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A Performance Review and Brief Overview of

VARIOUS POST-TENSIONING SYSTEMS

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Basic Prestressing Systems

Pre-Tensioning Systems Post-Tensioning Systems

Grouted Post-Tensioning System(Bonded PT System)

Unbonded Post-Tensioning System(Mono-Strand PT System)

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Pre-tensioning Systems

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Pre-tensioning Systems Prestressing cable is stressed before pouring

of concrete Strong abutments/supporting sides are needed

to hold the cable stressed well-before concrete

pouring Not feasible to provide strong abutments for

on-site (in-situ) concrete construction having

unique or non-typical geometry/periphery Suitable for pre-cast concrete members with

regular and typical (repetitive) size and shape

Not preferred for in-situ concrete prestressing

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Post-Tensioning Systems

Cables are stressed at 6-7 days after

pouring of concrete depending upon earlystrength gain of concrete

Does not require strong abutments at thestressing faces

Well suited for in-situ concrete

construction

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Grouted Post-Tensioning System(Bonded PT System)

Quite an old method

Predominantly meant for bridgeconstruction

Multi-strands (many cables) are anchoredwith a common anchorage

Grouting is necessary for

Protection of cables (Primary Reason)

Restricting the movement of cable within ductto surrounding concrete

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Grouted Post-Tensioning System(Bonded PT System)

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All dimensions are in mm (UNO).

Grouted Post-Tensioning System(Bonded PT System)

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Grouted Post-Tensioning System(Bonded PT System)

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All dimensions are in mm (UNO).

Grouted Post-Tensioning System(Bonded PT System)

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Evolution in Post-Tensioning System

Main reasons of the evolution:

Great potential of PT in Building Construction Applications To get-rid-of the uncertainties in grouting activity

Difficult to assure that grouting is properly achieved

Difficulties in installation due to the stiffness of duct as wellas in managing multi-strands in the duct

Lesser eccentricity achieved due to the size of ductrequired for grouting

Multi-strands make more stress concentration in thegreen (early age) concrete at the anchorage zones

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Evolution in Post-Tensioning System

Problems related to grouting:

Good expertise requiredConsiderations at high & low points

Provision of vent pointsChecking of the quality of grouting activityEnsuring effective grouting throughout the length of duct

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Unbonded Post-Tensioning System Evolved from Grouted Post-Tensioning System before

1950 for Building Construction Application No need of grouting (Grouting activity is eliminated) Saving of Cost and Time and Material Installation made easier and flexible

Mono-strand System Each cable can be managed individually Induces less stress concentration to green concrete

It can work efficiently in lesser depths where ducts can

not work efficiently Better elastic behavior as far as earthquake event is

concerned. Post-quake residual deformation is lesser.

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Monostrand Unbonded PT System

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Grouted and Unbonded PT Systems

All dimensions are in mm (UNO).

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Grouted and Unbonded PT Systems

Low Point Eccentricities Generated at Mid Span of PT Element

All dimensions are in mm (UNO).

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Grouted and Unbonded PT Systems

High Point Eccentricities Generated at Support of PT Element

All dimensions are in mm (UNO).

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Few statements directly from the literature

Ref.: Unbonded and Bonded Post-Tensioning Systems in Building ConstructionA Design and Performance Review, PTI Technical Notes, Issue 5, Sept 1994

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Ref.: Unbonded and Bonded Post-Tensioning Systems in Building ConstructionA Design and Performance Review, PTI Technical Notes, Issue 5, Sept 1994

Few statements directly from the literature

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Ref.:

UnbondedandB

ondedPost-TensioningSystemsin

BuildingConstru

ction

ADesignan

dPerformanceReview,PTITechnicalNotes,Issue5,Sept1

994Few statements directly from the literature

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Few statements directly from the literature

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Few statements directly from the literature

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Few statements directly from the literature

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Ref

.:

ACIJournalFe

b1971,68-13C

omparativeStudyofPrestressed

Con

creteBeams,WithandWithoutBo

nd

Few statements directly from the literature

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Ref

.:

ACIJournalFe

b1971,68-13C

omparativeStudyofPrestressed

Con

creteBeams,WithandWithoutBo

nd

Few statements directly from the literature

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POST-TENSIONING MANUAL, sixth edition

Ref.:Post-Tensionin

gManual,SixthE

dition,Chapter8

,PTIPhoenix,AZ

,USA

Few statements directly from the literature

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Ref.:Post-Tensionin

gManual,SixthE

dition,Chapter8

,PTIPhoenix,AZ

,USA

Few statements directly from the literature

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Ref.:Post-Tensionin

gManual,SixthEdition,Chapter8

,PTIPhoenix,AZ

,USA

Few statements directly from the literature

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Ref.:ACI318M-08BuildingCodeRequirementsforStructuralConcrete

and

Com

mentaryYear20

08,Chapter18

PrestressedCon

crete,Clause:18.3.3Few statements directly from the literature

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Ref

.:ACI318M-08BuildingCodeRequirementsforStructuralConcrete

and

Com

mentaryYear20

08,Chapter18

PrestressedCon

crete,Clause:18.3.3Few statements directly from the literature

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Ref

.:IS:13431980IndianStandar

dCodeofPractic

eforPrestressed

Con

creteBIS2003

Clause:22.7

Few statements directly from the literature

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Ref.:IS:13431980IndianStandardCodeofPractic

eforPrestressed

ConcreteBIS2003

Clause:22.7

Few statements directly from the literature

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Cutout/modification in slabmade easier in

Monostrand Unbonded PT System

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Thank you