Japan's longest bridge built with "extradosed" external tendons
In 1996 the Kajima/Oriental/P.S.Joint Venture was awarded the contract to build a new bridge over the Tokachi River based on the design by Hokkaido Engineering Consultants.
The design required special post-tensioning systems. In order to adjust the girder heights to the specific local conditions, the quantity and eccentricity of the tendons had to be adjusted. The longitudinal post-tensioning was carried out using external DYWIDAG tendons 19-0.6" in two configurations:
"extradosed" tendons for cantilever construction were anchored in the pylon and main girder
"extradosed" tendons for service loads were continuous from one pier to the next deflected by couplers embedded inside the box girder.
To maximize the dynamic and fatigue capacity of the tendons, fretting fatigue at the points of inflection was eliminated using plastic spacers installed at the embedded couplers inside the box girder and at the exit points of the pylon anchorages. The structural integrity of these innovative tendons was demonstrated by comprehensive preconstruction tests. The project was successfully completed in 2000.