Influence of Environmental Conditions and Damage on Closely Spaced Modes

Abstract

AbstractIn this work, the influence of environmental conditions and damage on structures with closely spaced modes is investigated. Closely spaced bending modes are typical for symmetrical structures, such as towers. When monitoring such structures, identifying the mode shapes in particular is a challenge. In addition to environmental effects, the identification uncertainty is elevated for closely spaced modes, which leads to higher scatter in the identified mode shapes.In order to be able to investigate and quantify the influences, data from a structure with repairable damage is used. In particular, the investigation is carried out on long-term measurement data of the Leibniz University Test Structure for Monitoring (LUMO). LUMO enables the examination of different damage positions under ambient excitation and environmental conditions. For the identification, Bayesian Operational Modal Analysis (BAYOMA) is used.By considering the uncertainty of the modal parameters, especially for the mode shapes, a better understanding of the influence of damage and environmental conditions on the structure can be obtained. This is helpful for further monitoring stages, such as damage localisation using modal updating.KeywordsDamage detectionClosely spaced modesEnvironmental effects