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

Steve Barker LT wrote:
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!

Frankly I would have an engineer take a look at what you are doing. You
really have not provided enough information for someone to make an
intelligent recommendation. I recommend the professional because they would
look at the actual situation, You might unintentionally leave out some
important fact in describing it that could be important.

--
Joseph Meehan

Dia duit

An engineer is your only safe answer, as Meehan says.
I would not depend on a carpenter or contractor to "design" the
structural system.
You need to look at the load path all the way to the ground.
If you have a building department, they will want documentation.
TB

An engineer is your only safe answer, as Meehan says.
I would not depend on a carpenter or contractor to "design" the
structural system.
You need to look at the load path all the way to the ground.
If you have a building department, they will want documentation.
TB

Joseph Meehan wrote:
Steve Barker LT wrote:
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?

Depends on the kind of wood and the load and its distribution.

... You really have not provided enough information for someone to make an
intelligent recommendation.

Like, what's the load on the beam? With bending moment M = WL/8 in-lb and
a total uniform load W in pounds and L = 14x12" and S = M/f = bd^2/6 in^3
and f = 1000 psi and d = 11.25" and b = 5" (3x1.5+0.5, if half the plywood
grain runs lengthwise), W = 8bd^2f/(6L) = 8x5x11.25^2x1000/(6x14x12) = 5022
pounds. You might make it stronger by substituting some metal for plywood.

Nick

try your local lumberyard. usually manufacturers of engineered wood
beams have engineers on staff who will size beams provided you are
buying their product. LVL's would likely be the way to go here,
anyway.

"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!

Sounds very strong, but what is the load? Anyone here would be guessing
since none of us know the total load to support.

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. 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
Stilwell, KS



"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

Steve Barker LT wrote:

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!

Hi,
Time to talk to an engineer with your blue print, REALLY!

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. 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.

Hmmm,
I bet you don't have a building permit either since engineer is out of
question. And no house insurance either....., LOL!

You are correct. No permit. I'm not building, I'm remodeling. No permit
required to do what I please in my own house. Thanks for your useless
reply. And BTW, yes the house is insured.

--
Steve Barker


"Tony Hwang" wrote in message
news:0SfTf.160633$H%4.115857@pd7tw2no...
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. 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.

Hmmm,
I bet you don't have a building permit either since engineer is out of
question. And no house insurance either....., LOL!

I don't think 3 2X12's will span 14 feet. You might look here
http://www.apawood.org/pdfs/managed/Z416.pdf or here
http://www.apawood.org/level_c.cfm?c...ub_glu_libmain

Thanks Pat, for the very USEFUL reply.

--
Steve Barker



"Pat" wrote in message
...
I don't think 3 2X12's will span 14 feet. You might look here
http://www.apawood.org/pdfs/managed/Z416.pdf or here
http://www.apawood.org/level_c.cfm?c...ub_glu_libmain

"Steve Barker LT" wrote in
:

You are correct. No permit. I'm not building, I'm remodeling. No
permit required to do what I please in my own house.

Not true, at least anywhere in the world that I know about. I have no idea
where you live, but you should *really* look at your government's
regulations covering your situation. Where I live, permits are required
for all structural, plumbing, HVAC, or electrical work done on (or in) my
property.

And BTW, yes the house is insured.

Not if it falls down or is damaged due to work done without a permit. As
soon as they discover work done without a permit, your insurance company
will walk away.

You could build a box beam using a 2x top and bottom plate with 2x
stiffeners every 16" and then box it in on the sides and ends with 3/4 ply

======================================= 2x
ll ll ll ll ll ll ll ll
ll 2x stiffeners 16"oc
======================================== 2x

There are span tables around the net for them

CR


"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

You are scaring me more now. If you remove(d) an outside bearing
wall, it is not just a matter of carrying the vertical load.
Almost a bigger issue is allowing the ridge to sag due to
spreading of the outside walls. Perhaps your efforts should be
being spent carrying the ridge. How were you planning to maintain
the integrity of the roof rafter/ceiling joist/top plate
connection? Has the roof load been changed by extending new roof
rafters to the new outside wall?
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)




"Steve Barker LT" wrote in message
...
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. 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
Stilwell, KS



"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

On 19-Mar-2006, "Steve Barker LT" wrote:

I figured if four 2x4's can hold it for 50
years or so, then what I propose should do the job.

Did the 2x4s hold it because the were the correct strength or because of
luck? Just because it survived doesn't mean it was properly designed.

There is a picture at this link:
http://www.barkerranch.net/images/DSCN8772.jpg

Could you highlight the 2x4s you're talking about? That ceiling is hiding
a lot of detail that would be pertinent.

You should contact a professional for interior or exterior structural changes.
That _will_ be required unless you live in some far corner of a third world country.

Mike

PS - Ignore Nick, his posting is nonsense as usual.

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

--
Joseph Meehan

Dia duit

Steve Barker LT wrote:
You are correct. No permit. I'm not building, I'm remodeling. No
permit required to do what I please in my own house. Thanks for your
useless reply. And BTW, yes the house is insured.

While there may be places in the civilized world where this kind of worm
might not require a permit, most areas would require a permit. Don't be too
sure about your insurance. Many insurance policies will not cover you if
you did not have a permit or did not follow proper building procedures and
in this case it calls for an engineer.



"Tony Hwang" wrote in message
news:0SfTf.160633$H%4.115857@pd7tw2no...
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. 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.
Hmmm,
I bet you don't have a building permit either since engineer is out
of question. And no house insurance either....., LOL!

--
Joseph Meehan

Dia duit

Steve Barker LT wrote:
You are correct. No permit. I'm not building, I'm remodeling. No permit
required to do what I please in my own house. Thanks for your useless
reply. And BTW, yes the house is insured.

Steve, if you want people to be a cheering section for you, well,
asking structural questions on a construction newsgroup is not the way
to go, particularly if you're not prepared to listen. You have not
received a single useless reply yet.

As far as it being your house - no mortgage? The mortgage holder would
be extremely upset to find out that you've made major structural
modifications without pulling a permit. But even with no mortgage, you
should be concerned as least as much as a bank would about not cutting
corners on your own home.

I took the opportunity to cross post this reply. Since you've asked
this question on both groups without crossposting (cross posting is not
always a bad thing - it's bad only when it's to non-related groups),
you are not allowing people to see the replies you've received and
given. Partial information won't help your cause.

Remodeling _is_ building. If you modify the structure of your house
you are required to pull a permit. Other factors will trigger the need
for a permit, but a structural modification always requires a permit.

If you were in an area that didn't require permits - which, from your
reply, you're not - you'd still be foolish to skip out on an engineer's
review. Your picture shows more information, but still lacks critical
information. Which way does the ceiling framing run? What are the
required design loads? Are you in an earthquake or high wind zone? I
could keep asking questions, but hopefully you've caught my drift.
Only someone who has seen your house, inspected the current situation,
and is familiar with you local code and area can design you a solution.

Beginners often mistake the strength of the beam as being the only
factor in removing a wall. It's not - not by a long shot. The bearing
area of the supports, designing connections to transmit loads other
than gravity, adequacy of foundation supports, etc., are all critical.
Simply picking a beam that can support a specific load is just a start.

You may have overestimated the cost and underestimated the value of an
engineer in you situation? Have you called around to get an idea of
the cost?

R

hi again. you really ought to look into calling a company such as
truss joist macmillan or weyerhauser and asking them to size one of
their products. I have done this on a number of occasions, and i
didn't always have a set of blueprints. a pencil sketch will do. i
have found engineers that work for truss companies or beam companies to
be very helpful and practical. an LVL, microlam, or parallam is more
expensive, but will give you peace of mind that it isn't going to sag.
14' is a fairly long span for a homemade beam..

it is also true that there are span tables around for sawn beams, and
you could fairly easily figure out your tributary loads and size your
beam that way, if you have an aptitude for that sort of thing.. (do it
like a professional engineer and overbuild it!)

As for hiring an independent engineer to design this for you, i
wouldn't recommend it. I've gone this route and felt like the result
was overbuilt--which I could have done without spending money on an
engineer. you can't really blame them...they are liable if a beam sags
or building collapses or whatever.

I used to work in a "non-coded" area. (technically you must follow
codes, but they are not enforced). Kind of miss it in a way.

"RicodJour" wrote in message
oups.com...
Steve Barker LT wrote:
You are correct. No permit. I'm not building, I'm
remodeling. No permit
required to do what I please in my own house. Thanks for
your useless
reply. And BTW, yes the house is insured.

Steve, if you want people to be a cheering section for you,
well,
asking structural questions on a construction newsgroup is
not the way
to go, particularly if you're not prepared to listen. You
have not
received a single useless reply yet.


Errr Steve? Rico is exactly correct and for some reason is
showing you polite consideration... you do not deserve ..by a
long shot.

Will you pay attention to Rico and thank him for his superb
and accurate advice on these issues..... or will you just
demonstrate your combination of ignorance and abuse.

ah yes... the latter.
Impressive.


Phil Scott


As far as it being your house - no mortgage? The mortgage
holder would
be extremely upset to find out that you've made major
structural
modifications without pulling a permit. But even with no
mortgage, you
should be concerned as least as much as a bank would about
not cutting
corners on your own home.

I took the opportunity to cross post this reply. Since
you've asked
this question on both groups without crossposting (cross
posting is not
always a bad thing - it's bad only when it's to non-related
groups),
you are not allowing people to see the replies you've
received and
given. Partial information won't help your cause.

Remodeling _is_ building. If you modify the structure of
your house
you are required to pull a permit. Other factors will
trigger the need
for a permit, but a structural modification always requires
a permit.

If you were in an area that didn't require permits - which,
from your
reply, you're not - you'd still be foolish to skip out on an
engineer's
review. Your picture shows more information, but still
lacks critical
information. Which way does the ceiling framing run? What
are the
required design loads? Are you in an earthquake or high
wind zone? I
could keep asking questions, but hopefully you've caught my
drift.
Only someone who has seen your house, inspected the current
situation,
and is familiar with you local code and area can design you
a solution.

Beginners often mistake the strength of the beam as being
the only
factor in removing a wall. It's not - not by a long shot.
The bearing
area of the supports, designing connections to transmit
loads other
than gravity, adequacy of foundation supports, etc., are all
critical.
Simply picking a beam that can support a specific load is
just a start.

You may have overestimated the cost and underestimated the
value of an
engineer in you situation? Have you called around to get an
idea of
the cost?

R

Michael Daly wrote:

PS - Ignore Nick, his posting is nonsense as usual.

Joseph Meehan wrote:

Steve Barker LT wrote:

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?

Depends on the kind of wood and the load and its distribution.

... You really have not provided enough information for someone to make an
intelligent recommendation.

Like, what's the load on the beam? With bending moment M = WL/8 in-lb and
a total uniform load W in pounds and L = 14x12" and S = M/f = bd^2/6 in^3
and f = 1000 psi and d = 11.25" and b = 5" (3x1.5+0.5, if half the plywood
grain runs lengthwise), W = 8bd^2f/(6L) = 8x5x11.25^2x1000/(6x14x12) = 5022
pounds. You might make it stronger by substituting some metal for plywood.

You doubt it will hold up a 5022 lb uniform load? Seems conservative, IMO.
Concerned about torsional longitudinal stability again? How many pounds
would you estimate Steve's beam would support?

My PE friend says Unistrut has several failure modes. It's stronger with
the open side down, supporting a hanging load. Nuts to hold the sides
together might help in that case. Short lengths with the open side up
have a local buckling mode, with the upper edges developing waviness.
I wonder how to predict that.

Nick

wrote:

Like, what's the load on the beam? With bending moment M = WL/8 in-lb and
a total uniform load W in pounds and L = 14x12" and S = M/f = bd^2/6 in^3
and f = 1000 psi and d = 11.25" and b = 5" (3x1.5+0.5, if half the plywood
grain runs lengthwise), W = 8bd^2f/(6L) = 8x5x11.25^2x1000/(6x14x12) = 5022
pounds. You might make it stronger by substituting some metal for plywood.

You doubt it will hold up a 5022 lb uniform load? Seems conservative, IMO.
Concerned about torsional longitudinal stability again? How many pounds
would you estimate Steve's beam would support?

I'm thinking of a number, Nick. What's your estimate of what that
number is? That is _exactly_ what you're asking. There are too many
missing variables to make anything more than a wild assed guess.
Precise calculations, or even yours, will not offset the missing
information.

My PE friend says Unistrut has several failure modes. It's stronger with
the open side down, supporting a hanging load. Nuts to hold the sides
together might help in that case. Short lengths with the open side up
have a local buckling mode, with the upper edges developing waviness.
I wonder how to predict that.

My PE friend... Please state for the record that you are not a civil
engineer and have no business pretending you are one. Consider it a
public service.

What does Unistrut have to do with the topic of this thread? You're
not obsessing again, are you?

R

While it is true that one would need to see your house in order to give
any kind of idea as to what to use, and an engineer is not a bad idea,
I have a couple of comments. First of all, why the half inch plywood.
This is not going to add to the strength. The only reason plywood is
added to headers and beams is to expand the width. (two 2x12=3in. and a
2x4 is 3 and half inches). Also, I have been building custom homes for
many years and I can't think of any situation where three 2x12's
weren't sufficient for a span of only 14ft, but it is always better to
be safe than sorry when it comes to an investment such as your house.

RicodJour wrote:

wrote:

... With bending moment M = WL/8 in-lb and a total uniform load W
in pounds and L = 14x12" and S = M/f = bd^2/6 in^3 and f = 1000 psi
and d = 11.25" and b = 5" (3x1.5+0.5, if half the plywood grain runs
lengthwise), W = 8bd^2f/(6L) = 8x5x11.25^2x1000/(6x14x12) = 5022 pounds...

And your estimate is...?

... There are too many missing variables to make anything more than
a wild assed guess.

Nonsense :-)

Nick

On 20-Mar-2006, wrote:

... There are too many missing variables to make anything more than
a wild assed guess.

Nonsense :-)

This is exactly why you should not be taken seriously. You have your
equations, but you haven't got a clue.

Mike

Michael Daly wrote:
On 20-Mar-2006, wrote:

... There are too many missing variables to make anything more than
a wild assed guess.

Nonsense :-)

This is exactly why you should not be taken seriously. You have your
equations, but you haven't got a clue.

But he is a chipper fellow. It doesn't offset his tenuous grasp of
logic and engineering - still, it must count for something.

Do you know that TV show NUMB3RS? Nick would be a great "guess" star.
While he was running off half-cocked and making stupefying assumptions,
the stars of the show could proceed to resolve things in a rational
manner. Kind of a Point/Counterpoint thing.

R

On Sun, 19 Mar 2006 06:29:03 GMT, "Steve Barker LT"
wrote:

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!


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

Michael Daly wrote:

With bending moment M = WL/8 in-lb and a total uniform load W in pounds
and L = 14x12" and S = M/f = bd^2/6 in^3 and f = 1000 psi and d = 11.25"
and b = 5" (3x1.5+0.5, if half the plywood grain runs lengthwise),
W = 8bd^2f/(6L) = 8x5x11.25^2x1000/(6x14x12) = 5022 pounds.

... You have your equations, but you haven't got a clue.

You have my numbers. Where are your numbers? :-)

Nick

wrote:
Michael Daly wrote:

With bending moment M = WL/8 in-lb and a total uniform load W in pounds
and L = 14x12" and S = M/f = bd^2/6 in^3 and f = 1000 psi and d = 11.25"
and b = 5" (3x1.5+0.5, if half the plywood grain runs lengthwise),
W = 8bd^2f/(6L) = 8x5x11.25^2x1000/(6x14x12) = 5022 pounds.

... You have your equations, but you haven't got a clue.

You have my numbers. Where are your numbers? :-)

Nick, this is not a mental exercise. We're not playing with numbers
because we're bored. It's a real guy's house, with a real question
about the structure. With out real information about snow loads,
earthquake, wind loading, all of that fun stuff you ignore, and which
can _easily_ supercede any occupancy or dead load, the numbers are
imaginary. They have no meaning. So what's the point in _guessing_ at
a solution?

The fact is, you really don't care whether it's a real situation of not
- a real house or not. You see no difference because your first love
is juggling numbers. To each, his own. But please don't go selling
your "solution" as anything other than a mental exercise.

R

On 20-Mar-2006, wrote:

You have my numbers. Where are your numbers? :-)

Your numbers are useless in the absence of load information and
details on the beam support. There are two sides to the general
problem of building a structure, P and R - loads and resistance.
You are focussing on only one.

Mike

On 19-Mar-2006, wrote:

My PE friend says Unistrut has several failure modes.

PE in what? - Electrical? Chemical? Transportation? If he isn't a structural
engineer, he isn't likely to know what I've pointed out to you.

It's stronger with [...] waviness.

Show him the Unistrut manual and ask him to explain the column on the
extreme right that lists load reduction factors. Let us know what he has
to say.

I wonder how to predict that.

Plate and shell theory. FEA would be easier.

Mike

RicodJour wrote:
wrote:
Michael Daly wrote:

With bending moment M = WL/8 in-lb and a total uniform load W in pounds
and L = 14x12" and S = M/f = bd^2/6 in^3 and f = 1000 psi and d = 11.25"
and b = 5" (3x1.5+0.5, if half the plywood grain runs lengthwise),
W = 8bd^2f/(6L) = 8x5x11.25^2x1000/(6x14x12) = 5022 pounds.

This is Beams 101. I'm surprised anyone would argue about it,
unless they don't understand it or just love to argue :-)

... You have your equations, but you haven't got a clue.

You have my numbers. Where are your numbers? :-)

And engineering is done with numbers. Or perhaps feeble arm-waving,
for the numerically-illiterate :-)

... With out real information about snow loads, earthquake, wind loading,
all of that fun stuff you ignore, and which can _easily_ supercede any
occupancy or dead load, the numbers are imaginary. They have no meaning.

The USENET bestiary also includes those who say "We can't see it from here"
and "You must hire an engineer" and "WATCH OUT!!! WHAT YOU ARE DOING COULD
BE DANGEROUS!!!" :-)

So what's the point in _guessing_ at a solution?

The OP described a beam and asked if it would be strong enough.

Estimating its strength is a reasonable first step.

Nick

Michael Daly wrote:

My PE friend says Unistrut has several failure modes.

PE in what?

Structural engineering, which he also teaches and writes books about.
He's the lead engineer on a $20 million building now. He uses lots of
Unistrut in his work.

It's stronger with [...] waviness.

Local buckling.

Show him the Unistrut manual and ask him to explain the column on the
extreme right that lists load reduction factors.

We talked about that ("page 61") and I asked where the curve came from.

Let us know what he has to say.

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

I wonder how to predict that.

Plate and shell theory. FEA would be easier.

Perhaps you can answer this question: "Exactly how much perturbation is
needed to cause torsional longitudinal failure as a function of load?"
You might say "Exactly zero, at full load," or "Exactly zero, at the
derated load on page 61," but neither of us would believe that :-)

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...

Nick

"Michael Daly" wrote in message

PE in what? - Electrical? Chemical? Transportation? If he isn't a
structural
engineer, he isn't likely to know what I've pointed out to you.

To be a PE, don't you have to have knowledge of various fields?

Edwin Pawlowski wrote:

"Michael Daly" wrote in message

PE in what? - Electrical? Chemical? Transportation? If he isn't a
structural engineer, he isn't likely to know what I've pointed out to you.

To be a PE, don't you have to have knowledge of various fields?

Yes, esp after the FIT exam, with questions about dam design, crystallography,
electronic controls, and so on. In PA, an electrical PE can legally design
bridges and skyscrapers. And pediatricians can do brain surgery...

Nick

wrote:

In PA, an electrical PE can legally design
bridges and skyscrapers. And pediatricians can do brain surgery...

What's your point? That there are stupid regulations with lots of
loopholes in existence?

Or are you suggesting that since you don't know anything about the
specific design requirements of the original question, you can
concentrate on Beam Theory 101 to "offset" the lack of information?

Gee, my car's not starting, but I don't know anything about engines.
Let me make sure the tires are at the right pressure...

R

Yes, esp after the FIT exam, with questions about dam design, crystallography,
electronic controls, and so on. In PA, an electrical PE can legally design
bridges and skyscrapers. And pediatricians can do brain surgery...


Well... Brain Surgery isn't exactly rocket science...

On 21-Mar-2006, wrote:

The OP described a beam and asked if it would be strong enough.

Estimating its strength is a reasonable first step.

Estimating its strength doesn't answer his question. The bafflegab
you post might mislead the naive into believing it is an answer.
You're being irrisponsible and can't bring yourself to admit it.
Most of the other responses have been of the "you haven't provided
enough information" sort, because - he hasn't provided enough information.

Mike