Bay Bridge closed indefinitely: unanswered questions

October 28, 8:29 AMSF Architecture & Design ExaminerGeorge Calys

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 Suddenly and with no apparent warning, a structural component of the Bay Bridge failed, falling to the upper bridge deck and striking three cars. The incident is especially worrisome as the failed component, the so-called saddle brace, was recently installed after the discovery of a cracked eyebar during the Labor shutdown of the Bridge. The saddle was rapidly designed, fabricated, and installed when the cracked eyebar was detected. The Bridge reopening of the Bridge was delayed by only a day.

Last night’s failure of the saddle has resulted in CalTrans closing the Bridge indefinitely.

The causes of the problem are, as yet, unknown and because bridges are structurally complex, there may in fact be multiple causes. At the time of this writing, CalTrans is just beginning the investigation and analysis, so there really aren’t any answers. But there are plenty of questions.

Why did the eyebar initially crack? The cracked portion of the eyebar was discovered in September during the shutdown of the bridge for work related to the new span. Was the eyebar crack due to the age of the component (the behavior of steel can change with time)? Was corrosion an issue? Or were new stresses being placed on this particular eyebar due to forces else where on the bridge?

Was the design of the saddle (the component intended to repair the eyebar) adequate? Reports indicated that an miscalculation in the design of the saddle required an additional steel spacer to be quickly fabricated during the repair. Were there other miscalculations in design of the saddle?

Were the saddle and accompanying system of cables correctly installed? In the rush to reopen the bridge, was something overlooked?

Are there other structural components in the bridge that are not performing correctly that may have contributed to the saddle brace failing?

These are obviously serious questions that represent only a starting point in the forensic analysis of this failure. CalTrans, it’s your turn.