# Seismic Effectiveness of Multiple Seismic Measures on a Continuous Gider Bridge
## 5 Calculation Analysis and Discussion
### Displacement of Girders, Bearings, and Pier Top
In different cases, the displacement is much higher under the action of the Northridge and large earthquakes than moderate and small earthquakes, regardless of sliding rubber bearings (Figure 8a) or laminated rubber bearings (Figure 8b). Laminated rubber bearings have a similar displacement, of about 4 cm, than sliding rubber bearings, but a smaller displacement change than sliding rubber bearings under the action of the small earthquake. For the sliding rubber bearings and laminated rubber bearings, their displacement exceeds their allowable shear deformation (8.12 cm and 9.1 cm, respectively) when the magnitude of the earthquake increases to a moderate earthquake. This indicates that the bearing is largely destroyed, and the girder may fall from the piers. Figure 7: Displacement of girders in different cases under different earthquakes. Figure 8a shows that, in different combinations of seismic measures, the displacement of sliding rubber bearings is greater than 8.12 cm, especially in Cases 1, 2 and 3, but there are slight changes in Cases 4, 5, and 6 under the action of moderate, large, and Northridge earthquakes. That is mainly due to the fact that, when the magnitude of the earthquake increases, the restrainer is unable to restrict the excessive displacement of the structure sufficiently, and the unseating prevention devices effectively control the relative displacement of the substructure and superstructure of the bridge under the action of the earthquake due to its relatively large rigidity. In Cases 3 and 5, the displacement of the bridge bearings is slightly larger under the action of the large earthquake than the Northridge earthquake, mainly due to the fact that the restrainer is damaged so much under the action of the large earthquake that it is impossible to control the displacement of the bearings. Figure 8b shows that the maximum displacement of the laminated rubber bearings is 19.38 cm, which is smaller than that of the sliding rubber bearings (23.78 cm), under the action of the Northridge earthquake. That means that the displacement of the sliding rubber bearings is larger than that of laminated rubber bearings under the action of the same earthquake, and #1 and #5 piers with sliding rubber bearings bear fewer seismic loads and are safer than #2, #3, and #4 piers in the earthquake. In addition, in Cases 3, 5 and 6, the displacement of the laminated rubber bearings under the action of the large earthquake is greater than the Northridge earthquake for the same reason as that of the sliding rubber bearings. Both Figure 8a,b show that, in the combinations of seismic measures in Case 5 or 6, both the sliding rubber bearings and laminated rubber bearings have small displacement, but this is only slightly larger than the allowable shear deformation under earthquakes of different magnitudes. This means that these two combinations of seismic measures can reduce the probability of the unseating from the bearing more significantly than other combinations of seismic measures. The displacement reduction of sliding rubber bearing is larger than that of laminated rubber bearings. The displacement of the bearings decreases most under the action of the Northridge earthquake. When there is no seismic measure in Case 1, the displacement of the sliding rubber bearings is 23.78 cm. In Case 6, the displacement of the sliding rubber bearings is 8.57 cm--about 36% of the displacement of the sliding rubber bearings in Case 1. The displacement of the laminated rubber bearings decreases from 19.38 cm in Case 1 to 9.59 cm in Case 6 by about a half. The simulation results indicate that the effectiveness of seismic measures significantly prevents potential pounding and unseating damage to bridges due to the interaction between adjacent bridge segments caused by impacts. The result confirms [PERSON]'s research result and shows the importance of setting up seismic measures to prevent bridge collision [14].