Probabilistic Estimation of Seismic Story Drifts in Reinforced Concrete Buildings

Probabilistic techniques are of vital use in predicting the seismic story drifts of buildings, which vary due to uncertainties in the characteristics of future earthquake motions. This paper proposes a procedure for evaluating the expected mean and standard deviation of seismic story drifts of reinforced concrete buildings by considering both total and story failure mechanisms. The estimation process consists of a pushover analysis of the structure against inverted triangular forces to evaluate the most probable mechanism during earthquakes, followed by consideration of the relative reserve strengths to evaluate the probability of other mechanisms. The relative reserve strengths against story and total mechanisms are expressed by two newly defined story-safety and total-reduction factors, respectively. In this paper, the proposed procedure is verified by conducting dynamic response analyses of 9-story wall and frame structures with various storysafety and total-reduction factors using 36 records from 14 different earthquakes. The proposed procedure well predicted the mean and standard deviation of story drifts of the structures. Application to wall-frame structures is also discussed.