Increased Damage to Uphill Rigid Pavements from Full- Trailers


Design charts for truck equivalence factors for full-trailer on uphill rigidpavements were developed for a terminal level of serviceability pt=2.5. Each chartis devoted to a certain rigid pavement slab thickness giving the truck equivalencefactor versus the total weight of the full-trailer for an uphill gradient of 0, 6, 12and 18% as well as a certain ratio of the height of center of gravity of each unit ofthe full-trailer to the corresponding wheel base (H/B). Five values for slabthickness were considered namely D = 6, 8, 10, 12, and 14 inches (15.2, 20.3,25.4, 30.5, 35.6 cm respectively) and one value for H/B ratio of 1.0 were used.Due to axle load redistribution on upgrades, the axle loads for the full-trailerswere calculated assuming uniform motion and taking into account the effect of themoment of the component of the weight of the tractor and trailer unit parallel tothe upgrade and acting at the center of gravity of each unit.A strong linearcorrelation between the rolling resistance and total weight of the trailer unit wasobtained to arrive at the pull force in the rod when travelling on uphill pavements.The paper reveals the significant effect of the upgrade magnitude as well as ofthe H/B ratio on the truck equivalence factor. The truck equivalence factorsincrease non-linearly with increasing truck weight, H/B ratio and upgrademagnitude. This increase is quite significant for the higher values of upgrade, H/Bratio as well as the slab thickness. The critical full-trailer is that having a totalweight exceeding about 400 kN beyond which the corresponding equivalencyfactor on uphill pavement diverges significantly from that on level highway.