Numerical analyses of rigid and flexible pavements responses under heavy vehicles’ loading

In an attempt to better understand the interaction between heavily loaded trucks and the pavement structure; rigid and flexible pavements’ responses (stresses, strains and deflections) were evaluated under simulated loading of 11-axle trucks (MI-20, MI-18, MI-14, MI-13) at gross vehicle weights (GVW) of 164,000 lb with different axle configurations, which are allowed in the state of Michigan. These responses were compared against results of a standard 5-axle semi-trailer at GVW nearing the common 80,000 lb standard in most states. Using these heavy truck types, the combined effects of truck loading, pavement thickness, joint spacing, material properties and thermal conditions on the pavement damages were evaluated. The major fatigue and faulting damages for rigid pavements as well as fatigue damage and subgrade rutting for flexible (asphalt) pavements are analysed. The finite element method (FEM) based program ISLAB2000 and multilayer elastic theory (MLET) based program JULEA were used to compute rigid and flexible pavements responses, respectively. Results show that the standard 5-axle truck yields up to 50% more fatigue damage potential under positive temperature gradient across slab (during daytime) even at a much lower gross vehicle weight than that of Michigan (MI) trucks. However, the 11-axle MI trucks provide up to 45% higher fatigue damage potential under negative temperature gradient (during nighttime). In comparison with the standard truck, the 11-axle MI trucks yield up to 17% less faulting damage for the typical rigid pavement with a thickness of 8 mm and up to 18% more faulting for larger pavement thickness. In flexible pavements, the standard truck exhibits up to 39% higher asphalt concrete fatigue damage than MI trucks. However, up to 80% more subgrade rutting damage for typical flexible pavements is observed for MI trucks with the multi-axles group configuration and larger GVW than the standard truck.