Varying Profiles of CFRP Ropes for Strengthening Concrete Beams

The efficacy of flexural strengthening of concrete beams using near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) ropes at varying profiles along the beams' opposite-side covers is investigated in this work. Seven reinforced concrete beams (150 x 250 x 1400 mm(3)) were prepared then cured until matured before later retrofitted using straight, trapezoidal, and parabolic profiles of CFRP ropes; the eighth was designated as control. Another beam was strengthened using a single trapezoidal rope (equivalent to two ropes) inserted in an internal hole (20-mm-in-diameter) along the beam's span. Use of variable instead of straight rope profiles imparted higher increases in load capacity, stiffness, and toughness of strengthened beams reaching 56, 37, and 33%, respectively, with a reduced loss in rotational ductility in the range of 7-10%. The CFRP rope with an internal trapezoidal profile of 20 degrees inclination imparts the best enhancement on structural performance. The strain induced in the CFRP ropes at failure point at (72-99%) of their ultimate strain capacity spurs adopting the present technique for practical applications. A comparison in performance between concrete beams with CFRP ropes and those with CFRP strips indicates a higher advantage of strengthening with the former composites.