## 3 Results and Discussion  
### Bar-Shaped Investigations for Load Bearing Optimization of RDJ  
#### 3.1.1 Bar-Shaped Investigations  
Load-Bearing Part of the Tenon Base and Flanks Equal-height GLT beam combination of 120 \(\times\) 160 mm with a 10\({}^{\circ}\) opening angle  
When evaluating the GLT girder combinations series REF 01, ZGR 01, FLA 01, it can be seen that the failure modes of the reference form REF 01 as well as the basic tenon form ZGR 01 are almost identical. In both cases, a transverse tension failure of the main girder occurs, see Figure 10. The effective depth \(t_{\text{eff}}\) in the test runs is approximately 0.75-\(b_{\text{HT}}\). This value is significantly lower than the uniform calculation value of \(t_{\text{eff}}\) = 100 mm for transverse connection failure (mode 1) for single-sided dovetail connections specified in Z-9.1-649 [1]. Since \(t_{\text{eff}}\) is a significant factor in the calculation formula for the load-bearing capacity of the transverse connection, it can be determined that the calculated characteristic load-bearing capacity for mode 1 according to [1] is not achieved in the test runs of series ZGR 01, which takes the shrinkage of the flanks into account, if the pre-timber height \(h_{\text{VH}}\) = 0.15 \(h_{\text{HT}}\) is given. The REF 01 series reaches the calculated value during the test, but only due to the existing flank load components. These are not taken into account in the calculation formula of the Z-9.1-649 [1] approval. Lower pre-timber heights \(h_{\text{VH}}\) = 0.05 \(h_{\text{HT}}\) (REF 03 series under 3.1.2) lead to lower connection depths \(t_{\text{eff}}\) and thus to larger deviations of the bearing capacity of the tapping base from the calculated value for mode 1 according to [1]. Figure 10: Damage patterns and cracks for series with 120 mm \(\times\) 160 mm beam combinations—REF 01 (**top**), ZGR 01 (**middle**) and FLA 01 (**bottom**). To determine the separately investigated load-bearing components of the tapping base and the flanks, their stiffness is determined by means of series ZGR 01 and FLA 01. These are then related to the total stiffness of the reference form series REF 01. In the course of the investigation of REF 01, it is found that the stiff tenon base is initially the main force transmission path of the joint. With increasing changes in the stiffness ratios, due to incipient damage in the tenon base, rearrangement processes occur towards the flanks. The residual load-bearing capacity of the wood connection, which is approximately 75% of the ultimate load, is ensured by the flanks. Since the force transmission via the flanks has little stiffness, noticeable deformations occur after failure of the bearing capacity of the tenon base. This effect is clearly visible in series FLA 01, since the trunnion does not rest on the bottom of the tenon hole. That means, the bottom of the main beam remains undamaged, see Figure 10, and the stiffness of the connection is represented only by that of the flanks. For series FLA 01 the stiffness is therefore very low. All load-deformation mean value curves for 120 mm \(\times\) 160 mm beam combinations are shown in Figure 11. Their loads and stiffnesses are listed in Table 2.  
The investigations of the stiffness on GLT girder combinations with cross sections of 120 \(\times\) 160 mm show that the participation of the load transfer over the flanks, which contributes to series REF 01, amounts to 15% (see Figure 12). As already mentioned, in common calculation models the flank load transfer part is not considered. However, at low pre-timber heights, redistribution processes from the bottom of the journal to the flanks already occur at small load steps. The flanks guarantee a residual load-bearing capacity