Theoretical Analysis On The Behavior Of I-steel And Concrete Composite Beam Bridge Under Fire Condition

Steel-concrete composite beam structure has outstanding seismic performance and economic benefit, because it can give full play to material property of steel and concrete. It is one of the important development directions of bridge structural system. If fire accident occurs under the bridge(e.g, the cross-line composite beam bridge), the temperature will rise quickly due to the gasoline(or diesel) combustion. strength and stiffness of the steel beam will decrease rapidly, the failure of composite beam bridge may occur in a very short time, due to the exposure of the steel beam. Research work on the fire-resistant performance of composite beam bridge is almost in a blank at home and abroad, therefore studying on this area is of great theoretical significance and practical value.The primarily contents of this paper are as following:Based on analysis and research of current achievements on thermal and mechanical properties of concrete and steel under high temperature, thermal parameters and constitutive relationship for steel and concrete are determined.A general finite element analyzing software(ABAQUS) is utilized to establish the 3D model for â… -steel and concrete composite beam bridge simply supported at both ends, which was verified the experimental data.Then the model was used to do some analysis on the deformation of the composite beam bridge with different fire position and different load. Influences to fire-resistant performance of composite beam bridge including cross-sectional parameters, strength of steel and concrete, protection cover thickness of reinforcing bar, reinforcement diameter and strength of reinforcing bar are analyzed when whole-span is exposed to fire (beneath bridge deck).To study the fire resistance of composite beam bridge when whole-span is exposed fire (beneath bridge deck), a series of influence parameters, such as changing lane loading, section size of steel and concrete slab thickness were analyzed. Based on the parametric analysis results of plenty of parameter analysis, simplified calculation formula is put forward for fire-resistant design of composite beam bridge, and it can provide reference for the fire-resistant design of I-steel and concrete composite beam bridge simply supported at both ends.