Moving mass identification based on virtual distortion method

In the inverse analysis of vehicle-bridge coupled system, moving mass (load) identification is a crucial problem. However it is difficult to perform because that moving mass identification usually needs the construction of the variant system matrix which causes the huge computational work and makes the optimization rather slow, and that moving load identification is a well known ill-conditioned problem, which is very sensitivity to noise. Aiming at improving these deficiencies, this paper presents a fast and accurate method to identify moving mass based on Virtual Distortion Method (VDM), of which the basic concept is: the response of the modified structure equals to the response of an intact structure subjected to the same external load and to certain virtual distortions which model the changes of the actual structure. The measured structural response is used to identify the moving mass; unknown mass are taken as the optimization variables instead of the usually chosen moving mass-equivalent force. In this way well-conditioning of the identification is ensured and the number of the necessary sensors is decreased. The numerical costs are considerably reduced by using the introduced concept of the moving dynamic influence matrix. Numerical experiments of a beam and a frame with 5% measurement error demonstrate that moving masses can be identified using fewer sensors.