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Direct stiffness method

About: Direct stiffness method is a research topic. Over the lifetime, 2584 publications have been published within this topic receiving 53131 citations.


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Journal ArticleDOI
TL;DR: In this article, a modified finite strip method embracing the harmonic coupled Fourier series treatment is described, where all harmonics are coupled, and the stiffness matrix order and bandwidth are proportional to the number of harmonics used.
Abstract: The paper describes a modified finite strip method embracing the harmonic coupled Fourier series treatment. The well known uncoupled formulation, first developed in the context of thin plate bending analysis, represents a semi-analytical finite element process. As far as linear analysis is concerned, it takes advantage of the orthogonality properties of harmonic functions in the stiffness matrix formulation. However in the case of the geometric stiffness matrix calculation, the integral expressions contain the products of trigonometric functions with higher-order exponents, and here the orthogonality characteristics are no longer valid. All harmonics are coupled, and the stiffness matrix order and bandwidth are proportional to the number of harmonics used.

22 citations

Journal ArticleDOI
TL;DR: In this article, the static behavior of thin-walled laminated composite closed cross-section beams having variable stiffness is investigated and the analytical model used accounts for flexural-torsional coupling and warping effects as well as the variable stiffness along the contour of the crosssection of the beam.

22 citations

Journal ArticleDOI
TL;DR: In this article, a set of undamped critical speed mode shapes calculated from the average horizontal and vertical bearing stiffness is used to transform the equations of motion into a set coupled modal equations, coupled by the generalized bearing coefficients and the gyroscopic moments.
Abstract: The generalized dynamic equations of motion have been obtained by the direct stiffness method for multimass flexible rotor bearing systems including the effects of gyroscopic moments, disk skew, and rotor acceleration. A set of undamped critical speed mode shapes calculated from the average horizontal and vertical bearing stiffness is used to transform the equations of motion into a set of coupled modal equations of motion. The modal equations are coupled by the generalized bearing coefficients and the gyroscopic moments. An analysis using only undamped critical speeds or decoupled modal analysis assuming proportional damping may lead to erroneous results. This paper presents a rapid method of calculating rotor resonance speeds with their corresponding amplification factors, stability and unbalance response of turborotors. Examples of the application of this modal approach are presented and results are compared to those of other methods such as matrix transfer analysis.

22 citations

Proceedings ArticleDOI
01 Apr 1996
TL;DR: In this paper, a new optimal update method for the correlation of dynamic structural finite element models with modal data is presented, which computes a minimum-rank solution for the perturbations of the elemental stiffness parameters while constraining the connectivity of the global stiffness matrix.
Abstract: A new optimal update method for the correlation of dynamic structural finite element models with modal data is presented. The method computes a minimum-rank solution for the perturbations of the elemental stiffness parameters while constraining the connectivity of the global stiffness matrix. The resulting model contains a more accurate representation of the dynamics of the test structure. The changes between the original model and the updated model can be interpreted as modeling errors or as changes in the structure resulting from damage. The motivation for the method is presented in the context of existing optimal matrix update procedures. The method is demonstrated numerically on a spring-mass system and is also applied to experimental data from the NASA Langley 8-bay truss damage detection experiment. The results demonstrate that the proposed procedure may be useful for updating elemental stiffness parameters in the context of damage detection and model refinement.

22 citations

Journal ArticleDOI
TL;DR: In this article, an analytical procedure based on the dynamic stiffness method was proposed for the study of rotor dynamics problems on the grounds of the governing differential equations of a continuous beam, including the effects of translational and rotational inertia, gyroscopic moments and shear deformation of the shaft.
Abstract: An analytical procedure, based on the dynamic stiffness method, is proposed for the study of rotor dynamics problems. On the grounds of the governing differential equations of a continuous beam, the dynamic stiffness matrix of the rotating Timoshenko beam is derived, including the effects of translational and rotational inertia, gyroscopic moments and shear deformation of the shaft. Concentrated disks and isotropic, elastic bearings are taken into account in the element formulation. The results obtained by the proposed method are compared with both classical closed form solutions and finite element analyses taken from the literature.

22 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202334
202270
202123
202022
201930
201842