In addition to general shear loading, perfobond shear connectors (PBLs) also undertake tensile uplift forces at the interfaces between steel parts and concrete components. The tensile behavior of PBLs is as significant as the shear behavior to the safety of composite bridge structures. For further evaluating the combined shear-tensile response of PBLs, it is necessary to first investigate the tensile mechanism of PBLs. Accordingly, uplift tests with three specimens under static and cyclic loading were performed to investigate the tensile behavior of PBLs. The test results showed that the breakouts of concrete blocks dominated the failure of PBLs in tension. The residual separation was negligible when the tension force was below 30 percent of the capacity. Subsequently, a detailed finite element (FE) model for the uplift test was established and validated based on the test results. The strain path inside concrete blocks was presented as a cup shape, whose dimension was relevant to the embedded depth of holes and the boundary conditions. Further, 360 FE models with varying hole diameters, perforated rebar diameters, embedded depths, and concrete strength were conducted to explain the tensile mechanism and provide databases for the theoretical analyses. The results showed that the diameter of perforated rebars was irrelevant to the tensile capacity and stiffness of PBLs, while both the tensile capacity and stiffness increased with the embedded depth and concrete strength. Besides, the tensile stiffness was also related to the hole diameter. Consequently, according to the forms of existing tensile capacity expressions for headed studs and Mindlin's solution, the equations for the tensile capacity and stiffness of PBLs were derived.

@en

To improve the shear behavior and design applicability of rubber ring perfobond connectors (RPBLs), a new rubber ring that aims to make the shear stiffness of RPBLs controllable was proposed. Firstly, the conceptual design and configuration of the new rubber rings were presented and discussed. Subsequently, finite element (FE) models for modified push-out tests of new RPBLs were established based on the validated modeling method. The initial shear stiffness is dominated by the horizontal projected contact area between hole walls and concrete dowels. γ is defined as the ratio of the horizontal projected length of hollows to the diameter of holes. The shear stiffness of new RPBLs is about 35%, 60%, and 82% of the shear stiffness of PBLs when γ equals 0.25, 0.5, and 0.75, respectively. Employing the new rubber rings with varying central angles on conventional PBLs is feasible to obtain the required stiffness for RPBLs. Further, the effects of the number of sectors, the size of side wings, the central angle of hollows, the offset angle, and the thickness of rubber rings were analysed. Based on the numerical results, the proper thickness of side wings is no larger than 2 mm. The thicker side wing could reduce the confinement effects provided by surrounding concrete on concrete dowels, resulting in a drop of the yield load of new RPBLs. The number of sectors is suggested to be no less than 6 so that the shear behavior of new RPBLs is irrelevant to the offset angle. Besides, the shear stiffness is not related to the thickness of rubber rings. To improve the yield load of RPBLs and obtain the moderate recovered stiffness, the thickness of rubber rings is recommended as 2 mm. Finally, the expression for the shear stiffness of new RPBLs was proposed.@en

Perfobond shear connectors (PBLs) are increasingly applied in steel-concrete composite structures. The out-of-plane (lateral) shear behavior of PBLs is still unknown to researchers and designers, although the connectors undertake considerable out-of-plane shear forces in some applications. Thus, push-out tests with three specimens were first conducted to investigate the lateral shear performance of PBLs and further used to validate the corresponding numerical models. The test results show that perforated rebars and concrete dowels are irrelevant to the lateral shear capacity, while they can reduce the separations and improve the ductility. Secondly, parametric FEA (finite element analysis) models for the push-out tests were built and validated based on the test results. The plastic strains in concrete mainly develop at the regions close to the fillet welds. Further, 144 extended FEA models with varying height, length, and thickness of perfobond plates and concrete compressive strength were conducted to reveal the lateral shear mechanism of PBLs. By enlarging the plate height, the lateral shear capacity slightly increases, while the shear stiffness remains as constant. The shear capacity and stiffness increase with the plate length and thickness, as well as the concrete compressive strength. Finally, based on the existing shear capacity equations for channel and angle connectors, and the theory of elastic foundation beams, the expressions for the lateral shear capacity and stiffness of PBLs were put forward. The proposed equations agree with the results of the parametric study.

@en

This paper proposed an easy-installed rubber-ring perfobond connector (RPBL) to mitigate the shear concentration of partial holes in perfobond connector (PBL) groups. Four modified push-out tests with different rubber ring thicknesses were conducted to investigate the shear behavior of RPBLs. The test results showed that specimens experienced four stages, including (i) damage of bond, (ii) shear fractures of concrete dowels, (iii) tension-shear yielding of perforated rebars, and (iv) hardening and fractures of perforated rebars. The rubber rings can significantly improve the slip capacity and drop the shear stiffness of perfobond connectors. Compared with ordinary perfobond connectors, the yield slips of specimens with 2 mm, 4 mm and 6 mm thick rubber rings increase by 304%, 509% and 745%. Further, three-dimensional nonlinear parametric FEA (finite element analysis) models of modified push-out tests were established and verified by the test results. The shear mechanism of each component and the effects of rubber ring thickness on shear behaviors were discussed. Finally, the shear yield load equations and shear capacity equations of PBL and RPBL were proposed based on the collected modified push-out test results. The calculated results agree well with the test results.@en

To evaluate the mechanical and fatigue behavior of composite suspender-girder anchorage joints in arch bridges, fatigue tests of two composite joints including pure-shear and shear-compression types were conducted and the load transfer mechanisms were evaluated based on the static loading. The experimental results indicated that both proposed composite anchorage joints presented great combined behavior. The load ratio of PBLs dropped sharply with the increase of embedded depth. Approximately 1/3 of the suspender tensile load was carried by the PBLs in the first row. Due to the redundant PBLs and large embedded depth, few loads were resisted by the bearing plate. Before and after the fatigue loading process, the shear amplitude of PBLs and the vertical stress distribution of concrete were almost consistent, indicating the favorable fatigue performance of joints. Parameterized solid nonlinear finite element models were established and verified by the test results to investigate the effect of total row number of PBLs and presence of bearing plate on the load transfer mechanics. The numerical results showed that the increase of total row number of PBLs enlarged the degree of irregularity of load distribution and reduced the load ratio of bearing plate. Finally, the load ratio formula of PBLs and bearing plate under serviceability stage was derived. The calculated load ratios were in good agreement with the test and numerical results. It was proposed that the total row numbers of PBLs were no >4 or 6 for the joints with or without bearing plate.

@en