Optimum stiffened panel design with fundamental frequency constraint

A generic analysis/design method for prismatic plate assemblies, using exac t plate stiffnesses which are transcendental Functions of loading and/or vi bration frequency, has long been validated by the established program VICON OPT. Hitherto vibrations were permitted only in analysis because design use s the Wittrick-Williams algorithm to modify the design predicted by a linea r optimiser to be 'just stable' by scaling all layer thicknesses by F. This works because buckling loads, unlike the fundamental frequency f(1), vary monotonically with F. The paper considers additionally scaling all plate br eadths by F-alpha such that the buckling loads and f(1) all vary monotonica lly with F. Theoretical consideration of simple limiting cases establishes bounds on the permitted values of ct as 0.1 less than or equal to alpha les s than or equal to0.4. Then VICONOPT results for typical stiffened panels d emonstrate the method to be correct and are used to investigate the value o f ex which is most effective in returning stabilised designs of least mass and with least computation. (C) 2001 Elsevier Science Ltd. All rights reser ved.