古塔整体平移后的抗震性能分析与隔震改造

Analysis of Seismic Characteristics of Ancient Pagoda after Monolithic Translation and Isolation Retrofitting

利用数值模拟方法研究龙溪塔整体平移后的动力特性及其抗震性能。考虑塔檐、塔刹以及开洞等构造,建立平移后古塔的三维实体有限元模型,进行了模态分析和时程分析,通过输入不同地震波,计算出结构在多遇地震与罕遇地震情况下塔体的位移反应、层间位移角以及应力等。结果表明:在不同地震波作用下古塔一层墙体和二层墙体与塔檐连接处应力较大,一层角部最大应力值已超过材料极限强度;塔刹的位移反应与塔身相比较大;层间位移角随层高增加而增大,在多遇地震下塔刹处层间位移角远小于层间位移角限值,古塔主体结构处于弹性状态,不发生破坏;在罕遇地震作用下,除一层以外各层的层间位移角均超过限值,二三层结构有轻微破坏,四至七层结构出现中等破坏,塔刹严重破坏甚至倒塌。提出龙溪塔整体平移后的隔震改造建议,对比分析隔震前后古塔的抗震性能,结果表明在平移后的建筑物下设置隔震支座减震效果明显。

The dynamic characteristics and seismic behaviors after monolithic translation of Longxi Pagoda is studied by numerical simulation method. Its finite element model of three entities is built considering constitutions such as pagoda eaves,pagoda finial,openings and so on. A model analysis and a transient analysis are then conducted. The displacement of the pagoda and the inter-story drift angle of the floors under frequent seismic actions and infrequent seismic actions are calculated by inputting different seismic waves. It is shown through the results that the walls of the bottom layer and the joint of the second layer and pagoda eaves have larger stress,and the maximum stress value of the bottom layer has already exceeded the ultimate strength of materials. The displacements of pagoda finial are larger than the body of pagoda. The inter-story drift angle increases with the increasing height of the pagoda. The inter-story drift angle of pagoda finial is far less than inter-story drift angle limitation under frequent seismic actions so that the main structure is in the elastic state and will not be damaged. Under infrequent seismic actions,the inter-story drift angle of each layer exceeds the limitation except the first layer,the second and third layers of structure damage slightly and the forth layer to seventh layer are in moderate damage,the pagoda finial is seriously damaged or even collapses. The isolation retrofitting proposals for protecting Longxi Pagoda after monolithic translation and the contrast analysis of the seismic performance of the ancient pagoda before and after isolation retrofitting are proposed. The results indicate that the seismic response of structure which is placed the isolation bearings after the monolithic translation is reduced sharply.