RC框架结构地震易损性分析方法研究进展

21世纪我国经济急速发展,人口也急剧增长,这也使得地震对人类生命和财产安全造成的威胁更大,结构抗震研究需求日益增加。地震易损性分析技术对于结构破坏和损失预测都有着非同一般的应用价值,因此受到了国内外土木工程抗震界的广泛关注和研究。首先介绍了地震易损性分析的基本概念,具体地论述了用于地震易损性分析的三种方法,同时总结出此三种方法各自的优缺点;其次以RC框架结构为例论述了国内外地震易损性分析领域的研究发展,从上个世纪90年代开始进行了系统的梳理和分析。说明了地震易损性分析在研究过程中由于不确定性的存在而导致对分析结果准确度的影响;最后指出要想得到更接近于真实的易损性分析结果,还需考量易损性分析中的不确定参数,揭示了地震易损性分析研究领域所面临的挑战。     

基于震害资料的川西农居地震易损性研究

基于汶川地震等6次典型破坏性地震的震害调查资料,采用基于震害数据调查的经验分析法得出了川西地区农居建筑基于地震烈度的地震易损性矩阵,并采用房屋震害矩阵曲线化分析方法转化计算得出该地区基于地震峰值加速度的地震易损性矩阵。通过分析该地区5类农居建筑的破坏概率和对易损性指数的计算分析,得出不同结构农居建筑的抗震性能排序和抗倒塌能力排序,即穿斗木结构的抗震性能最好,土木结构的抗震性能最差,其余结构类型的抗震性能顺序依次是未设防砖混结构、砖木结构、砖石结构。同时,穿斗木结构的抗倒塌性能最好,然后依次是未设防砖混结构和砖木结构,而土木结构和砖石结构是抗倒塌性能最差的2种结构类型。     

基于地震易损性的框架结构的优化方法

给出了一种框架结构地震易损性优化的准则算法．根据优化准则构造了一种修改设计变量的格式,提出了设计方案可行性调整的方法并推导了计算公式,给出了优化算法的计算步骤,并通过一个算例阐述了这种算法的应用。     

配筋砌体结构地震易损性评价方法初探

本文首先简要介绍了考虑空间协同的配筋砌体结构弹塑性地震反应分析程序EDAPSC；然后提出了一种利用空间协同时程分析结果，对配筋砌体结构地震易损性进行定量评价的方法，并以上海园南小区住宅楼为例进行了地震易损性分析，说明本文提出的地震易损性评价方法是可行和合理的；另外作者还对设计人员提出了提高结构抗震安全性的建议。     

沈阳市浑南新区场地地震易损性分析

地震易损性分析是进行场地抗震性能划分的一种有效方法。根据沈阳市浑南新区的地震、地质和地貌特点 ,选取场地地基土、断层、地表地震动参数、地下水埋深和第四系厚度作为场地地震易损性分析的因素 ,并采用灰色统计方法对专家意见进行分析以确定易损性指数系数。计算结果表明 ,浑南新区的大部分地区属于抗震有利地段 ,占总面积的 81 6 8% ,抗震不利地段只占 1 8 32 %。     

青海省农居地震灾害易损性研究

青海省靠近我国南北地震带,是一个地震频发的省份,而农居相对于城市建筑的抗震性能而言较为薄弱,也是造成地震损失的重要因素。本文通过对青海省的地理状况、历史震灾情况、农居建筑结构等进行研究,总结出青海省各结构类型农居震灾破坏率,评估乡级空间尺度的农居震灾易损性并分级,最后简单分析造成易损性较高的因素并提出建议。     

隧道工程地震易损性分析研究综述与展望

易损性分析是隧道工程领域防震减灾研究的重要方法。首先,详细综述了国内外隧道地震易损性研究历史与现状;其次,归纳了国内外隧道地震易损性分析主要方法,并总结了各种方法的实际适用性;接着,提出了隧道地震易损性评估步骤,并且讨论了以数值模拟为主要手段的理论易损性曲线建立中的3个关键内容:(1)输入参数确定;(2)破坏状态分级;(3)相关不确定性参数计算;最后,指出该领域一些亟待解决的问题和未来研究发展的方向。结果表明:隧道地震易损性分析能通过考虑相关不确定性因素,反映了隧道在地震荷载作用下的性能,有利于未来的风险评估和损失估算,对基于性能的隧道抗震设计的发展具有重要意义。     

建筑物地震易损性分析研究

本文系统地总结了近几十年来结构地震易损性分析及地震破坏损失预测的发展 ,指出了建筑物地震易损性分析存在的一些重要问题 ,如缺乏震害经验的建筑物地震易损性估计、采用地震动参数进行建筑物地震易损性估计等问题。本文重点研究了理论计算的易损性估计方法 ,给出了对于不同地震动建筑物出现或超越不同状态的概率 ,将多层砖房的理论易损性估计结果同实际震害资料进行了对比 ,并对经正规设计但缺乏震害经验的高层建筑地震易损性进行了估计。另外 ,本文也着重研究了以地震动峰值加速度及反应谱作为地震动输入参数时的结构地震易损性分析方法…     

建筑结构地震易损性分析研究综述

地震易损性是指在不同强度水平的地震作用下建筑结构发生各种破坏的条件概率。本文对地震易损性分析的发展历程进行回顾和总结,介绍了地震易损性的相关概念、研究目的和意义以及5个表达工具。随后,针对国内外学者对建筑结构的易损性分析方法开展了系统的梳理和分析,特别是从基于震害调查的经验分析法和基于数值模拟的理论计算法方面展开了重点综述,并简单介绍了一些不常用的方法。最后指出了国内外对建筑结构易损性分析研究的不足和未来的研究方向。     

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...     

油浸式高压变压器地震易损性分析

油浸式变压器是由多种材料组成的复杂结构。本文对油浸式高压变压器建立了较为精确的有限元模型，考虑了各组件之间相互作用的影响。对该设备进行了动力性能和地震响应分析以及易损性分析。分析结果表明，大型高压变压器在地震中的首要破坏模式为瓷套破坏，其地震响应的离散度较高。易损性分析得到设备的地震易损性曲线，可直接应用于电力系统的抗震分析。     

Seismic fragility assessment of low-rise stone masonry buildings

Many historic buildings in old urban centers in Eastern Canada are made of stone masonry reputed to be highly vulnerable to seismic loads.Seismic risk assessment of stone masonry buildings is therefore the first step in the risk mitigation process to provide adequate planning for retrofit and preservation of historical urban centers.This paper focuses on development of analytical displacement-based fragility curves reflecting the characteristics of existing stone masonry buildings in Eastern Canada.The old historic center of Quebec City has been selected as a typical study area.The standard fragility analysis combines the inelastic spectral displacement,a structure-dependent earthquake intensity measure,and the building damage state correlated to the induced building displacement.The proposed procedure consists of a three-step development process:(1) mechanics-based capacity model,(2) displacement-based damage model and(3) seismic demand model.The damage estimation for a uniform hazard scenario of 2% in 50 years probability of exceedance indicates that slight to moderate damage is the most probable damage experienced by these stone masonry buildings.Comparison is also made with fragility curves implicit in the seismic risk assessment tools Hazus and ELER.Hazus shows the highest probability of the occurrence of no to slight damage,whereas the highest probability of extensive and complete damage is predicted with ELER.This comparison shows the importance of the development of fragility curves specific to the generic construction characteristics in the study area and emphasizes the need for critical use of regional risk assessment tools and generated results.     

Development of seismic fragility surfaces for reinforced concrete buildings by means of nonlinear time‐history analysis

Fragility curves are generally developed using a single parameter to relate the level of shaking to the expected structural damage. The main goal of this work is to use several parameters to characterize the earthquake ground motion. The fragility curves will, therefore, become surfaces when the ground motion is represented by two parameters. To this end, the roles of various strong‐motion parameters on the induced damage in the structure are compared through nonlinear time‐history numerical calculations. A robust structural model that can be used to perform numerous nonlinear dynamic calculations, with an acceptable cost, is adopted. The developed model is based on the use of structural elements with concentrated nonlinear damage mechanics and plasticity‐type behavior. The relations between numerous ground‐motion parameters, characterizing different aspects of the shaking, and the computed damage are analyzed and discussed. Natural and synthetic accelerograms were chosen/computed based on a consideration of the magnitude‐distance ranges of design earthquakes. A complete methodology for building fragility surfaces based on the damage calculation through nonlinear numerical analysis of multi‐degree‐of‐freedom systems is proposed. The fragility surfaces are built to represent the probability that a given damage level is reached (or exceeded) for any given level of ground motion characterized by the two chosen parameters. The results show that an increase from one to two ground‐motion parameters leads to a significant reduction in the scatter in the fragility analysis and allows the uncertainties related to the effect of the second ground‐motion parameter to be accounted for within risk assessments. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of the angle of seismic incidence on the fragility curves of bridges

This study examines the effect of the angle of seismic incidence θ on the fragility curves of bridges. Although currently, fragility curves of bridges are usually expressed only as a function of intensity measure of ground motion (IM) such as peak ground acceleration, peak ground velocity, or S_a(ω₁), in this study they are expressed as a function of IM with θ as a parameter. Lognormal distribution function is used for this purpose with fragility parameters, median c_m and standard deviation ζ to be estimated for each value of θ chosen from 0 < θ < 360°. A nonlinear 3D finite element dynamic analysis is performed, and key response values are calculated as demand on the bridge under a set of acceleration time histories with different IM values representing the seismic hazard in Los Angeles area. This method is applied to typical straight reinforced concrete bridges located in California. The results are validated with existing empirical damage data from the 1994 Northridge earthquake. Even though the sample bridges are regular and symmetric with respect to the longitudinal axis, the results indicate that the weakest direction is neither longitudinal nor transverse. Therefore, if the angle of seismic incidence is not considered, the damageability of a bridge can be underestimated depending on the incidence angle of seismic wave. Because a regional highway transportation network is composed of hundreds or even thousands of bridges, its vulnerability can also be underestimated. Hence, it is prudent to use fragility curves taking the incident angle of seismic waves into consideration as developed here when the seismic performance of a highway network is to be analyzed. Copyright © 2012 John Wiley & Sons, Ltd.     

Simplified seismic fragility analysis of structures with two types of friction devices

This paper presents a method and results of seismic fragility estimation of frame structures with friction devices and with friction devices and restrictors. The seismic intensity parameter, defined as the mean value of the pseudovelocity spectrum in a specified periods band, is proved to allow the use of linear regression analysis of the response parameters of the considered non‐linear structures on seismic intensity. A simplified method of fragility estimation is proposed, based on the concept of ‘mean seismic excitation’ and linear regression of the seismic response parameters on seismic intensity parameter. The key risk contributors for the system with friction devices and for the system with friction devices and restrictors are identified on the basis of the fragility analysis, and recommendations for improvement of the seismic response of the respective systems are derived. The results of the fragility study show that when the initial ‘bare’ frame is retrofitted by rigidly connected bracings the effect is much lower than in the case of connecting the bracings by friction devices and especially by friction devices and restrictors. Copyright © 2000 John Wiley & Sons, Ltd.     

考虑非结构构件损伤的钢筋混凝土框架建筑多维地震易损性分析

基于单一指标的传统地震易损性分析忽略了非结构构件损伤对建筑抗震性能的影响。首先基于多维性能极限状态理论建立了三维性能极限状态方程,并对几种特殊情况下的三维阈值曲面进行了讨论。进而以最大层间位移角作为整体结构与位移敏感型非结构构件的性能指标,以峰值楼面加速度作为加速度敏感型非结构构件的性能指标,对建筑的结构损伤和非结构损伤进行描述。考虑各性能指标之间的相关性和各性能指标所对应的极限状态阈值的不确定性,建立了建筑在地震作用下的三维性能极限状态的超越概率函数。最后,采用Open Sees有限元软件对一7层钢筋混凝土框架填充墙建筑进行增量动力分析,得到其各性能水平下的地震易损性曲线。分析结果表明,当忽略非结构构件损伤时,各性能极限状态的超越概率均降低,从而高估了建筑剩余功能水平,进而导致低估建筑的损失。在考虑各性能指标的极限状态阈值的不确定性时,对任一性能极限状态,不同变异系数取值下的易损性曲线会出现交点,在交点之前超越概率随着变异系数的增大而增大,交点之后则随着变异系数的增大而减小。在考虑性能指标间的相关性时,对任一性能极限状态,超越概率随着相关系数的减小而增大。另外,性能指标阈值的不确定性与性能指标间的相关性对地震易损性的影响随着性能水平的提高而逐渐降低,且对低性能水平下建筑地震易损性有明显影响。     

抗震结构最优设防水平决策与全寿命优化设计的简化易损性分析方法

地震破坏状态概率分析是抗震结构最优设防水平决策与全寿命优化设计的关键问题之一,作者们曾根据"三水准"设防原则和地震烈度的危险性分析结果提出了二种实用分析方法.本文建立了结构破坏状态概率分析的地震易损性理论基础,提出了极限状态地震易损性和破坏状态地震易损性的概念.从地震易损性理论的角度,对二种地震破坏状态概率简化分析方法进行了深入分析,指出第1种方法是一种考虑结构宏观抗震能力不确定性的半理论半经验易损性分析方法,而第2种方法则是一种不考虑结构宏观抗震能力不确定性的简化易损性分析方法,根据地震破坏状态概率的计算结果对二种方法进行了对比分析,并提出了相关的建议.     

基于增量动力分析方法的砌体结构地震易损性分析

砌体结构是一种脆性结构,变形能力和承载力均较低,因取材方便、施工简单和造价低等优势在中国被广泛应用。为了评估砌体结构的抗震性能,本文基于增量动力分析（Incremental Dynamic Analysis,IDA）方法研究了多层砌体结构的地震易损性,分析了影响砌体结构地震易损性的主要因素以及群体多层砌体结构地震易损性。研究结果表明:在相同场地条件情况下,砌体结构的房屋层数、砌筑砂浆强度、设防烈度和墙体面积率对结构的地震易损性影响较明显;当结构层高在2.8~3.3 m之间时,层高对结构地震易损性的影响不大。抗震设防砌体结构抗震能力比不设防结构有明显提高,说明构造柱和圈梁等构造措施能显著提高砌体结构的抗倒塌能力,这与目前的基本认识相同,也证明了增量动力分析方法的有效性。     

Multi‐angle,multi‐damage fragility curves for seismic assessment of bridges

The scope of this study is to investigate the effect of the direction of seismic excitation on the fragility of an already constructed, 99‐m‐long, three‐span highway overpass. First, the investigation is performed at a component level, quantifying the sensitivity of local damage modes of individual bridge components (namely, piers, bearings, abutments, and footings) to the direction of earthquake excitation. The global vulnerability at the system level is then assessed for a given angle of incidence of the earthquake ground motion to provide a single‐angle, multi‐damage probabilistic estimate of the bridge overall performance. A multi‐angle, multi‐damage, vulnerability assessment methodology is then followed, assuming uniform distribution for the angle of incidence of seismic waves with respect to the bridge axis. The above three levels of investigation highlight that the directivity of ground motion excitation may have a significant impact on the fragility of the individual bridge components, which shall not be a priori neglected. Most importantly, depending on the assumptions made for the component to the system level transition, this local sensitivity is often suppressed. It may be therefore necessary, based on the ultimate purpose of the vulnerability or the life cycle analysis, to obtain a comprehensive insight on the multiple damage potential of all individual structural and foundation components under multi‐angle excitation, to quantify the statistical correlation among the distinct damage modes and to identify the components that are both most critical and sensitive to the direction of ground motion and carefully define their limit states which control the predicted bridge fragility. Copyright © 2015 John Wiley & Sons, Ltd.