Research On Shear Behavior Of UHPC Wet Joints In Precast Segmental Bridge

Joints are the weak parts of precast segmental bridges and the overall performance of segmental precast bridges is greatly affected by the shear performance of the joints.In this paper,the push-out tests of UHPC wet joint were carried out and the influence of factors such as joint material,joint structure and interface stress on the shear performance of UHPC wet joint was studied.Based on the test results,numerical simulation and related theoretical analysis were carried out.The main research contents are as follows:(1)The shear performance tests of UHPC wet joint were carried out.The effects of UHPC age,normal stress of joint interface,joint structure type,joint material and whether reinforcement lap on shear performance and failure mode of UHPC wet joints were discussed.The influence of various parameters on the mechanical performance of UHPC wet joints was summarized.During the test,the cracking load,ultimate load,relative slip of joint interface,cracking condition and failure mode of UHPC wet joint model were observed and recorded.The failure mechanism of different types of UHPC wet joint model was analyzed.Results show that UHPC can significantly improve the shear performance of wet joints;the lapping reinforcement in the joint can effectively improve the shear performance of wet joints;the interface normal stress level is positively correlated with the cracking load of joints.(2)The interface bonding model and shear failure mechanism of three different UHPC wet joint push-out test models were analyzed.According to the mechanical characteristics of different joint models,the test results were compared and evaluated by using the existing capacity formulas,such as AASHTO recommended formula and Mohr-Coulomb criterion formula.Calculation formula and suggestion of ultimate shear capacity suitable for different UHPC wet joint structures were put forward.(3)The finite element models of UHPC wet joints with different parameters were established to simulate the mechanical behaviors of the specimens.The material nonlinearity,geometric nonlinearity and contact behavior of the joint interface were considered.The accuracy of the finite element model was verified by comparing the load slip curve,ultimate shear capacity,strain distribution and failure mode of the test and the finite element models.Finally,the application of different interface simulation methods was compared.Results show that the contact element and the cohesive force model can accurately simulate the interface behavior of various types of wet joints.