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  1. briancpotter

    1980 spancrete load tables

    Spancrete series are named as follows: First digit is plank thickness, second is strand diameter (in 16ths of an inch), third and fourth are number of strand, T indicates structural topping. So 8504T would be 8" thick plank with (4) 5/16" strand, and 8510T would have (10) 5/16" strand The...
  2. briancpotter

    Code specified minimum rerinforcement for retaining walls?

    Worth pointing out that in 318-14 (section 8.6.1.1), ACI clarifies the provision under debate in that thread, and states in the commentary that Asmin should be placed entirely in the tension face. Brian C Potter, PE Simple Supports - Back at it again with the engineering blog.
  3. briancpotter

    Water tank ring foundation partial removal

    Do you have the original calculations? Good chance the foundation is designed for hoop stresses, which cutting away a portion of would compromise. Brian C Potter, PE Simple Supports - Back at it again with the engineering blog.
  4. briancpotter

    Vehicular Load: 3,000 lbs acting on an area of 4.5 in. by 4.5 in. Distribution Factor?

    DETstru- I believe those provisions are from BS8110 (or at least, that code uses the same formula). Personally, I've only ever used the wheel load to check localized shear failure, and otherwise used the 40 psf garage load. But if your span is short enough, the 3k load would control for...
  5. briancpotter

    Live Load Reduction on a Double Tee

    After the previous discussion about this, I did a bit of digging. There's a report from the Texas DOT (will see if I can find it) that did tests on tee load sharing. As I recall, load sharing only takes place if something like a shear key or notched grout joint is in place on the edges of the...
  6. briancpotter

    RC Beam-column Joint with one beam connected to the column at a different level

    Kootk- I'm not sure assuming the low beam as not part of the lateral system is conservative. The issue I see is that the low beam(s) are probably going to attract lateral force regardless of whats assumed - my guess is the heavier lateral elements of the larger, left portion of the building...
  7. briancpotter

    Earthquake Design Magnitude

    There's a variety of equations relating Richter Magnitude to Peak Ground Acceleration. Blume 1965 gives one: http://www.iitk.ac.in/nicee/wcee/article/vol3_IV-53.pdf Here's a table of PGA and magnitude for California earthquakes: The relationship between PGA (what the ground experiences) and...
  8. briancpotter

    Thin Plates for Moment and Torsion connection

    Not sure if this is the reason, but I'd be a little worried about the weld unzipping due to load concentrations at the top/bottom of the weld Typically when moment is placed on a weld, the weld is detailed to have an extra line of weld at the top and the bottom to give it a C-shape, but your...
  9. briancpotter

    Thin Plates for Moment and Torsion connection

    I think instead of torsion, your P4 load is more likely to induce a couple on the two plates, with positive shear on one and negative shear on the other (superimposed on top of the vertical loads and the bending from the uniform loading). Brian C Potter, PE Simple Supports - Back at it again...
  10. briancpotter

    ACI 318 Shear Provisions and Modified Compression Field Theory

    Reading up on the failure of the Sleipner A drilling platform, much of the blame is not-so-subtley placed on the unconservativeness of the ACI 318-95 shear provisions - specifically, the ones that provide shear capacity for members under compression. These provisions (eq. 11-6 in every...
  11. briancpotter

    Rebar Callout Question

    Referring to steel, OQ can refer to "oil quenching", a heat treating process sometimes used in the production of steel to give it more ductility (I think it used to be common on prestressing steel, not sure now?). Seems unlikely to be the case here, but it's not impossible the designer wanted...
  12. briancpotter

    fixing a steel console with only 2 anchors?

    Seems I have, color me surprised. Like TME, I'd still be pretty skeptical of this as it's frighteningly close to the edge, and an expansion anchor is going to push outward against it's hole. And you've still dramatically overestimated your shear capacity. Brian C Potter, PE Simple Supports -...
  13. briancpotter

    fixing a steel console with only 2 anchors?

    With less than 3" clearance from the edge, I'd be willing to bet that this doesn't meet the minimum edge distance requirements of the anchor, even if you can technically get the concrete breakout calculation to work. Edit: It looks like you've overestimated your anchor's shear capacity...
  14. briancpotter

    RC Columns Strengthened by Steel Jacket

    Assuming you're sticking with the steel beam/concrete column for the moment... Why not instead of a jacket, use an embedded steel plate with 90 degree hooked bars welded to it? Something like that could be made as big as you needed it to be, really. Fabricating a plate to match the curvature of...
  15. briancpotter

    Water Tank Wall (Tension Limit)

    In ACI-350, I believe this is handled by a maximum allowable stress in the reinforcing (I think it's 20 or 24 ksi depending on what the reinforcing is used for). This, in turn, is a refinement of earlier provisions that specified a maximum allowable crack width (limiting steel stress...
  16. briancpotter

    Slab Depressions in Double Tee Floor Systems

    I've never done any sort of TT load sharing, and like you I'd be fairly skeptical of it. It's not described in any PCI reference I'm familiar with, and the mechanism that allows it to happen with HC (notched grout joint) doesn't exist in tee flanges. The side plate connections could...
  17. briancpotter

    Slab Depressions in Double Tee Floor Systems

    KootK- I've done a fair share of tees, and I don't think fabrication will really be your issue here. Contra TME, I think casting these would actually be fairly trivial. As you say, all they have to do is block out the flange and a chunk of the stems, which (shouldn't) be a problem. All they'll...
  18. briancpotter

    Slab Depressions in Double Tee Floor Systems

    As far as solutions, I can think of a couple options (assuming "frame it in a sensible way with a beam where the depression edge is" is a no go): 1) Cast on a flange at the correct height after the double tee has been poured, prior to erection (it would have to be post-pour as I'm not aware of...
  19. briancpotter

    Slab Depressions in Double Tee Floor Systems

    What's the purpose of this depression? I'd think ANY flooring system would have difficulty handling what in essence is an unframed 12' x ~50' opening, it seems unfair to blame the double tees, heh. What's the loading on the floor? 42' is well in the ballpark of 12" HC for most uses. Brian C...
  20. briancpotter

    Corbel -reinforcement Af to resist factored moment

    Without knowing what design book you're reading, the 0.9 factor is likely an attempt to calculate the depth of the compression block (the same reason that the moment arm in for typical beam reinforcing is d - a/2). I'm not sure this is really necessary since your concrete will extend past the...

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