This thesis is concerned with the free vibration analysis of stiffened circular cylindrical and conical shells. The study was carried out with a view to improving the accuracy and efficieny of various modelling techniques for the prediction of the stiffened shells natural frequencies and mode shapes. A review of the existing literature covering various aspects of the shell vibrations problem and modelling techniques has been given at the beginning of each chapter with a critical appraisal of the assumptions made and results obtained. Initially the continuum energy approach was used for the analysis. The developed method allows for discrete consideration of stiffeners having arbitrary location and properties. Energy of bending in two planes and rotary inertia have been included in the analysis. Various types of stiffened shells with shear diaphragm ends condition were analysed using this method for the prediction of their natural frequencies. The predicted results have been compared with published experimental results. The finite element technique was also used for the prediction of natural frequencies and mode shapes of stiffened shells. Axisymmetric shell of revolution element, Facet shell element, semi-100f element and various types of beam elements, which are available within the PAFEC 75 suite of programs, were used for these studies. An efficient modelling technique has been introduced for ring stiffened cylindrical and conical shells by the use of the shell of revolution element. For improved accuracy of the predicted frequencies and a more economical model, shell symmetry was utilized for the free vibration analysis of unstiffened and stiffened shells. Half, quarter and one eighth models were studied by developing the appropriate boundary conditions and are discussed here. The free vibration characteristics of orthogonally stiffened cylindrical shells and an orthogonally stiffened cylindrical panel have been studied. An eight noded stiffened super shell element was developed for this study. This element was used for modelling various other types of stiffened shells and the predicted natural frequencies have been compared with known published experimental and theoretical results. Experimental verification of theoretical predictions of natural frequencies and mode shapes of an orthogonally stiffened cylindrical panel was carried out and is reported here.

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Thesis (M. Sc) -- University of the Western Cape, 2007. / Includes bibliographic references, (leaves 77-80).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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This thesis establishes why the Shell Oil Company produced a series of seventy-one posters of the British landscape in the 1930s. Through an examination of the 76 cm. x 114cm. posters that were attached to the sides and backs of the company’s delivery lorries, the thesis determines why Shell chose this form of publicity. The thesis examines the posters as historical, if ephemeral, artefacts and analyses the social, economic and cultural context of their production. Whilst there has been some historical analysis of poster design within the field of design history, the significance of the poster within these contexts has been largely neglected. The unique hybrid nature of the Shell posters as advertising based upon fine art using over fifty artists and designers makes them a unique repository of British visual culture of the 1930s. This thesis describes how Shell created three landscape poster campaigns, not through the enlightened patronage of its publicity manager, Jack Beddington, but through a complex set of circumstances that included: the cartel that was formed by the oil companies supplying Britain; the development and encouragement of motoring tourism and its effect on the countryside; the middle-class rejection of working class holiday destinations; concern about the preservation of the countryside; the effect of the ‘slump’ on the working lives of artists; economic and aesthetic arguments about the relationship between fine and commercial art and the relationship between landscape and national identity. Chapter 1 explores the background and influences that led to the creation of the posters, including the precursors of Beddington and the development of the poster as a medium. Chapter 2 investigates the inter-war debate that exposed the uneasy relationship between fine art, commercial art and industry. Chapter 3 investigates the concept of ‘place’ and uses case studies of places Shell wished to portray as destinations. Chapter 4 examines, through case studies, how the landscape, as portrayed by the posters, is represented for tourists and also the posters’ function within tourism.

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