Shear strengthening of RC beams with FRP grid-reinforced ECC matrix

Fabric reinforced cementitious matrix (FRCM) composites are increasingly used for flexural and shear strengthening of reinforced concrete (RC) beams. This paper presents the results from an experimental study on the effectiveness and performance of a new FRCM system made of FRP grid-reinforced ECC matrix (referred to as "FGREM" for brevity) for shear strengthening of RC beams. A total of twelve shear-critical RC beams were constructed and tested. The parameters varied between the tests included the type of FRP grids, the type of cementitious matrix, the installation method of the shear strengthening system (prefabricated or cast-in-place), and the shear span-to-depth ratio of the beams. The crack patterns of all the tested beams were monitored using the digital image correlation (DIC) technique. Test results indicated that interfacial debonding of the shear strengthening layer and separation of the concrete side covers were two typical failure modes for the beams strengthened with the cast-in-place method and the prefabricated method, respectively. The gains in the shear capacity of the strengthened beams ranged from 50.9% to 160.6% with respect to the reference beams. Compared to the cast-in-place installation method, the prefabricated FGREM was demonstrated to be more efficient for shear strengthening of the RC beams.