Seismic Fragility Assessment of Regular and Irregular Special RC Moment-resisting Frames Considering Nonlinear Joint Panel Effect and Soil-Foundation-Structure Interaction

Document Type : Original Article

Authors

1 Ph.D. Student, Department of Civil Engineering, Faculty of Engineering, University of Mo-haghegh Ardabili, Ardabil, Iran.

2 Associate Professor, Department of Civil Engineering, Faculty of Engineering, University of Mohaghegh Ardabili, Ardabil, Iran.

Abstract

Accurate assessment of the seismic fragility of special reinforced concrete (RC) moment-resisting frames requires consideration of the factors influencing the nonlinear response of the structure. In the present study, a novel and unified framework for assessing the seismic fragility of such frames is developed, in which the effects of soil-foundation-structure-interaction (SFSI), nonlinear beam-to-column joint behavior, span length, and the type and vertical location of structural irregularities are simultaneously considered. For this purpose, five-story structures were designed in accordance with the seismic provisions of the Iranian codes and ACI 318-19, and the finite-element models were developed using OpenSees. Seismic performance was evaluated through incremental dynamic analysis using a suite of far-field ground-motion records selected in accordance with FEMA-P695. The maximum interstory drift ratio was adopted as the engineering demand parameter, and the fragility curves were developed based on four seismic performance levels. The results showed that lateral stiffness irregularity in the first-story had the most adverse effect on the seismic fragility of structures in both configurations. In addition, mass concentration at the first-story in short-span frames and at the third-story in long-span frames increased seismic vulnerability. Accordingly, it was observed that the effects of the type and location of irregularities depend on the geometric characteristics of the frame, and this dependency becomes more pronounced in the presence of SFSI and nonlinear beam-to-column joint behavior. Therefore, neglecting these factors in the seismic fragility assessment of special RC moment-resisting frames with various irregularity patterns may lead to inaccurate estimates of structural seismic vulnerability.

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Articles in Press, Accepted Manuscript
Available Online from 15 September 2026

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