Abstract
Structural resistance against earthquakes largely depends on the energy absorption capacity or the inelastic deformation capacity of the structure. One of the main causes which force restriction to the deformation capacity is local buckling of plate elements of the member. In this paper, the effects of the local buckling on the inelastic structural behavior of H-shaped steel members were investigated experimentally. A series of tests was carried out using H-shaped members having large variety of width-to-thickness ratio of the plate element and slenderness. Most important loading condition in the structural members of the rigid frame subjected to seismic forces is bending moment about the strong axis of the member combined with axial compression, and this condition is simulated by a cantilever beam-column subjected to a constant axial force and increasing lateral force applied at it's top. The load-deflection relation of such a cantilever beam-column can be outlined by decomposing it into three components; elastic part up to fully plastic state, strain-hardening part without local buckling and degrading part due to local buckling. Each part of the load-deflection relation was found to be approximated by a linear relation. Thus it became essential to know the stress increase beyond fully plastic state and the slopes of strainhardening part and the degrading part. A large number of experimental data was used to establish simple empirical formulas predicting the stress increase and slopes at representative parts of the idealized load-deflection relationship. Obtained results are applicable to almost all practical H-shaped steel members fully stiffened against lateral torsional buckling.
