1 & 2 way Slabs
One way & Two way are the two basic type of slab which is used in construction and it is necessary to distinguish between one-way and two-way acting slabs, when it comes to concrete slabs. This depends on the support conditions and refers to the direction that the forces and moments mainly are transferred in. Slabs with two-way action require bending reinforcement in two directions, while slabs with one-way action work similar to beams and need bending reinforcement in essentially one direction.
One-way slabs, supported by parallel walls or beams, bend in only one direction and transfer their loads to the two opposite support walls or beams.
Even when a rectangular slab is supported on all the four edges, the slab may be considered as a one-way slab if the length-to-breadth (Ly/Lx) ratio of the slab is >=2.
Two way slabs transfer their load in four directions as as shown,(2 trapezoidal sections and 2 traingular sections) to the beams under it. Two way Slabs must satisfy the formula (Ly/Lx) < 2. Designing of two way slab is done for two types 1)Restrained Slab , 2)Simply supported slabs
As load distribution in 1-way and 2-way slabs are different so is the reinforcement placement. For the former one, main bar is provided in tension zone of the slab and only in one direction (shorter span) as bending takes place only in one direction and distribution bar in longer span for shrinkage shear stress, cracks developed in the longer span, later one has bending in both directions so main bar is provided in both direction, no distribution bar is placed in two way slab.
The main bar resists the bending of slab in shorter direction as bending of slab is generally governed by shorter span only. Hence to resist maximum bending moment, lever arm is kept more. Hence you would find main bars are kept below the distribution bars in a slab (tension zone).
HOPE U HAVE GOT A CLEAR IDEA ON ONE-WAY & TWO-WAY SLAB
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