As the Bay Area celebrates the opening of a new Bay Bridge—an eastern span that transportation officials are hailing as elegant and seismically secure—UC Berkeley engineers are expressing serious misgivings about whether the structure is safe. And at least one professor labels it far less stable than the old bridge.
Cal professor of civil and environmental engineering Abolhassan Astaneh-Asl told us only a few hours before Wednesday night’s closing of the old span that he believed the new span is so deficient in its design and execution that it is much less safe than the old one. It was Astaneh-Asl who led a Cal team that investigated damage to the old Bay Bridge after the 1989 Loma Prieta earthquake and determined that the structure’s foundations were sound.
The old Bay Bridge, unlovely as it is, was engineered for strength and durability, Astaneh-Asl said; the only significant failure during Loma Prieta was the collapse of a section of the upper deck, which he attributed to some relatively minor and localized truss shifting.
He said state and regional transportation officials “have been telling everyone who will listen that the old bridge is unsafe, and now it’s widely accepted. That’s simply not true. For one thing, Caltrans knows that the Federal Highway Administration requires the immediate closure of a bridge if state transportation department officials conclude it is unsafe. Caltrans has been claiming the old bridge is unsafe for ten years. If they truly believe that, then they willingly broke federal law, because they kept the old bridge open.”
The new bridge, by contrast, is a ‘fracture critical’ bridge, Astaneh-Asl said. “That means that if a single component fails, the whole thing comes down. Fracture critical bridges have been out of favor since the 1960s. And when you look at this new span, there are many things that can go wrong.”
But transportation officials maintain that the opening of the new Bay Bridge is cause for celebration, and that despite a series of snafus over several years, the result will be a beautifully designed and seismically safe bridge—so safe that it will withstand a once-every-1,500-years earthquake.
The most recent of those snafus struck in March, when three dozen earthquake-safety anchor bolts were discovered to have snapped. Replacing them was expected to yet again delay the opening of the new Bay Bridge, this time until at least December.
But the state moved forward with a temporary fix: steel plates rigged in the vicinity of the fractured anchor bolts. These devices, state engineers concluded, will minimize bridge movement during an earthquake. The plates must suffice until a more robust steel “saddle” is installed as a permanent anchoring mechanism.
This solution seemed to satisfy everyone—everyone who counts, anyway. Vincent Mammano, the administrator for the California division office of the Federal Highway Administration, wrote that he was impressed by the state’s efforts, and saw no reason to delay opening the span to traffic while the long-term repairs were completed. That pleased the Toll Bridge Oversight Committee, which subsequently voted unanimously to green light the September 3 opening.
“We had four independent groups all verify and endorse this idea on their own,” said Andrew Gordon, spokesman for the Bay Bridge project and a guest on KQED’s Forum program. “We had the Seismic Safety Peer Review Panel, which is made up of world renowned seismic experts, we had the Federal Highway Administration, and two engineering firms all on their own review this proposal to use the shims—these steel plates—in this way.
“And they all came to the same conclusion: That we could use the shims to protect the bearings that are under the bridge while we’re fixing those broken bolts permanently, and also use those to achieve the level of seismic safety necessary to get traffic onto the bridge.”
Defenders of the new span have suggested that Astaneh-Asl bears a grudge because his own design proposal for the Bay Bridge was not selected. He is perhaps the most outspoken engineering critic of the project. But he is hardly alone.
Emeritus professor of civil and environmental engineering Bob Bea—one of the nation’s foremost authorities on large project risk management—responded to our query with an email in which he took pains to separate the engineering wheat from the chaff of media hysteria and political posturing.
“This is a very challenging engineering problem that needs to be carefully addressed and the concerns properly managed,” he wrote. “It is not a time for political rhetoric that will further contribute to the fog…” That said, Bea observed that tests on the bridge and its supporting components were underway, “…(and) yes, the results are encouraging. But there are significant concerns with the validity of the testing and the testing results.”
Further, Bea wrote, “…the problems with this structure are much more extensive than the seismic support bolts. (There are) corroded post tensioning tendons in the concrete girders (and) flawed welds in the suspension span support tower. (There are) lots of identified defects with high uncertainties concerning their effects on performance and safety. And to my knowledge, there still has not been a comprehensive analysis of the potential defects on the ‘safety’ and ‘performance’ (short and long-term) of our new ‘signature’ bridge…”
Considering its location in one of the most seismically active regions on earth, the new Bay Bridge project has seemed cursed for years. Almost from the beginning, there were questions about its design. Then came financial problems at Caltrans, worries about the soundness of many of the welds on the new bridge’s supporting members, and then the snapping of the very bolts designed to ensure the seismic safety of the span. UC Berkeley professor of material sciences Thomas Devine and Bea both expressed concerns about the safety of the bolts and other issues, and urged a thorough assessment.
A quarter century has passed since the Loma Prieta quake struck. The new Bay Bridge, when it debuts next week, will have been under construction for two decades and come in hugely over budget, at a cost of more than $6.4 billion
As for Astaneh-Asl, he continues to cite his original concern over basic design: self-supported spans are inherently unstable, he said, because they are not anchored to the earth like conventional suspension bridges. Then there is the matter of the anchor bolts – they’re all a problem, he said, not just the ones that snapped.
“We know the steel they used has an issue with hydrogen embrittlement, which makes the bolts inadequate to the stresses they could face,” he said. “There is also the matter of the 20 main welds that connect the legs of the tower to the tower’s foundation. These are each about 30 feet long, and they have hundreds of visible cracks—and at least one of them is seven inches long. That’s incredibly bad news. Cracks in welds are always a problem, but you usually can only detect them by sonic testing—and these can be seen with the naked eye.”
Everything considered, continued Astaneh-Asl—“and by that I mean the 2,300 faulty anchor bolts, the cracked welds, the corroded tendons in the girders, the basic flawed design—there’s no doubt in my mind that the old bridge is much, much safer than the new bridge. (The new span) should not be opened to the public. All the evidence that Caltrans has indicates this bridge will collapse when the Hayward Fault ruptures.”
California Magazine delved into the troubled history of the redesigned Bay Bridge in its Summer 2013 issue and also here. We also filed a follow about the bitter dispute between Professor Astaneh and Bay Bridge officials here.
Posted on August 28, 2013 - 10:37am