California’s new San Francisco-Oakland Bay Bridge project is in turmoil as the failure of a large number of bolts continues to dog the scheme.
Last month crews working on the all steel self anchored suspension section of the crossing, which makes up part of the link between Oakland and San Francisco Bay, snapped 30 bolts as they were tightened.
The 76mm diameter bolts, also called anchor rods, are between 3m and 8m long and are part of two huge steel and concrete anti earthquake
components known as shear keys, which are sandwiched between the bridge deck and the top of the single tower that will support the suspended deck.
Now the Californian Department of Transportation (Caltrans), which is overseeing the $6bn (£3.92bn) scheme, has confirmed that the firm that supplied the bolts, Dyson Corp, also supplied other key components, including the rods that secure cables on the bridge’s central tower.
Caltrans director Malcolm Dougherty has now called for an inspection of all other bridge components supplied by the Ohio-based firm.
One theory under investigation is that hydrogen was present when the bolts were made. Hydrogen atoms can weaken bonds making the metal brittle.
The all steel structure is a self anchored suspension bridge with a single 160m tall tower and a 385m main span and a 180m back span.
The project is a joint venture between the Bay Area Toll Authority and Caltrans, with Hatch Mott MacDonald and URS working in a technical review team to a design by TY Lin International. The new section is due to open on 3 September.
New build follows quake
The new section of the Oakland Bay Bridge, will replace the eastern section of the existing crossing between Yerba Buena Island and Oakland.
Following the 1989 Loma Prieta earthquake the double deck east span partially collapsed.
After the quake, the three tower suspension bridge between Yerba Buena and San Francisco underwent seismic strengthening work. Caltrans decided the most cost-effective solution to remedy the badly damaged East Span, was to build a new bridge