Effect of Openings’ Configurations on the Stress Concentration Factor of RC Beams under Different Loading Conditions

Nowadays, providing web openings in RC beams became a common practice in order to allow the utility ducts to pass through them. These openings interrupt the loading trajectories and result in the presence of weak points around the openings owing to the stress concentrations. Accordingly, stress concentration factor (SCF) is used to measure these concentrations of stresses. The current paper investigates numerically the effects of different parameters on the SCFs for RC beams such as the shapes of opening (circular, octagonal, hexagonal, square), size of openings (small, medium, large) having opening size-tobeam depth ratios of 0.25, 0.5 and 0.625, respectively. The beams having various combinations of sizes and shapes are subjected to different types of loading conditions such as bending moment, bending moment accompanied by axial tension force, bending moment plus axial compression force and shearing force. 2D linear finite element analysis was employed to estimate the SCFs for different combinations. It was found that under bending moment, the SCFs ranged from 1.07 to 2.1. For large and medium openings, the best shape of opening is the square one and the worst one is the octagonal. However, for small openings, the best shape is the octagonal and the worst one is the circular opening. Under bending moment and axial force either tension or compression, the SCFs ranged between 1.7 and 4.24. Similar observations as those for the bending moment case were noticed for the best and the worst opening shape and size from the viewpoint of the SCF. Under shearing force, SCFs ranged from 1.04 to 6.8. For large and medium openings, the best shape is the octagonal one and the worst shape is the square. However, for small openings, the best shape is the square one and the worst shape is the circular.