Showing papers on "Modal testing published in 1974"
TL;DR: In this article, a method for modal damping determination, based on the principle of transfer function matching at the natural frequencies of the interaction system, is presented. But this method is physically realistic and consistent, and is shown to be adequate for engineering purposes.
Abstract: Normal mode analysis for soil-structure interaction is an approximation. Its adequacy depends largely on the technique used to determine the overall modal damping values. A method is presented herein for the modal damping determination, based on the principle of transfer function matching at the natural frequencies of the interaction system. This method is physically realistic and consistent, and is shown to be adequate for engineering purposes.
63 citations
01 Jan 1974
TL;DR: In this article, a technique for identifying the modal properties of an elastic structure in a testing laboratory is presented, which is based upon the use of digital processing and the fast Fourier transform (FFT) to obtain transfer function data, and then use of a least squared error estimator t o identify modality properties from the transfer function.
Abstract: A technique for identifying the modal properties of an elastic structure in a testing laboratory is presented. The technique is based upon the use of digital processing and the fast Fourier transform (FFT) to obtain transfer function data, and then the use of a least squared error estimator t o identify modal properties from the transfer function data. Both analytical and experimental results are presented.
47 citations
TL;DR: In this paper, the first five frequencies and modal shapes for the free lateral vibration of uniform double-span uniform beams are derived for the entire family of beams regardless of the location of the intermediate support.
27 citations
29 Oct 1974
TL;DR: In this paper, an approach is formulated by which structural dynamics of ships may be analyzed in a linear modal form, by employing the principal modes of the ship in vacuo, simple orthogonality relations can be retained without dependence on the necessarily approximate techniques used to estimate fluid forces.
Abstract: An approach is formulated by which structural dynamics of ships may be analysed in a linear modal form. By employing the principal modes of the ship in vacuo , simple orthogonality relations can be retained without dependence on the necessarily approximate techniques used to estimate fluid forces. It is also possible to identify modal contributions to mass, damping and stiffness for the hull and for the hydrodynamic actions separately. Those contributions of hydrodynamic origin may depend significantly on time history effects which can be measured by means of a model test; these effects can be admitted into the ship strength analysis, it is believed for the first time. It is shown how existing modal theories of ship strength and theories of seakeeping (i. e. of ‘rigid body’ motion in a seaway) fit into this more general analysis.
21 citations