Reduced web section (RWS) connections and welded flange plate (WFP) connections can both effectively improve the seismic performance of a structure by moving plastic hinges to a predetermined location away from the column face. In this paper, two kinds of steel frames—with RWS connections and WFP connections—as well as different frames with welded unreinforced flange connections were studied through seismic fragility analysis. The numerical simulation was conducted by using multiscale FE modelling. Based on the incremental dynamic analysis and pushover analysis methods, probabilistic seismic demand analysis and seismic capability analysis were carried out, respectively. Finally, combined with the above analysis results, probabilistic seismic fragility analysis was conducted on the frame models. The results showed that the RWS connection and WFP connection (without double plates) have little influence on reducing the maximum inter-storey drift ratio under earthquake action. RWS connections slightly reduce the seismic capability in non-collapse stages and improve the seismic collapse resistance of a structure, which exhibits good structural ductility. WFP connections can comprehensively improve the seismic capability of a structure, but the seismic collapse resistance is worse than that of RWS connections when the structure has a large number of storeys. The frame with WFP connections has a lower failure probability at every seismic limit state, while the frame with RWS connections sacrifices some of its structural safety in non-collapse stages to reduce the collapse probability.

减小的腹板截面（RWS）连接和焊接的法兰板（WFP）连接都可以通过将塑料铰链移动到远离柱面的预定位置来有效地提高结构的抗震性能。本文通过地震脆性分析研究了两种钢框架（具有RWS连接和WFP连接）以及具有焊接的无筋法兰连接的不同框架。使用多尺度有限元建模进行了数值模拟。基于增量动力分析和推覆分析方法，分别进行了概率地震需求分析和抗震能力分析。最后，结合以上分析结果，对框架模型进行了概率地震易损性分析。结果表明，在地震作用下，RWS连接和WFP连接（无双板）对减小最大层间漂移比影响很小。RWS连接会稍微降低非塌陷阶段的抗震能力，并提高结构的抗震塌陷性，这显示出良好的结构延展性。WFP连接可以全面提高结构的抗震能力，但是当结构具有许多层时，其抗震倒塌性能比RWS连接差。使用WFP连接的框架在每个地震极限状态下的破坏概率都较低，而使用RWS连接的框架在非塌陷阶段会牺牲一些结构安全性，以降低倒塌概率。