Acta Scientiarum Polonorum

Abstract: The study analyzed the impact of additional tower structure masses on the change of the frequency of its natural vibrations; it also made attempts to mathematical description of this impact. Considerations apply to the tower supporting the lighting system of the city stadium in Ostrowiec Świętokrzyski. The source of additional masses is the icing (frost, rime) and non-structural components constituting the technical equipment of the tower. The analysis was made by modeling by means of the Finite Element Method (FEM) of the structure with the assumption of a one parameter variation of its mass (i.e., the additional mass of all components, structural and non-structural, changes in proportion to one parameter, which is the outer surface of the element on which the ice layer is deposited). Solving the problem of natural vibrations, for subsequent models, representing different intensity of tower’s icing, the following natural frequencies have been established. Thus, the increase of the ice-layer thickness on the surfaces from 0 to 2.4 cm caused the reduction of basic natural frequencies by a value, consecutively: for f₁ → 26.9%; for f₂ → 27.2%. These values are important from the point of view of technical applications. The findings allow to formulate a postulate that, in the analysis of tower’s structure susceptibility to gusts of wind, structure’s mass variability resulting from its possible icing was taken into consideration.