Specialized techniques are needed to solve global optimization problems, due to the existence of multiple local optima or numerical noise in the objective function. The complexity of the problem is aggravated when discontinuities and constraints are present, or when evaluation of the objective function is computationally expensive. The global (minimization) programming problem is defined as finding the variable set for which the objective function obtains not only a local minimum, but also the smallest value, the global minimum. From a mathematical point of view, the global programming problem is essentially unsolvable, due to a lack of mathematical conditions characterizing the global optimum. In this study, the unconstrained global programming problem is addressed using a number of novel heuristic approaches. Firstly, a probabilistic global stopping criterion is presented for multi-start algorithms. This rule, denoted the unified Bayesian stopping criterion, is based on the single mild assumption that the probability of convergence to the global minimum is comparable to the probability of convergence to any other local minimum. This rule was previously presented for use in combination with a specific global optimization algorithm, and is now shown to be effective when used in a general multi-start approach. The suitability of the unified Bayesian stopping criterion is demonstrated for a number of algorithms using standard test functions. Secondly, multi-start global optimization algorithms based on multiple local searches, com¬bined with the unified Bayesian stopping criterion, are presented. Numerical results reveal that these simple multi-start algorithms outperform a number of leading contenders. Thirdly, parallelization of the sequential multi-start algorithms is shown to effectively re¬duce the apparent computational time associated with solving expensive global programming problems. Fourthly, two algorithms simulating natural phenomena are implemented, namely the rel¬atively new particle swarm optimization method and the well known genetic algorithm. For the current implementations, numerical results indicate that the computational effort associated with these methods is comparable. Fifthly, the observation that no single global optimization algorithm can consistently out¬perform any other algorithm when a large set of problems is considered, leads to the de¬velopment of a parallel competing algorithm infrastructure. In this infrastructure different algorithms, ranging from deterministic to stochastic, compete simultaneously for a contri¬bution to the unified Bayesian global stopping criterion. This is an important step towards facilitating an infrastructure that is suitable for a range of problems in different classes. In the sixth place, the constrained global programming problems is addressed using con¬strained algorithms in the parallel competing algorithm infrastructure. The developed methods are extensively tested using standard test functions, for both serial and parallel implementations. An optimization procedure is also presented to solve the slope stability problem faced in civil engineering. This new procedure determines the factor of safety of slopes using a global optimization approach. / Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted

No description available.

A numerical investigation was conducted to evaluate the geotechnical safety and slope stability of Municipal Solid Waste (MSW) landfills, considering the effects of geosynthetic reinforcements, biodegradation of the waste, and associated changes in material properties, and extreme wind force simulating hurricane conditions. Three different landfill slopes, 1:1, 1:2, and 1:3 having the height of 122m and width of 2134m, were analyzed using Limit Equilibrium Method (SLOPE/W) and Finite Element Modeling (ANSYS). Techniques developed in this study were used to analyze a case history involving a geogrid reinforced mixed landfill expansion located in Austria. It was found that few years after construction of the landfill, there is a significant decrease in the FS due to biodegradation. Extreme wind loading was also found to cause a substantial loss in the FS. The geosynthetic reinforcement increased the slope stability and approximately compensated for the damaging effects of biodegradation and wind loading. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Includes bibliographical references / xii, [291] leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil Engineering, 1992

Made available in DSpace on 2015-03-26T13:28:31Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2857097 bytes, checksum: 6b461d27fbface3dd178a5bbe1ed092c (MD5) Previous issue date: 2014-02-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Slopes of soil and/or rock exist naturally or are manmade in excavations (cut slopes) or landfills. When precipitation occurs on the slope, part of the rainwater infiltrates and, as the ground layers are being saturated, the suction forces decrease, eventually leading to the slope failure. This paper discusses the effect of infiltration of rainwater on the variation of safety factor values of a slope made of gneiss residual soil located at the Federal University of Viçosa (UFV) campus, next to another slope that failed in December, 2011. Results of laboratory tests - characterization, direct shear, water retention curve, and saturated permeability - in disturbed and undisturbed soil samples of the different soils existing in the slope and identified by standard penetration tests (SPT), are presented. Following, The variation of water content and suction in the slope are calculated, together with the safety factor along the year 2011, considering the climatic data measured at the UFV weather station - precipitation, temperature, speed and direction of winds. The infiltration of water in the slope was calculated using the commercial program VADOSE / W and the daily stability analyzes by the program SLOPE/W both from GeoStudio. The analyses showed that during rainy periods the value of the safety factor decreases, the lowest value being 1,545, in December. In dry periods, the safety factor tends to increase, but with lower rates compared to the decrease occurred during rainy periods. By analyzing the suction and the safety factor together throughout the year, it was observed that the behavior of the two variables is similar, ie, as described in the literature, when suction decreases, resistance also decreases, and the safety factor diminished. / Taludes de solo e/ou rocha existem naturalmente, ou são construídos pelo homem em escavações (taludes de corte) ou aterro. Em países tropicais, como o Brasil, muitos taludes encontram-se em parte ou totalmente com os solos na zona vadosa. Nestes casos, ocorrem forças de sucção que aumentam a resistência dos materiais que compõem o talude. Quando acontece uma precipitação sobre o talude, parte das águas pluviais infiltra e, à medida que as camadas de solo vão sendo saturadas, as forças de sucção diminuem o que, eventualmente, pode ocasionar a ruptura do talude. Neste trabalho discute-se o efeito da infiltração das águas pluviais na variação dos fatores de segurança de um talude de solo residual de gnaisse localizado no campus da Universidade Federal de Viçosa (UFV), ao lado de outro talude onde houve um significativo escorregamento em dezembro de 2011. São apresentados resultados de ensaios de laboratório caracterização, cisalhamento direto, curva de retenção de água e permeabilidade saturada em amostras deformadas e indeformadas dos solos identificados no talude por meio de sondagem à percussão. Em seguida, descreve-se a variação da umidade volumétrica, da sucção e do fator de segurança do talude ao longo do ano de 2011, considerando os dados climáticos medidos na estação meteorológica da UFV precipitação, temperatura, velocidade e direção dos ventos. O balanço hídrico e a infiltração de água no talude foram feitos com o auxílio do programa VADOSE/W e a análise diária de estabilidade feita com o programa SLOPE/W da GeoStudio. As análises mostraram que em períodos chuvosos o valor do fator de segurança diminui, tendo obtido o menor valor de 1,545, em dezembro, o que justifica numericamente a estabilidade observada em campo. Em períodos secos o valor tende a aumentar, porém em taxas menores quando comparados com a diminuição ocorrida em períodos chuvosos. Ao analisar a sucção e o fator de segurança conjuntamente ao longo do ano, observou-se que comportamento similar para as duas variáveis, ou seja, assim como descrito na literatura, quando a sucção diminuiu a resistência do talude também diminui, o que diminuiu o valor do fator de segurança.