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

The choice of the master DOF defines the domain where the Guyan condensation is valid. If f_g is the smallest eigenfrequency of all the substructures with the master DOF grounded, then the eigenfrequenciesf_g of the complete structure, calculated by condensation and assembly of the substructures, will be of acceptable precision if f_g < . The eigenmodes and the eigenfrequencies will be affected by increasingly large errors as f_g, approache f_g. For f_gf_g, the results can be totally erroneous. It is thus very important to select the master DOF of each substructure so that f_g 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.