Assessing the effectiveness of embedding CFRP laminates in the near surface for structural strengthening

Abstract

Near Surface Mounted (NSM) is a recent strengthening technique based on bonding Carbon Fiber Reinforced Polymer (CFRP) bars (rods or laminate strips) into pre-cut grooves on the concrete cover of the elements to strength. To assess the effectiveness of the NSM technique, an experimental program is carried out involving reinforced concrete (RC) columns, RC beams and masonry panels. In columns failing in bending the present work shows that the failure strain of the (CFRP) laminates can be attained using the NSM technique. Beams failing in bending are also strengthened with CFRP laminates in order to double their load carrying capacity. This goal was attained and maximum strain levels of about 90% of the CFRP failure strain were recorded in this composite material, revealing that the NSM technique is also very effective to increase the flexural resistance of RC beams.The effectiveness of externally bonded reinforcing (EBR) and NSM techniques to increase the flexural resistance of masonry panels is also assessed. In the EBR technique the CFRP laminates are externally bonded to the concrete joints of the panel, while in the NSM technique the CFRP laminates are fixed into precut slits on the panel concrete joints. The NSM technique provided a higher increase on the panel load carrying capacity, as well as, a larger deflection at the failure of the panel.The performance of EBR and NSM techniques for the strengthening of RC beams failing in shear is also analyzed. The NMS technique was much more effective in terms of increasing the beam load carrying capacity, as well as, the beam deformability at its failure. The NSM technique was easier and faster to apply than the EBR technique.

New Proposal for Flexural Strengthening of Reinforced Concrete Beams Using CFRP T-Shaped Profiles

“…Failure modes of the beams. This did not have any significant impact on the behavior of the strengthened RC members or on the ultimate loads, confirming the observations of [14,22,23]. Table 4.…”

Experimental and analytical investigation into the flexural performance of RC beams with partially and fully bonded NSM FRP bars/strips

“…Several experimental investigations have been performed to assess the load carrying capacity of the NSM technique [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. These have shown that the technique is greatly affected by bond behavior mainly depending on FRP properties, groove surface and dimensions, adhesive and concrete properties and the position of the FRP reinforcement.…”

Advancements in Retrofitting Reinforced Concrete Structures by the Use of CFRP Materials

“…To assess the effectiveness of the NSM strengthening technique for concrete columns submitted to static axial compression load and cyclic horizontal increasing load, Barros et al [19] carried out the three series of reinforced concrete columns indicated in Table 1. Series NON consisted of non-strengthened columns, series pRE was composed of concrete columns strengthened with CFRp laminate strips before testing and series POS consisted of previously tested columns of series NON that were post-strengthened with CFRP.…”

“…The properties of all the intervening materials are described elsewhere [19]. The test set-up is illustrated in Fig.…”