Strengthening of high-strength RC continuous deep beams having rectangular web openings using bolted steel plates

Abstract

Continuous high-strength concrete (HSC) deep beams are commonly encountered in various structures, often requiring the incorporation of post-construction openings for electrical and sanitary facilities, as well as utility pipes. This research focuses on experimental testing of three two-span HSC deep beams: one reference specimen without openings, one specimen having post-construction rectangular openings, and one strengthened specimen having rectangular openings. Two asymmetrical rectangular openings were made (one in each span). One opening simulated cutting the exterior strut of the first span, and the other one represented cutting the interior strut of the second span of the continuous deep beam. The strengthening technique involved attaching steel plates with anchor bolts around the cutouts. It is revealed that the beam having openings experienced a 45 % reduction in the peak load compared to the reference specimen. However, the upgraded specimen not only restored the peak load but also surpassed it by 9 % compared to the reference specimen and 98 % enhancement over the specimen with openings. Nonlinear two-dimensional (2D) finite element (FE) modeling validated the test outcomes and facilitated a parametric study on the strengthened beam. The analysis revealed that welding of the upper and lower chords with interior steel box had more significant impact on the strengthening effectiveness than steel plate thickness alone. The analysis indicated that the steel plate used in tests was on the higher side, as a lesser plate thickness was sufficient. Moreover, the interior steel box alone within the opening produced a 28 % enhancement in the peak strength.