三心圆柱面网壳弹塑性地震响应分析

Analysis of elasto-plastic seismic responses of three-centered cylindrical reticulated shells

通过对不同跨度、不同长度、不同支承形式以及不同厚度的三心圆柱面网壳进行数值计算,考察其在设防烈度及罕遇地震作用下的弹塑性动力响应特点.所有柱面网壳模型的杆件截面均根据非抗震设计工况满应力优化设计确定,并满足多遇地震作用的验算.通过对杆件进行单元细分并引入初始缺陷以有效模拟压杆的失稳.由规范反应谱生成三向人工波,采用非线性时程法计算网壳的弹塑性响应.基于计算结果,统计了7度、8度中震及大震作用下的结构塑性变形发展特点和塑性杆件分布区域.研究表明:网壳长度、跨度和厚度的改变会使结构出现较大的弹塑性响应差异;仅满足小震验算的三心圆柱面网壳在中震和大震作用下可能会失效,且失效结构的薄弱位置主要位于距支座1/4跨度的区域;网壳从薄弱区域杆件出现塑性应变到整体结构失效的时间间隔很短.为满足"三水准"的抗震设防目标,建议三心圆柱面网壳的抗震设计进行中震及大震验算.

By analyzing structural models with different span,different length,different supports and different thickness,elasto-plastic dynamic responses of three-centered cylindrical reticulated shells under fortification intensity earthquake and rare earthquake are investigated.The cross-section size of bars in the shell models is determined by the full stress design under non-seismic load cases and also satisfied by the check of frequently-occurred earthquake.The effect of member buckling is considered by subdividing the element and introducing initial imperfection in members.A three-direction artificial earthquake wave generated according to the code response spectrum is adopted,and structural elasto-plastic dynamic responses are calculated by nonlinear time-history analysis method.The distribution of plastic bars and magnitude of plastic strain are analyzed respectively for 7and 8degree fortification intensity earthquake and rare earthquake.The result indicates that the change of length,span and thickness of structure will sharply influence the dynamic performance of the structure.Under fortification intensity earthquake and rare earthquake,failures may happen to cylindrical reticulated shells only checked by frequently-occurred earthquake.The weak region mainly locates in the area about 1/4span away from support lines.The time interval from the first appearance of plastic strain in weak region to the failure of structure is very short.In order to meet the three seismic for tification levels,it is necessary to check the dynamic performance ofcylindrical reticulated shells for fortification intensity earthquake and rare earthquake respectively.