Response of an Asphalt Pavement Mixture under a Slow Moving Truck

In this paper, the responses of two different pavement structures (10 and 20 cm HMA layer), were analyzed under the steering, driving and trailer axles of an eighteen-wheeler truck during braking on a 6% downhill grade. The response of the asphalt pavement to the decelerated truck during the braking period was estimated at three different traveling speeds: 64, 32, and 3.2 km/h using the computer code 3D-Moving Load Analysis (3D-MOVE). Significant load redistribution, which occurs between the truck axles under deceleration, has been accounted for in the analysis. The time dependent behavior of the HMA layer as the truck approaches the stopping point is incorporated by using the complex shear modulus and the internal damping as a function of loading frequency. The base course and subgrade layers are treated as linear elastic materials with an internal damping assumed to be 5%. The non-uniform stress distributions at the tire-pavement interface were interpolated from measured contact stress distributions at various speeds made with the Kistler MODULAS Quartz Sensor Array by the Nevada Automotive Test Center (NATC). Braking forces at each tire were included as interface shear stresses with a distribution that was estimated by multiplying the vertical stress distribution by the calculated coefficient of friction between each tire and the pavement surface. The study reveals that rutting in the HMA layer is more prone under the steering single tire while shoving is mainly caused by the dual tandems driving tires.