Abstract
This study investigates both the static and dynamic behaviors for the uniform beam supported at its ends by rotational supports. The stiffness coefficients of these supports are treated as interval variables. It is first demonstrated on the static problem that the classical interval analysis may lead to overestimation of the response. The paper introduces a remedy for this "ill" of the classical interval analysis. The artificial interval parameter is introduced and the extrema of the static displacements and natural frequencies are determined. Finally, the hybrid case of uncertain boundary conditions and uncertain mass density is treated with attendant interesting results.