dc pt contractors role responsibilities ptia ieaust newcastle
TRANSCRIPT
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D&C PT Contractors Role &Responsibilities
Chris M. Harris
Contracts Manager, Structural Systems& PTIA Technical Committee
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Why do PT contractors get involvedin the design of the project to start
with
Commercial desire
S!ecialist engineers, design dra ts!ersons, &design so t#are
)is* & re#ard allocation
Time Constructa%ility
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What are the co!!on efficienciesintroduced to the structure by a PT
contractor
(lement thic*nesses
Su!!ort o!timisation Sla% structure ty!e o!timisation & orm#or* )ein orcement rationalisation
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What aspects of the e#isting designwill the PT contractor
review$change
+e!ends on the ty!e o !ro"ect
Ie ' Igross or %uildings- Concrete grade ' volume ' thic*ness Structure ty!e lat !late ' lat sla% ' %anded- )estraint design )e%ar content
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%ure a Tower
Conforming design )ein orced sla%s
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%ure a Tower
Non conforming design PT %ands and sla%s +riving orce TIM(
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Conclusions
Pro"ect (ngineers to coordinate #ith
contractors Involve a PT contractor early
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PT in buildingsPT is li*ely to %e considered or most !ro"ects.
I the consultant doesn t consider it, then thecontractors #ill
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Why PT Savings in materials Savings in construction
time
Im!roved dura%ility and
ro%ustness Cost savings
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'o!e perceived down sideissues
Time consuming to design %y theoccasional designer $
PT a!!lies real orce into a structurehence analysis incl. secondary e ects-needs to %e realistic and s!eci ic.
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'o!e perceived down sideissues
System and !rocessneeds to %e understoodand details coordinatedsu iciently
/inding most economical!ro!ortions o concrete,PT & rein orcement can%e a lengthy iterative!rocess, %ut usually
yields su%stantial%ene its. So t#are &e !erience is *ey.
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(ther effects to consider Secondary e ects in all
indeterminate PTstructures, %ut can %e%ene icial
Structural movements
cree!, shrin*age, thermal- Structural restraints
#alls, sta%ility elements- +ynamic %ehaviour may %e
a lighter, livelier structure-If doubt exists, talk to a
specialist PT designer (orthe PTIA)
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PT design is not differenthowever"""
( ective & e icient design does re0uiree !erience With sound engineering *no#ledge and
!ractice this can %e done success ully. Assistance and guidelines can normally
%e o%tained rom the s!ecialist contractors
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Design philosophy
Consider the generalconce!t o !artially!restressed concrete
A!!ro!riate!ro!ortions orein orcement and!restressing steelde!ends on thea!!lication restrainedv. unrestrainedconcrete-
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The D&C route for PT delivery
The usual variants hereare1
+&C %y tenderinvitation
+&C %y alternativedesign
If D C is expected and
planned for, timeefficiencies and
inno!ations can occur
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D&C Design )rief A Post Tensioning Design )rief is
critical or a success ul +&Carrangement.
It should ocus on the !er ormancere0uirements on the design
The e tent o +&C area re0uired
The loads and load !aths
Mem%er si2es #ith acce!tance tolerances
Servicea%ility and dura%ility re0uirements
Movements and 3ointing strategy
+e ine the +esign, certi ication & a!!roval!rocess
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Perfor!ance re*uire!entsAs ar as !ossi%le indicate1 Architectural re0uirements tolerances, inishes etc-Site constraints and constructa%ility issuesPour se0uence & any limitations on edge stressing access4imitations o the su!!orting structure.
Any rame actions that need to %e considered in loor design.( !ected areas o restraint and strategy or its management incl.
location & ty!es o !our stri!s &'or tem!orary movement "oints &'or!ermanent %uilding "oints.
)oles and res!onsi%ilities in the design !rocessIns!ections and installation signo s5uality and sa ety re0uirements.
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Types of PT Contract
Su!!ly and Install S&I- 6 Structural design, documentation, ins!ection &certi ication %y engineer
6 Sho! dra#ings, install, 5A %y s!ecialist contractor +esign and Construct +&C-
6 structural loor design, documentation %y s!ecialistcontractor
6 Install, ins!ection & certi ication %y s!ecialist contractor 6 (ngineer remains res!onsi%le or vertical elements,stairs, #ind & earth0ua*e design, etc.
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Design Considerations for PT Price
Pour Si2eStrand +iameter 7um%er o Strands !er TendonCou!lers
( icient A!!roval Process
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Concrete Properties and Profiles
Concrete outlines and grade needs to %e!rovided #ith PT !rice or client todetermine total cost o solution.
8e a#are o concrete testing & strengthre0uirements or initial & inal stressing,these are essential or !er ormance oconcrete & sa ety at PT anchorages.
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'tructural Design Certificate
4oads +ura%ility )e0uirements +e lection Criteria
Analysis Assum!tions
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Detailed 'cope of Wor
+esign +elivera%les or +&C, usually1 6 Concrete outlines 6 PT dra#ing design & sho! in one- 6 %ottom rein orcement dra#ing 6 to! rein orcement dra#ing 6 sections & details
Construction Services
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Client $ )uilder Responsibilities
Site Amenities Su!!ly o Po#er and Water 4i ting o our Materials on to the +ec*s Su!!ly and Install o Conventional )ein orcement
including Studrails #here a!!lica%le Concrete In ill o To! Sur ace Stressing Pans
Anything else "o% s!eci ic-
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Contract Conditions
)e erence to Standard Conditions o Contract )e erence to (8A 9ariation )ates
Payment Terms )etentions 4i0uidated +amages Insurances
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Project RelationshipsDeveloper
+ead Contractor
,or!wor 'ub-Contractor
.rchitect'tructural %ngineer
Post TensioningD & C
'ubcontractor
Reinforce!ent 'upplier 'teel ,i#er Concreter
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Ti!ely Co-ordinationCo:ordination %et#een1services consultants
architectstructural engineer %uilder s services alima*s etc-all %y others.
Co:ordination %et#een1structural engineer !t designshared %y engineer & s!ecialist !t designer.
Timeliness & in ormation sharing is critical.
4ate in ormation #ill lead to re:#or* & additional costs./ailure to co:ordinate #ill lead to re:#or* & additional costs.
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.c nowledge!ents3ohn /air#eather /ran* /ili!!one
3amie Mac*en2ie#ho are the authors o most o these slides.Ho#ever any errors are mine.