KLK585: Calibration of the AASHTOWare Pavement Design Software for PCC Pavements in Idaho

ITD Research Project 268; Task Order Number UI-17-04

Principal Investigators

• Fouad Bayomy
• Emad Kassem
• Ahmed Muftah

ITD Project Manager

• Michael J. Santi

FHWA Project Advisor

• Kyle Holman

Research Problem Statement

The AASHTOWare Pavement ME Design Software is a comprehensive tool for the analysis and design of new and rehabilitated flexible and rigid pavement structures based on mechanistic-empirical pavement design principles. It is to be noted that the ME Software predicts pavement performance based on nationally calibrated performance models. The national calibration is based on field data from LTPP sections distributed all over the United States. Thus, for successful implementation of the ME design system in Idaho, these models need to be locally calibrated for Idaho conditions. In 2009, ITD initiated major efforts toward the implementation of the new design system (Then known as Mechanistic Empirical Pavement Design Guide, MEPDG). The implementation process started by the ITD research project RP193 in which a comprehensive material, traffic, an climactic database for the flexible pavements was developed. In 2014, Applied Research Associates, ARA), Inc. completed the ITD project RP211A and B where they developed a roadmap for implementing Pavement ME in Idaho (RP211A), and developed a user's guide for the ME software (version 1.1.) A key outcome from the roadmap was the need to develop local calibration factors for Idaho for both flexible and rigid pavements. The calibration process for flexible pavements followed and is currently in progress under ITD project RP235, which is planned to be completed in April 2018. To proceed with the calibration process for rigid pavements, we needed to first develop the PCC material database. It has just been completed under the ITD project RP253 in cooperation with Washington State University (WSU). This task order will utilize the PCC database developed in RP253 to develop the calibration factors for rigid pavement models in the ME software.

Project Objectives

The main objective of this research project is to develop local calibration (adjustment) factors for the performance models in the AASHTOWare Pavement ME Design Software for PCC(rigid) pavements. This is an important step for the full implementation of the new design software for Idaho.

Project Tasks

In order to achieve the project main objective, the following tasks will be conducted:

Task 1: Review the distress prediction models for rigid pavements in the ME Software

The AASHTOWare ME Software includes three main performance models for jointed JPCP (Jointed Plain Concrete Pavements). These are Transverse Slab Cracking, Transverse Joint Faulting and Smoothness (IRI) models. Furthermore the software includes an additional model for CRCP Punchouts. In this task, the team will review PCC performance models in the latest version of the software, and identify the design input parameters required by these models. A summary of the review will be submitted at the end of the tasks 1 and 2 (Deliverable 1).

Task 2: Evaluate the inputs required for the design of new rigid pavement systems

The work in task one will lead to the identification of all required design inputs that need to be evaluated including materials, climate, traffic and pavement types doweled or undoweled. These parameters will be summarized and included in the review report submitted as part of Deliverable #1.

Task 3: Identify LTPP rigid pavement sites for calibration process

As per the local calibration guide and the roadmap developed by ARA, we need to have at least 20 pavement segments to cover the different tiers of the sampling matrix. The matrix variables include type of joints (doweled or undoweled), truck traffic volume, new as well as rehabilitated pavements. In addition, sites need to reflect the type of subgrade sol and base materials. The data required to be collected at these sites shall include as built design conditions, which are expected to be available from the ITD Phase Reports.  Missing data may be completed by drilled cores or from historical files if available. To make sure all climactic regions are represented, the team will try to include as a minimum 2 sites from each geographical area. Full cooperation with state material / district engineers will be essential for this task.

Task 4: Develop a  performance database required for the ME calibration

The key performance data shall be procured from TAMS database as well as video logs that are available at ITD. For LTPP sites, the data can be uploaded from the LTPP Infopave.fhwa.dot.gov website.

Upon the identification of the rigid pavements sections all over the state(Task 3), the team will procure all performance data from TAMS and develop the additional needed information from the Video Logs. The Video Logs will be essential to aid in transferring the descriptive and subjective performance information into performance indicators as defined by the ME software.  For example, the ME software presents the Transverse Slab cracking by percent of cracked slabs. But, TMS provides this information as low, medium, and high severity levels. in this regard, the video logs will be necessary to obtain this type of information.

All the collected information will be tabulated in a performance database (Excel files). This will not only facilitate the calibration process, but will provide a wealth of information that could be used in the future when the calibration process is to be updated as recommended by the AASHTOWare developing team.

Task 5: Run the ME software

At a start, we will run the software using nationally calibrated models, with the assembles database and compare the predicted performance (using the nationally calibrated factors) with Idaho's field measured performance. This will help us assess the precision and bias in the design recommendations of the nationally calibrated performance models, and assess the need for the local calibration.

Task 6: Develop Idaho Calibration Factors

This task will involve running the software for each selected pavement site with many trials. in each trial, the regional calibration factors will be changed to increase precision and minimize the bias between the predicted and the measured performance. This process will be done for all recruited pavement segments and for each distress model. Depending on how many sites we were able to recruit and obtain performance data under Tasks 3 and 4, few sites will be left un-used in the calibration to utilize them for validation. In addition, the team will rely on the LTPP sites in Idaho to validate the calibration process. Other LTPP rigid pavement sites from adjacent states could be also used in the validation process. Depending on the total number of sites with complete data that will be readily available, the team may use the Jackknifing method for validation. the jackknife estimator of a parameter is found by systematically leaving out which observation from a dataset and calculating the estimate and then finding the average of these calculations. Given a sample size of n, the jackknife estimate is found by aggregating the estimates of each n-1 sized sub-sample.

Upon completing the calibration process for the distress models, the process will be repeated for the smoothness (IRI) model. That is because IRI model includes other predicted distress parameters (cracking and faulting). Hence, the distress models must be calibrated first.

Task 7: Develop implementation guidelines and training workshop for ITD engineers

The workshop will be developed in parallel with he preparation of the final report. The workshop is intended to have a hands-in practice for ITD engineers. The workshop document will include a brief guide to enable the use of the software with the developed database and the regional calibration factors.

Task 8: Prepare Final Report

Draft Final Report will be developed and peer reviewed by a technical expert approved by ITD's Project Manager. A copy of the review comments and a summary of changes made to address the peer reviewer's comments will be submitted with the draft. The draft will also be reviewed by report editor prior to initial submission to ITD. The final report addressing ITD/FHWA review comments will be submitted at the conclusion of the project. The report will be consistent with ITD style requirements.

Project Communication Schedule

The research team will prepare the typical monthly progress report in ITD 771 form, regular contact with ITD project oversight committee will occur as needed. Project meetings, as requested by the research team or the technical advisory committee, will be held to update ITD project team on the status. The meetings may also be held via telephone or video conference depending on the scheduling. At least three face-to-face meetings will be scheduled. One at the beginning to kick-off the project. An interim project meeting to be scheduled near end of 2018, and a final meeting to present the final results and project findings prior to the submission of the final report.

Needs and Requirements

Full cooperation with ITD is essential to the success of this project.

• The research team will rely on the recently developed ME-PCC materials database as the main source for the PCC mix properties required for the design inputs. The team will seek the help of the ITD concrete group for any additional and missing data as needed.
• ITD shall provide the research team with access tot he latest version of the ME Software and manual. The software version 2.2 was released in 2016 and it has been in use by ITD. However, version v2.3 has been released recently. The research team will work with the most recent software version as installed and approved by ITD. ITD shall provide performance data for the selected pavement projects for calibration. It is anticipated that performance data would be obtained from TAMS as well as video logs at ITD.

Required Outputs/Deliverables

There are two main outputs that shall be delivered to ITD:

• A Final report that summarizes all project tasks and the results related to the calibration factors, and
• A Training Workshop. A hands-on training will be developed and provided to ITD engineers.

Throughout the project period, there is a set of deliverables that will be delivered to coincide with the project tasks:

Deliverable No. 1

A document summarizing the reviewed ME-PCC performance models that are included in the ME software. This will be submitted at the end of Tasks 1 and 2.

Deliverable No. 2

Identification of pavement sections used for the calibration process. This deliverable will be submitted at the end of Task 3. It shall include all sections identified by ITD as well as other LTPP sections to be used in the calibration process. LTPP sections will be those from Idaho as well as the neighboring states due to the small number of LTPP PCC sections in Idaho.

Deliverable No. 3

Performance database. This document will be developed at the end of Tasks 4 and 5. it shall include all performance data collected wither from the ITD TAMS and Video Logs for Idaho sites or from the LTPP sites.

Deliverable No. 4

Calibration factors. Upon the completion of the software runs (Task 5) and the developing of the local calibration factors (Task 6), the team will submit final calibration factors for the PCC models.

Deliverable No. 5

Training workshop. This workshop will be scheduled with ITD to suit the availability of most ITD engineers who are expected to use the software. As per the time schedule (See Gantt chart), this task is expected to be done around May 2019.

Deliverable No. 6

Final report. The final report will be prepared in accordance to ITD process providing the details of the completed research work with the findings and conclusions.

Implementation

The outcomes of the project will enable ITD engineers to use the AASHTOWare Pavement ME Software to design rigid pavements with conditions calibrated for Idaho. To implement the project outcomes, the team will conduct a training workshop to provide a hands-on training for the ITD engineers. The Project Sponsor, Project Manager, and TAC members will meet with the researchers to discuss study recommendations as part of the report review process. The researchers will assist the ITD Project Sponsor, Project Manager, and Technical Advisory Committee in developing a plan to implement study recommendations as appropriate. The plan will identify the steps needed to implement recommendations requiring action, a schedule for implementation activities, and the individuals responsible for specific implementation steps.

Expected Outcomes/Savings to ITD

Outcomes

• Locally calibrated distress/IRI models specific to Idaho conditions.
• Full implementation of the AASHTOWare Pavement ME Design method in Idaho.
• Training on the use of the latest version of the software with the local calibration factors.

Savings

• This project allows the pavement design engineers to assess pavement distress and design the pavement accordingly. It also ties material and pavement design together. This approach reflects more realistically the performance in the field which shall lead to more effective and optimal design of the pavement structure.
• Implementation of ME design method shall result in significant savings in pavement construction cost due to the expected reduction of pavement thickness when compared to the old conservative AASHTO 1993 design method. The 1993 method has a high factor of safety to account for the uncertainty impeded in the design process and for the lack of knowing the level of performance at any point of the pavement service life.

Monthly Progress Reports (ITD 771) and Task Progress Charts

Project status

Active

Draft report

Due May 2019

Final report

Due July 2019

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