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Braces for concrete support safety question

  1. May 18, 2009 #1

    morrobay

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    3545064612_0f8998ed8e.jpg These braces were installed on the concrete support pillers at ground level of a very large 6
    level mall.
    Would the engineers comment on the safety of this construction, in particular drilling through the concrete support structure
     
    Last edited: May 18, 2009
  2. jcsd
  3. May 19, 2009 #2

    morrobay

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    The above braces were installed after the original construction of a very large mall.
    50 views and no evaluation from a mechanical or civil engineer ?
     
  4. May 19, 2009 #3
    69 views, and I'm not a civil engineer.

    What is the effect of drilling holds, and inserting lags with plates into a tunnel wall? It strengthens the brittle wall material from shear forces. The lags in the concrete column together with the steal plates have about the same effect, I should guess.

    How long are the lag bolts? We don't know. In any case this places the concrete surface elements under the braces under additional shear upon vertical loading. We still don't know why the plates were added in the first place.
     
    Last edited: May 19, 2009
  5. May 20, 2009 #4

    morrobay

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    This subject came up on thaivisa, a discussion forum in Thailand, in the Pattaya section.
    The pillars are under a very massive newly constructed 6 level + mall in this seaside town.
    Some members on the above forum recently felt tremers and shaking while inside the new mall. Another member observed and took photos of these after construction braces.
    There is no communication between the members on the forum and the Thai construction company that did the work.
    The concern by the forum members is the danger of the mall collapsing.
    Since this could be very serious im trying to research it as fast as possibe.
     
  6. May 20, 2009 #5

    MATLABdude

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    You should contact the Civil (or Mechanical) Engineering Departments of your local university (or the one that's closest to you), and not be looking for advice on the internet (especially if you don't have a background in structural engineering). For the record, I am also not a civil (and especially, structural) engineer.

    If this is a newer structure, unbraced and unsupported columns MAY (and I stress this, MAY) be subject to punch through, especially if there are large distributed loads on the floor(s) above, and insufficient columns (or insufficient girth of columns). If this is an older structure, and it hasn't yet punched through, then it's probably okay. If those bolts don't go all the way through (e.g. they're drilled in part way and then epoxied in place) it just puts the concrete (at the top of the pillar) in tension. Unless there is sufficient rebar (or similar support) concrete usually works in compression, and not tension.

    If the denizens of the building actually are feeling quakes and shaking, this could be a sign that something is wrong. Or it could just be that the building is settling. However, the people at Sampoong also felt quakes and shaking inside their building shortly before collapse:
    http://en.wikipedia.org/wiki/Sampoong_Department_Store_collapse

    (There, the owner / architect got engineers to do preliminary work, got it approved, fired the engineers, and then started redesigning things and building bigger while removing supports). So contact a civil engineering academic, and do it ASAP! If they're the ones that do the analysis and figure out that this is a disaster in the waiting, it's both serving the public good (usually part of the academic / engineering mission) and good publicity.
     
  7. May 20, 2009 #6
    I think you've nailed it, MATLABdude.

    This begins to sound very much like retrofitting in response to the building breaking up. As they are strengthening the floor-column connections, it's likely this is where cracks have been found on other columns. By the way, concrete columns are normally constructed around a rebar cage, so it should be the concrete-rebar composite that would be in tension from the extra hardware.

    An additional avenue may be to push for legal injunction to condemn the building (but I aint a lawyer, either :smile: )

    Is this a new construction or has the interior been changed? Has additional load been added recently, such as water storage or larger airconditioning units on the roof? Have any upper-story columns been removed to increase open space?
     
    Last edited: May 20, 2009
  8. May 21, 2009 #7

    morrobay

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    Thanks for the information and well taken advice.
    This is a very new construction. Regarding recent additional loading;
    Yes, there is a large crane on the roof and some sort of 2-3 story high unfinished construction ongoing above the completed 6 level.
     
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