The retrofit was needed after 32 high-strength anchor rods holding the devices in place broke. The rods could not be replaced as they are directly below the deck and embedded in concrete.
The fix will cost US$5 million to US$10 million and may affect the scheduled opening of the bridge in September.
Two retrofit solutions had been considered, known as the saddle and the collar. “The saddle will provide the equivalent clamping force as the original bolt design to hold down the shear keys,” said Andre Boutros, executive director of the California Transportation Commission. “We have selected the saddle as the retrofit strategy because while requiring more detailed fabrication, it will be less difficult to install and require less coring of the concrete cap beam.”
Caltrans and prime contractor American Bridge/Fluor (Joint Venture) determined that the 96 failed anchor rods, fabricated in 2008, broke due to hydrogen embrittlement.
An additional 192 anchor rods, fabricated in 2010, have been tightened since March and have shown no signs of failure. Engineers are subjecting them to a battery of tests to confirm integrity.
