Three-dimensional modeling of steel portal frame buildings

The realistic strength and deflection behavior of industrial and commercial steel portal frame buildings are understood only if the effects of rigidit y of end frames and profiled steel claddings are included. The conventional designs ignore these effects and are very much based on idealized two-dime nsional (2D) frame behavior. Full-scale tests of a 12 x 12 m steel portal f rame building under a range of design load cases indicated that the observe d deflections and bending moments in the portal frame were considerably dif ferent from those obtained from a 2D analysis of frames ignoring these effe cts. Three-dimensional (3D) analyses of the same building, including the ef fects of end frames and cladding, were carried out, and the results agreed well with full-scale test results. Results clearly indicated the need for s uch an analysis and for testing to study the true behavior of steel portal frame buildings. It is expected that such a 3D analysis will lead to lighte r steel frames as the maximum moments and deflections are reduced.