EFFECT OF FROZEN SUPPORT AND TRIDEM AXLES ON CONCRETE PAVEMENT PERFORMANCE

A field program of strain and deflection measurements was conducted by the Construction Technology Laboratories for the Minnesota Department of Transportation. The objective of the program was to evaluate the effects of frozen support, tied-concrete shoulders, and tridem-axle loading on concrete pavement performance. The effects of frozen support and tridem-axle loading are presented. Field measurements were obtained during October 1982 and February 1983 at five pavement project sites located on I-90 in Minnesota. Measurements included edge and corner deflections and edge strains. Loadings applied were a 20-kip single axle, a 34-kip tandem axle, a 42-kip tandem axle, and a 42-kip tridem axle. Theoretical analysis was also conducted by using a finite-element program. Study results indicate that pavement deflections and strains are greatly reduced during winter months when the support is forzen. Based on analysis of these results, it is concluded that the effect of axle loads applied during the winter can be considered to be only one-seventh as damaging as the same loads applied during the fall. Study results also indicate that for application to the AASHTO thickness design procedure, tridem axles can be considered as equivalent to a single axle weighing about 50 percent of the tridem axles and to tandem axles weighing about 80 percent of the tridem axles. Traffic equivalence factors are presented for tridem axles on concrete pavements.