Journal of Steel & Structure

Journal of Steel & Structure

Finite Element Modelling of Seismic Damage in a Steel Stair Ramp Using the Compression Post Separation Method

Document Type : Original Article

Authors
1 Department of Civil Engineering, Faculty of Engineering, University of Qom, Qo
2 Department of Civil Engineering, Faculty of Engineering, University of Qom, Qom, Iran
Abstract
Stairs, as critical non-structural components, play a vital role in the safe evacuation of occupants during seismic events. However, conventional design practices often neglect the seismic interaction between the stair assembly and the primary structure. This oversight can lead to the stair acting as an unintended brace, causing stress concentration and vulnerability, which ultimately may obstruct the emergency egress route. This study aims to investigate the seismic damage of a steel switchback ramp staircase within a reinforced concrete (RC) moment-resisting frame. It also evaluates the efficacy of two methods for preserving its functionality: a conventional "connected" method and a "separated" method utilizing a compression post. To this end, the Finite Element Method (FEM) was employed using ABAQUS software. A single-story RC moment-resisting frame was modeled in three different configurations. The seismic behavior of the models was evaluated using nonlinear static (Pushover) analysis under a 10 cm lateral displacement in two principal directions: parallel (X-axis) and perpendicular (Z-axis) to the stair's span. Furthermore, time-history analysis was conducted, applying displacement records derived from an analysis of the overall structural model to the modeled stair frame. The analysis results indicated that the system's seismic behavior is dependent on the stair-structure interaction, particularly in the direction parallel to the stair stringers. In the "connected" model, a maximum increase of 9% in strength and 8% in stiffness was observed. This participation in lateral load-bearing resulted in stress concentration and the formation of plastic hinges in critical regions of the stair, such as at the stringer breaks (landings) and connections. However, the damage was not severe enough to compromise the serviceability of the stair assembly. Conversely, the "separated" method utilizing a compression post sustained significantly less damage. This approach effectively decoupled the stair assembly from the frame's lateral movement, preventing the transfer of destructive forces and maintaining the primary stair components and isolation elements within the elastic range.
Keywords
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  • Receive Date 12 October 2025
  • Revise Date 15 November 2025
  • Accept Date 05 December 2025
  • First Publish Date 05 December 2025
  • Publish Date 23 September 2025