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CA Transit Center Fixes Complete

Wednesday, May 15, 2019

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Repairs and reinforcements at San Francisco’s plagued Salesforce Transit Center are reportedly complete, though a timeline of precisely when the $2.2 billion facility will reopen remains unclear.

Some Background

On Sept. 25, 2018, workers discovered a cracked steel beam in the third-level bus deck of the 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.

Fullmetal2887, CC-BY-SA 4.0, via Wikimedia Commons

Repairs and reinforcements are San Francisco’s plagued Salesforce Transit Center are reportedly complete, though a timeline of precisely when the $2.2 billion facility will reopen remains unclear.

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 Transbay Joint Powers Authority 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. Testing included scanning electronic microscopy, Charpy V toughness tests, Rockwell hardness tests, tensile tests, fractographic analysis and metallographic analysis.

A peer review was also initiated, overseen by the Metropolitan Transportation Commission.

In December, the report from LPI Inc., a metallurgical lab that investigated the issue, concluded that the problem started with weld access holes that were created in the beam during the joining process.

Also at that time, the transit center’s engineer-of-record, Tomasetti, presented a fix that called for bolting 20-inch-wide steel cover plates above and below the area around each fractured bottom flange, similar to a “14-foot-long double splint.”

The independent peer review panel said that it was in “general concurrence” with the proposed fix, and on Jan. 10 the authority confirmed that it is in the process of gathering materials for the approved scheme.

That repair, which is now completed, was reportedly made not only to the girders with cracks, but to a pair of identical girders along First Street that had not fractured.

In February, the TJPA put a June completion date on all the fixes.

In looking closer at the causes for the fissures, TJPA executive director Mark Zabaneh revealed at a March 14 meeting that multiple inspections failed to miss a lapse in the building process. Had the error been caught, the steel beams never would’ve cracked, Zabaneh said.

Zabeneh reported that four layers of inspections—conducted by steel fabricator Herrick, steel installer Skanska, Webcor-Obayashi and the authority’s quality-assurance contractor Turner Construction—failed to detect a failure of a necessary part of the process.

Michael Pearce / Getty Images

On Sept. 25, 2018, workers discovered a cracked steel beam in the third-level bus deck of the Transit Center, just six weeks after the structure opened to the public. The next day, another fissure was found on an adjacent beam.

Grinding the edges of the weld access holes smooth before welding can eliminate micro-cracking; Zabeneh said that had that failure been caught, the micro cracks never would have turned into the large fissures that compromised the integrity of the structure.

“The execution was not done properly, and that is something we are looking into,” Zabaneh said Thursday after an authority meeting. “It’s an area of great concern for us.”

Skanska, along with Webcor and Herrick disagreed with TJPA’s opinion that a construction error was the root cause of the fissures.

What’s Happening Now

In a May 10 press release, the TJPA said that all repairs and reinforcements have been completed and that shoring from Fremont and First streets has been removed.

Despite the fixes coming to completion ahead of schedule, the TJPA says that it’s still looking at a June reopen date.

“Throughout May, the building will be recommissioned, an intensive quality assurance process that includes retesting and re-inspecting fire and life safety systems throughout the facility, retesting the building’s mechanical elements, such as elevators, escalators, and HVAC systems and retesting the electrical elements of the building,” the agency said. “The San Francisco Fire Department, Department of Building Inspection and others are providing independent oversight.”

TJPA officials have also gone on record to say that they expect the MTC peer review to be complete at the end of this month as well.

The last bit of business comes with the center’s rooftop park, which needs a new pathway. The original decomposed granite walkway will reportedly be replaced with concrete, also this month.

   

Tagged categories: Maintenance + Renovation; Mass transit; NA; North America; Ongoing projects; Public Transit; Rehabilitation/Repair

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