# Calibrating of a Simulation Model to Predict the Flexural Capacity of Pre-Stressed Concrete Beams
## 2 Materials and Methods
### Experimental Flexural Tests  
The experimental tests were conducted using a free-standing gantry (Figure 2a) for testing flexural elements, located in the Construction and Geotechnical Laboratory at the Higher Technical School of Agricultural and Forestry Engineering and Biotechnology at the University of Castilla-La Mancha (Albacete, Spain). It is a gantry especially designed for the mechanical flexural characterization of pre-cast or reinforced concrete elements (hollow core slabs, beams, joists, etc.).  
To carry out the experimental tests, the recommendations published by the Eduardo Torroja Institute were followed, extrapolating the indications of the UNE-EN 12390-4 standard to determine the flexural strength of concrete specimens. Two to three repetitions of each type of element tested were performed according to the elements supplied.  
In these tests, the corresponding load and displacement readings of the central point were recorded, which allow the diagram to be configured until rupture. In addition, the cracks obtained were characterized by high-resolution video, and the cracking map was  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Type** & **Repetitions** & **Length** & **Amount Reinforcement** & **Losses** & **Resistance Characteristics** \\ \hline  & & **(m)** & \begin{tabular}{c} _A\({}_{lower}\)_ \\ **(\%a)** \\ \end{tabular} & \begin{tabular}{c} _A\({}_{higher}\)_ \\ **(\%a)** \\ \end{tabular} & \begin{tabular}{c} _A\({}_{lower}\)_ \\ **(\%)** \\ \end{tabular} & \begin{tabular}{c} _A\({}_{higher}\)_ \\ **(\%)** \\ \end{tabular} & \
\begin{tabular}{c} _M\({}_{ultimate}\)_ \\ **(\%)** \\ \end{tabular} &
\begin{tabular}{c} _M\({}_{cracking}\)_ \\ **(kN\(\cdot\)m)** \\ \end{tabular} \\ \hline T13.1 & 2 & 2.40 & 3.0 & 1.5 & 18.6 & 17.5 & 3.8 & 1.7 \\ T13.2 & 3 & 2.40 & 4.5 & 1.5 & 20.3 & 18.5 & 4.6 & 2.3 \\ \hline T18.1 & 3 & 2.40 & 2.3 & 1.2 & 17.7 & 16.4 & 5.9 & 2.5 \\ T18.3 & 2 & 2.40 & 4.7 & 1.2 & 21.6 & 16.5 & 9.8 & 5.0 \\ \hline T35.3 & 2 & 4.10 & 4.1 & 1.0 & 18.2 & 11.2 & 67.5 & 49.6 \\ T35.4 & 3 & 2.03 & 5.1 & 1.0 & 20.3 & 11.2 & 76.1 & 56.8 \\ T35.5 & 2 & 3.70 & 5.1 & 2.0 & 21.9 & 11.3 & 82.2 & 63.2 \\ T35.6 & 2 & 3.26 & 6.1 & 1.0 & 22.7 & 10.9 & 86.0 & 66.2 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Structural elements analyzed and their resistance parameters according to the manufacturer’s technical data sheets.  
Figure 2: Free-standing gantry for flexural tests on linear elements of concrete (**a**) and example of strength vs. deformation graph with its characteristic values (**b**).  
then developed to compare it with that obtained in the simulation. The force was obtained by means of a 500 kN load cell located in the loading piston, while the deformation was obtained using a 0.01 mm precision LVDT deformimeter. The recorded measurements were plotted in a FORCE--DEFORMATION diagram to be compared to the analytical tests (Figure 2b). These diagrams were used to determine the following: the CRACKING FORCE (Fs) (load supported by the element at the instant the first crack appears, after which the concrete and steel begin to work together); the BREAKING FORCE (\(F_{\text{MAX}}\)) (maximum load that the element is able to withstand before total rupture); and the CRACKING DEFORMATION (Def\({}_{\text{S}}\)) and RUPTURE DEFORMATION (DEF\({}_{\text{MAX}}\)) (deformation values measured in the beam at the moment of the first crack or the failure of the beam, respectively).