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

Good old days More responsible More structured Let the market dictate

Pavement Type Selection Typical Basic Components

Equivalent designs Cost estimates Life Cycle Cost Analysis (LCCA) Innovative Contracting (e.g., alternate bids)

What are equivalent sections?

•Traffic•Reliability •Subgrade•Terminal Condition

•Traffic•Reliability •Subgrade •Terminal Condition

=

• Provide reasonably similar level of service• Designed with the same procedure

• Same structural capacity

• Similar traffic-carrying capacity over the analysis period

Equivalent Designs

Different Pavement Types

Subbase

Subgrade Subbase

Subgrade

Base

Asphalt Layer

Concrete Section Asphalt Section

How Pavements Carry Loads3000 kg.3000 kg.

pressure < 0.2 MPa

pressure 2.0 MPa

Concrete’s Rigidness spreads the load over a large areaand 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

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

What is it ?

Life-Cycle Cost Analysis

A Magical Black Box

– There is no concrete LCCA or asphalt LCCA

Complicated

– Does not need a computer program

What it is Not

Life-Cycle Cost Analysis

Pavement A

Pavement A - Rehabilitation Schedule

Pavement A - Present Worth Calculation

Discount Rate =

Yr Cost (1+i)^n PWInitial Const.. 0 1.000Rehab 1.Rehab 2.Rehab 3.Rehab 4.Rehab 5.Rehab 6.Rehab7.Rehab 8.Rehab 9.Rehab 10.Salvage

Total Cost Total NPV

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.

2 6 84 10 12 14 2016 18 22 24 3026 28 32 34 4036 38 42 44 5046 480

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:

PW = Rehab Cost / (1+i)n

Where i = discount rate n = year rehab takes place

Present Worth Analysis (PW) Equivalent Uniform Annual Cost

Analysis (EUAC)

How it is done:

Life-Cycle Cost Analysis

Present Worth Analysis: Discounts all future costs (benefits) to the present

Co

sts

Initial Cost

Rehabilitation CostMaintenance

Cost

Salvage Value

Years

Co

sts

Present Worth

Years

Life-Cycle Cost Analysis

Economic Factors– Discount rate

– Analysis Period

Engineering Factors– Comparable sections

– Rehabilitation selection

– Agency Costs

– User costs

Basic Factors:

Life-Cycle Cost Analysis

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

Analysis Period:

Life-Cycle Cost Analysis

Delay-of-use – Time delays - New construction & Rehabilitation– Fuel consumption

– Driver discomfort

Roadway deterioration– Cargo damage– Vehicle wear

Accidents

User Costs:

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.

Life-Cycle Cost Analysis

Pavement Type SelectionOverview 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– Duration of Construction– Maintenance of Traffic– Maintenance of Access – (utilities & future maint, material sources, reliability of construction)

Design and Environment Factors– Traffic and Geometry– Adjacent Pavement and Structures– Environmental Impact – (community concerns, future planning)

Project Level PTST

Chief Engineer for MDSHA Operations. Chief Engineer for MDSHA Operations. District Engineer of MDSHA District that project District Engineer of MDSHA District that project

resides.resides. Director of Highway Development (OHD) for Director of Highway Development (OHD) for

MDSHA.MDSHA. Director of Materials & Technology (OMT) for Director of Materials & Technology (OMT) for

MDSHA.MDSHA. Pavement Division Chief of 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:– Alabama– Kansas– Kentucky– Louisiana– Maryland– Michigan– Missouri– Ohio– Pennsylvania– West Virginia

Alternate Pavement Bidding Account for Bid Adjustment Method A + B A + B + C 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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