## 3 Calculation Method of Stable Bearing Capacity of Tower
### Influence Coefficient of Axial Stiffness of Joints  
In order to obtain the influence law of the axial stiffness of the joint on the stable bearing capacity of the tower, take the section sizes as \(A_{1}=A\), \(A_{2}=A/5\), \(A_{j}=\zeta A\), respectively, the tower root opening and the height of the joints are the same, and take the height of the joints as \(h\), that is \(b=h\), take the two-layer tower cells as the research object, that is \(l=nh\), \(n=2\), take the length coefficient of the connecting joint is \(k=0.3\), combined with Equation (14) and Equation (20), The calculation expression of the stable bearing capacity of the tower with and without the axial stiffness of the joint is obtained. The ratio coefficient of the two is taken as \(\chi\), and the expression obtained by calculation is shown in Equation (21). \[\chi=\frac{\left(32\sqrt{2}+5\pi^{2}\right)\zeta}{32\sqrt{2}\zeta+3.5\pi^{2} \zeta+0.3\pi^{2}} \tag{21}\]  
In Equation (21), \(\chi\) is the ratio coefficient of the tower bearing capacity considering and not considering the axial stiffness of the joint, and \(\zeta\) is the axial stiffness variation coefficient of the equivalent spring connected joint. With the increase of axial stiffness variation coefficient, the bearing capacity ratio coefficient \(\chi\) increases first and then tends to be stable. The variation curve is shown in Figure 12. According to the curve change curve, the proportion coefficient \(\chi\) of bearing capacity changes significantly in the range of axial stiffness change coefficient 0-0.4, then the change of proportion coefficient \(\chi\) tends to be gentle, and finally the value of \(\chi\) is stable at about 1.16. According to Equation (18), take \(\zeta=1/5\) to calculate the tower bearing capacity as the reference bearing capacity, and \(\zeta=1/5\sim 3\) to calculate the stable bearing capacity of the tower, respectively, and take the ratio coefficient to the benchmark bearing capacity as \(\chi_{1}\), The relationship curve between the ratio coefficient \(\chi_{1}\) and the axial stiffness change coefficient \(\zeta\) is obtained, as shown in Figure 13.  
According to Section 3.2, the tower connection joint can be equivalent to a spring element with a cross-sectional area of \(A_{j}\). According to the elastic deformation calculation formula of the joint, the calculation expression of the cross-sectional area of the equivalent spring joint \(A_{j}\) can be obtained as following. \[A_{j}=\frac{Fl}{E\Delta l} \tag{22}\]  
According to Equation (22), we can acquire Equation (23). \[\frac{A_{js}}{A_{jid}}=\frac{\kappa_{s}l_{s}}{\kappa_{d}l_{d}} \tag{23}\]  
In Equation (23), \(A_{js}\) and \(A_{jid}\) are the equivalent cross-sectional areas of equivalent spring of SLSPJ and DLDPJ, respectively; \(\kappa_{s}\) and \(\kappa_{d}\) are the equivalent elastic stiffness of SLSPJ and DLDPJ, respectively, which are the tangent stiffness of the elastic deformation  
Figure 12: Bearing capacity variation coefficient curve. Figure 13: Bearing capacity variation coefficient curve. part in the test of SLSPJ and DLDPJ, respectively; \(l_{s}\) and \(l_{d}\) represent the connection length of SLSPJ and DLDPJ, respectively. Combined with the bearing capacity test results of SLSPJ and DLDPJ, under the actual working state, most of the gusset plates are in the elastic state, according to the elastic part data of the load displacement curve in Figure 9. The following Equation is obtained through calculation. \[\kappa_{s}=35.6\ \text{kN}/\text{mm}\ \ \ \ \ \ \kappa_{d}=11.4\ \text{kN}/\text{mm} \tag{24}\]  
In the actual model, \(l_{s}=l_{d}\), which can be obtained by calculation as following. \[A_{js}/A_{jd}=3.12 \tag{25}\]  
Take the section sizes as shown in Equation (26). Figure 12.0  
Take the tower root opening and the height of the joints as \(h\), take the two-layer tower cells, i.e., \(l=nh\), \(n=2\), and the length coefficient of the connecting joint is \(k=0.3\).