When the Salesforce Transit Center and Park opened last fall, the $ 2.2 billion architectural miracle promised to revolutionize the commuter traffic in the Bay Area as the cornerstone of an extensive and improved network of trains, buses and trams.
Six weeks after a triumphant ribbon cutting in the so-called & # 39; Grand Central of the West & # 39; that promise was fulfilled when engineers discovered a few substantial cracks in the beams of the building.
The STC was immediately closed to the public awaiting the answer to a daunting question: how many more cracks could there be?
The alarming discovery turned San Francisco's newest downtown monument into a ghost town and halted the city's $ 6 billion plans for a sustainable and efficient transportation network.
The closure of STC was especially devastating for Salesforce, the online software products company that had wiped out millions of people to associate its name with the building and the innovative spirit it represented.
When the Salesforce Transit Center and Park opened last fall, the $ 2.2 billion architectural wonder promised to revolutionize commuter traffic in the Bay Area as the cornerstone of an efficient, environmentally-friendly network of trains, buses and trams. Six weeks after a triumphant ribbon cutting in the so-called & # 39; Grand Central of the West & # 39; that promise was fulfilled when engineers discovered a few substantial cracks in the beams of the building
The STC was immediately closed to the public after the cracked beams were discovered on September 25, 2018, while engineers started answering a daunting question: how many more cracks could there be? The closure was especially devastating for Salesforce, the online software company that had wiped out millions of people to associate its name with the building and the innovative spirit it represented
For founder and co-CEO of Salesforce Marc Benioff it was a gamble to acquire the naming rights for the transit center. On the one hand, he ran the risk of linking the company name to a wreck, derailment or other disaster that could occur there.
On the other hand, he had the opportunity to make Salesforce CRM synonymous with something that could forever change the face of transportation into one of & # 39; the world's largest financial hubs – and his hometown.
Benioff found that the benefits outweigh the risks and in 2017 he promised to invest $ 25 million over a 25-year period.
The structure was finally opened in August 2018 after 10 years of construction. Bus traffic began to flow through the terminal and the train was expected to start shortly thereafter, pending the completion of a tunnel connection.
The modern building spans more than a million square feet and four city blocks in the South of Market neighborhood, flooded with natural light, enveloped in sheets of wavy white aluminum and covered with a park on the roof, has earned its place among the architectural wonders of San Francisco and had already become a popular tourist attraction.
That is until six weeks later on September 25, 2018, when workers who installed panels in the ceiling under the park on the roof discovered a whimsical crack in a steel beam.
Ambassadors who have been trained to welcome commuters into the STC began to wave them furiously when the building & # 39; out of an abundance of caution & # 39; was closed to visitors until inspectors could assess the situation.
An inspection revealed a similar crack in a second steel beam.
About a month after the opening of the STC in August 2018, workers who installed panels in the ceiling below the park on the roof discovered a serrated crack in a steel beam (photo)
The STC was closed to visitors & # 39; from an abundance of caution & # 39; when inspectors came in to assess the broken beams. Police tape can be seen outside the building on September 26, 2018
Michael Engelhardt, chairman of the peer review committee who oversees the STC's response to the cracked beam debacle, described the ordeal in an article published by Popular mechanics this week.
Engelhardt explained that structural steel is exceptionally strong, but under certain circumstances such as heavy loads and low temperatures or in the event of defects during manufacture, it can be vulnerable to cracks.
There are two types of cracks: ductile fractures, which develop over time, and brittle fractures, which occur suddenly.
The STC cracks were brittle fractures, which was bad news for the builders.
& # 39; Engineers can predict ductile fractures and make adjustments during design, such as redistributing the load across different parts of the structure, & # 39; said Engelhardt, professor of civil engineering at the University of Texas at Austin.
& # 39; Brittle fractures, on the other hand, happen suddenly and release a lot of energy. They are worried. They are not supposed to happen. & # 39;
The two fractures led to an investigation into how they happened and whether any other could be hidden in the 23,000-ton structural steel of the building.
The STC covers more than a million square feet and four city blocks in the South of Market district of San Francisco. The park on the roof is shown before the opening of 2018
The crisis shocked both commuters in the city and the construction sector given the renowned names that built the STC.
Pelli Clarke Pelli Architects and Thornton Tomasetti, who worked together on the iconic Petronas Twin Towers in Kuala Lumpur, designed the building and the construction was led by Webcor / Obayashi, based in Bay Area.
Skanska, the construction company behind the World Trade Center Transportation Hub and Oculus of New York City, supplied the structural steel.
The steel beams were manufactured in-store by Herrick Corporation using steel plates from two subcontractors.
Construction teams broke ground in 2010. The following year it crashed after the Transbay Joint Powers Authority, the agency that manages STC, ordered a comprehensive assessment of its seismic stability, given San Francisco's vulnerability to earthquakes along the San Andreas Fault.
Chief architect Fred Clarke (photo) once stated that the STC & # 39; probably one of the safest buildings in the world & # 39; would be
The review and subsequent revision of the seismic plan took 18 months, after which chief architect Fred Clarke stated that the STC & # 39; probably one of the safest buildings in the world & # 39; would be.
The first reaction to the cracks of the steel beam was quick, when workers installed 20-foot-high hydraulic jacks to prop up the viaduct of the bus terminal on Fremont Street.
When engineers started an inspection, contractors went to work to gather proof that the plans were not the problem and brainstorm for involved parties for litigation.
Within days of the cracks being discovered, the Metropolitan Transport Commission convened an elite peer-review committee led by Engelhardt to oversee the investigation and repair.
& # 39; It was not our job to decide who we would sue, & # 39; said Engelhardt.
& # 39; Our job was to find out what went wrong, determine the scope of the problem, approve the solutions and make recommendations for the future. & # 39;
He said he was in favor of hiring a welding expert because: & # 39; In the world of structural steel, the connections and connections tell the story. & # 39;
Robert Vecchio, CEO of LPI Inc, a New York company providing forensic metallurgy services, was hired for the & # 39; cause & # 39; to determine the fractures.
Vecchio presented his preliminary findings at a TJPA board meeting in December 2018 and explained that there is a & # 39; perfect storm & # 39; had been of three factors that characterize brittle fractures: weakness in the metal, damage during manufacture, and the load of load during use.
He described the results of a series of tests that showed that microcracks sustained during welding were completely broken under the combination of stress and load.
Vecchio said the metal met all specifications and requirements, but faults in the welding process caused microcracks, which extended to full brittle fractures under the weight of the hundreds of 15-ton buses that drove through the terminal every day.
After Vecchio's presentation, silence fell in the room until a board member asked: & # 39; Would such a failure suggest other places to look at when designing and manufacturing this structure? & # 39; – or can the same problems affect other rays?
Mark Zabaneh, executive director of the Transbay Joint Powers Authority, addresses the media about the crisis with cracks in the day after the closure of the STC
Within days of the cracks being discovered, the Metropolitan Transportation Commission convened an elite peer-review committee to oversee the investigation and repair
TPJA Director Mark Zabaneh replied: & # 39; These reports are being transferred to the peer review panel. We will follow their recommendation. & # 39;
& # 39; We want to make sure that the building is secure before we let the public in again & # 39 ;, he told reporters after the meeting.
The STC remained vacant for the next six months.
Benioff, whose Salesforce Tower office overlooks his colossal investment, remained silent about the closure as officials began the massive task of finding out how to fix it.
Engineers studied every inch of the building and viewed around 21,000 inspection reports. They eventually focused on the steel beams that supported the bus deck above 1st Street, which were designed in the same way as those above Fremont Street but were not broken.
They found a crucial difference in the building order causing micro-cracks in the beams of Fremont Street, where welding access holes were cut before main welding took place.
The weld holes on the beams of 1st Street were cut after main welding, so there were no microcracks.
During a board meeting in March, Zabaneh explained that the microcracks could have been lighted if the weld openings were properly polished before welding, but they weren't.
Zabaneh said that the Fremont Street bars & # 39; were not installed to encode both dimensions and handling & # 39 ;, and the TJPA finally determined that & # 39; the steel subcontractor & # 39; was responsible for the break, but did not specify which company.
The unpolished microcracks were apparently overlooked in four inspection levels by Skanska, Herrick, Webcor / Obayashi and Turner.
Engineers concluded that the problems were limited to the beams of Fremont Street and started repairing them with steel plates before inspectors came in to re-certify the building.
The affected steel beams were reinforced with metal plates before the STC could open again
The STC reopened on July 1, 2019, with very little fanfare.
Three months later it is still a long way from the busy hub it was intended for. Bus service resumes, but trains are still not running and it is unclear when they will do so.
Speaking to Popular Mechanics after the reopening, Engelhardt said that the whole test feels much less consistent than it did when it unfolded.
& # 39; Most importantly, no one was injured, & # 39; he said. & # 39; And the assessment showed that the two affected rays, both more than 60 feet long, barely moved an inch because of the fractures. The redundancies in the design guaranteed the stability of the beams.
& # 39; The overall safety of the building has never been compromised. If those workers had not discovered the cracks by accident, we may still not know them. & # 39;
He sees the entire test as a valuable learning experience that is likely to force changes in city code requirements and inspection processes.
The official peer review report was released earlier this month, with a recommendation to introduce new leadership to monitor train service.
& # 39; The panel was strongly convinced that the project runs a high risk of not going any further unless issues of governance and supervision are addressed & # 39 ;, commissioner John Porcari said publicly after the report came out.
San Francisco County Transportation Authority board chairman Aaron Peskin, a supervisor of the city's Downtown Rail Extension project, said that while recruiting new leadership would delay the process, it may be necessary to ensure that it is properly implemented.
& # 39; We know that this project was behind schedule, more than exceeded the budget and had to cope with a number of construction deficits & # 39 ;, Peskin said. & # 39; (But) the whole substantiation of this discussion and the reason why we asked employees to hire this expert panel is that we do not want to repeat those mistakes. & # 39;
The STC reopened on July 1, 2019, with very little fanfare. Three months later it is still a long way from the busy hub it was intended for. Bus service resumes, but trains are still not running and it is unclear when they will do so
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