Study On Static Performance Of UHPC Anchorage New Structures Of Expansion Device

In order to comprehensively solve the problems of serious concrete damage in the anchorage zone and the complicated field welding process of embedded parts in the bridge expansion joint,based on UHPC(ultra high performance concrete),two new types of UHPC expansion joint structures without welding on site were proposed:in anchorage new structure 1,an anchorage reinforcement was arranged on one side of the anchorage plate and short studs on the other side;in anchorage new structure 2,short studs were arranged on both sides of the anchorage plate,while long studs were added to the side of the section steel.In terms of the above two expansion joints,the anchorage plates and embedded reinforcements were staggered rather than being welded,and then the anchorage zone was poured with UHPC.The two new types of expansion joints can simplify the operation process in the construction site,and realize the visualization for the installation qual ity of the expansion device.In this paper,the local static finite element model of the bridge expansion joint structure was established according to the single-joint expansion device used in the bridge,which was based on the background of a simple suppo rted and then continuous concrete T girder bridge.The load distribution basis was provided for the static load test of expansion device.In order to explore the anchorage performance of the two new expansion joints which were compared with the traditional expansion joint,twelve expansion joint specimens for 1:1 scale were tested.As for the traditional expansion joint,the anchorage reinforcement was welded on one side of the anchorage plate and the embedded reinforcement on the other side,then the ancho rage zone was poured with SFRC(steel fiber reinforced concrete).The whole process of the test model was analyzed by ABAQUS finite element software.The main results are as follows:(1)The rigidity,strength,crack resistance and anchorage performance of the two new expansion joint specimens are significantly improved.The initial crack loads and ultimate loads of UHPC anchorage new structure 1 are 2.3 times and 1.4 times that of the traditional expansion joint,while the initial crack loads and ultimate loads of UHPC anchorage new structure 2 are 2.2 times and 2.3 times that of the traditional expansion joint.(2)When UHPC is used in the anchorage zone,the surface cracks are relatively concentrated,small and thin,but scattered,numerous and wide crack s on the SFRC surface.Comparing the bending and tensile properties of the two materials,the ultimate bending strength of UHPC is 4.86 times that of SFRC,and it had good ductility after cracking.(3)For UHPC anchorage new structure 1,the bond anchorage capacity of UHPC to expansion device is relatively more than the ultimate bearing capacity of weld fracture.When the anchorage performance of the concrete is reliable for the expansion device,the weld fracture will occur to the specimen,and whether the anchorage plate is installed eccentrically or not has little effect on the structural stress.(4)For UHPC anchorage new structure 2,the pull-out resistance of the lateral long studs of the section steel strengthens the connection between the expansion device and UHPC,effectively limits the development of the interface separation displacement under the load,significantly reduces the strain of the anchorage plate,and improves the stress at the weld position,and has higher carrying capacity.The comparative study shows that the two new types of expansion joint structures have the advantages of convenient construction,without welding on site and high installation tolerance,while they improve the mechanical performance and anchorage performance as well,which provides a reference for the design of bridge expansion joint.(5)Based on the static test and the single-joint expansion device of the background bridge,the local static finite element model of the expansion joint with the new structure 1 anchorage zone of UHPC was established.The stress under the wheel load at different positions of the expansion joint structure was analyzed: when the wheel passes through the section steel,the interface displacement and weld stress increase increase at first,then stabilize at a certain section and then decrease;the interface displacement and weld stress increase with the expansion joint,which further verifies the feasibility of applying the new UHPC anchorage structure to the actual expansion joint structure.