MTC Launches Expert Study of Salesforce Transit Center’s Cracked Beams
December 13, 2018 Update: This page has been updated with a December 13, 2018, letter sent by MTC Executive Director Steve Heminger to S.F. Mayor London Breed and Oakland Mayor Libby Schaaf, outlining progress on the Transit Center Peer Review to date (see Related Documents to the right). MTC's expert Peer Review Panel, or PRP, is evaluating analyses being conducted by the Transbay Joint Powers Authority (TJPA) — the public entity overseeing the design, construction and operation of the Salesforce Transit Center — on the causes of and proposed repairs to the cracked beams that closed the facility back in September.
The letter states, "TJPA's consultant, LPI, Inc, is leading the analysis of the cause of failure of the two girders over Fremont Street. LPI has developed a fracture hypothesis based on studies completed to date and supported by available evidence. LPI's findings also provide an explanation as to why the two similar girders over First Street were at a lower risk of brittle fracture. TJPA's engineer of record, Thornton Tomasetti, has considered several ways to repair the fractured girders over Fremont, and is converging on a preferred design. The design team is still considering how to address the girders on First Street."
The letter goes on to say, "The PRP met with TJPA and its consultants several times over the last two months as these analyses progressed, and provided feedback along the way. Review is ongoing, but the PRP is satisfied with the general level of progress being made in understanding the root causes of the fractured beams over Fremont Street. The PRP will also evaluate whether it recommends TJPA perform additional analyses to those already identified."
At today's meeting of the TJPA Board in San Francisco, TJPA's engineering consultants presented their latest findings on the root causes for the beam fractures along with a proposed fix, while MTC's Peer Review Panel gave a status report on their progress to date. Both presentations can be viewed here: "Root Cause Assessment — Fractured Girder Flanges." Watch the video of the meeting.
November 13, 2018 Update: This page has been updated with a Nov. 7, 2018, letter sent by MTC Executive Director Steve Heminger to S.F. Mayor London Breed and Oakland Mayor Libby Schaaf, outlining progress on the Transit Center Peer Review to date (see Related Documents to the right).
The letter states, "Working with the full cooperation of the Transbay Joint Powers Authority (TJPA), we have divided the review into the following five stages:
- Load capacity of the temporary shoring system
- Sampling and testing plan for the material from the fractured steel girders
- Cause of failure, as informed by the material test results and design analysis
- Current condition of structural elements directly affected by the steel fractures
- Repair solution, as informed by the cause of failure and current condition.
"The MTC-organized peer review panel currently is focused on material from the first two stages. It has reviewed the shoring at Fremont Street to insure its stability during the sampling of material from the fractured girders. The panel has also reviewed and takes no exception with the TJPA's [Transbay Joint Powers Authority] current sampling and testing plan. Material samples have been removed and shipped to a materials testing laboratory in New York City, where the samples are being machined for testing."
Original Story Posted October 11, 2018
At the request of San Francisco Mayor London Breed and Oakland Mayor Libby Schaaf, MTC has assembled a panel of independent experts to investigate the causes of and potential fixes to the new Salesforce Transit Center’s cracked support beams. The two mayors requested the study in an October 4, 2018, letter to MTC Executive Director Steve Heminger.
“The Transbay Transit Center provides a crucial transportation link between our two cities,” the mayors wrote in their joint letter. “The Transit Center is too important to the future and the people of the Bay Area for there to be any uncertainty around its structural soundness.”
In his response to the two mayors dated October 10, 2018, Heminger reported that “We have assembled a nationally-recognized panel with expertise in steel structures, fracture mechanics and metallurgy.”
The panel members are:
- Michael D. Engelhardt Ph.D., P.E. — professor, Department of Civil, Architectural and Environmental Engineering at the University of Texas at Austin and director of the Ferguson Structural Engineering Laboratory (chair of the expert panel)
- John W. Fisher, PhD. — professor emeritus of Civil Engineering at Lehigh University and director emeritus of the ATLSS Engineering Research Center
- Brian Kozy, PhD., P.E. — principal engineer at the Federal Highway Administration
- Thomas A. Sabol, Ph.D., S.E. — principal at Englekirk Structural Engineers and an adjunct professor of the Civil and Environmental Engineering Department at UCLA
- Robert E. Shaw, Jr., P.E. — president of the Steel Structures Technology Center and member of the D 1 Structural Welding Committee at the American Welding Society
Spanning three blocks in the South of Market area of San Francisco, the four-story Salesforce Transit Center opened in mid-August 2018 after some 20 years of planning and construction. It is currently configured to accommodate several intercity bus systems operating in the Bay Area as well as S.F. Muni lines, and ultimately will also serve as a rail hub where high-speed rail and Caltrain’s downtown extension will converge, making it the “Grand Central Station of the West.”
Officials closed the Transit Center in late September after just six weeks of operation when workmen discovered cracks in two massive steel beams. The beams support the elevated bus deck that runs the length of the terminal, as well as the facility’s 5.4-acre rooftop park. The cracks appeared in a section of the terminal that forms a bridge over Fremont Street.
“There are many questions about what might have caused the beams to crack, who might be responsible, and how the beams will be repaired so that the Transit Center can reopen to the public,” the mayors wrote in their letter to MTC. “These questions must be answered quickly and the public needs to trust the answers.” Schaaf serves as the city of Oakland's representative on MTC's governing Commission.
The panel will produce a final report for presentation to and the Transbay Joint Powers Authority, the owner/operator of the facility. MTC was a major funder for the Transit Center, providing more than $360 million for the $2.3 billion project.