2013 Session: 318

• Global Sensitivity Analysis of Mechanistic-Empirical Pavement Performance Predictions for Flexible Pavements
  Abstract: The new AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG) provides pavement analysis and performance predictions under various feasible design scenarios. The MEPDG performance predictions for the anticipated climatic and traffic conditions will depend on the values of the input parameters that characterize the pavement materials, layers, design features, and condition. This paper focuses on comprehensive global sensitivity analyses (GSA) of flexible pavement performance predictions to MEPDG design inputs under five climatic conditions and three traffic levels. Design inputs evaluated in the analyses include traffic volume, layer thicknesses, material properties, groundwater depth, geometric parameters, and others. Correlations among design inputs were considered where appropriate. The GSA varied all design inputs simultaneously across the entire problem domain for each of the 15 base cases (5 climates x 3 traffic levels). Two response surface modeling (RSM) approaches, multivariate linear regressions (MVLR) and artificial neural networks (ANN or NN), were developed to model the GSA results for evaluation of design input sensitivities across the entire problem domain. The ANN-based RSMs for MEPDG flexible pavement performance predictions not only provide robust and accurate representations of the complex relationships between design inputs and distress outputs but also capture the variation of sensitivities across the problem domain. The design limit normalized sensitivity index (NSI) adopted for this study provides practical interpretation of sensitivity relating a given percentage change in a design input to the corresponding percentage change in predicted distress relative to its design limit value.
  Authors: Schwartz, Charles W.; Li, Rui; Ceylan, Halil; Kim, Sunghwan; Gopalakrishnan, Kasthurirangan
  Authors: Schwartz, Charles W.; Li, Rui; Ceylan, Halil; Kim, Sunghwan; Gopalakrishnan, Kasthurirangan
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 318
  Paper Number: 13-1572
• Local Calibration of MEPDG Distress Models for Flexible Pavements Using Ontario’s Long-Term PMS Data
  Abstract: Local calibration is an important step before a transportation agency adopts the AASHTO mechanistic-empirical pavement design guide (MEPDG). This paper presents the challenges of and findings from the local calibration of flexible pavements in provincial highways under the jurisdiction of the Ministry of Transportation of Ontario (MTO). A calibration database was developed that involved a hierarchical framework of the input parameters required for DARWin-ME (the MEPDG software) and the historical field performance data based on the MTO’s second-generation pavement management system (PMS-2). A calibration-clustering-validation approach was taken for the local calibration. The analysis suggested that whereas the MEPDG provided fairly unbiased prediction of the IRI value, it often over predicted the total rutting. A further clustering analysis based on functional class and geographical zone for the rutting and IRI, respectively, improved the precision of the locally calibrated models.
  Authors: Yuan, Xian-Xun; Jannat, Gulfam; Shehata, Medhat
  Authors: Yuan, Xian-Xun; Jannat, Gulfam; Shehata, Medhat
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 318
  Paper Number: 13-2303
• Mechanistic-Empirical Pavement Design Guide Calibration for Pavement Rehabilitation in Oregon
  Abstract: The performance prediction models within the AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG) were calibrated primarily using design inputs and performance data largely from the national Long-Term Pavement Performance (LTPP) program. Before implementing the MEPDG at the state level, performance (distress) prediction models warrant detailed validation and calibration because of potential differences between national and local conditions. The Oregon Department of Transportation (ODOT) is in the process of implementing the new MEPDG for new pavement sections. However, the vast majority of pavement work conducted by ODOT involves rehabilitation of existing pavements. Hot mix asphalt concrete (AC) overlays are the preferred rehabilitation treatment for both flexible and rigid pavements in Oregon. However, like new work sections, AC overlays are also susceptible to fatigue cracking (alligator cracking and longitudinal cracking), rutting, and thermal cracking. Additional work is therefore needed to calibrate the design process for rehabilitation of existing pavement structures. A detailed comparison of predictive and measured distresses was made using recently MEPDG released software Darwin M-E (version 1.1). It was found that Darwin M-E predictive distresses did not accurately reflect measured distresses, calling for a local calibration of performance prediction models is warranted. While the local calibration of rutting and thermal cracking prediction models is currently underway, alligator (bottom-up) cracking and longitudinal (top-down) cracking models were calibrated. The Microsoft Excel Solver was employed to optimize the calibration coefficients by minimizing the sum of the squared errors (SSR) between the predictive and measured distresses. A comparison was made between the results before and after the calibration to assess the improvement in accuracy of the distress prediction models provided by the local calibration. Both alligator cracking and longitudinal cracking models were improved by local calibration. However, there was a high degree of variability between the predicted and measured distresses, especially for longitudinal cracking, even after the calibration. It is recommended that additional sites, which would contain more detailed inputs (mostly Level 1), be established to be included in the future calibration efforts and thus, improve the accuracy of the prediction models.
  Authors: Rahman, Md Shaidur; Williams, Ronald Christopher; Scholz, Todd
  Authors: Rahman, Md Shaidur; Williams, Ronald Christopher; Scholz, Todd
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 318
  Paper Number: 13-4347
• DARwin-ME Evaluation of Flexible Pavements in Louisiana
  Abstract: This paper presents a recent study on using the DARWin-ME pavement design software to evaluate the performance of typical Louisiana flexible pavement structures as compared to pavement performance data available in the pavement management system. The overall comparison results indicated that the DARWin-ME rutting models over-predicted the total rutting for Louisiana flexible pavements; whereas, both fatigue and smoothness models in DARWin-ME seemed to be adequate for most pavements evaluated. A special optimization approach was used to determine a set of preliminary local calibration factors for DARWin-ME rutting models based on Louisiana conditions. A sensitivity analysis of DARWin-ME was also performed to determine if a small variation in design inputs would significantly affect the design asphalt concrete layer thicknesses. The results revealed that a 20 percent variation among each of primary design inputs could result in a design thickness variation of approximately 1.5 in.
  Authors: Wu, Zhong; Yang, Xiaoming; Zhang, Zhongjie
  Authors: Wu, Zhong; Yang, Xiaoming; Zhang, Zhongjie
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 318
  Paper Number: 13-4516
• Global Sensitivity Analysis of Mechanistic-Empirical Pavement Performance Predictions for Flexible Pavements
  Authors: Li, Rui
  Authors: Li, Rui
  Year: 2013
  Document Type: Presentation
  Subject: Design; Pavements
  Session: 318
  Paper Number: 13-1572
• Local Calibration of MEPDG Distress Models for Flexible Pavements Using Ontario's Long-Term PMS Data
  Authors: Yuan, Xian-Xun
  Authors: Yuan, Xian-Xun
  Year: 2013
  Document Type: Presentation
  Subject: Design; Pavements
  Session: 318
  Paper Number: 13-2303
• Mechanistic-Empirical Pavement Design Guide Calibration for Pavement Rehabilitation in Oregon
  Authors: Rahman, Md
  Authors: Rahman, Md
  Year: 2013
  Document Type: Presentation
  Subject: Design; Pavements
  Session: 318
  Paper Number: 13-4347
• DARwin-ME Evaluation of Flexible Pavements in Louisiana
  Authors: Yang, Xiaoming
  Authors: Yang, Xiaoming
  Year: 2013
  Document Type: Presentation
  Subject: Design; Pavements
  Session: 318
  Paper Number: 13-4516