Which Slab Is Better – Ribbed Slab Or Solid Slab (One Way Or Two Way):
First of all, It depends on the use of the structure.
Slabs are structural members forming floors and roofs in buildings. They may be solid of uniform thickness or ribbed with ribs running in one direction or two directions( waffles).
Ribbed slabs are slabs cast integrally with a series of closely spaced joist which in turn are supported by a set of beams.
The main advantage of ribbed floors is the reduction in weight achieved by removing part of concrete below the neutral axis. This makes this type of floor economical for buildings with a long span with light or moderate loads. This includes apartment buildings and hospitals.
Solid slabs of uniform thickness can be one-way or two way.
ONE WAY SLAB:
When a slab is supported on all four sides and the ratio of long span to short span is equal or greater than two, it will be considered as one way slab. The load on the slab is carried by the short span in one direction. However main reinforcement bar and distribution bar in transverse direction.
Longer span (l)/Shorter span (b) ≥ 2
Example: Verandah slab, cantilever slab etc.
TWO WAY SLAB:
When the slab is supported on all its four sides and the ratio of the long span to the short span is less than 2, it will be considered as two way slab. The load on the slab is carried by the short span and long span. Generally greater amount of load is carried by the shorter span.
Longer span (L)/b < 2
Example: Slab used in multistorey building.