Restoration of concrete beams presubjected to cycles of shear damage

The shear response of reinforced concrete beams predamaged in shear and then retrofitted with near-surface-mounted (NSM) composite strips has been investigated in this paper. A total of 18 tests were conducted. Prior to restoration, the specimens were: undamaged; precracked after three cycles of loading up to first shear cracking-unloading; or prefailed in shear after one cycle of loading-unloading. The NSM composite reinforcement remarkably improved the shear response. The shear strength gain decreased with an increase in the amount of internal stirrups. Changing the angle of inclination of the NSM composites from 90 to 45 degrees increased the shear strength gain of the specimens without stirrups but had a less pronounced effect on the shear strength gain of the specimens with internal stirrups/prefailed in shear. The presence of shear cracks prior to restoration did not reduce the shear strength gain provided by the NSM composites. The NSM composite system fully restored the shear capacity of the prefailed specimens. The contributions of the NSM composites to the shear resistance determined experimentally were compared with predictions of a published analytical approach.