Conditioning of Structural Stiffness Matrices

Author(s):  
A. Kaveh ◽  
I. Ghaderi
2003 ◽  
Vol 03 (02) ◽  
pp. 299-305 ◽  
Author(s):  
F. W. Williams ◽  
D. Kennedy

Transcendental dynamic member stiffness matrices for vibration problems arise from solving the governing differential equations to avoid the conventional finite element method (FEM) discretization errors. Assembling them into the overall dynamic structural stiffness matrix gives a transcendental eigenproblem, whose eigenvalues (natural frequencies or their squares) are found with certainty using the Wittrick–Williams algorithm. This paper gives equations for the recently discovered transcendental member stiffness determinant, which equals the appropriately normalized FEM dynamic stiffness matrix determinant of a clamped ended member modelled by infinitely many elements. Multiplying the overall transcendental stiffness matrix determinant by the member stiffness determinants removes its poles to improve curve following eigensolution methods. The present paper gives the first ever derivation of the Bernoulli–Euler member stiffness determinant, which was previously found by trial-and-error and then verified. The derivation uses the total equivalence of the transcendental formulation and an infinite order FEM formulation, which incidentally gives insights into conventional FEM results.


1976 ◽  
Vol 4 (2) ◽  
pp. 197-226 ◽  
Author(s):  
Ichiro Konishi ◽  
Naruhito Shiraishi ◽  
Takeo Taniguchi

1997 ◽  
Vol 63 (4) ◽  
pp. 719-725 ◽  
Author(s):  
A. Kaveh ◽  
I. Ghaderi

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Zdeněk Dostál ◽  
Tomáš Brzobohatý ◽  
Oldřich Vlach

Abstract Bounds on the spectrum of Schur complements of subdomain stiffness matrices with respect to the interior variables are key ingredients of the convergence analysis of FETI (finite element tearing and interconnecting) based domain decomposition methods. Here we give bounds on the regular condition number of Schur complements of “floating” clusters arising from the discretization of 3D Laplacian on a cube decomposed into cube subdomains. The results show that the condition number of the cluster defined on a fixed domain decomposed into m × m × m cube subdomains connected by face and optionally edge averages increases proportionally to m. The estimates support scalability of unpreconditioned H-FETI-DP (hybrid FETI dual-primal) method. Though the research is most important for the solution of variational inequalities, the results of numerical experiments indicate that unpreconditioned H-FETI-DP with large clusters can be useful also for the solution of huge linear problems.


2001 ◽  
Vol 20 (2) ◽  
pp. 277-298 ◽  
Author(s):  
T. Panzeca ◽  
H. Fujita Yashima ◽  
M. Salerno

1986 ◽  
Vol 108 (4) ◽  
pp. 394-400
Author(s):  
Z. N. Ibrahim

The inertia concept of modal mass was developed to provide a consistent methodology for establishing an analytically equivalent dynamic model of any discrete section within a complex piping network. The multidegree of freedom system is reduced to several multiple excitation single degree of freedom (SDOF) systems representing its modal masses and modal stiffnesses. The multiple excitation residual mass and residual stiffness matrices were also formulated. The combination of modal mass-modal stiffness SDOF systems and residual mass-residual stiffness matrices can simulate the complete dynamic characteristic of any desired portion of the piping network. This technique was extended to cover substructuring applications, and was proved mathematically to be equivalent to the conventional modal synthesis formulation.


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