Past editions of the American Association of State Highway and Transportation Officials （AASHTO） Guide for Design of Pavement Structures have served well for several decades; nevertheless, many serious limitations e...Past editions of the American Association of State Highway and Transportation Officials （AASHTO） Guide for Design of Pavement Structures have served well for several decades; nevertheless, many serious limitations exist for their continued use as the nation＇s primary pavement design procedures. Researchers are now incorporating the latest advances in pavement design into the new Mechanistic-Empirical Pavement Design Guide （MEPDG）, developed under the National Cooperative Highway Research Program （NCHRP） 1-37A project and adopted and published by AASHTO. The MEPDG procedure offers several dramatic improvements over the current pavement design guide and presents a new paradigm in the way pavement design is performed. However, MEPDG is substantially more complex than the AASHTO Design Guide by considering the input parameters that influence pavement performance, including traffic, climate, pavement structure and material properties, and applying the principles of engineering mechanics to predict critical pavement responses. It requires significantly more input from the designer. Some of the required data are either not tracked previously or are stored in locations not familiar to designers, and many data sets need to be preprocessed for use in the MEPDG. As a result, tremendous research work has been conducted and still more challenges need to be tackled both in federal and state levels for the full implementation of MEPDG. This paper, for the first time, provides a comprehensive bird＇s eye view for the MEPDG procedure, including the evolvement of the design methodology, an overview of the design philosophy and its components, the research conducted during the development, improvement, and implementation phases, and the challenges remained and future developments directions. It is anticipated that the efforts in this paper aid in enhancing the mechanistic-empirical based pavement design for future continuous improvement to keep up with changes in trucking, materials, construction, design concepts, computers, and so on.展开更多
A research project was initiated by INDOT to estimate the structural contribution and feasibility of FDR bases for pavement structure under a low-medium volume traffic loading. FWD tests were conducted and the layer m...A research project was initiated by INDOT to estimate the structural contribution and feasibility of FDR bases for pavement structure under a low-medium volume traffic loading. FWD tests were conducted and the layer moduli were back calculated on different construction phases： the surface of existing HMA pavement, the FDR base, the new HMA final surface, and the nine months＇ traffic opening, respectively, for a total of four times. The results indicate the promise of this recycled base material in pavement construction compared to traditional granular base. In addition, this paper discusses how the lab test results relate to the expected performance in a pavement structure by the MEPDG software and its parameter effects. Research indicated the MEPDG provided comparable thickness to the 1993 AASHTO Guide if the failure criteria are set up reasonably. Therefore, the MEPDG could be used as a design tool to estimate layer thickness for FDR pavement with a low-medium traffic volume.展开更多
Curling results from the temperature differential across the concrete slab thickness and may induce undue stresses in newly placed slab. This study deals with the finite element （FE） analysis of curling, curling str...Curling results from the temperature differential across the concrete slab thickness and may induce undue stresses in newly placed slab. This study deals with the finite element （FE） analysis of curling, curling stresses, field measurement of curling on a newly built jointed plain concrete pavement, and comparison of its long-term performance using both Mechanistic-Empirical Pavement Design Guide （MEPDG） and HIPERPAVII software. The FE analysis was performed with a software program, ANSYS. The test section was modeled as a three-layer system with 300 mm concrete slab, 100 mm treated drainable base, and 150 mm lime-treated subgrade. All layers were assumed to be linear elastic. Temperature data was collected at five different depth locations across the concrete slab with digital data loggers. Curling was measured on five different days with a simple setup. The effect of temperature nonlinearities across the slab thickness was also examined. The results show that both upward and downward curling increase as the temperature differential increases. The maximum stress resulting from the combined effect of curling and traffic loading due to positive temperature differential is higher than that due to the negative temperature differential of the same magnitude. Since temperature differential has a significant influence on curling, both curling and curling stresses can be mitigated at an early age with temperature control, namely via enhanced curing. Both MEPDG and HIPERPAVII showed approximately the same performance for the PCC thickness ranging from 215 mm to 300 mm for this project. Performance prediction from HIPERPAVII is very sensitive to the change in PCC thickness less than 230 mm whereas MEPDG prediction is not as sensitive to the thickness change as with HIPERPAV 1I.展开更多
Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resil...Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resilient modulus values at only a specific stress state from DCP data, corresponding to the predefined thicknesses of pavement layers（a 50 mm asphalt wearing course, a 100 mm asphalt binder course and a200 mm aggregate base course）. In this study, field-measured DCP data were utilized to estimate the resilient modulus of low-plasticity subgrade Piedmont residual soil. Piedmont residual soils are in-place weathered soils from igneous and metamorphic rocks, as opposed to transported or compacted soils.Hence the existing empirical correlations might not be applicable for these soils. An experimental program was conducted incorporating field DCP and laboratory resilient modulus tests on "undisturbed" soil specimens. The DCP tests were carried out at various locations in four test sections to evaluate subgrade stiffness variation laterally and with depth. Laboratory resilient modulus test results were analyzed in the context of the mechanistic-empirical pavement design guide（MEPDG） recommended universal constitutive model. A new approach for predicting the resilient modulus from DCP by estimating MEPDG constitutive model coefficients（k;,k;and k;） was developed through statistical analyses. The new model is capable of not only taking into account the in situ soil condition on the basis of field measurements,but also representing the resilient modulus at any stress state which addresses a limitation with existing empirical DCP models and its applicability for a specific case. Validation of the model is demonstrated by using data that were not used for model development, as well as data reported in the literature.展开更多
The KDOT （Kansas Department of Transportation） is currently adopting MEPDG （mechanistic-empirical pavement design guide） to replace the 1993 AASHTO （American Association of State Highway and Transportation Offici...The KDOT （Kansas Department of Transportation） is currently adopting MEPDG （mechanistic-empirical pavement design guide） to replace the 1993 AASHTO （American Association of State Highway and Transportation Officials） design method. The main objective of this study was to compare flexible pavement design using 1993 AASHTO design guide and MEPDG. Five newly built Superior PERforming Asphalt PAVEments （Superpave）, designed using the 1993 AASHTO Design Guide, were selected as test sections for the design simulation study. Deflection data were collected approximately 8 to 10 weeks after construction using FWD （falling weight deflectometer）. The FWD deflection data were used to back-calculate the pavement layer moduli using three different back-calculation programs. The existing pavement structures were analyzed for a 10-year analysis period. The maximum numbers of years the existing pavement structures will be in a serviceable condition as well as the minimum thicknesses of different layers to serve for 10-years were also determined. Effects of changing subgrade modulus, target distress, and reliability were also investigated. The MEPDG design analysis shows that the 1993 AASHTO Guide-designed flexible pavements do not show the distresses currently observed in Kansas for the 10-year design period. The MEPDG design simulation shows that the thinner the pavement sections, the higher the permanent deformation. The existing pavement structures can serve for more than 20 years as per the MEPDG design analysis if the default failure criteria and nationally-calibrated models are used.展开更多
Pavement rehabilitation is a major activity for all highway agencies.Accurate and efficient measurement of the rehabilitated pavement performances becomes more and more important in this procedure.In the last 10 years...Pavement rehabilitation is a major activity for all highway agencies.Accurate and efficient measurement of the rehabilitated pavement performances becomes more and more important in this procedure.In the last 10 years,significant improvements have been made in pavement nondestructive evaluation.NDT(non-destructive testing)has gained popularity because of its advantage in comparison to laboratory testing.Some of these advantages include minimal or no damage to structure,in-situ full-scale testing,relatively low operational cost,and short test duration.The INDOT(Indiana Department of Transportation)has a project level pavement evaluation program that began several years ago.This project level evaluation program employs FWD(falling weight deflectometer),GPR(ground penetration radar)and video logging.The program provides valuable information about pavement performance characteristics and offers useful tools for developing pavement rehabilitation strategies,specifically overlays and pavement underseals.On the other hand,the state of Indiana had rehabilitated its flexible,rigid or composite pavement almost exclusively with asphalt.This AC(asphalt concrete)overlay can improve the condition of existing pavement and extend the service life of the existing pavement structure.This paper thus describes the experiences of pavement overlay with AC thickness design for the INDOT(Indiana State Department of Transportation)using the AASHTO(American Association of State Highway and Transportation Officials)1993 Guide,the MEPDG(Mechanistic-Empirical Pavement Design Guide).In order to do that,backcalculation program was compared and evaluated to obtain subgrade resilient modulus and k value for pavement rehabilitation using FWD data.Video logging provides IRI(international roughness index)and rut depth for existing pavement condition and GPR provides thickness or pavement bonding conditions in pavement.Emphasis is placed on observations and issues encountered using the current AASHTO 1993 Guide and the MEPDG.展开更多
文摘Past editions of the American Association of State Highway and Transportation Officials （AASHTO） Guide for Design of Pavement Structures have served well for several decades; nevertheless, many serious limitations exist for their continued use as the nation＇s primary pavement design procedures. Researchers are now incorporating the latest advances in pavement design into the new Mechanistic-Empirical Pavement Design Guide （MEPDG）, developed under the National Cooperative Highway Research Program （NCHRP） 1-37A project and adopted and published by AASHTO. The MEPDG procedure offers several dramatic improvements over the current pavement design guide and presents a new paradigm in the way pavement design is performed. However, MEPDG is substantially more complex than the AASHTO Design Guide by considering the input parameters that influence pavement performance, including traffic, climate, pavement structure and material properties, and applying the principles of engineering mechanics to predict critical pavement responses. It requires significantly more input from the designer. Some of the required data are either not tracked previously or are stored in locations not familiar to designers, and many data sets need to be preprocessed for use in the MEPDG. As a result, tremendous research work has been conducted and still more challenges need to be tackled both in federal and state levels for the full implementation of MEPDG. This paper, for the first time, provides a comprehensive bird＇s eye view for the MEPDG procedure, including the evolvement of the design methodology, an overview of the design philosophy and its components, the research conducted during the development, improvement, and implementation phases, and the challenges remained and future developments directions. It is anticipated that the efforts in this paper aid in enhancing the mechanistic-empirical based pavement design for future continuous improvement to keep up with changes in trucking, materials, construction, design concepts, computers, and so on.
文摘A research project was initiated by INDOT to estimate the structural contribution and feasibility of FDR bases for pavement structure under a low-medium volume traffic loading. FWD tests were conducted and the layer moduli were back calculated on different construction phases： the surface of existing HMA pavement, the FDR base, the new HMA final surface, and the nine months＇ traffic opening, respectively, for a total of four times. The results indicate the promise of this recycled base material in pavement construction compared to traditional granular base. In addition, this paper discusses how the lab test results relate to the expected performance in a pavement structure by the MEPDG software and its parameter effects. Research indicated the MEPDG provided comparable thickness to the 1993 AASHTO Guide if the failure criteria are set up reasonably. Therefore, the MEPDG could be used as a design tool to estimate layer thickness for FDR pavement with a low-medium traffic volume.
文摘Curling results from the temperature differential across the concrete slab thickness and may induce undue stresses in newly placed slab. This study deals with the finite element （FE） analysis of curling, curling stresses, field measurement of curling on a newly built jointed plain concrete pavement, and comparison of its long-term performance using both Mechanistic-Empirical Pavement Design Guide （MEPDG） and HIPERPAVII software. The FE analysis was performed with a software program, ANSYS. The test section was modeled as a three-layer system with 300 mm concrete slab, 100 mm treated drainable base, and 150 mm lime-treated subgrade. All layers were assumed to be linear elastic. Temperature data was collected at five different depth locations across the concrete slab with digital data loggers. Curling was measured on five different days with a simple setup. The effect of temperature nonlinearities across the slab thickness was also examined. The results show that both upward and downward curling increase as the temperature differential increases. The maximum stress resulting from the combined effect of curling and traffic loading due to positive temperature differential is higher than that due to the negative temperature differential of the same magnitude. Since temperature differential has a significant influence on curling, both curling and curling stresses can be mitigated at an early age with temperature control, namely via enhanced curing. Both MEPDG and HIPERPAVII showed approximately the same performance for the PCC thickness ranging from 215 mm to 300 mm for this project. Performance prediction from HIPERPAVII is very sensitive to the change in PCC thickness less than 230 mm whereas MEPDG prediction is not as sensitive to the thickness change as with HIPERPAV 1I.
文摘Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resilient modulus values at only a specific stress state from DCP data, corresponding to the predefined thicknesses of pavement layers（a 50 mm asphalt wearing course, a 100 mm asphalt binder course and a200 mm aggregate base course）. In this study, field-measured DCP data were utilized to estimate the resilient modulus of low-plasticity subgrade Piedmont residual soil. Piedmont residual soils are in-place weathered soils from igneous and metamorphic rocks, as opposed to transported or compacted soils.Hence the existing empirical correlations might not be applicable for these soils. An experimental program was conducted incorporating field DCP and laboratory resilient modulus tests on "undisturbed" soil specimens. The DCP tests were carried out at various locations in four test sections to evaluate subgrade stiffness variation laterally and with depth. Laboratory resilient modulus test results were analyzed in the context of the mechanistic-empirical pavement design guide（MEPDG） recommended universal constitutive model. A new approach for predicting the resilient modulus from DCP by estimating MEPDG constitutive model coefficients（k;,k;and k;） was developed through statistical analyses. The new model is capable of not only taking into account the in situ soil condition on the basis of field measurements,but also representing the resilient modulus at any stress state which addresses a limitation with existing empirical DCP models and its applicability for a specific case. Validation of the model is demonstrated by using data that were not used for model development, as well as data reported in the literature.
文摘The KDOT （Kansas Department of Transportation） is currently adopting MEPDG （mechanistic-empirical pavement design guide） to replace the 1993 AASHTO （American Association of State Highway and Transportation Officials） design method. The main objective of this study was to compare flexible pavement design using 1993 AASHTO design guide and MEPDG. Five newly built Superior PERforming Asphalt PAVEments （Superpave）, designed using the 1993 AASHTO Design Guide, were selected as test sections for the design simulation study. Deflection data were collected approximately 8 to 10 weeks after construction using FWD （falling weight deflectometer）. The FWD deflection data were used to back-calculate the pavement layer moduli using three different back-calculation programs. The existing pavement structures were analyzed for a 10-year analysis period. The maximum numbers of years the existing pavement structures will be in a serviceable condition as well as the minimum thicknesses of different layers to serve for 10-years were also determined. Effects of changing subgrade modulus, target distress, and reliability were also investigated. The MEPDG design analysis shows that the 1993 AASHTO Guide-designed flexible pavements do not show the distresses currently observed in Kansas for the 10-year design period. The MEPDG design simulation shows that the thinner the pavement sections, the higher the permanent deformation. The existing pavement structures can serve for more than 20 years as per the MEPDG design analysis if the default failure criteria and nationally-calibrated models are used.
文摘Pavement rehabilitation is a major activity for all highway agencies.Accurate and efficient measurement of the rehabilitated pavement performances becomes more and more important in this procedure.In the last 10 years,significant improvements have been made in pavement nondestructive evaluation.NDT(non-destructive testing)has gained popularity because of its advantage in comparison to laboratory testing.Some of these advantages include minimal or no damage to structure,in-situ full-scale testing,relatively low operational cost,and short test duration.The INDOT(Indiana Department of Transportation)has a project level pavement evaluation program that began several years ago.This project level evaluation program employs FWD(falling weight deflectometer),GPR(ground penetration radar)and video logging.The program provides valuable information about pavement performance characteristics and offers useful tools for developing pavement rehabilitation strategies,specifically overlays and pavement underseals.On the other hand,the state of Indiana had rehabilitated its flexible,rigid or composite pavement almost exclusively with asphalt.This AC(asphalt concrete)overlay can improve the condition of existing pavement and extend the service life of the existing pavement structure.This paper thus describes the experiences of pavement overlay with AC thickness design for the INDOT(Indiana State Department of Transportation)using the AASHTO(American Association of State Highway and Transportation Officials)1993 Guide,the MEPDG(Mechanistic-Empirical Pavement Design Guide).In order to do that,backcalculation program was compared and evaluated to obtain subgrade resilient modulus and k value for pavement rehabilitation using FWD data.Video logging provides IRI(international roughness index)and rut depth for existing pavement condition and GPR provides thickness or pavement bonding conditions in pavement.Emphasis is placed on observations and issues encountered using the current AASHTO 1993 Guide and the MEPDG.
