## 6 Conclusions  
The present paper reports the results of the comprehensive experimental investigation designed to verify the effectiveness of a prototype base isolation system made of PBs in reducing structural vibrations. In order to get an insight into the basic mechanical characteristics of the polymer used, \begin{table}
\begin{tabular}{l c c c} \hline \hline  & \multicolumn{3}{c}{**Peak Acceleration at the Top of**} \\  & \multicolumn{3}{c}{**the Tested Model (m/s\({}^{2}\))**} \\ \cline{2-4}
**Dynamic Excitation** & **Fixed-Base Model** & **Model Isolated with PBs** & **Reduction (\%)** \\ \hline
1940 El Centro earthquake & & & \\ NS component, original record with PGA = 3.070 m/s\({}^{2}\) & 5.98 & 3.99 & 33.3 \\ \hline
1971 San Fernando earthquake & & & \\ Pacoima Dam station, N74\({}^{\circ}\)E component, scaled & 8.41 & 3.63 & 56.8 \\ record with PGA = 5.688 m/s\({}^{2}\) & & & \\ \hline
1989 Loma Prieta earthquake & & & \\ Corzalitos station, NS component, scaled record with PGA = 3.158 m/s\({}^{2}\) & 5.49 & 3.95 & 28.1 \\ \hline
1994 Northridge earthquake & & & \\ Santa Monica station, EW component, scaled record with PGA = 4.332 m/s\({}^{2}\) & 7.68 & 5.14 & 33.1 \\ \hline
2002 Polkovice mining tremor & & & \\ NS component, original record with PGA = 1.634 m/s\({}^{2}\) & 2.67 & 2.34 & 12.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of the seismic tests for the two-storey structure model. material testing was firstly performed. The results clearly demonstrated that the analyzed polymer is markedly nonlinear and its mechanical behaviour strongly depends on the strain rate. Moreover, a relatively high value of the loss factor was obtained from the DMA tests, which confirms high damping properties of the material. The next stage of the study was to conduct sine sweep tests to analyze the dynamic behaviour of the structure models with and without the PBs. As expected, the results obtained from the sine sweep tests confirmed that application of the prototype PBs leads to a significant decrease in the acceleration values experienced by the tested models during sinusoidal excitation. Peak accelerations were reduced by approximately 58% (from 7.74 to 3.25 m/s\({}^{2}\)) and 45% (from 4.42 to 2.44 m/s\({}^{2}\)) for the single-storey and two-storey structure models, respectively. In the final stage of the current investigation, the structure models, both fixed-base and base-isolated, were subjected to the El Centro earthquake of 1940, the San Fernando earthquake of 1971, the Loma Prieta earthquake of 1989, the Northridge earthquake of 1994, and finally the Polkowice (Poland) tremor of 2002 as an example of mining-induced seismicity. The shaking table tests confirmed very high effectiveness of the isolation devices in improving dynamic behaviour of the experimental models. Peak lateral accelerations recorded at the top of the tested structures were reduced by approximately 11-39% and 12-57% for the single-storey and two-storey structure models, respectively. The results obtained clearly demonstrate that, due the application of the prototype base isolation system made of PBs, the peak lateral accelerations recorded at the top of the tested structures were markedly reduced. Additionally, it should be underlined that the horizontal displacement capacity of the PBs has not been exceeded under any tested earthquake excitation, which also confirms proper design of seismic bearings. The results of the current study confirmed relatively high effectiveness of the prototype PBs in reducing structural vibrations of two experimental models. Nevertheless, there is a need for further development of the seismic isolation system based on the application of polymeric material. The studies are necessary to be conducted so as to fully verify the effectives of a full-scale multi-dimensional PBs as a base isolation system for real structures. These should include numerical simulations as well as experimental tests conducted on a large six degrees-of-freedom shaking table.