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RE: The stand

Title: RE: The stand

Yeah, don't pull up the carpet. The only way you could tell anything from that is if all the nail heads are exposed, and even then it can be difficult.

        I'll have to retract my alarmist statement from before, I'm sorry about that. The refrigerator example puts things into perspective. Or a piano. Anything that sits there longterm, with small feet.

        Let me try some numbers, using bending stress as the limiting factor. (Don correct me on anything I get wrong.) The bending stress of the joists is lowest at the supports and highest in the center of the span. A conservative maximum allowable bending stress for wood might be 1000psf.

Eq. 1 : M = 12" * W

where M is the internal bending moment of the joist, W is the tributary load placed on the joist, and 12" is the assumed distance the tank is placed from the wall. We want to find W, but first we must find M.

Eq. 2 : f_b = M / S

where f_b is the allowable bending stress (1000 psi, above), M is the moment from Eq. 1, S is the 'section modulus' (for a 2X12 joist, S=31.64 in^3; for a 2X10, S=21.39 in^3).

so M = 1000 psi * 31.64 in^3 = 31,640 inch-lbs = 2,637 ft-lbs.

and W = 2,637 ft-lbs / 12" (= 1 ft.) = 2,637 lbs are allowable on a joist in bending, at 12" away from a vertical support.

That seems like an awful lot, so I'm guessing that at that distance from the wall, allowable shear is going to be the governing factor. As luck would have it, I don't have that figure available.  :-( Maybe tonight when I get home...


-----Original Message-----
From: IDMiamiBob@aol.com [mailto:IDMiamiBob@aol.com]
Sent: Wednesday, August 18, 1999 5:11 PM
To: apisto@admin.listbox.com
Subject: Re: The stand

In a message dated 8/18/1999 12:50:12 PM Mountain Daylight Time,
francinebethea@excite.com writes:

> I will take your advice, however, and pull up the carpet to see which way
>  the joists are going.  If my tanks are not perpendicular to the joists, I
>  will move them.

I think you should be able to figure it out by using a studfinder over the
linoleum section.  Also, if there is a basement, you can go down and look up.
 I've never seen a house with beams on different floors going different
directions, except where a wing was added on.  Architects, jump in here if
I'm wrong.

Bob Dixon

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