## 2 Experiment Setups
### Mean Wind Pressure Coefficient at a Wind Incidence Angle of 0 deg  
Figure 5 shows the contour plot of wind pressure coefficients \(C_{p}\) on the front, side, and back surfaces of the building with various extensional depths of vertical rib at the wind incidence angle of 0 deg. It can be observed that the wind pressure near the top of the building shows relatively smaller values compared to that in the other regions due to the three-dimensional flow effect. The maximum wind pressure coefficient of the basic model (i.e., smooth facade) is slightly smaller than that of the other models. This is because the vertical rib behaves like \"wind catching\" near the middle of the windward surface and keeps the air stationary between the two neighboring ribs, resulting in a larger positive pressure than that without ribs. Compared to the basic model, the negative pressure area on the left and right edges of the front surface shows an increasing trend with the increase in the rib extensional depth. This may result from the local air recirculation at the outermost vertical rib, which enhances the flow separation around the edge of the front surface. The side surface is mainly subjected to negative wind pressure due to the flow separation, and the wind suction on this surface increases slightly with the increase in the rib extensional depth, which may be partially attributed to the superposition of the local air recirculation  
Figure 4: Illustration of the base forces, base bending moment, and layer forces of the building.  
from the outmost vertical rib and the flow separation at the building corner. Regarding the back face located in the wake zone, the negative wind pressures on the models with \(b/B=3\%\) and \(b/B=4\%\) are larger than those of the other models.  
To compare the difference in the wind pressures between different rib cases in detail, the wind pressure coefficient \(C_{p}\) at the middle height of 55 m is illustrated in Figure 6 for various extensional depths. It shows that \(C_{p}\) in the middle of the front surface is very close for the five tested cases, whereas that near the left and right edges varies from a positive value of 0.4 to a negative value of about \(-0.8\) with the increase in \(b/B\). For the side surface, the negative wind pressure, i.e., wind suction, increases with the rib extensional depth. Under the case of \(b/B=4\%\), the largest increment appears at the windward end of the side surface (i.e., measuring point 13), reaching about 50%, while in the cases of \(b/B\) within 2%, the wind suctions are quite similar on the side walls. A similar phenomenon can also be found on the back surface, that is, the models with \(b/B=3\%\) and 4% result in much larger negative wind pressures while the other rib cases show an insignificant difference in wind pressure. Therefore, it may be concluded that for test cases, the use of a large extensional depth (e.g., \(b/B\geq 3\%\)) of surface-attached vertical rib could significantly affect the wind pressures on the side and back surfaces and the left and right edges of the front surface.  
Figure 5: Distribution of the mean wind pressure coefficients on the front, side, and back faces (\(\theta=0^{\circ}\)).