The ultimate slip strength of a perfobond strip (called "PBL" hereafter) depends significantly on the concrete confinement conditions around PBL hole as well as concrete shear fractures at the hole. If the hole is small, the effect of concrete confinement will still more strongly appear. In this paper, focusing on the concrete confinement due to concrete cover, the ultimate slip strength of PBL with a small hole is investigated experimentally through push-out tests, in which the diameter of PBL hole is set at 30 mm and the thickness of the concrete cover is varied from 0 to 100 mm. Test results show that the concrete separates into two blocks with concrete crack parallel to the PBL plate and that the ultimate slip strength of a 50-mm-thick concrete cover is 34.4 kN, which is about 10 times of the slip strength without concrete cover (3.5 kN). Thus, it can be concluded that thicker concrete cover makes the slip strength remarkably larger, in the case of small-hole PBLs.
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