published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

This thesis presents a theoretical study into the behaviour of thin-walled metal tubes that are filled with elastic material. The study has considered the behaviour and design of concrete-filled steel columns by analysing the effect of the combined actions of axial compression and bending on closed stainless steel cross-sections with a concrete infill as well as the elastic buckling of square, circular and elliptical thin-walled steel tubes, when filled with elastic material. The elastic local buckling of a rectangular plate having four edges clamped and subjected to in-plane linearly varying uniaxial loading with and without juxtaposition with a rigid infill has also been studied. Concrete-filled composite columns find widespread use globally in engineering structures because of their optimal strength and ease of construction. Enhancing the strength of filled columns by utilising newer materials such as stainless steel or shape memory alloys for the skin of the cross-section of the column will increase the construction cost of the column. In order to circumvent this increased construction cost, or to minimise it, the metal skin should be as thin as possible. Members with thin-walled cross-section are prone to lateral torsional buckling, and in particular they are prone to local buckling, with the latter buckling mode playing an important role in the strength of a composite column with a concrete infill. The local buckling coefficient is enhanced by the provision of a rigid concrete infill, and efficient design must make use of this fact to minimise the cost of the skin. The initial portions of this thesis demonstrate the beneficial effects that the rigid concrete core has on the overall strength, and also on the local buckling behaviour of thin-walled metal tubes. The local buckling of the metal skin has been modelled in this thesis by using a Ritz-based energy method. In bi-lateral and uni-lateral buckling studies of rectangular plates, a more general trigonometric function has been selected by application of boundary conditions to the chosen shape function, with these boundary conditions being implemented to make the chosen shape function satisfy the edge conditions for the problem under consideration. The restraining medium is modelled as a tensionless foundation and this restraint condition is introduced through a penalty method formulation. Extensive comparative, convergence, and parametric studies have been carried out by considering a wide range of uni-laterally constrained plates. Following a concise review of the available literature, techniques for analysing the elastic local buckling of thin-walled square tubes, fully filled with elastic materials and subjected to concentric uni-axial compression, are formulated by means of a simple stiffness approach and a proper Ritz-based technique. This method is then extended to account for the local buckling of thin-walled circular and elliptical cylinders with elastic infill. By representation of a proper trigonometric displacement function in the formulation which is capable of incorporating the effects of the penetration zone in a harmonic form, in addition to satisfying all the necessary boundary conditions, it is shown that the buckling solution reduces to a dimensionless representation for which the relevant geometrical and material properties that govern the local buckling coefficient can be identified. It was found that the provision of lightweight and low density infill is functional and attractive with respect to an increase in the efficacy of the restraint. A comparison was made, and good agreement was found to exist, between the results obtained from this study and results that are available in the literature. Finally, a strength to weight index is introduced that quantifies the enhancement in the local buckling coefficient for a number of materials with a wide range of stiffness and density. This index has potential applications for optimal design in aerospace and other specialized engineering applications.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [165]-173).

Thesis (Ph.D.). / Written for the Dept. of Mechanical Engineering. Title from title page of PDF (viewed 2009/06/10). Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 1991.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 107-112).

This thesis examines the effects of cold forming on the material properties of steel and stainless steel structural members. Extensive research has been carried out over many years on both of these materials as they are used to manufacture structural sections to various design specifications which exist in many different countries. However, to date, no design code exists in the UK for cold formed stainless steel structural members. A significant amount of research has focused on the localised effect of cold forming on material properties such as the yield and ultimate tensile strengths, particularly of steel, and this is discussed at length in Chapter 1- Literature Review. Less attention has been placed on stainless steel, but over the last 20 years with the advent of design specifications particularly in the USA, stainless steel has gained popularity for cold forming. Chapter 1 describes the research that has been carried out on stainless steel, with particular emphasis on localised forming effects. Chapter 2 gives a general introduction to Thin-Walled Structures since cold-formed structural sections are commonly used as thin-walled members. The deformation and properties of metallic materials are described in Chapter 3 showing the particular relevance to the cold forming process. This chapter is extended into Chapter 4 where the strengthening, forming and properties of metallic materials are discussed in detail, with particular attention given to the cold forming processes. Chapter 5 describes existing analytical and design code approaches to determine the increase in strength of cold formed steel structural sections, along with an empirically derived relationship to calculate the increased yield strength of stainless steel sections. Chapter 6 describes the recommendations provided by various design specifications on evaluation of the axial compression capacity of short struts subject to varying degrees of cold forming. This chapter also describes the recommendations provided by various design specifications on evaluation of both the axial compression and the combined bending and axial compression load capacities of cold formed lipped channel section stainless steel columns of short-to-medium length. The results obtained from Chapters 5 and 6 are compared to the results obtained from an extensive experimental approach as described in Chapter 7. A finite element non-linear analysis using the ANSYS finite element software package is presented in Chapter 8 which models the behaviour of cold formed stainless steel lipped channel section columns of short-to-medium length subject to pure axial compression loading and also combined bending and axial compression loading. Chapter 9 presents the experimental findings showing the relationship between material hardness and material yield strength for cold-formed areas. The results are then compared to the theoretical results from Chapter 6 to determine their accuracy in prediction of the structural behaviour of full cold formed structural member cross-sections. The load capacity obtained for axially compressed steel and stainless steel struts from experiments are compared to those obtained from the various design code predictions described in Chapter 6. Also presented are the experimental findings, design code recommendations and finite element predictions for the load capacity of stainless steel columns. Chapter 10 concludes on the work by discussing the various issues arising from the experiments, from the design code recommendations and from finite element analysis 11 M. Macdonald

Lai, Kim Fung = 幼樑之振動與力學特性 / 黎劍鋒. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 99-102). / Abstracts in English and Chinese. / Lai, Kim Fung = You liang zhi zhen dong yu li xue te xing / Li, Jianfeng. / Chapter I --- Vibrations of Timoshenko Beams --- p.1 / Chapter 1 --- Introduction --- p.2 / Chapter 1.1 --- Overview --- p.2 / Chapter 1.2 --- Simple theory of static beam bending --- p.6 / Chapter 1.3 --- Foundation of problem --- p.7 / Chapter 1.4 --- Literature review --- p.12 / Chapter 1.4.1 --- Euler-Bernoulli Beam Theory (EBBT) --- p.12 / Chapter 1.4.2 --- Timoshenko Beam Theory (TBT) --- p.16 / Chapter 1.5 --- Preview of our results --- p.20 / Chapter 2 --- 3-D problem --- p.22 / Chapter 2.1 --- Elastic theory --- p.23 / Chapter 2.2 --- Boundary conditions --- p.24 / Chapter 2.3 --- Plane waves in uniform thin beams --- p.25 / Chapter 2.4 --- Solving order-by-order analytically --- p.26 / Chapter 2.5 --- Minimization approach --- p.36 / Chapter 3 --- 2-D problem --- p.50 / Chapter 3.1 --- Boundary conditions and effective moduli --- p.51 / Chapter 3.2 --- Expansion for thin beams --- p.54 / Chapter 3.3 --- Plane waves in uniform thin beam --- p.56 / Chapter 3.4 --- Boundary conditions --- p.57 / Chapter 3.5 --- Truncation --- p.58 / Chapter 3.6 --- Numerical solution --- p.58 / Chapter 3.7 --- Analytic results for soft mode --- p.60 / Chapter 3.8 --- EBBT and TBT for 2-D problem --- p.62 / Chapter 3.9 --- Analytic results for hard mode at q = 0 --- p.64 / Chapter 3.10 --- Higher-order corrections for hard mode --- p.66 / Chapter 4 --- Summary --- p.71 / Chapter II --- Vibrations of Single-Walled Carbon nanotubes --- p.73 / Chapter 5 --- Introduction --- p.74 / Chapter 5.1 --- General properties --- p.74 / Chapter 5.2 --- Graphene sheet --- p.76 / Chapter 5.3 --- Rolling up a graphene sheet --- p.78 / Chapter 5.4 --- Foundation of problem --- p.79 / Chapter 5.5 --- Literature review --- p.79 / Chapter 5.6 --- Preview of our results --- p.80 / Chapter 6 --- Structure and strain energy under zero stress --- p.81 / Chapter 6.1 --- Description of the structure --- p.81 / Chapter 6.2 --- Description of the strain energy --- p.83 / Chapter 6.3 --- Minimization of energy --- p.86 / Chapter 7 --- SWCNT under strain --- p.89 / Chapter 7.1 --- Subject to an axial strain --- p.89 / Chapter 7.2 --- Subject to a radial strain --- p.94 / Chapter 7.3 --- Subject to a torsional strain --- p.95 / Chapter 8 --- Summary --- p.98 / Bibliography --- p.99 / Chapter A --- "Expressing elastic moduli G, λ and M in terms of Y andv" --- p.103 / Chapter B --- Simplification of the functional E to a neat expression --- p.105 / Chapter C --- Expressing effective elastic moduli G' and M' in terms of Y' and v' --- p.106 / Chapter D --- Illustration of the lowest non-trivial truncation --- p.107 / Chapter E --- The proof of Self-adjointness of H(q) --- p.109 / Chapter F --- Proof of the identity KeVec= KeVel --- p.112

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Thesis (M.S.)--Mississippi State University. Department of Mechanical Engineering. / Title from title screen. Includes bibliographical references.