## 4 Experimental Setup
### Design of the TMD  
Considering the difficulty of manufacturing and installing a TMD, a simple and practical method was adopted in the shaking table test. The installation strategy is to fix the mass on the steel spring plate to form the TMD device and fix it to the top of the structural column using a connecting damp such that the connecting fixture can realize a two-way connection. Therefore, many forms of TMD control schemes can be implemented. To study the effects of various control schemes on the damping effect of the TMD, the following schemes were adopted: single-tuned mass damper (STMD), dual-tuned mass damper (DTMD), multiple-tuned mass damper (MTMD), multiple dual-tuned mass damper (MDTMD), quadruple TMD, and spatial multi-point TMD. Among them, DTMD and MTMD are two sets of TMD forms, and MDTMD, quadruple TMD, and spatial multipoint TMD are four sets of TMD forms. The mass ratio of the TMD was 2.09%, where the mass of the model X with respect to the second-order mode was 7.4 kg, the corresponding TMD mass was 0.155 kg, and the mass ratio of TMD to the total mass was 0.27%. Via the addition of mass, the natural frequency of the TMD can be made close to the controlled frequency of the model structure. To further study the effects of the arrangement position on the vibration damping performance of the structure, various forms of TMDs were arranged at various positions in the structure. Figure 4 shows photographs of the arrangements of various TMD control strategies in the structure.  
Based on the pressure pulsation of the unit and the high frequency at which the powerhouse structure components resonate, the test identifies the modal parameters of the model structure. Based on the numerical analysis results, the structure was subjected to a sweep analysis over 5-200 Hz to cover its main mode to obtain the modal parameters of the structural excitation direction. According to the analysis of modal parameters, 90-140 Hz was determined to be the high-frequency sweep analysis frequency band of the structure, and the high-frequency natural frequency of the structure was 111.3 Hz.  
Simple harmonics were used to simulate the vibrational response of the pressure pulsation. The load frequency was analyzed with a natural vibration frequency of 111.3 Hz as the excitation frequency band to analyze the structural response under a high-frequency resonance. When the various forms of TMDs were added, the simulated pressure pulsation frequency remained the same and the damping structure was excited at the same load frequency to observe the vibrational response of the structure with and without TMD. In the test, the vibration table excitation direction was defined as the X-direction, and the vibration reduction test conditions are listed in Table 2, where suffix B indicates that the TMD device was arranged at the top of the bottom structure, suffix T indicates that the TMD device was arranged at the top of the two-layer structure, and spatial multi-point TMD indicates that four groups of TMDs are arranged on top of the two-layer structure and the bottom structure. IPE piezoelectric acceleration sensors were used to measure the vibrational response of the structure, and were placed on top of the first and second layers to measure the acceleration response.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Material** & **Modulus of Elasticity E (GPa)** & **Density P (Kg/M\({}^{3}\))** & **Poisson’s Ratio** \\ \hline steel & 200 & 7850 & 0.3 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Structural material parameters.  
Figure 4: _Cont._