Structural Connections
Structural Connections
(OP)
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?






RE: Structural Connections
Firstly that is how they do it in Australia where I started
Secondly, you often spend just as much time checking the fabricators engineers drawings as you would just designing them.
RE: Structural Connections
When that happens, and it almost always does, we've spend time designing and documenting connections only to have to review what they want to change to anyway. Some say just design and document and don't allow changes, but that often gets a lot of pushback from owners, because the contractor and fabricator are in their ear telling them they can save money if they can change the connections.
It's even to the point where this happens with braced frame connections. The fabricator sees the details and wants to do something different, again, because it's easier for them.
RE: Structural Connections
BA
RE: Structural Connections
Plus we wouldn't get the job if we included connection design. Our competitor's would underbid us because they are design delegating connections among other items.
RE: Structural Connections
Connections are where most of the structural issues come about- I don't want to delegate this to someone I don't know.
RE: Structural Connections
AISC pretty clearly indicates that if you delegate connection design, you must show the reactions and whether ASD/LRFD. As the specialty engineer I obviously like it when people delegate the connection design, as these are pretty nice, clean jobs. We submit details and calcs as needed. EOR's have usually been very responsive to any questions or comments also.
I have often wondered whether an architect or owner has ever been savvy enough to ask the EOR up front during fee and contract negotiation, does this include the connection design? Because essentially the EOR is subtly shedding scope and pushing cost over onto the construction side. The fabricator hopefully catches this during their bid and adds the specialty engineer's bid into their fee, although its usually a drop in the bucket of a mutli-story steel frame fab package....
I think everyone in Florida should delegate their connection design :)
RE: Structural Connections
Plus, when acting as a consultant for others, I have found they shy from the double or triple fee they are made aware will have to be charged if with a complete design and check of the connections; in the end they want to believe the connections will be changed at the shop and everything will go fine. This usually goes fine in behaviour mainly because the fabricators themselves use not to be fools, otherwise would be recipe for disaster. We have scarce disasters on this as of now, so it is more than anything an attempt to scrape off some bucks at design time.
Roughly as Lion06 says.
RE: Structural Connections
In Australia, the main designer almost always designs the connections.
In the UK the main designer most often does not design the connections for larger buildings but probably will do for smaller ones.
I have worked both ways.
RE: Structural Connections
RE: Structural Connections
RE: Structural Connections
On a recent project, the final bids from 100% construction drawings where $1.1 million less than the 75% CD estimates (without connection design). The total tonnage estimates by all bidders were within 15 tons. The total connection design cost was $160k, which would have been more if the fabricator had designed for the connections, and determined the reinforcement which was eliminated by our coordination with the EOR. Obviously the fabrication and erection would have also increased due to the reinforcement. Our results will certainly vary based on the complexity of the structure and magnitude of the forces. For simple shear connections nearly anyone can provide adequate design. And in the near future standardized tables for most simple conditions will be available. But for complex geometry and design systems with significant load paths, a connection engineer should be involved. These projects also benefit from direct coordination between the EOR and the connection designer. Over the last 15-20 years connection design has become a specialty within structural engineering. Very little connection design is taught in school. And even in graduate programs, the connection courses are more theoretical than practical.
http://www.FerrellEngineering.com
RE: Structural Connections
Some very good points there.
I agree that most consultants are not very good at the connection side of things, though how much of that is symptom and how much is cause I am not too sure.
In buildings where there is considerable complexity to the connections then there is a great deal of merit for it to be looked at concurrently with the member design. Often heavier members or differently configured members can make the connections much simpler and lead to overall savings.
I find that sizing the members is often the easy part and it is the connections that hold all the major complexity.
RE: Structural Connections
I think I have told Connect on a few occasions that I admire his vocation.
I worked for a firm at one point that did a lot of power plant design. IMO, the connection design was the lion's share of the design work and was much, much more difficult.
Half of the battle in connection design is simply know what to check!
Throw in seismic requirements and there is simply no doubt that connection design is considerably more difficult.
These are just my opinions and maybe I'm just not that bright.
RE: Structural Connections
BA
RE: Structural Connections
However, in the case of one wood girder truss framing into another wood girder truss though, I leave the specification of the connection to the girder truss designer, as the structural engineer for the trusses has the truss member size and loads required to properly sizr the hanger.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Structural Connections
RE: Structural Connections
I just returned from the NASCC and as usual there were presentations concerning what the fabricator/detailer need for estimating projects and/or providing connection calculations. The comments were full or "I never get this" and "we don't understand this". The 2010 AISC Specification provides a role for connection engineer, for the first time. I think communication between the EOR and a specialty engineer is always a benefit to a project. This year is my 18th consecutive NASCC. This topic of contract drawing information and bidding information has been present ever year in some form. Perhaps a solution is for an intermediary, a connection engineer. Not necessarily the fabricators in-house engineer. But a professional with shared liability and an understanding of both design and construction. In my opinion, the EOR should be involved in the selection of connection engineer. This relationship can minimize errors, RFI's, and provide the best example of the EOR's intent. However, when the EOR simply delegates responsibility to the fabricator, and enormous barrier is created. In the best cases, RFI's and approval comments eat any remaining EOR fees. In worst cases, a lowest bidder detailer in some third world country makes engineering decisions which can significantly impact the structural system. The hope is that these decisions or clarifications are clearly show by their engineer or by the software program used. The challenge we are finding is in educating the owner/client on where this connection design cost will apply and what potential advantages available.
As a company we don't design structures or provide shop drawings. Thankfully I don't have to entertain architects or contractors (although another excuse for golf would be nice). Or study the latest structural analysis trends or detailing software. We concentrate all our attention on the specialty design of connections. I am sure that other consultants make the same sacrifices in providing the most current and economical solution within their specialty. We are constantly updating our software for the changes in the specifications and fabrication trends. In some cases, such as seismic, this is a constantly moving target. A specialty connection engineer, allows the EOR to concentrate on what they do best.
Sorry, I am preaching...
http://www.FerrellEngineering.com
RE: Structural Connections
RE: Structural Connections
I agree with what you are saying, however the answer probably lies more with $$$ than knowledge.
I see no problem with a Structural teaming up with another firm like Connectegr runs.
On big projects (especially those with A-Typical connections), connection design can really bog down schedules.
Having said that, I have always designed my own.
RE: Structural Connections
RE: Structural Connections
I believe it is mostly a regional (US) thing. I'm on the west coast and it is customary for the SEOR to design all the connections. However, it is not fair to classify someone as a 90% engineer just because local custom dictates that they don't design the connections. As others have alluded to, connection design can be very time consuming, so if the SE is going to design all the connections he should be compensated for it. If the owner is refusing to do so, then let the fabricator do it.
Also, would you call an awesome bridge engineer with 30 years of bridge experience a 50% engineer because he can't design an extension for his next door neighbor's house? Or because a bridge engineer is a civil PE and not a legal SE? I think as SE's we sometimes get a little caught up in our own arrogance.
RE: Structural Connections
RE: Structural Connections
RE: Structural Connections
Also, I don't know how it works out for the guys who do document connections, but there is no benefit to us to design and document them, because, as noted above, 80% of the time the fabricator will want to change them. Do you guys never get asked to change from shear tabs to double clip angles?
We never blindly publish reactions. We always check to make sure a connection will actually work without web doublers or anything crazy. I also don't think that farming that out makes you less of an engineer. Metal studs get delegated all of the time, so do stairs. Are the engineers who delegate these things less-than engineers?
As for other professionals who farm stuff out - the medical profession is noteious for this. If you have two different afflictions you can be sure you're going to see three different medical professionals. When is the last time a tax attorney tried a murder case?
RE: Structural Connections
I must have started typing my post before yours was up.
We don't purposefully fail to cut sections where delegated connections exist. We don't go out of our way to cut one there, either. If that's where a section wants to be cut, we cut it there. If a section is cut where a delegated connection exists, we show a generic connection (typically double angles), but don't call anything out.
We provide a Beam Reaction Table that lists reactions for each beam depth. Sometimes, if there is one very large reaction for a particular beam depth, we will show that one on plan and eliminate from the schedule so that all beams of that depth aren't being designed for that reaction (i.e. say all but one W16 has a 30 K max reaction, but one has a 80 K reaction; I'll show 30 K in the schedule and 80 K on plan at the one particular location).
For moment connections, our typicals call for full-pen welds, so there is no design to do there. Occasionally, we'll have a fabricator ask for design moments so that they can design them and not use full-pen welds.
We've even, on recent jobs, delegated braced frame connections. What we've had happen is we go through the design and detailing of the gussets, welds, bolts and then the fabricator comes back and says, "You know what, we prefer to make our braced frame connections with double angles field bolting to the gusset instead of the field welding you show". That's a LOT of time and effort wasted for no reason.
I'd be interested to know how the guys that design and document connections deal with those situations.
RE: Structural Connections
For unusual beams... ie, those with point loads or whatever, I generally spec the factored loads.
For connections with both a moment and a shear, I always spec the factored loads and the typical detail generally shows an end plate type of connection.
RE: Structural Connections
RE: Structural Connections
RE: Structural Connections
How to show the reactions for connection design? I have seen every combination mentioned and more. Actual forces shown on the plans, 50% UDL, even 150% UDL, tables related to beam depth, and in many cases no information at all. "fully develop the beam/brace", that is a good one. I have even received an EOR's RISA analysis with all the load cases. I don't think some engineers know what to design the connections for. What is a transfer force? What is column shear related to moment frames? What is the seismic resisting system? What is the response modification? Let the RFI's begin...
http://www.FerrellEngineering.com
RE: Structural Connections
When brought into the project in the contract stages and you are working with another firm who is handling the structural design, what do you request in terms of how connection forces are given to you?
There can be many combinations for which a connection need be designed.
RE: Structural Connections
RE: Structural Connections
Dik
RE: Structural Connections
Most of our time is spent on relatively normal moment connections, vertical bracing, and seismic connections. Designing for real forces and discussion of member shapes and sizes can significantly decrease stiffeners and reinforcement. When working directly with the EOR, all the these options are on the table. We can compare results and find quick solutions. This interaction is rarely available when our contract is with the fabricator.
http://www.FerrellEngineering.com
RE: Structural Connections
aren't there instances where using envelop forces is not correct?
Seismic ?
RE: Structural Connections
Seismic is a special condition. Connections are design to exceed the plastic capacity of the member. But, there can be a large diffence in design for the actual "maximum force" or RyAgFy. I have only seen one project that provided the "maximum forces that can be developed by the system" to the fabricator for connection design. Usually the seismic inform shown on contract drawings is conflicting or confusing.
http://www.FerrellEngineering.com
RE: Structural Connections
Recently we have bee doing some work for a connection only engineer (he hires us when he is overly busy) and the %UDL is used by him, unless noted otherwise on the design drawings.
RE: Structural Connections
IS this used for simple shear connections only?
How does this work in braced frames?
What about axial forces and bending moments?
RE: Structural Connections
SrVaro - AISC as an organization (not necessarily in the Manual) does not recommend it as it is poor practice that can result in ridiculously oversized connections (for instance in the case where say you are using a very short deep member to support another deep member, the UDL on the short deep member will most likely be way higher than necessary). On the other hand, if you had a point load from a beam framing in near the very end, using a % of UDL could be unconservative. Both issues resolved with putting the actual shear reactions on the drawings, which again is about 20 mins worth of effort in many cases.
The case for showing reactions:
From AISC Solutions Center: ht
See Myth 3: http
Read this entire paper which gives real world examples of what can happen with UDL: http://0
And just about every article ever published in Modern Steel etc. on steel economy mentions showing reactions on the drawings as a method of economy - just one recent example here: http://ww
RE: Structural Connections
Its the crazy bracing and moment frame connections that can messy.
RE: Structural Connections
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.
RE: Structural Connections
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
RE: Structural Connections
RE: Structural Connections
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.
RE: Structural Connections
Dik
RE: Structural Connections
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
RE: Structural Connections
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
RE: Structural Connections
I agree that is what it says, but the EOR must provide factored reactions to the fabricator.
BA
RE: Structural Connections
Dik
RE: Structural Connections
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.
RE: Structural Connections
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.
RE: Structural Connections
RE: Structural Connections
RE: Structural Connections
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.
RE: Structural Connections
If everyone charged higher fees the fees would go up.
RE: Structural Connections
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.
RE: Structural Connections
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.
RE: Structural Connections
Dik
RE: Structural Connections
Dik
RE: Structural Connections
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
RE: Structural Connections
Do you really think that connections represent 50% of the structural design of a building?
RE: Structural Connections
One of our newer fab clients just won the steel packages on a building design we did, and is probably going to have us modify some of our connections to all-bolted (how their shop is set up), and have us do the stairs and landing design too. Anyone ever else do this? I am 99% sure there is no ethical problem here, do we need to send a courtesy email to our architect client letting them know what we are up to? It won't cost the architect any more fees, nor the owner, since any work we do for the fabricator comes out of his contract...
RE: Structural Connections
You should make sure everyone knows about this and agrees with it before getting further involved. See 4.a. and 4.b. of NSPE Code of Ethics.
4. Engineers shall act for each employer or client as faithful agents or trustees.
a. Engineers shall disclose all known or potential conflicts of interest that could influence or appear to influence their judgment or the quality of their services.
b. Engineers shall not accept compensation, financial or otherwise, from more than one party for services on the same project, or for services pertaining to the same project, unless the circumstances are fully disclosed and agreed to by all interested parties.
BA
RE: Structural Connections
RE: Structural Connections
RE: Structural Connections
BA
RE: Structural Connections
I agree with you. My response was a bit over the top.
BRENG, please accept my apologies.
I guess its just frustrating to me that someone (or some people) could lump an entire group of people together and criticize them for not designing their own connections and call them things like "lazy" or "90 % engineers". This is something they have absolutely zero control over. If they feel that strongly about it, one could argue that it's the SE's working for the fabricators that are to blame, after all aren't they the ones responsible for allowing the custom of delegating steel connections to fabricators to even exist in the first place? However, that's even more ridiculous than the original argument. You could spin this topic in so many directions it would never end.
I work in an area where it is expected that the SEOR design all the steel connections. The thought of delegating connections is not even an option. However, I personally feel that on many of the more complicated projects (stadiums and arenas I have been involved with), the SE's at the fabricators can design much better connections, both from a design and a constructability perspective. A lot of complicated steel projects I've worked on I would say connection design was probably 20 or 30% of the design effort. Why not let guys like connectegr design the connections from the start? SEORs are typically like general internal medicine doctors, why not let the specialists handle the specialties? I wouldn't want my general practictioner to remove my brain tumor (if I had one)...
If the concern is engineering fees, there are much more deep-rooted issues with the way engineering businesses operate that we need to address than demanding to the client that we design all our own steel connections.
I'm just making a stand for all the lazy 90% engineers out there that are forced to delegate their steel connection designs and who have no control over the situation -- they're just doing their jobs and trying to get through the day to pay their bills and raise their kids.
RE: Structural Connections
As I understand you work for a fabricator, or subcontracted at the least.
You must understand that from a EOR point of view we are all in a far too competitive market. For example, if three engineering consultants are to bid on a project, we do not clarify to the Owner that 'connection designs' are included in our cost... quite simply put because they DO NOT CARE. These connection designs are a part of the 'hard costs' and not the 'soft costs'. Soft costs to the Owner are a drop in the bucket and if we are 10k higher than the lowest bidder in order to do connection designs they will 100% of the time pick the lower costing engineer, regardless of the connection service provided; again this is buried in the hard cost.
We understand your frustration but you must understand the complexities of both angles here.
Dik, I agree with you completely as it seems we may have been bidding on similar projects.
RE: Structural Connections
"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."