Shear behavior of reinforced concrete beams with vertical holes externally strengthened with near surface mounted bars

Electromechanical and other service ducts must be vertically carried out through structural components. Most research have examined the strengthening of the transverse opening region in concrete beams. Since no studies have examined beams with vertical openings, the current study focuses on examining the effect of a vertical opening within the shear region on the behavior of RC beams. The shear behavior of RC beams externally strengthened with near surface mounted (NSM) steel bars. Six NSM-strengthened beams as well as four un-strengthened specimens were tested. The hole region was traversed by cold-formed steel sheet, straight horizontal and vertical NSM bars, and horizontal NSM bars with bent ends. The study's primary characteristics are the hole diameter (20, 30, and 50 mm) and the strengthening provided by various NSM systems. Performance of the tested specimens were presented, and the findings were examined and compared. The results showed that the vertical openings had no discernible effect on the stiffness of unstrengthened beams. However, the load capacity of the unstrengthened beams with hole diameters of 20 mm, 30 mm, and 50 mm, respectively, was decreased by 4.5%, 9%, and 20%, while the energy dissipation capacity of the same specimens was decreased by 4.2%, 8.6%, and 16.5%, respectively. In comparison to an un-strengthened specimen with a 50 mm diameter hole, the shear resistance increased by 95% when horizontal NSM bars, with or without end anchorages, were installed in the beams. When compared to the un-strengthened specimens with holes, all NSM techniques improved the energy dissipation capability for all specimens. Referring to the control solid specimen, the used strengthening length increased the shear resistance in the opening area by 28.26%. Ultimate load of the tested beams was predicted and compared with experimental ones.