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Transversely Loaded Framework Members

Published online by Cambridge University Press:  28 July 2016

N. J. Hoff
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Extract

The standard method of strength calculation of a framework is based on the assumption that members are freely pinned together and external forces are applied only at nodes. Actually aircraft fuselage members are stiffly joined and transverse forces are often acting on them at considerable distances from nodes, e.g., weights of crew, instruments and oil, reactions of controls, stabiliser adjusting gear, etc.

The safest method of computing stress in such members is to assume both ends pin—jointed. As they actually are stiffly connected to adjacent members, they are not allowed to twist freely, i.e., the truss exerts moments on the loaded member. The effect of these end moments consists in diminishing deflection andfield moments. The decrease of maximum bending moment may attain nearly 50 per cent.

Since framework members are designed to withstand axial forces only, viz., tension or compression, they are comparatively weak against bending and have to be strengthened appreciably if transverse forces are present.

Type
Research Article
Information
The Aeronautical Journal , Volume 39 , Issue 296 , August 1935 , pp. 718 - 749
Copyright
Copyright © Royal Aeronautical Society 1935

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References

Note on page 718 * This method of graphical representation of moments is dealt with in extenso in Mr. Howard's book on “The Stresses in Aeroplane Structures.”

Note on page 719 * See “Strain Energy Methods,” by A. J. S. Pippard

Note on page 728 * Dr.Algyay—Hubert found the hyperbolic law to be in best agreement with experimental results when calculating secondary stresses of steel bridges. (See “Technika,” February,1934. Budapest.)

Note on page 745 * The law for the variation of J here used is not quite the same as given by equation (18b).Equation (30) has been chosen in order to get a linear law in case of a moment diagram according to Fig. 23.