基于整体刚度参数的空间结构模态推覆分析

由于空间结构具有三维受力特性,用静力推覆方法计算其地震反应存在如下问题,结构代表性节点荷载-位移关系难以选择、结构荷载-节点位移-支座反力之间的对应关系不够直观、结构能力曲线难以确定.利用振型形态确定荷载模式,对空间结构进行静力弹塑性分析;引入结构整体刚度参数,得出不依赖于支座反力变量的各主要模态的等效单自由度(ESDOF)体系力-位移关系;结合模态周期值,确定ESDOF体系等效质量,并将该体系应用于模态推覆分析.数值算例分析结果表明,基于整体刚度参数的模态推覆分析方法可避免空间结构能力曲线难确定的问题,计算耗时仅为时程分析方法的10%,沿地震输入方向计算得到的结构节点位移结果相对时程分析结果的平均误差为28%.

Modal Pushover Analysis of Spatial Structures Based on the Overall Structural Stiffness Parameter

Due to the three dimensional force transmission mechanism, the application of pushover method for seismic response analysis of spatial structures is limited by the following issues: firstly, the representative nodal load displacement relationship can hardly be specified; secondly, there are no direct interrelationship among structural load, nodal displacement, and support reaction for spatial structures; thirdly, it is difficult to compute the capacity curves of spatial structures. In this paper, static elasto plastic analysis is carried out by using the load patterns generated from the structural vibration modes. Based on the overall stiffness parameter, the load displacement relationship of the modified equivalent single degree of freedom (ESDOF) system of each dominating mode, independent on support reactions, is obtained accordingly. And the equivalent mass of the modified ESDOF system is calculated by utilization of the mode period. Then the newly established ESDOF systems of the dominate modes are adopted in a modified modal pushover analysis (MPA) procedure. Numerical example shows that the modified MPA method, based on the overall structural stiffness parameter, overcomes the problem existing in the establishment of the structural capacity curve for the spatial structures. The computing consumption of the method given in this paper is 10% of the elasto plastic time history analysis (THA) method, meanwhile, in the seismic input direction, the nodal displacement data generated by the proposed method shows a 28% deviation compared with the THA method.