ESDU STRUCT 03.06.17
Flexible circular frames supporting a shell. The effect of adjacent frames and the longitudinal flexibility of the shell.
Abstract:ESDU Struct 03.06.17 provides, for a stringer stiffened skin supported by a frame, curves of effective skin-frame stiffness ratio (involving the equivalent frame spacing) plotted against actual skin-frame stiffness ratio. The skin-frame stiffness ratio includes the ratio of the shear modulus of the shell material to the elastic modulus of the frame material; that ratio is factored by frame radius to the power four multiplied by shell thickness and divided by the frame spacing times the moment of inertia of the cross-section of the frame about an axis through its centroid. The curves are plotted for selected values of a second non-dimensional parameter. It is given by the frame radius to the power six multiplied by the effective thickness of the shell (which includes an allowance for the cross-sectional area of the stringers supporting longitudinal load) divided by the moment of inertia as defined above and the actual frame spacing cubed. It is assumed that the end load carrying material of the shell is distributed uniformly longitudinally and circumferentially and that the frames are identical and equally spaced. Methods are suggested for treating unequal frame spacing, the presence of a rigid frame, and the situation arising when adjacent frames are also loaded. The effective skin-frame stiffness ratio is required to use the data in ESDU Struct 03.06.06.to 03.06.16. A worked example illustrates the use of the curves.
|Data Item ESDU STRUCT 03.06.17|