Citation

Huhtala M, Pihlajamaaki J, Miettinen V. Proc. Int. Tech. Conf. Enhanced Safety Vehicles 1992; 1992: 211-217.

Copyright

(Copyright © 1992, In public domain, Publisher National Highway Traffic Safety Administration)

DOI

unavailable

PMID

unavailable

Abstract

This article compares the behaviour of road pavements under both dual and wide based lorry tyres. The project included the comparison of two dual tyres and three wide based tyres. All were radial. All tyres were measured at three axle loads: 10 tonnes (the nominal maximum for Finland), 9.5 tonnes, and 10.5 tonnes. Three different tyre pressures were used: the pressure recommended by the manufacturer, and pressures of 20% more and 20% less than this level. The horizontal strains in the bottom of the bituminous layers, and the vertical stress measurements on the subgrade and in the subbase and formation (unbound) layers were measured as the vehicle passed over them. The strain or stress values were converted into an equivalence number of axle passes using appropriate failure (fatigue) criteria (the exponent of the fourth power law). Equivalence numbers were compared with that of a standard (reference) axle (a ten tonne single axle with 12R22.5 dual tyres and a tyre pressure of 700kPa). This value, (the "equivalency factor") describes the damaging power or aggressiveness of the axle. The results were developed further to include the equivalencies of various truck combinations. Trucks, trailers, and semi trailers were equipped with different type combinations and corresponding loading equivalencies for 80 mm bituminous layers were obtained. Special problems encountered when comparing the effects of dual and wide based tyres are discussed. These include uneven load distribution and transverse wander. The results indicate that wide based tyres are more aggressive than dual tyres by a factor of 2.3-4. Increasing tyre width and decreasing tyre pressure reduces aggressiveness.