post slab structure

1. Group 3
1004
1017
1020
Report on
Post-Slab
Structural System

2. Post-Slab
Post slab or flat slab is a structural
system of horizontal slab and vertical
post. In this system a reinforced
concrete slab is supported directly by
concrete columns without the use of
beams.

3. Historical Background
C.A.P Turner is the first inventor of post-slab system. In 1906
he built the first practical post-slab structure, Johnson- Bovey
Building in Minneapolis, Minnesota. Robert Maillart was also
one of the founding fathers of the system from Europe.
However this structural system is made famous by Le
Corbusier after the first world war when rapid and low cost
constructions were needed.

4. Corbusier’s Five Point
1. Pilotis
2. Open Plan
3. Free facade
4. Ribbon window
5. Rooftop garden

5. Load Transferring Method
Dead load and live load transferred to the slab.
The entire slab act as a beam.
Slab transferred its own load along with the
imposed load to the post
Then post than distributed in to the ground
• Punching Shear: The portion of the slab around the columns have the
tendency of failure due to punching shear

6. Classification
flat slab with drop flat slab with capital flat slab with capital & drop flat plate post slab
Mainly are of two types
· flat plate
· flat slab: with capital, with drop,
with capital & drop

7. Thumb Rules
• Span
clear span: horizontal distance between internal faces of two
vertical supports
effective span : horizontal distance between center points of
two vertical support
Economic Span: 24’-26’
Maximum Span: 30’
Clear Span
Effective Span

8. • Slab
Minimum Slab Thickness for
Flat slab with drop panel = L/36
Flat plate without drop panel = L/33
(L = span)
• Column
Column thickness = L/15
Not less then 10”x10”
• Cantilever
In post-slab system slab must be cantilevered.
Minimum cantilever = L/3
Maximum cantilever = L/2

9. • Void
Punch can be cut as freely as possible in slab
in the area common to the slab middle strip
in the area common to two columns strips. not more than one- eighth
of the width of the strip in either span should be interrupted by
openings
in the area common to one column strip and one middle strip more
than one- fourth the re enforcement in either strip should be
interrupted by the opening
• Openings
Continuous opening in side wall(ribbon window) can be used
As the walls are not bearing any load, opening can be used as
Much as desired
• Wall
· wall can be built freely as desired in different floors
· it is recommended to built walls on the column strips
avoid the middle strips from first floor

10. • Column layout
Both regular and irregular grid pattern can be used
depending upon the shape of the slab
Irregular Grid Pattern
Regular Grid Pattern

11. • Stair
Domino type stair are used
Stair can be created from middle
strip
Stair can be created by using
cantilever as landing

12. Expression
• Lofty or floating like effect.
• Strong solid void relationship
• Exposed slab. Free facade
• Composition of lines and plates
• Absence of arches and vaults

13. Advantages
• The total height can be reduced due to absence of beam
• Different plans can be possible in different floor by building frequent
walls as desired
• Any types of plan like curve line plan can be possible
• Strong solid void relationship can be achieved because of the
scope of continuous opening
• Continuous opening can be used to ensure light and vent elation
• Columns help vehicular circulation in the basement of the ground
floor parking
• It is commercial for high-rise building, Low cost , first construction

14. Limitations
• Large dead load is undesirable when difficult foundation condition
are encountered
• Small depth to span ratio can cause the appearance off excessive
deflection of slabs
• The relatively short span capability
• Cost of the construction increases if capital and drop panels are to
be committed thus
• The system is less economical for the low rise structure
• Each slab should have cantilever
• Not show adequate stability against lateral forces such as wind
earth quack then its in shear walls to get stable

15. Case-study
MRF Headquarter
Charles chorea

16. • Load Transferring system

17. • Span

18. • Column Layout

19. • Cantilever

20. •Walls

21. • Punch in slab

22. • Openings
Continuous opening is provided
• Stairs
Stairs are placed in middle strip

23. • Expression
Wave look is created by curved façade.