Shoring Complete at San Francisco Transit Center
San Francisco’s Transbay Joint Powers Authority confirmed earlier this week that the shoring systems for the sections where cracked steel beams were found in the Salesforce Transit Center have been completed.
The four-level shoring system completion makes way for technicians to get into the center to take samples to send off for analysis, which should give officials a reason for why the fissures appeared in the first place and guide the direction on how to remedy the situation.
On Sept. 25, workers discovered a cracked steel beam in the third-level bus deck of the $2.2 billion Transit Center, just six weeks after the structure opened to the public. The next day, another fissure was found on an adjacent beam.
The beams are part of the support system for the 5.4-acre rooftop garden and park, which includes a 5-foot layer of soil.
According to the Engineering News-Record, the bottom-flange cracks are near the 8-foot-deep midspan of each shop-welded girder. In the structure, the hanger plate slots through the bottom flange.
However, the TJPA’s senior construction manager told ENR that the cracks do not touch the hanger and are only in the flange.
Skanska USA Civil West was the structural steel engineer on the project and the beams in which cracks appeared were manufactured by Herrick Corp. Oregon Iron Works made girders and basket columns, while XKT Engineering fabricated some of the transit center’s “seismic load resisting system.”
General contractors Webcor and Obayashi managed the center’s construction, which lasted from August 2010 to August 2018. The architect was Pelli Clarke Pelli, with Thornton Tomasetti serving as structural engineer.
While the general contractors and architect were tapped to install the shoring, TJPA officials are choosing an independent metallurgical lab in New York to analyze the samples of the beams. Officials also announced that a regional transportation agency, MTC, will oversee the peer review of the permanent fix, once determined.