Effect of longitudinal circular hollows on the flexural strength of reinforced concrete beams

In this study, the effect of hollows passing through reinforced concrete (RC) beams in the longitudinal direction on flexural strength was examined. 4 RC beams were designed to satisfy the conditions for implementation. One of the beams was fabricated as a reference specimen and 3 of the remaining beams were fabricated with total of 5 pipes in the tension, neutral axis and compression regions. All experimental beam specimens were subjected to 4-point axial flexural tests with the request for constant flexural moments at the limits of loading. Experimental beams with pipes in the compression region, tensile region and neutral axis regions were confronted with the reference beam in terms of initial stiffness, ductility, load-bearing capacity and energy absorption capacity. It was verified that to provide that both the sufficient stiffness and sufficient ductility conditions for the reinforced concrete beams, do not establish any structural discontinuity, the longitudinal orbicular cross-section hollows created by pipes should be passed through the neutral axis region as much as possible. The results of the present study not only align with those of previous research (e.g., the correlative results) but also extend the current state of research (e.g., the revealed differences) and provide starting points for future research. Conclusions are drawn from these results at the end of the paper.