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Showing papers on "Direct stiffness method published in 1974"


Journal ArticleDOI
TL;DR: In this paper, a method is formulated for systematically using experimental measurements of the natural frequencies and mode shapes of a structure to modify stiffness and mass characteristics of a finite element model, and an additional feature is that the engineer's confidence in the modeling of the various finite elements is quantified and incorporated into the revision procedure.
Abstract: A method is formulated for systematically using experimental measurements of the natural frequencies and mode shapes of a structure to modify stiffness and mass characteristics of a finite element model. Throughout the modification process, which does not require complete data, the finite element model remains consistent. An additional feature is that the engineer's confidence in the modeling of the various finite elements is quantified and incorporated into the revision procedure. Examples demonstrate the convergence and versatility of the method.

430 citations


Journal ArticleDOI
TL;DR: In this paper, Likins et al. extended their work on finite element appendage equations for hybrid coordinate dynamic analysis and on the dynamic analysis of a system of hinge-connected rigid bodies with nonrigid appendages to the simulation of non-rigid spacecraft.

24 citations


Book ChapterDOI
01 Jan 1974
TL;DR: In this paper, it is shown that the normal and shear stiffness of machine surfaces can be calculated from the parameters that define the normal stiffness of the machine surfaces, which can then be used to calculate the shear stiffness.
Abstract: This paper presents in the first place some remarks on the normal and shear stiffness of machine surfaces. It is shown that the shear stiffness can be calculated from the parameters that define the normal stiffness of the machine surfaces.

23 citations



Journal ArticleDOI
TL;DR: An error analysis of the solution of linear systems of the form A t Ax = b is presented, and it is shown that the relative solution error using QR methods is usually considerably smaller than that using the Cholesky procedure.

17 citations


Journal ArticleDOI
TL;DR: In this article, a combination of isoperimetric elements and bar elements are used for the representation of reinforced concrete plane elements and the analysis includes the effects of the propagation of cracking as well as the yielding of both steel and concrete.
Abstract: Two finite element procedures which utilize the constant and the variable stiffness methods are presented. A combination of isoperimetric elements and bar elements is used for the representation of reinforced concrete plane elements. The analysis includes the effects of the propagation of cracking as well as the yielding of both steel and concrete. The analytical results of both methods are compared to the experimental results of others. The constant stiffness method is found to be inaccurate for the problems involving the prediction of cracking. Direct use of corner nodes is made in the computation of stiffness of the cracked element and the unbalanced nodal forces due to cracking or yielding.

14 citations


Journal ArticleDOI
TL;DR: In this paper, a general computer algorithm for handling topology, merging and solution of the sparse system equation with mixed force and displacement variables is presented, which can be used for decomposition of the system equation or for releasing inner nodes in superelements.
Abstract: Use of mixed force and displacement variables may be the key to a reliable solution of many physical problems. For the analysis of elastic structures with large rigid motion the displacement method may fail due to illconditioning, but use of mixed variables (diacoptics) may work due to the possibility of using relative displacements within substructures. Analysis with mixed variables complicates the topology (the number of nodes and the number of variables at the nodes may vary in the same problem) so a careful study of the system analysis is required. Some general computer routines are given for handling topology, merging and solution of the sparse system equation. The solution routine handles constraints in a rational way and can also be used for decomposition of the system equation or for releasing inner nodes in superelements.

11 citations


Book
01 Jan 1974
TL;DR: Matrix structural analysis as discussed by the authors, Matrix structural analysis, matrix structural analysis and matrix structural models, Matrix Structural Analysis, Matrix Structure Analysis, MSA, Matrix SSA, matrix SSA.
Abstract: Matrix structural analysis , Matrix structural analysis , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

10 citations


Proceedings ArticleDOI
Curtis F. Vail1
01 Feb 1974
TL;DR: In this paper, the authors outline the procedure for using the modes of the original system to determine the dynamic characteristics of the changed system and demonstrate the results from an analysis using the reconstructed mass and stiffness matrices and the modal synthesis.
Abstract: The purpose of this paper is to outline the procedure for using the modes of the original system to determine the dynamic characteristics of the changed system. The method also results in computational savings for boundary condition changes and for large systems that are nearly-symmetric except for a few mass and stiffness changes. To illustrate the method several changes are made to a ladder frame. The results from an analysis using the reconstructed mass and stiffness matrices and the modal synthesis are compared to show the accuracy and freedom requirements.

9 citations


Journal ArticleDOI
TL;DR: DYPLAS is a computer program designed to compute the response history of general three-dimensional structures subjected to transient thermal and mechanical loadings, and considers nonlinearities arising from material behavior as well as from large deformations that may occur in the structure.

6 citations


Journal ArticleDOI
TL;DR: In this paper, the authors presented a method of deflection analysis which treats the castellated beam as an assemblage of typical segments and utilizes the finite element method to form the stiffness matrix for the typical segment.

Journal ArticleDOI
Isaac Fried1
TL;DR: A simple transformation of displacements considerably eases the explicit derivation of the finite element stiffness matrix for the axisymmetric elastic solid without causing a decline in the rate of convergence.

Journal ArticleDOI
TL;DR: In this article, a method for the computer-aided design of a six degree-of-freedom vibration isolator system is presented, which is predicated on the description of the desired mode shapes of the final system and a range of allowed frequencies for those modes.
Abstract: A method for the computer-aided design of a six degree-of-freedom vibration isolator system is presented. The method is predicated on the description of the desired mode shapes of the final system and a range of allowed frequencies for those modes. Use is made of the Kronecker or direct matrix product to restructure the system mass and stiffness matrices so that the elemental mass and stiffness properties are available as variables. A linear program is formed from these representations and the values of the elemental properties that are necessary to provide the desired mode shapes are determined. It is shown that the method is accurate and that the effects of viscous damping can be easily included. An example is given of a mounting system design. A = geometric stiffness B = geometric damping C = damping D = double index to matrix operator di = variables used in sweeping technique

01 Apr 1974
TL;DR: In this paper, a nonconforming plate-bending finite element of triangular shape and associated quadrilateral elements is developed, where the transverse displacement is approximated within the element by a quintic polynomial.
Abstract: A nonconforming plate-bending finite element of triangular shape and associated quadrilateral elements are developed. The transverse displacement is approximated within the element by a quintic polynomial. The formulation takes into account the effects of transverse shear deformation. Results of the static and dynamic analysis of a square plate, with edges simply supported or clamped, are compared with exact solutions. Good accuracy is obtained in all calculations.

Journal ArticleDOI
01 Jan 1974
TL;DR: In this article, a direct stiffness method of analyzing the elastic ftexural-torsional buckling of rigid-jointed plane frames composed of l-section members and subjected to in-plane loads is presented.
Abstract: A direct stiffness method of analyzing the elastic ftexural-torsional buckling of rigid-jointed plane frames composed of l-section members and subjected to in-plane loads is presented. The in-plane stiffness matrix and the fixed-end resultants are obtained from the member stiffness matrices derived from the in-plane differential equations. These member stiffness matrices are assembled and solved, and their solutions are used to linearize the flexural-torsional buckling equations. The out-of-plane member stiffness matrices are then obtained numerically from the buckling equations by the method of finite integrals. The out-of-plane frame -stiffness matrix is assembled, and the critical loads are obtained when its determinant is zero. A computer program is developed which carries out either a first- or second-order in-plane analysis, and then determines the flexural-torsional buckling loads. The effects of in-plane deformations prior to buckling can be included. Very good agreement is obtained betwe...

Journal ArticleDOI
TL;DR: In this paper, a substructure model is proposed to calculate the stress intensity factors of cracked plates, which has great freedom in choosing crack-tip-element characteristics and reduces the dimension of the stiffness matrix.
Abstract: Many authors, Yamamoto et al., Byskov, Rao et al., Walsh, Tong et al., etc. have discussed the availability of finite element methods to the calculation of stress intensity factors of cracked plates. Some of them successfully tried the use of special finite elements at the crack-tip-region in order to obtain a higher accuracy. But these are not always very easy to apply to the practical problems because of the complexity of calculation models. The present paper surveys some general relations among variables in finite elements, and proposes a substructure model, as a general extention of Walsh's method, which has great freedom in choosing crack-tip-element characteristics and reduces the dimension of the stiffness matrix. Some simple numerical examples are given to verify the utility of this model and to examine the influence factors to the accuracy of solutions.

Journal ArticleDOI
TL;DR: In this article, the stiffness center of a skeletal elastic system is defined as a configuration of elastic springs, and it is shown that about such a center the stiffness of the system is balanced.
Abstract: A approximate analysis of rigid frames using a new concept, called the stiffness center, is presented. It has been shown that when a skeletal elastic system is idealized as a configuration of elastic springs, about such a center the stiffness of the system is balanced. The concept of elastic center in closed-ring types of structures, the instantaneous center of rotation in a group of fasteners, the center of gravity in the cantilever method, the neutral axis in solid as well as in composite cross sections are all special interpretations of the stiffness center. The method is compared with the existing approximate methods.

01 Sep 1974
TL;DR: In this article, transfer matrices are derived from finite elements to provide an efficient approach for structural analysis of complicated structures with a principal direction, which is particularly appropriate for ship structures.
Abstract: : It is shown that transfer matrices can be derived from finite elements to provide an efficient approach for structural analysis of complicated structures with a principal direction. This new substructing technique is particularly appropriate for ship structures. The method is demonstrating using transfer matrices formed with the aid of the finite element program ELAS. (Author)

Journal ArticleDOI
TL;DR: In this article, a method of determining the torsional stiffness of a wide range of structural sections, both homogeneous and composite, is presented, where the stiffness is determined to acceptable accuracy by the solution of very few equations.
Abstract: A method of determining the torsional stiffness of a wide range of structural sections, both homogeneous and composite, is presented. Prandtl's stress function along the boundaries of component sections is approximated by finite Fourier series with coefficients chosen to minimize a functional. An example indicates that the stiffness may be determined to acceptable accuracy by the solution of very few equations.