Strengthening of Reinforced Concrete Beams using Anchored Near Surface Mounted Bars

Abstract

<p>To delay the onset of delamination and to ensure the CFRP continues to supply strength after initial delamination of reinforced concrete beams strengthened with near surface mounted CFRP bars, a new mechanical anchoring system was developed and tested in this investigation. The anchors were integrally connected to the CFRP bars and extracted from a proprietary product commonly known as NEFMAC. The anchored bars were installed by cutting grooves into the concrete cover, boring holes at anchor locations and using epoxy to bond the strengthening bars to the groove surfaces.<br /> <br /> A total of seven simply-supported reinforced concrete beams were tested in fourpoint bending to study the effectiveness of the proposed anchoring system. One beam served as a control specimen, two beams were strengthened with unanchored near surface mounted bars and the remaining four beams were strengthened with the anchored bars. As an exploratory study two of the four anchored beams were also strengthened with anchored near surface mounted CFRP transverse bars to determine if the system is an acceptable substitute for internal steel stirrups.<br /> <br /> Results of this study reveal that the anchors can delay delamination and after initial delamination, the anchored beams continued to carry the applied load whereas the unanchored beams lost strength immediately following concrete cover delamination. Although there was not a significant gain in flexural capacity in the anchored beams relative to the unanchored beams, the improved ductility provided by the new system shows promise. Further investigation is needed to determine the number of anchors needed, depth of penetration, size and location of such anchors to achieve composite behaviour between the strengthening bars and the reinforced concrete section.</p>