Study On The Shear Performance Of Assembled Steel-concrete Composite Beam PSCC Connector

The assembled structure and steel-concrete combination structure can be regarded as the development trend of conventional span bridge construction.This thesis is based on the National Natural Science Foundation of China(NSFC)project "Study on the corrosion-fatigue coupling damage mechanism of post-cast UHPC-bolted connection system of assembled composite beams"(52278147),the NSFC youth project "Modeldata assimilation-based corrosion-fatigue coupling deterioration characteristics of welded weathering steel bridge node corrosion-fatigue coupled degradation characteristics"(52208182),the major science and technology program of Hainan Provincial Science and Technology Department "manufacturing and construction technology of assembled bridges in tropical islands"(ZDKJ2021048),and the key R&D program of Tibet Autonomous Region "(XZ202001ZY0054G),the group has conducted in-depth research on the structure and mechanical properties of PSCC shear connectors for assembled steelconcrete composite girder bridges.The main studies are as follows:(1)For assembled steel-concrete composite girder bridges,the PSCC shear connection structure,which is more suitable for industrial construction,was explored,meaning the connection structure C formed by the precast bridge deck P and the steel girder S through the infusion of the bond cavity concrete C.The structural details are preburied shear reinforcement in the prefabricated deck slab,welded studs and side baffles on the steel girders to form a bonding cavity,lifting the bridge deck in place on the steel girders,filling the bonding cavity with concrete,so that the shear reinforcement of the prefabricated slab and the studs on the top surface of the steel girders are connected through the bonding cavity concrete to become a whole steel-concrete combination structure.(2)Four groups of 11 PSCC connectors were designed and fabricated to launch specimens using post-infusion bond cavity material and precast debonding rate as the main parameters for investigation,and the mechanical behavior of assembled PSCC connectors under monotonic and cyclic shear loading was studied.The results show that the 30% debonding rate at the bond interface has a small effect on the shear strength of PSCC connectors;60% debonding rate has a significant effect on the shear performance of PSCC connectors,with a small reduction in shear bearing capacity and stiffness;The shear resistance of the post-infused UHPC specimens was significantly better than that of the C50 specimens,indicating that UHPC has stronger binding and gripping properties than C50 on studs.(3)The whole process of the push-out test was simulated using finite element software,and the effects of shear reinforcement diameter,bond cavity width,side baffle and interface debonding rate on the shear resistance of PSCC connectors were systematically investigated.An increase in shear reinforcement diameter was found to change the PSCC failure mode and to improve the shear resistance,but an upper limit exists;The appropriate width of the PSCC bonding cavity is proposed to be 4d(n+1)for n studs of diameter d arranged in a horizontal row;the presence of side baffles greatly reduces the stress level of the studs;PSCC connectors with less than 45% debonding at the bonding interface have less effect on shear strength.(4)PSCC connectors use UHPC as a post-infusion bonding material.When the stud shear failure,UHPC no crushing traces,specimen shear bearing capacity mainly depends on the stud shear strength,propose a formula for calculating the shear bearing capacity based on the shear failure of studs.When the PSCC connector is shear reinforcement shear failure,the calculation formula of shear bearing capacity based on shear reinforcement failure is proposed.For the project engineering bridges,the PSCC connectors were designed and verified based on the calculation equations in this paper.