Academic literature on the topic 'Finite element analyses'

Cellular cofferdams have primarily been used as temporary systems which serve to allow construction of facilities in open bodies of water. Applications for these structures have been increasing and today they may serve as permanent retaining walls or as navigation or waterfront structures. Conventional design methods for cellular cofferdams are based on semi-empirical approaches largely developed in the 1940s and 1950s. None of the available traditional procedures are capable of predicting cofferdam deformations, a parameter of key importance to the cofferdam performance, and which is often observed during construction for purposes of safety monitoring. Also, there is evidence that much of the conventional design technology is conservative, in some cases predicting loading by more than twice that which actually occurs. Recently, the finite element method has shown promise as a tool which can be used to help resolve some of the outstanding problems with cofferdam design. There are three primary objectives of this work: (1) enhance existing finite element program to allow for more accurate and refined analysis of cellular cofferdams, (2) use the enhanced finite element programs to assess the degree of conservatism in conventional design methods for cofferdams founded on sandy soils, and (3) use the results of parametric studies of cofferdams founded on sandy soils to develop a simplified procedure to predict cofferdam movements and determine potential for internal failure. The first of the objectives involves adding better bending elements to the program SOILSTRUCT to represent the sheet pile system In axisymmetric and plane strain analyses. Also, in the case of the plane strain program, a new method is developed to allow shear transfer through the sheet pile system. Through case history and theoretical analyses, the enhanced programs are demonstrated to yield accurate and realistic results. Parametric studies using the axisymmetric program show that conventional design methods overpredict, in some areas strongly, the interlock forces which develop during filling of the cofferdam. Parametric studies using the plane strain program suggest that there is also considerable conservatism in design methods to predict internal stability of the cofferdam. A new, simplified method is proposed for this type of analysis. In addition, it is shown that the deformations of cofferdams on sand follow consistent trends and can be set into a nondimensionalized context which can be used to predict future cofferdam movements.<br>Ph. D.<br>incomplete_metadata

In contrast to concrete, masonry is a complex inhomogenous material, which exhibits distinct directional properties due to the presence of mortar joints. In the past, both finite element and discrete element techniques have been used for modelling of masonry structures. However, no comparison of these two different approaches has been made. In this study, to achieve a fundamental insight into the behaviour of masonry structures, a series of numerical analyses have been carried out using Finite and Discrete Element methods for structures such as shear walls with/out opening, masonry panel under point load, and masonry arches. In Discrete Element analyses, bricks were modelled as conventional continuum elements, while an interface contact law (instead of mortar joints) was used to capture masonry failure mechanisms in the <i>2D</i> plane-strain analyses. The contact law included softening in tension, shear and compression modes. In Finite Element modelling of the same structures, separate continuum elements were used for both constituents, i.e. the brick and mortar. The results were compared with experimental data. Both methods were able to reproduce the complete deformation pattern of the structures up to and beyond the peak until total degradation of strength, without major numerical difficulties. Parametric studies of the above problems have also been carried out to demonstrate the crucial role of some of the parameters. Comparative studies using the Finite Element and Discrete Element methods have shown that collapse load as well as mechanisms of failure are significantly influenced by the choice of interface parameters used in the Discrete Element method. These parameters are also difficult to determine from experiments. On the other hand, Finite Element analyses indicate lesser influence of parameters of the constituents and no anomalies arise in their choice from experimental data.

The prediction of P-Y curves for undrained clay and sand based on the results of finite element analyses is presented in this thesis. A higher-ordered finite element program was used in the analyses. The ability of the program to accurately model the undrained soil condition was verified by comparing predicted load-deflection responses with closed form solutions for the cylindrical cavity expansion problem. Pressuremeter curves were predicted from plane strain axisymmetric finite element analyses. The effect of pressuremeter size on the predicted results was examined. P-Y curves were predicted for plane strain and plane stress conditions. Values for the initial slope and Pun- of the curves were obtained. The curves were normalized for comparison, and simplified methods presented for determining P-Y curves. Finite element predictions for the pressuremeter and laterally loaded pile problems were also compared. Factors were determined from these comparisons to generate P-Y curves from pressuremeter curves.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate

Within the Finite-Element Plasticity Research Group at the University of Birmingham the interest in finite elements is principally confined to their use in the modelling of elastic-plastic problems (specifically metal-forming processes). The methods employed allow a process to be studied as it develops through time. A number of problems in the modelling of such processes give rise to errors, most notably due to singularities and other complex geometrical anomalies which are the result of complicated die surfaces and other boundaries. These boundary conditions can give rise to severe mesh distortions. The results of this thesis will show that improvements may be made to the modelling of such processes, by using a computer tool to allow remeshing to be carried out where such inaccuracies occur. A number of investigations have been made into such tools in other areas of study and it is hoped, eventually, that those techniques, together with ones developed here may be applied to metal forming in 3-dimensions. The aims of this thesis are to formulate the initial steps towards such an analysis. The work demonstrates how the basics of such techniques might be implemented, concentrating specifically on the transfer of data from an old mesh to a new mesh and simple error measures. Once this data transfer has been implemented it is hoped that future work will produce a fully self-adaptive process, ensuring that remeshing occurs based on algorithms continuously monitoring the potential for errors throughout the process The initial work in this thesis was confined to plane-strain applications. Its methods and implementation are discussed and some results shown. This gave some understanding of the difficulties which would be involved when transferring the techniques developed to a fully 3-dimensional solution. In the 3-dimensional application area are more quantitative work was also undertaken to assess the errors arising from element degeneracy and the ability of the mesh to model steep strain gradients. It should be noted by that full 3-dimensional remeshing, when applied to general metal forming problems, will involve far more sophisticated mesh generation software than is currently, or in the short term future, available.