Osaka Bay Bridges: Nada Bridge (2)

With its bright red arches and Y-shaped blue bents, the Nada Bridge is almost cartoonish in appearance. Note how the bents are attached to reinforced concrete pile caps.

I never heard of any damage to this bridge from the 1995 Kobe earthquake, which considering the amount of soil liquefaction and damage to port facilities in the area is pretty remarkable.

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

Osaka Bay Bridges: Nada Bridge (1)

Moving northwest of Rokko Island and the Wangan Expressway we come to the Nada District (famed for its sake) and the Nada Bridge. It's a two span steel through arch bridge on Y-shaped bents. The bridge connects Nada Island (an artificial island that also supports the north end of the Rokko Bridge) and the Kobe Steel Works.

The Nada Bridge is 370 m long with spans of 190 m and 180 m. Its 18 m wide and has four vehicle lanes on the east side but it widens to six lanes to provide two off-ramps on the west side of the bridge. It has big steel floor beams under the deck which are directly supported by steel V-shaped cables coming down from the arch. It was built in 1983.

We'll take a closer look at the Nada Bridge tomorrow.

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

Osaka Bay Bridges: Higashi-Kobe Bridge (2)

The Higashi-Kobe Bridge crosses the Higashi-Kobe Channel in Osaka Bay. Because it's a location of high winds, the weather patterns were carefully studied at the bridge site. The bridge was designed and tested for a 60m/s wind load on the superstructure and a 67m/s wind on the towers. The model was tested in a wind tunnel for diagonal and transverse wind loads.

Because the tower crossbeam is located so low, the tops of the towers had to be carefully designed for wind loads. Among the issues was that galloping of the towers could occur at wind speeds of 20m/s. The solution was to cut the corners of the tower legs. Since the towers were most vulnerable during construction (and before the cables were attached), tuned-mass dampers were installed in the top of the tower legs and raised repeatedly as the towers were built.

The warren truss superstructure was found to perform well for wind loads and the decks were made into structural elements to make the truss stiffer. The cables were covered in polyethylene tubes with ribs to prevent rain-induced vibrations.

Like most cable-stayed bridges, wind controlled much of the design, although seismic loads would probably control if the bridge was designed today.

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

Osaka Bay Bridges: Higashi-Kobe Bridge (1)

Similar in form to yesterday's Rokko Bridge, the Higashi-Kobe is a little more elegant in appearance. Its a three-span, double-deck, cable-stayed bridge with a truss superstructure. The tall H-shaped towers are supported on closed caissons. The bridge is located just east of Rokko Island on reclaimed land over a wide shipping channel. The main span is 485 m long and the side spans are 200 m. The deck is only 13.5 m wide, just enough for three vehicle lanes on the top and bottom decks.

The bridge was completed for the HPEC in 1992 at a cost of 28.8 billion yen (about $288 million U.S.). Three years later, the bridge was closed due to damage from the Kobe earthquake.

The fault running through Kobe was well known, but seismic bridge design in the 1990s didn't consider it. However the damage was (mostly) to non-structural elements and it was soon repaired. The steel towers and piers had quite a bit of local buckling, but stiffeners were provided around the buckles and the towers and piers remained in service. In fact, the Wangan Expressway was used to carry emergency vehicles within a couple weeks after the earthquake.

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

Osaka Bay Bridges: Rokko Bridge

Parallel to yesterday's Rokko Island Bridge is the double-deck Rokko Bridge. It's a three-span, cable-stayed bridge with steel, H-shaped towers mounted onto concrete piers. The double-deck truss superstructure is supporting by cables in a fan arrangement. The main span is 220 m long and the side spans are 90 m long. The bridge was completed in 1976 and it was the first bridge of this type in the world.

A pair of monorails runs on the top deck and they were damaged along with waterlines during the 1995 Kobe earthquake.

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

Osaka Bay Bridges: Rokko Island Bridge

The westernmost structure on the Wangan Expressway is the Rokko Island Bridge. It is a 217 m long double-deck steel Lohse Arch. The arch is supported on two-column steel bents on closed caisson foundations. It was completed in 1992 at a cost of 7.5 billion yen.

During the 1995 Kobe Earthquake, the arch almost fell off the bent but it was stopped by a jacking box at the east end of the bent caps. However, the arch had been damaged and so it was replaced using floating cranes (like those seen in the background of this photo).

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

Osaka Bay Bridges: Nakajima-Gawa Bridge

Another basket-handle arch bridge, but this one makes a pretty picture. The photo's in color, but the smog has reduced the spectrum to shades of gray.

The Nakajima-Gawa Bridge carries traffic on the Wangan Expressway along with the Kanzaki-Gawa Bridge (another basket-handle arch) across the mouth of the Yodo River in Osaka Bay. Like the other Wangan arch bridges, this structure is recognizable by its distinctly shaped piers.

The span length for the Nakajima-Gawa Bridge is 160 m and the width is 27.3 m. The piers are supported on steel pipe piles.

The Hanshin Expressway Public Corporation had both bridges built in 1991 at a total cost of 8 billion yen. The superstructure was lifted by floating cranes and placed onto the piers. Because the Wangan Expressway is wide, the steel deck had to be designed to prevent buckling due to the bending compressive stress in the transverse direction.

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

Osaka Bay Bridges: Shin-Hamadera Bridge

The Wangan Expressway is built almost entirely of steel bridges and it includes many basket-handle arches. I can identify the Shin-Hamadera from the other basket-handle arch bridges because of its distinctive trapezoidal piers. It's located a few kilometers south of the Nanko Ferry Terminal and near Hamadera Park (and several emperors' tombs).

In this photo, you can see the tension tie securely attached to the ends of the arch rib and supported on a bearing above each pier. The tubular cross-bracing between the arch ribs and the diagonal hanger cables can also be clearly seen.

The hangers on the arches are spaced at 70% of the in-plane buckling length and the cross-bracing is spaced at 70% of the out-of plane buckling length of the arch ribs. The superstructure was carried on pontoons to the site and lifted into place using the rising tide. The piers are supported by cast-in-place concrete piles.

The span length is 254 m and the width is 20.3 m. The bridge was built for the Hanshin Expressway Public Corporation (HEPC) in 1991 at a cost of 4.6 billion yen. The HEPC must have placed an arch or cable-stayed bridge on the expressway wherever they needed a large opening for ship traffic.

Unlike the western part of the Wangan Expressway, there was no damage to bridges on the eastern part due to the 1995 Kobe Earthquake. The easternmost bridge where I saw damage was the Nishinomiya-Ko Bridge.

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

Osaka Bay Bridges: Nishinomiya-Ko Bridge (2)

One more photo of the Nishinomiya-Ko Bridge (on the Wangan Expressway in Osaka Bay) before we move on.

I was tempted to show the bridge after the 1995 earthquake, but I think I'd rather show bridges at their best, since I spend too much time at work looking at bridge damage.

The Hanshin Expressway Public Corp. (HEPC) calls the Nishinomiya-Ko Bridge a Nielsen-Lohse arch with a steel deck. I'm not sure if this is quite accurate since the steel hangers cross each other. The arch is supported on W-shaped piers on closed caissons (by which I mean that pressurized air is pumped into the caisson to keep the water out while its excavated from within until it reaches its proper depth).

I've gone into the airlock of several closed caissons, but when they pressurize it, my nose starts to bleed and my ears feel like they are about to burst. Also, you sometimes have to wait before they'll let you back onto the surface (so you don't get 'The Bends').

The Nishinomiya-Ko Bridge is 252 m long and about 30 m wide. It was built for the HEPC in 1993 at a cost of 7.4 billion yen. Since a steel tie under the deck restrains the arch force, a pontoon system was used to place the arch onto big spherical bearings (that split in two during the earthquake).

The little red things in the water are wind surfers who were all over the Bay.

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

Osaka Bay Bridges: Nishinomiya-Ko Bridge

There are so many basket-handle arch bridges on the Wangan Expressway that it's hard to tell them apart. I can recognize the bridge in today's photo as the Nishinomiya-Ko Bridge because of its distinctive W-shaped piers.

This bridge is famous, among other reasons, because the east approach span came off of its support (on the arch side) and fell to the ground during the 1995 Kobe earthquake. This was surprising because the seat was about one meter long and the approach span was attached to the arch bridge with steel plates. Although some engineers assumed the damage was due to liquefaction of the surrounding soil, the bridge was well-supported on deep caissons and a better explanation was that out-of-phase motion between the long-period arch bridge and the shorter period approach spans caused enough displacement to drop the span.

I took this photo in 1998 while standing on a tower of the Higashi-Kobe Bridge. I was in Kobe to study bridge repairs after the earthquake. My family and I spent a month in a little hotel by the Shin Kobe station. Every morning, while I rode an old bike to the Hanshin Expressway Corporation downtown, my family would take the Shinkansen (bullet train) to some exotic destination.

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

Osaka Bay Bridges: Kishiwada Bridge

About halfway between the Nanko Ferry Terminal and Kansai International Airport is the city of Kishiwada, which is famous for the Danjiri Festival with its many colorful floats. When the Hanshin Expressway Public Corporation built a bridge in Kishiwada, they designed it to represent one of the floats.

The Kishiwada Bridge is a three-span middle-through arch, which means the deck is in the middle of the arch. The main span is 255 m (837 ft) long and the side spans are 95 m (312 ft) long. The bridge varies from 21.9 m (72 ft) to 27.7 m (91 ft) in width. The arch is supported by cast-in-place concrete piles. The bridge was completed in 1993 at a cost of 7.3 billion yen (about $73 million).

The arch ribs are inclined towards each other (like the handle of a basket) and they support the bridge deck with steel hanger cables. The Wangan Elevated Expressway from Osaka to Kobe has many spectacular arch and cable-stayed bridges along Osaka Bay.

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

Osaka Bay Bridges: Nanko Suiro Bridge

The Nanko Suiro Bridge crosses the Nanko Channel and carries the Wangan Expressway between Sakishima Island and the Nanko Ferry Terminal in Osaka, Japan.

This bridge is a little different. Its a single span, single-rib, double deck Lohse arch. The arch is supported on a pair of steel, two-column bents (and on steel pipe pile foundations). You can see the structural steel hangers supporting the two decks. The top deck is on steel box girders with floor beams (or diaphragms) at the hangers. The bottom deck is on steel I-girders and the floor beams are clearly visible supporting the cantilevered deck.

This bridge is 163 m (535 ft) long and 29.5 m (97 ft) wide. It was built in 1980 for the Hanshin Expressway Public Corporation at a cost of 3.6 billion yen (about 36 million U.S. dollars).

I had written that multi-column bents are uncommon in Japan. However, they are used for wide bridges but usually with two arch ribs. Also, it looks like the lower deck has a shorter span with additional piers at the edges of the channel.

My understanding is that a Lohse Arch is a bow-string arch where the arch and tie elements can carry some of the load in bending. I would assume that the tie is part of the box girder system in the upper deck. Any additional thoughts or information about this unusual bridge would be appreciated.

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

Osaka Bay Bridges: Tsuneyoshi Bridge

There are three interesting bridges that carry traffic on and off Maishima Island in Osaka Bay. We previously studied the Konohana, a self-anchored suspension bridge. There is also the Yumemai, a floating arch bridge that can be moved out of the way to allow ships to pass between Yumeshima and Maishima Islands in an emergency. Today's bridge was being built when I visited the Konohana Bridge in 1999.

The Tsuneyoshi Bridge is a two span continuous steel box girder cable-stayed bridge completed in 1999. It links Konohana ward with Maishima Island. The bridge is 340 m long, with a main span of 250 m and a side span of 90 m. It has a single steel, two-legged tower supported on a short reinforced concrete pier wall. The tower legs are sloped to come together on top. The bridge is extremely unbalanced and so the short span must be securely tied down at the abutment.

The bridge has that turquoise girder and white tower design that we've seen on several bridges in Osaka Bay. Maishima Sports Island and its bridges were built as a possible site for the 2008 Olympics that eventually went to Beijing.

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

Osaka Bay Bridges: Namihaya Bridge

The shoreline of Osaka Bay is crowded with artificial islands. Consequently, hundreds of interesting-looking bridges are used to connect these islands and to cross the many rivers around Osaka Bay.

The Namihaya Bridge crosses at the mouth of the Shirinashi River just south of the Minato Bridge in Osaka. It is a long viaduct that includes a 580 m three-span continuous steel box girder bridge.

It is difficult to tell from this photo, but the Namihaya is the longest horizontally curved box girder bridge in Japan. The viaduct is 1573 m long with a haunched girder center span of 250 m. The superstructure is supported on large, single column reinforced concrete bents. Perhaps because land is so expensive in Japan, bridges are seldom supported on multi-column bents. The bridge is 11 m wide and serves as an evacuation route for the Taisho-naiko port area in times of disaster. It was completed in 1994.

It seems like all the bridges in Osaka Bay are painted either red, white, or turquoise. I wonder if there is some significance to the color or if they just look good on bridges?

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

Osaka Bay Bridges: Yamatogawa Bridge

The Yamatogawa Bridge is a three span continuous steel cable-stayed bridge that carries the Wangan Expressway across the Yamato River in Osaka. It is located about 5 km south of yesterday's Minato Bridge. It was built for the Hanshin Expressway Public Corporation in 1982 at a cost of 13.9 billion yen. It crosses the Yamato River at a very high skew and so it required a long main span of 355 m (1166 ft).

The Yamatogawa is an unusual looking cable-stayed bridge. The single pylon towers are not attached to the substructure and they support a single plane of only four cables. The steel box girders sit on hammerhead bent caps supported on steel pipe piles. The bridge carries two lanes of traffic in each direction.

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

Osaka Bay Bridges: Minato Bridge (2)

I thought we'd take one more look at the Minato Bridge before we moved on.

It's a really big bridge, with the third longest center span of any truss bridge in the world (after the Firth of Forth Bridge that was built in 1890). Since the Minato Bridge was built in the 1970's, this record may be a reflection on the lack of interest in truss bridges in recent years.

Suspension, arch, and cable-stayed bridges increase in length and ingenuity every year. However, truss bridges are expensive to build, difficult to maintain, and limited in length.

However, the fact that cantilever trusses need no falsework, may make them the best choice in some situations.

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

Osaka Bay Bridges: Minato Bridge

The Minato Bridge is a Gerber truss structure that spans between Sakishima Island and the Port of Osaka in Osaka Bay. The center span was brought to the site on a barge and lifted into place with winches attached to the cantilevered ends.

It is a double-deck bridge with side spans of 235 m and a center span of 510 m. The bridge is part of the Wangan Expressway and is just south of the Tempozan Bridge. It was built in 1974 for the Hanshin Expressway Public Corporation (HEPC) at a cost of 25 billion yen.

The seismic criteria for Japan has changed quite a bit since 1974 and so this bridge was retrofitted a couple years ago with isolation bearings between the decks and the floor beams and with buckling restrained devices for the towers. More information on the retrofit is at: www.idi.or.jp/tech/quarterly/idi37.pdf

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

Osaka Bay Bridges: Tempozan Bridge

On the east side of Osaka Bay is a jumble of prefectural and city highways crossing canals, rivers, streets, ports, and each other. From Konohana Bridge a dozen interesting bridges can be seen. A few hundred meters from the Konohana Bridge is the Tempozan Bridge on the Wangan Expressway. It looks similar to the Konohana Bridge but with two diagonal planes of cable-stays along the sides of the towers instead of a single suspension cable on the top of the towers.

It is a three span continuous steel cable-stayed bridge on cast-in-place piles that crosses the Tempozan Canal in Osaka. The main span is 350 m long and the side spans are 170 and 120 meters. It was built in 1988 for the Hanshin Expressway Public Corporation and cost 25 million yen.

In 1998, we lived for a month in Kobe on the west side of Osaka Bay. Every day I would watch the smog fill the sky until I could barely see bridges a few hundred meters away.

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

Osaka Bay Bridges: The Konohana Bridge (2)

The Konohana Bridge was built in 1987 by the Hitachi Zosen Corporation for the City of Osaka. The chief construction engineer was Hiroshi Tanaka who kindly agreed to meet me at the bridge and discuss its design and construction.

Q: Does the Konohana Bridge have balanced spans? If it is unbalanced, how did you address the unbalanced load?

A: It is almost balanced however it is slightly wider at the entrance of the Konohana-side (for an on-ramp). Therefore the distribution of the dead loads is unbalanced in the longitudinal direction. This effect is considered by the static analysis by making the sag lengths in the side span of the main cable are different; Konohana-side (6.995m) and Yumeshima-side (7.OO8m).

Q: How accurate were the dead load displacements?
A: The displacements of the diaphragm at the anchorage were measured after the removal of supporting beams. The measured displacements corresponded closely with the displacements from the analysis.

Q: What do you believe was the most challenging parts of the construction?

A:The tension adjustments of the inclined hangers were the most challenging (apparently vertical hangers are fairly easy to adjust, but the longitudinal vector component makes the adjustment more problematic).

Q: What made the City of Osaka choose this bridge type in the type selection?
A: The cable-stayed bridge might be the reasonable selection at the time of the construction. However the construction of the cable-stayed bridge (i.e., Tenpozan Bridge) was also being planned very close to the site by the Hanshin Expressway Public Corporation. Therefore other bridge types were explored by the Osaka Municipal Government. The mono-cable and self-anchored suspension bridge was selected from the economical and aesthetic aspects. (Also, poor soil conditions probably influenced the decision to self-anchor the cables).

Q: What is the seismic criteria for the bridge?
A: Seismic design intensity (e.g., seismic coefficient = 0.3 g) was determined according to the Highway Code of 1980, which provides a method of modified seismic design. The ground condition is very weak at the site. The safety was verified by doing dynamic analyses considering soil-structure interaction.

Q:What is the foundation type?
A: The foundation is a pile cap with 1.5 m. dia. pipe piles. Because of the poor soil, the pipe piles were driven 51.4 m into the ground.

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

Osaka Bay Bridges: Konohana Bridge

We are leaving Tokyo for Osaka Bay to look at a self-anchored suspension bridge.

The Konohana Bridge is a suspension bridge with its cable anchored into the bridge superstructure rather than into the ground. Self-anchoring is an advantage when the soil is weak or the bridge is in deep water. The disadvantage is that the superstructure must be designed to handle the very large forces that are transferred from the suspension cable.

There are very few self-anchored suspension structures in the world. The State of California is replacing the seismically vulnerable East Crossing of the San Francisco-Oakland Bay Bridge with a new bridge that includes a self-anchored suspension span. South Korea has built one. Another self-anchored suspension bridge is the Konohana Bridge in Osaka, Japan.
Although the Konohana Bridge and the East Bay Crossing are both self-anchored bridges, they are very different. The Bay Bridge has a single tower, unbalanced spans, a wide deck, and two planes of suspension cables. The Konohana Bridge is narrow, it is almost perfectly balanced, it has two towers, but only a single cable. It is like yesterday's Tsurumi Tsubasa Bridge except with a suspension cable.

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

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.