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Re: Connections

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Amen to all you have said.  Canadian detailers tell me
American drawings are better prepared than those by
Canadian engineers--see my e-mail of 27 Nov.  The Canadians are 
relying on the fabricator to do some of their work.
Anyway, I forgot about the US thanksgiving yesterday
(ours was in October), so my best wishes for a good
holiday.
Gary

On 27 Nov 2003 at 3:51, G Vishwanath wrote:

> Sub: Connections
> 
> My thoughts and opinions are:
> 
> The Structural engineer need not design all the
> connections.
> 
> That would involve considerable additional work on his
> part for which the compensation may not be adequate.
> 
> He could reserve his time for other tasks that cannot
> be delegated.
> 
> Connection can be successfully delegated to an
> engineer who specializes in it and is hired by the
> detailer or fabricator.
> 
> The advantage is that the fabricator can make  choices
> that suit his shop practices (without  clashing  with
> design intent.)
> 
> For this to work out, the engineer has the
> responsibility to give at least general specifications
> for connection design. This is often neglected.
> 
> Shear Connections are possible using single shear
> plates, double angle clips, stiffened or unstiffened
> seats, with welding, or bolting or a combination of
> both.
> 
> The engineer must indicate his preference if any,  so
> that time is not wasted in correcting the shop
> drawings after they are submitted for approval.
> 
> Routine connections can be taken care of by the
> detailers themselves by referring to tables in the
> AISC manual.
> 
> But for this, the reactions must be given for all
> beams.
> However too many engineers avoid this and take short
> cuts by specifying "half uniform load capacity".
> This results in an over designed connections.
> 
> At times the half uniform load specification results
> in an impossible connection when the spans are very
> small.
> Instructions must be given clearly to cover cases of
> short span simply supported beams so that a reasonable
> connection is possible.
> 
> A table giving the number of bolts and dia and type to
> cover short span beams would be convenient.
> 
> Alternatively there could be a note to the detailer
> specifying that for short span beams where reactions
> are not indicated, a full depth connection with A325
> 3/4" dia (or higher dia) must be provided. The span
> (say 8') less than which beams are considered "short
> span" must also be specified.
> 
> Moment connections must be sketched out in a general
> way and the engineer must at least indicate whether he
> prefers beams to be butt welded to the column, or a
> connection using flange plates.
> 
> His preference, if any, for bolting or welding  of the
> flange plates must also be indicated.
> If he does not do so he must be willing to accept what
> the detailer/ fabricator has chosen and not make
> changes while approving the drawings.
> 
> It is necessary to indicate the moments for which the
> connection is to be designed.
> Too many engineers avoid this and take the easy way
> out by asking for full moment capacity.
> 
> The requirement of doubler plates and stiffeners must
> not be left to a detailer.
> They must be indicated clearly if really required and
> an effort must be made to avoid them. This effort can
> be made only by the engineer. Doublers and stiffeners
> are expensive and also a nuisance during detailing,
> fabrication and erection. 
> 
> Axial forces in bracing members must be clearly
> indicated.
> Many engineers shirk their responsibilities by
> specifying "full tension capacity" which results in
> over kill.
> 
> These responsibilities are fully discharged by
> Structural engineers in India and I personally have
> gone far beyond this when I designed steel structures
> in my career.
> 
> I am now associated in an advisory capacity with
> detailing for US Fabricators and I must say I am
> terribly disappointed with the structural drawings
> that I have to work with.
> 
> Happy Thanksgiving
> 
> Regards
> G Vishwanath
> Bangalore, India
> 
> 
> 
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