A COMPUTATIONAL DEVICE FOR PRESCRIBING INCIDENT WAVES TO A STRUCTURE VIA A RAYLEIGH–TIMOSHENKO BEAM

Abstract

The vibrational behaviour of a complex structure depends on the transmission and reflection properties of its substructures, and parametric studies of these properties are often desirable. In standard FE programs for numerical vibration analysis, however, only forces and/or displacements of the structural nodes can be prescribed. This means that no first-hand input option is available for controlling the magnitudes and combinations of incident and reflected waves in a cross-section of a beam or at a boundary point of a (sub)structure. Moreover, since the magnitudes and combinations of waves from excitation through prescribed harmonic forces and/or displacements will change with the frequency, parametric studies have hitherto been complicated. To remedy this situation, the possibility is considered in this paper of setting up waves in a controlled manner to be carried, into the structure to be numerically investigated, by a damped second order Rayleigh–Timoshenko space beam. A prescribed combination of near field and far field waves can then serve as incident waves when parametric studies are performed over a frequency interval. For the waves reflected from the structure, the same beam will serve as an anechoic receiver. The (sub)structure may be any mathematical model having six cross-sectional translations and rotations as kinematic degrees of freedom at the position of incidence. Energy flow relations are clarified in the present study. Numerical examples demonstrate the use of the new computational device when studying wave scattering in thick beam junctions.