Tests on reinforced concrete deep beams with circular and square openings

Abstract

Eight reinforced concrete deep beams with circular or square openings were tested and the results are reported here. The main variables studied were the shape of the openings, the compressive strength of the concrete and parameters for the horizontal stirrups. The test results show that the shear strengths of deep beams made with high-strength concrete were higher than the shear strengths of deep beams made with normal-strength concrete. In addition, the shear strengths of deep beams with circular openings were found to be higher than those of deep beams with square openings. The first inclined cracking loads of the deep beams with circular openings were larger than those of the beams with square openings. The shear strengths of deep beams with horizontal stirrups were higher than those of deep beams without horizontal stirrups. Horizontal steel bars on top of the openings were found to be very important for the design of deep beams. A previously proposed softened strut-and-tie model was used to calculate the shear strengths of reinforced concrete deep beams with circular, rectangular and square openings. Comparison of the results proved the accuracy of the softened strut-and-tie model.