pt flat slab
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Construction Aspects of Post-Tensioned Flat SlabGuided by- Prof. Patil V S Prof. Khurth V GPresented By
Mr. Mulla Amanulla Liyakatali
Session Outline Quick review of basic prestressing
technique General applications of prestressing What is PT flat slab & its Types Construction aspects &materials Used
in PT flat slab Benefits over conventional RCC slab Discussion References
What Is Prestressing???? Prestressing is process of subjecting member
under compressive stresses (compression) by external longitudinal loading.
Also.Prestressed concrete can most easily be defined as precompressed concrete. This mean that compressive stress is put into concrete member before begin its working life and its position to be in areas where tensile stress develop under working load.
Prestressed Concrete vs. RCCThe main difference between PC and RC is the fact that steel reinforcement in the Prestressed Concrete is ACTIVE and the same is PASSIVE in Reinforced Concrete
Types of Prestressing.
What is Pre-tensioning???Steel reinforcement are stressed prior to concrete placement, usually at a precast plant remote from the construction site. How Pre-tensioning is done ???
What is Post-tensioning ???Steel tendons are stressed after the concrete has been placed and gained sufficient strength at the construction sites. Example : Post Tensioning of Floor Slab,
How Post-tensioning is done ???
STRESSING AFTER CASTING
Application of Prestressed Concrete
COMMERCIAL / INDUSTRIAL FLOORS
SLAB ON GROUND
What is PT Slab ???
The slab constructed with posttensioning technique and having top and bottom surfaces parallel to each other.
Types of Flat Slab
STEPS IN CONSTRUCTION OF PT SLAB AND MATERIALS
Stages in formwork and reinforcementShuttering Marking Profiling
PLACING OF BOTTOM REINFORCEMENT
POSITION OF CHAIRS FOR PROFILING OF TENDONS
LayoutSetting out of the cable profile, spacing of strands.
ElevationIt is the arrangement of Duct/strands +ve and ve moment.
PLACING OF TOP REINFORCEMENT
LIVE END BLOCK REINFORCEMENT
BALLOONING AT DEAD END
DEAD END R/F
STRANDS USED FOR BONDED PT CONSTRUCTION
STRANDS USED FOR UNBONDED PT CONSTRUCTION
IDENTIFICATION OF TENDONS
FLAT DUCTS RESTED ON CHAIRS
MONOSTRAND ANCHORS FOR UNBONDED P T
MULTISTRAND ANCHORS FOR UNBONDED P T
POSITIONS OF COMPONENTS
SHEAR RESESTING STUDS
CONCRETING OF SLAB.Before casting, some precautions are taken such as checking the sheath joints and connection of grouting vents.
To minimize manual errors in casting and compaction, equipments like concrete pumps, surface compactor, Needle Vibrator are used.
CONCRETE MIXING PLANT
REMOVE POCKET FORMER
CLEAN THE STRANDS
MARK THE TENDONS
E.O.H PUMPThis is used to give hydraulic pressure to the jack. Gauge-1:- used to control pressure of the jack.
Gauge-2:- used to block the strand into the jack.
CLEAN END PACKETS
PATCH END POCKETS
Grout Mixer & Collection Unit
REDUCED SHORING COST
Reduced construction cost Faster construction Elegant structure Improved Water resistant Early formwork stripping Floor to floor height reduction Reduced foundation load Improved deflection control Greater column free areas Reduced seismic risk Flexible planning Reduced cladding cost
BENEFITS OF FLAT SLAB
HOW CONSTRUCTION IS FASTER?
HOW SECTION SIZES GET REDUSED ?
Post-tensioning reduces overall building mass, which is important in zones of high seismicity.
Profiled tendons result in balanced gravity loads, significantly reducing total deflections.Permanent compressive forces result in greater control of cracks, deflection, and camber.
The flat-plate building clearly behaves like the strong column-weak beam mechanism
DISCUSSIONSComparative cost of PT & RCC durability of structure. innovative technique and the unavailability of materials and if PT slab get implemented on large scale which ultimately increase demand of materials resulting in production of PT materials. And the material will be easily available If we observe todays situation which is exactly in favors of PT construction that is the number of companies entering in the production of PT materials is going on increasing. Resulting in the lesser cost of material which affects the economics of PT. Also due to advanced portable stressing equipment and sophisticated design software helping in complex tendon profile and rigorous reinforcement details promoting the construction of PT and maximizing the use of todays engineering skill.
ONLINE REFERENCES: http://www.pci.org http://pubs.asce.org/books/ http://www.bassbeams.co.za http://www.sciencedirect.com/ http://www.bbrnetwork.com http://www.vsl.net http://www.gostructural.com http://enr.construction.com http://www.noorps.com http://www.structureae.de.com http://www.wisegeek.com http://www.tech9.in http://www.concretenetwork.com http://www.infolink.com.au http://www.ntpholdings.com/project s.asp http://www.cclstressing.com/ http://www.yde.co.il/ http://www.conforce.co.uk/ http://www.istructe.org.uk/
BOOKS Prestressed concrete by krishnaraju Prestressed concrete by Dayaratnam Modern prestressed concrete by James R.Libby. STANDARD CODES IS: 1343 for prestressed concrete ACI 318-77 ACI Standard building code requirements for reinforced concrete. CP 110: Part I: 1972 Code of practice for the structural use of concrete: Part I Design, materials and workmanship. AS 1481-1974 SAA Prestressed concrete code. Standards Association of Australia.