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Local Calibration of the MEPDG Using Pavement Management Systems

Chapter 6. Final Framework

Introduction

The final framework itemizes specific activities (e.g., links to other data sources, establishing roles and responsibilities) that are needed prior to populating the MEPDG calibration database. The following summarizes the data and process for finalizing the framework for integrating state pavement management data for calibration of the MEPDG. The majority of the MEPDG input data were extracted from the NCDOT pavement management system. Input data associated with materials and traffic was acquired from other NCDOT files and/or databases.

NCDOT is interested in calibrating the MEPDG to Level 2 only. There are several reasons for this. Typically, NCDOT pavement designs occur one to two years prior to letting and the ability to obtain material specific data is not a reality until the project has been awarded. In addition, NCDOT is unable to justify the expense for collecting data according to Level 1 standards; data collection to Level 2 inputs is more justifiable and realistic at this time.

The NCDOT highway network is comprised of primarily HMA pavements, with a lower percentage of PCC pavements. The NCDOT PMS contains sufficient pavement sections, construction history, and performance data for the HMA pavements that no major issues are anticipated for calibrating the MEPDG. For PCC pavements (of which NCDOT only constructs JPCP), the quality and existence of construction and performance data is similar to that of HMA pavements; however, the number of PCC pavement sections and the length of in-service life is considerably less. At a minimum, the framework will provide NCDOT with the step-by-step calibration process as additional pavement history is obtained on PCC pavements.

As a first step, data contained in the NCDOT pavement management system was identified (table 23 through table 31) for applicability with the preliminary framework. In addition, where appropriate, MEPDG default values were established (e.g. analysis parameters, surface shortwave absorptivity, coefficient of thermal expansion).

Table 23. Project summary information.
Description Variable HMA PCC
Design properties Project name and description PMS1 PMS1
Design life (years)2 20 30
Base/subgrade construction (date)3 Assumed Assumed
Restoration/overlay
Existing pavement construction (date) PMS1 PMS1
Pavement restoration/overlay (date) PMS1 PMS1
Traffic opening (date) PMS1 PMS1
Site/project identification Location PMS1 PMS1
Project ID PMS1 PMS1
Section ID PMS1 PMS1
Stationing (format, beginning and end)4 PMS1 PMS1
Traffic direction PMS1 PMS1
Analysis parameters6 Initial IRI (in/mi) 60 75
Terminal IRI (in/mi) 170 170
AC surface down cracking (ft/mi)5 n/a n/a
AC bottom up cracking (%)5 10 n/a
AC thermal fracture (ft/mi)6 n/a n/a
Chemically stabilized layer fatigue fracture (%)7 n/a n/a
Permanent deformation – total (in)8 n/a n/a
Permanent deformation – AC only (in)8 ¾ n/a
Transverse cracking (% slabs cracked)9 n/a 10
Mean joint faulting (in) n/a ¾

1Data contained within the NCDOT PMS.
2 Based on current NCDOT pavement design practice.
3
Data is typically not collected and will be assumed to be equivalent to the opening to traffic date.
4
NCDOT PMS uses a referencing system based on milepost. Latitudes and longitudes will also be determined for each project for locating weather and soils data.
5
NCDOT does not distinguish between surface down (longitudinal) and bottom up (alligator) cracking. Distress is collected by NCDOT as alligator cracking.
6 Distress not present on NCDOT highways.
7 Distress not collected by NCDOT.
8 Based on NCDOT pavement investigations’, rutting is almost exclusively confined to the top or second lift of the HMA surface. Therefore, total pavement rutting will default to the rut depth of the HMA surfaces.
9
NCDOT does not distinguish between various forms of PCCP cracking.

Table 24. Traffic data.
Description Variable Data Location
Design properties Initial two-way AADTT PMS1/ , Project Plans
Number lanes in design direction PMS1
Trucks in the design direction (%) Project Plans
Trucks in the design lane (%)2 Project Plans, Variable
Operational speed DOT Universe/, Project Plans, PMS1
Traffic volume adjustment factors Monthly adjustment factors Traffic3
Vehicle class distribution (%) Traffic3
Truck hourly distribution factors (%) Traffic3
Traffic growth factors (%) Traffic3
Axle load distribution factors Axle load distribution factors by axle type Traffic3
General traffic inputs Mean wheel location (inches from lane marking) Default4
Traffic wander standard deviation (in) Default4
Design lane width (in) Default4
Number axles per truck class Default4
Axle configuration Default4
Axle width (ft) Default4
Dual tire spacing (in) Default4
Tire pressure (psi) Default4
Axle spacing (ft) Default4
Wheel base distribution Default4

1Data contained within the NCDOT PMS.
2Based on current AASHTO lane distribution factors.
3Data contained within the NCDOT Traffic database.
4MEPDG default values (level 3, where applicable).

Table 25. Existing pavement structure.
Description Variable Data Location HMA PCC New Overlay New Overlay
Structure properties Layer type PMS1 PMS1 PMS1 PMS1
Layer material PMS1 PMS1 PMS1 PMS1
Layer thickness (in) PMS1 PMS1 PMS1 PMS1
Milled thickness (in) n/a PMS1 n/a PMS1
Pavement rating2 n/a PMS1 n/a PMS1
Total rutting (in) n/a PMS1 n/a PMS1
Surface short-wave absorptivity3 Default Default Default Default

1Data contained within the NCDOT PMS.
2NCDOT PMS rating based on a scale of 0 – 100; the MEPDG condition categories, ranging from very poor to excellent, will be defined in increments of 20 points.
3MEPDG default values (Aged PCC: 0.70-0.90; weathered asphalt: 0.80-0.90; new asphalt: 0.90-0.98).

Table 26. HMA layer characterization.
Description Variable Data Location
New Overlay1
Design properties HMA E* predictive model MATS2 MATS2
HMA rutting model coefficients MATS2 MATS2
Fatigue analysis endurance limit MATS2 MATS2
Include reflective cracking in analysis n/a MATS2
Mix properties Aggregate gradation (% retained, % passing) MATS2 MATS2
Asphalt binder type MATS2 MATS2
Asphalt binder grade MATS2 MATS2
General properties Reference temperature (oF) MATS2 MATS2
Effective binder content (%) MATS2 MATS2
Air voids (%) MATS2 MATS2
Total unit weight (pcf) MATS2 MATS2
Poisson's ratio MATS2 MATS2
Thermal properties Thermal conductivity (BTU/hr ft oF) MATS2 MATS2
Heat capacity (BTU/lf oF) MATS2 MATS2
Thermal cracking Average tensile strength at 14oF (psi) MATS2 MATS2
Creep compliance (1/psi) MATS2 MATS2
Coefficient of thermal contraction (in/in/oF) MATS2,
Project files
MATS2,
Project files
Rehabilitation (HMA overlay of PCC)3 Poisson’s ratio of PCC n/a n/a
Elastic resilient modulus of fractured slab n/a n/a
Type of slab fracture n/a n/a
Thermal conductivity of PCC slab n/a n/a
Heat capacity of PCC slab n/a n/a
Slabs with transverse crack before restoration (%) n/a n/a
Repaired slabs after restoration (%) n/a n/a
Dynamic modulus of subgrade reaction (psi/in) n/a n/a
Month measured n/a n/a

1HMA overlays include: overlays of HMA, JPCP, and fractured JPCP.

2Data contained within the materials database developed by North Carolina State University.

3Due to incomplete data contained within the NCDOT PMS, this rehabilitation treatment will not be included in the calibration process.

Table 27. PCC layer properties
Description Variable JPCP
New Overlay
Design properties Permanent curl/warp effective temperature difference (oF) Default1 Default1
Joint spacing (ft) 15 15
Sealant type Silicone Silicone
Dowel diameter (in) CD2 CD2
Dowel bar spacing (in) 12 12
Edge support - tied PCC (% LTE)3 n/a n/a
Edge support - widened slab (ft)4 n/a n/a
PCC-base interface Full Full
Base erodibility index Resistant Resistant
Loss of full friction (age in months) 360 360
General properties Layer thickness (in) PMS5 PMS5
Unit weight (pcf) 150 150
Poisson's ratio 0.20 0.20
Thermal properties Coefficient of thermal expansion (per oFx10-6) Project
Files
Project
Files
Thermal conductivity (BTU/hr ft oF) MATS6 MATS6
Heat capacity (BTU/lf oF) MATS6 MATS6
Mix properties Cement type Type II Type II
Cementitious material content (lb/yd3) 526 526
Water/cement ratio 0.559 0.559
Aggregate type ? ?
PCC zero-stress temperature 1
Default
Default1
Ultimate shrinkage at 40% R.H. (microstrain) Default1 Default1
Reversible shrinkage (% of ultimate shrinkage) Default1 Default1
Time to develop 50% of ultimate shrinkage Default1 Default1
Curing method Compound Compound
Strength properties7 28-day Elastic modulus (psi) n/a n/a
28-day Modulus of rupture (psi) n/a n/a
Compressive strength (psi) 4500 4500
Splitting tensile strength (psi) n/a n/a
Rehabilitation8 Slabs with transverse cracks before restoration (%)3 n/a n/a
Repaired slabs after restoration (%) n/a n/a
Dynamic modulus of subgrade reaction (psi/in) n/a n/a
Month measured n/a n/a

1MEPDG default values.
2 Dowel bar diameter varies with pavement thickness, use construction drawings for selecting dowel bar diameter.
3NCDOT does not use tied shoulders.
4NCDOT does not use a widened slab.
5Data contained within NCDOT PMS.
6 Data contained within the materials database developed by North Carolina State University.
7 Only one strength property is required.
8 Due to the relatively young age of NCDOT PCC pavements, rehabilitation has not been conducted and will not be included in the calibration process.

Table 28. Stabilized layer inputs.
Description Variable Data Location
General properties Material type (cement and lime alternatives) PMS1, Project Files
Layer thickness (in) PMS1
Unit weight (pcf) MATS2
Poisson's ratio MATS2
Strength properties Elastic/resilient modulus (psi) MATS2
Minimum elastic/resilient modulus (psi) MATS2
Modulus of rupture (psi) MATS2
Thermal properties Thermal conductivity (BTU/hr ft oF) MATS2
Heat capacity (BTU/lf oF) MATS2 ,
Project Files

1Data contained within NCDOT PMS.
2 Data contained within the materials database developed by North Carolina State University.

Table 29. Unbound layer inputs.
Description Variable Data Location
General propertiesMaterial type MATS1
Layer thickness (in) MATS1
Poisson's ratio MATS1
Coefficient of lateral pressure MATS1
Strength properties2Modulus (psi) MATS1
CBR MATS1
R-value MATS1
Layer coefficient (ai) MATS1
Penetration DCP MATS1
Plasticity index and gradation MATS1
ICM propertiesGradation (% passing) MATS1
Plasticity index MATS1
Liquid limit MATS1
Compacted layer (Yes/No) Yes

1 Data contained within the materials database developed by North Carolina State University.
2 Only one strength property is required.

Table 30. Bedrock layer inputs.
Description Variable Data Location
General propertiesMaterial type MATS1
Layer thickness (in) MATS1
Unit weight (pcf) MATS1
Poisson's ratio MATS1
Resilient modulus (psi) MATS1

1 Data contained within the materials database developed by North Carolina State University.

The key pavement performance indicators, and source of NCDOT data, used by the MEPDG for HMA and PCC are summarized in table 31 and 32, respectively.

Table 31. HMA pavement performance indicators.
Description MEPDG Variable Data Location Comment
Performance IndicatorIRI (in/mi) PMS Collected and summarized in 0.1 mile increments.
Surface down cracking (ft/mi) PMS Collected as alligator cracking in accordance with severity level (light, moderate, and severe) and as a percentage of roadway area – conversion to feet of cracking per mile will be necessary.
Bottom up cracking (%) PMS Distress not specifically collected by NCDOT.
Thermal fracture (ft/mi) -- Distress generally not present on NCDOT highways.
Chemically stabilized layer fatigue fracture (%) PMS Distress not collected by NCDOT.
Permanent deformation -total pavement (in) -- Based on NCDOT pavement investigations’, rutting is almost exclusively confined to the top or second lift of the HMA surface. Therefore, total pavement rutting will default to the rut depth of the HMA surfaces.
Permanent deformation -AC layers only (in) PMS Collected with three point laser and summarized on 0.1 mile increments.
Table 32. PCC pavement performance indicators.
Description MEPDG Variable Data Location Comment
Performance IndicatorTerminal IRI (in/mi) PMS
Transverse cracking (% slabs cracked) PMS Cracking (all types) is collected according to severity level (light, moderate, and severe). Calculation as a percent of slabs will be necessary.
Mean joint faulting (in) PMS

Integration of Input Data into the MEPDG Calibration Database

The following work was conducted by NCDOT Pavement Management staff and the APTech project team to integrate the NCDOT PMS and other database(s) information into the MEPDG calibration database:

  • Customize the relational MEPDG calibration database to meet the data definition (e.g. integer, decimal) format of NCDOT data fields;
  • Provide step-by-step details for integrating MEPDG input data into the MEPDG calibration database which is not currently contained within the PMS (e.g. traffic, materials)
  • Document the process for collecting data to populate the MEPDG calibration database for at least one pavement section. The allowed NCDOT and the research team the ability to evaluate and ensure that proper definitions were being used for all input values, to determine if there was any missing or needed data, and to provide insight for integration of the larger data set.
  • Populate the MEPDG calibration database with all intended NCDOT pavement sections.

Summary

This section documented the implementation of the final framework using data contained within a single state highway agency. This demonstration showed that the majority of the data can be obtained from a pavement management system; however, some of the needed input data, such as material properties and construction data will require an interface with other data sources. The importance of having a common referencing system also became evident during this activity. A common referencing system becomes important when data is being retrieved from specific project locations amongst the various data sources. Additionally, the availability of a database to store the information that would be used for calibration proved beneficial.

More Information

Contact

Nastaran Saadatmand
Office of Asset Management, Pavements, and Construction
202-366-1337
E-mail Nastaran

 
 
Updated: 10/12/2011
 

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