Lecture for November 22, 2006

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Lecture for November 22, 2006

• Pavement RehabilitationPart 2

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Pavement Rehabilitation

• PGI, Module 9, Pavement Evaluation
• PGI, Module 10, Maintenance and Rehabilitation
• PG, Volume 2, Section 7
• PG, Volume 3

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November 22, 2006

• On November 20, the three topics were presented
  that relate to pavement rehabilitation (pavement
  evaluation, rehabilitation, maintenance, repair)
• C-130 pavement issue
• Whitetopping HMA pavement
• Rapid runway repair in Iraq

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November 22, 2006

• Today, November 22, the following topics will be
  covered
• Life cycle cost analyses (refer to Nov 20 notes)
• Begin discussion on HMA overlay design

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User ManualAvailable Online
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RealCost Overview
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Minimum Inputs/Requests for RealCost 2.2

• Project Details
• Analysis Options
• Alternative 1
• Alternative 2
• Results

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LCCA

• Life cycle cost analysis for Stevens Waya few
  items to consider
• Construction Costs Roadway Excavation New
  Pavement
• New Pavement
• Flexible HMA CSBC
• Rigid PCC Pavement Base (either HMA or CSBC)

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LCCA

• The extra credit problem is
• Use RealCost 2.2 to compare the agency costs of
  the flexible and rigid options for Stevens Way.
  Use your own designs.
• To use the RealCost software
• Download the software from the link provided.
• Compare only the agency costsnot user costs.
• The Agency Construction Cost is the item
  calculated in Total Project Cost in the
  preceding image.
• Select a reasonable discount rate and analysis
  period. Justify your selections.

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LCCA

• Miscellaneous material costs
• Roadway Excavation 15/yd3
• Crushed Surfacing 20/ton
• HMA 120/ton
• PCC Pavement 250/yd3
• Steel reinforcing bar 1.25/lb
• Epoxy coated steel dowel bars 5.00/each

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LCCA

• Other costs (these percentages vary)
• Traffic control Add 25 to the Construction
  Costs (varies widely)
• Mobilization Add 5
• Taxes Add 8
• Preliminary Engineering Add 10
• Project Engineering Office and Contingencies Add
  15

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LCCA

• Total Project Cost
• (Construction Costs)(1Traffic Control)(1Mobiliza
  tion)(1Taxes)
• (1Engineering)(1Project Engineering Office and
  Contingencies)
• Agency Construction Cost for RealCost 2.2

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RealCost 2.2Project Level Inputs
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Analysis Options
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Analysis Options
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RealCost 2.2Alternative-Level Inputs
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RealCost 2.2Alternative-Level Inputs

• Alternative 1 Make this one the flexible option
• Initial Construction
• Input Agency Construction Cost and Activity
  Service Life. If wearing course must be replaced
  after 15 years of service, then input 15 years
  into the ASL. This requires Rehabilitation at the
  15 year point.
• Rehabilitation 1, 2, etc
• Generally these will be HMA overlaysmill and
  replace about 2 inches.
• Alternative 2 Make this one the rigid option
• Initial Construction
• Rehabilitation 1, 2, etc
• Will your PCC design require rehabilitation
  during its design life?

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Alternative 1Initial Construction
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Alternative 1Rehabilitation 1
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RealCost 2.2Simulation and Outputs

• Select Deterministic Results
• Go to Worksheet and print this. This must be
  turned in with your solution.

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Deterministic Results
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Go to Worksheet
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RealCost 2.2Project Level Inputs

• Assignment submittals
• Summarize your two designs for Stevens Way. Just
  a simple statement of layer thicknesses and types
  will do.
• Show all calculations used to determine the
  Agency Construction Costs for both the flexible
  and rigid options.
• Reference all major assumptions, to include
• Analysis Period
• Discount Rate
• Activity Service Lives
• Attach Worksheet from Deterministic Results
  from RealCost.
• Finally, state which option you would
  choseflexible or rigidit should be obvious.

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End of LCCA Discussion
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Pavement Evaluation

• Pavement evaluation processes allow for
• Establish maintenance priorities.  Condition data
  such as roughness, distress, and deflection are
  used to establish the projects most in need of
  maintenance and rehabilitation.  Once identified,
  the projects in the poorest condition (low
  rating) will be more closely evaluated to
  determine repair strategies.
• Determine maintenance and rehabilitation
  strategies.  Data from visual distress surveys
  are used to develop an action plan on a
  year-to-year basis i.e., which strategy
  (patching, surface treatments, overlays,
  recycling, etc.) is most appropriate for a given
  pavement condition.
• Predict pavement performance.  Data, such as
  ride, skid resistance, distress, or a combined
  rating, are projected into the future to assist
  in preparing long-range budgets or to estimate
  the condition of the pavements in a network given
  a fixed budget.

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Pavement Evaluation

• Pavement performance is largely defined by
  evaluation in the following categories
• Roughness (or smoothness or pavement profile)
• Surface distress
• Friction or skid resistance
• Structural evaluation

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Example of Pavement Evaluation Data in the WSDOT
PMS
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Roughness

• Ranges of International Roughness Index (IRI)
• All types of roads
• Interstate highways
• Comparison of states and the US
• Vehicle operating costs versus IRI

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Roughness
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FHWA IRI Thresholds for Interstate Highways
Description PSR Rating IRI NHS Ride Quality
Very Good ?4.0 ?1.0 m/km (?60 in/mi) Acceptable (0-2.7 m/km)
Good 3.5-3.9 1.0-1.5 m/km (60-94 in/mi) Acceptable (0-2.7 m/km)
Fair 3.1-3.4 1.5-1.9 m/km (95-119 in/mi) Acceptable (0-2.7 m/km)
Mediocre 2.6-3.0 1.9-2.7 m/km (120-170 in/mi) Acceptable (0-2.7 m/km)
Poor 2.5 gt2.7 m/km (gt170 in/mi) Less than Acceptable (gt2.7 m/km)
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IRI for Rural Interstates2001
Source FHWA, Highway Statistics, 2001
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VOC versus IRI for HMA
2.7
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2.7
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Roughness
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Surface Distress(from PGI, Module 9, Section 7)
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Surface DistressExampleFatigue Cracking(from
PGI, Module 9, Section 7)
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Surface Distress
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Friction or Skid Resistance
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Friction or Skid Resistance
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Friction or Skid Resistance
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Structural EvaluationPavement Deflections

• A tolerable level of deflection is a function of
  traffic and the pavement structural section.
• Overlaying a pavement with HMA will reduce its
  deflection. The thickness needed to reduce the
  deflection to a tolerable level can be estimated.
• The deflections experienced by a pavement varies
  throughout the year due to temperature and
  moisture changes.

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Primary Types of Deflection Measure Devices Used
in the US

• Static (Benkelman Beam)
• Impulse (Falling Weight Deflectometer)

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Benkelman Beam
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Falling Weight Deflectometer (FWD)
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Structural Evaluation with Deflections

• Maximum deflection (D0)
• Area Parameter (A)
• Subgrade Modulus (MR)

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Area Parameter
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Area Parameter
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Subgrade Modulus (quick estimate)(from AASHTO 93
Guide)
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Typical Values of Subgrade Moduli(from PG,
Volume 2, Section 7.3)
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Pavement Rehabilitation

• Introduction
• Most of PG, Section 7.0 is about HMA overlays
  however, pavement rehabilitation is much more
  than that one rehabilitation technique. HMA
  overlays receive substantial treatment in this
  section since they are by far the most common
  type of flexible pavement rehabilitation
  technique in use in the US and most other
  countries.
• PGI, Module 10 (Maintenance and Rehabilitation),
  Section 3 (RehabilitationFlexible) and Section 5
  (RehabilitationRigid)
• Another rehabilitation technique commonly used by
  WSDOT is dowel bar retrofit of PCC slabs. This
  will be described later in this section.

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WSDOT Structural Design Policy
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Pavement Rehabilitation

• Types of HMA overlay design procedures
• Engineering judgment
• Component analysis Widely used in a number of
  applications/design procedures
• Nondestructive testing with limiting deflection
  Still used with measurement instruments such as
  the Benkelman Beam.
• Mechanistic-empirical This is the primary HMA
  overlay design method used by WSDOT. This
  approach is gaining acceptance in other states
  and countries.

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Pavement Rehabilitation

• Component Analysis
• The Asphalt Institute (AI) approach is
  illustrated in the PG, Section 7, Paragraph 1.3
  and the PGI, Module 10, Section 3.1.2. A number
  of HMA overlay design procedures use a similar
  approach. In effect, you start by determining
  the effective thickness of the existing
  pavement structure. Then, a new pavement
  structure is designed and the difference in the
  two structures (new effective) amounts to the
  overlay thickness. To use the AI approach, the
  following is required
• Subgrade analysis
• Traffic analysis
• Pavement structure thickness analysis ( determine
  effective thickness of existing and all new
  design for the given subgrade and traffic).

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Pavement Rehabilitation

• Limiting pavement surface deflectionsAsphalt
  Institute, PGI, Module 10, Section 3.1.3.
• Surface deflections can be taken with a variety
  of deflection devices. Typically, this is either
  the Benkelman Beam (BB) or the Falling Weight
  Deflectometer (FWD).
• Compute the Representative Rebound Deflection
  (RRD). You must consider the time of the year
  during which the deflections are taken.
• The overlay thickness is a function of ESALs and
  RRD (PG, illustrated by the sketch in Figure 7.3).

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Pavement Rehabilitation

• WSDOT Mechanistic-Empirical Approach
• Used to design HMA overlays
• Can be used to design all new pavements
• Computer program is EVERPAVE
• Failure criteria
• Ruttingsame as you used in Assignment No. 4
• Fatigue cracking
• Nfield (Nlab)(SF)
• The SF is approximately equal to 10 for HMA
  thicknesses of less than 100 mm, 7 if the HMA is
  100-175 mm thick, and 4 if greater than 175 mm.
  Part of the reason for these shift factors is due
  to environmental deterioration as well as traffic
  effects. Additionally, for HMA layers thicker
  than 175 mm, the fatigue cracks often start at
  the top of the pavementnot at the bottom of the
  layer as traditionally viewed.
• EVERPAVE Inputsreview information in PG,
  Paragraph 1.6.4
• EVERPAVE is the primary design procedure used by
  WSDOT

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Pavement Rehabilitation

• AASHTO Overlay Design Procedure (1993)
• Introduction WSDOT Pavement Guide, PG, Paragraph
  1.8.1 Note types of overlays that are possible.
  WSDOT primarily uses the AASHTO procedure as a
  design check for HMA overlays placed on flexible
  pavement.
• Overlay design considerations
• Pre-overlay repair including level-up or milling
• Reflection crack control
• Traffic (ESALs mostly)
• Subdrainage
• Ruttingunderstand cause(s)

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Pavement Rehabilitation

• AASHTO Overlay Design Procedure (1993)
• HMA Overlay of HMA Pavement
• SNol (aol)(Dol) SNf - SNeff
• In effect, this is similar to the component
  analysis approach discussed earlier. Further, MR
  and SNeff can be determined from nondestructive
  tests. WSDOT uses the FWD for this purpose.

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Pavement Rehabilitation

• Availability of Software
• WSDOT has placed all software (EVERSTRESS,
  EVERCALC, and EVERPAVE) on the current version of
  the WSDOT Pavement Guide CD. You must obtain the
  DARWin software from AASHTO to run that overlay
  design procedure (or develop your own
  spreadsheet).