@article{wang_underwood_kim_2022, title={Development of a fatigue index parameter, S-app, for asphalt mixes using viscoelastic continuum damage theory}, volume={23}, ISSN={["1477-268X"]}, DOI={10.1080/10298436.2020.1751844}, abstractNote={ABSTRACT Fatigue cracking is one of the major distresses in asphalt pavements. Engineers have used many methods, from sophisticated numerical simulations to experience-based knowledge, to address fatigue cracking and deliver pavements that perform well. One strategy that has become increasingly widespread is the use of a fatigue index parameter that identifies the cracking potential of asphalt mixtures independent of the pavement structure. The use of such indices allows pavement engineers to make quick and targeted decisions with regard to mix design, mix acceptance, and mix quality assurance. This paper proposes a new fatigue index parameter, Sapp , which represents the damage capacity of a mixture and is based on the viscoelastic continuum damage theory. Unlike other indices, this new index considers the effects of both material toughness and stiffness. Sapp was employed in this study to evaluate 105 different asphalt mixtures with varied design factors. The results indicate that Sapp is able to distinguish the fatigue resistance of asphalt mixtures with varied properties, including different binder contents, binder performance grades, reclaimed asphalt pavement contents, types of binder modifier, air void contents, aggregate gradations, and aging levels. This paper also presents a set of recommended Sapp threshold values for different expected traffic volumes.}, number={2}, journal={INTERNATIONAL JOURNAL OF PAVEMENT ENGINEERING}, author={Wang, Yizhuang David and Underwood, Benjamin Shane and Kim, Youngsoo Richard}, year={2022}, month={Jan}, pages={438–452} }
 @article{wang_ghanbari_underwood_kim_2021, title={Development of framework of the predictive performance-engineered mix design procedure for asphalt mixtures}, volume={6}, ISSN={["1477-268X"]}, url={https://doi.org/10.1080/10298436.2021.1938044}, DOI={10.1080/10298436.2021.1938044}, abstractNote={ABSTRACT This paper presents a new asphalt mixture design framework for predictive performance-engineered mix design (PEMD) and the theory and procedures that underlie the proposed design method. This method allows pavement engineers to determine an optimized mix design based on the predicted pavement/mixture performance for all possible combinations of a given set of component materials (i.e. aggregate and binder) in the design space. The proposed PEMD process is based on the ‘performance-volumetrics relationship’ (PVR) concept. The calibration of the PVR is based on the mixture performance predicted from FlexPAVETM, a three-dimensional finite element program that performs viscoelastic analysis under moving loads, using the material properties of the asphalt mixture in question at widely spaced volumetric conditions. Three mixtures of different nominal maximum aggregate sizes and binder types are used to demonstrate the proposed PEMD process. Finally, the predicted performance results obtained from different design approaches are compared.}, journal={INTERNATIONAL JOURNAL OF PAVEMENT ENGINEERING}, author={Wang, Yizhuang David and Ghanbari, Amir and Underwood, Benjamin Shane and Kim, Youngsoo Richard}, year={2021}, month={Jun} }
 @article{ashouri_wang_choi_kim_2021, title={Development of healing model and simplified characterization test procedure for asphalt concrete}, volume={271}, ISSN={["1879-0526"]}, DOI={10.1016/j.conbuildmat.2020.121515}, abstractNote={Fatigue cracking is one of the major distresses in asphalt pavement. Numerous and significant efforts have been undertaken to predict the fatigue life of pavements. One of the mechanisms that affects fatigue life is healing, and thus, including healing in fatigue performance prediction models is necessary. For this study, twelve healing tests at three temperatures and four rest periods were conducted to evaluate the healing characteristics of asphalt materials. The percentage of healing (%Hs) used in this study is defined as the ratio of the internal state variable (S) before the rest period to the incremental internal state variable due to the rest period. A %Hs mastercurve was constructed by applying the time–temperature superposition (t-TS) principle to the %Hs versus rest period curves and thereby proved that the t-TS principle works for healing. The %Hs mastercurves at different damage levels were shifted vertically to construct one reference %Hs mastercurve. The amount of vertical shifting is referred to as the vertical healing shift factor. The reference %Hs mastercurve with the vertical healing shift factor and t-TS principle led to the proposed shift healing model as a function of rest period, temperature, and damage level. A test protocol to calibrate the model also is suggested in this work. The protocol requires only three specimens, and thus, testing can be completed within a day. The proposed shift healing model characterized by the suggested protocol test was implemented successfully in twelve healing tests to predict the healing behavior of the test specimens, which indicates the prediction capability of the suggested model and test protocol.}, journal={CONSTRUCTION AND BUILDING MATERIALS}, author={Ashouri, Morteza and Wang, Yizhuang and Choi, Yeong-Tae and Kim, Youngsoo}, year={2021}, month={Feb} }
 @article{wang_ghanbari_underwood_kim_2021, title={Development of preliminary transfer functions for performance predictions in FIexPAVE (TM)}, volume={266}, ISSN={["1879-0526"]}, DOI={10.1016/j.conbuildmat.2020.121182}, abstractNote={Mechanistic-empirical design and performance-related specifications are state-of-the-art tools for designing pavements and determining incentives/disincentives for paving contracts. These methods require the reliable prediction of pavement performance throughout the pavement’s design life. One such prediction program is FlexPAVE™, which applies three-dimensional viscoelastic finite element analysis with moving loads to calculate the pavement’s mechanical responses under traffic loading and given climate data. The simplified viscoelastic continuum damage model and shift model are used to calculate the fatigue damage in the pavement’s cross-section and the rut depths, respectively. With regard to fatigue damage, a fatigue transfer function is needed to convert the computed cross-sectional damaged area (i.e., the damage level) to the cracked area on the pavement surface. With regard to rut depth, a rutting transfer function is needed to calibrate the predicted rut depths. In this study, preliminary transfer functions for the predicted fatigue damage and rut depths were developed using four sets of field measurement data obtained from test sections in the United States, Canada, and South Korea that include interstate highways and an accelerated testing facility. Good agreement between the predicted performance and field observations was found after calibration of FlexPAVE™.}, journal={CONSTRUCTION AND BUILDING MATERIALS}, author={Wang, Yizhuang David and Ghanbari, Amir and Underwood, Benjamin Shane and Kim, Youngsoo Richard}, year={2021}, month={Jan} }
 @article{wang_kim_2021, title={Effects of Aging on Pavement ME Predictions of Permanent Deformation for HMA and WMA Mixtures}, volume={147}, ISSN={["2573-5438"]}, DOI={10.1061/JPEODX.0000319}, abstractNote={AbstractThis paper presents an experimental investigation into the effects of aging on the rutting performance of both hot-mix asphalt (HMA) and warm-mix asphalt (WMA) mixtures and an analytical st...}, number={4}, journal={JOURNAL OF TRANSPORTATION ENGINEERING PART B-PAVEMENTS}, author={Wang, Yizhuang David and Kim, Youngsoo Richard}, year={2021}, month={Dec} }
 @article{wang_jeong_kim_2020, title={Comparison of Treatment Timing between Aggregate Base and Full-Depth Asphalt Roads}, volume={146}, ISSN={["2573-5438"]}, url={https://doi.org/10.1061/JPEODX.0000216}, DOI={10.1061/JPEODX.0000216}, abstractNote={AbstractAggregate base-course (ABC) pavements and full-depth asphalt (FDA) pavements are the two most commonly used types of asphalt pavements. During pavement design and pavement management, engin...}, number={4}, journal={JOURNAL OF TRANSPORTATION ENGINEERING PART B-PAVEMENTS}, publisher={American Society of Civil Engineers (ASCE)}, author={Wang, Yizhuang David and Jeong, Jaehoon and Kim, Youngsoo Richard}, year={2020}, month={Dec} }
 @article{jeong_wang_ghanbari_nash_nener-plante_underwood_kim_2020, title={Pavement performance predictions using performance-volumetric relationship and evaluation of construction variability: Example of MaineDOT shadow project for the development of performance-related specifications}, volume={263}, ISSN={["1879-0526"]}, DOI={10.1016/j.conbuildmat.2020.120150}, abstractNote={This paper describes the process chain for a shadow project of the Federal Highway Administration’s Asphalt Mixture Performance-Related Specifications (PRS) by the MaineDOT. Eleven mixture samples were acquired from a field project selected by MaineDOT and were performance-tested for calibration (a ‘four corners’ procedure) and verification to develop the performance-volumetric relationship (PVR) for the selected mixture. The PVR function for the selected mixture worked reasonably well to predict pavement performance at the volumetric conditions that were not included in the PVR development and reflected reasonable trends with regard to various field densities.}, journal={CONSTRUCTION AND BUILDING MATERIALS}, author={Jeong, Jaehoon and Wang, Yizhuang David and Ghanbari, Amir and Nash, Casey and Nener-Plante, Derek and Underwood, Benjamin Shane and Kim, Y. Richard}, year={2020}, month={Dec} }
 @article{ding_wang_gulzar_kim_underwood_2020, title={Uncertainty Quantification of Simplified Viscoelastic Continuum Damage Fatigue Model using the Bayesian Inference-Based Markov Chain Monte Carlo Method}, volume={2674}, ISSN={["2169-4052"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85083645522&partnerID=MN8TOARS}, DOI={10.1177/0361198120910149}, abstractNote={ The simplified viscoelastic continuum damage model (S-VECD) has been widely accepted as a computationally efficient and a rigorous mechanistic model to predict the fatigue resistance of asphalt concrete. It operates in a deterministic framework, but in actual practice, there are multiple sources of uncertainty such as specimen preparation errors and measurement errors which need to be probabilistically characterized. In this study, a Bayesian inference-based Markov Chain Monte Carlo method is used to quantify the uncertainty in the S-VECD model. The dynamic modulus and cyclic fatigue test data from 32 specimens are used for parameter estimation and predictive envelope calculation of the dynamic modulus, damage characterization and failure criterion model. These parameter distributions are then propagated to quantify the uncertainty in fatigue prediction. The predictive envelope for each model is further used to analyze the decrease in variance with the increase in the number of replicates. Finally, the proposed methodology is implemented to compare three asphalt concrete mixtures from standard testing. The major findings of this study are: (1) the parameters in the dynamic modulus and damage characterization model have relatively strong correlation which indicates the necessity of Bayesian techniques; (2) the uncertainty of the damage characteristic curve for a single specimen propagated from parameter uncertainties of the dynamic modulus model is negligible compared to the difference in the replicates; (3) four replicates of the cyclic fatigue test are recommended considering the balance between the uncertainty of fatigue prediction and the testing efficiency; and (4) more replicates are needed to confidently detect the difference between different mixtures if their fatigue performance is close. }, number={4}, journal={TRANSPORTATION RESEARCH RECORD}, author={Ding, Jing and Wang, Yizhuang David and Gulzar, Saqib and Kim, Youngsoo Richard and Underwood, B. Shane}, year={2020}, month={Apr}, pages={247–260} }
 @article{wang_ghanbari_underwood_kim_2019, title={Development of a Performance-Volumetric Relationship for Asphalt Mixtures}, volume={2673}, ISSN={0361-1981 2169-4052}, url={http://dx.doi.org/10.1177/0361198119845364}, DOI={10.1177/0361198119845364}, abstractNote={ This paper aims to establish the relationship between the volumetric performance of asphalt mixtures and their performance in relation to pavement fatigue cracking and rutting. A good performance-volumetric relationship (PVR) can dramatically improve the working efficiency of mixtures and can be used in future performance-engineered mixture design and performance-related specifications. For this study, three asphalt mixtures were first designed to incorporate systematic changes in volumetric conditions, then fatigue cracking and rutting performance tests were conducted at each condition. Statistical analyses of the results suggest that a first-order (linear) model and power model would be an appropriate form of the PVR function. The number of volumetric conditions required to calibrate the PVR function is also investigated. Finally, a rule of thumb for selecting the volumetric conditions for the model calibrations is provided. The verification results show that the proposed PVR function is able to capture the response of mixture performance to changes in volumetric conditions. }, number={6}, journal={Transportation Research Record: Journal of the Transportation Research Board}, publisher={SAGE Publications}, author={Wang, Yizhuang David and Ghanbari, Amir and Underwood, Benjamin Shane and Kim, Youngsoo Richard}, year={2019}, month={May}, pages={416–430} }
 @article{wang_kim_2019, title={Development of a pseudo strain energy-based fatigue failure criterion for asphalt mixtures}, volume={20}, ISSN={["1477-268X"]}, DOI={10.1080/10298436.2017.1394100}, abstractNote={Abstract This paper presents a new energy-based failure criterion that is based on the simplified viscoelastic continuum damage model. This study found that the average reduction in pseudo stiffness up to failure, referred to here as D R , is a material constant that is independent of mode of loading, temperature, and stress/strain amplitude. Twenty different asphalt mixtures were used to validate the proposed method. This paper presents typical values of D R and shows that the D R changes with the mixture characteristics. The advantages of the D R failure criterion over a previous failure criterion (known as the G R criterion) are that it: (1) allows the prediction of fatigue failure in arithmetic scale, which reduces possible errors due to extrapolation of the accelerated laboratory fatigue test data to realistic traffic volumes encountered in the field and (2) reduces the number of tests required to characterise the failure criterion. Statistical analysis was performed in this study and the results show confidence levels that can be obtained from two or three fatigue tests.}, number={10}, journal={INTERNATIONAL JOURNAL OF PAVEMENT ENGINEERING}, author={Wang, Yizhuang and Kim, Y. Richard}, year={2019}, month={Oct}, pages={1182–1192} }
 @article{etheridge_wang_kim_kim_2019, title={Evaluation of Fatigue Cracking Resistance of Asphalt Mixtures Using Apparent Damage Capacity}, volume={31}, ISSN={["1943-5533"]}, DOI={10.1061/(ASCE)MT.1943-5533.0002870}, abstractNote={AbstractThe prediction of fatigue cracking is one of the critical items to assess the service life of flexible pavements. Accordingly, researchers have developed several test methods and index para...}, number={11}, journal={JOURNAL OF MATERIALS IN CIVIL ENGINEERING}, author={Etheridge, Robert Austin and Wang, Yizhuang David and Kim, S. Sonny and Kim, Y. Richard}, year={2019}, month={Nov} }
 @article{zhang_wang_su_2019, title={Fatigue damage evolution model of asphalt mixture considering influence of loading frequency}, volume={218}, ISSN={["1879-0526"]}, DOI={10.1016/j.conbuildmat.2019.05.029}, abstractNote={In view of shortcomings for the traditional fatigue theory in addressing fatigue cracking distress of asphalt pavement, this paper attempts to adopt fatigue damage theory, which is more consistent with the essence of pavement fatigue distress, to study the fatigue damage characteristic of asphalt mixture, and mainly focuses on its pivotal content—damage evolution model. Considering the important influence of loading frequency on the fatigue life and damage evolution characteristics of asphalt mixture, a new damage evolution model is constructed by introducing the influence of loading frequency into the classical Chaboche damage evolution model, as well as the theoretical analysis and laboratory tests are used to analyze and verify the model proposed in the paper. The results show that the calculated results of the model agree well with the measured, which can not only reflect the basic law of damage evolution and accumulation for asphalt mixture, but also reflect the influence of loading frequency on fatigue damage characteristics of mixture. Consequently, it is worthy of further application and promotion in the research of fatigue damage of asphalt pavement.}, journal={CONSTRUCTION AND BUILDING MATERIALS}, author={Zhang, Jun and Wang, Yizhuang David and Su, Yongtao}, year={2019}, month={Sep}, pages={712–720} }
 @article{wang_keshavarzi_kim_2018, title={Fatigue Performance Analysis of Pavements with RAP Using Viscoelastic Continuum Damage Theory}, volume={22}, ISSN={["1976-3808"]}, DOI={10.1007/s12205-018-2648-0}, number={6}, journal={KSCE JOURNAL OF CIVIL ENGINEERING}, author={Wang, Yizhuang David and Keshavarzi, Behrooz and Kim, Youngsoo Richard}, year={2018}, month={Jun}, pages={2118–2125} }
 @article{wang_keshavarzi_kim_2018, title={Fatigue Performance Prediction of Asphalt Pavements with FlexPAVE (TM), the S-VECD Model, and D-R Failure Criterion}, volume={2672}, ISSN={["2169-4052"]}, DOI={10.1177/0361198118756873}, abstractNote={ Reliable predictions of asphalt materials and pavement performance are important elements in mixture design, mechanistic-empirical pavement design, and performance-related specifications. This paper presents FlexPAVE™, a pavement performance prediction program. FlexPAVE™ is a three-dimensional finite element program that is capable of moving load analysis under realistic climatic conditions. It utilizes the simplified viscoelastic continuum damage (S-VECD) model to predict asphalt pavement fatigue life. This S-VECD model currently incorporates the so-called GR failure criterion to define the failure of asphalt mixtures. In this study, a new failure criterion for the S-VECD model, designated as the DR criterion, has been developed to remedy some of the shortcomings of the GR failure criterion. This DR criterion has been implemented successfully in FlexPAVETM. In this paper, FlexPAVETM is used to simulate the fatigue performance of field test sections. These test sections include various pavement structures, such as perpetual pavements and accelerated load facility test pavements in the United States, South Korea, and China, as well as various materials, such as warm-mix asphalt, reclaimed asphalt pavement, and mixtures with modified binders. The DR-based FlexPAVETM predictions have yielded good agreement with the field measurements and show more reasonable trends compared to predictions obtained using the GR failure criterion. }, number={40}, journal={TRANSPORTATION RESEARCH RECORD}, author={Wang, Yizhuang David and Keshavarzi, Behrooz and Kim, Y. Richard}, year={2018}, month={Dec}, pages={217–227} }
 @article{wang_norouzi_kim_2016, title={Comparison of Fatigue Cracking Performance of Asphalt Pavements Predicted by Pavement ME and LVECD Programs}, ISSN={["2169-4052"]}, DOI={10.3141/2590-06}, abstractNote={ Mechanistic–empirical pavement design has received significant attention from the pavement community as the method for designing asphalt pavements in the future. Currently available software for mechanistic–empirical pavement design includes the AASHTOWare Pavement ME Design (Pavement ME) program. The Pavement ME program allows users to predict pavement distresses by applying layered elastic theory for the mechanical responses and using empirical models for the distress predictions. The layered viscoelastic pavement design for critical distresses (LVECD) program, which employs three-dimensional viscoelastic finite element analysis with moving loads, can also be used to predict the fatigue and rutting performance of pavements. The LVECD program employs the simplified viscoelastic continuum damage (S-VECD) model as the material model for the fatigue performance predictions of asphalt mixtures under complex loading and environmental conditions. This paper examines and compares the performance of 33 pavement sections from five research projects located in the United States, Canada, and South Korea by using both the Pavement ME and LVECD computer programs. To verify the results obtained from these two programs, the simulations were compared with the field performance data. In terms of ranking, the LVECD simulations provided better agreement with the field performance data than did the Pavement ME simulations. One of the main reasons for the better predictions obtained by the LVECD program is that its fatigue performance predictions depend on the mixture properties of all the layers, whereas the Pavement ME program considers the fatigue properties of only the bottom layer mixture. }, number={2590}, journal={TRANSPORTATION RESEARCH RECORD}, author={Wang, Yizhuang and Norouzi, Amirhossein and Kim, Y. Richard}, year={2016}, pages={44–55} }
 @article{sabouri_choi_wang_hwang_baek_kim_2016, title={Effect of Rejuvenator on Performance Properties of WMA Mixtures with High RAP Content}, volume={11}, ISBN={["978-94-017-7341-6"]}, ISSN={["2211-0852"]}, DOI={10.1007/978-94-017-7342-3_38}, abstractNote={The production of warm mix asphalt (WMA) mixtures with high percentages of reclaimed asphalt pavement (RAP) is gaining attention as a way to save costs and efficiently utilize existing resources. However, WMA must perform at least as well as hot mix asphalt (HMA) before it can be used as a replacement for HMA. In this study, the performance of a WMA mixture with a high percentage of RAP (40 % RAP) and a WMA additive (1.5 % of binder weight) that works as a rejuvenator was evaluated and compared with the performance of a HMA mixture with the same amount of RAP in order to evaluate the effects of the WMA rejuvenator. These mixtures were evaluated in terms of fatigue cracking using the simplified viscoelastic continuum damage (S-VECD) model and in terms of rutting using the triaxial stress sweep (TSS) test. In addition, layered viscoelastic pavement analysis for critical distresses (LVECD) was used to predict the fatigue resistance of these mixtures for future use. The WMA rejuvenator was found to improve the mixing and compaction ability of the WMA mixture. Also, compared to the HMA mixture, the WMA mixture showed better fatigue resistance, but the rejuvenator found to have an adverse effect on the rutting resistance of the mixture.}, journal={8TH RILEM INTERNATIONAL SYMPOSIUM ON TESTING AND CHARACTERIZATION OF SUSTAINABLE AND INNOVATIVE BITUMINOUS MATERIALS}, author={Sabouri, Mohammadreza and Choi, Yeong-Tae and Wang, Yizhuang and Hwang, Sungdo and Baek, Cheolmin and Kim, Richard Y.}, year={2016}, pages={473–484} }