Retrofitting of shear-damaged RC T-beams using U-shaped SHCC jacket

Abstract

Strengthening of Reinforced Concrete (RC) beams using Strain-Hardening Cementitious Composites (SHCC) material became a worldwide practice. Previous investigations showed significant improvement in the shear resistance of SHCC-strengthened (undamaged) beams. However, a little effort has been devoted to study the ability of SHCC material in retrofitting shear-damaged RC beams. Thus, the current study aims to evaluate the shear response of shear-damaged RC beams repaired with SHCC material. In this context, eleven RC beams were prepared and configured to be failed in shear. One beam was considered as control specimen; while, four beams were strengthened with 20 mm thick U-shaped SHCC jackets having four different transversal reinforcement ratios (0, 0.65, 0.86 and 1.08%). The remaining six beams were pre-cracked (preloaded) with three different preloading levels (0.75, 0.85 and 0.95% of the ultimate capacity), then, three differently preloaded beams were repaired with SHCC jackets, whereas, for the remaining three beams, the developed shear cracks were injected by epoxy prior to the application of SHCC jackets. All beams were tested under four point loading scheme with shear span-to-depth ratio of 2.5. The test results showed that the strength, post-peak deformability and shear-crack response of the repaired beams were improved compared to those of the control beams. In addition, the use of epoxy injection prior to the application of the SHCC jacket showed its ability to restore a significant value of the lost strength gain due to preloading. However, the repairing technique was not able to restore the initial stiffness of the uncracked beams. Finally, based on analytical analysis, the design equations of JSCE code underestimated the ultimate shear capacity of the strengthened/repaired beams with average safety margin of about 27%.