## 2 Prototype Experiment
### Experimental Results
#### 2.3.2 Joint Response  
By employing displacement meters at the extrados and intrados of the joint, the opening and compression of the joint on each side can be obtained. Subsequently, the joint rotation angle \(\theta\) can be computed [34] using Equation (1).  
\[\theta=\frac{u_{ii}-u_{ex}}{b}, \tag{1}\]  
\(u_{in}\) and \(u_{ex}\) are the axial opening/closing deformations of the joint intrados and joint extrados, respectively, and \(b\) is the thickness of the segment.  
The joints with intrados in tension and extrados in compression are defined as positive moment joints. Therefore, Joints 1, 5, 6, and 10 located at the top and bottom of the structure are categorized as positive moment joints, while Joints 2, 3, 4, 7, 8, and 9 located at the left and right waists of the structure are categorized as negative bending moment joints. The development of joint rotation angles for positive moment joints (Joints 1, 5, 6, and 10) and negative moment joints (Joints 3, 4, 7, and 9) is presented in Figure 8. For Joint 2 and Joint 8 negative moment joints, their deformations are not presented due to sensor damage. According to Figure 8a, among these positive moment joints, Joint 1 and Joint 5, situated closer to the short axis (top and bottom) of the structure exhibit faster development of joint rotation angles compared to Joint 6 and Joint 10, with augmentations of about 10%-43%. Moreover, the deformation of Joint 1 surpasses that of Joint 5. As for negative moment joints presented in Figure 8b, the joint rotation angle of Joint 3, positioned closer to the  
Figure 7: Development of structural deformations: (**a**) Overall structural deformation; (**b**) Convergence deformations of short and long axes.  
waist of the structure, experiences faster development compared to those of Joints 4, 7, and 9. Notably, the deformations of Joint 4 and Joint 9 develop rapidly in the initial stage of the load-bearing process but subsequently decelerate swiftly after P1 reaches 50 kN.  
Bolt axial forces are monitored, with their development presented in Figure 9. According to Figure 9a, the axial force of the M30 bolt in Joint 1 is about 6.7% greater than that of the M30 bolt in Joint 5, aligning with the observed joint rotation angles in Figure 8a. Additionally, at Joint 5, it is noted that the bolt axial force of the M30 bolt, located closer to the internal surface, exceeds that of the M48 bolt by about 10.5%. This phenomenon underscores the necessity for further optimization of joint design to fully exploit the bearing capacity of bolts. As shown in Figure 9b, the bolt axial force developments of Joint 3 and Joint 8 are basically the same.  
Based on the test results of joint deformations and bolt axial forces, it can be concluded that among the positive moment joints, Joint 1 exhibits a higher response compared to Joint 5 and surpasses Joints 6 and 10. Negative moment joints can be categorized into three  
Figure 8: Development of joint rotation angles: (**a**) Positive moment joints; (**b**) Negative moment joints.  
Figure 9: Development of bolt axial forces: (**a**) Positive moment joints; (**b**) Negative moment joints.  
groups. Joint 3 and Joint 8 constitute the group with the most significant response, followed by Joint 2 and Joint 7. Joint 4 and Joint 9 exhibit the smallest response. Additionally, compared with structural deformation, it is discerned that the positive bending moment region is smaller than the region corresponding to inward deformation.