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Simple models for drift estimates in framed structures during near-field earthquakes

Erdoğan, Burcu
Maximum interstory drift and the distribution of this drift along the height of the structure are the main causes of structural and nonstructural damage in frame type buildings subjected to earthquake ground motions. Estimation of maximum interstory drift ratio is a good measure of the local response of buildings. Recent earthquakes have revealed the susceptibility of the existing building stock to near-fault ground motions characterized by a large, long-duration velocity pulse. In order to find rational solutions for the destructive effects of near fault ground motions, it is necessary to determine drift demands of buildings. Practical, applicable and accurate methods that define the system behavior by means of some key parameters are needed to assess the building performances quickly instead of detailed modeling and calculations. In this study, simple equations are proposed in order for the determination of the elastic interstory drift demand produced by near fault ground motions on regular and irregular steel frame structures. The proposed equations enable the prediction of maximum elastic ground story drift ratio of shear frames and the maximum elastic ground story drift ratio and maximum elastic interstory drift ratio of steel moment resisting frames. In addition, the effects of beam to column stiffness ratio, soft story factor, stiffness distribution coefficient, beam-to-column capacity ratio, seismic force reduction factor, ratio of pulse period to fundamental period, regular story height and number of stories on elastic and inelastic interstory drift demands are investigated in detail. An equation for the ratio of maximum inelastic interstory drift ratio to maximum elastic interstory drift ratio developed for a representative case is also presented.