## 4 Proposed Methodology of Monitoring  
### Finite Element Modeling  
In this section, the influence of intelligent active control on the stress, deformation, and stability of the tower is simulated by the finite element software MIDAS/Civil. The three-dimensional structure tower model is established, and the half-span is analyzed to model the suspended arch rib of Matan Hongshui He Arch Bridge and Pingnan Third Bridge [30] (as seen in Figure 9).  
Tower structure is simulated according to the actual construction sequence. The wind cable is simulated by the cable element, and the stiffness reduction is also considered [31]. The rest is simulated by beam element, and there are 6756 nodes and 13,678 elements in this model. Since the tower bottom is build-in on bedrock, the tower is fixed in this model. Based on the lifting weight, the impact effect and the influence of small wheel pressure are considered. Besides, the wind load is six degree (from the river to the bank direction) under normal working conditions. The arch rib is constructed by cantilever construction with cable-stayed button-hanging method, and it includes 12 installation sections. The mass of the arch rib will produce force on the button-hanging point of the tower through the cable when the arch rib is button-hanging. As for the initial tension of the wind cable, the tower is connected with the cable by nodal plates and bolts. Therefore, during modeling, the actual dead weight of the tower is multiplied by a coefficient of 1.2 times before it is input into the model for calculation. In a cable-arch bridge or in a cable-stayed bridge, the flexural rigidity of slender cables can generally be neglected. Conversely, it cannot be negligible for the shortest ones. The accuracy of cable force calculation is directly related to the boundary conditions and calculation model at both ends of the cable. Stiffness and boundary conditions are the two most important factors in the establishment of short cable model. The accurate measurement method of cable force is adopted [32], which comprehensively considers the influence of bending stiffness and boundary conditions. At the same time, the bending stiffness is taken as an implicit calculation parameter, which avoids the problem that it is difficult to identify accurately, reduces the measurement difficulty, and improves the measurement accuracy [33; 34; 35].  
The cable lifting load and buckle load are equivalent to node load, and the wind load is equivalent to surface load. The initial cable tension and active control force are applied to the wind cable element as the initial tension load. Active control only occurs in the working state. In the paper, model for the normal working state and the active regulation under normal working state is established respectively. Because load combination 1 is the most unfavorable working condition under the working status, the most unfavorable condition is actively adjusted to load combination 2. The five types of load combination effect are shown in Table 2 below. Moreover, the static characteristics are studied under each load combination.  
Figure 9: Model diagrams of Matan Hongshui He Bridge and Pingnan Third Bridge. (**a**) Model diagram of Matan Hongshui He Bridge; (**b**) Model diagram of Pingnan Third Bridge.