A COMBINATION OF THE LANCZOS-ALGORITHM WITH THE SUBSTRUCTURE TECHNIQUE

A modified Lanczos method combined with a substructure technique was u sed for calculating natural frequencies and mode shapes of large struc tural systems. The method does not require generation and storage of s tiffness and mass matrices of the original structure. It uses only the stiffness and mass matrices of each substructure. No approximating as sumptions are needed other than the usual assumption of a linear elast ic system modelled by finite elements. Thus, natural frequencies and t he mode shapes for the finite element model employed are the same as t hose with or without the substructuring algorithm. The method is demon strated by calculating the first ten natural frequencies and the corre sponding mode shapes for an open truss helicopter tail-boom structure. (C) 1995 Academic Press Limited