The confinement of FRP wrappingchan

The confinement of FRP wrappingchanged the initial behaviour of the slip. Rteil (2007) observed a high increase in slip duringthe first5 to 10 percent of the beam‟s life (Figure 2.18)than the unwrapped beam specimens. This was explained as follows:at the start of the loading cycles, the confinement effect of FRP sheets was not fully utilized(shown from the FRP strain reading).The concrete cover was pushed away by the hoop stresses generateddue to slip increased which pushed the concrete cover outward. Due to this,FRP sheet wasunder tensile stresses and bottom concrete cover was under compressive forces. Therefore, the concrete around the steel ribs was crushed and propagated the cracks along the reinforcing steel bar towards the concrete surface,which ultimately increased the stress in the FRP sheet.Due to this,the slip behaviour showed a constant increaseup to 85 to 90 percent of the beam‟s life (Figure 2.18)due to the contribution of the FRP sheets which held the cracks from further propagation. The last 5 to 10 percent of the beam‟s life showed a dramatic increase in the slip(Rteil, 2007).