Flexural Behavior of Reinforced Concrete Beams with Openings Created by PVC Pipes: An Experimental and Numerical Study

It is a very common practice in several countries to find service pipes passing through beams transversely and vertically during construction. This practice has the potential of threatening the full-strength capacity of the structural element. This paper presents an experimental and numerical investigation on the flexural, deflection and crack performance of reinforced concrete (RC) beams with embedded conduit pipes. A total of ten (10) reinforced concrete beams were made and tested. Two of the RC beams served as control beams while the remaining eight RC beams had embedded conduit pipes of different sizes (50mm and 100mm) and at different positions (vertical and transverse). Loads were applied in increments of 2kN to the beams until failure. From the experimental results, the two control beams had an average failure load of 50kN, while the RC beams embedded with conduit pipes had an average failure load capacity of 44.75kN, which represents a 10.5% reduction. Similarly, the control beams had an average experimental first crack load of 17kN, whereas the conduit pipe embedded beams averaged 16.88kN first crack load. The RC beams with conduit pipes inserted transversely recorded an average failure load of 43kN, lower than RC beams with conduit pipes inserted vertically, which had an average failure load of 46.5KN. Reinforced concrete beams embedded with PVC pipes were observed to produce more cracks than the control beams, especially at the openings due to stress concentration. The embedment of PVC pipes in the beams resulted in a significant 20.47% increase in the average mid-span deflection. The numerical simulation of the beams performed with ABAQUS software demonstrated an adequate estimate with the experimental results obtained. The percentage variation between the ultimate load results obtained from the experimental test and finite element analysis ranged from 2% to 9%.