Concrete Rebar Placement Drawings 3

[strguy11]

Do you require Concrete Rebar Placement Drawings/Shop drawings for every job? If not, when do you make the requirement necessary.

I have a contractor saying he never has had to submit these. Even though this is a relatively simple building concrete wise, we have a number of embeds on the project and required them. I told him he needed to submit them because they were required as part of the specs and drawings, but now he is going to the Owner and Arch saying we are adding un-neccesary costs to the job.

What are your typical practices?

 

[Ron]

There's more to a shop drawing than just placement details. The primary purpose of the shop drawing is to reflect the contractor's understanding of the structural engineer's intent. If there's a disconnect, it will show in the shop drawing...that's why the structural engineer reviews them.

The system is a good "check and balance".

Yes, the structural engineer could provide all the details necessary for the construction. That will increase the engineer's fee (or it should!). While there are some positive aspects for doing it this way, the more common method in the US is to have the fabricator reflect the design, giving HIS most expedient way of doing the job...not the engineer's shot at directing the fabricator.

Agree completely with Mike.

 

[dik]

Subject to my comments, Ron and Mike are correct.

Dik

 

[Zambo]

This discussion as highlighted by csd72 shows that different countries have different ways of working.

If you look at a UK structural engineers rebar drawing alongside his bending schedule it is very clear. The shape and location of each bar is known and it isn't possible to misunderstand where the bars should go or the intent of the designer.

The advantage is that both engineer and contractor know the basis of the design. Then both can look for any clashes with built in items or any differences between the structural drawings and the architectural drawings.

I haven't worked in the UK for 20 years but I find UK rebar detailing practices alive and well in several countries.

 

[MaddEngineer]

strguy11,

What type of embeds are you concerned about?

Is it the location(s) that you are concerned about or that the assembly is correctly placed or fabricated?

Are they required for other trades such as the ironworker or the curtainwall contractor to complete his/her work? If so than the GC should be coordinating this with his subcontractors.

From what I understand ACI 318 and the model building codes don't explicitly require "Placing Drawings". If required as part of the "Contract Documents" (i.e., Drawings and Specifications) then you should have explicitly stated that the reinforcing details shall comply with ACI 315 & ACI 315R which are part of ACI Detailing Manual (SP-66). The embeds that you are concerned about should also have been specifically noted on the "Contract Documents" since it may not be the Detailers Responsiblity based on ACI 315 and 315R. Also ACI 315/315R states that the only dimensions required by the Detailer are what is required to place the bars, they do not have to show any other dimensions of the structure as these should be shown on the engineering drawings.

Based on the ACI Detailing manual it is understood that for Highway Type Projects the Placing Details are typically done by the Engineer and on Building Type Projects the Placing Details are typically done by the Fabricator.

 

[phuduhudu]

I am interested to see how these things are done in the US then. How do you convey the design intent to the fabricator? Do you tell them what no. of bars you need in the tops and bottoms of beams and then leave the detailing to him?

As others have said, if we do it for steel connections then why not for rebar as well? Makes sense to me and as others say there is a lot of extra work in doing the detailing yourself.

 

[MaddEngineer]

It should be understood that having placing drawings and details done by the fabricator does not relieve the engineer of providing details and relavent information.

The engineer must show sizes of structural members, required cover, number and/or spacing of bars, number and/or spacing of stirrups, hook requirements, lap requirements, etc. on some kind of prescriptive details.

The detailer/fabricator will then based on the prescriptive requirements figure the actual bar lengths and bending details. Engineer may say #6 Top bars at 12" o.c. with hooked ends. The detailer/Fabricator will then check lap lengths provided by Engineer and Hook Requirements and what bars lengths he has in stock. And will say 10#6 x 28'-6" @ 12" o.c. Top Bars + MK6A01 ea. end. MK6A01 may be looked up on the bending schedule which shows a hooked bar with exact length and hook length.

I think the purpose is that the fabricator and placer knows what lengths of stock he can easily handle, or has on hand, etc. And can decide how he wants to maximize efficency in the field or the shop. The engineer is mearly giving the guidelines or requirements not the actual lengths ea. member should be and not exact quantities of bars to be placed.

 

[strguy11]

MaddEngineer:

The embeds are for structural steel support. The embeds are just a plate with anchor bolts, with a shear tab for steel connecton, and typical beam bearing plates for beams bearing on concrete, and diaphragm shear transfer plates.

These were detailed and shown on the drawings. However, sometimes not, I find these installed at the wrong elevations, even though we show what they should be at.

This is kind of why I ask for the drawings, to show that the contractor is doing his coordination between disciplines, and that he understands the drawing intent. Sometimes these embed are omitted from the drawings, even though our specs and drawings require all embeds to be shown on these drawings. This is why we have always been requesting these, so that we know the contractor knows they are required.

We do require that all the bar bends, details, etc comply with ACI, so I think we are ok technically.

Thanks for your input.

 

[MaddEngineer]

Strguy11,

From my experience those items typically are the responsibility of the steel contractor via the GC. The steel shop drawings should show the exact placement of the items along with top of steel elevations. The steel contractor typically will also provide (plywood or steel) templates for placing the anchor bolts. This is all up to the GC to enforce or coordinate... I don't know if you should start trying to take responsibility for them (I know you are trying to be proactive which is why I keep contemplating design-build myself), but, it might make sense to state GC shall coordinate location and placing of embeds with steel and concrete contractor.

 

[MaddEngineer]

Strguy11,

Have steel shop drawings been submitted yet? If yes then I would place the GC note on the drawings. If not then they are taking a little bit of a risk. This is why a lot of guys like using post-installed anchors, then the steel guy does not have to rely on the concrete guy and his anchor bolts won't be all banged up by the time he gets to the site.

 

[mtu1972]

Let me preface this by saying that my name is a misnomer as I have been doing this for over 35+ years.

My 2 cents. Any "Building Contractor" would not have a problem with providing shop drawings or the expectation to do so. A "Highway Contractor" might.

My first attempt at State work was for a pedestrian tunnel under a State Highway in a mid-size city. I designed and detailed it as I had done numerous tunnels for industrial clients. All of which had been successfully built after the review of shop drawings.

The State had us redo the drawings with the addition of bar bend schedules, etc., so the contractor would know exactly what to bid and what to build. There would be no shop drawings to review as the fabricator would provide the material directly from our design drawing.

Maybe in this tight economy, a contractor has ventured into new territory.

 

[strguy11]

I agree that they are usually supplied by the steel guy, but I think they are actually installed by the concrete guy. I have not recieved steel shop drawings yet, so there is nothing that I have that shows that the GC understands the requirements. (Another reason I usually require them)

As a side note, we have all of the notes you discussed on our plans, and our shop drawing review stamp indicates that our review does not relieve the contractor of his responsiblity of complying with the contract documents, so i dont see that I am taking on any extra liability.

 

[jdonville]

A bit of a tangent here, but as a "highway contractor", I get simultaneously amused and scared whenever I see rebar represented on a drawing (for any job) as a thin line.

Rebar has real-world thickness and should be shown to scale (as appropriate) on detailing drawings, as this will help prevent as-built conflicts between bars shown as occupying the same space, show areas where cover will not be maintained, and indicate areas where it will be difficult for the concrete to flow and possibly create a void.

Also remember that cover needs to apply to the shear steel, and that the logitudinal bars will usually be placed deeper within the section as they are tied to the shear steel supports.

How many times have you seen a requirement for cover, and a dimension from the outside edge of the member to the center of the bar that was exactly the cover depth? Will it be tied and poured that way? Maybe...

Jeff

 

[MaddEngineer]

strguy11,

I'm not trying to scare you or anything I would probably be doing the same thing you are doing, but just remember to look ahead and make sure whatever actions you take (writing or for that matter not writing something on the drawings, etc.) are not going to add undue risk to you or your organization. Like they say everything is okay until its not okay and then everyone starts pointing fingers.

For instance your Shop Drawing Stamp probably says something like Reviewed for Impact on Structure Only, etc., etc. Now if the dimensions of the embedments are noted on the drawings and they are wrong and you said nothing it could be construed that you reviewed them and since they do have an impact on the structure you may have some liability issues. Now suppose you corrected them and the contractor took note of them and it turns out the corrected dimensions are wrong and nobody else picked up on it, again you have some liability issues.

In each case most of the time on most projects things are handled as they say "Like Gentlemen" however, when something goes wrong its everyman (or woman) for themselves.

Since it appears that you have a little bit of a "rogue" or a "cowboy" contractor it is best to look ahead and Cover Your A$$.

Now if you let them get away with not providing the shop drawings or info requested in the Contact Documents you may also have some liability issues since you did not enforce the contract and may have not exercised your due diligence to the owner. In that case I would issue some kind of memo stating that the drawings are a required part of the contract and by not providing them the contractor is proceeding at his own risk and the owner should determine if they wish to enforce that part of the contract.

I'm not a lawyer, however, but I have worked for a GC/CM, a large Subcontractor, as well as Design Firms and have learned a little from each and now I work for myself (in theory at least, you still work for someone which is your clients) and I have also never been in a bad situation (luckily), but, what I learned from the GC/CM end is to be careful with documentation (or lack of) and how you state things in correspondence can be construed should things go awry.

Good Luck...

Also I have done my fair share of Steel Shop and Rebar Placing Drawings and They can be a pain in the a$$, but, I would recommend every engineer to do a few it makes you a better engineer. I wish I could say the same for some contractors (that is they should do some engineering it might make them better contractors or maybe just give them a headache).

 

[Zambo]

This seems very different from a UK type system.

In this case there seems to be a GC who has some coordination role for other contractors, specifically a structural steelwork contractor. In the UK in most cases the steelwork contractor would be employed by the GC and he would manage, not coordinate, the various disciplines.

Assuming these embedded items are not huge they should fit into the rebar with allowable amounts of bar movement, this is the GC's responsibility. Not sure why he needs to make a drawing for this.

In other cases such as a prestressing system there may be an element of design and build, in this case the contractor would usually have to make shop drawings for the rebar.

Again it just shows differences in the way the industry runs in different countries. In the UK a structural engineer would be surprised to be told that the contractor better knows the legths of rebar available. The answer's 12m lengths.

 

[strguy11]

I appreciate your comments, and yes our stamp does say that they are "reviewed" for general conformance only, and that our review does not relieve the contractor for his responsibility of complying with the shops.

I liken it to Steel shop drawings. Do you check every single dimension on the steel piece drawings?? My guess is that you dont, and only check the overall dimensions (grid lines, top of steel elevs, and don't review the actual shop dimensions (setbacks, etc) because the contractor is still responsible for fit up. Same way here on the elevations of the embeds, he is still responsible, even if he showed them. I am just trying to head things off before the become an issue, but the contractor is still responsible. Remember, they have reviewed them as well before we get them, right?

I do agree, that if I correct an actual elevation and it is wrong, then I do have some liability.

 

[StructuralEd]

For those of us who have reviewed shop drawings and seen that they rarely get them correct the first time, and therefore don't fully understand the design requirements, know the value of requiring them.

 

[StructuralEd]

Just to add another thought, if something goes wrong and you were the one to not require shop drawings to show that the contractor understood your design intent, you might expect to share the blame.

 

[hokie66]

Even with reinforcing shop drawings, you wouldn't use them to check the reinforcing on site. You would use your design drawings, at which time any deficiencies should be found and corrected.

 

[Dennis59]

I have always required (and received) rebar shop drawings for my work in upper midwest USA. StructuralEd and Ron have already said what I would have said...

And I couldn't agree more with DRW75's comment:
[NEVER trust anyone who says they've "never had to submit this before" or "the have never had to do it like this before". This is a very common tactic. And an annoying one I might add.]
In my experience, those two quotes are usually preceded with the phrase, "I've been doin' this for 30 years, and I've..."


Related story: (I'm sure most of you have similar stories)
I went to look at Contractor's progress on a metal deck roof, and noticed that there were no sidelap screws where we had specified them (and where they were clearly shown on metal deck submittal). I pointed this out to Contractor, who said, "Oh those? We've ~never~ had to put ~those~ in before..."

Right...

Good contractors don't say stuff like that - sadly there are some bad ones who do.

 

[MaddEngineer]

Since this thread seems to be sparking quite a bit of interest I thought I should look at my handy dandy A/E Liability Law Book and see what it says concerning Shop Drawings, it was pretty interesting...

1. The courts treat shop drawings as an expression of the design

2. If the A/E reviews and approves an erroneous shop drawing it can be construed as an interpretation of the intent of the contract documents

3. The term "consistency with design intent" has been construed by some courts as an ambiguous and meaningless statement

4. It noted one case where a contractor took field measurements, prepared shop drawings, submitted the drawings for review and secured approval. It was discovered during erection that the elevations in the approved drawings were inaccurate. A claim was submitted for costs expended in correcting the installation. It was claimed that it was industry practice to rely on shop drawing submittals approved by the engineer. The claim was rejected, but, only because the design documents did not have elevations noted so it was understood that the contractor had sole responsibility to verify them.

5. It also states some ways to reduce risk and liability: 1.) the contract should clearly state the shop drawing submittal and review process, 2.) that the shop drawings are not an extension of the design documents and are not a vehicle for communication between the A/E and the Contractor, 3.) and how changes and substitutions to the design shall be submitted. It is noted that this is part of the standard AIA and EJCDC (Engineers' Joint Constract Documents Committee) contracts.

6. Also items not specified for shop drawing submittal should be returned not reviewed.