Document Type : Structural Earthquake Engineering
International Institute of Earthquake Engineering and Seismology (IIEES)
Floor response modification factor (R) under near-field strong ground motions (SGMs) with directivity pulses are proposed in this paper. The R factor is defined as the floor response spectrum (FRS) for linear elastic primary structures normalized by the FRS for an inelastic primary structure. The terms ‘elastic’ and ‘inelastic’ refer to the behavior of the supporting structure while only elastic nonstructural components (NSCs) are used in this study.Considering the lack of comprehensive study on the behavior of NSCs under near-field SGMs with directivity pulses, this study evaluates the dependence of the proposed response modification factor (R) under bunches of near-field records with wide ranges of directivity pulse periods. A statistical analysis of the peak response of NSCs supported on inelastic regular moment-resisting frame structures exposed to near-field pulse-like SGMs is presented. Peak component demands were quantified based on the FRS method with considering dynamic interaction effects. In This paper the main factors affecting the FRS caused by inelasticity in the primary structures represented by parameter R has been evaluated. The results show that FRS values at the initial modal periods of the supporting structure are reduced due to the inelastic action in the primary structures. Comparing the results with the same earthquake events without directivity pulses shows that the reduction factor in near-field pulse-like SGMs is considerably larger than R factor in far-field SGMs.