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We analyze the frequency response of structural dynamic systems with uncertainties in load and material properties. We introduce uncertainties in the system as interval numbers, and use Interval Finite Element Method (IFEM). Overestimation due to dependency is reduced using a new decomposition for the stiffness and mass matrices, as well as for the nodal equivalent load. In addition, primary and derived quantities are simultaneously obtained by means of Lagrangian multipliers that are introduced in the total energy of the system. The obtained interval equations are solved by means of a new variant of the iterative enclosure method resulting in guaranteed enclosures of relevant quantities. Several numerical examples show the accuracy and efficiency of the new formulation.

Solutions to partial differential equations describing behavior of physical systems are often imprecise. This uncertainty is due to numerical approximations and uncertainty in physical parameters. In elastostatics, these parameters include uncertain material behavior, uncertain boundary conditions, and uncertain geometry of the system. This paper addresses the treatment of geometrical uncertainty for elasticity problems. The new method predicts fuzzy responses for the given membership functions, describing the range of tolerances for the system’s geometry. To obtain exact bounds on the solution to the resulting fuzzy linear system of equations, fuzzy matrix parameterization is developed. Numerical example is shown to illustrate the behavior of the method.