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Natural vibrations of a tower structure in mass-changing conditions due to the icing

100%

Kowalski W., Swierczek E.

Acta Scientiarum Polonorum. Architectura

2016

tom 15

nr 2

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 f → 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.

The role of glacier system in migration of calcium carbonate on Svalbard

84%

Bukowska-Jania E.

Polish Polar Research

2007

tom 28

nr 2

The general objective of this research has been to identify the factors and conditions of migration of CaCO3 within glaciers and their marginal zones in Svalbard. Special attention has been paid to the cryochemical processes responsible for precipitation of calcium carbonate in icing (naled ice) formed near fronts of polythermal glaciers during winter. Estimates of the importance of those processes in respect of the general mineral mass transfer in the glacier system are attempted here. Field studies concerning the carbonate contents in proglacial sediments and icing fields were carried out in the Werenskioldbreen and the Elisebreen basins (S and NW Spitsbergen respectively). A functional model of CaCO3 migration in a glacier system is proposed which indicates the various paths of the mineral mass flow. Considerations on intensity of glacial processes permitted quantitative estimation of the particular components in respect to the Werenskioldbreen basin. Cryo- chemical processes do not appear to be of overriding importance in such migration but, clearly, they play a specific role in retaining CaCO3 in the proglacial zone on land. The crystalline forms present in the icings, which have many lattice defects, are very easily re-dissolved or removed by wind.

Ograniczanie wyników

1 Acta Scientiarum Polonorum. Architectura

1 Polish Polar Research

1 Bukowska-Jania E.

1 Kowalski W.

1 Swierczek E.

1 2016

1 2007

Wyniki wyszukiwania

Natural vibrations of a tower structure in mass-changing conditions due to the icing

The role of glacier system in migration of calcium carbonate on Svalbard