@article{AbdelnourZabel,
  author    = {Abdelnour, Mena and Zabel, Volkmar},
  title     = {Modal identification of structures with a dynamic behaviour characterised by global and local modes at close frequencies},
  series = {Acta Mechanica},
  volume    = {2023},
  journal   = {Acta Mechanica},
  publisher = {Springer},
  address   = {Wien},
  doi       = {10.1007/s00707-023-03598-z},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20230525-63822},
  pages     = {1 -- 21},
  abstract  = {Identification of modal parameters of a space frame structure is a complex assignment due to a large number of degrees of freedom, close natural frequencies, and different vibrating mechanisms. Research has been carried out on the modal identification of rather simple truss structures. So far, less attention has been given to complex three-dimensional truss structures. This work develops a vibration-based methodology for determining modal information of three-dimensional space truss structures. The method uses a relatively complex space truss structure for its verification. Numerical modelling of the system gives modal information about the expected vibration behaviour. The identification process involves closely spaced modes that are characterised by local and global vibration mechanisms. To distinguish between local and global vibrations of the system, modal strain energies are used as an indicator. The experimental validation, which incorporated a modal analysis employing the stochastic subspace identification method, has confirmed that considering relatively high model orders is required to identify specific mode shapes. Especially in the case of the determination of local deformation modes of space truss members, higher model orders have to be taken into account than in the modal identification of most other types of structures.},
  subject      = {Fachwerkbau},
  language  = {en}
}
@article{ChowdhuryZabel,
  author    = {Chowdhury, Sharmistha and Zabel, Volkmar},
  title     = {Influence of loading sequence on wind induced fatigue assessment of bolts in TV-tower connection block},
  series = {Results in Engineering},
  volume    = {2022},
  journal   = {Results in Engineering},
  number    = {Volume 16, article 100603},
  publisher = {Elsevier},
  address   = {Amsterdam},
  doi       = {10.1016/j.rineng.2022.100603},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20221028-47303},
  pages     = {1 -- 18},
  abstract  = {Bolted connections are widely employed in structures like transmission poles, wind turbines, and television (TV) towers. The behaviour of bolted connections is often complex and plays a significant role in the overall dynamic characteristics of the structure. The goal of this work is to conduct a fatigue lifecycle assessment of such a bolted connection block of a 193 m tall TV tower, for which 205 days of real measurement data have been obtained from the installed monitoring devices. Based on the recorded data, the best-fit stochastic wind distribution for 50 years, the decisive wind action, and the locations to carry out the fatigue analysis have been decided. A 3D beam model of the entire tower is developed to extract the nodal forces corresponding to the connection block location under various mean wind speeds, which is later coupled with a detailed complex finite element model of the connection block, with over three million degrees of freedom, for acquiring stress histories on some pre-selected bolts. The random stress histories are analysed using the rainflow counting algorithm (RCA) and the damage is estimated using Palmgren-Miner's damage accumulation law. A modification is proposed to integrate the loading sequence effect into the RCA, which otherwise is ignored, and the differences between the two RCAs are investigated in terms of the accumulated damage.},
  subject      = {Schadensakkumulation},
  language  = {en}
}