I was switching TV channels the other day and there was Bart Ney, the lead spokesman for Caltrans’ Bay Bridge project, taking questions from the media. Now what’s going on? I asked myself. As I listened, I could see frustration on Ney’s face as he talked about the bridge’s safety. Ah, it must be about the Sacramento Bee’s reporting of questionable safety testing, of which we’ve been covering for some time, I thought, most recently about a state senate panel investigation regarding the newest claims. Then suddenly, Ney started talking about the start of the next major segment of the project, the load transfer at the self-anchored suspension span (SAS).
It now seems regardless of the milestone-esque moments of the historical $6.3-billion project, the local media will keep dredging up the Bee’s allegations, based on, mostly, Caltrans’ own reports. And as Caltrans keeps saying, including at the recent webinar in June, that the SAS foundation and other aspects of the bridge construction are so over-engineered that safety shouldn’t be a concern, as many proponents and critics have indicated, it still seems the media will have none of it. On projects this large and complex, every element of every process is overly studied and planned and the reports on the efforts always include any and all remotely questionable procedures. Caltrans is as prepared as any large transportation agency in this regard and takes every criticism seriously.
Okay, so in Ney’s words, here is what’s coming next:
“The load transfer operation will transform the bridge, now held up with temporary steel supports, into a self-supporting structure – the largest such bridge in the world. The load transfer operation on the single-cable bridge – unique in its own right – is designed to shift the weight of the 35,200-ton decks from the temporary steel that currently supports them and onto the tower, suspender ropes and main cable, which is the longest single looped suspension bridge cable in the world.”
Ney adds that load transfer is a time- and labor-intensive process that involves a series of phases which will take about three months to complete. The operation began in mid-August with crews using hydraulic jacks (which exert up to 400 tons of force) to gradually tension the 200 suspender ropes that will connect the main cable to the decks. Once 104 of the 200 ropes are tensioned, the bridge is self-anchored and self-supporting. As the suspender ropes are tensioned, they will pull the main cable toward the deck causing it to move down about 16 ft and out about 30 ft. This will cause the decks to lift up approximately 1.6 ft from their temporary supports. When the temporary steel is no longer needed to support the decks, crews will prepare to remove it.
“Unlike traditional suspension bridges where the cables are anchored into the ground, a self-anchored suspension bridge’s cable is anchored in the road decks,” says Ney.
Here is further media coverage of the procedure.
And here is a Caltrans simulation of the deck rising process and other load transfer steps.