# Seismic Behaviour of CFST Space Intersecting Nodes in an Oblique Mesh
## 6 Discussion
### Symmetry Coefficient of Plane Intersecting Angle  
The mechanical performance parameter curves of components with different plane symmetry coefficients are shown in Figure 7. As shown in Figure 7a-c, the ultimate bearing capacity of the node was negatively correlated with the plane angle symmetry coefficient. When the symmetry coefficient was \(\geq\)0.70, the degree of attenuation of the node's ultimate bearing capacity was insignificant, and the descending segment of the hysteresis curve after the peak load was not noticeable, indicating an excellent load-carrying capacity. When the symmetry coefficient was \(<\)0.70, the degree of attenuation of the node's ultimate bearing capacity was significant. The descending segment of the hysteresis curve after the peak load was prominent, indicating an insufficient load-carrying capacity. It is worth noting that the vertical residual deformation of the node at the loading end of the component with a symmetry coefficient of 0.70 was as high as 12.8781 mm, and the hysteresis curve moved towards the positive direction of the \(x\)-axis as a whole. The component with a symmetry coefficient of 0.50 also exhibited the same trend. This indicates that the asymmetric arrangement of the plane angle will increase the vertical residual deformation of the node and weaken its safety. The tensile and compressive stiffness of the node was proportional to the symmetry coefficient. When the symmetry coefficient was \(\geq\)0.70, the degradation curves of the overall axial stiffness in the positive and negative directions tended to overlap, and the degradation rate was consistent. When the symmetry coefficient was less than 0.70, the positive overall axial stiffness decreased significantly, and the initial stiffness in the negative direction was larger than that of the other specimens. However, the rate of stiffness degradation increased in the later stages. This was mainly due to the asymmetry, which caused the lower limb steel tube concrete to be in a compression, bending, and shear stress state. The existence of bending moments and shear forces will weaken the component's axial tensile and compressive stiffness. In the later stage, due to the increase in axial displacement, the bending deformation of the lower limb steel tube concrete gradually increased with the increase in asymmetry. Therefore, the impact on the rate of stiffness degradation increased. As shown in Figure 7d, the out-of-plane displacement of the nodes of the components with symmetry coefficients of 0.50 and 0.70 both exhibited nonlinear development in the later stages of loading, while the out-of-plane displacement of the nodes of the component with a symmetry coefficient of 0.39 was only 6.41 mm, which was still within a controllable range compared to the former two. This was mainly due to the significant difference in the plane angles of the upper and lower limbs of the component with a symmetry coefficient of 0.39, with the larger angle of the lower limb steel tube concrete experiencing a greater bending moment, resulting in bending failure at a lower load and smaller out-of-plane displacement. However, the out-of-plane displacement of components with a symmetry coefficient of 0.39 also showed a nonlinear growth trend, indicating that stricter out-of-plane constraints were required when the plane angles of the upper and lower limbs were asymmetric. Based on Figure 7a, it can be seen that in practical application, more enormous out-of-plane constraints and vertical deformation constraints should be set for  
Figure 7: Relevant mechanical property parameter curves of members with different symmetry coefficients. (**a**) Displacement load curve. (**b**) Skeleton curve. (**c**) Stiffness degradation curve. (**d**) Axial displacement-out of plane displacement curve. (**e**) Energy consumption curve. nodes with inconsistent upper and lower limb plane angles.