San Francisco-Oakland Bay Bridge (East)

Opened to traffic.

An inspection reveals cracking in a critical eyebar component of the main span. Found in one of eight bars sharing the same load, the crack was not present two years earlier. The bridge is closed and emergency repairs are carried out.

During the evening commute, a saddle, crossbars, and two tension rods (parts of the emergency repair during the previous month) weighing over 2.25 tons collapses onto the deck. The failure of the repair was caused by two design defects: first, the tie rods closely fit the holes in the cross pieces over the saddles and second, wind caused vibrations in the rods, which in turn caused wear and bending at the through holes, eventually causing a rod fracture. The catastrophic dropping of the cross pieces was caused by a lack of structural attachment to the saddle, being retained only by tack welds, friction and the tension of the tie rods. The rework of the design includes six significant modifications:

1. Structural welding of the cross pieces to the saddles to avoid catastrophic disassembly
2. Enlargement of the through holes to avoid contact with the tie rods
3. Addition of a spherical seat and matching tie rod tensioning nut to eliminate concentrated bending loads at the nut
4. Addition of tie rod cross ties between the rods and the eyebar at three locations to reduce wind induced vibrations and to secure the rods from falling in case of failure.
5. Installation of protective sleeves to prevent direct contact of tension rods where they cross other structural members
6. Addition of strain gauges and associated instrumentation to continuously monitor component loading

The bridge is re-opened after emergency repairs.