###### Abstract
He studied the impact of timber-glass I-beams with flanges attached directly to the glass web using polyurethane adhesive. He saw the advantage of such beams mainly in terms of their transparency or light transmission through the room, and their attractive appearance. Eight specimens were tested to the failure limit in a four-point bending test. The glass web was 10 mm thick, and the timber flanges varied from 30 \(\times\) 50 mm to 50 \(\times\) 60 mm. The specimens were 4000 mm long and 250 mm high. The reason for choosing this design was to transfer the loads from the timber to the glass via a suitable adhesive. All eight samples tested showed similar behaviour. The tests showed that timber and glass act as a homogeneous material in these composites. The timber even acts as a reinforcement for the glass, increasing the load-bearing capacity of the entire element when the first crack occurs. He observed up to a 200% increase in load from the first crack to the ultimate failure of the beam, which is called post-breakage reinforcement. [PERSON] (1977, 1978) has written extensively on this topic. In 2004, he introduced the concept of timber-glass I-beams, following the example of [PERSON]. The cross-section consisted of timber flanges of different sizes, the lower 30 \(\times\) 30 mm and \begin{table}
\begin{tabular}{c c c c c c} \hline  & **Density** & **Compress. Strength \(\ell_{\mathrm{c}}\)** & **Tensile Bending** & **Modulus of Elasticity E** & **Coeff. of Thermal Expansion \(\alpha_{\mathrm{T}}\)** \\  & \(\rho\) [kg/m\({}^{2}\)] & [N/mm\({}^{2}\)] & [N/mm\({}^{2}\)] & [N/mm\({}^{2}\)] & [10\({}^{-5}\) K\({}^{-1}\)] \\ \hline Float glass & 2500 & 800 & 45 & 70,000 & 0.90 \\ \hline Timber C30 & 460 & 23 & 30 & 12,000 & 0.50 \\ \hline Ratio glass/timber & 5.43 & 34.78 & 2.9 & 5.83 & 1.80 \\ \hline \end{tabular}
\end{table} 
Table 1: Material properties of float glass and softwood C30 [1]. the upper 50 \(\times\) 50 mm, which he glued together with polyurethane. For the glass web he used three different types of glass: annealed float glass, heat strengthened float glass, and fully temperate glass, with thicknesses of 4 mm and 6 mm. From a materials testing point of view, these thicknesses are sufficient, mainly because of the smaller range of samples tested, but for everyday use he recommended thicker glass. In this case, the specimens with annealed float glass also showed a 70% increase in load-bearing capacity after the initial crack and ductile fracture. This phenomenon, of course, was not observed with tempered and fully tempered glass. [PERSON]'s beam concept was tested by [PERSON] on a natural scale. Due to the good results of the tests, they were installed as roof beams in the conference hall of the Hotel Palafitte in Switzerland, which was built as part of the Swiss national exhibition Expo 0.2 in 2002. The built-in beams supporting the lightweight roof are designed to transfer snow and wind loads to the steel columns embedded in the exterior walls. The length of all the I-beams installed was 6000 mm and the height was 580 mm. Twelve mm thick single tempered glass was used. The upper timber flanges were made from two rectangular wooden blocks of 100 \(\times\) 160 mm and the lower flanges from two smaller wooden blocks of 65 \(\times\) 65 mm. The researcher justified the choice of these dimensions based on fire safety and load transfer. The dimensions of the upper flanges ensure that all loads are transferred even in the event of a complete failure of the glass, which in this case has no post-critical load bearing capacity after the initial crack. Samples of these beams were previously tested in a four-point bending test, in which they were subjected to a load three times higher than the maximum external load envisaged in the hotel. In 2008, Portuguese researchers [PERSON] and [PERSON] [5; 6] studied and tested 15 timber-glass I-beams. All beams were 550 mm high and varied in length from 650 mm to 3200 mm.