Pull-out performance of perfobond rib connectors in steel high-strength concrete composite bridge pylons

Perfobond rib connectors (PBLs) used in steel high-strength concrete composite pylons of cable-bearing bridges are subjected to considerable pull-out forces caused by the local buckling tendency of the steel panels. In order to investigate the pull-out performance of PBLs embedded in high-strength concrete, an experimental study was conducted with twelve single-hole PBL specimens constructed of concrete with a cubic compressive strength of 80 MPa. The test results indicate that the failure of shallowly embedded PBLs was dominated by the concrete breakout. Then a numerical investigation was conducted using the validated finite element method to figure out the failure mechanism of the shallowly embedded PBLs, followed by a parametric study to identify the sensible parameters concerning the pull-out resistance. The numerical results show that increasing the embedded depth, concrete strength, and rib hole diameter can increase the pull-out resistance of the PBLs with an embedded depth smaller than 140 mm. In contrast, the thickness of perforated ribs exhibits a negligible impact on the pull-out resistance. It is recommended that the transverse rebar diameter should not exceed the difference between the rib hole diameter and the maximum coarse aggregate particle size of the concrete to avoid the possible decrease in the concrete strength near the rib hole. Finally, a concrete breakout model was developed to predict the pullout resistance of PBLs shallowly embedded in high strength concrete with reasonable accuracy.