Evaluating the Impact of Trunnion and Tridem Configurations on North Dakota’s Flexible Pavements

Abstract: An increasing number of heavy load trucks with trunnion axle configurations have been trending on North Dakota’s highways in recent years. A trunnion axle group consists of 16 tires compared to a 12 tire tridem group. This study examines and compares the impact of trunnion and tridem axle load configurations on North Dakota’s flexible pavement systems. The Abaqus three-dimensional finite element method (3D FEM) was used to simulate axle loadings of trunnion and tridem configurations over 3- and 6-inch asphalt concrete (AC) layers. Pavement responses in the form of stresses, strains, and displacements under 60-kip load of each configuration were obtained from the 3D FEM model and analyzed. Results of this study indicate that the trunnion axle configuration caused lower tensile strains, lower vertical stresses, and lower displacements than the tridem axle configuration for both AC layers and the 60-kip loading. For the 6-inch layer, all stresses, strains, and displacements were lower than those imposed on a 3-inch layer for both the trunnion and tridem axle configurations. Overall, the trunnion configuration imposed lower impact on the pavement of any thickness compared to the tridem configuration due to spreading the load over more tires. The lower impact of a trunnion configuration compared to the tridem configuration would be a welcoming sign to increase the reach of trunnion truck services over North Dakota’s pavement system.