Numerical modeling and performance assessment of FRP-strengthened full-scale circular-hollow-section steel columns subjected to vehicle collisions

Axial load-bearing structural members often experience significant damage or failure when subjected to moving-vehicle or vessel collisions. Hollow steel tubular columns are highly vulnerable under transverse impact loading. Thus, strengthening/retrofitting of existing steel tubular columns may be required if these members are not designed to withstand expected transverse impact from transport accidents. This paper investigates the performance of full-scale circular-hollow-section (CHS) tubular columns strengthened with fiber-reinforced polymer (FRP) and subjected to vehicular impact. Initially, finite-element (FE) models of bare and FRP-strengthened CHS medium-scale specimens were developed to conduct transverse impact analysis for the model validation purpose. The impact simulation results were compared with the drop-mass impact test results and good agreements were found between the FE and experimental tests. The validated FE models were extended to full-scale bare and FRP-wrapped CHS columns. The full-column vehicle collisions were simulated using a realistic vehicle model by considering varying axial static forces and vehicle impact velocities. The results showed that strengthening with carbon-fiber-reinforced polymer (CFRP) improved the impact resistance capacity of a bare CHS column by preventing plastic hinge formation due to excessive local buckling when subjected to accidental vehicular impact. Three-layer CFRP strengthening proved to be an effective strengthening system compared with two-layer CFRP strengthening system. The effect of load eccentricity was assessed further, and it was found that CFRP strengthening contributed significantly to preventing the failure of CHS columns with varying eccentricities when subjected to credible vehicular impact events.