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Re: ASD vs. LRFD

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In 1963 I received, as compliments of The Structural Steel Fabricating 
Industry through it's Iowa Representatives, a copy of the 1959 Steel 
Construction manual of AISC. My first employer, a heavy steel 
construction company, and the supervisor(s) required us in 
the "backroom" to design and detail all end connections to develop 
the "full capacity" of the connections. As young bulls, we complained 
about the economics, material quantities, difficulties, and manhours 
necessary to achieve the directed results. We did not prevail. During 
that policy period, their field sites never had failures of temporary 
structures and were most forgiving for unanticipated laods or events. 
However, that company is no longer in business. It has been replaced by 
other cutting edge companies. Procedures for analysis and design are 
now cutting the material to less and less to improve the economy of 
design and minimize the use and effect on the environment. Those who 
embraced LRFD 20 years ago are much better off today.
Quo Vadis?
Pax e Gratia
Bob Ross
Robert P. Ross, P.E.
Civil-Structural Engineer Project Manager
Washington Group International,Inc.
Industrial Processes
17320 Red Hill, Suite 300
Irvine, Ca. 92614 
Mobile 562-254-4604
Office 949-222-3978
FAX 949-222-3985
Nite; 714-389-0820
E-mail: Bob.Ross(--nospam--at)WGINT.com
E-mail: rprossi(--nospam--at)yahoo.com

----- Original Message -----
From: Keith Fix <kefix(--nospam--at)yahoo.com>
Date: Wednesday, December 19, 2001 8:36 am
Subject: Re: ASD vs. LRFD

> I indicate only the ultimate load.  Where there are several 
> combinations of
> loads that may require multiple design checks, I design the 
> connection myself.
> 
> Generally, I design all connections that are not simple beam-to-
> column or
> beam-to-beam connections.  This means I generally design all 
> braced frame
> connections, all hanger connections, all chord and diaphragm 
> connections, all
> base plates, all moment connections, etc.  This requires a 
> significant amount
> of work on the front end, but I've found it saves enormous time 
> during shop
> drawing checks; if the connection is not as I designed it, it is 
> not acceptable
> without explanation from the detailer/fabricator/contractor.
> 
> The DL/LL argument came up early in my career when I and another 
> juniorengineer convinced the boss to use LRFD (1st ed. - sucked!) 
> on a rare
> earthquake governed project in NE Arkansas.  For that project, I 
> recallspecifying all connections as full depth because the boss 
> couldn't get his
> brain around the separation of DL and LL with separate "load" 
> factors.  I don't
> see this as a major problem with anything except the rarest beam-
> to-beam or
> beam-to-column connections that have some special load.  The boss 
> also had
> several qualms about time spent (I've since developed a greater 
> appreciationfor his apprehension, though I still favor LRFD).
> 
> Notation generally looks like this:
> 
>    23k         W16x31           20k
> |-|--------------------------------|-|
>        8     |   2   |      8
>              |       |
>              |       |
> 
> Of course, it can be shortened for beams with no studs and equal 
> end reactions.
> 
> None of this is new.
> 
> -Keith Fix, PE
> -Little Rock, AR
> 
> --- michael.barbetta(--nospam--at)swec.com wrote:
> > 
> > 
> > Keith,
> > 
> > How does the fabricator's engineer know which LRFD load factors 
> to apply to
> > your
> > end reactions? Do you indicate both DL & LL reactions at the 
> ends of every
> > beam
> > and girder?
> > 
> > Thanks.
> > 
> > Mike Barbetta, P.E.
> > Stone & Webster
> > Cherry Hill, NJ
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > Keith Fix <kefix(--nospam--at)yahoo.com> on 12/19/2001 09:37:59 AM
> > 
> > Please respond to seaint(--nospam--at)seaint.org
> >                                                                  
>            
> >   
> >                                                                  
>            
> >   
> >                                                                  
>            
> >   
> > 
> > 
> >                                                               
> >                                                               
> >                                                               
> >  To:      seaint(--nospam--at)seaint.org                                   
> >                                                               
> >  cc:      (bcc: Michael Barbetta/Civil-Structural/SWEC)       
> >                                                               
> >                                                               
> >                                                               
> >  Subject: Re: ASD vs. LRFD                                    
> >                                                               
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > --- "Mitchell J. Sklar" <MJS(--nospam--at)bala.com> wrote:
> > > I have been doing some cost comparisons between ASD & LRFD 
> design. My
> > > LRFD designs are consistently lighter that ASD (No Big 
> surprise). The
> > > GC/Fabricator are insisting that due to the connection design 
> and safety
> > > factors involved that it is cheaper to go with an ASD design. 
> Is the
> > > something that I am missing. I have just recently attended the 
> AISC> > Connection seminar and must of step out of the room when 
> pricing was
> > > discussed.
> > >
> > > Besides, most (almost most) fabricators use computerized 
> software to do
> > > their designs, so where is the extra effort. If I was going to 
> really> > design all my connections, I would also buy or make a 
> spreadsheet to
> > > automate this. In addition, if my specs call out full depth 
> double angle
> > > or shear tab connections, and lets say I have a W16 w/ 4 
> bolts. What is
> > > the difference whether it is ASD or LRFD? Four Bolts will give 
> me a
> > > certain capacity either way.
> > >
> > > Has anybody heard of special safety factors when doing 
> schools? Say in
> > > New Jersey?
> > >
> > > Mitchell J. Sklar, P.E.
> > > Senior Structural Engineer
> > >
> > > BALA Consulting Engineers, Inc.
> > > (mjs(--nospam--at)bala.com)
> > > p 610-649-8000 x345
> > > f 610-649-8475
> > >
> > 
> > About half my career has been in ASD, the second half in LRFD.  
> Generally I
> > prefer LRFD, if for no other reason than that the code is 
> written better.
> > 
> > I began putting all my beam reactions on my drawings beginning 
> two or three
> > years ago.  I began doing this so that I could check shop 
> drawing connections
> > more quickly (it works!).  I have not had any complaints, 
> besides the usual,
> > "We usually design with ASD....".  Since I put reactions on my 
> drawings, none
> > of my connections are designed as "full depth".  If a 
> fabricator/detailer> insists on using them, its his profits down 
> the drain.
> > 
> > If you design with LRFD, I recommend you stick to you guns.  
> LRFD is not
> > "visible" to the public, and saves ME time and effort.  I find 
> ASD a time
> > waster, and am glad I no longer work for men than insist on its use
> > (something
> > to point out when hiring).  All that said, I still use ASD for 
> masonry> design.
> > 
> > ;-)
> > 
> > As for schools and extra safety factor: I recently designed an 
> expansion to
> > Children's Hospital in Little Rock.  The only "safety factor" I 
> needed was
> > the
> > thought of something going wrong with dozens of kids in hospital 
> beds.  My
> > school building design has been simalarly governed.
> > 
> > -Keith Fix, PE
> > -Little Rock, AR
> > 
> > __________________________________________________
> > Do You Yahoo!?
> > Check out Yahoo! Shopping and Yahoo! Auctions for all of
> > your unique holiday gifts! Buy at http://shopping.yahoo.com
> > or bid at http:
> > 
> 
> 
> __________________________________________________
> Do You Yahoo!?
> Check out Yahoo! Shopping and Yahoo! Auctions for all of
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> 
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