Flexure strengthening of lightweight reinforced concrete beams using carbon fibre-reinforced polymers

A series of 40 lightweight reinforced concrete (LWRC) beams of 1400mm length and a rectangular cross section of 150x200mm were cast, strengthened and then tested under four-point bending test to study the effectiveness of using externally applied carbon fibre-reinforced polymer (CFRP) composites as a method of increasing the flexural strength of under-reinforced LWRC beams. Parameters investigated include reinforcement ratio, ; =0.55(b) and =0.27(b), CFRP sheet length; 600, 800 and 1000mm, CFRP sheet width; beam width and half-beam width. Three types of strengthening schemes were used: jacketing covers the beam from bottom and two sides with total width of 500mm, sheets at the tension side with width equal to beam width and sheets with width equal to half-beam width. Test results showed a limited increase in ultimate load-carrying capacity accompanied with some reduction in mid-span deflection for the strengthened beams. Among the strengthening schemes investigated, jacketing was the most effective for strength enhancement (about 41%) with respect to control beam; however, it reduced ductility significantly. An analytical model was proposed for predicting the ultimate load-carrying capacity of LWRC beams strengthened with CFRP composites.