# Seismic Behaviour of CFST Space Intersecting Nodes in an Oblique Mesh
## 6 Discussion
### Plane Intersecting Angle  
Figure 9 presents the mechanical performance parameters of components with different plane angles. As shown in Figure 9a,b, the specimens' ultimate load and overall compressive stiffness were positively correlated with the plane angle. The effect of the plane angle on the positive ultimate load was more significant than that on the negative ultimate load. The negative initial stiffness of all specimens had a significant difference. However, the difference in the stiffness degradation curve was slight in the later loading stage, indicating that the change in the plane angle had little effect on the tensile perfor  
Figure 8: Mises stresses of members with different plane symmetry coefficients. (**a**) Symmetry coefficient = 0.70. (**b**) Symmetry coefficient = 0.50. (**c**) Symmetry coefficient = 0.39.  
mance of the node. The positive residual loads of the specimens with plane angles of 70\({}^{\circ}\) and 90\({}^{\circ}\) were 0.854 and 0.868 of their ultimate loads, respectively. The degradation rate of positive stiffness was higher, and the load-bearing capacity was lower than other components. Notably, the hysteresis curves of these two types of components exhibited obvious left and right shifts, indicating that the plastic deformation and vertical residual displacement of the node were large. According to Figure 9d, except for the component with a plane angle of 35\({}^{\circ}\), the energy consumption of the other components increased nonlinearly. Especially, the component with a plane angle of 50\({}^{\circ}\) showed a decrease in energy consumption capacity in the seventh cycle, and the total energy consumption was only 0.5269 of that of the component with a plane angle of 70\({}^{\circ}\).  
Figure 10 shows the Mises stress cloud map and overall displacement cloud map of specimens with different plane angles. It can be seen from the figure that there was no obvious bending of the member in the ultimate state of the component with a plane angle of 20\({}^{\circ}\). The failure mode was the bulging of the steel tube in the node area. The components with plane angles of 70\({}^{\circ}\) and 90\({}^{\circ}\) experienced obvious bending failure, and the extreme displacement values mainly occurred in the CFST in the non-node area, which were 17.92 mm and 15.79 mm, respectively. The steel tube stress at this location reached its ultimate tensile strength, and plasticity develops fully, resulting in a large z-direction displacement at the node's centre, leading to large residual deformations of \(-\)7.19871 mm and 9.57204 mm, respectively. The failure of these two types of components occurred in the CFST in the non-node area, and the outer steel tube at the node was still in the elastic-plastic stage. The mean values of the Mises stress of the concrete were 31.39 MPa and 45.32 MPa, respectively, which still had a large safety margin. Therefore, the design criterion of \"component failure before node failure\" was satisfied. However, considering  
Figure 9: Relevant mechanical property parameter curves of members with different plane angles. (**a**) Displacement load curve. (**b**) Skeleton curve. (**c**) Axial displacement-out of plane displacement curve. (**d**) Energy consumption curve.  
the safety of the node, vertical constraints should be applied to components with plane angles greater than or equal to 70\({}^{\circ}\).