Numerical simulations of bonded post-tensioned concrete bridge girders under hydrocarbon fire

A sequentially coupled 3-step modelling approach is adopted to study the failure mechanism of bonded post-tensioned concrete bridges under hydrocarbon fire. Firstly, a furnace fire model was built and solved. The adiabatic surface temperature (AST) obtained from fire modelling was then applied on the surfaces of the finite element model of the structure to determine the inner temperature field. Finally, the structural response under full range of fire was analysed based on this temperature field. It is noting that the bonding layer between strand and surround grout was modelled at both grouting and fire stages. Special attention was paid to the establishment of the furnace fire model. The calibrated models can be used for estimating the results of new fire tests. The numerical models were validated by fire tests on six scaled bridge beams. Results shows that the fire resistance of prestressed concrete structures depends largely on the strand temperature. In comparison, the box-section bridge beams have better fire resistance than the tee-section bridge beams.