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    <title>Transport Research International Documentation (TRID)</title>
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    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>A mechanistic-empirical model for predicting top-down fatigue cracking in an asphalt pavement overlay</title>
      <link>https://trid.trb.org/View/1629232</link>
      <description><![CDATA[Climate, pavement structure, traffic and material properties were identified and incorporated into a new mechanistic-empirical model to predict top-down cracking in an asphalt pavement overlay. The shear strain at the edge of the tyre was determined as a critical pavement structural response for initiating top-down cracking. The horizontal failure strain, dynamic modulus and shear strain at the edge of the tyre were incorporated in the model for characterising the fatigue life of asphalt pavements. The model was calibrated and verified using the data collected nationwide and is recommended to supplement the current models in the mechanistic-empirical pavement design guide (MEPDG). To mitigate top-down cracking in the asphalt pavement overlay, it is recommended to design an asphalt mix with relatively a higher horizontal failure strain value to reduce the shear strain response along the edges of the tyre.]]></description>
      <pubDate>Wed, 12 Jun 2019 09:21:10 GMT</pubDate>
      <guid>https://trid.trb.org/View/1629232</guid>
    </item>
    <item>
      <title>A Calibrated Mechanics-Based Model for Top-Down Cracking of Asphalt Pavements</title>
      <link>https://trid.trb.org/View/1591473</link>
      <description><![CDATA[A calibrated mechanistic-empirical model was developed to analyze top-down cracking (TDC) performance with actual traffic load and thermal stress. The traffic-induced and thermal-induced J-integral were employed in the Paris’ law with fracture parameters A′ and n′ estimated using asphalt mixture properties. Number of days for initiated TDC to reach the medium severity level was then calculated mechanistically, which was related to field performance for calibration purposes. It was observed that when TDC reached a critical length, the TDC length diminished and area of fatigue cracking increased. An associated computer program was also developed, which normally completed a 30-year performance analysis within 1 min.]]></description>
      <pubDate>Thu, 18 Apr 2019 11:04:20 GMT</pubDate>
      <guid>https://trid.trb.org/View/1591473</guid>
    </item>
    <item>
      <title>Calibrated Mechanics-Based Models for Top-Down Cracking of Asphalt Pavements</title>
      <link>https://trid.trb.org/View/1572345</link>
      <description><![CDATA[This study develops a new mechanistic-empirical (ME) model to predict top-down cracking (TDC) performance of asphalt pavements. Two mechanisms including traffic contact stress and thermal stress are accounted to predict the crack increment. Paris’ law is utilized as the fracture mechanics fundamental to compute the cumulative TDC growth. The ME model consists of J-integral and asphalt mixture fracture properties, which considers the effects of traffic load spectra, layers material properties, location of crack tip, field aging, pavement structure and temperature. To facilitate the J-integral calculation, a factorial design of J-integral under different conditions is generated based on numerous finite element computations. With the aid of the database, six artificial neural network (ANN) models for different tire lengths and tire numbers and three ANN models for different coefficients of thermal contraction are constructed to predict the traffic-induced and thermal-induced J-integral, respectively. The fracture parameters can be either experimentally determined or reasonably predicted with asphalt material properties. The cumulative crack growth and number of days to reach the medium severity level are calculated mechanistically. Field performance is characterized with a sigmoidal-shaped curve, and the calculated number of days is related to the scale and shape of the performance curve for calibration purposes. It is observed that when TDC reaches a critical length, the TDC length diminishes and fatigue cracking level increases. The developed ME model is proven to be consistent with field performance, and a computer program is developed which can complete a 30-year analysis within 1 min.]]></description>
      <pubDate>Sat, 02 Mar 2019 15:41:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/1572345</guid>
    </item>
    <item>
      <title>Review of Mechanistic-Empirical Modeling of Top-Down Cracking in Asphalt Pavements</title>
      <link>https://trid.trb.org/View/1565261</link>
      <description><![CDATA[Top-down cracking has been identified worldwide and is regarded as a major type of asphalt pavement distress. Along with a comprehensive review of the existing work, this study is intended to propose a roadmap for developing a mechanistic-empirical model and associated design software for top-down cracking in asphalt pavements. This paper reviews eleven sub-models relevant to material, structure, traffic, and climate to account for the key factors that affect top-down cracking. Over 120 published studies are located and reviewed in terms of modeling techniques, model types, and model components. In addition, the methods and sources to identify and collect the data required to develop these sub-models are presented. Within the scope of this work, this study discusses several sub-models as examples and provides a roadmap for future development. The introduced sub-models emphasize some critical issues, such as the modulus gradient due to non-uniform aging, different cracking mechanisms, and computation of the J-integral (energy release rate) that drives the crack downward from the pavement surface. Finally, this study provides an assembling plan to put all of the sub-models together into a Top-Down Cracking Program, which could predict and calibrate the growth of top-down cracking in asphalt pavements.]]></description>
      <pubDate>Fri, 30 Nov 2018 09:41:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/1565261</guid>
    </item>
    <item>
      <title>Field performance of top-down fatigue cracking for warm mix asphalt pavements</title>
      <link>https://trid.trb.org/View/1563304</link>
      <description><![CDATA[As a result of repeated rehabilitation efforts over the past few decades, often asphalt pavements have become deep-strength pavements. Consequently, top-down cracking has become a primary distress type. In particular, the top-down cracking performance of warm mix asphalt (WMA) pavements, i.e. how does it compare with similar hot mix asphalt (HMA) pavements is largely unclear mainly due to the lack of field performance data. This paper presents an effort of monitoring the top-down cracking performance of 28 pavement projects including WMA pavements and their corresponding HMA control pavements with service lives ranging between 4 and 10 years. These pavements cover different climate zones, WMA technologies, service years, pavement structures and traffic volume levels. Two rounds of distress surveys were conducted at a two-year interval, and the material (asphalt binder and mixture) properties of the pavements were determined using field cores. The top-down cracking performance of the HMA and WMA pavements was compared based on the first and second round distress surveys. It was found that the HMA and WMA pavement in general exhibited comparable performance. The significant determinants (material properties) for top-down cracking were determined, which were vertical failure deformation of mixes measured at 20 °C from indirect tension test.]]></description>
      <pubDate>Sat, 03 Nov 2018 15:17:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/1563304</guid>
    </item>
    <item>
      <title>A study of top-down cracking in the state of Oregon</title>
      <link>https://trid.trb.org/View/1549703</link>
      <description><![CDATA[A major concern from the Oregon Department of Transportation (ODOT) in recent years has been the prevention of top-down cracking in hot mix asphalt (HMA) pavements shortly into their design lives. To this end, the ODOT has identified HMA pavements that have displayed top-down cracking within three years of construction for evaluation. This study’s main objective is the evaluation of top-down cracked pavement sections against results collected from non-cracked pavement sections, and the identification of practices that will prevent top-down cracking from occurring. Six surface cracked pavements and four non-cracked pavement sections were used for conducting this research. Extensive field and laboratory investigations were done through distress surveys, falling weight deflectometer testing, dynamic cone penetrometer (DCP) testing, coring from cracked and non-cracked pavement sections, and testing of cores for HMA mixture rheology and asphalt binder rheology. The laboratory investigation included dynamic modulus, indirect tensile strength, and specific gravity testing on the HMA cores, rheological tests on asphalt binder and aggregate gradation analysis. Results suggest that prevention of top-down cracking can be improved through tighter control on density (air void requirements) and asphalt binder selection during material selection and initial construction.]]></description>
      <pubDate>Fri, 05 Oct 2018 09:27:06 GMT</pubDate>
      <guid>https://trid.trb.org/View/1549703</guid>
    </item>
    <item>
      <title>Investigation of mechanisms of top-down fatigue cracking of asphalt pavement</title>
      <link>https://trid.trb.org/View/1516821</link>
      <description><![CDATA[Various types of responses have been selected in the past as the driving forces of the top-down cracking. However, the most appropriate candidate for top-down cracking is the horizontal tensile strain at the pavement surface, considering the horizontal tensile strain at the bottom of asphalt layer has been historically used as the critical response for bottom-up cracking in the ME design. In this study, the mechanisms of top-down cracking are investigated based on the horizontal tensile strain at the surface. A multi-layered elastic computer code, APRA, was utilized to compute the horizontal strains at the pavement surface. APRA uses the Lucas algorithm and integration, summation and extrapolation methods to accurately determine the surface responses. The results show that traffic loading may induce significant horizontal tensile strain in the transverse direction at the surface, which is a major cause of the top-down cracking. The critical location of the tensile strain is just outside the tyre edges. It is pointed out that although the newly developed Mechanistic-Empirical Pavement Design Guide (MEPDG) uses the horizontal strain at the surface for the prediction of top-down cracking, the analysis locations adopted in the MEPDG may not be able to identify the maximum tensile strain. It is observed in this study that the maximum tensile strain at the surface increases rapidly with temperature. For the pavement with cement-treated base, the top-down cracking is the dominant type of fatigue cracking, while the bottom-up cracking is unlikely due to the strong support from the base. For the pavement with granular base, the bottom-up cracking is more likely to occur at medium or low temperatures, while the cracking is more likely to initiate from the top at high temperatures. The likelihood of top-down cracking occurrence increases with increasing temperature and asphalt layer thickness.]]></description>
      <pubDate>Thu, 19 Jul 2018 14:45:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/1516821</guid>
    </item>
    <item>
      <title>Evaluation of top-down cracking potential for asphalt pavements with 4.75 mm nominal maximum aggregate size mixture layer using full-scale field tests and finite element analysis</title>
      <link>https://trid.trb.org/View/1513364</link>
      <description><![CDATA[This study primarily focused on evaluating top-down cracking resistance for pavement structures with 4.75 mm nominal maximum aggregate size asphalt mixtures (i.e. SP-4.75) that will help determine more effective application of these mixes for layered flexible pavement system. Crack evaluation and pavement surface response measurements were conducted using full-scale field test sections. In addition, a three-dimensional (3-D) viscoelastic finite-element (FE) pavement model was developed to further validate the results of field tests using analytical solution. The results indicated that the pavement structure with SP-4.75 mixture at the top becomes more prone to top-down cracking when a thin layer with unmodified asphalt binder is applied. It was found that both layer thickness and binder type are key parameters to control top-down cracking potential. Also, the comparative observations between analytical and experimental results confirm that the FE model developed was able to provide accurate, reliable, and realistic prediction for change in pavement surface strain responses due to different conditions of SP-4.75 layer application. It was concluded that adequate thickness and binder type should be considered for proper application of SP-4.75 mixture as a surface course of layered flexible pavement system to effectively resist top-down cracking.]]></description>
      <pubDate>Wed, 30 May 2018 16:35:27 GMT</pubDate>
      <guid>https://trid.trb.org/View/1513364</guid>
    </item>
    <item>
      <title>Highlighting of the viscoelastic behaviour of interfaces in asphalt pavements – a possible origin to top-down cracking</title>
      <link>https://trid.trb.org/View/1502767</link>
      <description><![CDATA[Top-down cracking (TDC) is known to initiate and remain near the surface of bituminous pavements. The aim of this paper is twofold: (i) show experimental evidence of the viscoelastic behaviour of interface in asphalt pavements under some temperature conditions and (ii) show that taking into account such a behaviour could provide an explanation to the mechanism involved in the initiation of TDC. This paper documents the methodology used to investigate the behaviour of the upper interface from experimental tests. The mechanical response of the experimental pavement is evaluated using three models: (1) the elastic model, (2) the Huet–Sayegh viscoelastic model to account for the behaviour of asphalt layers and (3) same as 2, but with additional very thin viscoelastic layers to represent interfaces between the asphalt layers. The software ViscoRoute 2.0© is used to evaluate the stresses and the strains at different depths of the pavement. The comparison between the experimental results and the models clearly shows that model 3 is that yields the best fit. This model shows that significant tensile stresses and strains occur near the surface and at the interface between two asphalt layers. The transposition of the viscoelastic behaviour of interfaces to real traffic conditions could explain TDC as one of the damaging modes of asphalt pavements.]]></description>
      <pubDate>Fri, 16 Mar 2018 09:51:59 GMT</pubDate>
      <guid>https://trid.trb.org/View/1502767</guid>
    </item>
    <item>
      <title>Evaluation of Top-Down Cracking Performance of In Situ Asphalt Mixture Based on Accelerated Pavement Testing and Laboratory Test</title>
      <link>https://trid.trb.org/View/1496222</link>
      <description><![CDATA[The purpose of this study is to evaluate the pavement top-down cracking performance with accelerated pavement testing (APT) and laboratory test for in-situ asphalt mixture. The full-scale accelerated pavement test is carried out at two field test sections with different accelerated loading passes on a selected expressway ramp in Shanghai. During the APT test, the portable seismic property analyzer (PSPA) is used to measure hot mix asphalt layer modulus. The PSPA modulus decreases with the increasing of accelerated loading passes. A new equation is put forward to describe the relation between the PSPA modulus and accelerated loading passes. Based on the proposed equation, the pavement damage parameter is analyzed. For the selected in-situ asphalt pavement, the damage develops a little faster at the outer edge of wheelmark than at the center of wheelmark. Field cores are taken from the APT test sections and used for making specimens for uniaxial penetrating test and indirect tensile test. Laboratory test results show that the uniaxial shear resistance and indirect tensile fatigue resistance of wearing course mixtures are related with accelerated loading passes. According to the findings from laboratory test, a hypothesis that the mechanisms for top-down cracking are a combination of shear-induced initiation and tension-induced propagation is proposed.]]></description>
      <pubDate>Wed, 28 Feb 2018 13:25:59 GMT</pubDate>
      <guid>https://trid.trb.org/View/1496222</guid>
    </item>
    <item>
      <title>A Computer Program for Top-Down Cracking of Asphalt Pavement Layers Under Thermal Loading</title>
      <link>https://trid.trb.org/View/1495740</link>
      <description><![CDATA[Top-down cracking is primarily fatigue cracking and exists in asphalt pavement layers that initiates at the surface of the pavement and propagates downward through the asphalt layer. Top-down cracking is affected by multiple factors including pavement materials, pavement structures, heavy traffic, and the climate. The “thermal loading”, also called temperature variation, is primarily considered for top-down cracking in this paper. The paper develops a mechanistic-empirical approach to predict the top-down cracking under thermal loading in the asphalt pavement layer. This proposed mechanistic-empirical method is based on the modeling of pavement temperature, thermal stress and Artificial Neural Network (ANN) of thermal J-integral and crack growth. The climate data used in our model including hourly solar radiation, daily air temperature, and wind speed are collected from the Long-Term Pavement Performance (LTPP) database and National Climate Data Center (NCDC) database for development of the pavement temperature model. The viscoelastic thermal stress model has been developed by the finite difference solution to the viscoelastic constitutive equation based on Boltzmann’s Superposition Principle using the Prony series representation of relaxation modulus. The prediction of top-down cracking in asphalt pavement layer is established by using Paris law and computed by programming in the C# language. Its fracture coefficients are determined by pavement materials and the thermal J-integral is determined by results from the ANN model. Aging of asphalt mixture is taken into consideration for prediction of the thermal J-integral in this study.]]></description>
      <pubDate>Wed, 28 Feb 2018 09:26:11 GMT</pubDate>
      <guid>https://trid.trb.org/View/1495740</guid>
    </item>
    <item>
      <title>Mechanistic–Empirical Model for Top-Down Cracking Initiation of Asphalt Pavements</title>
      <link>https://trid.trb.org/View/1495690</link>
      <description><![CDATA[Top-down cracking (TDC) has become a major concern in pavement design and maintenance. In this study, a new mechanistic-empirical model is developed to predict TDC initiation of asphalt pavements. TDC initiation phase herein is defined as the stage for micro-cracks to coalesce into a visible macro-crack at pavement surface. With the aid of J-integral, micro-fracture mechanics and Miner’s hypothesis are first used as the fundamental mechanistic approaches to calculate the numbers of loading cycles at different load spectrum levels and the corresponding cumulative damage in the TDC initiation phase. A prediction model for air void distribution within asphalt layer is developed based on the X-ray Computed Tomography measurement since the air voids are initial flaws in asphalt mixtures especially for the pavement surface. The Long-Term Pavement Performance (LTPP) data including traffic loads, pavement distresses, material properties, pavement structures and environmental effects are collected and analyzed for 60 pavement sections distributed in different climatic zones. Traffic load is characterized using the load spectra model and the TDC initiation time is predicted from historical distress observations. The collected LTPP data are utilized to develop the prediction models for the energy parameter and TDC initiation time.  Annual average daily truck traffic (AADTT), unaged modulus, environmental effects and pavement structure are the key factors for the energy parameter. Unaged modulus, AADTT, energy parameter and air void content are critical to the TDC initiation time. As illustrated in the development and validation process, the prediction model shows good agreement with the field performance.]]></description>
      <pubDate>Wed, 28 Feb 2018 09:26:10 GMT</pubDate>
      <guid>https://trid.trb.org/View/1495690</guid>
    </item>
    <item>
      <title>Selecting a Laboratory Loose Mix Aging Protocol for the NCAT Top-Down Cracking Experiment</title>
      <link>https://trid.trb.org/View/1496136</link>
      <description><![CDATA[The objective of this study was to select a laboratory loose mix aging protocol for the NCAT top-down cracking (TDC) experiment. Field aging of asphalt mixtures was characterized using cumulative degree-days (CDD), which was defined as the accumulation of daily high temperature throughout mixtures’ service life. Performance data from over 80 existing pavements showed that TDC typically initiated after a critical field aging condition of approximately 70,000 CDD. A laboratory experiment was conducted to select an aging protocol that was representative of this critical CDD. Materials used in the experiment were from five projects in Michigan, Washington, and Alabama. Four loose mix aging protocols were evaluated in terms of their effects on the rheological and oxidation properties of asphalt binders. Results from the dynamic shear rheometer (DSR), bending beam rheometer (BBR), and Fourier transform infrared spectroscopy (FT-IR) tests showed that the 24-h, 135°C protocol yielded the most significant level of asphalt aging, followed by the 12-h, 135°C protocol, 5-day, 95°C protocol, and 6-h, 135°C protocol, respectively. No significant difference in the oxidation–hardening relationship of asphalt binders was observed for mixes aged at 95°C versus 135°C. Among the four aging protocols, the 5-day, 95°C protocol was most representative of 70,000 CDD of field aging. Additionally, DSR and FT-IR results indicated that loose mix aging of 8-h at 135°C and 5 days at 95°C were likely to achieve an equivalent aging level; thus, the 8-h, 135°C protocol was recommended as an alternative protocol to simulate 70,000 CDD of field aging.]]></description>
      <pubDate>Tue, 27 Feb 2018 09:46:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/1496136</guid>
    </item>
    <item>
      <title>Energy-Based Crack Initiation Model for Load-Related Top-Down Cracking in Asphalt Pavement</title>
      <link>https://trid.trb.org/View/1494661</link>
      <description><![CDATA[This paper aims at investigating the mechanisms of load-related top-down cracking (TDC) and developing a framework to predict the TDC initiation life for asphalt pavements. Firstly, a three-dimensional model is constructed to simulate the pavement responses to traffic load. The critical pavement responses (e.g., shear and tensile stresses) are identified and related to the TDC initiation at different locations (i.e., longitudinal wheel path, longitudinal non-wheel path, and transverse direction). Secondly, an energy-based TDC initiation model is developed, which involves seven submodels and one cracking initiation criterion. The cracking initiation model takes into account the effects of aging and healing on the cracking performance of asphalt mixtures. If the load-induced damage to asphalt pavement exceeds the limited strain energy of asphalt mixture, the crack will initiate at the pavement surface. Accordingly, this study develops the submodels to calculate the tensile and shear stresses induced damage to asphalt pavement, and the limited strain energy of asphalt mixture in tension and shear modes of fracture. Finally, the TDC initiation model is used to predict the six pavement sections at National Center for Asphalt Technology (NCAT) Test Track. The prediction results indicate that the load-related TDC always first initiates at the longitudinal wheel path. The increase of compaction density slightly prolongs the TDC initiation life of asphalt pavement, while the decrease of compaction density significantly diminishes the TDC performance. The use of soft binder with more reclaimed asphalt pavement (RAP) and the use of highly polymer modified asphalt are both beneficial for the improvement of TDC performance, but the addition of reclaimed asphalt shingles (RAS) is detrimental to the resistance of asphalt pavement to TDC. The model prediction results are in good agreement with the field observations.]]></description>
      <pubDate>Mon, 29 Jan 2018 17:53:19 GMT</pubDate>
      <guid>https://trid.trb.org/View/1494661</guid>
    </item>
    <item>
      <title>Energy-Based Crack Initiation Model for Load-Related Top-Down Cracking in Asphalt Pavement</title>
      <link>https://trid.trb.org/View/1492102</link>
      <description><![CDATA[This paper aims at investigating the mechanisms of load-related top-down cracking (TDC) and developing a framework to predict the TDC initiation life for asphalt pavements. Firstly, a three-dimensional model is constructed to simulate the pavement responses to traffic loading. The critical pavement responses (e.g., shear and tensile stresses) are identified and related to TDC initiation at different locations (i.e., longitudinal wheel path, longitudinal non-wheel path, and transverse direction). Secondly, an energy-based TDC initiation model is developed, which involves seven sub-models and one cracking initiation criterion. The cracking initiation model takes into account the effects of aging and healing on the cracking performance of asphalt mixtures. If the load-induced damage to the asphalt pavement exceeds the limited strain energy of the asphalt mixture, the crack will initiate at the pavement surface. Accordingly, this study develops the sub-models to calculate the tensile and shear stress induced damage to the asphalt pavement, and the limited strain energy of the asphalt mixture in tension and shear modes of fracture. Finally, the TDC initiation model is used to predict TDC development for six pavement sections at National Center for Asphalt Technology (NCAT) Test Track. The prediction results indicate that the load-related TDC always initiates in the longitudinal wheel path. Increased compaction density slightly prolongs the TDC initiation life of the asphalt pavement, while decreased compaction density significantly diminishes the TDC performance. The use of soft binder with more reclaimed asphalt pavement (RAP) and the use of highly polymer modified asphalt are both beneficial for the improvement of TDC performance, but the addition of reclaimed asphalt shingles (RAS) is detrimental to the resistance of asphalt pavement to TDC. The model prediction results are in good agreement with the field observations to date.]]></description>
      <pubDate>Wed, 27 Dec 2017 10:24:17 GMT</pubDate>
      <guid>https://trid.trb.org/View/1492102</guid>
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