A computational study on a nature inspired novel doubly curved folded shell structural form

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Date
2007
Authors
Abdulrazzack, Suhail Abdulaziz
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Abstract
In this research, the leaves of Johannesteijsmannia altifrons (J. altifrons) which belong to the palm family have been investigated. These leaves are doubly curved cantilever shell structures with folds extending from the central spine. The target of the study is in two folds: to investigate the influence of shape and folds on the structural behaviour of the J. altifrons and to investigate the structural behaviour of the J. altifrons like scaledup, realistic models under practical considerations using finite element analysis. A noncontact method called structured lighting method has been used for capturing the surface data of the leaf. An algorithm based on the actual geometry of the imaging setup has been developed and used in this study. The leaves have been analysed using orthotropic material properties of eleven species of wood. The results show efficient structural performance of the leaves in terms of stiffness and strength. In order to study the influence of the folds on structural behaviour, non-folded versions have also been generated and analysed. Folded models showed better performance in terms of stiffness and strength compared to the non-folded versions. The synclastic and anticlastic folded models yielded maximum deflection values of about 70% and 30% of the values in the corresponding flattened models, respectively. Similar comparison in terms of stresses yielded values of about 40% and 20% of the corresponding stresses in flattened models for both tension and compression. In view of the biomimetic nature of the study, a simple method called Source Referenced Classification (SRC) to classify nature inspired technological achievements is also presented. Novel CAD based procedures have also been developed for the purpose of generating doubly curved surfaces with folds. These procedures have been implemented to generate leaf-like scaled-up models. A computational study is carried out on these models to evaluate their structural performance under self weight condition, using light weight concrete. The results show satisfactory performance in terms of stiffness and strength with considerable reserve in material capacity particularly in compression (about 88%). All 6 models showed maximum deflection values of less than 15 mm over cantilever spans of about 10 m.
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PhD
Keywords
Civil Engineering , Computational , Folded shell
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