Enhancing Fire Resistance: A Thermal and Structural Optimization Approach for Fire Door Frame Using Numerical Simulation

Fire resistance is a critical aspect of passive fire protection, particularly in door systems that must maintain integrity under extreme conditions. This paper presents the thermal and structural performance of a single-leaf sandwich fire door, with the goal of improving its fire resistance through numerical optimization. An initial numerical assessment identified the door frame as the thermally weakest component, guiding the subsequent optimization process. Then, a one-way coupled transient thermal–structural Finite Element Method (FEM) analysis was performed using ANSYS Mechanical to evaluate the influence of frame material, frame geometry, and insulation type and placement on the door–frame assembly when exposed to fire. Results show that the frame material plays a decisive role where aluminum alloys performed poorly, whereas wooden frames significantly reduced temperatures in both the door and frame by approximately 55% relative to the original configuration. Additional improvements were achieved by increasing frame thickness and placing rock wool within the thermal break, resulting in temperature reductions of 58.3% in the door and 57.3% in the frame. However, these thermal improvements had limited impact on structural deformation, which remained nearly unchanged.