基于随机Pushdown方法的钢筋混凝土框架结构抗连续倒塌能力概率评估

为了评估钢筋混凝土框架结构的不确定性参数对其抗连续倒塌能力的影响，将确定性Pushdown分析与可以控制相关性的拉丁超立方体抽样方法（LHS）相结合，提出一种随机Pushdown方法。为说明方法的建立和应用，选择一栋8层4跨的钢筋混凝土框架结构，考虑结构的荷载、材料强度以及几何尺寸等17个不确定性参数，采用Pushdown方法分析获得的结构所能承受的最大竖向荷载作为其抗连续倒塌能力，统计得到结构连续倒塌易损性函数，并采用“龙卷风图”方法对不确定性参数的灵敏度进行了分析。结果表明，结构不确定性参数对抗连续倒塌能力影响显著，结构的抗连续倒塌能力的变异系数达到20%，其中，活荷载、楼层恒荷载、钢筋极限应力以及梁截面钢筋面积等参数对结构抗连续倒塌能力的影响最为显著。

Probabilistic assessment of structural resistance of RC frame structures against progressive collapse usingrandom Pushdown analysis

A random Pushdown method, which combined the deterministic pushdown analysis with the correlation-reduced Latin hypercube sampling (LHS) method, was proposed to evaluate the effects of structural uncertainties on resisting capacity of reinforced concrete (RC) frames to mitigate progressive collapse. To illustrate the development and application of the proposed method, an 8-story and 4-bay RC frame structure was used as a case. A total of 17 structural uncertain parameters covering the types of loading, material strength, and structural geometric dimension, were taken as random variables. The peak vertical load of Pushdown analysis was defined as the structural capacity to resist progressive collapse. The probabilistic results, namely, progressive collapse fragility function, were obtained by statistical analysis. The sensitivities of the uncertain parameters under consideration were illustrated by the tornado diagram method. The results indicate that the influences of structural uncertainties on resisting capacity of the structure to resist progressive collapse are significant. The coefficient of variation of the structural capacity to resist progressive collapse could be up to 20%. Among these uncertain parameters, live load, dead load on the floor, ultimate stress of the steel and the reinforcement areas of the beam are the dominantly significant ones.