Damage mitigation strategies for progressive collapse of modular steel buildings following sudden corner module removal

This study evaluates gravity-induced progressive collapse performance and damage mitigation strategies in modular steel buildings (MSBs) A typical three-dimensional six-story structure was modeled and analyzed using the finite element method, focusing on the instantaneous removal of a corner module. The study includes a parametric evaluation of the influence of beam moment capacity on progressive collapse and investigates the effect of using concrete as an infill for square hollow section columns. Additionally, the effectiveness of short K-shaped braces in limiting gravity-induced collapse was assessed. A response/damage index (DI) was proposed to quantify the overall structural response. The findings indicate that semirigid beam-column connections outperform fully rigid connections. Both concrete-filled columns and K-shaped braces mitigate structural damage, with K-shaped braces proving more effective in preventing collapse. Although increasing the beam moment-resisting capacity reduced the DI, improvements were marginal beyond 50% of the fully rigid connection capacity. Higher beam moment capacities reduced local vertical displacement at the corner joint but led to undesirable lateral deformations. Reducing beam rigidity/capacity by 25% mitigated global structural deformations. The optimal beam moment capacity was identified as 75% of the total section capacity when using concrete-filled columns. K-shaped braces applied at the column midpoint entirely prevented progressive gravity-induced collapse and no lateral deformations were observed in braced structures with fully rigid beam-column connections, unlike unbraced structures. Concrete-filled columns offer a cost-effective solution for preliminary production of MSBs, while K-shaped braces are suitable for retrofitting existing buildings. Further research is necessary to address other parameters influencing the mitigation of progressive collapse in MSBs.