Experimental and numerical study of high strength reinforced concrete continuous deep beams with circular and rectangular openings

Abstract

Many modern structures require openings in the reinforced concrete (RC) beams, especially deep beams, to pass utility pipes such as sanitary, electronic, water, communications, and electrical services, especially in low floor heights. Since most of the beams are continuous and use high-strength concrete (HSC), this study investigates the effect of creating two post-construction openings in two-span HSC continuous deep beams. Five two-span HSC beams of 150 (width) × 400 (depth) × 2640 mm were cast, with each span of 1120 mm. The main variables investigated were the shape and location of openings. The circular opening was large of 150 mm diameter and the height and area of the rectangular openings were kept the same. Both openings were located either in one span or one opening in each span having asymmetrical layout. Each opening was located in the critical shear zone at the strut lines, as it is the most critical location in deep beams. The HSC continuous beams were tested till total collapse under two point loads acting at mid of the beam spans. The performance of beams having openings was compared with the reference beam having no opening. The presence of the two openings in the same span caused 38% reduction in failure load irrespective of the shape of opening. For the second opening layout having one opening in each span, the reduction was slightly higher but almost the same for the two shapes of openings (41% for circular and 45% for rectangular opening). To assess the load capacity of HSC continuous deep beams having circular and rectangular openings, 3D numerical models were prepared. The numerical results were compared with the experimental values, which were found to exhibit good agreements.