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Nonlinear stability of prestressed stayed columns with multiple crossarm systems

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Title: Nonlinear stability of prestressed stayed columns with multiple crossarm systems
Authors: Yu, Jialiang
Item Type: Thesis or dissertation
Abstract: Prestressed stayed steel columns are increasing in popularity in the construction industry. This type of structure possesses a considerably higher buckling resistance as compared to the conventional column without a commensurate increase in self-weight, owing to the extra stiffnesses provided by the system of crossarms and cable stays. Most of the previous literature focused on the buckling load of the stayed column while systematic studies on the post-buckling behaviour of the single-bay column have only been conducted more recently. Although the significance of the post-buckling behaviour of such structures has already been demonstrated, certain relevant topics have not been satisfactorily studied for the stayed columns with multiple crossarm systems, which potentially possess even higher buckling resistances as compared to the single crossarm cases. Therefore, the aim of the current thesis is to reveal the post-buckling behaviour of the prestressed stayed column with multiple crossarms along the length. A finite element model of a prestressed stayed column with multiple crossarms along the length is developed with the initial imperfections and the prestress taken into consideration. Interactive buckling is found to be the most dangerous case particularly when the critical buckling mode is anti-symmetric. It is found that the post-buckling behaviour is strongly linked to the actual geometric arrangement of the structure. Sensitivities to the levels of the prestress and the initial imperfections are also presented. The observations obtained from the FE model are first validated qualitatively by a simplified analytical model. The simplified model also reveals the process for how the pure buckling modes interact during the post-buckling stage. To compare with the results of the FE model quantitatively, a more sophisticated analytical model is subsequently developed. The total potential energy of the system is formulated in conjunction with the Rayleigh--Ritz method. The slackening of the stays is also successfully simulated. An identical observation, in that interactive buckling governs the post-buckling response when anti-symmetric buckling is critical, is obtained also. Excellent quantitative agreement is found between the results from the FE and the more sophisticated analytical model. Parametric studies on the geometric configurations where interactive buckling is most significant are also presented. Finally, a large number of separate cases with different structural geometries and levels of prestress are studied. The actual optimal prestress, which accounts for the load carrying capacity of the column and the required material resistances of different structural components, is determined for the triple-bay stayed column. This demonstrates that the nonlinear response of the stayed column system is practically important from a safety as well as an efficiency perspective.
Content Version: Open Access
Issue Date: Aug-2016
Date Awarded: Feb-2017
URI: http://hdl.handle.net/10044/1/44529
DOI: https://doi.org/10.25560/44529
Supervisor: Wadee, Ahmer
Department: Civil and Environmental Engineering
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Civil and Environmental Engineering PhD theses

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