# Dynamic Response Analysis of Mega-Sub Isolated Structures under Multiaxial Earthquakes
## 6 Conclusions  
This paper analyzed the dynamic response of the mega sub-isolated structure under horizontal and coupled earthquakes. In addition, the collision of the main and sub-frames of the mega-sub isolated structure was simulated, and the parameters that affect the collision response were studied. The following conclusions were drawn:  
1. The study found that changes in the damping ratio, mass ratio, and frequency ratio will influence the displacement and acceleration peaks of the dynamic response of the main and sub-frames. In this paper, the optimal parameter values of each item are obtained through numerical method research. The horizontal isolation effect is the best when the horizontal damping ratio is 0.3, the horizontal frequency ratio is 0.6, and the mass ratio is 3.0, while the vertical damping ratio of 0.2 and the vertical frequency ratio of 1.2 have the best effect on isolation, thus the parameters need to be set according to the actual requirements during engineering design. Figure 22: Influence of substructure height variation on the peak collision acceleration force in the main and substructures at different seismic waves: (**a**) El Centro wave; (**b**) Taft wave; (**c**) Artificial wave. 2. Through collision simulation, it is found that instantaneous and huge collision force will be generated when the main structure and the sub-structure collide, and the response value of acceleration and base shear force will be amplified instantaneously. It will have a significant impact on the safety and comfort of the structure. The amplification factor of peak acceleration of the main structure is smaller than that of the sub-structure, and the peak value of collision force is not positively correlated with the peak value of acceleration. With the increase of peak acceleration, the collision force curve will appear decline section. Similarly, the peak value of the collision force does not decrease with the increase in the distance between the main structure and the substructure. The peak value of the collision force is not at the minimum distance, but the increase in the peak collision force will also lead to an increase in the occurrence frequency of collisions between the main and substructure. 3. Under the excitation of coupled earthquakes, the vertical earthquake component will amplify the collision response between the main structure and the substructure and slightly advance the collision occurrence time. Furthermore, under the one-way excitation, the acceleration after the collision will be amplified due to the small stiffness of the isolation bearing. In addition, the change in acceleration and collision force is not positively correlated with the change in story height, and there is no necessary connection between the two. When considering the impact of story height on collision, it is necessary to conduct a specific analysis according to the number of floors and wave type. Under different earthquake actions, the dynamic response patterns of the mega substructure isolated structure vary. Therefore, it is important to consider and compare various aspects during the structural design process to select the optimal parameters. Through the above conclusions, we can know the optimal parameter values of the mega sub-isolated structure under multiaxial earthquakes and, at the same time, understand the dynamic response of the structure in the case of collision and the influence of related parameters on it, which provides a basis for further optimization of the mega sub isolated structure and practical application in engineering. Data curation, H.M.; Formal analysis, W.L. ; Investigation, W.L. and G.L. ; Project administration, X.Y. ; Resources, X.Y. ; Supervision, X.Y. ; Writing--original draft, G.L. ; Writing--review and editing, W.L. and J.L. All authors have read and agreed to the published version of the manuscript. This work was financially sponsored by National Natural Science Foundation of China [Grant NO. 52278490], the Science and Technology Planning Project of Fujian [Grant NO.