Study On Flexural Behavior Of UHPC Wet Joint Of Transverse Multi Beam System Bridge

In recent years,with the rapid development of China’s infrastructure,the status of assembly construction is higher and higher.At present,assembly construction has become a construction technical means used by many bridges.The wet joint used for the connection between precast bridge decks is the key and difficult point of bridge assembly construction.How to make the wet joint better transmit shear force and bending moment is a point that needs to be deeply explored.In order to simplify the internal reinforcement structure of the joint and improve the safety and durability of the joint,ultra high performance concrete(UHPC)has been applied to the wet joint of the bridge because of its excellent mechanical properties.Based on the wet joint project in the actual construction of transverse multi beam system bridge in Yao Luan section of Zheng Luan expressway,this paper explores the influence of UHPC wet joint cracking load and ultimate bearing capacity,and whether the use of UHPC wet joint can simplify the structural form of reinforcement in wet joint.Based on the strut and tie model,the bearing capacity of wet joint is calculated theoretically.The main contents and achievements of this paper are as follows:(1)This paper introduces the mix proportion of UHPC and the composition of materials in this test,prepares the UHPC needed in this test,and tests its mechanical properties.The test found that the strength of UHPC increased rapidly,and the strength reached 110MPa three days after pouring.(2)According to the actual engineering needs,a total of 12 UHPC wet joint members are designed in this paper.The width of the wet joint is 412mm.The specimens take the structural form of reinforcement,the overlapping length of reinforcement,the interface shape and the reinforcement ratio as variables,and set the integral cast-in-situ concrete slab as the control group.The test results show that UHPC will not crack in the whole test process;The bond strength between UHPC and ordinary concrete is high,and the main cracks of wet joint specimens are located under C50 precast concrete slab;The ultimate bearing capacity of all specimens is higher than or basically equal to the cast-in-situ concrete slab,and the mid span stiffness is greater than the overall cast-in-situ concrete slab;Densified reinforcement will significantly improve the ultimate bearing capacity and cracking load of wet joints.(3)The 12 specimens are divided into two groups according to whether the reinforcement in the joint is continuously overlapped or not.The continuous lap is calculated by the calculation formula of flexural capacity of rectangular normal section;The wet joint specimen with discontinuous lap is introduced into the tension compression bar model to calculate its flexural capacity.It is found from the calculation results that the test does not reach the ultimate bearing capacity of the wet joint,but the test results are higher than the section calculation results,which is consistent with the failure of the specimens in the C50 concrete precast section.