Thesis (M.Eng.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 108-112.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "December, 2006." Includes bibliographical references (leaves 82-85). Online version available on the World Wide Web.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 107-109).

A postbuckling analysis procedure for simply-supported, symmetrically laminated, rectangular, generally orthotropic plates under uniaxial compression based on a Marguerre-type energy method was developed. The analysis assumes the out-of-plane displacement to be represented by using a truncated Fourier sine series. The unknown coefficients of the displacement function were obtained from a system of nonlinear algebraic equations by using the principle of minimum potential energy. The number of terms that are to be retained in the out-of-plane displacement function to obtain an accurate response was studied and identified for a wide range of generally orthotropic plates. In the postbuckling load range, plates are also allowed to change their buckled form. The magnitudes of the total potential energy for possible different deformed shapes of a plate were compared to determine the actual deformed shape. The effect of bending-twisting coupling terms on the postbuckling behavior of anisotropic laminates was also investigated. Several postbuckling problems for isotropic, orthotropic, and anisotropic plates were considered and the results obtained by the present approach were compared with available literature results and finite element solutions to demonstrate the present analysis procedure. The analysis procedure developed was, then, applied to minimum-weight design of laminated plates for postbuckling performance. Laminate failure load used in the postbuckling regime was calculated based on a maximum strain failure criterion. The failure criterion was demonstrated to predict the failure load reasonably well when compared with available test results. Weight comparison between the plates designed against buckling and the ones designed for the postbuckling strength was made to quantitatively evaluate the weight savings achieved for plates that are allowed to buckle. The design variables were assumed to be the layer thicknesses with specified fiber orientations and assumed to take only discrete values. A simple approach based on the penalty method was proposed to achieve the discrete-valued designs. In addition to the regular penalty terms for constraint violation, the proposed approach introduces penalty terms to reflect the requirement that the design variables take discrete values. A variable magnitude penalty term in the form of a sine function was implemented with the extended interior penalty method of the optimization package NEWSUMT-A. The proposed discrete optimization technique was applied to the classical truss and laminated composite plate design problems to demonstrate the performance of the procedure. / Ph. D.

Master of Science

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 1992. / This thesis presents the results of theoretical and experimental investigations into the behaviour and ultimate load capacity of latticed lower panels with cross-bracing diagonals made of equal-leg, hot-rolled steel angles under the effects of in-plane loads. Loading tests to collapse are carried out on cross-bracings in reduced-scale two-dimensional frames of various arrangements. The Southwell-plot of deflection measurements immediately prior to first yield of the diagonals is used to define equivalent end eccentricities and effective length factors, which therefore account for geometric and material imperfections of the test specimens. A proposal for new design formulae for calculating the resistance of struts is presented. The new design equations are based on the secant formula and are calibrs"ed against the experimental results. A computer model is developed based on flexibility equations which do not require an narative analysis procedure. The non-linear effects are given through the inclusion of Berry stability functions. The effects of eccentric forces and nodal restraints are simulated at all joints in which diagonals and main chords are connected . An additional model is formulated using a mainframe finite-element cod, demonstrating that it is now possible to perform non-linear analyses of complex frames including asymmetric members. Experimental results from this and other investigations are compared with ultimate load predictions based on the new design equations and the computer models and also usual buckling curves for design of steel transmission towers. In all cases the proposed models give acceptable predictions ot the behaviour and ultimate capacity of the bracings. In particular, failure loads calculated with the new design equations show improvements with respect to predictions based on current design buckling curves. These equations, therefore, can be used for design of steel latticed tower structures with angle members.

Not available

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (p. 109-112).

Clean Development Mechanism (CDM), is a market-based mechanism under the Kyoto Protocol. It allows developed countries to implement emission reduction projects in developing countries, to assist their sustainable development; meanwhile, developed countries gain credits which could be used to meet part of their emission reduction targets under this protocol. There is a wide range of various types of CDM projects, among which, wind power projects account for the largest share. Additionality is a key component for CDM projects’ eligibility and to ensure CDM’s environmental integrity. It means that the emission reduction after the implementation of the project is additional to any that would have occurred in the absence of the certified CDM project. For wind CDM projects, the controversy on additionality raised debate and attention internationally, especially the concern if project developers deliberately underestimated Plant Load Factor (PLF) so as to meet the CDM additionality criterion. At the United Nations Framework Convention on Climate Change (UNFCCC) CDM Executive Board 63rd meeting, the UNFCCC Secretariat and the Registration and Issuance Team (RIT) proposed different decisions regarding a request forissuance of a Wind CDM project due to different views on the estimated PLF. The Board discussed the issue andrequested a study on the PLF variations, which is the origin, and also a partial content of this thesis.In this thesis, relevant parameters are firstly defined – parameters such as Estimated PLF, Actual PLF, etc, and to better illustrate the magnitude of the PLF variation, the concept of Relative Variation of PLF is adopted, which is measured as the absolute difference of Estimated PLF and Actual PLF compared with Estimated PLF. Then a database in spreadsheet with all defined parameters of sampled projects is set up on the basis of collected information and calculation. Afterwards an investigation of PLFs and comparison analyses of Estimated PLFs and Actual PFLs is conducted. Considering there are two groups of Wind CDM projects, i.e. small-scale and large-scale; and considering the distributions of projects’ hosting countries, the comparison analyses are then conducted firstly for all projects, and then separated for small-scale and large-scale projects, and lastly separated for projects based on different hosting countries. The final results show that a minority of projects have underestimated PLFs, and a very small proportion of projects, either in all projects, or on different scales or in different hosting countries have underestimated PLFs to a level that is out of acceptable range. Therefore, thestudy concludes that there should be no concern on the PLF issue in Wind CDM projects.

This study presented a substructure based parallel linear solution framework for the static analysis of linear structural engineering problems having multiple loading conditions. The framework was composed of two separate programs designed to work on PC Clusters having the Windows operating system. The first program was responsible for creating the optimum substructures for the parallel solution and first partitioned the structure in such a way that the number of substructures was equal to the number of processors. Then, the estimated condensation time imbalance of the initial substructures was adjusted by iteratively transferring nodes from the substructures with slower estimated condensation times to the substructures with faster estimated condensation times. Once the final substructures were created, the second program started the solution. Each processor assembled its substructures stiffness matrix and condensed it to the interface with other substructures. The interface problem was solved by a parallel variable band solver. After computing the interface unknowns, each processor calculated the internal displacements and element stresses or forces. Examples which illustrate the applicability and efficiency of this approach were also presented. In these examples, the number of processors was varied from one to twelve to demonstrate the performance of the overall solution framework.