Research On High Temperature Mechanical Behavior And Structural Remaining Bearing Capacity Of Urban Highway Tunnels

Due to traffic congestion,various cities began to build road tunnels to relieve traffic pressures.Compared with other tunnels,urban road tunnels have large traffic flows,which can easily lead to accidents and subsequent fires,leading to deterioration of tunnel segment material performance.Therefore,fire is a major hidden danger affecting the safety of urban road tunnels.Therefore,it is of great significance to study the change of high-temperature mechanical behavior and the change of bearing capacity of tunnel segments during a fire.This article mainly studies the tunnel segment under high temperature from the following aspects:First of all,through the investigation of the tunnel fire experiment and simulation data,it is concluded that fire scenes are suitable for fire accidents in highway tunnels.When the fire scene is different,the distribution of the temperature field inside the tunnel segment is not the same.When choosing a fire scene,it is necessary to analyze three aspects of fire case analysis,fire test and theoretical analysis,and then obtain the temperature rise curve and key parameters of the fire scene suitable for the fire scene of the underground road tunnel in the city.Then the finite-element software abaqus is used to establish a predefined temperature field for the tunnel segment to simulate the temperature field.The temperature field distribution cloud diagram of the segment is obtained,and then the temperature field distribution of the tunnel segment is analyzed.Secondly,the high temperature mechanical behavior of the tunnel segment is analyzed based on the above temperature field simulation.The abaqus finite element analysis software was used to analyze the thermal stress temperature-displacement coupling of tunnel segments.In the analysis process,the tunnel segment is mainly studied from four aspects:First,when there is no fire,the stress map,bending moment value,internal force value and displacement cloud map of the tunnel segment are analyzed in depth;Secondly,when a fire occurs and the maximum temperature reaches 500?,the stress cloud diagram,bending moment value,internal force value and displacement cloud map of the tunnel segment are analyzed in depth;Thirdly,when a fire occurs and the maximum temperature reaches 800?,the stress cloud diagram,bending moment value,internal force value and displacement cloud map of the tunnel segment are analyzed in depth;Fourth,when a fire occurs and the maximum temperature reaches 1000?,the stress cloud diagram,bending moment value,internal force value and displacement cloud map of the tunnel segment are analyzed in depth.Through the above analysis,this paper has obtained the variation distribution of the stress of the tunnel segment,the variation distribution of the internal force value,the variation distribution of the bending moment value and the displacement change.Finally,this paper studies the change of bearing capacity of the tunnel segment at high temperature.Based on the simulation of the temperature field of the tunnel segment and the study of the mechanical behavior of the tunnel segment under fire,this paper studies the bearing capacity of the tunnel segment.Firstly,the calculation method of the residual bearing capacity of the tunnel tube at high temperature is given,and then the drawing principle of the axial force bending moment envelope diagram is summarized.Then,the damage depth of tunnel segment segments at different fire times is analyzed,and the cumulative damage depth of the tunnel segment is calculated by using the compressive strength reduction coefficient of the concrete under high temperature.Finally,the paper summarizes the cumulative damage rate of tunnel segments at different fire times.In addition,a method for preventing structural damage is given for tunnel segments in terms of fire prevention measures.