Structural fire performance of modified steel shipping containers for modular buildings

Abstract

Steel shipping containers are being modified and used for modular structures internationally. However, information on their structural performance in fire is limited. This study investigates the performance of load-bearing elements in modified shipping containers. Numerical heat transfer and structural analyses have been conducted on the 20-foot (6.096 m) intermodal ISO container with, and without, passive protection. Structural elements have complex geometries based on the container’s design, doors and practical requirements. Due to door and window openings effective lengths of members are modified to account for these. Analysis results with up to 120 min standard fire exposure are presented. Thermal gradients in container corner column are analysed and incorporated. It was identified that it is important to prevent high thermally induced forces from occurring between adjacent containers by permitting thermal expansion/slip. If passive protection boards are used, of a thickness generally required for ambient insulation requirements (10-20 mm), such structures will have adequate load-bearing capacity to resist design loads typical for multi-storey modular housing even with holes being cut in walls. It was identified that the containers have high design capacities, for carrying heavy maritime loads, typically far in excess of low-rise building requirements which is of benefit for fire design. • Technical guidance for structural fire safety for modified shipping container buildings. • Heat transfer and structural analyses of load-bearing elements investigated. • Thermal restraint from adjacent containers critical due to high axial loads induced. • Insulation may govern fire protection more than resistance for unrestrained columns. • High ambient structural capacity identified and beneficial for fire design.