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Showing papers on "Earthquake resistant structures published in 2006"


Proceedings ArticleDOI
10 Oct 2006
TL;DR: Building code provisions for the seismic resistant design of structures incorporate two basic types of requirements as mentioned in this paper : strength and stiffness requirements and prescriptive criteria on the detailing practice for the structural elements.
Abstract: Building code provisions for the seismic resistant design of structures incorporate two basic types of requirements. The first of these is very similar to the code requirements for most other types of loading and comprises specification of minimum permissible strength and structural stiffness. The second is unique to design for seismic resistance and consists of prescriptive criteria on the detailing practice for the structural elements. While strength and stiffness requirements have been part of building codes for nearly 100 years, these detailing practice requirements, which include such things as prescription of the volumetric ratio and spacing of reinforcing in concrete structures, and permissible width/thickness ratios for elements of members in steel structures are a recent addition to the code. They were first introduced into the codes in the late 1960s and primarily affected the design of reinforced concrete structures. However, as researchers have continued to understand the importance of detailing to seismic performance and actual earthquakes have made clear to the profession that poor detailing practice directly leads to adverse structural behavior, the volume and complexity of these detailing requirements has steadily increased. Extensive detailing requirements for reinforced concrete structures were introduced into the building codes following the 1971 San Fernando earthquake. Requirements for timber and masonry structures were also added throughout the 1970s and 1980s as relatively modest earthquakes, such as the 1979 Imperial Valley, California; 1983 Coalinga, California and 1984 Morgan Hill, California earthquakes indicated problems associated with improperly detailed structures of this construction type. However, relatively few requirements for detailing of steel structures were placed in the codes during this period, largely because there were few examples of poor performance of steel structures. This began to change with the 1985 Mexico City, Mexico earthquake in which several large steel buildings in the lake bed region of Mexico City collapsed. Additional requirements for detailing of steel structures were introduced following the 1987 Whittier Narrows, California earthquake. Most of these requirements pertained to the detailing of braced steel frames. The 1994 Northridge, California earthquake resulted in the introduction of extensive code detailing requirements for moment-resisting steel frames. Immediately following the earthquake, brittle fractures were discovered in the beam to column connections of several buildings in the San Fernando Valley (Figures 1, 2). This damage was

420 citations


Journal ArticleDOI
TL;DR: In this article, a new moment resisting detail for use in earthquake resistant structures is proposed, which is based upon the idea of inducing a plastic hinge away from the column face to dissipate the energy that would otherwise yield the connection.

78 citations


Journal ArticleDOI
TL;DR: In this article, buckling-restrained braces (BRBs) are investigated as ductile end cross frames and compared against the performance of yielding X braces, and the results showed that the relatively large deformation capacity of the BRBs is necessary to achieve a significant reduction in base shear.
Abstract: Ductile end cross frames have been proposed in the past for seismic design of steel plate girder bridges. In this paper buckling-restrained braces (BRBs) are investigated as ductile end cross frames and compared against the performance of yielding X braces. Component experiments on the BRBs showed that these braces dissipated energy very efficiently and have stable hysteretic behavior. Shake-table experiments on a large scale bridge model investigated the performance of braces with both pin-ended connections and fixed-end connections. Despite slippage, the pin-ended connections are considered more effective as flexural action in the relatively short braces is prevented. The base shear in the bridge model in response to 2.0 times the El Centro earthquake was 69% of the elastic base shear at an average drift of 2.5% during experiments. The relatively large deformation capacity of the BRBs, although not as great as the X braces, is necessary to achieve a significant reduction in base shear. The maximum cross frame displacements with the BRBs are consistently smaller than those in X braces at the same level of base shear.

56 citations


Journal ArticleDOI
TL;DR: In this paper, the results of a numerical study on seismic deformation demand to sheathed cold-formed steel structures are presented and elaborated on in order to both judge the seismic performance of the structure under increasing seismic intensity levels and develop an ad hoc cyclic loading protocol for physical tests.
Abstract: This paper presents and discusses the results of a numerical study on seismic deformation demand to sheathed cold-formed steel structures. It is part of a wider research, involving also physical tests on oriented strand board-sheathed stud walls. Numerical results have been obtained using an ad hoc mathematical model of the hysteresis response of sheathed stud walls, also taking into account the strong nonlinearity of the response for small lateral displacements and the strong pinching of hysteresis loops. This model has been calibrated against data coming from physical tests, using both old available experimental results and newly obtained ones. Numerical results have been elaborated on in order to both judge the seismic performance of the structure under increasing seismic intensity levels and develop an ad hoc cyclic loading protocol for physical tests.

41 citations


Journal ArticleDOI
TL;DR: In this article, a structural system, named weld-free system, was developed to overcome the difficulty in the quality assurance encountered in construction of steel moment resisting frames with conventional welded connections.
Abstract: This paper presents an innovative structural system, named weld-free system, developed to overcome the difficulty in the quality assurance encountered in construction of steel moment resisting frames with conventional welded connections. The proposed structural system adopts a mechanical joint equipped with metallic-yielding damper as beam-to-column connection, wherein slip-critical joints are made by recently developed super high-strength bolts. The structural configuration and load-carrying mechanism of weld-free steel structures are described herein. Key features of the super high-strength bolts are also introduced. Furthermore, an experimental verification is presented. Cyclic tests were conducted on full-scale models of weld-free beam-column subassemblies and one base-line specimen with conventional welded connection. The test results clearly reveal the efficiency of the weld-free system in enhancing large and stable hysteresis loops while maintaining the beams and columns virtually in the elastic range until the ultimate state of the structure. It is also verified that the load-carrying mechanism of weld-free systems can be predicted very well by the presented theoretical solutions.

39 citations


Journal ArticleDOI
TL;DR: In this article, large-scale shake table experiments were performed on a straight steel I-girder bridge model to evaluate the performance of a superstructure with ductile end cross frames using single angle X braces.
Abstract: Ductile end cross frames have been proposed in the past as a seismic design and retrofit strategy for steel plate girder bridges. In this paper it is shown that with good connection details, single angles are able to undergo large cyclic deformations in excess of 6% average axial strain before failure occurs. Large-scale shake table experiments were performed on a straight steel I-girder bridge model to evaluate the performance of a superstructure with ductile end cross frames using single angle X braces. The cross frames exhibited no apparent overall strength degradation, but also a comparatively low postyield stiffness, allowing the cross frames to act as effective structural fuses. The measured base shear was 61% of the elastic base shear in response to 2.0 times the El Centro earthquake at an average drift of 3.4%. Large girder drifts were achieved without distress in the deck slab by removing selected studs between the slab and top flange of the girders at the end cross frame locations, with axial deformations in the angles well below their deformation capacity based on component experiments.

30 citations


Book ChapterDOI
01 Jan 2006
TL;DR: In this paper, the authors discuss the seismic bridge design philosophy and conceptual design in general as well as discuss U.S. seismic design practice to illustrate the process of seismic design.
Abstract: Bridges are very important elements in a modern transportation system. Recent earthquakes, particularly the 1980 Loma Priets and the 1994 Northridge Earthquakes in California, the 1995 Hyogo-Ken Nanbu Earthquake in Japan, the 1999 JiJi Earthquake in Taiwan, and the 1999 Kocaeli Earthquake in Turkey, have caused collapse of, or sever damage to, a number of major bridges. Since the 1989 Loma Prieta Earthquake, extensive research has been done on seismic design and retrofit of bridges in Japan and the United States, especially in California. This chapter will discuss the seismic bridge design philosophies and conceptual design in general as well as discuss U.S. seismic design practice to illustrate the process. The chapter will also briefly presents seismic design practice in Japan.

21 citations


Journal ArticleDOI
TL;DR: In this article, an analytical study investigating how changes in the mechanical properties of individual seismic isolators affect the response of isolated bridge structures subjected to earthquake excitation is summarized using nonlinear response-history analyses utilizing bins of recorded earthquake ground motion pairs.
Abstract: An analytical study investigating how changes in the mechanical properties of individual seismic isolators affect the response of isolated bridge structures subjected to earthquake excitation is summarized Nonlinear response-history analyses are conducted utilizing bins of recorded earthquake ground motion pairs Twenty bilinear isolation systems are considered so that the results of this study are broadly applicable to the design of seismic isolation systems in the United States Variations in the mechanical properties are considered using a property modification factor, λ , to modify the appropriate bilinear isolator parameter The results of analyses considering nominal and modified isolation systems are used to systematically identify changes in system response as a function of the property modification factor These results are used to determine threshold values of the property modification factor that should aid engineers in the preliminary design and assessment of an isolation system prior to perf

17 citations


01 Jan 2006
TL;DR: In this paper, the authors discuss the damage that can be done to structures from an earthquake and discuss the types of structural problems that can result from the failure of the surrounding soil or from strong shaking.
Abstract: This chapter will discuss the damage that can be done to structures from an earthquake. Structural damage does not usually occur until the earthquake approaches 5.0 and is caused by the failure of the surrounding soil or from strong shaking. Damage also results from surface ruptures, the failure of nearby lifelines, or the collapse of more vulnerable structures. Problem soils and structural problems can also be a result of damage. The chapter discusses liquefaction, landslides, weak clay, foundation failure foundation connections, soft story, torsional moments, shear, flexural failure, connection problems, and problem structures.

13 citations


DOI
01 Aug 2006
TL;DR: In this article, the authors describe how, after the Hanshin-Awaji earthquake, the volume of lateral reinforcement used in reinforced concrete structures in Japan was increased in order to improve seismic performance.
Abstract: This paper describes how, after the Hanshin-Awaji earthquake, the volume of lateral reinforcement used in reinforced concrete structures in Japan was increased in order to improve seismic performance. Although a large volume of closely spaced lateral reinforcement will be effective in preventing elastic buckling of the longitudinal reinforcement, it does not prevent plastic buckling. Under severe earthquake loading, longitudinal reinforcement will be subjected to large reversed-cyclic deformation demands into the plastic regime in tension and the buckling regime in compression. The paper presents the results of low cycle fatigue testing of deformed bars and examination of failure criteria for these bars.

9 citations


Book
01 Jan 2006
TL;DR: In this paper, a general overview of structural design in dynamic situations is presented, including the dynamic response of structures dynamic equilibrium of forces Energy in structural vibrations Linear and nonlinear response of existing structures Vibrations in existing structures.
Abstract: Chapter 1: Structural design in dynamic situations PART 1: Basics Chapter 2: General overview The dynamic response of structures Dynamic equilibrium of forces Energy in structural vibrations Linear and nonlinear response of structures Vibrations in existing structures Working with the computer Superposing static and dynamic effects PART 2: Dynamics in design Chapter 3: Dynamic events and effects Introduction Dynamic events and effects Response of structures Chapter 4: Dynamic loads on structures General description Working machines Vehicle loads Human activities Construction loads Chapter 5: Vibrations Introduction Vibrations of structures Sources of vibrations Vibrations in the design process PART 3: Structural materials in dynamic situations Chapter 6: The rate of strain Introduction The rate of loading The rate of strain Structural materials Structural elements Chapter 7: Fatigue The phenomenon Fatigue in structural materials Fatigue in structural elements Chapter 8: Damping Introduction Viscous damping Hysteretic damping Damping in structures PART 4 Structural dynamics design Chapter 9: Mathematics Introduction Chapter 10: Single degree of freedom system Introduction to SDOF Free vibration Forced vibrations Dynamic modi Ocation factor Resonance Dynamic loads Mathematical approaches The time domain The frequency domain Elastoplastic systems Nonlinear systems Torsion dynamic forces Chapter 11: Multidegree of freedom: lumped mass system Introduction to MDOF Vibration modes Forced vibrations Pulsating load Modal analysis Damping in MDOF The lumped masses Chapter 12: Distributed mass system Introduction Mathematical approach Design of a beam PART 5: Natural dynamic loads Chapter 13: Earthquakes Introduction Earthquakes Earthquake loads Earthquake response analysis Static force procedure Linear elastic response spectrum Analytic procedures for linear elastic response Nonlinear inelastic response Ductility Pushover analysis Soil-foundation interaction Chapter 14: Wind loads Introduction Quasi-static wind loads The dynamic response Aeroelastic phenomena Vortex Buffeting Galloping Flutter instabilities

01 Jan 2006
TL;DR: In this paper, the effects of seismic risk on life cycle cost analysis for bridge maintenance were evaluated for reinforced concrete (RC) bridge piers by consideration of the uncertainties emanating from earthquakes.
Abstract: This paper aims to evaluate the effects of seismic risk on life-cycle cost (LCC) analysis for bridge maintenance. With a focus on deterioration due to corrosion of steel from chloride attack, LCC is examined for reinforced concrete (RC) bridge piers by consideration of the uncertainties emanating from earthquakes. Seismic risk is defined in terms of the seismic loss calculated by the earthquake motion with random quantities. Next, LCC is determined using the seismic loss, by which optimal maintenance plans are obtained using a genetic algorithm. It is concluded, based on numerical computations, that: 1) considering the seismic risk, it is possible to evaluate the effects of earthquake retrofitting methods; 2) the seismic risk greatly affects the selection of repair methods; and 3) the initial seismic performance is very important to establish earthquake resistant design.

Dissertation
01 Jan 2006
TL;DR: Results show that the seismic efficiency and the structural response of the analysed beam-column concrete connection under monolithic horizontal imposed displacement are satisfactory and the comparison of the finite element analysis and the analytical calculations converge quite well in the non-linear response.
Abstract: In the past decade, a large number of precast concrete structures have been built all over many earthquake prone countries. This has been one answer to past statements of uneconomical construction and that construction activity should be automated. The connections between precast members normal1y constitute the weakest link in the structure, and the satisfactory performance and economy of precast concrete structures depend to a great extent on the proper selection and design of the connections. In the design of earthquake resistant structures that incorporate precast concrete elements the main difficulty has been to find efficient and economical methods for connecting the precast concrete members together, and create connections that give adequate strength, stiffness and ductility. The aim of the master’s project was to select by means of conceptual design and to examine by finite element analysis and analytical models the effectiveness of a precast prestressed beam-column concrete connection of a jointed system and to discuss alternative solutions. Various choices of structural solutions were to be studied within the project with regard to serviceability, production methods, maintenance and costs. The works should include literature studies and FE-analyses with the DIANA V9 program. This thesis presents the results of the finite element analysis to examine the effectiveness of a precast prestressed beam-column concrete connection of a jointed system and compares it with an analytical model. Results show that the seismic efficiency and the structural response of the analysed beam-column concrete connection under monolithic horizontal imposed displacement are satisfactory. The comparison of the finite element analysis and the analytical calculations converge quite well in the non-linear response. The design of the column of the selected beam-column concrete connection could be improved.

03 Apr 2006
TL;DR: In this paper, an earthquake simulation test of a circular reinforced concrete bridge column specimen is conducted under a three dimensional loading condition, and the results of the test are used to evaluate the effect of multidirectional loading on the dynamic response and seismic performance of reinforced concrete bridges in order to develop more advanced and reliable design procedures.
Abstract: This paper describes how structures behave multi-directionally when subjected to earthquake excitation. Therefore, it is essential to evaluate the effect of multidirectional loading on the dynamic response and seismic performance of reinforced concrete bridge columns in order to develop more advanced and reliable design procedures. To investigate such effect, an earthquake simulation test of a circular reinforced concrete bridge column specimen is conducted under a three dimensional loading condition. The diameter of the specimen is 600 mm, and the effective height is 3 m, resulting in an effective aspect ratio of 5. The longitudinal reinforcement ratio and the axial force ratio are set to similar values of actual bridge columns constructed in Japan such as 1% and about 2.4%, respectively. The volumetric ratio of confining reinforcement is 0.3%. To investigate the nonlinear dynamic response, two horizontal and one vertical components of a strong motion recorded on the ground surface near the Tsugaru Bridge during the 1983 Nihonkai-Chubu, Japan, earthquake are selected for the test input signals based on results from a series of nonlinear dynamic analyses. The amplitude of the ground motion is scaled up by 400% since the peak ground acceleration of the largest component is 2.8 m/sec2, which is much smaller than the capacity of the specimen. During the excitation, slight spalling of cover concrete occurs after 4 times repetition of larger displacements than an ultimate displacement that is computed based on a current seismic design code of Japan. When the displacement increases up to 3.4 times of the ultimate displacement, the several reinforcing bars are fractured. At the end of the test, 22 of 40 longitudinal reinforcing bars are fractured, and the core concrete is totally crushed at the bottom of the column. A series of dynamic analyses with a fiber element is also conducted. The analysis with almost no viscous damping predicts the response of the specimen with sufficient accuracy before the rebar buckling occurs. The analyses also demonstrate that two horizontal ground motions results in 15% larger response than one horizontal ground motion due to the bidirectional bending effects for the ground motion used in this study.

Proceedings ArticleDOI
03 Feb 2006
TL;DR: In this article, the feasibility of composite MR frame structures with partially encased columns and partial strength beam-to-column joints to provide strength and ductility was evaluated in a full-scale two-storey composite building.
Abstract: This paper shows the feasibility of composite MR frame structures with partially encased columns and partial strength beam-to-column joints to provide strength and ductility. In detail, energy dissipation is concentrated both in column web panels which are not surrounded by concrete and in composite beam-to-column connections. A full-scale two-storey composite building was used to validate the system performance of composite MR frames with partial strength joints. The frame structure was subjected to pseudo-dynamic tests in order to simulate the structural response under ground motions. The ground motion for 10 % chance of exceedence in 10 years earthquake hazard caused minor damage while the one for 2 % chance of exceedence in 10 years earthquake hazard entailed column web panel yielding, connection yielding and plastic hinging at column base joints. An earthquake level chosen to approach the collapse limit state induced more damage and was accompanied by further column web panel yielding, connection yielding and inelastic phenomena at column base joints without local buckling. Successively, the structure was subjected to a final quasi-static cyclic test with interstory drift ratios over 4.6 %. Moreover, test offered additional opportunities to validate the performance of simulation FE models. Exploiting inelastic static pushover and time-history analysis procedures, behavior factors, design overstrength factors and the ductility demand of the structure were estimated.

Proceedings ArticleDOI
10 Oct 2006
TL;DR: In this paper, passive and semi-active control devices combined with base isolation bearings are used to generate desirable hysteretic loops to reduce seismic responses. But, the authors did not consider the effect of seismic energy absorption capability of structural components.
Abstract: Active and semi-active control methods for reduction of the dynamic response of structures are emerging and some are being implemented in buildings and bridges. This vast growing technology ows to recent developments of sensing and digital control techniques. Semi-active control is a promising approach for the seismic response reduction in which the control offers the adaptability of active control without requiring the associated large power sources [1-10], since the external energy is only used to modify the dynamic properties (e.g., stiffness, damping, and friction level) of semi-active device during an earthquake attack. Therefore, the semi-active control devices can be considered as controllable passive devices. The problem lies on what algorithm should control this device so that the structural response is favorable under earthquake excitation. Earthquake input energy absorption capability of structural components described by hysteretic loops plays the key role in ensuring proper seismic performance of structures. Members that have stable and large hysteretic loops are considered as ductile have been proved successful in reducing seismic responses. For very important structures, energyabsorbing devices are added to structures so that the hysteretic loops are localized only at the devices. For seismic isolation techniques, for example, hysteretic loops are also employed at the isolation devices to reduce excessive displacement. In this study, passive and semi-active control devices combined with base isolation bearings are used to generate desirable hysteretic loops. The control algorithm is designed so that the combination of the variable damper and isolation bearings yields the desirable hysteretic loops [6-11]. SEMI-ACTIVE SKYHOOK CONTROL SYSTEM

01 Jan 2006
TL;DR: In this article, a direct displacement-based design (DDBD) methodology was proposed for the design of new seismic resistant steel moment frames, where the beam geometry was used to construct a yield displacement profile and the total energy dissipated by the frame from beam yielding was estimated by evaluating the base shear.
Abstract: In recent years the tenets of Performance-Based Seismic Engineering (PBSE) have been introduced for design of earthquake resistant structures. Thus, it is necessary that a design methodology be capable of producing a system that can achieve a performance target. Research has identified limitations in conventional force-based design practices in meeting the needs of PBSE. In response, a significant movement has been made towards displacement- based design in an attempt to bypass these limitations. This research proposes a Direct Displacement-Based Design (DDBD) methodology for design of new seismic resistant steel moment frames. Two crucial issues in earlier DDBD methods that need resolution are (1) assumption of frame yield displacements and (2) determination of system equivalent damping. To resolve the first, a procedure using beam mechanics is proposed to construct a yield displacement profile. The procedure illustrates that yield displacement is essentially a function of beam geometry, suggesting that displacement ductility demand can be controlled via design. Secondly, the total energy dissipated by the frame from beam yielding is commonly estimated by evaluating the base shear - roof displacement hysteresis. From which an estimate of equivalent damping is computed by applying a damping function developed for a single yield mechanism. This is limiting in that ductility contributions from each mechanism or the effects of higher mode contributions are not considered. A more rational procedure is proposed where floor ductility contributions are accounted for and an equivalent modal damping computed. In so doing, a better estimate of equivalent damping for design can be made

Proceedings ArticleDOI
10 Oct 2006
TL;DR: In this article, the authors present a nonlinear analysis of a 2000 ft guyed tower with and without mass irregularities, and compare the results with the results obtained using the equivalent lateral force method.
Abstract: Beginning in 2006, the tower industry will begin using the new revision of the Structural Standard for Antenna Supporting Structures and Antennas, TIA/EIA-222-G. Revision G incorporates several significant changes from previous revisions. It moves form allowable stress design to limit state design, and incorporates the wind and ice provisions of ASCE 7. However, the most significant change is the addition of seismic provisions for communication towers. This is the first time the Standard has seismic loading requirements for tower in regions of high seismicity. Because towers are special structures, current seismic provisions in building codes do not always adequately predict their behavior in earthquakes. Revision G provides methods that better estimate the performance of communication structures subjected to ground motion. Revision G provides: methods for determining 1) when earthquake loads need to be considered in the design of communication towers, 2) the fundamental period of various classes of towers, 3) seismic forces. In general, communication structures can be classed as self-supporting and guyed. For design purposes, the response of self-supporting towers can be predicted using linear elastic methods of analysis. Pole structures fall under this category. However, guyed towers are intrinsically nonlinear. Despite their nonlinear behavior, studies at the University of Windsor and McGill University show that the equivalent lateral force method provides an adequate estimate of the seismic forces in guyed towers when using the equations for the fundamental frequency defined in Revision G. As a precaution, the writers of Revision G put a limit on the use of the equivalent lateral force method on guyed towers with mass or stiffness irregularities taller than 450 m (1500 ft) and when any guy radius exceeds 300 m (1000 ft). Under these conditions, the Revision G requires that a time history analysis be performed. Furthermore, when any guy radius exceeds 300 m, out-of-phase motion of the anchor points needs to be considered. This paper presents a nonlinear analysis of a 2000 ft guyed tower with and without mass irregularities. The analysis considers both in-phase and out-of-phase base motion for comparison. The results of the nonlinear analyses are compared to the results obtained using the equivalent lateral force method.

Journal ArticleDOI
TL;DR: In this article, an innovative and cost-effective earthquake resistant design technique using a novel geosynthetic materials that can reduce the damages of structures during devastating earthquakes was developed using tire chips.
Abstract: In this research, an innovative and cost-effective earthquake resistant design technique is developed using a novel geosynthetic materials that can reduce the damages of structures during devastating earthquakes. In the developed earthquake resistant technique a smart geosynthetic material known as tire chips is utilized as a seismic performance enhancer . A series of underwater i g shaking table test was conducted on a model gravity type quay wall. Two test cases were examined. One case involves a quay wall with the conventional backfill. Another case involves a similar quay wall but reinforced with tire chips. The seismic increment of the load acting on the quay wall and the associated displacement , as well as the excess pore water pressure in various locations of the backfill were measured during the tests. The results reveal that the seismic load against the caisson quay wall could be significantly reduced using the sandwiching technique. In addition, the technique could significantly reduce the earthquake-induced residual displacement of the quay wall.

Journal ArticleDOI
TL;DR: In this paper, a step-by-step procedure for linear analysis of building structures with rigid floor beams is developed and presented, which outputs the maximum story drift envelope, and consists of a series of explicit formulas that do not require iteration.
Abstract: A step-by-step procedure for linear analysis of building structures with rigid floor beams is developed and presented. The method outputs the maximum story drift envelope, and consists of a series of explicit formulas that do not require iteration. The basis of the method is an internally damped shearbeam model. Drift demand spectra are used to provide information on the ground motion hazard of the site. In addition to the drift demand spectra, two additional spectra are incorporated, which describe the higher mode behavior. To test accuracy, three sample buildings structures (3-, 9-, and 20-story buildings at Los Angeles) are analyzed for five sample earthquake records using the proposed procedure, and conventional time history analysis. A comparison of the results shows that the proposed procedure is accurate enough for quick evaluation of seismic performance.

03 Apr 2006
TL;DR: In this paper, an analytical idealization of the seismic torsion of C-bent columns that shows complex combined action is proposed in order to show the effectiveness of the proposed model, a correlation analysis is conducted on experimental results.
Abstract: In urban areas peculiar bridges that are supported by C-bent columns have been constructed due to space limitation. Since bending and torsion are combined as well as axial force, C-bent columns exhibit complex seismic behavior. Furthermore extensive residual drift develops in the eccentric compression side because of the eccentric dead load of the deck during an earthquake. An analytical idealization of the seismic torsion of C-bent columns that shows complex combined action is proposed in this study. In order to show the effectiveness of the proposed model, a correlation analysis is conducted on experimental results.


Proceedings ArticleDOI
10 Oct 2006
TL;DR: In this article, an analysis of the seismic performance of a hospital building located in Southern California in seismic zone 4 is presented. But the performance of the hospital building was not satisfactory, in particular, story drifts and member nonlinear flexural rotations exceeded the limits specified in the design guidelines.
Abstract: Analytical investigations were undertaken to assess the seismic performance of a hospital building located in Southern California in seismic zone 4. The structure consists of a eight-story steel, and a bottom story reinforced concrete superstructure constructed over four levels of sub-grade parking stories. The building is rectangular, is 125 ft tall, and has total floor area of 130,000 ft 2 . Steel and concrete moment-resisting frame along the grid lines of the building provide resistance to lateral loading. Project-specific design guidelines and FEMA, and SAC guidelines were used for evaluation. A comprehensive three-dimensional mathematical model of the structure was prepared. Nonlinear response history analysis of the existing building revealed that the performance was inadequate. In particular, story drifts and member nonlinear flexural rotations exceeded the limits specified in the design guidelines. The building rehabilitation consists of adding fluid viscous damper frames to the exterior faces of the building. The structure was then re-analyzed in the new configuration, and its performance was satisfactory.


01 Jan 2006
TL;DR: Kircher et al. as discussed by the authors addressed the topic of Protecting Older Buildings with Seismic Isolation and Damping Systems and made significant contributions to the field of earthquake engineering including the development of earthquake damage and loss estimation methods.
Abstract: Proceedings of the 17th Analysis and Computation Specialty Conference 2006, held in conjunction with Structures Congress 2006 in St Louis, Missouri, May 18-21, 2006 The collection of 44 papers highlights recent research in the broad areas of applied structural analysis, optimal structural design, structural control, and emergent computing technology Dr Kircher’s presentation addressed the topic of Protecting Older Buildings with Seismic Isolation and Damping Systems Dr Kircher has made significant contributions to the field of earthquake engineering including the development of earthquake damage and loss estimation methods, seismic hazard criteria, and isolation and damping system design criteria used in building codes

Proceedings ArticleDOI
06 Sep 2006
TL;DR: In this article, an optimal cost base isolation design or retrofit design method of bridges subject to transient earthquake loads is studied, which can be achieved by combining nonlinear time history analyses with optimization procedures to select base isolators to achieve the objective of minimum cost of the isolation system.
Abstract: Seismic isolation and energy dissipation systems are innovative strategies for seismic design, and upgrade or retrofit of bridges. In a retrofit design, base isolation devices can be easily incorporated into existing bridges to replace conventional bearings and to improve the overall structural performance. In this paper, an optimal cost base isolation design or retrofit design method of bridges subject to transient earthquake loads is studied. The aim of this study is to push forward the concept of retrofit design optimization of structures using the special case of isolation retrofit design. This can be achieved by combining nonlinear time history analyses with optimization procedures to select base isolators to achieve the objective of minimum cost of the isolation system while satisfying certain design requirements. Such design procedures are iterative and involve repeated analyses before an optimum solution can be achieved. Due to the discrete nature of the problem, an improved genetic algorithm (GA) – Micro-GA is employed to find the optimal solutions. An example of the optimal design of a highway bridge is presented and the minimum cost expense of isolation system is achieved with improved structural response under transient earthquake loads.