Conceptual design of a concrete staircase based on topology optimization : A feasibility study on the development and application of topology optimization on a concrete staircase

Master's thesis in Civil and structural engineering (BYG508

Performance Analysis of Simulation-based Multi-objective Optimization of Bridge Construction Processes Using High Performance Computing

Bridges constitute a crucial component of urban highways due to the complexity and uncertain nature of their construction process. Simulation is an alternative method of analyzing and planning the construction processes, especially the ones with repetitive and cyclic nature, and it helps managers to make appropriate decisions. Furthermore, there is an inverse relationship between the cost and time of a project and finding a proper trade-off between these two key elements using optimization methods is important. Thus, the integration of simulation models with optimization techniques leads to an advancement in the decision making process. In addition, the large number of resources required in complex and large scale bridge construction projects results in a very large search space. Therefore, there is a need for using parallel computing in order to reduce the computational time of the simulation-based optimization. Most of the construction simulation tools need an integration platform to be combined with optimization techniques. Also, these simulation tools are not usually compatible with Linux environment which is used in most of the massive parallel computing systems or clusters. In this research, an integrated simulation-based optimization framework is proposed within one platform to alleviate those limitations. A master-slave (or global) parallel Genetic Algorithm (GA) is used as a parallel computing technique to decrease the computation time and to efficiently use the full capacity of the computer. In addition, sensitivity analysis is applied to identify the promising configuration for GA and analyzing the impact of GA parameters on the overall performance of the specific simulation-based optimization problem used in this research. Finally, a case study is implemented and tested on a server machine as well as a cluster to explore the feasibility of the proposed approach. The results of this research showed better performance of the proposed framework in comparison with other GA optimization techniques from the points of view of the quality of the optimum solutions and the computation time. Also, acceptable improvements in the computation time were achieved for both deterministic and probabilistic simulation models using master-salve parallel paradigm (8.32 and 20.3 times speedups were achieved using 12 cores, respectively). Moreover, performing the proposed framework on multiple nodes using a cluster system led to 31% saving on the computation time on average. Furthermore, the GA was tuned using sensitivity analyses which resulted in the best parameters (500 generations, population size of 200 and 0.7 as the crossover probability)

Integrating the finite element method and genetic algorithms to solve structural damage detection and design optimisation problems

This thesis documents fundamental new research in to a specific application of structural box-section beams, for which weight reduction is highly desirable. It is proposed and demonstrated that the weight of these beams can be significantly reduced by using advanced, laminated fibre-reinforced composites in place of steel. Of the many issues raised during this investigation two, of particular importance, are considered in detail; (a) the detection and quantification of damage in composite structures and (b) the optimisation of laminate design to maximise the performance of loaded composite structuress ubject to given constraints. It is demonstrated that both these issues can be formulated and solved as optimisation problems using the finite element method, in which an appropriate objective function is minimised (or maximised). In case (a) the difference in static response obtained from a loaded structure containing damage and an equivalent mathematical model of the structure is minimised by iteratively updating the model. This reveals the damage within the model and subsequently allows the residual properties of the damaged structure to be quantified. Within the scope of this work is the ability to resolve damage, that consists of either penny-shaped sub-surface flaws or tearing damage of box-section beams from surface experimental data. In case (b) an objective function is formulated in terms of a given structural response, or combination of responses that is optimised in order to return an optimal structure, rather than just a satisfactory structure. For the solution of these optimisation problems a novel software tool, based on the integration of genetic algorithms and a commercially available finite element (FE) package, has been developed. A particular advantage of the described method is its applicability to a wide range of engineering problems. The tool is described and its effectiveness demonstrated with reference to two inverse damage detection and quantification problems and one laminate design optimisation problem. The tool allows the full suite of functions within the FE software to be used to solve non-convex optimisation problems, formulated in terms of both discrete and continuous variables, without explicitly stating the form of the stiffness matrix. Furthermore, a priori knowledge about the problem may be readily incorporated in to the method

Aeronautical Engineering: A special bibliography, supplement 60

This bibliography lists 284 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1975

Elastic timber gridshells. from the finding form process to the erection of efficient lightweight structures

Doctoral Thesis (International Doctoral Programme in Sustainable Built Environment)Elastic timber gridshells emerged in the last century, essentially related to ephemeral buildings, setting a ‘new’ benchmark for lightweight, cost-effective, sustainable and temporary constructions. Timber gridshells are adaptable and can be used in rehabilitated buildings as well as, new buildings, new systems like roofs, or as small additions in nonstructural elements and act as a simple partition. However, the main feature is not its use, but its shape and how it allows some freedom in its design; an attractive characteristic for designers due to its structural behaviour. Based on the advantages of the structural system, it should be expected that timber gridshells have a wider presence in contemporary architecture. However, this is not the case, there are very few examples being built. One reason why this happens, is because of the difficulty to reach the desired design since there is a lack of information about the tools that can help to define such complex systems. Until today, the design and construction of elastic, or post-formed timber gridshells, have only been based on a case to case basis and have not been studied or used as a type of structure that can be repeated in several different applications. The aim of this thesis is to contribute to answer this difficulty, i.e. working on overcoming the lack of design guidelines, by presenting a state of the knowledge on elastic timber gridshells and by case studies analysing the process involved in building this kind of a structures. The thesis is addressing elastic timber gridshells, from the design phase to the construction phase. The results obtained show that this type of structure can be very interesting at a functional level with numerous tectonics characteristics that make elastic timber gridshells attractive as a structural solution in contemporary architecture.As malhas elásticas de madeira surgiram no século passado, essencialmente relacionadas com construções temporárias, estabelecendo uma "nova" referência para construções leves, econômicas, sustentáveis e efêmeras. As malhas de madeira são adaptáveis e podem ser usadas em edifícios a reabilitar, bem como, novos edifícios, coberturas, ou em pequenas modificações como elementos não estruturais. No entanto, a principal característica não é seu uso, mas sua geometria e como isso permite uma enorme liberdade formal torna-se uma característica atraente para todos os projetistas. Com base nas vantagens deste sistema estrutural, é de esperar que as malhas elásticas de madeira tivessem uma presença mais ampla na arquitetura contemporânea. Contudo, não é o caso, existem poucos exemplos construídos. Um motivo para isso acontecer é a dificuldade em projetar as formas desejadas, pois existe uma lacuna de informação sobre as ferramentas que podem ajudar a definir estas geometrias complexas. Por exemplo, as ferramentas baseadas em softwares computacionais têm um grande potencial para o processo de projeção das malhas de madeira nas fases de projeto e construção, onde a localização da malha e a otimização ocorrem, seguidas por um processo de produção industrial. Até hoje, o projeto e a construção destas estruturas, foram estudados apenas de caso a caso e não foram estudados ou usados como um tipo de solução que pode ser repetida em várias aplicações diferentes. O objetivo desta dissertação é contribuir para a resolução desse problema, ou seja, trabalhar na superação da falta de diretrizes de projeto, apresentando um estado do conhecimento sobre as malhas elásticas de madeira e analisando e explicando o processo envolvido na construção deste tipo de estruturas. Esta tese aborda as malhas elásticas de madeira, desde a fase de projeto até à fase de construção. Os resultados obtidos mostram que este tipo de estrutura pode ser muito interessante a um nível funcional, com numerosas características com valor tectônico que tornam as malhas elásticas de madeira atrativas como uma solução estrutural na arquitetura contemporânea.This work it was financed by FEDER funds through the Competitively Factors Operational Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007633. The support of the Foundation for Science and Technology (FCT) through doctoral fellowship SFRH/BD/104677/2014 is grateful

IOP PUBLISHING

Artificial evolution of the morphology and kinematics in a flapping-wing mini-UA

Multidisciplinary Design Optimization for Space Applications

Multidisciplinary Design Optimization (MDO) has been increasingly studied in aerospace engineering with the main purpose of reducing monetary and schedule costs. The traditional design approach of optimizing each discipline separately and manually iterating to achieve good solutions is substituted by exploiting the interactions between the disciplines and concurrently optimizing every subsystem. The target of the research was the development of a flexible software suite capable of concurrently optimizing the design of a rocket propellant launch vehicle for multiple objectives. The possibility of combining the advantages of global and local searches have been exploited in both the MDO architecture and in the selected and self developed optimization methodologies. Those have been compared according to computational efficiency and performance criteria. Results have been critically analyzed to identify the most suitable optimization approach for the targeted MDO problem

Very large floating container terminal and optimal layout of gill cells

Master'sMASTER OF ENGINEERIN