Progressive collapse mechanisms of multi-story steel-framed modular structures under module removal scenarios

Abstract

Due to different assembly requirements and novel integration strategies, the modular structures may have undesirable loading mechanisms and distinct structural behaviors. However, there are limited data on the progressive collapse performances of modular structures, which impedes their industrial applications. This study numerically investigates the structural robustness of multi-story steel-framed modular structures against progressive collapse by using pushdown analysis. A six-story structure with five modules per floor is designed and established. The applied load, failure process and load redistribution mechanisms are studied under module removal scenarios. Parametric analyses are also conducted to investigate influences of cross-sectional dimensions of frame members, number of stories and bays, arrangements of bracings, and module removal scenarios on the robustness of the modular structures. The results show that the prototype modular structure designed with Hong Kong design code can withstand collapse under module removal scenarios. The load redistribution mechanisms among columns are significantly influenced by the overturning action and bracing effects. The ceiling beam in the lower module and the floor beam in the upper module form a double beam system. The column section, beam section, arrangement of bracings and number of stories significantly influence the robustness of the modular structure. Finally, a design method based on buckling load equation for columns is proposed to estimate the progressive collapse resisting capacity of modular structures with good accuracy and efficiency.