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More ASD vs LRFD

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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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