Resumen de Análisis numérico de los efectos del pretesado sobre estructuras textiles laminares tensoestáticas. Evaluación del esfuerzo de pretesado en estructuras textiles laminares tensoestáticas parabólicas, para analizar sus efectos y determinar criterios para su predimensionamiento
Xavier Gimferrer Vilaplana
The main objective of this Thesis is to determinate the behaviour of the prestress effect of a fabric structure. On the understanding that the prestress of a fabric structure is a fundamental part of its stability and mechanical behavior that it must be preserved throughout its useful lifetime, it is necessary to obtain an overall view of its effects. To achieve that, the prestress study is done in its three possible levels of analysis: first, the predimensioning level, second, structural analysis and stress distribution, third, tension verification in pre-existing structures. Specifically in the Thesis is analysed one of the basic typologies of fabric structures, the paraboloid, of which the basic laws of behavior of the tensioning effect can be achieved and extrapolated to other geometries. The analysis is done from the study of computer models which are constructed from a particular basic geometry, upon this geometry are applied specific progressive geometric variations, tensioning and applied load. This succession of models generates a series of results that, connected them with each specific variation which allow to determine the affectation level of contribution of that parameter to the value and distribution of stress tension. To achieve these objectives it is necessary to establish the basic mechanical principles and structural behavior of tensioned fabric structure, as well as to describe the analysis process necessary for the realization of structural analysis. These precepts are exposed in Chapter 1 of the Thesis, establishing the knowledge base that will allow the development and analysis of the calculation models. This chapter also defines and makes a first analysis of the effect produced by different methods of tensioning, demonstrating that to obtain a tensioning distribution as much uniform as possible, it is necessary to carry out the prestress as uniformly as possible and stiffen the edge of the surface. Chapter 2 is divided in two blocks. The first one is where are made and analyzed a serie of conceptual models, starting from the simplest models of isolated bars and increasing its complexity until reaching membrane models, which allow a first approximation to the tensioned structure behavior. In the second block the boundaries of the defining parameters of the models are specified, to proceed with the creation of calculation models using a generation module of fabric parabolic geometries that has been developed for the Wintess program. The results of these models are summarized and classified in the third chapter, analyzing the evolution of the distribution and stress magnitude of tension for each parametric variation, demonstrating that tension distribution is not uniform , and better performance is obtained at higher curvatures. In Chapter Four, the minimum and maximum allowable values of prestress are determined, so it can be established criterions and formulations for prestress depending on the geometry of the paraboloid and external loads. Chapter 5 is dedicated to the evaluation of the tension state in executed structures, analyzing the existing evaluation methods of the stress, determining that depending on the type of tensile structure must be used ones or other methods, the most general methods are based on the relationship between the tension of the element and its fundamental vibration period. Finally, the sixth chapter is dedicated to the exposition of the conclusions achieved from the analysis and it is formulated the possible future research lines that will deepen on the knowledge of the behavior of prestress fabric structures.
