Flat slab Structures VI

Introduction A reinforced concrete slab supported directly by concrete columns without the use of beams. A flat slab is a one-way or two-way system with thickenings in the slab at the columns and load bearing walls called ‘drop panels’. Drop panels act as T-beams over the supports.

Understanding of Flat Slab Column and column heads are required to be proportioned. Size of main part of column for two way slab is normally about 1/16th of the length of larger span & 1/8th to 1/9th of storey height of the building. Column head/capital will be 1/5th of the shorter span but not more than 1/4th of the shorter span. Height to thickness ratio will be greater than 15. H/ T > 15.

Advantages Simple formwork Aesthetic More clear height Flexibility in design Faster construction Uniform access to daylight Stiffness Additional floor in high rise building No beams—simplifying under-floor services outside the drops Minimum structural depth Usually does not require shear reinforcement at the columns.

Disadvantages Costly Medium spans Generally not suitable for supporting brittle masonry partitions Drop panels may interfere with larger mechanical ducting Vertical penetrations need to avoid area around columns For reinforced flat slabs, deflection at the middle strip may be critical.

Example

Folded plate slab

Introduction Folded plates are assemblies of flat plates rigidly connected together along their edges in such a way so as to make the structural system capable of carrying loads without the need for additional supporting beams along mutual edges.

Types of folded plates : Prismatic : if they consist of rectangular plates. 2. Pyramidal : when non-rectangular plates are used. 3. Prismoidale , Triangular or Trapezoidal.

Classified as : Single. Multiple. Symmetrical. Unsymmetrical. Simple. Continuous. Folded plates with simple joints. Folded plates with multiple joints. Folded plates with opened cross sectional. Folded plates with closed cross sectional.

Behaviors : Each plate is assumed to act as a beam in its own plane, this assumption is justified when the ratio of the span “length” of the plate to its height “width” is large enough. But when the ratio is small, the plate behaves as a deep beam.

Example :

Thank you  Jeel Jhaveri 1231 Studio 3 B