designing concrete pavements best practices · 2020. 9. 30. · dowel bars tie bars – not for...
TRANSCRIPT
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Designing Concrete PavementsBest Practices
PaveWise Concrete Conference 2020September 23 – 24, 2020
Eric Ferrebee, P.E.Director Technical Services
American Concrete Pavement Association
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Design… for What?
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Lots of design considerations…
GeometricsCurb and GutterShoulder
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Lots of design considerations…
TrafficClimateDrainageEtc.
Are consistent.
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What Design Considerations are Concrete Specific?
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Concrete Pavement Specific Design Considerations
Thickness DesignDesign Programs/GuidesStructural Response and Support
JointingJoint spacingJoint LayoutDowel & Tie Bar Design
Materials / Mixture Design
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Concrete Pavement Specific Design Considerations
Thickness DesignJoint DesignMaterials / Mixture Design
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Selecting a Pavement Design Tool
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AASHTOWarePavement ME (previously known as DARWin-ME and MEPDG)
AASHTO 93 (software as ACPA WinPAS)
FREE Industry Developed Method
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AASHTO 931962-199810 inputs
“Performance”Field Data
StreetPave2005-201712 inputs
Crack & FaultFEA + Field Data
Pavement ME2009 - Present≈ 1,000 inputsCrack, Fault, IRIFEA + Field Data
Increasing Complexity = More Accurate Models & More Optimization Options
THE
40 Y
EAR
DIVI
DECurrent Design ToolsOutdated
PavementDesigner2018 - Present
12 inputsCrack & Fault
FEA + Field Data
Selecting a Pavement Design Tool
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Concrete Pavement Structural Response / Failure
CrackingFaultingRoughness (IRI)
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What Impacts Cracking Performance?
Pavement ThicknessMix Design (Strength)Joint SpacingClimateLane WidthShoulder DesignSupport Stiffness
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What Impacts Faulting Performance?
Dowel DesignSize/Spacing
Joint SpacingLane WidthSupport System
Erodibility of Support
Thickness (Inverse)
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Increasing Support System NOT Best Optimization
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Concrete Pavement Specific Design Considerations
Thickness DesignJoint DesignMaterials / Mixture Design
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Why Joint Concrete Pavement?
Other reasons we joint concrete pavements:
Control CrackingDivide pavement into construction lanes or increments.Accommodate slab movements.Provide load transfer via placed dowels.Provide uniform sealant reservoir.
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Designing Joints
Joint SpacingJoint types:
ContractionConstructionIsolation (and, if necessary, expansion)Transitions (PCC/AC)
Load transfer and edge supportJoint Layout
Contraction
Construction
Isolation
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Load Transfer / Maintaining Joint Continuity
Aggregate InterlockMaximum aggregate size………………………………………….is important!
Mechanical connectionDowel barsTie bars – NOT FOR LOAD TRANSFER
Subbase support
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Joint Design – Dowel Bar Considerations
Goals are:Faulting resistanceLoad transfer
.Design for Load TransferSizeSpacingShapeMaterial
http://www.acpa.org/dowelcad/Dowel Design Tool:
http://www.acpa.org/dowelcad/
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Joint Design - Tiebar Considerations
Goals are:Keeping joint tightNOT FOR LOAD TRANSFER
Design for Edge Support:SizeSpacingEmbedment depthMaterial
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Joint Design – Layout for Complex Geometries
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Joint Layout – Intersections
10 Step Method for Intersections
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Joint Layout – Roundabouts
6 Step Method for Roundabouts
http://wikipave.org/index.php?title=Joint_Layout
http://wikipave.org/index.php?title=Joint_Layout
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Joint Layout – DDI
11 Step Method for Diverging Diamond Interchanges (DDI)
http://wikipave.org/index.php?title=Joint_Layout
Quadrant Method Pave-Through Method
http://wikipave.org/index.php?title=Joint_Layout
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Concrete Pavement Specific Design Considerations
Thickness DesignJoint DesignMaterials / Mixture Design
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Materials – Mixture Design
Optimized gradation – Tarantula Curve / Shilstone ChartReduced paste content – durability and shrinkageMinimize the use of accelerated mixturesFocus on project sequencing to accommodate maintenance of trafficInclusion of Fibers?
Sieve Size
Perc
ent
Pass
ing
• Performance Engineered Mixtures - https://cptechcenter.org/performance-engineered-mixtures-pem/
Webinars and resources at https://cptechcenter.org/concrete-overlays/
https://cptechcenter.org/performance-engineered-mixtures-pem/https://cptechcenter.org/concrete-overlays/
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Mixture Design Considerations
• Structural design concerned with:• Strength (resistance to cracking)
• Flexural (modulus of rupture)• Compressive (cube or cylinder)
• Stiffness (resistance to deformation)• Modulus of elasticity (E)
• Property altering additions• Fibers• Chemical admixtures• Mineral admixtures (SCMs)
Focus in design is hardened properties such as strength and stiffness. Many of the chemical and mineral admixtures also alter fresh concrete properties.
L/3Span Length = L
d=L/3
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Mixture Design Considerations
Goals are:Uniformity and consistencyWorkability until placedAbility to be consolidatedAbility to hold edge if slipformingFinishabilityRequired strength/stiffnessDurability
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Summary
Many design considerations are the sameConcrete specific design considerations:
Thickness DesignSame tools as asphalt, but different approaches!Can’t just increase thickness
Joint DesignSpacing matters!Must design for load transferLayout for complex geometries is critical
Materials / Mix DesignMust meet design AND construction requirements
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Thank You!
Any Questions?
Eric Ferrebee, P.E.Director Technical Services
American Concrete Pavement Association
[email protected] | 847-423-8709
mailto:[email protected]