The beam-to-column connections are the most vulnerable locations in steel Moment Resisting Frames (MRFs) subjected to seismic loading. The cyclic deterioration of these structural elements during the earthquakes may cause their failure under subsequent earthquakes. This paper evaluates the post-earthquake behavior of steel moment resisting frames with Welded Unreinforced Flange (WUF) connections modified by introducing Reduced Beam Section (RBS) to improve their seismic behavior. In this regard, investigations were carried out on the connection and structure scales. At the connection scale, a T-shaped beam-to-column connection was modeled numerically and analyzed under several two-phase consecutive cyclic loading in which the maximum displacement amplitude of the first loading phase was varying. Results of this part were used to investigate the effect of multiple loading on the behavior of conventional and modified moment connections and provide data on the range of ultimate rotation capacity for the studied connections. At the structural scale, steel MRFs with WUF and modified RBS connections were compared by performing Incremental Dynamic Analysis (IDA) and extracting fragility curves. Based on the results, it can be concluded that the seismic collapse capacity of the frame with modified connections subjected to consecutive earthquake is considerably higher than that of the conventional MRF.

梁柱连接是钢抗弯框架 (MRF) 中承受地震荷载最脆弱的位置。这些结构构件在地震期间的周期性恶化可能会导致它们在随后的地震中失效。本文评估了采用焊接无筋法兰 (WUF) 连接的钢抗弯框架的震后性能，通过引入减少梁截面 (RBS) 来改善其抗震性能。对此，对连接和结构尺度进行了调查。在连接尺度上，对T形梁柱连接进行了数值模拟，并在几个两相连续循环荷载下进行了分析，其中第一荷载阶段的最大位移幅值是变化的。这部分的结果用于研究多重载荷对传统和修正力矩连接行为的影响，并提供有关所研究连接的极限旋转能力范围的数据。在结构尺度上，通过增量动态分析 (IDA) 和提取脆性曲线，对采用 WUF 和改进的 RBS 连接的钢 MRF 进行了比较。结果表明，改进连接框架在连续地震作用下的抗震倒塌能力明显高于传统MRF。