Modeling vertical acceleration in truck shipments using the International Roughness Index for pavement

This study investigates the suitability and use of the pavement roughness index IRI (International Roughness Index) for predicting vertical acceleration in truckload shipments at usual highway speeds. The investigation resulted in the development of a mathematical procedure for predicting the expected PSD (Power Spectrum Density) vertical acceleration in a truck as a function of IRI, pavement category, vehicle dynamic characteristics and speed of travel.;The data for this study was collected from twenty different sections of highway pavements using two devices: a profilometer which recorded elevation profiles of the pavement sections, and an accelerometer which recorded vertical acceleration in the rear of a tractor-semitrailer truck bed travelling at three different speeds.;A Quarter-Car Simulation was used to compute IRI and spectral analysis was used to compute the PSD's for pavement elevation and the truck bed acceleration. The pavement elevation profile was transformed into input acceleration to the vehicle based on the speed of travel. Transmissibilities for the truck were computed for different speeds over different categories of pavements. A set of equations was developed to estimate the PSD pavement elevation as a function of IRI and pavement category.;The result is a procedure for estimating the PSD vertical acceleration at the rear of the truck bed for selected pavement categories and truck speeds using only the pavement IRI and the vehicle transmissibility.;Previously-obtained measurements of IRI and truck bed vertical acceleration were used to check the validity of the procedure. Very good correlation was observed between the expected and the obtained truck bed vertical accelerations, showing that it is possible to predict levels of vibrations in truck shipments accurately using the IRI.;The use of the proposed procedure is very advantageous because it eliminates the need for extensive vehicle vibration measurements in the field, a common and growing practice in the packaging today.