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The behaviour of a structural member subjected to a torsional load may be defined by its torsional rigidity and the stress distribution over its cross section. As distinct from the solid or hollow cross section which is homogeneous in the axial direction, the semi-closed box section represents a three-dimensioned problem of a complex nature. This Paper attempts a solution by the Strain Energy method leading to expressions of torsional rigidity of a particular type of design and also analyses the stress distribution, the results being expressed in terms of the applied torque.
F. Laszlo, Dr. Ing and and H. Nolle
The analysis of a structure composed of beams integral with a slab is properly a three dimensional problem. In this paper, the need for a three dimensional treatment is obviated by an analysis of the slab according to thin plate theory and of the beams,
treated separately from the slab, by the theory of simple bending. The fact that the beams are actually integral with the slab is then recognised by enforcing displacement and strain compatibility at the slab-beam junctions. Both the stress-function, describing forces in the plane of the slab, and the transverse deflection of the slab are governed by a biharmonic equation; series solutions for these two quantities are obtained subject to typical, specified, boundary conditions and to conditions of compatibility at the slab-beam junctions. The calculation of the coefficients in the series solutions would be extremely laborious if carried out by hand-computation so that a digital computer programme has been written (for the Ferranti Pegasus Computer) by use of which the complete computation can be carried out in a few minutes; thus the effect of any prescribed variation in the parameters describing either the geometry of the structure or its loading can be quickly followed through. Details of the computer programme are given.
D. N. de G. Allen and R. T. Severn
Design of any structure for minimum weight is essentially based on the determination of optimum proportions on the basis of simultaneous failure in all the critical modes. The critical modes for a thin-walled beam subjected to bending loads would be due to yielding of the extreme fibre in tension or compression and local buckling of the compression flange.
S. Krishnan and K. V. Shetty