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Recent content by JDWright

  1. JDWright

    Manhole Buoyancy

    Lets try this again. lol. Assume, theoretically, that a deep, precast concrete manhole with a water tight lid is designed based on all standard methods and criteria (following DD-41: http://www.concretepipe.org/wp-content/uploads/2014/09/DD_41.pdf). A lower lip on the base is even added to be...
  2. JDWright

    Manhole Buoyancy

    CVG, I agree with your analysis. The situation I'm exploring would have water tight lids. These are good to about 20 psi. Failure of a joint would be slow and rare. Again, this is a mental exercise and exploration.. I created a little model: https://youtu.be/IM0gyPWD1jE
  3. JDWright

    Manhole Buoyancy

    Bimr, I am using standard methodology and have no objections to it at all, I am just curious as to how the forces are acting on the structure in various "theoretical" situations. Everyone mentions buoyancy forces, but all I am asking is if a structure has no bottom (say, due to a joint failure...
  4. JDWright

    Manhole Buoyancy

    Thanks for the responses guys. I am over thinking things...as an engineer its my job! And its also a fun thought experiment. I don't ever just *accept* what I am told without fully understanding to the best of my ability. My questions dont apply to basic design and installation principles, Im...
  5. JDWright

    Manhole Buoyancy

    After much exploration and even building a scale proof of concept model, I have made some conclusions. The important key here is the joints of the precast sections should be water tight as necessary for the depth (about 15 PSI for a 35' deep submerged manhole excluding air pressure). If the...
  6. JDWright

    Manhole Buoyancy

    I am specifying some relatively deep 5' diameter precast concrete manholes (25'-35' deep) which are located in a floodplain (will be fully submerged during floods) and thus they will have water tight lids with MH rims at existing ground level. I have ran the standard buoyancy calculations and...
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