Design of reinforced concrete beams with circular openings

Abstract

This study examines the adequacy of the ACI Code approach, modified for the inclusion of transverse openings, for shear design of a beam with circular openings. Seven T-beams with circular web openings were designed for moderate to high shear force and tested in an inverted position to simulate the conditions that exist in the negative moment region of a continuous beam. Test results indicate that crack control and preservation of ultimate strength may be achieved by providing reinforcement around the opening. Diagonal bars were found to reduce the high stress in the compression chord, thus avoiding premature crushing of the concrete. The modified ACI approach has been found to give conservative design provided the reinforcement is properly detailed near the opening region.