A modified dynamic inelastic analysis of tall buildings considering changes of dynamic characteristics

Pushover analysis is commonly used to evaluate the inelastic ultimate capacity of structures. However, pushover analysis is carried out based on constant distributions throughout the incremental analysis, which cannot capture the variation in the acceleration profile due to inelastic behavior. For this reason, when plastic hinges form in structure, constant distributions of lateral forces cannot be used any longer. Conventional dynamic inelastic method by time-history analysis can be used for specific earthquakes to consider the changes in the distribution of lateral forces. This alternative approach, however, is not practical due to the volume of calculations required. In this study, Modified Dynamic Inelastic Analysis (MODIA) is introduced to capture a distribution proportional to changing mode shapes affected by the change of stiffness. In this method, as a structure enters into the inelastic range, the distribution of lateral forces is changed according to the mode shapes of structure. The efficiency of the proposed method is verified by comparing the results from DRAIN. A 7-story moment resisting frame and a 36-story existing structure were analysed by both methods. The comparison showed a good agreement. The story shear-drift relationship, base shear, drift, ductility and overturning moment for the structures are also evaluated.