建筑结构基于性能的抗震评估的等ζy延性谱法

利用水平地震作用下单自由度体系的运动方程,以屈服承载力系数ζy为参量,推导出适时延性系数动力方程,从而建立了基于屈服承载力系数的延性需求谱。结合结构的非线性静力pushover分析,提出了基于性能的抗震评估方法——等ζy延性谱法。用等yζ延性谱法对一个6层钢筋混凝土框架结构进行了抗震评估,并与非线性时程分析进行了比较。结果表明,用等yζ延性谱法对结构进行抗震性能评估是可行的,并且具有较高的精度。     

Probabilistic estimation of inelastic displacement demands in soil–structure interaction systems on cohesive soils

Inelastic displacement ratios (IDRs) of nonlinear soil–structure interaction (SSI) systems located at sites with cohesive soils are investigated in this study. To capture the effects of inelastic cyclic behavior of the supporting soil, the Beam on Nonlinear Winkler Foundation (BNWF) model is used. The superstructure is modeled using an inelastic single-degree-of-freedom (SDOF) system model. Nonlinear SSI systems representing various combinations of unconfined compressive strengths and shear wave velocities are considered in the analysis. A set of strong ground motions recorded at sites with soft to stiff soils is used for considering the record-to-record variability of IDRs. It is observed that IDRs for nonlinear SSI systems are sensitive to the strength and the stiffness properties of both the soil and the structure. For the case of SSI systems on the top of cohesive soils, the compressive strength of the soil has a significant impact on the IDRs, which cannot be captured by considering only the shear wave velocity of the soil. Based on the results of nonlinear time-history analysis, a new equation is proposed for estimating the mean and the dispersion of IDRs of SSI systems depending on the characteristic properties of the supporting soil, dimensions of the foundation, and properties of the superstructure. A probabilistic framework is presented for the performance-based seismic design of SSI systems located at sites with cohesive soils.     

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.     

A statistical approach to determine 2D optimal equivalent linear parameters with application to earthquake engineering

The equivalent linearization method approximates the maximum displacement response of nonlinear structures through the corresponding equivalent linear system.By using the particle swarm optimization technique,a new statistical approach is developed to determine the key parameters of such an equivalent linear system over a 2D space of period and damping ratio.The new optimization criterion realizes the consideration of the structural safety margin in the equivalent linearization method when applied to the performance-based seismic design/evaluation of engineering structures.As an application,equations for equivalent system parameters of both bilinear hysteretic and stiffness degrading single-degree-offreedom systems are deduced with the assumption of a constant ductility ratio.Error analyses are also performed to validate the proposed approach.     

盐岩地下储气库风险分级机制初探

能源储备是国家重大战略需求,目前国内已经开始大规模兴建盐岩能源地下储库群,由于国内的盐岩储库地层具有埋深浅、盐层薄、夹层多、品位低等特点,导致建库难度大、运行风险高,因此,开展盐岩地下油气储库风险分析研究具有重要的理论意义和工程应用价值。针对国内盐岩地下油气储库现状,在风险分析中引入功能设计理念,以体积收缩率作为储库运营期风险的单项分级指标,初步提出了地下油气储库运营风险分级机制的基本方法,以国内某盐岩地下储气库为例,通过流变计算获得不同储气内压变化条件下,储库风险随时间的变化规律,较好地验证了所提方法的合理性和有效性。     

基于单地震动记录IDA方法的结构倒塌分析

增量动力分析(Incremental Dynamic Analysis, IDA)作为静力Pushover分析的动力拓展,可以全面、准确地分析结构的性能变化,尤其可以很好地分析结构倒塌这一动力失稳问题.本文基于单地震动记录的IDA方法,提出了"折半取中"原则,以确定结构倒塌极限状态点.以一榀五层三跨钢筋混凝土框架结构为例,分别考虑钢筋强化模型、理想弹塑性模型和软化模型,对其进行倒塌分析.结果表明:钢筋的屈服后强化特性对结构抗倒塌能力具有显著的影响.     

对《建筑工程抗震性态设计通则(试用)》的评述

《建筑工程抗震性态设计通则（试用）》（以下简称《通则》）是一部对我国抗震设计规范修订具有重大指导意义的试用标准.本文对《通则》和现行规范的某些不同和改进之处进行了比较,讨论了《通则》所具有的先进性和行业指导性,同时也对应用《通则》的原理,对修订和完善下一代规范还需要研究的问题提出了若干建议.     

基于性能的黏弹性阻尼器减震结构抗震设计

根据黏弹性阻尼器的特点和抗震规范的要求,分别提出了用于黏弹性阻尼器减震结构抗震分析的弹性及弹塑性需求谱,前者是基于黏弹性阻尼器减震结构等效阻尼比的简化计算公式及规范规定的反应谱;后者是基于修正的V id icRμ-μ-T关系。在此基础上,借助模态推覆分析,提出了可以考虑高阶振型影响的黏弹性阻尼器消能减震结构体系的能力谱分析方法,并对一8层钢筋混凝土消能减震框架结构进行了"中震不坏,大震可修"性能水准下的抗震分析。算例结果表明,采用该方法分析黏弹性阻尼器减震结构体系是可行的、有效的。     

基于变形的土石坝地震风险分析

土石坝抗震安全的设计一般立足于预防结构的倒塌,如何使土石坝结构地震破损控制在可接受的风险水平是一个值得研究的重要课题。应用地震风险分析理论,建立了土石坝地震风险分析方法,包括地震危险性分析、地震易损性分析和地震灾害损失评估3个方面。在场地地震危险性分析基础上,将基于性能的抗震设计思想应用于土石坝结构地震易损性分析中,以土石坝坝顶相对沉陷为评价指标,划分土石坝震损等级,最后结合地震经济损失分析,建立了土石坝地震风险计算模型,在技术和经济上对土石坝地震破损风险进行分析计算。以某高土石坝为例,用该模型对大坝的震害和经济损失进行了预测分析,其结论可为土石坝安全评价及投资决策等提供依据。     

弹塑性位移谱法的振动台模型试验验证

弹塑性位移谱法求解结构在指定强度地面运动作用下的位移需求是一种简便合理的方法。本文将弹塑性位移谱法就具体地震波计算的楼层位移需求、层间位移角需求与一比例为1／10的12层钢筋混凝土模型框架振动台试验结果作了比较。设计的12层钢筋混凝土模型框架结构在振动台上经历了7种强度等级地震波的作用,输入峰值加速度依次为：0．090g、0．258g、0．388g、0．517g、0．646g、0．775g和0．904g。求出了弹塑性位移谱法计算的楼层位移和层问位移角需求与振动台试验结果的比值,研究了二者比值的均值及方差沿楼层的分布情况。结果表明：弹塑性位移谱法的计算结果与振动台得到的位移需求值吻合较好,在基于性能的抗震设计中具有较好的应用前景。