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.     

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.     

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.     

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.     

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。     

高烈度区隔震砌体结构的抗震设计讨论

我国《建筑抗震设计规范》于2001年颁布实施,其中关于隔震砌体结构的设计要求过严.针对罕遇烈度地震作用下隔震砌体结构隔震层的位移进行了讨论分析.由算例可知,相比于89规范,按等效侧力法计算时隔震砌体结构隔震层的位移提高了47.4%;而按时程分析法,仅提高了27.5%.为使两种结构相一致,建议对隔震砌体结构不采用新规范中罕遇地震验算对场地土特征周期关于0.05 s的延长.     

基于性能的方钢管混凝土框架结构地震易损性分析

钢-混凝土组合结构由于兼有钢结构和混凝土结构的优点,近年来得到了迅速发展和广泛应用,目前已成为我国高层建筑领域内应用较多的一种结构形式。虽然在地震区越来越多地采用这种新型的结构,但迄今为止还没有发现对钢-混凝土组合结构的地震易损性进行过研究的文献。因此给出一种基于性能的结构整体地震易损性分析方法,该方法既考虑了结构本身的不确定性,又考虑了地震动输入的不确定性。并定义了结构整体和楼层的四个极限破坏状态,从而提出了基于结构极限破坏状态确定结构抗震性能水平限值的方法。最后采用该方法对两个不同类型的方钢管混凝土框架结构进行基于性能的地震易损性分析,得到结构的易损性曲线,对结构的易损性能进行评估和分析,并比较了两个结构的易损性能。     

基于IDA的阀厅结构地震易损性分析

尽管近年来大型换流站阀厅结构越建越多,但是对阀厅结构的易损性研究仍十分缺乏。考虑到大型换流站阀厅结构在电力系统中的重要性,对这类结构易损性开展深入地研究是十分必要的。在数值模型正确性得到验证基础上,对阀厅结构开展在不同类型地震动作用下的增量动力分析(IDA),基于增量动力分析结果建立阀厅结构处于不同破坏状态的地震易损性曲线。研究结果表明当地震动峰值加速度小于0.5g时,阀厅结构刚度降幅比较缓慢,而随着峰值加速度增大,其刚度降幅逐渐增快。由地震易损性曲线可知,在罕遇地震作用下阀厅结构处于不同破坏状态的超越概率均小于5%,该阀厅结构抗震设计满足要求并具有较大安全储备。     

匀质化方法在砌体结构地震反应分析中的应用

利用匀质化方法,得到一个三层砌体结构等效体积单元的各力学参数,再运用ANSYS软件对该砌体结构进行了地震反应模拟。最后把计算结果与试验结果进行了对比,二者基本吻合,说明采用砌体匀质化方法进行非线性分析是合理可行的。     

Nonlinear analysis of a one-story low-rise masonry building with a flexible diaphragm subjected to seismic excitation

This paper investigates the response of a half-scale one-story reinforced masonry building with a flexible diaphragm subjected to shaking table tests in prior research. A simplified multiple degrees-of-freedom approach developed by the authors is applied to the building. The study focuses on defining appropriate structural properties for accurate prediction of the dynamic response. A model calibration process is performed to determine the required structural properties based on the elastic and inelastic test responses. This approach is necessary since it is difficult to quantify accurately the in-plane and out-of-plane stiffness, strength, and hysteresis using simplified equations specified in current seismic codes and standards. Comparisons are made between the structural properties obtained by this calibration process and by simple strength of materials type procedures.     

Diagonal shear behaviour of unreinforced masonry wallettes strengthened using twisted steel bars

The in-plane shear behaviour of URM wallettes strengthened using near surface mounted high strength twisted stainless steel reinforcement (TSNSM) was investigated and in particular, the effectiveness of the reinforcing schemes to restrain the diagonal cracking failure mode was studied. A total of 17 URM wallettes, each being 1.2 m × 1.2 m in size, were structurally tested in induced diagonal compression. Of these, 3 wallettes were tested as-built and 14 wallettes were tested after being strengthened using different patterns of TSNSM bars. Several parameters pertaining to the in-plane shear behaviour of strengthened URM walls were investigated, including failure modes, shear strength, maximum drift, pseudo-ductility, and shear modulus. It was inferred from the results that as-built tested wallettes exhibited sudden post-peak strength degradation and failed along a stepped diagonal joint crack, whilst strengthened wallettes failed along distributed diagonal cracks in a more ductile fashion and exhibited a shear strength increment ranging from 114% to 189%.     

砌体结构中基础拉梁的计算分析

介绍了砌体结构中载体桩上部拉梁的几种设计方法,其中有墙梁设计法、连续梁法和弹性地基梁法。通过工程实例,对三种方法的计算结果进行了比较、分析,并分析了上部墙体和洞口对计算结果的影响,以供设计人员参考借鉴。     

Seismic design in reinforced masonry

CIB working commission W23, which deals with structural walls, has published design Recommendations for both reinforced and unreinforced masonry. The procedures set out for seismic design in reinforced masonry have been tested in a research project in Italy, and the results are presented here by Professors Calvi and Macchi from the University of Pavia. They show that buildings of 4 storeys in high-risk zones and of 5 storeys in moderate-risk zones can safely be designed in reinforced masonry according to the Recommendations, using highly perforated blocks only 300 mm thick.     

Seismic fragility analysis of a buried gas pipeline based on nonlinear time-history analysis

Seismic fragility analysis was performed for API X65, a type of buried gas pipeline that is widely used in Korea. For this purpose, nonlinear time-history analyses were carried out using 15 different analytical models of the pipeline, which represent variations of modeling parameters. The nonlinear Winkler approach was adopted to simulate the soil-pipeline interaction during an earthquake loading. A set of 12 recorded ground motions were selected for the time-history analyses and scaled to represent a range of earthquake intensity levels. Then, fragility functions were developed with respect to the damage states, which are defined in terms of the maximum axial strain of the pipeline. The parameters under consideration for subsequent seismic fragility analyses are the soil conditions, boundary conditions, burial depth, and type of pipeline. Comparative analyses revealed that the first three parameters, most notably the soil conditions, influence the fragility curves, but the last parameter negligibly affects the fragility curves. It is concluded in short that this study is promising to give a useful insight for a rapid seismic performance evaluation of a buried gas pipeline based on nonlinear and fragility analyses.     

Analysis of hurricane wind loads on low-rise structures

Time series of pressure coefficients collected on the roof of a house by the Florida Coastal Monitoring Program during landfall of Hurricane Ivan on the Florida panhandle in 2004 are analyzed. Rather than using peak values, which could vary due to the stochastic nature of the data, a probabilistic analysis is performed to characterize extreme values of pressure coefficients and associated wind loads. It is shown that the pressure coefficient time series follows a three parameter Gamma distribution, while the peak pressure follows a two-parameter Gumbel distribution. The analysis yields a probability of non-exceedance of a given threshold of the pressure or load coefficients. For this specific house and specific storm, the 80 percentile load coefficient value of the probability of non-exceedance is −1.7. This is discussed in the context of ASCE 7 GCp values.     

考虑填充墙影响的防屈曲支撑-钢框架抗震性能分析

按照7度设防标准设计一20层平面钢框架,采用层刚度比方法布置防屈曲支撑,通过计算分析选出合理的刚度比例。采用Wael三撑杆模型、改进的Atkinson和Yan本构关系曲线模拟填充墙,并建立含填充墙的20层防屈曲支撑-钢框架模型。采用增量动力分析(IDA)方法并结合ATC委员会的提出的倒塌储备系数(CMR)评价方法,对防屈曲支撑-钢框架和含有填充墙的防屈曲支撑-钢框架进行了抗震性能对比研究。结果表明,填充墙可以显著提高结构的抗侧刚度,并能增强结构在罕遇地震下的抗倒塌能力,通过合理的布置防屈曲支撑可使7度设防钢框架基本实现8度"大震不倒"的设防目标,同时表明CMR抗震性能评估方法在长周期结构中的应用需进一步研究。     

砌体结构的耐久性

在总结国内外有关工程实践、标准规范及研究成果的基础上,概括了砌体结构耐久性的基本内涵、设计概况、耐久性常见的问题、耐久性设计措施对策和耐久性检测方法简化的建议。相关内容也已成为砌体规范修订相应条文的背景材料。