中文摘要：

大跨度拱形立体桁架结构在强震下发生的失效模式有动力失稳破坏和动力强度破坏．依据已有的B-R动力失稳判定准则和评定网壳结构动力强度破坏行为的方法，研究结构在强震作用下进入塑性杆件数目及比例，以及结构最大位移变化规律．研究表明，如果超过某一荷载时，结构进入塑性的杆件比例显著增长，则该荷载即被认为是拱形立体桁架结构的动力强度破坏l临界荷载，以某拱形立体桁架为背景，选取三向El-Centro波和三向天津波作为地震输入进行弹塑性时程分析，进一步验证本文的结论，通过分析可以得出该拱形桁架在强震作用下发生动力失稳破坏．

英文摘要：

Failure mode of large-span steel arch truss under severe earthquakes includes dynamic strength failure and dynamic instability failure. According to the B-R criteria for assessing dynamic instability failure and the method of the dynamic strength for assessing the reticular dome, the number and the plastic element ratio of large-span steel arch truss, displacement of the key joint on large-span steel arch truss in pace with the increasing seismic input are investigated. When the load exceeds one value, the number and the plastic element ratio of large-span steel arch truss increase significantly. This load is the critical load of dynamic strength failure for large-span steel arch truss. Taking the real project as a case study, the performance of the structure under severe earthquakes with E1-Centro Wave and Tianjin Wave as earthquake input was investigated by the elastic-plastic time-history analysis. Results validate the above conclusions and show that the dynamic instability is prone to take place in this large-span steel arch truss structure under the severe earthquake.