Displacement Based Design Optimization of Steel Moment Frames

Abstract

Optimization of steel moment resisting frames considering the displacement as the fundamental element is the main aim of the present study. DDBD (Direct Displacement Based Design) methodology have been used for the subject purpose. This design methodology have been developed to cater for the shortcomings in the current FBD (Force Based Design) methodology that is in practice. Steel moment frame have been analyzed and designed with both FBD and DDBD methodologies. Strength constraints imposed by AISC-LRFD (American Institute of Steel Construction Load and Resistance Factor Design) and maximum allowable displacement constraints set forth by the FEMA-356 (Federal Emergency Management Agency) against the different performance levels are checked during the optimization process. Load combinations selected are in accordance with ASCE 7-05 (American Society for Civil Engineers) Numerical example presented exhibit the advantages of DDBD over FBD methodology. It was observed that the drift experienced by the structure designed according to DDBD varies more uniformly with height as compared to FBD.