考虑地基侧向永久位移的钢筋混凝土框架结构地震反应分析

SEISMIC RESPONSE ANALYSIS OF REINFORCED CONCRETE FRAME STRUCTURE CONSIDERING PERMANENT LATERAL DISPLACEMENT OF FOUNDATION

定量评价场地破坏对建筑物震害的影响是一个亟需解决的难点问题,现阶段结构震害预测以及灾情再现等震害防御技术中多未考虑场地破坏的影响。地基侧向永久位移(变形)是场地破坏的一种典型破坏形式,往往会引起较严重的建(构)筑物震害。采用OpenSees软件构建一个简化的6层2跨钢筋混凝土框架结构模型,通过输入不同强度且含有永久位移的位移时程,模拟地震中地基侧向永久位移对结构震害的影响。分析结果显示:(1)地基侧向永久位移对结构底层的最大层间位移角起控制作用,即使地基产生0.05 m的侧向永久位移,在地震动强度小于0.4g情况下,底层的最大层间位移角远大于地基未发生永久位移的工况;在地震动强度为0.4g时,结构的最大层间位移角发生在第二层,此时地震动强度决定结构的破坏状态;(2)地基发生0.1 m的永久位移时,永久位移对结构的破坏等级起决定性影响,且影响主要体现在底层的层间位移角,对其他楼层破坏等级影响较小;(3)通过简化模型的数值计算,分析地基侧向永久位移对结构震害等级的影响,解释了地震中场地破坏多会加重房屋结构震害的现象。

Evaluating the impact of site damage on building damage is a difficult subject,and the impact of site damage has not been considered in most of the current earthquake damage mitigation techniques,such as structural seismic damage prediction and disaster reconstruction.Lateral permanent displacement(deformation)of soil is a common type of site damage,which causes serious earthquake damage to buildings.A simplified model of a 6-story and 2-span reinforced concrete frame structure was constructed by OpenSees software,and the impact of lateral permanent foundation displacement on seismic damage during an earthquake was assessed by inputting displacement time courses of different strengths and permanent displacements.The calculation results show that:(1)the impact of lateral permanent displacement of the foundation on the maximum story-drift angles of the bottom story is significant,even if only a lateral permanent displacement of 0.05 m occurs on the foundation with the seismic intensity is less than 0.4g,the maximum story-drift of the bottom story is much larger than that of the condition which no permanent displacement occurs on the foundation;When the seismic intensity is increased to 0.4g,the maximum story-drift of the structure occurs at the second story,at this time the impact of permanent displacement is smaller than that of seismic intensity;(2)When the permanent displacement of 0.1 m occurs in the foundation,the permanent displacement has a decisive influence on the damage level of the structure,and the influence is mainly reflected on story-drift of the ground floor,little impact is showed on the damage level of other floors;(3)Through numerical calculation of the simplified model,the impact of lateral permanent displacement of the foundation on the damage level of the structure is analysed to explain the phenomenon that site damage in earthquakes mostly aggravates the seismic damage of the structure.