Free Vibration Analysis Using Substructuring

The method of substructuring is developed and applied to the solution of free vibration problems for large structural systems. Modifications to the substructure stiffness and mass matrices permit the substructure mode shapes to more accurately conform to the complete system mode shapes. These modifications account for the elastic and inertial effects of the surrounding structure on each substructure. Computational algorithms are described which determine the substructure mode shapes associated with the lowest natural frequencies. These algorithms are based on an iterative scheme with an automatic starting method. The synthesis method for the determination of the system mode shapes from the substructure mode shapes is demonstrated. An example problem is solved and the solution compared to that obtained by a conventional method.