Dynamic evaluation of the solar chimney
Thesis (MEng (Civil Engineering))--University of Stellenbosch, 2005.
Previous studies on the solar chimney have shown that its structural integrity might be compromised by the occurrence of resonance. A structure may displace excessively when a load of the same frequency as a structural eigen-frequency is applied. The wind gust spectrum peaks near the solar chimney’s fundamental resonance frequency. This phenomenon poses a reliability threat, not only to the solar chimney, but also to all high-rise, slender structures. Structural dynamics describe the response of a structure to a varying load. The dynamic equation incorporates four terms that bind the factors responsible for resonance: kinetic energy, dissipated energy (damping), stiffness energy and input energy (loading). After a brief literature study on classical chimney design procedures, the study scrutinises each of these terms individually in the context of the solar chimney as designed to date. A dynamic analysis is undertaken with all the above-mentioned parameters as defined and estimated by the study. The results from the analysis show amplifications of approximately three times the static displacements. In load cases where the wind direction inverts along the height, higher eigen-modes are excited. However, the most severe dynamic amplification occurs at the fundamental eigen-mode. In the context of solar chimney research, this study brings valuable new insights regarding the dynamic behaviour of the chimney structure to the fore.