A time domain approach for reconstruction of moving loads acting on bridges from dynamic response data

An accurate knowledge of the moving forces acting on existing bridges could offer the engineers the possibility of a less conservative but still reliable reassessment process, which could lead to an improved safety assessment and to important extensions of the remaining service life and thus to considerable financial benefits for both the bridge owners and the society. However, the direct measurement of dynamic forces acting on bridges is in most cases either not possible or very cumbersome. On the contrary, time histories of the structural responses (e.g. accelerations, displacements, strains) can be recorded with reasonable effort. In this sense, this contribution presents a novel formulation of an inverse problem for the identification of unknown time dependent moving loads acting on a bridge structure based on dynamic measurements of structural responses. The problem is solved in the time domain using acceleration and/or displacement time histories recorded at different locations on the structure as input data. The method is computationally effective and allows an accurate reconstruction of the dynamic forces, e.g. for each axle of a complete railway vehicle, even with a reduced number of measurement points. The practicability and accuracy of the method is evaluated using a series of numerical examples.