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Caltrans Finishes New $1B Bay Bridge Skyway

Fri March 21, 2008 - West Edition
Frank Hartzell

In Portland, Ore., a unique piece of gigantic construction equipment is being prepared for shipping to China, so that it can play a key role in the biggest bridge building project in California history.

Come again?

Yes, two trips across the Pacific Ocean are only the beginning for a 400-by-100-ft. barge that has been dubbed “The Left Coast Lifter.”

When it arrives on the job site in October, the Lifter will be the platform of a spectacular self-anchored suspension segment of the Oakland-San Francisco Bay Bridge, a job whose scale has made a mockery of traditional construction contracts and the biggest equipment available.

With completion of the $1.04 billion skyway work (in early February), the construction of the Self Anchored Suspension is now taking center stage on the job, said Mike Flowers of American Bridge Company.

“This is in effect the signature span of the entire project,” said Flowers.

The $6 billion plus Bay Bridge replacement and retrofit project is the biggest public works project in California history, according to Caltrans. Initially famous for the meteoric growth of the costs before the job even got started, its physical shape has begun to coalesce, while the budget overruns have slowed.

The eastern span work has a current tab of $5.5 billion. Beginning in Oakland, the Oakland touchdown project will involve building a viaduct to launch the two roadway sections and a new electrical substation. That work is just getting started.

The Oakland touchdown will connect on a gradual, upward slope to the just completed eastern skyway, two side-by-side elevated 1.2 mi. (1.9 km) long roadways on piers. The now nearly complete skyway is now a bridge to nowhere, as work on both ends proceeds. The skyway will eventually link to the self-anchored suspension (SAS) portion, which includes a lone 525-ft.-tall (160 m) tower. According to Caltrans, it is the world’s longest SAS, and one of the few to use just one gigantic tower rather than two smaller ones.

What is an SAS?

Traditional suspension bridges have twin cables with smaller suspender cables connected to them, which hold up the roadbed and are anchored to separate structures in the ground.

The SAS tall tower, grasps the 1,860-ft.-long (566 m) steel bridge to itself as if giving a bear hug, with cables composing the hugging arms. This means the roadway on both sides of the tower do not have separate anchors into the ground, allowing for much greater seismic safety. There is only one main cable on the SAS span, which will anchor to the deck itself and will wrap around the west end of the structure and connect back into the deck.

For commuters, the SAS will offer something the Bay Bridge has always failed to provide, a spectacular view and a distinctive look. The self-anchored suspension (SAS) design was selected in 1998 following an international design competition to give the bridge a “signature” look.

California Gov. Arnold Schwarzenegger at one point tried to kill the SAS and get the Bay Area to go with a cheaper and more mundane design.

When the entire project is completed in 2013, pedestrian and bike trails will allow the adventurous to ride to Yerba Buena Island and back. The Bay Bridge is now entirely off limits to bikes and pedestrians.

The project to replace the Bay Bridge began in 1989, when part of the upper deck of the eastern span collapsed onto the lower deck.

The demolition of the rest of the existing eastern span will be another major, separate project. At Yerba Buena Island, a transition structure will join the upper and lower decks of the existing tunnel to the new roadways of the Skyway/Self-Anchored Structure. To do this while not stopping bridge traffic, a new temporary structure is being built to reroute the often bumper-to-bumper drivers.

The western portion, between Yerba Buena Island and San Francisco, is composed of two complete suspension bridges connected at a center anchorage, dating from 1936. Each of the spans has an upper and lower deck in a single bridge structure, while the new eastern half will be side-by-side. Retrofit work, completed in 2004, included adding massive amounts of steel and concrete along with other seismic innovations.

Demolition of the existing western landing of the bridge will be another big challenge. Regular users of the bridge know that tall buildings are as close as inches from the existing structure as it enters “The City.” Western landing construction work is nearing an end, according to the San Francisco Chronicle.

Even with the replacement and retrofitting of the Bay Bridge being split into separate jobs, each project is so massive that companies who are usually rivals have teamed up. And nearly every bridge building company has some contract on the bridge.

The skyway completed by KFM is a joint venture partnership of three construction giants: Kiewit Pacific of Vancouver, Wash.; FCI Constructors Northern Division of San Jose; and Manson Construction Company of Seattle.

Although American Bridge Company has plenty of experience building bridges as a lone general contractor, it partnered in with the Fluor Corporation to get the SAS contract with a low bid of $1.4 billion.

“With the size of this job in mind, this partnership that works out great. If you look at American Bridge’s history, you will see an old line bridge builder, now partnered with a very, very strong large corporation.”

American Bridge has been based in Pennsylvania since the birth of the steel industry, but has no problem with California sized jobs. The company built the original Bay Bridge in 1936, whose commuters now can catch glimpses of the current work unfold just to the north (which seems like west to many people who see the ocean in the distance).

American Bridge’s steel work portfolio also includes the Empire State Building, Sears Tower, the Houston Astrodome and Disneyland’s Matterhorn.

The 3,920-ton (3,560 t) barge and the sheer-legged crane being attached to it in China will be impressive equipment by the standards of even those jobs, Flowers said. The sheer-legged crane will stand 328 ft. (100 m) tall and be able to lift an incredible 1,870 tons (1,700 t).

“The sheer-legged crane will basically be setting all the big box girder roadway sections,” said Flowers.

“We have two [Manitowoc] 4100s working on the job, which are pretty impressive pieces of equipment, but they will look like toys next to the sheer-legged crane,” Flowers said

The Italian-made straddle carrier used on the skyway was the largest machine of its type in the world, said Caltrans spokesman Bart Ney.

“It was comparable to the shuttle carrier that NASA used,” Ney said. “The big machine picked up 452 individual segments on that portion of the job.”

“This job involves use of the biggest equipment there is,” said Flowers. “But most of the equipment has to be custom made, due to the particular challenges of this job.”

The self-erecting custom crane is to be attached to the barge in China, then laid down and stowed for transport. The barge will be carried by what Flowers called a “monster” special semi-submersible ship.

“When the ship gets to the job site, it will partially submerge and allow the barge to float off, while the ship literally slides out from underneath and goes on its way,” said Flowers.

While the crane’s size will be breathtaking, its top will still be 200 ft. (60 m) below the completed top of the SAS.

The SAS won’t stand on its own until it is complete and cables pulled tight. That means two gigantic temporary trestles must be built, using 27,500 tons (25,000 t) of steel, only to be torn down later. These trestles will in fact be bridges in their own right, complete with piles and earthquake protections.

Those involved say the cables used to hold the structure tight are among the most amazing innovations.

The cable just passed its first tests on the Oakland docks in January. The 17,400 cables are each composed of 137 prefabricated strands, to be wound on-site. They will weigh approximately 5,290 tons (4,800 t), Ney said.

The SAS features 7,160 tons (6,500 t) of steel piling, and 4,730 tons (4,300 t) in the tower frames.

Other innovations on the Bay Bridge jobs include 60-ft.-long (18 m) hinge pipe beams, which will connect the Skyway to the SAS. The beams will allow deck segments on the Skyway to move, enabling the deck to withstand greater movement and to absorb more earthquake energy. In the event of an earthquake, the damaged hinge-pipe beams, which will have absorbed the brunt of the earthquake’s energy, can be removed and replaced.

The Skyway is a roadway on stilts. The “stilts” consist of 160 hollow steel-pipe piles measuring 8 ft. in diameter and dispersed among 14 sets of piers. The piles were driven at an angle, and as much as 310 ft. (94 m) deep, and weigh approximately 365 tons (331 t) each. The existing eastern span consists of the original 85-ft.-long (25.9 m) timber piles.

The Skyway’s decks are composed of the world’s largest pre-cast concrete segments (standing three-stories high) for the deck, and contain approximately 200 million lbs. (90 million kg) of structural steel, 120 million lbs. (54 million kg) of reinforcing steel, 200,000 linear ft. (60,960 m) of piling, and about 450,000 cu. yd. (344,000 cu m) of concrete. CEG

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