Modified linear analysis for steel frame limit state design

This paper describes the application of modified linear structure analysis computer program in the ultimate limit state design of unbraced steel frames. The elastic-plastic hinge zone concept and linear elastic structural analysis computer program, SAP90, were used to simplify the nonlinear steel frame structural analysis model. Up to today, most steel structure was designed by plastic theory called the ultimate limit state design. In practice, most steel structure analysis was performed by linear elastic computer program which does not take into account of inelastic behavior nor the calculation of the ultimate strength. A modified analysis approach is introduced, and its design implications are discussed. The results obtained from the modified approach was presented and compared with both experimental data and inelastic structural analysis computer program "DRAIN-2DX" with regard to the ultimate strengths and the lateral displacements of unbraced steel frames.