# Dynamic Response Analysis of Mega-Sub Isolated Structures under Multiaxial Earthquakes
###### Abstract  
With the use of seismic isolation techniques on mega-sub structures, several scholars have carried out research on them. However, little research has been carried out on mega-sub isolated structures under multiaxial earthquakes. There have been instances in actual engineering where the peak vertical acceleration exceeded the horizontal direction, and the vertical seismic component will also amplify the dynamic response of the structure in the horizontal direction, so in practice, it is necessary to consider the influence of the vertical component of the earthquake on the structure. To investigate the dynamic response of mega-sub isolated structures under unidirectional earthquake and coupled earthquake, this paper used numerical methods to analyze the influences of the horizontal and vertical damping ratio of  
found that the introduction of tuned mass dampers can significantly reduce the response of structures under earthquake loads. They also proposed that it is feasible to apply dampers to mega structures (forming mega sub-controlled structural systems, i.e., MSCSS). [PERSON] et al. [12] established a two-dimensional equivalent model of MSCSS and mega frame structure and analyzed the elastic-plastic time history of the structure using observed data, and the result showed the control effect of the mega control structure is better than that of the mega frame structure. At the same time, [PERSON] et al. [13] studied the damping coefficient of the sub-structure, as well as the dynamic influences of the stiffness ratio and mass ratio of the main and sub-structures on the mega-controlled structure (MSCSS). The study concluded that there was a significant decrease in the dynamic response of the structure when the mass ratio was 2.38, and the stiffness ratio was 0.15-0.32. [PERSON] et al. [14] optimized the placement of viscous dampers between the main structure and sub-structure and studied the optimal damper parameters, which further reduced the dynamic response of the structure. [PERSON] et al. [15] added inverted V-shaped support to MSCSS. Built on the dynamic characteristics of the structure under seven seismic waves, it was found that this method can greatly improve the control ability of the structure response under strong earthquakes. In addition to the use of dampers to control the dynamic response of the mega sub-structure, it also can use isolation sub-structure to control the dynamic response of the structure, and this method can avoid the structure from the P-delta influence caused by large overturning moments and high center of gravity [16; 17]. [PERSON], et al. [18; 19] proposed setting laminated rubber bearings between the main and sub-structures and conducted experimental research, and the results showed that this method could significantly reduce the dynamic response of the structure. However, it is necessary to optimize the number and location of isolation sub-structures. Subsequently, [PERSON] et al. [20] studied the dynamic characteristics of the structure under different parameters, considered the number and location of sub-structures, and proposed a parameter optimization scheme with the base shear force as the optimization objective. They found that increasing the number of isolation sub-structures can improve the control performance of the structure. Further, [PERSON] et al. [21] established the equations of motion of the mega-sub isolated structure and investigated the principle of isolation of the structure by using a simplified concentrated mass model, and it was found that the performance of both the seismically isolated and non-seismically isolated sub-structures in the mega sub isolated structure was better than that of the aseismic structure through experimental studies. [PERSON] et al.