Shared CFRP activation anchoring method applied to NSMR strengthening of RC beams

The paper presents a novel strengthening system, which provide a shared carbon fiber reinforced polymer (CFRP) Near surface mounted reinforcement (NSMR) activation anchoring method. Nine T-section reinforced concrete (RC) beams were used in the testing scheme which contained both un-activated and activated strengthening configurations. The activated system applied a stress of 50% and 70% of the recommended ultimate capacity (2200 MPa) to a 8 mm CFRP rod. It was seen that, what seemed to be, the ultimate capacity of the CFRP rod (3300 MPa) was reached when using the activated anchoring method. A stable failure seemed to occur at this level with controlled cracking. The 50% activation provided IC-debonding as the ultimate failure mode, with an ultimate stress of approximately 3100 MPa. The shared activation method worked well, and no premature failures were experienced in the anchor system and adhesive interface between the CFRP NSMR system and the concrete substrate. A good correlation was found in the comparison of theory and test results, where following four stages were investigated: 1) initial strain of the activated NSMR CFRP bar, 2) transition zone between the un-cracked and linear elastic cracked state, 3) change from linear elastic cracked state to steel yielding and finally 4) failure.