Reinforcement Around Cores in Slab on Deck 1

[TylerM94]

I am working on a project that has a typical detail showing added rebar around openings blocked out prior to slab pour in composite slab on deck. The detail shows the maximum size of the opening as 4 ft perpendicular to the deck span. Are there any limitations to the size of the opening parallel to the span of the deck? See the attached photo showing (6) 6 inch diameter cores in a row. Does this look acceptable to reinforce with (3) #4 bars on all sides extending 2 ft beyond the cores on all sides or is this something where you need supplemental steel below the deck.

 

[KootK]

Ultimately, this is something that should be evaluated by the design professional who designed the slab system.

It is true that, in a one way spanning system like this, a row of penetrations parallel to the span is generally much less critical than a row of penetrations perpendicular to the span.

 

[TylerM94]

Thanks KootK. Now that I think about this more, the longer the opening, the shorter the section of concrete/ tributary width the rebar and concrete has to support. So the critical dimension is the width of the opening.

 

[WesternJeb]

You bring up a valid point. A opening this large/long could decrease the capacity of the beam significantly based on how it was designed and how long the span is, due to the decreased effective width of composite slab for the beam below.

 

[KootK]

A opening this large/long could decrease the capacity of the beam significantly based on how it was designed and how long the span is, due to the decreased effective width of composite slab for the beam below.

Meh. I'd agree if it were one, long, continuous opening. Normal practice would be for a bunch of circular openings like this to be spaced apart by 2X or 3X the diameter of the openings. And that should allow plenty of space for horizontal shear to spread out laterally to the adjacent concrete.