Medical Tuesday Blog
The Saga of the Leaning Millennium Tower of San Francisco
The Millennium High Rise Tower in San Francisco, which was built on a large cement platform on bay area “fill in,” rather than on piles to bedrock, began sinking and leaning a few years after being built in 2009. It has sunk about 16 inches and the top leans about 6 feet at this time despite buttressing the foundations on one side with tons of concrete. The price of some of the condominiums was reduced from $10,000,000 to $9,000,000.
While we were in SF for our monthly American Conservatory Theater this weekend, the SF Chronicle reported that a large window cracked on the 36th floor on Sept 1, 2018 at 2:30 AM. The owners were awakened with a massive banging sound which they described “like a huge, thick vault door had slammed shut” and for the next 30-minutes, the homeowners described hearing what sounded like the glass splintering in the window. The evaluators comforted the owners assuring them that this was not caused by the building’s leaning and sinking, but by an “external force” hitting window.
The building inspectors ordered the tower managers to tape up the window and install overhead scaffolding to prevent glass from falling onto the sidewalks below. The replacement glass has to be ordered from Shanghai and will arrive in mid-November 6-weeks after the break. It appears that SF prefers to do business with non-American companies and countries.
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The new San Francisco Transit center next to the Leaning Towers of the Millennium buttressed their common side with many more tons of concrete. It opened recently and closed shortly afterwards when a large crack was found in a support structure. This defect has not been attributed as yet.
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Another SF disaster
They also acknowledged that one of four high-strength tower anchor rods they have examined apparently snapped after it was exposed to water and became brittle. That was the same headache that cost the agency $45 million to fix in 2013 when 32 rods on seismic stabilizers failed after sitting in water.
The chief engineer on the bridge project, said the microscopic cracks found on at least two rods lead him to believe that the problem could be widespread. “As an engineer, if I have these micro-cracks, I have to assume they exist in every rod.”
A Berkeley engineer and corrosion expert who has studied the problem on the bridge project, said the discovery “means that there doesn’t have to be a lot of force on those rods for them to break.”
“That could indicate that we don’t need an earthquake for them to snap, that they are unreliable in the service loads that they are under now,” she said. “The micro-cracking is a sure sign of hydrogen attack. It’s a portent of catastrophe.”
A metallurgical failure expert and retired San Jose State University professor, said the results are ominous. He scoffed at Caltrans’ statements that all but a handful of the bolts passed pull tests to determine their strength. It can take years for water to cause hydrogen embrittlement in steel, he said.
“That’s one failed rod already in two years,” he said. “But what about tomorrow? What about 10 years? Fifty years? How many would be left in 150 years?” Members of the committee, clearly frustrated at the continuing bad news, declined to approve new expenditures for cleaning and protecting the rods, saying they wanted to wait for recommendations from a panel of experts to determine the extent of the problem.
There’s been a lot of back-and-forth news over Bay Bridge troubles, and it’s frustrating to everyone involved. In May, a mechanical pull test found at least one fractured rod among the group, and it’s been reported that about a quarter, or a full 100 of the rods, are sitting in “sleeves” that were improperly sealed and regularly allow seawater to “flood” into them within days of being drained. The concern now is that the bridge is not only not earthquake safe, but potentially not safe even to drive on as-is.
The bridge already cost $6.4 billion to construct, and $4 million is being spent just to investigate this problem.
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The Chinese company hired to build key parts of the San Francisco-Oakland Bay Bridge had never built a bridge. Shanghai Shenhua Port Machinery Co. Ltd., after all, was a manufacturer of giant cranes for container ports.
The California Department of Transportation agreed to contract the company known as ZPMC in 2006 because it had established a reputation as fast and cost-effective, offering savings of about $250 million compared to the competing bidder. (That’s not even 5% with a $3 billion overrun)
Bridge officials were racing to finish the span, pushed years behind schedule and billions of dollars over budget by political squabbles and construction delays. Fearful that the old bridge might not survive a major quake, they wanted speed and savings.
Caltrans asked an outside expert to assess whether ZPMC could do the job, and Jim Merrill, a senior materials contractor for the bridge project, gave the company a “contingent pass.” He also labeled it “high risk.” Among other problems, ZPMC didn’t have enough qualified welders or inspectors, the audit noted, and routinely welded in the rain, a basic error that often causes defects.
Undeterred, Caltrans signed off.
The company later boasted of “zero defects” in a news release. Brian Maroney, chief engineer for the bridge, said in a recent interview the audit’s “contingent pass” heightened vigilance to head off problems.
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This underground swamp and the overwater incompetence in SF has no relationship to the Washington, DC, above ground swamp.
San Francisco likes to keep its swamp tied to non-American Companies & Countries