Numerical Simulation Analysis Of Concrete Segments And Its Joints Characteristics

As the main lining of shield tunnel,the mechanical properties of concrete segment have great influence on the whole tunnel structure.To analysis of mechanical properties of concrete segments and its joints,the finite element method and the calculation method are presented in this paper.Taking a shield interval of Beijing metro line 4 as an example,the bearing capacity of concrete segments and its joints and variation of bending stiffness are studied,the main research contents are as follows:1)In order to analyze the mechanical properties of concrete segments and its joints,the finite element method is used to simulated the bearing capacities of the concrete segments and its joints.Three-dimensional concrete segment and its joint model are established.The ultimate bearing capacity of concrete segments and its joints are studied under the action of bending moment with different axial force.The bearing capacities of concrete segment joints are also studied under the action of the positive and negative bending moments.The investigation shows that the ultimate bending moment of concrete segments and its joints increases with the increase of the axial force.The existence of joint greatly reduces the bearing capacities of the concrete segments.Ultimate bending moment of segment joint is mainly controlled by the joint bolt strength and position.2)In order to solve the problems of section design and verification of concrete segments,the computational models are proposed for designs of concrete segments with symmetrical reinforcement bars under the action of bending moments and axial forces.Based on the constitutive model of steel bars and similarity criterions of strains in beam section,the analytical expression of ultimate bearing capacity of concrete lining segments is derived.Ultimate bending moments of concrete segments calculated by analytical models agree with ones computed by FEM.The accuracy of proposed computational model is verified.3)In order to study the influences of axial forces on the bending stiffness of concrete segment joints.Based on strain energy principle,a simplified linear model of concrete is proposed.The calculation models of bending stiffness of segment joints in different stress states are derived.The bending stiffness and ultimate bearing capacity of segment joints are studied by numerical calculation and finite element simulation.The results show that the bending stiffness of concrete segment joints decreases with the increase of axial force when the bolts are yielding.The bending stiffness of concrete segment joints and the axial force approximate linear relationship when the bolts are yielding.The calculation models can accurately describe the stress of concrete and bolt at the segment joints,which can provide some suggestions for the design of segment joints.