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Re: More ASD vs LRFD

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Sorry everbody, I can't let this one go.

I SPEND ABOUT 15% OF MY "DESIGN" TIME ON MEMBER SIZING.

The remainder is spent on details, constructability, specificaions,
coordination, meetings, "changes", review, drafting (yes, sometimes I draft),
and finally, project management; construction phase hours not withstanding.

In my experience, the men (never worked with a female engineer) who skimp on
design details, especially connections, are all ASD'ers.  "LRFD takes too much
time (and so do details)."  For me, most of the impetus behind drawing good
details has been saving time during shop drawing review; but I would be remiss
if I did not praise the excellent AISC guidance for connection design.

If you want to design in ASD, go for it.  As long as your structures stand, I
couldn't care less.  Just leave those of us using LRFD alone.  You like your
way, I like mine.

Live and let die.

-Keith Fix, PE
-Little Rock

--- ADFPE(--nospam--at)aol.com wrote:
> I want to throw one more vote in favor of ASD.  I design temporary structures
> 
> for heavy civil/structural construction projects and have tried LRFD, but 
> found no benefit to its use.  Determining actual deflections is almost always
> 
> necessary.  Material quantity is a minor portion of the total cost and the 
> use of "one size fits all" thinking minimizes the opportunity to put things 
> together wrong.
> 
> My primary concern with this whole topic though is that the focus is on 
> structural design analysis  and not on structural design detailing.  The 
> impression from the field is that consulting engineers spend an inordinate 
> amount of time picking sizes and almost no time assuring constructability.  
> This marginalizes their contribution to a project in the eyes of an owner, 
> when time and again the contractor can play the " I am just a dumb 
> contractor, but this thing can't be built as shown" card.  The saving of a 
> few pounds of steel per foot seems pretty trivial then.  "Skinned down" 
> designs often increase costs by requiring more elaborate construction 
> engineering solutions.
> 
> The increased delegation of connection design, often the hardest part of a 
> structures design, encourages contractors to prefer a design-build approach. 
> 
> Detailers often end up re-analyzing the structure to get the needed reactions
> 
> and do the entire analysis process for themselves.  It is not a big jump then
> 
> for the owner to decide to eliminate having a separate consultant and just 
> let the contractor manage the whole process.  I have been traditionally 
> opposed to this, but as we continue to find ourselves redesigning projects 
> due to constructibility problems, I may have to change my thinking.  That 
> would be unfortunate as the owner is usually best served by having an 
> indepenent consultant on his side, but if that consultant is perceived to  be
> 
> a liability, eventually owners will switch to a contractor controlled design 
> process.
> 
> Please, please, please spend more time on checking constuctability and on 
> providing clear, accurate documents. Create this time by reducing time spent 
> refining otherwise "close enough" designs.  In a free market economy, owners 
> will go where they perceive the greatest value.  The tradition of engineer 
> led construction will continue only as long as owners perceive that this 
> system brings them the most value.
> 
> Alan Fisher, PE
> Manager, Construction Structures Design Group
> Cianbro Corporation
> Portland, Maine
> 
> 207-773-5852
> afisher(--nospam--at)cianbro.com
> 
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