On 21-Mar-2006, wrote:

Structural engineering, which he also teaches and writes books about.

Writes books? - give us his name.

He'd better brush up on his engineering skills...

He said Unistrut has several failure modes. I guessed the curve came from

Guesses are not what you need - you need knowledge.

the main twisting one with the open side up, vs the local buckling one for
short lengths, with a safety factor. Where do you think it came from?

Tell your idiot friend to look up "lateral-torsional buckling" in a real structural
engineering book - e.g. page 203 of "Structural Steel Design". Lambert Tall
ed. 2nd edition Ronald Press Company, NY.

Lateral-torsional buckling is critical in slender beams - and a ten foot long
unistrut supported only at the ends qualifies. Open channel sections
are more sensitive to it than closed sections (as I have already pointed out).
To prevent this, you have to either brace the beam along the length or limit
the load and that's what the load reduction factors are for. The OP was
asking for a closet rod unsupported along its length, hence only the latter
approach is appropriate.

Then again, from a quantum-mechanical point of view, there is an
infinitestimal but finite probability that every molecule in a 10'
strut will suddenly decide to be somewhere else for an instant...

You're an blowhard that thinks he know more than he does.

Mike

On Sun, 19 Mar 2006 19:13:01 GMT, "Joseph Meehan"
wrote:

Steve Barker LT wrote:
Thanks for the many replies. I'm sorry I didn't supply enough info. It's
an old house that we're fixing up for our own use. An engineer
is out of the question.

After reading your additional information and viewing the photo, I would
have to say that I feel all the stronger than an engineer is not optional.

I can't express this in any other way, but to say:

It would be extremely foolish not to pay the cost of an engineer. Keep
in mind that if it fails and you did not use an engineer, your home
insurance will likely be voided.

What I failed to mention is that this is a
kitchen ceiling where the house was added on to many years ago. The
kitchen is 14x20 and the ceiling joists run across the 14. What they
did is basically remove the entire end wall (the original outside
wall) and left only 2 rough cut 2x4's on either side of a brick
chimney holding what ever load there is there. There is a picture at
this link: http://www.barkerranch.net/images/DSCN8772.jpg We do not
want this mini wall and chimney in the middle of our kitchen. None
of the wood members is tied to the chimney in any manner, so I
figured if four 2x4's can hold it for 50 years or so, then what I
propose should do the job.

"Steve Barker LT" wrote in message
...
I need to place a beam to support a ceiling (and roof above that). The
span is 14 feet. Supported only on the ends. I'm thinking of 3
2x12's with a half inch of plywood between each. Is this overkill,
not enough, or just right? I don't really want anymore beam than
necessary, but also don't want it sagging 5 years from now.

thanks!

--
Steve Barker
Stilwell, KS



First off, I am a structural engineer and second, forget about the
insurance costs or voided policy. If the building fails and someone
is inside, you may lose lives.

To the OP: Would the cost of an engineering opinion be worth the cost
of losing a family member?

I followed most of this thread and while I understand the concepts of
engineering design and code, most of the thread is valid. I will say,
rather than get stuck on "too" much theory, I'd follow the local
building codes for this situation (I didn't look at any pictures tho).
And besides the sizing of the beam, the number of fasteners or
location in the flitch beam and the ends will also matter
(inotherwords, what good is a correct beam size if the connections
fail). And I don't think live load reductions will come into play
here tho I'm not up on all local codes but I've used the UBC codes
some time ago.

Thanks for your reply. As it turns out, the wall nor the chimney were
holding anything. The wall was merely a partition added later in life and
the ceiling joist run parallel to it. All of it is gone now. No beam
needed. Just a few more verticals in the walk in attic to tie the joists to
the rafters.

--
Steve Barker


"Goedjn" wrote in message
...

I think that, if you're not willing to hire a pro to do the
math for you, and given the level of understanding implied
by your posting(s), you're foolish to be attempting this
major a renovation by yourself.

That said, If this a single-story section and a gable-end,
and you're expanding onto a porch, which is what it looks
like, then you're PROBABLY ok with a built up glued and
screwed beam of 3 or more 2x12s. Assuming that you post
down properly through the floor and land on something solid
underneath. This "you're ok" only applies if the
surrounding structure looks like this:
(www.goedjn.com/sketch/kitchen.gif)

If there's another floor above you, or this is a side
wall, you should probably rebuild most of that wall
and content yourself with a pair of wide doorways and
a window.

Note that there's a very good chance that that masonry stack
is holding up a beam in the ceiling and/or the ridgepole
of the roof, depending on how old it is. Don't get
too enamoured of the idea of taking it out until you
know for sure what it's holding up.

You really need to open up a hole in the ceiling above to
look at what that wall is holding up, and how the ceiling/roof
structure is put together. and get pictures of what's
underneath in the cellar/crawlspace.

My suggestion, If you're not going to do the sensible
thing and hire a pro, is to leave the chimney in place,
flank it with a pair of 4x6 posts, put another pair
of 4x6 posts at the ends of the 14' opening,
like so: (www.goedjn.com/sketch/kit2.jpg)

And then design around the chimney. It MIGHT be
overkill, and it's not quite what you wanted to do,
but an abundance of caution is a good response to
working outside your area of competence.

--Goedjn