POST TENSIONED FLOOR SYSTEM Prepared byAditya Shah (M.Tech CPM)

Building Construction System

INTRODUCTION

Post-tensioning is

simply a method of producing

prestressed concrete,

masonry, and other

structural elements

process of introducing

internal stress into a concrete

during the construction

process in order to counteract the external loads applied

when the structure is put

into use

Internal forces are applied by

tensioning HS steel

WORKING OF PT FLOOR

EXECUTIONMETHODOLOGY

Construction of post-tensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. Step wise construction of post tension floor is given below.

1. Form work setup 2. Placing of bottom reinforcement 3. Fixing of bar chair for PT tendon 4. Placing PT tendon 5. Fixing anchorage burstling reinforcement 6. Placing of top reinforcement 7. Placing anchorage pocket former and grout vent 8. Fixing slab edge formwork with pocket former 9. Concreting of slab

10. Removal of slab edge formwork 11. Remove pocket former 12. Placing anchor head and wedge in position 13. Stressing 14. Cutting end of strand 15. Capping stressing recess with cement mortar 16. Grouting 17. Repeat for next floor slab

COMPONENTS

ADVANTAGES OF PT FLOOR

Lighter and Slender

members are

possible.

remains un-cracked

under Service load.

improves serviceabili

ty

Fast constructio

n can achieved

Flat soffit reduces

shuttering, plastering

and painting

cost.

Reduces building height

DISADVANTAGES

Chances of corrosion are high

Complexity of work

Lead to accidents

ECONOMICS

• Post-tensioned

should be considered as a possible economic alternative for most structures when spans exceed 7.0 meters.

ECONOMICS

P-T reduces the concrete volume by 10 to 20%.

Cost of PT is typically 20 to 30% less as compared to conventional reinforced structure.

For flat slab in 8m x 8m or 9m x 9m Grid, P-T costs approximately Rs. 40 to 50 per sq. ft. with any kind of desired geometry availed better than R.C.C.

Since the reinforcement is protected, P-T reinforced structures have lower annual maintenance costs overtime

SPEED OF CONSTRUCTION

The comparison of PT and RCC slab is carried out on Strata SE1 project located in center London. The building is a residential high-rise 147 meters in height with 41 post-tensioned flat slabs.

The average area of the slab is 630 sqm.

The floor cycle estimates using the same criteria for PT and RCC are respectively 5 and 6.5.

This yields a total increase of 60 working days between PT and RCC.

Time saving on the PT option is due to less material and hence less installation time and labor, to stressing of the tendons and consequently early deshoring.

The actual floor-cycle achieved on the PT slab was 4.5 days on average.

REFERENCES

[1] “POST-TENSIONING IN BUILDING STRUCTURES”, Ed Cross1 BE, Grad.Dip(Tech.Mgt), MIEAust, CPEng.

[2] POST-TENSIONED SLABS, PUBLISHED BY VSL INTERNATIONAL LTD.

[3] Sanfield (India) LTD., PT Slab brochure. [4] “A PROJECT-BASED COMPARISON BETWEEN

REINFORCED AND POST-TENSIONED STRUCTURES FROM A SUSTAINABILITY PERSPECTIVE.”, Carol Hayek & Saleem Kalil.

[5] www.concreteconstruction.net

Thank you