Subject: Re: " I " beam size needed

From: [email-masked] (StevenD280)
Date: 19 Mar 1996 14:51:59 -0500

In article <[email-masked]>,
[email-masked] (Dustin Harris) writes:

>	Steel or wood? Steel might be better since a wood I-beam might
tend to
>separate with use. Unfortunately, I don't know much about steel.
>	Wood I-beam? Extrapolating from my code book shows that a double
2x12
>#2 douglas fir beam 30' long would work, but those aren't very
>available. How about a homemade solution: a 16" tall wood I beam? Make
>it of 3/4" ply sandwiched at top and bottom between two pairs of 2x4s.
>	materials: 
>		3 pc of 2x4x20 lumber
>		2 sheets of 3/4" cdx plywood
>		8d and 16d nails
>		1 gallon woodworking glue
>	Cut ply into 30' of 16" strips. Cut two 2x4 into 10' pieces.
Layout
>two rows of 2x4 laid down on their 3.5" sides and separated by about
>9" (yes, I would build it on its side), glue well, and tack the ply on
>with the 8d nails. Lay the other 2x4 pieces on top with glue, making
>*darn* sure to *stagger the joints* rather than matching those under
>the ply. Nail the heck out of it with the 16d nails and let it dry a
>day. Install it and test it with a double load before trusting it.
>	I'd certainly trust it myself without testing since I build for a
>living, but if you aren't sure of your carpentry or my instructions
>please do test it carefully. Above all, make sure that the joints on
>the 2x4s lap eachother as much as possible and the joints on the ply
>miss those of the 2x4 by at least 2'. Just my rule of thumb: use it at
>your own discretion.
>
>
>

Fortunately I did not start this thread.  I only made the suggestion that
a solid "I" beam would not be able to span 30 feet and carry a load of
1,000#.  I further suggested that a built-up truss of a steel design would
be more suitable for the task.  All this was predicated on a discussion
with a qualified structural engineer for specific sizes.

Another suggestion was a solid glu-lam beam.  My experience further
dictates that there can be a beam depth of over 30 inches.  Once again,
check with a qualified structural engineer.

Bottom line: Check with a qualified structural engineer.  The subtleties
have too much impact on the outcome for this to be left to anyone other
than a qualified structural engineer.

Steven P. Dahlberg, Architect

[email-masked]

---

From: Kelly S Docter <[email-masked]>
Date: Tue, 19 Mar 1996 23:38:29 -0500

The calculations are not that difficult for such an example.  A standard
text of structures/physics should explain the methods clearly...  one
thing that no one has mentioned is the nature of the 1000#.  Is it a
point load or distributed?  What is the weight of the floor per square
foot, etc.  Sizing is not difficult, but without previous knowledge of
this I would recommend a licenced struuctural engineer.