Simplified Design Method for the Shear Capacity of Steel Plate Shear-Strengthened Reinforced-Concrete Beams

Abstract

Recently, a steel plate concrete composite technique has been developed for the shear strengthening of RC bridges. The steel plate shear-strengthened (SPSS) beam is composed of an old RC beam, new concrete, and steel web. To investigate the shear behavior of SPSS beams strengthened in the shear span, six SPSS beams and four RC beams were tested. The test results showed that the failure mode of the SPSS beams was peeling failure at the interface between the old concrete and new concrete. The proposed technique showed a significantly enhanced shear capacity even when the tensile strength of the interface between the old and new concrete was relatively low. The initial interface failure appeared at the loading point, support, and corner of the new concrete and then expanded to the entire shear span. A finite-element (FE) model of the SPSS beam was established with the use of the FE software MSC.Marc, and the cohesive element was used to model the interface between the old and new concrete. The modeling scheme, material constitutive law, and material parameters are illustrated in this article. The results of the proposed FE model were found to agree fairly well with the test results in terms of the overall load-displacement curve, ultimate shear capacity, and interface failure pattern. Based on the FE model, the shear force contribution of the old concrete, new concrete, and steel web were decomposed with sufficient accuracy. The effects of the ratio of shear span to depth, material strength, and interface strength were investigated by an FE parametric analysis, and the interface strength between the old and new concrete was found to be the most important parameter. The shear contribution of the steel web was mainly affected by the interface strength. Finally, 1,296 elaborate FE models of SPSS beams were established with the use of MSC.Marc, and a practical design formula considering peeling failure with a reasonable level of accuracy was developed.