Structural performance of modular buildings subjected to fire

Modular construction is increasingly adopted for mid to high-rise buildings due to its cost, speed and sustainability benefits, making fire safety a critical concern. However, research on composite modular structures under fire remains limited. This study investigates the fire-induced structural performance of a composite modular building with concrete-filled steel tubular (CFST) columns. Validation was conducted at both the component and system levels. A full building model was developed and analysed using SAFIR, a finite element-based software for thermal-structural analysis. A parametric analysis was then performed to explore the effects of fire curves, fire locations, multi-compartment fire spread and vertical spread to the upper module’s floor beams. Results show that the modular building exhibited good overall fire resistance, primarily due to the presence of CFST columns and system redundancy. Corner fires trigger earlier failure due to reduced restraint, while lower-floor fire causes earlier failure due to higher loads. Multi-compartment and vertical fire spread increase vulnerability by raising force demands on fire-exposed and adjacent members. The findings underscore the need for system-level modelling, as isolated analyses miss complex redistribution and failure mechanisms. • Fire behaviour of a composite modular building is numerically investigated. • Validation is performed at both component and system levels. • Good overall fire resistance is achieved due to CFST columns and redundancy. • Corner and lower-floor fires cause earlier failure due to restraint and loads. • Multi-compartment fire spread significantly increases structural vulnerability.