| Asphalt Concrete behavior under impulse loading has been experimentally studied. A series of uniaxial compression tests were conducted by subjecting cylinder specimens of asphalt concretes to triangular stress pulses of various loading rates. The loading matrix followed during the testing program consists of three loading durations of 0.05, 0.1, and 0.2 seconds, three stress levels of 30, 60, and 120 psi, and three temperatures of 75, 95, and 105 F. The experimental results on asphalt concrete samples indicated that the material displays elastic/viscoplastic response under uniaxial stress pulses. The viscoplastic response is characterized by the rate dependency of the plastic response and is found to be linearly strain hardening. The developed model uses a yield criterion based on the loading function defined by Drucker-Prager. In addition, a specially designed pavement simulation test was conducted to generalize uniaxial constitutive relations to multiaxial states. Identification of the material parameters included in the constitutive relations was achieved through an optimization procedure consisting of a series of iterations between an optimization program, CONMIN, and a finite element program, ABAQUS. Analysis of a flexible pavement under a moving load using the developed model indicated that this model describes quantitatively the response phenomena of such pavement system. A comparison study between finite element results and collected field data of the deformation of the top layer indicated an excellent agreement between both responses. |
