No description available.

No description available.

Foldable and deployable space structures refer to a broad category of pre-fabricated structures that can be transformed from a compact folded configuration to a predetermined expanded configuration. Such deployable structures are stable and can carry loads. These structures are also mechanisms with one degree of freedom in their entire transformation stages whether in the initial folded form or in the final expanded configuration. Usually, pantograph mechanisms or a scissor-like elements (SLEs) are part of such deployable structures. A new analysis tool to study kinematic and static analyses of foldable and deployable space structures /mechanisms, containing SLEs, has been developed in this thesis. The Cartesian coordinates are used to study the kinematics of large deployable structures. For many deployable structures the degree of freedom derived using the standard Grubler-Kutzback criteria, is found to be less than one even though the deployable structure /mechanism can clearly move. In this work the dimension of nullspace of the derivatives of the constraint equations are used to obtain the correct degrees of freedom of deployable structure. A numerical algorithm has been developed to identify the redundant joints /links in the deployable structure /mast which results in the incorrect degrees of freedom obtained by using the Grubler-Kutzback criteria. The effectiveness of the algorithm has been illustrated with several examples consisting of triangular, box shaped SLE mast and an eighteen-sided SLE ring with revolute joints. Further more the constraint Jacobian matrix is also used to evaluate the global degrees of freedom of deployable masts/structures. Closed-form kinematic solutions have been obtained for the triangular and box type masts and finally, as a generalization, extended to a general n-sided SLE based ring structure. The constraint Jacobian matrix based approach has also been extended to obtain the load carrying characteristics of deployable structures with SLEs in terms of deriving the stiffness matrix of the structure. The stiffness matrix has been obtained in the symbolic form and it matches results obtained from other commonly used techniques such as force and displacement methods. It is shown that the approach developed in this thesis is applicable for all types of practical masts with revolute joints where the revolute joint constraints are made to satisfy through the method of Lagrange multipliers and a penalty formulation. To demonstrate the effectiveness of the new method, the procedure is applied to solving (i) a simple hexagonal SLE mast, and (ii) a complex assembly of four hexagonal masts and the results are presented. In summary, a complete analysis tool to study masts with SLEs has been developed. It is shown that the new tool is effective in evaluating the redundant links /joints there by over coming the problems associated with the well –known Grubler-Kutzback criteria. Closed-form kinematic solutions of triangular and box SLE masts as well as a general n-sided SLE ring with revolute joints has been obtained. Finally, the constraint Jacobian based method is used to evaluate the stiffness matrix for the SLE masts. The theory and algorithms presented in this thesis can be extended to masts of different shapes and for the stacked masts.

No description available.

Thesis (M. Eng.), Memorial University of Newfoundland, 1999. / Bibliography: p. 107-109.

Guyed masts are special type of structures that are widely used in the telecommunication industry. In the past, there was no guideline for seismic design of these types of structures in the corresponding design codes. On the other hand, in the latest &ldquo / G&rdquo / revision of the ANSI/TIA-EIA code there is a comprehensive design criterion for the seismic design of the guyed masts. However, during the design process of these structures the most common approach is to ignore the effect of seismic loading and use only the internal forces developed from the wind load and ice load analysis. In this study firstly the efficiency and accuracy of the commercial SAP2000 and PLS-TOWER software were investigated, then finite element models of three guyed masts that had been designed in Turkey with the heights 30m, 60m and 100m in the SAP2000 and PLS-TOWER software were analyzed under the effect of earthquake, wind and ice loadings. The most common design code recognized all over the world used for the design of the guyed masts is ANSI/TIA-EIA 222-G &ldquo / Structural Standards for Steel Antenna Towers and Supporting Structures&rdquo / . Thus, the corresponding sections of this code were followed during the study. The main objective of this research is to check the correctness of commercial SAP2000 and PLS-TOWER software and to investigate the effect of seismic actions on the guyed masts and also to gain a better understanding of the behavior of guyed masts under the effects of the wind, ice and earthquake loadings.

As de torres treliçadas estaiadas são muito utilizadas e são foco de atenção na pesquisa da engenharia moderna, apresentando-se como um desafio na avaliação das excitações que sobre elas atuam, assim como a determinação das respostas dos elementos que as compõem. Para realizar um estudo neste sentido se realiza no presente trabalho a avaliação estrutural de uma torre treliçada estaiada, localizada na Universidade de Passo Fundo. Esta torre se encontra instrumentada, registrando velocidades de vento de forma contínua, sendo possível determinar nos registros existentes ventos característicos de tormentas TS e EPS. Se conta também com a caracterização dinâmica desta torre para qual foram determinadas suas freqüências naturais de vibração. Utilizando a informação supracitada foram criados modelos estruturais de diferentes níveis de complexidade que foram calibrados utilizando as informações disponíveis. A excitação devida a tormentas foi montada, comparando espectros de excitação clássicos disponíveis na literatura técnica e os registros experimentais de tormentas reais disponíveis. Também foi analisado um montante da torre submetido à compressão onde sua seção transversal é uma cantoneira de abas iguais. Foi determinada a carga de colapso deste perfil considerando as não linearidades físicas e geométricas incorporadas no mesmo. Foi prestada singular atenção ao estudo da influência das imperfeições, utilizando para isto expressões propostas pela bibliografia especializada e o quadro de imperfeições que foi extraído do escaneamento tridimensional de um montante real. Finalmente os diferentes aspectos estudados são discutidos nesta dissertação os quais permitem conhecer melhor o comportamento estrutural de torres estaiadas, em forma global, dos componentes que as compõem e das solicitações que atuam sobre elas. A forma em que se estudaram estes aspectos sem duvida enriqueceram a discussão do complexo tema da incerteza de modelo um dos atuais frentes na pesquisa da engenharia moderna. / The analysis of frames guyed masts are widely used and are the focus of attention in the research of modern engineering, presenting a challenge in the evaluation of excitations that act on them, and determining the responses of the component elements. To undertake a study to that effect, in this essay is made the evaluation of a structural truss of guyed masts, located at the University of Passo Fundo. This tower has equipments that record wind speeds in a continuous manner, being able to determine data about TS and EPS storms in the existing records. It also determines the natural frequencies of vibration as a dynamic characteristic of the tower. Using the above information, structural models of different levels of complexity were created, being calibrated using the available data. The excitement caused by storms was created by comparing the excitation spectra classics available in the technical literature and the experimental records of actual storms available. Also discussed was an amount subject to compression of the tower where its cross section is a corner of tabs equal. Was determined from the load profile given the collapse of physical and geometric nonlinearities embedded in it. Individual attention was given to the study of the influence of imperfections, using it to expressions proposed by the specialized literature and the framework of imperfection that was extracted from three-dimensional scanning of an actual amount.

As de torres treliçadas estaiadas são muito utilizadas e são foco de atenção na pesquisa da engenharia moderna, apresentando-se como um desafio na avaliação das excitações que sobre elas atuam, assim como a determinação das respostas dos elementos que as compõem. Para realizar um estudo neste sentido se realiza no presente trabalho a avaliação estrutural de uma torre treliçada estaiada, localizada na Universidade de Passo Fundo. Esta torre se encontra instrumentada, registrando velocidades de vento de forma contínua, sendo possível determinar nos registros existentes ventos característicos de tormentas TS e EPS. Se conta também com a caracterização dinâmica desta torre para qual foram determinadas suas freqüências naturais de vibração. Utilizando a informação supracitada foram criados modelos estruturais de diferentes níveis de complexidade que foram calibrados utilizando as informações disponíveis. A excitação devida a tormentas foi montada, comparando espectros de excitação clássicos disponíveis na literatura técnica e os registros experimentais de tormentas reais disponíveis. Também foi analisado um montante da torre submetido à compressão onde sua seção transversal é uma cantoneira de abas iguais. Foi determinada a carga de colapso deste perfil considerando as não linearidades físicas e geométricas incorporadas no mesmo. Foi prestada singular atenção ao estudo da influência das imperfeições, utilizando para isto expressões propostas pela bibliografia especializada e o quadro de imperfeições que foi extraído do escaneamento tridimensional de um montante real. Finalmente os diferentes aspectos estudados são discutidos nesta dissertação os quais permitem conhecer melhor o comportamento estrutural de torres estaiadas, em forma global, dos componentes que as compõem e das solicitações que atuam sobre elas. A forma em que se estudaram estes aspectos sem duvida enriqueceram a discussão do complexo tema da incerteza de modelo um dos atuais frentes na pesquisa da engenharia moderna. / The analysis of frames guyed masts are widely used and are the focus of attention in the research of modern engineering, presenting a challenge in the evaluation of excitations that act on them, and determining the responses of the component elements. To undertake a study to that effect, in this essay is made the evaluation of a structural truss of guyed masts, located at the University of Passo Fundo. This tower has equipments that record wind speeds in a continuous manner, being able to determine data about TS and EPS storms in the existing records. It also determines the natural frequencies of vibration as a dynamic characteristic of the tower. Using the above information, structural models of different levels of complexity were created, being calibrated using the available data. The excitement caused by storms was created by comparing the excitation spectra classics available in the technical literature and the experimental records of actual storms available. Also discussed was an amount subject to compression of the tower where its cross section is a corner of tabs equal. Was determined from the load profile given the collapse of physical and geometric nonlinearities embedded in it. Individual attention was given to the study of the influence of imperfections, using it to expressions proposed by the specialized literature and the framework of imperfection that was extracted from three-dimensional scanning of an actual amount.

As de torres treliçadas estaiadas são muito utilizadas e são foco de atenção na pesquisa da engenharia moderna, apresentando-se como um desafio na avaliação das excitações que sobre elas atuam, assim como a determinação das respostas dos elementos que as compõem. Para realizar um estudo neste sentido se realiza no presente trabalho a avaliação estrutural de uma torre treliçada estaiada, localizada na Universidade de Passo Fundo. Esta torre se encontra instrumentada, registrando velocidades de vento de forma contínua, sendo possível determinar nos registros existentes ventos característicos de tormentas TS e EPS. Se conta também com a caracterização dinâmica desta torre para qual foram determinadas suas freqüências naturais de vibração. Utilizando a informação supracitada foram criados modelos estruturais de diferentes níveis de complexidade que foram calibrados utilizando as informações disponíveis. A excitação devida a tormentas foi montada, comparando espectros de excitação clássicos disponíveis na literatura técnica e os registros experimentais de tormentas reais disponíveis. Também foi analisado um montante da torre submetido à compressão onde sua seção transversal é uma cantoneira de abas iguais. Foi determinada a carga de colapso deste perfil considerando as não linearidades físicas e geométricas incorporadas no mesmo. Foi prestada singular atenção ao estudo da influência das imperfeições, utilizando para isto expressões propostas pela bibliografia especializada e o quadro de imperfeições que foi extraído do escaneamento tridimensional de um montante real. Finalmente os diferentes aspectos estudados são discutidos nesta dissertação os quais permitem conhecer melhor o comportamento estrutural de torres estaiadas, em forma global, dos componentes que as compõem e das solicitações que atuam sobre elas. A forma em que se estudaram estes aspectos sem duvida enriqueceram a discussão do complexo tema da incerteza de modelo um dos atuais frentes na pesquisa da engenharia moderna. / The analysis of frames guyed masts are widely used and are the focus of attention in the research of modern engineering, presenting a challenge in the evaluation of excitations that act on them, and determining the responses of the component elements. To undertake a study to that effect, in this essay is made the evaluation of a structural truss of guyed masts, located at the University of Passo Fundo. This tower has equipments that record wind speeds in a continuous manner, being able to determine data about TS and EPS storms in the existing records. It also determines the natural frequencies of vibration as a dynamic characteristic of the tower. Using the above information, structural models of different levels of complexity were created, being calibrated using the available data. The excitement caused by storms was created by comparing the excitation spectra classics available in the technical literature and the experimental records of actual storms available. Also discussed was an amount subject to compression of the tower where its cross section is a corner of tabs equal. Was determined from the load profile given the collapse of physical and geometric nonlinearities embedded in it. Individual attention was given to the study of the influence of imperfections, using it to expressions proposed by the specialized literature and the framework of imperfection that was extracted from three-dimensional scanning of an actual amount.

MASTS is an extensible, feature rich, software architecture based on tabu search (TS), a metaheuristic that relies on memory structures to intelligently organize and navigate the search space. MASTS introduces a new methodology of rule based objectives (RBOs), in which the search objective is replaced with a binary comparison operator more capable of expressing a variety of preferences. In addition, MASTS supports a new metastrategy, dynamic neighborhood selection (DNS), which “learns” about the search landscape to implement an adaptive intensification-diversification strategy. DNS can improve search performance by directing the search to promising regions and reducing the number of required evaluations. To demonstrate the flexibility and range of capabilities, MASTS is applied to two complex decision problems in conservation planning and groundwater management. As an extension of MASTS, ConsNet addresses the spatial conservation area network design problem (SCANP) in conservation biology. Given a set of possible geographic reserve sites, the goal is to select which sites to place under conservation to preserve unique elements of biodiversity. Structurally, this problem resembles the NP-hard set cover problem, but also considers additional spatial criteria including compactness, connectivity, and replication. Modeling the conservation network as a graph, ConsNet uses novel techniques to quickly compute these spatial criteria, exceeding the capabilities of classical optimization methods and prior planning software. In the arena of groundwater planning, MASTS demonstrates extraordinary flexibility as both an advanced search engine and a decision aid. In House Bill 1763, the Texas state legislature mandates that individual Groundwater Conservation Districts (GCDs) must work together to set specific management goals for the future condition of regional groundwater resources. This complex multi-agent multi-criteria decision problem involves finding the best way to meet these goals considering a host of decision variables such as pumping locations, groundwater extraction rates, and drought management policies. In two separate projects, MASTS has shaped planning decisions in the Barton Springs/Edwards Aquifer Conservation District and Groundwater Management Area 9 (GMA9). The software has been an invaluable decision support tool for planners, stakeholders, and scientists alike, allowing users to explore the problem from a multicriteria perspective. / text