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Jul
2013
18

Bay Bridge Authorities Consider Rushed, Risky Solution to Chinese Steel and Bolt Failures

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CALTRANS, the authority which oversees the iconic San Francisco Bay Bridge, is asking the Federal Highway Administration (FHA) to consider an alternative plan that will allow the bridge to open as scheduled despite repairs being incomplete.

The new plan was sought after renovated portions of the bridge experienced dangerous bolt failures.   This news brought about further scrutiny from critics who have complained from the beginning about CALTRANS’ use of imported Chinese steel on the project.  

The new plan would involve temporary shims as a safety measure and keep the bridge’s predicted opening date of Labor Day Weekend in tact:

… the Bay Bridge construction oversight team is asking the Federal Highway Administration to evaluate a proposal to install temporary shims in four bridge bearings adjacent to the seismic stabilizers where bolts snapped in March. While the federal peer review is advisory, the request signals the Toll Bridge Program Oversight Committee could reconsider its decision to hold off on the planned post-Labor Day traffic switch if federal engineers bless the wedge plan.

Plans were originally hatched to protect the bridge from seismic activity until December when the repairs were projected to be complete. CALTRANS never planned on applying these plans to achieve a Laor Day opening, but last week the agency requested an outside peer review from the FHA.  Bay Bridge spokesman Andrew Gordon spoke of the letter and the new plans to open by Labor Day:

The (committee) said they would take this into consideration, and the letter is a reflection on moving forward on that consideration,”  

The nuts and bolts (pun intended) are broken down by Contra Costa Times writer Lisa Vorderbruggen:

20130712_090631_ssjm0713shim90_400

To understand how the bearings and shear keys work, picture the rocker bearing as a pair of men’s suspenders and a shear key as a belt.

The suspenders are a bit loose so he can move but the belt is cinched tight so his pants stay up.

On the bridge, the bearing, or “suspenders,” move back and forth with traffic loads and temperature changes. The shear key, or the “belt,” clamps together the bearings, columns and deck, and keeps them aligned during an earthquake.

But with two of the four shear keys out of service due to the broken bolts, the bearings are exposed.

The shims may be a good insurance policy for the bearings, but Seible has repeatedly said the bad shear keys are unnecessary for day-to-day traffic operations. And given the known vulnerability of the existing 1936 eastern span, he has for years urged the Bay Area to open the new bridge without delay.

Caltrans bridge engineer Brian Maroney concurred with Seible ( Toll Bridge Program Seismic Safety Peer Review Chairman Frieder Seible)  in the engineering analysis sent to the Federal Highway Administration.

The data “overwhelmingly drives a shift of public traffic to the replacement bridge from the old bridge based on a desire for public safety … as soon as feasible,” Maroney wrote.

Every step in the Bay Bridge reconstruction has been met by public scrutiny and debate.  But after ten years of waiting and working, it is difficult to understand how saving a couple of months, and potentially sacrificing safety and quality, makes sense.

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