Heavy vehicle design affecting dynamic pavement loading

This paper considers the influence of heavy vehicle design on dynamic pavement loads induced by road roughness. Four linear, stochastic models representing the pavement loading process are described, and the effect of various parameter changes on their predictions are investigated. Results indicate that an axle's dynamic load is not determined by the design of its suspension alone. Characteristics of the whole vehicle such as the design of other suspension groups and the distribution of sprung mass are also important. Predicted speed load relations show a general increase of load with speed, but superimposed on this trend is a series of oscillations which can be substantial compared to the mean effect. The location of the oscillations is sensitive to certain whole vehicle effects, in particular the distances between axle centres, suspension stiffnesses and sprung mass characteristics. The complicated and variable nature of the predicted speed load relation indicates that the dynamic loading performance of a vehicle should be assessed at a number of speeds closely spaced over its usual operating range rather than at just one or two speeds. Modelling results indicate the existence of optimal suspension damping values for dynamic loading. Decreased suspension stiffness tends to reduce low frequency load components. Reduced tyre stiffness tends to decrease high frequency loading, but reductions below the level of suspension stiffness may increase low frequency loads. Vehicles with tandem suspensions for which pitch motions are poorly damped are predicted to have high dynamic pavement loads over certain speed ranges (a).