Research On Local Compression Performance And Bearing Capacity Calculation Formula Of Ultra High Performance Concrete

Prestressed concrete structure is widely used in the infrastructure construction of our country and plays an extremely important role.In the whole force transfer system of prestressed structure,the final force transfer path can be attributed to the force transfer between anchor plate and concrete.First of all,the pressure transmitted by the anchor plate will form vertical compression in the concrete.In addition,because the action area of the anchor plate is relatively concentrated,the higher compressive stress will cause a transverse expansion in the concrete.However,this local transverse expansion will be constrained by the outer concrete.The above deformation and constraints affect each other causing the extremely complication of the stress and deformation of concrete in anchorage zone.The application of UHPC material to the prestressed structure can light the weight and increase the structural span.However,the existence of prestress amplify the problem of local pressure in the end anchorage zone of small-size structure.In order to get a better application,it is necessary to carry out relevant experimental research on prestressed UHPC structure,which has important theoretical significance and engineering application value for the development of prestressed UHPC structure.In view of the local compression of the anchorage zone of prestressed UHPC structure,we carried out the following work:(1)Eighteen UHPC prism specimens were tested under axial local compression with steel fiber length diameter ratio,steel fiber content and local compression area ratio as basic parameters.The failure process,ultimate failure mode and load displacement relationship of the specimens were obtained,and the crack development mode was recorded.We analyzed the influence of such three parameters on the local compression performance of UHPC material,and verified working mechanism of UHPC material under local compression.(2)Through the reasonable selection of axial compression and axial tension constitutive relation of UHPC material,we established the nonlinear finite element model of UHPC local compression specimen under different parameters.The whole process nonlinear finite element analysis of the model under local compression load is carried out.The stress-strain relationship,ultimate local compression bearing capacity,failure mechanism and load deformation relationship of local compression specimen are obtained,and the results were compared and analyzed.(3)On the basis of the formula given in the code,considering the influence of steel fiber length diameter ratio,steel fiber content and local pressure area ratio,we proposed a new formula for calculating the local pressure bearing capacity of UHPC material,and compared calculated values of the formula with experimental values and the finite element numerical simulation results.