Experimental Study On Shear Transfer Behavior Of Joints Of Precast Segmental Bridges Using UHPC

Ultra-high Performance Concrete(UHPC)precast segments technology combines UHPC materials and assembly of the advantages expected for the bridge structure encountered by the lightweight,high strength and direction of the rapid development of the construction of the problem solving approach provided.But the segment seam is its weak link.According to the "short board effect",the shear resistance at the segment seam greatly affects the bearing capacity of the segment beam.Then,8 UHPC segment direct shear specimens and 9 UHPC segment oblique joint shear specimens were tested,and the effects of the number of key and normal stress on the shear performance of the specimen were analyzed and discussed.The finite element software ABAQUS establishes the corresponding finite element model and analyzes its parameters.Finally,the UHPC segment beam joint resistance formula and bending shear capacity calculation formula are proposed.1、By group 8 UHPC segment joints direct shear tests of the pressure stress,affect the performance of the shear bond by the number of teeth of the seam.At the same time,the load-displacement curve,failure form,cracking load and ultimate load of components with different parameters are obtained.The analysis results show that the failure mode of UHPC specimens is mainly brittle failure.When the normal stress is small,the failure mode is direct shear failure along the key.When the normal stress is large,the failure mode is local crushing of the key concrete.Normal stress and ultimate bearing capacity of the specimen exhibits a linear relationship increased;Shear Strength specimens polydentate 17.4% ～29.3% higher than the monodentate specimen under the same conditions.2、In order to study the effect of large normal stress on the shear resistance of segment beams,a diagonal joint specimen was designed which decomposed the vertical bearing capacity into normal pressure perpendicular to the joint and shear force parallel to the joint.The effectsof different key number and different segment seam inclination angle on bearing performance were studied through 9 groups of segment seam specimens,and the ultimate bearing capacity and failure mode of the segment seam specimens were analyzed.The analysis shows that the failure modes of the inclined joint specimens are shear failure and splitting failure,both of which show obvious brittle failure;when the inclination angle is less than 45 °,the number of key has a small effect on the bearing capacity.When it is not less than 45 °,the vertical bearing capacity of the test piece decreases as the tilt angle increases.3、The finite element software ABAQUS was used to simulate the UHPC direct shear test and diagonal shear test,and analyze the influence of different parameters on the shear performance of UHPC precast segmental beams.The analysis results show that comparing the simulation and test of the direct shear test specimen,the failure of the test specimen is brittle failure,and the load-displacement curve of the finite element simulation test specimen has an obvious slow decline process.And comparing their ultimate loads,the ultimate load of the finite element specimen is slightly larger than the ultimate load of the specimen.Simulate the oblique shear specimens.When the inclination angle of the joint is 30 °,the ultimate bearing capacity of the single-key specimen and the multi-key specimen are similar.When the specimen joint angle is 45 °and 53 °,multidentate ultimate bearing capacity significantly higher than specimens key specimen,which coincide with the experimental value.4、The calculation method of the shear bearing capacity of UHPC joints was studied.First,the existing UHPC direct shear test data was collated,and the calculation formulas of joint bearing capacity for UHPC in domestic and foreign codes were calculated and evaluated.Comparing the normative data with the experimental values,it can be found that the calculated values of the French UHPC code and DIN code are lower than the test value when the normal stress is large,and the predicted value of the JSCE code and the American AASHTO design guideline are larger than the test value when the normal stress is large.Then,based on the principle of circular molar stress and tension stress to reach critical conditions for the destruction of UHPC tensile shear capacity seamderivation formula,using the test data comparison and verification.Finally,considering the influence of the bending moment of the joint shear surface on the shear bearing capacity,the calculation formula of the bending shear capacity of the UHPC segment splicing beam and the calculation formula of the shear capacity of the inclined section with diagonal cracks are proposed.