On the Construction of the Stiffness Matrix of a Naturally Twisted Rod

A simplified geometric stiffness in stability analysis of thin-walled structures by the finite element method

A simplified geometric stiffness in stability analysis of thin-walled structures by the finite element method

In the mechanical analysis of steel structures, whether it is static analysis or dynamic analysis, it is necessary to establish the structural stiffness matrix first. In the process of building the structural stiffness matrix, the same element usually has different node code connection orders, and it has never been argued whether the different connection orders of the same element will have an effect on the building of the stiffness matrix. In this study, the influence of the difference in the node connection order on the construction of the element stiffness matrix is studied. First, the structural element stiffness matrix in the global coordinate system is established when the node connection order is different. It is found that the element stiffness matrix in the global coordinate system is indeed inconsistent for the same element with different connection orders. In this study, the elements of the established element stiffness matrix are extracted into the global stiffness matrix of the structural system based on the law of energy conservation; it is found that the global stiffness matrix finally established by using two different connection relationships is the same. The research results of the example show that in the stress analysis of steel structures, selecting different node connection sequences to establish the structural stiffness matrix will obtain the element stiffness matrix under different global coordinate systems. However, through the aggregation process of the global stiffness matrix of the structural system, the global stiffness matrix obtained is consistent, so the different connection sequences of nodes will not affect the stress analysis of steel structures. The example further analyzes the static stress and dynamic responses of the steel structure. The conclusions of this study provide a reliable theoretical basis for the situation that the order of node connections need not be consistent in the finite element modeling of steel structures and are of reference value for the finite element modeling of steel structures.

Meshfree methods are effective tools for solving partial differential equations. The radial point interpolation method, a partial differential equation solver based on a meshfree approach, enables accurate imposition of displacement boundary conditions and has been successfully applied to elastostatic analysis of various kinds of three-dimensional solids. In this method, stiffness matrix construction accounts for the majority of CPU time required for the entire process, resulting in high computational costs, especially when higher-order numerical integration is applied for accurate matrix construction. An alternative method, modified radial point interpolation, was proposed to overcome this shortcoming and has accomplished fast computation of elastostatic solid analysis. The purpose of this study is to develop an algorithm for time-dependent simulation of three-dimensional elastic solids. We show that the modified radial point interpolation method also accelerates the construction of the mass matrix required for time-dependent analysis in addition to that of the stiffness matrix. In our approach, the problem domain is assumed to have an implicit function representation that can be constructed from a set of surface points measured using a three-dimensional scanning system. Several numerical tests for elastodynamic analysis of complex shape models are presented.

Local/global stiffness matrix formulation for composite materials and structures

A new hierarchical partition of unity formulation of EFG meshless methods

The paper deals with a method of high speed construction of stiffness matrix in FEM. The stiffness matrices of each element becomes to equal in following conditions. 1) Components of the B and D matrices are independent of global coordinate. 2) Elements have the same material properties and the same local coordinates respectively. This equality gives possibility of associable calculation to us. Hence, we can generate the global stiffness matrix at high speed by use of this feature. In this paper, a method of associable calculation by using equality of object ELEMENT based on object oriented concept is proposed. Futhermore, in comparison between conventional method and proposed one, relationship between accelerative rate and ratio of equal object and result of numerical experiment are described.

An approach to numerical modeling of the stress-strain state of composite structures with discrete inclusions is presented in the paper. The finite element method is used as the main method, namely its modification – the moment finite-element scheme. The moment scheme, in contrast to the classic scheme of finite elements, allows to avoid such negative properties as not taking in consideration the rigid rotation of the finite element and “false” shear. If both the material of the matrix and the material of the reinforcing inclusions are weakly compressible, then problems arise due to the fact that some elastic constants approach very large values. The Taylor series expansion of the components of the displacement vector, the components of the strain tensor, and the volume change function is used in order to eliminate the mentioned shortcomings, after that, according to the moment scheme, certain sums are removed from these expansions. Homogenization of the material with lamellar inclusions, a small proportion of spherical inclusions, and a large proportion of spherical inclusions is used for modeling the elastic properties of the composite. The chaotic nature of the location of inclusions after homogenization makes it possible to present a non-homogeneous composite material as a homogeneous quasi-isotropic one. The described approaches are used in the construction of the stiffness matrix of the spatial hexagonal finite element. The obtained expressions for the stiffness matrix are done in the software package for calculating structures from composite materials. The calculation of a thick-walled pipe under the action of internal pressure from a composite material with lamellar inclusions, a small proportion of spherical inclusions, and a large proportion of spherical inclusions was carried out using the software package. For different volume fractions of discrete inclusions, the numerical convergence of the results with different finite element meshes has been investigated, which shows great congruence with analytical solutions.

The objective of the present paper is to review and implement the most recent developments in the Spectral Element Method (SEM), as well as improve aspects of its implementation in the study of wave propagation by numerical simulation in elastic unbounded domains. The classical formulation of the method is reviewed, and the construction of the mass matrix, stiffness matrix and the external force vector is expressed in terms of matrix operations that are familiar to earthquake engineers. To account for the radiation condition at the external boundaries of the domain, a new absorbing boundary condition, based on the Perfectly Matched Layer (PML) is proposed and implemented. The new formulation, referred to as the Multi-Axial Perfectly Matched Layer (M-PML), results from generalizing the classical Perfectly Matched Layer to a medium in which damping profiles are specified in more than one direction.

A new approach is presented for efficient capacitance extraction. This technique utilizes wavelet bases and is kernel independent. The main benefits of the proposed technique are as follows: (1) it takes a full advantage of the multiresolution analysis and gives accurate total charge on a conductor without obtaining an accurate solution for the charge density per se; (2) the method employs an extremely aggressive thresholding algorithm and compresses the stiffness matrix to an almost diagonal sparse matrix; and (3) construction of the stiffness matrix is performed iteratively, which facilitates easy and simple control of convergence and provides means of trading accuracy for speed. The proposed method has computational cost of O(N), versus O(N/sup 3/) for conventional methods. The proposed algorithm has a major impact on the speed and accuracy of physical interconnect parameter extraction with speedup reaching 10/sup 3/ for even moderately sized problems.

Beam model refinement and reduction

Plate‐bending elements with the inclusion of transverse shear effects are important in analysing problems of transverse bending of relatively thick plates. Several such elements are available. Recently another element with a triangular geometry has been suggested. The construction of the element stiffness matrix follows conventional procedure which involves rigorous matrix computations. An alternative method of obtaining the stiffness matrix explicitly for such an element is suggested in the present work. Thus the process of matrix inversion and a considerable degree of matrix multiplications can be avoided in constructing the element stiffness matrix. Explicit expressions worked out may be conveniently used in microcomputers.

The derivation of element stiffness will be discussed in this chapter. When element stiffness matrix is given, the solution will be obtained through the following process: 1. The construction of global stiffness matrix through the assembling of given element stiffness matrixes 2. The provision of the boundary condition 3. The solution of the simultaneous equation

A nonlocal operator method for solving partial differential equations

Parametric finite-volume method for Saint Venant’s torsion of arbitrarily shaped cross sections