"Wayne Whitney" wrote in message
...
On 2004-11-04,
wrote:

Wayne Whitney wrote:

In the scenario I was considering, a header would pick up
two 12' floor joists 16" on center

Like this, viewed in a fixed font like Courier?

| 16" |
floorfloorfloorfloorfloor
j j
o o
i i
s s
t t
headerheaderheaderheaderheader
s s
t t
u u
d d
. .
. .
. .

Close, sorry if my descriptions were not clear. The stud wall would
be parallel to the joists, so eliminate the lefthand "stud..." in your
diagram; the righthand "stud..." is the stud wall viewed on edge. If
I understand correctly, that's why the header presents a point load to
the stud wall; if the stud wall is perpendicular to the floor joists,
they present a distributed load to the stud wall.

and one end would be supported by the stud wall.

One end of what?

One end of the header would be supported by the stud wall.

As to the specifics of the stud wall, that is flexible. Anyway,
it is not a lot of weight, as 12' x 4' = 48 sq ft,

Where does the 4' come from?

Sorry, 4' is the header length, since it spans 4 joists (3 * 16"),
carrying the middle two. Actually, I guess I'm assuming it carries 3
joists if I use the 4' figure.

but the end of the header only carries 1/4 of that,
so 12 sq ft @ 50 lb/sqft = 600 lbs.

Where do the 1/4 and 12 square feet come from?

The 12' x 4' floor area I'm considering is supported on one short side
by a concrete retaining wall, and on the other short side by a header.
One end of the header bears on another concrete retaining wall; the
other end would bear on a stud wall. So the header carries half the
floor area, and the stud wall carries half of the header, hence 1/4.
12 square feet = 1/4 * 4' * 12'.

Anyway, this is not my current design, but a reality check on the
analysis is welcome. The original question was "does the stud wall
spread out the point load?". If the 4" conrete slab can support 300
lbs/foot, and if the point load from the header is 600 ft, then it
would be OK as long as the stud wall spread the point load out over at
least 2 feet.

Thanks, Wayne

P.S. In my current design, I just have beams big enough to carry
everything and bearing on the concrete retaining walls. The header
still presents a point load to the beam parallel to the joists, but
I've figured out how to do the analysis of a beam with a point load.