| 1. |
- Jelagin, Denis, Docent, 1979-, et al.
(författare)
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Asphalt layer rutting performance prediction tools
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Flexible pavement rutting due to permanent deformation accumulation in asphalt layers is one of the most common modes of road failures. In addition to creating high maintenance costs, rutting is a major concern for traffic safety, as the rut development increases the risk of hydroplaning and introduce difficulties in vehicle steering. In this context, accurate methodologies for pavement rutting performance prediction are crucial for decision support in pavement design and rehabilitation. In particular, better rutting performance models are needed to evaluate, new asphalt materials as well as to evaluate the impact of different vehicle types on roads’ service life.The main goal of this report is to present a summary of the existing asphalt rutting performance prediction tools. The present review is limited to available and/or frequently referred to tests and models with an established link to field rutting performance. Accordingly, models focusing solely on permanent deformation on the material level are beyond the framework of the present study.Road structure and its materials, heavy vehicle parameters and climate affecting rutting accumulation in the field are identified. Their significance has been evaluated based on the experimental and numerical findings reported in the literature. Several rutting performance prediction models recently proposed in the literature are summarized along with the material characterization tests used in the models. The reviewed models’ capability to quantify the influence of various structural, material and traffic parameters on the pavement’s rutting performance is examined.It is concluded that implementation of rutting performance models incorporating experimentally measured viscoelastic and permanent deformation properties of asphalt mixtures is a promising way to improve the accuracy of pavement performance predictions. In particular since they allow the effect of novel materials, e.g. polymer-modified, on the pavement’s rutting performance to be quantified.
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| 2. |
- Ahmed, Abubeker W., et al.
(författare)
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An Algorithm to Estimate Rational Values of Phase Angles and Moduli of Asphalt Mixtures
- 2013
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Ingår i: International Journal of Pavement Research and Technology. - Taiwan : Chinese Society of Pavement Engineering. - 1996-6814 .- 1997-1400. ; 6:6, s. 745-754
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to develop and evaluate an algorithm based on Fast Fourier Transform (FFT) that can calculate rational values of phase angle (f) and moduli of the variants of asphalt mixtures for the data obtained from the different frequency sweep tests. f and moduli for ten different asphalt mixtures resulting in over 690 data points collected from both USA and Sweden were computed using FFT. Theoretical observations revealed that there were significant differences for f between FFT and other methods to the order of 10-50%; however, there was no difference in moduli estimates for any mix and was independent of the test. Precisely, the FFT method produced rational f for mixtures that deviate from conventional mixture properties. Furthermore, statistical comparisons corroborated the predicted f estimates indicative of significant differences between the analysis techniques; but, the moduli were unaffected by the analysis methods. The study successfully illustrated the FFT technique, a user-friendly analytical procedure that can obviate the errors in the rational estimation of the acutely sensitive viscoelastic parameters.
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| 3. |
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| 4. |
- Ahmed, Abubeker W., 1981-, et al.
(författare)
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Characterization of heavy traffic axle load spectra for mechanistic-empirical pavement design applications
- 2015
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Ingår i: The international journal of pavement engineering. - : Taylor & Francis Group. - 1029-8436 .- 1477-268X. ; 16:6, s. 488-501
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Tidskriftsartikel (refereegranskat)abstract
- Heavy traffic axle load spectrum (ALS) is one of the key inputs for mechanistic-empirical analysis and design of pavement structures. Frequently, the entire ALS is aggregated into Equivalent Number of Single Axle Loads (ESAL) or assumed to have Constant Contact Area (CCA) or Constant Contact Pressure (CCP). These characterizations affect the accuracy and computational performance of the pavement analysis. The objective of this study was to evaluate these characterizations based on predicted performances to rutting and fatigue cracking of several pavement structures subjected to ALS data collected from 12 Bridge-Weigh-In-Motion stations. The results indicated that for layers below the top 25 cm, all characterizations produced similar values of predicted rutting. However, for the top 25 cm, the methods differed in the predicted performances to rutting and fatigue cracking. Furthermore an improvement to the CCA approach was proposed that enhanced the accuracy while maintaining the same level of computational performance.
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| 5. |
- Ahmed, Abubeker W., 1981-, et al.
(författare)
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Evaluation of a permanent deformation model for asphalt concrete mixtures using extra-large wheel-tracking and heavy vehicle simulator tests
- 2015
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Ingår i: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 16:1, s. 154-171
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Tidskriftsartikel (refereegranskat)abstract
- This paper evaluates a mechanistic–empirical permanent strain model for asphalt concrete mixtures. The evaluation was carried out based on two different types of tests: an extra-large wheel-tracking (ELWT) test and a full-scale accelerated pavement test using a heavy vehicle simulator (HVS). Asphalt slabs from three different types of asphalt mixtures were prepared for the ELWT test and tested at several pavement temperatures and tyre inflation pressures. Lateral wandering was also incorporated.The measured permanent deformations in the asphalt slabs were thereafter modelled using the permanent strain model from the US Mechanistic-Empirical Pavement Design Guide and model parameters were estimated for the three types of mixes. For validation, data from an HVS tested pavement structure consisting of the same asphalt mixtures as those tested using the ELWT were used. A set of calibration factors for the three mixtures were therefore obtained between the two tests. In all cases, the calibration factors were within ±20% from unity. Differences in geometry, scale, wheel loading configuration as well as the speed of loading between the two test devices could be the possible reasons for the differences in observed calibration factors.
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| 6. |
- Ahmed, Abubeker W., et al.
(författare)
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Evaluation of permanent deformation models for unbound granular materials using accelerated pavement tests
- 2013
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Ingår i: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 14:1, s. 178-195
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Tidskriftsartikel (refereegranskat)abstract
- Mechanistic-empirical (M-E) pavement design methods have become the focus of modern pavement design procedure. One of the main distresses that M-E design methods attempt to control is permanent deformation (rutting). The objective of this paper is to evaluate three M-E permanent deformation models for unbound granular materials, one from the US M-E pavement design guide and two other relatively new models. Two series of heavy vehicle simulator (HVS) tests with three different types of base material were used for this purpose. The permanent deformation, wheel loading, pavement temperature, and other material properties were continuously controlled during the HVS tests. Asphalt concrete layers were considered as linear elastic where stress-dependent behaviour of unbound materials was considered when computing responses for the M-E permanent deformation models with a nonlinear elastic response model. Traffic wandering was also accounted for in modelling the traffic by assuming it was normally distributed and a time-hardening approach was applied to add together the permanent deformation contributions from different stress levels. The measured and predicted permanent deformations are in general in good agreement with only small discrepancies between the models. Model parameters were also estimated for three different types of material.
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| 7. |
- Ahmed, Abubeker W, 1981-, et al.
(författare)
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Impact of longer and heavier vehicles on the performance of asphalt pavements : A laboratory study
- 2018
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Ingår i: Bearing Capacity of Roads, Railways and Airfields - Proceedings of the 10th International Conference on the Bearing Capacity of Roads, Railways and Airfields, BCRRA 2017. - : CRC Press/Balkema. - 9781138295957 ; , s. 483-490
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Konferensbidrag (refereegranskat)abstract
- Historically, Longer and Heavier Vehicles (LHVs) have been permitted to operate in Sweden. Since 1996 and as of the beginning of 2015, the maximum gross vehicle weight of 60 tons and a length of up to 25.25 m have been permitted. The Swedish Transport Administration has decided to further increase the maximum gross vehicle weight to 74 tons and studies are undergoing to evaluate the impact of the proposed LHVs on existing transport infrastructure. To this end, repeated load triaxial tests and indirect tensile fatigue tests were conducted on selected conventional asphalt mixtures to investigate and quantify the impact of single, tandem and tridem axle configurations on permanent deformation and fatigue performances of conventional asphalt pavements. In addition, fatigue tests for selected LHV scenarios were conducted. This paper presents the results of the laboratory tests and simulations conducted. The test results have clearly demonstrated the impact of the different axle configurations on the rutting and fatigue performances of the mixture. Furthermore, such results can explain the significance of axle configuration on modelling the rutting and fatigue performances of asphalt pavements.
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| 8. |
- Ahmed, Abubeker W, 1981-, et al.
(författare)
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Impact of tire types and configurations on responses of a thin pavement structure
- 2018
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Ingår i: Advances in Materials and Pavement Performance Prediction. - London : CRC Press. - 9781138313095 ; , s. 271-274
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Konferensbidrag (refereegranskat)abstract
- The objective of this study was to assess the impact of tire and tire configurations on the responses of a thin asphalt pavement structure by means of full-scale tests using a Heavy Vehicle Simulator (HVS). A total of six different types of tires, four single and two dual tire configurations, were investigated. The structure was instrumented to measure tensile strains at the bottom of the asphalt layer and vertical stresses and strains in the unbound base, subbase and subgrade layers. The results indicated that, in general, single tire configurations produced higher tensile strain at the bottom of the asphalt layer and higher vertical stresses and strains in unbound base, subbase and subgrade layers.
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| 9. |
- Ahmed, Abubeker W., 1981-
(författare)
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Mechanistic-Empirical Modelling of Flexible Pavement Performance : Verifications Using APT Measurements
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mechanistic-Empirical (M-E) pavement design procedures are composed of a reliable response model to estimate the state of stress in the pavement and distress models in order to predict the different types of pavement distresses due to the prevailing traffic and environmental conditions. One of the main objectives of this study was to develop a response model based on multilayer elastic theory (MLET) with improved computational performance by optimizing the time consuming parts of the MLET processes. A comprehensive comparison of the developed program with two widely used programs demonstrated excellent agreement and improved computational performance. Moreover, the program was extended to incorporate the viscoelastic behaviour of bituminous materials through elastic-viscoelastic correspondence principle. A procedure based on collocation of linear viscoelastic (LVE) solutions at selected key time durations was also proposed that improved the computational performance for LVE analysis of stationary and moving loads. A comparison of the LVE responses with measurements from accelerated pavement testing (APT) revealed a good agreement. Furthermore the developed response model was employed to evaluate permanent deformation models for bound and unbound granular materials (UGMs) using full scale APTs. The M-E Pavement Design Guide (MEPDG) model for UGMs and two relatively new models were evaluated to model the permanent deformation in UGMs. Moreover, for bound materials, the simplified form of the MEPDG model for bituminous bound layers was also evaluated. The measured and predicted permanent deformations were in general in good agreement, with only small discrepancies between the models. Finally, as heavy traffic loading is one of the main factors affecting the performance of flexible pavement, three types of characterizations for heavy traffic axle load spectrum for M-E analysis and design of pavement structures were evaluated. The study recommended an improved approach that enhanced the accuracy and computational performance.
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| 10. |
- Ahmed, Abubeker W, et al.
(författare)
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Mechanistic modelling of HVS flexible pavement structure
- 2012
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Ingår i: EPAM 2012: Malmö, Sweden, 5–7 September: 4th European pavement and asset management conference. - Linköping : Statens väg- och transportforskningsinstitut.
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Konferensbidrag (populärvet., debatt m.m.)abstract
- A response model to be employed in a mechanistic-empirical pavement performance prediction model based on multilayer elastic theory has been developed. An iterative approach using a method of successive over-relaxation of stress dependency model is used to account for the nonlinear behaviour of unbound materials. Asphalt and subgrade materials are assumed as linear elastic. The response model is verified using heavy vehicle simulator (HVS) response measurements made under variety of wheel load configurations and at different pavement temperatures. The permanent deformation behaviours of the HVS structure is also modelled using mechanistic empirical approach and by employing permanent deformation prediction models. A time hardening approach has been applied to combine permanent deformation contributions from stress levels of different magnitude. The response model outputs and the predicted permanent deformations are in general in good agreement with the measurements.
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