Structural Connections 4

[BRGENG]

I am seeing more and more SE’s not design the Steel connections and instead leave this item to be done by the fabricator. I don’t mind because we are often hired by fabricators to complete their work. But if you are hired to do a job, do it, don’t just spec “connections by others”. What do you do, design the Connections or Specify them?

 

[a2mfk]

When we are the specialty engineer, if the EOR has not provided the service shears and moments, we request those in writing "Please provide actual service reactions, these are preferred for more economical and accurate connection design." We do this even if they have stated to use the capacity of the beam, because especially with moment connections we have gotten some very unreasonable designs without them.

So if they resist they look like they are not being a team player Although I guess at that point, the fabricator usually has the job and we are only saving them money. But in most instances they are our client. Having been the EOR plenty of times, especially if they are using a modeling software I know they have the service reactions handy. We often put the service reactions on our drawings even if we design the connections, for our own review, and then so we can use typical schedules with the reactions and beam types..

The EORs have always complied with our request.

 

[connectegr]

a2mfk
You have been lucky. Unless given initially, we rarely get actual reactions after the project is awarded to a fabricator. We are referred to the General Notes or specifications for the reaction guidelines. If the loads result in ridiculous connection details, we will RFI for additional information on specific locations and explain the concerns. I do like the wording of your RFI and I have asked the same question on many projects.

http://www.FerrellEngineering.com

 

[dik]

We clearly state in our fee proposal that a detailed connection design will not be undertaken and that this can be provided for an additional fee... almost never will a client agree to the added fee...

 

[a2mfk]

connect- you are probably right in our fortune, but we don't do that much connection design. You've probably seen it all.

The phrasing is meant to sound like we are being reasonable to the EOR in our request, sort of explain our intent to them and the architect/owner/fabricator, and then maybe make them look like they are not being a team player if they refuse what to everyone seems like a reasonable request and a simple task for them.

I think it is nothing short of laziness to not put the service reactions on your drawings when delegating connection design. If you use RAM or similar you can simply print the results and hand that to your CAD person. I think Modern Steel and AISC are also of this position. As I said before, I think its a good piece of info to have on your plans even if you are designing the connections.

 

[dik]

It's not laziness... it's being beaten down in fees... even when given the choice, the client rarely requires connection design if he has to pay for it...

Dik

 

[BAretired]

The CISC Handbook contains typical Double Angle, Single Angle, End-Plate, Shear Tab and Tee Type connections wth factored load resistances for each.

The EOR's drawing is supposed to contain factored reactions, but in my experience, the fabricators elected to use the minimum connection for a specific size of beam, which meant they often used more bolts than necessary to carry the reaction. For example, if I specified a 3 bolt connection for a 16" beam, they would use 4 bolts because it was their shop standard.

I'm not completely sure why they did this, but I had no objection. I suppose it was easier for them to use a standard such as one bolt for every 4" of beam depth and not get embroiled in too many individual details. I don't remember ever finding a case where that rule failed to work, but I was usually not involved with extremely heavy loads.

BA

 

[dik]

BAretired... The Canadian code for steel design and construction, CSA S16-09, does not require that the doecuments stipulate the connections... in fact, the opposite is stated.

4.3.1.Connection Design Details
Connection design details shall be prepared before the preparation of shop details and submitted to the structural designer for confirmation that the intent of the design is met...

Dik

 

[BAretired]

dik,

I agree that is what it says, but the EOR must provide factored reactions to the fabricator.

BA

 

[dik]

Only for oddball connections... I regularly spec that they be sized to accommodate a maximum UDL...

Dik

 

[sandman21]

This is not always true, "Connections are design to exceed the plastic capacity of the member", what is always true is the connection should be designed to have a ductile failure mode.


Someone really provided this? "maximum forces that can be developed by the system" I would be very surprised if someone took the time to find the actual maximum force and not the short cuts I have seen done.

 

[csd72]

dik,

RE: 'It's not laziness... it's being beaten down in fees... even when given the choice, the client rarely requires connection design if he has to pay for it...'

Yes it is because the structural engineer fees usually come out of the architects budget and the connection design fees come out of the builders budget.

 

[BRGENG]

csd72, But both budgets come from the owner.

 

[BRGENG]

JennyNakamura, my boss would never sign a contract where we only perform part of the structural design. The steel fabricators are always made aware when bidding that we are willing to consider alternatives connections to those on the plans if they believe a potential cost savings is possible. Very seldom do fabricators make this request and with about a dozen bidding each job I think they would in this current bidding environment. Maybe if everyone started designing items instead of specifying work onto others everyone’s fees would go up.

 

[csd72]

BRGENG,

Yes it does not make a difference to the owner but it does to the architect who has quoted a bulk rate for design from which the engineers fee often comes out.

I like you bosses philosophy.

 

[apsix]

Yes, if....
If everyone charged higher fees the fees would go up.

 

[JennyNakamura]

BRGENG,

Does your firm also design all your own wood and cfs roof trusses, anchorage details for granite cladding on fancy office buildings, aluminum curtain wall anchorage details, anchorage systems for door and window openings in blast-resitant structures, support rails and connectors for commercial PV systems, open-web steel joists, etc.? Do you design your own concrete mix designs or do you rely on the readymix supplier to design based on your specs? I sincerely appreciate the point you are trying to make, I really do, but your argument is a bit naive and narrow-minded; almost hypocritical.

I really believe, and I am sure that you do too, that probably most of the engineers that delegate connection design to fabricators would love to design their own connections; because we are all engineers and that is our intrinsic nature. But in regions where the custom is to delegate, how many engineers are in a position to try to change that? Not many I'm guessing. Regional differences are like regional accents -- they are what they are and they are not gonna change. If someone absolutely can't stand the annoying valley-girl accent in San Diego, then should move to Texas.

 

[csd72]

Jenny,

i disagree with the first half of your answer though the second half is valid.

All the examples you give are items that are not really part of the core function of the structural engineer i.e. they are not part of the main structural stability system. They are also all clear and distinct items as opposed to the connection issue which is about designing only half the system and delegating the difficult half to someone else.

I can see both sides of this arguement and I think calling someone naive and narrow minded is a bit over the top.

 

[dik]

csd72... even though the owner is involved in paying for the connection design, money for design usually is usually funded 'up front' and is limited... moreso, than construction money.

Dik

 

[dik]

Jenny... connection design and the associated drafting is something that I'm quite happy to foist off on the suppliers...

Dik

 

[connectegr]

dik
I thank you, and my kids thank you. Please continue happily passing the connections on to the fabricator. And if you change your mind, don't hesitate to call.

http://www.FerrellEngineering.com