Investigation Of Shear Performance Of Tie-bars And Studs In Steel Plate-concrete Composite Members

The steel plate-concrete(SC)composite structures include two steel plate,one concrete core and some shear connectors.American Westinghouse adopted SC composite structure in AP1000 nuclear containment building,which adopted two kinds of shear connectors,i.e.stud and tie-bar.Tie-bar connects two steel plates,and stud connects one steel plate.During construction,the two steel plates connecting tie-bars could be used as temporary formwork for pouring concrete,which could eliminate formwork and reduce the construction period as well as cut costs.In SC composite structure,tie-bar and stud are the important components to transfer interaction between steel plate and concrete,and the most vulnerable components.The shear capacities of tie-bar and stud subjected to cyclic loading plays an important role in seisimic performance of SC composite structures.Currently,the shear behavior of tie-bars in SC composite structure subjected to cyclic loading has not been investigated.Considering the usage of tie-bars and studs in SC composite structure,the difference of shear behavior between tie-bars and studs should be studied.The shear behavior of studs and tie-bars under monotonic and cyclic loadings were investigated through push-out tests and finite element model simulation.Meanwhile,based on the shear capacities of tie-bars subjected to cyclic loading,and the seismic behavior of SC composite beams under cyclic loading,the design method for tie-bars in SC composite cantilever beams was proposed.The main conclusions are shown in the following:(1)The push-out test about the shear behavior of tie-bars and studs using groove fillet welding under monotonic loading was carried out.The influence of diameter on the shear behavior of tie-bars and studs was investigated.The failure mode,shear-slip curves,shear skeleton stiffness curves,and ductility were compared between studs and tie-bars.The distribution of axial strain in tie-bars was analyzed.(2)The push-out test about the shear behavior of tie-bars and studs under cyclic loading was carried out.The influences of welded joint structure type and diameter on the shear behavior of tie-bars and studs were investigated.The failure mode,shear-slip curves,skeleton curves,shear effective stiffness curves,and energy dissipation were compared between studs and tie-bars.In addition,the shear behavior of tie-bars and studs under monotonic and cyclic loading were compared.(3)Based on Xue-Wierzbicki fracture criterion and CVGM fracture criterion,the fracture criterion for predicting ultra-low cycle fatigue of metal under cyclic loading was developed.The refined finite element models of push-out specimens with studs and tie-bars was developed by using ABAQUS finite element software,which were used to simulate the shear behavior of studs and tie-bars in monotonic and cyclic loading conditions.According to the propsed fracture criterion and finite element model,the influence of concrete strength,tie-bar and stud strength,tie-bar and stud diameter,and aixial tension on the ultimate shear capacities of tie-bars and studs were investigated.Based on the puths-out test results and simulation results,the formulas for ultimate shear capacities of studs and tie-bars under cyclic loading were developed.(4)According to the simulation results of out-of-plane behavior of SC composite beams under monotonic and cyclic loading,the interfacial shear force distribution of tie-bars was analyzed at different loading phases.According to the existing codes about the out-of-plane bend moment and shear capacity of SC composite structure,the interfacial shear force distribution of tie-bars,and the ultimate shear capacities of tie-bars under cyclic loading,the design method for tie-bars in SC composite cantilever beams subjected to out-of-plane cyclic loading was developed.