Identification of multi-axle vehicle loads on bridges

Both the time domain method (TDM) and frequency-time domain method (FTDM) are introduced and modified for the indirect identification of multi-axle vehicle loads from the bending moment responses of bridges. Two solutions to the over-determined set of equation involved in the identification methods are adopted. One is direct calculation of the pseudo inverse and another calculation of the pseudo inverse via the singular value decomposition technique for the ill-conditioned problems encountered. A few multi-axle vehicles were designed and constructed in the laboratory for validation purposes based on the ASSHTO standard specifications of highway bridges. Two kinds of frames between the tractor and trailer of trucks and, three types of vehicle suspension systems were simulated. Different multi-axle vehicle loads were identified from the measured bending moment responses of bridges under different operation condition in the laboratory. The effects of various vehicle and bridges parameters were evaluated. Comparative studies show that both TDM and FTDM methods involved in the moving force identification system (MITIS) are good identification methods and could efficiently identify the multi-axle vehicle loads on bridges.