Abstract

End anchors have been shown to significantly reduce premature plate end debonding failure of plate bonded strengthened reinforced concrete (r. c.) beams. One of the main interest in designing end anchors is to determine the minimum or optimal length of end anchors for a given thickness and height of the end anchor. This paper presents experimental and numerical studies in determining those optimum lengths for steel plate and carbon fibre reinforced polymer (CFRP) laminate flexurally strengthened r. c. beams. In the experimental programme, seven r. c. beams were cast. One beam was tested in the un-strengthened condition to act as the control beam. Three beams were strengthened with steel plates and another three beams were strengthened with CFRP laminates. From each group of the strengthened beams, one beam was strengthened without any end anchor, one was end anchored using the optimum anchorage length and the last one was end anchored using an arbitrarily 200 mm anchorage length. The optimum length for the end anchor used in this study was derived from analyzing the interfacial stress diagram of the strengthened beams and was found to be approximately 100 mm. The beams were also modelled using FEM (LUSAS). The results indicate that the optimized 100 mm anchorage length plates were able to prevent premature plate end debonding failure of steel plate and CFRP laminate strengthened beams satisfactorily. It could also be seen from the results that beams with end anchors had a higher failure loads and had more ductile behaviour than the un-anchored strengthened beams. Results also show that the optimized end anchored strengthened beams had identical structural behaviour to that of the longer end anchored strengthened beams. The numerical results are able to predict the behaviour of the beams satisfactorily.

Key words: Premature debonding, end peeling, CFRP laminate, steel plate, end anchors.