基于备用荷载路径Pushover方法的结构连续倒塌鲁棒性分析

Robustness analysis for progressive collapse of structures using ALP-based pushover analysis approach

鲁棒性不足是造成"5.12"汶川大地震中建筑结构大量倒塌的重要原因之一,而我国现行建筑抗震设计规范并没有相应的避免由于承重构件失效引起连续倒塌的分析方法和抗倒塌设计方法。采用备用荷载路径方法,考虑移除框架柱瞬间的动力效应,对框架柱突然失效的建筑物进行Pushover分析,对损伤结构的极限承载能力进行评估。采用三种冗余度指标作为损伤结构鲁棒性评定的定量指标,从而确定结构的关键构件,并判断损伤结构在遭遇原设计荷载时是否会发生连续倒塌。以钢筋混凝土平面框架结构为例进行了数值分析,得到了不同情况下结构倒塌临界状态时塑性铰的发展顺序及变形图。研究结果表明:采用备用荷载路径Pushover方法和冗余度指标可以有效地对发生偶然情况下承重构件失效时结构的抗连续倒塌能力进行定量的分析和评估。

Lack of robustness was one of the main reasons of the collapse of many buildings in the great Wenchuan earthquake.However,the current seismic design code of buildings has not specified progressive collapse analysis approaches and corresponding progressive collapse resistant design methods for structures due to the loss of some key weight-bearing members.In this paper,an alternate load path(ALP) based pushover analysis approach is applied to the damaged structures assuming that one column is removed,in which the dynamic inertial effect is considered.The ultimate load-carrying capacity of the damaged structure is then evaluated.Three redundancy indices are taken as the quantitative indicators of structural robustness to determine the key elements,and to assess the progressive collapse resistance of the damaged structure when encountered the original design load.As a case study,a three-bay,five-story reinforced concrete plane frame structure is taken as a numerical example.The forming order of plastic hinges and the corresponding deformation graph of the structure in the critical collapse state are investigated.It is shown by the research results that the ALP-based pushover analysis approach and the redundancy indices can be used to efficiently analyze and quantitatively evaluate the progressive collapse resistance of the damaged structures when the main load-carrying members are suddenly lost under the exceptional events.