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RE: Wood Truss Bracing

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Jim,

This is not as difficult as it sounds. The Wood Truss Council of American and the Truss Plate Institute has a document titled WTCA 1-1995 “Standard Responsibilities in the Design Process Involving Metal Plate Connected Wood Trusses”. The commentary for this document is available in PDF format at: http://www.sbcmag.info/past/2001/01jun_jul/images/commentary.pdf  and the original document is available at: http://www.woodtruss.com/images/dresp.pdf

You can also contact Kirk Grundahl, PE who is the Executive Director of the Wood Truss Council of America in Madison Wisconsin and who is deeply involved with not only setting up the standards but making sure that they are adhered to. He can be reached through the http://www.woodtruss.com/index.php  website or at mailto:contactus(--nospam--at)woodtruss.com

 

The majority of building constructed here in Southeastern California are constructed using metal side plate wood trusses. For the most part, the quality is excellent and the companies adhere to the standards listed above. There are instances with truss companies who don’t adhere to the design quality yet their construction equipment and quality of wood is decent enough – they simply don’t pay attention to the adage “garbage in – garbage out”. They rely upon the computer software and hire low paid non-engineer professionals (Architects) to wet-seal the package. The only answer (and this includes their specific standards for lateral bracing and when the Engineer of Record should be involved in the bracing design and when the truss manufacturer maintains responsibility) is for the Engineer in Responsible charge to closely scrutinize the truss package for connections, loads and quality of wood prior to releasing it during the plan review cycle.

 

I’m currently at odds with a client – the owner of the home because I keep finding mistakes in the truss package and keep sending it back to be fixed. I’ve discussed this with Kirk Grundahl, PE who referred me to the standards. Sending the standards to the truss designer was as good as reading him the riot act – he jumped on the corrections and it came back to me as good as it can be. The owner who is in the industry (a pool contractor) believes that engineers are just an inconvenience to obtain a building permit and we have been battling over what he perceives as my bias against the truss company he chooses to use.

 

For whatever reason, I will not approve the truss calculations until they are correct – even if it means stepping out of the project and letting another engineer start over from scratch.

 

Dennis S. Wish, PE

 

-----Original Message-----
From: Kestner, James W. [mailto:jkestner(--nospam--at)somervilleinc.com]
Sent: Thursday, December 11, 2003 3:12 PM
To: seaint(--nospam--at)seaint.org
Subject: RE:Wood Truss Bracing

 

If the majority of us think that the way the wood truss suppliers currently design and build trusses leads us down the road to  unsafe structures, we should join forces and express our concerns. Individually, we just sound like a bunch of whiney little kids. I am confident that working together as a group, we can get this changed. A coordinated letter writing campaign could be very effective. Working thru several professional organizations is also a possibility. We could enlist the help of building inspectors and insurance companies also. 

 

If the truss people start hearing from structural engineers, building inspectors and insurance companies all over the country on this issue, they are going to sit up and take notice.

 

I do not do residential work but the same problems exist in commercial construction.

 

Jim K.

 

 

 ----Original Message-----
From: Rand Holtham, P.E. [mailto:rand(--nospam--at)sigmaengineers.com]
Sent: Thursday, December 11, 2003 7:50 AM
To: seaint(--nospam--at)seaint.org
Subject: Residential Truss Bracing

I usually specify that lateral bracing of the web members is prohibited unless shown on the drawing. If a web member gets to be over 6' long l/d =50 then we note the lateral bracing on the drawings. This forces to use heavier members otherwise the truss guy will put bracing for the webs all over. Of course the top and bottom chord is braced by sheathing or strapping are these are carfully noted on our drawings

 

However if no engineering documents are present and a home owner buys a roof truss system who fills in the gap then? The carpenter? I think its a pretty chicken note from TPI and it can be dangerous to the public. City officials should watch this because I believe they bear the responsibility in the absence of a design professional.

 

 

Rand W. Holtham, P.E.
Sigma Engineers, Inc.
Beaumont, Texas

From: "Chris Banbury" <cbanbury(--nospam--at)nicholson-engineering.com>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Residential Truss Bracing

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We have similar difficulties.  The TPI-95 document is referenced by the =
state statues here in Florida. By default the document requires the EOR =
to design lateral bracing as located by the truss design engineer.  The =
individual truss drawings should indicate the location of any required =
lateral truss bracing. Diagonal bracing and gable end bracing seems to =
fall to the EAR entirely.

However, the document also states that it is not intended to supercede =
the contract documents (drawings/specs/etc).  This can be an important =
clause to defending your intent on how the design =
responsibilities/liabilities should be assigned.=20

The truss designer/supplier, however, may argue that they are _only_ =
responsible for doing what is in their sub-contract and are not bound by =
the contract documents.  It would then fall to the GC to make sure that =
the requirements of the contract documents had been put into the =
truss-designers sub-contract. There is a helpful discussion about this =
in the May 2003 Structure magazine.