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Thread: starplate connectors and cheap housing

  1. #11

    The top story makes me nervous

    I'm with your husband ... I'd take off the top story to reduce the wind load ..... the other thing you can do is put out a few bucks to a structural engineer to get his opinion .... just a thought.

  2. #12
    LHBA Member loghousenut's Avatar
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    I say go for it....

    You're in Alabama aren't you. Look around you! Unless things have changed a bit in rural Alabama since I was last there 30 years ago, you have a well engineered mansion on your hands. No offense intended.

  3. #13
    LHBA Member StressMan79's Avatar
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    I have a similar thing

    However, it is much worse. I have a shipping container that weighs roughly 15k#, topped with a lightweight shed. We call it the "penthouse." The structure is ~18 ft high and only 8 ft wide... and the only thing holding it down is the mass of the container. Wind loads are pretty low, however...I have no guy wires, and it has been fine for at least two years now.



  4. #14

    The sonotubes have rebar in them

    and rebar wire wraoped around the threaded rod, but no bend in the threaded rod. some have a washer with a nut at the end. So, it's not very anchored...don't ask. We used Home depot tubes so I think they were 4ft? 5ft? Some of it is sunk in 3 ft some are 18" in the ground.
    Stessman, do you mean cable wire at the base of it attached to more concrete sunk in the ground? The penthouse is great, maybe we should have built that on our 40' hi cube.
    I do want to make this something lasting for later on. But we plan on laying low for a year and really see if this is where we want to build a log house.
    thanks

  5. #15
    LHBA Member StressMan79's Avatar
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    The tubes/wires

    it is unfortunate that there is no bend in the rod, this will be the weakest part of the connection with the ground, the tubes won't fail.
    the guy wires would go into something that is anchored in the ground. If you have a stump, that would be OK. Otherwise, sink some 10" tubes 3 ft deep, and put a loop of rebar out of the top of each, and then hook a wire to the top of the roof (or 3/4 the way up, put a brace across the two sides on the inside), through some eye hooks, then cinch it up taught (don't put 10,000# of tension in the wire, just don't let it slack). at the connection to the ground.
    Anyway, the wire will effectively stop any side to side movement, at the same time, it will put downforce on the structure. If you have 500# of tension in each wire at 45 deg, you'll have 500#*6 wires.sine(45 deg) or just over 2000 lb downforce on the structure, at zero deflection. if the house budges even a little (say 1/2 inch) and you are using 3/8 inch wires, you have an additional force in each of the three wires on that side of
    pi/4*d^2*E*deltaL/L0, say that L0=45'=540", deltaL = 1/2 inch, E (steel) = 30(10^6) psi and d=.375,
    so the increased tension in each wire is over 3000#.
    You then have 3x(3500-0)x cosine(45 deg) restorative force (the zero is b/c with a movement of half an inch, the the wires on the leaning side, will slack and no longer apply any force), or almost 7,300# of restorative lateral (side to side) force on the structure, also a total of 7300 pounds down force on the structure as well.
    Also note the center of pressure is going to be half way up the side face. that is the place where you can put the effective point load due to the distributed wind loading. that looks to be roughly 8' off the tubes, but the restorative lateral force will be applied at the eyes, and will therefore have roughly twice the "moment arm." this means that 1 lb of wind load needs only .5 lb of cable load to react it.
    I don't know what the size of your place is, but this means that you'd have to have zero strength in the rod, and have a wind load of roughly 14,500# to even lift the structure half an inch. In fact you need more than that, since the down force will also serve to counteract the wind load.
    wind load is:
    Force, F = A x P x Cd
    Where A is the side area of the wall, P is the air pressure (due to wind) and Cd is the "drag Coefficient". P varies as the velocity squared, so a 10mph wind will have 100 x the wind load of a 1 mph wind. You'll see that to get P in PSF, it is .00256 x V^2, where V is in mph. For a flat wall, Cd is 2. I'm just guessing here, but your wall is roughly 15'high and 30' long, or 450sf, say you are designing for a half inch deflection in a 100mph wind, your pressure is then 25.6psf, and you get a side force of 23,000lbf. I would simply allow the deflection to be what it will in this unknown situation (we are ignoring the restraint of the tubes) and just get wire that can hold at least double the required for a 100 mph wind. A: you'll never see it, and B: 3/8 inch cable will easily hold this much load (you have 3 of them).Anyway, as you can see, guy wires are very effective means to stop top heavy or "unstable" structures upright. You'll notice every radio antenna has them all around

  6. #16

    Beware of Hurricanes

    Beware of Hurricanes ...

    I live in Texas ... Wind loading is our primary concern here .....

    See what your max recorded wind speed is and design for a bit above that ....

  7. #17
    LHBA Member rreidnauer's Avatar
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    Nervous

    Quote Originally Posted by miltonjoy

    The sonotubes have rebar in them and rebar wire wraoped around the threaded rod, but no bend in the threaded rod. some have a washer with a nut at the end. So, it's not very anchored...don't ask. We used Home depot tubes so I think they were 4ft? 5ft? Some of it is sunk in 3 ft some are 18" in the ground.
    Stessman, do you mean cable wire at the base of it attached to more concrete sunk in the ground? The penthouse is great, maybe we should have built that on our 40' hi cube.
    I do want to make this something lasting for later on. But we plan on laying low for a year and really see if this is where we want to build a log house.
    thanks
    I'd be worried about the sonotube depths. The ones only 18" in really have me worried. That's not much soil to resist toppling, especially if there is more sticking out of the soil than what is in the soil. Wrapping rebar around the threaded rod doesn't do much either, though the nut and washer will help alot.
    That said, it is just a temporary structure, and the house portion looks to be built plenty strong, so probably the worst that would happen is the piers would topple and the house would be sitting on the ground. Chances of actually being blown over, I think, would be far less likely. If it were me, and this is strictly just a suggestion, I would build forms and pour concrete walls in between the piers. (you could also ad additional threaded rods this way) That would lock the piers together making their collapse far less likely, as well as adding weight to the foundation lowering the (much slimmer) chance of the house toppling.

  8. #18

    Thanks men

    We value your input. I think we have decided to take off the top floor just so any potential future buyers won't balk at the sight of our tower. I think we'll just add on to the sides for extra space next time with a j bend in the rods. Love you engineers and builders out there, you're such...what can I say...engineers and builders! Thanks
    Joy

  9. #19
    LHBA Member ChainsawGrandpa's Avatar
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    Tall & narrow

    Sounds just like a temporary cabin I built, except mine was 2' wider,
    and 2' taller. Still standing after being hit with 60 mph wind storms.
    G'pa

  10. #20
    Chiming in a bit late, but I just got back on the forums (life took a twist --what's new!?). Sonotubes ARE a great option IF you do them correctly for your building, weather, and soil.

    Here's a 14 x 24 that I'd love to build: http://www.countryplans.com/nash.html The website talks about how to insulate piers, etc. Best of luck!

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