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RE: Details

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Dave,

I won't disagree with anything Charlie said...I think that he covered it
rather well.

I will add that _IF_ the engineer is expecting the steel fabricator to
design "typical" connections, then there is no excuse for them to not give
what they want the those connections to be designed for.  I would not
expect a fabricator to have to determine the reactions for a beam to
design the simply supported end connection.  This is assuming that you are
operating East of the Rockies where is becomes more common to see the
"passing" of the typical connection design to the fabricator.  So, in my
opinion, if the engineer wants someone else to do the final design of such
a connection, then that engineer should at least be providing the
connection forces.  FWIW, I also believe that if that engineer "passes"
off the connection design, it is still his/her responsibility to ensure
that those connections designed by others are adequate when they review
the shop drawings.

In my past life when I was doing steel buildings on a regular basis, I/we
would always provide end reaction forces.  We would also have "minimum
typical details" for single angle, double angle, shear tab, etc that we
know would carry the loads, but the final choice of which type connection
and exact final specifics of the connection (i.e. edge distance, cope
sizes, etc) would be up to the fabricator.  I/we would then check the
connections (at a minimum "spot" checks of a certain percentage of them)
to make sure that they would in fact carry the loads when we reviewed the
shop drawings.

FWIW, for the type of connection that you are talking about, we would
always do the engineering for dealing with the column stability.  This
would frequently result in the use of a stiffner being shown by default
unless I could find another way to do it.  But, then the type of buildings
that I did would not frequently have this type of a connection in them, so
my experience with having to detail/engineer such "animals" is limited.

Regards,

Scott
Adrian, MI


On Fri, 30 Dec 2005, Carter, Charlie wrote:

> The stability of girders that frame over the tops of columns can be provided in several different ways. Typical means include: beams framing on the column line and covering at least three-quarters of the girder web, joists or joist-girders framing on the column line with bottom chord extensions to brace the tops of the columns, or stiffeners.
>
> Regardless of how stability is addressed, this is not just a matter of calculating the concentrated force and deciding based upon that if a stiffener is required. This is a critical engineering concern and not something that any engineer should rely upon a fabricator's judgement to provide. It is easily easily addressed by any of the above-mentioned means (or other suitable alternatives) but must be addressed by the engineer.
>
> Even if the fabricator has loads from the engineers, loads will not help here because the stability concern is not directly related to the load transfered. Rather, it is a matter of stabilizing the top of the column -- the web of a girder framing continuously over a column top will rarely have enough strength and stiffness on its own to do so.
>
> I respectfully think that the engineer who told you that it is up to the fabricator is playing Russian roulette and probably does not understand the stability issue. He or she is probably not alone. I can show you pictures of collapses to emphasize how critical this is.
>
> Charlie
>
>
>
>
>
>
> -----Original Message-----
> From: dave lowen [mailto:jatech(--nospam--at)kwic.com]
> Sent: Fri 12/30/2005 8:00 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Details
>
> Comments, please.
>
>
>
> When designing 'big box' buildings, engineers sometimes (at least in this
> area of North America) do not indicate that web stiffeners are required for
> beams that cantilever over columns. In many cases, stiffeners are not
> required but the fabricator and detailer have no way of knowing this. Some
> fabricators and detailers share the view that if you didn't 'call for it',
> they will not 'quote it' and you will not 'get it'. Beam and column
> stiffeners are a high priced item and can make or break a bid.
>
>
>
> In discussion with a local engineer, I find his position on the matter is
> "it is the fabricators responsibility to determine if stiffeners are
> required and supply them, if needed". His position on this matter is similar
> to beam/column moment connections; the design of column flange and web
> stiffeners is also the fabricators responsibility. His thinking is that this
> area falls under the scope of connection design.
>
>
>
> If the engineering drawings provided loads, I would be inclined to agree
> with this position but most engineers don't supply them so it is impossible
> to any calcs. Also, the majority of engineers around here will not provide
> any loads when asked. I think their insurance providers tell them not to.
>
>
>
> In many states, connection design must accompany the contract documents but
> for those jurisdictions that do not, what are your views? Do you leave these
> tasks up to the bidder or fabricator?
>
>
>
> Regards,
>
> Dave Lowen
>
> V 519 587 5797
>
> F 519 587 5138
>
> E jatech(--nospam--at)kwic.com
>
>
>
>
>

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