Probabilistic seismic assessment of steel gabled frames with web-tapered members under near-fault ground motions along strike-normal and strike-parallel components

Abstract

The seismic assessment of steel gabled frames (SGFs) is of great importance and a key problem in any high-seismicity region, given the enormous costs of industrial equipment and the remarkable number of individuals working in such structures. Near-fault ground motions, especially their strike-normal component that usually contain a long-period pulse in the velocity time-history, can lead to a significant demand in these structures in comparison to the far-fault ground motions. Although numerous studies have confirmed the destructive effects of near-fault ground motions on concrete and steel structures, no research has been devoted to the impact of this ground motions on steel gabled structures yet. Hence, the findings of this research can unveil novel dimensions of such structures. In this regard, in the present paper, an incremental dynamic analysis (IDA) was conducted for the first time on four SGFs with the spans of 20 m and 60 m and heights of 6 m and 12 m using far-fault ground motions (OR set), as well as near-fault ground motions along the strike-normal and strike-parallel components (SN and SP sets, respectively). The results were presented in the form of multi-record IDA curves, summarized IDA curves, probabilistic seismic demand models (PSDMs) and probabilistic seismic demand analysis (PSDA) curves. The outcomes indicated that compared to far-fault ground motions, near-fault ground motions (especially pulse-like ones) produced significant changes on the seismic behavior of long-period SGFs, resulting in raises the changes of stiffness and demand sensitivity, reduces the dynamic capacity, enhances the data dispersion and uncertainty, and increases the mean annual frequencies (MAFs) in such structures. However, the results of PSDA analysis showed that under any type of ground motion (OR, SN and SP), short-period SGFs are more vulnerable than long-period SGFs and should be prioritized for retrofitting. Finally, the importance of combining the hazard curve of the study region with the results of IDA analysis of the structure in evaluating the seismic behavior of SGFs is highlighted.