Three dimensional contact stresses under the LINTRACK wide base single tyres, measured with the Vehicle-Road Surface Pressure Transducer Array (VRSPTA) system in South Africa

Abstract

This report describes an international cooperative study into the 3 dimensional tyre/pavement contact stresses measured under slow moving free rolling wide base single tyres from the Netherlands. These tyres, a used tyre from the Dutch Lintrack system at TuDelft and a new tyre, were sent to South Africa for a comprehensive set of contact stress measurements under the South African Heavy Vehicle Simulator (HVS), which was used to provide the loading and speed requirements needed for the stress testing. The vertical, transverse (or lateral) and longitudinal contact stresses between the tyres and the pavement were measured with the Vehicle-Road Surface Pressure Transducer Array (VRSPTA), developed in South Africa as part of the ongoing Accelerated Pavement Testing (APT) program with the HVS. This study consists mainly of a raw data base of various contact stress measurements from these tyres, together with a detailed description of the VRSPTA system used to perform the measurements. a preliminary investigation of all the results grouped together indicated that the average ratios between maximum (peak) stress and the transverse (or lateral) stress are much lower than expected. The average ratio found between the Vertical : Transverse : Longitudinal stresses is: 10 : 1,5 : 1,0. This is much lower than that found in similar studies on bias/cross ply tures, which resulted in transverse stresses of up to 3 or 4 times than those found in the free rolling mode. However, when the data is divided into sub-groups the maximum (peak) stress ratios reached values up to 10 : 2,7 : 2,0. It was also found that the transverse stress component of the wide base single tyres increased roughly 2,5 times under sideways shear compared to the free rolling case investigated her. Although the measured stresses should be further analysed in more detail, a very tentative observation is that owing to the relatively low peak transverse stresses found for the two tyres tested in the different moded it is doubtful whether this omponent alone could be responsible for the development of large enough transverse tensile strains close to the ture edge which may lead to longitudinal fatigue cracking starting at the surface of the asphalt layers in the Netherlands. The total 3-D stress conditions should, however, be used in a thorought pavement analysis in order to study the problem of load/stress associated longitudinal cracking (from the surface) in greater detail