Base Plate Thickness
Base Plate Thickness
(OP)
The larger the base plate (area), in general, the thicker the plate must be.
However,
If the bearing stress, on concrete, is acceptable, within an area smaller than the anchor bolt layout perimeter (square), I'm convinced that I do not need to increase the plate thickness just because I must increase the plate area to accommodate the anchor bolt quad.
In other words, whatever plate thickness i have when the bearing stress is acceptable, that is the max thickness my plate needs to be regardless of the anchor bolt layout, and thus, the base plate plan dimensions.
I feel this is elementary principles. But, a program i use requires increased plate thickness whenever the plan dimensions increase. And after all these years, i thought I'd seek a second opinion.
However,
If the bearing stress, on concrete, is acceptable, within an area smaller than the anchor bolt layout perimeter (square), I'm convinced that I do not need to increase the plate thickness just because I must increase the plate area to accommodate the anchor bolt quad.
In other words, whatever plate thickness i have when the bearing stress is acceptable, that is the max thickness my plate needs to be regardless of the anchor bolt layout, and thus, the base plate plan dimensions.
I feel this is elementary principles. But, a program i use requires increased plate thickness whenever the plan dimensions increase. And after all these years, i thought I'd seek a second opinion.






RE: Base Plate Thickness
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Base Plate Thickness
If the bearing pressure is truly uniform under a base plate (which it isn't, by the way), and the base plate is too thin, the base plate will deflect, causing the bearing pressure to concentrate itself under the center of the base plate. Thus, your assumption is justified.
DaveAtkins
RE: Base Plate Thickness
To expand a little, you're arguing that for a larger baseplate, the bearing pressure isn't effectively uniform over the entire area, but could be assumed to be uniform over a smaller patch area concentric to the column.
If your assumption happened to be wrong, and the edges of your base plate saw high bearing stresses, they would yield and deflect away, reducing the bearing pressure and causing your premise to be self-fulfilling.
For a ductile steel plate controlled by bending in the weak axis, makes sense to me.
RE: Base Plate Thickness
RE: Base Plate Thickness
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Base Plate Thickness
RE: Base Plate Thickness
RE: Base Plate Thickness
Of course, structural engineers may not be in their right minds...
DaveAtkins
RE: Base Plate Thickness
Yeah. Them there oscillating horizontal gravity waves get tricky when you're trying to get the grout under the 1 mile x 1 mile flat baseplates .....8<)
RE: Base Plate Thickness
www.PeirceEngineering.com
RE: Base Plate Thickness
RE: Base Plate Thickness
www.PeirceEngineering.com
RE: Base Plate Thickness
I can't say that I have.
DaveAtkins
RE: Base Plate Thickness
Ditto for my mentor. And it was in response to my concern over a column coming down on the corner of an 8" frost wall that shouldn't have remotely worked by the numbers.
Me neither for gravity only. For base plates with bending, they seem to fail pretty much all the time when tested.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Base Plate Thickness
RE: Base Plate Thickness
RE: Base Plate Thickness
Does your code have something similar?
RE: Base Plate Thickness
I recognise the tp ; c and Aeff denominations, but not this figure.
RE: Base Plate Thickness
Seems like a resonable approach to me - I remember ,in books only unfortunately, seing gravity columns of really tall bldgs having huge *stiffened* base plates to distribute gravity loading on mile wide base plate as DaveAtkins would say.
RE: Base Plate Thickness
RE: Base Plate Thickness
Enercalc software has an option to design it like this. I call it the "magic button".
When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.
-R. Buckminster Fuller
RE: Base Plate Thickness