Behavior of concrete beams with short shear span and web opening strengthened in shear with CFRP composites

This paper presents test results of 16 reinforced concrete (RC) beams with web openings strengthened in shear with externally bonded carbon fiber reinforced polymer (CFRP) composite sheets. Test specimen was 2,600mm long with a cross section of 85 ^mm400mm and a shear span to beam depth ratio of a/h=2. All specimens had the same geometry and main longitudinal top and bottom reinforcement. No internal web reinforcement was provided in the test region to resemble the case of inclusion or enlargement of an opening in an existing beam which would typically result in cutting the internal web reinforcement around the opening. The test parameters were the width and depth of the opening and the amount of the CFRP sheets used for shear strengthening. Test results showed that the inclusion of web openings drastically reduced the beam shear capacity and stiffness. External strengthening with CFRP sheets around the opening was found to be very effective in improving the beam shear resistance and stiffness. Increasing the opening width or depth reduced the gain in the shear capacity caused by the CFRP. Doubling the amount of the vertical CFRP sheets from one to two layers increased the shear capacity but the additional shear capacity gain was not in proportion to the added amount of the CFRP. An analytical approach for prediction of the shear capacity of RC beams with openings strengthened in shear with CFRP was introduced on the basis of the American Concrete Institute (ACI) 440.2R-08 and other formulas published in the literature. The analytical approach showed good agreement with the test results.