The Experts below are selected from a list of 5904 Experts worldwide ranked by ideXlab platform
Eyal Levenberg - One of the best experts on this subject based on the ideXlab platform.
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viscoelastic genetic algorithm for inverse analysis of Asphalt Layer properties from falling weight deflections
Transportation Research Record, 2013Co-Authors: Sudhir Varma, Emin M Kutay, Eyal LevenbergAbstract:The falling weight deflectometer (FWD) is a nondestructive test whose results are typically used for backcalculating in situ Layer properties of pavements. Most backcalculation methods assume the pavement to be a Layered elastic half-space. However, Asphalt pavements behave more like multiLayered viscoelastic systems, especially in response to small or short-duration load applications. Hence, although elastic analysis is computationally efficient and well accepted in the engineering community, the theory cannot produce the viscoelastic properties of the Asphalt concrete (AC) Layer. In this study, a new inverse analysis method is proposed to backcalculate both linear elastic and viscoelastic properties of pavement Layers as well as the AC time-temperature shift factor. In this method, the FWD load-response history of a single FWD drop and variation in temperature along the depth of the AC Layer during the drop are used for performing the computations. The underlying (viscoelastic) forward solver is approxi...
M. R. Islam - One of the best experts on this subject based on the ideXlab platform.
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Effect of Cross-Anisotropy of Hot-Mix Asphalt Modulus on Falling Weight Deflections and Embedded Sensor Stress-Strain
Transportation Research Record, 2013Co-Authors: M. U. Ahmed, Rafiqul A. Tarefder, M. R. IslamAbstract:In this study, the effects of cross-anisotropy on Asphalt pavement responses are examined. A dynamic finite element model (FEM) was developed in ABAQUS to simulate pavement responses under falling weight deflectometer (FWD) and truck loads on a pavement section on I-40 at Mile Post 141 in New Mexico. This section was recently instrumented with strain gauges, moisture probes, and pressure cells. Pavement response (i.e., stress, strain, deflection) from the instrumented section is compared with the FEM-predicted values. Two combinations of cross-anisotropy are considered. The first combination considers cross-anisotropy of modulus in every Layer of the pavement, and the second combination considers it only in the hot-mix Asphalt Layer. Time-deflection histories, stress, and strain are predicted from the FEM under FWD and truck loads. Results show that predicted deflections, stress, and strain are highly sensitive to cross-anisotropy. Predicted deflections, stress, and strain increase with a decrease in n-va...
Sheng Li - One of the best experts on this subject based on the ideXlab platform.
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interlaminar shear fatigue and damage characteristics of Asphalt Layer for Asphalt overlay on rigid pavement
Construction and Building Materials, 2014Co-Authors: Sheng LiAbstract:Abstract According to the failure characteristics of Asphalt overlay on rigid pavement, a special-purpose test apparatus and method were developed for interlaminar shear fatigue tests to evaluate interlaminar shear fatigue of Asphalt overlay on rigid pavement, and an interlaminar shear fatigue equation was determined by analyzing the correlation between fatigue life and shear stress obtained from interlaminar shear fatigue tests. The damage mechanics theory, heat transfer theory and the Finite Element Method (FEM) were adopted to analyze fatigue damage characteristics and cracking mechanism of Asphalt Layer. The result showed that under repeated traffic loading, the Asphalt Layer located at the existing transverse joints of the rigid base on the side of traffic loading, is prone to fatigue cracking, and the crack extends upward along the tip due to the tensile stress; thermal fatigue damage occurs mainly on the surface of Asphalt overlay, the horizontal tensile stress on the surface of Asphalt overlay decreases linearly with the increase of temperature variation times, and the fatigue life of Asphalt overlay decreases with the increase of the amplitude of temperature variation; and it is recommended to choose Asphalt mixtures with features such as relatively low thermo-contraction character, low modulus and high tensile strength to guarantee the expected cracking resistance and durability of Asphalt overlay on rigid pavement.
Sergio Fernandez Cerdas - One of the best experts on this subject based on the ideXlab platform.
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theoretical analysis on ground vibration attenuation using sub track Asphalt Layer in high speed rails
Journal of Modern Transportation, 2015Co-Authors: Mingjing Fang, Sergio Fernandez CerdasAbstract:Using a finite element method (FEM) program, a Portland cement concrete slab trackbed (S0), and a sub-track Asphalt roadbed (RAC-S) were modeled under high-speed train loads to analyze their responses to ground vibration attenuation, by considering 10, 15, 20, 25, and 30 thick sub-track Asphalt Layer replaced on the top of the upper subgrade. FEM results show that the vibration amplitude of RAC-S is at least three times lower than the vibration for S0. The maximum vibration amplitude of RAC-S is linearly increased with train speed. The vertical acceleration is found to be reduced by more than 10 % when the Asphalt Layer thickness is increased from 10 to 20 cm. However, the reduction in vertical acceleration is only about 1 % when the thickness of the Asphalt Layer changes from 20 to 30 cm. The vibration level is slightly lower if the Asphalt Layer has higher resilient modulus in the seasons of autumn or winter. This theoretical analysis indicates that a railway substructure that consists of a 10–20 cm thick high modulus Asphalt Layer located at the top of trackbed shows a good performance in ground vibration control for high-speed rails.
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numerical determination for optimal location of sub track Asphalt Layer in high speed rails
Journal of Modern Transportation, 2013Co-Authors: Mingjing Fang, Sergio Fernandez CerdasAbstract:Well-graded Asphalt mix with the merits of high sound absorption, low water permeability, excellent strength, and easy construction is an important option for high-speed railway substructures. On the basis of finite element method, a model with conventional ballasted trackbed (T0) and four ballasted trackbeds models with different positions of Asphalt Layer were analyzed, in which 15 cm thick Asphalt Layer was used to replace the different sub-track Layers, the bottom and the top of upper subgrade and of ballasted trackbed, named as T1, T2, T3, and T4, respectively. The results showed that the range of peak vertical accelerations on the top of subgrade surface of T2 and T4 were smaller than T1 and T3; T1 and T2 perform better in decreasing the maximum vertical deformation of subgrade than T3 and T4; the maximum transversal tensile strain of T4 is almost twice than the other three. The trackbed bears more stress when the Asphalt Layer is located at the lower part of railway trackbed.
Sudhir Varma - One of the best experts on this subject based on the ideXlab platform.
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viscoelastic genetic algorithm for inverse analysis of Asphalt Layer properties from falling weight deflections
Transportation Research Record, 2013Co-Authors: Sudhir Varma, Emin M Kutay, Eyal LevenbergAbstract:The falling weight deflectometer (FWD) is a nondestructive test whose results are typically used for backcalculating in situ Layer properties of pavements. Most backcalculation methods assume the pavement to be a Layered elastic half-space. However, Asphalt pavements behave more like multiLayered viscoelastic systems, especially in response to small or short-duration load applications. Hence, although elastic analysis is computationally efficient and well accepted in the engineering community, the theory cannot produce the viscoelastic properties of the Asphalt concrete (AC) Layer. In this study, a new inverse analysis method is proposed to backcalculate both linear elastic and viscoelastic properties of pavement Layers as well as the AC time-temperature shift factor. In this method, the FWD load-response history of a single FWD drop and variation in temperature along the depth of the AC Layer during the drop are used for performing the computations. The underlying (viscoelastic) forward solver is approxi...
