Performance investigation of highway bridge pier columns under the sequential effects of fire followed by vehicle collision and subsequent air blast: A numerical investigation

Historically, it has been demonstrated that bridges may be vulnerable to fire, and in many circumstances, resulting damage might not be apparent, and bridges could maintain acceptable levels of serviceability. In the absence of proven assessment tools and given the limited research that addresses bridge fire, research that better understands response and strives to improve highway bridge resiliency to fire is needed. Extending the work carried out during an earlier research stage, the present study focused on investigating performance of bridge pier columns that survive fire under coupled vehicle collision and air blast. Numerical models of single reinforced concrete columns supported by a pile foundation system and surrounded by air and soil volumes were created using LS-DYNA. As explicit solvers such as those available in LS-DYNA are infrequently used for fire analysis, an indirect two-step approach that integrated heat transfer and structural analyses was developed and validated against published fire-induced impact and blast test results. A parametric study that examined the effects of various fire exposure conditions and column diameters was completed. Performance was comprehensively assessed based on various structural response parameters, which included failure modes, lateral displacement, residual axial capacities, and shear demand-to-capacity ratios. Column damage was then categorized into six levels to qualitatively assess column performance under the aforementioned multi-hazards. The developed modeling approach was shown to be viable, and results indicated that larger column diameters could potentially remain in service in their final damage states after being repaired for fire durations of less than 120 min.