Transcript Concrete Pavement Rehabilitation Stategy selection

Pavement Type Selection
(Designs, Costs & Bidding)
9th Annual Concrete Conference for
the Maryland Transportation Industry
March 24, 2009
Timonium, MD
Presented by Bob Long
American Concrete Pavement Association
Mid-Atlantic Chapter
Pavement Type Selection
Evolution of the Process
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Good old days
More responsible
More structured
Let the market dictate
Pavement Type Selection
Typical Basic Components
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Equivalent designs
Cost estimates
Life Cycle Cost Analysis (LCCA)
Innovative Contracting (e.g., alternate bids)
Equivalent Designs
What are equivalent sections?
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Same structural capacity
Similar traffic-carrying capacity over the analysis period
Provide reasonably similar level of service
Designed with the same procedure
•Traffic
•Reliability
•Subgrade
•Terminal
Condition
=
•Traffic
•Reliability
•Subgrade
•Terminal
Condition
Different Pavement Types
Concrete Section
Asphalt Section
Asphalt Layer
Subbase
Base
Subgrade
Subbase
Subgrade
How Pavements Carry Loads
3000 kg.
3000 kg.
pressure < 0.2 MPa
pressure
 2.0 MPa
Concrete’s Rigidness spreads the load over a large area
and keeps pressures on the subgrade low.
Costs
 Accurate estimates are essential
 Take into account volume, production, and
availability of materials
 Update regularly
Costs
 Liquid AC index jumped from $340 to $842 per ton
in just over 4 months (April—August 2009) – that’s
a $25 per ton increase for in-place asphalt
pavement
 Availability of liquid AC was becoming a concern
 Over the last 2 years, the price of asphalt pavement
has jumped from about $55 to over $75 and as
high as $130 per ton
 Although cement prices did rise for a while before
the big AC increases, prices are lower and stable
Materials Costs
Life-Cycle Cost Analysis
What is it ?
 Economic procedure
– That uses Engineering inputs
 Compares competing alternates over their life
– by considering all significant costs (and benefits)
 Construction, Maintenance, Rehabilitation
 User
 Performance
 Expressed in equivalent dollars
Life-Cycle
Cost Analysis
Pavement A
Pavement A - Rehabilitation Schedule
Determine the stream of flow for expenditures. The cash flow diagram (below) shows the
inflow and outflow of cash due to construction and rehabilitation. Arrows indicate a major
cash expenditure (construction, rehabilitation, etc.). An up arrow indicates the outflow of
cash. Down arrows show inflows. With pavements the inflow of cash only occurs at the
end of the analysis period to show either continued-use or salvage value. The height of the
arrow indicates the magnitude of the expenditure.
What it is Not
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 A Magical Black Box
– There is no concrete
LCCA or asphalt LCCA
 Complicated
– Does not need a
computer program
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4
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8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Pavement A - Present Worth Calculation
Using the the expenditure stream above, calculate the Present Worth (PW) for each
rehabilitation activity (PW for the initial cost is the initial cost).
PW is calculated using the following formula:
n
PW = Rehab Cost / (1+i)
Where
i = discount rate
n = year rehab takes place
Discount Rate =
Initial Const..
Rehab 1.
Rehab 2.
Rehab 3.
Rehab 4.
Rehab 5.
Rehab 6.
Rehab7.
Rehab 8.
Rehab 9.
Rehab 10.
Salvage
Yr
0
Total Cost
Cost
(1+i)^n
1.000
Total NPV
PW
Life-Cycle Cost Analysis
How it is done:
 Present Worth Analysis (PW)
 Equivalent Uniform Annual Cost
Analysis (EUAC)
Life-Cycle Cost Analysis
Present Worth Analysis:
Discounts all future costs (benefits) to the present
Costs
Initial Cost
Rehabilitation Cost
Maintenance
Cost
Years
Costs
Salvage
Value
Present Worth
Years
Life-Cycle Cost Analysis
Basic Factors:
 Economic Factors
– Discount rate
– Analysis Period
 Engineering Factors
– Comparable sections
– Rehabilitation selection
– Agency Costs
– User costs
Life-Cycle Cost Analysis
Analysis Period:
 Normally equal for each alternative
– Highway: 30-50 years
– Street: 20-30 years
– Airport: 30 years
 Include at least one rehabilitation
– Needed to capture the true economic benefit of each alternate
Life-Cycle Cost Analysis
User Costs:
 Delay-of-use
– Time delays - New construction & Rehabilitation
– Fuel consumption
– Driver discomfort
 Roadway deterioration
– Cargo damage
– Vehicle wear
 Accidents
Life-Cycle Cost Analysis
Some basic insights:
 Initial Costs
– Account for about 65-90% of Life Cycle Cost.
– Selection of features plays an important role
– Need to account for added features on the pavement
performance.
 Timing of Activities.
– After initial costs and discount rate, the next most important
factor.
– The longer an activity is delayed, the greater it is discounted
and the less impact it has on present worth.
Pavement Type Selection
Overview of Maryland Process
 Policy on application of process
 Three tiered approach
– Life cycle cost comparison
– Component analysis
– Innovative contracting
 Probabilistic approach to LCC
 Weighting of component factors based on project
priorities
 Project team formed to make final decision
Application Policy
 All projects developed through the Project
Planning Division ready for design,
and
 Any projects with a construction estimate >
$15 million (with at least $5 million
dedicated to pavement/MOT items)
 Estimated to be 6 to 8 projects per year.
(Staff resource levels were a limiting factor
in the number of projects that could be
identified.)
Three Tiered Approach
1st Tier – LCC Analysis within 20%
• Initial Cost
• Future Rehab Costs over 40 Years
• User Delay Costs
2nd Tier – Component Analysis
• Cost Factors
• Construction Factors
• Design & Environment Factors
• Form Team and Consider Industry Input
3rd Tier – Innovative Contracting
• Alternate Bidding
• Warranty Contract
• Design/Build Contact
Life Cycle Cost Factors
 Based on historical data and expert opinion
– Material unit costs
– Pavement service life
– Construction sequencing
– Construction duration
– General analysis inputs
 Variability represented by average and
standard deviation
Example Input – Service Life
Component Analysis
 Cost Factors
– Present worth Agency Costs – Initial & Future
– Present worth User Delay Costs
 Construction Factors
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Duration of Construction
Maintenance of Traffic
Maintenance of Access
(utilities & future maint, material sources, reliability of construction)
 Design and Environment Factors
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Traffic and Geometry
Adjacent Pavement and Structures
Environmental Impact
(community concerns, future planning)
Project Level PTST
 Chief Engineer for MDSHA Operations.
 District Engineer of MDSHA District that project
resides.
 Director of Highway Development (OHD) for
MDSHA.
 Director of Materials & Technology (OMT) for
MDSHA.
 Pavement Division Chief of OMT for MDSHA.
Example Component Score
Component Matrix
Alternate Pavement Bidding
Alternate pavement bidding involves the
bidding of two equivalent pavement designs
in order to determine the most economical
solution to the owner.
Use of Alternate Bidding
 FHWA traditionally discouraged use of alternate
bids for pavements
 FHWA approved a Special Experimental Project for
use of alternate bids in Missouri 1996.
 AASHTO recognizes Alternate Bids as a contracting
technique that will be utilized in the 21st century
 Recommended when more than one alternate is
judged “equal” by an agency and that the least
costly design approach will result from a competitive
bid.
 Alternate bidding should be used when there is no
clear cut choice between two alternates and have
similar life cycle costs
Use of Alternate Bidding
 Federal Aid policy suggests that alternative designs
are considered for large projects
 A life cycle cost economic analysis should be
conducted to compare the total cost of each
alternate.
 If the alternates do not provide equivalent designs
then an adjustment must be made to the bid to
equate the alternates.
 Pavements should be bid in the same units and
materials costs escalators should not be used.
Use of Alternate Bidding
 The following States/Provinces have experience
with alternative bidding:
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Alabama
Kansas
Kentucky
Louisiana
Maryland
Michigan
Missouri
Ohio
Pennsylvania
West Virginia
Alternate Pavement Bidding
Account for Bid Adjustment Method
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A+B
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A+B+C
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C is usually a product of the following
example:
C = User Delay Cost + (periodic) Rehab
Cost + Annual Maintenance Cost
C is added to the actual bid amount
West Virginia’s Alternate Bids
 Three projects so far with 3 more coming this
year
 No C factor so far
 First project went asphalt
 Next two went concrete with the concrete bid
10% less than asphalt
 WV is getting the lowest unit prices for
asphalt they seen in years
Available Software
 AASHTO DARWIN design
 WinPAS (ACPA’s Windows version of
DARWIN)
 Mechanistic Empirical Pavement Design
Guide (MEPGD – coming soon)
 RealCosts (LCCA)
 Concrete Pavement Analyst (NRMCA
parking lot design and cost analysis
program)
THANK YOU!
www.midatlantic.pavement.com
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