Smarting from a second emergency closure of the Oakland-San Francisco Bay Bridge in two months, the California Dept. of Transportation is exploring long-term repairs for a cracked eyebeam until the crossing’s $6.3-billion modernization is completed in 2013.
Caltrans engineers are considering replacing part or all of the truss system that has a cracked eyebeam, discovered by inspectors on the 73-year-old cantilevered eastern span during a Labor Day closure. Rancho Cordova, Calif.-based C.C. Myers Inc. was installing a 288-ft detour ramp as part of the reconstruction when inspectors found the 1½ in. crack in a 2-in.-thick, chain-like steel beam. The cracked eyebeam was unrelated to the detour installation. CCM worked around the clock to install a saddle to hold the cracked beam, with only a minor delay in reopening. But on Oct. 27, one of the repair beams cracked, dropping a 5,000-lb crossbeam and steel connectors onto the deck. During the ensuing six-day closure, North Highlands, Calif.-based MCM Construction Inc. repaired the work with enhancements.
Because it can moderate the damaging effects of earthquakes, base-isolation is a technique used primarily in seismically active regions. ENR takes a look at some of the largest applications of base-isolation technologies in the world.