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CA Transit Center to Reopen Next Month

Thursday, June 13, 2019

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The Transbay Joint Powers Authority on Tuesday announced that after a review of the fixes made to San Francisco’s $2.2 billion Salesforce Transit Center, officials confirmed that the structure is ready to reopen to the public.

The Center and public rooftop park will reportedly reopen at 6 a.m. on July 1.

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.

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

The Transbay Joint Powers Authority on Tuesday announced that after a review of the fixes made to San Francisco’s $2.2 billion Salesforce Transit Center, officials confirmed that the structure is ready to reopen to the public.

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.

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

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.

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.

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

Regardless, the repairs were finished in early May.

What Now

“We are pleased to welcome the public back to the transit center and sincerely apologize for the inconvenience this temporary closure has caused,” said Mohammed Nuru, Chair of the TJPA’s Board of Directors.

“I thank Mayor Breed and Mayor Schaaf for calling for the Metropolitan Transportation Commission’s independent review, which has now concluded. They provided thorough, proper and independent oversight. We can now reopen this critical piece of our transportation network and important source of open space to commuters, the neighborhood and the entire region.”

The MTC panel was responsible for reviewing and approving TJPA’s sampling and testing plan; identifying of the root cause of the failure; the temporary shoring design; and the steel girder repair and reinforcement.

In addition, it affirmed the designer’s findings that no other areas were susceptible to brittle fracture and oversaw the designer’s efforts and independently affirmed the designer’s conclusion that the transit center can now reopen to the public.

The MTC’s full report isn’t expected to be released for a few more months, according to ENR.

In terms of transportation at the center, bus service from street level will begin in early July and bus deck service is slated to resume later in the summer.

   

Tagged categories: Accidents; Maintenance + Renovation; Mass transit; NA; North America; Public Transit; Safety; Structural steel; Terminals

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