Hyung Suk Lee - Profile on Academia.edu (original) (raw)

Papers by Hyung Suk Lee

Current Situation The relationship between pavement friction and roadway safety may seem obvious:... more Current Situation The relationship between pavement friction and roadway safety may seem obvious: the more friction a roadway provides, the more control a driver will have, and the safer the roadway will be. However, crashes are complex events, and pavement friction is only one factor to consider along with driver distraction, tire wear, braking, visibility, and others. As engineers strive to make highways safer, balancing these factors requires a more precise understanding of the factors that contribute to safety. With friction, this is difficult because the desirable amount of friction itself depends on many factors, such as speed limits, type of traffic, type of road, etc. Most highway authorities use values for desirable friction that have been developed over time, but with changes in scientific methods of analysis as well as methods of design and construction, it is important to revisit issues like this one periodically to bring the latest techniques to bear and develop better ...

This report documents a study conducted to review the status of falling weight deflectometer (FWD... more This report documents a study conducted to review the status of falling weight deflectometer (FWD) equipment, data collection, analysis, and interpretation, including dynamic backcalculation, and to develop enhanced analysis procedures and recommendations for the effective use of FWD technology as it relates to the flexible pavement models and procedures incorporated within the Mechanistic-Empirical Pavement Design Guide developed by the National Cooperative Highway Research Program and subsequently adopted by the American Association of State Highway and Transportation Officials. In this context, dynamic backcalculation refers to the modeling of the dynamic or impact nature of the FWD loading and resulting pavement response of in-service flexible pavements for pavement structural analysis and rehabilitation design. The research effort resulted in development analysis methodologies, software tools implementing those analysis methodologies and a potential list of recommendations for FWD equipment enhancements, all of which are detailed in this report. This report is intended for use by pavement engineers involved in structural evaluation and rehabilitation design of flexible pavements and researchers involved in development of new procedures for the modeling and analysis of in-service flexible pavements.

Segregation of asphalt mixtures, which denotes the non-uniform distribution of coarse and fine ag... more Segregation of asphalt mixtures, which denotes the non-uniform distribution of coarse and fine aggregate components, either causes short term premature failures or affects the long term pavement performance. Since segregation may result in a significantly altered aggregate structure of an asphalt mixture, it may increase the potential for rutting, among all other distresses. In this study, the effect of segregation or change in aggregate gradation that may negatively influence the rutting potential of asphalt mixtures was evaluated. The Dominant Aggregate Size Range (DASR) gradation model and the DASR porosity parameter, which have previously been identified to be well correlated with rutting performance, were used to identify the potential degradation of rutting performance due to segregation. A total of four roadway sections with different severity levels of segregation were selected and evaluated. The analysis results of mixture gradation, volumetric properties, and DASR porosity...

Due to the viscoelastic nature of asphalt materials and the dynamic nature of pavement structures... more Due to the viscoelastic nature of asphalt materials and the dynamic nature of pavement structures, it is important to consider both effects simultaneously in modeling of asphalt pavements. In this study, a new computational algorithm, namely ViscoWave, has been developed and implemented for modeling the pavement dynamics and viscoelasticity under an impact load generated by a Falling Weight Deflectometer (FWD). The primary advantage of the proposed solution over some of the existing solutions is that it uses continuous integral transforms (Laplace and Hankel transforms) that are more appropriate for the FWD time histories whose signal characteristics are transient, nonperiodic, and truncated. Prior to the mathematical formulation of the developed algorithm, the fundamental properties of a viscoelastic material and the theory of uniaxial viscoelasticity are reviewed. Then, the theory of linear, uniaxial viscoelasticity is extended to multi-axial viscoelasticity. The multi-axial theory of viscoelasticity is, in turn, applied to develop a methodology for analyzing the laboratory Indirect Tensile (IDT) test data. The theoretical development of ViscoWave follows similar steps to those used for the development of the spectral element method. However, in place of the discrete transforms adopted in the spectral element method, ViscoWave utilizes the continuous integral transforms (namely Laplace and Hankel transforms) that are more appropriate for transient, nonperiodic signals. The theory behind ViscoWave was verified by comparing the ViscoWave simulation results to other existing solutions such as the Finite Element Analysis (FEA) and spectral element method. To backcalculate the pavement layer parameters, two of the well known unconstrained optimization algorithms (Gauss-Newton and Levenberg-Marquardt methods) were adopted for use with ViscoWave. The backcalculation was conducted using both theoretically-generated and field-obtained FWD time histories. The results indicate that ViscoWave has great potential for modeling the viscoelastic and dynamic effects of a pavement structure under an impact load. iv To my beloved daughter Lena Dah-Ye Lee, my mother Ok Hee Seo, my father Doo Seon Lee, and my sister Seung Eun Lee v TABLE OF CONTENTS LIST OF TABLES .

With the adoption of the new mechanistic-empirical pavement design method and the employment of a... more With the adoption of the new mechanistic-empirical pavement design method and the employment of axle load spectra, the question of evaluating the pavement damage resulting from different axle and truck configurations has become more relevant. In particular, the state of Michigan is unique in permitting several heavy truck axle configurations that are composed of up to 11 axles, sometimes with as many as 8 axles within one axle group. Thus, there is a need to identify the relative pavement damage resulting from these multiple axle trucks. The study looked at both flexible and rigid pavement systems, and comprised of three main components: (1) inservice pavement performance data; (2) laboratory testing under multiple axles, and (3) mechanistic-empirical analyses. The results from in-service pavement performance data indicated that multiple axle groups appear to cause less damage in fatigue per load carried for both pavement types, whereas they cause more damage in rutting of flexible pavements and roughness for rigid pavements. Laboratory testing of asphalt concrete confirmed that multiple axles cause less fatigue damage per load carried, and that rutting is nearly proportional to the number of axles within an axle group. Results from flexural concrete beam fatigue testing showed significant variability; multiple linear regression analysis (independent variables: stress ratio, stress impulse and initial modulus of elasticity) indicated, on average, similar findings to asphalt concrete fatigue for a given stress ratio; however, mechanistic analysis showed that multiple axles cause considerable stress reduction leading to significantly lower fatigue damage. The mechanistic analysis also showed that multiple axles cause more faulting in rigid pavements. Mechanistic analyses of flexible pavements confirmed that multiple axles cause less fatigue damage per load carried, and rutting damage that is nearly proportional to the number of axles within an axle group. However, the mechanistic-empirical results suggest that the AASHTO Load Equivalency Factors (LEF) for large axle groups may be unconservative. Finally, Full scale slab testing to study joint/crack deterioration in plain concrete pavements was inconclusive.

Journal of Engineering Mechanics, 2010

For this study, the Binzhou perpetual pavement test sections constructed in Shandong Province, Ch... more For this study, the Binzhou perpetual pavement test sections constructed in Shandong Province, China, were simulated for long-term fatigue performance using the layered viscoelastic pavement analysis for critical distresses (LVECD) finite element software package. In this framework, asphalt concrete was treated in the context of linear viscoelastic continuum damage theory. A recently developed unified fatigue failure criterion that defined the boundaries of the applicable region of the theory was also incorporated. The mechanistic modeling of the fatigue mechanisms was able to accommodate the complex temperature variations and loading conditions of the field pavements in a rigorous manner. All of the material models were conveniently characterized by dynamic modulus tests and direct tension cyclic fatigue tests in the laboratory using cylindrical specimens. By comparing the obtained damage characteristic curves and failure criteria, it is found that mixtures with small aggregate particle sizes, a dense gradation, and modified asphalt binder tended to exhibit the best fatigue resistance at the material level. The 15-year finite element structural simulation results for all the test sections indicate that fatigue performance has a strong dependence on the thickness of the asphalt pavements. Based on the predicted location and severity of the fatigue damage, it is recommended that sections 1 and 3 of the Binzhou test sections be employed for perpetual pavement design.

Economics, and environmental issues have spurred the introduction of the Warm Mix Asphalt (WMA) t... more Economics, and environmental issues have spurred the introduction of the Warm Mix Asphalt (WMA) technology in the pavement construction industry. The Florida Department of Transportation (FDOT) started using the WMA technology in 2006 based on reported benefits due to lower asphalt mixing and compaction temperatures. Limited field and laboratory studies have indicated that WMA may have similar performance as traditional Hot Mix Asphalt (HMA). However, some studies have also suggested that the use of WMA may increase long-term rutting and stripping potential and hence the long-term performance evaluation of the WMA mixtures is still warranted. With the primary objective of obtaining long-term field performance data of Florida’s WMA, the respective field performance of six representative WMA projects using five different technologies (one additive and four water foaming technologies) was monitored and documented in this paper. The performance of the WMA projects was then compared to t...

The Florida Department of Transportation (FDOT) has historically used a combination of handheld d... more The Florida Department of Transportation (FDOT) has historically used a combination of handheld devices and visual surveys to evaluate the retroreflectivity of pavement markings. However, visual surveys have the inherent limitations of operator bias while the use of a handheld device is slow, labor intensive, and presents safety hazards. Many highway agencies have recognized that a Mobile Retroreflectivity Unit (MRU) may be a safer and a more efficient alternative to the handheld retroreflectometers. Since the measurement process relies on the operator-driven instrument, a level of uncertainty is always a concern in evaluating pavement markings with the MRU. This research is aimed at assessing the precision and bias of the MRU while using the handheld retroreflectometer as a reference device. A total of ten 1.0 mile long field sites were selected to include various pavement surface types and pavement marking materials (paints and thermoplastics). The results indicated that, when compared to the handheld retroreflectometers, the MRU demonstrated no statistical differences or bias at a 95 percent confidence level for the retroreflectivity values ranging between 200 and 800 mcd/m 2 /lux. In addition, it was determined that the retroreflectivity values from two properly conducted tests using a single MRU on the same pavement marking should not differ by more than 7.8 percent and when different MRUs are used on the same pavement marking, the retroreflectivity values should not differ more than 13.3 percent. This paper presents a description of the testing program, the data collection effort, and the subsequent analyses and findings.

Current Situation The relationship between pavement friction and roadway safety may seem obvious:... more Current Situation The relationship between pavement friction and roadway safety may seem obvious: the more friction a roadway provides, the more control a driver will have, and the safer the roadway will be. However, crashes are complex events, and pavement friction is only one factor to consider along with driver distraction, tire wear, braking, visibility, and others. As engineers strive to make highways safer, balancing these factors requires a more precise understanding of the factors that contribute to safety. With friction, this is difficult because the desirable amount of friction itself depends on many factors, such as speed limits, type of traffic, type of road, etc. Most highway authorities use values for desirable friction that have been developed over time, but with changes in scientific methods of analysis as well as methods of design and construction, it is important to revisit issues like this one periodically to bring the latest techniques to bear and develop better ...

This report documents a study conducted to review the status of falling weight deflectometer (FWD... more This report documents a study conducted to review the status of falling weight deflectometer (FWD) equipment, data collection, analysis, and interpretation, including dynamic backcalculation, and to develop enhanced analysis procedures and recommendations for the effective use of FWD technology as it relates to the flexible pavement models and procedures incorporated within the Mechanistic-Empirical Pavement Design Guide developed by the National Cooperative Highway Research Program and subsequently adopted by the American Association of State Highway and Transportation Officials. In this context, dynamic backcalculation refers to the modeling of the dynamic or impact nature of the FWD loading and resulting pavement response of in-service flexible pavements for pavement structural analysis and rehabilitation design. The research effort resulted in development analysis methodologies, software tools implementing those analysis methodologies and a potential list of recommendations for FWD equipment enhancements, all of which are detailed in this report. This report is intended for use by pavement engineers involved in structural evaluation and rehabilitation design of flexible pavements and researchers involved in development of new procedures for the modeling and analysis of in-service flexible pavements.

Segregation of asphalt mixtures, which denotes the non-uniform distribution of coarse and fine ag... more Segregation of asphalt mixtures, which denotes the non-uniform distribution of coarse and fine aggregate components, either causes short term premature failures or affects the long term pavement performance. Since segregation may result in a significantly altered aggregate structure of an asphalt mixture, it may increase the potential for rutting, among all other distresses. In this study, the effect of segregation or change in aggregate gradation that may negatively influence the rutting potential of asphalt mixtures was evaluated. The Dominant Aggregate Size Range (DASR) gradation model and the DASR porosity parameter, which have previously been identified to be well correlated with rutting performance, were used to identify the potential degradation of rutting performance due to segregation. A total of four roadway sections with different severity levels of segregation were selected and evaluated. The analysis results of mixture gradation, volumetric properties, and DASR porosity...

Due to the viscoelastic nature of asphalt materials and the dynamic nature of pavement structures... more Due to the viscoelastic nature of asphalt materials and the dynamic nature of pavement structures, it is important to consider both effects simultaneously in modeling of asphalt pavements. In this study, a new computational algorithm, namely ViscoWave, has been developed and implemented for modeling the pavement dynamics and viscoelasticity under an impact load generated by a Falling Weight Deflectometer (FWD). The primary advantage of the proposed solution over some of the existing solutions is that it uses continuous integral transforms (Laplace and Hankel transforms) that are more appropriate for the FWD time histories whose signal characteristics are transient, nonperiodic, and truncated. Prior to the mathematical formulation of the developed algorithm, the fundamental properties of a viscoelastic material and the theory of uniaxial viscoelasticity are reviewed. Then, the theory of linear, uniaxial viscoelasticity is extended to multi-axial viscoelasticity. The multi-axial theory of viscoelasticity is, in turn, applied to develop a methodology for analyzing the laboratory Indirect Tensile (IDT) test data. The theoretical development of ViscoWave follows similar steps to those used for the development of the spectral element method. However, in place of the discrete transforms adopted in the spectral element method, ViscoWave utilizes the continuous integral transforms (namely Laplace and Hankel transforms) that are more appropriate for transient, nonperiodic signals. The theory behind ViscoWave was verified by comparing the ViscoWave simulation results to other existing solutions such as the Finite Element Analysis (FEA) and spectral element method. To backcalculate the pavement layer parameters, two of the well known unconstrained optimization algorithms (Gauss-Newton and Levenberg-Marquardt methods) were adopted for use with ViscoWave. The backcalculation was conducted using both theoretically-generated and field-obtained FWD time histories. The results indicate that ViscoWave has great potential for modeling the viscoelastic and dynamic effects of a pavement structure under an impact load. iv To my beloved daughter Lena Dah-Ye Lee, my mother Ok Hee Seo, my father Doo Seon Lee, and my sister Seung Eun Lee v TABLE OF CONTENTS LIST OF TABLES .

With the adoption of the new mechanistic-empirical pavement design method and the employment of a... more With the adoption of the new mechanistic-empirical pavement design method and the employment of axle load spectra, the question of evaluating the pavement damage resulting from different axle and truck configurations has become more relevant. In particular, the state of Michigan is unique in permitting several heavy truck axle configurations that are composed of up to 11 axles, sometimes with as many as 8 axles within one axle group. Thus, there is a need to identify the relative pavement damage resulting from these multiple axle trucks. The study looked at both flexible and rigid pavement systems, and comprised of three main components: (1) inservice pavement performance data; (2) laboratory testing under multiple axles, and (3) mechanistic-empirical analyses. The results from in-service pavement performance data indicated that multiple axle groups appear to cause less damage in fatigue per load carried for both pavement types, whereas they cause more damage in rutting of flexible pavements and roughness for rigid pavements. Laboratory testing of asphalt concrete confirmed that multiple axles cause less fatigue damage per load carried, and that rutting is nearly proportional to the number of axles within an axle group. Results from flexural concrete beam fatigue testing showed significant variability; multiple linear regression analysis (independent variables: stress ratio, stress impulse and initial modulus of elasticity) indicated, on average, similar findings to asphalt concrete fatigue for a given stress ratio; however, mechanistic analysis showed that multiple axles cause considerable stress reduction leading to significantly lower fatigue damage. The mechanistic analysis also showed that multiple axles cause more faulting in rigid pavements. Mechanistic analyses of flexible pavements confirmed that multiple axles cause less fatigue damage per load carried, and rutting damage that is nearly proportional to the number of axles within an axle group. However, the mechanistic-empirical results suggest that the AASHTO Load Equivalency Factors (LEF) for large axle groups may be unconservative. Finally, Full scale slab testing to study joint/crack deterioration in plain concrete pavements was inconclusive.

Journal of Engineering Mechanics, 2010

For this study, the Binzhou perpetual pavement test sections constructed in Shandong Province, Ch... more For this study, the Binzhou perpetual pavement test sections constructed in Shandong Province, China, were simulated for long-term fatigue performance using the layered viscoelastic pavement analysis for critical distresses (LVECD) finite element software package. In this framework, asphalt concrete was treated in the context of linear viscoelastic continuum damage theory. A recently developed unified fatigue failure criterion that defined the boundaries of the applicable region of the theory was also incorporated. The mechanistic modeling of the fatigue mechanisms was able to accommodate the complex temperature variations and loading conditions of the field pavements in a rigorous manner. All of the material models were conveniently characterized by dynamic modulus tests and direct tension cyclic fatigue tests in the laboratory using cylindrical specimens. By comparing the obtained damage characteristic curves and failure criteria, it is found that mixtures with small aggregate particle sizes, a dense gradation, and modified asphalt binder tended to exhibit the best fatigue resistance at the material level. The 15-year finite element structural simulation results for all the test sections indicate that fatigue performance has a strong dependence on the thickness of the asphalt pavements. Based on the predicted location and severity of the fatigue damage, it is recommended that sections 1 and 3 of the Binzhou test sections be employed for perpetual pavement design.

Economics, and environmental issues have spurred the introduction of the Warm Mix Asphalt (WMA) t... more Economics, and environmental issues have spurred the introduction of the Warm Mix Asphalt (WMA) technology in the pavement construction industry. The Florida Department of Transportation (FDOT) started using the WMA technology in 2006 based on reported benefits due to lower asphalt mixing and compaction temperatures. Limited field and laboratory studies have indicated that WMA may have similar performance as traditional Hot Mix Asphalt (HMA). However, some studies have also suggested that the use of WMA may increase long-term rutting and stripping potential and hence the long-term performance evaluation of the WMA mixtures is still warranted. With the primary objective of obtaining long-term field performance data of Florida’s WMA, the respective field performance of six representative WMA projects using five different technologies (one additive and four water foaming technologies) was monitored and documented in this paper. The performance of the WMA projects was then compared to t...

The Florida Department of Transportation (FDOT) has historically used a combination of handheld d... more The Florida Department of Transportation (FDOT) has historically used a combination of handheld devices and visual surveys to evaluate the retroreflectivity of pavement markings. However, visual surveys have the inherent limitations of operator bias while the use of a handheld device is slow, labor intensive, and presents safety hazards. Many highway agencies have recognized that a Mobile Retroreflectivity Unit (MRU) may be a safer and a more efficient alternative to the handheld retroreflectometers. Since the measurement process relies on the operator-driven instrument, a level of uncertainty is always a concern in evaluating pavement markings with the MRU. This research is aimed at assessing the precision and bias of the MRU while using the handheld retroreflectometer as a reference device. A total of ten 1.0 mile long field sites were selected to include various pavement surface types and pavement marking materials (paints and thermoplastics). The results indicated that, when compared to the handheld retroreflectometers, the MRU demonstrated no statistical differences or bias at a 95 percent confidence level for the retroreflectivity values ranging between 200 and 800 mcd/m 2 /lux. In addition, it was determined that the retroreflectivity values from two properly conducted tests using a single MRU on the same pavement marking should not differ by more than 7.8 percent and when different MRUs are used on the same pavement marking, the retroreflectivity values should not differ more than 13.3 percent. This paper presents a description of the testing program, the data collection effort, and the subsequent analyses and findings.