Flexural strengthening of reinforced concrete beams using externally bonded FRP laminates prestressed with a new method

Paper in proceeding, 2017

This paper presents a new method and a device for applying prestressed carbon fiber reinforced polymer (CFRP) laminates to flexural structural members without the need for mechanical anchorage of the laminates. An experimental test was conducted aiming to verify the feasibility of the stepwise prestressing method and investigate the flexural behavior of beams strengthened with passive (non-prestressed) CFRP and prestressed CFRP, respectively. Three RC beams with 4.2-meter-span were tested under four-point bending--one beam not strengthened as the control group, one with EB passive (non-prestressed) CFRP, and one with EB prestressed CFRP using the new prestressing technique. The strain values monitored during prestressing process demonstrated that a gradually decreasing prestressing force profile towards the CFRP ends was achieved by using this new prestressing method which eliminated the need for mechanical anchorage at laminate ends. The test results from four-point bending also revealed that using prestressed CFRP led to higher flexural stiffness, postponed yielding load, increased ultimate load bearing capacity, higher utilization of CFRP material tensile strength and reduced crack width.