Flat slabs are reinforced concrete slabs that are supported directly by columns without beams. They provide minimum depth, fast construction, and flexible column placement. There are four main types: slabs without drops and with column heads, slabs with drops and without column heads, slabs with both drops and column heads, and typical flat slabs. Column heads increase shear strength while drops increase shear strength and negative moment capacity. Flat slab systems can be either one-way or two-way depending on span ratios and load distribution. Advantages include simple formwork, no beams, and minimum depth, while disadvantages include potential interference from drops.

1. FLAT SLABS
K.TARUN KUMAR

2. What is mean by Flat Slab?
• A reinforced concrete slab supported directly
by concrete columns without the use of beams.
• Flat slabs are highly versatile elements widely
used in construction, providing minimum depth,
fast construction and allowing flexible column
grids.

4. Construction:
The benefits of choosing flat slabs include a
minimum depth solution, speed of construction,
flexibility in the plan layout (both in terms of the
shape and column layout).

5. Types:
1. Typical flat slab
2. Slab without drop and column with column head.
3. Slab with drop and column without column head
4. Slab with drop and column with column head.
Uses of column head:
•Increase shear strength of slab .
•Reduce the moment in the slab by reducing the clear or effective span.
Uses of drop panels :
•Increase shear strength of slab
•Increase negative moment capacity of slab.

6. 1. Typical flat slab:-
• This may be called as beam-slab construction.
Hence in warehouses, offices and public halls some
times beams are avoided and slabs are directly
supported by columns.
• This types of construction is aesthetically
appealing also. These slabs which are directly
supported by columns are called Flat Slabs.

8. 2.Slab without drop and column with column head:
• The column head is some times widened so as to reduce
the punching shear in the slab.
• The widened portions are called column heads. The
column heads may be provided with any angle from the
consideration of architecture but for the design, concrete
in the portion at 45º on either side of vertical only is
considered as effective for the design.

10. 3.Slab with drop and column without column head:

11. • Moments in the slabs are more near the column.
Hence the slab is thickened near the columns by
providing the drops.
• Sometimes the drops are called as capital of the
column.

12. 4.Slab with drop and column with column head:

13. Flat slab system:
• 1.One way system:
• One way slab is supported on two opposite side
only thus structural action is only at one direction.
Total load is carried in the direction perpendicular
to the supporting beam.
• If a slab is supported on all the four sides but the
ratio of longer span to shorten span is greater than,
then the slab will be considered as one way slab.

15. 2. Two way slab:
• Two way slabs are the slabs that are supported on
four sides and the ratio of longer span to shorter
span is less than.
• In two way slabs, load will be carried in both the
directions. So, main reinforcement is provided in
both direction for two way slabs.

17. Advantages:
• Simple formwork
• No beams—simplifying under-floor services
outside the drops
• Minimum structural depth.
Disadvantages:
• Drop panels may interfere with larger mechanical
ducting.
• Vertical penetrations need to avoid area around
columns.