The collapse period of degrading SDOF systems considering a broad range of structural parameters

Abstract

This paper attempts to extract a period-based pseudo IDA (PBP IDA) curve in the incremental dynamic analysis (IDA). The main focus of the paper is to study the nonlinear period and the collapse period of single degree of freedom (SDOF) systems and to produce the collapse period spectrum. The parameter, Ωcol, defined as the ratio between the period increase due to the nonlinear deformations of the system at the collapse state and the elastic period, is introduced. The IDA is implemented for SDOF systems with a wide range of periods to identify the condition under which the collapse period of the system is determined. The IDAs are performed using various sets of seismic ground motions selected based on epsilon and SaRatio as spectral shape indicators for SDOF systems with different periods. A broad range of structural parameters – ductility capacity, post-capping stiffness ratio, P-Δ effect, and system degradation is included in this investigation. To consider the hysteretic behavior, the modified Ibarra-Krawinkler deterioration model is utilized. The results indicate that all the above-mentioned parameters have a significant effect on the nonlinear period. On the other hand, the collapse period is affected by some structural parameters such as the P-Δ effect and system degradation, while the effect of the spectral shape on the collapse period is not clearly predictable.