罕遇地震下弦支穹顶的弹塑性动力响应分析

Analysis of elasto-plastic dynamic responses of suspendome under rare earthquake

基于18个算例模型,对弦支穹顶在罕遇地震下的弹塑性响应特点进行考察,分析初始预张力、下部结构刚度及其对称性、支座连接条件以及矢跨比等因素的影响.结果表明,罕遇地震下大多数模型的塑性杆件主要出现在上部网壳的中部而不在临支座区域;增加初始预张力会造成结构的塑性杆件数及残余塑性应变明显增加;下部结构的对称性和网壳矢跨比对弦支穹顶的弹塑性响应最为敏感.提出一个定量评价罕遇地震作用后弦支穹顶破坏程度的极限承载力剩余率指标.利用该指标进行分析表明,7度时弦支穹顶结构的杆件按小震弹性设计、8度时按中震弹性设计,则罕遇地震后结构的极限承载能力一般能够保持在90%以上.

The characteristics of elasto-plastic dynamic response of suspendomes under rare earthquake are investigated based on 18 illustrative structural models, and the effects caused by initial pretension, rigidity and symmetry of substructure, connection condition of abutments and rise-span ratio are analyzed. The re- sults reveal that, for most of models, the members with residual plastic strain under rare earthquakes mainly located in the central of the upper lattice shell instead of the area near the abutments. Raising the initial pretension will contribute to significant increases in both the number and the residual plastic strain of plastic members. The elasto-plastic responses of suspendomes are more sensitive to the symmetry of substructure and the rise-span ratio of roof. An index, named as the ratio of residual ultimate bearing ca- pacity, is defined to quantitatively evaluate the damage level of suspendome after rare earthquakes. By means of this index, it is analyzed that the ultimate bearing capacity of suspendome can keep a level of more than 90% after rare earthquake if its members are satisfied with the elasticity check under frequently- occurred earthquake in the 7-degree zone, or under fortification earthquake in the 8-degree zone.