Burning Bridges: Development of an integrated methodology to assess the thermal and structural (GMNIA) response of a bridge under fire loading using CFD and LS-DYNA

This paper details an integrated methodology for a structural reliability assessment where the thermal and structural response are considered in the same model, and benchmarks the outcomes for a case study of a 300-meter span steel arch bridge against Eurocode methods used more generally on projects. In the new framework, the fire is modelled with CFD to determine radiant heat fluxes and air temperatures, which are mapped onto the bridge geometry to determine the resulting time-varying steel temperatures and properties. The temperature-dependent structural response is then assessed in a GMNIA analysis in LS-DYNA. The method demonstrates an increase in predicted capacity for the considered critical fire scenarios compared to a Eurocode based approach. The increased performance under fire loading was also shown to be significant even after controlling for the inherent increase in capacity when comparing a Eurocode verification to a GMNIA analysis.