## 3 Experimental Analysis
### Material Properties
#### 3.3.2 Glass  
Today, soda-time-silica glass is mainly used in the construction industry. Table 3 shows general physical properties. In general, we must consider the fact that glass has no built-in safety mechanism. It deforms to its elastic limit or breaks brittle. Depending on the failure mechanisms of structural glass, we distinguish: float glass, annealed float glass, heat-strengthened glass, fully tempered glass, chemically strengthened glass and laminated glass.  
Three types of structural glass were used for comparison in this study--annealed float glass (AF), fully tempered glass (FT) and heat-strengthened glass (HS).  
Annealed float glass is essentially float glass made by a process in which the float glass is cooled slowly enough to avoid internal stresses. Glass can be made more load- resistant by inducing the compressive stresses on the surface. It is annealed when it is heated beyond the transition point and then allowed to cool slowly [36]. All annealed float glass becomes brittle during the production process. The tensile bending strength of tempered glass is 45 N/mm\({}^{2}\) (Table 4). Such glass is very brittle and breaks into large pieces that can cause serious injury and damage. Such glass should not be used for large glazing or anywhere where there is a greater risk of injury to people if it breaks.  
Fully tempered glass (FT) is made from annealed glass by a thermal tempering process. Unlike annealed float glass, this type of glass breaks into small pieces and reduces the risk of breakage. The tensile bending strength of tempered glass is 120 N/mm\({}^{2}\) (Table 4). After tempering, the temperature resistance, impact strength, and bending strength increase. FT glass must be cut to the correct size and pressed into shape before tempering, as it cannot  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Material** & **Modulus of Elasticity E [N/mm\({}^{2}\)]** & **Tensile Bending Strength f\({}_{\text{mt}}\) [N/mm\({}^{2}\)]** \\ \hline AF glass & 70,000 & 45 \\ HS glass & 70,000 & 70 \\ FT glass & 70,000 & 120 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Material properties of used structural glasses [35].  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Property** & **Symbol with Units** & **Value** \\ \hline Density & \(\rho\) [kg/m\({}^{3}\)] & 420 \\ Bending strength & fm [N/mm\({}^{2}\)] & 24 \\ Compressive strength & fc [N/mm\({}^{2}\)] & 25 \\ Modulus of elasticity & E [N/mm\({}^{2}\)] & 11,000 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Material properties of timber C24 [34].  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Property** & **Symbol with Units** & **Value** \\ \hline Transition temperature & T\({}_{\text{g}}\) [\({}^{\circ}\)C] & 564 \\ Liquid temperature & T\({}_{\text{1}}\) [\({}^{\circ}\)C] & 1000 \\ Density & \(\rho\) [kg/m\({}^{3}\)] & 2500 \\ Coefficient of thermal expansion & \(\pi\) [K\({}^{-1}\)] & \(0.9\times 10^{-5}\) \\ Thermal conductivity & \(\lambda\) [W/(m K] & 1.0 \\ Specific heat capacity & c [J/(kg K] & 720 \\ \hline \hline \end{tabular}
\end{table}
Table 3: General physical properties of soda-line-silica glass [35].  
be reworked after tempering. Therefore, no post-critical strength is observed here. The first crack corresponds to the final failure.  
Heat-strengthened glass is the most common type of toughened glass used in safety components. It is less than 12 mm thick and is tempered to produce residual stresses at the surface, but at a lower temperature and cooling rate than fully toughened glass. It has lower residual stresses and breaks into what appear to be larger pieces, but they are still smaller than annealed glass. Its tensile bending strength is about 70 N/mm\({}^{2}\) (Table 4).