Incorporation of Endurance Limit in the Mechanistic-Empirical Flexible Perpetual Pavement Design

2018 ◽  
Vol 2672 (40) ◽  
pp. 108-121 ◽  
Author(s):  
Sheng Hu ◽  
Sang-Ick Lee ◽  
Lubinda F. Walubita ◽  
Fujie Zhou ◽  
Tom Scullion
Keyword(s):  
Endurance Limit ◽  
Design Method ◽  
Field Performance ◽  
Fatigue Cracking ◽  
Climatic Conditions ◽  
Influential Factors ◽  
Pavement Design ◽  
Design System ◽  
Viscoelastic Continuum Damage ◽  
Perpetual Pavement

In recent years, there has been a push toward designing long-lasting thick hot mix asphalt (HMA) pavements, commonly referred to as a perpetual pavements (PP). For these pavements, it is expected that bottom-up fatigue cracking does not occur if the strain level is below a certain limit that is called the HMA fatigue endurance limit (EL). This paper proposed a mechanistic-empirical PP design method based on this EL concept. The ELs of 12 HMA mixtures were determined using simplified viscoelastic continuum damage testing and the influential factors were comparatively investigated. It was found that HMA mixtures seem to have different EL values based on mix type and test temperatures. There is not just a single EL value that can be used for all mixtures. Thus, default EL criteria for different mixtures under different climatic conditions were developed and incorporated into the Texas Mechanistic-Empirical Flexible Pavement Design System (TxME). As a demonstration and case study, one Texas PP test section with weigh-in-motion traffic data was simulated by TxME. The corresponding TxME inputs/outputs in terms of the PP structure, material properties, traffic loading, environmental conditions, and ELs were demonstrated. The corresponding TxME modeling results were consistent with the actual observed field performance of the in-service PP section.

Study on Flexible Base Asphalt Pavement Design System Based on the Dynamic Modulus

2013 ◽  
Vol 788 ◽  
pp. 619-622
Author(s):  
Li Yin
Keyword(s):  
Mechanical Properties ◽  
Dynamic Modulus ◽  
Design Method ◽  
Asphalt Pavement ◽  
Asphalt Mixture ◽  
Pavement Design ◽  
Pavement Performance ◽  
Design System ◽  
Determination Method ◽  
Flexible Base

Pavement design adopts the static index pavement design method; it has significant limitations for flexible asphalt pavement. This paper proposes asphalt mixture dynamic modulus determination method on the basis of existing research results at home and abroad. Dynamic modulus effect is studied on the mechanical properties of flexible base asphalt pavement, and the flexible base asphalt pavement performance is preestimated by the use of the dynamic modulus indicators in the paper.

Field Calibration of Fatigue Models of Cementitiously Stabilized Pavement Materials for Use in the Mechanistic-Empirical Pavement Design Guide

2019 ◽  
Vol 2673 (2) ◽  
pp. 427-435
Author(s):  
Xiaojun Li ◽  
Jingan Wang ◽  
Haifang Wen ◽  
Balasingam Muhunthan
Keyword(s):  
Field Performance ◽  
Fatigue Cracking ◽  
Pavement Design ◽  
Fatigue Properties ◽  
Bottom Up ◽  
Freeze Thaw ◽  
State Highway ◽  
Design Guide ◽  
Fatigue Model ◽  
Pavement Structures

The use of cementitiously stabilized materials (CSM), such as lean concrete, cement-stabilized aggregate, and soil stabilized with cement, lime, fly ash, or combinations thereof in the subgrade, sub-base, and base layers of flexible and rigid pavement structures, is a widely accepted practice by many state highway agencies. However, the bottom-up fatigue cracking models of cementitiously stabilized layers (CSL) described in the AASHTO Interim Mechanistic-Empirical Pavement Design Guide Manual of Practice (referred to as the MEPDG) have not been calibrated for CSM based on their field performance. In addition, top-compression fatigue as well as the effects of increases in the modulus and strength values of CSM over time, erosion, and freeze–thaw and wet–dry cycles on the fatigue properties of CSM are not considered in the MPEDG. To address these deficiencies, this research calibrated the bottom-up fatigue model, and developed and calibrated the top-compression fatigue model, with consideration of modulus and strength growth, erosion, and freeze–thaw and wet–dry cycles. Reasonable correlations between the predicted modulus values and measured modulus values are found for CSL. Further study is needed to refine the calibration and validate the models based on a larger population of field data that covers different material types, climatic zones, and traffic conditions.

Further Evaluation of Limiting Strain Criteria for Perpetual Asphalt Pavement Design

2017 ◽  
Vol 2640 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Alfredo J. Castro ◽  
Nam Tran ◽  
Mary Robbins ◽  
David H. Timm ◽  
Chris Wagner
Keyword(s):  
Asphalt Concrete ◽  
Asphalt Pavement ◽  
Fatigue Cracking ◽  
Pavement Design ◽  
Threshold Values ◽  
Bottom Up ◽  
Test Track ◽  
Climatic Regions ◽  
Concrete Layer ◽  
Perpetual Pavement

Perpetual asphalt pavements have been designed with single threshold values for the horizontal strains at the bottom of the asphalt concrete layer and for vertical strains on top of the subgrade to prevent the occurrence of bottom-up fatigue cracking and subgrade rutting. Several thresholds have been utilized for design based on laboratory and field test results. Limiting strain distributions were recently proposed for perpetual pavement design instead of single threshold values for controlling the horizontal and vertical strains. These design criteria were developed with data collected from test sections at the National Center for Asphalt Technology pavement test track. The objective of this study was to conduct additional analyses of eight perpetual pavement sections located in different climatic regions, to support the proposed limiting strain criteria. These sections were simulated in the PerRoad perpetual pavement design software to determine the horizontal strains at the bottom of the asphalt concrete layer and the vertical strains on top of the subgrade. The strains were then analyzed to evaluate the proposed limiting strain criteria. Based on the simulations, the limiting horizontal strain distribution above the 60th percentile can effectively differentiate the calculated strain distributions of the eight perpetual pavement sections from those of the test sections that failed due to bottom-up fatigue cracking on the test track. In addition, the calculated vertical strains on top of the subgrade at the 50th percentile were lower than the proposed 200-microstrain limit. These results provide additional support for utilizing the proposed strain criteria in perpetual asphalt pavement design.

scholarly journals Local calibration of cracking models of MEPDG for Ontario's flexible pavement

2021 ◽  
Author(s):  
Chowdhury Jannatul Sifat E Ahmed
Keyword(s):  
Design Method ◽  
Fatigue Cracking ◽  
Thermal Cracking ◽  
Pavement Design ◽  
Local Calibration ◽  
Local Conditions ◽  
Significant Difference ◽  
Design Guide ◽  
And Performance ◽  
Engineering Practices

The AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG) introduces a pavement design method which uses both the mechanistic analyses and empirical models to predict pavement distresses and performance, which needs to be calibrated to local conditions and engineering practices based on local pavement performance data. This thesis focuses on the local calibration of fatigue (both bottom-up and top-down) and thermal cracking models in MEPDG for superpave flexible pavements on Ontario’s highways. Simulations were run in the software, after developing a calibration database of Ontario’s provincial highway and the predicted data is compared to the observed data. Significant difference is found in the comparisons which need to be minimized by calibrating the distress models. A new regression model is used to optimize the calibration parameters by minimizing the standard deviations of the residuals between the predicted and observed distresses. The challenges encountered and concluding remarks developed during the local calibration process are discussed. Keywords: Local Calibration, Mechanistic Empirical Pavement Design Guide (MEPDG), Cracking Models, Fatigue Cracking, Thermal Cracking, superpave

scholarly journals Local calibration of cracking models of MEPDG for Ontario's flexible pavement

2021 ◽  
Author(s):  
Chowdhury Jannatul Sifat E Ahmed
Keyword(s):  
Design Method ◽  
Fatigue Cracking ◽  
Thermal Cracking ◽  
Pavement Design ◽  
Local Calibration ◽  
Local Conditions ◽  
Significant Difference ◽  
Design Guide ◽  
And Performance ◽  
Engineering Practices

The AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG) introduces a pavement design method which uses both the mechanistic analyses and empirical models to predict pavement distresses and performance, which needs to be calibrated to local conditions and engineering practices based on local pavement performance data. This thesis focuses on the local calibration of fatigue (both bottom-up and top-down) and thermal cracking models in MEPDG for superpave flexible pavements on Ontario’s highways. Simulations were run in the software, after developing a calibration database of Ontario’s provincial highway and the predicted data is compared to the observed data. Significant difference is found in the comparisons which need to be minimized by calibrating the distress models. A new regression model is used to optimize the calibration parameters by minimizing the standard deviations of the residuals between the predicted and observed distresses. The challenges encountered and concluding remarks developed during the local calibration process are discussed. Keywords: Local Calibration, Mechanistic Empirical Pavement Design Guide (MEPDG), Cracking Models, Fatigue Cracking, Thermal Cracking, superpave

scholarly journals A Simplified Mechanistic-Empirical Flexible Pavement Design Method for Moderate to Hot Climate Regions

2021 ◽  
Vol 13 (19) ◽  
pp. 10760
Author(s):  
Ahmed S. El-Ashwah ◽  
Sherif M. El-Badawy ◽  
Alaa R. Gabr
Keyword(s):  
Prediction Accuracy ◽  
Transfer Functions ◽  
Design Method ◽  
Fatigue Cracking ◽  
Flexible Pavement ◽  
Pavement Design ◽  
Pavement Performance ◽  
Climatic Data ◽  
Pavement Structure ◽  
National Cooperative

Flexible pavement structure design is a complex task because of the variability of design input parameters and complex failure mechanisms. Therefore, the aim of this study is to develop and implement a simplified Mechanistic-Empirical (M-E) pavement design method based on the 1993 American Association of State Highway and Transportation Officials (AASHTO), the National Cooperative Highway Research Program (NCHRP) 9-22, and NCHRP 1-37A and 1-40D projects. This simplified methodology is implemented into a computer code and a user-friendly software called “ME-PAVE”. In this methodology, only two equivalent temperatures, as per the NCHRP 9-22 project, are estimated to adjust the dynamic modulus of the asphalt layer(s) for Asphalt Concrete (AC) rutting and AC fatigue cracking prediction instead of using the hourly climatic data, as in the AASHTOWare Pavement ME. In ME-PAVE, the structural responses at critical locations in the pavement structure are determined by a Finite Element Module (FEM), which is verified by a Multi-layer Elastic Analysis (MLEA) program. To ensure that the simplified methodology is practical and accurate, the incorporated transfer functions in the proposed simplified methodology are calibrated based on the Long-Term Pavement Performance (LTPP) data. Based on statistical analyses, the built-in FEM results exhibit very similar trends to those yielded by MLEA, with a coefficient of determination, R2 of 1.0. For all practical purposes, the proposed methodology, despite all simplifications, yields acceptable prediction accuracy with R2 of 0.317 for the rut depth compared to the current practices, NCHRP 1-37A and 1-40D (R2 = 0.399 and 0.577, respectively); while the prediction accuracy for fatigue cracking with R2 of 0.382 is comparable to the NCHRP 1-40D with R2 of 0.275. Nonetheless, the standard error for both distresses is in good agreement based on the investigated data and the developed methodology. Finally, the conducted sensitivity analysis demonstrate that the proposed methodology produces rational pavement performance.

Load Spectra–Incorporated Fatigue Cracking Model Implementation and Case Study

2017 ◽  
Vol 2640 (1) ◽  
pp. 1-10
Author(s):  
Sheng Hu ◽  
Fujie Zhou ◽  
Tom Scullion
Keyword(s):  
Asphalt Concrete ◽  
Fatigue Cracking ◽  
Pavement Design ◽  
Design System ◽  
Key Factors ◽  
Spectra Analysis ◽  
Traffic Loading ◽  
Load Spectra ◽  
Comparison Results ◽  
Asphalt Concrete Pavement

Traffic loading is one of the key factors that may cause asphalt concrete pavement fatigue cracking. Axle load spectra input provides an opportunity for evaluating the pavement response under real traffic loads throughout the pavement design life. This paper describes the methodology of incorporating axle load spectra into the mechanistic–empirical fatigue cracking model that uses a fracture mechanics method to determine crack propagation. The paper also presents the incorporation of the method into the Texas mechanistic–empirical flexible pavement design system. Several load spectra cases were studied, and the percentages of the corresponding fatigue cracking areas were predicted and compared. The comparison results confirmed the necessity of load spectra analysis. Overall, the implemented load spectra–incorporated asphalt concrete fatigue cracking model generated rational results. Further research is continuing on field validation and calibration.

Field performance and early test results of offspring from two Norway spruce seed orchards containing clones transferred to warmer climates

2007 ◽  
Vol 37 (3) ◽  
pp. 515-522 ◽  
Author(s):  
Tore Skrøppa ◽  
Ketil Kohmann ◽  
Øystein Johnsen ◽  
Arne Steffenrem ◽  
Øyvind M. Edvardsen
Keyword(s):  
Norway Spruce ◽  
Field Performance ◽  
Seed Orchard ◽  
Field Trials ◽  
Climatic Conditions ◽  
Test Results ◽  
Seed Orchards ◽  
Low Altitude ◽  
Natural Stands ◽  
Seed Crops

We present results from early tests and field trials of offspring from two Norway spruce ( Picea abies (L.) Karst.) seed orchards containing clones that have been transferred from high altitudes to sea level and from northern to southern latitudes. Seedlings from seeds produced in the low-altitude seed orchard developed frost hardiness later at the end of the growth season, flushed later in field trials, and grew taller than seedlings from seeds produced in natural stands. They had the lowest mortality rate and the lowest frequency of injuries in the field trials. Similar results were observed in seedlings from seeds produced in the southern seed orchard. We found no adverse effects of the changed growth rhythm. Seedlings from two seed crops in the southern orchard, produced in years with a warm and a cold summer, had different annual growth rhythms. The results are explained mainly by the effects of the climatic conditions during the reproductive phase. Seed crops from different years in the same seed orchard may produce seedlings that perform as if they were from different provenances. It is argued that the effects of the climatic conditions during seed production must contribute to the variation among provenances of Norway spruce.

Intelligent design technology of automobile inspection tool based on 3D MBD model intelligent retrieval

2021 ◽  
pp. 095440702110001
Author(s):  
Qi Cheng ◽  
Shuchun Wang ◽  
Xifeng Fang
Keyword(s):  
Machine Learning ◽  
Information Integration ◽  
3D Model ◽  
Product Information ◽  
Design Method ◽  
Equipment Design ◽  
Design System ◽  
Process Equipment ◽  
Utilization Rate ◽  
Model Based

The existing process equipment design resource utilization rate in automobile industry is low, so it is urgent to change the design method to improve the design efficiency. This paper proposed a fast design method of process equipment driven by classification retrieval of 3D model-based definition (MBD). Firstly, an information integration 3D model is established to fully express the product information definition and to effectively express the design characteristics of the existing 3D model. Through the classification machine-learning algorithm of 3D MBD model based on Extreme Learning Machine (ELM), the 3D MBD model with similar characteristics to the auto part model to be designed was retrieved from the complex process equipment case database. Secondly, the classification and retrieval of the model are realized, and the process equipment of retrieval association mapping with 3D MBD model is called out. The existing process equipment model is adjusted and modified to complete the rapid design of the process equipment of the product to be designed. Finally, a corresponding process equipment design system was developed and verified through a case study. The application of machine learning to the design of industrial equipment greatly shortens the development cycle of equipment. In the design system, the system learns from engineers, making them understand the design better than engineers. Therefore, it can help any user to quickly design 3D models of complex products.

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