Estimation of Tire Contact Area Using a Radial Spring Tire Model Coupled with a Deformable Surface

Historically, most pavement design and analysis procedures make simplified assumptions on the tire load-contact pressure-contact area relationship. First, most procedures assume the contact area is circular. It is also assumed that the contact pressure is equal to the tire inflation pressure at the tire-pavement interface. Next, the contact pressure is assumed uniform across the circular contact area. These assumptions lead to the final concluded relationship that the contact area is simply the applied load divided by the inflation pressure. For conventional thick pavements, the manner of loading is less significant since this statically equivalent loading produces similar responses as the true loading at depth. However, for contingency and overloaded low volume roads, the shape of the contact area and contours of the non-uniform contact pressure produce noticeably different near-surface responses. This study presents a numerical procedure for estimating the loaded contact area of a flexible tire coupled with a deformable surface. The tire is represented as a radial spring tire model. Comparisons are made between measured tire imprints of known load and inflation pressure to the proposed model's predictions under the same simulated conditions. Estimated contact areas made by the model compared well with the measured areas from different loaded aircraft tires. Further investigation also showed that the proposed model indicated that the shape and size of the contact area depended on factors such as the load, inflation pressure, and pavement structures' overall stiffness. Results showed that the proposed model produced contact areas that necessitated non-uniform contact areas, which caused relatively larger near-surface responses than those produced by the conventional uniform, circular pressure approach.