国内外延性抗震设计的比较

1971年美国发生圣.费尔南多地震,许多新建的桥梁结构遭到严重破坏之后,延性抗震得到重视,抗震设计方法正在从传统的单一强度理论向延性抗震理论过渡。目前,大多数国家的桥梁抗震设计规范已经采纳了延性抗震理论。本文针对几个主要的抗震设计规范,包括EC8、Caltrans、AASHTO、日本和我国公路桥梁抗震设计规范中的延性抗震设计做一个概述。主要内容有延性指标的定义及其计算方法和延性构件钢筋锚固和搭接长度的规定,本文对我国公路桥梁的延性抗震设计有一定的参考价值。     

桥梁抗震设计规范与建筑抗震设计规范的分析与比较

对我国现行《公路工程抗震设计规范》(JTJ004-89)与《建筑抗震设计规范》(GB50011-2001)进行了较为详细的对比。分别从抗震设计的基本思想、设计地震动参数、地震反应分析和计算方法、构造细节等方面对这两本规范进行了比较,并指出了今后我国各行业工程结构抗震设计规范宜逐步统一。     

关于抗震设计规范与地震动区划图的有关探讨

本文总结了国内外桥梁抗震设计规范和建筑结构抗震设计规范的设计思想和设计方法,介绍了我国和美国地震动参数区划图的发展和现状,对比分析了抗震规范使用地震区划图的情况。针对我国抗震设计规范和地震动参数区划图的现状,提出了两条建议：（1）地震动参数区划图编制部门应直接提供多水准的地震动参数区划图;（2）抗震设计规范应彻底抛弃设防烈度概念,以地震重现期取代原地震危险程度标示方法。     

基于反应谱理论的复模态抗震设计方法

本文结合我国现行《建筑抗震设计规范》，采用复模态理论分析技术对结构非正交阻尼阵进行解耦，导出了基于反应谱理论的耗能减震结构的复模态抗震设计方法。文中提出了完整、系统的耗能减震结构复模态抗震设计方法的程序，并给出若干抗震设计实例。算例结果表明：该设计方法准确、实用，具有一定的理论意义与工程意义。     

铁路桥梁抗震规范与新版公路桥梁抗震规范的比较

2020年6月交通运输部发布了新版《公路桥梁抗震设计规范》（JTG/T 2231-01-2020）（简称"《公规》"）。本文比较了现行《铁路工程抗震设计规范》（GB 50111-2006）（2009年版）（以下简称"《铁规》"）与《公规》的抗震设计相关内容,并分别采用两本规范对25m墩高（D类）、35m墩高（C类）和40m墩高（B类）简支梁进行抗震设计,比较二者地震力和配筋设计结果差异。结果表明:《公规》和《铁规》的抗震设计框架和内容基本一致,在具体规定上如E2或罕遇地震设计最大加速度响应值以及桥墩强度和延性验算方法等方面不同;D类桥梁《铁规》地震力明显大于《公规》,C类和B类桥梁《铁规》和《公规》地震力相当;地震力相同时,《铁规》配筋率计算值大于《公规》,因《铁规》配筋设计基于容许应力法,而《公规》基于极限状态法。     

基于建筑抗震设计规范的设计用地震动分析

首先利用我国《建筑抗震设计规范》(GB 50011-2001)中的地震影响系数曲线,制成适合于我国抗震设计规范的人工地震波形,然后使用该人工波和日本现行设计用地震动,对隔震结构进行地震响应分析,最后由地震响应结果对所提出的模拟设计用地震动大小进行评价,得到一些有意义结论,供抗震设计人员在设计时参考。     

芦山地震楼梯间震害调查及思考

楼梯间作为地震中人员疏散和救援通道,其抗震设计应引起足够的重视.我国2010年实行的《建筑抗震设计规范》(GB50011-2010)中加强了结构中楼梯间的设计要求,结合该规范的实施,本文总结了芦山地震中各类结构中楼梯间的震害现象.通过对梯板、楼梯间墙体、与楼梯间相连的主体结构等位置的震害分析,指出了规范中关于楼梯间新增条文的必要性;提出了一些抗震设计建议,为规范修订和工程设计提供参考.     

基于公路工程规范地震需求谱研究

从解决桥梁结构的实际问题出发,根据桥梁结构的抗震能力及计力法的需要,由于强度折减系数R与延性系数μ的关系建立弹塑性反应谱的原理,建立了基于《公路工程抗震设计规范》(JTJ 004-89)给出的弹性反应谱的非弹性地震需求谱,为桥梁结构抗震性能评价的研究提供参考意见。     

不同版本规范设计的底框砌体结构地震易损性对比

历次地震震害表明,底框砌体结构在遭遇大地震时破坏严重.本文比较了《GBJ11-89建筑抗震设计规范》和《GB50011-2001建筑抗震设计规范》中关于该类结构的抗震设计要求.参考某地一个实际底框砌体结构建筑设计资料,分别按上述两版本规范设计了2个具有代表性的底框砌体结构.采用层间剪切模型基于IDA方法对结构进行了地震...     

基于性态的建筑工程抗震设计——《建筑工程抗震性态设计通则》述评

《建筑工程抗震性态设计通则(试用)》对抗震设计具有重要的指导意义,其中的抗震设计理念同以往的抗震设计规范在抗震设防的思路、概念和方法上有较大的区别。从工程实践的角度,比较了《通则》和现行抗震设计相关规范的区别并对具体应用提出一些看法。     

铁路工程抗震设计规范中桥梁抗震 相关规定与发展沿革

生命线基础设施抗震安全对我国防震减灾与抗震救灾工作具有重要意义,铁路桥梁更是关乎人员转移与物质运输的安全与稳定。基于地震区铁路桥梁震害资料分析和震害调查研究,结合我国铁路桥梁抗震设计工作的经验、教训及相关科研成果,我国陆续出版了3本《铁路工程抗震设计规范》。文章回顾我国铁路桥梁抗震设计规范60年的发展历程,对我国开展铁路桥梁抗震设计工作的历史时期进行划分;通过对比和总结1977、1987、2009年颁布的《铁路工程抗震设计规范》中的铁路桥梁部分,发现该系列规范的发展逐步体现了基于性能的设计理念,场地分类更加精细,地震作用考虑更为科学,且对于铁路桥梁的抗震构造措施有了更加明确的规定。研究可为改进和完善地震区铁路桥梁震害预测方法提供参考依据。     

RC jacketing parameters to retrofit highway bridges

Highway bridges are essential structures in the transportation system of any country in the world. Many highway bridges are reinforced concrete (RC) bridges that were constructed before the 1980s, prior to current seismic regulation codes. The continuous modification of regulation codes makes it necessary to evaluate structures, and in many cases, existing bridges require interventions to increase their seismic capacity. Among the different techniques used to improve bridge capacity, encasing the columns with RC jackets increases the strength and stiffness of the substructure. RC jacketing increases the column cross sections, improves the seismic capacity and reduces the seismic vulnerability of the bridge substructures. This work presents a parametric study to assess the expected demands of seismically deficient medium length highway bridges retrofitted with RC jacketing aimed at determining the best jacket parameters. A suite of twenty strong ground motions, recorded from a subduction seismic source close to the Pacific Coast in Mexico, was selected to characterize the seismic demand. The bridge superstructures are simply supported with five 30 m long spans for a total length of 150 m. The bridge models have five possible pier heights of 5, 10, 15 20 and 25 m and three different jacket thicknesses and steel ratios. Pushover analyses and capacity spectra of the family of accelerograms allow for the determination of the pier demands by obtaining the performance point as the intersection of the capacity and demand curves. The results allow for the determination of the influence of each parameter on the expected seismic behavior of the bridge models, with the aim of selecting the most suitable jacket characteristics to improve the seismic bridge performance.     

A comparative study of bridge damage due to the Wenchuan, Northridge, Loma Prieta and San Fernando earthquakes

A comparative study of selected bridge damage due to the Wenchuan, Northridge, Loma Prieta and San Fernando earthquakes is described in this paper. Typical ground motion effects considered include large ground fault displacement, liquefaction, landslide, and strong ground shaking. Issues related to falling spans, inadequate detailing for structural ductility and complex bridge configurations are discussed within the context of the recent seismic design codes of China and the US. A significant lesson learned from the Great Wenchuan earthquake, far beyond the opportunities to improve the seismic design provisions for bridges, is articulated.     

Impact of seismic excitation direction on the fragility analysis of horizontally curved concrete bridges

The focus of this study is the impact of the seismic excitation direction on the fragility of horizontally curved bridges. Nonlinear time history analyses are performed on a typical, curved concrete bridge in China using a set of real ground motions with different incident angles. To build reliable probabilistic seismic demand models, ten commonly used intensity measures (IMs) are assessed in terms of various metrics to determine the optimal IMs, which account for the influence of the seismic excitation directions. Subsequently, fragility surfaces with respect to both the optimal IM and incident angles are generated to qualify the fragility sensitivity for various components and the bridge system to the seismic excitation directions. Moreover, the rationality and applicability of the methods recommended by the Caltrans, Eurocode 8 and Chinese codes for determining the seismic excitation direction of curved bridges are evaluated. The results indicate that the excitation direction imposes a minor impact on the optimal IM rankings. Compared to structure-independent IMs, structure-dependent IMs are more appropriate for predicting the demands of horizontally curved concrete bridges. However, the seismic excitation direction significantly affects the component fragilities, and the level of the effect intensifies with increasing limit states. If the incident angle occurrence probability is not provided, the Chinese code method for the seismic excitation direction is more suitable for the horizontally curved concrete bridge fragility assessment, which has the advantages of computational efficiency when compared to the Caltrans code and relatively conservative results when compared to Eurocode 8.     

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。     

Effects of isolation on the seismic response of bridges designed for two different soil types

The objective of this study was to investigate the effect of lead rubber isolators on the seismic response of bridges designed according to current codes for two different soil conditions: hard and medium type soils, in order to assess their applicability for the design of new bridges or retrofit of existing ones. The study was conducted for two levels of earthquake, one corresponding to a return period of 50 years and a service limit state, the other with a return period of 1,000 years and a failure limit state. Twenty one subduction earthquake records on the two types of soil were used to evaluate the linear and nonlinear dynamic response of a set of bridges designed for this purpose with and without base isolation. The response parameters evaluated are the maximum relative displacement on top of the piers, the maximum pier distortion, the maximum shear forces in the piers and the ductility demands for the isolators. The results presented are the average of these maxima for the various earthquakes. This study is an expansion of a previous one in which the seismic response of 36 bridges considering models with and without base isolators, structures with linear base isolators and bridges with nonlinear isolators. The results of this study confirm the conclusions previously obtained and show that the isolation can have beneficial effects even for bridges located in medium soil types.     

规则桥梁抗震性能水准的定义及其量化描述

基于性能的结构抗震设计是各国结构抗震设计规范未来的主要发展方向,虽然其理论框架已基本形成,然而其中至关重要的结构抗震性能水准的定义及其量化描述问题,目前仍处于研究探讨阶段.本文从公路梁式桥震害现象出发,采用极限状态设计概念,对规则桥梁在地震作用下的性能水准予以明确的定义;并以墩顶漂移率作为设计参数,通过对大量试验数据的...     

Extension of modal pushover analysis to seismic assessment of bridges

Nonlinear static (pushover) analysis has become a popular tool during the last decade for the seismic assessment of buildings. Nevertheless, its main advantage of lower computational cost compared to nonlinear dynamic time‐history analysis (THA) is counter‐balanced by its inherent restriction to structures wherein the fundamental mode dominates the response. Extension of the pushover approach to consider higher modes effects has attracted attention, but such work has hitherto focused mainly on buildings, while corresponding work on bridges has been very limited. Hence, the aim of this study is to adapt the modal pushover analysis procedure for the assessment of bridges, and investigate its applicability in the case of an existing, long and curved, bridge, designed according to current seismic codes; this bridge is assessed using three nonlinear static analysis methods, as well as THA. Comparative evaluation of the calculated response of the bridge illustrates the applicability and potential of the modal pushover method for bridges, and quantifies its relative accuracy compared to that obtained through other inelastic methods. Copyright © 2006 John Wiley & Sons, Ltd.