Browsing by Author "Menen, Getachew"

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    Finite Element Analysis of Permanent Deformation and Responses under Different Vehicular Load Speeds
    (Addis Ababa University, 2020-01) Menen, Getachew; Ephrem, Taddesse (PhD); Asres, Simeneh (Mr.) Co-Adisor
    The increase of dynamic loads exerted on the pavement is one of the major causes that shorten the pavement service life. The current pavement design procedure which incorporates static loads in the structural design of pavement makes the situation critical. Hence, decreased riding quality, discomfort and increased vehicle operating cost that influences overall transportation costs are seen. Thus, a vehicle loading speed must be given attention in dynamic analysis due to its effect on tire-pavement interaction and pavement response values. In the study, three-dimensional finite element analysis used to simulate the deformation of the pavement surface and sub-grade by different vehicular speeds. ABAQUS software is employed to develop total of five three-dimensional finite element models. Each pavement models represent selected vehicular speeds by considering similar material characterization, single axle single tire load configuration and necessary boundary conditions. The vehicle speed along the wheel path is simulated by progressive shift of the tires over the pavement loading area. From the analysis of the pavement models, it was found that lower speeds have longer contact time with flexible pavement than higher speeds. This is due to time of loading is the function of tire imprint length and speed. Also, asphalt concrete behavior as viscoelastic material plays an important role. Moreover, the greater static effect of loading makes the reduction in lower speeds is more than higher speeds. Though increasing velocities make the dynamic's effects of loading more than static's effect of that, it cannot higher than load's static's effect at low speeds. Hence, accumulated strain increases with an increase in loading time. In addition, vertical strain and stress distribution increase and decrease linearly along the wheel path as loading amplitude varies in each step time. As a result, maximum stress magnitude under load center for single axle configuration is higher in 20Km/hr than 100Km/hr speed. It is also worthy to mention, load's dynamic effect is less considerable at the top of subgrade. This is due to deeper position of extracted data and the effect of layers' weight. Hence when speed increases higher than 60Km/hr, a low decrease in strain magnitude is observed.