Experimental and analytical investigations on the behavior of steel bolt-connected industrialized building frames under sudden pendulum impact

Flood events frequently cause severe damage to buildings, highlighting the need for structural systems capable of resisting debris impact while enabling rapid economic reconstruction. This study investigates the structural behavior of a novel steel bolt-connected industrialized building system (IBS) subjected to horizontal pendulum impact. A 1:5 scaled IBS frame was designed, fabricated, and experimentally tested under progressive pendulum impacts at distances of 0.5, 1.0, 1.5, and 2.0 m. Prior to testing, nonlinear static finite element analysis (FEA) was performed to predict stress concentrations, deformation patterns, and critical failure zones, providing guidance for the experimental program. The numerical analysis served as a qualitative design tool to support the experimental investigation. The FEA predictions agreed well with the experimentally observed crack locations at the column-footing interfaces. The steel bolt-connected IBS frame resisted a maximum horizontal impact force of 69.27 kN without global collapse. Damage was limited to localized concrete cracking and spalling at connection interfaces, while failure propagation between structural components was prevented. A damage classification (DS0–DS3) was established to correlate increasing impact intensity with progressive structural deterioration, and a displacement ductility index of 2.75 confirmed the system’s ductile response. Experimental impact forces showed good agreement with predictions from FEMA-P55, FEMA-P646, and the Aghl analytical method. The proposed steel bolt connection demonstrated effective energy dissipation, failure-arrest capability, and replaceability of damaged components while maintaining overall structural stability. These findings demonstrate the potential of the proposed IBS connection system for improving the resilience of modular structures in flood- and impact-prone regions.