On The Mechanical Behavior Of The UHPC Diamond Wet Joint Beam With T-shaped Strip

Prefabricated concrete bridges are widely used because of their convenient construction and excellent mechanical behaviors.Compared with the cast in place bridge,the biggest difference is the joint between the segments,the concrete interface of the joint is separated,and its reinforcements are not continuous,so the mechanical behaviors and durability of the joint is the most important factor that affects the overall support against the load and applicable performance of the prefabricated bridge.Under the influence of external factors such as the vehicle and weathering,some early-built bridges have begun to have different degrees of damage,and their applicable performance and durability have been seriously reduced before reaching the design life,resulting in great safety hazards.UHPC joint can solve the above problem of weak joints of the prefabricated concrete bridge with its superior mechanical performences and durability.In this paper,we conducted the test of 6 UHPC beams with joints and 2 complete beams,built the analysis of Abaqus finite element model and the comparative analysis of the theoretical calculation methods of shear capacity to research the mechanical performance of the test beams.The main work and analysis results are as follows:(1)The of 3 beams is introduced,and the main test results are described.The test results show that the ultimate load of the beam with haunch rebar is slightly less than that of the complete beam,and its ductility is very good,which proves that this joint structure has excellent bending performance.The different reinforcement of the joint beam has little effect on the development of the crack,but the reserved rebar can effectively improve the ultimate load of the joint beam.(2)The test of 5 beams is completed,and their behaviors are analyzed,such as the load-displacement relationship,the cracking load,the ultimate load,their crack development and distribution,the strain of reinforcements and the strain of UHPC,etc.The test results demonstrate that the joint beam and complete beam without steel plate has finally flexural failure,and the ultimate load of the beams are similar,while the ductility of joint beam is much better than that of the complete beam,which proves that this joint structure has excellent shear performance.With the increase of shear span,the ductility gradually increases,and the ultimate load decreases.The failure mode of the UHPC beam with joint is different from ordinary concrete beams: when the shear span ratio is in 2.09,3.14,the shear compression failure occurs;when the shear cross ratio is 1.41,the diagonal compression failure occurs.(3)Using the CECS38:2004 recommended method,UHPC SETRA-AFGC 2016 recommended method,the upper bound theory of soil plasticity,the modified compression field theory,truss-arch model to calculate the above test beams.The results show that the above methods can all predict the shear capacity of the UHPC diamond wet joint beam with T-shaped strip.The results of the CECS38: 2004 recommended method and the modified compression field theory are slightly higher than the experimental values,while the results of the UHPC SETRA-AFGC 2016 recommended method,the upper bound theory of soil plasticity and truss-arch model are slightly lower than the experimental values,which has a certain safety margin.The discreteness of the upper bound theory of soil plasticity and truss-arch model is greater,and the discreteness of the modified compression field theory is smallest.In general,the modified compression field theory can predict the shear capacity the best.It can also be seen that the calculation value is much smaller when the shear span ratio is bigger than 3;the calculation value is much larger when the shear span ratio is smaller than 1.5;when the shear span ratio is 1.5～3,the calculation value is in good agreement with the experimental value.(4)The Abaqus is used to establish the finite element model of the test beams.The model is loaded with forced displacement to simulate the whole test process.The concrete plastic strain cloud maps and load-displacement curves are obtained.It can be seen that simulation results and test results are in good agreement,indicating that the selected material parameters,interface contact parameters and other parameters are accurate,which can provide a good reference for design and engineering applications.