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RE: Glu-Lam beam with Steel Channel calc

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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
V (949) 248-8588 F(949) 209-2509

-----Original Message-----
From: Bill Cain [mailto:bcainse(--nospam--at)]
Sent: Thursday, August 02, 2007 6:22 PM
Subject: Re: Glu-Lam beam with Steel Channel calc


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

Berkeley CA

-----Original Message-----
From: Tarek Mokhtar <tarooky(--nospam--at)>
To: seaint(--nospam--at)
Sent: Thu, 2 Aug 2007 11:42 am
Subject: RE: Glu-Lam beam with Steel Channel calc



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

Laguna Beach







When you say "taking off a few laminations" it sounds to me as if you are proposing cutting off the lower portion of the existing glulam beam, is that correct?  If so, you'll want to be sure to take into account the new grade of lumber that you have at the tension face of your beam when figuring F'b.

-----Original Message-----
From: erik gibbs [mailto:erik.gibbs(--nospam--at)]
Sent: Thursday, August 02, 2007 10:59 AM
To: seaint(--nospam--at)
Subject: Glu-Lam beam with Steel Channel calc

I previously posted a question about a plan check question for out of plane loading on a shearwall and to all that posted I thank you, it cleared up any questions that I had.


Now to my new question. I have an existing 5-1/8" x 15"  Glu Lam beam that spans 21'-6" in a garage of an existing residence. The owner wants to turn this into a flush beam, which means taking a few laminations off and sistering a new beam next to the GLB. I want to use a steel channel, C10x15.3, but this section, when checked in bending fails under the full load. Also the GLB fails under the full load when checked by itself. My question is how would you check/calc both beams in a rational method, instead of just saying that the GLB takes 50% of the load and the steel beam takes the other 50%?




Erik Gibbs





Tarek Mokhtar, SE
TMM Structural Engineers, Inc
31645 S. Coast Hwy
Laguna Beach, CA., 92651
949-499-2777 Fax

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