Crews are scrambling at the Transbay Transit Center in downtown San Francisco after a second cracked beam was discovered in as many days.
The $2.2-billion transportation hub opened Aug. 11 and was heralded as a “flashy centerpiece of city infrastructure” two decades in the making, as the San Francisco Chronicle reported. But the center was quickly closed Sept. 25 after the first cracked beam was discovered.
The Transbay Joint Powers Authority (TJPA) – which built and now operates the center – said the tear was 2.5 feet long and 4.5 inches deep on a 60-foot beam that holds a 5.4-acre rooftop park above a bus deck. Then workers found a second, slightly smaller crack on a different beam that runs parallel to the first. Crews are now shoring up the building by installing steel supports to reduce the pressure on the beams.
Officials don’t know what caused the cracks yet, but several possibilities are considered likely: fabrication problems, installation error, too much weight, or an issue in the initial design. The beams are among more than 22,000 tons of steel in the building’s skeleton.
In a statement, Mayor London Breed said “someone needs to be held accountable once the cause is determined.”
According to the Architect’s Newspaper, the companies involved are Pelli Clarke Pelli Architects, the architect of the center and nearby Salesforce Tower; structural engineering firm Thorton Tomasetti, which also acted as the engineer of record along with performing some construction work; the project contractor was a joint venture between Webcor and Obayashi; and, finally, the fabrication of the steel beams was contracted out to Stockton-based Herrick Corp. by Skanska USA Civil West of New York and the TJPA.
Around the transit center, the city plans to create 6 million square feet of office space, 4,400 housing units, 100,000 square feet for retail, and 11 acres of park space. [SF Chronicle]–Gregory Cornfield