25. A New Approach to Dynamic Analysis of a Multi-Span Beam Structure with Multiple Moving Oscillators

A multi-span beam structure carrying multiple moving oscillators is seen in a variety of engineering applications, including highway bridges, elevated guideways and railways with moving vehicles, and tubes conveying fast-moving pods. With the oscillators having different speeds and varying inter-distances, the dynamic interactions between the supporting structure and the moving oscillators are usually complicated. Indeed, the number of moving oscillators on the structure is time-varying, and as such, a conventional solution method must frequently check the number of oscillators on the structure and adjust the numerical algorithm accordingly. Because of this, most investigations have been limited to just one or a few moving oscillators. Proposed in this paper is a new semi-analytical method that can systematically handle a beam structure with an arbitrary number of moving oscillators, without tedious number checking and algorithm adjustment. In the development, an extended solution domain (ESD) is firstly defined and a generalized assumed-mode method is then developed based on the ESD, which eventually yields a set of time-varying state equations. Solution of the state equations by a standard numerical integration algorithm gives the dynamic response of the coupled beam-oscillator system. Because the proposed method makes use of the exact eigenfunctions of the multi-span structure that are obtained by a distributed transfer function method, it is highly accurate and efficient in computation, as shown in a numerical study.