On behalf of Alimak, a theoretical model that predicts the vibration characteristics and eigenfrequencies in mast and hoist has been developed and carried out. The demand of this thesis originates from the problems regarding vibrations observed when using bus bars instead of cables for the access of electricity to power the construction hoist. Alimak aims to theoretically evaluate risks rather than discover them later to ensure no potential serious problems occur.

The mast has been modeled in the finite element software Ansys using both beam elements and shells. An analytical solution of the mast's axial eigenfrequencies has also been carried out. To be able to validate the results, the theoretical model is the same as the setup in the test. A construction hoist with cables and a 30m high squared 650 mast have been analyzed. All steps for constructing the theoretical model are carefully documented in this work. The tests were conducted using an enDAQ accelerometer. An analysis was performed on a separate mast segment as well as on the complete model involving the 30m mast, the hoist and ties.

The result has produced two models, beams and shells, both of which generate results that correspond well with the tests. The analytical solution differs from the test results and is probably not accurate enough to use when calculating the axial eigenfrequencies. The axial mode present at 27 Hz has been of particular interest as the mast and the hoist appear to oscillate in sync at this frequency. Finally, suggestions have been made on how the vibrations can potentially be reduced, along with a brief discussion of future work.