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The Flexibility and Strength of Corrugated Diaphragms and Folded Plates

Lawson, RM 1976, The Flexibility and Strength of Corrugated Diaphragms and Folded Plates , PhD thesis, University of Salford.

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    Abstract

    Trapozoi, lally corrugated sheeting has been previously studied with regald to applications in shear diaphragms, making use of its inherent strength and stiffness prepeitios by suitable connections. The in-plane deflection is an important design factor and the shear distortion component, due to eccentric transfer of fastener force into profile shear, is a major contributor to the total. A design formu]a is developed for the distortional shear flexibility for .ets taste ed in every trough and in intermediate purlins which takes account of the localized distortion at the sheet ends by using an energy method analysis of assumed displacement functions to represent plate bending. For fastening in alternate or multiple of troughs, an additional profile concertina distortiOn occurs, resulting in a large increase in the shear flexibility. A similar energy method is performed as for the previous case, developing the same basic formula for the distortional deflection. A corresponding study is made for sinusoidally corrugated sheeting. A nuMber of practical design factors have been examined - including the effect of longitudinally overlapping sheets, and purlin restraint on profile distortion. For sheets spanning over rafters into different shear fields, the expressions for shear flexibility have been modified. The strength of diaphragms has been investigated, especially with regard to fastening on two sides only, which includes the torsional and bending stiffness of laterally weak purlins. Diaphragm openings cause an increase in the sheet flexibility and constrain purlins to follow the resulting displaced shape. Consequently locally high purlin bending stresses and sheet-purlin forces may be generated, as revealed by differential equation and finite element studies. Corrugated sheeting has many applications in frameless structures such as folded plates and hyperbolic paraboloids. The flexibility and • strength expressions have been used to design a prototype three bay folded plate roof Which utilizes specially pressed sheeting to reduce the shear distortion component of roof deflection, The shear buckling strength of corrugated diaphragms is an impottant factor in such construction. For larger roof diaphragms with only periodic intenrediate fixings to purlins, buckling may occur over the complete diaphragm depth rather than separately in each bay, and design tables are shown for this condition.

    Item Type: Thesis (PhD)
    Contributors: Davies, JM(Supervisor)
    Themes: Built and Human Environment
    Schools: Colleges and Schools > College of Science & Technology
    Colleges and Schools > College of Science & Technology > School of Computing, Science and Engineering > Civil Engineering Research Centre
    Depositing User: Institutional Repository
    Date Deposited: 22 Jul 2011 16:20
    Last Modified: 13 Feb 2014 14:47
    URI: http://usir.salford.ac.uk/id/eprint/14884

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