Response of Hollow Steel Structure Moment‐Resisting Frame Subjected to Post‐Earthquake Fire Loading

This study investigates the performance of a 10‐storey hollow steel moment‐resisting frame (MRF) under post‐earthquake fire (PEF) conditions using finite element modelling based on Eurocode provisions. Seismic response was modelled using a response spectrum analysis (peak ground acceleration [PGA] = 0.36 g), while fire was simulated via the ISO 834 standard curve. Maximum inter‐storey drift ratio (IDR) during the earthquake reached 0.0049, with a top displacement of 78.98 mm. Thermal analysis revealed that the critical column and beam temperatures reached 637.3°C at 26.46 min and 770.6°C at 35.63 min, respectively, marking their failure points. Compared to standalone fire scenarios, PEF exposure reduced time‐to‐failure by 40% for columns and 60% for beams, indicating significant structural vulnerability due to prior seismic damage. Vertical temperature gradients showed a progressive increase of 19°C from the 2 nd to the 10 th floor. Storey displacement increased by 14%, with peak vertical deflection on the top floor. Fire insulation design using gypsum board and spray coating demonstrated improved fire resistance, achieving 64.24 and 61.74 min with 15 and 10 mm thicknesses, respectively. Critical members were identified as the first‐storey inner columns and the ninth‐storey corner beams. The study confirms that seismic‐induced residual drifts and insulation degradation significantly reduce structural fire resistance, necessitating an integrated multi‐hazard design approach. These results emphasise the urgency of incorporating PEF scenarios in high‐rise steel design and demonstrate the effectiveness of passive fire protection systems in restoring performance close to original design standards.