# Experimental Testing of Reinforced Concrete Deep Beams Designed by Strut-And-Tie Method
## 3 Experimental Program
### Specim Details  
The geometric characteristics of all three tested reinforced concrete members are the same and shown in Figure 6b. The members were simply supported with a span of 180 cm and with symmetrically arranged openings. The thickness of all three experimental specimens is 10 cm. The elements are symmetrically loaded with two concentrated forces in the thirds of the span length.  
For each of the tested specimens, the Strut-and-Tie model was individually determined using the software \"ST method\". The node density was analyzed in [16] and the optimal density was adopted as \(9\times 6\) nodes in the horizontal and vertical direction, respectively. Strut-and-Tie models are individually shown in Figures 6a, 7a and 8a, where the solid red lines show the tensioned Strut-and-Tie model elements, and the dashed blue lines represent the compressed elements. Also, the values of the axial forces of truss elements are shown, as well as the initial node network and connectivity of nodes by rods.  
The Strut-and-Tie model for the W1 specimen was determined without limitation in relation to the direction of the reinforcement layout, Figure 6a. The holes in the static system used in the program \"ST method\" for the design of the beams are increased by one half of the thickness of the compressed and tensioned rods that extend along the very edge of the opening. This implies an iterative calculation in which the static model is corrected after each design and determination of the Strut-and-Tie model, until the change in geometry between the two models is small. In this way, it is ensured that the rods of the Strut-and-Tie model pass through the concrete mass of the real member along their entire height. The same principle is applied to the rods of the Strut-and-Tie model that are located along the outer edges of the member. The span and the load position of the real member and the numerical member are the same.  
Strut-and-Tie models were used for the design of the tested reinforced concrete members according to [21], with the design load of \(2\times 100\) kN. The adopted layout and quantity of reinforcement are shown in Figures 6b, 7b and 8b, for each specimen individually. Also, when reinforcing the specimens, reinforcement was only adopted at the places of the ties of the Strut-and-Tie model.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Diameter of the** & **Yield Strength** & **Relation between Tensile Strength** & **Elongation at Maximum** \\  & **Tested Specim** & **Re [MPa]** & **and Yield Strength, Rm/Re** & **Force, Agt [\%]** \\ \hline R1 & \(\mathcal{O}\)6 & 422 & 1.24 & 6.92 \\ R2 & \(\mathcal{O}\)6 & 405 & 1.18 & 7.12 \\ R3 & \(\mathcal{O}\)6 & 424 & 1.21 & 7.04 \\ R4 & \(\mathcal{O}\)6 & 403 & 1.20 & 7.08 \\ \hline \hline \end{tabular}
\end{table}
Table 6: The results of tensile splitting strength of steel for reinforcement.  
Figure 5: (a) Testing of the concrete compressive strength, (b) tensile strength testing of the steel for reinforcement.  
For the W2 specimen, the Strut-and-Tie model was determined provided that the horizontal direction of the reinforcement was favorable, Figure 7a.  
The favorable orientation of the reinforcement for the W3 specimen was set at an angle of 45\({}^{\circ}\) in relation to the outer edges of the element, Figure 8a. Reinforcement layout of the lower zone of the specimen W3 is not common in practice, so the equivalent amount of reinforcement in the horizontal direction within that zone is adopted, Figure 8b.  
Figure 8: (**a**) Strut-and-Tie model for W3, (**b**) reinforcement layout.  
Figure 6: (**a**) Strut-and-Tie model for W1, (**b**) reinforcement layout.  
Figure 7: (**a**) Strut-and-Tie model for W2, (**b**) reinforcement layout.  
Preparation of Specimens  
The formwork, the reinforcement of walls W1-W3 and reinforcement spacers are shown in Figure 9a-c. Three reinforced concrete members after concreting are shown in Figure 9d.