Effect of Reinforced Concrete Beams with Circular Opening in Flexural and Shear Zone

Reinforced concrete beams often incorporate transverse openings to accommodate various utility services such as air-conditioning pipes, fire safety lines, internet cables, and electrical wires. However, the introduction of these openings results in a notable reduction in the stiffness and ultimate load capacity of the beams, primarily due to heightened stress concentrations near the openings. This research focuses on RC concrete beams with circular openings of varying diameters at flexure and shear locations. Utilizing ANSYS software, the study employs multilinear isotropic concrete material models and bilinear inelastic steel material models to analyze the nonlinear behavior through the finite element method. The investigation specifically explores the effects of different opening diameters and their locations within the beams. Circular openings with varying diameters are assessed at both the middle and quarter span section of the beam. The impact of different openings is examined through load–deflection plots, crack patterns, and stress distribution evaluations. Additionally, a finite element convergence study is conducted to determine an optimal mesh density, while time stepping is employed to estimate the ultimate load. The research aims to assess the ultimate load capacity and failure modes resulting from different opening diameters, considering both flexure and shear locations. Notably, the study reveals that increasing the diameter of the beam opening to half of the overall beam depth significantly diminishes the ultimate load capacity compared to an equivalent solid beam, particularly in the quarter-section opening. The findings contribute valuable insights for the development of design rules for reinforced concrete members with openings. A comprehensive three-dimensional nonlinear finite element analysis using ANSYS simulations further enhances the understanding of the structural behavior in real-world scenarios.