Investigation of the Seismic Responses of Base isolated Buildings Under the Influence of Near field Round Motions

Document Type : Research Article


Department of Civil Engineering, Sahand University of Technology, Tabriz, Iran


Due to destructive effects of near-field earthquakes on building structures, this paper attempts to investigate the seismic behavior of base-isolated building frames under the effect of near-field ground motions using the non-linear time history analyses (NLTHAs). For this purpose, two steel moment-resisting medium-rise frames including 9 and 12-story ones were isolated using the lead-rubber base isolation system considering three levels of stiffness i.e. Hard (H), Normal (N) and Soft (S) isolators. Non-linear time history analyses (NLTHAs) were conducted using different sets of near-field ground motions with forward directivity, fling step and no pulse characteristics. Also, for the purpose of comparison, the NLRHA was carried out using a set of far-field ground motion records. The effect of isolator stiffness under different types of ground motions as well as the effect of pulse period on the seismic responses is scrutinized. The results showed that the change in the stiffness of isolation system from hard type to soft and moderate types (that increases the damping and period of the structure) reduces the seismic demands of the structure. Also, the story drifts of base-isolated building frames with soft isolator (more damping) are smaller than those with hard and moderate types for different values of pulse period, Tp. On the other hand, the sensitivity of the responses of base-isolated building frames with hard isolators (low damping) to pulse period is large.


Main Subjects

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