• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.34-42
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• 2018

In order to minimize the deformation of asphalt concrete track(ACT) and ensure the structural safety, a wide type concrete sleeper is necessary to distribute vehicle loading and reduce the exposure of the asphalt roadbed. In this research, the wide prestressed concrete(PSC) sleeper for ACT was developed through the shape design and the structural safety was reviewed using finite element analysis. Furthermore, static test, dynamic test and fatigue test were carried out according to EN13230-2 to verify the design appropriateness of the wide PSC sleepers for ACT. The performance test showed that the developed wide PSC sleeper for ACT meets all the performance requirements by European standard.

• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.331-340
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• 2016

Wheel load, design velocity, traffic amount (MGT), stiffness and thickness of sub-layers of asphalt concrete track are selected as performance design parameters in this study. A pseudo-static wheel load computed considering the dynamic amplification factor (DAF) based on the design velocity of the KTX was applied to the top of asphalt concrete track for full three dimensional structural analysis using the ABAQUS program. Tensile strains at the bottom of the asphalt concrete layer and vertical strains at the top of the subgrade were computed from the structural FEA with different combinations of performance parameter values for one asphalt concrete track section. Utilizing the computed structural analysis results such as the tensile strains and the vertical strains, it was possible to develop design graphs to investigate proper track sections for different combination of the performance parameters including wheel load, design velocity, traffic amount(MGT), stiffness and thickness of asphalt concrete layers for any given design life. By analyzing the proposed design graphs for asphalt concrete track, it was possible to propose simple design tables that can be used by engineers for the effective and fast design of track.

• International Journal of Highway Engineering
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• v.2 no.1
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• pp.135-145
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• 2000

A new procedure needs to be developed to predict the dynamic layer properties under moving truck loads. In this study, a computer code to evaluate layer moduli of asphalt concrete pavement from measured interior deflections at various depths were developed and verified from numerical model tests. Interior deflections of the pavement are measured from Multi-Depth Deflectometer(MDD). It was found that errors between the given and backcalculated moduli in numerical analysis were less than 0.32% for several numerical models tested. When impact loads were used, a technique to determine the depth to virtual rigid base was proposed through the analysis of compressive wave velocity and impulse loading durations. It was found that errors between the given and backcalculated moduli in numerical analysis were less than 0.114% when virtual rigid base was considered in numerical analysis. The pavement behavior must be evaluated under various vehicle speeds when determining the dynamic interaction between the loading vehicle and pavement system. To evaluate the dynamic behavior on asphalt concrete pavement under various vehicle speeds, truck moving tests were carried out. From the test results with respect to vehicle speed, it was found that the vehicle speed had significant effect on actual response of the pavement system. The lower vehicle speed generates the higher interior deflections, and the lower dynamic modulus.

• Journal of the Korean Society for Railway
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• v.19 no.1
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• pp.67-76
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• 2016

The asphalt-concrete trackbed system has many advantages in terms of maintenance and economics. However, methods to investigate practical use corresponding to the development of the trackbed system must be developed. The primary objective of this study was to evaluate the dynamic performance of the asphalt system in accordance with both the elastic and viscoelastic material characteristics and design thickness of the asphalt trackbed. More specifically, in order to reduce the uncertainty error of the Finite Element(FE) model, a three-dimensional full scale FE model was developed and then the infinite foundation model was considered. Finally, to compare the condition of viscoelastic materials, performance evaluation of the asphalt-concrete trackbed system was used to deal with the dynamic amplification factors; numerical results using isotropic-elastic materials in the FE analysis are presented.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.21-25
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• 2009

The results of a recent case study for material characterizations and structural evaluation to design asphalt overlay thickness of William P Hobby airport in Houston, Texas are presented herein. The existing runway 12R-30L of Hobby airport consisted of thick asphalt overlay over Portland Cement Concrete (PCC) and the localized surface shoving as evident in the closure of surface groove has been observed recently. Using the field cored asphalt concrete mixtures, measurements of percent air voids, asphalt content and aggregate gradation were conducted to find out the causations of surface shoving and groove closure. The FAA layered elastic program, LEDFAA was utilized to evaluate pavement structural conditions for new asphalt overlay. Two different composition assumptions for existing pavement were made to evaluate the pavement as followings: 1) APC, Asphalt Concrete Overlay over PCC pavement and 2) AC, Asphalt Concrete pavement. Based on laboratory testing results, a ratio of percent passing #200 to asphalt content ranged 1.1 to 2.2, which is considered a high ratio and a tendency of tender mix design was observed. Thus, the localized surface shoving and groove closure of the runway 12R-30L could be attributed to the use of excessive fine contents and tender mix design. Based on the structural evaluation results, it was ascertained that the analysis assuming the pavement structure as AC pavement gives more realistic structural life when the asphalt overlay is thicker enough compared to PCC layer because the existing PCC pavement under asphalt overlay acts more like a high quality base material.

• Computational Structural Engineering
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• v.10 no.4
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• pp.229-238
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• 1997

Mechanical behavior of asphalt concrete that accounts for viscoelasticity and damage evolution under cyclic loading conditions is modeled and presented in this paper. An elastic-viscoelastic correspondence principle in terms of pseudo variables is applied to separately evaluate viscoelasticity and time-dependent damage growth in asphalt concrete. A microcrack growth law, which is commonly employed in linear viscoelastic fracture mechanics, is successfully used for describing the damage growth in the body. A constitutive equation in terms of stress and pseudo strain is first established for controlled-strain mode, and then transformed to controlled-stress constitutive equation by simply replacing stress and pseudo strain with pseudo stress and strain. The transformed constitutive equation in terms of pseudo stress satisfactorily predicts the mechanical behavior of asphalt concrete all the way up to failure under controlled-stress modes.

• International Journal of Highway Engineering
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• v.6 no.1 s.19
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• pp.13-23
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• 2004

This paper presents the results of a study that was performed to evaluate structural behaviors and related distress of asphalt pavements on concrete bridge deck based on the visual inspection and 3-dimensional finite element analysis. As a result, three most failure types were found such as permanent deformation, potholes, and fatigue crackings. In addition, the failure mechanisms of different types of concrete bridge deck were investigated. An increase in fatigue of asphalt pavements on concrete bridge deck was observed and confirmed by the results from the visual inspections. In consequence, the aging and stripping of asphalt surfacing materials are relatively dominant factors on fatigue rather than traffic loadings.

• Journal of the Society of Disaster Information
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• v.10 no.1
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• pp.25-32
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• 2014

The main objective of materials testing is to simulate in-situ field conditions as closely as possible, including loading conditions, climatic conditions, etc. Also, the test method should be easy, inexpensive, simple, and efficient to conduct to become an acceptable standard laboratory testing method for many agencies. Based on these reasons, a new test method employing repetitive axial loading with confinement was developed to evaluate the rutting(permanent deformation) of asphalt concrete. The new laboratory test protocol was developed based on the study of the various structural analysis and field data. This protocol divides asphalt layer(s) into three categories depending upon the depth. Different temperatures and vertical stress levels were used in these areas.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.67-76
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• 1992

A procedure to determine the axle load limits of asphalt concrete pavements are proposed in this study. Axle load limits are determined by calculating maximum tensile strains at the bottom of the asphalt stabilized base layer and maximum vertical strains at the top of the subgrade. In order to investigate the efficiency of axle configuration, calculated influence line of wheel load on domestic expressway pavement system is used. Limiting strains are selected through the analysis of conventional failure criteria. From the analysis of axle load limits about axle composition(single-axle, tandem-axle, tridem-axle), it is found that the axle load limits of tandem-axle and tridem-axle can be calculated by muitipling the axle load limits of single-axle by axle numbers and that axle load limits are closely related to the thickness of each layer of pavement structure. It is also found that the axle load limits by tensile strains are more critical than those by vertical strains on asphalt concrete pavement models of YOUNG-DONG, KYONG-IN and KYONG-BU expressways.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.121-129
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• 2010

The purpose of this study is to present the resonable guideline of asphalt concrete pavements in apartment complex. To achieve this purpose was performed review of domestic and foreign guidelines, investigation of main distresses of asphalt concrete pavement, and structural analysis for the investigated cross-sections of the pavements in apartment complex. According to results of structural analysis, this study presented the standard cross-section of the pavement with subbase of 20cm, asphalt base of 5cm, and surface of 5cm in apartment complex. In urban areas, traffic is generally opened after asphalt base course is placed because of civil complaint by dust. Surface course is placed after all of work are completed. Considering these conditions, this study also presented the standard cross-section of the pavement with subbase of 20cm, asphalt base of 7cm, and surface of 5cm for urban areas that expect civil complaints by dust.