| Ultra High Performance Concrete(UHPC)has been widely studied and paid attention to by scholars in the bridge field because of its high compressive and tensile strengths and better durability.As an important form of segmental connection and weak location of force in segmental construction bridges,the keyed epoxy joint has an important influence on the overall force of the bridge,especially the shear performance.However,there is a serious lack of research on the shear performance of UHPC keyed epoxy joints,and the test data on the shear performance of UHPC keyed epoxy joints are quite limited,and the effects of important parameters such as steel fiber content,keyed size,and the shear reduction effect of multi-keyed epoxy joints have not been studied.For this reason,this paper will focus on the experimental research,finite element simulation and theoretical analysis of the direct shear performance of UHPC single and multi-keyed epoxy joints and the reduction factor of multi-keyed epoxy joints.The main work and results are as follows.(1)UHPC keyed epoxy joint shear performance testThe direct shear tests of 22 UHPC epoxy joints were carried out to study the effects of joint type,joint configuration,steel fiber content,keyed depth to height ratio,lateral prestress and number of keys on the direct shear performance of UHPC key joints.The results show that:the increase of steel fiber content can improve the ultimate shear load and ductility of the keyed epoxy joints,and the increase of steel fiber content is more significant from 1%to 2%;the UHPC keyed epoxy joints have higher shear load capacity when the keyed depth to height ratio D/H is 0.5;the damage of UHPC flat and single keyed epoxy joints is direct shear damage,while the direct shear damage of multi-keyed epoxy joints has synchronous and stepwise shear damage.Shear damage in two modes(multi-keyed epoxy dry joint damage for step-by-step shear damage);step-by-step shear damage of UHPC multi-keyed epoxy joint ductility is better,its top and bottom key teeth shear damage generally before the middle key,step-by-step shear damage of multi-keyed epoxy joints relative to single key joints there is a certain shear reduction effect;flat keyed epoxy joint specimens of shear damage basically only experienced the elastic stage,that is,after cracking Soon after the rapid destruction,the shear damage of the keyed epoxy joint specimen force process includes elastic force,shear cracking,ductile force(some specimens are not)and residual force and other stages.(2)Finite element shear performance analysis of UHPC keyed jointsThe full simulation of UHPC epoxy joint test was carried out by the finite element software Abaqus,and the simulated shear capacity was in good agreement with the test value.The average ratios of the calculated values to the tested values were 1.05,1.00 and 0.97 for flat,single and multi-keyed joints,respectively,with standard deviations of 0.04,0.05 and 0.07.On this basis,the effects of parameters such as joint configuration,steel fiber content,keyed depth to height ratio,lateral prestress and number of key on the shear performance of the joints were analyzed.The results show that the final damage is sheared at the root of the key,regardless of whether the joint is a single keyed epoxy joint or a multi keyed epoxy joint.The shear capacity and elastic stiffness of the keyed epoxy joint increase with the increase of lateral stress and the number of key.With the increase of the number of key,the multi-keyed epoxy reduction factor decreases gradually,and the average ratio of the multi-keyed epoxy reduction factor is 0.75.(3)Calculation model of shear capacity of UHPC keyed epoxy jointsThe shear reduction coefficient and shear capacity calculation method of UHPC keyed epoxy joints were studied.The test data of the existing RPC and UHPC keyed epoxy joints were counted,and the more widely used formulas for calculating the shear capacity of joints were listed for comparison.multi-keyed epoxy joint shear capacity formula based on the improved UHPC will be verified with the existing UHPC test data.The results show that the average ratios of the theoretical and experimental values of UHPC multi-keyed epoxy joints in this paper,Gopal test and Zhengfan test are 0.99,1.08 and 0.90,respectively,and the standard deviations are 0.08,0.14 and 0.20,respectively,which show that the formula has good applicability. |
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