East Span Tower Construction Begins Final Phase With Capping of Legs

Update…It took nearly 17 hours, but the process to transport and lift a crowning piece of the new East Span tower went methodically and smoothly today. The steel "grillage" piece placed today — so named because of its internal network of steel plates — caps the tower's four steel legs and ties them together into a single, tapering unit. Work started at 2:30 a.m. as the grillage was barged from Pier 7 in Oakland to the job site on the Bay near Yerba Buena Island. With ironworkers carefully guiding the faceted, 500-ton slice of steel as it was lowered into place by overhead strand jacks, contact was made at 6:50 p.m. tonight — with nary a sound as metal met metal some 500 feet above the Bay. The surprising quietude surrounding the hoisting, lowering and final placement of this massive hunk of steel was soon broken as ironworkers worked furiously to secure the piece and the air filled with the cacophony of sledge hammers slamming metal pins.

The delicate lifting operation saw the 500-ton steel piece come within a couple feet of the adjacent tower legs as it inched its way up the length of the tower. “The wind will push that thing like a sail,” East Span Spokesman Bart Ney said during a morning boat tour for the press. But the weather was on the project’s side, with clear skies and mild conditions helping to prevent any swinging of the mammoth segment, which will distribute the weight of the cable saddle that will sit on top of it. “If you think of it (the tower structure) as a stool, we’re right at the point of putting a seat on the stool,” Ney said.

The din will continue over the next three weeks as ironworkers drill 5,600 holes into the grillage and start to plug them with bolts that will firmly secure it to the splice plates that connect it to the top of the tower legs. Both the grillage and the tower legs were fabricated at Zhenhua Heavy Industry Co., Ltd. in Shanghai, as were the structure's deck segments. — Brenda Kahn

Friday, April 15, 2011, 10 a.m.

The Self-Anchored Suspension Span (SAS) tower will grow 15 feet taller as the latest steel segment is placed today, bringing the tower to 495 feet, about 94 percent of its final 525 foot height.

Unlike the previous four tower lifts, which were comprised of four individual sections, this latest lift is a single segment that will sit atop all four independent legs. The section — known as the “grillage” — will evenly distribute the weight of the 480-ton cable saddle that will hold the SAS’s nearly mile-long single cable as it passes over the tower. The section is nicknamed the “grillage” due to the position of internal steel plates which create the appearance of a grill grate.

This latest tower section arrived in the Bay Area on February 14. The grillage weighs approximately 500 tons, and is 30 feet by 30 feet. When completed, the SAS, the signature element of the new East Span, will take its place on the list of iconic Bay Area landmarks.

Two strand jacks will hoist the grillage nearly 500 feet into the air, so that it can be carefully placed onto the four tower legs. While lifting the grillage will not take as long as it did for the tower legs, which had to be lifted from a horizontal position off a barge into a vertical position, placing this section could take longer, as it must fit over all four tower legs.

Crews will take approximately one day to lift and place the grillage onto the tower legs. Once it has been set down, crews will connect the grillage with bolts, welds and splice plates.

The cable saddle is tentatively scheduled to be placed in late May. Workers successfully placed the cable saddle onto the grillage during a test last week to ensure the two pieces would fit.

For more information visit BayBridgeInfo.org/projects/sas-tower.

See also:

• Grillage Fact Sheet (PDF)