Local buckling of steel sections under cyclic loading

In order to understand the influences of local buckling under cyclic loading conditions, experimental studies were carried out on W8 × 10 A-36 structural steel members subjected to selected monotonic, cyclic and non-proportional loading paths under combined axial force and bending moment. Test results show that strength of the member deteriorates after local buckling. The critical deformation capacity for the cyclic loading condition is lower than 60% of the value for the monotonic pure bending condition. The influence of local buckling on the behavior of pure bending for monotonic and cyclic loading condition is small, but the one under monotonic bending with a large initial axial strain as well as the one under combined bending and axial for both monotonic and cyclic loading condition is serious. A simple analytical model, based on the stress resultant plasticity model developed earlier at the University at Buffalo for predicting cyclic post-local buckling behavior, has been proposed. This model utilizes the cyclic post-local buckling moment-curvature relationship, and can describe the strength and the stiffness deterioration which are the important factors in the cyclic post-local buckling behavior of thin-walled structural members.