Virtual Constant Load Method for Moving Force Identification on Simply Supported Beam

During operation of a simply supported beam bridge, moving forces are a primary load on the bridge. Therefore, moving force identification (MFI) is essential for ensuring bridge safety. Nevertheless, current theories for identifying moving forces present shortcomings. To ascertain the force through the bridge beam response, it is essential to know the beam's bending stiffness. Practical or laboratory measurements of this bending stiffness are difficult to record, limiting practical implementations of MFI theory. Therefore, a virtual constant load (VCL) method is developed to achieve MFI when the beam bending stiffness is unknown. The proposed method uses a vehicle with a known axle load to efficiently traverse a simply supported beam. Upon establishing a correlation between the dynamic responses and the MFI model under the influence of the known axle load, a correction coefficient is derived for characterizing the strain response of the MFI model. This coefficient includes bending stiffness information, eliminating the need to explicitly solve for the beam bending stiffness. The updated model effectively achieves force identification when the bridge bending stiffness is unknown. To validate this method, MFI was conducted using numerical and laboratory analyses. The results demonstrate that the proposed method can accurately identify moving forces acting on beams with unknown bending stiffness.