Natural frequencies of structures with uncertain-but-bounded parameters

The present paper deals with the solution of the interval eigenvalue problem for structural systems with uncertain-but-bounded parameters. The proposed approach for evaluating the bounds of the interval eigenproperties may be viewed as an appropriate extension of a procedure originally developed by the third author. The original contribution consists in the use of the so-called improved interval analysis, recently pro-posed by the first two authors to limit the effects of the dependency phenomenon. Mass and stiffness uncer-tainties are considered either coincident, completely disjoint or partially disjoint, so as to cover all possible situations occurring in real structural problems. The accuracy of the proposed estimates of the bounds of the interval natural frequencies is demonstrated by comparisons with the vertex method solutions.