An experimental investigation into the effect of externally bonded CFRP fabrics on the shear behaviour of reinforced concrete t-beams

The cost of assessing and strengthening deficient bridge structures has been estimated as being in excess of £4 billion for the UK and $140 billion for the US. One option for strengthening concrete slab-on-beam structures that are deficient in shear capacity is the U-wrapping of the downstand beam portion of the shear span with bonded FRP fabric. This technique is currently in use worldwide. To investigate the effectiveness of this technique and the accuracy of the existing design guidance, a series of 3-point bending tests were carried out on 360 mm and 540 mm deep reinforced concrete T-beams strengthened with externally bonded CFRP fabric. This investigation found that in some cases the CFRP 'strengthening' enhanced the shear capacity of the beams relative to nominally identical control specimens, while in other cases, an apparent reduction in shear capacity was found. This paper presents some of these counterintuitive results and discusses their implications for our understanding of strengthened beam behaviour