Investigation of dynamic characteristics of tall industrial chimney based on GPS measurements using Random Decrement Method

• The dynamic characteristics of the tall chimney can be determined using RDM.
• The characteristics of a background noise of GPS system were examined.
• In order to improve the accuracy estimation by RDM the filtering procedure was used.
• The influence of filter parameters on a stability of RD signature was examined.
• It was proved that the chimney has two axes of symmetry in the horizontal plane.

The paper is concerned with the investigation of dynamic characteristics, i.e. the natural frequencies and structural damping ratios, of a tall industrial chimney, located in the power station of Belchatow in Poland, excited by the wind, based on GPS measurements using Random Decrement Method (RDM). The GPS receiver was able to measure only the first natural frequency of the chimney. The basic characteristics of a background noise of GPS technology based on the result of a static test were examined thoroughly. In order to increase the accuracy of GPS measurements as well as the dynamic characteristics estimation the filtering procedure using Type 1 Chebyshev band-pass digital filter was adopted. Then, the principles of RDM taking into account the influence of GPS measurement random noise were considered. The influence of filter parameters on the stability of the RD signature was also examined. Based on the filtered record of chimney dynamic response, the dynamic characteristics of the chimney were investigated using RDM for response considered in ten various directions in the horizontal plane. The results delivered some important practical information about two symmetry axes of the chimney. The effective investigation of a damping ratio should be made based on the analysis of the chimney response considered only in the directions of symmetry axes of the chimney. The number of time segments of the chimney response taken into account in averaging of the RD signature as well as the time interval of the RD signature was also recommended. The obtained results proved that the dynamic characteristics of tall slender structures under wind excitations can be effectively determined based on GPS measurements using RDM.