Collapse mechanisms of multi-story steel-framed modular structures under fire scenarios

Abstract

Modular building is an innovative construction method and imposes unique assembly requirements. Modular structures may exhibit different global responses and unexpected resisting mechanisms under loading scenarios. However, there is limited research dealing with collapse behavior of steel-framed modular structures exposed to fire. This paper studies numerically the fire-induced collapse behavior of the modular framed steel structures. A six-story modular structure is designed. Finite element analysis is conducted to investigate global deformation, load transfer pattern, structural resisting mechanisms and collapse process of the structures exposed to fire. A series of parametric analysis is conducted to study influences of load ratio, cross-sectional dimensions of columns and fire locations. Results show that the modular structure designed based on Hong Kong building code survives against single module fire, but collapses during traveling fire. The overturning action, bracing effect and double-beam system are developed under fire scenarios. A geometrically unstable system is developed against traveling fire. Moreover, damage spreads from the columns close to the fire compartment to those far away. The robustness of modular structures is greatly influenced by its load ratios and cross-sectional dimensions of the columns. The findings can be adopted as valuable tools for recognizing the vulnerable structural components and critical loading mechanisms of modular structure exposed to fire. A practical design method is proposed to evaluate the final collapse state of the modular structures exposed to fire with good accuracy and efficiency and this provides a practical solution for the structural engineers to process the collapse state of modular structures.