Skyscraper Leaning 3 Inches Per Year As Architects Scramble To Prevent Disaster
The Millennium Tower in San Francisco’s financial district is now tilting 26 inches.
According to structural engineer Ronald O. Hamburger, who is attempting to stabilise the tower, the luxury residential building is now tilting three inches per year.
Opening to residents in 2009, the 58-story, 645-foot tall skyscraper is settling unevenly. Efforts to stabilise the tower seem to have only worsened matters and engineers were forced to stop their attempts last year.
They paused efforts to ‘determine why increased foundation movement was occurring and how this could be mitigated’.
On Tuesday, January 4, Hamburger proposed slashing the number of support piles beneath the tower to ‘minimise additional building settlement’.
According to a letter sent to the building’s general manager, the new fix was needed after engineers identified two potential causes for the issue.
The letter detailed how the issue may be due to the ‘vibration of the soils associated with pile installation activity, and unintentional removal of excessive soil as the piles were installed’.
Currently, the building has 52 support piles and it’s being proposed that this be reduced to just 18 steel piles that will be anchored into bedrock under the tower.
In a document relating to the plan, the engineer said:
We judge that the 18-pile solution offers an optimal solution between additional settlement and benefit gained.
However, if more than 18 piles are needed, ‘the construction schedule will be extended, and the building will settle and tilt a little more during this period’.
The tower is situated beside the Salesforce Transit Centre, a bus terminal and potential terminal for California’s under-construction high-speed rail service.
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