Steel Plates Versus Hybrid CFRP/Steel Stirrups for Strengthening of Shear-Deficient Concrete Wide Beams Supporting Columns

Joist floor systems are usually employed in buildings of the Middle Eastern regions. These systems usually have reinforced concrete (RC) wide beams, which in many cases have planted columns in non-seismic regions due to architectural requirements. Changes in building use can increase the loads on these columns, which may increase the shear demand of beams to a level that may exceed their capacity. Consequently, upgrading of such wide beams against shear is crucial. This study investigates two strengthening techniques to enhance the shear performance of RC wide beams with planted columns through experimental testing and analytical evaluation. Four half-scale specimens were tested: two unstrengthened beams (one code-compliant and one shear-deficient) and two strengthened beams, using either externally bonded steel plates or a combination of CFRP U-wraps with planted steel U-stirrups. The performance of the retrofitting schemes was assessed based on failure modes and load-deflection responses. The second strengthening scheme improved the shear resistance of wide beams by 82% compared to the control specimen. Additionally, the shear capacity of the tested beams was analytically predicted, and the results were compared with the test findings, providing insights into the effectiveness of both strengthening methods.