bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of Free-Field Vertical Ground Motion during the Northridge Earthquake
Authors: Bozorgnia Youself , Niazi Mansour , Campbell Kenneth W.
Published: July 2003

Characteristics of response spectra of free-field vertical ground motion recorded during the 1994 Northridge earthquake are examined. Dependence of vertical and horizontal response spectra, and their ratio, on the site-to-source distance is investigated through development of attenuation relationships for vertical and horizontal spectral ordinates. The database includes 123 response spectra of the motions recorded at 41 alluvial sites. Vertical-to-horizontal (V/H) response spectral ratio is found to be strongly dependent on period and distance of site to the seismic source. V/H spectral ratio largely exceeds the commonly assumed value of 2/3, at short periods in the near-field region. The main characteristics of V/H spectral ratio for the Northridge earthquake are found to be qualitatively similar to those observed in the 1989 Loma Prieta, California, and in several other earthquakes recorded over the SMART-1 array in Taiwan. These characteristics are very likely to be universal.
Seismic Vulnerability Evaluation of Essential Facilities in Memphis and Shelby County, Tennessee
Authors: Chang T. S. , Pezeshk S. , Yiak K. C. , Kung H. T.
Published: July 2003

This study is designed to assess potential seismic vulnerability of highly occupied or heavily used essential facilities, including 202 schools, 22 hospitals, and 74 fire stations, in Memphis and Shelby County, Tennessee which may be strongly affected by earthquakes in the New Madrid seismic zone (NMSZ). The seismic evaluation system uses existing data such as site, subsurface condition, foundation, structural characteristics, and results of previous site-specific seismic hazard studies. Results of the study reveal the current overall risk of damage of the essential facilities subject to the recognized seismic hazard in the study area and identify a preliminary pool of the most vulnerable facilities for the highest priority to be used in developing a detailed study to identify retrofit/replacement plans in the near future. Results also provide useful information for long-term upgrade strategies for essential facilities and general buildings in the Memphis area. The study results are important for future detailed study, facility maintenance and improvement, earthquake loss estimates, seismic hazard/risk reduction, and earthquake preparedness/rescue plans in the region.
Behavior of Metallic Plate Dampers in Seismic Passive Energy Dissipation Systems
Authors: Dargush G. F. , Soong T. T.
Published: July 2003

Metallic plate dampers, when incorporated into a structure, provide one of the most effective energy dissipation mechanisms available during an earthquake. Increasingly, they are applied in the seismic retrofit of structures which are found to be deficient. The design of these devices, however, has been largely based upon experiments and macroscopic modeling. In order to gain more insight into the response behavior of metallic plate dampers, a microscopic mechanistic approach is followed in this paper. Included is the development of an inelastic constitutive model for the damper material. Numerical results obtained for a class of metallic plate dampers are presented and comparisons are made with experimental data for validation of the mathematical model. It is also shown that this approach sheds light on several aspects of the damper response which heretofore have not been addressed adequately.
A Clarification of the Orthogonal Effects in a Three-Dimensional Seismic Analysis
Authors: Wilson Edward L. , Suharwardy Iqbal , Habibullah Ashraf
Published: July 2003

For response spectra analyses it is shown that the “design of elements for 100 percent of the prescribed seismic forces in one direction plus 30 or 40 percent of the prescribed forces applied in the perpendicular direction” is dependent on the user's selection of the reference system. These commonly used “percentage combination rules” have no theoretical basis and can underestimate the design forces in certain members and can produce a member design which is relatively weak in one direction. It is proven that the alternate code approved method, in which a SRSS combination of two 100 percent spectra analyses with respect to any user defined orthogonal axes, will produce design forces which are not a function of the reference system and results in a structural design which has equal resistance to seismic motions from all directions.
Cyclic Loading Histories for Seismic Experimentation on Structural Components
Authors: Krawinkler Helmut
Published: July 2003

In order to utilize results obtained from quasi-static cyclic load tests on structural components for a general performance evaluation, the need exists to establish loading histories that capture critical issues of component capacity as well as seismic demands. In inelastic seismic problems capacity and demands cannot be separated since one may strongly depend on the other. Because of cumulative damage issues the capacity depends on the number of inelastic excursions and the magnitude of each excursion (not just the largest one). These two parameters depend on the frequency content of the ground motion, the period(s) of the structure, and the strength and inelastic deformation characteristics of the structure. The paper presents procedures how these characteristics can be considered in the selection of suitable loading histories.
Standardized Experimental Testing Procedures for Low-Rise Structures
Authors: Shepherd Robin
Published: July 2003

This paper reports the progress made, over an eighteen month period, by an ad hoc committee of the Structural Engineers′ Association of Southern California in the development of guidelines to be followed if consistent experimental investigations, representative of the structural performance of mixed material systems under strong seismic excitation, are to be achieved.

Aspects covered include the issue of load or deflection control, the rate of load application, the pattern of repetitive load or displacement application, the number of components or systems to be tested and the interpretation of the results.
Implications of Experiments on the Seismic Behavior of Gravity Load Designed RC Beam-to-Column Connections
Authors: Beres Attila , Pessiki Stephen P. , White Richard N. , Gergely Peter
Published: July 2003

This paper summarizes recent experimental research at Cornell University conducted on the behavior of gravity load designed reinforced concrete building frame components subjected to reversing cyclic loads (simulated seismic effects). Reinforced concrete framing systems, designed primarily for gravity loads, with little or no attention given to lateral load effects, are typically characterized by non-ductile reinforcing details in the joint regions and in the members. The seismic response of connection regions for gravity load design (GLD) frames has received relatively little attention in earlier studies, thus making it difficult to reliably evaluate GLD frames and to properly plan repair or retrofit strategies. Thirty-four full scale bare interior and exterior beam-to-column joints have been tested under reversed cyclic bending to identify the different damage mechanisms and to study the effect of critical details on strength and deformations. The discussion of test results focuses on the definition of joint shear strength factors for GLD frames to complement those provided by ACI-ASCE Committee 352 for frames designed with better details.
Probabilistic Assessments of the Seismic Hazard in Northern Armenia (Spitak Region)
Authors: Chernov Yu K. , Sokolov V. Yu
Published: July 2003

The Spitak (Armenia) earthquake of December 7, 1988, (M=6.9) revealed the necessity to revise the assessments of seismic hazard obtained in the past. We used recently developed method for quantitative probabilistic assessment of seismic shaking to resolve the problem. The assessments of probable intensity of shaking in terms of MSK - 64 intensity scale showed that for this region the intensity with return period T=1000 years must be taken as MSK IX instead of MSK VII and MSK VIII assigned to Armenia by the building code. Probable Fourier and response spectra of ground acceleration have been estimated also, and may be used for design and construction of new building and structures in this region.
Sensitivity of Seismic Assessment of a Double-Deck, Reinforced Concrete Bridge
Authors: De la Colina Jaime , Eberhard Marc O. , Ryter Stanley W. , Wood Sharon L.
Published: July 2003

Engineers are assessing the seismic vulnerability of thousands of reinforced concrete bridges located throughout the United States. Many of the bridge evaluation procedures are new, and the engineering effort necessary to implement them varies. Consequently, the assessment methodology varies among the responsible agencies, and in some cases, from one bridge to the next. This paper documents the sensitivity of an evaluation of a double-deck, reinforced concrete bridge to the manner in which the assessment was conducted. Large differences arose from the selection of linear versus nonlinear models. The computed splice vulnerabilities and concrete contribution to shear capacity varied also. In contrast, the assessment results were relatively insensitive to the way in which the investigators estimated the flexural ductility capacities, the transverse reinforcement's contribution to shear resistance, and the joint vulnerability. Even if the variations among the evaluation procedures are reduced, the results of the evaluations will still be sensitive to the selection of the ground motion and foundation stiffness.
A Refined Model for Base-Isolated Bridges with Bi-Linear Hysteretic Bearings
Authors: Hwang J. S. , Chiou J. M. , Sheng L. H. , Gates J. H.
Published: July 2003

Recognizing that the inelastic displacement spectra with constant ductility ratios of an earthquake ground motion can be approximated by the equivalent elastic displacement spectra with the consideration of appropriate effective period shifts (or effective stiffness) and equivalent damping ratios, a refined equivalent linear model for the seismic analysis of base-isolated bridges with bi-linear hysteretic bearings is established in this paper using a system identification method. The parameters necessary to completely define a bi-linear hysteresis loop such as the elastic stiffness, yielding force, strain harden ratio and ductility ratio are all considered in the modeling. Eighteen California, one Washington and one Japan earthquake ground motions are used for the identification. The equivalent linear model established through the identification process is characterized as a modification of the current equivalent linear model provided by the AASHTO isolation guide specifications. Numerical comparisons indicate that the proposed model in general can predict accurately compared against the inelastic solutions and, therefore, the proposed model can be applied to the practical analysis of base-isolated bridges.
Seismic Analysis and Design of Modern Steel Highway Connectors
Authors: Itani Ahmad M. , Rimal Prem P.
Published: July 2003

This paper discusses the seismic analysis and design of modern steel plate girder connectors. Full 3-D finite element analyses were conducted on a two-span two-girder bridge to determine its seismic load path and to establish the seismic performance of the bridge with several cross frame configurations. The results of the study showed that the cross frames play a significant role in the seismic behavior since they transfer the inertia forces to the substructure, a phenomenon not accounted for in the current design bridge codes.
A More Rational Approach to Capacity Design of Seismic Moment Frame Columns
Authors: Bondy K. Dirk
Published: July 2003

Inelastic time history analyses typically indicate that the traditional sub-assembly “capacity” approach used in the design of ductile moment frames grossly underestimates the maximum moments experienced by the columns during a maximum credible earthquake. In addition, these analyses predict that the maximum column demand moments often occur near the mid-height of concrete structures, whereas a conventional elastic analysis predicts maxima at the lowest levels of these structures. Incremental displacement analyses using modal properties and displacements predicted by a maximum credible response spectrum should be used to more accurately predict the maximum anticipated column demand moments in the analysis of existing structures or the design of new structures.
Use of Loss Estimates by Government Agencies in the Northridge Earthquake for Response and Recovery
Authors: Goltz James D.
Published: July 2003

The rapid availability of estimated shaking intensities, dollar losses and social impacts following the Northridge earthquake of January 17, 1994, proved to be a valuable resource to the California Office of Emergency Services (OES) and the Federal Emergency Management Agency (FEMA) in response and recovery decision making. These estimates were used to supplement standard reconnaissance procedures and expedite decisions which in previous disasters were delayed until observational assessments had been completed. Based on extensive, in-depth interviews with state and federal emergency managers, this paper will focus on how these estimates were used in making decisions. Methods and models employed in generating estimates will be addressed only briefly. Discussion will include an assessment of the potential benefits and pitfalls of near real-time loss estimation in emergency management.
Evaluation of Reinforced Concrete Members Damaged by Earthquakes
Authors: Hanson Robert D.
Published: July 2003

A number of building authorities have included or are proposing to include loss in lateral capacity of the structural system caused by earthquake damage as a basis for requiring specific degrees of seismic repair and upgrades of the damaged members or of the entire structural system. Attempts have been made to apply this criteria through the size of cracks in reinforced concrete walls. This paper reviews experimental results which demonstrate that size of wall crack is not directly related to a reduction in wall capacity. The effectiveness of various wall crack repair techniques on restoring wall characteristics is discussed.
1996 EERI Student Paper Award Modeling of the Nonlinear Seismic Behavior of Gravity Load Designed Frames
Authors: Mosalam Khalid M.
Published: July 2003

Evaluating and, if necessary, retrofitting seismically loaded Gravity Load Designed (GLD) infilled frames requires accurate analytical models. This paper gives an overview of experimental and analytical investigations conducted on GLD steel frames infilled with unreinforced concrete block masonry walls. The presented analytical models can reasonably predict the seismic response of such structures. The experimental study adopts both quasi-static and pseudo-dynamic methods. Detailed finite element models and a more practical compression-only strut model for the infills are the analytical tools considered in the present study.
Earthquake Performance of Gas Transmission Pipelines
Authors: O'Rourke T. D. , Palmer M. C.
Published: July 2003

Over 61 years of earthquake performance of steel transmission and distribution supply pipelines operated by the Southern California Gas Company are reviewed. The seismic record includes 11 major earthquakes with ML ≥ 5.8 and epicenters within the transmission system. An evaluation is made of the most vulnerable types of piping, failure mechanisms, break statistics, threshold seismic intensity to cause failure, and damage induced by permanent ground displacement. The database assembled represents one of the most comprehensive and detailed records of seismic response in a large, complex gas transmission system.
Seismic Input Modelling for Zoning and Microzoning
Authors: Panza G. F. , Vaccari F. , Costa G. , Suhadolc P. , Fäh D.
Published: July 2003

The strong influence of lateral heterogeneities and of source properties on the spatial distribution of ground motion indicates that the traditional methods require an alternative when earthquake records are not available. The computation of broadband synthetic seismograms makes it possible, as required by a realistic modelling, to take source and propagation effects into account, fully utilizing the large amount of geological, geophysical and geotechnical data, already available. For recent earthquakes, where strong motion observations are available, it is possible to validate the modelling by comparing the synthetic seismograms with the experimental records. The realistic modelling of the seismic input has been applied to a first-order seismic zoning of the whole territory of several countries. Even though it falls in the domain of the deterministic approaches, the method is suitable to be used in new integrated procedures which combine probabilistic and deterministic approaches and allow us to minimize the present drawbacks which characterise them when they are considered separately. Detailed modelling of the ground motion for realistic heterogeneous media (up to 10 Hz) can be immediately used in the design of new seismo-resistant constructions and in the reinforcement of existing buildings, without having to wait for a strong earthquake to occur. The discrepancies between the ground responses computed with standard methods and the results of our detailed modelling cannot be ignored when formulating building codes and retrofitting the built environment.
Issues on the Seismic Retrofit of a Building near Resonant Response and Structural Pounding
Authors: Tena-Colunga Arturo , Del Valle Enrique , Pérez-Moreno Dalila
Published: July 2003

Paper presents an analytical study on the possible application of commonly used retrofit schemes for an existing nine-story apartment building in Mexico City. The building, located in Mexico City's lake-bed region, was originally conceived as a RC waffle-flat slab structural system and was built in the late sixties. The building suffered important structural damage during the March 14, 1979 Petatlán Earthquake, primarily caused by structural pounding with neighboring structures due to its flexibility and resonant response with the ground. The building was retrofitted shortly after the Petatlán Earthquake with steel bracing in the direction of pounding. The retrofitted building survived the September 19, 1985 Michoacán Earthquake with light structural damage. Some evidence of pounding with one neighboring structure was again observed.

Because of the chronic pounding problems with adjacent structures, which are separated eight to fifteen cm from the apartment building, it is felt that an additional upgrade of the structure may be needed for the safety of the building if a strong earthquake similar to the 1985 Michoacán Earthquake may strike Mexico City soon again. Different retrofit schemes were studied, which can be grouped as follows: a) weight reduction, b) column and waffle-slab jacketing, c) addition of energy dissipation devices, d) removal of top floors, e) replacement of diagonal bracing with newer bracing and, f) a combination of previous solutions. The effectiveness of the studied retrofit schemes is discussed by comparing their dynamic structural response with respect to the response of the actual retrofitted structure using nonlinear dynamic analyses for a postulated Ms=8.1 earthquake, as well as construction process, property value, and building use considerations. It is concluded that many aspects need to be evaluated in a seismic retrofit plan for a given building structure and often, the best alternative from the structural viewpoint may not be the best alternative overall.
Friction-Damped Moment-Resisting Frames
Authors: Way Douglas
Published: July 2003

Friction-Damped Moment-Resisting Frames are discussed as an alternative to steel ductile moment-resisting frames. The design involves replacing all full penetration welds with bolted friction connections, thereby eliminating the problem of failures at welded connections as exhibited during the Northridge earthquake. Energy dissipation is achieved at the friction interface in lieu of inelastic behavior of the frame. Analytical methods that perform an energy accounting are discussed.
Seismic Design and Testing of an RC Slab-Column Frame Strengthened by Steel Bracing
Authors: Masri Adnan C. , Goel Subhash C.
Published: July 2003

This study is concerned with developing a rational design procedure for use of ductile steel bracing for strengthening existing seismically “weak” RC slab-column building structures. A one-third scale, two-bay, two-story RC slab-column frame model was selected to represent existing seismically inadequate structures of its type. The design procedure, construction and test results of the steel bracing system for strengthening the RC frame are presented in this paper. The strengthened frame was subjected to a combination of gravity and cyclic lateral loads up to 2% overall frame drifts. The behavior of the strengthened frame improved dramatically over that of the bare RC frame. A maximum 2.75% drift in the first story was reached which is highly probable during severe earthquake motions.
Lateral Response of Older Flat Slab Frames and the Economic Effect on Retrofit
Authors: Dovich Laurel , Wight James K.
Published: July 2003

Seismic retrofit schemes for older flat slab frames are commonly designed to carry the full design lateral loads, based on the assumption that the existing slab-column frame has low lateral stiffness and may fail in a brittle manner during earthquake loading. An experimental study was conducted to probe the actual response of a two story by two bay frame, and two isolated connection specimens, under cyclic lateral load reversals. The behavior observed indicated that for reasonable gravity loads, the lateral load response of these older slab-column frames is more ductile than anticipated. Therefore, structural engineers should be encouraged to utilize the strength and stiffness of the existing slab-column frame when designing a seismic retrofit system for the frame. Such a design will be less conservative, and thus less expensive, than is common in current design practice.
Seismic Evaluation of Existing Reinforced Concrete Building Columns
Authors: Lynn Abraham C. , Moehle Jack P. , Mahin Stephen A. , Holmes William T.
Published: July 2003

Past earthquakes have emphasized the vulnerability of reinforced concrete columns having details typical of those built before the mid-1970's. These columns are susceptible to axial-flexural, shear, and bond failures, which subsequently may lead to severe damage or collapse of the building. Research was undertaken to investigate the lateral and vertical load-resisting behavior of reinforced concrete columns typical of pre-1970's construction. Eight full-scale specimens were constructed and were loaded with constant axial load and increasing cyclic lateral displacement increments until failure. Test data are presented and compared with behavior estimated by using various evaluation methods.
Seismic Rehabilitation of Reinforced Concrete Beam-Column Connections
Authors: Ghobarah A. , Aziz Tarek S. , Biddah Ashraf
Published: July 2003

As building codes are updated, some of the existing important structures may fall short of complying with current standards even though they may have been properly designed and constructed according to earlier codes. Many existing structures may be inadequate and may pose severe risk during seismic events. Rehabilitation measures to upgrade the capacity of these structures can be performed at some point in their useful lives especially when located in seismically active zones. A new method for improving the seismic performance of existing reinforced concrete structures is by jacketing the deficient connections using corrugated steel jackets. An experimental program was conducted to evaluate this method of rehabilitation. Corrugated steel jacketing addresses the particular weakness that is often found in existing reinforced concrete structures, namely the lack of sufficient shear reinforcement and the required confining reinforcement within the joints and in adjoining beams and columns. The performance of four reinforced concrete connections was determined experimentally. The test specimens include one connection representing existing structures, one designed according to current seismic codes and two rehabilitated connections. The test results showed satisfactory performance at high cyclic load levels and significant increase in the shear capacity and ductility of connections rehabilitated with corrugated steel jackets.
Measured Response of Roof Diaphragms and Wall Panels in Tilt-Up Systems Subjected to Cyclic Loading
Authors: Fonseca Fernando S. , Wood Sharon L. , Hawkins Neil M.
Published: July 2003

An experimental program was developed to study the strength and deformation capacity of tilt-up structures with plywood roof diaphragms. Two models of tilt-up systems were constructed and tested in the laboratory. The structures were representative of one-story warehouse construction in the western U.S. The overall dimensions of the two test specimens were the same; however, the number and distribution of reinforced concrete wall panels were varied. Each specimen was subjected to a series of lateral load reversals.

Two aspects of the measured response of the test specimens are discussed in this paper: the in-plane displacements of the plywood roof diaphragm and the transverse response of the perimeter wall panels. The wall panels experienced nearly rigid-body rotation during the entire testing series, and the observed nonlinear response of the test specimens may be attributed to the inherent flexibility of the plywood diaphragm.
Seismic Strengthening of Unreinforced Masonry Piers with Steel Elements
Authors: Rai Durgesh C. , Goel Subhash C.
Published: July 2003

The system of wall piers and spandrels, created by openings, largely controls the inplane lateral resistance of the wall. For the “rocking-critical” masonry wall piers, the overall hysteretic behavior can be significantly improved by installing a steel framing system consisting of vertical and horizontal elements around the wall — without any braces. Vertical elements provide the necessary hold-down forces to stabilize the rocking piers. The stabilized piers “rocked” through a number of cycles of large displacements (up to 2.5%) without crumbling or shattering, displaying a ductile response. The strengthened system has excellent strength, stiffness and ductility, despite the brittleness of the masonry because of considerable load sharing between the existing masonry and the added steel elements. FE analyses predicted the envelope response of the rocking piers accurately. A simple mechanics based model was developed to predict the load-deflection behavior of a stabilized rocking pier which can be used to design the strengthening system more rationally.
Seismic Rehabilitation of Infilled Non-Ductile Frame Buildings Using Post-Tensioned Steel Braces
Authors: Terán-Gilmore Amador , Bertero Vitelmo V. , Youssef Nabih F. G.
Published: July 2003

In recent years, it has been shown that the seismic performance of existing buildings can be enhanced considerably by bracing them with post-tensioned rods or cables. This upgrading technique has several advantages, which include architectural versatility, low cost and fast construction. Furthermore, it does not add a significant mass to the existing building. The objectives of the present paper are to: investigate the use of post-tensioned steel bracing for seismic retrofit of non-ductile reinforced concrete frames with unreinforced masonry infills, discuss some of the issues that need to be addressed in the design of the rehabilitated building, assess the advantages of this rehabilitation technique by studying the seismic performance of an infilled non-ductile frame building before and after it has been upgraded with post-tensioned braces, and propose research recommendations.
Some Retrofit Options for the Seismic Upgrading of Old Low-Rise School Buildings in Mexico
Authors: Tena-Colunga Arturo
Published: July 2003

An analytical study regarding the seismic upgrading of typical 60's and 70's designs for public school buildings in Mexico is presented. Some schools with these designs were moderately damaged during the 1985 Michoacán Earthquake in Mexico City. The damage was primarily observed in their longitudinal direction where existing slender RC columns have their weak axis. In addition, these columns are confined and shortened by masonry walls that do not run all the story height. These walls are supposed to be non-structural components, however, they experienced shear cracking during the quake due to the distress of the confined columns. Some school buildings were retrofitted after the Michoacán Earthquake adding post-tensioned bracing systems composed of prestressed high-slenderness steel strands (tension-only bracing systems), a retrofit option that is economical. In fact, there is an interest on assessing the effectiveness of this retrofit scheme in other regions with different soil conditions, as for example, the hard soils of the Mexican Pacific Coast. Therefore, the post-tensioning retrofit scheme used for the school buildings in Mexico City was also evaluated for hypothetical locations in the Mexican Pacific Coast. Another option that seems economical for the seismic retrofit of old school buildings in the Mexican Pacific Coast is the use of base isolators. Then, a retrofit plan using lead-rubber bearings was also evaluated. Acceleration time-histories recorded in the Mexican Pacific Coast during the 1985 Michoacán and the 1995 Manzanillo Earthquakes were used to assess the effectiveness of the studied retrofit schemes. Records in Mexico City for the 1985 Michoacán Earthquake and postulated ground motions for a Ms = 8.1 earthquake in Mexico City were also used. The effectiveness of each retrofit scheme is discussed through the comparison of the seismic behavior of original and retrofit structures using a comprehensive set of analyses.
Repair and Retrofit of Unreinforced Masonry Structures
Authors: Manzouri Teymour , Schuller Michael P. , Shing P. Benson , Amadei Bernard
Published: July 2003

A comprehensive study was conducted to evaluate the efficacy of different repair and retrofit techniques for unreinforced masonry (URM) structures. The study was to identify suitable grouting materials and procedures for the repair and retrofit of URM structures, quantify the efficacy of different repair and retrofit techniques, and develop analysis tools to evaluate the performance of masonry structures before and after retrofit. To this end, a number of grouting materials and procedures were evaluated with material tests, masonry component tests and shear wall tests. The experimental results indicate that the strength and stiffness of damaged walls can be fully restored with grout injection. Furthermore, the strength and ductility of a URM wall can be greatly enhanced by the introduction of steel reinforcement.
The Role of Building Foundations in Seismic Retrofit
Authors: Roeder Charles W. , Banerjee Sunirmal , Jung Debbie R. , Smith Sean K.
Published: July 2003

Existing buildings which do not satisfy modern seismic design requirements may be rehabilitated economically by the addition of steel bracing or reinforced concrete shear walls. However, steel bracing and concrete shear walls can place severe demands on the building foundation, and the existing foundations are likely to be inadequate. Strengthening of existing foundations may be exceedingly expensive, and the cost of the foundation work may dominate the seismic retrofit effort. Several foundation retrofit strategies are described and discussed. These strategies are invariably expensive, and the engineer may be tempted to place the major investment into strengthening or stiffening the structure with minimal work on the foundation. This concept may lead to increased potential for uplift and temporary overload of footings. In some cases this practice may have beneficial effect regarding the overall seismic response of the structure. It may reduce both seismic forces and maximum displacements experienced by the structure. The reduced foundation retrofit is unlikely to increase the collapse potential or life-safety risks of the building, while the structural retrofit should significantly improve the life-safety concerns. However, the combination of structural rehabilitation combined with minimal foundation rehabilitation are likely to increase the potential damage and economic loss during an earthquake.
Evaluation of Bridge Abutment Capacity and Stiffness during Earthquakes
Authors: Goel Rakesh K. , Chopra Anil K.
Published: July 2003

The “actual” capacity and stiffness values of the abutment-soil systems at the US 101/Painter Street Overpass, determined from its earthquake motions, are used to investigate how abutment stiffness varies during earthquakes and to evaluate current modeling procedures. It is found that the “actual” abutment stiffness may be significantly different during different phases of the shaking and decreases significantly as the abutment deformation increases. The CALTRANS modeling procedure leads to a good estimate of the transverse abutment stiffness and capacity. However, this procedure may overestimate the normal abutment stiffness and capacity by a factor of over two, indicating that the assumed value of 7.7 ksf for the ultimate passive resistance of the soil, used in the CALTRANS procedure, may be too high. The AASHTO-83 and ATC-6 procedures lead to an initial estimate of the abutment stiffness that is too high in both directions.
Enduring Lessons and Opportunities Lost from the San Fernando Earthquake of February 9, 1971
Authors: Jennings Paul C.
Published: July 2003

Twenty-five years have passed since the San Fernando earthquake of February 9, 1971. The paper reviews the lessons learned and not learned from this notable event. Most of the major lessons were reported within a few weeks of the earthquake by a panel appointed by the National Academies of Sciences and of Engineering. In this paper, the status of each of the eighteen general lessons cited by the panel is reviewed, plus two additional lessons selected from other studies of the earthquake. The lessons learned ranged broadly and concerned measures needed to reduce future earthquake hazards, as well as recommended scientific and engineering efforts. Although all of the lessons learned were not heeded, the San Fernando earthquake represented a turning point in public awareness and in actions taken to reduce earthquake hazard. Recent earthquakes have shown, however, that much remains to be done.
Enduring Land-Use Planning Lessons from the 1971 San Fernando Earthquake
Authors: Mader George G.
Published: July 2003

Recommendations contained in the report of the Joint Committee on Seismic Safety of the California Legislature on the 1971 San Fernando Earthquake serve as a basis for reviewing progress in reducing seismic hazards through land use planning in California during the last twenty-five years. Progress since 1971 in the use of normal planning tools to increase seismic safety is summarized. Finally, as a statement of remaining needs, recommendations for improvement of land use planning at state and local levels, as contained in the California Seismic Safety Commission's report on the Northridge Earthquake, are presented.
Correlation Study of Shear Wave Velocity in near Surface Geological Formations in Anchorage, Alaska
Authors: Nath S. K. , Chatterjee D. , Biswas N. N. , Dravinski M. , Cole D. A. , Papageorgiou A. , Rodriguez J. A. , Poran C. J.
Published: July 2003

In the summer of 1995, surface measurements of shear wave velocity (β) was conducted at thirty six sites, approximately, in the 0-50 m depth range. Of these, at seven sites values of β, soil log and blow count (N) from borehole measurement were available from previous investigations by others. Using these seven sites for calibration, we compared the velocity profiles yielded by the surface and borehole measurements for these sites. The results show broad similarities. Using the soil logs and shear wave velocity variations at the seven sites, four site classes (SC-Ic, SC-II, SC-III and SC-IV) could be identified. The surface method corresponding to the mean value of β tends to underestimate β between about 1 and 18 percent for site classes SC-Ic, SC-II and SC-III compared to the downhole method. For SC-IV, β is overestimated by 11 percent using surface method. Moreover, the blow count (N) data for each site class shows a linear relationship with β obtained by the surface measurement.
Effects of the Hinge Restrainers on the Response of the Aptos Creek Bridge during the 1989 Loma Prieta Earthquake
Authors: Abdel-Ghaffar Saber M. , Maragakis E“Manos” , Saiidi M“Saiid”
Published: July 2003

This paper presents the results of a study for the effects of the cable restrainers on the nonlinear seismic response of the Aptos Creek Bridge during the 1989 Loma Prieta earthquake. The earthquake analyses focus on the relative displacements of the hinge, the absolute displacements of the bridge, the restrainer force levels, the shear key and the shear pipe forces, the hinge impact, and the abutment and pile forces in both the longitudinal and the transverse directions. At the estimated earthquake excitation levels at the bridge site, it was found that the restrainers did not play a major role on the overall structural response. However, at higher acceleration levels they contributed significantly to the reduction of displacement and force responses.
Correlation between Strain-Based Low-Cycle Fatigue and Energy-Based Linear Damage Models
Authors: Chai Y. H. , Romstad K. M.
Published: July 2003

Although the potential for cumulative damage of structures during long duration earthquakes is generally recognized, most design codes do not explicitly takes into account the damage potential of such events. In this paper, a strain-based low-cycle fatigue model commonly used for the prediction of fatigue life in metals is adapted for cumulative damage assessment of structures under seismic conditions. By defining the number of load cycles in terms of the total plastic strain energy dissipated by the structure, the model is presented in a form capable of predicting the plastic strain energy capacity of the structure at the ultimate limit state. The plastic strain energy is expected to decrease rapidly with increased displacement in the small displacement range and to decrease gradually in a near linear manner with increased displacement in the large displacement range. The model is shown to calibrate reasonably well with small-scale aluminum cantilever specimens tested under large-amplitude reversed cyclic loading. At the ultimate limit state, the modified Park and Ang damage model may be considered as a linear approximation to the low-cycle fatigue model in the large displacement range.
Seismic Retrofitting of Rectangular Bridge Columns with Composite Straps
Authors: Saadatmanesh H. , Ehsani M. R. , Jin L.
Published: July 2003

Behavior of typical rectangular bridge columns with substandard design details for seismic forces was investigated. The poor performance of this type of column attested to the need for effective and economical seismic upgrading techniques. A method utilizing fiber reinforced polymer (FRP) composites to retrofit existing bridge columns is investigated in this paper. High-strength FRP straps are wrapped around the column in the potential plastic hinge region to increase confinement and to improve the behavior under seismic forces. Five rectangular columns with different reinforcement details were constructed and tested under reversed cyclic loading. Two columns were not retrofitted and were used as control specimens so that their hysteresis response could be compared with those for retrofitted columns. The results of this study indicated that significant improvement in ductility and energy absorption capacity can be achieved as a result of this retrofitting technique.
Analysis of Northridge Damaged Thirteen-Story WSMF Building
Authors: Maison Bruce F. , Kasai Kazuhiko
Published: July 2003

The case study building experienced moment connection fractures and has instructure recorded response. Correlative analyses are performed using a probability approach to describe the connection rotational capacities. The Northridge calibrated model is then subjected to other scenario earthquake records. The main points include:

-Northridge connection damage can be reasonably simulated using models that idealize the rotation capacities as random variables,

-Many of the connection fractures occurred from beam moment demands that were less than the beam yield moments,

-Vertical earthquake excitation and gravity loads did not play a major role in the connection fractures,

-The damaged building can withstand another Northridge intensity quake,

-Near-source ground motions from great quakes have the potential to collapse the building with pre-Northridge type connection details, and

-Connection rotation capacity can make the difference between building survival or collapse during severe quakes.
Ethical Dilemmas and Seismic Design
Authors: Spector Tom
Published: July 2003

Most research in the ongoing effort to improve building seismic safety has been devoted to improving building code methodology by refining the techniques of analysis and prediction of seismic forces. This agenda has left little room for the observation that how the code is regarded and interpreted by structural designers may have as much to do with overall seismic safety as do the code's written provisions. The purpose of this investigation is to look at both how the seismic code is viewed by practicing professional engineers and explore a range of ethical dilemmas entailed by interpreting the code. In conclusion, a case is made to consider interpretation of the seismic code to be an ethical, as well as technical matter; one that can be successfully addressed by a community of professionals acting together.
Seismic Isolation of Buildings Subjected to Typical Subduction Earthquake Motions for the Mexican Pacific Coast
Authors: Tena-Colunga Arturo , Gómez-Soberón Consuleo , Mun~oz-Loustaunau Abel
Published: July 2003

An analytical study on the application of different base isolation systems for original design or retrofit of typical building structures of the Mexican Pacific Coast is presented. The subject hypothetical buildings are located on hard soil conditions at Acapulco. Typical accelerograms for the Mexican subduction zone recorded during recent earthquakes were used for 3-D time-history analyses. Bidirectional input was used for the time-history analyses. The studied base isolation systems reported in this study are lead-rubber bearings (LRB) and steel-hysteretic dampers (SHD). For the original design case studies, the superstructures were designed: a) according to the seismic provisions of the building code of Guerrero state (RCGS-90) for the fixed-base condition and, b) according to an elastic design based upon a 3-D lateral force distribution consistent with dominant mode shapes for the isolated structure to yield the peak dynamic base shear transmitted by the isolation system. Material volumes for the superstructure were estimated for both the fixed-base code designs and the base-isolation designs. Important savings on the volume of concrete and steel reinforcement can be attained for the base isolated designs with respect to their counterpart fixed-base designs. Dynamic responses for the isolated structures compare favorably with those for the fixed-base structures. The study confirms many findings published in the literature regarding the effectiveness of base isolation and the effect of torsional responses. However, the study also shows that the dynamic stability of isolators is not always achieved using rational design procedures. The dynamic stability and design of the studied base isolators can be controlled by acceleration records associated to moderate earthquakes when these records are near the fault plane and by torsional responses.
Methodologies for Evaluating the Socio-Economic Consequences of Large Earthquakes
Authors: King Stephanie A. , Kiremidjian Anne S. , Basöz Nesrin , Law Kincho , Vucetic Mladen , Doroudian Macan , Olson Robert A. , Eidinger John M. , Goettel Kenneth A. , Horner Gerald
Published: July 2003

A comprehensive methodology for evaluating the socio-economic impacts of large earthquakes was developed during a three-year project carried out by a team of researchers assembled by the nonprofit organization California Universities for Research in Earthquake Engineering (CUREe). New models were developed for some of the methodology components, such as the identification and ranking of critical facilities. For other components, such as the estimation of building and lifeline component damage, existing models from the ATC-13 and NIBS studies were adopted and modified for use within a GIS environment. The methodology was illustrated through a case study for the city of Palo Alto, California. Damage and loss estimates were made for several earthquake scenarios. Critical buildings were identified and the water distribution system for the city was analyzed in terms of its post-earthquake service capacity. An analysis of the hospital facilities in Palo Alto was made to illustrate the use of benefit-cost analysis for seismic rehabilitation decisions.
Loss Estimation Due to Seismic Risks to Highway Systems
Authors: Werner Stuart D. , Taylor Craig E. , Moore James E.
Published: July 2003

Earthquake losses due to highway damage depend not only on the response characteristics of the highway components, but also on the nature of the overall highway system (e.g., redundancies, capacities, traffic demands, etc.). This paper describes recent developments for addressing these issues by using seismic risk analysis (SRA) of the highway system. It outlines a new SRA procedure, describes its application to the Memphis, Tennessee highway system, and summarizes research being conducted to further develop the procedure.
An Earthquake Loss Estimation Methodology for Buildings Based on ATC-13 and ATC-21
Authors: McCormack Thomas C. , Rad Franz N.
Published: July 2003

A survey of the seismic hazards for about 30,000 nonresidential buildings in Portland, Oregon was conducted, and an earthquake damage and loss estimation model was developed. To conduct the buildings survey, ATC-21's Rapid Screening Procedure was used. For each building the data included: address, year built, area, number of stories, building name, use, occupancy type, estimated range of number of people, nonstructural falling hazards, building type, and performance modifiers such as soft story and torsion. Soil data were provided by the Earthquake Hazard Maps published by the Oregon Department of Geology and Mineral Industries. The algorithm set up on the GIS was to compute the structural score based on ATC-21 score, modify the score based on the geologic condition of the site, and finally, compute the damage. The proposed loss estimation model is based on ATC-13, and the scoring system developed by ATC-21. The results are in terms of percent (or dollar) damage to buildings in the survey and loss of life and serious injuries.
Development of a National Earthquake Loss Estimation Methodology
Authors: Whitman Robert V. , Anagnos Thalia , Kircher Charles A. , Lagorio Henry J. , Lawson R. Scott , Schneider Philip
Published: July 2003

This paper summarizes the development of a geographic information system (GIS)-based regional loss estimation methodology for the United States funded as part of a four-and-one-half year project by the Federal Emergency Management Agency (FEMA) through the National Institute of Building Sciences (NIBS). The methodology incorporates state-of-the-art approaches for: characterizing earth science hazards, including ground shaking, liquefaction, and landsliding; estimating damage and losses to buildings and lifelines; estimating casualties, shelter requirements and economic losses; and data entry to support loss estimates. The history of the methodology development; the methodology's scope, framework, and limitations; supporting GIS software; potential user applications; and future developments are discussed.