## 3 Finite Element Method (FEM): Seismic Performance of Curtain Wall
### Static Seismic Analysis of Curtain Wall by AAMA 501.4 Standard  
To assess the structural performance of the curtain wall subjected to simulated static displacements based on the AAMA 501.4 standard, first, static seismic analysis was performed in the lateral (\(X\)-axis) direction for the full-frame curtain wall. The displacement applied to the entire frame curtain wall was set to connect the rigid beam and the aluminum frame using the same method as that used in the seismic test, and to impose a static displacement in the horizontal (\(X\)-axis) direction to the middle rigid beam; the peak displacement was 150 mm. The deformation when 150 mm of static lateral displacement was applied to the full-frame curtain wall is shown in Figure 18. Table 8 shows the major vulnerabilities of the full-frame curtain wall derived after performing the FE simulation. In particular, the gasket, which is a super-elastic material that restrains the glass facade, incurred a separation from the frame while applying a drift that exceeds the clearance. This indicates that the glass facade may break and fallout may occur. The vulnerabilities of the conventional curtain wall confirmed through the FE simulation showed similar results to the vulnerabilities confirmed through the experiment, as shown in Figure 19.  
Figure 17: Designed model for each linear guide length. Figure 18: Response of the conventional curtain wall under static lateral drift. Based on the FE simulation of the full-frame curtain wall, it was confirmed that the numerical model normally operates similarly to the static seismic experiment. However, it is essential to review each of the three axis (X-, Y-, and Z-axis) directions. To accurately analyze the interaction between the members constituting the curtain wall when it behaves due to earthquakes, FE simulations were performed on the single-frame numerical model composed of the largest glass facade. To compare the seismic performance of the non-seismic curtain wall and the curtain wall, the load on a single frame was set to apply a 50 mm displacement along the three axes (X-, Y-, and Z-axis). The aluminum frame and rigid beam were fixed by fasteners. Then, a lateral static displacement was applied to the upper rigid beam. Figures 20-25 show the stress distribution applied to the curtain wall during static drift in the three axis  
Figure 19: Major vulnerabilities of conventional curtain wall simulation: (**a**) mullion-to-fastener connection twist; (**b**) stress concentration on the edge of the glass; (**c**) aluminum frame fallout from the glass; (**d**) gasket twist; (**e**) expansion joint detachment; (**f**) stress concentration at expansion joint connection. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Components** & & **Vulnerability Type** \\ \hline Aluminum & \(\bullet\) & Mullion-to-fastener connection section distortion \\  
Through FE analysis of the stress distribution applied to the non-seismic curtain wall that was subjected to simulated static displacements based on the AAMA 501.4 standard, it was confirmed that the yielding of the gasket caused the sliding trigger between the glass facade and the aluminum frame. That is, it was predicted that glass-to-frame collision occurs as the aluminum frame deforms and the gasket is distorted, which ultimately causes the glass facade to fall out. However, in the case of a seismic curtain wall to which the fastener model proposed in this study is applied, which can control the displacement up to a maximum displacement of 150 mm, it is possible to adapt to changes in the geometry of the curtain wall system and the inter-story drift. It was confirmed that there was no damage in the event of earthquakes because the displacement applied to the curtain wall through the proposed fastener was dissipated and the stress was not transmitted to other members. As can be seen in Table 9, it was confirmed that the stress in the maximum drift of the seismic curtain wall was significantly reduced in all axes, except the \(Z\)-axis, compared to the non-seismic curtain wall.