ESTIMATION OF SEISMIC STORY DRIFTS IN RC FRAME STRUCTURES SUBJECTED TO SEVERE EARTHQUAKES

Accurately predicting the maximum story drift of structures is the most important content of performance based aseismic design. However, a predicting method that is both simple and effective is currently lacked. In this work, aiming at the low storey reinforced concrete (RC) frames for which the first mode is predominant, a methodology is proposed to determine whether the structure will perform a global failure mode, by which the large dispersion in elasto-plastic analysis due to the soft-story failure mode is avoided. Then, based on a series of rational assumptions, the method to predict the maximum story drifts and the corresponding deviations of RC frames with global failure modes is proposed. The equations and analytical procedures are suggested. Finally, by comparing with the statistic results of elasto-plastic time-history analyses, the predictions using the proposed method agree well with the time-history results, both on average values and on deviations. Hence, the proposed method can be used to predict the maximum story drift of RC frames subjected to severe earthquakes.