J. Clarke wrote:
j walker wrote:
I think that I use the term "beam" in a different manner.
I call a floor joist a beam and apparently that is incorrect.
A floor joist is a beam.
This clarifies one thing; why the sagulator refers to a beam "standing
on end."
To the sagulator a beam is like a shelf stood on its edge in a manner of
speaking. Remember, the sagulator was intended for shelf deflection. The
math is the same for anything rectangular in cross section and of uniform
material properties, what is different is the words one might use to
describe different measurements. "On end" is I suspect careless
terminology--I suspect that "on edge" was meant.
To the sagulator, looking at your beam from the end, (i.e. so that you're
looking into the end grain in my pathetic attempt at ASCII art below)
(this is the top, the load you are supporting would be up here)
____________________ __
| | /|\
| | |
| | |
| | |
| | |
| | |
| | |
| | |
| | thickness
| | |
| | |
| | |
| | |
| | |
| | |
| | |
|____________________|_\|/
|----- depth ------|
And the "width" in the sagulator is the "length" of your beam (i.e. 8
feet, only expressed in inches).
So, how do I get the sag in a floor joist?
What I am attempting to understand is how much sag should occur in a
2X8 floor joist if the span is 8 feet. The application is for a water
tank stand which will measure 8X8 and will hold an 1100 gallon water
tank. The rim joists are 2X12 and the floor joist ends rest on a
ledger nailed to the side on the 2X12. There are 9 joists in between
the 2X12.
If I read you correctly there are 9 2x8s supporting this tank, with the
2x8s being supported on the ends by 2x12s.
To use the sagulator to get an approximation of the sag in the 2x8s, you
would plug 1100 pounds as the weight,
My apologies I misread "gallons" as "pounds"--that should be 8800 pounds (1
gallon weighs 8 pounds to a good approximation--8.33 to be exact).
uniform load (I'm assuming that the
tank covers the full span--if you want to be safe call it a "center load",
which will calculate a higher deflection), 96 inches as the width (8 ft x
12 inches), 18 as the depth (2 inches per beam x 9 beams), and 8 as the
thickness. You'd also of course have to pick the appropriate species of
wood. You'd then want to do the same calculation for the 2x12s to make
sure that they're up to the task.
On Sat, 16 Apr 2005 22:50:20 -0400, "J. Clarke"
wrote:
j walker wrote:
Thanks for this reply. This site is easy to use for shelves but I
found the terminology when applying the application to a beam to be
difficult.
Just make the "depth" equal to the width of the beam and the "thickness"
equal to the height.
A shelf is just a "deep", "thin" beam. A beam is just a "thick" shelf
that is not very "deep".
Thanks again!
On Thu, 14 Apr 2005 00:58:45 GMT, "Mike Wenzloff" mwenz *@*
wenzloff.com wrote:
Hi J Walker, --gotta love that...
Try these online calculators:
http://www.woodbin.com/calcs/index.htm
The one you may want is called the sagulator, about the 6th link down.
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)