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1.
Horizontal curved bridges are very common at intersections and at the changing angle of bridge alignment. Almost in every previous earthquake report, it can be seen that the columns of a curved segment experience torsional damage, and the curved decks are unseated from the abutment support. The main reason behind that phenomenon is the in‐plane deck rotation which results because of the complex dynamic coupling between two longitudinal directional vibrations. The curved decks are susceptible to deck rotation because in a curved segment, the centre of mass and the centre of stiffness generally lie outside the bridge deck and are not located at the same point. The pounding with the abutment often increases the rotational tendency of the deck. In this paper, a classical mechanics‐based approach is adopted to analytically estimate the deck rotation potential of curved bridge considering the deck‐abutment pounding interaction. The deck‐abutment pounding is modelled using non‐smooth techniques considering the Newton's impact law in the normal and Coulomb's friction in the tangential direction. Within the scope of this paper, a parametric study is performed to get the ideal combination of the column and bent arrangement and the gap distance. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

2.
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3.
Cable‐stayed bridges require a careful consideration of the lateral force exerted by the deck on the towers under strong earthquakes. This work explores the seismic response of cable‐stayed bridges with yielding metallic dampers composed of triangular plates that connect the deck with the supports in the transverse direction. A design method based on an equivalent single‐degree of freedom approximation is proposed. This is proved valid for conventional cable‐stayed bridges with 200‐ and 400‐m main spans, but not 600 m. The height of the plates is chosen to (1) achieve a yielding capacity that limits the maximum force transmitted from the deck to the towers, and to (2) control the hysteretic energy that the dampers dissipate by defining their design ductility. In order to select the optimal ductility and the damper configuration, a multi‐objective response factor that accounts for the energy dissipation, peak damper displacement and low‐cycle fatigue is introduced. The design method is applied to cable‐stayed bridges with different spans and deck–support connections. The results show that the dissipation by plastic deformation in the dampers prevents significant damage in the towers of the short‐to‐medium‐span bridges under the extreme seismic actions. However, the transverse response of the towers in the bridge with a 600‐m main span is less sensitive to the dampers. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

4.
Ambient and forced vibration tests were carried out on the Beauharnois bridge, a unique, 177‐m combined suspension and cable‐stayed structure near Montreal, Canada. A rehabilitation program was completed on the bridge during which the deck was completely rebuilt with an orthotropic slab on two steel trusses. The rehabilitation program also included the addition of two pairs of stay cables on both towers, creating a hybrid suspension system. The paper presents a series of dynamic tests performed to evaluate the dynamic properties and the dynamic amplification factor (DAF) for the rehabilitated bridge. The experimental program involved the measurement of vertical, transverse, and longitudinal acceleration responses of the deck and tower under ambient and controlled traffic loads. Displacement, strain, and integrated acceleration DAFs were computed under different loading conditions. Modal properties were evaluated and used to correlate a three‐dimensional finite element model for the bridge, including non‐linear cable behaviour. The paper discusses the experimental setup as well as the techniques used to evaluate vibration frequencies, mode shapes, and the DAF. Correlation of numerical dynamic properties and experimental results is also presented. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

5.
In Italy, as in other high seismic risk countries, many bridges, nowadays deemed ‘strategic’ for civil protection interventions after an earthquake, were built without antiseismic criteria, and therefore their seismic assessment is mandatory. Accordingly, the development of a seismic assessment procedure that gives reliable results and, at the same time, is sufficiently simple to be applied on a large population of bridges in a short time is very useful. In this paper, a displacement‐based procedure for the assessment of multi‐span RC bridges, satisfying these requirements and called direct displacement‐based assessment (DDBA), is proposed. Based on the direct displacement‐based design previously developed by Priestley et al., DDBA idealizes the multi DOF bridge structure as an equivalent SDOF system and hence defines a safety factor in terms of displacement. DDBA was applied to hypothetical bridge configurations. The same structures were analyzed also using standard force‐based approach. The reliability of the two methods was checked performing IDA with response spectrum compatible accelerograms. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

6.
A Markov method of analysis is presented for obtaining the seismic response of cable‐stayed bridges to non‐stationary random ground motion. A uniformly modulated non‐stationary model of the random ground motion is assumed which is specified by the evolutionary r.m.s. ground acceleration. Both vertical and horizontal components of the motion are considered to act simultaneously at the bridge supports. The analysis duly takes into account the angle of incidence of the earthquake, the spatial correlation of ground motion and the quasi‐static excitation. A cable‐stayed bridge is analysed under a set of parametric variations in order to study the non‐stationary response of the bridge. The results of the numerical study indicate that (i) frequency domain spectral analysis with peak r.m.s. acceleration as input could provide more r.m.s. response than the peak r.m.s. response obtained by the non‐stationary analysis; (ii) the longitudinal component of the ground motion significantly influences the vertical vibration of the bridge; and (iii) the angle of incidence of the earthquake has considerable influence on the deck response. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

7.
The analysis of dynamic responses of cable-stayed bridges subjected to wind and earthquake loads generally considers only the motions of the bridge deck and pylons. The influence of the stay cable vibration on the responses of the bridge is either ignored or considered by approximate procedures. The transverse vibration of the stay cables, which can be significant in some cases, are usually neglected in previous research. In the present study, a new three-node cable element has been developed to model the transverse motions of the cables. The interactions between the cable behavior and the other parts of the bridge superstructure are considered by the concept of dynamic stiffness. The nonlinear effect of the cable caused by its self-weight is included in the formulation. Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed model. The impact of cable vibration behavior on the dynamic characteristics of cable-stayed bridges is discussed. Supported by: Natural Science and Engineering Research Council of Canada  相似文献   

8.
In damage‐based seismic design it is desirable to account for the ability of aftershocks to cause further damage to an already damaged structure due to the main shock. Availability of recorded or simulated aftershock accelerograms is a critical component in the non‐linear time‐history analyses required for this purpose, and simulation of realistic accelerograms is therefore going to be the need of the profession for a long time to come. This paper attempts wavelet‐based simulation of aftershock accelerograms for two scenarios. In the first scenario, recorded main shock and aftershock accelerograms are available along with the pseudo‐spectral acceleration (PSA) spectrum of the anticipated main shock motion, and an accelerogram has been simulated for the anticipated aftershock motion such that it incorporates temporal features of the recorded aftershock accelerogram. In the second scenario, a recorded main shock accelerogram is available along with the PSA spectrum of the anticipated main shock motion and PSA spectrum and strong motion duration of the anticipated aftershock motion. Here, the accelerogram for the anticipated aftershock motion has been simulated assuming that temporal features of the main shock accelerogram are replicated in the aftershock accelerograms at the same site. The proposed algorithms have been illustrated with the help of the main shock and aftershock accelerograms recorded for the 1999 Chi–Chi earthquake. It has been shown that the proposed algorithm for the second scenario leads to useful results even when the main shock and aftershock accelerograms do not share the same temporal features, as long as strong motion duration of the anticipated aftershock motion is properly estimated. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

9.
In this study the inelastic behavior of steel arch bridges subjected to strong ground motions from major earthquakes is investigated by dynamic analyses of a typical steel arch bridge using a three‐dimensional (3D) analytical model, since checking seismic performance against severe earthquakes is not usually performed when designing such kinds of bridge. The bridge considered is an upper‐deck steel arch bridge having a reinforced concrete (RC) deck, steel I‐section girders and steel arch ribs. The input ground motions are accelerograms which are modified ground motions based on the records from the 1995 Hyogoken‐Nanbu earthquake. Both the longitudinal and transverse dynamic characteristics of the bridge are studied by investigation of time‐history responses of the main parameters. It is found that seismic responses are small when subjected to the longitudinal excitation, but significantly large under the transverse ground motion due to plasticization formed in some segments such as arch rib ends and side pier bases where axial force levels are very high. Finally, a seismic performance evaluation method based on the response strain index is proposed for such steel bridge structures. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

10.
This study examines the efficacy of using seismic isolation to favorably influence the seismic response of cable‐stayed bridges subjected to near‐field earthquake ground motions. In near‐field earthquake ground motions, large amplitude spectral accelerations can occur at long periods where many cable‐stayed bridges have significant structural response modes. This combination of factors can result in large tower accelerations and base shears. In this study, lead–rubber bearing seismic isolators were modeled for three cable‐stayed bridges, and three cases of isolation were examined for each bridge. The nine isolated bridge configurations, plus three non‐isolated configurations as references, were subjected to near‐field earthquake ground motions using three‐dimensional time‐history analyses. Introduction of a small amount of isolation is shown to be very beneficial in reducing seismic accelerations and forces while at the same time producing only a modest increase in the structural displacements. There is a low marginal benefit to continue to increase the amount of isolation by further lengthening the period of the structure because structural forces and accelerations reduce at a diminishing rate whereas structural displacements increase substantially. In virtually all cases the base shears in the isolated bridges were reduced by at least 50several instances by up to 80individual near‐field records showed large variability from one record to the next, with coefficients of variation about the mean as large as 50assessing the characteristics of near‐field ground motion for use in isolation design of cable‐stayed bridges. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

11.
基于环境振动的斜拉桥拉索基频识别   总被引：16，自引：1，他引：16  
斜拉索是现代斜拉桥最重要的结构构件，索力在斜拉桥的施工控制和长期监测中起着重要作用。振动测试法是斜拉桥索力测定、监测和状态评估中应用最广泛的一种方法。振动法测索力的关键在于准确地识别出索的基频。本文使用自功率谱和倒频谱方法，基于MATLAB平台，开发出了斜拉桥拉索环境振动模态分析图形用户交互(GUI)工具箱，实现了斜拉索基频的快速自动识别。应用本文的方法，对福州青洲闽江主跨605m斜拉桥拉索的环境振动实测加速度数据进行了分析处理，斜拉索基频识别方便直观，结果可靠。  相似文献   

12.
The dynamic behaviour of two curved cable‐stayed bridges, recently constructed in northern Italy, has been investigated by full‐scale testing and theoretical models. Two different excitation techniques were employed in the dynamic tests: traffic‐induced ambient vibrations and free vibrations. Since the modal behaviour identified from the two types of test are very well correlated and a greater number of normal modes was detected during ambient vibration tests, the validity of the ambient vibration survey is assessed in view of future monitoring. For both bridges, 11 vibration modes were identified in the frequency range of 0ndash;10Hz, being a one‐to‐one correspondence between the observed modes of the two bridges. Successively, the information obtained from the field tests was used to validate and improve 3D finite elements so that the dynamic performance of the two systems were assessed and compared based on both the experimental results and the updated theoretical models. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

13.
Ambient accelerations due to dynamic excitation by wind and traffic were measured on the deck, towers, cables and hangers of the Fatih suspension bridge. From these measurements it was possible to obtain natural frequencies, mode shapes and damping ratios for vertical, lateral, torsional and associated modes in the deck and tower up to a maximum of 2 Hz. The objective of the test was to validate the mathematical modelling used in seismic analyses of the bridge. The agreement between the experimental and theoretical modes was acceptable for vertical modes below 1 Hz, and for torsional modes, but it was difficult to identify the lateral modes due to low levels of response. The dynamic behaviour of this bridge and two other major European suspension bridges is discussed in relation to the differences in loading and structural design.  相似文献   

14.
The traffic‐induced variability in the dynamic properties of a cable‐stayed bridge is investigated using ambient vibration measurements. Under a relatively steady wind and temperature environment, the ambient vibration test was conducted on the bridge with normal traffic conditions and totally 24 h acceleration response time histories were recorded. These data are divided into 12 sections with each data section containing 2 h measurements. Thereby the modal variability due to changing traffic loading is investigated through post‐processing of the data in each section in both amplitude and frequency domains. The result indicates that the natural frequencies of the global modes can exhibit as much as 1% variation within a day. The modal amplitudes of each mode as well as the modal deflection at each measurement position vary insignificantly. The damping ratios however are sensitive to the vibration intensity, especially when the deck vibration exceeds a certain level. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

15.
This paper carries out a parametrical study of the pounding phenomenon associated with the seismic response of multi‐span simply supported bridges with base isolation devices. In particular, the analyses focus on the causal relationship between pounding and the properties of a spatially varying earthquake ground motion. In order to include the effect of the torsional component of pounding forces on the seismic response of the whole structure, a three‐dimensional (3D) finite element model has been defined and 3D non‐linear time‐history analyses have been performed. A parametrical study on the size of the gaps between adjacent bridge decks has highlighted that the pounding effects are amplified when the spatially varying ground motion time histories at each support are considered. Because of a spatially varying input, the pounding forces can assume values 3–4 times larger than those derived by a conventional seismic analysis with uniform input or with spatial input but considering ground motion wave passage effect only. The numerical results show that in order to achieve an acceptably safe structural performance during seismic events, a correct design of the isolation devices should take into account the relative displacements calculated by means of a non‐linear time‐history analysis with multi‐support excitation. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

16.
With the launch of the high‐speed train project in California, the seismic risk is a crucial concern to the stakeholders. To investigate the seismic behavior of future California High‐Speed Rail (CHSR) bridge structures, a 3D nonlinear finite‐element model of a CHSR prototype bridge is developed. Soil‐structure and track‐structure interactions are accounted for in this comprehensive numerical model used to simulate the seismic response of the bridge and track system. This paper focuses on examining potential benefits and possible drawbacks of the a priori promising application of seismic isolation in CHSR bridges. Nonlinear time history analyses are performed for this prototype bridge subjected to two bidirectional horizontal historical earthquake ground motions each scaled to two different seismic hazard levels. The effect of seismic isolation on the seismic performance of the bridge is investigated through a detailed comparison of the seismic response of the bridge with and without seismic isolation. It is found that seismic isolation significantly reduces the deck acceleration and the force demand in the bridge substructure (i.e., piers and foundations), especially for high‐intensity earthquakes. However, seismic isolation increases the deck displacement (relative to the pile cap) and the stresses in the rails. These findings imply that seismic isolation can be promisingly applied to CHSR bridges with due consideration of balancing its beneficial and detrimental effects through using appropriate isolators design. The optimum seismic isolator properties can be sought by solving a performance‐based optimum seismic design problem using the nonlinear finite‐element model presented herein. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

17.
This paper presents the application of system identification (SI) to long‐span cable‐supported bridges using seismic records. The SI method is based on the System Realization using Information Matrix (SRIM) that utilizes correlations between base motions and bridge accelerations to identify coefficient matrices of a state‐space model. Numerical simulations using a benchmark cable‐stayed bridge demonstrate the advantages of this method in dealing with multiple‐input multiple‐output (MIMO) data from relatively short seismic records. Important issues related to the effects of sensor arrangement, measurement noise, input inclusion, and the types of input with respect to identification results are also investigated. The method is applied to identify modal parameters of the Yokohama Bay Bridge, Rainbow Bridge, and Tsurumi Fairway Bridge using the records from the 2004 Chuetsu‐Niigata earthquake. Comparison of modal parameters with the results of ambient vibration tests, forced vibration tests, and analytical models are presented together with discussions regarding the effects of earthquake excitation amplitude on global and local structural modes. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

18.
Earthquake‐induced deck‐abutment contact alters the boundary conditions at the deck level and might activate a different mechanical system than the one assumed during the design of the bridge. Occasionally this discrepancy between the assumed and the actual seismic behavior has detrimental consequences, for example, pier damage, deck unseating, or even collapse. Recently, an insightful shake‐table testing of a scaled deck‐abutment bridge model 1 , showed unexpected in‐plane rotations even though the deck was straight. These contact‐induced rotations produced significant residual displacements and damage to the piers and the bents. The present paper utilizes that experimental data to examine the validity and the limitations of a proposed nonsmooth dynamic analysis framework. The results show that the proposed approach satisfactorily captures the planar rigid‐body dynamics of the deck which is characterized by deck‐abutment contact. The analysis brings forward the role of friction on the physical mechanism behind the rotation of the deck, and underlines the importance of considering the frictional contact forces during deck‐abutment interaction even for straight bridges, which typically are neglected. Finally, the paper investigates the sensitivity of the rotation with respect to macroscopic contact parameters (i.e., the coefficient of friction and the coefficient of restitution). Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

19.
Unseating of bridge girders/decks during earthquakes is very harmful to the safety and serviceability of bridges. Evidence from recent severe earthquakes indicates that in addition to damage along longitudinal direction, lateral displacement and rotation of bridge girders caused by pounding to adjacent girders can also lead to unseating. To simulate this effect, 3D modelling of the dynamic performance of whole bridge structures, including pounding, is needed strongly. This paper presents a 3D model that is practically suitable to precisely analyse pounding between bridge girders. Experiments have been conducted to verify the proposed pounding model. The 3D non‐linear modelling of steel elevated bridges is also discussed. A general‐purpose dynamic analysis program for bridges, namely dynamic analysis of bridge systems (DABS) has been developed. Seismic analyses on a chosen three‐span steel bridge are conducted for several cases including pounding as a case study. The applicability of the proposed pounding model is illustrated by the computations. The effects of poundings on the response of bridge girders are discussed and the computation results are given. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

20.
The seismic response of elasto‐plastic structures to both recorded and generated accelerograms is characterized by a large scattering of the results, even for accelerograms with similar peak ground acceleration values and frequency content. According to current code recommendations a design value of the seismic response of an elasto‐plastic structure can be computed as the mean of the responses to a certain number of spectrum‐fitting generated accelerograms. A more effective probabilistic approach is presented herein. It allows the analyst to calculate a design value of the seismic response characterized by a predefined non‐exceedance probability using a limited number of generated accelerograms. The results of the performed analyses are presented in diagrams that can be used for structural design applications. The applicability of the proposed method is demonstrated in the case of an elasto‐plastic structural system and the results are compared with those obtained applying current code recommendations. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

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