bluuebunny/crossref_metadata_2025 huggingface dataset:
Communication Between Scientists and Practitioners: The Important Link in Knowledge Utilization
Authors: Gori Paula L.
Published: July 2003

Personal interaction between investigators doing research and potential users of results of research is essential for the incorporation of new information into policy and practice. Interactive workshops, advisory committees, interdisciplinary research projects, and professional societies are some of the arenas where this interaction takes place. Researchers, practitioners, and society benefit from increased interaction through better focused and directed research and receptive clientele for results of research.
Foam Rubber Modeling of the Lotung Large-Scale Seismic Experiment
Authors: Brune James N. , Anooshehpoor Abdolrasool
Published: July 2003

Results from a layered foam-rubber model of the Lotung Large-Scale Seismic Experiment are compared with the observed data. A Forced Vibration Test of the model predicts a peak response frequency at 4.0-4.1 hz. The actual peak response frequency of the 1/4-scale structure is 3.8 hz. Data from five earthquakes (designated, by EPRI, as events 6, 7, 8, 14, and 16) are used in this study. Events 7 and 16 are mainshocks and high-strain events; event 8 is the aftershock of event 7. Transfer functions from downhole stations to the surface for events 6, 7, 8, and 16 are compared with the corresponding transfer functions in the foam-rubber model. The foam-rubber results agree well with the observed data except for event 7 (the largest event). Transfer functions from the control motion to the top of the 1/4-scale containment for events 6, 7, 8, 14, and 16 are compared with the corresponding transfer functions in the foam-rubber model. For events 6, and 14, results of modeling using a low-strain assumption agree with the observed data. For events 7 and 16, results of modeling using a high-strain assumption agree with the observed frequency response of the containment, but the amplitudes are overestimated. For event 8, the experimental results agree well with the observed data when the high-strain assumption is used. In this study, structure response in a foam-rubber model with a stiff backfill does not support the existence of a stiff backfill at the Lotung site.
Displacement Control Device for Base-Isolated Bridges
Authors: Constantinou M. C. , Reinhorn A. M. , Mokha A. , Watson R.
Published: July 2003

An isolation system consisting of sliding Teflon bearings and displacement control devices is described for the seismic protection of bridges. The system utilizes multidirectional Teflon bearings for accommodating thermal movements and for providing the isolation mechanism and displacement control devices which exhibit bilinear behavior with controlled stiffness and characteristic strength. The devices provide rigidity for service loads below their characteristic strength and restoring force and energy dissipation for strong earthquake forces.
Ground Motion Model for Puget Sound Cohesionless Soil Sites
Authors: Ho Carlton L. , Kornher Karen , Tsiatas George
Published: July 2003

Surface response spectra for earthquake events must be based upon proper input seismic modelling. The surface response spectrum can be determined by convoluting a base response spectrum with a spectral amplification for the site. This required that an appropriate base spectrum of the earthquake motion and soil response model must have been used to develop the surface response spectra. Earthquakes in the Puget Sound basin are generally deep focus subduction zone events. These earthquakes are significantly different than the shallow focus strike slip events of California which are commonly used for this purpose. The spectral site amplification must be determined for the soils of the region. This paper considers the cohesionless soil sites only. The computer program SHAKE was used to evaluate the spectral amplification of different sites. Parameters for SHAKE were determined from Standard Penetration Test data. Parametric sensitivity studies were conducted for the spectral site amplification.
Maximum Likelihood Estimation of Strong-Motion Attenuation Relationships
Authors: McLaughlin K. L.
Published: July 2003

Strong-motion attenuation relations are commonly derived from earthquake ground motion collected on triggered recorders. Parametric attenuation relations are estimated from these data using standard least squares methods. The variance of ground acceleration is relatively large and for any given earthquake, there is a distance range for which only stations with larger than average amplitudes will trigger recording. Consequently observed accelerations at these distances are higher than the mean ground acceleration and a bias may be introduced into an attenuation relation regression by non-detection data censoring.
Ambient Vibration Tests of the Mexicali General Hospital
Authors: Mendoza L. , Reyes A. , Luco J. E.
Published: July 2003

Results of ambient vibration tests of the eight-story reinforced-concrete hospitalization tower of the Mexicali General Hospital are described. The structure suffered some damage during the November 1987 Superstition Hills earthquakes. The tests were conducted in April and August 1989 before and after major alterations of the building were made. The frequencies, modal damping ratios and mode shapes of some of the longitudinal, transverse and torsional modes were determined for the April and August 1989 conditions. It was found that the removal of the facade of the building resulted in a reduction of the longitudinal stiffness of the structure of the order of fifty percent. Measurements of the translation and rocking of the base indicate that soil-structure interaction effects play a moderate role in the transverse response of this structure and a negligible role in its longitudinal response.
The Earthquake-Resistant Properties of Chinese Traditional Architecture
Authors: Shiping Hu
Published: July 2003

This article explains why Chinese traditional architecture has effective earthquake-resistant properties. First the many factors that affect the response of buildings to earthquakes are presented. The article goes on to describe the features of Chinese traditional architecture that contribute to reduction of earthquake actions: the shape, configuration, and integrality of the traditional structure, particularly the excellent damping effect of the ductile tenon-mortise joint and the bracket set. Yingxian Pagoda and the Guanying Pavilion, two timber structures built around 1,000 years ago, have resisted many strong earthquakes, and an explanation is given for their excellent performance. The ability of masonry pagodas to withstand earthquakes is discussed with respect to non-occurrence of resonance, and the integrality and configuration. In the conclusion, the author answers the question of whether the good aseismic behavior of Chinese traditional building resulted from measures deliberately taken by the ancient builders.
The California Earthquake Insurance Program: Developments in 1990
Authors: Mittler Elliott
Published: July 2003

In the 1989-1990 legislative session, the state of California enacted over 130 bills related to earthquake safety. Among those was the passage of the Green, Hill, Areias, Farr California Residential Earthquake Recovery Act (SB 2902) establishing mandatory earthquake insurance for all single-family dwellings with homeowners insurance in the state. The reasons why and how this legislation was enacted are examined, as are the act's contents and implications for future legislation. The impact of this act on a national earthquake insurance program is also explored.
Repair and Strengthening of Reinforced Concrete Buildings for Seismic Resistance
Authors: Rodriguez M. , Park R.
Published: July 2003

This paper summarizes a review of the literature on the repair and strengthening of reinforced concrete buildings in seismic areas, with emphasis on the repair and strengthening of reinforced concrete columns. In particular, experimental and analytical investigations are described which provide information on the strength, ductility, and seismic behaviour of reinforced concrete columns repaired and strengthened by jacketing with or without added longitudinal reinforcement placed through the floor structure.
Improvements in the Tsunami Warning Center in Alaska
Authors: Sokolowski Thomas J.
Published: July 2003

The Alaska Tsunami Warning Center (ATWC) has implemented many major changes in order to provide timely and effective tsunami warning services for coastal populations in Alaska, and the west coasts of Canada and the lower 48 States. The basis for these improvements was the integration of computers and associated applied research developments into the operations. New concepts, developments, procedures, computers, and equipment resulted in a highly automated tsunami warning system which analyzes data from potential tsunamigenic earthquakes in real-time, and disseminates critical information to affected coastal populations via satellite and high speed teletypewriter communication systems. Seismic and tide networks have been enlarged to improve the accuracy and timeliness in determining earthquake parameters and confirming the existence of a tsunami. The ATWC's system has been exercised for seven recent potential tsunamigenic earthquakes with warnings being issued in an average of 11 minutes after an earthquake's origin time. The ATWC's community preparedness program has been expanded to aid those who may be caught in the immediate vicinity of a violent earthquake and its subsequent tsunami.
An Overview of Active Structural Control under Seismic Loads
Authors: Soong T. T. , Masri S. F. , Housner G. W.
Published: July 2003

The concept of active structural control as a means of structural protection against seismic loads, developed over the last 20 years, has received considerable attention in recent years. It has now reached the stage where active systems have been installed in full-scale structures. It is the purpose of this paper to provide an overview of this development with special emphasis placed on laboratory experiments using model structures and on full-scale implementation of some active control systems. Included in this paper is a report on the formation of a U.S. Panel on Structural Control Research and some discussion on possible future research directions in this exciting research area.
Observations on Two Seismic Strengthening Schemes for Concrete Frames
Authors: Bush Thomas D. , Wyllie Loring A. , Jirsa James O.
Published: July 2003

A large-scale model of a nonductile concrete frame with columns susceptible to shear failure was retrofitted with two strengthening schemes. In the first scheme, full-height concrete piers were added to the original columns. Tests showed that the strengthened column section behaved monolithically and the failure mode was shifted to hinging of the spandrel beams. Large increases in frame strength and stiffness were also realized. In the second scheme, a steel X-bracing system was attached to the frame's exterior face. Lateral capacity was governed by yielding and buckling of the braces. The system exhibited substantially increased frame stiffness and strength. Both systems were quite constructable and relied extensively on epoxy-grouted dowels. The pier system required a lower level of construction skill but was somewhat more labor intensive. The bracing system required a higher level of construction skill due to local variations in fit-up requirements and the need for field welding.
Status of U.S. Research on Structural Control Systems
Authors: Liu S. C. , Lagorio H. J. , Chong K. P.
Published: July 2003

This paper assesses the current status of control technology and its potential application to structural safety against seismic, wind and other dynamics loads. An intensive effort underway to develop a national research program is described. Research needs and important problems remaining from both the technological and practical standpoints are suggested.
Feasibility of the use of Microtremors in Estimating Site Response during Earthquakes: Some Test Cases in Italy
Authors: Rovelli Antonio , Singh Shri K. , Malagnini Luca , Amato Alessandro , Cocco Massimo
Published: July 2003

We explore the feasibility of the use of microtremors in estimating the amplification of seismic waves at soft sites in Italy. Microtremors were measured at three soft sites and nearby hard sites at night when the cultural noise was minimum. These soft sites were selected as those showing the largest amplifications of ground motion during earthquakes as compared to the records on the hard sites or with respect to the predicted spectra. We compare the soft-to-hard site microtremor spectral ratios with the corresponding acceleration spectral ratios. A rough estimate of the shape and level of spectral amplification is obtained from the microtremor data in all three cases. However, the details of the soft-to-hard site spectral ratio are not reproduced and some differences appear in (a) the frequency at which the maximum amplification occurs, and (b) the bandwidth of the significant amplification. More testing of the method is needed before its wider use for microzonation in Italy can be recommended.
Performance of Reinforced Concrete Buildings during the 1985 Chile Earthquake: Implications for the Design of Structural Walls
Authors: Wood Sharon L.
Published: July 2003

The 1985 Chile earthquake provided a rare opportunity to study the seismic response of buildings with reinforced concrete walls. More than 230 moderate-rise reinforced concrete buildings were located in the coastal city of Vin~a del Mar at the time of the earthquake. The majority of these buildings relied on structural walls to resist vertical and lateral loads. However, the walls did not have the reinforcement details required in current U.S. codes to ensure ductile response. A survey of damage following the earthquake indicated that most of these buildings sustained no structural damage. Analyses of the buildings indicated that the structural walls provided sufficient stiffness to limit the displacement response and the earthquake damage. The Vin~a del Mar building inventory is used to evaluate current building code provisions in the U.S. for structural walls. The excellent performance of the Chilean buildings during the 1985 earthquake suggests that requirements for boundary elements in walls may be relaxed if sufficient wall area is provided.
Seismology and Tectonics
Authors: Jacob Klaus H. , Pacheco Javier , Santana Guillermo , Arscott Elizabeth
Published: July 2003

The earthquake of April 22, 1991 was located in the eastern foothills of the Cordillera de Talamanca in Valle de la Estrella with epicentral coordinates of 9°38.62′N and 84°5.92″W and a focal depth of 21.5 km (Figure 2-1). An analysis of the seismograms recorded at teleseismic distances indicates that the causative fault was a shallow-angle thrust fault striking in a southeast-northwest direction and dipping at less that 30° gently towards the southwest. The lower block moved in a westerly direction while uplifting the upper-block east coast of Costa Rica by 1 to 1.5 meters. The plane of this fault rupture may either have reached the surface some distance offshore, or, possibly, failed to reach the surface. Aftershock data are consistent with this interpretation.
Geotechnical Aspects
Authors: Singh J.P. , Youd T. Leslie , Rollins Kyle M.
Published: July 2003

The earthquake caused severe damage that extended over a large region, including the provinces of Limon and Cartago in Costa Rica and the province of Bocas del Toro in Panama. Areas most affected in Costa Rica were the alluvial plains along the Caribbean Coast located west, northwest and southeast of Limon. These areas underwent extensive soil liquefaction and soil failures. Soil liquefaction caused severe damage to roads, bridges, railways, ports, water systems and banana plantations. Geotechnical aspects of bridge and roadway damage are covered in Chapter 6—Bridges.
Industrial Facilities
Authors: Swan Sam W. , Hamburger Ronald O.
Published: July 2003

This earthquake illustrates the seismic vulnerability of an agriculture-based economy that is centered in sparsely populated regions. Agricultural operations depend on lifelines—roads, railways, electrical power, potable and wastewater systems, and port facilities. There is an indirect dependence on refineries and oil pipelines to ensure a supply of fuel to the region, in order to keep the machinery of other lifelines running. The earthquake caused severe damage to roads, railways, bridges and water systems. As a result, shipments of produce were severely impaired. With loss of the means to transport products, damage to operations, such as shipping centers, assumed a secondary importance.
Socioeconomic Aspects
Authors: Aguirre Benigno E.
Published: July 2003

As of September, 1991, according to estimates furnished by the Banco Internacional de Desarrollo, the overall cost of the infrastructure damage and loss of export revenue occasioned by the earthquake was approximately $500 million. Over 7,000 houses were destroyed or damaged severely enough to require demolition. Approximately 30,000 people were left homeless. Forty-five public buildings were damaged.
California at Risk: Where Do We Go from Here?
Authors: Tobin L. Thomas , Turner Fred , Goodfellow James F. , Stoner Brian L.
Published: July 2003

In 1986, the state of California embarked on a comprehensive earthquake hazard reduction program described in California at Risk: Reducing Earthquake Hazards 1987-1992. This Program identifies hazard reduction efforts for existing development, emergency response, future development, recovery planning, education, and research. The goal is to reduce the state's earthquake hazards significantly by the year 2000. This paper reviews the development of the Program, the state's progress toward hazard reduction, seismic safety legislation and refinements in the Program's second five years.
Improving Measures to Reduce Earthquake Casualties
Authors: Durkin Michael E. , Thiel Charles C.
Published: July 2003

Current earthquake casualty reduction measures are examined and recommendations made for needed changes. Key new approaches are outlined and a new framework for understanding casualty reduction measures presented. The framework considers both issues of demand for medical services and supply within primary, secondary and tertiary prevention aspects of each. It is used to assess current measures against recent empirical data and to suggest changes that incorporate new data and methods. Issues include the management of emergency medical services, messages for individual protective actions and assumptions about the nature of injuries. Research has tended to consider primarily the demand side of earthquake injury prevention, focusing on the injured rather than the uninjured. Case series investigations have tended to be descriptive rather than analytical and be undertaken from a clinical rather than an epidemiological perspective, documenting medical aspects of earthquake injuries. Linking these injuries to the risk factors associated with them has not been as systematically studied. Proposed here is an approach for casualty reduction research to fill knowledge gaps. It includes steps to integrate future casualty data and assessment efforts into casualty modeling and into ongoing earthquake policy formation.
Design Professions and Earthquake Policy
Authors: May Peter J. , Stark Nancy
Published: July 2003

This article addresses the role of the design professions in enhancing seismic safety as evidenced by interviews with design professionals in the Pacific Northwest. Key policy issues of relevance to this discussion concern the role of codes and other regulatory efforts in influencing design practices. The findings indicate seismic design practices are driven by seismic codes and related norms of “good” engineering and seismic design. Economic and liability considerations constrain practices beyond those of code provisions. As a consequence, policy reforms for seismic risk reduction are highly dependent upon seismic code revision. Variation in seismic design practice is reduced through professional educational efforts, professional licensing and registration requirements, and code enforcement. These findings serve as qualified endorsement of the current federal “limited regulatory” strategy in working with private code-setting authorities to improve seismic code provisions. The qualifications concern the disjunctive impacts of the limited regulatory strategy.
Earthquake Engineering: Observations from California's Experience
Authors: Scott Stanley
Published: July 2003

A building's structural quality and seismic resistance are determined by decisions at each step in design, construction, management and maintenance. Key determinants are design-team skills, grasp of seismic-design issues, and ability to communicate with each other and the owner. In seismic regions, the design of all structures should incorporate adequate resistance to earthquake forces. First in the process come the crucial early decisions on a structure's budget, configuration, siting, and design. Major or critical structures should have their designs peer reviewed. Construction of all significant structures should be observed and inspected by qualified personnel who report to the owner. Plan checking and inspection by the building department should verify code compliance. Good construction work complying with design intent and detail will help assure a quality building that should perform as expected. After a building is put in use, its serviceability and life will be affected by the way it is operated, maintained and remodelled. At each step, effective strategies for applying knowledge increase the chances of success. Conclusions and appendix questions suggest further study and action useful in any seismic region to help assure actual compliance with goals discussed.
A Note on Inelastic Response Spectra for Systems with Bilinear Spring Force and Kinematic Strain-Hardening
Authors: de Béjar L. A. , Ganapathi K.
Published: July 2003

Parametric studies on inelastic response spectra for systems with bilinear spring resistance and kinematic strain-hardening, low-to-moderate viscous damping, and standing on firm soil, indicate that aseismic design of such systems based on the associated elasto-plastic spectra is not always conservative, in particular, for systems in the intermediate frequency range. By contrast, present understanding of the effect of viscous damping on inelastic spectra is thoroughly verified. In addition, mathematical expressions for a tripartite model of design spectra for inelastic systems are presented and tested for a ground motion record representative of a major destructive earthquake. These formulas provide generally conservative estimates of parameters of response for undamped systems, as compared with both numerically generated spectra and spectral upper bounds previously reported in the literature; however, for damped systems, the inelastic design spectra provide safe envelopes for most of the frequency range, but often make unconservative predictions over a small portion of the intermediate frequency range.
A Spectral Difference Method to Estimate Building Separations to Avoid Pounding
Authors: Jeng Van , Kasai Kazuhiko , Maison Bruce F.
Published: July 2003

A method to estimate the likely minimum building separation necessary to preclude seismic pounding is presented. The method is based on random vibration theory. The accuracy is demonstrated by numerical experiments using 9 artificial and 6 actual earthquake records. The relation between the minimum separation, period, height, damping and earthquake type are discussed. Example applications of the theory are presented. The effects of inelastic hysteretic building behavior are also discussed.
A Preliminary Model of Firm Foundation Acceleration Hazard in the San Francisco Bay Area
Authors: Litehiser J. , Marrone J. , Abrahamson N.
Published: July 2003

The results of a study of earthquake peak horizontal component acceleration hazard is presented for the nine counties of the San Francisco Bay Area. The main objective of the study is to develop an interim and simple estimate of the regional earthquake acceleration hazard using an extended hazard algorithm that allows a more complete consideration of recently published regional earthquake source parameters. Complexities of source directivity, soft foundation conditions, and site topography are not considered. Results are presented in the form of contour maps of acceleration on rock or stiff soil with a probability of exceedance of 10% for the next (as of 1990) 20 and 50 years. As would be expected, the locations of greatest earthquake shaking hazard in the Bay Area are near major active faults. When characteristic earthquake size, characteristic earthquake recurrence interval, and time of occurrence of the last earthquake along specified fault segments (if known) are explicitly used in the source model for larger earthquakes, the hazard computed depends significantly on these parameters. If smaller earthquakes are not constrained to major faults, but are considered to occur randomly throughout the Bay Area, significant high-frequency motion hazard at points away from the immediate vicinity of active faults comes from these smaller, randomly located earthquakes. All results show considerable variation of peak accelerations over areas generally treated as homogeneous in conventional engineering design practice for seismically active regions.
Stability of R-FBI Bearings: Analysis and Experiment
Authors: Mostaghel N. , Kelly J. M. , Clark P. W.
Published: July 2003

The Resilient—Friction Base Isolator (R—FBI) is a device which can be incorporated into the foundations of new and existing structures to protect them from damaging earthquake ground motions. The device consists of a short column composed of a set of identical flat rings with an elastic core (reinforced rubber plug). The elastic core is positioned such that it carries no axial load and distributes the lateral displacement uniformly across the clear height of the column. In this paper, considering an R—FBI bearing as a short column, an approximate analytical model for the analysis of its stability is presented. Assuming no negative pressure at the interfaces of the flat rings, the values of the critical lateral displacement and the critical vertical load are defined and calculated in terms of the system's parameters. The upper limit of the safe lateral displacement, the lateral displacement beyond which the lateral load carrying capacity of the isolator deteriorates, is also defined. To validate the analysis method, a single bearing was fabricated and tested under various normal loads. The test results strongly confirm the analytical predictions.
Performance of Elastomers in Isolation Bearings: A Literature Review
Authors: Taylor Andrew W. , Lin Albert N. , Martin Jonathan W.
Published: July 2003

Laminated elastomeric bearings have been used for about 30 years in the United States to isolate bridge substructures from the lateral forces induced by shrinkage and creep of their superstructures. More recently, elastomeric bearings have been increasingly employed in buildings and bridges as a means of decoupling the structure from seismic ground motions. Since most buildings and bridges have service lives of at least 30 to 60 years, questions about the long-term behavior of base-isolation bearings arise. This paper presents a review of literature relating to the long term performance of the elastomers used in seismic isolation bearings. Bearing performance requirements are discussed and material characteristics and fabrication procedures are outlined. Field experience and laboratory findings are reviewed. Finally, long-term environmental effects are discussed, including ozone degradation, corrosion, temperature effects, and the influence of bombardment of elastomers by high energy radiation.
Seismic Evaluation of Unreinforced Masonry Structures with Flexible Diaphragms
Authors: Tena-Colunga Arturo
Published: July 2003

A discrete linear-elastic, multi-degree-of-freedom (MDOF) dynamic model developed for the dynamic analysis of unreinforced masonry (URM) structures with flexible diaphragms is presented. The discrete MDOF dynamic model represents the dynamic response of the structure in a given direction by a reduced number of discrete masses associated to translational degrees of freedom acting in that direction. The discrete model considers the flexibility of the diaphragms and the rotations of the walls, which are included into the global translational degrees of freedom through static condensation. Soil-structure interaction effects can be easily incorporated in the method. The applicability of the method in the study of the dynamic response of a URM structure with flexible diaphragms is presented. The structure, an old firehouse located at Gilroy, California, has been instrumented by California Strong Motion Instrumentation Program (CSMIP). Instrumented records of the dynamic response of the firehouse of Gilroy during the Loma Prieta Earthquake are available. The firehouse survived the earthquake with little damage. The discrete dynamic model presented in this work has been able to reproduce well the recorded dynamic response of the firehouse of Gilroy during the Loma Prieta Earthquake.
Displacement-Based Design of RC Structures Subjected to Earthquakes
Authors: Moehle J. P.
Published: July 2003

Earthquake induced structural displacements are a main case of damage in structures subjected to earthquakes. Simple techniques for estimating structural displacements enable development of a design approach based explicitly on expected displacements. This approach is useful both in planning stages where decisions can be made to control displacement demands and in final design stages where details for structural and nonstructural elements are established. Comparison with more conventional force- or ductility-based approaches to design indicates that a displacement-based approach to design is both simple and effective.
Digital Instrument Response Correction for the Force-Balance Accelerometer
Authors: Novikova Elena I. , Trifunac M. D.
Published: July 2003

Correction for the instrument response of acceleration records obtained by force balance accelerometers (FBA) is necessary (a) to eliminate phase distortion at high frequencies, and (b) to broaden the useful frequency band up to, and beyond, the corner frequency of the system. The proposed algorithm contains operations in the time domain only and can be applied to any digitized record obtained from a FBA with known characteristics. The adequacy of the procedure depends on the accuracy of the information on the transducer's constants: damping ratio and natural frequency. An appropriate testing procedure is also presented.
Pilot Study of Crude Oil Transmission System Seismic Vulnerability in the Central U.S.
Authors: O'Rourke M. , Shinozuka M. , Ariman T. , Dobry R. , Grigoriu M. , Kozin F. , O'Rourke T.
Published: July 2003

This study evaluates the reliability of three crude oil transmission systems for a recurrence of the 1811-12 New Madrid earthquakes. The seismic hazards considered are seismic shaking, lateral spreading and slope failures. The vulnerability of the pipelines and associated pump station components as well as the overall system reliability are determined.
Strong Ground Motion and Source Parameters for Earthquakes in the Apennines, Italy
Authors: Capuano Paolo , Gasparini Paolo , Peronaci Marcello , Scarpa Roberto
Published: July 2003

Strong motion data from significant earthquakes recorded in the Apennines, Italy, over the period 1975-1985 are analyzed in this paper. We have developed an inversion procedure for studying accelerometer data in the frequency domain and for estimating some basic earthquake source parameters. Spectral models, characterized by a single or two corner frequencies have been tested by utilizing variable high frequency decay parameters to simulate a variety of attenuation and rupture models. A best fit of available data was obtained for mid-crustal Q values around 100-250, decay parameter γ in the range 2-3 and a model consisting of two corner frequencies. This last result is explained in part by the source complexity and in part by a spectral shape contaminated by resonance peaks. The data analyzed are confined to the seismic moment range 1015 - 1019 Nm, with stress drops 100-200 bars (1 bar = 0.1M Pa). We have compared results with scaling laws of source parameters for regions having different tectonic regimes or displaying seismic patterns such as swarms. A trend towards an asymptotic value for regions with extensional tectonics of stress drops around 200 bars is observed.
Seismologists Can Help Attenuate some Post-Earthquake Vibrations among the Public
Authors: Lamontagne Maurice , Du Berger Reynald , Stevens Anne E.
Published: July 2003

Very often after a strongly felt earthquake, the media and the general public consider seismologists to be the source of all information, particularly in regions where earthquakes occur infrequently. Widely felt earthquakes can have a strong social impact (“the post-earthquake vibrations among the public”) whenever the population is unprepared. Since 1935, eastern Canadian seismologists have been involved in four cases of post-earthquake communications with social impact. Recently, seismologists of the Geological Survey of Canada developed a communications strategy to help people cope with post-earthquake stress, particularly that component of stress arising from an insufficient knowledge of earthquakes. A communications plan is prepared before the emergency response period; a high priority is given to those persons who felt the earthquake most strongly; basic information on earthquake phenomena and preparedness is provided; and finally, seismologists make themselves both known and available before and after the earthquake. With this strategy, seismologists can help to relieve unnecessary anxiety and to promote positive preparation.
Seismic Analysis of Base-Isolated San Bernardino County Building
Authors: Maison Bruce F. , Ventura Carlos E.
Published: July 2003

The authors investigate the seismic behavior of an existing base isolated building and interpret its recorded response to the 1990 Upland California earthquake. They formulate a linear-elastic model that accurately represents the building during the earthquake and infer its response behaviors. Additional analyses using severe earthquake excitations demonstrate the building behavior in major events and hypothetical seismic gap pounding situations. Key findings include the following:

• The Upland earthquake resulted in relatively low intensity shaking at the site, and the building did not exhibit a classic soft story effect in the isolation system.

• A linear-elastic model can accurately idealize the building during this event.

• Under major earthquake excitation, base isolation can lead to peak story drifts, shears, overturning moments, and accelerations that are much smaller than those of nonisolated buildings.

• Pounding at seismic gaps can produce large story drifts, shears and accelerations. These peak pounding responses can be greater than those from nonisolated buildings (i.e., having no pounding).
A GIS-Based Assessment of Earthquake Property Damage and Casualty Risk: Salt Lake County, Utah
Authors: Emmi Philip C. , Horton Carl A.
Published: July 2003

This paper offers a probabilistic assessment of expected property damage and casualty risk due to the earthquake ground shaking hazard affecting Salt Lake County, Utah (population = 725,600). Salt Lake County is bisected by a segment of the Wasatch Fault. It is also at risk from twenty-one other nearby fault segments. Findings are based on (1) a microzonation of the earthquake ground shaking hazard, (2) an inventory of buildings by value, structural frame type and use, (3) earthquake damage functions defining the performance of buildings as a function of ground shaking intensity, (4) data on the density of residential and employee populations, and (5) earthquake casualty functions defining casualty risk as a function of building damage. The analysis is supported by the algebraic combination of digital map layers within a vector-based geographic information system. Triangular irregular network models show the expected distributions of casualties. Hazard mitigation policy implications are also considered.
On the Dynamic Analysis of Regular Shear Structures
Authors: Grigorian Mark
Published: July 2003

This study presents a new solution for the classic problem of multistory shear buildings composed of equal masses and springs connected in series and fixed in position at the ground level. The governing equation of motion of this close-coupled system is derived in terms of the finite difference operators. Discrete sinusoidal functions are used to describe the time dependent excitations of such structures under arbitrarily applied joint loading. Typical mode shapes and eigenfrequencies are worked out to demonstrate the applications of the proposed formulae. It is argued that these solutions are exact within the bounds of the theoretical assumptions since they satisfy both the governing difference equation of motion as well as the prescribed boundary conditions. The concept of the “Affine” oscillator is also introduced to assess the base shear of the multidegree of freedom structure by means of a corresponding single degree of freedom system. The investigation of active control of an existing problem is reworked to demonstrate the accuracy and the simplicity of the proposed solution. The Affine oscillator is also used to study the total shear reduction of a base isolated shear type building. It is concluded that the proposed solutions provide simple yet powerful means of manual analysis for the class of structure considered in this paper.
Response of R/C Buildings during the 1987 Whittier Narrows Earthquake
Authors: Maragakis Emmanuel , Saiidi Mehdi , Abdel-Ghaffar Saber
Published: July 2003

Strong motion records from several reinforced concrete structures were recovered after the 1987 Whittier, California earthquake. The objective of this paper is to present the highlights of a research study which was performed to review the available data from reinforced concrete buildings, to select representative buildings, and to analyze these buildings using available computer programs for linear analysis. Linear-elastic mathematical models were built for each structure based on the physical properties of the structural members. A comparison of the results of the computer analysis to the available measured responses data showed good agreement for the majority of the buildings studied. Limited studies on the effects of damping variation and soil-structure interaction were performed. The results of this study have led to the conclusion that the linear dynamic analysis can realistically predict the response of reinforced concrete structures subjected to small to moderate earthquakes. The deviations from the elastic response were consistent with the observed damage of the structures during the Whittier earthquake.
Earthquake Microzoning from Soil Properties
Authors: Hodder A. P. W. , Graham M. Z.
Published: July 2003

The extent of damage caused by an earthquake in Wellington, New Zealand, in 1968 to buildings erected on a variety of regoliths and foundation materials is correlated with the thickness of the regolith, the depth to the water table and semi-quantitative parameters derived from soil profile descriptions, particularly related to soil type and soil structure. From linear regression correlations, the expected damage for a comparable earthquake elsewhere can be determined. The model was tested for soil data for the Edgecumbe area, hit by a damaging earthquake in 1987. The predictions were sufficiently in accord with observations to suggest that soil properties that reflect the geotechnical properties of the upper parts of the regolith, particularly those that measure the shear strength, shear wave velocity and viscous damping of that material, may be useful for earthquake microzoning purposes in areas where there is a considerable thickness of unconsolidated materials above bedrock.
Evaluation of Seismic Design Criteria for Highway Bridges
Authors: Miranda Eduardo
Published: July 2003

After an overview of the development of U.S. seismic design specifications for highway bridges an evaluation of current Caltrans and AASHTO seismic criteria is presented. Linear and nonlinear response spectra of ground motions recorded on different soil conditions in the Loma Prieta earthquake and other recent earthquakes are compared with code recommendations. Special emphasis is placed on how present design procedures reduce elastic forces to take into account the energy absorption capacity of the structure, and on the estimation of maximum inelastic deformations. Results indicate that current design recommendations may underestimate strength and deformation demands, particularly for short-period bridges and for bridges on soft soils. Finally, recommendations are made on how seismic design specifications may be improved.
Ground Motion Model for the 1989 M 6.9 Loma Prieta Earthquake Including Effects of Source, Path, and Site
Authors: Schneider John F. , Silva Walter J. , Stark Cathy
Published: July 2003

The objective of this study is to assess the effects of source finiteness, crustal wave propagation, and site response upon recorded strong ground motions from the 1989 Loma Prieta earthquake. Our analysis uses band limited white noise (BLWN) with random vibration theory (RVT) to produce site-specific estimates of peak acceleration and response spectral ordinates for both a point-source and finite-source model. Effects of nonlinear soil response are modeled through an equivalent-linear approach. The point-source model additionally accommodates crustal propagation effects in terms of direct-plus-postcritical reflections.
Variation of Site Response at the UCSB Dense Array of Portable Accelerometers
Authors: Steidl Jamison H.
Published: July 2003

Ten Kinemetrics model SSA-2 Solid State Accelerographs were deployed in two dense arrays following the Landers-Big Bear earthquake sequence. The two arrays were separated by approximately three km, the first at a shallow alluvial soil site and the second at a rock site. We examine the soil and rock sites in terms of spectral ratio and cross-spectrum estimates of the site response. In order to construct an accurate representation of the motion in the horizontal plane, we treat the two horizontal components simultaneously as a complex signal. The Fourier transform of this complex signal represents the true motion in the horizontal plane as expressed in the frequency domain. The spectral ratio estimate is the ratio of this Fourier transform at the soil sites to the rock sites. The cross-spectrum estimate is the ratio of the cross-spectral density between the soil and rock sites to the power spectral density of the rock site. Spectral ratio estimates of site amplification are consistently higher than cross-spectrum estimates. On average the soil sites show amplification factors on the order of 2 to 4 relative to the rock sites between the frequencies of 4 to 15 Hz. There are, however, large variations in the ground motion recorded at sites with separations as small as 80 m. These variations demonstrate that site response studies can be biased by the choice of location of the sensor at distances of 80 m. We conclude that in the analysis of site-specific amplification both cross-spectrum and spectral ratio techniques should be used along with ensemble averages over many events.
Supplemental Damping for Improved Seismic Performance
Authors: Hanson Robert D.
Published: July 2003

The results of several studies on the effects of supplemental viscous damping on the response of elastic and elasto-plastic single-degree-of-freedom systems are used to provide insight to the effects of large damping on the earthquake response of buildings and the interpretation of studies reporting the equivalent damping and increased stiffness characteristics of specific types of supplemental energy dissipation devices. Extension to multi-story buildings is discussed briefly. Conversion of the properties of viscous, viscoelastic, friction, and metallic yield device characteristics to equivalent viscous damping are proposed. Specific recommendations for the incorporation of the effects of supplemental energy dissipation devices in the code design process are given.
Testing of Passive Energy Dissipation Systems
Authors: Aiken Ian D. , Nims Douglas K. , Whittaker Andrew S. , Kelly James M.
Published: July 2003

Over the period 1986 to 1991, seven different passive energy dissipation systems were studied in experimental research programs at the Earthquake Engineering Research Center of the University of California at Berkeley. This paper presents an overview of these studies, describing the different types of devices, the results of the shake table experiments, and associated analytical work. Four of the systems studied are friction systems, and of these, three (Sumitomo, Pall, and Friction-Slip) are based on Coulomb friction. The fourth is the Fluor-Daniel Energy Dissipating Restraint, which is a device capable of providing self-centering friction resistance that is proportional to displacement. The three other systems all have different energy dissipation mechanisms: ADAS elements, which utilize the yielding of mild-steel X-plates; viscoelastic shear dampers using a 3M acrylic copolymer as the dissipative element; and Nickel-Titanium alloy shape-memory devices that take advantage of reversible, stress-induced phase changes in the alloy to dissipate energy. The effectiveness of the various systems is evaluated by comparing the response of the test structures without and with the energy dissipators. In some cases, where devices were studied using the same test structure, they are compared directly. All of the systems investigated exhibited characteristics beneficial to improved structural response to earthquake loading.
Seismic Response Control of Buildings Using Friction Dampers
Authors: Cherry S. , Filiatrault A.
Published: July 2003

In the last decade, many energy dissipating systems have been proposed to raise the seismic design of structures beyond the conventional ductility design approach. Among these new systems, friction damping has shown some great potential. In a friction damped system, friction damping devices are inserted in a structure and slip at a predetermined optimum load during severe seismic excitations, before any yielding of the structural members has occurred. Slipping of the devices allows the structure to dissipate the input seismic energy mechanically by friction rather than by inelastic deformation of the structural elements. This paper presents an overview of the recent research and development in Canada on a particular type of friction damped bracing. Analytical and shake table test results are first summarized to illustrate the earthquake performance of friction damped structures compared to the performance of conventional building systems. The development of a design slip load spectrum for the rapid estimation of the optimum slip load distribution is then presented. Finally, two practical examples of the implementation of this system are described: (1) the design of a reinforced concrete library building; and (2) the retrofit of a precast concrete school building.
The Use of the Energy Dissipating Restraint for Seismic Hazard Mitigation
Authors: Nims Douglas K. , Richter Phillip J. , Bachman Robert E.
Published: July 2003

This paper describes the mechanical operation and presents parametric studies for the Energy Dissipating Restraint (EDR). The EDR is a strongly self-centering passive friction-based seismic energy dissipator with a wide range of hysteretic behaviors. In the behaviors of most interest in seismic design, the slip load is proportional to displacement. Typically the EDR would be installed in a building as part of the bracing system which resists seismically induced lateral forces.