| Ultra High Performance Concrete(UHPC)is widely used in precast segmental bridges due to its excellent mechanical properties.There is a special structure of UHPC segment prefabricated bridges—splicing joints,which are the weak link in the force,which greatly affects the overall mechanical properties of the bridge.In order to explore the compression and shear performance of UHPC splicing joints,this thesis uses 50 UHPC segment static load tests and 25 UHPC segment repeated load tests to study the compression shear performance of the splice joints,and then analyzes the parameters of the specimens through finite element analysis.Finally,the calculation formula for the shear bearing capacity of the glued joints of UHPC segment beams is summarized through relevant data.The main research contents and conclusions are as follows:(1)Through the static load test of 50 UHPC segment joints,the effects of rigid fiber content,different joint angles and key tooth heights on the mechanical properties of the joints are studied respectively.And collect its load-displacement curve respectively,and record the failure form and ultimate bearing capacity of the specimen.The test results show that when the seam angle is small(the greater the positive pressure stress is than the shear stress),the UHPC specimens mainly undergo local compression and shear failure in the key tooth area.When the joint angle is small,the UHPC specimens mainly undergo shearing.Failure,manifested as shear failure at the root of the key tooth.Under the same condition of steel fiber content,the ultimate bearing capacity of 15 mm key tooth height is 8.76%～26.60%higher than that of 7.5mm key tooth height;when the key tooth structure is the same,the UHPC ultimate bearing capacity increases with the steel fiber content Increase and increase.When the steel fiber content is at a low level,its bearing capacity cannot be significantly improved.At the same time,when the steel fiber reaches a certain "saturation value",continue to increase the steel fiber content and its bearing capacity has not been greatly improved.;For the same type of UHPC specimens,the larger the seam angle,the smaller the compression-shear ratio and the lower the bearing capacity.(2)Through repeated load tests of 25 UHPC segment specimens,the effects of rigid fiber content,different joint angles and key tooth heights on the mechanical properties of the joints were studied separately,and the load-displacement of each specimen was recorded at the same time.Curve,failure form and bearing capacity limit.The results show that the ultimate bearing capacity of 15 mm key tooth specimens is reduced by 9.14% on average compared with static load,while the bearing capacity of 7.5mm key tooth specimens is reduced by 57.60%.The bearing capacity of 15 mm key tooth specimens under repeated loads is obvious.Better than 7.5mm key teeth.The content of steel fiber plays a vital role in the repeated load test.The higher the content of steel fiber,the higher the bearing capacity.With the change of the content of steel fiber,the bearing capacity of the specimen decreases by 53.53% from 0.5% to 3%.～9.14%.The larger the joint angle,the more obvious the bearing capacity decreases compared with the static load.(3)The UHPC static load test was simulated and calculated by ABAQUS finite element analysis,and the influence of different parameters on the shear capacity of UHPC segment precast assembled beams was simulated respectively,and the simulation results were compared with the test results.(4)Analyze the test value and the calculation method of shear resistance in national standards.The calculated value of the French UHPC and DIN standards is lower than the test value.The American AASHTO code greatly overestimates the shear bond bearing capacity,while the Japanese The specifications are in good agreement with the test results.Finally,based on the test results and the collected data,the UHPC segment shear capacity calculation formula is derived and checked. |
PDF Full Text Request