The New Zealand Transport Agency (NZTA) is trying to determine if it is correct to use gross or net (area of tyre tread grooves subtracted) contact area for heavy vehicle tyres when assessing the damage on the road. They are interested at this stage about the effect of the tyres on the subgrade.
This query has arisen because new generation truck tyres are not only wider but also have wider or more grooves. As a result the gross area increases over conventional tyres but the net area reduces. If contact pressure is worked out on net area, they give higher contact pressure yet they are spreading the load over a wider area.
Any thoughts on what would be more appropriate - gross contact area or net contact area in assessing the damage potential to pavement subgrade will be most welcome.
Thanks in anticipation,
Peter Cenek
Research Manager
Physical & Engineering Sciences
Opus Central Laboratories
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