On the characteristics of brace-frame interaction in diagonally and X-braced moment resisting frames

The nonlinear performance of Braced Moment Resisting Frame (BMRF) dual systems comprises the influence of gusset-brace post buckling response together with the flexural action of boundary moment resisting frame members (i.e., BMRF boundary frame), which are well treated as two subsystems. The BMRF behavior might be considered as the summation curves of the gusset-brace subsystem and a corresponding moment frame system acting alone. Nonetheless, the BMRF boundary frames behave differently from the similar moment frame system; also, due to the interaction effect between the subsystems, the overall performance of BMRFs may not be justified from the superposition of subsystems. In this paper, using high fidelity 3D finite element model of the such systems, the actual behavior of BMRFs are accurately evaluated to inspect the influence of gusset-brace subsystem on the behavior of BMRF boundary frame, to examine the characteristics of interactions between the subsystems, and to measure the effectiveness of gusset-brace configurations.