For a given mode, global force balance measures the accuracy of an Eigenvector, which should always have small error. Since lower Ritz modes converge to Eigenvectors, they too should have small error. Higher Ritz modes, on the other hand, will demonstrate larger error since they are linear combinations of higher-mode Eigenvectors, which do not exactly satisfy the formulation K v - w2 M v = 0. When sufficient lower-frequency modes are provided, higher-frequency modes should respond statically, minimizing the degree and importance of this violation of dynamic equilibrium.
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Integrations