摘要:

AbstractThis paper describes a method for introducing line searches into the arc‐length solution procedure. Such line searches may be used at each iteration to calculate an optimum scalar step‐length which scales the normal iterative vector. In practice, a loose tolerance is provided so that on many iterations the line searches are avoided. However on ‘difficult iterations’, the line searches are shown to lead to a substantial improvement in the convergence characteristics. A simple single‐parameter acceleration is also developed using line search concepts. The new arc‐length method is applied to both the geometrically nonlinear analysis of shallow shells and the materially nonlinear analysis of reinforced concrete beams and slabs. Significant improvements are demonstrated in relation to the standard arc‐

ISSN:0029-5981    

DOI:10.1002/nme.1620190902

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA family of high‐order, conforming triangles for the finite element analysis of plate bending problems is developed, using the displacement method of formulation.The development proceeds in two steps. A family of non‐conforming triangles, based on polynomial expansions of order>4 is first generated, and its performance found to be unacceptable. Nodal variables for the non‐conforming family are selected from the setw,wx,wy,wn. The elements are then made to conform, by adding a twist nodal variablewntat the mid‐side nodes. Rational functions define the three additional degrees‐of‐freedom. Simple and very accurate procedures solve the problems associated with the use of such functions.Numerical results are presented for the conforming triangles of order 4 and 7, following a brief description of the two elements. A listing of the explicit shape functions for the quartic triangle is included.The numerical results are very good. In particular, they are superior per degree‐of‐freedom to the results predicted by the various non‐conforming and conforming, cubic and related elements at present used in computer packages. Together with a similar performance by the quintic member10of the family, they validate the proposed the

ISSN:0029-5981    

DOI:10.1002/nme.1620190903

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe authors' aim was the development of a suitable procedure for the structural design of railway vehicles within an existing general purpose finite element package. A previous application to railway vehicles was based on the use of a sequence of linear programming steps incorporating move limits on the design variables. This approach was slow and in other fields mathematical programming techniques tended to give way to methods based on optimality criteria.Nevertheless because of its simplicity of concept, and because some apparently successful alternatives to the move limit idea were available, the use of linear programming was returned to and the method is now incorporated in the British Rail finite element program NEWPAC. Couched in terms of inverse variables and using linearized forms of the stress constraints, the linear programming approach converges with the optimality criteria method. Details of the implementation and of some standard examples are given.

ISSN:0029-5981    

DOI:10.1002/nme.1620190904

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe development and implementation of a comprehensive interactive computer package for the generation of finite element meshes for two‐dimensional problems is described. The package, AGTHOM, minimizes the user defined input and attempts to maximize the flexibility for the user with regard to modifying the mesh. An important feature of AGTHOM is its independence of expensive graphics hardware by using approximate terminal plots. Versions are available in both extended BASIC and FORTRA

ISSN:0029-5981    

DOI:10.1002/nme.1620190905

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThis paper presents boundary integral equation procedures for calculating the added mass matrix required to determine hydroelastic vibrational modes of tanks or immersed structures. The liquid is assumed inviscid and incompressible and no surface waves are admitted. Two symmetric variational formulations of the boundary integral equation are derived, including the free surface condition and possible conditions of symmetry. These are approximated by a curved finite element method and numerical results are presented for an axisymmetric tank, immersed cantilever plates and a three‐dimensional fuel storage containe

ISSN:0029-5981    

DOI:10.1002/nme.1620190906

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractA recursive, shape controlling triangulation method is described. The method is designed to produce a labelling which implies reduced fill in the solution of (finite element) equations assembled from such a triangulation and allows simple implementation of a nested disection algorithm for irregular domains. This approach saves a substantial amount of time usually spent on discovering a suitable relabelling of the triangulation. In addition, the matrix of the resulting system is then endowed with a recursive doubly bordered block diagonal form. This allows us to develop a recursive parallel bisection method for the solution of the system of equations.

ISSN:0029-5981    

DOI:10.1002/nme.1620190907

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThis convergence criterion is proved for any ‘legalizable’ finite element formulation, i.e. any model for which a conforming displacement version is possible, using the same nodal variables. Engineers may therefore take control of (and responsibility for) convergence, for most of the elements in service today. Stummel's counter‐example is explained as a technical misunderstanding, due to inadequate documentation of the patch test. It is suggested, without proof, that the test (properly applied) is universal, provided that it is always combined with an adequate test of stab

ISSN:0029-5981    

DOI:10.1002/nme.1620190908

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractIn this paper we present a stream function‐vorticity finite element formulation for Navier‐Stokes equations which does not require an iterative procedure for satisfying the boundary conditions, and show that this formulation is of great advantage in solving the flow problems in a multi‐connected d

ISSN:0029-5981    

DOI:10.1002/nme.1620190909

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620190910

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe design of nuclear facilities requires dynamic analysis to evaluate their performance during an earthquake. In modal analysis, a method recommended for dynamic analysis by the Nuclear Regulatory Commission, the natural frequencies and mode shapes of the structure are commonly calculated using a stiffness matrix computed using the finite element method.A primary goal of this study was to design a finite element mesh, capable of modelling a reactor structure, with a minimum number of nodes and elements. This is necessary since analysis using a mesh fine enough to include all of the structural elements is not feasible because of exorbitant computer time and storage requirements. It was found that for lateral motion, a representative reactor structure could be accurately modelled using a simplified mesh with only one isoparametric quadratic quadrilateral element per floor. In this mesh essentially infinite springs must be placed between the masses at each floor level to prevent internal movements of the lumped masses within the quadratic quadrilateral elements.It was also found that a structure with rigid heavy bottom floors and a light top floor can be subjected to large displacements in the top floor during earthquakes. It was concluded that the properties of that light top floor (especially shear area) controls the value of the fundamental frequency of the building.

ISSN:0029-5981    

DOI:10.1002/nme.1620190911

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY