## 2 Experimental Process  
### Specimen Design  
Three bearings, including HDRB-LSF, TLRB, and LRB were adapted in the test. Figure 1 only displays the configuration of HDRB-LSF. All the bearings were fabricated with a diameter of 600 mm. The thickness and the diameter of the upper and lower sealing plate were 20 mm and 600 mm, respectively. The thickness and the diameter of the upper and lower connecting plates were 25 mm and 700 mm, respectively. The three bearings were designed according to a principle that the total thickness of 156 mm for the rubber pads in the bearings equals. The first shape factor of the rubber bearing (S\({}_{1}\)) is defined as (D \(-\) d)/(4t\({}_{\text{r}}\)), and the second shape factor (S\({}_{2}\)) is defined as D/(n\({}_{\text{r}}\)t\({}_{\text{r}}\)). D and d denote the diameter of the effective bearing surface and the diameter of the central opening for a bearing, respectively. If the central hole in the bearing is filled with rubber or lead, the opening can be ignored on the basis of the Specification GB/T20688.1-2007 [22]. n\({}_{\text{r}}\) and t\({}_{\text{r}}\) are the number and the thickness of rubber layers, respectively. S\({}_{1}\) value of LRB is 37.50, while the S\({}_{1}\) value of TLR and HDRB-LSF is 12.50. Based on the research experience, t\({}_{\text{r}}\) and S\({}_{1}\) are important parameters determining the bearing stiffness. The S\({}_{1}\) of LRB is three times that of TLRB and HDRB-LSF, indicating that LRB possesses greater vertical stiffness and more stable bearing capacity vertically. The S\({}_{2}\) value of all the above bearings keeps unchanged at 3.85, explaining that their horizontal stiffness is consistent. Figure 1: _Cont_. The other dimension parameters of each bearing are listed in Table 1, where d\({}_{l}\) is the diameter of lead core; n\({}_{\text{s}}\) and t\({}_{\text{s}}\) are the numbers and the thickness of steel plates. In the specimens steel plates were made from Q345 material; the rubber pads of HDRB-LSF were made from high damping rubber with a shear modulus of 0.392 MPa and a rubber hardness of 56 HA (Shore hardness); the rubber pads of TLRB and LRB were made from ordinary rubber material with a shear modulus of 0.6 MPa and a rubber hardness of 42 HA. Here, it should be noted that each of the two thick rubber bearings had a small hole in the center when fabricated to facilitate vulcanization. According to the specification: after vulcanization, specimens with a total height of less than 250 mm should be rested for at least 24 h, while other specimens should be rested for more than 48 h. Hence, all the test specimens were rested for more than 48 h after vulcanization and then kept in the testing environment for another 24 h before the test. The vertical stiffness (K\({}_{\text{v}}\)) and the horizontal stiffness (K\({}_{\text{h}}\)) of the ordinary rubber bearing were calculated by Equations (1) and (2) according to the specification GB/T20688.3-2006 [23], where A is the whole effective cross-section area of the bearing; E\({}_{\text{c}}\) is the modified compressive elastic modulus of laminated rubber under vertical pressure load, which can be obtained from Equation (3); E\({}_{\text{v}}\) is the volumetric elastic modulus of rubber; E\({}_{\text{cb}}\) is the apparent elastic modulus of rubber obtained from Equation (4); E\({}_{0}\) represents the elastic modulus of rubber; k is a correction coefficient for the elastic model of rubber material related to rubber hardness; and G is the shear modulus of laminated rubber. \[\text{K}_{\text{v}}=\frac{\text{E}_{\text{c}}\text{A}}{\text{wt}\text{E}}= \frac{\text{dT}}{\text{E}}\text{E}_{\text{c}}\text{S}_{2} \tag{1}\]  
\[\text{K}_{\text{h}}=\frac{\text{CA}}{\text{wt}\text{E}} \tag{2}\]