NSMR strengthening of short rc beams using activated anchorage

NSMR (Near surface mounted reinforcement) systems often provides brittle failure mechanisms as well as little ductility compared to conventional steel reinforced concrete beams. Additionally the most common failure modes occur in the concrete adherent, which means that the high capacity of the CFRP material often is left un-utilized at failure. One of the aims in the ongoing research at DTU Civil Engineering concerns anchoring of NSM CFRP reinforcement in a way that provides utilization, ductility, and controlled failure mechanisms. The work presented in this paper concerns the effect of NSMR system activation by the use of specially developed anchor blocks. The anchored NSMR rods are activated to a little tension magnitude, before curing of the adhesive. An anchored strengthening effect of approximately 45% of the reference beam was reached when using the 6mm circular rods (ANSMR-6) whereas this effect increased to 60% when using the 8mm CFRP rod (ANSMR-8) configurations. In addition, a strengthening effect of 34% was obtained, in the un-anchored NSMR configurations. The anchored configurations furthermore provided significantly increased ductility compared to the un-anchored systems, where some of the strengthened beam reached deformations identical to the reference beams.