## 2 Magnetorheological Smart Isolation System
### Isolation Bearing  
For this experiment, four ordinary rubber sandwich isolation pads were fabricated. They were placed on the four corners of the model structure. The isolation bearing diameter used in the experiment is 100 mm and the total thickness of the rubber layer is 22.5 mm. Other basic parameters for the rubber bearings have been shown in Table 2.  
In order to test the actual performance of the rubber pad, the test of 100% horizontal shear deformation for the rubber bearings was performed. The pressure shear test for the rubber bearing was carried out under the compressive stress level of 10 MPa, while the horizontal shear deformations were 50% and 100%, respectively. The test setup is shown in Figure 4.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Total Height** & **87.5 mm** & **Thickness of Protective Layer** & **5 mm** \\ \hline External diameter & 110 mm & Middle hole diameter & 18 mm \\ Height (excluding connection plate) & 63.5 mm & Rubber layer thickness & 1.5 mm \\ Effective diameter, \(D\) & 100 mm & No. of rubber layer & 15 \\ Design bearing capacity & 75 kN & Total rubber thickness, \(T_{r}\) & 22.5 mm \\ Standard displacement (\(d_{\max}\)) & 55 mm & Thick laminated sheet & 1.5 mm \\ maximum displacement & 23 mm & Thickness of connecting plate & 12 mm \\ Layers of laminated sheet & 14 & Sealing plate thickness & 10 mm \\ Design surface pressure & 10 MPa & - & - \\ \hline \hline \end{tabular}
\end{table}
Table 2: The basic parameters of designed rubber bearing.  
Vertical stress check: The upper structure was approximately 10 tons. The calculated compressive stress for each bearing was around 3.2 MPa. This met the allowable stress limit of 10 MPa.  
Horizontal deformation check: for the second category site within the eighth degree zone (rare earthquakes), calculation values for the equivalent load (kN) was:  
\[F_{ek}=\alpha\times G_{eq}=0.3471\times 0.85\times 100=31.8 \tag{7}\]  
Maximum deformation of the isolation layer in mm was:  
\[D_{m}=F_{ek}/K_{d}=31.8/1112=28.6 \tag{8}\]  
For the fourth category site within the eighth degree zone (rare earthquakes), the calculated value for the equivalent load (kN) was:  
\[F_{ek}=\alpha\times G_{eq}=0.507\times 0.85\times 100=43.08 \tag{9}\]  
In the above formula \(F_{ek}\) is the standard value of total horizontal seismic force; \(\alpha\) is the seismic influence coefficient; \(G_{eq}\) is the equivalent Total Gravity Load.  
Maximum deformation of the isolation layer in mm was:  
\[D_{m}=43.08/1112=38.7 \tag{10}\]  
According to the seismic code, horizontal deformation of the rubber bearing was:  
\[\text{min}(0.55\ \times\ D=55\ \text{mm}\ |\ 3\ \times\ T_{r}=67.5\ \text{mm}) \tag{11}\]  
In the above formula \(T_{r}\) is total thickness of rubber layer; \(D\) is the diameter of rubber bearing.  
Therefore, the allowable deformation of the bearing was 55 mm. The structure of the base isolation bearing was used to satisfy the deformation constraints for the second category site condition; however, for the fourth category site condition, the maximum deformation of the rubber bearing was noticeably too large, having exceeded the deformation limit value of 1.5 times the rubber layer thickness. The experimental results also prove that the rubber pad is not stable and an additional damper must be used to control the significant deformation requirement.  
Figure 4: Shear test of rubber bearing under axial pressures.