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There are various condensation methods for substructure techniques in structural dynamics. A generalized condensation method that comprises most of the classical condensation techniques and allows for arbitrary mode shapes within a standardized approach is described here. Within the framework of this method, a flexible boundary method is introduced that allows for elastic and mass-loaded boundaries for eigenmode determination, as well as for mode shapes that reflect the influence of damping. The relationship to other approaches taken from existing literature is examined. For damped structures, the flexible boundary method provides a condensation process that takes into account the influence of the complex eigenmodes of structures with nonproportional and high damping. To couple substructures with different component damping, the equivalent structural damping approach is provided. The problems associated with diagonal system damping of substructures and the full triple matrix product are overcome.Nomenclature A = attachment modes B = flexibility matrix C = structural damping matrix D = viscous damping matrix fFg = external force vector G = condensation matrix G = matrix of Ritz vectors K = stiffness matrix M = mass matrix P = projection matrix fqg = vector of generalized degrees of freedom R = residual flexibility T = transformation matrix fxg = vector of physical displacements = complex eigenmodes = static modes ' = real eigenmodes = frequency domain variable ! = eigenfrequency

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