Effects of Staircase Core Configuration on the Seismic Behaviour of Reinforced Concrete Frame Structures

Abstract:

This study investigates the seismic response of reinforced concrete (RC) moment-resisting frame structures by analyzing the structural implications of integrating the staircase core. A six-story RC building, regular in plan and elevation, was adopted as the reference configuration (Model A), excluding the staircase. Three alternative models (B, C, and D) incorporated the staircase at varying plan locations to assess its influence. A comprehensive modal and response spectrum was conducted in accordance with RPA99/Version 2003 and BAEL91 design provisions. The introduction of the staircase core resulted in notable reductions in the fundamental period, emergence of torsional modes, particularly in models C and D, and significant redistributions of internal forces in both beams and columns. Short-column effects were observed in members adjacent to the staircase, raising concerns about potential brittle shear failure. The presence of the staircase core increased longitudinal and transverse reinforcement demands in critical columns, with amplification rates reaching up to 60%. These results show that the staircase plays a crucial role in modifying global stiffness, torsional response, and local demand concentrations. Neglecting the staircase core in structural modelling can lead to unconservative seismic assessments and increased vulnerability to damage or collapse under seismic excitations. The study provides an argument for its systematic inclusion in analytical models to ensure resilient and code-compliant design strategies.

• Periodical: Advanced Engineering Forum (Volume 59)
• Pages: 73-89
• DOI: https://doi.org/10.4028/p-SCQUh5
• Online since: June 2026
• Authors: Samia Louadj*, Amar Louzai, Lisa Tahraoui, Mouloud Ouanani
• Keywords: Internal Force Redistribution, Reinforced Concrete Frames, Response-Spectrum Analysis, Short-Column Effect, Staircase Core

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