Ductility-based strength reduction factor for pulse-like and non-pulse-like ground motions

Document Type : Research Article

Authors

Faculty of Civil Engineering, Tabriz University of Technology, Tabriz, Iran

Abstract

Reduction in forces, which results in inelastic deformations, is controlled by a coefficient called the strength reduction factor (R_µ). In the vicinity of active faults, ground motions are influenced by forward directivity and fling step (characterized by permanent ground displacement) effects. Previous studies have not addressed the R_µ factor considering the influence of fling step and non-pulse-like near-fault ground motion records. This paper attempts to evaluate the strength reduction factor for single-degree-of-freedom (SDOF) systems subjected to 78 pulse-like and non-pulse-like near-fault and far-fault ground motions recorded on the site classes C and D. The influence of the period of vibration, pulse period, and ductility level was studied in this paper. Moreover, in order to investigate the effect of cyclic deterioration, the modified Ibarra-Medina-Krawinkler (IMK) deterioration model with bilinear hysteretic behavior was employed. Finally, equations were proposed to obtain R_µ for different types of earthquakes. The results indicate that R_µ is strongly influenced by the period of vibration, ductility level, and cyclic deterioration. The results also show that the existing equations for calculating R_µ which are based on far-fault ground motions, can not be used for pulse-type near-fault records. Especially, for near-fault ground motions with fling step effect, applying the existing equations makes the design unsafe.

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AUT Journal of Civil Engineering
Volume 9, Issue 4
in progress
December 2025

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