Towards probabilistic seismic performance of vehicle-bridge interaction systems: From stochastic dynamic model to fragility analysis

This paper aims to assess the seismic fragility of vehicle-bridge-interaction (VBI) systems considering the effects of vehicle types, traffic conditions, and road surface qualities. A stochastic nonlinear mechanical model for the earthquake-VBI system is developed, and the fragility functions for the proposed VBI model are derived by considering the relevant probabilistic seismic demand parameters. On the basis of a typical four-span continuous prestressed concrete highway bridge in China, a complete numerical model for the VBI system is built considering multiple uncertainties from bridge and vehicle parameters, as well as the road surface qualities. A total of 120 real ground motion records with different combinations of magnitude-source-to-site distance (M-R) and earthquake intensity characteristics are selected. Meanwhile, 80 scenarios in terms of different combinations of vehicle types, vehicle speeds, and road surface irregularities are defined. In this context, 96,000 nonlinear time-history analyses are performed, and the developed fragility models are applied to the VBI system at both component and system levels. Results indicate that the fragilities of pier drift, bearing shear strain, and the overall VBI system increase with the increase of the vehicle weight or the decrease of the vehicle speed, while the vertical deck displacement is dominated by the vehicle weight. It is also found that the road surface quality has a negligible effect on both component and system fragilities.     

Shaking table tests of a reinforced concrete bridge pier with a low-cost sliding pendulum system

After the occurrence of various destructive earthquakes in Japan, extensive efforts have been made to improve the seismic performance of bridges. Although improvements to the ductile capacities of reinforced concrete (RC) bridge piers have been developed over the past few decades, seismic resilience has not been adequately ensured. Simple ductile structures are not robust and exhibit a certain level of damage under extremely strong earthquakes, leading to large residual displacements and higher repair costs, which incur in societies with less-effective disaster response and recovery measures. To ensure the seismic resilience of bridges, it is necessary to continue developing the seismic design methodology of RC bridges by exploring new concepts while avoiding the use of expensive materials. Therefore, to maximize the postevent operability, a novel RC bridge pier with a low-cost sliding pendulum system is proposed. The seismic force is reduced as the upper component moves along a concave sliding surface atop the lower component of the RC bridge pier. No replaceable seismic devices are included to lengthen the natural period; only conventional concrete and steel are used to achieve low-cost design solutions. The seismic performance was evaluated through unidirectional shaking table tests. The experimental results demonstrated a reduction in the shear force transmitted to the substructure, and the residual displacement decreased by establishing an adequate radius of the sliding surface. Finally, a nonlinear dynamic analysis was performed to estimate the seismic response of the proposed RC bridge pier.     

Seismic response analysis of an interacting curved bridge–train system under frequent earthquakes

This paper establishes a scheme for the seismic analysis of interacting vehicle–bridge systems. The focus is on (horizontally) curved continuous railway bridges and frequent earthquakes. Main features of the proposed scheme are (i) the treatment of the dynamics in all three dimensions (3D), employing an additional rotating system of reference to describe the dynamics of the vehicles and a realistic 3D bridge model; (ii) the simulation of the creep interaction forces generated by the rolling contact between the wheel and the rail; and (iii) the integration of the proposed scheme with powerful commercial finite element software, during the pre‐processing and post‐processing phases of the analysis. The study brings forward the dynamics of a realistic vehicle–bridge (interacting) system during seismic shaking. For the (vehicle–bridge) case examined, the results verify the favorable damping effect the running vehicles have on the vibration of the deck. By contrast, the study stresses the adverse influence of the earthquake‐induced bridge vibration on the riding comfort but, more importantly, on the safety of the running vehicles. In this context, the paper unveils also a vehicle–bridge–earthquake timing problem, behind the most critical vehicle response, and underlines the need for a probabilistic treatment. Among the 20 sets of historic records examined, the most crucial for the safety of the vehicles are near‐fault ground motions. Finally, the study shows that even frequent earthquakes, of moderate intensity, can threaten the safety of vehicles running on bridges during the ground motion excitation, in accordance with recorded accidents. Copyright © 2016 John Wiley & Sons, Ltd.     

减隔震桥梁设计方法及抗震性能研究综述

桥梁作为交通系统中的生命线工程,其抗震性能问题尤为重要。桥梁减隔震技术主要通过减隔震装置来降低结构的地震损伤,目前已发展成为提高强震区桥梁抗震能力的重要措施。为促进减隔震技术在中国桥梁工程领域的进一步发展,首先总结减隔震桥梁的设计方法,归纳其地震反应和震害情况,对采用不同减隔震装置桥梁的非线性动力性能、减隔震效果、地震随机响应、易损性及性能优化方法等研究情况进行梳理;其次,概述减隔震技术在斜交桥、曲线桥及铁路桥梁中的应用情况与研究进展,并介绍新型韧性抗震设计理念在桥梁工程领域中的应用情况和发展前景;最后,总结减隔震桥梁的试验研究情况,指出目前减隔震桥梁研究中的不足和发展趋势。     

Seismic fragility analysis of highway bridges considering multi-dimensional performance limit state

Fragility analysis for highway bridges has become increasingly important in the risk assessment of highway transportation networks exposed to seismic hazards. This study introduces a methodology to calculate fragility that considers multi-dimensional performance limit state parameters and makes a first attempt to develop fragility curves for a multi-span continuous (MSC) concrete girder bridge considering two performance limit state parameters: column ductility and transverse deformation in the abutments. The main purpose of this paper is to show that the performance limit states, which are compared with the seismic response parameters in the calculation of fragility, should be properly modeled as randomly interdependent variables instead of deterministic quantities. The sensitivity of fragility curves is also investigated when the dependency between the limit states is different. The results indicate that the proposed method can be used to describe the vulnerable behavior of bridges which are sensitive to multiple response parameters and that the fragility information generated by this method will be more reliable and likely to be implemented into transportation network loss estimation.     

隔震与非隔震支座对混凝土箱梁桥地震易损性的影响

为评估隔震和非隔震支座对桥梁地震易损性的影响,以一座3跨连续混凝土箱梁桥为分析对象,首先建立采用铅芯橡胶隔震支座与非隔震型盆式橡胶支座下桥梁的数值模型,求得不同程度地震作用下墩顶与支座的最大位移响应;再定义转角延性比损伤指标,结合支座剪应变,分析桥墩和支座的地震易损性情况;最后通过宽界限法建立全桥地震易损性曲线。研究结果表明,支座是较容易发生损坏的构件,而桥梁系统比桥墩或支座更易发生破坏,同时铅芯橡胶支座的破坏概率明显低于非隔震型盆式支座,可见采用隔震支座能有效减小桥墩墩顶在地震作用下的最大位移,此时桥墩地震易损性优于采用非隔震支座的情况。     

高强钢筋ECC-RC复合桥梁地震易损性分析

考虑高强钢筋、ECC等高性能材料在桥梁工程中的推广应用,针对普通钢筋混凝土桥墩抗震性能相对较差的情况,研究高强钢筋ECC-RC复合桥墩的桥梁抗震性能。通过OpenSees平台建立普通RC桥墩桥梁、ECC-RC复合桥墩桥梁及高强钢筋ECC-RC复合桥墩桥梁非线性有限元模型,采用增量动力法和"能力需求比"分析方法建立桥梁各构件及系统的地震易损性曲线,探讨高强钢筋及ECC对桥梁抗震性能的影响。研究表明:ECC-RC、高强钢筋ECC-RC复合桥墩及其桥梁系统的地震易损性均有改善,且高强钢筋ECC的改善效果更显著,高强钢筋ECC-RC复合桥墩支座的地震易损性有所降低,高强钢筋及ECC的应用有助于提高桥墩和桥梁系统抗震性能和安全性,特别是在中震及大震作用下这一现象更加明显。     

大跨度斜拉桥地震响应非线性时程分析

以有限元分析理论为基础,结合某大跨度斜拉桥工程实例,利用ANSYS软件建立有限元模型,通过修正后的El Centro波分别考虑横向、竖向及纵向输入,采用时程分析方法对其进行地震反应分析.计算分析表明:考虑几何非线性后,结构的内力和位移响应明显增大,且对主梁和索塔内力与位移的影响程度及规律也不尽相同,须区别对待分析.同时表明该桥抗震性能良好,地震荷载不控制设计.由此得出结论,对于斜拉桥这类柔性体系, 不可忽视结构几何非线性的影响.     

Vehicle effects on seismic response of a simple‐span bridge during shake tests

Presence of vehicles on a bridge has been observed many times during past earthquakes. Although in practice, the engineers may or may not include the live load contribution to seismic weight in design, current bridge design codes do not specify a certain guideline. A very limited research has been conducted to address this issue from design point of view. The focus of this research is to experimentally assess the effect of a vehicle on the seismic response of a bridge through a large‐scale model. In this scope, a 12‐meter long bridge, having a one lane deck with concrete slab on steel girders, has been shaken under five different ground motions obtained from recent earthquakes that occurred in Turkey, in its transverse direction, both with and without a vehicle on top of the deck. The measured results have indicated that top slab transverse acceleration and bearing displacements can reduce up to 18.7% in presence of a vehicle during seismic tests, which is an indication of reduction in substructure forces. The main reason for the reduction in seismic response of the bridge in the presence of live load can be ascribed to the increase in damping of the system due to mass damper‐like action induced by the vehicle. This beneficial effect cannot be observed in vertical seismic response. Copyright © 2014 John Wiley & Sons, Ltd.     

基于损伤分析的旧曲线梁桥抗震性能评估

曲线桥梁在役期间可能面临地震灾害,导致结构损坏甚至坍塌,为了评估在役桥梁的抗震性能,提出基于损伤分析的曲线梁桥抗震性能评估方法。建立旧曲线梁桥有限元模型,基于损伤分析的原理,提出适合曲线梁桥地震响应特性的构件损伤模型,在全桥有限元模型中输入不同类型地震动,计算各构件的损伤指数,并结合旧桥检算系数,由各构件损伤指数综合得到桥梁的整体损伤指数。结果表明:不同地震动下主梁会发生碰撞破坏,桥梁两端的支座容易发生移位,桥墩沿横桥向或顺桥向均会产生位移;不同地震动对主梁、支座、桥墩等构件造成的损害程度有较大差异,各构件的地震响应会影响桥梁整体结构的抗震性能,其中桥墩对桥梁整体抗震性能的影响最大,桥墩位移超过极限值可能导致倒塌;主梁反复碰撞会加剧桥梁的破坏程度,桥梁两端支座在地震作用下更容易发生损坏。     

Dynamic analysis of train–bridge system subjected to non‐uniform seismic excitations

Based on the theory of dynamic wheel–rail interactions, a dynamic model of coupled train–bridge system subjected to earthquakes is established, in which the non‐uniform characteristics of the seismic wave input from different foundations are considered. The bridge model is based on the modal comprehension analysis technique. Each vehicle is modelled with 31 degrees of freedom. The seismic loads are imposed on the bridge by using the influence matrix and exerted on the vehicles through the dynamic wheel–rail interaction relationships. The normal wheel–rail interaction is tackled by using the Hertzian contact theory, and the tangent wheel–rail interaction by the Kalker linear theory and the Shen–Hedrick–Elkins theory. A computer code is developed. A case study is performed to a continuous bridge on the planned Beijing–Shanghai high‐speed railway in China. Through input of typical seismic waves with different propagation velocities to the train–bridge system, the histories of the train running through the bridge are simulated and the dynamic responses of the bridge and the vehicles are calculated. The influences of train speed and seismic wave propagation velocity on the dynamic responses of the bridge–vehicle system are studied. The critical train speeds are proposed for running safety on high‐speed railway bridges under earthquakes of various intensities. Copyright © 2006 John Wiley & Sons, Ltd.     

横桥向地面运动作用下独塔部分斜拉桥易损性分析

桥梁作为交通生命线系统中的重要工程,屡次在中等强度地震的作用下,遭受严重破坏甚至整体损毁,因此桥梁结构地震易损性研究在世界各国得到重视和发展。部分斜拉桥作为一种新桥型,由于兼有经济性和美学特性,近十年来在国内外发展迅速,但这种新桥型尚未经受地震的考验,在可能的地震灾害下,部分斜拉桥的地震破坏损伤概率还不明确,有必要开展有关的易损性研究。本文在桥梁地震易损性研究的基础上,分析在横桥向地面运动作用下独塔部分斜拉桥的易损性,定义五级损伤极限状态,建立桥墩、桥塔、限位器和全桥的易损性曲线,研究结果表明在横桥向地面运动作用下,独塔部分斜拉桥全桥易损性主要受到限位器和中墩的控制。     

大跨度桥梁结构多级地震响应研究

大跨度桥梁结构在地震发生时其支承点受到的地震动激励均不相同,使得在多级地震中其桥梁结构对于地震的响应程度也不同。通过分析多级地震作用下,水中结构的运动引起桥梁墩部周围水体辐射波浪运动对桥梁结构的影响,分析大跨度桥梁墩-水耦合边界。基于反应谱理论,计算大跨度桥梁结构承受的地震力最大值,得出多级地震响应曲线,以分析其多级地震响应;并以某地六跨桥为例,以多级地震下桥梁的位移、剪力、弯矩等响应时程为指标进行分析,得出有效结论。     

Effect of train dynamics on seismic response of steel monorail bridges under moderate ground motion

This study is intended to investigate the seismic response of steel monorail bridges using three‐dimensional dynamic response analysis. We particularly consider monorail bridge–train interaction when subjected to ground motion that occurs with high probability. A monorail train car with two bogies with pneumatic tires for running, steering and stabilizing wheels is assumed to be represented sufficiently by a discrete rigid multi‐body system with 15 degrees of freedom (DOFs). Bridges are considered as an assemblage of beam elements with 6 DOFs at each node. Modal analysis is used for dynamic response analysis under moderate earthquakes. The seismic response of an advanced monorail bridge that adopts a simplified structural system and composite girders is investigated through comparison with seismic responses of a conventional bridge. The acceleration response of a monorail train is also calculated to investigate the effect of structural types of bridges on the train's dynamic response during earthquakes. Results show that the seismic responses of the advanced bridges are greater than those of the conventional monorail bridge because of the simplified structural system and increased girder weight that is attributable to composite girders of the advanced bridge. Moreover, the train on the advanced bridge shows greater dynamic response than that on the conventional bridge. Observations reveal that the dynamic monorail train system acts as a damper on the monorail bridge. That fact shows that the existing design, which considers a train as additional mass, yields a conservative result. Copyright © 2006 John Wiley & Sons, Ltd.     

不同地震激励方向下隔震曲线梁桥易损性分析

为进一步评估隔震曲线梁桥在地震激励下的抗震性能,从地震易损性角度出发并兼顾考虑地震激励方向对其易损性的影响。利用APDL建立采用板式橡胶支座的隔震曲线梁桥有限元模型,从PEER中选取同一地震事件中的近断层地震动,按规范规定比例输入水平双向地震动进行非线性动力时程分析,结合地震响应与损伤指标计算得到各构件地震易损性曲线;考虑地震激励方向的变化,通过MATLAB编程绘制得到桥梁结构构件(桥墩与支座)以及整体系统的地震易损性曲面,分析探讨地震激励方向对隔震曲线梁桥易损性的影响。结果表明：不同极限状态下各桥墩切向损伤条件概率明显大于其径向,各支座的切向与径向易损性相差不大,但仍是各支座的切向易损性略大于径向易损性;桥梁各构件(桥墩与支座)切向易损性对地震激励方向均表现出很强依赖性,而径向易损性对其的依赖性相对较弱,且伴随损伤等级的提高,构件易损性对地震激励方向更加敏感;桥梁整体系统易损性对地震激励方向的变化不太敏感,且因各构件响应之间的相关性较高,其系统易损性更接近于易损性最大的构件——易损性下限;当进行隔震曲线梁桥抗震性能评估时,应考虑不同地震激励方向对其地震易损性的影响,从而使得易损性分析...     

连续弯箱梁自行车桥地震响应分析

为研究厦门市弯箱梁自行车桥的地震响应规律,采用SAP2000有限元软件建立自行车高架桥三维壳体模型,在考虑多遇地震和罕遇地震水准作用及不同加载方向的基础上,分别采用反应谱分析法和时程分析法进行该桥的动力响应分析。结果表明：自行车桥z方向位移分量最大,且z方向分量极值均发生在曲线分叉段;相对剪力而言,桥墩竖向支反力相对较小;E1和E2地震水准响应情况随时间的变化趋势基本一致,桥梁结构未进入塑形状态,抗震性能良好,安全性指标较高;反应谱法计算得到的响应包络值相对3条不同的地震时程结果的峰值大,在实际桥梁抗震分析过程中需要综合考虑两者的分析结果。文章研究结果对今后自行车桥设计和抗震性能分析具有指导意义,并可为研究者对该类桥的进一步研究提供借鉴。     

板式支座与铅芯支座连续梁桥振动台试验对比分析

通过对分别采用板式支座和铅芯支座的2座3跨连续梁桥模型进行振动台试验,对比分析了这2类桥梁的动力特性、破坏过程及2种支座对连续梁桥地震反应的影响。研究结果表明：地震波特性对桥梁结构的地震反应有较大影响,在对桥梁结构进行抗震设计时,需选择合理的地震动输入;在地震强度较小时,板式支座的滑动能够起到一定的隔震效果,铅芯支座的隔震性能能得到较好的发挥;在地震强度较大时,铅芯支座的隔震性能不能得到很好的发挥,采用铅芯支座的桥梁地震反应不一定小于普通桥梁;通过合理的设计,2类桥梁都完全可以实现大震不倒的设防目标。     

超大跨度斜拉桥考虑行波效应的地震动随机响应研究

斜拉桥地震反应不同于其它桥型,具有明显的空间耦合效应.利用有限元理论对苏通长江公路大桥的空间抗震性能进行分析,重点研究行波效应对结构响应的影响,并与一致激励计算的结果进行比较,为大跨度斜拉桥抗震分析采用随机方法提供了一定的参考依据.研究结果表明,行波效应对斜拉桥结构内力有显著的影响,大跨度斜拉桥抗震性能分析必须考虑行波效应.而行波效应的影响与结构自身动力特性、视波速、构件位置及研究响应类型(位移与内力)相关.     

Effects of structural characterizations on fragility functions of bridges subject to seismic shaking and lateral spreading

This paper evaluates the seismic vulnerability of different classes of typical bridges in California when subjected to seismic shaking or liquefaction-induced lateral spreading. The detailed structural configurations in terms of superstructure type, connection, continuity at support and foundation type, etc. render different damage resistant capability. Six classes of bridges are established based on their anticipated failure mechanisms under earthquake shaking. The numerical models that are capable of simulating the complex soil-structure interaction effects, nonlinear behavior of columns and connections are developed for each bridge class. The dynamic responses are obtained using nonlinear time history analyses for a suite of 250 earthquake motions with increasing intensity. An equivalent static analysis procedure is also implemented to evaluate the vulnerability of the bridges when subjected to liquefaction-induced lateral spreading. Fragility functions for each bridge class are derived and compared for both seismic shaking （based on nonlinear dynamic analyses） and lateral spreading （based on equivalent static analyses） for different performance states. The study finds that the fragility functions due to either ground shaking or lateral spreading show significant correlation with the structural characterizations, but differences emerge for ground shaking and lateral spreading conditions. Structural properties that will mostly affect the bridges＇ damage resistant capacity are also identified.     

Ground motion spatial variability effects on seismic response control of cable-stayed bridges

The spatial variability of input ground motion at supporting foundations plays a key role in the structural response of cable-stayed bridges (CSBs); therefore, spatial variation effects should be included in the analysis and design of effective vibration control systems. The control of CSBs represents a challenging and unique problem, with many complexities in modeling, control design and implementation, since the control system should be designed not only to mitigate the dynamic component of the structural response but also to counteract the effects of the pseudo-static component of the response. The spatial variability effects on the feasibility and efficiency of seismic control systems for the vibration control of CSBs are investigated in this paper. The assumption of uniform earthquake motion along the entire bridge may result in quantitative and qualitative differences in seismic response as compared with those produced by uniform motion at all supports. A systematic comparison of passive and active system performance in reducing the structural responses is performed, focusing on the effect of the spatially varying earthquake ground motion on the seismic response of a benchmark CSB model with different control strategies, and demonstrates the importance of accounting for the spatial variability of excitations.