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RE: Connections

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The source of our disagreement on the approach of connection design has to do with the size and complexity of the particular projects that we deal with. This is also why professional organizations, code officials, insurance underwriters and others can't seem to come up with one magic approach that makes all of us happy. There isn't one approach that always works. I do projects both ways depending on the complexity. 

In the meantime, we are competing against one another for projects and may be using different approaches. We even tend sometimes to bad mouth the other guy for taking the approach that we may not agree with. Maybe we should not be second guessing each other's approach to projects.

On a one or 2 story building, I can imagine that everything or just about everything can be engineered in the design phase. On a 20 story building, there will be many connections that need to be engineered to the forces shown on the drawings. It is just impractical to expect the engineer of record to design and detail of all these connections on a large project. 

Here are a couple examples of recent projects:

I am working with a larger fabricator right now on a 7 story building. They are using SDS/2 v. 6.322 as their detailing program. We specified the shear load for all beams. We have also specified the loads for loads diagonal bracing and collector beams and column splices (in tension) and the program produces connection calculations for our review. This particular fabricator prefers this approach because he can use the connection detail that is most efficient for his shop production. I believe this is the wave of the future. It has been an absolute pleasure working with this particular fabricator. This was a fast track project.

I have recently worked on an 8 story with another large fabricator. We specified the shear load for all beams. We detailed all the bracing and collector beams and column splices. The fabricator wanted to change all the bracing members and connections (initially without the approval from the structural engineer....just with agreement of the GC). They subsequently had problems with the size of substitute bracing not be compatible with architectural dimensional constraints. The detailers wanted to use shear tabs at some locations with insufficient capacities for the specified loads. They would show a beam with a 5 row bolted double clip angles at one end and a 5 row shear tab at the other end with the same size bolts in both connections. Obviously, if they needed a 5 row double clip angle at one end (and that is what was needed), how could they justify a 5 row shear tab at the other end? This was also a fast track project.

The particular fabricator (and his knowledgeable detailers, project managers and procedures) seem to be the specific ingredient that made the first project work so well. The approach to design/detailing did not seem to make any difference. 

Two different approaches, two different fabricators, two different results.... one pleasurable experience and one not so pleasurable. Which approach is correct? I will let you decide for yourself. 

Jim K.









 

-----Original Message-----
From: Gary Hodgson & Associates [mailto:ghodgson(--nospam--at)vaxxine.com]
Sent: Tuesday, December 02, 2003 7:04 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Connections


Roger
I disagree.  Most shop drawings have engineering in them--size and 
length of welds, no of bolts, edge distance for tear-out, etc.
Fotunately most of this is pre-engineered in the AISC or CISC 
handbook.  However, most shops i.e detailers, these days don't know 
these books inside out and often err- they don't know minimum weld
sizes, for example, a lot of engineers also don't know these.  That 
is why we have to check shop drawings.
Seldom do I check drawings without having to red-line something.
Gary

On 1 Dec 2003 at 16:28, Roger Turk wrote:

> Scott,
> 
> Since shop drawings are instructions to the shop, and have *no*
> engineering involved in them at all, they do not need to be and should
> not be sealed.  Shop drawings are *not* design or engineering
> drawings.
> 
> Engineering calculations and engineering drawings, whether performed
> by the project's structural engineer or delegated to a fabricator, and
> involve determining what is necessary to resist loads and forces, are
> required to be sealed.  If the "intent" of the working drawings is to
> have the fabricator design some aspect of the product, then the
> engineering calculations and the engineering drawings reflecting that
> design need to be sealed by the person responsible for the design. 
> Shop drawings are then prepared from the engineering drawings, so that
> the shop can cut, drill, assemble, weld, etc., the product in the shop
> for transportation to the jobsite and erected in accordance with
> erection drawings.  Erection drawings that just show where the pieces
> that come out of the shop are placed do not need to be sealed unless
> they involve engineering.  Erection drawings remove all the clutter
> that normally is on working drawings and shows just the product to be
> erected.
> 
> I refer you to AISC's "Detailing for Steel Construction" for examples
> of the differences between engineering drawings, erection drawings,
> and shop drawings.
> 
> Do not confuse bidding/construction documents with engineering
> drawings prepared by the fabricator.  Do not confuse shop drawings
> with any other drawing prepared by either the fabricator or the
> project structural engineer.
> 
> I think that a lot of fabricators rely on most architects and
> engineers not knowing what the difference is between shop, erection
> and engineering drawings and submit only erection or engineering
> drawings instead of shop drawings.
> 
> A. Roger Turk, P.E.(Structural)
> Tucson, Arizona
> 
> Scott Haan wrote:
> 
> . > I was calling engineering drawings = plans.  I agree.  My point
> was the . > engineer is responsible for design intent on the
> engineering drawings . > and if connections are not on engineering
> drawings then who is . > responsible for design intent for connections
> if the state does not . > require the detailer to have an engineering
> license. 
> 
> . > Alaska state law exempts specialty contractors preparing "shop
> drawings" . > from the practice of engineering.  This would appear to
> mean that . > connections do not need to be engineered, if the
> engineer chooses not to . > show connections on the plans.  My belief
> would be that the intent of . > the state law is for connections to be
> engineered by someone.  
> 
> . > Do other states exempt people preparing shop drawings from the
> practice . > of engineering? If exempted and the local practice is for
> is for the . > engineer of record to not design connections, who is
> engineering the . > connections?
> 
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