| In ordinary steel-UHPC lightweight composite deck structures,the UHPC layer thickness is generally 45-60mm and the UHPC layer and the steel plate are generally connected by 13 X 35mm(diameter X height)short headed studs.The super span bridge is extremely sensitive to self-weight,so in order to reduce the weight of structures,it is necessary to further reduce the thickness of UHPC layer(such as reducing the height to 35mm)in the light-weight composite deck structure.However,the conventional shear connector is difficult to meet its thickness requirements.Hence,the author's project group proposed a new type of shear connector:which is made by partially welding the rebars mesh on the surface of steel deck and forms the welded rebar mesh(hereinafter referred to as welded shear-resistant connectors).It can resist the shear and uplift force between orthotropic steel deck and UHPC layer.In this paper,the research object is to investigate static and fatigue interfacial performance of the welded shear-resistant connectors in composite deck system composed of orthotropic deck and ultra-thin UHPC layer.The following works have been done:(1)The static performance of welded shear-resistant connectors is studied by conducting push-out tests.Twelve specimens with different weld lengths as well as different surface roughness were tested.The load-slip curves?failure modes and the ultimate shear bearing capacities were obtained.In addition,the finite element analysis of different weld lengths,considering two different failure models,is carried out by using ABAQUS.The experimental results indicate that the ultimate bearing capacity of the welded shear is increased with the increase of the weld length,and the interfacial bonding has no significant effect on the shear bearing capacity of the specimen but it will increase the shearing stiffness of the elastic stage,up to 50%;There are two kinds of failure modes,which are affected by the welding ratio of longitudinal rebars,are the shearing failure of weldings and pull-out of longitudinal rebars.Both of them are brittle failure.The numerical results show that by utilizing explicit analysis method,the load-slip curves obtained from FE analysis,which is based on material damage plastic theory,matched well with experimental results.(2)The fatigue performance of welded shear-resistant connectors is preliminarily studied by conducting fatigue push-out tests.The test results show that the welding shear-resistant connectors were loaded to 5 million times without fatigue damage under 80MPa nominal shear stress amplitude.With the increase of loading times,the stiffness of specimen decreases slowly.Afterwards,the specimen was sequentially loaded 2.1 million times while shear stress amplitude was increased to 96MPa,and the fatigue failure occured in the steel plate near the welded toe,while the UHPC remained intact;Based on data analysis,the dynamic slip growth rate and the curve equation of the shear stiffness attenuation coefficient of the welding shear-resistant connectors are obtained;Based on the Miner fatigue cumulative damage law,the fatigue strength under 2 million loading times of welded shear-resistant connector is 110.9MPa.(3)Based on the nominal stress method,the fatigue evaluation of the welded shear-resistant connector and the nearby steel plate is performed.Taking Runyang Yangtze River bridge as engineering background,the finite element model of segmental section is established by using ANSYS.The numerical results indicate that the two kinds of details(welded shear connector and steel deck near welding toe)meet the design requirement when the welded shear-resistant connectors are arranged by 300mm x 400mm(transverse x longitudinal). |
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