نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
The use of moment-resisting frames as one of the most common seismic lateral load–resisting systems has attracted significant attention from engineers due to their favorable ductility and energy dissipation capacity. In special moment-resisting frames, the formation of flexural–axial plastic hinges at column bases is one of the most critical failure mechanisms, which can lead to local buckling of flanges and webs, degradation of stiffness and cyclic strength, reduction of post-earthquake gravity load–carrying capacity, and difficulties in repair. This study proposes an analytical relationship that provides conditions to ensure the formation of shear plastic hinges instead of flexural–axial plastic hinges at column bases. For evaluation purposes, a series of two-bay steel special moment-resisting frames with 2, 4, 6, 8, and 10 stories were designed using ETABS and modeled and analyzed in OpenSees. The results indicate that although structures exhibiting shear-dominated behavior at column bases provide higher strength compared to conventional special moment-resisting frames, they lack sufficient ductility in low-rise structures. Therefore, three approaches—including (1) enhancement of shear capacity, (2) reduction of flexural capacity, and (3) a combination of both strategies at the column base section—were investigated through nonlinear static analysis and nonlinear time-history analysis using 22 far-field ground motion records scaled to the maximum peak ground acceleration. The results demonstrate that the combined strategy provides the best performance in terms of stiffness, strength, ductility, and energy dissipation. Moreover, in time-history analyses, it satisfactorily meets the code-prescribed maximum drift limits, and none of the shear or flexural–axial plastic hinges enter the strength degradation region.
کلیدواژهها English