Seismic performance of high-rise steel storage racks in the down-aisle direction on soft soil

This study evaluates the seismic fragility of high-rise steel storage racks under long-distance and short-distance earthquake excitations using Incremental Dynamic Analysis (IDA). Two representative sites were selected to represent long- and short-distance earthquake scenarios. A numerical model of the high-rise rack system was developed and validated against substructure experimental results and benchmark data reported in the literature. The IDA results show that the earthquake scenario significantly influenced the seismic response of the investigated rack. Long-distance ground motions generally resulted in severe damage and collapse at lower seismic intensity levels, particularly for global deformation responses. Long-distance excitation also resulted in a more abrupt transition from severe damage to collapse, indicating a limited deformation reserve once severe damage was reached. In contrast, short-distance ground motions produced more localized damage and a more gradual progression toward collapse. In addition, serviceability assessments showed a higher susceptibility to residual misalignment under long-distance ground motions, highlighting potential risks to automated warehouse operations even at relatively low seismic intensities. Overall, the results indicate greater vulnerability of the investigated high-rise rack to long-distance ground motions in terms of global deformation, damage progression, and residual misalignment.