As work advances on the final phase of the so-called fix of the tilting Millennium Tower, a recent computer model predicts that when complete, the $100 million project will offset about half of the additional tilt the high-rise has experienced since the effort to secure it began in 2021.
Crews are now excavating around the Fremont Street side of the building as they prepare to shore up the high-rise to bedrock on the two sides where it’s leaning the most – tying it to six steel piles along Mission Street and 12 along Fremont.
“No building should really have that sort of tilt, not a modern building of this nature,” says Harry Poulos, an internationally recognized expert on tall building foundations. Currently, the tower is leaning 29.3 inches at the northwest corner, with more than a third of the tilt coming after crews started to install piles along two sides of the building.
Recently, a resident videotaped an experiment to show what the tilt looks like on the inside – twice rolling a marble uphill, toward the center of a unit near the corner of the building leaning the most. Both times, the marble quickly ran out of steam and came back toward that northwest corner.
“If I was a resident, I’d still be worried that I can’t put something on the table without it rolling off,” Poulos said.
While the fix was billed as providing some relief, it turns out that the fix engineers’ latest computer model shows the construction project will only offset about 4.5 inches of lean, less than half the roughly ten inches of tilt triggered so far during construction.
The model projects that once it is secured, the tower will permanently tilt about two feet at the northwest corner.
Lead fix engineer Ronald Hamburger said in a statement that the primary objectives “have always been to arrest building settlement at the northwest corner … and stop tilting by transferring a portion of the building’s weight to bedrock. Recovery of some of the tilt that has already occurred is a secondary benefit, not a primary objective.”
City-appointed experts are satisfied with the model’s conclusions, Hamburger said in the statement. But some critics fear that the model’s predictions could be overly optimistic.
“There’s a lot of uncertainty,” said David Williams, a deep foundation expert who worries that computer analysis doesn’t specifically simulate the factors that triggered the construction related sinking. He also worries the tower ended up tilting more than the model predicted last year.
“There’s a lot of factors that they have not accounted for,” Williams said.
Residents NBC Bay Area talked to said they are still coming to grips with the reality that the tower will likely lean forever. If all goes as planned now, the tower foundation is expected to be extended and supported to bedrock on two sides by this spring.
Source: NBC Bay Area
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