From: "Mark E. Deardorff" <MarkD(--nospam--at)DandDEng.com>
Date: Fri, 28 Jan 2000 14:57:03 -0800
The variation is accounted for statistically. The reality is that there is very little net difference between the design resulting from ASD or LRFD. LRFD is always a better approach than ASD only because the safety factors are more consistent and are based on the nature of the loading.
The funny thing about wood LRFD relates to the origins of ultimate strength design. Wood is not a plastic material like reinforced concrete (can be if detailed correctly) or steel. It definitely is not a ductile material so the safety factors as represented by the ultimate strengths have a higher margin than steel.
The actual factors used in LRFD and ASD for wood just give it a common reference point. Now when will ACI make their load factors the same as everyone else's?
> -----Original Message-----
> From: SEConsultant [mailto:seconsultant(--nospam--at)earthlink.net]
> Sent: Friday, January 28, 2000 11:14 AM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: ASD or LRFD for Wood Design
> So I hear, but who really has been designing sawn lumber
> structures with
> LFRD - I know I haven't and probably because there is too
> much variance in
> quality of lumber to attempt to tweak out designs safely. Any other
> opinions - I really am interested.