Free Vibration and Earthquake Behavior of Solar Power Plant Chimneys

Abstract eng:
In this paper, the basic mechanical principles for structural modeling of shells of revolution using ring elements are briefly summarized. For the representation of mechanical variables in hoop direction, Fourier series are used within this numerical model. Further, solution properties for free vibration and for transient dynamic problems are presented with special regard to ring element models. The presented algorithms are implemented in computer code ROSHE [7] which has been successfully applied to the analysis and design of a large number of cooling towers world wide. In this contribution, the challenging step from natural draft cooling towers which are currently built with standard heights up to 200 m towards large solar upwind power plant chimneys with heights of approximately 1000 m is dared. Hereby, the pre-design of a 1000 m solar chimney by Krätzig is taken as reference geometry. With this design, the dynamic behavior of this large 1000 m solar chimney subjected to horizontal earthquake acceleration is studied. The behavior of this tower is compared to dynamic behavior of cooling towers subjected to horizontal earthquake acceleration. While significant non-linear effects such as uplift from ground, cracking of columns and shell arise in cooling towers, the behavior of solar chimneys is totally different. Due to very high period of the first relevant eigenmotion, these structures behave similar to base isolated structures. The structure will not follow the ground motion in upper parts. Despite of the large height, uplift or loss of stability due to tilting will not become a problem. Tensile meridian membrane forces occur only in upper parts of the shell between 600 m and 1000 m. In this paper, the transient response of the 1000 m solar chimney is studied in comparison to a standard natural draft cooling tower of height 180 m. They are both subjected to NS component of Kern County earthquake acceleration with peak ground acceleration 0.35 g. Simplified response spectrum analysis with presentation of modal contributions is further conducted for a simplified beam model of the solar power plant chimney which confirms the obtained results. Powerful post processing tools have been developed and will be utilized within the presentation to visualize the structural response of both systems.

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