Numerical Investigation of Post-Earthquake Fire Resistance of Reinforced Concrete Column

Post-earthquake fire (PEF) is a critical multi-hazard scenario that can cause severe structural degradation and collapse, even in buildings designed for modern seismic and fire codes. This study conducts a comprehensive numerical investigation of a reinforced concrete columns behaviour under seismic lateral loading and post-earthquake fire loading. We developed a validated 3D finite element (FE) model in ANSYS Mechanical to simulate coupled thermal–mechanical behaviour, incorporating nonlinear concrete damage, reinforcement yielding, and heat-dependent material properties. Experimental results reported in the literature were used for validation analyses using FEA tools such as ANSYS, and a comprehensive parametric study was subsequently carried out to examine the influence of axial load ratio (0.1–0.4), concrete cover thickness (25–50 mm), and number of fire-exposed faces (one, three, four) on PEF resistance. Results show that higher axial load ratios significantly reduce ductility and fire resistance, while more fireexposed surfaces accelerate reinforcement heating and stiffness degradation. Thicker concrete cover improves thermal protection but can reduce lateral resistance by reducing effective depth. Finite element validation results showed good agreement with experimental residual lateral load capacity, with margins of error of 4.7 parcent and 2.2 parcent for lateral load capacity and ductility ratio, respectively. Concrete cover size influenced insulation efficiency and residual strength. Compared with 35, 40, and 50mm concrete cover, a nominal 25mm concrete cover showed a 3.2 parcent, 19.1 parcent, and 59.63 parcent increase in rebar reinforcement temperature. Postearthquake fire (PEF) peak lateral load capacity and fire resistance also decreased by 8.1 parcent compared with seismic lateral loading alone. The findings highlight critical design-sensitive parameters governing PEF resistance and emphasise the need for integrated multi-hazard design approaches in structural engineering practice.