The effect of longitudinal hole shape and size on the flexural behavior of RC beams

Abstract

The building's electro-mechanical piping systems can pass through transverse or longitudinal holes inside the reinforced concrete (RC) secondary beams, thus increasing the available floor height. These holes induced a reduction in the beam stiffness and strength. This work analytically and experimentally investigates the impact of longitudinal hole shape on the flexural behavior of RC beams. The interaction between hole shape and hole location has also been studied. The test program includes nine beams with the same cross section dimensions and steel reinforcement. Holes have been made using two circular PVC pipes (50 and 75 mm in diameter), and wooden medium-density fiberboard (MDF) square tubes (50×50 mm) and rectangular tubes (50×100 mm). Each hole shape was installed at two locations (90 and 160 mm) from the top of the beam. All beams were tested to failure using a four-point bending test. The results show that the hole shape and size up to half the beam width does not affect the failure mode compared to the solid control beam. The reduction in the ultimate strength of hollow beams compared to the control beam depends on the hole shape and size, with a maximum reduction of 20%. The developed analytical models were validated using experimental test results and can be employed to accurately predict the full flexural behavior of hollow RC beams, including cracking, yielding, and ultimate moments/loads.