# Experimental Testing of Reinforced Concrete Deep Beams Designed by Strut-And-Tie Method
## 1 Introduction
The authors concluded that the behavior of experimentally tested members was in accordance with the position of the compressed and tensioned elements of the chosen Strut-and-Tie models. Similarly to the conclusion in the paper [11], it has been also shown that the strength determined by the Strut-and-Tie method is lower than the experimentally determined load capacity, which confirms that the Strut-and-Tie method is reliable. [PERSON] and others [13] were examining the behavior of reinforced concrete wall members designed by means of the Strut-and-Tie method. Out of the total of four members, two were made with normal reinforced concrete and the other two were made from reinforced concrete with the addition of steel fibers in the amount of 1.5% of the total member volume. The members with steel fibers were reinforced so that the reinforcing bars, unlike ordinary reinforced members, were positioned only at certain critical locations in the member. The conclusions of the study in the paper [13] indicated that the Strut-and-Tie method underestimates the ultimate limit strength of the tested specimens. The specimens with normal reinforced concrete reached the designed strength value, but without the failure. Similar to the previous research papers, this study also showed that the designed strength is three to four times lower than the experimentally determined load capacity. The behavior of specimens in experimental testing has shown that steel fibers can replace a certain amount of reinforcement bars. For the purpose of the researches presented in this paper, a software \"ST method\" for the automatic determination of Strut-and-Tie models and their application in the automatic design of reinforced concrete plane members has been developed by the authors of this paper. In Figure 2 different members are given with corresponding Strut-and-Tie models, obtained with the software \"ST method\". Deep beams loaded with vertical and horizontal concentrated forces are shown in Figure 2a,b, and deep beams with openings loaded with vertical forces are shown in Figure 2c,d. The main advantage of this program, which is described in detail in [14], lies in the fact that based on the previously adopted parameters that affect the layout of the reinforcement in the element, it automatically determines the shape of the Strut-and-Tie model and its stress state. The obtained model is then used for automatic design. By varying the parameters that influence the layout of the reinforcement in the member, various forms of the Strut-and-Tie model can be obtained, whereupon the optimum shape can be achieved by establishing certain criteria, i.e., conditions, such as the simplicity of the reinforcement scheme or the amount of reinforcement. The advantage of the program is reflected in the fact that, according to the proposed algorithm, replacing truss models of the real members, Strut-and-Tie models, can be obtained, with the corresponding values of axial forces in truss elements, which are required for the design according to the Strut-and-Tie method. The main goal of the research presented in this paper is the experimental confirmation of the numerically defined forms of the Strut-and-Tie models obtained from the software \"ST method\". These models were used for the design of the tested-reinforced concrete deep beams and the optimal model is selected on account of the simplicity of member reinforcement and its serviceability. Three reinforced concrete wall members with the length of 200 cm, the height of 130 cm and two openings measuring 30 \(\times\) 30 cm were experimentally tested. The members were differentially reinforced and loaded with two concentrated forces of 2 \(\times\) 100 kN. Based on the experimental results, it can be concluded that the proposal manner, implemented in the software ST method, is applicable for obtaining the Strut-and-Tie models.