Residual Axial Capacity of Wide-Flange Steel Columns after Close-In Blasts: Tests and Numerical Simulations

Abstract Assessing the residual axial capacity (RAC) of structural columns is critical for determining the postblast occupancy and safety of buildings. This study presents the first experimental investigation of large-scale axial compression tests on wide-flange steel columns subjected to close-in blast loading, addressing a significant gap in current knowledge. A total of six tests were conducted: two on undamaged columns (with and without stiffeners) and four on blast-damaged columns with detonations applied along both the strong and weak axes, again with and without stiffeners. The role of stiffeners was closely examined. Axial and out-of-plane displacement responses were measured experimentally and independently validated using optical motion tracking. The experiments were complemented with numerical simulations that were performed using ANSYS LS-DYNA to replicate both the blast and subsequent axial compression phases. The simulations showed strong agreement with the experimental results in terms of damage patterns, displacement histories, and residual axial capacities. The results demonstrate that stiffeners enhance residual capacity given strong-axis blast loading but can reduce performance given weak-axis detonations due to localized pressure pocketing among the flange, web, and stiffeners. Relative to the maximum axial capacity, RAC reductions were 61.3% (with stiffeners) and 83.3% (without stiffeners) for strong-axis blasts and 63.5% (with stiffeners) and 38.7% (without stiffeners) for weak-axis blasts. These findings provide new insights into the interaction between geometric detailing and blast-induced damage for close-in detonations for the tested wide-flange column geometry and stiffener configuration. Together, the experimental and numerical results establish a validated framework for predicting the residual performance of blast-damaged steel columns and support more reliable assessments of structural integrity and building reoccupancy following close-in detonation events.