# Performance Analysis of an Improved Gravity Anchor Bold Expanded Foundation
## 2 Load Transfer Mechanism and Failure Mode  
The load transfer mode of spread footing mainly relies on the bond between the foundation ring and the concrete, and the friction between the concrete and the side wall of the foundation ring to transfer the upper load to the lower foundation concrete. The foundation force characteristics, as well as the transfer characteristics, have been studied by scholars [33; 34]. The damage around the steel ring of the spread footing is more obvious, which is prone to the problems of sliding of the steel ring and cracking of the surrounding concrete. The anchor foundation solves the above problems well. There is no contact \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Name** & **Sign** & **Value** & **Unit** \\ \hline Radius of the foundation plate & \(R_{1}\) & 10.00 & m \\ Radius of the foundation column & \(R_{2}\) & 4.0 & m \\ Foundation edge height & H\({}_{1}\) & 0.85 & m \\ Variable cross-section height of the foundation & H\({}_{2}\) & 1.65 & m \\ Column height & H\({}_{3}\) & 1.90 & m \\ Upper cavity radius & \(r_{1}\) & 1.7 & m \\ Radius of the lower cavity & \(r_{2}\) & 2.975 & m \\ Upper cavity height & \(h_{1}\) & 3.0 & m \\ Lower cavity height & \(h_{2}\) & 1.4 & m \\ Distance between the ground bolt and the inner cavity & \(b_{1}\) & 0.775 & m \\ Distance from the ground bolt to the side wall & \(b_{2}\) & 0.5 & m \\ The thickness of the side wall of the column & \(b_{3}\) & 1.025 & m \\ Tower bucket force width & \(b_{f}\) & 0.64 & m \\ Load acting force elevation & H\({}_{f}\) & 0.465 & m \\ Original buried depth of the foundation & h\({}_{d}\) & 3.9 & m \\ Foundation backfill thickness & h\({}_{b}\) & 0.4 & m \\ Excavation slope & p & 1.0.5 & / \\ Width of the foundation working face & b & 1 & m \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The size of each part of the foundation. Figure 5: New turbine foundation size and anchor bolt details. between the anchor rods and the concrete. There is usually a layer of pipe on the outside of the anchor. Both ends of the anchor are fixed to the surface of the upper and lower anchor plates. There is face-to-face hard contact between the anchor plate and the foundation. The bottom flange transfers the upper load to the foundation through the anchor. As shown in Figure 6, the moment can be converted into the pressure of the anchor ends on the concrete. The relationship between them is as follows:  
\[\text{M}=\text{P}\cdot\text{D}_{1} \tag{1}\]  
The vertical force is converted into a homogeneous pressure on the foundation of the flange. The torque and the horizontal force are mainly converted into shear forces on the anchor rod. The shear force is converted through the anchor into pressure on the concrete by the anchor. The foundation is always under pressure throughout the entire stressing process. This takes full advantage of the excellent compressive capacity of the concrete, thus avoiding tensile cracking of the concrete foundation around the foundation ring. In the event of corrosion or fracture of the anchor rods, the lower space can be accessed for timely replacement. As shown in Figure 6, the annular foundation is divided into three parts: the corbel, side wall, and bottom plate. According to the specification, the reinforcement calculation of each part is completed. The upper load is transmitted to the side wall through the corbel of the foundation. Finally, it is transmitted to the foundation plate, causing the pressure to change between the foundation and the ground. The foundation may undergo structural damage under external loads. For example, the concrete cracking area being too large, the bolt being broken in a large area, punching failure, shear failure, local compression failure of the concrete, and so on. In addition, the separation area between the foundation and the soil, the Inclination of the foundation itself, the settlement of the foundation, and the inclination of the foundation should be strictly controlled.