Numerical study on mechanical behavior and ultimate bearing capacity of shield segment joints under different load conditions.

• Refined numerical model of segment joints considering complex geometric structure. • Clear insight into damage of concrete, stress of reinforcement and bolts. • Bearing capacity and deformation of joints under different load conditions. The lining of a shield tunnel consists of thousands of precast segments that are connected by bolts, resulting in many joints in the shield tunnel structure. The mechanical behaviour of segment joints, which are the most vulnerable part in structures, determine the bearing capacity and deformation characteristic of the overall tunnel structure. Therefore, it is necessary to study the stiffness, bearing capacity and deformation behaviour of joints under different load conditions. However, previous studies have mainly focused on the capacities of longitudinal joints (LJs) against bending moments, and circumferential joints (CJs) against shear forces. Actually, the interaction between segments can be much more complicated, and the joints may suffer other loads, but there have been few relevant studies on this topic. In this study, a series of three-dimensional numerical models were established to investigate the bearing capacity and deformation behaviour of the joints under different kinds of loads. The results showed that when LJs and CJs were subjected to tension or shear forces, the failure was caused by the damage of segment concrete, in other words, the mechanical properties of the concrete determined the ultimate bearing capacity of the joints. [ABSTRACT FROM AUTHOR]