Effect of a pothole on the dynamics of an MDOF vehicle

A technique is developed to assess the dynamic contact forces arising from passage of road surface irregularities by a vehicle modeled as a general MDOF system. The equations governing vibration of a vehicle moving along an uneven profile are, first, transformed to the state-space form and, then, to a system of uncoupled first-order complex differential equations. For a local roadway irregularity described functionally, all equations are solved analytically. The solutions obtained are combined to give dependencies of the harmonic components of the contact forces on the vehicle speed and irregularity dimensions. The technique developed is applied to the calculation of the coefficients of the harmonic components of the contact forces arising after the passage of a "cosine" pothole. One interesting phenomenon reported in the DIVINE project, regarding the replacement of a steel suspension by an air suspension resulting in an increase in the maximum response of short-span bridges, is explained by applying the technique suggested. The discussion is amply illustrated by examples of the application of the technique to the calculation of the tire forces due to a pothole for two simple vehicle models.