Natural vibrations of thin, flat-walled structures with different boundary conditions

Abstract The natural frequencies of thin, flat-walled structures with different boundary conditions are analyzed by the finite strip method. This class of structures includes plates with eccentric stiffeners, thin multi-celled box girder bridges, and folded plate roofs, etc. The method is simple and at the same time very powerful and versatile, and can treat problems with variably-spaced stiffeners, and with orthotropic and variable thickness plates without any difficulty. The finite strip method is an extension of the now well-known finite element method. This method is, however, semi-analytical in nature, since the displacement functions chosen are always of the form φ ( x ) ψ ( y ), in which φ ( x ) is a polynomial with undetermined parameters, and ψ ( y ) a function series satisfying a priori the two end conditions. Thus a two-dimensional strip is reduced to a one-dimensional problem, with a corresponding reduction in computational efforts.