Theoretical Analysis On The Behavior Of Steel Box Girder Bridge Under Fire Condition

Steel box girder is one of the important development directions of bridge structure system,which has the advantages of high bearing capacity,high rigidity,good torsion resistance and fast construction speed.With the rapid development of transportation,bridge fire occurs.Because the steel exposed,if fire accident occurs under the bridge(such as city overpass,bridge,railway bridge),fuel burning short time can reach a high temperature,the rapid deterioration of material properties of steel box girder,steel girder bridge will be destroyed in a very short period of time.At present,scholars at home and abroad do not study the fire resistance of steel box girder bridge,so it is of great theoretical significance and application value to carry out research in this area.The main contents of this paper include:(1)By comparing and analyzing the research results of concrete and steel at home and abroad,the material thermal parameters and constitutive relation at high temperature are determined.(2)Finite element software ABAQUS is used to establish the finite element model of simply supported steel box girder bridge at high temperature.(3)Using the above model,analysis of the bridge under different fire scenarios and different load mode,temperature distribution and deformation characteristics of steel box girder bridge sections;analysis of strength of steel and concrete,rebar diameter,the thickness of bridge deck,diaphragm distance of bridge under full span steel box girder under fire fire resistance;analysis of the effect of torsion on fire resistance performance of steel box girder bridge.(4)The fire resistance of the steel box girder bridge under the bridge is analyzed,and the main parameters affecting the fire resistance of the steel box girder bridge are determined.Based on the analysis of parameters,a simplified formula for calculating the fire resistance of the steel box girder bridge under fire is presented.