Study on Structural Characteristics of Corrugated Steel Utility Tunnels under Fire Cases

In order to provide reference data for the fire protection design of corrugated steel utility tunnels, the damage and deformation laws of a corrugated steel utility tunnel under fire were studied. Based on FDS software, the fire dynamic model of the power compartment of the circular corrugated steel utility tunnel was established, and the temperature evolution of the compartment in the case when the fire extinguishing system fails was obtained. The results show that when the cable fire occurs, the fire spreads upward rapidly, and the maximum temperature can reach 1000 ℃. And the fire can last for 20~25 min. On this basis, the general finite element software ABAQUS is used to establish the thermal-mechanical coupled model of corrugated steel utility tunnel. The temperature boundary obtained by FDS simulation is input, and the influence of temperature on various material properties of corrugated steel is considered comprehensively. The structural mechanical properties of corrugated steel utility tunnel under fire are simulated. The results show that the temperature of corrugated steel increases rapidly, and the elastic modulus and strength decrease accordingly. When the fire continues to burn for 4~5 min, the corner of the inner ground and the middle partition wall of the power compartment of the utility tunnel will yield first. At about 7 minutes, the bearing capacity of the steel structure decreases rapidly, and then the deformation of the steel structure developed rapidly until it was completely destroyed Especially, the horizontal displacement of the tunnel waist was large. Along with the yield failure of lining structure, the pavement above the utility tunnel also appears large settlement displacement.