footing detail gone wrong ??

[boffintech]

Am inspector on this job that has a number of 8'x'8 isolated column footings with 9#5 T&B EW. In the detail the top mat of column footing rebar is at the same elevation as the rebar in the SOG. The weather proved to be too difficult for the monolithic placement so the bottom half of the footings were placed and then the SOG was placed. The slab-on-grade rebar is specified as #4 at 16" EW so the contractor switched to #5 @ 16" EW and didn't place anything extra at the columns.

problems:
1. I say he's short 2#5 EW at each column. Is my math incorrect?
2. He placed the SOG construction joint 1-foot from a column line and placed 2' long x 1" dia. smooth dowels through the CJ. So the top mat of rebar specified for the columns along this grid line is discontinuous at this CJ. He says it's OK because the smooth dowels lap it out???

Now I have not asked the EOR about that yet yet, but is there any way that could be right?

Thanks.

 

[hokie66]

It certainly doesn't sound right. So as I understand it, the footing was detailed as a thickened section of the slab, but the contractor made a unilateral decision not to cast it monolithically. That is the first issue for referral to the EOR. Then the issue of a CJ in the top part of the footing, with discontinuous top bars, is something only the EOR can rule on. If the top bars are required for uplift, I would say the as built situation is definitely not adequate. The smooth dowels do nothing. Smooth dowels are used to allow for shrinkage movement of slabs, but in this case, the slab at the joint would be restrained by the thickening. Very poor detail.

 

[BAretired]

9-#5 bottom bars seems like very light reinforcement for a footing of that size. It is quite normal to have no reinforcement on top, but you are correct that #5 @ 16 slab reinforcement would be 2 or maybe 3 bars short of what was specified for the top steel.

I would be concerned about a cold joint between the bottom of footing and the slab even without the construction joint in the slab. I would certainly be concerned about a construction joint placed in the slab above the lower portion of the footing if they were intended to act as a monolithic unit. It would have been much better to pour the footing full depth below the slab with the specified reinforcement, then to pour the slab over it.

Two foot long smooth dowels don't "lap it out". They are intended to slip so that the control joint can function properly.

By all means, express your concerns to the EOR. He will likely reject the work.

BA

 

[dhengr]

Wow... contractors are developing wilder imaginations every day, to cover their A$$es and save a buck. I wonder how many continuing education hours he needed to come up with that solution and to maintain his contractor’s licence. And, they tell us we need CEU’s to maintain our licences. However deep that 8'x8' ftg. was intended to be, and wherever the top of that ftg. was intended to be w.r.t. the top of the SOG, you have lost considerable depth of integral concrete to the bot. rebar mat. This significantly reduces its bending strength on what already appears to be a lightly reinforced ftg. The concrete infill with the slab pour does not bring the ftg. back to its intended strength, it fills a void, and leaves a cold (slip) joint some distance down in the ftg. monolith. Although, if uplift was the reason for the top rebar, the SOG may serve that purpose. But, that DL may have already been figured into the ftg. sizing. I agree with Hokie and BA, take this to the EOR.

 

[boffintech]

Just to be clear:
1: the footing was detailed as a thickened section of the slab
2: apparently he got permission for the non-monolithic placement
3: my bad on the rebar: 9#6 bot & 9#5 top

I'll call the EOR tomorrow. Those steel guys are fast; they have red iron at every one of those footing locations.

 

[ztengguy]

In my opinion, that footing is half the depth needed, or specified. Unless there was rebar between the first pour and second, that footing wont act monolithic, thus the footing will more than likely fail, unless it was that size for uplift. Not sure who your working for, but might want to give the super a heads up not to keep moving forward with teh steel erection until this is settled.

 

[nac521]

There should be an EOR approved RFI or field clarification for a change of this magnitude.

 

[Archie264]

This sounds like a case of a contractor building what he jolly well feels like, regardless of what the drawings may happen to show. He and the EOR need to have a discussion.

 

[ztengguy]

Sorry, didnt see that he got permission. I just hope it was from the EOR and its ok.