Joist structural details vs. shop drawings 1

[conceng]

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

 

[struengineer]

Unless specific indicated by engineer, usually shop drawing will not supersede the contract drawing.

 

[Bobber1]

One of the purposes of shop drawings is to show how the shop will build the product in specific conformance with the design intent. As such, the welds should be the same. This is why shop drawings are submitted, to verify that the design intent is attained.

 

[rowingengineer]

"This is why shop drawings are submitted, to verify that the design intent is attained"
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

 

[JAE]

You refer to joist bearing welds. If I understand you correctly, this is the weld that attaches the joist to the supporting member.

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.

 

[conceng]

I think in most cases JAE is correct...the engineer of record is not familiar with SJI's typical details, and I've only ever seen the joist supplier give the standard SJI weld details. We often times see the situation where the SOR calls for a 3/16"x2" weld, and the joist seat angle material is only 5/32".

I'll have to check with the SOR to see what he really wants on a case by case basis.

Thanks,

Greg

 

[jimstructures]

In rowingengineer(structural)'s post I beleve a mis-statement was made. He say's "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)." I feel this was resolved to a certain degree in the Hyatt-Regency's collapse court decree. I think that decree said the engineer of record is always responsible for checking that every detail is correct. I think if I remember correctly the judge said the engineer was responsible for checking that the detailer changed detail on the hanger rod joint at the landing was correct. The detailer changed a detail and the engineers of record did not catch it and lost their license to practice in the State of Missouri. If I remember correctly Two (2) engineers lost their licenses. I don't know if there was any fines or penalties beyond that, but I am sure there where enormous insurance settlements that turned on that issue. I hope I have remembered correctly.

jimstructures, EIT

 

[paddingtongreen]

I find rowingengineer's post, of 6 Jan 10 18:26, counter to my understanding.

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.

 

[Lion06]

I don't have a lot of experience, but in my short tenure what I have noticed is that virtually everything gets built from the shop drawings. The shops are not just for fabrications purposes, that is what the guys in the field reference to build.

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.

 

[paddingtongreen]

A couple of points.

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.

 

[JAE]

StructuralEIT,

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.

 

[Lion06]

JAE-

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?

 

[Lion06]

I didn't finish my thought. I think they would agree with that (in general), but they expect much more to be checked. I don't think they believe we are required to, but they expect us to.

 

[cntw1953]

At one location I worked from my junior to senior years, I followed company rules - check mark everything on each shop drawing and save it for future reference.

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.

 

[paddingtongreen]

Further on referencing standards in the project specifications; the AISC Code of Standard Practice says that if the detail drawings are submitted to the Engineer, the Engineer becomes responsible for the content (I don't remember the exact wording). We used to reference it with an exception to that clause.

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.

 

[rowingengineer]

jimstructures & paddingtongreen,
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://matdl.org/failurecases/Building Cases/Hyatt.htm

for all those that are not familiar with what Jim was referencing; there are probably more links with different conclusions but this one came up first on my google search, they use this case often for ethics class’s at uni (as they did at mine).

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

 

[JAE]

I wanted to post again to append my comments above - while I don't do an exhaustive check of our shop drawings, I didn't want to leave the impression that I just glance at them and call them good.

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).

 

[cntw1953]

Intent of design shouldn't be a guessing game. As a rule of thumb, industry practices/standards do not override the design unless the discrepancy/dispute is resolved and a revision is issued. Not everyone involved in the shop drawing review process will be legally held for ultimate responsibility, but shares the guilt if something happens, for which your act of care may prevent.

Just some feelings about this subject.

 

[BAretired]

The safest course of action for the Engineer of Record is to accept the proposition that he and he alone, is responsible for the proper design and ultimate safety of the structure. This includes checking the adequacy of all connections shown on the 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

 

[Lion06]

We do farm out the standard shear connections to the fabricator, but we always check what they've provided, both calcs and that the connections provided on each beam exceed the demand.

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.