Tokyo Bay Bridges: Tsurumi Tsubasa Bridge (2)

I was on Ohgishima Island (in 1994) looking at underground natural gas tanks the next time I saw the Tsurumi Tsubasa Bridge. The name means 'flying into the future' and it was suggested by the public. The bridge has a 510 m (1675 ft) main span and 255 m (837 ft) side spans. The towers open to carry the superstructure and then close to carry a single vertical plane of cables. This tower shape has become very popular for both single and double planes of cables. This bridge may still have the longest main span for a single plane of cables. However, it strikes me that the superstructure is less stable, especially for wind and seismic loads. That may be why the Tsurumi Tsubasa Bridge has special dampers and an orthotropic deck.

Cable-stayed bridges have filled a gap between arch or cantilever bridges and the longer suspension bridges.  However, they have had problems such as corrosion of the cables, vibration of the cables, etc.  Also, they are difficult to build and usually require an engineer to design their construction.

Tokyo Bay Bridges: Tsurumi Tsubasa Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Tokyo Bay Bridges: Tsurumi Tsubasa Bridge (1)

Immediately east of the Yokohama Bridge on the Shuto Expressway is the Tsurumi Tsubasa Bridge. We visited it while it was being built in 1992. It is a three span continuous steel cable-stayed bridge. To speed the construction, a non-moored barge was used to lift the superstructure segments into place for the first time in Japan.

The bridge was carefully designed for wind and seismic loads. Wind testing was conducted with and without an adjacent structure that was planned to be built in the future. The edge of the structure has a special aerodynamic shape to reduce drag. An oil-damping system was used to control vibrations during earthquakes. We'll look at the completed bridge tomorrow.

Tokyo Bay Bridges: Tsurumi Tsubasa Bridge (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Tokyo Bay Bridges: Yokohama Bay Bridge

The City of Yokohama is just south of Tokyo along Tokyo Bay. The Yokohama Bay Bridge is a viaduct that includes a cable-stayed bridge that connects Daikoku and Honmoku Piers in Yokohama Harbor. Yokohama has a busy port clustered with piers and human-made islands that were dredged from the Bay. The Yokohama Bay Bridge is part of the Shuto Expressway.

The Japanese are proud of their bridges and so bridge owners provide parks, walkways, and viewing platforms so that visitors can appreciate a bridge's form, much as Hokusai did for the Ryogoku Bridge 200 years ago. The Yokohama bridge is a symbol of the City of Yokohama and it was carefully designed to appear beautiful from the parks and hills surrounding the bridge. Moreover, a walkway and viewing platform have been provided on the bridge.

The Yokohama Bridge has a double-deck truss superstructure with six vehicle lanes on the top and bottom decks.  The bridge has 55 m (180 ft) vertical clearance to allow big container and cruise ships access into Yokohama Harbor. The suspension cables have a fan arrangement between the towers and the girders. The main span is 460 m long and the side spans are 200 m. Because this area has large earthquakes, the bridge was designed to allow the heavy superstructure to move out of phase with the towers during strong shaking.

Japan had a huge spurt of infrastructure development in the 1980s and 1990s (much like China is going through today). The Yokohama Bridge was completed in 1989. 

Tokyo Bay Bridges: Yokohama Bay Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Tokyo Bay Bridges: Aqua-Line Bridge

Tokyo Bay is really big and so considerable time and effort has been spent to get people and goods across the Bay. The biggest effort so far has been the Trans-Tokyo Bay Highway. A 4.4 km long elevated highway carries vehicles into a 9.6 km long tunnel under Tokyo Bay.  The project includes a giant ventilator shaft in the middle of Tokyo Bay to supply fresh air to the tunnel. The highway goes from Kawasaki City on the west side of the Bay to Kisaruzu City on the east side of the Bay.

We were taken to visit the project in 1994, a couple of years before it was completed. The steel box girder segments were made continuous after they were set onto the 'Y' shaped piers. Span lengths decreased gradually from the two 240 m center spans.

Tokyo Bay Bridges: Aqua-Line Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Tokyo Bay Bridges: Rainbow Bridge (3)

Another interesting thing about the Rainbow Bridge is the prominent anchorages for the suspension cables. The anchorages include elevators to the south and north walkways on the lower bridge deck.  The north walkway provides views of Tokyo and the south walkway provides views of Odaiba (and of Mt Fuji on clear days). The walkways can pitch and roll when there's a strong wind. The anchorages also include observation platforms for viewing Tokyo Bay.

Note how the Yokoso Rainbow Tower (on the left side of the photo) matches the color and shape of the anchorage. It was built in 1995, two years after the bridge.

Tokyo Bay Bridges: Rainbow Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Tokyo Bay Bridges: Rainbow Bridge (2)

At 570 m, the Rainbow Bridge is very short for a suspension structure. The Tatara (cable-stayed) Bridge is 890 m. The Lupu (arch) Bridge is 550 m. Perhaps the engineers felt obligated to build a suspension bridge because the nearby long-span structures are cable-stayed bridges.

The Rainbow Bridge spans between Shibauru Wharf and the Daiba District. Considering the span length is so short, it's surprising that the east tower sits in Tokyo Bay. Maybe there was no place to put the tower on land, since the bridge swings to the north from the eastern tower before reaching Daiba.

Tokyo Bay Bridges: Rainbow Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Tokyo Bay Bridges: Rainbow Bridge

In 1991, we were taken to see a new bridge being built a little downstream from the mouth of the  Sumida River in Tokyo Bay. The Rainbow Bridge is a double-deck truss suspension bridge supported on steel, two-legged towers. The upper deck carries the Metropolitan Expressway and the lower deck carries mass transit, pedestrians, and port traffic.

The name 'Rainbow Bridge' is because of an automated lighting system that continuously changes the bridge's color depending on the day of the week and the time of the day. We'll look at the completed bridge tomorrow.

Tokyo Bay Bridges: Rainbow Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.