Activated Ductile CFRP NSMR Strengthening

Abstract

Significant strengthening of concrete structures can be obtained when using adhesively-bonded carbon fiber-reinforced polymer (CFRP) systems. Challenges related to such strengthening methods are; however, the brittle concrete delamination failure, reduced warning, and the consequent inefficient use of the CFRP. A novel ductile near-surface mounted reinforcement (NSMR) CFRP strengthening system with a high CFRP utilization is introduced in this paper. It is hypothesized that the tailored ductile enclosure wedge (EW) end anchors, in combination with low E-modulus and high elongation adhesive, can provide significant strengthening and ductility control. Five concrete T-beams were strengthened using the novel system with a CFRP rod activation stress of approximately 980 MPa. The beam responses were compared to identical epoxy-bonded NSMR strengthened and un-strengthened beams. The linear elastic response was identical to the epoxy-bonded NSMR strengthened beam. In addition, the average deflection and yielding regimes were improved by 220% and 300% (average values), respectively, with an ultimate capacity comparable to the epoxy-bonded NSMR strengthened beam. Reproducible and predictable strengthening effect seems obtainable, where a good correlation between the results and applied theory was reached. The brittle failure modes were prevented, where concrete compression failure and frontal overload anchor failure were experienced when failure was initiated.

In Situ Concrete Bridge Strengthening Using Ductile Activated NSMR CFRP System

“…Only minor variations were seen when comparing the force development and FE simulations. Consequently, given the correlation of the responses depicted in Figure 11 combined with earlier studies [43,44] provided background for using the 60 kN design for inclusion in the anchor system.…”

“…In addition, it can be tailored to provide a desired response combined with a significant ductility fitting to the existing structure. The effectiveness of the system for strengthening purposes was demonstrated through strengthening of concrete T-section beams [44,45]. It is seen from Figure 2 that the system seemed to work as desired, and that significant ductility was gained.…”

“…"REF" represents the un-strengthened concrete beam with full ductile behavior. "PCF" represents a beam strengthened with the CFRP anchor system bonded with epoxy resin and The effectiveness of the system for strengthening purposes was demonstrated through strengthening of concrete T-section beams [44,45]. It is seen from Figure 2 that the system seemed to work as desired, and that significant ductility was gained.…”

Advanced Structural Concrete Materials in Bridges

“…Another novel method for strengthening was proposed in [13], in which carbon-fiberreinforced polymer (CFRP) was applied as a near-surface-mounted reinforcement (NSMR). The resulting system had a high ductility and, thus, an advantage over typical adhesivelybonded CFRP systems that can result in a brittle concrete delamination failure, reduced warning, and the consequent inefficient use of the CFRP.…”

Advanced Structural Concrete Materials in Bridges

“…Another novel method for strengthening was proposed in [ 13 ], in which carbon-fiber-reinforced polymer (CFRP) was applied as a near-surface-mounted reinforcement (NSMR). The resulting system had a high ductility and, thus, an advantage over typical adhesively-bonded CFRP systems that can result in a brittle concrete delamination failure, reduced warning, and the consequent inefficient use of the CFRP.…”