Reinforcing of discontinuity regions in concrete deep beams with GFRP composite bars

The behavior of concrete deep beams internally-reinforced with glass fiber-reinforced polymer (GFRP) bars around regions of discontinuity is investigated. Twelve deep beam specimens were tested. One specimen was solid whereas the remaining eleven specimens included an opening in the shear span. Test variables included the opening height, concrete grade, and GFRP reinforcing configuration around the discontinuity regions. Three different GFRP reinforcing schemes around the discontinuity regions were employed. The scheme with diagonal GFRP reinforcement crossing the bottom chord was more effective in improving the shear resistance than that having diagonal GFRP reinforcement crossing the top chord. The strength gain caused by the GFRP reinforcement was more significant for the deep beams with the greater opening height. In contrast, increasing the opening height reduced the strength enhancement caused by increasing the concrete grade. Test results were compared to the strut-and-tie modeling (STM) predictions. The STM tended to provide reasonable predictions for the nominal shear strength of the beams reinforced with GFRP bars around the discontinuity regions. Provisions of the Canadian Standards Association provided more conservative predictions for the nominal strength compared with those provided by provisions of the American Concrete Institute.