SEISMIC PERFORMANCE EVALUATION OF STRUCTURES CONSIDERING THE COMBINATION OF MODAL LATERAL FORCES FOR PUSHOVER ANALYSIS

The structural vibration induced by earthquakes is contributed by all modal responses. In the present study, a pushover analysis procedure was developed by considering the combination of modal lateral forces based on existing researches. Using the modal contribution factor to weigh the relative participation of each mode and considering the direction of modal forces, lateral force patterns were constructed based on the combination of modal forces,and the envelope of all load patterns was used as the seismic response. For the cases of 5-story and 12-story moment resisting frames, the capacity curves of structures and floor lateral displacement profiles were obtained. Using energy approach and inelastic response spectrum to construct the capacity curve and demand curve of structures, respectively, the paper assessed and compared the inter-story drift ratio and floor lateral displacements. The results indicate that capacity curves were jointly determined by four load patterns while the seismic response for performance point was determined by two load patterns. It also demonstrates that the present approach can predict the seismic response effectively and achieves a better result than common lateral patterns.