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| August 2007 (37.3168 Degrees, 138.4348 Degrees) Yonahime Bridge |
This is a 120 m long through truss
arch, crossing over a narrow canyon south of Kashiwazaki. We saw
a landslide scarp on the uphill side of this bridge, but since the bridge is founded on
piles, it was probably strong shaking that caused it to rack during the
earthquake.
When we visited the bridge (on Aug. 4th) we saw many of its
members had buckled and some of its connections were damaged along with its bearings.
Still, the bridge remained in service (jacked up and sitting on metal
boxes), which shouldn’t be a problem unless another strong earthquake occurs.
This very common bridge type is sensitive to shaking, because the struts and
bracing can’t resist compression. A deck arch bridge immediately to the north
was undamaged by the earthquake.
It might be possible to redesign the Yonahime and other tied arch bridges for large earthquakes by supporting it on isolation bearings. Certainly, these fixed bearings, which we saw damaged on several of the longer span bridges, are a lot of trouble to replace.
Niigata, Japan's Bridges: Yonahime Bridge on Route 8 by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.
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