Simplified analytical and finite element models of the vibration frequencies and buckling loads of a metallic tapered hollow tower.

Resumo

Structural analysis of slender structures, goes through the study of the static, dynamic and instability.
This requires the evaluation of natural frequencies and buckling loads. The Rayleigh method was an analytical
formulation used to access these data. To verify the accuracy of the formulation we applied the analytical method
to a cantilever metallic hollow tower, used as a small wind turbine tower, to estimate the first eigenfrequency and
the buckling load, assuming different shape functions, the results are carefully compared with the results obtained
by a finite-element model using the SAP2000 software. The frequency values are also compared with vibrations
measurements in the real structure. Results showed that Rayleigh quotient are reliable to evaluate the frequency,
with the first frequency in good concordance with FEM simulations and experimental results. Nevertheless, the
analytical prediction of buckling loads shows some incongruent results with differences in the range of (3-50)%
and highlights the importance of select the appropriate model to represent the structure.