2013 Session: 242

• Framework for Determination of Load Equivalencies Using DARWin-ME
  Abstract: This paper presents a methodology for determination of load equivalencies for different axle configurations and loads using mechanistic-empirical design procedures. The focus was on oversize/overweight (OS/OW) vehicles. The study uses the DARWin-ME system for pavement analysis and computation of Equivalent Damage Factors (EDF). In the context of this study, the EDF for a given axle load and configuration consists of two partial factors: Axle Load Factor (ALF) and Group Equivalency Factor (GEF). The framework adopted in this study defines a given axle load and configuration as equivalent to a reference axle load, as based on equivalent pavement responses that result in the same distress level. The study uses a modular approach to determine the EDF for different vehicle configurations. The load equivalency for a given truck configuration is equal to the sum of the EDF of its constituent axles. To that effect, the EDFs for single, tandem, tridem, and quad axles were evaluated over a wide spectrum of varying loads using three different failure criteria: rutting, fatigue cracking, and roughness. This approach provided the basis for developing the models for predicting the EDF of any given axle configuration for any given load.With the exception of rutting, the research yielded no strong evidence suggesting that the EDFs are affected by the structural capacity of the pavement sections. For single axles, however, the structural capacity had an inverse relationship with the EDFs, which suggests that thicker pavement structures are less sensitive to traffic loads. In the case of tandem, tridem, and quad axles, the relationship was non-monotonic, with the EDFs reaching their peak for structural numbers between 3.5 and 4.0. In the case of fatigue cracking, even though the structural number did not clearly influence the EDFs, a linear relationship exists between the ALF and the number of axles per axle group. Finally, in the case of roughness, the EDFs did not show any systematic trend for different structural numbers, which led the researchers to propose an average ALF that is independent of the axle group or the structural capacity of the pavement section.
  Authors: Banerjee, Ambarish; Prozzi, Jorge A.; Buddhavarapu, Prasad N. V. S. R.
  Authors: Banerjee, Ambarish; Prozzi, Jorge A.; Buddhavarapu, Prasad N. V. S. R.
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 242
  Paper Number: 13-1770
• Calibration of Traffic Distributions and Model Coefficients Within MEPDG for Local Energy-Affected Roads in Wyoming
  Abstract: The Mechanistic-Empirical Pavement Design guide was developed in 2004 under NCHRP Project 1-37B. Since this time, considerable efforts to calibrate the program and its performance prediction models for local conditions have taken place in multiple states attempting to implement the program. Currently, Wyoming DOT is in the process of implementing the MEPDG on the interstate and the state highway systems. In order to compliment that effort, this study attempted to develop a set of calibration coefficients and localized inputs that can be used on local paved roads. Wyoming is an energy rich state and has seen an increase in the amount of heavy truck traffic that its roadways encounter, thus requiring calibrated inputs for the MEPDG. Predicted distresses using the MEPDG were largely different from measured distresses on local paved roadways included in the study, particularly alligator cracking, rutting, transverse cracking, and longitudinal cracking. These distresses were measured on the local paved roads using Pathway Services Inc. and the surface imaging that it provided. Inputs for trial runs using the MEPDG were determined through work with local county road maintenance superintendents as well as previous research regarding climatic data in Wyoming. Localized traffic inputs were developed using Weigh-In Motion (WIM) data collected on non-interstate roadways across Wyoming. Once a significant error was found between predicted and measured distresses, calibration coefficients for alligator cracking, rutting, and longitudinal cracking were altered to reduce bias. The final calibration coefficients settled on in this study reduced the error between predicted measured distresses by nearly one hundred percent for the three calibrated models. The process followed in this study can be utilized by other local governments around the country to help them implement the MEPDG.
  Authors: Kasperick, Taylor; Ksaibati, Khaled
  Authors: Kasperick, Taylor; Ksaibati, Khaled
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 242
  Paper Number: 13-3866
• Assessment of Reliability and Load Factor Design Approach Against Fatigue Cracking in Flexible Pavements
  Abstract: A reliability based approach to design flexible pavements against bottom-up and top-down fatigue cracking has been developed. The approach involves the use of load factors applied to the nominal fatigue cracking values to obtain the failure values in field. The uncertainty in input parameters has been modeled via Weibull and Lognormal distribution of the damage index with different values of skewness and coefficient of variation. The field data from Long Term Pavement Performance database have been used to model the uncertainty in prediction between the nominal (predicted) and the field cracking. The probability density function of fatigue cracking was found to be unsymmetrical in nature; the skewness of the distribution changes with the level of damage. The nonlinear limit state performance function has been used to determine the reliabilities and the load factors using Monte Carlo simulation. The differences between the failure values obtained from the standard Gaussian assumption and the simulation have been observed. Design charts and load factor tables have been developed which can be used with the newly developed Mechanistic Empirical Pavement Design Guide for designing new and rehabilitated pavements. Finally, the use of the load factors in flexible pavement design has been presented via practical examples.
  Authors: Bhattacharjee, Sudip
  Authors: Bhattacharjee, Sudip
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 242
  Paper Number: 13-4632
• Combined Effect of Three-dimensional Tire-Pavement Contact Load and Thermal Load on Cracking Performance of Heavy-Duty Asphalt Pavements
  Abstract: Top-down cracking (TDC) has been well recognized as a major distress for the heavy duty asphalt pavements yet the mechanism is still not fully understood. Studies indicated the non-uniform tire-pavement contact stress might play a significant role in the initiation of TDC, and thermal stress due to temperature gradient might contribute to the initiation and development of TDC. For this concern, a sophisticated three-dimensional (3-D) viscoelastic finite element model was developed to study cracking performance of heavy duty flexible pavements under combined 3-D tire-pavement contact stress and thermal stress induced by temperature gradient. It was found the stress distribution in asphalt concrete (AC) layer is continuously changing as the pavement is loaded due to rheological behavior of AC. Significant maximum principal tensile stresses are presented at the edge of tire at AC surface, which may result in an accumulation of dissipated creep strain energy (DCSE) over time (or with number of loads) and may eventually lead to the initiation of a crack. And pavement near-surface responses associated with top-down cracking under 3-D contact pressure is more severe as compared to uniform contact pressure. Comparing with pavements without thermal effect, the negative temperature gradient increases the potential for top-down cracking while the positive temperature gradient increases the potential for bottom-up cracking. The study may provide some meaningful insight into crack mechanisms and help improve current heavy duty asphalt pavement design procedures for cracks.Key words: Viscoelastic; 3-D; TDC; Temperature; Contact Stress; Pavement.
  Authors: Wang, Guangming; Morian, Dennis A.; Frith, Douglas
  Authors: Wang, Guangming; Morian, Dennis A.; Frith, Douglas
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 242
  Paper Number: 13-4699
• Comparing MEPDG Distress Predictions with Automated and Manual Interpretations
  Abstract: The Mechanistic-Empirical Pavement Design Guide (MEPDG) software was designed on a nationally calibrated basis, thus calibrating the existing parameters to suit local conditions is necessary for accurate distress predictions. The process of calibration involves iterating distress model coefficients until the predicted results match a desired outcome. This desired outcome is typically associated with monitored pavement distress results, documented through manual methods and stored in pavement management systems. However, the calibration process can be very time consuming, thus sufficient automated methods of data collection are desirable. The cracking protocol used by MEPDG is consistent with the cracking definitions provided by the Long Term Pavement Performance (LTPP) program. Due to the difficulties involved with the development of cracking recognition algorithms for automated distress survey software, many have made attempts to promote alternative cracking protocols that are more suitable for automated technologies. Significant efforts for the enhancement of the MEPDG software have also been taking place, thus recent research has been pulled in two directions. This paper portrays the implementation of a post-processing tool used to modify the cracking interpretations of an existing surveying software called the Automated Distress Analyzer (ADA). This tool incorporates wheelpath boundaries in order to establish a means of defining cracks in regards to LTPP. The results indicated that the automated post-processing tool has the ability to replicate nationally-calibrated MEPDG distress predictions better than a surveying method involving human intervention as well as ADA by itself.
  Authors: Byram, Daniel; Xiao, Danny X.; Wang, Kelvin C. P.; Hall, Kevin D.; Li, Qiang
  Authors: Byram, Daniel; Xiao, Danny X.; Wang, Kelvin C. P.; Hall, Kevin D.; Li, Qiang
  Year: 2013
  Document Type: Paper
  Subject: Design; Pavements
  Session: 242
  Paper Number: 13-5260
• Framework for Determination of Load Equivalencies Using DARWin-ME
  Authors: Banerjee, Ambarish
  Authors: Banerjee, Ambarish
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Design; Pavements
  Session: 242
  Paper Number: 13-1770
• Calibration of Traffic Distributions and Model Coefficients Within MEPDG for Local Energy-Affected Roads in Wyoming
  Authors: Ksaibati, Khaled
  Authors: Ksaibati, Khaled
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Design; Pavements
  Session: 242
  Paper Number: 13-3866
• Assessment of Reliability and Load Factor Design Approach Against Fatigue Cracking in Flexible Pavements
  Authors: Bhattacharjee, Sudip
  Authors: Bhattacharjee, Sudip
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Design; Pavements
  Session: 242
  Paper Number: 13-4632
• Comparing MEPDG Distress Predictions with Automated and Manual Interpretations
  Authors: Li, Qiang
  Keywords: poster presentation; poster design; poster template
  Authors: Li, Qiang
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Design; Pavements
  Session: 242
  Paper Number: 13-5260