Demands on Reduced Beam Section Connections with Out-of-Plane Skew

Abstract

Some architectural designs for steel buildings require skew at moment frame connections. Reduced beam section (RBS) moment connections with out-of-plane skew have not been tested experimentally, and it is unclear how much skew, if any, should be permitted. In this study, finite-element models were used to investigate the effect of out-of-plane skew on RBS moment connection rotation capacity. The parameters investigated were the column depth, amount of skew, and model configurations (boundary conditions). The models simulated inelastic buckling in the RBS and corresponding strength degradation under cyclic loading. A low-cycle fatigue damage model was used to evaluate the results to determine if out-of-plane skew made the RBS or weld regions more susceptible to fracture. It was found that out-of-plane skew resulted in increased column twisting and minor yielding at the column flange tips, but not lower connection rotation capacity or increased susceptibility to fracture.