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RE: Glulam Beam Retrofit

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Bob Powell has spent a lot of time in court as an expert witness testifying that the load sharing between a Glu lam beam and steel plates or steel channels doesn’t work in reality like we would like it to in theory. After Bob first told me this (probably about 10 years ago now), I created a model with a Glu-Lam beam and two steel channels connected at 2 feet on center. The steel channels received very little load; much less than relative moment of inertias x modulus of elasticity. Additionally, there’s slop in the bolt holes and the mechanism is not nearly as perfect as a cover plate welded to the flange of a steel beam.

 

If you’re interested in more, I suggest you contact Bob himself. He’s the expert.

 

T. William (Bill) Allen, S.E. (CA #2607)

ALLEN DESIGNS

Consulting Structural Engineers

http://www.AllenDesigns.com

V (949) 248-8588

F (949) 209-2509

 

-----Original Message-----
From: Michael Bryson [mailto:mbryson(--nospam--at)NYASE.com]
Sent: Thursday, December 16, 2004 7:23 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Glulam Beam Retrofit

 

I have designed reinforced GLB’s with steel channels to act compositely i.e. share the load. This can be more economical than designing a channel to span the entire length of the GLB. The drawback is that the thru-bolt connections can get rather heavy.

 

The Wood Engineering & Construction Handbook has a section on composite beam design. Mathematically it looks quite accurate.

 

-----Original Message-----
From: Bill Allen, S.E. [mailto:T.W.Allen(--nospam--at)cox.net]
Sent: Wednesday, December 15, 2004 8:11 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Glulam Beam Retrofit

 

What I have done in the past is either use two steel channels (one each side of the GLB) connected to the GLB with through bolts. I have designed the steel channels to take 100% of the load, using the existing GLB as a mechanism to transfer the load to the steel channels. What’s critical with this approach is that the steel channels must be connected to the existing support in some manner.

 

Alternatively, I have hired Bob Powell (805) 486-2670 in the past as a consultant who provides a retrofit design using a post tensioning approach.

 

What I won’t do is bolt a steel member to the existing GLB and expect some sort of load sharing to occur. This mechanism is not nearly as mathematically accurate as say welding a cover plate on a steel beam with regards to estimating the load distribution.

 

If you would like more information about Bob Powell, you can e-mail me privately.

 

Regards,

 

T. William (Bill) Allen, S.E. (CA #2607)

ALLEN DESIGNS

Consulting Structural Engineers

http://www.AllenDesigns.com

V (949) 248-8588

F (949) 209-2509

 

-----Original Message-----
From: Eknrinc(--nospam--at)aol.com [mailto:Eknrinc(--nospam--at)aol.com]
Sent: Wednesday, December 15, 2004 1:39 AM
To: seaint(--nospam--at)seaint.org
Subject: Glulam Beam Retrofit

 

I have a glulam beam overstressed in flexure. Anyone have any great retrofit ideas?