FORMULATION FOR VISCOELASTIC RESPONSE OF PAVEMENTS UNDER MOVING DYNAMIC LOADS

This paper provides a time-domain solution to the problem of viscoelas tic pavement response under moving dynamic loads. It assumes linear ma terial behavior and uses Boltzman's principle to superimpose the effec t of a loading function with time-dependent amplitude to the influence function of a pavement response parameter. The unique element of this formulation is that it takes into account the variation of the dynami c load within the area of influence of the moving load at any particul ar location. This formulation is applied, in evaluating the effect of two suspension types, generically referred to as air and rubber. Dynam ic load data for these suspensions was experimentally obtained with an instrumented vehicle. The accumulation of strain cycles along the roa d was translated into number of repetitions to fatigue failure assumin g spatial repetitiveness of dynamic loads. Overall pavement section fa ilure was defined as the number of repetitions corresponding to the 90 th percentile of the subsection survival curves. The relative damaging effect of the two suspensions was evaluated in terms of the ratio of the number of repetitions to failure for a load of constant magnitude divided by the number of repetitions to failure for the dynamic load.