# Study on Wind Resistance Performance of Transmission Tower Using Fixture-Type Reinforcement Device
## 4 Results and Discussion
### Enhancement Effect of the FRD  
In order to investigate the enhancement effect of wind resistance performance of the transmission tower with the installation of the FRD, the first reinforcement scheme is to only add FRD to the failure component shown in Figure 9. To accurately analyze the behavior of this component when enhanced by the FRD, the solid element is used to build this component while the other components are still modeled by the beam element. The four feet of the tower are set to be totally constrained to the ground. This multi-scale finite element model is presented in Figure 10. At the connection points of different elements, the six freedoms of the node of the beam element are completely constrained to the adjacent surface of the solid element, and therefore the force can be transferred among these components. It should be noted that the FRD used here has three fixture pairs, as analyzed in Section 2.  
In Figure 10, the length of the reinforced component is 1.5 m, which is identical to the case analyzed in Section 2. To assess the necessity of reinforcing more components of the tower, three more reinforcement schemes are also analyzed here, namely reinforcing the components with the respective lengths of 3 m, 4.5 m, and 6 m, as shown in Figure 11.  
Figure 11: The illustration of the reinforcing length.  
Figure 10: Multi-scale model of the transmission tower with the FRD.  
To better compare with the original model, the wind loads are applied to the tower when the wind speeds are respectively set as 38.1 m/s along the direction of the cable and as 44.7 m/s perpendicular to the direction of the cable. Figure 12 presents the displacement of the top component of the tower when different reinforcing lengths of the component are selected. It can be seen in Figure 12a that when the wind load is applied along the direction of the cable, the displacement of the top of the tower gradually decreases with the increase in the reinforcing length, which means the more components above the failure one are reinforced, the better the performance of the tower under the wind load. When the tower is not reinforced, the top displacement reaches 1455 mm, and it gets smaller until it reaches 977 mm, when the failure components are reinforced by the FRD. When the reinforcing length is 3 m, which corresponds to the case that two adjacent components in the vertical column are reinforced, the top displacement reduces to 658 mm and remains steady when the reinforcing length is enlarged. That is to say, the installation of the FRD can reduce the top displacement of the tower by 55%.  
Figure 12b demonstrates the results of the tower when the wind load is applied in the direction perpendicular to the cable. The varying trend of the results is similar to that in Figure 12a. When the tower is not reinforced, the displacement of the top of the tower is about 2047 mm, and it decreases to 1493 mm when the reinforcing length is 1.5 m. When the reinforcing length reaches around 4.5 m, the top displacement of the tower becomes stable and is around 670 mm, which is about a reduction of 67% of that of the original model.