## 3 Finite Element Modeling of the Main Tower
### Meshing of the FE Model  
In this model, the concrete entity of the main tower is meshed by 4-node and 4-dihedral primary units. Meanwhile, since the main tower is composed of different components and there are many chamfers in the contact area between the beam and the tower column, the meshed entity technology is adopted by segmenting cutting. To avoid the phenomenon of non-automatic coupling of contact node elements in the grid division of entities with different sections, it is necessary to use the entity difference set operation of Boolean operation in advance for mutual printing of contact surfaces. The meshing size is a key parameter in finite element modeling. For determining the meshing size to be adopted in the present study, mesh sensitivity analysis was conducted by employing the meshing size of 1.0 m, 0.5 m and 0.2 m, respectively. The thermal stresses on the outer surface of east tower wall at 3:00, 6:00, 9:00, 12:00, 15:00 and 18:00 were extracted, as listed in Table 1. It can be seen from Table 1 that the results corresponding to a meshing size of 1.0 m, 0.5 m and 0.2 m show minor difference. Therefore, for improving the computing efficiency, a meshing size of 1.0 m was adopted in the present study.  
Figure 5: Finite element model of the main tower.  
The size of the solid grid units on both sides of the tower columns, as well as on the upper and lower beams, is set to be 1 m. In general, there are 266,500 concrete 3D units.  
Since the transverse prestressed steel bundle is arranged in a curved direction, the B-spline curve is generated by using the function of \"defining line\", and the reinforcement in the solid unit is selected at the same time. The common node combined with embedded constraint and adaptive comparison line grid division method is used to ensure the common force between reinforcement and concrete in the model calculation. The generated prestressed steel beam grid elements are all one-dimensional low-order line elements (regardless of the influence of curvature on friction), and the number is 88,868, as shown in Figure 6. The temporary cross bracing is built with one-dimensional, two-node beam elements. For adaptive grid division, there are 230 beam elements and 45 rigid connection elements at both ends of the temporary cross-bracing, as shown in Figure 7. The grid division diagram of the tower column and the lower beam is shown in Figure 8. There are 157,950 nodes and 355,643  
As the thin-walled concrete tower is constrained, the thermal stress will be generated due to the influence of temperature change. The equilibrium equation to determine the thermal stress could be determined by Equation (2) [13]:  
\[\begin{cases}\varepsilon_{x}=\dfrac{1}{E}\big{[}\sigma_{x}-\
u(\sigma_{y}+\sigma _{z})\big{]}+\alpha\Delta T\\ \varepsilon_{y}=\dfrac{1}{E}\big{[}\sigma_{y}-\
u(\sigma_{x}+\sigma_{z}) \big{]}+\alpha\Delta T\\ \varepsilon_{z}=\dfrac{1}{E}\big{[}\sigma_{z}-\
u(\sigma_{x}+\sigma_{y}) \big{]}+\alpha\Delta T\end{cases} \tag{2}\]  
where \(\sigma_{x}\), \(\sigma_{y}\), and \(\sigma_{z}\) is the stress component along \(x\), \(y\), and \(z\)-axis, respectively; \(\varepsilon_{x}\), \(\varepsilon_{y}\), and \(\varepsilon_{z}\) is the corresponding strain component; \(E\) is the elastic modulus; \(\
u\) is the Poisson's ratio; \(\alpha\) is the coefficient of thermal expansion; and \(\Delta T\) is the temperature change.