Research On Ultimate Bearing Capacity Of Steel Plate-concrete Composite Continuous Beam After Fire

Steel plate-concrete composite continuous beams are widely used in bridge construction.However,the high temperature of fire seriously threatens the safety performance and durability of steel-concrete composite continuous beams,and even causes structural collapse and casualties,resulting in significant economic losses and adverse social impacts.Therefore,it is very important to study the ultimate bearing capacity of steel-concrete composite continuous beams after a fire.The domestic and foreign scholars’ research on bridge fire mainly focuses on the response of the structure under fire.The research of the bridge after the fire is mainly based on the appearance inspection and the analysis of repair and reinforcement methods.The research on the decay law and safety evaluation of the bridge’s bearing capacity after different fire scenarios is more The paper is based on the National Natural Science Foundation of China(51878057),the Basic Research Program of Natural Science of Shaanxi Province(2018JM5018)and the Anhui Jiaotong Group Science and Technology Project(JKKJ-2018-14).The decay law of the bearing capacity of steel-concrete composite continuous beams after a fire scene was studied.The main research work is as follows:(1)The mechanical properties of concrete and steel after fire were studied,and the characteristics of bridge fire were analyzed.A fire scene database was constructed considering the average temperature of the fire layer of the bridge structure,the longitudinal fire position,the longitudinal fire length,and the space fire position.(2)The finite element model of steel plate-concrete composite continuous beam is established,and the load-displacement curve of the structure after different fire scenarios is calculated,and the ultimate bearing capacity of the structure after different fire scenarios is obtained.The decay law of the bearing capacity of steel plate-concrete composite continuous beams with temperature changes after encountering different fire scenarios is revealed,and a formula for calculating the bearing capacity reduction of the mid-span and fulcrum sections of steel plate-concrete composite continuous beams after different fire scenarios is established.(3)Aiming at the decay law of bearing capacity of steel plate-concrete composite continuous beams after encountering different fire scenarios,a rating standard for bearing capacity damage was established.The average temperature of the fire layer of the structure during the backfire is combined with the fire location and fire length to determine the fire scene and the damage level of the bearing capacity of the bridge.Suggestions for disposal measures of steel plate-concrete composite continuous beams under different load-bearing capacity damage levels after fire are given.