WHAT IS AASHTOWare PAVEMENT ME –

VDOT’s New Pavement Design Software?

Affan Habib, PE

Pavement Program Manager

VDOT Materials Division

October 3, 2017 - Richmond, VA

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Outline

I. Introduction and background of

MEPDG

II. Overview of MEPDG design

process

III. VDOT MEPDG Implementation

Overview

IV. Impact of MEPDG Implementation

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I. INTRODUCTION AND BACKGROUND OF MEPDG

PROCEDURE

What is AASHTOWare

PavementME?

• VODT’s New Pavement Design Software

• From 1/1/2018

• Developed by AASHTO

• Software for a totally different method of pavement

design: MEPDG

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VDOT’s MEDG Implementation

Plan At a Glance

▪ Where does VDOT plan to use MEPDG?

• Interstate and Primary routes.

▪ New alignment, reconstruction, and lane widening

▪ Rehab design: sometime in the future

• Continue to use VDOT’s Secondary & Subdivision

Pavement Design Guide & Procedures on Secondary

& Subdivision streets

▪ Some high volume secondary roads with AADT >

10,000 maybe designed using MEPDG at discretion of

Districts Material Engineer.

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What is Mechanistic Empirical Pavement

Design Guide (MEPDG)?

▪ Design based on measurable performance (e.g.,

rutting, cracking etc.)

▪ Based on Mechanistic-Empirical principles

Mechanistically:It calculates pavement responses(stresses, strains, and

deflections) due to loading and environment and uses those

responses to compute incremental damage overtime.

Empirically:

It relates the cumulative damage to observed pavement

distresses (i.e. IRI, rutting, cracking, faulting, and punchout etc.)6

Why Do We Need a New Pavement

Design Procedures/Software?

▪ Current practice is 1993 AASHTO pavement design guide• Developed between late 50s and late 90s

• Based on AASHO Road test

▪ VDOT adopts 1993 process in early 2000

▪ AASHTO declared sun set on 1993 design software (e.g., Darwin)

▪ 1993 design has lot of limitations (one location, one subgrade, < 2 Million ESALs, and 1950s construction)

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MEPDG Development

• 1993 pavement design method paved the way for MEPDG

▪ Developed based on the LTPP performance data

▪ Across USA and Canada

▪ Various NCHRP studies

▪ Balloted and accepted in 2007

▪ Enhancements ongoing

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▪ Implemented (Asphalt pavement and/or overlays):

14 states

▪ Planning to implement (Asphalt pavement and/or

overlays): 31 states

9Source: MEPDG National User Group

Meeting , December 2016

How many states are adopting

MEPDG?

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II. OVERVIEW OF MEPDG DESIGN PROCESS

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MEPDG Design Process

Climate

Traffic

Layer Properties

Stress,

Strain, or

DeflectionTRANSFER

FUNCTION

Materials

Distress

Performance Threshold

Adjustment

▪ Minimizes the limitations of the 1993 process

▪ Improved handling of climatic effects and traffic

loadings

▪ Various hierarchical Input Levels

▪ Depending on availability and importance

▪ Relating between design and performance

▪ Ability to calibrate and set threshold limits to local

conditions

▪ It is not all about thickness

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Benefits of MEPDG Design

MEPDG: It’s Not All About

Thickness (all the time)

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6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

22.00

24.00

0.00 10.00 20.00 30.00 40.00 50.00 60.00

AC

Th

ickn

ess, In

ch

ESAL, Millions

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▪ Ability to analytically assess impact of specification

changes (ex. Binder content, air void, and gradation).

Other Potential Benefits of

MEPDG

0.1

0.15

0.2

0.25

0.3

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

3.0 4.0 5.0 6.0 7.0 8.0 9.0

Ru

ttin

g in

inch

es

Bo

tto

m-u

p C

rack

ing

(%)

Binder Content by weight (%)

Effect of Binder Content on Bottom-up Cracking and Rutting

Bottom-up Cracking

Rutting

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Other Potential Benefits of

MEPDG

2

3

4

5

6

7

8

9

4 5 6 7 8 9 10 11 12

Bo

tto

m-u

p C

rack

ing

(%)

Air Void (%)

Effect of Increased Density on Performance

Bottom-up Cracking

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Other Potential Benefits of

MEPDG

Study Average Reduction in Fatigue Life for 1% Air

Void Increase

UC Berkeley (1969) 27.20%

UCB (1996 15.10%

WesTrack (2002) 11.90%

Al (2010) 9.20%

1

2

3

4

5

6

7

8

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Bo

tto

m-u

p C

rack

ing

(%)

Year

Effect of Air Voids to Bottom-Up Cracking

7% Air Void

8% Air Void

III. VDOT MEPDG

IMPLEMENTATION OVERVIEW

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▪ VDOT planned MEPDG implementation in mid 2000

▪ VDOT was one of the 15 lead agencies to implement

MEPDG

▪ Significant works were deemed needed

• Materials, traffic, local calibration, training etc.

▪ Started ‘shadow’ design from 2014

▪ Official implementation date set at January 1, 2018

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VDOT’s MEPDG Implementation

at a Glance

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Develop Inputs

Materials

Traffic

Climate

Training

Staff

Software

Review Models

Local Calibration

Understanding output

Policy

Connect with VDOT business practices

Current status

VDOT’s MEPDG

Implementation Plan/Status

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▪ Objective: “No Surprise”

▪ Technical Working Group (TWG)

• Members (VDOT, VTRC, Industry, FHWA)

• Work on technical issues

(user manual, modelling, and input values)

• Meets once a month to discuss on technical issues

▪ Stakeholder Group

• Consists of VDOT, FHWA, VTRC and Industry

• Periodic updates on progress & timeline

MEPDG Implementation: Extensive

Outreach

▪ VDOT has developed MEPDG User Manual. Available

in VDOT external site for downloading: http://www.virginiadot.org/business/materials-download- docs.asp

▪ VDOT will change the User Manual periodically

▪ Updates on MOI Chapter III and VI were included in

regards to MEPDG

▪ All VDOT specific inputs files are available in VDOT

external site for downloading:http://www.virginiadot.org/business/materials-download-docs.asp

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How Does All These Incorporated

into Practice?

IV. IMPACT OF MEPDG

IMPLEMENTATION

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▪ Different input parameters

▪ Good News - Input parameters were developed and available

for VDOT and external users.

▪ Traffic

▪ No change in data collection

▪ ADT, truck %, growth rate etc.

▪ Subgrade investigation & testing

▪ Some changes in the investigation/reporting

• AASHTO soil classification

• Estimation of Resilient Modulus (RM) from unconfined

compressive strength test

• No CBR – Resilient Modulus correlation to determine (RM)

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What Will MEPDG Change for

Contractors, Consultant & DBer?

▪ Materials input

• Designer does not need to gather additional data (AC, PCC, and

aggregate).

(http://www.virginiadot.org/business/materials-download- docs.asp)

▪ Environmental Input

• Designer does not need to gather additional data.

(http://www.virginiadot.org/business/materials-download- docs.asp)

▪ Personnel Training

▪ Different Software - AASHTOWare Pavement ME version

2.2.6

• $ 5,500 per license/year

• Can be procured through AASHTO

http://www.aashtoware.org/Pavement/Pages/default.aspx24

What Will MEPDG Change for

Contractors, Consultant & DBer?

VDOT’s MEPDG Implementation

Plan At a Glance

▪ Where does VDOT plan to use MEPDG?

• Interstate and Primary routes.

▪ New alignment, reconstruction, and lane widening

▪ Rehab design: sometime in the future

• Continue to use VDOT’s Secondary & Subdivision

Pavement Design Guide & Procedures on Secondary

& Subdivision streets

▪ Some high volume secondary roads with AADT >

10,000 maybe designed using MEPDG at discretion of

Districts Material Engineer.

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Any Questions?

Affan Habib (affan.habib@vdot.virginia.gov)

Thank You