Traffic is a key element influencing design and subsequent performance of Jointed Plain Concrete Pavements (JPCP). The newly developed National Cooperative Highway Research Program (NCHRP) Mechanistic-Empirical Pavement Design Guide (MEPDG) uses highway traffic distribution by means of axle load spectra. The procedure also requires a number of other traffic inputs. This paper discusses the development of some of these important traffic inputs in Kansas. A sensitivity analysis of typical Kansas JPCP designs with respect to the traffic inputs using MEPDG national default and Kansas-specific data has also been done. The results show that the monthly adjustment factors for truck traffic are necessary in Kansas since traffic is heavier during the winter and spring months. Truck traffic type distributions for some functional classes in Kansas are dissimilar to those in the MEPDG default. In contrast to the MEPDG default axle load spectra, Kansas has a higher percentages of trucks distributed in the lower axle load categories. Predicted JPCP roughness (IRI) by MEPDG is very sensitive to the slab thickness at varying traffic levels. However, traffic inputs studied in this project did not affect the predicted IRI for a JPCP with widened lane and tied concrete shoulder. No faulting was observed for a JPCP with widened lane and tied concrete shoulder for both Kansas and MEPDG traffic inputs. MEPDG traffic input causes more severe JPCP slab cracking than the Kansas input. Effects of higher AADT and truck traffic on predicted roughness, faulting, and slab cracking are more pronounced on the JPCP pavements with thinner slabs or lower concrete strength. Variation in truck type does not affect the predicted distresses on JPCP.
Samenvatting