## 4 Methods
### Numerical Modelling
#### 4.2.3 Full-Size Sandwich Element Model  
A concept building consisting of residential apartments was defined to calculate the loading schemes. The building is assumed to be situated on the west coast of Sweden. The building is prescribed dimensions of \(20\times 72\times 12.4\) m (height \(\times\) length \(\times\) width). This scenario is limited to a typical element design, as illustrated in Figure 1, which consists of the materials and layer thicknesses, previously presented in Section 3. However, in this model, the TRRPC facings were limited to one layer of carbon grid reinforcement placed in the center of the facing, as this was found to be a sufficient amount of reinforcement for the applied design wind loads. Moreover, the study of the full-size sandwich element was limited to consider only the double connector configuration developed in this project. The boundary conditions were the same as for the wind load test model described in Section 4.2.2, i.e., vertical (\(V\)) and horizontal (\(H_{\text{I}}\)) forces are transferred to the load bearing structure via the lower anchor points, while the horizontal (\(H_{\text{u}}\)) force is transferred by the upper anchor points. The structural performance of the facade element was verified according to the limit state principle of EN 1990 [31]. Typically, two types of loads are included in normal design situations: vertical permanent loads from the facing's self-weight (\(G\)) and variable horizontal loads from wind (\(W\)); see Figure 1. The wind produces wind actions on the external (\(W_{\text{ext}}\)) and internal (\(W_{\text{int}}\)) surfaces according to EN 1991-1-4 [32]. Three load cases (\(LC\)) are thus investigated for the ultimate limit state (ULS) and  
Figure 10: Schematic of FE model developed for the wind load testing with (**a**) single connector (S) configuration (**a**) and double connector (D) configuration (**b**). the serviceability limit state (SLS). In _LC1_, the facing's external surface is under pressure, while the internal surface is under suction. In _LC2_, the external facing of the sandwich element is loaded in suction, while the internal layer is loaded in pressure. As for _LC3_, the external and internal facings are exposed to wind suction. The considered load combinations are stated in Equation (1) for SLS and in Equation (2) for ULS:  
\[1.0G+1.0\left(W_{\text{ext}}+W_{\text{int}}\right) \tag{1}\]  
\[1.35G+1.5\left(W_{\text{ext}}+W_{\text{int}}\right) \tag{2}\]  
These load cases correspond to different wind directions to which the building could be exposed. The wind loads, given in Table 3, are calculated based on a concept building situated in Gothenburg (basic wind velocity \(v_{\text{b}}\) = 25 m/s) in terrain category IV, which is defined as an area in which at least 15% of the terrain surface is covered by buildings with an average height greater than 15 m. Furthermore, the presented numbers correspond to the most exposed parts of the building (worst case). The external and internal wind load acting on the doors and windows are assumed to act on the edges of the openings at the outer facing. In the developed model, the sandwich element was first loaded by the self-weight and the wind load actions up to the SLS. Thereafter, the additional self-weight and wind load actions corresponding to the ULS were applied. Finally, the wind load actions were increased further until failure of the element, if not reached at the ULS. Verification at the ULS corresponds to the failure of the elements and related to human safety. For the sandwich element, this mainly concerns checking for connector failure, connector pull-out failure, textile grid failure and anchor failure. Concerning anchor failure, it should be verified that the horizontal reaction force, i.e., shear load at the anchor, at the different anchor positions and load combinations, are smaller or equal to the corresponding design shear load capacity according to Equation (3).