THE CONVERGENCE OF THE ITERATED IRS METHOD

Static or Guyan reduction is widely used to reduce the number of degre es of freedom in a finite element model, but it is exact only at zero frequency. The Improved Reduced System (IRS) method makes some allowan ce for the inertia terms and produces a reduced model which more accur ately estimates the modal model of the full system. The IRS method may be extended to produce an iterative algorithm for the reduction trans formation. It has already been shown that this reduced model reproduce s a subset of the modal model of the full system if the algorithm conv erges. In this paper it is proved that the iterated IRS method converg es. It is also shown that the lower modes converge more quickly than t he higher modes and that the master co-ordinates should be chosen to g ive an accurate static reduction. (C) 1998 Academic Press Limited.