University of Qom Civil Infrastructure Researches 2783-140X 11 2 2025 12 22 Numerical Evaluation of the Seismic Performance of a Concrete Staircase Isolated with Compression Struts Numerical Evaluation of the Seismic Performance of a Concrete Staircase Isolated with Compression Struts 171 183 3969 10.22091/cer.2025.13975.1655 FA Mohammad Chavoshi Department of Civil Engineering, Faculty of Engineering, University of Qom, Qom, Iran 0009-0002-7204-2763 Ehsan Dehghani Department of Civil Engineering, Faculty of Engineering, University of Qom, Qom, Iran 0000-0002-7030-5948 Shakiba Kamali Department of Civil Engineering, Faculty of Engineering, University of Qom, Qom, Iran 0009-0000-9905-2414 Journal Article 2025 09 28 The reinforced concrete stair system, as a critical component of a safe egress path in buildings, has shown considerable vulnerability during past earthquakes. Despite the widespread use of seismic separation techniques, their effectiveness requires careful evaluation. The objective of this study is to numerically assess the performance and failure mechanisms of a commonly used separation method—namely, the use of compression struts in reinforced concrete moment-resisting frames. To this end, four finite element models were developed: a bare frame (baseline), a fully connected stair–frame system, and two separated configurations using compression struts (one with a continuous flight and another with the flights separated at the mid-landing). These models were subjected to nonlinear static analysis in ABAQUS. The results indicate that the commonly used configuration with continuous flights is ineffective in reducing stiffness and seismic interaction with the main structure. This model exhibits similar behavior to the fully connected stair system, with plastic hinges forming in the stair flights. In contrast, separating the flights at the mid-landing eliminates damage in the flights but concentrates it within the compression struts, which may still compromise the safety of the egress path. This study highlights the inherent limitations of the compression-strut separation method and emphasizes the necessity of complete flight separation at the mid-landing as a design requirement. The reinforced concrete stair system, as a critical component of a safe egress path in buildings, has shown considerable vulnerability during past earthquakes. Despite the widespread use of seismic separation techniques, their effectiveness requires careful evaluation. The objective of this study is to numerically assess the performance and failure mechanisms of a commonly used separation method—namely, the use of compression struts in reinforced concrete moment-resisting frames. To this end, four finite element models were developed: a bare frame (baseline), a fully connected stair–frame system, and two separated configurations using compression struts (one with a continuous flight and another with the flights separated at the mid-landing). These models were subjected to nonlinear static analysis in ABAQUS. The results indicate that the commonly used configuration with continuous flights is ineffective in reducing stiffness and seismic interaction with the main structure. This model exhibits similar behavior to the fully connected stair system, with plastic hinges forming in the stair flights. In contrast, separating the flights at the mid-landing eliminates damage in the flights but concentrates it within the compression struts, which may still compromise the safety of the egress path. This study highlights the inherent limitations of the compression-strut separation method and emphasizes the necessity of complete flight separation at the mid-landing as a design requirement. https://cer.qom.ac.ir/article_3969_941141ffcdb9ca1b2662f6b1d839271a.pdf