Effect of cyclic flange local buckling on the capacity of steel members

摘要

Cyclic flange local buckling typically occurs when plastic hinges form in the beams and columns of special moment resisting frames subject to seismic excitation. While local buckling in beam plastic hinges has been investigated in the past for monotonic loading situations, the effect of cyclic flange local buckling on beam and column behaviours is not yet well understood. In order to address this shortcoming, nineteen half-scale T-section specimens are tested under cyclic axial loads in a configuration intended to replicate the cyclic demands imposed on flanges of beams and columns in their plastic hinge region. The main experimental variables are flange slenderness ratio, level of web restraint, and loading scheme (monotonic versus cyclic). Validated computational studies are performed to expand the parameter space. The test data and computational results show that T-section members that meet the current highly ductile limit can suffer excessive axial strength degradation under cyclic axial loading. The effect of slenderness ratios on column compression capacity due to strength degradation of flanges is evaluated and quantified.