Behaviour and strength of FRP-strengthened RC structures: a state-of-the-art review

A large wall with vertical cracks at mid-span, varying in width of up to 3 mm wide, had been declared capable of resisting a postulated seismic load. It was not straightforward to subsequently confirm, analytically, what influence the crack had on the wall’s capacity for lateral loading. It was assumed that it was likely that the horizontal reinforcement had yielded across the crack and thus the basis of the strengthening scheme was to replace it with external reinforcement in the form of CFRP plates such that flexural capacity was restored. It was known that the crack’s width was variable with temperature. CFRP plates were applied when the wall was ‘cold’ (with adjacent plant off-load) and the crack widths at their minimum value. On return to service of the plant the crack widths increased and one of the plates failed by bond failure between the adhesive and the concrete surface.