## 3 Results and Discussion
### Bar-Shaped Investigations for Load Bearing Optimization of RDJ
#### 3.1.1 Bar-Shaped Investigations
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Series** & **Tests** & **\(\omega_{\text{mean}}\)** & **\(\rho_{\text{mean}}\)** & **\(F_{\text{mean}}\)** & **\(F_{\text{vk}}\)** & **COV** & **\(K_{\text{ser,mean}}\)** & **\(K_{\text{ser,k}}\)** & **COV** \\
**[-]** & **[-]** & **[-]** & **[\%]** & **[kg/m\({}^{3}\)]** & **[kN]** & **[kN]** & **[\%]** & **[N/mm]** & **[N/mm]** & **[\%]** \\ \hline REF 01 & 5 & 13.1 & 446 & 22.1 & 16.5 & 12.1 & 9246 & 8884 & 11.8 \\ ZGR 01 & 5 & 12.2 & 426 & 15.2 & 13.0 & 6.2 & 8031 & 7897 & 5.0 \\ FLA 01 & 5 & 12.7 & 435 & 13.8 & 11.3 & 7.8 & 1419 & 1357 & 11.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Evaluation of the tests—loads and stiffnesses according to EN 14358 [21]. Figure 11: Load-deformation mean value curves (thick colored lines, listed in legend) of the related single tests (thin colored lines) for 120 mm \(\times\) 160 mm beam combinations. of almost 75%, which is important for the robustness of the connection and the structure as a whole. The characteristic load of the reference geometry REF 01 achieved in the test, corresponds exactly to the calculated value according to [1]. However, the value of the pure tenon base form ZGR 01 is lower. In the case of beam combinations of the same height, the calculated value according to [1] is only achieved in the present test runs if the flank load-bearing component is taken into account. Equal-height GLT girder combination of 160 \(\times\) 160 mm with an opening angle of 33\({}^{\circ}\)  
In order to demonstrate the optimization potential for shapes with a larger notch taper angle \(\gamma\), GLT beam combinations series REF 02, ZGR 02, FLA 02 were investigated in the same way as in the previous series. The failure mode of the reference geometry REF 02 now differs from the corresponding basic tenon shape ZGR 02 by a multi-step force application due to the load-bearing components of the flanks. This leads to a higher total resultant force transmission, which is shown by a greater effective depth \(t_{\text{eff}}\) of the reference shape compared to the basic tenon shape. The FLA 02 series flank form is again tested without the tenon base. The load achieved with the FLA 02 series is higher than with the FLA 01 due to the wider flank angle. This is also visible in the damage patterns of the main beam (see Figure 13). Figure 12: Weighted stiffnesses of Series 01 (graphs). Figure 13: Damage patterns and cracks for series with 160 mm \(\times\) 160 mm beam combinations—REF 02 (**top**), ZGR 02 (**middle**) and FLA 02 (**bottom**). The basic tenon form, ZGR 02, shows exactly the same values as the corresponding basic tenon form, ZGR 01. Its calculated load-bearing capacity can also be estimated on the safe side by using the calculation formula for mode 1 in [1]. The significant increase in the load-carrying capacity of the reference form REF 02 compared to REF 01, therefore results exclusively from the higher flank load-bearing component because of the wider notch taper angle. The ductile behavior of the connection and the robustness of the structure as a whole can also be guaranteed by widening the notch taper angle \(\gamma\). The increase in load-bearing capacity before failure and the residual load-bearing capacity at failure of the connection depend exclusively on the flank load-bearing component and thus on the inclination of the flanks. The potential of this load increase for the REF 02 series is 66%, compared to the ultimate load of the basic tenon form ZGR 02, which is relevant for the design. After failure of the tenon base, approximately 90% of the ultimate load at an opening angle of 33\({}^{\circ}\) is available as residual load-bearing capacity through the flanks in the case of large deformations. Taking the flank load-bearing components into account in the calculation formulas would lead to a significant increase in the ultimate load potential of the timber connection at large opening angles.