Shear behaviour of deep beams strengthened with high-strength fiber reinforced concrete jackets

The study addresses the pressing need for effective strengthening of reinforced concrete (RC) members, specifically focusing on shear-critical deep beams. One of the most effective methods for strengthening RC members is the fiber reinforced concrete (FRC) jackets. However, limited number of studies have been conducted on deep beams strengthened with FRC. To address this gap, this paper presents an experimental investigation for strengthening of shear-critical deep beams using high-strength fiber reinforced concrete (HFRC) jackets. The experimental program involves testing three large-scale deep beams, including a reference specimen and two strengthened beams with thin HFRC jackets of different thicknesses (34 mm and 26 mm). The HFRC jackets featured straight steel fibers with a volumetric ratio of 1.13 %. According to the experimental results and analysis, it is found that an HFRC jacket of 34 mm thickness upgraded the strength by around 25 % and enhanced the crack control by reducing crack widths by around 50 % at the same absolute load with respect to the reference specimen. From the measured deformed shapes of the compression zone of the specimens, it is concluded that the main principles of the two-parameter kinematic theory of deep beams remain valid for HFRC-strengthened members, and these principles can be used to establish a complete modelling approach for such members.