A method for selecting master DOF in dynamic substructuring using the Guyan condensation method

Abstract The choice of the master DOF defines the domain where the Guyan condensation is valid. If fg is the smallest eigenfrequency of all the substructures with the master DOF grounded, then the eigenfrequenciesfg of the complete structure, calculated by condensation and assembly of the substructures, will be of acceptable precision if fg 1 2 f g . The eigenmodes and the eigenfrequencies will be affected by increasingly large errors as fg, approache fg. For fg⩾fg, the results can be totally erroneous. It is thus very important to select the master DOF of each substructure so that fg will be a maximum. A method of selecting master DOF is proposed which allows the limits of the validity of the Guyan reduction to be defined while conserving a minimum of master DOF.