Summary of Progress on Prior 

NCST Investigations

June 14-15, 2023

NCST Advisory 

Committee Meeting

Fahim Sadek

Research Structural Engineer, Structures Group

Marc Levitan

Research Engineer, Structures Group
NOTE – Summaries of the 

recommendations are 

included in the following 

slides for context. The 

complete recommendations 

are available in the final 

report of the NIST Technical 

Investigation, at 

https://www.nist.gov/el/fin

al-reports-nist-world-tradecenter-disasterinvestigation

World Trade Center 

Investigation

June 14-15, 2023

NCST Advisory 

Committee Meeting

2
Recommendation 1 Progress Update: Complete

NIST recommends that progressive 

collapse be prevented in buildings 

through the development and 

nationwide adoption of consensus 

standards and code provisions, along 

with the tools and guidelines needed 

for their use in practice

WTC

Progress on Implementation of WTC Recommendations

ASCE 76-23 Standard for 

Mitigation of Disproportionate 

Collapse Potential in Buildings 

and Other Structures published 

(May 2023)

3 Image © ASCE 2023. Used with Permission.
WTC

Progress on Implementation of WTC Recommendations

Recommendation 2 Progress Update: Complete

NIST recommends performance 

standards be developed for:

(1) conducting wind tunnel testing of 

prototype structures that result in 

repeatable and reproducible 

results among testing laboratories; 

and 

(2) estimating wind loads and their 

effects on tall buildings, based on 

wind tunnel testing data and 

directional wind speed data.

• As reported last year – a revision to 

wind velocity pressure profiles to 

better reflect the state-of knowledge 

on atmospheric boundary-layer flows 

was incorporated in ASCE 7-22

• ASCE 7-22 wind loads have now been 

approved for incorporation into the 

2024 International Building Code

Image © ASCE 2022. Used with Permission.

4
WTC Recommendations

The implementation of the WTC recommendations is 

now complete. 30 recommendations have resulted in:

• Adoption of 40 code changes to the I-Codes (International 

Building Code [IBC] and International Fire Code, [IFC]).

• Adoption of 10 code changes in the Life Safety Code (NFPA 101) 

and 2 code changes in the Uniform Fire Code (NFPA 1).

• New Standard for Mitigation of Disproportionate Collapse 

Potential in Buildings and Other Structures (ASCE/SEI 76-23).

• Revision to existing standards on wind tunnel testing and 

estimation of wind loads and effects on buildings (ASCE 49-21 

and ASCE 7-22, respectively).

5

IBC

NFPA 1

IFC

NFPA 101

ASCE 76

ASCE 7

ASCE 49
NOTE – Summaries of the 

recommendations are 

included in the following 

slides for context. The 

complete recommendations 

are available in the final 

report of the NIST Technical 

Investigation of the Joplin 

Tornado, at 

https://dx.doi.org/10.6028/

NIST.NCSTAR.3

Joplin Tornado Investigation

June 14-15, 2023

NCST Advisory 

Committee Meeting

6
• 16 recommendations for improving:

• Tornado hazard characterization

• Design and construction of buildings and shelters in 

tornado–prone regions

• Emergency communications that warn of threats from 

tornadoes

• Implementation of recommendations began in Spring 

2014, immediately following publication of final report 

http://dx.doi.org/10.6028/NIST.NCSTAR.3

The first tornado study to include storm 

characteristics, building performance, emergency 

communication and human behavior together - with 

assessment of the impact of each on fatalities

NIST Joplin Tornado Investigation

7
List of Joplin Recommendations 

Hazard 

Characteristics

Buildings, Shelters, Designated 

Safe Areas, and Lifelines

Emergency 

Communication

R # RECOMMENDATION SUMMARY 1 Development and deployment of technology to measure tornado wind fields 2 Archival of tornado event data 3 Development of tornado hazard maps 4 Improvement of EF Scale; means for continued improvement; adoption by NWS 5 Development of performance-based standards for tornado-resistant design 6 Development of performance-based tornado design methodologies 7 a) Development of tornado shelter standard for existing buildings; 

b) Installation of tornado shelters in more buildings in tornado-prone regions

8 Development of guidelines for public tornado sheltering strategies 9 Development of guidelines for selection of best available refuge areas 

10 Prohibition of aggregate roof coverings and ballast in tornado-prone regions

11 Development of requirements for enclosures of egress systems in critical facilities

12 a) Development of tornado vulnerability assessment guidelines for critical facilities;

b) Performance of vulnerability assessments by critical facilities in tornado-prone

13 Development of codes, standards, and guidance for emergency communications; 

Development of joint plan by emergency managers/media/NWS for consistent alerts

14 Deployment of “push” technologies for transmission of emergency information

15 Research to identify factors to enhance public perception of personal risk

16 Develop technology for real-time, spatially-resolved tornado threat information

8
List of Joplin Recommendations 

Hazard 

Characteristics

Buildings, Shelters, Designated 

Safe Areas, and Lifelines

Emergency 

Communication

R # RECOMMENDATION SUMMARY – PROGRESS UPDATES IN THIS BRIEFING

1 Development and deployment of technology to measure tornado wind fields 2 Archival of tornado event data 3 Development of tornado hazard maps 4 Improvement of EF Scale; means for continued improvement; adoption by NWS 5 Development of performance-based standards for tornado-resistant design 6 Development of performance-based tornado design methodologies 7 a) Development of tornado shelter standard for existing buildings; 

b) Installation of tornado shelters in more buildings in tornado-prone regions

8 Development of guidelines for public tornado sheltering strategies 9 Development of guidelines for selection of best available refuge areas 

10 Prohibition of aggregate roof coverings and ballast in tornado-prone regions

11 Development of requirements for enclosures of egress systems in critical facilities

12 a) Development of tornado vulnerability assessment guidelines for critical facilities;

b) Performance of vulnerability assessments by critical facilities in tornado-prone

13 Development of codes, standards, and guidance for emergency communications; 

Development of joint plan by emergency managers/media/NWS for consistent alerts

14 Deployment of “push” technologies for transmission of emergency information

15 Research to identify factors to enhance public perception of personal risk

16 Develop technology for real-time, spatially-resolved tornado threat information

JOPLIN

9
Progress – Improvement of the EF Scale (1/2)

R4: Standardize the Enhanced Fujita (EF) scale and improve through addition of scientific/quantifiable 

damage indicators, particularly those that distinguish between the most intense tornado events

Smart^DI Advancement

• Initial field data on Quad-State Tornado reported last year

• Collected additional images for more accurate damage 

assessment/wind speed estimation:

o Photos from Damage Assessment Toolkit (DAT)

o Various aerial imageries

o Street level camera

• Smart^DI tested on Mayfield, KY

o Acquired year built of residential houses from Graves KY county 

tax records (year built is an input for Smart^DI tool)

o Made suggestions for further improvements

Credit: NWS

10
Progress – Improvement of the EF Scale (2/2)

• Independent wind speed estimation of Mayfield, KY using tree damage (i.e., treefall pattern 

analysis) to validate Smart^DI estimates

o Treefall analysis method: tornado wind field estimation by analyzing the tree-fall pattern

o Treefall pattern acquired by identifying trees from aerial imagery; analysis by automated software 

o Reduced uncertainties in the parameters from physical evidences (e.g., structural damage, radar)

• Preliminary treefall analysis estimation supports Smart^DI estimation of wind speeds

Radar

9.7 km

Credit: NWS. Enhancements by NIST

11
Adoption of Tornado Standard (1/5)

R5: Develop PBD standards for tornado-resistant design and adopt in model codes and local regulations

Multi-part strategy to maximize likelihood of success for incorporation 

of ASCE 7-22 tornado loads into the 2024 IBC and adoption into federal, 

state and local codes

1. Documentation of tornado impacts to critical facilities

2. Economic analysis of ASCE 7-22 tornado load provisions

3. Extensive stakeholder communications

4. Develop IBC proposal, in collaboration w/ ASCE and FEMA

5. Develop Tornado Load Design Guide, in collaboration w FEMA

Wynne High School, 

Wynne, AR, March 2023 

Credit: NWS

https://doi.org/10.6028/NIST.TN.2214

Crestview Elementary 

School, Covington, TN 

March 2023

Credit: NWS

12
Adoption of Tornado Standard (2/5)

Stakeholder Communication Highlights since June 2022

• 15 presentations/webinars/seminars, including:

o SEI Standards Series - ASCE 7-22 Preview Session #3 – Wind and Tornado 

Webinar

o US Economic Development Administration and US Small Business Administration

o National Institute of Building Sciences (NIBS) Building Innovation Conference 2022

o 2022 Storm Shelter Conference

o Roofing Industry Committee on Wind Issues (RICOWI) Spring Seminar, 2023

o ASCE Architectural Engineering Conference, 2023

o 6th International Conference on Protective Structures

o Metal Building Manufacturers Association Design Seminar

• 8 media interviews, including:

o FEMA Video for Building Safety Month, 2023

o The Infrastructure Show Podcast

o NewsNation

o CBC Radiothe Infrastructure Show

o WFLD-TV/Fox 32 Chicago, KTVI St. Louis, KSDK St. Louis

o YouTube documentary on the Jarrell, Texas Tornado

https://www.nist.gov/news-events/news/2021/06/major-newbuilding-standard-can-map-out-tornado-threat-first-time

13
Adoption of Tornado Standard (3/5)

2024 International Building Code

• NIST led development of the proposal to incorporate ASCE 7-22 

Tornado Load requirements into the 2024 IBC

o with ASCE and FEMA, Proposal S63-22

• Coordinated testimony for the Committee Action Hearings

• IBC Structural Committee voted 14-0 to approve 

• Since June 2022 NCSTAC Meeting

o Public Comment Period

– no comments received

o Online Government Consensus Vote 

– approved via Consent Agenda

Also approved for inclusion in the 2024 NFPA 5000 

Building Construction and Safety Code

Credit; NOAA/OAR/ERL/NSSL

© ASCE 2022. Used with Permission.

Approved 

for the 

2024 IBC

14
Adoption of Tornado Standard (4/5)

First Local Adoption: 

2023 Florida Building Code

• NIST provided technical input on 

the proposal submitted to Florida 

Building Commission

• Tornado loads approved by the 

Commission in December 2022

15
Adoption of Tornado Standard (5/5)

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935883

Developed and published joint FEMA/NIST 

Design Guide for ASCE 7-22 Tornado Loads

• explanation of terminology and procedures

• example tornado load calculations

• comparisons with wind load provisions and 

calculations

16
Tornado Resistant Design

R6: Develop risk–balanced, performance–based tornado design methodologies 

Developed and published FEMA/NIST interim guidance for 

tornado resistant design and retrofit of one- and two-family 

residences

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936075

17

Supported FEMA in development 

of the updated P-804 publication 

“Wind Retrofit Guide for 

Residential Buildings”

Credit: FEMA
• Existing Standard

─ NFPA 1600-2019, Standard on Continuity, Emergency, and Crisis Management

─ ICC 500-2020, Standard for Design and Construction of Storm Shelters

─ ASCE/SEI 7-22, Minimum Design Loads and Associated Criteria for Buildings and Structures

─ ICC 500-2023, Standard for Design and Construction of Storm Shelters

• New Standards

─ NFPA 1616-2017, Standard for Mass Evacuation and Sheltering

─ ASCE/AMS Standard for Estimation of Wind Speeds in Tornadoes

• Building Codes

─ 2018 International Building Code (IBC)

─ 2018 International Existing Building Code (IEBC)

─ 2023 Florida Building Code

─ 2024 International Building Code (IBC)

─ 2024 NFPA 5000 Building Construction and Safety Code

• Guidelines

─ FEMA P-320, Taking Shelter from the Storm, 4th ed.

─ FEMA P-320, Taking Shelter from the Storm, 5th ed.

─ FEMA P-361, Safe Rooms for Tornadoes and Hurricanes, 3rd ed.

─ FEMA P-361, Safe Rooms for Tornadoes and Hurricanes, 4th ed.

─ ICC 500-2014, Commentary on the Standard for Design and Construction of Storm Shelters

─ ICC 500-2020, Commentary on the Standard for Design and Construction of Storm Shelters

─ FEMA P-2062, Guidelines for Wind Vulnerability Assessments of Existing Critical Facilities

─ NIST Technical Note, Alerting under Imminent Threat: Guidance on alerts by outdoor siren & short message alerting systems

─ Nat. Hazards Rev., Alerts and warnings on short messaging channels: guidance from an expert panel process

─ FEMA P-431, Tornado Protection: Selecting Refuge Areas in Buildings, 3rd ed.

─ FEMA/NIST, Design Guide for New Tornado Load Requirements in ASCE 7-22

─ FEMA/NIST, Fact Sheet: Improving Windstorm and Tornado Resilience: Recommendations for 1- and 2-Family Residential Structures

─ Guidelines for Tornado Resistant Design of Risk Category II Buildings

─ Guidelines for Public Tornado Sheltering Strategies

In press

Published Sept 2022

Published Jan 2023

Pub. Feb 2023

In press

Published

In Progress

In Planning / 

Development

Updates Since June 

2022 Briefing

Workshops

• 1st NIST/ASCE Tornado Map Stakeholder Workshop, 2015

• Federal Agency Tornado Map Workshop, 2015

• Workshop on Outdoor Siren Policies, 2016

• Workshop on Short Message Alerting, 2017

• Public Tornado Shelter Workshop: Opportunities and 

Challenges for Improving Tornado Safety, 2019

• 2nd NIST/ASCE Tornado Map Stakeholder Workshop, 2019

• Quad-State Tornado Outbreak Workshop, 2022

Impacts/Engagement Summary 

18

In press
Remaining Implementation Tasks

R# RECOMMENDATION SUMMARY

1 Develop and deploy technology to measure tornado wind fields

2 Archival of tornado event data

3 Development of tornado hazard maps

4 Improvement of EF Scale; adop�on by NWS

5 Develop PBD standard for tornado loads/incl. in model code/local adop�on

6 Develop performance-based tornado design methodologies

7 a) Develop tornado shelter standard for exis�ng buildings;

b) Installa�on of tornado shelters in more buildings in tornado-prone regions

8 Develop guidelines for public tornado sheltering strategies

9 Develop guidelines for selec�on of best available refuge areas

10 Prohibi�on of aggregate/ballast roof coverings in tornado-prone regions

11 Develop req. for enclosures of egress systems in cri�cal facili�es

12 a) Develop tornado vulnerability assessment guidelines for cri�cal facili�es;

b) Performance of vulnerability assessments by cri�cal facili�es

13 Develop codes, standards, and guidance for emergency communica�ons;

Develop joint plan by emergency mgrs/media/NWS for consistent alerts

14 Deploy “push” technologies for transmission of emergency informa�on

15 Research to iden�fy factors to enhance public percep�on of personal risk

16 Develop technology for real-�me, spa�ally-resolved tornado threat informa�on

Hazard 

Characteristics

Buildings, Shelters, Designated 

Safe Areas, and Lifelines

Emergency 

Communicatio

n

Legend

Primarily Completed

Significant Activities/Progress

Modest Progress

Next Steps

Complete the new ASCE/AMS Standard

Linked with efforts for R4

Coordinating w/ FEMA

NOAA

Develop guidance for RC II Buildings

Revise/Resubmit to IBC

Develop guidance w/ FEMA and NOAA

Complete guidance w/ FEMA

Propose for ANS 2.3 Std on Tornado Characterization for 

Nuclear Facility Sites

R&D for 

improvements to 

ASCE 7-28 

tornado load 

provisions

Tools and outreach 

to support local 

adoption

19
June 14-15, 2023

NCST Advisory 

Committee Meeting

Progress on Implementation of Past 

Investigation Recommendations

Fahim Sadek

Research Structural Engineer, Structures Group

QUESTIONS?

Marc Levitan

Research Engineer, Structures Group

20