Topic
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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TL;DR: In this article, the exact dynamic stiffness matrix for a high-order beam element is derived from the solutions of the differential equations that describe the deformations of the cross-section according to the high order theory, which include cubic variation of the axial displacements over the beam.
Abstract: This work presents the derivation of the exact dynamic stiffness matrix for a high-order beam element. The terms are found directly from the solutions of the differential equations that describe the deformations of the cross-section according to the high-order theory, which include cubic variation of the axial displacements over the cross-section of the beam. The model has six degrees of freedom at the two ends, one transverse displacement and two rotations, and the end forces are a shear force and two end moments. Using the dynamic stiffness matrix exact vibration frequencies for beams with various combinations of boundary conditions are tabulated and compared with results from the Bernoulli-Euler and Timoshenko beam models.
19 citations
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TL;DR: In this paper, a stiffness matrix evaluation method based on the boundary curve approximation by piecewise oblique curves which can cross several elements was proposed for the discretized system by the fixed-grid method.
19 citations
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07 Aug 2002
TL;DR: An analysis of the stiffness of redundant manipulators is undertaken, where in the planar case the stability conditions for the force dependent stiffness (and gravity-dependent stiffness) are obtained in the analytical form.
Abstract: An analysis of the stiffness of redundant manipulators is undertaken in this paper. First, the matrix of the force-dependent stiffness is derived and its basic properties are analyzed. In particular, in the planar case the stability conditions for the force dependent stiffness (and gravity-dependent stiffness) are obtained in the analytical form. Next, dual properties of the stiffness and compliance are exploited to establish a decomposition of the joint stiffness and compliance in the form similar to the decomposition of the joint velocities and torques. Finally, a minimal, nonredundant parameterization of the joint stiffness and compliance is commented.
19 citations
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TL;DR: This work uses a passivity approach to establish the requirements for the control law for a structure equipped with semi-active stiffness devices, and solves an optimal control problem that demonstrates that the passive, resetting feedback control law approximates the optimal control.
Abstract: This paper addresses control of structural vibrations using semi-active actuators that are capable of manipulating stiffness and/or producing variable stiffness. Usually vibration suppression is achieved using damping devices rather than stiffness ones. However, stiffness devices can produce large forces and have significant advantages for shock isolation purposes. In this work we use a passivity approach to establish the requirements for the control law for a structure equipped with semi-active stiffness devices. We also solve an optimal control problem that demonstrates that our passive, resetting feedback control law approximates the optimal control. Simulation and experimental results are presented in support of the proposed approach.
19 citations
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TL;DR: In this paper, the position of the supports is now a continuous parameter and the shape functions are used to produce the global stiffness matrix, which is then used to detect the support locations.
19 citations