Investigating Flexible Pavement Responses and Performance under Trunnion Axle Loading Using Three-Dimensional Finite Element Modeling and Field Validation

The growing demand for high-capacity freight vehicles has heightened the need to evaluate the impact of heavy truck axle configurations on pavement behavior. This study employed a validated three-dimensional (3D) finite element (FE) model to evaluate the structural response of flexible pavements under trunnion and tandem axle configurations at two vehicle speeds (35 and 55 mph), using legal load levels of 60 and 34 kip, respectively. Then, key pavement responses (i.e., tensile strain, stress, and vertical displacement) were assessed. Also, pavement performance (i.e., fatigue cracking and subgrade rutting) was evaluated. The results showed that the trunnion axle generated higher tensile strain, von Mises stress, maximum principal stress, vertical stress, and vertical displacement than the tandem axle. This increase in pavement responses is primarily attributed to the trunnion’s shorter axle spacing, which causes overlapping stress zones and amplifies strain concentrations within the asphalt and subgrade layers. Concerning pavement performance, the trunnion axle exhibited lower fatigue life and lower resistance to subgrade rutting. Vehicle speed was also found to influence pavement response, with lower speeds producing higher stress, strain, and displacement levels for both axle types. Model predictions were validated using field measurements from the MnRoad test site in Minnesota, USA, confirming consistent trends in pavement responses under dynamic axle loading. These findings offer insight into the roles of axle configuration, maximum load, and truck speed in determining flexible pavement performance, thereby supporting better-informed design and evaluation practices.