Experimental and numerical study on the performance of externally prestressed reinforced high strength concrete beams with openings

This study investigates experimentally and numerically the performance of externally prestressed reinforced high strength concrete (HSC) beams with central openings. Seven externally prestressed rectangular HSC beams (six with central openings and a reference solid beam) are loaded incrementally to failure. All the beams have the same dimensions, reinforcement ratio and openings of variable size. Experimentally, the results show that, the appearance of the first flexural crack and the flexural stiffness reduction are largely governed by opening height. In contrast, the opening length greatly affects the presence of the first shear crack and the obtained values of strains in stirrups. Additionally, the opening length and height when combined can affect the strains in top- and bottom-bars and the failure load of the teste beams. Numerically, a three-dimensional nonlinear finite element analysis using ANSYS has been carried-out to analyze seventy (70) externally prestressed HSC beams with central openings. Based on the numerical results, a general formula to predict the ultimate moment is generated and verified. It can be used to predict the load carrying capacity of aging concrete elements with openings retrofitted using external prestressing techniques.