Development of A Base Isolation System for Existing Bridges


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Title: Development of A Base Isolation System for Existing Bridges

Author(s): Hiroyuki Nagumo, Osamu Hasegawa and Yoji Suizu

Publication: Special Publication

Volume: 164


Appears on pages(s): 507-528

Keywords: Base isolation; bearings; bridges (structures); earthquake-resistant structures; tests.

Date: 11/1/1996

Base isolation is one of the effective systems for providing earthquake resistance to structures, since it can reduce to a great extent a structural response to earthquakes. However, base isolation systems applied to existing road bridges cannot exhibit their full capabilities during an earthquake because the narrow space between girders of the bridge limits the movement of girders along longitudinal direction. Replacing bridge bearings is thought to be difficult since it requires extensive chipping of piers and girders, and causes lengthy traffic jams on the bridge. A recently developed base isolation system solves all these problems. The system is verified through performing three-dimensional shaking table test. The experimental results demonstrate that the acceleration of girder could be reduced to one third compared with the case without base-isolation. It is also confirmed that the relative displacement between pier and girder in a miner earthquake was 5mm. Analysis can simulate the experimental results by modeling the system into a bilinear spring. Furthermore it is showed with non-linear dynamic analysis that the model bridge, which was damaged due to Hyogo-Ken Nanbu Earthquake, can secure the aseismic safety for the earthquake by applying the system. Installation method for this system is described at the last part.