# PTMD Control on a Benchmark TV Tower under Earthquake and Wind Load Excitations
## 6 Vibration Control with PTMD
### Optimization Control Effectiveness under Earthquake Excitation  
The feasibility of the proposed PTMD on enhancing earthquake safety of the host structure is verified by subjecting the structure to real earthquake records. The El Centro earthquake (NS, 1980) and Tianjin earthquake records (NS, 1976) are adopted to excite the structure. A simulation is performed by tuning the peak acceleration of the excitations along the long-axis from 0.1 \(g\) to 0.3 \(g\). The earthquake records are chosen based on the sites and the suggestions from the local design codes. Earthquake components along the long and short axes are considered simultaneously, and the ratio of peak acceleration is set to be 1:0.85 according to the Chinese Aseismic Design Code.  
Unlike wind load excitation cases, earthquakes can generate more severe impacts between the mass and the host structure. Thus, a certain amount of energy can be consumed through the impact behavior. As mentioned before, the original gap value between the mass and the limitation should be selected carefully to guarantee beyond a certain impact level. Here the maximum gap value is decided based on the maximum relative displacement of the mass and the structure derived from TMD-controlled simulation results. Time history of uncontrolled, TMD-controlled, and PTMD-controlled displacement responses on the tower top are compared in Figure 11 when a 300 t mass is connected and the gap is set as 0.25 m. The corresponding bounding force is also shown in the figures. It is clearly observed from these results that the PTMD can produce much better performance on the reduction of earthquake-induced displacement. When the Tianjin earthquake strikes, the TMD failed to reduce the peak responses. On the contrary, the peak and RMS displacement responses are  
Figure 10: Control results under a stochastic wind load.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**Respenses**} & \multicolumn{1}{c}{**Uncontrolled**} & \multicolumn{1}{c}{**TMD Controlled**} & \multicolumn{1}{c}{**PTMD Controlled**} \\ \hline \multirow{4}{*}{Mast top (_long axis_)} & Peak displacement (m) & 0.662 & 0.280 & 0.276 \\  & RMS displacement (m) & 0.203 & 0.102 & 0.101 \\  & Peak acceleration (m/s\({}^{2}\)) & 3.976 & 3.170 & 3.139 \\  & RMS acceleration (m/s\({}^{2}\)) & 1.068 & 0.935 & 0.929 \\ \hline \multirow{4}{*}{Tower top (_long axis_)} & Peak displacement (m) & 0.042 & 0.026 & 0.026 \\  & RMS displacement (m) & 0.014 & 0.009 & 0.009 \\  & Peak acceleration (m/s\({}^{2}\)) & 0.043 & 0.037 & 0.037 \\  & RMS acceleration (m/s\({}^{2}\)) & 0.013 & 0.011 & 0.011 \\ \hline \multirow{4}{*}{Mast top (_short axis_)} & Peak displacement (m) & 0.691 & 0.305 & 0.301 \\  & RMS displacement (m) & 0.213 & 0.105 & 0.104 \\  & Peak acceleration (m/s\({}^{2}\)) & 4.253 & 3.359 & 3.323 \\  & RMS acceleration (m/s\({}^{2}\)) & 1.130 & 0.955 & 0.949 \\ \hline \multirow{4}{*}{Tower top (_short axis_)} & Peak displacement (m) & 0.031 & 0.020 & 0.020 \\  & RMS displacement (m) & 0.011 & 0.008 & 0.008 \\ \cline{1-1}  & Peak acceleration (m/s\({}^{2}\)) & 0.029 & 0.027 & 0.027 \\ \cline{1-1}  & RMS acceleration (m/s\({}^{2}\)) & 0.009 & 0.008 & 0.008 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Comparison of peak and RMS responses under stochastic wind excitation.  
Figure 12: Comparison of the seismic responses. (El Centro earthquake record, 0.3 _g_).