Foundation Of Luxury Condo Tower Sinking

Discussion in 'Off-Topic' started by Glenn Holland, Aug 2, 2016.

  1. Glenn Holland

    Thread Starter Active Member

    Dec 26, 2014
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    The foundation for the 54 floor luxury Millennium Tower in San Francisco has settled at least 16 inches and the building is also leaning 2 inches out of plumb.

    http://www.sfchronicle.com/bayarea/article/SF-s-landmark-tower-for-rich-and-famous-is-8896563.php

    The same thing happened to the brand new 32 floor Ocean Tower condo on Padre Island in Texas and it finally had to be demolished.



    There haven't been any strong earthquakes since the Millennium Tower was built in 2009 and I suspect a moderately severe quake will finish it off.
     
  2. SLK001

    Senior Member

    Nov 29, 2011
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    Nothing that a couple of 10 ton hydralic jacks can't fix!
     
  3. #12

    Expert

    Nov 30, 2010
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    Will all the geologists and architects on Allaboutcircuits please raise one hand?
    I need to know if the sky is falling.
     
  4. Glenn Holland

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    Dec 26, 2014
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    Seems like there are more high profile cases of engineering negligence, especially in structural engineering.

    The new eastern span of the S.F. - Oakland Bay Bridge is also plagued with engineering and construction defects. The 60 story One Rincon Hill Tower in S.F. also failed approval because of inadequate seismic tolerance and it was sent back to the design board several times . When the Big One hits, that will really "Separate the men from the boys.
     
  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    There's a world famous tower in Italy that leans, maybe this one in S.F. will make it world famous too.
     
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  6. crutschow

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    Mar 14, 2008
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    Obviously the foundation didn't extent to the bedrock.
     
  7. Glenn Holland

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    Dec 26, 2014
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    The most serious problem is differential settling that places shear stress on the foundation and the frame itself. The concrete frame of the Ocean Tower in Texas was deforming and cracking and that would eventually lead to a catastrophic failure.

    The floors in modern concrete buildings are reinforced by tensioned cables instead of rebar. If the concrete is solid and intact, the tension will overcome bending stresses and keeps the floor rigid. However, if the concrete is "abfractured" or continuously cracked at a right angle to the cables, the tension will cause the floors to buckle. Then the tension will bend the columns inward until they fail and progressive collapse will occur.

    The concrete floors of the Murrah Building in the Oklahoma City bombing used tensioned cables and it was determined that the blast ruptured the 1St and 2nd floors which allowed the cables to pull the columns inward and that set off a progressive collapse.

    In the case of the Ocean Tower and the Millennium Tower, the foundations did not extend to solid rock and that was a fatal mistake that should have never happened.
     
  8. shortbus

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  9. hrs

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    Jun 13, 2014
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    ifixit will know what to do.
     
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  10. GopherT

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    Nov 23, 2012
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    That was in the story in the Wall Street journal a few days ago. All the buildings in the same neighborhood have pilings down to the bedrock. For some reason, the engineers didn't think it needed bedrock support. Either the designers or the investors wanted the project to stay on budget - or it was somehow magical ground that didn't need bedrock pilings when core samples were done and became un-magical when someone stepped on a crack.

    Someone also implied that the project went from an original plan of rental/lease space to a condo format just as construction started. Now the residents/owners get to deal with it instead of the developer - who will likely pull the bankruptcy lever when a lawsuit is filed.
     
  11. Glenn Holland

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    Dec 26, 2014
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    The worst case scenario is the structure further deteriorates to the point that it has to be taken down like the Ocean Tower.

    However, San Francisco does not allow explosive demolition so they will have to remove the top 30 of all 54 floors, then use conventional wrecking ball to knock down the rest.

    The combination of a big demo job and 100s of lawsuits will be a really messy party right in the middle of an upscale neighborhood.
     
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  12. shortbus

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    But it's life as usual in other parts of big cities.
     
  13. Glenn Holland

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    Dec 26, 2014
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    Here's the latest and not so greatest news about this ill-fated multi-million dollar condo development.

    The place is literally coming apart at the seams and cracks are appearing in the basement walls. Many owners are now selling off there hyper expensive condos at a 25% to 30% loss over what they paid. They've hired engineers to try to retrofit the foundation, but that doesn't look like a workable plan.

    Millennium Tower Cracks 1.jpg Millennium Tower Cracks 2.jpg Millennium Tower Cracks 3.jpg .
     
  14. GopherT

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  15. Glenn Holland

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    When your dealing with foundation problems in a 54 floor high rise in an earthquake zone, old news is rapidly becoming new news.

    The faults have been very quiet in the Bay Area, but if seismic activity picks up, that building's (and the price of condos) is going go on an accelerated path over and downward.
     
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  16. shortbus

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    Oh, the humanity! The ultra rich are going to have a crisis.
     
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  17. Glenn Holland

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    The most obvious question is how did a 54 floor building in San Francisco with a deficient foundation get approval and permits for construction.

    A plain vanilla 4 floor apartment building requires at least 50 pages of plans and other documents to get the go ahead for construction. Furthermore, how did these apparently incompetent engineers get a license to practice a safety critical profession in California?
     
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  18. GopherT

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    They followed code. Why do you blame the engineers who were meeting city code? Blame the city code writers. It's existed for a long time.

    Blame the condo buyers who elected to buy into the cut-rate building. Condos were cheaper per square foot than competing spaces. Did any buyers ask why? Notice the ads from competing buildings today, they announce bedrock foundations.
     
  19. tranzz4md

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    Apr 10, 2015
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    I'll willingly blame the engineers; they either knew they weren't supporting the structure properly, or they didn't. I'll not say which is worse. One of them had to have a PE stamp, counterfeit or otherwise.
     
  20. Glenn Holland

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    I don't believe the engineering details were originally disclosed in the buyer's disclosure package and the construction defects were disclosed only after the defect was discovered and the problem went public.

    Furthermore, I don't believe the building's engineers or the engineers at the San Francisco Bureau Of Building Inspection (SFBBI) followed the guidelines for geotechnical analysis and foundation engineering. I had my condo building seismically upgraded after the earthquake in 1989 and I'm very familiar with the city's code requirements for foundation analysis. As a result of the ground failure during the 1989 quake, the foundation for all new buildings in the San Francisco Marina District are required to have piles going all the way to bedrock.

    From my personal knowledge of all the complexities associated with putting up a building in San Francisco, there's no way in hell any competent engineer (working for the building's developer or the SFBBI) would approve a deficient foundation for a 54 floor building in an earthquake zone.
     
    Last edited: Dec 24, 2017
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