307 research outputs found
A new finite element formulation of three-dimensional beam theory based on interpolation of curvature
A new finite element formulation of the `kinematically exact finite-strain beam theory' is presented. The finite element formulation employs the generalized virtual work in which the main role is played by the pseudo-curvature vector. The solution of the governing equations is found by using a combined Galerkin-collocation algorithm
The three-dimensional beam theory: Finite element formulation based on curvature
article introduces a new finite element formulation of the three-dimensional `geometrically exact finite-strain beam theory'. The formulation employs the generalized virtual work principle with the pseudo-curvature vector as the only unknown function. The solution of the governing equations is obtained by using a combined Galerkin-collocation algorithm. The collocation ensures that the equilibrium and the constitutive internal force and moment vectors are equal at a set of chosen discrete points. In Newton's iteration special update procedures for the pseudo-curvature and rotational vectors have to be employed because of the non-linearity of the configuration space. The accuracy and the efficiency of the derived numerical algorithm are demonstrated by several examples. (C) 2003 Civil-Comp Ltd. and Elsevier Ltd. All rights reserved
Analytical integration of stress field and tangent material moduli over concrete cross-sections
This paper presents a novel stress field and tangent material moduli integration procedure over a cross-section of a biaxially loaded concrete beam. The procedure assumes a sufficiently simple analytical form of the constitutive law of concrete, the polygonal shape of the boundary of the simply- or multi-connected cross-section and the monotonically increasing loading. The area integrals are transformed into the boundary integrals and then integrated analytically. The computational efficiency of the procedure is analyzed by comparing it with respect to the number of floating-point operations needed in various numerical integration-based methods. It is found that the procedure is not only exact, but also computationally effective. (c) 2005 Elsevier Ltd. All rights reserved
On ``A proposed standard set of problems to test finite element accuracy'': the twisted beam
The standard test problem of MacNeal and Harder (Finite Elem. Anal. Des. 1 (1985) 3) for the verification of spatial beam finite elements, i.e. the deflection of the initially twisted beam, is commented through the analysis of three variants of initially twisted beams: (i) a linearly twisted beam with a constant cross-section; (ii) a non-linearly twisted beam with a constant cross-section; and (iii) a non-linearly twisted beam with variable cross-sections. Our numerical results lead to the conclusion that the twisted beam problem (Finite Elem. Anal. Des. 1 (1985) 3) assumes the linearly twisted, curved-edge beam. (C) 2003 Elsevier B.V. All rights reserved
The linearized three-dimensional beam theory of naturally curved and twisted beams: the strain vectors formulation
This paper presents the equations of the linearized geometrically exact three-dimensional beam theory of naturally curved and twisted beams. A new finite-element formulation for the linearized theory is proposed in which the strain vectors are the only unknown functions. The linear form of the consistency condition that the equilibrium and the constitutive internal force and moment vectors are equal, is enforced to be satisfied at chosen points. An arbitrary curved and twisted axis of the beam is taken into account which demands proper consideration of the non-linearity of spatial rotations. The accuracy and the efficiency of the derived numerical algorithm are demonstrated by comparing present numerical results with various analytical and numerical results. (c) 2005 Elsevier B.V. All rights reserved
Finite-element formulation of geometrically exact three-dimensional beam theories based on interpolation of strain measures
This paper presents a new finite element formulation of the `geometrically exact finite-strain beam theory'. The governing equations of the beam element are derived in which the strain vectors are the only unknown functions. The consistency condition that the equilibrium and the constitutive internal force and moment vectors are equal, is enforced to be satisfied at chosen points. The solution is found by a collocation algorithm. The linearity of the strain space not only simplifies the application of Newton's method on the non-linear configuration space, but also leads to the strain-objectivity of the proposed method. The accuracy and the efficiency of the derived numerical algorithm are demonstrated by several examples. (C) 2003 Elsevier B.V. All rights reserved
Convergence properties of materially and geometrically non-linear finite-element spatial beam analysis
The way the non-linear constitutive equations in the spatial beam formulations are solved, influences the rate of convergence and the computational cost. Three different approaches are studied: (i) the direct global approach, where the constitutive equations are taken to be the iterative part of the global governing equations, (ii) the local (or indirect global) approach, where the constitutive equations are solved separately in each step of the global iteration, and (iii) the partly reduced approach, which is the combination of (i) and (ii). The approaches are compared with regard to the number of global iterations and the total number of floating point operations. The direct global approach is found to be the best choice. (C) 2008 Elsevier B. V. All rights reserved
The Rattling of Euler's Disk
The motion of a disk spinning on a horizontal surface has drawn a great deal of interest recently. The objectives of the researches are to find out what produces an increasing rattling sound and why the spinning ends so abruptly. In order to understand the behaviour of the spinning disk better, we derived a mathematical model of the rolling/sliding motion of a thin, rigid disk on a rigid, rough horizontal plane, and found the numerical solution of the related initial value problem. Then we studied the motion of the commercially available Tangent Toy disk [3]. The results show that the normal contact force becomes very large whenever the inclination of the disk becomes small. As the inclination of the disk oscillates with time, the time-graph of the normal contact force exhibits periodical peaks, which correlate well with the peaks in the recorded sound response. They could well be responsible for the rattling sound heard during the motion.\u
The quaternion-based three-dimensional beam theory
This paper presents the equations for the implementation of rotational quaternions in the geometrically exact three-dimensional beam theory. A new finite-element formulation is proposed in which the rotational quaternions are used for parametrization of rotations along the length of the beam. The formulation also satisfies the consistency condition that the equilibrium and the constitutive internal force and moment vectors are equal in its weak form. A strict use of the quaternion algebra in the derivation of governing equations and for the numerical solution is presented. Several numerical examples demonstrate the validity, performance and accuracy of the proposed approach. (C) 2009 Elsevier B.V. All rights reserved
Energy conserving time integration scheme for geometrically exact beam
An energy conserving finite-element formulation for the dynamic analysis of geometrically non-linear beam-like structures undergoing large overall motions has been developed. The formulation uses classical displacement-based planar beam finite elements described in an inertial frame. It takes into account finite axial, bending and shear strains. A theoretically consistent approach is used to derive a novel and simple energy conserving scheme, using the unconventional incremental strain update rather than the standard strong form. Numerical examples demonstrate perfect energy and momenta conservation, stability and robustness of the scheme, and good convergence properties in terms of both the Newton-Raphson method and time step size. (c) 2006 Elsevier B.V. All rights reserved
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