bluuebunny/crossref_metadata_2025 huggingface dataset:
Slotted Bolted Connection Energy Dissipators
Authors: Grigorian C. E. , Yang T. S. , Popov E. P.
Published: July 2003

Slotted Bolted Connections (SBCs) are modified bolted connections designed to dissipate energy through friction during rectilinear tension and compression loading cycles. Experimental results on two types of SBCs are reported. In one type, friction occurs between clean mill scale steel surfaces; in the other, friction is between clean mill scale steel and brass surfaces. The behavior of connections with brass on steel frictional surfaces is found to be more uniform and simpler to model analytically than that with steel on steel surfaces. These connections maintain essentially constant slip force, and unlike those with steel on steel surfaces, require minimal overstrength of the system in design. The frictional mechanisms giving rise to the observed behavior are explained. As an example of application a one story diagonally braced frame was designed and its behavior determined for four different earthquakes. Experimental results are presented for the fabricated SBC for this frame subjected consecutively to the four displacement histories derived from these earthquakes. The agreement between the analytical and experimental results is found to be excellent. Because of the intrinsic simplicity of the SBCs and their very low cost, their use in seismic design and retrofit applications appears to be very promising.
Design of Steel Triangular Plate Energy Absorbers for Seismic-Resistant Construction
Authors: Tsai Keh-Chyuan , Chen Huan-Wei , Hong Ching-Ping , Su Yung-Feng
Published: July 2003

Building structures must be constructed to dissipate a large amount of seismic energy in order to achieve economical earthquake-resistant constructions. In this paper, recent research findings on the effectiveness of using steel triangular plates welded as the added damping and stiffness (ADAS) device for earthquake-resistant structures are presented. Experimental results indicate that a properly welded steel triangular-plate added damping and stiffness device (TADAS) can sustain a large number of yielding reversals without any stiffness or strength degradation. The effects of the ratio of the TADAS element stiffness to that of the bare frame, and the ratio of the entire frame yield strength to that associated with the TADAS element on the seismic response of the added damping and stiffness structures are discussed. Based on these studies, a design methodology and an example are developed for the application of the TADAS device in earthquake-resistant constructions.
Friction-Dampers for Seismic Control of Canadian Space Agency Headquarters
Authors: Pall Avtar , Vezina Serge , Proulx Pierre , Pall Rashmi
Published: July 2003

Friction-dampers have been used for the aseismic design of the headquarters building of the Canadian Space Agency. Three-dimensional nonlinear time-history dynamic analysis was used to determine the seismic response of the structure. Comparison of seismic response with conventional structural systems demonstrated the enhanced performance of a friction-damped structure. The introduction of supplemental damping provided by the friction-dampers eliminated the necessity of dependence on ductility while the structure remained elastic without damage. The chosen structural system provides an economical design solution and significantly increases its damage control potential to safeguard the building and its valuable contents against earthquakes.
Seismic Upgrade in San Francisco Using Energy Dissipation Devices
Authors: Perry Cynthia L. , Fierro Eduardo A. , Sedarat Hassan , Scholl Roger E.
Published: July 2003

For the first time in the United States, earthquake energy dissipation devices have been used for the seismic upgrade of a building located in San Francisco, California. The devices used are Added Damping and Stiffness (ADAS) elements which consist of 50 ksi steel plates which deform plastically during severe earthquakes to dissipate energy. The ADAS elements were used in conjunction with steel chevron braces as part of the seismic upgrade of a 2-story nonductile concrete frame structure built in 1967. The building suffered both structural and nonstructural damage during the 1989 Loma Prieta Earthquake and appeared to be a life safety hazard for a major earthquake. The ADAS upgrade scheme was selected over other more conventional schemes, in part, because the design seismic force could be limited to the capacity of the existing foundation system. The paper provides a case study and summarizes the seismic evaluation and upgrade design, the linear and nonlinear analyses performed, modeling assumptions, unique design details, the permit approval process, and final construction. In addition, comparisons are presented showing shear forces and displacements for the original building and the final design with chevron braces and ADAS elements.
Experiences on the Use of Supplementary Energy Dissipators on Building Structures
Authors: Martinez-Romero Enrique
Published: July 2003

Ductility, or deformation energy, is by far the largest source of energy dissipation of structures, since normal levels of internal damping represent only a small portion of energy dissipation. However, large material deformations such as those required in building components to perform in a ductile manner, are often associated with cracking and degradation of its strength, particularly in concrete structures. The installation of some manufactured devices to critical regions of structural systems, specifically engineered to concentrate on them the largest part of the dissipated energy during an earthquake, increases the structure's overall thoroughness and improves its performance and reliability during major seismic events.

This paper describes the retrofit of three buildings in Mexico City using damping devices. The size and number of these added elements are a function of the dynamic characteristics of the specific structure, the amount of previous damage, the anticipated earthquake motion imposed to the structure and the design performance level intended.
Fundamental Design Issues for Supplemental Damping Applications
Authors: Scholl Roger
Published: July 2003

In considering supplemental damping for a project, immediate questions that the structural engineer must address are: 1) Is the building suitable for supplemental damping; 2) How much damping should be provided; and 3) How should the dampers be distributed in the building? These are issues that need to be resolved irrespective of the type of damper used. The evaluation in this paper shows that supplemental damping is ideally suited for flexible frame buildings, or buildings detailed to accommodate interstory drift ratios of about 0.01 without significant damage. Providing 10% to 20% supplemental damping reduces response significantly for most structures. Providing more damping is difficult to justify from a cost-benefit perspective. Providing less supplemental damping can reduce earthquake response for structures having only small amounts of inherent damping; e.g., 1% to 2%. For most buildings having predominant fundamental mode response, the distribution of dampers in a structure is determined mostly from designing to carry the damper lateral forces. Frame member stresses, plan stiffness regularity, and elevation stiffness regularity are critical design considerations for establishing damper distributions in buildings.
Analysis of Strong Motion Records from Uttarkashi Earthquake for Assessment of Code Provisions for Different Seismic Zones
Authors: Jain Sudhir K. , Das Satrajit
Published: July 2003

Strong motion records have been obtained at 13 stations during the Uttarkashi earthquake of October 20, 1991 (magnitude 6.6). A study has been conducted on these time histories to assess the codal provisions in India. Emphasis of the study is on evaluating relative consistency of design provisions for different seismic zones in India. The average response spectra from this earthquake show concentration of significantly more energy in low period range and less energy in high period range. The magnitude of seismic design force for zones I, II, and III is consistent while it is too low for zone IV; no records were obtained in area with shaking intensity corresponding to zone V. It is seen that for buildings in zones I, II, and III, the present design provisions may be lowered either by relaxing the requirement of special ductile detailing, or by reducing the design force. On the other hand, design provisions for zone IV need to be revised upwards.
Tests on Steel and Composite Beam-to-Column Connections Strength and Stiffness Aspects
Authors: Kakaliagos Aristotle K. , Bouwkamp Jack G.
Published: July 2003

The connection interface of seven welded and bolted beam-to column connections under cyclic alternating loads, has been studied. Three fully welded connections were designed to compare the effect of filled-in concrete in a typical steel column section (a composite section) with the response of typical welded connections with and without column-web stiffeners. A similar set of three specimens were tested to assess the composite effect for connections with bolted endplates. A final, seventh, bolted beam-column connection, with composite sections for both the column and the beam, was also tested. The test results have demonstrated the effectiveness of concrete in replacing the stiffeners. Compared to the welded unstiffened connection, the use of bolted endplate connections or of composite column sections can increase the elastic moment-rotation stiffness of the connection, introducing however cyclic stiffness degrading phenomena when stressed beyond the elastic limit.
Assessment and Retrofit of a Reinforced Concrete Bridge Pier for Seismic Resistance
Authors: Park R. , Rodriguez M. E. , Dekker D. R.
Published: July 2003

Typical structural deficiencies in some reinforced concrete bridges designed for seismic resistance before current seismic codes were introduced are briefly outlined. Results of simulated seismic load tests conducted on the critical region of a reinforced concrete bridge pier designed in New Zealand in 1936 are presented. The tests involved the application of compressive axial loading and quasi-static cyclic lateral loading to a full-scale subassemblage representing the column-cap beam region of the as-built pier. Subsequent loading tests were conducted on the pier retrofitted mainly by the addition of steel plates welded to the ends of the plain round longitudinal bars to improve anchorage. The improved bar anchorage enabled the pier to develop its full theoretical flexural strength, but the considerable loss of stiffness due to bond degradation which occurred in the initial test on the as-built pier was not restored.
Design Strategies for the Seismic Retrofit of Reinforced Concrete Frames
Authors: Pincheira José A.
Published: July 2003

Due to economical and practical considerations, the seismic rehabilitation of buildings is generally confined to strategic areas of the structure in which only selected elements are modified or new elements are added. While these modified or new elements can be designed to have substantial strength and ductility, studies have shown that unless the retrofit scheme is stiff enough to control lateral drifts, significant damage to existing non-strengthened elements can be expected. This paper summarizes some of the results of a series of analytical studies conducted on prototype reinforced concrete frames strengthened with some of the most commonly used rehabilitation techniques. Based on the results of these studies, a design strategy that uses lateral drift rather than lateral strength as the main criterion for the design of retrofit schemes is presented.
Earthquake Code for Design and Construction
Authors: Celebi Mehmet
Published: July 2003

The first earthquake code in Turkey was enacted in 1944. Revisions were issued in 1949, 1953, 1961, 1968 and 1975.

At the time of March 13, 1992 Erzincan earthquake, the seismic resistant design code in effect was the code adopted in 1975, Specifications for Structures to be Built in Disaster Areas. The code has provisions for other disasters—avalanches, landslides, floods, and fire—in addition to earthquakes. The code was prepared under the auspices of and issued by the General Directorate of Disaster Affairs of the Ministry of Public Works and Settlement (formerly Ministry of Reconstruction and Resettlement) and enacted into law by ruling of the Council of Ministers. The complete code is included in the latest issue of Earthquake Resistant Regulations: A World List, published by the International Association for Earthquake Engineering (1988). A draft of revisions to the 1975 Turkish building code is currently in the final review process. This proposed code revision was being circulated for review at the time of the March 13 earthquake.
Buildings
Authors: Malley James O. , Celebi Mehmet , Bruneau Michel , Saaticioglu Murat , Erdik Mustafa , Gulkan Polat
Published: July 2003

The performance of building structures in the March 13, 1992 Erzincan, Turkey, earthquake caused considerable loss of life and property. Studying the reasons for both the good and poor performance of the buildings affected by this earthquake adds to the knowledge base used to improve the seismic resistance of these structures.
Industrial Facilities
Authors: Celebi Mehmet
Published: July 2003

The industries as well as the economic structure of the Erzincan basin is oriented toward agriculture. Two of the larger industrial facilities are the Erzincan Sugar Refinery and the Sumerbank Cotton Textile Factory. In addition, lighter industries such as flour mills, machine shops and copper molding and processing shops exist in the area.
Lifelines
Authors: Tilford Norman R. , Ballantyne Donald B.
Published: July 2003

It is a tribute to the hardiness of the Turkish people and the experience of Turkish agencies over the past few decades in dealing with civil emergencies (many of which were earthquakes), that lifeline damage was so well contained in the March 13, 1992, event. The severe winter weather contributed to the potential for adverse lifeline impacts. The loss of all three local hospitals and a significant part of the local medical community was extremely demoralizing.
Special In-Country Report
Authors: Gulkan Polat
Published: July 2003

At the request of the LFE Committee, this special in-country report was compiled by the author in the days following the March 13, 1992, event. It is both personal and technical in nature and is presented here in full. Readers are advised that topics covered elsewhere in this volume may have been prepared using data made available only after this special in-country report was completed. EERI is grateful to the author for his contribution and insights into problems and effects that only someone in-country could offer.
The Impact of Seismic Strengthening and Code Related Issues in Restoration, Renovation, and Re-Use of Historic Buildings
Authors: Levin Brenda , Bach Margaret
Published: July 2003

The need to reconcile seismic strengthening and other code-related issues with historic preservation objectives poses a variety of challenges for the design professional. A thorough knowledge of the local, state and national regulatory contexts, along with an understanding of two underlying principles, equivalency and life safety, provide a necessary framework for undertaking renovation projects. Two case studies involving important Los Angeles historic buildings, the Wiltern Theater and Grand Central Square, illustrate the complexities of code compliance with respect to preservation and programmatic goals, specifically in the areas of seismic retrofit, fire-life safety and disabled access. Successful historic preservation projects can benefit from a thorough pre-design phase and an experienced project team. Modifications and refinements to regulatory procedures, particularly at the local level, could also significantly facilitate restoration, renovation and re-use of historic buildings.
The Architectural Heritage of Campania: Protection from and Prevention of Seismic Hazards
Authors: Pezzullo Adele
Published: July 2003

This paper concerns the rehabilitation of historical buildings located in seismic areas, and is organized in two parts. The first part considers some of the new trends in the field of research in preservation and rehabilitation. These are elaborated in the following five-point summary:

1) Maintenance of historical buildings as an efficient means of minimizing damage from an earthquake.

2) Reduction of consolidation. The present-day policy is that of limiting “strengthening work” intervention in favor of “small and timely repairs.”

3) In-depth knowledge as a necessary premise to plan a rehabilitation project.

4) Re-evaluation of traditional techniques by incorporating modern materials

5) Preservation of the function and character of monuments in their changing life (use) and new technological needs.

The second part of the paper describes examples of rehabilitation undertaken in the aftermath of the 1980 Irpinia earthquake.
The Diagnosis Research Project
Authors: Binda Luigia , Roberti Giulio Mirabella , Abbaneo Silvia
Published: July 2003

The Friuli and Irpinia earthquakes, and subsequent experiences, have underscored the need for adequate damage assessment prior to seismic rehabilitation. Furthermore, assessment can be enhanced by preventive studies under the guidance of those in charge of hazard mitigation (architects, engineers, etc.). Research procedures must be defined so that findings can be used for damage assessment and as input data for structural analysis and control models. This paper provides evaluations of in-situ and laboratory tests on materials for existing unreinforced masonry structures and, in particular, touches upon the difficulty of interpreting the results of NDE tests. Furthermore the need for a design of the investigation prepared by persons responsible for the rehabilitation is pointed out.
Repair and Upgrading Techniques of Unreinforced Masonry Structures Utilized after the Friuli and Campania/Basilicata Earthquakes
Authors: Modena Claudio
Published: July 2003

The current Italian seismic code and recommendations include extended sections dedicated to the repair and strengthening of existing unreinforced masonry structures. Besides giving the general guidelines of what is required to assure structural safety, the code also furnishes detailed specifications regarding the techniques which can, and in some cases, must be used to do so. Originally developed in emergency conditions, i.e., for the urgent interventions in the zones stricken by the Friuli and Campania-Basilicata earthquakes, they progressively became the current practice systematically applied in the restoration of masonry structures. Such a trend caused major concern not only with regard to the conservation aspects of the cultural heritage, but also from the point of view of structural safety. In fact, a better understanding of the needs of repair and strengthening of masonry structures, a better knowledge of the behaviour and of the efficiency of the various possible techniques, and a renewed reliance on traditional materials and techniques are needed. In recent years, increasing efforts have been made to provide the scientific basis required to meet such needs.
Monument Safety in Seismic Areas
Authors: Gavarini Carlo
Published: July 2003

The safety philosophy underlying current technical codes mainly addresses new buildings, with little or no attention paid to existing structures and in particular to monuments. The objective of the underlying philosophy is the safeguarding of human lives, and material goods, whereas cultural values are not directly considered. Therefore, if monuments and the cultural values which they represent are to be protected, new basic standards resulting from interdisciplinary research and debate have to be established. This critical process will eventually lead to a set of guidelines which will constitute what could be called a Code for the Seismic Protection of Monuments.
Policies and Standards for Reoccupancy Repair of Earthquake-Damaged Buildings
Authors: Holmes William T.
Published: July 2003

Following a damaging earthquake, many buildings may be closed pending determination of safety and necessary repairs. A lack of repair standards and criteria for reoccupancy created controversy and denied owners use of their buildings after recent earthquakes. Conservative standards may delay the economic recovery of the community. Unconservative standards could lead to an equal or worse situation in the next earthquake. In order to develop technical standards that will solve this problem, the acceptable levels of safety for reoccupancy first must be established. Development of rational standards has been hindered by a limited ability to estimate actual lateral-load capacity of buildings of various materials and in various damage states. Once a policy for acceptable levels of safety is established, however, technical guidelines could be developed which would improve the current situation.
Post Earthquake Reconstruction Regulation by Local Government
Authors: Russell James E.
Published: July 2003

Decisions regarding reconstruction of earthquake damaged buildings are crucial to the effectiveness of a community's recovery and to its future safety. Two California cities are the focus of a comparison of the formulation and results of reconstruction policies and standards following the 1989 Loma Prieta earthquake. The Town of Los Gatos and the City of Oakland are very different in size and demography but suffered similar levels of earthquake damage. The technical content of the repair standards and the methods of administration adopted by these two cities provide a contrast in the way local governments handle these issues in the post-earthquake environment. A summary and comparison of the effectiveness of these standards is provided and recommendations are included for efforts to assist and prepare others to establish effective and balanced post-earthquake reconstruction policy.
Design Forces for Drift and Damage Control: A Second Look at the Substitute Structure Approach
Authors: Bonacci John F.
Published: July 2003

This paper explores the development of a method that is useful for design of reinforced concrete (RC) frame structures to resist earthquakes. The substitute structure method, originally proposed in the 1970s, makes an analogy between viscously damped linear and hysteretic response for the purpose of estimating maximum displacement. The evolution of the method is retraced in order to emphasize its unique reliance on experimental results, which are needed to establish rules for assignment of substitute linear properties. Recent dynamic test results are used to extend significantly the calibration of the method, which furnishes design loads on the basis of drift and damage control.
New Seismic Design Specifications of Highway Bridges in Japan
Authors: Kawashima Kazuhiko , Hasegawa Kinji
Published: July 2003

This paper presents the new seismic design specifications for highway bridges issued by the Ministry of Construction in February 1990. Revisions of the previous specifications were based on the damage characteristics of highway bridges that were developed after the recent earthquakes. The primary revised items include the seismic lateral force, evaluation of inertia force for design of substructures considering structural response, checking the bearing capacity of reinforced concrete piers for lateral load, and dynamic response analysis. Emphasis is placed on the background of the revisions introduced in the new seismic design specifications.
Evaluation of Strength Reduction Factors for Earthquake-Resistant Design
Authors: Miranda Eduardo , Bertero Vitelmo V.
Published: July 2003

Strength reduction factors which permit estimation of inelastic strength demands from elastic strength demands are evaluated. Results from various investigations of strength reduction factors carried out over the last 30 years are reviewed, and their results are presented in a common format which facilitates their comparison. The main parameters that affect the magnitude of strength reductions are discussed. The evaluation of the results indicates that strength reductions are primarily influenced by the maximum tolerable displacement ductility demand, the period of the system and the soil conditions at the site. Simplified expressions of strength reduction factors to estimate inelastic design spectra as functions of these primary-influencing parameters are presented.
Behavior of Mobility-Disabled People in Earthquakes: A Simulation Experiment
Authors: Rahimi Mansour
Published: July 2003

Disabled people are considered a high risk group in earthquake emergencies. A simulation experiment was conducted to assess the behavior of disabled occupants in earthquakes. A living room was set-up to show the after-effects of two simulated California earthquakes (low intensity R4.0 and high intensity R6.5) to a building's contents. Seventy-two participants were selected: 24 users of manual wheelchairs, 24 users of powered wheelchairs, and 24 able-bodied persons as a comparison base-line. Participants' movements were video taped and later analyzed based on a number of task performance measures. It was found that the users of manual wheelchairs performed the instructed tasks significantly faster than the users of powered wheelchairs under both low and high intensity simulations. Using a pathway analysis, the disabled groups faced a significantly greater number of obstacles and maneuvered around the objects more than the control group only in the high intensity damage scenario. The users of powered wheelchairs were forced to seek alternate escape routes and found it very difficult to maneuver around especially to carry an emergency bag while exiting (a success rate of 23%). The feasibility and weaknesses of this type of experimental approach is elaborated.
The Effects of Seismic Pore Water Pressure on Ground Surface Motion
Authors: Zorapapel George(Bebe)T. , Vucetic Mladen
Published: July 2003

The effects of the gradual buildup of seismic pore water pressures and associated degradation of stiffness on the ground surface motion are examined for shallow saturated liquefiable deposits. Ground surface displacements and accelerations, the Fourier Transforms of the acceleration-time histories and layer gain factors are analyzed. The analysis is based on the ground surface and sub-surface accelerations and pore water pressures recorded at sites that either fully liquefied or built up considerable pore water pressures during strong earthquakes. The analysis shows that: (i) the seismic pore water pressures within the deposit and the ground surface motion are intimately related, (ii) relatively small seismic excess pore water pressures can cause a considerable lengthening of the predominant period of the ground surface motion, and (iii) these phenomena may lead to a limited maximum ground surface acceleration of approximately 0.2g, and a considerable increase of maximum ground displacements.
Discussion of “Passive Control of Building Response Using Energy Dissipating Cladding Connections” by J. P. Pinelli, J. I. Craig, G. J. Goodno, and C. C. Hsu
Authors: Cohen Julie Mark
Published: July 2003

The authors should be commended for their pioneering research work on structural cladding and energy-dissipating connections. This discussion has been written to help ensure that this research, which is multidisciplinary in nature, leads to practical applications. All structural engineering researchers must recognize that structural cladding design is one of the broadest building-related research topics that can be tackled. They should not focus only on topics that have roots in structural engineering alone, and thus deny the integral role of structural cladding in building design. The importance of a building systems approach must be recognized. In doing so, the role of the architect will become obvious, and a promising collaborative effort will be established.

This discussion is made from the perspective of a background in structural engineering and architectural research and practice.
Modeling Site Response in the Paducah, Kentucky Area
Authors: Harris J. B. , Street R. L. , Kiefer J. D. , Allen D. L. , Wang Z. M.
Published: July 2003

Site conditions at 37 locations in Paducah, Kentucky, and the surrounding area were modeled using seismic refraction and reflection data to determine site response to a suite of Canadian strong-motion records and a hypothetical central United States earthquake. The seismic data, integrated with local borehole information, indicated that depths to bedrock range from less than 300 to more than 500 ft. The site-response analysis shows that the study area can be subdivided into three zones and the highest spectral amplifications are associated with thick alluvial and lake-bed deposits. The magnitude of spectral ratios ranges from less than five to more than 20 times, and dynamic site periods range from 0.7 to 1.5 sec. Although this study relates directly to the Paducah area, the methods and types of data collected are applicable for other Upper Mississippi Embayment communities for land-use planning and the design of critical structures.
Optimal Trends in Seismic Design of Single Column Circular Reinforced Concrete Bridge Piers
Authors: Verma Ravindra , Priestley M. J. Nigel
Published: July 2003

An algorithm is developed to incorporate seismic capacity design philosophy in a computer program for the optimal design of single column circular reinforced concrete bridge piers for seismic loading. The program designs the circular column as a single degree of freedom system under the combined effect of axial and lateral seismic loads over a broad range of axial load ratio, column height and design displacement ductility capacity. Flexural, confinement and shear reinforcement requirements are then assessed for the entire range of parameters and cost calculations performed. For a given column height, design displacement ductility and axial load level, results indicate the existence of an optimal column diameter and ductility level. As the column diameter is reduced, cost savings are effected by reduced volume of concrete, but tend to be offset by P-Δ effects, increased longitudinal reinforcement for flexure, and increased transverse reinforcement for confinement and shear. Based on common trends, solutions are provided for the most economical range of the axial load ratio and design displacement ductility capacity for a given column height.
Practical Analysis of Bridges on Isolation Bearings with Bi-Linear Hysteresis Characteristics
Authors: Hwang J. S. , Sheng L. H. , Gates J. H.
Published: July 2003

Various equivalent elastic models specified in current bridge engineering practices for the seismic analysis of base-isolated bridges are summarized and evaluated. Two additional methods proposed by the California Department of Transportation (CALTRANS) are validated based on their predictions of the maximum inelastic seismic responses of base-isolated bridges. The CALTRANS proposed methods are implemented with an empirical model for the determinations of the effective stiffness and equivalent viscous damping ratios of isolation units and base-isolated bridges. A modal strain energy method combined with the concept of component energy ratio is utilized to formulate the “composite damping ratio” of an entire base-isolated bridge. A five-span regular bridge subjected to four design earthquakes and ten recorded ground motions is employed to investigate the accuracy of prediction using various equivalent elastic methods.
Dynamic Analyses of a Skewed Short-Span, Box-Girder Overpass
Authors: McCallen David B. , Romstad Karl M.
Published: July 2003

A number of recent research studies have provided insight into the seismic response characteristics of short-span overpass bridge systems. Application of system identification techniques to measured earthquake response data for this class of bridges has indicated that the bridge superstructure, abutments and approach embankment soil constitute a strongly coupled system. The dynamical behavior of the foundation and embankment soil have a first order influence on the dynamic response of the bridge superstructure. Analysis of measured strong motion response data has also indicated that localized nonlinear behavior of the embankment soil can result in significant nonlinear global behavior of the entire system, even when the bridge superstructure remains linear.

The current paper presents the results of detailed numerical simulation studies of the dynamic response of a short-span overpass bridge system. Two distinctly different modeling approaches are investigated. The first approach utilizes simple reduced order “stick” model idealizations of the bridge, and the second approach utilizes a detailed, large scale, three dimensional finite element model. The detailed model includes a discretization of the soil embankments and a simple nonlinear material model is used to represent the hysteretic soil behavior. The sensitivity of bridge response to various parameters, such as deck skew, embankment soil stiffness and soil mass, stick model modal damping values, and soil nonlinearity has been investigated. Earthquake response predictions are performed with both model types and the response computations are compared to earthquake response data measurements. The ability of the models to accurately represent the bridge seismic response is discussed, and the two modeling approaches are compared and contrasted.
Effects of Column Flexural Strength on the Seismic Response of a Multiple-Column Bridge Bent
Authors: Marsh M. Lee , Brown Colin B.
Published: July 2003

The effect of varying column flexural strengths on the seismic performance of a pre-1970, reinforced concrete multiple-column bridge bent was investigated. The strength variations may arise from poor detailing, retrofitting of existing structures, over- or under-design, or construction errors. The seismic behavior of the system was determined using inelastic response history analysis. The effects of possible strength variations were evaluated with respect to a base level of expected performance, with respect to various foundation flexibilities, and with respect to ground shaking intensity. The analyses show that the distribution of inelastic demands within the system is sensitive to foundation restraint and relatively insensitive to small flexural strength changes. The analyses also show that changes in the column strength in one location may increase the damage potential at other locations within the structure.
Evaluation of a Loss Estimation Procedure Based on Data from the Loma Prieta Earthquake
Authors: Jones Nicholas P. , Thorvaldsdóttir Sólveig , Liu Anqi , Narayan Prakash , Warthen Thomas
Published: July 2003

Over the several past decades, methods have been developed to predict structural damage on a regional basis. This paper describes an effort to collect damage and loss data from the Loma Prieta Earthquake and the comparison of these data with the results calculated by an existing loss estimation model. First the intensity prediction was evaluated by comparing the model results with the Modified Mercalli Intensity (MMI) maps issued by the U.S. Geological Survey in areas affected by the Loma Prieta earthquake. Then, the study concentrated on losses of the City of Watsonville in the County of Santa Cruz. The sensitivity of the loss due to variation in some of the basic parameters, such as intensity, deductible and liquefaction potential, were studied and discussed. The damage distribution of wood-frame buildings was also investigated. Results of calculations were compared with the collected real loss data (on-site estimate and permit estimate) from the City of Watsonville. The comparison shows that while the extant model offers some insight into loss distributions, more research is clearly necessary to improve the physical underpinnings of the methodology and to provide the necessary statistical data on which these approaches are based.
Inelastic Structural Response to Cascadia Subduction Zone Earthquakes
Authors: Marsh M. Lee , Gianotti Christopher M.
Published: July 2003

The effects of postulated Cascadia subduction zone earthquakes on inelastic structural response are examined. The earthquakes considered ranged in size from those previously recorded to the largest plausible event, a magnitude 9.5 earthquake. Artificial acceleration records were generated and used as input for inelastic response history analyses of single-degree-of-freedom systems with bilinear or degrading stiffness hysteretic relationships. The results indicate that the maximum displacements are not significantly greater than those produced by previously recorded events. The inelastic energy dissipated and the numbers of displacement cycles are somewhat greater for the largest events, although the energy demands and the cyclic displacement demands are similar to those from the recorded events for magnitudes up to 8.5.
Seismic Hazard Assessment in the Southeastern United States
Authors: Rizzo Paul C. , Vaidya N. R. , Bazan E. , Heberling C. F.
Published: July 2003

Comparisons of response spectra from near and far-field records to those estimated by attenuation functions commonly used in evaluating seismic hazards show that these functions provide reasonable results for near-field western North American sites. However, they estimate relatively small motions for far-field eastern North American sites, which is contrary to the empirical evidence of the 1886 Charleston and 1988 Saguenay Earthquakes. Using the 1988 Saguenay records scaled for magnitude, and several western North American records scaled to account for the slower attenuation in the east, we have developed deterministic median and 84th percentile, 5 percent damped response spectra to represent ground motions from a recurrence of the 1886 Charleston Earthquake at a distance between 85 to 120 km. The resulting 84th percentile spectrum has a shape similar to, but is less severe than, the USNRC Regulatory Guide 1.60 5 percent damped spectrum tied to a peak ground acceleration of 0.2g.
The Microzonation of Perth, Western Australia, Using Microtremor Spectral Ratios
Authors: Gaull Brian A. , Kagami Hiroshi , Taniguchi Hitoshi
Published: July 2003

This paper indicates new microzonation maps of Perth, Western Australia, utilising microtremor spectral ratios. This metropolitan area has been developing in recent times on Perth Basin which is one of the most active seismic zones in the country. The authors carried out simultaneous measurings of microtremors over most of metropolitan Perth, using a 3 km grid as a basis and hard rock reference site throughout. They calculated spectral ratios of microtremors at deposit site to rock reference site and plotted and contoured on maps for 6 frequency bands from 0.2 to 5.0 Hz. Spectral ratio contours appeared to correlate well with various geological subsurface contours. They also showed that previously estimated earthquake risk estimates underestimated ground motions by up to a factor of two.
Seismic Damage Control with Passive Energy Devices: A Case Study
Authors: McNamara Robert J.
Published: July 2003

This paper presents a theoretical case study of the effectiveness of supplemental passive damping devices in reducing structural response during seismic excitation. A six story special moment resistant reinforced concrete frame is studied with and without the aid of supplemental dampers. Response predictions are presented for each case. Preliminary damper design requirements are presented for a new facility implementing the supplemental damping system to reduce seismic damage and improve the post earthquake operational capability of the facility.
Estimation of Ground Motions in the Valley of Mexico from Normal-Faulting, Intermediate-Depth Earthquakes in the Subducted Cocos Plate
Authors: Pacheco Javier F. , Singh Shri Krishna
Published: July 2003

The Valley of Mexico is exposed to seismic risk from normal-faulting, large intermediate-depth earthquakes. We explore two approaches to estimate future ground motions from such events at CU, a hill-zone site in the valley. In the first we obtain parameters of an ω2 seismic source model and determine amplification of seismic waves due to local site effects at CU. This permits estimation of Fourier spectrum of expected ground motion at CU from postulated earthquakes. We find that the S-waves suffer an amplification of 2.5 between 0.2 to 3.0 Hz. This amplification is similar to that observed from deep teleseismic events but differs from that obtained from shallow coastal events. In the second approach the available recordings at CU are used as empirical Green's functions (EGF) to synthesize motions from future large earthquakes. This approach is very powerful if the smaller event is truly an empirical Green's function for the postulated earthquake.
The Seismic Response of a 1:3 Scale Model R.C. Structure with Elastomeric Spring Dampers
Authors: Pekcan Gokhan , Mander John B. , Chen Stuart S.
Published: July 2003

In this experimental study, elastomeric spring dampers, which have a distinct re-centering characteristic, are used to retrofit a non-ductile, previously damaged 1/3 scale model reinforced concrete building frame structure which is subjected to a variety of ground motions in shaking table tests. A velocity dependent analytical model is developed and verified for the elastomeric spring dampers. This model is implemented in the widely available non-linear dynamic time history analysis computer program DRAIN-2DX to produce response predictions which are in good agreement with experimental observations. The elastomeric spring damper devices significantly attenuate the seismic response of the structure and provide a considerable amount of energy dissipation while the main non-ductile reinforced concrete structural load carrying elements remain elastic. The effect of varying the damper configuration on the structural response was also investigated.
Toward a Strategic Plan for the National Earthquake Risk Reduction Program
Authors: Whitman Robert V.
Published: July 2003

Every day actions are taken that reduce the risks associated with earthquakes. This national, amorphous but action-oriented effort is NERRP (different from nehrp—the federally-funded information-gathering-and-disseminating effort). There is today no well articulated list of goals for NERRP, let alone a well understood plan for achieving such goals—although there are some de facto goals and plans. Such goals and plans are needed—to enlist support for earthquake risk reduction, and to permit effective planning for the nehrp effort. A set of national goals, together with a strategic plan to achieve these goals, are presented—as a “strawman.” The aim is to stimulate discussion and launch action toward achieving consensus on goals and a plan for NERRP.
Seismic Performance of Architectural Glass in a Storefront Wall System
Authors: Behr Richard A. , Belarbi Abdeldjelil , Brown Adam T.
Published: July 2003

An experimental investigation was conducted to evaluate the seismic performance of common types of architectural glass used in a typical storefront wall system. Two seismic loading histories were developed and employed in the laboratory to simulate the effects of moderate and severe earthquakes on a full-scale storefront wall system test assembly. Serviceability limit states and ultimate limit states of storefront glass and related glazing components were defined and assessed at moderate and severe earthquake loading levels. Experimental results indicated that for all glass types tested, serviceability limit states of glass edge damage and gasket seal degradation in the storefront wall system were exceeded during the moderate earthquake simulation. Ultimate limit states of major cracking and glass fallout were reached for the most common storefront glass type, 1/4 in. annealed monolithic glass, during the severe earthquake simulation. Annealed laminated glass, fully tempered monolithic glass, and insulating glass units constructed with either annealed or fully tempered glass were highly resistant to glass fallout and major cracking during the severe earthquake simulation.
A National Strategy for Natural Disaster Reduction: A Call for Coordination of Disaster Reduction Activities
Authors: Cassaro M. A. , Johnson K. , Cooper J. , Beavers J. , Taylor C.
Published: July 2003

A need exists to improve the effectiveness of the network of communities, organizations, and agencies that are concerned with reducing the negative impact of natural hazards in the USA. The issue is to find ways to integrate community need assessment, research and development, education and training, policy formulation, implementation, and evaluation to improve practices that reduce vulnerability at the community, regional, and national levels. To this end, we propose to create a disaster reduction network that supports a cycle of development and application activities relating to natural hazards mitigation standards, diffusion of loss reduction practice, and consensus building in communities and in technical and professional associations. The expected benefit is a more efficient use of resources and a sustained and effective national infrastructure.
A Reliability-Based Dual Level Seismic Design Procedure for Building Structures
Authors: Collins Kevin R.
Published: July 2003

structural design, Limit design, Spectra

The seismic design provisions of most building codes in the United States specify ground motion parameters for various regions of the country and provide simple formulas to determine a distribution of lateral forces for which the structure should be designed. The simple formulas typically involve the use of one or more “factors” to account for anticipated inelastic behavior of the structure, relative importance of the structure, and site soil effects. Although these code provisions are very simple to use, they oversimplify a complex problem and are based on many implicit assumptions which many designers may not appreciate. Furthermore, the reliability of the final design is not known. This paper describes the key features of an alternative seismic design procedure in which the underlying assumptions are more clearly defined and which provides a more uniform level of reliability in the final design. The procedure requires the designer to consider two levels of earthquake excitation. An “equivalent” single-degree-of-freedom model and uniform hazard response spectra are used to predict structural performance. The alternative procedure should enable designers to achieve code-specified target performance objectives for moderate and severe levels of earthquake excitation.
Estimation of Liquefaction Potential by in Situ Methods
Authors: Glaser Steven D. , Chung Riley M.
Published: July 2003

This report examines the state-of-the-art of in situ methods of estimating liquefaction potential in sands. In situ methods are especially important since “undisturbed” samples of loose sand for laboratory testing are virtually unobtainable. Various penetration test methods are examined, such as the SPT, DMT, and the CPT and variants. These methods are completely empirical in nature, and have worked well to date. The current state-of-practice is an SPT-based method. Intrusive, seismic-based tests are also examined: the cross-hole, down-hole tests, and down-hole logger. The seismic velocity-based predictors have a stronger physical basis than the penetration test-based estimation methods, but need a larger database. A non-intrusive test, the Spectral Analysis of Surface Waves technique, seems especially suited for examining sites of large areal extent.