Slabs

[Wena]

Greetings. In ACI, Design of one way slabs need only bars parallel to the short span to support positive (center) and negative moments (beam support) of the slab. Is there any advantage by framing bars perpendicular to it or parallel to the long side (grid) in one way slab design? I'm aware that if long side is 2 times or more than short side. The load in the short side or span is only 1/16 that of the long side. This is why normally bars are not used. But would anyone happen to design slabs with grid bars even if it is one way (perhaps for more stability)?

 

[hokie66]

You need bars in that direction for restraint crack control, commonly called temperature and shrinkage reinforcement. Suggest you read further into the ACI code. In addition to crack control, these bars assist in distributing concentrated loads over a greater width.

 

[nibbi]

We normally do not consider the effect of these 'distribution bars' in flexure resistance of one way slabs. They just help in controlling cracking that's why they are also called as temperature and shrinkage reinforcement.

 

[Althalus]

Aside from temperature and shrinkage, here's another reason.

I have a condition where I need more steel in one direction than the other. But because of the relatively small slab size, I just gave the tighter spacing in both directions because I didn't want to confuse the drafters or the construction crews.