Numerical Study on the Effect of Multi-Compartment Spreading Fire Scenarios on the Fire Resistance of 3D Steel-Framed Structures

Abstract

Fire spreading across compartments or floors have been observed in realistic fires. However, structural responses in multi-compartment spreading fires are still not very clear. Unlike traditional studies focused on isolated compartment fires or uniform heating, this research simulates dynamic fire spread across compartments and evaluates the resulting structural behavior. A validated finite element model based on the full-scale travelling fire experiments was firstly developed using LS-DYNA. The effects of fire curve characteristics (short-hot, mid, long-cool), fire-source compartment location (corner, edge, center), and fire spread timing (simultaneous, delayed) were then systematically studied. Results show that early fire spread led to structural collapse within 160 min, while delayed fire spread extended structural stability beyond 600 min. Long-cool fires induced failure during the cooling phase, particularly in highly loaded central columns such as B2, which yielded at 153 min. Short-span beams formed catenary mechanisms with axial forces exceeding 2000 kN, while redistribution in adjacent columns amplified axial forces up to 2.4 times. This study provides quantified insights into internal force transfer, failure sequences, and collapse propagation under realistic fire conditions. By incorporating spatial–temporal fire dynamics in 3D, the proposed framework offers a significant advancement over prior work based on static, single-compartment scenarios, thereby informing robust performance-based fire design strategies.