Dive Brief:
- At a Dec. 13 meeting of the Transbay Joint Powers Authority board of directors, experts retained by the peer review panel formed to oversee the investigation into two cracked steel beams at the $2.2 billion Salesforce Transit Center in San Francisco proposed a repair that would restore the "original design capacity."
- A presentation from consulting engineer LPI said that testing thus far indicates that the fissures developed from small cracks that formed in welded areas of the beams, leading to cracks in the flanges. According to a report from Bruce Gibbons of engineering firm Thornton Tomasetti, the cracked beams still had the capacity to support the weight of the building and occupancy loads. The proposed fix would involve restoring the original design capacity by installing bolted cover plates to replace the flanges in the fracture areas.
- In an authority update, the next steps are for the Metropolitan Transportation Commission Peer Review Panel to accept the reports' findings and approve the recommended repair. Then crews would make the repair, perform a structural evaluation and make any other necessary inspections. Following that, the rooftop park, transit center and bus service could reopen, but the authority did not provide even a tentative date for when that might happen.
Dive Insight:
While Salesforce Transit Center officials deal with the building’s structural issues, their neighbors at the Millennium Tower are one step closer to solving their own.
The Millennium Tower Homeowners Association has filed a permit application with the City and County of San Francisco Building Department for a $100 million plan that engineers say will fix both the sinking and leaning problem the building has been experiencing since it opened almost 10 years ago.
The “Perimeter Pile Upgrade” would see 52-steel-and-concrete piles — each one measuring 24 inches in diameter and weighing 140,000 pounds — drilled into the bedrock 250 feet under the tower from two sides of the building.
According to engineer Ronald Hamburger of Simpson Gumpertz & Heger, this will relieve stress on the compressed soil under the Millennium Tower's north and west sides, correcting the tilt and limiting how much the building will sink in the future.
If the plan receives building department approval, the project should take approximately 18 months. Mission Street Development, an affiliate of Millennium Partners, is expected to pay for the retrofit and warrant the work out of a settlement of confidential mediation proceedings.
