Repeated loading-unloading cycles a

Repeated loading-unloading cycles at the same displacement in-creased the relative movement between the bar and the concreteblock. And as mentioned previously, the damage of BFRP bars’surface was the primary reason of the pull-out failure. With the in-crease of the relative movement, the bar surface suffered frommore abrasion caused by the friction between the bar and concretesurfaces. This friction flattened the bar ribs and smoothed the barsurface which, in turn, reduced the mechanical interlock and thefriction components of the bond resistance, respectively. Sub-sequently, the overall bond stress decreased in second and thirdreloading cycles with same displacement. Similarly, the repeatedloading of steel bars smoothed the concrete surface and allowedthe removal of the crushed concrete from the bar path. As a result,a reduction of the bond stress in subsequent reloading cycles wasobserved.