Bulletin of Earthquake Science and Engineering

Bulletin of Earthquake Science and Engineering

The Effect of Spectrum Damping on the Seismic Design of Single-layer Domes Using Response Spectrum Analysis

Document Type : Technical Note

Authors
Fatemeh Davodijam 1
Pooya Zakian 2
Ali Komeyzi 1
1 M.Sc. Student of Earthquake Engineering, Faculty of Engineering, Arak University, Arak, Iran
2 Associate Professor of Earthquake Engineering, Faculty of Engineering, Arak University, Arak, Iran
10.48303/bese.2024.2036073.1192
Abstract
The seismic design of space structures is very important due to the difference in their dynamic behavior compared to conventional structures. Damping is a dynamic characteristic of an engineering structure and  plays a key role in seismic design. Based on the previous studies on the damping of space structures, the damping ratio of these structures is assumed to be 2%, which is different from that of conventional structures. This study aims to compare the results of seismic design for single-layer domes when employing 2% and 5% damping of the design spectrum. Three domes consisting of diamatic, schwedler, and lamella are examined in this study. The seismic design of these domes was carried out using response spectrum analysis according to the ASCE7-16. Due to the special geometry of the domes, the vertical seismic force is very effective in the seismic behavior of these structures; therefore, the vertical earthquake component is also considered in this study. The member connections of these domes are modeled as rigid connections, while the supports are modeled as pinned connections. The structural loads include the dead, snow, and earthquake. The dead and snow loads were taken as 0.5 and 1 kN/m2, respectively. Two important structural demands, including displacement and member stress ratio, are considered in the seismic design. The results show that the reductions of the top node displacement and critical stress ratio when using the damping ratios 2% and 5% for the selected domes are different, and these reductions can vary depending on the type of dome. However, there are sometimes small differences in the displacements and stresses of the domes when considering the design spectra with damping ratios 2% and 5%. Based on the results presented, it can be concluded that to achieve a mode participation factor of 90% in the seismic design of these spatial domes, the required number of vibration modes are 142, 236, and 122 for the diamatic, lamella, and schwedler domes, respectively. The high number of vibration modes required for these structures is due to the special geometry of the space structures. Furthermore, regarding the top node displacement reduction when increasing the damping ratio from 2% to 5%, it has been shown that this reduction is approximately 8% for the diamatic dome, 17% for the lamella dome, and 18% for the schwedler dome. These results indicate that increasing the damping ratio reduces the displacements. Also, the critical stress ratio in the diamatic dome using the damping ratio of 5% compared to 2% is decreased by about 4%. This reduction is approximately 10% for the lamella dome but is negligible for the schwedler dome. These results can provide valuable insights into selecting the damping ratio of the design spectrum in seismic design of domes using the response spectrum method, because the damping ratio for the design spectrum in traditional design codes is usually selected as 5% that is more suitable for conventional structures.
Keywords
Dome Structure
Damping
Seismic Design
Response Spectrum Analysis

Subjects

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  • Receive Date 24 July 2024
  • Revise Date 13 September 2024
  • Accept Date 18 September 2024