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Strand Jacks

COMPUTER-CONTROLLED STRAND JACKS TO LIFT NEW BAY BRIDGE TRANSITION SPANS

SAN LEANDRO, Calif., December 5, 2005 -- Construction of the new San Francisco Oakland Bay Bridge reaches a milestone in mid-January when the first transition span, linking the concrete skyway bridge deck section with the yet-to-be-built suspension bridge, will be lifted into place using alternative lifting technology that has never been used in U.S. bridge construction before on a scale of this magnitude.  Specialist heavy lifting contractor Bigge Crane & Rigging will use computer-controlled Hydrospex strand jacks to precision lift the 2,000 ton steel span off a barge to a height of approximately 200 feet within 1/32 of an inch.  At the Oakland side (to the east), where the skyway bridge deck has already been constructed, the strand jacks will be mounted on a mobile jacking platform, supported by a pair of 60 foot girders, cantilevered 28 feet off the bridge deck.

At the San Francisco side (to the west), main contracting consortium Kiewit-FCI-Manson has constructed two steel lifting towers, founded on piles driven into the Bay for this purpose.  Bigge will furnish 2 girders that span 125 feet across the top of this lifting tower and strand jacks will be mounted on top of a mobile jacking platform that sits on the girders.  Both of Bigge's jacking platforms are capable of synchronized 8-inch longitudinal and transverse movement. 

At the Oakland end, Bigge is using four strand jacks, each of which has a lifting capacity of 365 tons. All of the jacks are synchronized for simultaneous operation and load control within 1/32 inch.  "No traditional crane, particularly a barge-mounted one on the water, could do this job with the required combination of capacity and precision," said Pete Ashton, Bigge's vice president of major projects.  This is the first major project for which Bigge has used its new strand jack equipment since becoming the exclusive representative of Hydrospex, the Dutch manufacturer that also supplied the strand jacks that raised the Russian Kursk submarine in 2002.

The first transition span, for the eastbound carriageway, is scheduled to be lifted on or around January 16, 2006.  The second span, parallel to the first to carry the westbound carriageway, is scheduled to be lifted into place in June.  Each lift will take approximately 10 hours, as the strand jacks raise the load at 30 feet per hour.  During the lifts, the tubs, as these transition spans are called, will be maintained with 1/8 inch of the required attitude.  Given that the tubs are 200 feet long by 85 feet wide, this can only be achieved by computerized monitoring.

Once the tub is lifted to elevation, a temporary support tower will be skid under the tub for support until the concrete joint with the existing skyway is poured and cured, filling a gap of some 6 feet.  The San Francisco (west) end of the tub will be supported with another tower until the suspension bridge is constructed.  When each of these towers is skidded into position, Bigge will lower the tub onto the towers and adjust it for exact crossfall and longitudinal elevation.  After the tub is secured to the temporary support towers, the San Francisco end lift system will be dismantled.  The Oakland end will be left in position for three months while the concrete closure pour cures.

Bigge's input, however, starts long before the lift.  It is also contracted to load the tubs onto a barge at Portland, OR, where they have been fabricated, and ship them to the site.  The first one will be loaded onto the barge on December 29 using 48 axle lines of a Scheuerle self-propelled hydraulic modular trailer (SPMT).  The barge will then be towed out of the mouth of the Columbia River to the Pacific Ocean where it will follow along the coastline to the San Francisco Bay.  It will then travel under the Golden Gate Bridge to the site wharf in Oakland.

However, because of bridge piers, the erection towers and other obstacles, there is not room for the barge to bring the tub into the correct orientation.  Instead, it has to position with the tub at 90 degrees to the bridge.  Therefore, Bigge will have to use its SPMT again to rotate the 200 foot-long tub on top of the barge by 90 degrees. 

"Transporting and lifting such a super-heavy load to such a height is a significant operation," said Weston Settlemier, president of Bigge Crane & Rigging.  "We are unaware of such a heavy load ever being lifted so high anywhere in the United States.  However, what makes this job possible is that we have an engineering solution using our own equipment, which is the very latest in computer-controlled lifting technology."

This project was also featured in an article inside the December 5th issue of Engineering News-Record; reprints are available.

Bigge Crane and Rigging Co. owns and operates one of the largest , most diversified , best maintained inventories of heavy rigging and hoisting equipment in the United States. This includes a fleet of well-maintained heavy lift cranes, hydraulic gantries and non-crane heavy lifting systems. These include tower lift and elevated gantry systems incorporating strand jacks, center hole rod jacks, chain jacks or heavy-lift hoists. Bigge has won numerous "Job of the Year" Awards from the Specialized Carriers & Rigging Association including the SC&RA's "Safety Award" and "Zero Accidents Award" and is the exclusive operator and sales dealer of the computer-controlled Hydrospex Equipment for North, South and Central America and the Caribbean region.

CONTACT:
Pete Ashton
Vice President, Major Projects
510-639-4077
510-639-4053 (fax)
pashton@bigge.com

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