Improving Performance of the Direct Displacement Based Design Method with Improving Yield Displacement Estimation of Steel MR Frames

Abstract

Direct displacement-based design method which established by Priestley et al. is one of the best methods for performance based design of structures. In this method, the structures are designed to achieve a targeted performance displacement instead of restricting it to a story drift. One of the important parameter in direct displacement-based design method is the estimation of yield displacement based on geometric characteristics of the structure. Incorrect estimation of this parameter may result in an error in determination of ductility and finally design base shear. Assessments performed on various steel structures show differences between non-linear analysis results and those presented by direct displacement-based design Regulation. A portion of this difference relates to equations that estimate the yield displacement values. In this study it is intended to investigate the available yield displacement equation of steel structures with moment-resisting frames in direct displacement-based design by performing various non-linear static and dynamic analyses on 36 moment-resisting frames with different number of stories including 3,6,9,12,15 and 20 stories considering two different numbers of spans (3 and 6 spans). Results showed that the equation used in direct displacement-based design method, is acceptable for structures with less than six stories, while it is recommended to decrease this equation by 25% for structures taller than 6 stories.