Rebar Callout Question

[stevenspm]

Hello All,
I am working on a building built back in 1935 and have come across a rebar call out I cannot figure out and I was hoping someone here may have seen it before. Does anyone know what OQ's is refering to in the circled callouts on the attached plan? I have not been able to find anywhere on the plans that defines that abbreviation.

Thanks,
Phil

 

[BAretired]

Boy, that is one crappy drawing! Looks like Panel 'G' and 'H' are waffle slabs with joist depth of 8" and slab thickness of 2".

The note on Panel 'G' calls for; OQ's 1-1[sup]∅[/sup] 10'-0" ST TOP EJ
Don't know what OQ's means but these appear to be 10' long straight bars of 1" diameter top in each joist which run over the W18x55 steel beam.

The note on Panel 'H' calls for; OQ's 1-3/4[sup]∅[/sup] BT EJ TOP
Don't know what OQ's means but these appear to be bent bars of 3/4" diameter in each joist which run over the W21x59 steel beam.


BA

 

[JAE]

I've never seen it before on many old sheets and designs.

Possibly "opposite quarters" or something like that? It appears to be a two-way joist system and E.J. appears to mean "Each Joist".

The OQ designation appears to be straight bars added in addition to the main joist bars.

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[briancpotter]

Referring to steel, OQ can refer to "oil quenching", a heat treating process sometimes used in the production of steel to give it more ductility (I think it used to be common on prestressing steel, not sure now?).

Seems unlikely to be the case here, but it's not impossible the designer wanted another, more ductile type of steel here for some reason.

Is there anything more you can tell us about the building?

Brian C Potter, PE
Simple Supports - Back at it again with the engineering blog.

 

[BAretired]

Outer Quadrant's? Doesn't make much sense either.

BA

 

[WARose]

It rings kind of a vague bell with me: It could refer to a re-bar truss. There was a company that did this way back when (i.e. Trussed Concrete Steel Company). I worked with a client that had some of their products in their concrete.

 

[hokie66]

It is a steel building, so I wonder why you consider those calls to be reinforcement. A bit like WARose, I suspect it is some type of steel joist system.

 

[JAE]

hokie,
Those are definitely the way old drawings called out rebar. As BAretired mentioned the 1- 3/4" dia. ST or BT EJ all refer to diameter of bars (they didn't use the bar numbers back then) as well as designating straight bars (ST) or bent bars (BT) which we sometimes refer to as "crank bars" or "truss bars".

The EJ looks like each joist to me.

It was also typical back then to use main steel beams and then form up reinforced concrete joists and just have the concrete wrap around the steel beam as fire protection.


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[hokie66]

Thanks, JAE. Guess I'm just not old enough to have seen that system.

 

[JAE]

Yes...I'm an old fart

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[hokie66]

I was just kidding, of course. As you well know, I'm older than you.

 

[BAretired]

I can't find any information about the web width or spacing of joists. Placement of two way alternating bent and straight bars in a 10" deep joist system would be difficult, particularly with thin webs and a combination of 3/4" and 1" diameter bars.

I don't suppose metal forms were available in those days. Hollow clay tiles might have been used to form the joists. Added straight top bars could have been placed outside the web of the joists, i.e. over the clay tiles. If so, they didn't have much cover in a 2" slab.

BA

 

[stevenspm]

All,
Thanks for the replies and sorry about the quality of the scan but I did not do it, it is a B&W scan of a photo copied drawing.
To answer some of the questions, the building is a school building, built in 1935, is constructed using a steel frame with concrete slabs for the floors and roof. The slab is a form of pan slab formed using either hollow clay tile or, in this case, steel pan forms to create a series of concrete joists, again in this case, 5" wide and at 25" o.c. The slab tile / pan form is 8" deep with a 2" topping slab placed monolithically for a total slab depth of 10". BT EJ does stand for bent bars at each joist and ST EJ stands for strait bars at each joist. The 8" +2" slabs are a two way system where the 6" +2" slabs are one way. The rebar with the mysterious OQ's are negative reinforcement bars placed over the top of the steel beams as column strip rebar in the left to right direction of Panel H & G are not bent over the steel beams, where as the middle strip is.
This appears to have been a popular building technique back in the 30's, at least where I am at, as I have come across this type of construction a few times before although without the OQ's preceding a rebar callout.

Again Thanks for the replies,
Phil

 

[JAE]

Would OQ possibly stand for "over quarry-tile"?...as opposed to over the joist web itself?



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[stevenspm]

Possible, but the tile used is a structural clay tile. The attached page shows how the clay tiles were used in this type of floor, but without the topping slab shown. For this building however instead of the structural floor tile shown they used a 20"x20"x8" steel form pan.

Phil

 

[BAretired]

The added top straight bars are in the column strips, hence Outer Quadrants may be the intent of OQ.

BA

 

[stevenspm]

I believe BAretired you may be correct. Looking at the plans again, I see that between Panel G and F they have the added top bars in the column strips but show them in both locations, where as at the 2 that I circled they did not have the room to write both seperatly.

Thanks for the responses,
Phil