ETD Collection

Permanent URI for this collectionhttps://wiredspace.wits.ac.za/handle/10539/104


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2015 - 20192

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    Optimisation of no sway plane rigid frames against buckling
    (2019) Naidoo, Devveena
    The report proposes a simple method which optimises the design of plane, rigid no sway frame structures based on the system buckling load. It is centred on either maximising the buckling load or minimising the weight of the structure, or both; and to have all stories buckling at the same time. The method is applied to various frames examples and the results are compared to that obtained from a system buckling analysis performed in the ANSYS Finite Element Analysis (FEA) software. The proposed optimisation procedure proved successful for no sway multi-story rigid frames, as validated by the acceptable percentage differences of below 5% from the FEA analysis. The optimisation method is however limited in its application to multi-story rigid no sway frames only. The methods attempted for the calculation of the system buckling load to account for the influence of adjacent stories of sway frames, was not successful and further development is required.
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    The snap-through stability of plastically designed steel pitched-roof portal frames
    (2015-01-12) Bryant, John Spencer
    Recent proposed rafter slenderness limits, to prevent snap-through of plastically designed pitched-roof portal frames, incorporate the elastic snap-through buckling load of such frames. It has been suggested that the elastic snap-through buckling load used in the proposals is over-estimated making these slenderness limits unconservative. This is supported by a more rigorous elastic analysis. To test the proposals, model frames lying on or close to the slenderness limits were tested to failure in the laboratory. Frame dimensions were chosen so that the frames were only susceptible to snap-through instability. Failure loads far lower than the expected plastic collapse loads were measured, showing that the elastic snap-through buckling load is over -estimated . Since plastic analysis is easily applied to portal frames, these slenderness limits are best replaced by a similar limit incorporating a more accurate elastic snap-through buckling load. A new limit is outlined which must still be tested by further research