The Modified Dynamic-Based Pushover Analysis of Steel Moment Resisting Frames

A modified dynamic-based pushover analysis (MDP) is proposed in which the demand parameters are estimated using the envelope results of two pushover analyses with a first mode and a proposed load patterns. The suggested load pattern is a dynamic-based elastic story force distribution (DSFD) which is modified with a nonlinearity modification factor (NMF) to consider the change in inertia loads due to structural softening. A linear time history analysis (L-THA) or a response spectrum analysis (RSA) can be used to construct the DSFD load pattern. The efficiency of the proposed MDP method is investigated employing the results of nonlinear time history analysis (NL-THA) as well as the MPA and MMPA procedures. For this purpose the 2-D, 9, 15 and 20-Story, SAC steel frame building models are considered for parametric studies using OpenSees program. Various comparative results indicate that the proposed MDP-THA leads to acceptable responses. The MDP-RSA has better performance than MPA and MMPA procedures especially at top stories, while it is a simpler and easier method to use. Considering the accuracy and calculation efforts, the MDP-RSA method is strongly suggested to be used in pushover analysis for practical structural design.