PREDICTING VERTICAL DYNAMIC LOADS CAUSED BY VEHICLE-PAVEMENT INTERACTION

Dynamic loads caused by vehicle-pavement interaction are either moving loads or random loads. Motion property of dynamic loads was described by means of Dirac-delta and Heaviside functions, and its randomness p roperty was studied using a quarter-truck vehicle model. A series of s tatistical characteristics of wheel loads in frequency domain and time domain are presented in this paper. It was found that dynamic loads a re a constant mean Gaussian stationary ergodic process whose power spe ctral density is in proportion Co the power spectral density of paveme nt roughness, whereas the ratio coefficient relates to dynamic propert ies of vehicle and velocities of travel. Numerical simulation based on the specifications of the International Organization for Standardizat ion (ISO) indicated that only at low speed could dynamic loads be trea ted as quasi-narrow band-width random processes, which covers the freq uency range of 1.0-4.0 Hz. At high speed, main frequency distributions of dynamic loads occur in 1.0-4.0 and 10.0-15.0 Hz. Further analysis also showed that according to the International Organization for Stand ardization specifications, the root mean square of dynamic loads is pr oportional to root C-Sp, the square root of an important index related to pavement levels.