One Way And Two Way Action

Depending on how slab is supported and dimensions of the slab, load transformation can either be by one way action or two way action. Slab which transfers load through one way action is known as one way slab and slab which transfers load through two way is known as two way slab.

 

One Way Slab

Irrespective of the dimensions when slab is supported on only two sides, we can straight away say that its a one way slab because load is only transferred in one direction. If we look at the figure given below slab is supported on two sides only making it a one way slab.

One way slab reinforcement
One way slab supported on two sides.

When slab is supported on all four sides and the ratio of longer span to shorter span is greater than 2, we assume that slab is one way. In both cases reinforcement is only needed in one direction along the shorter span.

Two Way Slab

A slab which is supported on all four sides having larger span to shorter span ratio less than two is known as two way slab. We call it two way because this slab transfer loads in both directions and because of that reinforcement is needed in both shorter and longer span directions.

Two way slab reinforcement
Slab having two way action

One Way And Two Way Slab Main Points

  • If slab is only supported on two opposite sides it is one way slab.
  • When beam is supported on all four sides it depends on span on slab that weather it is one way or two way slab.
  • If ratio of longer span to shorter span is greater than 2, we assume that slab is one way.
  • If ratio of longer span to shorter span is lesser than 2, we assume that slab is two way.
  • Main reinforcement is needed only in one direction in case of one way slab. (Along shorter span)
  • Main reinforcement is needed  in both directions in case of two way slab.

 

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