Numerical method for reducing the effect of spectral leakage on the frequency normalisation results of signals obtained in an asphalt pavement test using a FWD device

This paper provides an evaluation of the numerical method for limiting the effect of spectral leakage on the frequency normalisation results of the pavement load and displacement functions which were induced with a dynamic impulse generated during FWD tests. The main part of the paper is concerned with the presentation of a method, which can be used to effectively reduce the effect of spectral leakage on the frequency normalisation of signals obtained through pavement testing with FWD. The method developed is supported by the observed differences between the results of the backcalculations carried out for the measurement results of the test section pavement deflections, which were subjected to frequency normalisation with and without spectral leakage reduction. The signals, where the proposed spectral leakage mitigation method was applied, were the only ones for which the identified values of the elastic modulus of the asphalt layer package model increase as the frequency increases, which agrees with the generally accepted relationship observed under laboratory conditions.