Evaluation Of Mechanical Properties And Bearing Capacity Of Prestressed Concrete Beam And Slab Exposed To Fire

The bridge is an important part of the transport network,and provides important guarantee for safe,smooth and comfortable driving environment,which plays an important role in promoting national economic development and defense.With the increase of traffic volume,more and more vehicles with large overloaded vehicles and dangerous goods are transported,and the fire accidents are frequent,which leads to the damage of the bridge's appearance.The heavy traffic causes traffic paralysis and even the collapse of Bridges,which not only consumes a lot of financial and material resources,but also greatly affects the normal transportation.The prestressed concrete hollow slab has light weight,low cost,the characteristics of construction technology of mature and widely used.The prestressed concrete Bridges have different degrees of reduction of the original thermal parameters and mechanical parameters of concrete and steel materials under fire,resulting in the damage of bridge structure and the reduction of bearing capacity and the durability of the structure.Therefore,it is necessary to carry out the capacity assessment of the concrete Bridges of the fire,and to determine the performance of its use,so that we can propose a countermeasure.Based on the application of basic research project of transportation department--"study on fire damage mechanism and bearing capacity of highway reinforced concrete bridge",this paper uses finite element software(ABAQUS)to establish a fire bridge damage model to reveal the distribution of temperature field in concrete after fire and the influence of high temperature on the bond strength of steel and concrete.By conducting a secondary fire test of the body beam on the back of the fire,make sure that the beams are damaged in different fire conditions,and by a static load test to assess the power of the beams on the back of the fire.The main contents of this paper are as follows:(1)assess the technical status of the fire physical bridge,determine the technical status of the bridge,and put forward the measures for the disposal of fire Bridges.(2)establish the finite element analysis model of bridge fire damage,reasonably select the mechanical parameters and thermal parameters of concrete and steel,and analyze the temperature field of the beam body concrete;The temperature transfer gradient under different fire conditions is measured by the beam body fire experiment,and the internal temperature distribution of the beam body is revealed.(3)to establish the finite element analysis model of steel reinforcement and concrete bond force,and analyze the variation law of the adhesion force between steel bars and concrete under high temperature conditions;In this paper,the physical component is tested by fire experiment,and the degradation condition of the concrete and steel under different fire conditions is measured,and the influence of different fire conditions on the adhesion force is obtained.(4)to select fire back rest board for a second test,the determination of micro beam slab concrete under different working condition of fire performance and structure of the rebound value,carbonation depth and intensity index,the changes of beam and slab after fire technology condition of degradation law;At the same time,through the static load test of the beam board,the bearing capacity of the beam plate under different fire conditions is obtained,and the bearing capacity of the bridge under different fire conditions is determined.