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Spitballing Clear-span Loading Puzzle (heavy steel)

Discussion in 'Building' started by FrankRizzoPE, 14 May 2012.

  1. FrankRizzoPE

    FrankRizzoPE

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    Hey. All.

    Anybody. Ever see discussions on here or elsewhere, about how heavily one must support long (1@37’, 1@34’) wide flange beams with at least one auxiliary footing(s)?

    No bolts for steel mounting plates were cast into the new frostwall & half-foundation last fall. Next month we pour in the final 5” concrete pad.

    Talking four end-points of loading, 3 of which could bear upon existing 10” concrete.

    But! Haven’t been able to find info on the following:

    1. Whether there exists a code-acceptable product/method for drilling, installing (driving and epoxying) enough strong-enough bolts for heavy steel column mounting plates. Some wind loading being a given.

    2. Whether 3000psi concrete becomes sketchy for bolting such plates. I.E. You hit rebar halfway there.

    3. If was to design footings for 2 other independent columns, say 3’x4’x24”deep, are there mounting systems that exist which once mounted to cast in place bolts, allows for any eventual asymetrical settling of the heavily loaded footings. The inside of the new foundation was compacted 3/4” stone. Note: If I need to center this one key column onto a footing any wider than 4’ square, that will impact which framing approach will have to be taken for the floor (and loading) above.


    Hopeful somebody here might have run into a redesign situation like this. Our Engineer is going to be swamped with commercial work. Last time he appreciated ($) the fact I had gotten as much of the loading specs as close as I did.

    Or, if anyone knows of a lay-friendly engineering board I could check out, I’d be very grateful.

    Jim


    ...........................


    More Detail... Just in case.


    Before I focus on what this is about, I first need to say that I am not trying to end run any official building analysis and approval. Nor should ANYONE.

    I am posting this here because I am heavily this phase of PREPARING (designing an addition) a “best-shot”, followup, a REdesign which I fully intend to present to the same Structural Engineer who approved my September, 2011 design. Our Structural Engineer will either approve and/or conveniently adjust the lbs/linear/foot specs for a pair of W14-xx or W16-xx beams.

    Over the winter my wife and I agreed we had no option but to build more oomph ($) into this addition. We found out the barn we wanted could not go where we’d hoped, due to ledge, wind loads and a property line buffer requirement. Not to mention the extra $5000 worth of ledge we found while readying the site for the frostwall and half foundation, which survived the winter fine. Good drainage and a sloping sandy backfill atop was a must fix all along. With equal luck we’ll pour the pad in June.

    But only after our engineer’s EASY approval of the necessary (x#) additional footings, end-columns and pinnings, plus their exact locations and elevations.

    Just hope a couple people here can discuss common loading/footing solutions (dimensions) using 5000psi concrete. My problem is on our 2011 pour we did not cast in any bolts for customary steel mounting plates for columns. And so, at the front, where 2 parallel W-beams will carry a second story load rated at (guessing) 40lbs/ft^2, - the top of the 4’ deep frostwall (including 24”x12” footing) 3000psi concrete, probably should not carry those two columns. These front end columns will be trussed together (welded/bolted) over the new garage door, where it’s well braced steel cross-beam will bear the end load of one of the 35+foot, full span W-beams. Expansion/contraction/movement of foundation at the back ends should also be considered.

    More info available by request.
     
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  3. tony1851

    tony1851

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    There are a few engineers on this forum, but I doubt you will get much advice on this particular problem.

    US Codes differ in many regards from ours, paticularly on live-, wind- and seismic loads. The design methods also differ; on a simple level, engineers here are used to SI units rather than Imperial, Design for steelwork is also done on limit-state principles - is this the case in the US? - (I wouldn't know).
    One specific point you mentioned was 'some wind loading'. Presumably this implies a moment-connection at the base. This night need something more substantial than resin-fixing of the bolts; moment-bases usually have some anchorage device at the bottom of the bolt, which is cast-in. Admittedy it is a problem if you are dealing with an existing r.c. base.
    Anyway, good luck with your search.
     
  4. FrankRizzoPE

    FrankRizzoPE

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    Thanks for alerting me to the UK orientation, Tony.
    Never even noticed that.

    That specialized-"bolt" anchoring requirement is something I will surely be looking for, but under US and New Hampshire codes.

    Steel units here are often provided in both SAE and/or SI.

    I haven't a guess which named standard or (here in the US) corresponds to "limit-state principles". I can tell you only that I've repeatedly run into tables of tabulated "numbers" in columns; each column referring to individual modulii variables for material elasticity and shear thresholds, loading moments, etc., apparently as those advance according to size (linear, area, trigonometric and other calculations).

    .........................


    Anecdotally, our engineer approved last years design version based on a single W-Beam with only one intermediate support.

    To clarify (thinking aloud to myself) here, my new (2012) revision would share the load of the single story above, between/over/with two (2) W-Beams vs. the single W12-45 approved last year.

    If I am unable to find an acceptable top-face anchoring system, then I am inclined to believe that 4 independent footings is the best way to anticipate (solve for) inherent dimensional expansion/contraction and settling issues.

    If top elevation of said (say, 1mx1mx0.6m) said footings are installed below the lowest elevation of the as yet unpoured pad, with recesses blocked off from the pad for the column connections, then I am wondering if anyone can basically point me in the direction of which column mounting systems are ordinarily used in properly planned projects.

    Unfortunately, on the US sites I've found so far, one encounters a conveniently unhelpful culture of people who seem to be congratulating themselves as qualified, just because they recently found out what architects and engineers actually deal with. Rolls eyes.

    If only Americans could keep anything in perspective..

    Ah well.
     
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