Rebar Spacing Issue 3

[Greatone76]

I have a situation were it has come to light on the job I'm doing inspection work for that the contractor placed (3) #5 rebar all in one plane at the bottom of a standard 8" stem wall with only a max of 5/8" spacing. Per ACI-318 the requirement is a minimum spacing of 1". I'm not the engineer for this project, I'm an owner's rep, but it appears that the CM is going to have the design engineer sign off on the situation. Since ACI-318 is the building code is it right to allow a sign off of code requirements. Am I wrong to be completely opposed to a sign off in this situation. I'm of the understanding that the concrete will separate aggregate and cream and not bond well to the rebar and could create voids ann/or a weak spot in the concrete in this area, so I would think this would be a critical issue. Please give me any advise or perspective on this issue.

 

[BUGGAR]

Check your contract, but as an inspector, I believe you are responsible to observe and report. Do this well and then it is up to whoever you report to take the responsibility from there. In a perfect world.

 

[KootK]

As we've discussed in the past, it is generally the designer's prerogative to say yay or nay to these kinds of things.

For stem/frost walls, the intent of concentrated longitudinal reinforcing is generally to provide nominal flexural capacity in the wall/footing assembly so that it can span over soft spots in the soil that may occur. Since there's really no defined bending moment to be designed for in this situation, it's understandable that the designer may not be concerned about the loss of bond in the concentrated reinforcing.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[msquared48]

Well, there should be a strip footing (12" wide minimum) below the stem wall, and the #5 bars should be in that strip footing, not at the base of the stem wall.

Mike McCann, PE, SE (WA)

 

[Greatone76]

My major concern is due to the aggregate being strained out and getting pure cream underneath having a dead/ weak spot in the concrete.

 

[SteelPE]

I'm a little confused here. Is this a localized problem? If you observed this situation and it doesn't comply with the contract drawings shouldn't you have asked to contractor to move the bars to where they needed to be?

 

[JAE]

And if it is at the bottom of the wall, I'm wondering what good the bars do structurally. The SE on the project can certainly review the situation and determine if the loss of concrete aggregate or quality below these bars is an issue that would affect the performance of the wall.

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[darthsoilsguy2]

It doesn't sound like that big a problem to me from the info i have. you have a good understanding of what the code says and the materials used, but it sounds like you might find a lot of redundancy and unaccounted safety factors if you were to analyze the structure. you have to know whether that rebar is needed at all to judge and without reverse engineering off the construction documents, you won't get there unless it is a major red flag detail that makes no sense.

There was a comment "If you observed this situation and it doesn't comply with the contract drawings shouldn't you have asked to contractor to move the bars to where they needed to be?" posted which wasn't meant to harm and i'm not judging the writer on it because it is a very common statement... but as a manager of inspectors for over a decade, this is the most dangerous concept in inspection. usually there is 1 independent inspector (and many times just a guy earning ~$15/hour) to the entire construction team and realtime construction is fast-paced. It is very easy to internalize the 'it got pass me or i let it go, so i have to live with it.' Inspectors are not Referees for a Game. The door is always open to review after the concrete is hard, and in most cases the addition of more materials is what makes that defect that 'YOU signed off on!!!' obvious. it pisses people off and doing it all the time would leave one unemployed, but every inspector needs to have the courage to point out a defect when they are aware of it. Study the plans, understand how they are building it, and always make sure the contractor inspects their work first.

 

[Greatone76]

For the record I was invited to a rebar inspection on Friday afternoon. Was informed they were not ready. Appaerently on Saturday they conducted a rebar inspection without me and once on site on Monday they had set the exterior forms, so there was no good way to see those bars. For the record there are 4 layers of inspection before me.

The situation existing throughout the entire perimeter of the building. The contractor put the (2) continuoius bars and the regular middle reinforcement wall bars that were spaced at 12"o.c. and put all 3 in one line and spaced them using the #5 vertical bar and a piece of #5 for the other gap. This building was placed in concrete. When we went to the next sturcture all the sudden everyone is calling foul when they have the same detail and situation and they placed both the top and bottom bars that way. At that time they sent RFI's and followe the correct proccess. Respaced the middle bar, so that everything was correct and placed concrete. As soon as everyone called foul I said hey wait they did that same thing on this building why aren't we worried about that. So right away the question was asked and the request want made for proof of how the 1st buildings rebar was set. 6 weeks later they finally admit it was done incorrectly and now they want to have the designer sign off on issue.

 

[SteelPE]

darth

I don't quite get your statement as it seems like you do not agree with what I said. If someone sees something wrong they are they not to notify someone to make a correction? Especially if it is an inspector (which the OP does not appear to be).

As I suspected, this problem popped up during construction and come to find out, was applied to other areas. In this instance, it's up to the EOR to make the decision if there is a problem or not. It seems like the foundation crew isn't that experienced (which usually sends shivers up my spine).

 

[StrucDesignPE]

SteelPE,
Yes and no. It depends on the role of the inspector. A lot of 3rd party (or independent) inspectors don't have the authority (unless given to them in the construction documents) to tell the contractor that they cannot do something. Regardless, the deficiency should be well documented and reported to not only the superintendent and foreman, but also to the inspector's superiors via his/her report.

If the independent inspector is acting on behalf of the AHJ, then the contractor must comply or face a failed inspection. In my jurisdiction, many times the 3rd party inspector will be on site monitoring the construction activities while a county inspector will come and inspect such things as steel reinforcing.

 

[racookpe1978]

What is the actual aggregate size? And can that size be changed now - before the pour?

If already poured, how "thoroughly" was the concrete rammed past the mesh (the bars) at the bottom?

 

[msquared48]

3/8" pea gravel would work...

Mike McCann, PE, SE (WA)

 

[TXStructural]

The EOR (and the local code enforcement authority, if involved) has the responsibility to decide what is acceptable. The EOR has the authority under ACI 318 to design outside of prescriptive code requirements and allow exceptions.

As to whether the reinforcement is adequately embedded, from a generic perspective, my answer would be "maybe." There are a multitude of reasons why rebar needs embedment and having a wide plane of nearly solid reinforcement is a bad idea. But in this case, for such a narrow installation with the rebar concentrated in the center with adequate distance on each side (between outermost bars and the forms, the wall will likely functions properly. Aggregate was probably able to flow around the sides of the longitudinal reinforcement, and only needed to move laterally a couple of inches below the rebar. If an engineer was concerned, he could easily have the contractor excavate at a couple of locations and directly examine the extent of consolidation.

It is the role of an inspector to examine and report, so that the designer, contractor, and/or owner can make informed decisions about accepting the work, requiring rework, and needing better QC on future work.

 

[Greatone76]

The aggregate it 3/4". I'm the owner's inspector and I've done my inspector's job of reporting and supporting it with the spec. I'm a Structural Engineer liscensed in the state I'm working. The CM highered both the designer and the contractor, so to a certian extent this is a design build situation. Because of my professional backgorund I'm being asked to give my proffesional opinion to the owner if the they should consider taking a sign off from the engineer of record on this issue. My basic opinion to them has been that the violoation is of ACI-318 which is the building code reference, so therefore they should not be accepting any signoff when the work does not comply. I understand there is latitude when working with specification violations and different interpretation of the drawings and the engineer figuring out if what was installed is adequate. But it is my personal opinion that any owner should not be accepting any structure that does not meet any porition of the building code. Is this too rigid of a view? I'm really looking for feed back on the back end of this problem. As an inspector I did what I was suposed to, but becasue of my unique situation of being a structural engineer on the flip side I'm looking for some perspecive on my opinion of the overall idea of having an engineer sign off on a code violation.

 

[SteelPE]

So what are all of these "Program of Structural Tests and Inspections" I fill out to be in compliance with Chapter 17 of the IBC? So we have inspectors onsite who are doing nothing other than putting findings into a report and passing them onto the EOR for review after the concrete has hardened.

 

[StrucDesignPE]

Greatone,
I would tend to agree with you that a structure not built in compliance with the building code is not acceptable. As we are all so fond of saying, the building codes are the "minimum" necessary requirements for design. Anything below minimum is sub-par work, IMHO.

Have you seen any concrete break reports for the concrete in question? Have the forms been stripped where you can actually view the area of the wall?

 

[JAE]

But it is my personal opinion that any owner should not be accepting any structure that does not meet any portion of the building code. Is this too rigid of a view?

Yes - this is too rigid.

As TXStructural has indicated above, the EOR has the knowledge and ability to investigate the situation and determine if:
1. The technical code violation affects the public safety and welfare, or
2. if it affects the value of work that the owner paid for.

Those are two different things. But both are under the authority, ultimately, of the EOR, not the text of the code, in my view.

An example of this is the post above:
It may be (I'm not sure) that the bottom bars in the wall are not used specifically in stressed zones but may simply be an excess of steel in the bottom of the wall.
In this case the intent and purpose of the code provision just doesn't matter in any way to the integrity of the wall, or its function.
But the EOR would know this. The code provision doesn't.

The EOR could evaluate any and all negative effects of the poor spacing for either the code intent or in terms of the value to the client.
It is their call in my view.



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[SlideRuleEra]

I'm really looking for feed back on the back end of this problem.

Greatone76 - I am going to give you what I hope you will accept as true constructive criticism. All of this is strictly my opinion, but based on relevant experience.

I am a long-time, retired Owner's Representative (By that, I mean a permanent, full time, direct employee of the Owner - not some sort of "contract employee").

Because of my professional background I'm being asked to give my professional opinion to the owner

Unless you have been explicitly instructed otherwise, on that job site you are the Owner. You are "not seeing the forest for the trees". You have an Engineer of Record, a Construction Manager, a Contractor, and "4 levels of field inspection". It is obvious, to me, these people are NOT working together - that is the real problem. By concentrating on the nitty gritty details, you are allowing others to marginalize your authority and get away with inferior work. Quit worrying about the rebar - there are plenty of others on the job site who (should) have that responsibility. Your obligation is to report to your Employer the dysfunctional organization you are witnessing, and if authorized to do so, take the steps to straighten things out. If you want, I'll be happy to discuss exactly how to do this, without being a dictator. It is not a straightforward road, but it DOES work.

Now, off the soap box, the next step is yours. No problem for me to just be quiet. Good Luck.

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[Greatone76]

SlideRuleEra I have been able to convey the big picture of the problem to the level above me and they are attempting to get resolution in the levels above them, but as we wait we are left to debate the individual issues. I don't see how I can private message you otherwise I'm quite interesting in discussing my exact situation and learning the approach you would take to get the big picture across to the owner, because at this point it appears the full message might not be getting across well enough.