Resumen
The natural frequencies and eigenmodes of the tensegrity simplex are determined experimentally in impact hammer tests. To study an effect of prestressing, the tests are carried out on a physical model 1.2 m high and 0.5 m diameter with build-in transducers for measuring actual values of forces in cables at 13 prestress levels. The recorded data for each pre-stress level from three three-axial accelerometers are combined to extract the first five natural frequencies and modes by means of the method of experimental modal analysis. It was experimentally confirmed that the first rotational frequency depends on the pre-stress level and its sensitivity to the self-stress state is high enough to be successfully used in vibrational health monitoring. A proprietary formula was proposed for the relationship between frequency and the pre-stress level to control the dynamic properties of the simplex. An excellent comparison between the experimental results of the frequency and the formula was obtained. A comparison of numerical results of the finite element method with truss element and experiment is also shown.