Thermal-mechanical response and load-bearing capacity of large-span linings exposed to high temperatures

Large-span tunnel linings safety would decrease rapidly exposed to fire due to the section form. The three-dimensional finite element model, including the transient thermal strain, was developed based on ABAQUS software in the work. The accuracy of the model was verified through existing tests. This model was then employed to investigate the thermal-mechanical response of the linings exposed to fire. The results shown the deformation and internal of the large-span lining was significantly greater than that of the small-span lining when exposed to fire, especially on the side wall. Then three regions of stresses distribution for concrete along the lining depth with time were found. Besides, the stresses of outer reinforcement were shown to be from compressive to tensile after fire, and they increased gradually with time, whereas the inner reinforcement would be yield after half an hour of fire exposure. Finally, the residual load-bearing capacity of the large-span lining with time was theoretically studied. It was shown to decrease to 16.2 % after 6 h of fire exposure from the initial 83.4 %. •The transient creep strain was developed in the FE program.•The mechanical performances of different spans for tunnel linings were investigated.•The influence mechanism of concrete and reinforcement stresses of linings exposed to fire with time has been analyzed.•A method of residual bearing capacity design was proposed.