基于位移的结构静力弹塑性分析方法的研究

本文系统介绍了基于位移的一般结构静力弹塑性(pushover)分析方法、自适应结构静力弹塑性(pushover)分析方法,指出了基于力的结构静力弹塑性(pushover)分析方法与基于位移的结构静力弹塑性(pushover)分析方法的差别。应用各种结构静力弹塑性(pushover)分析方法对一7层和15层框架剪力墙结构进行了计算与比较分析。算例结果表明,应用基于位移的一般结构静力弹塑性(push-over)分析方法对结构的抗震性能进行评估时,不受高阶振型的影响,结果更加准确合理。     

基于能量原理的钢筋混凝土筒体结构抗震性能研究

本文通过能量法研究了钢筋混凝土筒体结构的抗震性能。文中采用振型分解法按等效单自由度体系求解筒体结构的滞回输入能;用pushover法分析了滞回耗能在结构层间的分布规律及结构自身的耗能能力;根据楼层滞回耗能与弹塑性层间位移的关系求出了薄弱层的弹塑性位移。对一高层钢筋混凝土框架-筒体结构在7度罕遇地震下的抗震性能进行了评估,通过与非线性动力时程分析的对比,证明了方法的可行性。     

模态pushover分析方法的研究和改进

鉴于传统pushover方法不能考虑结构高阶振型的贡献,从而难以应用到高层结构中,有学者提出采用考虑多阶振型组合作用的模态pushover分析方法。本文通过考虑结构屈服后地震作用发生变化这一特性,对此方法进行了改进并通过算例进行了验证。结果表明本文改进的方法有很好的精度。     

基于能量原理的钢筋混凝土简体结构抗震性能研究

本文通过能量法研究了钢筋混凝土简体结构的抗震性能。文中采用振型分解法按等效单自由度体系求解简体结构的滞回输入能；用pushover法分析了滞回耗能在结构层间的分布规律及结构自身的耗能能力；根据楼层滞回耗能与弹塑性层间位移的关系求出了薄弱层的弹塑性位移。对一高层钢筋混凝土框架-简体结构在7度罕遇地震下的抗震性能进行了评估，通过与非线性动力时程分析的对比，证明了方法的可行性。     

钢筋混凝土框架结构直接基于位移的抗震设计

直接基于位移的抗震设计方法是对基于力的抗震设计方法的重大改进。按此方法进行设计时,需要解决的关键问题是确定结构的目标位移和相应的侧移模式。提出用框架梁节点截面屈服时的位移作为目标位移,并推导了层间屈服位移的计算公式;然后用结构近似的第一振型曲线作勾其侧移模式,对层间屈服位移进行修正。算例表明,本方法计算结果合理。     

一种基于位移的改进静力弹塑性分析方法

静力弹塑性分析作为一种新的结构抗震性能评估方法，近些年得到很大的推广。本文在已有的研究基础上，通过一种基于位移控制的多阶振型组合的静力推覆分析，采用自适应的水平加载方式，考虑高阶振型的影响。对一中等高度的结构进行推覆分析，结果表明，与采用不变的水平菏载分布形式的一般静力推覆分析比较，基于本文Pushover分析所得的结构响应与非线性动力时程分析所得结构的响应更为近似，尤其在受结构高阶振型影响较明显的结构层间位移角及层间剪力方面，其结果同动力时程分析所得更为接近。     

框架剪力墙结构模态静力非线性抗震分析方法研究

本文在模态pushover分析方法基础上推导建立了模态静力非线性分析方法,对一栋10层框架剪力墙结构进行了静力非线性分析,提出了目标位移求解的等效单自由度体系弹塑性时程分析迭代法,计算结果与相应时程分析结果进行了比较,表明两者吻合较好,验证了本文计算方法的有效性。另外,对同一结构,计算分析了在不同水平荷载模式下的静力非线性分析结果,比较不同荷载模式对计算结果的影响,为静力非线性分析方法的推广使用提供参考。     

扭转不规则结构水平侧向力分布模式与pushover分析

水平侧向力分布模式的施加问题是合理进行pushover分析的关键环节。对于可以简化为平面模型的结构,传统的水平侧向力分布模式表现出较好的适用性,但对于因扭转不规则而导致必须采用空间模型的结构则并不适用。为此,针对扭转不规则结构的水平侧向力分布模式问题,并基于该类结构的地震响应特征,通过引入水平侧向力调整系数和水平侧向力分配系数,提出了扭转不规则结构改进的水平侧向力分布模式。对一具有典型扭转不规则特性的空间钢框架结构分别进行改进分布模式下的pushover分析和IV类场地典型地震动作用下的弹塑性时程分析,计算结果显示:改进分布模式下的pushover分析体现出扭转效应对结构反应的影响,并在一定程度上反映出更多的结构抗震信息,验证了所提出模式的可行性,说明pushover分析法也同样适用于扭转不规则结构。     

底商住宅在罕遇地震作用下的弹塑性时程分析

采用弹塑性时程分析程序CANNY对采用框架-非连续抗震墙结构的板式底商住宅进行了罕遇地震作用下的抗震性能分析。计算结果表明,在房屋的底层和端部布置适当数量的抗震墙,可有效提高结构的底层侧向刚度和房屋的整体抗扭刚度,改变了框架结构的抗震不规则形态。在7度罕遇地震作用下,结构弹塑性变形沿竖向分布均匀,无明显薄弱层,结构塑性铰分布合理,可满足规范的抗震设防要求。     

超大型冷却塔随机地震响应分析

为全面掌握核电超大型冷却塔的抗震性能,首先进行结构的模态分析,然后采用振型分解反应谱法和弹性时程分析方法,计算结构在多遇地震作用下的响应,并对结构进行考虑材料和几何非线性的动力弹塑性时程分析,得到结构在罕遇地震作用下的响应。由于超大塔支柱跨度达到170m,还首次对结构进行了考虑行波效应的多点激励分析。结果表明:结构前8阶振型以局部振动为主,直到第9阶出现整体倾覆振型。在多遇地震作用下,支柱的最大位移和基底剪力均满足规范要求,且水平地震反应远大于竖向地震反应。在罕遇地震作用下,支撑结构位移角远小于规范限值,出现的塑性铰数量较少,且主要分布在支柱与壳体的连接处。多点输入对支柱内力影响较为不利,而对支柱位移和塔筒内力影响较小,塑性铰出现的数量稍多且破坏程度更加严重。     

Influence of soil to structure stiffness on the accuracy of the pushover method for underground structures

The pushover method for underground structures is a seismic analysis method featured by high calculation accuracy and a simple implementation process. The method has been widely used in seismic design and other related scientific research; however, the influence of different soil-structure flexibility ratios on the accuracy of this method is still not well understood. In this study, we select the cross-section structures beneath the Daikai subway station as the research object and establish 12 finite element analysis models with different soil-structure flexibility ratios using ABAQUS. All models are computed by the dynamic time-history method or the pushover method. Furthermore, the dynamic time-history solution result is taken as the standard solution, and the precision and application of the pushover analysis method are discussed based on the parameters of peak interlayer displacement and peak internal force of the middle column section. The results show that the soil-structure flexibility ratio has a significant influence on the calculation accuracy of the pushover method, and the calculation accuracy of this method is the most ideal when the soil-structure flexibility is equal to 1. The research results can provide significant references for the seismic design of underground structures or the improvement of simplified seismic analysis methods.     

基于易损性的基础隔震结构地震动选取方法研究

对基础隔震结构进行动力弹塑性时程分析时,地震记录的选择是关键.提出基于基础隔震结构弹塑性动力放大系数谱进行地震记录选取的方法:首先采用动力弹塑性时程分析方法对基础隔震结构的两自由度简化模型进行分析,得到结构的动力放大系数谱;然后采用谱匹配的方法选取地震记录,对一8层混凝土框架结构的基础隔震结构进行增量动力分析、地震易损...     

An improved upper-bound pushover procedure for seismic assessment of high-rise moment resisting steel frames

In recent years, nonlinear static procedures (NSPs) have gained considerable popularity as an efficient tool in the performance based seismic design practice. This was backed by extensive corroboration studies that have demonstrated its good accuracy in estimating the seismic response of regular structures. Despite the numerous improvements of the original versions of NSPs, their use to assess the seismic response of irregular structures and high-rise buildings is still challenging; they are not able to predict with sufficient accuracy all the complexities associated to the seismic response of this type of structures. Thus, an improved upper-bound (IUB) pushover procedure for seismic assessment of plane frames is presented in this paper, aiming to enhance the accuracy of existing methods in predicting the seismic behaviour of high-rise buildings. The novelty of this proposal is based on the adjustment of the pattern of the lateral load of the upper-bound pushover method applied to tall structures. The accuracy of the procedure is tested using nine, twelve, fifteen and twenty storeys steel buildings. The results of the (IUB) are compared to those of the capacity spectrum method, the modal pushover analysis, the upper bound pushover analysis, the modified upper bound pushover analysis and the non-linear time history analysis (NTHA). In most cases, the proposed procedure shows better results and closer to those obtained by NTHA.     

The extended consecutive modal pushover procedure for estimating the seismic demands of two-way unsymmetric-plan tall buildings under influence of two horizontal components of ground motions

This paper aims to extend the consecutive modal pushover (CMP) procedure for estimating the seismic demands of two-way unsymmetric-plan tall buildings subjected to bi-directional seismic ground motions taking the effects of higher modes and torsion into account. Multi-stage and single-stage pushover analyses are carried out in both X and Y directions. Inelastic seismic responses obtained by multi-stage and single-stage pushover analyses for X and Y directions are combined using the SRSS combination scheme. The final seismic responses are determined by enveloping the combined results of multi-stage and single-stage pushover analyses. To evaluate the accuracy of the proposed procedure, it is applied to two-way unsymmetric-plan tall buildings which include torsionally stiff and torsionally flexible systems. The results derived from the CMP procedure are compared with those from nonlinear response history analysis (NL-RHA), as a benchmark solution. Moreover, the advantages of the proposed procedure are demonstrated by comparing the results derived from the CMP to those from pushover analysis with uniform and fundamental effective mode distributions. The proposed procedure is able to accurately predict amplification or de-amplification of the seismic displacements at the flexible and stiff edges of the two-way unsymmetric-plan tall buildings by considering the effects of higher modes and torsion. The extended CMP procedure can accurately estimate the peak inelastic responses, such as displacements and storey drifts. The CMP procedure features a higher potential in estimating plastic hinge rotations at both flexible and stiff sides of unsymmetric-plan tall buildings under bi-directional seismic excitation when compared to the uniform and fundamental effective mode force distributions.     

Enhanced nonlinear static analysis with the drift pushover procedure for tall buildings

In this study a new method for nonlinear static analysis based on the relative displacements of stories is proposed that is able to be implemented in a single stage analysis and considers the effects of an arbitrary number of higher modes. The method is called the extended drift pushover analysis procedure (EDPA). To define the lateral load pattern, values of the relative displacements of stories are calculated using the elastic modal analysis and the modal combination factors introduced. For determining the combination factors, six different approaches are examined. Buildings evaluated in this study consist of four special steel moment-resisting frames with 10–30 stories. Responses including relative displacements of stories, story shear forces and rotation of plastic hinges in each story are calculated using the proposed approaches in addition to modal pushover analysis and nonlinear dynamic time history analyses. The nonlinear dynamic analysis is implemented using ten consistent earthquake records that have been scaled with regard to ASCE7-10. Distribution of response errors of story shears and plastic hinge rotations show that a major part of error corresponds to the second half of the buildings studied. Thus, the mentioned responses are corrected systematically. The final results of this study show that implementing the EDPA procedure using the third approach of this research is able to effectively overcome the limitations of both the traditional and the modal pushover analyses methods and predict the seismic demands of tall buildings with good accuracy.     

延性需求谱在基于性能的抗震设计中的应用

基于性能的抗震设计理论涉及如何简便而合理地确定结构在指定强度地震下的弹塑性位移需求。本文给出了利用延性需求谱求解结构位移需求的一般步骤:借助模态Pushover分析将多自由度体系分解为几个非线性单自由度体系,以考虑各阶振型的影响;利用延性需求谱计算对应模态的等效单自由度体系的延性及位移需求,并以一定方式组合转化为多自由度体系位移需求。最后,通过算例分析表明:利用延性需求谱求解结构位移需求是一种具有一定精度可为工程接受的简便方法,在基于性能的抗震设计中具有较好的应用前景。     

Prediction of the largest peak nonlinear seismic response of asymmetric buildings under bi-directional excitation using pushover analyses

A simplified procedure is proposed to predict the largest peak seismic response of an asymmetric building to horizontal bi-directional ground motion, acting at an arbitrary angle of incidence. The main characteristics of the proposed procedure is as follows. (1) The properties of two independent equivalent single-degree-of-freedom models are determined according to the principal direction of the first modal response in each nonlinear stage, rather than according to the fixed axis based on the mode shape in the elastic stage; the principal direction of the first modal response in each nonlinear stage is determined based on pushover analysis results. (2) The bi-directional horizontal seismic input is simulated as identical spectra of the two horizontal components, and the contribution of each modal response is directly estimated based on the unidirectional response in the principal direction of each. (3) The drift demand at each frame is determined based on four pushover analyses considering the combination of bi-directional excitations. In the numerical example, nonlinear time-history analyses of six four-story torsionally stiff (TS) asymmetric buildings are carried out considering various directions of seismic inputs, and these results are compared with the predicted results. The results show that the proposed procedure satisfactorily predicts the largest peak response displacement at the flexible-side frame of a TS asymmetric building.     

剪切型结构的抗震强度折减系数研究

为了研究剪切型结构抗震强度需求的变化规律,本文基于单自由度体系的非线性时程分析,研究了不同场地条件下延性折减系数与位移延性系数和结构自振周期的关系;采用修正等效单自由度体系位移延性折减系数的方法,研究了剪切型多自由度体系的延性折减系数;以基于中国建筑抗震规范设计的代表不同抗震能力要求的RC框架结构为分析对象,通过静力弹塑性分析,研究了RC框架结构的体系超强能力。分析结果表明场地类别、位移延性水准和结构振动周期对单自由度体系的延性折减系数有显著的影响;多自由度体系的抗震延性折减系数明显比其相应的等效单自由度体系的抗震延性折减系数小;RC框架结构的超强系数一般随结构楼层数的增加而减小,随抗震设防烈度的增大而减小,内框架的超强系数比边框架的超强系数大。     

An improved displacement-based adaptive pushover procedure based on factor modal combination rule

An accurate estimation of the applied load pattern is an essential component in each pushover procedure. Recently, a number of adaptive pushover methods have been proposed in which the effects of the higher modes as well as the progressive changes in the dynamic characteristics of structures are taken into account to compute the applied load pattern. The basic shortcoming of these advanced pushover methods is related to employing the quadratic modal combination rule, whereby the sign reversals of the modal load vectors are suppressed. In this study, an improved displacement-based adaptive pushover method is developed in which the applied load pattern is computed using the factor modal combination rule(FMC). In the proposed procedure, multiple load patterns, depending on the number of the modes considered, are determined in order to take into account the sign reversals of different modal load vectors. The accuracy of the proposed method is verifi ed for seven moment resisting frame buildings of 3, 9 and 20 stories with regularity or vertically geometric and mass irregularities subjected to 60 earthquake ground motion records. The results showed that the proposed methodology is capable of reproducing the peak dynamic responses with very good accuracy.