This document compares reinforced concrete (RC) flat slab and post-tensioned (PT) slab systems. It analyzes slabs of varying panel sizes from 9x9m to 12x12m under different loading conditions using software. The PT slabs were found to have higher moment capacity, require less concrete thickness and rebar, and provide better serviceability than RC slabs. Construction photos of completed PT slab projects are also shown. The document concludes that PT slabs are more cost effective for building floor systems compared to RC flat slabs.

1. “A Comparative Study on
RC Flat Slab
&
Post-Tensioning Slab”
N.Ajay
Research Scholar, Dept of Civil
Engg, BMSCE.
And
S.Chethan Kumar
J.Vittal. Kashyap
Structural Engineers, BBR INDIA PVT.LTD, Bangalore

2. OUTLINE
INTRODUCTION
SCOPE OF STUDY
METHODOLOGY
ANALYSIS & DESIGN
RESULTS & CONCLUDING REMARKS
REFERENCES

3. INTRODUCTION
BEHAVIOUR OF RCC AND PSC STRUCTURE

4. METHODS OF PRE-STRESS
PRE-TENSIONING POST-TENSIONING
(Reference : NPTEL Web site)

5. APPLICATION OF POST-TENSION

6. Cont..
BUILDINGS
SLAB ON GRADE PAVEMENTS

7. Why PT for Buildings?
 Increased Clear Span.
 Thinner Slabs.
 Reduced Floor Loads, Lighter
Structures.
 Reduced Cracking and
Deflection.
 Reduced Storey Height.
 Rapid Construction.
 Large reduction in conventional
reinforcement.

8. SCOPE OF WORK
 Compare PT Flat slab and RC flat slab systems with respect to Strength
condition(moment carrying capacity),Service condition (long-term deflection) and
Cost (Only Rebar Kg/Sq-m).
PANEL SIZE
(m)
1 9 x 9
2 10 x 10
3 11 x 11
4 12 x 12

9. METHODOLOGY
Load Data:
Super Impose Dead Load=3.0kN/Sq-
m.
Live load = 3.0 kN/Sq-m.
Self-Weight of Slab= Actual.
Building Details:
Type: Commercial
Storey Height: 3.5 m
No of Bays: 4
Grade of Concrete: M-35.
Grade of Steel: Fe-500.
Post-Tensioning details:
HT Strand for pre stressing: 12.7mmdia,7 ply Class
II
Area of strand: 98.7 mm2
Design of PT Slab: Bonded system with Class-III
Structure (IS:1343-2012)
Modulus of Elasticity: 1.95xE5Mpa
Breaking load: 183.7 kN
Ultimate Tensile Strength: 1860 MPa
Jacking force 75% UTS: 137.7 kN
Wedge draw-in slippage loss: 6 mm.
Duct wobbles, K: 0.0020/m.
Friction coefficient µ: 0.03 rad/m.
Long term loss: 150 N/mm2 (For
creep/shrinkage/relaxation).

10. ANALYSIS
 Analysis by ADAPT-Builder Software.
 Finite elements are automatically created by software.
 LOAD COMBINATIONS:
 Service(Total Load) :
1.0 x Selfweight + 1.0 x DL + 1.0 x LL+1.0 x PS
 Service(Sustained Load) :
1.0 x Selfweight + 1.0 x DL+ 0.3 x LL+ 1.0 x PS
 Strength:
1.50 x Selfweight + 1.5 x DL+ 1.5 x LL+ 1.0 x Hypostatic
 Initial:
1.0 x Selfweight + 1.15 x Prestressing.
 Analyses of the both PT & RC slab floors are performed for
the gravity load and the post tensioning forces.

12. DESIGN
 Design of slab by Strip Method (ACI and BS)- Column Strip and Middle
Strip.
 The column strip width is considered as 0.4x bay width and balance as middle strip (ref TR-
43).
 The design sections along the various design strips are checked for strength at service stage
and ultimate stage conditions.
 The sections are designed for ultimate stage with post tensioning steel considered as an
internal resisting action.
 Additional rebar is provided, if required, in the section to provide adequate strength. The
section-designs are carried out internally by software.
 Punching shear calculations are carried as per code provisions of IS:456, considering the
vertical reactions and the moments transferred to the columns.
 Check for Deflection of Slab as per IS:456-2000.
 Check for Stresses of PT Slabs.
 If provide Slab thickness satisfies Deflection & Stresses.

14. RESULTS
Moment Carrying Capacity in RC& PT slab in Column Strip Moment Carrying Capacity in RC& PT slab in Middle Strip

15. CONCLUDING REMARKS
 RC slabs require more cross sectional dimensions compared to PT slabs.
 The amount of concrete required for a floor is more for RC flat slab while
compare to post-tensioned flat slab floor system.
 Moment carrying capacity of PT Slabs is more than RC Slab with slender
section when compared with RC Member.
 PT slab provides a better serviceability than RC slabs.
 The thickness of RC flat slab is 18.0% higher and cost is 13% more than
the post-tensioned flat slab for 12 x 12 panel.
 The quantity of steel per meter in RC Flat slabs are almost 45% higher
than post-tensioned flat slabs for 12 x 12 panel.

16. Construction of PT Slab

17. ITPL- Bangalore ONE HORIZON CENTRE- Delhi
Photos : Courtesy by BBR INDIA PVT.LTD

18. WTT- Delhi Shangrila-Bangalore
Photos : Courtesy by BBR INDIA PVT.LTD

19. Marathon-Futurex-Mumbai
Photos : Courtesy by BBR INDIA PVT.LTD

20. 1. Boskey Vishal Bahoria and Dhananjay K. Parbat,”Analysis and Design of RCC and Post-
tensioned Flat Slab Considering Seismic Effect”, IACSIT International Journal of Engineering
and Technology, Vol. 5, No. 1, PP10-13, February 2013.
2. Thayapraba M,” Cost Effectiveness of Post - Tensioned and Reinforced Concrete Flat Slab
Systems”, International Journal of Innovative Technology and Exploring Engineering (IJITEE)
ISSN: 2278-3075, Volume-3, Issue-12, PP107-109,May 2014.
3. Dr.Amlan.K.Sengupta&Prof.DevdasMenon,”Pre-stressed Concrete”, Indian Institute of
Technology Madras, NPTEL.
4. Dr.Manamohan,R.Kalgal,”Post-tensioned Concrete in Building Sector”.
5. Martin Williams/ Sami Khan,” Post-Tensioned Concrete Floors”, Report, 1995.
6. Code of Practice for Prestressed Concrete Is: 1343 – 1980, BIS, Indian Standard Institution,
New Delhi.
7. Plain and Reinforced Concrete Code of Practice Is: 456 - 2000, BIS, Indian Standard
Institution, New Delhi.
8. Lin, T.Y., and Burns, N., 1981. “Design of Prestressed Concrete Structures”, John Wiley &
Sons, New York.
REFERENCES

21. Thank you