One-third of 96 recently tightened steel rods have snapped, and they can't be easily repaired.
At least 30 rods on the under-construction new span of the San Francisco-Oakland Bay Bridge have snapped after being tightened, the San Francisco Chronicle reports. The steel rods have been in place since 2008, and were tightened in the first few weeks of March as part of the construction process. Officials said one-third of the 96 rods that were tightened had snapped.
The snapped rods were likely caused by hydrogen embrittlement, when steel is exposed to hydrogen and causes it to fracture, officials said at a briefing this morning. Caltrans is now evaluating whether it will need to replace all 288 rods before the new bridge span opens around Labor Day. The catch with these 96 tightened rods, however, is that they are not accessible to repair, so officials are now looking into design workarounds that would serve the same purpose of the rods.
This is the latest construction problem in a several-year saga of mishaps in the $6.4 billion bridge project, which involves replacing the eastern span of the bridge that partially collapsed during the 1989 earthquake. Back in 2009, 42 people got into an accident shortly after the current span was rerouted to the notorious "S-Curve," a temporary, sharp-angled detour of the eastern span near the Yerba Buena Island Tunnel. In November of that year, a big rig driver was killed when he lost control of his vehicle at the curve and went over the side of the bridge. A newly repaired rod and brace also fell into traffic during rush hour (by some kind of incredible luck, no one was hurt). Last month, a crane fell over while removing part of the bridge (again, no one was hurt).
Supervisor Scott Wiener asked at the briefing if the forced workaround could affect the seismic stability of the bridge, a key motivation behind the whole project to begin with. Officials reassured him that the solution would have the same seismic integrity of the initial rods.
The snapped rods set up a kind of race against time to keep the current span safe for traffic while also working to replace it entirely. Despite the assurances of bridge engineers, the project's history doesn't inspire much confidence. We can't help but wonder if San Francisco is destined for an experience like Vancouver, with its bridge that keeps trying to kill people.
Top image: The new Bay Bridge span on February 21, 2013, after a construction crane on a barge toppled. (Robert Galbraith/Reuters)