Performance of Orthotropic Steel Plate under Combined Fire Load and Axial Compression

The orthotropic steel plate systems have been used widely in decks of long span bridges because of their large capacity and economic advantages. Early experimental and analytical research on orthotropic steel plate systems has mainly focused on their behaviors during ambient conditions. This paper presents a detailed investigation on the axial capacity of the orthotropic steel plates under fire using a sequential thermal stress analysis framework. Temperature-dependent stress-strain relationship and thermal properties of steel have been taken into consideration in the finite element modeling. Different models and parameters such as fire model, material model, geometric imperfection, residual stress and rib wall thickness have been discussed, and their effects on the axial strength of the plate have been studied and compared. Simulation results indicate that fire has significant deteriorating effects on the plate’s axial capacity. Conventional simple fire models which assume uniform surface fire loads don’t represent the real fire scenarios, and tend to overestimate the axial capacity of the plate compared that during realistic fire scenarios. Initial imperfection and residual stress in the orthotropic steel plate has negligible effect on the axial capacity of the orthotropic steel plate system under fire conditions. Increasing the thickness of rib wall could improve the fire resistance of the plate.