Research on Shear Application of New Shear Rod Combined Structure of Immersed Tunnel
In order to improve the construction efficiency of segmental joints and the prefabrication level of immersed tunnels,and to solve the problems in existing segmental joint connection schemes,such as low utilization rate of joint sections,installation difficulties of buried waterstops,low work efficiency and poor pouring quality of shear keys,etc.,a new type of steel shear rod composite structure is proposed to replace the traditional shear key in segment joints.By carrying out single-bar and multi-bar shear experiments of the shear rod composite structure,the shear load,the relative displacement of the joint,the strain of the steel sleeve and the stress of the steel bar are measured,and the shear resistance of the shear rod is studied.Relying on the Dalian Bay submarine immersed tunnel,based on the material plastic damage constitutive model,considering the detailed structure of the segment joints,the effectiveness of the numerical simulation method is verified according to the shear experiment of the shear rod composite structure.The deformation law and failure characteristics of the horizontal and vertical shearing,bending around the horizontal and vertical axes of the segment joints were studied by numerical simulation,and a three-dimensional simulation model was further established to study the working conditions of the shear rod composite structure in Dalian Bay submarine immersed tunnel.The research shows that the failure of the shear rod composite structure is controlled by the shear failure of the shear rod,and the failure ductility characteristics are obvious.The failure load-displacement relationship of shear rods can be divided into three stages:elasticity,plastic strengthening and plastic failure.When there is a gap in the joint,the failure yield characteristics of the shear rod composite structure are obvious.The numerical results of the shear test are in good agreement with the field experimental results.Numerical experiments of segmental joints reveal that the failure process of joints under shearing and bending is complex,and all of them exhibit staged characteristics.Based on the joint damage analysis,a safety evaluation index of segmental joint displacement is proposed.The safety evaluation of the displacement index of the segment joints of the three-dimensional full-length numerical model under the control conditions is carried out.The evaluation results show that the shear rod composite structure is suitable for the Dalian Bay submarine immersed tunnel project and has good economy.
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