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Rationalization of trusses and yield-line patterns identified using layout optimization

He, Linwei (2015) Rationalization of trusses and yield-line patterns identified using layout optimization. PhD thesis, University of Sheffield.

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Abstract

To help engineers to design and analyse structures, various tools exist. However, many of them are complicated and difficult for engineers to master. In industry simple, accurate, and rapid tools are potentially very useful. The development of such tools has thus been the main focus of this thesis. One application is the design of lightweight truss structures. Although techniques have been available to identify efficient truss designs for more than half a century, these are not widely used in industry. A major problem is that the structures generated are often complex in form, so that manufacturing becomes problematic. To address this, the current research explores two rationalization techniques: (i) introducing joint lengths to control the number of joints that exist in the resulting structure; and (ii) utilising geometry optimization to adjust the locations of joints in a truss. The former involves a minor modification to the standard process such that it retains the linear nature of the original problem, while the latter solves a more challenging non-linear optimization problem that can simultaneously simplify (make less complicated) and improve (make lighter) a given truss layout. To ensure a rapid and reliable process for the latter, analytical expressions of functions and their derivatives are supplied to a general purpose non-linear optimizer and various practical issues are also considered. A number of benchmark problems are solved to show the efficacy of the two rationalization techniques. Another application is yield-line analysis of reinforced concrete slabs. Even in the modern computer age, with many engineering analysis procedures successfully computerized, a fully automated means of undertaking a yield-line analysis has been lacking, forcing engineers in industry to use hand-calculations in order to benefit from the power of the yield-line method. This thesis is therefore concerned with the development of techniques that automate this method. By utilising the novel discontinuity layout optimization (DLO) method, the process of yield-line analysis has been truly automated at last. In addition, motivated by the outcomes of the rationalization procedure developed for trusses, research has been conducted to rationalize yield-line patterns generated via DLO. Similar to the technique used in trusses, analytical expressions of functions and their derivatives are deduced and then supplied to a non-linear optimizer, leading to a rapid and reliable computational process. To make DLO and the rationalization ready for use in industry, various slab configurations found in practice are also considered, permitting challenging slab problems to be tackled using the method. A number of examples from the literature and industry are analysed to demonstrate the efficacy of DLO and the rationalization technique.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Civil and Structural Engineering (Sheffield)
Identification Number/EthosID: uk.bl.ethos.675055
Depositing User: Mr Linwei He
Date Deposited: 10 Dec 2015 11:38
Last Modified: 12 Oct 2018 09:23
URI: http://etheses.whiterose.ac.uk/id/eprint/10616

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