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  • Users: rholder98
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  1. rholder98

    Slab and wall joints in concrete tank

    In a liquid-filled tank, must construction joints in the wall align with the construction joints in the slab? These are construction joints, not contraction joints--i.e., continuous reinforcement. Specifically, this is for a circular tank, and according to the specs, the slab will be placed in...
  2. rholder98

    Density of Portland Cement?

    Why is portland cement 94 #/cf alone (SG=1.51), but is 197 #/cf (SG=3.15) when used in a mix design?
  3. rholder98

    Construction bracing of CMU walls

    I was a little worried, because I could not find any temporary bracing for these 28 ft cmu walls. Luckily, though, I finally found this. Enjoy. . . .
  4. rholder98

    Batch plant broke down. . .

    . . .40 yards into a 200+ yard pour for a section of slab in a carousel aeration basin. Now a large section of the slab has about half the thickness in place, with most of the top mat of steel exposed, and some of the bottom mat exposed. They at least had the quick-thinking to 'spread out'...
  5. rholder98

    Waterstops--Cast-in vs Synkoflex

    I'd like to get opinions. I keep getting requests to substitute Synkoflex for the cast-in pvc waterstops I specified. I can understand how it's probably a lot easier to construct, but how well does it perform in a liquid-containing structure?
  6. rholder98

    Are they practicing engineering without a license?

    I was EOR for a large industrial warehouse somewhere in America. The structure is to be a metal building (designed by a qualified metal building manufacturer). Basically, then, I only designed the foundation. There are several jib cranes scattered throughout the building. Believing it to be...
  7. rholder98

    CMU arching/thrust; deep lintels

    The caveat to using arching action is having not only enough wall height over the opening, but also having enough wall on either side of the opening to resist the resulting thrust. Can you resist this thrust with a tension tie--say, the steel in the lintel--instead of relying on the jambs...
  8. rholder98

    Leave rebar exposed for future construction?

    I have to plan for a future clarifier to be built adjacent to the pump station and clarifier I am currently designing. That is, eventually, it will be two clarifiers with a pump station between, but only the one clarifier will be built in this contract. What's the best way to detail the...
  9. rholder98

    PCA's rectangular concrete tanks--off the charts

    What do you do when your b/a is not on the charts? Just treat it as a vertical cantilever? What about horizontal bending stresses?
  10. rholder98

    Modifying an existing clarifier

    I am having to check an existing clarifier to see if we can add one foot of depth. I have the existing drawings (from 1969), so I have the geometry and the reinforcing. I do not have the design compressive strength, however, nor do I know the grade of rebar. I plan to design a 9 ft clarifier...
  11. rholder98

    Possible change in licensure process--early exam?

    At the August meeting of the Texas Board of Professional Engineers, the Board elected to consider the possibility of allowing EITs to take the PE exam at any time after graduation, provided they have already taken the FE. They would still have to wait the minimum of four years to gain...
  12. rholder98

    Interesting steel article from 1971

    http://aisc.org/Content/ContentGroups/Documents/MSC_Docs/wooten.pdf
  13. rholder98

    1927 Concrete Building

    I am analyzing a concrete building to determine the capacity of the 8th floor. Surprisingly, I have drawings. The joists and beams are scheduled, so I have the reinforcing. The schedules list, for example, '1 7/8" dia. mark 703'. The bar bending diagram tells me what mark 703 looks like...
  14. rholder98

    Circular Concrete Tanks

    Are the charts in PCA's "Design of Circular Concrete Tanks Without Prestressing" valid for negative loading? That is, can you check the empty condition with soil (and liquid, if applicable) on the exterior by simply using a negative load? Is it as easy as a matter of sign convention? The book...
  15. rholder98

    ACI 350--Durability Factor

    Does the durability factor S for liquid-containing structures apply to the "empty" load case? That is, do I apply it to the flexure imposed by the soil on the outside of the tank before it gets filled? Section 9.2.8 says "Required strength U shall be multiplied by the following environmental...
  16. rholder98

    Is anyone familiar with 'Xypex'?

    We had a rep come into the office yesterday, talking about this product. It reportedly waterproofs concrete by reacting with the unhydrated cement to form crystals. It can be spray or brush applied as a slurry, broadcast as a dry-shake, or cast as an admixture. I was wondering if anyone is...
  17. rholder98

    Roof Collapse in TX

    http://www.kcbd.com/Global/story.asp?S=4656603 Wind gusts were up to 61 mph yesterday.
  18. rholder98

    Light-Gauge Open Web Steel Joist?

    Is anyone familiar with such an animal? We have a building with these, and we're trying to change the use of the space, but the joists won't work with the new load. So, the questions are: a) where can I find info on such joists, and b) does anyone have any ideas on strengthening the system...
  19. rholder98

    Economy of PEMB

    This has come up again in my office--at what point to metal buildings lose their economic advantage over conventional construction? I contend that PEMB is better for simple, rectangular buildings with few frills, but when you start introducing plan irregularities and multiple roof heights...
  20. rholder98

    Early 20th Century Floor Framing

    Is anybody familiar with a type of construction where a concrete floor is supported by steel beams, but the beams are encased in the concrete? In section, it would look like a pan joist system, except that the joists are encased steel beams. The buildings were built sometime between 1900 and...

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