Vibration Analysis of Structures by Component Mode Substitution

A method is presented to determine the vibration modes of a complex structural system by using component vibration modes. The structural system is considered to be an assemblage of subsystems or components. The vibration modes for each component are determined separately and then used to synthesize the system modes. The number of component modes used may be truncated to reduce the number of generalized coordinates required for a vibration analysis. Only component vibration modes are retained as generalized coordinates when the system modes are obtained; hence, the method is particularly suitable for structures with a large number of component interface coordinates, such as finiteelement shell models. The boundary conditions used for determining component vibration modes can be either free-free or constrained. An optional technique to modify the component modes is included in order to obtain more accurate system modes. Numerical results from two examples are included.