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RE: ASD or LRFD for Wood Design

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IMHO, most residential construction performance seems to be limited by lack of design altogether, coupled with improper execution.  Recently, I was discussing with a contractor how to fix his 18' high 2x6 window wall to pass framing inspection.  "Is there room to add (3) plies there."  "Yah, there is some wiring but I can just notch the 2x6's half way through."  It's scary to think about optimizing design with the current status-quo.

Call me old and callused, but I can't see doing much better with residential wood construction without a). educating contractors 100 times better b). educating inspectors 100 times better and c).  spending 100 times more on engineering details.  

I'm sure things are much better in the seismic areas, where people do get fairly frequent reality checks though.

Ed Fasula EIT

BTW, here is some information on LRFD of wood, I have reviewed these publications, but they are pretty much a fudge to use the LRFD approach and get the exact same results as using ASD:

"The AF&PA/ASCE 16-95 Standard for Load and Resistance Factor Design (LRFD) for Engineered Wood Construction was approved in November 1995 as a consensus standard through the ASCE standards development process. It is currently approved by several model building codes."

> -----Original Message-----
> From: SEConsultant [mailto:seconsultant(--nospam--at)]
> Sent: Thursday, January 27, 2000 2:41 PM
> To: seaint(--nospam--at)
> Subject: ASD or LRFD for Wood Design
> I saw the thread on ASD and LRFD design and assumed off the 
> bat that they
> were referring to steel, concrete or masonry design. However, 
> yesterday I
> discovered that there is a movement to use LRFD for the design of wood
> structures. At first I thought this ludicrous since wood has 
> a higher factor
> of safety due to the variance in quality on the material. In 
> a discussion, I
> was reminded of the proprietary wood products on the market where the
> materials have much tighter tolerances and much less inclination to
> variance.
> So, a couple of questions come to mind:
> 1. What types of projects will engineers be most inclined to 
> design my LRFD
> methods?
> 2. Considering that framing represents around 17% of the 
> project cost - will
> the benefits of LRFD yield significant savings and if so, in what size
> projects.
> 3. Will this create a more competitive market for proprietary 
> wood products
> compared to the cost of sawn lumber. In other words if the 
> same project can
> be designed by LRFD to maximize the materials - will we start 
> seeing more
> residential structures designed by LRFD so as to use, what 
> some consider,
> better materials at the same cost associated with ASD design for sawn
> lumber?
> As a small office engineer - I have not used LRFD methods. Of 
> course, until
> lately I'd never used rigid analysis for wood structures. 
> Looks like most of
> us wood engineers are getting a real education. Seriously, I 
> would not mind
> the idea of using LRFD in order to use Proprietary wood products like
> Timberstrand which have not been well received because of the cost
> difference. This may make that material more attractive to 
> the home market.
> Any comments or opinions?
> Regards,
> Dennis S. Wish, PE
> Structural Engineering Consultant
> (208) 361-5447 E-Fax