### Browsing by Author "Doyle, WS"

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- ItemOpen AccessThe elastic rigidities of ribbed plates(1972) Little, Robert Dryden; Doyle, WSThis thesis deals with the flexural and twisting rigidities of orthotropic plates. Asymmetrically stiffened plates are examples of technically orthotropic plates and are found in civil engineering structures such as bridges and ribbed floor slabs. The formulae for the rigidities as found in the literature are reviewed. The writer has devised an experimental method of determining the rigidities. This involves a bending test using the Moire technique and a twisting test. In the writer's method only one model is needed to determine all the rigidities. This is compared to other methods for which two or three models are needed. Sixteen different models of asymmetrically stiffened plates with ribs running in one direction only were made. The flexural rigidities of eight of these models and the twisting rigidities of all sixteen models were determined. The objective of the tests was to compare the test values with the theoretical values. More specifically the objective can be defined as follows. a) To determine how well an asymmetrically stiffened plate behaves as an orthotropic plate, i.e. how far apart may the ribs be spaced before the plate becomes a system of plate elements and beam elements. b) To determine the influence, if any, on the rigidities Dx, D₁ and Dy of altering the spacing of the ribs of stiffened plates which have the same theoretical values of Dx. c) To determine whether there is any difference between the rigidities D₁₂ and D₂₁, which are the same for a true orthotropic plate and are usually assumed to be the same for an asymmetrically stiffened plate. Conclusions are drawn on these points.
- ItemOpen AccessExplicit stiffness matrices for triangular, plate bending finite elements(1973) Harrison, Robert Leeds; Doyle, WSExplicit stiffness matrices are available for rectangular plate bending elements, rectangular plane stress and plane strain elements and triangular plane stress and plane strain elements. Triangular plate bending elements can at present only be formed by using a numeric algorithm. The explicit version of a stiffness matrix is not only far more simple to program in a computer routine but its execution (as will be shown) requires approximately one twelfth of the time of a numeric version. Rectangular plate bending elements do not have a compliant shape (see definition) so their use is limited to plates which in many cases can be solved by other methods. Judging from the number of attempts to find a successful triangular plate bending element, the simplicity of a triangular shape appeals to most investigators. In the present investigation only triangular elements with a node on each corner and three degrees of freedom at each node will be considered. Some investigators have included extra nodes on the edges and/or at the centroid of the triangle. This is done in order to overcome difficulties experienced in choosing a suitable displacement function for a nine degree of freedom triangle. Except for comparison of results (table 4) such elements will not be considered. An explicit stiffness matrix for a small deflection theory, elastic, isotropic, triangular plate bending element will be developed.
- ItemOpen AccessA finite difference based finite strip method for the analysis of translational shell structures(1976) Barker, Roger; Doyle, WSA numerical, method for the analysis of translational shell structures is presented. The finite strip concept is utilised together with finite difference approximations to the differential, equations along nodal, tines. Numerical examples include open and closed translational shells with various end conditions and continuity over intermediate supports.
- ItemOpen AccessThe finite element analysis of reinforced concrete coupled shear walls(1987) Richardson, B W; Doyle, WSThis thesis is entitled 'The Finite Element Analysis of Reinforced Concrete Coupled Shear Walls', and contains an investigation_ into the use of the finite element analysis technique in predicting the behaviour of these structures. The increasing accessibility of fast, powerful computers to the practising engineer, has given him the capability of performing complex analyses of structures in which the behaviour of the material can be approximated to its actual behaviour.
- ItemOpen AccessFurther numerical techniques for planar elastostatic analysis by the boundary integral equation method(1984) Howell, Graham Conrad; Doyle, WSPrior experience of the Finite Element Method stimulated interest and led to research into the Boundary Integral Equation Method, specifically for the solution of planar elastostatic problems. A complete expose of the mathematical theory of the Boundary Integral Equation Method is given. The basis of the method is traced and the similarities and differences as opposed to the Finite Element Method, are highlighted. The numerical implementation of the method, using constant, linear and quadratic interpolation functions over the boundary segments is developed and then inclusion in computer programs is discussed. Attention is given to the problem of numerical integration over a singularity, for which detailed expressions are given. The verification and applicability of the technique is thoroughly investigated in five fully documented examples. Solutions to the problem of traction discontinuities at a corner are proposed and an analysis of the inclusion of body forces, together with documented examples, are described. Also investigated is the nonsymmetric form of the resulting matrices. It is proven that no direct and practical way can be found to render these matrices symmetric. By investigating the error in the numerical integration process, the suitability of segments is also discussed. Emphasis is placed on the solution of non-homogeneous domains and domains which extend to infinity. The development of the necessary numerical techniques required in both cases is discussed and fully documented. Finally, a method of automatically improving the accuracy of the solution of the Boundary Integral Equation Method by using p and h convergence adaptive processes is also presented.
- ItemOpen AccessAn investigation into the prediction of thermal and stress distributions set up during welding using finite-element analysis(1984) Kesler, David Jonathan; Doyle, WSDuring the welding process, thermal and stress distributions are set up in the workpiece. These thermal stresses are recognized as among the most important factors affecting the weldability of steels, producing distortion and cracking in weldments. This thesis examines the history and theory of the welding process, including the mathematical and finite-element theory of heat conduction. Using simple models, the finite-element method is also compared with theoretical Fourier analysis solutions. In addition, a complex: two-dimensional finite-element thermal and stress analysis of the welding process is performed, in which a thermo-elasticplastic finite-element model is used to predict the longitudinal welding stresses perpendicular to the weld. In this model, the weld is represented simply as a high temperature load acting at a predetermined position for a particular time interval. The metallurgical phase transformations and work hardening effects are ignored. The predictions from the finite-element analysis are then compared with experimental data obtained from a welding test.
- ItemOpen AccessPreslab - micro-computer analysis and design of prestressed concrete slabs(1988) Du Toit, André Johan; Doyle, WSA micro-computer based package for the analysis and design of prestressed flat slabs is presented. The constant strain triangle and the discreet Kirchhoff plate bending triangle are combined to provide an efficient "shell" element. These triangles are used for the finite element analysis of prestressed flat slabs. An efficient out-of-core solver for sets of linear simultaneous equations is presented. This solver was developed especially for micro-computers. Subroutines for the design of prestressed flat slabs include the principal stresses in the top and bottom fibres of the plate, Wood/Armer moments and untensioned steel areas calculated according to Clark's recommendations. Extensive pre- and post-processing facilities are presented. Several plotting routines were developed to aid the user in his understanding of the behaviour of the structure under load and prestressing.
- ItemOpen AccessStatic and dynamic analysis of linear elastic systems on non-prismatic three dimensional beam elements(1980) Resende, Luís Nuno da Costa; Doyle, WSA computer programme NONPRI, has been developed for the analysis of three dimensional skeletal assemblages consisting of non-prismatic members. It is capable of static and dynamic analysis of structures consisting of members whose constitutive relationship is linear elastic. The finite element formulation is based on the family of quadratic isoparametric finite elements. The three noded space frame element is quite versatile in that it can account for shear as well as flexural 9 axial and torsional deformation effects making it suitable for thin and thick beam analysis and for cases where the axial and torsional deformations are relevant. The element can be degenerated to a truss/frame transition element (3 translational degrees of freedom at each node - rotations ignored) and further degenerated to become a truss element. Furthermore, the element internal node is defined to lie at an arbitrary position inside the element. Thus, this flexibility in the non-prismatic element formulation makes it very powerful in practical analysis problems. An out-of-core solution technique is used for the equations of static analysis bearing in mind the capability for solving large structural systems. An in-core solution technique is used for the equations of dynamic analysis bearing now in mind that these equations represent an iterative process which can otherwise become computationally very expensive.