砌体结构地震危害性分析

在结构易损性分析的基础上,考虑了未来不同强度地震发生的可能性,利用地震危险性分析结果所给出的地震烈度概率分布,提出了砌体结构的地震危害性预测分析方法,最后结合计算实例,验证了该方法的可行性。     

Seismic fragility analysis of 3D structures

A statistical approach for time-variant system reliability problems is developed and investigated. The basic proposal is to use a response surface, characterised by a statistical model of the mixed type, to represent the capacity in an analytical limit-state function. The fragility function of the system is then calculated by FORM analysis, with the constructed empirical limit-state function as input. The methodology is applied in the assessment of a 3D RC frame structure. The application allows a number of detailed implementation issues to be clarified, and confirms the robustness and versatility of the method.     

自复位胶合木框架结构设计方法与地震易损性分析

自复位体系可以降低结构震后残余变形，提高震后快速恢复能力。将自复位体系与胶合木框架结构相结合，是提高木框架结构抗震韧性的重要途径之一。为此，提出了自复位胶合木梁柱节点(self-centering glulam post-and-beam joint)设计方法，并对自复位结构(self-centering structure)进行抗震性能评估。通过对两种构造的自复位节点（无耗能件节点和带特制角钢耗能件节点）进行拟静力试验。依据试验结果提出节点设计流程，并以一栋三层自复位胶合木框架结构为算例，采用OpenSees建立了算例的简化数值模型。对算例进行了两方面的抗震性能评估，一方面通过弹塑性动力时程分析，验证结构设计流程的可行性；另一方面，进行最大层间位移角与残余层间位移角的地震易损性分析。易损性分析结果表明，相比传统胶合木框架结构，依据所提流程设计的自复位胶合木框架结构，可以显著减小结构残余变形。     

考虑碰撞效应的相邻框架结构地震易损性分析

针对间距不足和高度不等的相邻钢筋混凝土框架结构,设置考虑碰撞刚度和阻尼非线性的碰撞单元,通过对三维非线性有限元模型的时程分析研究地震碰撞效应,并开展增量动力分析,分别以所有层和碰撞层最大层间位移角为工程需求参数,提出考虑碰撞效应的地震易损性分析方法。以6层和4层、6层和5层、6层和3层相邻钢筋混凝土框架结构为例,对比分析不同周期比下考虑与不考虑碰撞效应的相邻结构地震易损性曲线。结果表明：对于6层和4层相邻结构,考虑碰撞效应后,6层结构所有层的最大层间位移角对应的失效概率略有减小,4层结构的反之,而较低结构的碰撞层及较高结构的碰撞层以上层的最大层间位移角对应的失效概率明显增大,即碰撞效应对结构整体响应影响不明显,而对局部响应影响显著;6层和5层、6层和3层相邻结构地震易损性曲线具有类似规律,且相邻结构自振周期越接近,碰撞对结构地震易损性影响越小。     

自复位胶合木框架结构设计方法与地震易损性分析

自复位体系可以降低结构震后残余变形,提高震后快速恢复能力.将自复位体系与胶合木框架结构相结合,是提高木框架结构抗震韧性的重要途径之一.为此,提出了自复位胶合木梁柱节点(self-centering glulam post-and-beam joint)设计方法,并对自复位结构(self-centering struct...     

锈蚀钢筋混凝土结构地震易损性分析

钢筋锈蚀是影响钢筋混凝土结构耐久性的一个重要因素,会引起结构的自振周期延长、地震需求变化及抗震能力衰减,使得锈蚀钢筋混凝土结构的地震易损性分析不同于未锈蚀钢筋混凝土结构。以一栋按我国规范设计的RC框架结构为研究对象,分别建立了未锈蚀和锈蚀结构的非线性有限元模型并进行了模型验证。分别采用云图法和条带法计算得到了钢筋混凝土结构在未锈蚀和锈蚀两种工况下的地震易损性曲线和函数参数,对锈蚀钢筋混凝土结构地震易损性分析的特殊性及其对地震易损性分析结果的影响进行了分析。分析结果表明：不考虑钢筋锈蚀引起的结构自振周期延长会错误估计锈蚀钢筋混凝土结构的地震易损性水平。采用云图法分析锈蚀钢筋混凝土结构的地震易损性会出现锈蚀结构的极限状态失效概率低于未锈蚀结构的情况。而条带法比云图法可以更好地反映钢筋锈蚀对钢筋混凝土结构地震易损性的影响。忽略钢筋锈蚀引起的结构抗震能力衰减会低估锈蚀钢筋混凝土结构地震易损性水平,建议在锈蚀钢筋混凝土结构地震易损性分析中采用基于Pushover的极限状态定义方法。     

Seismic fragility analysis of reinforced concrete structures considering reinforcement corrosion

钢筋锈蚀是影响钢筋混凝土结构耐久性的一个重要因素，会引起结构的自振周期延长、地震需求变化及抗震能力衰减，使得锈蚀钢筋混凝土结构的地震易损性分析不同于未锈蚀钢筋混凝土结构。以一栋按我国规范设计的RC框架结构为研究对象，分别建立了未锈蚀和锈蚀结构的非线性有限元模型并进行了模型验证。分别采用云图法和条带法计算得到了钢筋混凝土结构在未锈蚀和锈蚀两种工况下的地震易损性曲线和函数参数，对锈蚀钢筋混凝土结构地震易损性分析的特殊性及其对地震易损性分析结果的影响进行了分析。分析结果表明：不考虑钢筋锈蚀引起的结构自振周期延长会错误估计锈蚀钢筋混凝土结构的地震易损性水平。采用云图法分析锈蚀钢筋混凝土结构的地震易损性会出现锈蚀结构的极限状态失效概率低于未锈蚀结构的情况。而条带法比云图法可以更好地反映钢筋锈蚀对钢筋混凝土结构地震易损性的影响。忽略钢筋锈蚀引起的结构抗震能力衰减会低估锈蚀钢筋混凝土结构地震易损性水平，建议在锈蚀钢筋混凝土结构地震易损性分析中采用基于Pushover的极限状态定义方法。     

面内往复荷载作用下足尺砌体填充墙的易损性研究

为了研究钢筋混凝土(RC)框架结构中砌体填充墙的地震易损性,进行了6个足尺含填充墙RC框架试件的面内往复加载试验。各试件中RC框架的设计参数均相同,其中3个试件含普通黏土砖填充墙,另外3个试件含水泥空心砌块填充墙。试验过程中,记录了砌体填充墙的损伤发展过程,并以墙体裂缝宽度和破碎坠落现象作为损伤指标,定义了"明显破坏"、"严重破坏"和"危及安全"等3个损伤状态。在此基础上,以层间位移角作为工程需求参数,建立了普通黏土砖和水泥空心砌块填充墙的易损性曲线。易损性分析结果表明,当试件的面内侧向变形达到GB 50011—2010《建筑抗震设计规范》规定的框架结构弹性层间位移角限值时,黏土砖和空心砌块填充墙均极有可能达到或超越"明显破坏"状态,且空心砌块填充墙尚有22%的概率达到或超越"严重破坏"状态。与黏土砖填充墙相比,水泥空心砌块填充墙的易损性参数具有更大的离散性,且其整体性更差,当侧向变形较大时会出现破碎砌块坠落的现象。根据试验结果,给出了砌体墙最大残余裂缝宽度、最大裂缝宽度和层间位移角之间的近似相关关系。     

Seismic intensity parameters for fragility analysis of structures with energy dissipating devices

The aim of the study is to develop a procedure for the identification of seismic intensity parameters, which make it possible to relate the fragility of linear and non-linear systems for a given design response spectrum, with the fragility for a set of different recorded accelerograms. The correlation between the response parameters of the studied systems and seismic intensity parameters is estimated. For the considered linear systems the higher the correlation coefficient for a given seismic intensity parameter, the closer the fragility line for recorded accelerograms to those for the considered spectrum. For the studied non-linear systems with energy dissipating devices the value of the correlation coefficient do not relate to the sequence of the fragility curves and consequently cannot be used as a single indicator of the appropriateness of the predictive linear equations. In this connection a criterion of appropriateness of the seismic intensity parameter is formulated as the ratio of the correlation coefficient to the coefficient of variation of the seismic intensity parameters. The proposed criterion helps to cluster the seismic intensity parameters, which exhibit the most appropriate predictive equations. Next, the predictive equations of all the parameters with highest values of the proposed criterion should be examined to obtain the intensity parameter the most relevant for the particular non-linear system and design spectrum. The results show that the spectral pseudo-velocity and the Kappos spectral intensity for the linear systems and the peak ground velocity, the mean spectral pseudo-velocity and the Kappos spectral intensity for the non-linear systems could be recommended as seismic intensity parameters for fragility analysis.     

基于响应面法的LRB基础隔震结构地震易损性分析

提出了一种基于响应面法的LRB基础隔震结构地震易损性分析方法,考虑了LRB基础隔震结构中各子结构之间(即上部结构和LRB隔震支座)地震需求的相关性。分析中考虑地震动与LRB基础隔震结构物理参数的不确定性,以均匀设计法建立地震动-LRB基础隔震结构样本,通过对有限元模型进行非线性时程分析,分别建立各子结构响应均值、方差及其相关系数与不确定参数之间的响应面模型。在此基础上,采用蒙特卡罗模拟得到LRB基础隔震结构在不同性能水准下的地震易损性曲线。分析结果表明,所建立的响应面模型精度高、结构可靠,减小了复杂有限元模型非线性时程分析计算的工作量,有效提高了LRB基础隔震结构地震易损性分析的时效性。为了准确建立LRB基础隔震结构的地震易损性曲线,应考虑各子结构地震响应需求之间的相关性。     

不同弯矩增大系数钢筋混凝土框架结构地震易损性分析

设计3个不同柱端弯矩增大系数的钢筋混凝土框架结构模型,考虑结构材料、荷载及地震动参数的随机性,分别对其进行随机增量动力分析（IDA）,以地震峰值加速度（a _pg）作为地震动强度指标,结构的顶点最大位移角θ_max作为结构的反应参数,得到各结构模型的IDA曲线。在IDA分析的基础上,对各结构模型进行地震需求概率分析,通过定义4个抗震性能水平,对各模型进行随机pushover分析,确定各性能水平的限值,分别对各结构模型进行易损性分析,得出各结构的地震易损性曲线。计算分析结果表明：弯矩增大系数的取值对结构的易损性有一定的影响,其取值越大时,结构在地震作用下倒塌的概率越小;在一定的范围内(0.2g≤a _pg≤1.0g),当结构的塑性程度发展越大时,提高弯矩增大系数对结构抗震性能的贡献越明显;建议规范修订时可适当增加柱端弯矩增大系数的取值。     

Seismic fragility and cost analyses of actively controlled structures

Seismic fragility represents the probability that structural response exceeds a given performance limit state due to a specified intensity of ground motion, and it has a direct relationship with the cost of rehabilitating the structural system. In this research, a cost analysis framework based on seismic fragility to quantify the expected loss of the structural system was proposed. Incremental dynamic analysis was used to generate the fragility curves, and plastic strain derived from plastic energy dissipation was used to quantify the structural damage at a local level. Two moment‐resisting steel frames and 100 nonstationary Gaussian earthquake ground motions were simulated, and correlations between local damage states and global performance limit states were performed to facilitate the cost analysis study. The results showed that good correlations exist in seismic fragilities, and therefore, the repair cost of the structural system becomes quantifiable. Active control based on the optimal linear control algorithm was included as an auxiliary study to identify the sensitivity of the correlations. It is observed that significant cost reduction can be achieved for structures with few stories when active control is used but may not be cost‐effective if it is installed in taller structures. Published 2011. This article is a US Government work and is in the public domain in the USA.     

Global sensitivity analysis of unreinforced masonry structure using high dimensional model representation

Sensitivity Analysis (SA) has very important implications in terms of model assessment. It is an important part of reliability studies as well. This paper presents global SA using High Dimensional Model Representation (HDMR) on a mesoscale model of unreinforced masonry shear wall. The mesoscale model contains both geometric as well as material nonlinearity. Prior to performing global SA: (a) mesh sensitivity study in order to determine the optimum mesh size; and (b) experimental validation of the finite element simulation using the data available in the literature, are conducted. The ability of two major variations of HDMR, namely RS (Random Sampling)-HDMR and Cut-HDMR, for conducting global SA is explored, first by solving analytical problem and later by analyzing the mesoscale model of unreinforced shear wall. From the study, recommendations are made to obtain the sensitive parameters of an unreinforced masonry structure with minimal computational effort.     

基于简化渐进破坏的低矮房屋围护结构风致易损性分析

轻质框架低矮房屋被广泛用于民宅、厂房以及其他基础设施建设.然而,多起风灾调查发现,低矮房屋在强风中破坏严重,其破坏形式主要表现为围护结构受损,因此有必要对低矮房屋围护结构风灾损失开展相关研究.基于简化的三阶段渐进破坏过程,提出了低矮房屋围护结构风致易损性分析方法.在该方法中,同时考虑飞掷物冲击和强风压造成的门窗破坏,以确定开孔工况;通过伯努利方程模拟内压响应;利用Copula函数考虑屋面构件关联破坏;提出基于蒙特卡洛随机模拟的易损性分析流程,并结合木质框架房屋开展算例分析;进一步通过建立风速风向联合概率模型以考虑风向效应.研究表明,迎风墙构件在强风中往往面临着较高风险,且忽略风向效应可能会低估房屋的风致损失程度.     

既有砌体结构的抗震缺陷与加固方法综述

对既有砌体结构房屋的抗震缺陷进行综合分析,根据抗震缺陷阐述了各种抗震加固技术方法,指出抗震加固技术方法应因时因地而异,在充分考虑房屋整体性的情况下,确定加固方式方法。     

基于简化渐进破坏的低矮房屋围护结构风致易损性分析

轻质框架低矮房屋被广泛用于民宅、厂房以及其他基础设施建设.然而,多起风灾调查发现,低矮房屋在强风中破坏严重,其破坏形式主要表现为围护结构受损,因此有必要对低矮房屋围护结构风灾损失开展相关研究.基于简化的三阶段渐进破坏过程,提出了低矮房屋围护结构风致易损性分析方法.在该方法中,同时考虑飞掷物冲击和强风压造成的门窗破坏,以确定开孔工况;通过伯努利方程模拟内压响应;利用Copula函数考虑屋面构件关联破坏;提出基于蒙特卡洛随机模拟的易损性分析流程,并结合木质框架房屋开展算例分析;进一步通过建立风速风向联合概率模型以考虑风向效应.研究表明,迎风墙构件在强风中往往面临着较高风险,且忽略风向效应可能会低估房屋的风致损失程度.     

Seismic damage and fragility analysis of structures with tuned mass dampers based on plastic energy

The effectiveness of using a tuned mass damper (TMD) to improve a structure's ability to dissipate earthquake input energy is investigated through the use of seismic fragility curves. The nonlinear material behaviour of the structure is captured using the force analogy method, the backbone for analytically quantifying plastic energy dissipation in the structure. Numerical analysis was performed to study the global response and local energy dissipation of a six‐storey moment‐resisting steel frame with and without a TMD installed for 100 simulated non‐stationary Gaussian earthquake ground motions. The effectiveness of the TMD, based on reduction of seismic responses and enhancement of the seismic fragility, is considered at structural performance levels for immediate occupancy and life safety as identified in FEMA 440. An ‘equivalent monotonic plastic strain’ approach—a local measure of structural damage—is used to correlate the seismic fragilities at different global performance levels based on storey drift. Results illustrate that a TMD can enhance the structure's ability to dissipate energy at low levels of earthquake shaking, while less effective during moderate to strong earthquakes, which can cause a significant period shift associated with major structural damage. This ‘de‐tuning’ effect suggests that an extremely sizable TMD is not effective in reducing damage of a structure. Published in 2010 by John Wiley & Sons, Ltd.     

墙体较少的砖混结构住宅楼抗震设计

提出了在砖混结构中设置一定数量的钢筋墙力墙的方法。以实例阐述了抗震验算和构造设计,指出这种做法造价虽比砖墙高4倍左右，但它满足了房屋开口大时的结构抗震设计要求。     

考虑结构不确定性的地震倒塌易损性分析

传统的地震倒塌易损性分析中通常只考虑地震动不确定性的影响。在结构临近倒塌时,通常处于高度非线性状态,会出现结构不确定性与地震动不确定性的耦合放大现象。针对这一问题,将平均值一次二阶矩方法（MVFOSM）与逐步增量动力分析（IDA）相结合,提出了一种可以考虑结构不确定性的基于MVFOSM的随机IDA方法。以五层三跨钢筋混凝土框架结构为例,采用基于MVFOSM的随机IDA方法对其进行了地震倒塌易损性分析,并利用“龙卷风图”方法对结构抗地震倒塌能力的灵敏度进行了分析。研究表明：结构不确定性的存在使得结构抗地震倒塌能力的对数标准差增加了70%,因此有必要在地震倒塌易损性分析中考虑结构不确定性的影响。