## 2 Methods and Materials
### Experimental Investigations  
Realizing a testing device for lateral-torsional buckling problems can be very challenging. This becomes clear also when coming across different test setups in literature [4; 10; 11]. The mentioned test setups were always developed for tests on single-span glass beams with load introduction at mid-span. For the present investigations, a testing device for cantilever beams was developed. For this reason, the glass beams were clamped at one side with bolts to lock all degrees of freedom. In order to avoid stress concentrations, POM-C layers were used as an interlayer between the glass and the steel construction. The load introduction at the free end of the beam was the most demanding task. Due to the necessary degrees of freedom, a universal joint was used between the glass beam and the load introduction. The universal joint was fixed on a bar, which was connected with tension rods on a trolley. The trolley was equipped with roller bearings. The testing device is shown in Figure 1a. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Test Specimen** & **Glass Type** & \begin{tabular}{c} **Cross-Section** \\ **[mm]** \\ \end{tabular} & \begin{tabular}{c} **Height h** \\ **[mm]** \\ \end{tabular} & \
\begin{tabular}{c} **Length** \\ **L [mm]** \\ \end{tabular} &
\begin{tabular}{c} **Number of** \\ **Specimens** \\ \end{tabular} \\ \hline FT\_150\_x & FT & 10/1.52/10/1.52/10 & 150 & 2100 & 7 \\ FT\_300\_x & FT & 10/1.52/10/1.52/10 & 300 & 2100 & 3 \\ HS\_150\_x & HS & 10/1.52/10/1.52/10 & 150 & 2100 & 5 \\ HS\_300\_x & HS & 10/1.52/10/1.52/10 & 300 & 2100 & 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overview of the test specimens. Figure 1: **(a)** Testing device, **(b)** coordinate system and definition of the imperfections, **(c)** definition of the measured displacements at the free end of the cantilever beam. After installing the glass beams, the imperfections were measured for each test specimen with a measuring device of the company FARO [20]. The displacements were measured over the whole beam length L of each glass beam at the top and the bottom edge. In doing so, the amplitude of the lateral imperfection v\({}_{0}\) (with respect to the length L and the gravity-center G) and the rotational imperfection \(\phi_{0}\) could be determined. As expected, the shape of the lateral imperfections corresponds in all cases in good approximation to a half sinus wave (see Figure 1b). The rotational imperfections consist of two parts; a (local) twist of the glass beam itself and an unavoidable (global) rotation due to the installation and the bearing arrangements. The measured rotational imperfections were clearly smaller than the measured lateral imperfections. Nevertheless, minor rotational imperfections can influence the load-displacement path. Because of this, and for simplification, only the maximum rotation of each glass beam was evaluated. The thickness of each test specimen was measured additionally. All obtained values are summarized in Table 2.  
The tests were performed \"displacement driven\", which means that the testing machine moves upwards with a constant velocity. The resulting forces were measured with load cells. The lateral displacements were measured with inductive displacement sensors at the free end of the glass beam (see Figure 1c). Figure 2 shows exemplary the testing device and the test of a FT glass panel. The load-deflection curves of all test specimens are shown in Figures 6 and 7. The ultimate loads and the loading durations are summarized in Tables 5 and 6.