Evaluation of Shear Strength Prediction on Steel Reinforced Concrete Deep Beams Using Simple Strut-and-Tie Model

In this paper, a practical method was proposed to predict the shear capacity of steel reinforced concrete (SRC) deep beams based on the simple strut-and-tie model (STM) for ordinary reinforced concrete (RC) members. Two alternatives were provided to consider the effect of encased steel shape. For Alternative 1, the SRC member is divided into two parts: the RC part and steel shape with inner concrete. The contribution of RC part is determined by the simple STM method, while that of steel shape is calculated with a proposed model from available literature. Alternative 2 directly considers the contribution of steel flanges and web to the ultimate strength of struts and tie of the STM. Totally 48 SRC deep beams were collected to evaluate the proposed method as well as the empirical methods from design codes. The results calculated by the selected code methods are overly conservative. The average test-to-predicted shear strength ratio of code methods ranges from 1.66 to 1.68, and the strengths of at most 2.1% of the specimens are overestimated. The prediction performance of Alternative 1 is close to code methods, with an average test-to-predicted shear strength ratio of 1.59. All the predicted results by Alternative 1 are higher than experimental results. Meanwhile, Alternative 2 provides the most accurate prediction with an average test-to-predicted shear strength ratio of 1.35 and an unsafe prediction ratio of 6.3%. Compared to code methods, the prediction accuracy of Alternative 2 is increased by 14% approximately. Furthermore, the influences of considered failure cases and width of horizontal strut for the STM of Alternative 2 were discussed in depth and the design recommendation was put forward.