: 1.00% for Level 2 (or 1-1/2 inches per story for 

Level 1) 

o	 Moderately High seismicity: 0.50% for Level 2 (or 1 inch per story 

for Level 1) 

o	 Moderate seismicity: 0.25% for Level 2 (or 1/2 inches per story for 

Level 1) 

o	 Low seismicity: 0.10% for Level 2 (or 1/2 inches per story for Level 

1) 

Typical story heights are approximately 12 feet to 13 feet, but they can 

be higher or as low as 9 feet. For the 13 feet story height, the 1-1/2” and 

1/2” dimensions for Level 1 High and Moderate seismicity, respectively, 

are approximately 1.0% and 0.3%. For the 9 feet story height, the 1-1/2” 

and 1/2” dimensions are nearly 1.5% and 0.5%. For shallow story 

heights, the Level 1 separation requirements are larger (and more 

conservative) than the Level 2 criteria. These values are considerably 

smaller than the 4% separation recommendation in ASCE/SEI 41-13, but 

somewhat in line with ASCE/SEI 41-13 drift limits for vertical building 

elements at Collapse Prevention averaged for all building types for High 

seismicity. The rationale for the reduction in Moderately High, 

Moderate, and Low seismicity regions recognizes the lower expected 

damage thresholds. See Section 6.3.1 for a more detailed explanation. 

FEMA P-155 6: Pounding 6-7 
 Floor and roof alignments. This criterion establishes a simple 

discernible offset of two feet as the threshold trigger. This distance is 

easy to see from street level and approximates a point at which impact to 

building columns is likely to cause significant structural damage. 

 Building height differences. The building height difference criterion of 

two stories is a reasonable measure at which point damage would accrue 

from both the roof and floor causing potential collapse. 

 End buildings in row. End buildings have been identified as the 

recipients of significant damage from pounding. A threshold of three 

buildings minimum in a row recognizes the inertial effects of the interior 

building mass required to cause damage. 

The effects of pounding in the Level 1 screening are acknowledged in a 

check box in the building data collection area and as a recommendation to 

consider an additional detailed structural evaluation in the Other Hazards 

summary area at the bottom of the form. The intent is to flag this potentially 

dangerous building feature for special consideration. The RVS Authority is 

then charged with determining the correct course of action. 

In the Level 2 form, pounding is recognized as a Score Modifier. When the 

separation gap is less than the Level 2 requirements described above, three 

possible Score Modifiers may apply: (1) floors not aligning vertically within 

two feet; (2) building height differences greater than two stories; and (3) 

whether the building is at the end of the block. Column damage between 

floor levels and substantial building height differences represent significant 

issues for potential collapse and were assigned Score Modifiers equal to the 

Severe Vertical Irregularity Modifier for the FEMA Building Type. The 

end-of-row building Score Modifier is set at 50% of this value reflecting its 

potential importance. Although each criterion may be present at a particular 

building site, it was felt that a cap equal to the worst Severe Vertical 

Irregularity for all the FEMA Building Types would be most appropriate on 

the Level 2 form so as not to overstate its significance. 

6.3.1 Rationale for Pounding Separation Determination 

ASCE/SEI 41-13 recommends a separation distance between buildings of 

0.04H, where H is the height of the shorter building. However, that value 

may be excessively conservative. Alternatively, analytical methods can be 

used to derive a threshold separation distance at which pounding could 

reasonably affect collapse probability. A separation distance higher than the 

recommended value would trigger a Score Modifier. 

6-8 6: Pounding FEMA P-155 
 

 

 

 

 

 

 

6.3.2 Calculation of Pounding Separation 

The following is a simplified calculation of the maximum out-of-phase 

relative displacement of two adjacent buildings: Two adjacent buildings of 

equal height H are each subjected to a level of shaking specified in terms of 

5%-damped 0.2-second spectral acceleration response for short-period 

buildings (T ≤ 0.4 second or so) or 5%-damped, 1.0-second spectral 

acceleration response for longer-period buildings, where T is the smallamplitude fundamental period of vibration. Let SA02 and SA10 denote the 

site-class-adjusted, risk-targeted (MCER) ground motions. Selected median 

values of SA02 and SA10 for each of five seismicity levels Low, Moderate, 

Moderately High, High, and Very High, as shown in Table 6-1, are 

considered. The table also shows SA10/SA02, which would be the period (in 

seconds) at which the constant-acceleration and constant-velocity portions of 

the idealized design spectrum intersect, the period below which a building is 

treated herein as primarily being sensitive to SA02 and above which it is 

treated as primarily sensitive to SA10. 

Table 6-1 Spectral Acceleration Response Parameters SA02 and 

SA10 

Seismicity SA02 SA10 SA10/SA02 

Low 0.20g 0.08g 0.40 

Moderate 0.40g 0.16g 0.40 

Moderately high 0.80g 0.32g 0.40 

High 1.20g 0.48g 0.40 

Very high 2.25g 0.90g 0.40 

For simplicity, the equal-displacement rule is assumed. Thus, the maximum 

roof displacement of each building, Dmax, is calculated as follows. 

D max 2 

2 

02 

10 

SA 

SA 

T 







 

2 

2 

2 

02 

4 

10 

4 

SA T 

SA T 









T 

T 

0.4sec 

0.4sec 





(6-1) 

where 

T 0.80  0.035H for FEMA Building Type S1 

0.90 

0.55 

0.018

0.032

H 

H 





 for FEMA Building Type C1 

 for FEMA Building Types W1, W1A, W2 

(6-2) 

0.75  0.025H for others 

The formulae for steel frame and concrete frame in Equation 6-2 are taken 

from the regression-line (best-fit) curves that Goel and Chopra (1997) 

FEMA P-155 6: Pounding 6-9 
derived from strong motion observations of actual buildings. The wood 

frame period formula was derived by Camelo (2003) from strong motion and 

forced-vibration tests. The formula for other buildings is taken from the 

(lower-bound) formula offered by ASCE/SEI 7-10 (ASCE, 2010), increased 

by 25% to approximate a best-estimate relationship as opposed to the lowerbound formula favored by the code for conservativeness. Height, H, is 

measured in feet, T in seconds, the angular frequency is denoted by ω = 2π/T. 

The term Γ is the modal participation factor, which is the approximate ratio 

of roof displacement to first mode spectral displacement response. This is 

the term labeled Γ1 in Chopra and Goel (1999). Freeman (2004) calls it PF, 

and offers several examples that each happen to have Γ ≈ 1.3. Multi-hazard 

Loss Estimation Methodology, Earthquake Model, HAZUS-MH MR4 

Technical Manual (FEMA, 2009a), referred to as HAZUS TM, uses a term 

the authors call the modal factor for height, denoted by α2, which is the 

inverse of Γ. It generally takes on values of 0.75 for low-rise and mid-rise 

construction and 0.6 for high-rise, equating with Γ = 1.33 for low-rise and 

mid-rise construction and 1.67 for high-rise. Because so much else of FEMA 

P-154 is calibrated to HAZUS TM, the present calculations use Γ = 1.3 for 

low-rise and mid-rise construction and 1.67 for high-rise. 

Damped elastic spectral displacement response Sd(T, 5%) among low-rise 

buildings in a given location will probably be greatest among the tallest of 

the low-rise buildings (because it will tend to be the low-rise building with 

the longest period). The minimum separation distance for low-rise buildings 

to avoid pounding would be governed by 3-story buildings. Similarly, 

7-story buildings likely govern pounding in mid-rise buildings. For high-rise 

buildings, the height chosen does not have an effect, thus 20 stories are 

considered here. Taking the typical story to be 13 feet tall, H is taken as 

H = 39 ft (3 stories, controlling low-rise) 

H = 91 ft (7 stories, controlling mid-rise) 

H = 260 ft (20 stories, representing high-rise) 

Both buildings are assumed to be of the same height and period, but during 

SA02 or SA10 shaking, the two buildings are π radians out-of-phase at the 

point in time when they both experience maximum displacement (i.e., both 

experience their spectral displacement response), and at the time of 

maximum displacement they are moving toward each other rather than away. 

The buildings can touch if the separation distance is less than or equal to 

2Dmax. 

6-10 6: Pounding FEMA P-155 
 

 

 

 

 

ASCE/SEI 41-13 takes the square root of the sum of the squares to calculate 

the required gap from the Dmax values of each building, but the rationale is 

unclear. The two buildings need not be moving toward each other at all at 

the moment of maximum displacement, nor must they even have the same 

moment of maximum displacement. Using an SRSS combination of the Dmax 

values would make sense if they represented the simultaneous maximum 

displacement of an object in two orthogonal directions and the important 

issue was the maximum absolute displacement regardless of direction, but 

that is not what is occurring here. Using an SRSS combination obscures the 

assumptions of timing and phase difference rather than reflecting a physical 

reality. 

In the worst case, the two buildings always reach their Dmax displacement at 

the same time in every earthquake, and always in a direction toward each 

other. Furthermore, in the worst case, for the two buildings merely to touch 

at that moment aggravates collapse. In the best case, the two buildings must 

have no initial gap between them for pounding to aggravate damage. Reality 

almost certainly lies between these two extremes: the separation must be less 

than some fraction, f where 0 < f < 1, of 2Dmax for pounding to occur and be 

severe enough to aggravate damage. To estimate f properly, a series of twoor three-dimensional nonlinear dynamic analyses could be performed of 

various combinations of buildings to find the maximum value of f where 

pounding occurs and aggravates collapse. Based solely on the authors’ 

judgment, f is probably less than 0.5, so 0.5 is probably conservative, 

meaning it will exaggerate the potential for pounding to aggravate collapse. 

Thus, it is assumed here that the collapse probability only significantly 

increases if D ≤ Dmax. 

Consider, for example, two seven-story C1 reinforced concrete moment 

frame buildings in High seismicity. Assume the typical story height is 13ft. 

Applying Equations 6-2 and 6-1, the gap width that can cause pounding is 

estimated as 

H = 13 ft/story × 7 stories = 91 ft 

T = 0.018 × (91ft)0.90 = 1.05 sec 

Dmax = 1.3 × 1.05 sec × 0.48g /(4π

2

) = 63.7 in = 5.3 ft 

Dmax/H = 5.3 ft/ 91 ft = 0.0058 = 0.6% 

The conclusion that pounding is a concern if D < Dmax may be conservative, 

since there remain four important sources of conservatism in the calculation 

of Dmax: 

FEMA P-155 6: Pounding 6-11 
1.	 Both buildings are maximum height among the height class, 

2.	 Both buildings experience maximum displacement at exactly the same 

time, 

3.	 They are exactly π radians out-of-phase and moving toward each other at 

the moment of maximum displacement, and 

4.	 They are located where SA02 or SA10 are the maximum value for their 

seismicity level. 

Equation 6-1 leads to the minimum separation distances as percentage of H 

in the following tables. 

Table 6-2 Minimum Separation Distance for FEMA Building Types W1, 

W1A, W2 as a Percentage of H 

Stories Low Mod Moderately 

High 

High Very High 

1 0.0% 0.1% 0.1% 0.2% 0.3% 

3 0.0% 0.1% 0.1% 0.2% 0.4% 

6 0.0% 0.1% 0.1% 0.2% 0.4% 

Table 6-3 Minimum Separation Distance for FEMA Building Type C1 as a 

Percentage of H 

Stories Low Mod Moderately 

High 

High Very High 

3 0.1% 0.2% 0.4% 0.6% 1.2% 

7 0.1% 0.2% 0.4% 0.6% 1.1% 

20 0.1% 0.2% 0.4% 0.7% 1.3% 

Table 6-4 Minimum Separation Distance for FEMA Building Type S1 as a 

Percentage of H 

Stories Low Mod Moderately 

High 

High Very High 

3 0.1% 0.3% 0.6% 0.9% 1.6% 

7 0.2% 0.3% 0.6% 0.9% 1.7% 

20 0.1% 0.3% 0.5% 0.8% 1.4% 

The results in Tables 6-2 through 6-5 indicate that to one significant figure, 

the minimum separation distance is fairly independent of height. Thus, for 

simplicity, a single threshold separation distance can be used, based on the 

largest values shown above (those of steel moment frame buildings, as 

shown in Table 6-4), rounded to a nominal value, as shown in Table 6-6. 

6-12	 6: Pounding FEMA P-155 
 

 

Table 6-5 Minimum Separation Distance for All Other FEMA Building 

Types as a Percentage of H 

Stories Low Mod Moderately 

High 

High Very High 

3 0.1% 0.2% 0.3% 0.5% 0.9% 

7 0.1% 0.1% 0.3% 0.4% 0.8% 

20 0.1% 0.1% 0.3% 0.4% 0.8% 

These are conservative for less-flexible building types, and particularly 

conservative for wood frame buildings. 

Table 6-6 Recommended Minimum Separation 

Distance Values as a Percentage of H 

Seismicity All types 

Low 0.10% 

Moderate 0.25% 

Moderately high 0.50% 

High 1.00% 

Very high 1.50% 

6.3.3 Validation 

The minimum separation distance value of 1% of building height, H, for 

buildings in the High seismicity region is consistent with the threshold 

recommended by the NZSEE Study (2012), though far less conservative than 

ASCE/SEI 41-13. One additional case study is provided for validation. 

In the 2011 Tohoku earthquake, Okazaki et al. (2013) observed that two 11­

story steel reinforced concrete (SRC) buildings separated by a 10-cm gap 

(approximately 0.4% separation) “pounded against each other. Despite the 

cosmetic damage, the SRC buildings seemed to have suffered minimal 

structural damage. At the time of investigation, many residents had returned 

to occupy the building.” The buildings are located near Sendai, where Sa(1.0 

second, 5%) ≈ 0.7g at the nearby station DCRC No 23 was very close to the 

high-seismicity value for SM1 ≈ 0.8g. These buildings had much less than the 

recommended 1.0% separation threshold, experienced motion very close to 

the high-seismicity SM1, and survived with only cosmetic damage. 

More detailed research would be needed to make more definitive statements 

about historical pounding damage among adjacent buildings subjected to 

near-design-level shaking. 

FEMA P-155 6: Pounding 6-13 

Chapter 7 

Building Additions 

7.1 Introduction 

Existing buildings are often expanded at a later time to increase the usable 

area. The expansions can be either vertical (adding stories over the entire 

floor area or over part of the floor area of the building) or horizontal (adding 

one or more stories adjacent to the one or more sides of the original 

building). This chapter summarizes the rationale behind the categorization of 

horizontal and vertical additions and the associated recommendations. 

7.2 Identifying Building Additions 

Penthouses are generally not considered to be additions since they are 

typically constructed as part of the original building and are thus likely to be 

integrally connected. If a penthouse has been added to an existing building 

and is not normally occupied, e.g., used as a mechanical penthouse, it can be 

excluded from consideration as an addition. Its framing system will not 

typically be an extension of the building framing. An occupied rooftop 

structure that has been added should be treated as a vertical addition. 

Residential structures in urban areas are commonly constructed as multiple, 

contiguous residences, often referred to as row houses. These row houses 

would not be considered as additions since there are usually common party 

walls that separate the units. Party walls are identified by extension of the 

walls above the roof that provides a fire separation. See Figure 7-1. 

Figure 7-1 Row houses are not considered additions. 

FEMA P-154 provides guidance for assessing the effects of the addition on 

FEMA P-155 7: Building Additions 7-1 
the overall response of the structure in cases where the addition and original 

building are well-defined. Where complex conditions regarding building 

additions are identified, e.g., where there is more than one interface plane 

between the addition and the original building or if it cannot be determined 

whether there is an addition or a separate structure, a Detailed Structural 

Evaluation should be recommended. 

The interaction of an addition with the original building could affect the 

seismic response of either one or both structures. The critical characteristics 

of the addition that affect the seismic response of the building and addition 

are: 

	 Details of the structural connection of the horizontal addition to the 

original building, 

	 Types of seismic force-resisting systems of the addition and the original 

building, and 

	 The size of the addition. 

These characteristics are discussed in the sections that follow. 

7.2.1 Structural Connections 

There are three types of structural connections between a horizontal addition 

and an original building. 

First, the addition can be constructed to be structurally isolated from the 

original building with a seismic joint, such that the original building and the 

addition respond to an earthquake independently. In this case, the two 

structures should be treated as separate structures. However, the potential for 

pounding should be checked using the RVS pounding criteria. 

Second, the building addition can be constructed as a separate and 

independent structure, but without a seismic joint to allow the original 

building and addition to respond separately to seismic motion. This will 

likely result in pounding between the building and the addition, as the two 

structures separate and then impact one another in subsequent cycles of 

shaking. The severity of potential pounding depends partly on the relative 

size of the structures and the degree of difference in structural systems 

between the structures. Additional guidance for RVS screening where the 

original building and addition are separate structures depends on factors 

described in Sections 7.4 and 7.5. 

Third, the addition can be constructed to rely partially on the original 

building for gravity or lateral support. In many instances, it may not be 

7-2 7: Building Additions FEMA P-155 
possible to accurately assess by visual observation whether an addition is 

structurally connected to the original building. The guidance provided in 

FEMA P-154 assumes that when horizontal additions are significantly 

smaller than the original building and constructed with a different building 

type, it is likely that the addition relies on at least a partial structural 

connection between the addition and the original building. Where a 

structural connection of the addition and the original building occurs, 

differential movement between the original building and the addition during 

an earthquake can result in damage to the gravity or lateral connection, which 

may result in damage or partial collapse. Although the seismic interaction of 

the addition and the original building may have been considered in the design 

of the addition, for RVS screening, it should be assumed that this interaction 

was not considered. 

7.2.2 Structural Framing 

Differences in the seismic force-resisting systems of the original building and 

the addition can significantly affect the overall response of the structure. 

Differences such as configuration and construction materials can result in 

differing stiffness of structures, which may lead to vertical or plan 

irregularities. 

Vertical additions may cause vertical irregularities due to differences in 

dynamic response of the addition and the original building. For multi-story 

vertical additions where the addition is constructed with the same seismic 

force-resisting system as the original building, the overall response of the 

structure will likely be similar to that of a single structure of the same height. 

Multi-story vertical additions with a seismic force-resisting system either 

stiffer or more flexible than the original building will cause potential 

irregularities in structural response. 

If a seismic joint is not specifically provided between the original building 

and a horizontal addition, there is a potential for interaction depending on 

differences in stiffness. If a horizontal addition is constructed with the same 

seismic force-resisting system as the original building and there is no seismic 

joint, the original building and the addition could be considered as either one 

structure or two structures depending on the relative size of the addition to 

the original structure. 

7.2.3 Size of Addition 

If the size of the addition, in terms of either the number of stories or the 

horizontal dimensions, is very small with respect to the original building, 

particularly if the addition is of lightweight construction, the addition may 

FEMA P-155 7: Building Additions 7-3 
 

have little, if any, influence on the overall behavior. For all other cases, the 

presence of the addition is likely to result in either a vertical or plan 

irregularity. 

Vertical additions, which are occupied and with a plan area smaller than the 

plan area of the floor of the original building below, should be considered to 

cause a soft or weak story irregularity. The number of stories of the vertical 

addition may also influence its effect on the response of the building. A 

single story addition is less likely to affect the overall response of the 

building than a multi-story addition. 

The effect of horizontal additions on the overall response depends on a 

number of factors including the relative size of the addition and the original 

building. The size difference may affect the mass distribution of the 

combined building relative to the original building. For RVS screening 

purposes, a determination of the center of mass and center of stiffness of the 

original and combined buildings is overly complex. A comparison of the 

floor area of the addition and original building may also be difficult unless a 

satellite image of the site is available. As a simplification, the relative length 

of the building and addition along the interface is used as a method of 

assessing the relative influence of the addition on the response of the original 

building. In the direction parallel to the interface plane, the possibility of 

significantly detrimental response due to stiffness differences between the 

original building and the addition is small and is not considered in the RVS 

procedure. 

7.3 Implementing Irregularity Recommendations from 

the Building Additions Reference Guide on the 

Screening Forms 

Neither the Level 1 nor the Level 2 form contains modifiers specific to 

additions. Instead, the effect of different addition configurations on the 

seismic performance of the building is addressed in Level 1 by either 

evaluating the original building and addition as a combined building or as 

separate buildings. In the Level 2 form, building additions are considered by 

assigning Score Modifiers (vertical or plan irregularities, pounding, or some 

combination of these) depending on the configuration of the original building 

and the addition. 

When the building and the addition are evaluated as separate structures, the 

Score Modifiers related to building codes (Pre-Code and Post-Benchmark) 

should be applied independently to the original building and addition based 

on their dates of construction. For screening purposes, it should not be 

assumed that the original building was retrofitted at the time of construction 

7-4 7: Building Additions FEMA P-155 
of the addition. Separate RVS screening forms for the building and the 

addition should be prepared if there are separate owners for the building and 

the addition. 

7.3.1 Level 1 Screening for Additions 

FEMA P-154 Table 3-2 provides a simple checklist for horizontal additions 

for identifying whether a building should be treated as a single building, as 

separate buildings, or as a single building with an addition. For Level 1 

screening, additions should be evaluated separately from the original 

building and the lower score should be recorded for the combined building 

since the seismic performance may be governed by either the original 

building or the addition. Conversely, separate structures should have RVS 

scores reported for each building. 

The first step in the process of identifying an addition is to determine 

whether there is a visible joint between parts of the building. The joint 

should exist along the full height of the building on two sides and across the 

roof. (If the structures are different height, the joint will only occur along the 

height of the shorter building.) If a joint exists, the buildings should be 

treated as separate buildings, and the two buildings should be separately 

evaluated. The potential for pounding between the structures should be noted 

on the Level 1 form if it conforms to the pounding criteria for Level 1. 

If there is no visible joint separating portions of a building, the building is 

assumed to be connected, and the second step is to assess whether there are 

other visual clues that can be used to determine whether a building was built 

as a single structure or as separate structures at different times. If built as a 

single structure, the building should be evaluated as a single building. 

One indication of the presence of a separately constructed building or 

addition would be if there is a visible difference in the floor elevations 

between separate portions of the structure. In most cases, a single building 

will be constructed with floor levels that align, although some offsets over a 

portion of a floor level may occur or the building is located on a sloped site. 

If differences in floor elevations of two feet or more are observed, the 

original building and addition should be considered as separately constructed 

structures. 

Another indication would be if there are obvious differences in the structural 

framing between portions of the building that may indicate that the portions 

of the building were constructed separately. The structural framing 

differences could be either the vertical framing (columns or walls) or the 

horizontal framing (roof or floors). The framing differences may be 

FEMA P-155 7: Building Additions 7-5 
 

 

differences in construction materials (e.g., concrete, steel) or may be 

differences in configuration, such as shear walls in one portion of the 

building and moment frames in another portion of the building or differences 

in column spacing. If there are differences in construction, the portions with 

differing construction should be treated as separate structures. 

Finally, noticeable differences in architectural style may be an indication that 

portions of the building were constructed separately. While some differences 

may exist along one side of a building, particularly for commercial buildings 

with different tenants, differences in architectural style that exist on more 

than one face of a building would tend to indicate that the portions of the 

building were constructed separately. The appearance of the street-facing 

sides(s) of a building may not accurately indicate differences in building 

construction, so careful observation of all sides of the building should be 

performed to identify the presence of construction differences. These 

differences in style may be variations in configuration of windows from one 

portion of the building to another or differences in exterior ornamentation or 

façade construction. 

If differences in construction between portions of the building have been 

identified using the three criteria above, then the individual portions of the 

building delineated by the observed difference should be evaluated as 

separate buildings. 

7.3.2 Level 2 Screening for Additions 

The Building Additions Reference Guide in Table B-6 of Appendix B of 

FEMA P-154 provides guidance for considering additions. Based on the 

characteristics of the addition, the Guide directs the screener to either 

consider the original building and addition as a single building or consider 

them as two separate buildings and perform two separate screenings. 

Additional notes and instructions are contained within the Guide to direct the 

screener to look for likely pounding and irregularity conditions depending on 

the relative configuration of the original building and addition. 

7.3.2.1 Vertical Additions 

When a building has a vertical addition that is smaller in footprint than the 

plan of the original building, the seismic force-resisting system of the 

addition and the original building are not likely to be aligned. When there 

are offsets in the seismic force-resisting system, a vertical setback 

irregularity may be present. For the purposes of the RVS screening, if more 

than one exterior wall of the vertical addition does not align with the exterior 

walls of the original building below, a setback of the seismic force-resisting 

7-6 7: Building Additions FEMA P-155 
system is assumed to be present. If the vertical addition has a plan area that 

is not less than 90% of the plan area of the original building below, the 

setback is considered to be minor, and the setback irregularity need not be 

assumed. See Figure 7-2. 

L1 

L2 < 0.9L1 

Figure 7-2 Vertical addition considered as a setback irregularity. 

When the vertical addition has a similar footprint to that of the original 

building below, the factors that affect the seismic performance are type of 

construction of the addition compared to that of the original building and 

number of stories. When the addition is of the same building type as that of 

the original building, the addition and original building are assumed for the 

purposes of rapid visual screening to be integrally connected such that they 

respond to earthquake shaking as a single structure. When the building types 

of the original building and the addition are different, it is likely that the 

structure’s response to earthquake shaking will be more complex, with the 

possible presence of a weak or soft story. 

Vertical additions that are more than one story are likely to be constructed 

with a different seismic force-resisting system than the original building. 

Often the additions are constructed with lighter framing systems; as a result, 

the added stories of the vertical addition are not likely to have similar story 

stiffnesses as the original building. See Figure 7-3. If the stiffness of the 

addition is less than that of the original building, there can be an 

amplification of the motion of the added stories. This condition is not 

directly considered in the Level 2 Score Modifiers, so to account for this 

FEMA P-155 7: Building Additions 7-7 
 

concern, the moderate Vertical Irregularity Score Modifier should be 

indicated. 

Stiff 

Original 

Building 

Flexible 

Addition 

Figure 7-3 Stiff original building with a flexible addition leading to a 

moderate vertical irregularity. 

7.3.2.2 Horizontal Additions 

If joints exist along the entire interface between an original building and a 

horizontal addition, the original building and the addition can be considered 

separate structures and evaluated separately. The separate structures should 

be evaluated for pounding using the guidance in the Level 2 form. Where the 

joints between the structures are covered, the width of the gap may be 

estimated based on the size of the cover. If joints do not exist, the horizontal 

addition should be considered as potentially integrally connected or that the 

buildings will interact with each other during seismic motion. FEMA P-154 

Table 4-1 provides guidance for horizontal additions that are not separated by 

gaps as described below. 

	 If the building types of the original building and the horizontal addition 

are similar, and if the heights of the buildings are the same, the two 

structures can be assumed to behave as a single structure. If there is a 

large difference in horizontal dimension of the original building and 

addition along the interface, there is a potential for torsional response due 

to the differences in stiffness between the building and the addition. A 

difference in horizontal dimension at the interface of less than 50% is 

assumed to create a potential for torsional response, and therefore the 

need to indicate a torsional irregularity. The reentrant corner plan 

7-8 7: Building Additions FEMA P-155 
irregularity should be applied if the difference in horizontal dimension is 

between 50% and 75% by denoting that the smaller horizontal building 

dimension at the interface is less than 75% of the length of the larger 

building. See Figure 7-4. 

If B < 0.5 A Torsional irregularity 

If 0.5A < B < 0.75 A Reentrant corner 

A 

B 

Original 

Building 

Addition 

Figure 7-4 Plan view illustrating irregularity caused by difference in 

horizontal dimension or original building and addition. 

	 If the height of the original building and the addition are different, there 

is a potential for pounding damage to either the taller portion or the 

shorter portion. Therefore, a pounding condition should be indicated as 

described in Section 6.2 if the height difference is two or more stories or 

if the floor levels do not align within 2 feet. Each portion should be 

scored separately considering the building type of each portion and the 

Pounding Score Modifier should be applied to both the shorter and taller 

building. The score should be based on the lower Final Score of the 

buildings. 

	 When the addition is constructed as a different building type than the 

original building, there may be a difference in stiffness of the original 

building and addition. A difference in stiffness may cause either 

torsional response of the buildings acting together or may cause the more 

rigid building to resist some of the lateral forces from the more flexible 

building. The buildings could be evaluated separately and include a 

Pounding Score Modifier for each building. Conversely, the building 

could be evaluated as a single, combined building, which would include 

FEMA P-155 7: Building Additions 7-9 
a Torsional Plan Irregularity Score Modifier due to the differences in 

stiffness. The combined building evaluation should consider the lower 

Basic Score of the building and the addition. If the horizontal dimension 

of the building and addition along the interface are different, a Reentrant 

Corner Plan Irregularity Score Modifier could be indicated; however, 

since the Torsional Plan Irregularity Modifier is more severe than the 

Reentrant Corner Plan Irregularity Score Modifier, considering the 

combined building with the Torsional Plan Irregularity Score Modifier 

would be more conservative and is thus the recommended approach. 

	 Another condition that may occur is when an addition is structurally 

attached to the original building in a manner that the original building 

provides gravity load support for a portion of the addition. If the addition 

is constructed with framing similar to the original building, the building 

and addition can be evaluated as a single building. If the addition is of 

different construction than the original building, the addition may 

become separated due to differences in stiffness or lack of adequate 

attachment and there is a risk of collapse of part of the addition. 

Therefore, the addition should be evaluated separately from the original 

building and a Severe Vertical Irregularity Score Modifier should be 

indicated to account for the potential loss of gravity load support. Since 

the potential for separation is reduced if the construction type of the 

addition and original building are the same, the separate evaluation of the 

building and the addition is not necessary if the construction types are the 

same. See Figure 7-5. 

Addition 

Roof framing of 

addition 

supported on 

original building 

Original 

Building 

Figure 7-5 Addition relying on the original building for gravity support. 

7-10	 7: Building Additions FEMA P-155 
Chapter 8 

Risk Associated with the RVS 

Score 

8.1 Introduction 

This chapter addresses how score relates to risk. As used here, risk means 

the rate at which collapse occurs, as opposed to collapse probability given the 

occurrence of MCER shaking. Previous editions of FEMA 154 did not 

address risk in this sense. Collapse can occur at higher and lower levels of 

shaking than MCER. Higher shaking generally produces higher collapse 

probability but occurs at a lower mean annual frequency than does MCER 

shaking. Lower shaking produces lower collapse probability but occurs more 

frequently than MCER shaking. This chapter shows how one can account for 

the entire range of shaking. 

Section 8.2 explains the difference between collapse probability in MCER 

shaking and the rate of collapse-causing earthquakes of any possible level of 

shaking. Section 8.3 introduces a new measure of performance called the 

Risk Score, denoted by SR, which measures building safety in terms of how 

frequently collapse-causing earthquakes occur. The Final Score, S, by 

contrast measures building safety in terms of the collapse probability given 

MCER shaking. Section 8.4 shows how the Risk Score is approximately one 

unit greater than the Final Score. 

Section 8.5 shows how the Risk Score relates to risk. It shows how different 

values of the Risk Score equate with the chance that an earthquake will cause 

the building to collapse during various periods of time. 

8.2 Risk versus Probability 

The Final Score, S, is intended as an estimate of the negative base-10 

logarithm of the collapse probability given MCER shaking. Mathematically, 

if P denotes the collapse probability in MCER shaking, then FEMA P-154 

derives scores S that satisfy the equation 

S = ‒log10(P) (8-1) 

and equivalently 

P = 1/10S

 (8-2) 

FEMA P-155 8: Risk Associated with the RVS Score 8-1 
 

 

 

For example, S = 2 equates with collapse probability P of 1 in 100, or 1%, or 

0.01, given MCER shaking. A Final Score of S = 3 implies a collapse 

probability P of 1/1000, or 0.1%, or 0.001 given MCER shaking. 

A building may experience many earthquakes during its economic life and 

almost none of them have shaking exactly equal to MCER shaking. Lower 

and higher levels of shaking can occur. Lower levels of shaking generally 

occur more frequently; higher levels, less frequently. Lower levels are 

generally less likely to cause collapse; higher levels, more likely. 

Prior editions of FEMA 154 do not address these other levels of shaking. A 

person making an expensive decision about whether to retrofit a building 

might ask: what about these other levels of shaking? Could the building 

collapse in a more frequent earthquake? What is the chance that an 

earthquake will occur and cause the building to collapse in the next 5 years? 

Or in the next 25 years? What is the chance that it will be an earthquake that 

causes the building to be demolished, rather than some other cause such as 

the building becoming obsolete and demolished in a safe, controlled, 

predictable way? Considering all these other possible levels of shaking, how 

risky is the building? 

The Final Score, S, does not speak to any of these points, because it relates 

only collapse probability given MCER shaking. It does not speak to shaking 

less than or greater than MCER shaking, or to the likelihood of collapse given 

those levels of shaking, or to the frequency with which those other levels of 

shaking occur. 

To deal with risk resulting from these other levels of shaking, one must 

consider three factors that were not considered in prior editions: 

	 The complete seismic hazard curve – the relationship between 

earthquake shaking and the frequency with which various levels of 

shaking occur. 

	 The building’s collapse probability when subjected to other levels of 

shaking. 

	 The design life of the building, which affects how long it is assumed to 

be exposed to earthquakes. 

8.3 Introducing the Risk Score 

This section introduces a new measure of performance called the Risk Score, 

denoted by SR, which measures building safety in terms of how frequently 

collapse-causing earthquakes occur. It is intended as an estimate of the 

negative base-10 logarithm of the number of earthquakes that could cause 

8-2	 8: Risk Associated with the RVS Score FEMA P-155 
building collapse during the design life of the building, which is commonly 

taken to be 50 years. Another way to say the same thing is that the expected 

number of collapse-causing earthquakes during the design life of the building 

is 1 per 10SR lifetimes. This is a different measure of performance from S. S 

has nothing to do with the design life of the building or the number of 

collapse-causing earthquakes. SR does. 

Thus, a value of SR = 2 means 1/102

 collapse-causing earthquakes per 50 

years, or 1 collapse-causing earthquake per 100 design lifetimes. SR = 3 

means 1/103 collapse-causing earthquakes per 50 years, or 1 collapse-causing 

earthquake per 1,000 building design lifetimes. That does not mean that a 

particular building that has a score of SR = 3 would wait 50,000 years to 

experience a collapse-causing earthquake. Rather it means that, if one were 

to pick 1,000 similar buildings at random, on average, 1 of them would 

experience an earthquake that would cause it to collapse during the next 50 

years. 

The Risk Score sums the probability of collapse given any particular level of 

shaking times the number of times in 50 years that that level of shaking will 

occur, summing over all levels of shaking, and taking the negative base-10 

logarithm of that value. It is like the rate at which people are killed in 

automobile accidents, considering that one is more likely to be killed in a 

higher-speed accident than in a lower-speed accident, considering the 

number of low- and high-speed accidents that occur per year. The Final 

Score is like the probability of being killed in an automobile accident that 

occurs at a given speed. 

8.4 Calculating the Risk Score 

Before calculating the Risk Score, it is worthwhile to review the 

development of risk-targeted design motion MCER. Luco et al. (2007) offer 

a method to relate collapse probability conditioned on a particular level of 

shaking to frequency of collapse-causing earthquakes, for a particular 

building and a particular location. Their purpose was to select a level of 

shaking at that site (which they named MCER, risk-targeted maximum 

considered earthquake) such that, if the building had a 10% collapse 

probability conditioned on MCER, it would also have a 1% probability of 

collapse in 50 years, considering all levels of shaking that could occur at that 

location, and how the probability of collapse varies with shaking. One could 

then design a new building at that location to have a 10% collapse probability 

at MCER shaking, and indirectly achieve a specified probability of collapse 

during the design life of the building. 

FEMA P-155 8: Risk Associated with the RVS Score 8-3 
 

 

In the following, the collapse probability conditioned on a particular level of 

shaking is referred to by the shorthand term “fragility,” and the frequency of 

collapse-causing earthquakes is referred to as “risk.” 

Luco et al. (2007) address new design, where design strength is under the 

control of the designer. They answer the question of whether one can design 

a building for a specified level of fragility and indirectly achieve a specified 

level of risk. In the present work, a different question arises: if one is 

interested in an existing building in a particular location, can one also 

somehow relate fragility to risk? The fragility is imposed: it is an attribute of 

the existing building. One can estimate it, but one cannot change it. FEMA 

P-154 provides an estimate of fragility, but not control over it. A building 

examined using FEMA P-154 may have a collapse probability given MCER 

shaking that differs from 10%. 

The question addressed here is: what if the Final Score is 1.5, or 3, or 4? Can 

one say anything about the risk to the building, in the sense of the frequency 

with which collapse-causing earthquakes occur? What if any relationship 

exists between collapse fragility and collapse risk for existing buildings? 

The question is addressed here using the fragility functions developed for 

FEMA P-154 for FEMA Building Types without vertical or plan 

irregularities, on Soil Type CD, and neither post-benchmark nor pre-code 

design. For simplicity, a factored lognormal cumulative distribution function 

was fit to the fragility estimates implied by the Basic Score of each FEMA 

Building Type for each seismicity region. By “a factored lognormal 

cumulative distribution function,” the following is meant: 

P   P y c  x (8-3) 

where 

 ln  x   

 y x    (8-4)    

and where P denotes the collapse probability given shaking of Sa(1.0 sec, 

5%) = x, Pc denotes the fraction of the building area that collapses given that 

the building is in the complete structural damage state (note that Pc is 

equivalent to the collapse factor, P[COL|Complete Damage], described in 

Chapter 4 and Chapter 5), y denotes the probability of complete structural 

damage,  denotes the cumulative standard normal distribution evaluated at 

the term in parentheses, and θ and β are parameters of the distribution, 

referred to here as the median and logarithmic standard deviation, 

respectively. The values of x are taken as the values of FVS1 for each of the 

seismicity regions used in FEMA P-154. The values of P and Pc are those 

8-4 8: Risk Associated with the RVS Score FEMA P-155 
 

 

 

 

 

assumed in developing the Basic Scores. The value of θ for each baselinecondition FEMA Building Type is found by interpolating (by parabolic 

spline) the function defined by the pairs (P/Pc, x) at P/Pc = 0.5. The value of 

β for each baseline-condition FEMA Building Type is found by interpolating 

the pairs (P/Pc, x) at P/Pc = 0.1. Let the value of x at this point be denoted by 

x0.10. Then β can be estimated as shown in Equation 8-5. Results are shown 

in Table 8-1. 

ln  x0.10   ln  x0.10   β  (8-5) 1 0.10  1.28 

Table 8-1 Parameters of Fragility Functions Used to 

Relate Fragility to Risk 

FEMA 

Building Type Pc x0.10 θ β

W1 0.05 1.04 2.09 0.55 

W1A 0.05 0.89 1.81 0.55 

W2 0.05 0.83 1.75 0.58 

S1 0.08 0.68 1.48 0.61 

S2 0.08 0.59 1.27 0.59 

S3 0.08 0.82 1.76 0.60 

S4 0.08 0.59 1.27 0.59 

S5 0.08 0.47 0.95 0.56 

C1 0.13 0.39 0.96 0.70 

C2 0.13 0.71 1.30 0.47 

C3 0.13 0.32 0.70 0.60 

PC1 0.15 0.50 1.21 0.70 

PC2 0.15 0.33 1.02 0.89 

RM1 0.13 0.44 1.12 0.73 

RM2 0.13 0.44 1.12 0.73 

URM 0.15 0.26 0.57 0.60 

MH 0.05 0.46 0.90 0.52 

There appears to be no functional relationship between θ and β values in 

Table 8-1. That means that the two are independent, so one can simulate θ as 

a random variable and β as another random variable whose distribution is 

unaffected by the value that θ takes on. (A mathematical test to support the 

assertion that θ and β are independent was also conducted.) This is important 

because it means one can explore the relationship between fragility and risk 

for the general case 0.7 ≤ θ ≤ 2.1 and 0.47 ≤ β ≤ 0.89 and apply the 

conclusions to the particular cases in Table 8-1. Furthermore, one can treat 

FEMA P-155 8: Risk Associated with the RVS Score 8-5 
 

the pair (θ, β) as jointly lognormally distributed with expected values (1.25, 

0.62) and standard deviations (0.41, 0.10); these parameter values come from 

the sample values of θ and β in Table 8-1. Both distributions pass a 

Lilliefors goodness-of-fit test at the 1% significance level. That fact is useful 

because it means one can examine the general case of a building with jointly 

lognormal median and logarithmic standard deviation and evaluate the 

probability that fragility relates to risk in some interesting way that this 

chapter seeks to discover. Let bold θ denote the uncertain median, and bold 

β denote the uncertain logarithmic standard deviation. 

A fragility function with uncertain, lognormally distributed median θ ~ 

LN(1.25, 0.41) and uncertain, lognormally distributed logarithmic standard 

deviation β ~ LN(0.62, 0.10) were chosen as the representative fragility 

function. This function is representative in the sense that it represents all of 

the baseline fragility functions before multiplying by Pc. The expression θ ~ 

LN(1.25, 0.41) means that θ is distributed like a lognormal random variable 

with mean 1.25 and standard deviation 0.41. Then 

 ln  x θ  

 y   (8-6)  β  

which is y of Equation (8-4) but with uncertain θ and β. The values of MCER 

and the hazard curves that might be encountered in a FEMA P-154 

evaluation are then considered in the following example. 

The seismicity regions considered in FEMA P-154 are defined in terms of 

ranges of MCER, each range with a specified central value of FASS and FVS1. 

The U.S. Geological Survey distributes gridded text files containing SS and S1 

parameter values from the 2012 International Building Code (USGS, 2014a). 

One of the files, which provides 0.2s and 1.0s risk-targeted MCE (MCER) 

ground motions on a 0.05-degree grid covering the range of latitudes 24.6°­

50° N and longitudes 125°-65° W, was acquired. For each gridpoint in the 

database, FA and FV for Soil Type CD were calculated, and the quantities 

FASS and FVS1 were calculated and rounded to the nearest 0.01g. Sites with 

FVS1 that match FEMA P-154’s central values were selected from all of the 

gridpoints. These were grouped into five sets, one set for each seismicity 

region. Ten sites were selected at random from each of the five sets, for a 

total of 50 sites. The selected sites are listed in Table 8-2. The 1-second 

hazard curve at each site was extracted from the USGS’s 2008 National 

Seismic Hazard Map gridded data archive (USGS, 2014b). The hazard curve 

for each site was adjusted to account for site amplification on Soil Type CD. 

8-6 8: Risk Associated with the RVS Score FEMA P-155 
 

 

 

 

 

 

 

 

 

 

Table 8-2 Sites with Hazard Curves that Were Used to Relate Fragility to Risk 

Seismicity Region Site ID Lat deg N Lon deg E FVS1, g 

Low L0 48.90 -112.35 0.16 

L1 36.60 -80.35 0.16 

L2 46.75 -77.75 0.16 

L3 37.00 -111.10 0.16 

L4 44.80 -69.20 0.16 

L5 33.20 -121.45 0.16 

L6 32.50 -83.45 0.16 

L7 31.25 -106.60 0.16 

L8 46.20 -68.45 0.16 

L9 32.75 -110.90 0.16 

Moderate M0 28.20 -113.25 0.30 

M1 38.90 -88.00 0.30 

M2 43.10 -119.85 0.30 

M3 38.70 -90.25 0.30 

M4 41.15 -116.40 0.30 

M5 34.35 -79.30 0.30 

M6 35.40 -115.30 0.30 

M7 44.20 -120.40 0.30 

M8 39.10 -115.65 0.30 

M9 48.00 -115.15 0.30 

Moderately High MH0 33.95 -115.45 0.52 

MH1 45.10 -122.20 0.52 

MH2 42.50 -121.85 0.52 

MH3 42.65 -111.25 0.52 

MH4 35.25 -89.70 0.52 

MH5 31.05 -113.80 0.52 

MH6 38.65 -124.10 0.52 

MH7 43.05 -122.85 0.52 

MH8 35.70 -116.20 0.52 

MH9 39.55 -118.35 0.52 

High H0 47.70 -122.20 0.68 

H1 39.50 -124.30 0.68

 H2 48.00 -122.20 0.68

 H3 33.60 -79.95 0.68

 H4 36.45 -121.30 0.68 

FEMA P-155 8: Risk Associated with the RVS Score 8-7 
 

 

Table 8-2 Sites with Hazard Curves that Were Used to Relate Fragility to Risk (continued) 

Seismicity Region Site ID Lat deg N Lon deg E FVS1, g 

High (continued) H5 41.05 -110.85 0.68

 H6 37.30 -118.55 0.68 

H7 35.10 -117.30 0.68 

H8 44.20 -123.35 0.68 

H9 34.95 -116.75 0.68 

Very High VH0 34.35 -118.25 1.26 

VH1 34.35 -119.35 1.26 

VH2 37.95 -122.35 1.26 

VH3 39.40 -122.90 1.26

 VH4 34.20 -119.10 1.26

 VH5 34.05 -117.10 1.26

 VH6 32.65 -115.35 1.26

 VH7 34.50 -119.90 1.26

 VH8 34.50 -119.95 1.26

 VH9 36.70 -89.80 1.26 

The hazard curves of each set were averaged. That is, at each x value of 

Sa(1.0 second, 5%) on Soil Type CD, the 10 values of the mean exceedance 

frequency for each seismicity region were averaged, resulting in what can be 

considered a sample-average hazard curve for the seismicity region. The 

resulting hazard curves, referred to as nominal hazard curves, are shown in 

Figure 8-1. Mean exceedance frequency, yr-1 

1 

0.1 

0.01 

0.001 

0.0001 

0.0 0.5 1.0 1.5
 

Sa(1.0 sec, 5%) on Soil Type CD, g 

Figure 8-1 Sample-average hazard curves used to relate fragility to risk. 

8-8 8: Risk Associated with the RVS Score FEMA P-155 
 

 

 

 

 

 

To recap: a random fragility function is created that represents the range of 

baseline-condition FEMA Building Types. Median values of MCER shaking 

in each seismicity region have already been selected; the values considered 

here are those of 5%-damped, 1-second spectral acceleration response on 

Soil Type CD. A sample-average hazard curve has also been evaluated for 

each seismicity region. 

The following new terms λ, τ, and PMFR, as shown in Equations 8-7 and 8-8, 

are defined: 

SR  log10   	 (8-7) 

PMFR  SR  S	 (8-8) 

where 

λ = collapse rate, measured in events per year, and defined as the 

expected rate of collapse-causing earthquakes per year at a 

given site and for a given building. 

τ = design life of the building, commonly taken to be 50 years 

PMFR = Risk Modification Factor, a number added to the Final 

Score, S, to get the Risk Score, SR 

The collapse rate, λ, for a given fragility function and location can be 

estimated as shown in Equation 8-9. In the two integrals, G(x) denotes the 

mean hazard curve, expressed in terms of mean rate of exceeding shaking x 

in events per year; φ denotes the standard normal probability density 

function,  denotes the standard normal cumulative distribution function, 

and θ, β, and Pc are as previously defined. The two integrals can be shown to 

be equal through integration by parts. 

  ln  x θ     Pc  G x     dx  β x0   (8-9)  dG   x  ln  x θ    Pc     dx  dx β x0  

It will be useful to ignore Pc. Note that by the definition of the Final Score S, 

  ln FV  S1 θ 

S  log 10  Pc  

  β    (8-10)   ln FV  S1 θ   log 10 

 

    log 10   P c β   

and by the definition of the Risk Score SR, 

FEMA P-155	 8: Risk Associated with the RVS Score 8-9 
 

 

 

 

 ln  x θ    

R log10 



Pc 









 G    dx 

 S   x     β    x0     (8-11)

   ln  x θ     log10   log   

   G x    dx 

 10 Pc β  x0   

If one substitutes Equations 8-10 and 8-11 into Equation 8-8, the log10(Pc) 

terms cancel out of the right hand side of Equation 8-8. Thus the particular 

value of Pc for any given FEMA Building Type does not affect PMFR. 

The integral in Equation 8-9 can be evaluated numerically, as shown in 

Equation 8-12, which is exact if y is linear between values of x, and G is 

loglinear between values of x. For the derivation of Equation 8-12, see 

Porter et al. (2006). 

 

n 

 y a  y b  (8-12) i1 i i i 

i1 

In this equation, i denotes an index to n + 1 values of shaking x and 

 ln  xi θ  

yi    β  

  xi i i xx  1 

yi = yi – yi-1 

m  lnG Gi1  x i i i

a i i  G 1 1 exp  m i i x 

G   1  1  i1 b i  expm x     i i  xi      x i   m m i  i 

One can evaluate PMFR of Equation 8-8 using the representative fragility 

function y(x) of Equation 8-6 and the five nominal hazard curves G(x) shown 

in Figure 8-1. Using Monte Carlo simulation to account for uncertain θ and 

β, it is found that the expected value of PMFR varies by seismicity region, but 

not very much, as shown in Table 8-3. 

Table 8-3 shows that, for all seismicity regions between Moderate and Very 

High, one can add approximately 1.0 to the Final Score to get the Risk Score. 

That is, 

SR  S 1 (8-13) 

8-10 8: Risk Associated with the RVS Score FEMA P-155 
Table 8-3 Expected Value of PMFR 

Seismicity Region PMFR

 Low 0.1 

 Moderate 0.9 

 Moderately High 1.2 

High 1.1 

 Very High 0.9 

This means that the collapse rate per 50 years is approximately 1/10th the 

collapse probability given MCER shaking. (Recall the negative base-10 

logarithmic nature of the Final Score and the Risk Score: a PMFR = 1.0 

means that the collapse rate per τ years is 10-1 = 0.1 times the collapse 

probability given MCER shaking.) Thus, the same ratio of collapse 

probability given MCER shaking to collapse rate per 50 years that Luco et al. 

(2007) established for new buildings also applies to existing buildings. 

Those authors set MCER such that the collapse probability given MCER 

shaking was 0.10, and the collapse probability per 50 years was 0.01. There 

is a difference between probability and rate: the former has no units, and the 

latter has units of yr-1, but for small values, less than about 0.1, the two take 

on approximately the same numerical value. 

The present results are somewhat more general than the one established by 

Luco et al. (2007). Whereas Luco et al. (2007) fixed the new-building 

collapse probability given MCER shaking and the collapse rate per 50 years 

at 0.10 and 0.01 respectively, the present results allow for other values of 

collapse probability given MCER shaking, like the values estimated using 

FEMA P-154. The present results show that, on average, the ratio of the two 

quantities is the same, even if the particular value of collapse probability 

given MCER shaking is not 0.10. Luco et al. (2007) also fixed the 

logarithmic standard deviation β = 0.80. The present results allow β to vary 

randomly according to the fragility functions derived elsewhere in FEMA 

P-154. 

8.5 Relating the Risk Score to Risk 

The Risk Score is useful in that one can use it to relate the FEMA P-154 

Final Score to fatality risk. Different stakeholders in a risk-management 

program may understand risk best in different ways, so it may be useful to 

explain the Risk Score several different ways. 

FEMA P-155 8: Risk Associated with the RVS Score 8-11 
First, the fatality risk posed by an existing building is compared with that of a 

new code-compliant building. Although the collapse risk in new buildings 

varies from building to building, one can use Equation 8-7 to estimate that 

they have collapse probabilities approximately equivalent to SR = 3.5. The 

value of λτ in the equation is taken from the FEMA P-695 (FEMA, 2009b) 

upper-bound limit of 1% collapse probability in 50 years, which is 

approximately equivalent to 0.01 collapses per 50 years, reduced (by 

judgment) to 0.005 per 50 years to account for conservativeness of the upper 

bound, multiplied by a collapsed portion of 0.1 as discussed in FEMA P-154 

Chapter 4, and the result of the equation rounded to the nearest 0.5 to avoid 

appearing excessively accurate. That is, SR = ‒log10(0.0005) = 3.3, rounded 

to 3.5. Table 8-4 presents relative risk for various values of SR in existing 

buildings to the risk posed by new buildings. 

Table 8-4 Fatality Risk in Existing Buildings 

Compared with New Buildings 

SR 

Fatality Risk Multiplier of Existing Buildings 

Compared with New Buildings 

1.5 100 x 

2.0 32 x 

2.5 10x 

3.0 3 x 

3.5 1 x 

4.0 0.3 x 

4.5 0.1 x 

Next, the improvement in life safety that comes about by strengthening a 

number of buildings is considered. Suppose a certain city contained 2,800 

soft-story high-occupancy woodframe residential buildings with S ≈ 1.25, 

and thus SR ≈ 2.25. Suppose that by retrofit, the buildings could be improved 

to SR ≈ 3.3 at a cost of approximately $260 million. Suppose the buildings 

provide residences for 64,000 people, all of whom are home at night and half 

of whom are home in the daytime. These are approximately the conditions 

of San Francisco’s soft-story high-occupancy woodframe residential 

buildings in 2008 (ATC, 2009). Suppose further that if one were in a 

collapsed portion of a building, one would have a 10% chance of being 

killed, as suggested by HAZUS. One can estimate using these figures that 

the retrofit program will reduce the fatality risk from approximately 27 

fatalities per 50 years to approximately 2 fatalities per 50 years, using 

 R s n 10S  f  t (8-14) 50 

8-12 8: Risk Associated with the RVS Score FEMA P-155 
 

 

 

 

 

 

where s denotes lives saved per t years, n denotes average number of 

occupants, and f denotes the expected fraction of occupants in the collapsed 

portion of a building who are killed. Given that these buildings have already 

stood for 90 years and seem reasonably likely to exist another 150, one can 

estimate that the retrofit program could realistically prevent on the order of 

75 fatalities. (That is, 25 statistical fatalities avoided in 50 years, and an 

estimated 150 years of useful life remaining, means 75 statistical fatalities 

avoided). One can then estimate the cost per statistical fatality avoided to be 

$3.4 million, which is less than the amount that the U.S. government deems 

to be a reasonable expense to avoid a fatality of an unknown person at an 

uncertain future date. For example, the figure used by the U.S. Department 

of Transportation (Trottenberg and Rivkin, 2013) is $9.1 million (2012 US 

dollars) value per statistical life (VSL) saved. The cost per statistical fatality 

avoided is lower than $3.4 million if one considers avoided repair and 

replacement costs, additional living expenses, business interruption costs, 

and nonfatal injuries avoided. Since the $3.4 million cost per statistical 

fatality avoided is less than the $9.1 million VSL, the retrofit is cost 

effective—it has a benefit cost ratio greater than 1.0—even before adding the 

reduced repair costs, living expenses, business interruption losses, and 

nonfatal injuries. 

The Risk Score can also be used to estimate the probability that at least one 

earthquake occurs during any given period of time that would cause collapse. 

Let t denote a particular number of years, let τ denotes the design life of the 

building, and let R(t) denote the probability that at least one earthquake 

occurs during t years that is strong enough to cause collapse. R(t) is given by 

Equation 8-15, which is evaluated in Table 8-5 for various combinations of 

SR and t. 

SR  10  R t  1 exp  t (8-15)   

  

Table 8-5 Relationship Between Risk Score SR and Collapse Probability R(t) 

SR t = 1 yr t = 10 yr t = 50 yr t = 100 yr t = 200 yr 

2.0 0.02% 0.2% 1% 2% 4% 

2.5 0.006% 0.06% 0.3% 0.6% 1.3% 

3.0 0.002% 0.02% 0.1% 0.2% 0.4% 

3.5 0.0006% 0.006% 0.03% 0.06% 0.13% 

4.0 0.0002% 0.002% 0.01% 0.02% 0.04% 

Table 8-5 can be used to consider the risk to a given building in light of how 

long it is expected to be useful. Suppose for example a building with a Risk 

FEMA P-155 8: Risk Associated with the RVS Score 8-13 
Score of 2 is likely to be demolished and replaced in 10 years. There is a 

0.2% (1 in 500) chance that it will experience earthquake-induced collapse 

during that time. If, on the other hand, it is an important building that is 

likely to remain in use for 200 years, there is a 4% (1 in 25) chance that an 

earthquake will cause collapse during its expected lifetime. 

8-14 8: Risk Associated with the RVS Score FEMA P-155 
Chapter 9 

Comparison of Paper-Based and 

Electronic Scoring 

Methodologies 

9.1 Introduction 

The purpose of the Electronic Scoring Methodology is to use the seismic 

hazard associated with the building site to improve the scoring. It is an 

alternative to using the paper forms. Site-specific seismic hazard and soil 

conditions can be used to develop Basic Scores and Score Modifiers for a 

given building that more accurately account for the seismic hazard compared 

with the relatively coarse step functions used in the paper forms. Another 

advantage is that the electronic scoring can be incorporated into the data 

collection system to avoid the need to transcribe data from the paper forms 

into an electronic database. 

The use of the Electronic Scoring Methodology is optional. The decision to 

use it should be based on consideration by the Supervising Engineer and the 

RVS Authority. The Electronic Scoring Methodology can be implemented 

into an RVS Program in a variety of ways, ranging from the use of simple 

tools, such as spreadsheets, to more complex tools, such as programming 

smartphones, tablet computers, or laptop computers. The use of any of the 

methods for incorporating electronic scoring is not a substitute for a Detailed 

Structural Evaluation. Electronic scoring can be used for Level 1 screening 

and for Level 2 screening. However, as Level 2 Score Modifiers have not 

been developed for the high end of the Very High seismicity region range, 

for Level 2 screenings, one cannot interpolate beyond the median value for 

Very High seismicity. 

9.2 Development of Scores for the Electronic Scoring 

Methodology 

Chapter 4 of this document describes the basis for the Basic Scores 

developed for the Third Edition. In the development of the Third Edition 

scores, the Basic Scores and Score Modifiers have been developed for six 

levels of seismic hazard values (SS and S1): the five pairs of values used as 

medians in the five seismicity levels, as described in Chapter 4, plus one 

FEMA P-155 9: Technical Background on Electronic Scoring Methodology 9-1 
hazard values, one can interpolate Basic Scores and Score Modifiers at 

seismic hazard values between these medians. The sixth level, at the high 

end of very high seismicity, allows the user to interpolate at seismicity values 

above the median of the Very High seismicity region. Note that one might 

still have to extrapolate in cases of buildings at sites with seismic hazard 

below the median values used for low seismicity. A seventh set of scores at 

very low seismic hazard levels was not created because the Low seismicity 

region scores are already sufficiently high enough that it is highly unlikely 

that further reduced seismicity levels would produce a Final Score below the 

recommended cut-off score and trigger a Detailed Structural Evaluation. 

9.3 Interpolating and Extrapolating Basic Scores and 

Score Modifiers 

To implement the electronic scoring methodology, first the site-specific 

seismic hazard is determined. The geographic coordinates for the site can be 

determined using a map or Global Positioning System (GPS) equipment. 

The SS and S1 hazard values for those coordinates can be determined from a 

map, such as those in ASCE/SEI 7-10 (ASCE, 2010), or from online tools, 

such as those provided by the U.S. Geological Survey. Then, SS and S1 are 

adjusted for Soil Type CD, by multiplying by FA and FV (per Table 9-1) to 

obtain values of FASS and FVS1. 

Table 9-1 Site Coefficients for Soil Type CD 

Spectral Acceleration 

on Soil Type B 

Amplification Factor 

for Soil Type CD 

Short-Period, SS (g) Short-Period Amplification Factor1 

, 

FA 

< 0.25 1.40 

0.50 1.30 

0.75 1.15 

1.0 1.05 

> 1.25 1.00 

1-second Period, S1 (g) 1.0-second Period Amplification 

Factor1 

, FV 

< 0.1 2.05 

0.2 1.80 

0.3 1.65 

0.4 1.50 

> 0.5 1.40 

1 Soil Type C and Soil Type D values of FA and FV for are taken from Table 5-3 and 

averaged to obtain the Soil Type CD values shown above. 

9-2 9: Technical Background on Electronic Scoring Methodology FEMA P-155 
 

 

 

 

 

Next, a decision is made on whether to interpolate (or extrapolate) the Basic 

Score and Score Modifiers on the basis of FASS values or FVS1 values. For a 

building estimated to have a small-amplitude fundamental period of 

vibration, T, where T ≤ SS / S1, the interpolation is made on the basis of FASS. 

For a building with T > SS / S1, the interpolation is made on the basis of FVS1. 

The reason is that, while the building remains elastic, its spectral acceleration 

response in a given earthquake will lie on the constant-acceleration portion of 

the idealized response spectrum if T ≤ SS / S1, and it will lie on the constantvelocity portion if T > SS / S1. The present document employs only a 

constant-acceleration portion and constant-velocity portion of the response 

spectrum. The building fundamental period, T, can be estimated from the 

following equations depending on FEMA Building Type: 

T = 0.035H0.80 for FEMA Building Type S1 

= 0.018H0.90 for FEMA Building Type C1 (9-1)

 = 0.032H0.55 for FEMA Building Types W1, W1A, W2 

= 0.025H0.75 for others 

where H is the building height measured in feet and T is measured in 

seconds. Lacking better information, H can be estimated as 12 ft per story. 

Chapter 6 provides the sources for Equation 9-1. 

As a simpler but more approximate alternative, one can interpolate and 

extrapolate the Basic Score and Score Modifiers on the basis of FASS for lowrise (1-3 story) buildings and on the basis of FVS1 for mid-rise and high-rise 

buildings (at least 4 stories). 

The Supervising Engineer should decide whether to require extrapolation for 

FASS or FVS1 values below the lowest values in the tables or whether to cap 

the values. 

Next, the Basic Scores and Score Modifiers are linearly interpolated (or 

extrapolated). Basic Scores and Score Modifiers provided in the FEMA 

P-154 Handbook and shown on the Data Collection forms are based on 

median values of FASS or FVS1 for each seismicity region. The median values 

are defined in Table 5-4 and repeated below in Table 9-2. For a given FASS or 

FVS1, Basic Scores and Score Modifiers can be interpolated using the 

seismicity regions immediately above and below it. 

Some spreadsheet programs and other software can perform the interpolation 

or extrapolation automatically, but for the user who needs to program the 

interpolation, the math is offered here. 

FEMA P-155 9: Technical Background on Electronic Scoring Methodology 9-3 
 

 

 

 

Table 9-2 Median Spectral Acceleration Values in Each Seismicity 

Region Adjusted for Soil Type CD 

Region Median FaSS (g) Median FvS1 (g) 

L 0.28 0.16 

M 0.54 0.30 

MH 0.90 0.52 

H 1.21 0.68 

VH 2.25 1.26 

VHmax 3.80 2.10 

For linear interpolation, choose the two (x, y) pairs that have x-values 

immediately below and above the site’s x-value, denoted by (x0, y0) and (x1, 

y1), and the site’s x-value (FASS or FVS1) simply by x. Then the y-value (the 

Basic Score or Score Modifier, as appropriate) is estimated as: 

 y  y   x 

1 0

y y0  x 0  (9-2)  x1  x0 

where y0 and y1 values for all FEMA Building Types and all seismicity 

regions are provided in Table 5-10. 

Alternatively, to avoid concerns about kinks in the functional relationship 

between shaking and Basic Score or Score Modifier, the interpolation is done 

by fitting a spline. A spline is a smooth curve fit to a set of (x, y) pairs such 

that there is no kink at the x-values in the (x, y) pairs. The hazard value (FASS 

or FVS1, as determined above) is treated as the x-value. The Basic Score and 

each Score Modifier are treated as the y-value in the interpolation. 

There are many ways to fit a spline; the Newton form of the quadratic 

interpolating polynomial is used here. Accordingly, three pairs of (x, y) data 

are chosen: (1) one pair with an x-value immediately above the site’s hazard 

value; (2) one with an x-value immediately below; and (3) one pair either 

above the higher x or below the lower x, as convenient. These data points are 

denoted by (x0, y0), (x1, y1), and (x2, y2), in increasing order of x-value. The 

Newton form of the quadratic interpolating polynomial is given by 

y b   b  x   x  b  x  x  x  x  (9-3) 0 1 0 2 0 1 

The coefficients b0, b1, and b2 are found by solving for the interpolating 

conditions: 

9-4 9: Technical Background on Electronic Scoring Methodology FEMA P-155 
 

 

 

 

 

 

 

	 

	 


 


 


 


 


 


 


 


 

	 
 


 

 
 
 


 


 

y0  b0 

y1   b0 b1  x1  x0  (9-4) 

y 2 0 1 2 0 2 2 0 2 1   b b  x x   b x   x  x x  

It can be shown that 

b0  y0 

b	   y1  y0  (9-5) 1	  
  x1  x0 
 

  y2  y1   y1   y0 
   
   x2  x1   x1  x0   b2    x  2  x0  

   

For example, consider a W1 building located where FASS = 0.322g. The 

building has a severe vertical irregularity, plan irregularity, and is on Soil 

Type E (and is a low-rise building). Its Basic Score is interpolated by the 

quadratic interpolating polynomial as follows: 

x = 0.322g
 

x0 = 0.28g (Table 9-2, FASS, L seismicity row)
 

x1 = 0.54g (Table 9-2, FASS, M seismicity row) 

x2 = 0.90g (Table 9-2, FASS, MH seismicity row) 

y0 = 6.2 (Table 5-10, Basic Score, W1, Low Seismicity Region)
 

y1 = 5.1 (Table 5-10, Basic Score, W1, Moderate Seismicity Region)
 

y2 = 4.1 (Table 5-10, Basic Score, W1, Moderately High Seismicity
 

Region) 

b0	  y0
 

 6.2
 

  y1  y0 b1   
  x1  x0 
 

 5.1 6.2      0.54  0.28 
 

 4.231
 

FEMA P-155 9: Technical Background on Electronic Scoring Methodology 9-5 
 


 


 

  y y 2 1 1 0    y y        x x  x x  2 1   1  0   b2   x x   2 0   

   
 

 4.1 5.1 5.1 6.2     0.90  0.54 0.54  0.28     0.90  0.28  

   
 

 2.344
 

y b b x x b x x x x  0 1 0 2 0 1         

  6.2 4.231 0.322  0.28  2.344 0.322  0.280.322 0.54

 6.0 

The Basic Score is calculated as 6.0. In comparison, the paper-based Basic 

Score is 6.2. Figure 9-1 illustrates the spline fit. The rest of the parameter 

values for this example are shown in Table 9-3. 

(x0, y0) 

(x1, y1) 

(x2, y2) 

(x, y) 

0.00 0.25 0.50 0.75 1.00 

x, g 

Figure 9-1 Spline fit to the example data. 

10.0 

7.5 

5.0 

2.5 

0.0 

y

9-6 9: Technical Background on Electronic Scoring Methodology FEMA P-155 
FEMA P-155 9: Technical Background on Electronic Scoring Methodology 9-7 

Table 9-3 Low-Rise W1 Building, FASS

Irregularity, on Soil Type E 

= 0.322g, with Severe Vertical Irregularity, Plan 

Interpolation Parameters Score 

y0 y1 y2 b1 b2 Electronic Paper 

Basic Score 6.2 5.1 4.1 -4.23 2.34 6.00 6.2

Severe Vert. Irreg. -1.5 -1.4 -1.3 0.38 -0.17 -1.48 -1.5

Mod. Vert. Irreg. 0 0 0 0 0 0 0

Plan Irregularity -1.6 -1.4 -1.3 0.77 -0.79 -1.56 -1.6

Pre-Code 0 0 0 0 0 0 0

Post-Benchmark 0 0 0 0 0 0 0

Soil B 0 0 0 0 0 0 0

Soil E - Low-Rise -1.2 -1.2 0 0.00 5.38 -1.25 -1.2

Soil E - Mid/High 0 0 0 0 0 0 0

Minimum Score 2.7 1.6 1.6 -4.23 6.82 2.46 2.7

Score = 2.46 2.7

9.4 Comparison of Scores Derived with Electronic 

Scoring versus Paper-Based Scores1

Within a given seismicity region, the seismic hazard can vary by a factor 

from about 1.5 to 2. The effect of changes in seismic hazard on the Basic 

Score values are less dramatic, but can still be significant in determining 

either the relative ranking of buildings or whether a building passes the 

screening based on a comparison with the cut-off score. 

One can estimate the chance that using electronic scoring will yield a 

different result from the paper-based methodology. The main difference of 

interest here is whether the paper-based methodology yields a Final Score 

less than or equal to 2.0 while the electronic methodology yields a Final 

Score of over 2.0 (referred to here as incorrect failure) or vice versa (referred 

to here as incorrect passing). These probabilities are estimated by calculating 

scores under both methodologies, and calculating the fraction of all 

combinations where the paper-based and electronic methodologies yield 

different results in terms of whether the Final Score is above or below the 

cut-off. The approach used here is to treat as equiprobable every combination 

of shaking (in equiprobable increments of FASS), FEMA Building Type, and 

 

1

 The comparisons presented in this section were made using draft values of Basic 

Scores and Score Modifiers. In a limited number of instances, Basic Scores and 

Score Modifiers were subsequently revised. Such revisions included adjustments to 

W1A Basic Scores and Post-Benchmark Score Modifiers, and are not expected to 

have a significant effect on the results of this section. 
9-8 9: Technical Background on Electronic Scoring Methodology FEMA P-155 

allowable Level 1 Score Modifier combinations (irregularities, era, and soil). 

Quadratic interpolation is used as described in Section 9.3. 

To calculate the probabilities of incorrect failure and incorrect passing, it was 

first necessary to determine the probability that a particular building is 

exposed to a particular level of FASS, and the probability of observing a given 

combination of FEMA Building Type and Score Modifiers. 

For the former, it was assumed that buildings are distributed similarly to the 

population. One can readily estimate how the population is distributed 

versus FASS. Two data sources provide the necessary information: 

 The U.S. Geological Survey’s seismic design data sets derived from 

2008 USGS Hazard Data (USGS, 2014a). These are text files containing 

risk-targeted SS and S1 parameter values from the 2012 International 

Building Code on a gridded basis: 0.01 or 0.05 degrees for the 

conterminous United States and Alaska, 0.02 degrees for Hawaii, and 

0.01 degrees for Puerto Rico and the U.S. Virgin Islands. 

 The U.S. Census Bureau’s “National Places Gazetteer.” This data set 

contains population and location data (among others) for all incorporated 

places and census designated places (CDPs) in the 50 states, the District 

of Columbia and Puerto Rico as of January 1, 2010. 

The value of risk-targeted FASS was calculated for each populated place in the 

Gazetteer using FA for Soil Type CD. One can then sort the population by 

increasing FASS and calculate the cumulative fraction of the population 

exposed to a given value of FASS or less, as a function of FASS, and fit a 

smooth curve to the cumulative distribution function of FASS for 

convenience. The cumulative distribution of the population of the United 

States was found to be approximately lognormally distributed, with median 

0.27g and logarithmic standard deviation 1.08g, as shown in the smooth 

curve of Figure 9-2. A set of 100 equiprobable values of FASS were then 

selected by inverting the cumulative distribution function at 0.005, 0.015, 

0.025, ... 0.995. 

There does not appear to be sufficient available evidence to estimate the 

probability that any arbitrarily selected building will exhibit a particular 

combination of FEMA Building Type and set of Score Modifiers, so each 

combination was treated as equiprobable. There are 96 possible sets of Score 

Modifiers for each FEMA Building Type, ignoring the fact that some Score 

Modifiers are not applicable to some building types and seismicity levels. 

By “possible sets” is meant that, for example, a building cannot have both 

moderate and high vertical irregularity. 
FEMA P-155 9: Technical Background on Electronic Scoring Methodology 9-9 

Figure 9-2 Distribution of the population of the United States by FASS.

0.00

0.25

0.50

0.75

1.00

0.01 0.1 1 10

Cumulative fraction of US population

FA·SS, g

With 100 levels of FASS, 96 sets of Score Modifiers per FEMA Building 

Type, and 17 FEMA Building Types, one can calculate paper and electronic 

scores for each of 163,200 samples of FEMA Building Type, Score Modifier 

set, and value of FASS. For electronic scoring, Basic Scores, Score Modifiers, 

and Minimum Scores were calculated using a quadratic interpolating 

polynomial, that is, by fitting a smooth spline as discussed above. 

Extrapolation below the lowest values of SS and S1 is allowed in these 

calculations. 

As shown in Table 9-4, among the 163,200 samples, if calculated using the 

paper methodology, 9,223 samples (approximately 6%) would produce 

incorrect-failure results, meaning that they would call for Detailed Structural 

Evaluation (S < 2) while the electronic scoring would not (S > 2). Another 

1,495 samples (approximately 1%) produce incorrect-passing results, 

meaning that the paper-based methodology yields S > 2 while the electronic 

scoring yields S < 2. 

Table 9-4 Errors avoided Using Electronic Scoring 

Error Cases Fraction of cases 

Incorrect failure 9,223 6% 

Incorrect passing 1,495 1% 

Table 9-5 shows an example that demonstrates how electronic scoring can 

avoid incorrect-passing scores produced by the paper-based methodology. It 
 

reflects FEMA Model Building Type W2, moderate vertical irregularity, plan 

irregularity, low-rise on Soil Type E, subject to FASS = 0.133g. 

Table 9-5 Low-Rise W2, FASS =0.133g, with Moderate Vertical Irregularity, Plan 

Irregularity, on Soil Type E 

Interpolation Parameters Score 

y0 y1 y2 b1 b2 Electronic Paper 

Basic Score 5.7 3.8 3.2 -7.31 9.10 7.32 5.7 

Severe Vert. Irreg. 0 0 0 0 0 0 0 

Mod. Vert. Irreg. -0.9 -0.9 -0.8 0.00 0.45 -0.87 -0.9 

Plan Irregularity -1.3 -1.2 -1.1 0.38 -0.17 -1.37 -1.3 

Pre-Code 0 0 0 0 0 0 0 

Post-Benchmark 0 0 0 0 0 0 0 

Soil B 0 0 0 0 0 0 0 

Soil E - Low-Rise -2.3 -1.4 -0.3 3.46 -0.65 -2.85 -2.3 

Soil E - Mid/High 0 0 0 0 0 0 0 

Min. Score 1.5 0.9 0.8 -2.31 3.27 2.04 1.5 

Score = 2.23 1.5 

Figure 9-3 shows how incorrect failures and incorrect-passing results tend to 

occur near boundaries between seismicity regions. Incorrect failures occur at 

the low values of FASS within each seismicity region; incorrect passing at 

high values. Table 9-6 shows that incorrect failures and incorrect-passing 

results occur in all FEMA Building Types. Table 9-7 shows that they occur 

in all seismicity regions, with the exception of incorrect failures in Low 

seismicity. 

Among the 163,200 samples, 56% of the Final Scores calculated using the 

electronic scoring methodology are higher than the Final Scores calculated 

using the paper-based scoring methodology, 14% are lower, and the 

remaining 30% are the same within ± 0.1. Figure 9-4 shows the distribution 

of the difference. The differences are to be expected. The ranges of FASS and 

FVS1 values for the five hazard regions are all substantial. The upper value is 

generally double the lower, so one would expect the Final Score for a 

building in a location at the high end of the seismicity region to be very 

different from one at the low end. The values of FASS and FVS1 used for the 

paper-based methodology were chosen to provide a conservative estimate of 

Final Score for their seismicity region, which is why one would expect more 

Final Scores in the electronic methodology to be higher than the Final Score 

for paper-based methodology rather than lower. That is, the characteristic 

9-10 9: Technical Background on Electronic Scoring Methodology FEMA P-155 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 
 


 


 


 


 

25% 25% 

20% 20% 

Incorrect failure 

Incorrect passing 

15% 

10% 

15% 

10% 

5% 5%

0% 0%

0.0 1.0 2.0 

FASS, g 

3.0 0.0 1.0 2.0 

FASS, g 

3.0 

(a) (b) 

Figure 9-3 (a) Incorrect failures and (b) incorrect-passing scores resulting from the use of the 

paper-based scoring, as a function of site-specific FASS. 

Table 9-6 Incorrect Failures and Incorrect Passing Resulting from the Use 

of Paper-Based Scoring, by FEMA Building Type 

Model Building Type Incorrect Failure Incorrect Passing 

W1 0.8% 0.8% 

W1A 1.0% 0.7% 

W2 3.1% 1.1% 

S1 8.4% 0.7% 

S2 7.2% 0.9% 

S3 3.4% 1.8% 

S4 7.4% 0.6% 

S5 8.8% 0.7% 

C1 6.8% 1.1% 

C2 6.1% 1.1% 

C3 10.5% 0.7% 

PC1 5.4% 0.8% 

PC2 6.0% 0.8% 

RM1 5.0% 1.3% 

RM2 4.6% 1.4% 

URM 8.3% 0.7% 

MH 3.2% 0.5% 

FEMA P-155 9: Technical Background on Electronic Scoring Methodology 9-11 
 

Table 9-7 Incorrect Failures and Incorrect Passing 

Resulting from the Use of Paper-Based 

Scoring, by Seismicity Region 

Seismicity 

Region 

Incorrect Failure Incorrect Passing 

Low 10.2% 0.0%

 Moderate 1.8% 1.4%

 Mod-High 1.2% 1.5%

 High 0.1% 2.2%

 Very High 3.3% 3.3% 

values of FASS and FVS1 for each seismicity range, the values used to 

calculate structural response and collapse probability for each seismicity 

range, are slightly higher than the average value of the range to avoid 

unconservative scores. In addition, the electronic scoring methodology is 

likely to produce a higher score in practice, because in practice each county 

is assigned the highest seismicity level of any place in the county. 

0.00 

0.10 

0.20 

0.30 

0.40 

Fraction of cases 

-0.8-0.6-0.4-0.2

0.00.20.40.60.81.01.21.41.61.82.02.22.4 

Electronic minus paper Final Score 

Figure 9-4 Distribution of the difference between the Final Score when 

calculated using the electronic method and the paper method. 

On average, the electronic scoring methodology produces a Final Score 0.5 

units higher than the paper-based scoring methodology. The standard 

deviation of the difference between the two is 1.8. 

9-12 9: Technical Background on Electronic Scoring Methodology FEMA P-155 
9.5 Conclusions 

The RVS methodology is approximate. Although it is a building-specific 

methodology, it only uses a few building-specific features, far fewer than are 

used in a Detailed Structural Evaluation. Its many approximations introduce 

substantial uncertainty into the estimate of risk, compared with the Detailed 

Structural Evaluation. However, using electronic scoring can reduce that 

uncertainty by avoiding the approximation of seismic hazard that comes with 

lumping seismic hazard into five seismicity regions. Based on the study 

described above, use of electronic scoring can avoid 6% of cases from 

incorrectly requiring a Detailed Structural Evaluation and 1% of cases from 

incorrectly not requiring a Detailed Structural Evaluation. Since a Detailed 

Structural Evaluation can take days or more of analysis, electronic scoring of 

100 buildings could reduce the required effort required for Detailed 

Structural Evaluation by five buildings (six fewer buildings flagged for 

Detailed Structural Evaluation and one added), potentially saving hundreds 

of labor hours and tens of thousands of dollars’ expense. 

Electronic scoring could potentially avoid other errors. If the electronic 

scoring is part of a system that geolocates buildings, it becomes easier to 

estimate Soil Type and thus avoid unnecessary assumptions and scoring 

errors associated with incorrect Soil Type. If the system also involves using 

satellite imagery, one may be able to more easily identify plan irregularities 

that may be hidden in mid-block buildings by adjacent buildings. If the 

system also involves data entry directly into an electronic database rather 

than paper, one may also avoid transcription errors, along with avoiding the 

expense of transcription. With electronic scoring and an electronic database 

of screened buildings, one can more easily use the screening data as part of a 

broader risk-management program. 

FEMA P-155 9: Technical Background on Electronic Scoring Methodology 9-13 

 

 

Chapter 10 

Benchmarking Studies and 

Trial Runs 

10.1 Purpose 

Throughout the three-year effort to update FEMA 154, numerous 

benchmarking studies and trial runs were performed. They served to check 

the evolving Data Collection Forms for usability and to assess the accuracy 

of the updated FEMA P-154 scores. Insight gained from these benchmarking 

studies and trial runs helped to shape the final Third Edition rapid visual 

screening procedure, resulted in additional guidance within the Handbook, 

and significantly influenced the content and layout of the Third Edition Data 

Collection Forms and Reference Guides. 

10.2 AOC Benchmarking Study1 

In 2003, California’s Administrative Office of the Courts (AOC) developed 

and implemented the Superior Courts of California Seismic Assessment 

Program. A summary report of preliminary findings was published in 2004 

(Administrative Office of the Courts, 2004). The database of seismic 

evaluations of California courthouses created for this program was used for 

benchmarking. The benchmarking study was performed in the first year, and 

again at the midpoint of the third year. The sections below focus on the 

results of the third year benchmarking efforts since they most closely relate 

to the final version of the Third Edition updates. 

10.2.1 Overview of the AOC Seismic Assessment Program 

The purpose of the AOC program was to develop reliable seismic risk 

assessments for California court buildings, of which ownership and 

management responsibility were to be transferred from the county to the state 

level. Seismic assessments of over 200 buildings were performed by 

engineers from eight consulting engineering firms. Each building was 

1

 The benchmarking study presented in this section was performed with draft values 

of Basic Scores and Score Modifiers. In a limited number of instances, Basic Scores 

and Score Modifiers were subsequently revised. Such revisions included adjustments 

to W1A Basic Scores and Post-Benchmark Score Modifiers, and are not expected to 

have a significant effect on the results of this study. 

FEMA P-155 10: Benchmarking Studies and Trial Runs 10-1 
 

assigned a “DSA Risk Level,” where Risk Level I represents repairable 

structural damage and negligible risk to life, and Risk Level VII represents 

total collapse and imminent threat to life. The vast majority of the court 

buildings are rated Risk Level IV (moderate risk to life) or V (substantial risk 

to life). 

The first phase of the evaluation process was an initial screening by the most 

experienced engineers of the eight firms. These engineers reviewed 

construction drawings and, for each building, decided using expert judgment 

whether the seismic performance of the building was obviously acceptable 

(rated as a Risk Level IV or better, indicated as “IVb”) or obviously 

unacceptable (rated as a Risk Level V or worse, indicated as “Vw”). Those 

that could not be obviously assigned a IVb or Vw were sent to a detailed 

evaluation. The detailed evaluation was performed using ASCE/SEI 31-03, 

Seismic Evaluation of Existing Buildings (ASCE, 2003). If the ASCE/SEI 

31-03 Tier 1 evaluation did not result in a conclusive rating, a Tier 2 

evaluation was performed. Based on the ASCE/SEI 31-03 evaluation results, 

each building was assigned to Risk Level IV, Risk Level V, or Risk Level 

VI. 

The buildings evaluated by the AOC are not only numerous, but diverse, 

making this database an attractive resource for benchmarking. The buildings 

include wood, steel, concrete, reinforced masonry, URM and precast 

structures. The oldest was constructed in 1854 and the most recent in 1993. 

They vary from one-story to 17 stories. There are buildings that have been 

retrofitted and buildings with pounding potential. 

The resources used for this benchmarking effort include the following: 

	 AOC Building Matrix: An Excel database that contains key information 

for all 225 buildings including building name, building location, building 

type, building age, number of stories, liquefaction potential, and dates of 

retrofits. Values of SS and S1 are also provided for each building. A 

DSA rating of IVb, IV, V, VI, or Vw is provided for each building. 

	 Initial screening forms for each building. 

	 Final evaluation reports for each building that underwent an ASCE/SEI 

31-03 evaluation. 

10.2.2 Selection of Buildings for Benchmarking 

Of the 225 court buildings that were evaluated, 45 are part of large 

complexes consisting of multiple, adjoining structures. To simplify the 

benchmarking effort and to focus on the accuracy of the Third Edition 

10-2	 10: Benchmarking Studies and Trial Runs FEMA P-155 
 

 

 

 

 

 

 

 

 

 

scoring rather than on the implementation of RVS on complex 

conglomerations of buildings, these 45 courthouses were not considered as 

part of the benchmarking effort. 

Of the remaining 180 buildings, a majority received a DSA Rating of V (114 

total). Roughly a quarter (49 total) of the buildings were selected for this 

benchmarking effort. The buildings were selected such that the 

benchmarking subset would be well distributed by DSA rating, building type, 

building height and building size, building age, and seismicity region. 

The seismicity region for each building was determined based on the AOC 

reported values of SS and S1. The AOC seismicity values are based on the 

1997 NEHRP maps considering Soil Type B and MCE ground motions. The 

MCE values are generally similar to the MCER values considered in the 

Third Edition. In California, the ratio of MCE to MCER varies between 0.9 

and 1.1 (ASCE, 2010). For the purpose of this benchmarking study, the 10% 

variation is ignored and the AOC reported values of SS and S1 are compared 

directly to the criteria of Table 5-1 to determine seismicity region. More 

than half of the buildings are in Very High seismicity (for both the full AOC 

Database and the benchmarking subset). 

Table 10-1 presents the characteristics of the 49 buildings. 

Table 10-1 Characteristics of 49 Benchmarked Buildings 

Building 

Number 

FEMA 

Building Type Building Age 

Number of 

Stories DSA Rating Seismicity Notes 

1 S4 1935 13 V VH 

2 C2 1961 5 V VH 

3 S1 1982 1 IV VH 

4 S4 1977 5 IVb VH 

5 C2 1958 2 V VH Retrofit 

6 RM2 1976 3 V VH 

7 URM 1928 1 V VH 

8 URM 1860 3 VI M 

9 RM1 1968 1 V MH 

10 W2 1963 1 IV MH 

11 RM1 1966 1 V MH 

12 PC1 1964 1 IV M 

13 RM1 1973 2 Vw VH 

14 W2 1982 1 IVb VH 

None of the buildings is identified by name or address in order to protect private information. 

FEMA P-155 10: Benchmarking Studies and Trial Runs 10-3 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 10-1 Characteristics of 49 Benchmarked Buildings (continued) 

Building 

Number 

FEMA 

Building Type Building Age 

Number of 

Stories DSA Rating Seismicity Notes 

15 W2 1950 1 IVb VH Retrofit 

16 S5 1911 3 V M Retrofit 

17 W2 1984 1 IVb M 

18 W2 1974 2 V VH Pounding 

19 URM 1894 2 V MH Retrofit 

20 C2 1923 3 V VH 

21 C2 1922 2 V H 

22 C1 1991 2 IVb MH 

23 C2 1978 1 IV MH 

24 W2 1965 1 IVb VH 

25 C3 1915 3 Vw MH 

26 C2 1983 4 IV VH 

27 RM1 1952 1 V VH 

28 RM1 1972 1 V VH 

29 RM1 1970 1 Vw VH 

30 RM1 1956 1 V VH 

31 S4 1964 7 IV VH 

32 S1 1989 10 V VH 

33 C2 1954 2 Vw VH 

34 C2 1969 2 Vw VH 

35 C2 1950 1 IV MH 

36 C2 1937 2 IV VH 

37 C1 1968 2 Vw VH Pounding 

38 S1 1989 6 IV VH 

39 C2 1926 4 VI VH 

40 S1 1981 3 V H 

41 S2 1976 2 V VH 

42 C1 1965 5 V VH Pounding 

43 W1 1974 1 IV VH 

44 URM 1920 2 Vw MH 

45 C2 1917 3 IV MH 

46 S2 1986 3 V VH Retrofit 

47 C2 1916 2 V VH Retrofit 

48 C2 1903 1 V VH Retrofit 

49 URM 1866 3 IVb VH Retrofit 

None of the buildings is identified by name or address in order to protect private information. 

10-4 10: Benchmarking Studies and Trial Runs FEMA P-155 
Figures 10-1 through 10-6 show the distribution of the building properties. 

Figure 10-1 Distribution of AOC database buildings and benchmarking subset by seismicity 

region. 

Figure 10-2 Distribution of AOC database buildings and benchmarking subset by DSA rating. 

FEMA P-155 10: Benchmarking Studies and Trial Runs 10-5 
Figure 10-3 Distribution of AOC database buildings and benchmarking subset by FEMA 

Building Type. 

Figure 10-4 Distribution of AOC database buildings and benchmarking subset by building 

height. 

10-6 10: Benchmarking Studies and Trial Runs FEMA P-155 
 

Figure 10-5 Distribution of AOC database buildings and benchmarking subset by building 

size. 

Figure 10-6	 Distribution of AOC database buildings and benchmarking subset by building 

age. 

10.2.3 Calculating the RVS Score 

For the benchmarking effort, it was necessary to calculate the RVS score for 

each building under consideration. Because the buildings are located 

FEMA P-155 10: Benchmarking Studies and Trial Runs 10-7 
throughout California, it was not practical to perform an actual rapid visual 

screening of each building. Rather, building characteristics were compiled 

from a variety of sources and the scores were calculated based on these 

characteristics using an Excel spreadsheet. In an actual RVS scenario, the 

building’s age, lateral system, and soil type are not always known and must 

be estimated. For this benchmarking exercise, these building characteristics 

were provided, resulting in more accurate scores than might be expected 

from an actual RVS program. 

Many of the building characteristics needed for RVS are provided in the 

AOC Building Matrix, such as building type and number of stories. 

Additional building characteristics, such as soil type, were determined by 

reviewing the initial screening forms or the final evaluation reports. The 

evaluation reports also provide some information about the presence of 

vertical and plan irregularities, pounding potential, damage and deterioration, 

and details about existing retrofits. Internet tools, such as Google Streetview, 

Google image searches, and http://www.ecourthouses.com, were used as 

secondary sources to view the building and identify irregularities and 

pounding potential. Site visits were made to three selected courthouses to 

confirm building properties. 

Some information on the Level 2 form was estimated. For example, the gap 

between buildings could not be measured, so an approximation was made 

based on available images as to whether pounding potential exists. Unbraced 

cripple walls in W1 buildings were never visible from the photographs. 

Therefore, the accuracy of this Level 2 statement modifier has not been 

verified as part of this benchmarking effort. 

Using a spreadsheet to calculate scores, the following was recorded for each 

building: 

 The Second Edition Score, S, and whether a Detailed Structural 

Evaluation is required. A Detailed Structural Evaluation is considered to 

be required when S < 2.0. 

 The Third Edition Level 1 Score, SL1, and whether a Detailed Structural 

Evaluation is required. A Detailed Structural Evaluation is considered to 

be required when SL1 < 2.0 or if there is another hazard present, such as 

liquefaction or deterioration. 

 The Third Edition Level 2 Score, SL2, and whether a Detailed Structural 

Evaluation is required. A Detailed Structural Evaluation is considered to 

be required when SL2 < 2.0 or if there is another hazard, such as 

liquefaction or deterioration present. 

10-8 10: Benchmarking Studies and Trial Runs FEMA P-155 
 

	 The DSA Risk Level converted to a numerical value (IVb = 3, IV = 4, V 

= 5, Vw and VI = 6). 

10.2.4 Benchmarking Results 

Summary results for the 49 buildings are shown in Table 10-2. “DSE Req’d” 

indicates that the screening triggers a Detailed Structural Evaluation. 

Table 10-2 Summary AOC Benchmarking Results 

Building 

Number 

DSA 

Rating 

Numerical 

DSA Rating 

Second Edition 

S Result 

Third Edition Level 1 

SL1 Result 

Third Edition Level 2 

SL2 Result 

1 V 5 1.2 DSE Req'd 0.5 DSE Req'd 0.9 DSE Req'd 

2 V 5 1.6 DSE Req'd 0.5 DSE Req'd 0.1 DSE Req'd 

3 IV 4 2.2 1.5 DSE Req'd 0.8 DSE Req'd 

4 IVb 3 2.7 1.7 DSE Req'd 2.7 

5 V 5 1.2 DSE Req'd 0.5 DSE Req'd 1.7 DSE Req'd 

6 V 5 1.2 DSE Req'd 0.4 DSE Req'd 0.6 DSE Req'd 

7 V 5 0.5 DSE Req'd 0.5 DSE Req'd 0.6 DSE Req'd 

8 VI 6 1.5 DSE Req'd 1.9 DSE Req'd 1.8 DSE Req'd 

9 V 5 2.2 1.8 DSE Req'd 1.8 DSE Req'd 

10 IV 4 3.0 3.2 3.5 

11 V 5 1.7 DSE Req'd 1.1 DSE Req'd 2.1 

12 IV 4 1.5 DSE Req'd 0.4 DSE Req'd 2.1 

13 Vw 6 1.7 DSE Req'd 0.7 DSE Req'd 1.1 DSE Req'd 

14 IVb 3 4.9 3.3 3.8 

15 IVb 3 2.5 1.2 DSE Req'd 2.8 

16 V 5 2.2 2.4 3.8 

17 IVb 3 2.9 6.0 7.5 

18 V 5 2.9 2.4 DSE Req'd 2.2 

19 V 5 0.5 DSE Req'd 0.7 DSE Req'd 2.2 

20 V 5 0.7 DSE Req'd 0.5 DSE Req'd 1.0 DSE Req'd 

21 V 5 1.8 DSE Req'd 1.2 DSE Req'd 1.2 DSE Req'd 

22 IVb 3 3.3 3.6 3.6 

23 IV 4 2.2 2.1 2.1 

24 IVb 3 5.4 3.8 3.8 

25 Vw 6 -0.1 DSE Req'd 0.6 DSE Req'd 1.0 DSE Req'd 

26 IV 4 1.1 DSE Req'd 0.3 DSE Req'd 0.7 DSE Req'd 

27 V 5 1.7 DSE Req'd 0.7 DSE Req'd 1.1 DSE Req'd 

28 V 5 1.7 DSE Req'd 0.7 DSE Req'd 1.1 DSE Req'd 

FEMA P-155 10: Benchmarking Studies and Trial Runs 10-9 
 

 

Table 10-2 Summary AOC Benchmarking Results (continued) 

Building 

Number 

DSA 

Rating 

Numerical 

DSA 

Rating 

Second Edition 

S Result 

Third Edition Level 1 

SL1 Result 

Third Edition Level 2 

SL2 Result 

29 Vw 6 1.9 DSE Req'd 0.7 DSE Req'd 1.3 DSE Req'd 

30 V 5 2.2 1.1 DSE Req'd 1.1 DSE Req'd 

31 IV 4 1.1 DSE Req'd 0.5 DSE Req'd 1.3 DSE Req'd 

32 V 5 1.3 DSE Req'd 0.5 DSE Req'd 1.0 DSE Req'd 

33 Vw 6 0.7 DSE Req'd 0.3 DSE Req'd 0.6 DSE Req'd 

34 Vw 6 2.4 1.2 DSE Req'd 1.2 DSE Req'd 

35 IV 4 1.7 DSE Req'd 0.6 DSE Req'd 1.2 DSE Req'd 

36 IV 4 -0.3 DSE Req'd 0.3 DSE Req'd 1.3 DSE Req'd 

37 Vw 6 -0.1 DSE Req'd 0.3 DSE Req'd 0.3 DSE Req'd 

38 IV 4 2.6 1.5 DSE Req'd 1.5 DSE Req'd 

39 VI 6 1.6 DSE Req'd 1.0 DSE Req'd 1.0 DSE Req'd 

40 V 5 0.9 DSE Req'd 0.5 DSE Req'd 0.5 DSE Req'd 

41 V 5 1.9 DSE Req'd 0.9 DSE Req'd 1.4 DSE Req'd 

42 V 5 2.3 1.0 DSE Req'd 0.3 DSE Req'd 

43 IV 4 4.4 2.1 2.1 

44 Vw 6 1.2 DSE Req'd 1.2 DSE Req'd 1.2 DSE Req'd 

45 IV 4 0.7 DSE Req'd 0.3 DSE Req'd 2.2 

46 V 5 0.9 DSE Req'd 0.7 DSE Req'd 1.7 DSE Req'd 

47 V 5 1.2 DSE Req'd 1.0 DSE Req'd 1.5 DSE Req'd 

48 V 5 0.4 DSE Req'd 0.3 DSE Req'd 0.7 DSE Req'd 

49 IVb 3 1.0 DSE Req'd 0.9 DSE Req'd 2.1 DSE Req'd 

Numerical DSA ratings are plotted against RVS scores for Second Edition, 

Third Edition Level 1, and Third Edition Level 2 in Figure 10-7, Figure 10-8, 

and Figure 10-9, respectively. Linear trendlines are also shown, including 

the R-squared values, which indicate the relative correlation between the 

numerical DSA rating and the resulting RVS score. An R-squared value of 

1.0 indicates perfect correlation, while an R-squared value of zero indicates 

that there is no correlation. The correlation is best for the Third Edition 

Level 2 screening results. 

The plots of RVS Score versus Numerical DSA Rating shown in Figure 10-7 

through Figure 10-9 show that for any given DSA rating, the RVS screening 

can result in a range of scores (S, SL1, or SL2). Averaging the scores of a 

group of buildings with similar DSA Ratings results in a trend of decreasing 

average score versus increasing DSA Rating, as desired. 

10-10 10: Benchmarking Studies and Trial Runs FEMA P-155 
Figure 10-7 Second Edition Score versus DSA Rating. 

Figure 10-8 Third Edition Level 1 Score versus DSA Rating. 

FEMA P-155 10: Benchmarking Studies and Trial Runs 10-11 
 

 

 

Figure 10-9 Third Edition Level 2 Score versus DSA Rating. 

Table 10-3 shows the RVS results by DSA Rating. 

Table 10-3 RVS Results by DSA Rating 

DSA Rating IVb IV V Vw or 

VI 

Number of Buildings 7 11 22 9 

Second Edition 

Average S 3.2 1.8 1.5 1.2 

Number of DSE Req’d 1 6 17 8 

Percentage of DSE Req’d 14% 55% 77% 89% 

Level 1 

Average SL1 2.9 1.2 0.9 0.9 

Number of DSE Req’d 3 8 21 9 

Percentage of DSE Req’d 43% 73% 95% 100% 

Level 2 

Average SL2 3.8 1.7 1.3 1.1 

Number of DSE Req’d 1 6 18 9 

Percentage of DSE Req’d 14% 55% 82% 100% 

“DSE Req'd” indicates that the screening triggers a Detailed Structural Evaluation. 

It is most helpful to consider the set of buildings with DSA Rating of IVb. 

Recall that buildings with DSA Ratings of IVb were those that were deemed 

obviously acceptable during the initial screening phase. The initial screening 

phase was performed by engineers highly experienced in the seismic design 

and evaluation of buildings. Each engineer had experience exceeding the 

requirements for Level 2 screeners defined in FEMA P-154 Chapter 2. 

10-12 10: Benchmarking Studies and Trial Runs FEMA P-155 
 

 

During the initial screening phase, these experienced engineers often had the 

benefit of access to construction drawings. The engineers worked in pairs, 

typically spending 30 minutes per building. Through this process, seven of 

the 49 selected buildings (14%) were given a DSA Rating of IVb (when 

considering the full AOC stock, approximately 10% of the buildings received 

DSA Ratings of IVb). The experienced engineers indicated that 42 of the 49 

buildings (86%) were either obviously unacceptable (DSA Rating Vw) or 

required more detailed evaluations. 

By comparison, the Second Edition screening sent only 65% of buildings to a 

Detailed Structural Evaluation, while the Third Edition Level 1 screening 

sent 86% of buildings to a Detailed Structural Evaluation. The Third Edition 

Level 2 screenings sent 70% of the buildings to a Detailed Structural 

Evaluation. 

10.2.5 Benchmarking Conclusions and Recommendations 

The AOC Benchmarking results show that the Third Edition Level 1 scores 

are typically smaller than the Second Edition scores. One cause of this is the 

increased seismicity considered by the Third Edition. Many of the buildings 

(33 out of 49) were considered Very High seismicity by the Third Edition, 

corresponding to ground motions of SS = 2.25g and S1 = 0.90g. All of these 

buildings were considered High seismicity by the Second Edition, 

corresponding to ground motions of SS = 1.23g and S1 = 0.45g. The increase 

in considered seismicity contributes to the decrease in score in the Third 

Edition. (If all the buildings in Very High seismicity were instead 

considered to be in High seismicity, the average Level 1 Score, SL1, increases 

from 1.2 to 1.5, which more closely aligns with the average Second Edition 

Score, S, of 1.8) In addition, the removal of the benefit for mid- and high-rise 

buildings also contributes to the decrease in scores from the Second Edition 

to the Third Edition. 

The AOC Benchmarking results show that Level 1 scores are typically 

smaller than the Level 2 scores. Level 1 screenings trigger Detailed 

Structural Evaluations more often than Level 2 screenings (86% versus 

70%), typically due to the more severe treatment of vertical and plan 

irregularities in the Level 1 screening and the absence of benefit for retrofits 

in Level 1. In particular, the criteria for reentrant corners in Level 2 are 

much narrower than in Level 1.2 

2

 The Level 2 criterion for reentrant corners was revised subsequent to this 

benchmarking study. The final Level 2 criterion is closer to the Level 1 criterion. 

FEMA P-155 10: Benchmarking Studies and Trial Runs 10-13 
 

 

The percentage of buildings that are sent to Detailed Structural Evaluations 

in the benchmarking study is consistent with the percentage of buildings 

recommended for detailed evaluations by experienced engineers in the initial 

screening phase for the AOC study and helps confirm the FEMA P-154 RVS 

methodology and cut-off score selection as appropriate. The AOC buildings 

are located in areas of high seismicity. It should be noted that screenings 

conducted in areas of lower seismicity should expect a smaller number of 

buildings to require Detailed Structural Evaluations. 

10.3 Trial Runs 

In order to study the usability of the Third Edition rapid visual screening 

procedure, trial runs were performed. Throughout the three-year update 

project, team members from around the country performed rapid visual 

screenings using continuously evolving Data Collection Forms. Feedback 

from team members was used to improve the forms and reference guides, as 

well as the screening advice in the Handbook. 

10.3.1 Year 1 Trial Runs 

In Year 1, the Data Collection Form was updated and expanded to include an 

optional Level 2 screening. Trial screenings were performed using an early 

draft of this updated and expanded Data Collection Form. 

Members of the Project Technical Committee screened seventeen buildings 

in Memphis, Salt Lake City, and the San Francisco Bay Area. FEMA 

Building Types screened included W2, S1, S4, C1, C2, C3, RM1, and URM. 

All the buildings were assumed to be in High seismicity so that a single form 

could be used. 

The screeners were asked to consider and provide feedback on the following 

topics: 

	 How long did each Level 1 screening take? How long did each Level 2 

screening take? 

	 Are the forms easy to use? 

	 Did the Level 1 and Level 2 scores appear appropriate? Were the Level 

2 scores generally higher than the Level 1 scores? 

	 Do the plan irregularity questions on the Level 2 form appear 

appropriate? In particular, is the first question (about torsional 

irregularity) too vague? Is the modifier too severe? 

10-14	 10: Benchmarking Studies and Trial Runs FEMA P-155 
	 Do you have any other recommendations on revisions to the form that 

would make it easier to use or more accurate? 

The Level 1 screening typically took 20 minutes (ranging from 10 to 30 

minutes), and the Level 2 screening typically took 10 minutes (ranging from 

5 to 20 minutes). The Level 2 scores were often lower than the Level 1 

scores. In many cases, this was due to the effect of pounding, which was not 

considered in the Level 1 score (the building is directed to go straight to a 

Detailed Structural Evaluation), but did reduce the Level 2 score. All the 

buildings that were found to pass the Level 1 screening also passed the Level 

2 screening. In one case, a building that failed the Level 1 screening passed 

the Level 2 screening. 

The screeners provided valuable comments on the content, formatting, and 

layout of the forms. For example, one screener noted that a place was 

needed on the top of the Level 2 form to identify the name of the building 

being screened. These comments were used to improve the form. The 

screeners also commented on additions that should be made to the 

Handbook. For example, one noted that guidance should be provided on 

when to consider two linked buildings as one or as separate. This later led to 

the Building Additions Reference Guide. 

The screeners also commented on issues relating to scoring. Several felt that 

the Level 2 form did not capture enough issues, and they provided 

suggestions for additional Level 2 statements. 

10.3.2 Year 2 Trial Runs 

In Year 2, a workshop was held in the San Francisco Bay Area. Participants 

of the workshop included the Project Technical Committee, the Project 

Review Panel, and past users of Second Edition FEMA 154. Workshop 

participants performed trial screenings at the workshop. They were provided 

with a packet of information that, for each of six buildings, contained a 

narrative description of the building, a Level 1 form and a Level 2 form filled 

with partial “pre-field” information, and photographs of the building. The 

Project Technical Committee members who developed the examples were 

available in the room to answer questions. The workshop participants were 

also given the Reference Guides and a listing of the benchmark years. 

The workshop participants performed the trial runs and then were asked for 

their feedback on the forms. Valuable feedback was provided on the Level 2 

statements. For example, a Level 2 statement meant to capture the benefit of 

a redundant gravity system was revised to emphasize redundancy rather than 

regularity. The exercise also highlighted items that required additional 

FEMA P-155 10: Benchmarking Studies and Trial Runs 10-15 
 

guidance, such as how to consider certain types of additions and how to 

avoid double counting of irregularities that may be both plan and vertical in 

nature. 

10.3.3 Year 3 Trial Runs 

In Year 3, members of the Project Technical Committee again performed 

trial runs using the latest Data Collection Forms. Screeners generally found 

the forms to be easy to use and the guidance in the Handbook complete. 

Some suggestions were made for updates to the forms and the reference 

guides in the Handbook. Revisions to the final forms and Handbook were 

implemented accordingly. 

As a second part to this Trial Run exercise, members of the Project Technical 

Committee used previously performed screenings to consider how Second 

Edition scores could be converted to Third Edition scores and to highlight 

potential issues. 

10.4 Conclusions 

Much effort has been spent attempting to optimize the Third Edition RVS 

procedure for ease of use and accuracy of results. The Third Edition 

procedure is more comprehensive than the Second Edition procedure, and it 

retains the layout and ease of use of the Second Edition. The benchmarking 

and trial run results generally show that RVS screening results are reasonably 

consistent with the judgment of experienced engineers. 

10-16 10: Benchmarking Studies and Trial Runs FEMA P-155 
 

 

 

 

 

Appendix A 

Third Edition Scoring Parameters 

Tables A-1 through A-11 provide the parameter values used in the Third 

Edition scoring update. See Chapter 4 and Chapter 5 for additional 

information. CAC (2010), FEMA (2009a), and FEMA (2003) contain the 

sources for OSHPD HAZUS, HAZUS TM, and HAZUS AEBM, 

respectively. 

Table A-1 Building Height, HR, and Elastic Period, Te 

No. 

Stories 

W1, W2 

HR Te 

S1 

HR Te 

S2 

HR Te 

S3, PC1 

HR Te 

S4, S5 

HR Te 

C1 

HR Te 

C2, C3, PC2, 

RM1, RM2, 

URM 

HR Te 

MH 

HR Te 

1 14 0.35 14 0.4 14 0.4 15 0.35 14 0.35 12 0.40 12 0.35 10 0.35 

2 24 0.38 24 0.5 24 0.43 25 0.39 24 0.35 20 0.40 20 0.35 

3 34 0.49 36 0.69 36 0.59 35 0.50 36 0.44 30 0.48 30 0.39 

4 44 0.60 48 0.87 48 0.73 48 0.55 40 0.62 40 0.48 

5 54 0.70 60 1.04 60 0.86 60 0.65 50 0.76 50 0.57 

6 72 1.20 72 0.99 72 0.74 60 0.89 60 0.65 

7 84 1.36 84 1.11 84 0.84 70 1.03 70 0.73 

8 96 1.51 96 1.22 96 0.92 80 1.16 80 0.81 

9 108 1.66 108 1.34 108 1.01 90 1.29 90 0.88 

10 120 1.81 120 1.45 120 1.09 100 1.41 100 0.95 

11 132 1.95 132 1.55 132 1.17 110 1.54 110 1.02 

12 144 2.09 144 1.66 144 1.25 120 1.67 120 1.09 

13 156 2.23 156 1.76 156 1.33 130 1.79 130 1.16 

14 168 2.36 168 1.86 168 1.40 140 1.91 140 1.23 

15 180 2.50 180 1.96 180 1.48 150 2.04 150 1.29 

Notes: 

1. Values of HR and Te are taken from OSHPD HAZUS Table A6-3 for all FEMA Building Types except MH.

2. Values for MH are taken from HAZUS TM Table 5.1.

FEMA P-155 A: Third Edition Scoring Parameters A-1 
 

 

 

 

 

Table A-2a Seismic Design Coefficient, CS, for Calculating Basic Scores 

No. 

Stories L 

W1, S3 

M MH 

H, 

VH 

W2, S1, S2, S4, C1, C2, PC1, 

PC2, RM1, RM2 

L M MH 

H, 

VH L 

S5, C3, URM 

M MH 

H, 

VH 

MH 

L M MH 

H, 

VH 

1 0.1 0.1 0.125 0.15 0.055 0.055 0.082 0.109 0.055 0.055 0.055 0.055 0.100 0.100 0.100 0.100 

2 0.1 0.1 0.125 0.15 0.046 0.046 0.069 0.092 0.046 0.046 0.046 0.046 

3 0.1 0.1 0.125 0.15 0.040 0.040 0.060 0.080 0.040 0.040 0.040 0.040 

4 0.1 0.1 0.125 0.15 0.036 0.036 0.053 0.071 0.035 0.035 0.035 0.035 

5 0.032 0.032 0.047 0.063 0.032 0.032 0.032 0.032 

6 0.029 0.029 0.043 0.057 0.029 0.029 0.029 0.029 

7 0.026 0.026 0.039 0.052 0.026 0.026 0.026 0.026 

8 0.024 0.024 0.036 0.048 0.024 0.024 0.024 0.024 

9 0.022 0.022 0.033 0.044 0.022 0.022 0.022 0.022 

10 0.021 0.021 0.031 0.041 0.021 0.021 0.021 0.021 

11 0.020 0.020 0.029 0.039 0.019 0.019 0.019 0.019 

12 0.018 0.018 0.027 0.036 0.018 0.018 0.018 0.018 

13 0.017 0.017 0.026 0.034 0.017 0.017 0.017 0.017 

14 0.016 0.016 0.024 0.032 0.016 0.016 0.016 0.016 

15 0.016 0.016 0.023 0.031 0.015 0.015 0.015 0.015 

Notes: (See Chapter 5 for additional explanation) 

1.	 Values of CS are taken from OSHPD HAZUS Table A6-2a and A6-2b using the following mapping (with exceptions

noted below): 

Seismicity Source 

L Zone 3, Pre-1961 

M Zone 3, Pre-1961 

MH Average of H and M values 

H,VH Zone 4, Pre-1961 

2. Values of CS for S5, C3, and URM are set equal to Zone 3, Pre-1961 values for all seismicity regions.

3.	 Values of CS for W1 and MH are taken from HAZUS TM Table 5.4 using the following mapping:

Seismicity Source 

L Pre-Code 

M Low-Code 

MH Average of H and M values 

H,VH Moderate-Code

4. Values of CS for S3 are set equal to W1 values.

A-2 A: Third Edition Scoring Parameters FEMA P-155 
 

 

 

 

Table A-2b Seismic Design Coefficient, CS, for Calculating Pre-Code Score Modifiers 

No. 

Stories L 

W1, S3 

M MH 

H, 

VH 

W2, S1, S2, S4, C1, C2, PC1, 

PC2, RM1, RM2 

L M MH 

H, 

VH L 

S5, C3, URM 

M MH 

H, 

VH 

MH 

L M MH 

H, 

VH 

1 0.1 0.1 0.1 0.1 0.055 0.055 0.055 0.055 0.055 0.055 0.055 0.055 0.100 0.100 0.100 0.100 

2 0.1 0.1 0.1 0.1 0.046 0.046 0.046 0.046 0.046 0.046 0.046 0.046 

3 0.1 0.1 0.1 0.1 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 

4 0.1 0.1 0.1 0.1 0.035 0.035 0.035 0.035 0.035 0.035 0.035 0.035 

5 0.032 0.032 0.032 0.032 0.032 0.032 0.032 0.032 

6 0.029 0.029 0.029 0.029 0.029 0.029 0.029 0.029 

7 0.026 0.026 0.026 0.026 0.026 0.026 0.026 0.026 

8 0.024 0.024 0.024 0.024 0.024 0.024 0.024 0.024 

9 0.022 0.022 0.022 0.022 0.022 0.022 0.022 0.022 

10 0.021 0.021 0.021 0.021 0.021 0.021 0.021 0.021 

11 0.019 0.019 0.019 0.019 0.019 0.019 0.019 0.019 

12 0.018 0.018 0.018 0.018 0.018 0.018 0.018 0.018 

13 0.017 0.017 0.017 0.017 0.017 0.017 0.017 0.017 

14 0.016 0.016 0.016 0.016 0.016 0.016 0.016 0.016 

15 0.016 0.016 0.016 0.016 0.015 0.015 0.015 0.015 

Notes: (See Chapter 5 for additional explanation) 

1.	 Values of CS are taken from OSHPD HAZUS Table A6-2a and A6-2b using the following mapping (with exceptions

noted below): 

Seismicity Source 

L Zone 3, Pre-1961 

M Zone 3, Pre-1961 

MH Zone 3, Pre-1961 

H,VH Zone 3, Pre-1961 

2. Values of CS for W1 and MH are taken from HAZUS TM Table 5.4 using the following mapping:

Seismicity Source 

L Pre-Code 

M Pre-Code

MH Average of H and M values 

H,VH Low-Code 

3. Values of CS for S3 are set equal to W1 values.

FEMA P-155 A: Third Edition Scoring Parameters A-3 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table A-2c Seismic Design Coefficient, CS, for Calculating Post-Benchmark Score Modifiers 

No. 

Stories L 

W1, S3 

M MH 

H, 

VH 

W2, S1, S2, S4, C1, C2, 

PC1, PC2, RM1, RM2 

L M MH 

H, 

VH 

S5, C3, URM 

L M MH 

H, 

VH 

MH 

L M MH H, VH 

1 0.100 0.150 0.219 0.300 0.055 0.109 0.204 0.327 0.100 0.100 0.125 0.150 

2 0.100 0.150 0.219 0.300 0.046 0.092 0.173 0.276 

3 0.100 0.150 0.219 0.300 0.040 0.080 0.150 0.240 

4 0.100 0.150 0.219 0.300 0.036 0.071 0.133 0.213 

5 0.032 0.063 0.118 0.189 

6 0.029 0.057 0.107 0.171 

7 0.026 0.052 0.098 0.156 

8 0.024 0.048 0.090 0.144 

9 0.022 0.044 0.083 0.132 

10 0.021 0.041 0.077 0.123 

11 0.020 0.039 0.073 0.117 

12 0.018 0.036 0.068 0.108 

13 0.017 0.034 0.064 0.102 

14 0.016 0.032 0.060 0.096 

15 0.016 0.031 0.058 0.093 

Notes: (see Chapter 5 for additional explanation): 

1. Values of CS are from Table A-2b adjusted by the following factors:

Seismicity W1, S3 MH 

All other FEMA 

Building Types 

L 1.0 1.0 1.0 

M 1.5 1.0 2.0 

MH 1.8 1.25 2.5 

H,VH 2.0 1.5 3.0 

2. Post-Benchmark Score Modifiers are not calculated for S5, C3, and URM.

A-4 A: Third Edition Scoring Parameters FEMA P-155 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table A-3 Gamma, γ, and Lambda, λ, Factors 

No. 

Stories 

MH 

All 

Other 

FEMA 

Building 

Types 

γ

W1, 

W2, S1, 

S3, C1, 

C2 S4, C3 

S2, S5, 

PC2, 

RM1, 

RM2 

PC1, 

URM 

λ, Basic Score 

MH 

W1, 

W2, S1, 

S3, C1, 

C2 S4, C3 

S2, S5, 

PC2, 

RM1, 

RM2 

PC1, 

URM 

λ, Pre-Code 

MH 

1 1.50 2.70 2.00 1.83 1.67 1.33 2.00 1.50 1.42 1.33 1.17 1.50 

2 2.50 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

3 2.25 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

4 2.00 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

5 1.88 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

6 1.80 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

7 1.75 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

8 1.71 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

9 1.69 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

10 1.67 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

11 1.65 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

12 1.65 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

13 1.65 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

14 1.65 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

15 1.65 2.00 1.83 1.67 1.33 1.50 1.42 1.33 1.17 

Notes: (See Chapter 5 for additional explanation) 

1.	 For all FEMA Building Types except S3 and MH:

Values of γ are taken from OSHPD HAZUS Table A6-5.

Values of λ for Basic Score calculations are taken from OSHPD HAZUS Table A6-5 considering Baseline

performance.
 

Values of λ for Pre-Code calculations are taken from OSHPD HAZUS Table A6-5 considering USB performance.

2.	 S3 values set equal to W1 values.

3.	 For MH:

Value of γ is taken from HAZUS TM Table 5.5.

Value of λ for Basic Score calculation is taken from HAZUS TM Table 5.5.
 

Value of λ for Pre-Code calculation is taken as 0.75 of the Basic Score value.

FEMA P-155 A: Third Edition Scoring Parameters A-5 
 

Table A-4 Ductility Factor, μ

No. Stories 

All FEMA Building Types 

Ductility, μ, Basic Score 

All FEMA Building Types 

Ductility, μ, Post-Benchmark 

1 6.00 7.98

2 6.00 7.98

3 4.94 6.57

4 4.41 5.87

5 4.07 5.41

6 3.82 5.08

7 3.63 4.83

8 3.48 4.63

9 3.35 4.46

10 3.24 4.31

11 3.15 4.19

12 3.07 4.08

13 3.00 3.99

14 3.00 3.99

15 3.00 3.99

Notes: (See Chapter 5 for additional explanation) 

1.	 Values of μ for Basic Score calculations are taken from OSHPD HAZUS Table

A6-6. 

2.	 Values of μ for Post-Benchmark calculations are taken as 1.33 of the Basic Score

value. 

A-6 A: Third Edition Scoring Parameters FEMA P-155 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table A-5 Alpha 1, α1, and Alpha 2, α2, Factors 

No. 

Stories 

S1, C1, PC1, 

URM 

W1, W2, S2, S3, S4, 

S5, C2, C3, PC2, RM1, 

RM2 

α1 

MH 

All FEMA 

Building Types 

(except MH) MH 

α2 

1 0.75 0.80 1.00 0.75 1.00

2 0.75 0.80 0.75

3 0.75 0.80 0.75

4 0.75 0.80 0.75

5 0.75 0.80 0.75

6 0.73 0.79 0.72

7 0.71 0.78 0.69

8 0.69 0.77 0.66

9 0.67 0.76 0.63

10 0.65 0.75 0.60

11 0.65 0.75 0.60

12 0.65 0.75 0.60

13 0.65 0.75 0.60

14 0.65 0.75 0.60

15 0.65 0.75 0.60

Notes: (See Chapter 5 for additional explanation) 

1. Values of α1 and α2 are taken from OSHPD HAZUS Table A6-4.

2. S5 values set equal to S4 values.

FEMA P-155 A: Third Edition Scoring Parameters A-7 
 

 

 

Table A-6 Alpha 3, α3, Modal Factors 

No. Stories α3, Basic Score 

α3, Moderate Vertical 

Irregularity 

α3, Severe Vertical 

Irregularity 

1 1.00 1.00 1.00

2 1.21 1.62 2.03

3 1.35 2.04 2.73

4 1.45 2.36 3.27

5 1.54 2.63 3.72

6 1.62 2.87 4.00

7 1.69 3.07 4.00

8 1.75 3.26 4.00

9 1.81 3.43 4.00

10 1.86 3.59 4.00

11 1.91 3.73 4.00

12 1.96 3.87 4.00

13 2.00 4.00 4.00

14 2.04 4.00 4.00

15 2.08 4.00 4.00

Notes: (See Chapter 5 for additional explanation) 

1.	 Values of α3 for Basic Score calculations are taken from OSHPD HAZUS Table A6-10

considering Baseline performance. 

2.	 Values of α3 for Moderate Vertical Irregularity calculations are taken from OSHPD HAZUS

Table A6-10 considering SubBase performance combined with SubBase Interstory Drift Ratios. 

3.	 Values of α3 for Severe Vertical Irregularity calculations are taken from OSHPD HAZUS

Table A6-10 considering USB performance combined with SubBase Interstory Drift Ratios. 

A-8 A: Third Edition Scoring Parameters FEMA P-155 
 

Table A-7 Elastic Damping, βE

FEMA 

Building 

Type Elastic Damping (βE) 

W1 10.00

W2 10.00

S1 5.00

S2 5.00

S3 5.00

S4 5.00

S5 7.00

C1 7.00

C2 7.00

C3 7.00

PC1 7.00

PC2 7.00

RM1 7.00

RM2 7.00

URM 7.00

MH 5.00

Notes: (See Chapter 5 for additional explanation) 

1.	 Values of βE are taken from OSHPD HAZUS Table A6-7 for all FEMA Building

Types except URM and MH. 

2.	 Value of βE for URM set equal to C3 and S5.

3.	 Value of βE for MH is taken from HAZUS AEBM Table 5.1.

FEMA P-155 A: Third Edition Scoring Parameters A-9 
 

 

 

Table A-8 Degradation Factor, κ

Seismicity Region 

L M MH H, VH 

Basic Score 0.3 0.3 0.4 0.4

Pre-Code 0.3 0.3 0.4 0.4

Post-Benchmark 0.45 0.45 0.6 0.668

Notes: (See Chapter 5 for additional explanation) 

1.	 Values of κ for Basic Score calculations are taken from OSHPD HAZUS

Table A6-8 using the following mapping: 

Seismicity 

Scenario Earthquake Criteria (Minimum Distance to 

Fault, Maximum Magnitude) 

L > 50 km, Baseline Performance, Pre-1961 

M 25 - 50 km, M > 7.0, Baseline Performance, Pre-1961 

MH 10 - 25 km, M > 7.0, Baseline Performance, Pre-1961 

H,VH 10 - 25 km, M > 7.0, Baseline Performance, Pre-1961 

2. Values of κ for Post-Benchmark calculations are based on scaled Basic

Score values using the following:

Seismicity Source 

L 1.5 x Basic Score Value 

M 1.5 x Basic Score Value 

MH 1.5 x Basic Score Value 

H,VH 1.67 x Basic Score Value 

A-10 A: Third Edition Scoring Parameters FEMA P-155 
Table A-9 Story Drift Ratio, ΔC

L 

W1, W2 

M MH 

H, 

VH 

S1, S2, S5, C2 S3, S4, PC1, RM1, RM2 

L M MH 

H, 

VH L M MH 

H, 

VH L 

C1 

M MH 

H, 

VH L 

PC2 

M MH 

H, 

VH L 

C3, U

M 

Basic Score 0.075 0.075 0.075 0.075 0.050 0.050 0.055 0.060 0.044 0.044 0.049 0.053 0.035 0.035 0.035 0.035 0.035 0.035 0.035 0.035 0.035 0.035 

Plan Irregularity 0.038 0.038 0.038 0.038 0.025 0.025 0.028 0.030 0.022 0.022 0.025 0.027 0.018 0.018 0.018 0.018 0.018 0.018 0.018 0.018 0.018 0.018 

Severe or Moderate Vertical Irregularity 

0.06 0.06 0.06 0.06 0.040 0.040 0.045 0.050 0.035 0.035 0.040 0.044 0.028 0.028 0.028 0.028 0.028 0.028 0.028 0.028 0.028 0.028 

Pre-Code Modifiers 0.075 0.075 0.075 0.075 0.05 0.05 0.05 0.05 0.044 0.044 0.044 0.044 0.035 0.035 0.035 0.035 0.035 0.035 0.035 0.035 0.035 0.035 

PostBenchmark Modifiers 

0.094 0.094 0.113 0.125 0.063 0.063 0.083 0.1 0.055 0.055 0.073 0.089 0.063 0.063 0.083 0.1 0.055 0.055 0.073 0.089 

Notes: (See Chapter 5 for additional explanation) 

1. Values of ∆C are taken from OSHPD HAZUS Table A6-9 using the following mapping (with exceptions noted below):

Seismicity Basic Score Source Plan Irregularity Source Severe or Moderate Vertical Irregularity Source Pre-Code Sourc

L Pre-61, Baseline Pre-61, USB Pre-61, SubBase Pre-61, Baseline M Pre-61, Baseline Pre-61, USB Pre-61, SubBase Pre-61, Baseline MH Average of H and M values Average of H and M values Average of H and M values Pre-61, Baseline 

H,VH Post-61, Baseline Post-61, USB Post-61, SubBase Pre-61, Baseline 

2. Values for S5 are set equal to values for S1, S2, and C2.3. Values for C1 are set equal to values for C3 and URM for all but Post-Benchmark calculations. Values of C1 for Post-Benchmark calculations are 

4. Values for PC2 are set equal to values for C3 and URM for all but Post-Benchmark calculations. Values of PC2 for Post-Benchmark calculations 

5. Values for MH are taken from HAZUS TM Table 5.9 using the following mapping:

Seismicity Basic Score Source Plan Irregularity Source Severe or Moderate Vertical Irregularity Source Pre-Code Source 

L Pre-Code 1/2 x Basic Score Value Basic Score Value Pre-Code 

M Low-Code 1/2 x Basic Score Value Basic Score Value Pre-Code 

MH Average of H and M values 1/2 x Basic Score Value Basic Score Value Average of H and M H,VH Moderate-Code 1/2 x Basic Score Value Basic Score Value Low-Code 

FEMA P-155 A: Third Edition Scoring Parameters 
 

 

Table A-10 Lognormal Standard Deviation, βC,D 

No. 

Stories 

All FEMA Building Types 

βC,D, Basic Score 

All FEMA Building Types 

βC,D, Pre-Code 

S1 

βC,D, 

Post-Benchmark 

All FEMA Building Types 

(except S1) 

βC,D, Post-Benchmark 

1 0.95 1.00 0.75 0.85 

2 0.95 1.00 0.75 0.85 

3 0.95 1.00 0.75 0.85 

4 0.94 0.99 0.75 0.84 

5 0.93 0.98 0.75 0.83 

6 0.92 0.97 0.75 0.82 

7 0.91 0.96 0.75 0.81 

8 0.90 0.95 0.75 0.80 

9 0.89 0.94 0.75 0.79 

10 0.88 0.93 0.75 0.78 

11 0.87 0.92 0.75 0.77 

12 0.86 0.91 0.75 0.76 

13 0.85 0.90 0.75 0.75 

14 0.85 0.90 0.75 0.75 

15 0.85 0.90 0.75 0.75 

Notes: (See Chapter 5 for additional explanation) 

1.	 Values of βC,D for Basic Score calculations are taken from OSHPD HAZUS Table A6-11 considering Post-61 

SubBase performance. 

2.	 Values of βC,D for Pre-Code calculations are taken from OSHPD HAZUS Table A6-11 considering Pre-61 SubBase 

performance. 

3.	 Values of βC,D for Post-Benchmark calculations are taken from OSHPD HAZUS Table A6-11 considering Post-61 

Baseline performance, except values of βC for Post-Benchmark S1 calculations are reduced by engineering 

judgment. 

Table A-11 Collapse Factor (P[COL|STR5]) 

W1, W2, MH S1, S2, S3, S4, S5 C1, C2, C3, RM1, RM2 PC1, PC2, URM 

Basic Score 0.05 0.08 0.13 0.15 

Severe Vertical Irregularity 0.20 0.30 0.50 0.60 

Moderate Vertical Irregularity 

and Plan Irregularity 0.10 0.15 0.25 0.30 

Notes: (See Chapter 5 for additional explanation) 

1.	 Values of P[COL|STR5] are taken from OSHPD HAZUS Table A6-12. 

2.	 Values for Basic Score calculations use Baseline performance. 

Values for Severe Vertical Irregularity use USB performance. 

Values for Moderate Vertical Irregularity and Plan Irregularity use SubBase performance. 

3.	 Values for URM are set equal to PC1, PC2 values. 

A-12 A: Third Edition Scoring Capacity and Fragility Parameters FEMA P-155 
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FEMA P-155 B: References B-1 
Cole, G.L., Dhakal, R.P., Carr, A.J., and Bull, D.K., 2010, “Building 

Pounding State of the Art: Identifying Structures Vulnerable to Pounding 

Damage,” New Zealand Society for Earthquake Engineering Conference, 

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Council for the Federal Emergency Management Agency, Washington, 

D.C. 

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Applied Technology Council for the Federal Emergency Management 

Agency, Washington, D.C. 

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Buildings, FEMA 273, prepared by the Applied Technology Council for 

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Emergency Management Agency, Washington, D.C. 

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Engineers for the Federal Emergency Management Agency, Washington, 

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of Buildings, FEMA 356, prepared by the American Society of Civil 

Engineers for the Federal Emergency Management Agency, Washington, 

D.C. 

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HAZUS 99 Service Release 2, prepared by the National Institute of 

Building Sciences for the Federal Emergency Management Agency, 

Washington, D.C. 

FEMA, 2002a, Rapid Visual Screening of Buildings for Potential Seismic 

Hazards: A Handbook, Second Edition, FEMA 154, prepared by the 

Applied Technology Council for the Federal Emergency Management 

Agency, Washington, D.C. 

B-2 B: References FEMA P-155 
 

FEMA, 2002b, Rapid Visual Screening of Buildings for Potential Seismic 

Hazards: Supporting Documentation, Second Edition, FEMA 155, 

prepared by the Applied Technology Council for the Federal Emergency 

Management Agency, Washington, D.C. 

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Model, HAZUS-MH MR1, Advanced Engineering Building Module, 

Technical and User's Manual, developed by the National Institute of 

Building Sciences under a contract with the Federal Emergency 

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Institute of Building Sciences under a contract with the Federal 

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FEMA P-154 ROVER CD Version 2, prepared by the Applied 

Technology Council for the Federal Emergency Management Agency, 

Washington, D.C. 

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Hazards: A Handbook, Third Edition, FEMA P-154, prepared by the 

Applied Technology Council for the Federal Emergency Management 

Agency, Washington, D.C. 

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Method,” ISET Journal of Earthquake Technology, Vol. 41, No. 1, Paper 

No. 438, 1-13. 

Goel, R., and Chopra, A., 1997, Vibration Properties of Buildings 

Determined from Recorded Earthquake Motions, Report UCB/EERC97/14, Berkeley, California. 

ICC, 2012a, 2012 International Building Code, International Code Council, 

Washington, D.C. 

ICC, 2012b, 2012 International Residential Code, International Code 

Council, Washington, D.C. 

FEMA P-155 B: References B-3 
 

 

Ingham J.M., and Griffith, M.C., 2011, The Performance of Unreinforced 

Masonry Buildings in the 2010/2011 Canterbury Earthquake Swarm, 

Report to the Royal Commission, New Zealand. 

Jeng, V., and Tzeng, W.L., 2000, “Assessment of Seismic Pounding Hazard 

for Taipei City,” Engineering Structures, Vol. 22, No. 5, pp 459-471. 

Luco, N., Ellingwood, B.R., Hamburger, R.O., Hooper, J.D., Kimball, J.K. 

and Kircher, C.A., 2007, “Risk-targeted Versus Current Seismic Design 

Maps for the Conterminous United States,” Structural Engineers 

Association of California 2007 Convention Proceedings, pp. 163-175. 

Maison, B., Bonowitz, D., Kornfield, L., and McCormick, D., 2011, 

Adjacency Issues in Soft-Story Wood-Framed Buildings, A Report to the 

Structural Engineers Association of Northern California, April. 

NZSEE (NZSEE Study Group on Earthquake Risk Buildings), 2012, 

Assessment and Improvement of the Structural Performance of Buildings 

in Earthquakes including Corrigenda Nos 1& 2, New Zealand Society 

for Earthquake Engineering. http://www.nzsee.org.nz/db/PUBS/ 

2006AISBEGUIDELINESCorr2_(incl_2012_updates).pdf. Last 

accessed September 1, 2014. 

Okazaki, T., Lignos, D.G., Midorikawa, M., Ricles, J. M., and Love, J., 

2013, “Damage to Steel Buildings Observed after the 2011 Tohoku-Oki 

Earthquake,” Earthquake Spectra, Vol. 29, No. S1, pp. S219-S243. 

Porter, K.A., 2009, “Cracking an Open Safe: HAZUS Vulnerability 

Functions in Terms of Structure-Independent Spectral Acceleration,” 

Earthquake Spectra, Vol. 25, No. 2, pp. 361-378. 

Porter, K.A., Scawthorn, C.R., and Beck, J.L., 2006, “Cost-effectiveness of 

Stronger Woodframe Buildings,” Earthquake Spectra, Vol. 22, No. 1, 

February 2006, pp. 239-266. 

So, E., 2012, Guide to Deriving Judgement-Based Fatality Rates for Use in 

Earthquake Loss Estimation Models, available from 

http://www.nexus.globalquakemodel.org/gem-vulnerability/posts. Last 

accessed September 29, 2014. 

Tokas, C., and Lobo, R., 2009, “Risk Based Seismic Evaluation of Pre-1973 

Hospital Buildings Using the HAZUS Methodology,” Proceedings of the 

2009 ATC & SEI Conference on Improving the Seismic Performance of 

Existing Building and Other Structures, San Francisco, California, 

December 9-11. 

B-4 B: References FEMA P-155 
Trottenberg, P., and Rivkin, R.S., 2013, U.S. Guidance on Treatment of the 

Economic Value of a Statistical Life in U.S. Department of 

Transportation Analyses, U.S. Department of Transportation, 

Washington D.C. Available at 

http://www.dot.gov/sites/dot.dev/files/docs/VSL%20Guidance%202013. 

pdf. Last accessed August 10, 2014. 

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/statab/2012/ranks/rank38.html. Last accessed May 14, 2014. 

USGS, 2014a, http://earthquake.usgs.gov/hazards/designmaps/datasets/. Last 

accessed September 24, 2014. 

USGS, 2014b, http://earthquake.usgs.gov/hazards/products 

/conterminous/2008/data/. Last accessed September 24, 2014. 

FEMA P-155 B: References B-5 

 

Project Participants 

ATC Management and Oversight 

Christopher Rojahn (Program Executive) 

Applied Technology Council 

201 Redwood Shores Parkway, Suite 240 

Redwood City, California 94065
 

Jon A. Heintz (Program Manager) 

Applied Technology Council 

201 Redwood Shores Parkway, Suite 240 

Redwood City, California 94065
 

FEMA Oversight 

Mike Mahoney (Project Officer)
 

Federal Emergency Management Agency 

500 C Street, SW, Room 416
 

Washington, DC 20472
 

Mai Tong (Task Monitor)
 

Federal Emergency Management Agency 

500 C Street, SW, Room 416
 

Washington, DC 20472
 

Project Technical Committee 

Bret Lizundia (Project Technical Director) 

Rutherford + Chekene Consulting Engineers
 

55 Second Street, Suite 600 

San Francisco, California 94105
 

Michael Griffin 

CCS Group, Inc. 

1415 Elbridge Payne Rd.
 

Suite 265 

Chesterfield, Missouri 63017
 

William T. Holmes 

Rutherford + Chekene Consulting Engineers
 

55 Second Street, Suite 600 

San Francisco, California 94105
 

Ayse Hortacsu (Project Manager) 

Applied Technology Council 

201 Redwood Shores Parkway, Suite 240 

Redwood City, California 94065
 

Thomas McLane (Project Manager) 

Applied Technology Council 

201 Redwood Shores Parkway, Suite 240 

Redwood City, California 94065
 

Erin Walsh (Task Monitor)
 

Federal Emergency Management Agency 

500 C Street, SW, Room 416
 

Washington, DC 20472
 

John Gillengerten (Technical Monitor)
 

5155 Holly Drive 

Shingle Springs, California 95682
 

Brian Kehoe 

Wiss Janney Elstner Associates, Inc.
 

2000 Powell Street, Suite 1650
 

Emeryville, California 94608 

Keith Porter 

SPA Risk, LLC 

2501 Bellaire Street 

Denver, Colorado 80207
 

Barry Welliver 

BHW Engineers 

13623 South Bridle Trail Road 

Draper, Utah 84020
 

FEMA P-155 C: Project Participants C-1 
 

 

Project Review Panel 

T. Charles Scawthorn (Chair) 

SPA Risk LLC 

P.O. Box 3326 

San Francisco, California 94119 

Timothy Brown 

Bureau of Reclamation 

P.O. Box 25007, Mail Code 86-68110 

Denver, Colorado 80225 

Melvyn Green 

Melvyn Green & Associates 

21311 Hawthorne Blvd., Suite 230 

Torrance, California 90503 

Laura Kelly 

U.S. Coast Guard Base 

Kodiak Cape Sarichef St., N38 

PO Box 195025 

Kodiak, Alaska 99619 

Project Working Group 

Sarah Durphy 

Rutherford + Chekene Consulting Engineers 

55 Second Street, Suite 600 

San Francisco, California 94105 

Charles A. Kircher 

Kircher & Associates 

1121 San Antonio Road, Suite D-202 

Palo Alto, California 94303 

Illustrators 

Andrew Bishop 

Wiss Janney Elstner Associates, Inc. 

2000 Powell Street, Suite 1650 

Emeryville, California 94608 

Workshop Participants 

John Aho 

CH2M Hill, Inc. 

2015 Shepherdia Drive 

Anchorage, Alaska 99508 

Stephanie King 

1045 Fulton Street 

Palo Alto, California 94301 

John Osteraas 

Exponent 

149 Commonwealth Drive 

Menlo Park, California 94025 

Steven Sweeney 

U.S. Army Engineer Research and Development 

Center Construction Engineering Research 

Laboratory 

P.O. Box 9005 

Champaign, Illinois 61826 

Christine Theodoropoulos 

Cal Poly San Luis Obispo 

College of Architecture & Env. Design 

San Luis Obispo, California 94407 

Nicolas Luco
 

Geologic Hazards Science Center
 

U.S. Geological Survey 

P.O. Box 25046, MS 966
 

Lakewood, Colorado 80225
 

Kenneth Rukstales 

Geologic Hazards Science Center
 

U.S. Geologic Survey 

P.O. Box 25046, MS 966
 Lakewood, Colorado 80225
 

Scott Hiner 

Creative Marketing Resources
 

447 Sheridan Circle 

Livermore, California 94551
 

Rebecca Collins 

Coughlin Porter Lundeen, Inc. 

413 Pine Street, Suite 300
 

Seattle, Washington 98101
 

C-2 C: Project Participants FEMA P-155 
Murat Saatcioglu 

University of Ottawa 

Dept. of Civil Engineering 

161 Louis Pasteur Street 

Ottawa, Ontario, K1N6N5 

Canada 

Alan Scott 

KPFF Consulting Engineers 

1630 Des Peres Road, Suite 100 

St. Louis, Missouri 63131 

Hope Seligson 

MMI Engineering 

2100 Main Street, Suite 150 

Huntington Beach, California 92648 

Nilesh Shome 

Risk Management Solutions 

1133 Langton Drive 

San Ramon, California 94582 

Jeff Soulages 

Intel Corp. 

2501 NW 229th Street, MS: RS6-101 

Hillsboro, Oregon 97124 

Yumei Wang 

Oregon Dept. of Geology & Mineral Industries 

800 NE Oregon Street, #28 

Portland, Oregon 97232 

FEMA P-155 C: Project Participants C-3 


FEMA P-155

Catalog No. 11206-1