No abstract

Based on measurements of the energy contents in single struts in a complex truss structure (109 struts, 35 joints) [Machens, Dyer. Acustica 81 (1995)], a numerical simulation of the truss dynamics using the direct dynamic stiffness method was performed. Great care was taken to account for flexural, longitudinal, and torsional waves in the struts, moments of inertia and masses of the joints, complex coupling stiffness (translational and rotational) including a loss factor between joints and struts, as well as material damping in the struts. The struts were modeled as Euler–Bernoulli–Beams and additionally as Rayleigh–Timoshenko–Beams. Frequency averaging proved to be important in the midfrequency range as a meaningful comparison with the measured data depends on a high accuracy in modeling and choice of material parameters. The broadband frequency averaged energy in single struts show a high sensitivity towards various factors such as small random variations of the geometry and of the complex coupling stiffnesses as well as the use of first- and second-order beam theory. The results show that a truss, which is built up from simple elements, becomes fuzzy merely by its high number of coupled elements.