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The Midwest States Accelerated Pavement Testing Pooled Fund Program, financed by the highway departments of Kansas, Iowa, and Missouri, has supported an accelerated pavement testing (APT) project to validate several models incorporated in the NCHRP 1-37A design method, popularly known as Mechanistic-Empirical Pavement Design Guide (MEPDG) for flexible pavements. The following models were investigated: the dynamic modulus estimation model, the relationship between the dynamic modulus and the pavement response; and the relationship between the pavement response (strains) and pavement performance. In addition to these, the experiment aims to compare the performance of the coarse and fine Superpave mixes, and to validate and calibrate the Asphalt Pavement Analyzer (APA) and Hamburg Wheel-Tracking Device Tester as screening tools for estimating rutting performance of Superpave asphalt mixes. The experiments were conducted at the Civil Infrastructure Systems Laboratory at Kansas State University. The test program consisted of constructing 12 flexible pavement structures and subjecting them to full-scale accelerated loading tests. The experiment found that the revised Witczak model predicts the dynamic modulus of asphalt concrete mixes with reasonable accuracy. The MEPDG structural response model under-predicted the longitudinal strains at the bottom of the asphalt concrete layers, while the MEPDG over-predicted the permanent deformation in the asphalt layer. The comparison between the results of the laboratory rutting tests performed at 35 degrees Celsius indicate that results of the Hamburg Wheel Rut Test correlate best with results of the APT experiment, followed by those from the APA.
This compendium gathers the latest advances in the area of Accelerated Pavement Testing (APT), a means of testing full-scale pavement construction in an accelerated manner for structural deterioration in a very short term. Compiling novel research results presented at the 5th International Conference on Accelerated Pavement Testing, San Jose, Costa Rica, the volume serves as a timely and highly relevant resource for materials scientists and engineers interested in determining the performance of a pavement structure during its service life (10+ years) in a few weeks or months.
Pack: Book and CD Internationally, full-scale accelerated pavement testing, either on test roads or linear/circular test tracks, has proven to be a valuable tool that fills the gap between models and laboratory tests and long-term experiments on in-service pavements. Accelerated pavement testing is used to improve understanding of pavement behavior, and evaluation of innovative materials and additives, alternative materials processing, new construction techniques, and new types of structures. It provides quick comparisons between current and new practice and the ability to rapidly validate and calibrate models with quality data, with minimal risk at relatively low cost. Advances in Pavement Design through Full-scale Accelerated Pavement Testing is a collection of papers from the 4th International Conference on Accelerated Pavement Testing (Davies, CA, USA, 19-21 September 2012), and includes contributions on a variety of topics including: - Overview of Accelerated Pavement Testing - Establishment of New Accelerated Pavement Testing Facilities - Review of the Impact of Accelerated Pavement Testing Programs on Practice - Instrumentation for Accelerated Pavement Testing - Accelerated Pavement Testing on Asphalt Concrete Pavements - Accelerated Pavement Testing on Portland Cement Concrete Pavements - Accelerated Pavement Testing to Evaluate Functional Performance - Relating Laboratory Tests to Performance using Accelerated Pavement Testing - Development and Calibration of Empirical and Mechanistic-empirical Pavement Design Procedures and Models - Benefit-cost Analysis of Accelerated Pavement Testing Advances in Pavement Design through Full-scale Accelerated Pavement Testing will be useful to academics and professionals involved in pavement engineering.
One of the challenges to the implementation of the mechanistic-empirical pavement design guide (MEPDG) comes from calibrating the transfer functions. This paper focuses on calibration of one of the major distress models in flexible pavement: permanent deformation or rutting. Two key aspects are critical to a successful rutting model calibration: data and method. Regarding the data, existing in-field information only provides total rut depth, which could not meet the requirement of permanent deformation in each structural layer by the MEPDG. Concerning the method, existing work either fails to address calibration factors from a holistic perspective by only focusing on individual sections separately or ignores variability inherent in those factors. In this study, layer-wise permanent deformation from instrumented pavement under accelerated pavement testing serves to accommodate the models calibration. A systematic calibration procedure is established, which globally optimizes all available information across all test sections. Through simulation and numerical optimization, optimal calibration shift factors for three typical flexible pavement materials, asphalt mixture, unbound granular base, and finegrain soil are obtained as 0.60, 0.49, and 0.84, respectively. This implies that the uncalibrated MEPDG is biased toward overprediction of rut depth. It is further suggested that a more rational result for each calibrated factor is to introduce an appropriate distribution to characterize its uncaptured variability. In addition, a case study involving using calibrated MEPDG to predict pavement performance or life indicates that (1) model calibration has a significant impact on the prediction and (2) the "fourth power law" is supported by the MEPDG.
This book, written for the benefit of engineering students and practicing engineers alike, is the culmination of the author's four decades of experience related to the subject of electrical measurements, comprising nearly 30 years of experimental research and more than 15 years of teaching at several engineering institutions. The unique feature of this book, apart from covering the syllabi of various universities, is the style of presentation of all important aspects and features of electrical measurements, with neatly and clearly drawn figures, diagrams and colour and b/w photos that illustrate details of instruments among other things, making the text easy to follow and comprehend. Enhancing the chapters are interspersed explanatory comments and, where necessary, footnotes to help better understanding of the chapter contents. Also, each chapter begins with a "recall" to link the subject matter with the related science or phenomenon and fundamental background. The first few chapters of the book comprise "Units, Dimensions and Standards"; "Electricity, Magnetism and Electromagnetism" and "Network Analysis". These topics form the basics of electrical measurements and provide a better understanding of the main topics discussed in later chapters. The last two chapters represent valuable assets of the book, and relate to (a) "Magnetic Measurements", describing many unique features not easily available elsewhere, a good study of which is essential for the design and development of most electric equipment – from motors to transformers and alternators, and (b) "Measurement of Non-electrical Quantities", dealing extensively with the measuring techniques of a number of variables that constitute an important requirement of engineering measurement practices. The book is supplemented by ten appendices covering various aspects dealing with the art and science of electrical measurement and of relevance to some of the topics in main chapters. Other useful features of the book include an elaborate chapter-by-chapter list of symbols, worked examples, exercises and quiz questions at the end of each chapter, and extensive authors' and subject index. This book will be of interest to all students taking courses in electrical measurements as a part of a B.Tech. in electrical engineering. Professionals in the field of electrical engineering will also find the book of use.
Pack: Book and CDInternationally, full-scale accelerated pavement testing, either on test roads or linear/circular test tracks, has proven to be a valuable tool that fills the gap between models and laboratory tests and long-term experiments on in-service pavements. Accelerated pavement testing is used to improve understanding of pavement behavior,
Permanent deformation (rutting) is the most critical load-associated distress that develops on asphalt pavements significantly affecting their performance. Past research work focused on estimating permanent deformation of asphalt mixes using empirical prediction models or prediction models based on linear elastic material models. In recent years, mechanistic and mechanistic-empirical prediction models have been developed to take into account the behavior of asphalt material (viscoelastic, viscoplastic or elasto-visco-plastic). This research project aims to evaluate existing mechanistic models that predict permanent deformation (rutting) in asphalt mixes by comparing computed permanent deformation to that measured in a full-scale accelerated pavement test. Six pavement sections were constructed in the Civil Infrastructure Systems Laboratory (CISL) of Kansas State University with six different asphalt mixes. The sections were loaded with up to 700,000 load repetitions of a 22,000lb single axle. The transverse profiles at the pavement surface were measured periodically. For material characterization, asphalt mix samples fabricated in the laboratory, were subjected to dynamic modulus (E*), static creep - flow time (Ft), dynamic creep - flow number (Fn), triaxial and uniaxial strength tests, repetitive shear at constant height (RSCH) and frequency sweep at constant height (FSCH). The finite element software, Abaqus, was used to simulate and evaluate four permanent deformation prediction models, which are: creep model, elasto-visco-plastic model, viscoelastic model and Drucker-Prager model. The predicted permanent deformation was then compared to permanent deformation measured in CISL for the six of asphalt pavement sections. It was found that, with some improvements, creep and elasto-visco-plastic models could be used to predict permanent deformation in asphalt mixes. The viscoelastic model greatly under-predict permanent deformation, and the Drucker-Prager model with hardening criteria over predicts permanent deformation as compared to values measured in CISL.
Cost effective design methodology demands accurate performance modeling. Fatigue cracking is one of the major performance indicators in flexible pavement systems. Through literature review, a decision was made to modify the fatigue cracking model in the original VESYS5 program. The revised model in VESYS5W has the same basic form as suggested by the Asphalt Institute (AI) and the 2002 Mechanistic-Empirical Pavement Design Guide (MEPDG). The main challenge in modeling fatigue cracking is to determine appropriate input parameters. Efforts were made to compare the experimental results of full-scale accelerated pavement testing (APT) to the VESY5W predictions using the material parameters suggested by AI and the 2002 MEPDG. The test data employed in this paper are obtained from the full-scale APT conducted by the Federal Highway Administration (FHWA) under a national pooled fund study TPF-5(019). Test results from five lanes at testing temperatures of 19°C were utilized in the comparisons. It was found that the VESYS5W prediction using the material parameters from 2002 MEPDG yielded a much better fit to the experimental results than those using AI material parameters. The VESYS5W predictions using the AI material parameters always underestimated the fatigue cracking life. To match experimental results, shift factors were applied. The shift factors ranged from 0.48 to 3.1 for the predictions using the material parameters from the 2002 MEPDG. However, the shift factors for the AI material parameters ranged from 3.6 to 14.4. In summary, VESYS5W predictions using 2002 MEPDG material parameters provided satisfactory fits to the experimental results with relatively small (?3.1) shift factors. Based on the FHWA's APT test results and the VESYS5W analyses, two equations are recommended for prediction of fatigue cracking in pavements with conventional mix and with asphalt modifier.
"TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 433: Significant Findings from Full-Scale Accelerated Pavement Testing documents and summarizes significant findings from the various experimental activities associated with full-scale accelerated pavement testing (f-sAPT) programs that have taken place between 2000 and 2011. The report also identifies gaps in knowledge related to f-sAPT and where future research may be needed. NCHRP Synthesis 433 is designed to expand the f-sAPT base of knowledge documented in NCHRP Syntheses 325 and 235, both with the same title of Significant Findings from Full-Scale Accelerated Pavement Testing. f-sAPT is the controlled application of a wheel loading, at or above the appropriate legal load limit, to a pavement system to determine pavement response in a compressed time period. The acceleration of damage is achieved by one or more of the following factors: increased repetitions, modified loading conditions, imposed climatic conditions, and thinner pavements with a decreased structural capacity which have shorter design lives"--
"TRB℗s Transportation Research Record: Journal of the Transportation Research Board 1896 examines a mechanistic-empirical model to predict transverse joint faulting, a multilayer boundary-element method for evaluating top-down cracking in hot-mix asphalt pavements, and one-way and two-way directional heavy-vehicle simulator loading in this four-part volume on education tools, rigid pavements, flexible pavements, and accelerated pavement testing. The K. B. Woods Award-winning paper on design and construction of transportation facilities, ©Computer-Based Multimedia Pavement Training Tool for Self-Directed Learning,♯ by Stephen Muench and Joe Mahoney of the University of Washington, also appears in this TRR: Journal volume."--TRB website.