不同底部层高的RC框架结构地震易损性分析

为研究不同底部层高的钢筋混凝土框架结构的易损性,应用SAP2000软件,采用动力增量分析法分别对设防烈度为7度和8度区6个不同底部层高的框架结构在地震作用下进行了非线性时程分析,得到了地震易损性曲线和结构在极限状态下的地震动强度指标,经回归拟合得到了不同设防烈度区的结构的失效概率公式和结构倒塌储备系数(CMR)。研究表明:结构在弹性阶段的耗能能力较差,在弹塑性阶段表现出较好的延性耗能能力。同一抗震设防烈度的RC框架结构倒塌储备系数CMR随着底部层高的提高而线性降低,底部层高较高框架结构的抗地震倒塌能力与底层层高负相关,基于IDA方法得到了不同底部层高RC框架结构的失效概率计算公式和抗倒塌储备系数线性拟合公式,可供工程设计参考。     

基于能量方法设计的RC框架结构易损性分析

基于“强柱弱梁”的屈服机制,依据能量平衡方法设计了某6层RC框架结构,采用震级-震中距条带地震动记录选取方法,选取12条随机地震动,利用Perform-3D有限元分析软件对结构进行增量动力（IDA）分析,得到了结构的地震易损性曲线、破坏状态概率曲线以及结构破坏概率矩阵。分析结果表明:该方法设计的结构能够形成预设的“强柱弱梁”屈服机制,可以保证结构中梁充分参与耗能,同时结构具有较强的抗倒塌能力,可以满足“小震不坏,中震可修,大震不倒”的性能要求。     

不同柱梁抗弯承载力比对框架结构抗倒塌性能的影响

设计不同柱梁抗弯承载力比(ηc-bua)的5个纤维增强混凝土(FRC)框架结构及3个钢筋混凝土(RC)框架结构,利用性能评估软件Perform-3D进行Pushover及IDA计算分析,得出其破坏机制及易损性曲线。结果表明,柱、梁端部局部采用FRC后,承载力有一定提高,峰值位移有较大提高;ηc-bua对FRC框架结构的破坏机制影响很大;ηc-bua对FRC框架结构地震反应也有一定的影响,其比值越大,超越概率越小,且随期望破坏程度的加重,这种影响也趋于明显,当ηc-bua在1.2以上时,结构的倒塌概率均小于10%,满足大震不倒的概率要求。     

型钢混凝土框架结构地震易损性数值模拟研究

基于地震工程模拟平台Open SEES,研究了型钢混凝土(SRC)框架的数值建模方法。根据试验结果对比了3种不同非线性梁柱单元模型的计算效果,确定了最优单元模型。基于Open SEES平台和增量动力分析(IDA)方法研究了型钢混凝土框架结构的地震易损性。设计了3个具有不同柱梁抗弯承载力之比的结构,对其进行IDA分析,获得了各模型的抗震能力曲线。根据结构抗震能力曲线,求解了结构的地震易损性曲线,得到了结构在地震作用下各性态点的超越概率。对场地地震危险性进行分析,获得了场地地震危险性概率模型。基于结构地震易损性曲线及场地地震危险性概率模型,计算了结构各性态点的年平均超越概率。结果表明:柱梁抗弯承载力之比对计算结果的影响显著,随着柱梁抗弯承载力之比的增大,结构在特定地震动作用下倒塌的概率呈减小趋势。     

基于推覆分析的RC框架地震倒塌易损性预测

基于倒塌率的结构倒塌易损性分析是目前评价结构抗倒塌能力最合理的方法.但是,目前基于增量动力分析(IDA)的倒塌率分析方法,工作量和实施难度大,很难直接用于工程设计,因此有必要研究便于工程应用的新方法.本文基于18个典型多层RC框架结构的IDA倒塌率分析和静力推覆分析,发现RC框架在大震下的倒塌率及抗倒塌安全储备(CMR)与静力推覆得到的结构位移安全储备之间存在较好的相关关系.依据此关系,建议了保证大震倒塌率的推覆位移安全储备,并通过9个RC框架结构算例进行了验证.本文方法简单易行,可供规则多层RC框架结构抗倒塌设计参考.     

罕遇地震下高层RC框架结构双地震动强度参数易损性分析

为研究高层RC框架结构罕遇地震下的易损性,设计了一个7度区典型11层RC框架结构。采用IDA方法进行时程分析,以地震动峰值地面加速度和结构第一自振周期对应的谱加速度为地震动强度指标,最大层间位移角为结构损伤指标,分别得到了单一地震动强度和双地震动强度参数下的IDA曲线和失效概率,绘制了双地震动强度参数下易损性曲面,并对单一地震动强度和双地震动强度参数下的易损性分析结果进行了对比。结果表明:罕遇地震下,采用双地震动强度参数结构失效概率明显低于采用单一地震动强度参数结构失效概率;对高层RC框架结构,采用双地震动强度参数进行易损性分析反映的地震动信息更全面;采用双地震动强度参数得到的结构失效概率公式更能真实量化不同强度地震作用下结构的失效概率。     

电涡流阻尼墙减震结构的地震易损性分析

齿轮齿条式电涡流阻尼墙(eddy current damping-rack and gear wall, ECD-RGW)是一种具有明显非线性特征的消能减震装置,为探究其对钢筋混凝土(reinforced concrete, RC)框架结构抗震性能的影响。基于OpenSees软件,建立了一栋5层RC框架结构的有限元模型,并实现了电涡流阻尼墙非线性力学模型的二次开发,并验证了其准确无误,进而对该模型进行非线性时程分析,使用数值方法评估了ECD-RGW减震结构的概率抗震性能。选取ATC-63项目中推荐的22条典型远场地震波,以最大层间位移角作为结构损伤指标,采用增量动力分析方法分别对安装和未安装ECD-RGW的RC框架结构进行了地震易损性分析。研究结果表明：相较于无控结构,安装了ECD-RGW的RC框架结构达到各级破坏状态的超越概率明显降低;ECD-RGW在各级地震作用下均具有优良的减震效果;且提高ECD-RGW的传动比可以进一步提高RC框架结构的抗震性能,降低结构损伤概率。     

基于IDA的方钢管混凝土框架-SPSW核心筒结构地震易损性研究

为研究方钢管混凝土框架-钢板剪力墙（SPSW）核心筒结构在不同强度地震下破坏概率,使用拉杆模型作为钢板剪力墙等效模型,与已有试验对比验证各参数有效性。以地震动峰值加速度（PGA）作为地震动强度参数,按照场地条件等要求选择11条地震动记录。以结构最大层间位移角作为损伤指标,对一典型方钢管混凝土框架-钢板剪力墙核心筒结构进行增量动力分析（IDA）,得到IDA曲线簇。基于增量动力分析进行易损性分析,得到易损性曲线,并计算结构的抗倒塌储备系数。结果表明:8度多遇地震作用下,此结构处于正常使用状态。8度设防地震作用下,处于修复后可使用状态。8度罕遇地震作用下,处于生命安全状态。表明该结构具有良好的抗震性能,满足规范中“小震不坏”、“中震可修”和“大震不倒”的抗震设防目标。该结构抗倒塌储备系数大于规范建议值,具有较好的抗倒塌能力。     

基于不同结构损伤模型的RC框架地震易损性研究

针对目前RC框架结构地震易损性分析中整体损伤模型研究的薄弱性以及广泛采用的层间位移角方法不能准确反应结构在地震作用下损伤机理的现状,本文基于现有损伤模型的对比分析,提出了一种较准确反映地震破坏机理同时便于应用的最大变形和滞回耗能非线性组合的双参数损伤模型。以8层RC框架结构为例,进行50条地震波作用下的结构增量动力分析,分别绘制了变形和能量2种单参数模型以及牛荻涛模型和本文模型两种双参数模型的结构损伤曲线与易损性曲线,并进行了模型的对比分析和检验评估。分析结果表明:仅以层间位移角作为结构整体损伤指标会高估结构的抗倒塌性能,仅以能量作为结构整体损伤指标会低估结构损伤的超越概率。本文模型能较好地平衡最大变形和累积损伤对结构损伤的影响程度。     

设计因素对RC框架结构地震易损性的影响

考虑到结构抵抗地震作用的机制为结构和地震动的不确定性与非线性相互耦合的过程,采用增量动力分析(IDA)考虑地震动的不确定性,选取16条地震动记录,基于OpenSEES的有限元建模理论对13榀平面RC框架结构进行基于IDA方法的地震易损性分析,分别讨论轴压比、高宽比、混凝土强度以及纵筋强度等结构参数对RC框架结构抗震性能的影响。结果表明:柱轴压比对结构抗震性能的影响显著,而高宽比对结构抗震性能的影响不明显;在保证柱轴压比相近的前提下,提高柱混凝土强度能够提升结构的抗震性能;相同地震作用下梁柱配置纵筋强度较高的框架结构达到立即使用(IO)状态和生命安全(LS)状态的概率较配置纵筋强度较低的大,配置纵筋强度较高的框架结构较配置纵筋强度较低的表现出更好的抗倒塌能力。     

钢筋混凝土框架结构震后功能恢复能力的量化研究

震后功能恢复能力是指建筑物、社区或城市等遭受地震影响后实现功能恢复的能力。以一钢筋混凝土框架结构为对象,基于OpenSees有限元分析平台,对其进行增量动力分析,得到其对应于不同损伤状态的地震易损性曲线。进而基于单体建筑损失评估理论,评估该结构在不同强度水准地震动作用下的地震损失,包括直接经济损失和间接经济损失等。在此基础上,分别利用直线型、指数型以及三角函数型功能恢复模型,在不同强度水准地震动作用下,分别计算该结构的震后功能恢复能力。结果表明:随着地震动强度的增加,基于3种恢复模型计算得到的震后功能恢复能力都在下降,而且直线型和三角函数型恢复模型得到的恢复能力均比指数型的下降更快;在同一强度水准地震动作用下,基于指数型恢复模型计算得到的震后功能恢复能力均高于直线型和三角函数型恢复模型,即使在较强水准地震动作用下,根据指数型恢复模型得到的恢复能力依然较大。而在各个强度水准地震动作用下,基于直线型和三角函数型恢复模型得到的震后功能恢复能力非常接近。     

Evaluation of collapse resistance of RC frame structures for Chinese schools in seismic design categories B and C

According to the Code for Seismic Design of Buildings (GB50011-2001), ten typical reinforced concrete (RC) frame structures, used as school classroom buildings, are designed with different seismic fortification intensities (SFIs) (SFI=6 to 8.5) and different seismic design categories (SDCs) (SDC=B and C). The collapse resistance of the frames with SDC=B and C in terms of collapse fragility curves are quantitatively evaluated and compared via incremental dynamic analysis (IDA). The results show that the coll...     

Pushover analysis of reinforced concrete frames considering shear failure at beam-column joints

Since most current seismic capacity evaluations of reinforced concrete(RC) frame structures are implemented by either static pushover analysis(PA) or dynamic time history analysis,with diverse settings of the plastic hinges(PHs) on such main structural components as columns,beams and walls,the complex behavior of shear failure at beam-column joints(BCJs) during major earthquakes is commonly neglected.This study proposes new nonlinear PA procedures that consider shear failure at BCJs and seek to assess the actual damage to RC structures.Based on the specifications of FEMA-356,a simplified joint model composed of two nonlinear cross struts placed diagonally over the location of the plastic hinge is established,allowing a sophisticated PA to be performed.To verify the validity of this method,the analytical results for the capacity curves and the failure mechanism derived from three different full-size RC frames are compared with the experimental measurements.By considering shear failure at BCJs,the proposed nonlinear analytical procedures can be used to estimate the structural behavior of RC frames,including seismic capacity and the progressive failure sequence of joints,in a precise and effective manner.     

C F RP加固震损钢筋混凝土框架结构的抗整体性倒塌能力分析

首先介绍了CFRP加固受损钢筋混凝土柱的数值模拟方法,通过OpenSees软件进行了建模分析,数值模拟结果与试验结果的对比验证了该数值模型的有效性;其次,对一6层钢筋混凝土框架以受极罕遇地震影响进行预损,采用损伤指数和折减系数的方法建立震损钢筋混凝土框架的分析模型,并选择5种不同的CFRP加固方案对其进行加固;最后,对CFRP加固的震损RC框架进行增量动力分析。定量的评价了CFRP加固震损RC框架的抗整体性倒塌能力和抗倒塌安全储备。结果表明:CFRP加固能有效提高震损钢筋混凝土框架结构的抗震性能。加固部位的选择对加固效果的影响很大,在所选用的5种CFRP加固方案中,对底层及第2层的梁柱进行加固的方案对提高震损钢筋混凝土框架的抗整体性倒塌能力效果最佳。     

基于性能的基础隔震钢筋混凝土框剪结构的倒塌可靠度分析

利用基于性能的结构可靠度分析方法,对基础隔震钢筋混凝土框剪结构进行分析研究。选取20条实际地震动记录,以0.2g为步长对结构地震动参数PGA进行调幅后,建立了140个结构-地震动样本空间。选取上部结构的最大层间位移角、隔震层位移为量化指标,对每一个样本进行动力非线性时程分析后,将结构响应进行统计得到结构在各地震动强度下超越极限破坏状态的概率,将其绘制成基础隔震钢筋混凝土框剪结构的易损性曲线并利用整体可靠度方法分析结构发生倒塌的可靠度指标。该方法直观地反映了结构发生倒塌的概率,为结构的地震损失评估提供依据。     

An experimental study of a damage‐controllable plastic‐hinge‐supported wall structure

The reinforced concrete (RC) shear wall serves as one of the most important components sustaining lateral seismic forces. Although they allow advanced seismic performance to be achieved, RC shear walls are rather difficult to repair once the physical plastic hinge at the bottom part has been formed. To overcome this, a damage‐controllable plastic hinge with a large energy dissipation capacity is developed herein, in which the sectional forces are decoupled and sustained separately by different components. The components sustaining the axial and the shear forces all remain elastic even under a rarely occurred earthquake, while the bending components yield and dissipate seismic energy during a design‐level earthquake. This design makes the behavior of the system more predictable and thus more easily customizable to different performance demands. Moreover, the energy dissipation components can be conveniently replaced to fully restore the occupancy function of a building. To examine the seismic behavior of the newly developed component, 3 one third‐scale specimens were tested quasi‐statically, including 1 RC wall complying with the current design codes of China and 2 installed with the damage‐controllable plastic hinges. Each wall was designed to have the same strength. The experimental results demonstrated that the plastic‐hinge‐supported walls had a better energy dissipation capacity and damage controllability than the RC specimen. Both achieved drift ratios greater than 3% under a steadily increasing lateral force.     

Aftershock collapse vulnerability assessment of reinforced concrete frame structures

In a seismically active region, structures may be subjected to multiple earthquakes, due to mainshock–aftershock phenomena or other sequences, leaving no time for repair or retrofit between the events. This study quantifies the aftershock vulnerability of four modern ductile reinforced concrete (RC) framed buildings in California by conducting incremental dynamic analysis of nonlinear MDOF analytical models. Based on the nonlinear dynamic analysis results, collapse and damage fragility curves are generated for intact and damaged buildings. If the building is not severely damaged in the mainshock, its collapse capacity is unaffected in the aftershock. However, if the building is extensively damaged in the mainshock, there is a significant reduction in its collapse capacity in the aftershock. For example, if an RC frame experiences 4% or more interstory drift in the mainshock, the median capacity to resist aftershock shaking is reduced by about 40%. The study also evaluates the effectiveness of different measures of physical damage observed in the mainshock‐damaged buildings for predicting the reduction in collapse capacity of the damaged building in subsequent aftershocks. These physical damage indicators for the building are chosen such that they quantify the qualitative red tagging (unsafe for occupation) criteria employed in post‐earthquake evaluation of RC frames. The results indicated that damage indicators related to the drift experienced by the damaged building best predicted the reduced aftershock collapse capacities for these ductile structures. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of ground motion selection methods on seismic collapse fragility of RC frame buildings

Variation in the seismic collapse fragility of reinforced concrete frame buildings predicted using different ground motion (GM) selection methods is investigated in this paper. To simulate the structural collapse, a fiber‐element modelling approach with path‐dependent cyclic nonlinear material models that account for concrete confinement and crushing, reinforcement buckling as well as low cycle fatigue is used. The adopted fiber analysis approach has been found to reliably predict the loss in vertical load carrying capacity of structural components in addition to the sidesway mode of collapse due to destabilizing P–Δ moments at large inelastic deflections. Multiple stripe analysis is performed by conducting response history analyses at various hazard levels to generate the collapse fragility curves. To select GMs at various hazard levels, two alternatives of uniform hazard spectrum (UHS), conditional mean spectrum (CMS) and generalized conditional intensity measure (GCIM) are used. Collapse analyses are repeated based on structural periods corresponding to initial un‐cracked stiffness and cracked stiffness of the frame members. A return period‐based intensity measure is then introduced and applied in estimating collapse fragility of frame buildings. In line with the results of previous research, it is shown that the choice of structural period significantly affects the collapse fragility predictions. Among the GM selection methods used in this study, GCIM and CMS methods predict similar collapse fragilities for the case study building investigated herein, and UHS provides the most conservative prediction of the collapse capacity, with approximately 40% smaller median collapse capacity compared to the CMS method. The results confirm that collapse probability prediction of buildings using UHS offers a higher level of conservatism in comparison to the other selection methods. Copyright © 2017 John Wiley & Sons, Ltd.     

最不利主余震序列型地震动作用下RC框架结构易损性研究

余震的发生会造成结构的累积损伤,不同类型的主余震序列地震动对结构的影响有所差异。鉴于此,以主震卓越周期小于或接近余震卓越周期为基本原则,确定了最不利主余震序列地震动。选择4层RC框架结构为研究对象,在增量动力分析的基础上,定义了4个性能水平,以此来研究该结构的易损性。依据破坏状态概率和震害指数,得到7度多遇、7度设防和7度罕遇地震的易损性指数。研究结果表明:依据我国规范设计的RC框架结构的4个性能水平的量化指标限值依次为1/495、1/263、1/108和1/45,余震的出现会加剧结构的破坏状态。当以易损性指数作为评价指标时,可认为该结构能够满足小震不坏、中震可修和大震不倒的抗震设防目标。