Experimental investigation on shear performance of reinforced concrete beams retrofitted by pre-stressed steel strips

Abstract

Due to the material deterioration and the update of design codes, some existing reinforced concrete (RC) beams need to be strengthened. The strapping method available in the packaging industry using pre-stressed steel strips can be applied in retrofitting engineering because of its low cost and high confinement effect. To guide the application of steel strips on RC beams under shear, the parameters in this paper are the steel strip spacing, strip layers and chamfer edges. The shear-compression failure and diagonal compression failure of the specimens were observed. The test results indicated that the shear strength of the retrofitted RC beams was enhanced by a maximum of 95%, and the displacement increased by 86% compared with the control specimen. Among the three parameters, the spacing of the steel strips exhibited the most significant effect on the strength and deformability of the retrofitted beams, while the strip layer and chamfer process improved the ductility more than the shear strength. The shear mechanism of the retrofitted RC beams was analyzed on the basis of the softened strut-and-tie model, and the steel strip was considered as a tie model to contribute to the shear strength. A theoretical equation and a design equation considering the parameters of steel strips were proposed to predict the shear capacity of the retrofitted RC beams and then validated by the experimental data.