Abstract
THE determination of the suitable breadth and depth of a timber beam to carry a given load involves consideration of strength, of stiffness, and of the capacity of the material to withstand the horizontal shear forces induced in it by the transverse loading. The calculations which these considerations necessitate can, however, be entirely eliminated by making use of a set of three charts recently published under the title “Charts for the Design of Timber Beams”. These charts have been prepared by V. D. Limaye, officer-in-charge of the Timber Testing Station, Forest Research Institute, Dehra Dun, United Provinces. The first of them is designed to ensure that a beam of adequate strength is chosen. In it two nomographs are provided which, from the given load per square foot, span, and spacing, ascertain the total load carried by the beam. Then, by the drawing of four horizontal and vertical lines terminated by suitably placed diagonal lines which are embodied in the chart, the breadth and depth of a sufficiently strong beam are obtained. In most cases in which timber beams are used, it is necessary to restrict the deflection under load to certain specified limits, and stiffness has therefore to be arranged. This is done by means of the second chart, which enables the correct amount of adjustment to be made in the sizes already determined so that the required degree of stiffness is assured, and the process involves only the drawing of another set of horizontal and vertical lines. In the third chart a third series of horizontal and vertical lines leading to a final nomograph either confirms the horizontal shear strength as adequate or shows the correction required so that, in the end, the section evolved is suitable for its purpose from all points of view.
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Selection of Sizes of Timber Beams. Nature 143, 371 (1939). https://doi.org/10.1038/143371c0
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DOI: https://doi.org/10.1038/143371c0