CA Transit Center Analysis Nearing Completion
MONDAY, DECEMBER 3, 2018
The Transbay Joint Powers Authority—the team in charge of San Francisco’s Salesforce Transit Center—has announced that the structural review is nearing its end.
A panel of 25 experts is currently reviewing what went wrong at the Center, which closed in September just six weeks after the multi-million project opened to the public.
What Happened Originally
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.
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| Fullmetal2887, CC-BY-SA 4.0, via Wikimedia Commons |
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The Transbay Joint Powers Authority—the team in charge of San Francisco’s Salesforce Transit Center—has announced that the structural review is nearing its end. |
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.
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.
In early October, the TJPA confirmed that the shoring systems for the cracked sections were complete, making way for technicians to get in to take samples for analysis at LPI Inc., a laboratory in New York. Testing includes scanning electronic microscopy, Charpy V toughness tests, Rockwell hardness tests, tensile tests, fractographic analysis and metallographic analysis, according to the ENR.
A peer review was also initiated, overseen by regional transportation agency MTC, and during a Nov. 8 meeting for the TJPA board of directors, members called for an inspection of the entire structure to ensure that there were no structural issues in additional to the two cracked beams.
What’s Next
On Nov. 27, the TJPA announced that the metallurgical analyses and structural engineering assessments are still continuing, but that the majority of testing is complete and results are currently being analyzed and all should be complete within the coming days.
The final analysis will then be presented to the MTC Peer Review Panel, followed by a design for repairs, which will also be reviewed.
Tagged categories: Cracks; Engineers; Health and safety; Maintenance + Renovation; Safety; Structural steel
