San Francisco County, California Bridges: West Bay Bridge (2)

July 2014 (37.8168°, -122.3519°) West Bay Bridge

As we continued west on the San Francisco-Oakland Bay Bridge the city of San Francisco slowly came into view. At one time you could continue from this bridge on expressways all the way to the Golden Gate, but now you quickly descend to street level, heavy traffic, and stop lights.

 
San Francisco County, California Bridges: West Bay Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

San Francisco County, California Bridges: West Bay Bridge (1)

July 2014 (37.8168°, -122.3519°) West Bay Bridge

The San Francisco-Oakland Bay Bridge is composed of several structures. There's the skyway and the self-anchored suspension spans of the East Bay Bridge, back to back suspension structures of the West Bay Bridge, and the Yerba Buena Island tunnel in the middle. The new East Bay Bridge replaced a seismically deficient steel cantilever truss bridge while the West Bay Bridge had better seismic details and was in good enough shape to only require a retrofit. 

San Francisco County, California Bridges: West Bay Bridge (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Peru's Bridges: Puente a Machu Picchu (2)

Another view of the suspension bridge we studied yesterday. I was wondering if the longitudinal planks on the deck were made to carry vehicles or just to hold the deck to the floor beams. I'm not even sure if a vehicle could get through the legs of the towers (or if the bridge could support vehicles).

Lately I've been noticing the difference between the rather humble bridges in my blog and the more elegant structures presented by The Happy Pontist.

I think if we were novelists, he would be Thomas Mann whose elegant prose examined the world of educated people and their ideas. I would be more like John Steinbeck who discussed the ordinary people he met in his travels. The Tall Bridge Guy would represent the American idealism of Jack Kerouac and The Bridge Hunter would be a populist writer like Mark Twain.

Peru's Bridges: Puente a Machu Picchu (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Portland's Bridges: St. Johns Bridge (3)

The back spans of St. Johns Bridge are supported on tall reinforced concrete piers in a Gothic arch shape similar to its towers. They also are reminiscent of the towers on the Brooklyn Bridge. Perhaps this shape, originally used for the churches of medieval Europe was consciously chosen by bridge engineers to add importance to their work.

This bridge was named after a saint and the piers are in Cathedral Park, so the church-like architecture could be appropriate. However, I think that bridge engineers like Roebling, Linderthal, Steinman, and McCullough were saying that big bridges were the churches of the industrial age because they best express our yearning for the spiritual. Perhaps there's also a touch of American Transcendentalism in using religious icons for structures that span rivers, canyons, valleys, and other landscapes that suggest a deeper meaning or revelation in nature.

Portland's Bridges: St. Johns Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

New York City's Bridges: George Washington Bridge (2)

One last look at New York City (well, New Jersey actually) and the George Washington Bridge. This photo (taken in 2002) shows preparations for painting the bridge's west tower. The tarp around the scaffolding may be required to prevent lead-based paint from entering the river. The steel towers are composed of arches above and below the bridge deck. The green cliffs behind each tower makes the bridge more attractive.

Note that two suspension cables hang from the top of each tower leg. The 107,000 miles of steel wire used for the suspension cables were manufactured by John Roebling & Sons, whose founder had designed the Brooklyn Bridge. Contractors were allowed to bid the job with either suspension cables or with suspension chains, which seems unthinkable now.

When the bridge was first built, the deck was supported by very thin (twelve-foot deep) plate girders under the roadway. The theory was that the enormous mass of the long deck would act as a stiffener to prevent large movements during windstorms. It may have been fortunate therefore, that they later put a lower deck on the bridge with a deep truss.

We've looked at every river crossing connected to Manhattan, but there are many other interesting bridges in the area. The Bayonne Bridge (1931), the Bronx-Whitestone Bridge (1939), the Throgs Neck Bridge (1961), and the Verrazano-Narrows Bridge (1964) were all designed by Othmar Ammann during the golden age of bridge engineering for New York City.

New York City's Bridges: George Washington Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

New York City's Bridges: George Washington Bridge

In contrast to the East and Harlem Rivers, there is only one bridge that crosses the Hudson River to Manhattan. The George Washington Bridge forms an important link in I-95/US-1 that speeds vehicles across the Hudson and through the most congested part of Manhattan. The bridge connects Fort Lee in New Jersey to the Washington Heights area of Manhattan. It was named after George Washington who unsuccessfully tried to prevent the British from entering Manhattan. After he failed, he quickly crossed from Fort Washington to Fort Lee where the bridge now stands.

The George Washington Bridge is an iconic landmark because of its huge skeletal towers. The design originally called for the towers to have a granite facade, but this was eventually abandoned, perhaps because the bridge was built during the Great Depression. When it was completed in 1931, it doubled the record for the longest suspension bridge with a main span of 3500 ft and with towers that were 650 ft tall. The Brooklyn Bridge was built in 1883 with a main span of 1600 ft and 280 ft towers. The Akashi Kaikyo Bridge was built in 1998 with a main span of 6500 ft and 930 ft towers.

The George Washington Bridge is owned by the Port Authority of New York, designed by Othmar H. Ammann, and with architectural support from Cass Gilbert. The bridge originally had six vehicle lanes and sidewalks. In 1946 two additional lanes were added in the middle of the deck. A lower deck was added in 1962, which gave the bridge a total of fourteen lanes (the most on any bridge) and allowing it to carry about 300,000 vehicles a day.

New York City's Bridges: George Washington Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

New York City's Bridges: Williamsburg Bridge

Continuing north, the next suspension bridge to cross the East River is the Williamsburg Bridge. When it was built in 1903 it had the longest main span in the world of 490 m (and 106 m tall towers). Although big, it's currently dwarfed by the Akashi Kaikyo Bridge with its 1991 m main span and 300 m towers.

Cities like London, Paris, and Tokyo are lucky to have narrow rivers that can be crossed by arch bridges while cities like Shanghai or New York have wide rivers that are more difficult to cross.

Like the nearby Mahattan Bridge, the Williamsburg Bridge carries bikes, pedestrians, trains, and vehicle lanes on two decks. However, it is much more attractive and presents a more unified appearance. The two-legged towers are built up of laced members that match the appearance of the truss superstructure.

New York City's Bridges: Williamsburg Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

New York City's Bridges: Manhattan Bridge

A little north of the Brooklyn Bridge is the Manhattan Bridge. It has a main span length of 1470 ft (448 m), which is a little shorter than the Brooklyn Bridge. It was designed and built by Ralph Modjeski and completed on December 31, 1909.

It has an open top deck with two lanes of vehicle traffic on each side and its bottom deck carries a pedestrian lane, a bicycle lane, four sets of subway tracks, and three reversible lanes.

The photo shows the east side of the Manhattan Bridge surrounded by a gentrified area of Brooklyn. The Manhattan Bridge is not nearly as attractive as the Brooklyn Bridge (in my opinion). Perhaps it looks a little kitschy with its squat steel towers painted a metallic blue. It's a favorite of movie directors and has appeared in many films. In Cloverfield the protagonists are trying to get across the Brooklyn Bridge, which is suddenly attacked by a monster while we see the undisturbed Manhattan Bridge in the background.

New York City's Bridges: Manhattan Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

New York City's Bridges: Brooklyn Bridge (3)

A view from the top deck of the Brooklyn Bridge. A nice thing about this bridge is that you can drive on it, ride on it, run on it, walk on it, or plop on a park bench and sit on it. As can be seen in the photo, the bridge makes for a relaxed and pleasant environment.

Construction of the Brooklyn Bridge was completed on May 24, 1883. It received major repairs after it's 100th anniversary, but it's currently the only New York City owned bridge to get a 'poor' rating. About half a billion dollars in repairs are scheduled over the next few years, which will hopefully bring the bridge back to a 'satisfactory' rating. However, thousands of heavy vehicles every day may be too much for this structure. A restricted load rating may do more than repairs to keep this bridge around for another 126 years.

New York City's Bridges: Brooklyn Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

New York City's Bridges: Brooklyn Bridge (2)

A view of the Brooklyn Bridge from Brooklyn. A nice thing about this view is the Manhattan skyline is behind the bridge.

John Roebling, a German immigrant, was a romantic, a follower of Hegel, and a tough dad. When the Civil War began, he saw his son sitting at the dinner table and demanded to know why he hadn't joined the army.

Colonel Washington Roebling conducted himself well in the war and then returned to help his father.

In those day, workers labored under the caissons, removing the soil to allow the tower foundations to slowly sink to the correct depth. Pressurized air was used to keep the area under the caisson's dry. When workers returned to the surface, the pressurized gas in their blood vessels exploded, injuring and sometimes killing them. Eventually, they learned to rest in the airlock while the air pressure in their bodies slowly returned to normal. This lesson came too late to help Washington, who was incapacitated by caisson disease and spent the next eleven years watching his wife build the bridge from his bedroom window. Despite his illness, he outlived his wife by many years and even remarried.

New York City's Bridges: Brooklyn Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

New York City's Bridges: Brooklyn Bridge

I still have more photos of Japan's bridges, but I thought we'd take a break to look at some New York City bridges.

Manhattan Island is separated from New York and New Jersey by the Hudson and the East Rivers. The East River is actually a swiftly moving tidal strait carrying water between New York Bay and Long Island Sound.

Traveling north, the first bridge that crosses the East River (between Manhattan and Brooklyn) is one of the world's most famous structures, the Brooklyn Bridge. Even the most cursory description of this bridge would take many pages. If you are interesting in learning more about this bridge, I would recommend reading The Great Bridge by David McCullough (I also enjoyed David's history of John Adams).

John Roebling was able to advance cable and cable bridge technology during an illustrious career in the United States. He successfully convinced politicians of the economics and feasibility of building a bridge across the East River after the Civil War. Unfortunately, he died of an infection after his foot was crushed by a barge at the start of the bridge's construction. His son took over, but he was soon incapacitated by the bends from working on the closed caisson construction. His wife Emily Roebling took over and spent the next eleven years completing the bridge.

However, it was John Roebling's design that makes this bridge such a pleasure to everyone who sees it. The large granite towers with their majestic gothic arches, the wonderful upper deck where runners and bicyclists fight their daily war, the splendid views of the Manhattan skyline, all make traveling under or across the bridge a rewarding experience.

Note that this bridge is a combination suspension/cable-stayed structure with the diagonal stays clearly seen in this photo.

New York City's Bridges: Brooklyn Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Honshu-Shikoku Bridges: Kurushima Bridge (2)

Bridge building can be a dangerous profession. There were 27 deaths building the Brooklyn Bridge including the death of the designer, John Roebling. There were 16 deaths building the Sydney Harbor Bridge.

The Kurushima Bridge was designed so that some of the back spans (spans 6, 7, and 9) were supported on piers rather than from the suspension cables. These spans were incrementally launched from the anchorages onto temporary steel platforms. A week before we visited the bridge, they were dismantling a platform when it suddenly slipped from it's cables, sending seven workers to their death. After the accident, the platform lowering system was replaced using ground-based cranes.

Unfortunately, it sometimes takes an accident before improvements can be made. A safety commission conducted a study of the accident and made recommendations to improve the safety of this widely used incremental deck launching system.

Although bridge construction remains a dangerous profession (about 60 deaths per 100,000 workers) it is eclipsed by pilots (70 deaths per 100,000 workers), fishermen (71 deaths per 100,000 workers), and loggers (118 deaths per 100,000 workers).

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

Honshu-Shikoku Bridges: Kurushima Bridge (1)

The rest of the bridges on the Honshu-Shikoku Expressway were in various stages of construction when I went on my tour in 1998.

Like the previously studied Ohmishima and Tatara Bridges, the Kurushima Bridge is part of the Nishi-Seto Expressway. It is the westernmost bridge and connects Shikoku to Oshima Island across Kurushima Strait in the Inland Sea. I say bridge, but its really three suspension bridges with four anchorages and six towers. In total, it's the world's longest suspension bridge at 4015 m (13173 ft). It's similar in construction to the west spans of the San Francisco-Oakland Bay Bridge, which has four towers and a third anchorage in the middle of the bridge.

Because of occasional rough seas and to protect the waters in the Kurushima Strait, several of the towers have energy absorbing devices to protect them and ships that may possibly collide with the towers. This has become a heated issue, especially after single hull oil tankers collide with bridges. Bridge owners are usually blamed for the resulting oil spill, even when the shipping channel under the bridge is wider than 600 m. In any event, the use of energy absorbing devices is suppose to prevent ship damage, although it is likely that a tanker going at 16.5 knots (the speed of the Exxon Valdez) would be seriously damaged by a stationary object, with or without the use of energy absorbing devices.

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

Honshu-Shikoku Bridges: Akashi-Kaikyo Bridge (3)

One more look at the bridge with the longest main span in the world. Cable-stayed bridges are getting bigger but there are no plans to build a longer suspension bridge than the Akashi-Kaikyo Bridge in the foreseeable future. At 2 km long between 300 m tall towers, this is one big bridge.

There is something interesting about big structures. The sculptor Claes Oldenburg took common objects like clothespins and made them hundreds of times their normal size in order to see them anew. Perhaps something like that takes place when we view a really big bridge.

John Ruskin, the 19th century art critic wrote about how landscape art creates an intense aesthetic experience because familiar details are transformed when seen at a distance and because the object is changed by the distorting effect of the the atmosphere.

These are just my first thoughts on the pleasures of looking at big bridges and other structures. I'd like to hear what you think!

Honshu-Shikoku Bridges: Akashi-Kaikyo Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Honshu-Shikoku Bridges: Akashi-Kaikyo Bridge (2)

Japan is composed of four main islands: Hokkaido, Honshu, Shikoku, and Kyushu.

Along the Inland Sea west of Kobe on Honshu Island is the city of Akashi. A narrow strait (the Akashi Kaikyo) separates Akashi from Awaji Island. When the Japanese economy was booming in the 1980s, the government decided to build a highway system to connect quiet Shikoku with booming Honshu.

One Golden Week many years ago, I boarded a ferry from Tokyo to Shikoku Island. It took a day to reach Tokushima on the northeast side of Shikoku. Today, one can drive and its about 350 miles.

In this photo, I'm standing atop the southern tower of the Akashi-Kaikyo Bridge looking north at Akashi. Actually, its a fairly clear day, since we can see a considerable distance before the brown smog appears on the horizon. To the right of the bridge is a tower that was put up to allow the public to view the construction of this bridge. Japanese engineers are quite adept at conducting effective publicity campaigns for their new bridges, which include viewing platforms and parks where families can learn about the bridge. Since the toll for crossing the Akashi-Kaikyo Bridge (also called the Pearl Bridge) is $20 U.S. (2300 Yen), this makes good sense. Also, bridges are considered beautiful objects in Japan. Landscapes showing river crossings are one of the favorite subjects in Japanese art.

Honshu-Shikoku Bridges: Akashi-Kaikyo Bridge (2) 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: 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.

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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.