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RE: Glu-Lam beam with Steel Channel calc[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Glu-Lam beam with Steel Channel calc
- From: "Jerry Coombs" <JCoombs(--nospam--at)carollo.com>
- Date: Tue, 07 Aug 2007 05:33:29 -0700
Some years ago, prior to the easy availability of LVL's, PSL's, etc, Contractors could buy off-the-shelf sectios of steel plate, 1/8" to 1/2". These plates came in 11", 9", and 7" widths, and cut to length. They were pre-punched, alt. holes at appropriate spacing.
The plate was then sandwiched between the appropriate 2X's. It's called a flitch beam, and has a rational design approach established using the "n" calculation (Es/Ew) similar to steel/ concrete composite, and as described by someone earlier.
>>> "Bill Allen" <t.w.allen(--nospam--at)cox.net> 8/7/2007 7:12 AM >>>
I would use the steel section to take the entire load regardless whether you remove the bottom laminations or not. Load sharing between the GLB and steel section is questionable (due to creep and other factors), especially when using through bolts with even 1/16” oversized holes. Bob Powell (and others) has made a good living providing expert witness testimony in cases such as yours. Is your E&O policy current?
When you say “I want to use a C10x15.3”, why would you want to use something that doesn’t work? Are you trying to stay with a 10” depth? If so, use a MC. You can go all the way up to an MC 10x41.3. If that still doesn’t work, use a built-up section. Jack the (E) GLB to take out all of the deflection, attach the new steel section to the GLB (using the GLB only to transfer the load) then remove the shoring.
T. William (Bill) Allen, S.E.
Consulting Structural Engineers
If you are removing the tension lams, Like Tarek, I'd make sure the steel could take the entire load. You would need to consult with APA or AITC to determine new allowable stresses for the GLB with the lams removed if you want it to take anything. It is difficult to get a good connection between the two materials.Regards,
Bill Cain, SE
There are a few issues with transferring the load, bolting, stiffness, etc from the glb to the steel section, and it also appears that you are removing some of the high strength laminations from the bottom of the beam,
I would design the new steel section to handle ALL the load, but that's just me
Tarek Mokhtar, SE
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