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Self-Anchored Suspension Span (SAS)

 

SAS CONSTRUCTION UPDATE: OCTOBER 28:

The 28th and final deck section for the Self-Anchored Suspension Span (SAS) was placed, marking a major milestone in the construction of the new East Span of the San Francisco-Oakland Bay Bridge.

Read the Press Release.

One signature element transforms the San Francisco- Oakland Bay Bridge into a new global icon – the Self-Anchored Suspension Span (SAS). The SAS is the largest bridge of its kind anywhere in world (2,047 feet), one of many firsts. This engineering and construction marvel raises the bridge building bar to new heights.

The span’s single 525-foot-tall tower will echo the height of the West Span’s towers. Its placement closer to the west end of the SAS creates a distinctive asymmetrical design. This means that the single mile-long main cable will present a sharper angle on the west side but a more sloping appearance on the east.
 
The prime contractor building this landmark is American Bridge/Fluor (A Joint Venture). The two engineering firms bring a combined 210 years of experience to this unprecedented project. American Bridge is no stranger to the Bay Bridge; in fact, American Bridge helped build the original bridge in 1936.
 
 

Building a Bridge to Build a Bridge

Traditional suspension bridges, such as the West Span and Golden Gate Bridge, have towers with two main cables that tie into anchorages in the ground. After the suspender cables are attached to the main cable, the deck is hung from the cables.

Building a different kind of suspension bridge requires a different kind of construction strategy. Because the SAS is self-anchoring with one cable, the roadway must be built first. But with nothing to hold up the roadway, a temporary bridge is required first – crews built a 20,000-ton temporary bridge to build the approximately 35,200-ton permanent span. With the falsework in place, crews build the road-decks and tower first, then the cable is anchored into the roadways. 
 
SAS Road Decks: Heavy Lifting
The SAS’s east and westbound roadways are each composed of 14 individual sections. These deck sections vary in weight from 559 tons to 1,669 tons, as well as in length, from 64-feet-long up to 229-feet-long. The roadways are connected by 19 crossbeams.
 
Helping with the heavy lifting is a massive 400- by 100- foot barge equipped with a 1,900 ton shear leg crane sporting a 328-foot-long boom. The crane’s boom weighs 992 tons, and is 328 feet long; the crane can lift up to 1,929 tons. The crane barge, dubbed the Left Coast Lifter, was custom built for this project and is the largest of its kind on the West Coast.
 
After a deck section is floated on a crane barge to the work site, the crane lifts and places the section onto a cradle on the temporary supports. The cradle, which slowly carries the section into place, is outfitted with ski-like appendages that are pushed by two horizontal hydraulic jacks along raised, PTFE-capped pedestals greased with a special solution, moving about 10 feet with each push. This process was only used for the west end of the SAS, where the waters were too shallow for the crane to put the deck sections directly into place on the temporary steel.
 
To connect one deck section to another, 4,500 bolts are used, with a one millimeter variance; 350,000 bolts will be used to connect all 28 deck sections.
 
 
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