Joist structural details vs. shop drawings
Joist structural details vs. shop drawings
(OP)
Often times engineers include the weld requirements for joist bearing that are not consistent with the shop drawings submitted by the joist supplier. Should one go with the more stringent of the two, or do the structural engineer approved shop drawings supersede the plan details?
Greg






RE: Joist structural details vs. shop drawings
Unless specific indicated by engineer, usually shop drawing will not supersede the contract drawing.
RE: Joist structural details vs. shop drawings
RE: Joist structural details vs. shop drawings
The important part of this sentence is the "design intent", design intent does not mean they checked every single weld, it means they checked to see if they are no huge screw-ups. The shop detailer is in charge of checking that his drawings conform to the engineers plans. The way I see it is the engineer is just being nice and checking that the intent of the drawings has followed through to the shop drawings (engineers normally do more than this to save time on site, but they don't have too).
NEVER should the shop drawings overrule the engineering drawings, unless the engineer has given permission. A check doesn't count as permission.
Talk to the engineer in charge and gets his direction.
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
RE: Joist structural details vs. shop drawings
SJI prescribes joist welds for most typical applications and these will work most of the time. For a K joist, it is usually a 1/8" fillet each side x 1" or 1 1/2" long (can't recall exactly).
What happens sometimes is either the engineer of record doesn't know about the SJI recommended welds or wants more weld due to perhaps some drag forces on the joist.
Some of these joist bearing assemblies are made up of fairly thin material so a 3/16" fillet may not even work.
I'd do what rowingengineer suggests - first talk with the engineer of record and refer them to the shop drawings - let the EOR punch it out with the joist supplier.
RE: Joist structural details vs. shop drawings
I'll have to check with the SOR to see what he really wants on a case by case basis.
Thanks,
Greg
RE: Joist structural details vs. shop drawings
jimstructures, EIT
RE: Joist structural details vs. shop drawings
I worked for more than fifty years as structural designer and PE, much of it as a structural steel specialist. I cannot remember ever doing a job and not reviewing the detail drawings. In fact, the sitework is done to the fabricator's erection drawings, often a sepia or xerox copy of the design plan, marked with beam numbers etc, the actual design drawing does not have this erection information.
I have not ever, heard of the engineer's review being a "favor" to the detailer, it is a favor to oneself because if something goes wrong, everybody bleeds; even if completely cleared, we may face huge legal costs.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Joist structural details vs. shop drawings
In our office, it is the engineer's responsibility to check EVERYTHING. My boss once mentioned to me that I missed a weld (on the shops) from a beam (over column) to cap plate. This was on a 150 shop submission and the only thing (to my knowledge) that I missed.
It is my understanding that the shops are produced to meet the design intent of the contract documents, and it is the engineer's responsibility to make sure that INTENT is met. The shops are often where the fabricator will offer a different detail (sometimes for cost reasons, sometimes for constructability reasons). I guess there's a case to be made that it should come through as an RFI, but it often doesn't. When those differences come through, you have to either approve it (with or without notes) or reject it, you can't not look at it and plead ignorance.
That being said, our shop drawing stamp has some disclaimer that whatever is on the shops doesn't relieve the contractor from meeting the contract documents..... so it seems like there is a lot of contradictory information out there.
RE: Joist structural details vs. shop drawings
There can be no real reason for asking for more weld than the SJI standards unless there are abnormal forces involved, and these should have been made known to the fabricator.
Most of us cover our butts by referencing standards such as the SJI in the specifications, but we also say these are only applicable insofar as they don't change the requirements of the project documents. All very well, but the waters are muddied when the engineering drawings don't indicate where they differ from industry standards. I'm not arguing right and wrong, but practicality; a detailer who knows the standards of his governing institution will work to them unless flagged that the engineer has a tougher requirement, it is much more work for her if she has to search the engineering drawing for different requirements.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Joist structural details vs. shop drawings
I don't see my review of shop drawings (when I'm the EOR) as requiring me to check EVERY detail on the shop drawings.
The requirement of having shop drawings prepared is based on:
1. The design drawings do not typically go into the precise detail required to actually fabricate the elements. (every bolt, hole, clip, etc.) So detailed shop drawings are required.
2. The preparation of shop drawings forces someone to work out these details, and this, in itself, creates another natural layer of quality review.
3. The review by me is not to check their work for TOTAL quality. Rather, my review is:
a. To spot check unique or critical details to verify whether I am successfully communicating my design to them
b. To verify special, difficult, or unique details and connections that may be culprits for mis-understanding or error.
Thus the disclaimer note on most shop drawing review stamps - that the EOR is checking for "general conformance" with the plans.
So you're in effect NOT checking their work, but you ARE checking your commmunication.
This same difference applies to site inspections vs. site observations. One checks work, the other checks communication level.
RE: Joist structural details vs. shop drawings
Interesting. That makes sense, and I believe that (in general) the senior engineers in my office would agree with that.
A couple questions then.
1) How detailed do you have your staff engineers get in checking the shops? I'm assuming that you don't check them yourself.
2) In your opinion, is missing something like a weld from a beam (over column) to a cap plate on the shops (that is shown on the CD's) a big deal?
We typically check:
That all bolt holes are coordinated (correct location and number).
Verify all shear connections provided.
Check all erection details against our own and make notes for ANYTHING at all that is missing or different.
Check for bolt counts on the BOM for pieces.
Verify all weld sizes and lengths.
There is more that I'm not thinking of.
Does this sound about right to you or does it sound like overkill?
RE: Joist structural details vs. shop drawings
RE: Joist structural details vs. shop drawings
Clear remarks should be provided for omissions and deviations, then request re-submittal, or approved as noted. We don't allow the reviwer to leave ambiguity, such as question/question mark, on the shop drawings.
Other locations could be more like JAE mentioned, but I didn't deal with shop drawings for a very long time. Quite controvesal subject.
RE: Joist structural details vs. shop drawings
We were advised to not specify institutions, only the particular standards that you want to be applicable to your work.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Joist structural details vs. shop drawings
I stand by the intent of my original statement, given conceng in this case is not the EOR by his opening statement (conceng can confirm what part of the chain he makes), I would assume most probably the project engineer or similar. He should not treat the stamp with as much respect as you are suggesting. Sure if he was the EOR I may suggest he gives the drawing a good check, but he is not the EOR. Thus conceng should treat the checked set of fabrication drawings with the respect they deserve: NOT MUCH (aka SFA).
I post a link for the Hyatt case http:/
however there are two points in this case that stand out,
1. The original detail was under-designed, the alternative was submitted for review and the engineer was contacted by many of the design team to query the connection both original and alternative.
2. The detail was non-standard.
The one statement that dose ring true in the conclusion: All of the contractor's modifications to design details should require written approval from the engineer of record (Kaminetzky, 1991).
Now I am Australian so it may be different in the USA, but there is no requirement that the EOR check the fabrication drawings that I know of in any legislation (USA or AUST). Sure it maybe considered professional to do the check, and even recommend by some groups, but at the end of the day unless the engineer is contracted to the check, there is no reason the engineer could be forced to do the check. When I am do my contracts up, generally it is worded such that the check is for design intent only with the responsibility to ensure the drawings are in accordance with the engineer drawings lies with the contactor.
Thus I submit that while you may check you drawings to a high degree which is your judgment, the checked set of fabrication drawings should never supersede the engineering drawings, and to not query the EOR if they are different could in the end have you up for negligence.
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
RE: Joist structural details vs. shop drawings
I think a review of the shops should be made to the level appropriate to the project, its complexity, magnitude, and also (per rowingengineer's post) based upon what portions of the design were delegated to the fabricator.
The ultimate results of the Hyatt Regency collapse was that the EOR can delegate design tasks, but cannot delegate design responsbility.
Thus, if you made the fabricator design all your connections, I think it is incumbent upon you to do a very thorough check of those connections (which didn't happen at the Hyatt).
RE: Joist structural details vs. shop drawings
Just some feelings about this subject.
RE: Joist structural details vs. shop drawings
In my locale, many engineers assign responsibility to the fabricator for connection design. They require the fabricator to retain an engineer to review and apply his professional seal to all shop drawings. In my view, this is a dereliction of duty on the part of the EOR, yet it appears to have become standard practice.
I usually do not check dimensions on shop drawings unless something is obviously wrong or an error is inadvertently discovered. The fabricator is responsible for calculating the proper dimensions from the contract drawings. If he makes a mistake, he bears the responsibility of correcting the problem. In fifty three years of practice, this has never been an issue.
BA
RE: Joist structural details vs. shop drawings
As for what to check, maybe it's a gray area, but in my opinion, I don't want to send something back "Approved" or "Approved as noted" unlness everything they've provided matches what we want exactly, or there substitutions are acceptable.
Some places where my office does go overboard (in my opinion) is checking architectural copes, duct opening locations, and other architecturally driven items.
I would not feel comfortable saying nothing about a weld that is missing in the shop drawing erection detail that is clearly shown in our CD's.
RE: Joist structural details vs. shop drawings
Here's an unusual one: I once worked for a large consultant on hydro projects and the company realized they were spending almost as much time reviewing all the shop drawings as they were putting into the design. On one contract, it was agreed with the owner that, instead of requiring and reviewing shop drawings, we would increase the level of detail in our design to make field inspection possible directly off the design drawings. The contractor prepared the shop drawings anyway since that was "industry standard". Differences were generally caught in the field. This concept worked faily well - "catching the differences in the field" caused some extra costs but generally our overall cost to the owner was less. This method was abandoned when company attorneys advised against it because it opened up the box of "not meeting the standard level of practice".
RE: Joist structural details vs. shop drawings
The Hyatt Regency skyway system was not underdesigned; unbuildable perhaps, but not underdesigned. The fabricator, through the shop drawing review process, suggested an alternative design which looked quite similar at a glance (to a non professional, or even a careless professional) but which effectively doubled the load on the nut and rod system. Whatever the review process in that engineer's office, the alternative got through, got built, and the rest is history.
Means and methods are the province of contractors. Members and connections are the province of engineers.
RE: Joist structural details vs. shop drawings
If you review the NDS report on the Hyatt - the original design was also slightly under-strength as the rods were bearing at a seam weld between flange tips (per NDS physical tests)
The splitting of the hangers just made it very worse.
RE: Joist structural details vs. shop drawings
I learned in my practice from Kansas City to take shop drawings very seriously. Detailers are not engineers. Fabricators are not engineers. They are not licensed to insure public safety.
RE: Joist structural details vs. shop drawings
Our involvement in projects is QA/QC where we are inspecting the welded connections. Typically if there is a discrepancy due to insufficient thickness of base metal (3/16" weld required for 1/8" thick short-span joist bearing angles), we just note it on the inspection which typically makes it to the structural engineer.
For now we will continue with our status quo and base inspection deficiencies on the most restrictive between the plans and shop drawings. If the contractor thinks the engineer is asking too much, he can pursue a change.
In our market we have structural engineers who detail all the welds and those that just reference SJI or the shop drawings.
Thank you all for the very interesting discussion.
Greg