La atención a la evacuación del agua de lluvia y a la protección de la estructura ante los agentes meteorológicos ha dado lugar a un conjunto de propuestas de estructuras desplegables de aspas sobre planta rectangular en las que estas estructuras definen limas y faldones de pendiente suficiente. El trabajo parte de la resolución del trazado de estructuras desplegables de aspas planas simétricas y base cuadrangular con directriz quebrada, garantizándose el correcto funcionamiento cinemático mediante la construcción de modelos. Se estudian desplegables con directrices poligonales, curvas compuestas y también combinaciones de curvas y rectas. Se repasan los problemas de estabilización de la solución en el estado desplegado, incorporando la cobertura textil y cables de arriostramiento. Finalmente se desarrollan y analizan geométrica y cinemáticamente una serie de propuestas con superficies de intradós y extradós diferentes y otro grupo de ellas en las que los sentidos de despliegue no siguen los ejes del recinto a cubrir.

Deployable structures are a good solution for emergency buildings, due to their lightness and compact nature which means they can be transported to where they are needed. Nevertheless, the deployable structures studied to date have the drawback of being too deformable, so that larger and therefore heavier sections had to be used. This paper proposes a new type of deployable structure that uses reciprocal linkages which give rise to greater strength and rigidity. The geometrical and mechanical conditions of the linkages are analysed, as several different types which perform better can be designed, and a calculation method is developed to analyse structures of this type. The features and behaviour of a flat mesh with articulated reciprocal linkages are also compared analytically and experimentally. The theoretical calculations and experimental tests make it possible to prove the viability and efficacy of this new structural type.

Expandable structures have certain qualities in terms of lightness and transportability which make them very useful as emergency buildings, a research line that is being developed by the authors. However, these structures have some disadvantages due to their reduced rigidity and great deformability, issues that could limit their use. This paper analyzes a reciprocal linkage that considerably improves one of the main problems of expandable structures, which is their lack of rigidity. The extremely strict geometrical conditions for this proposed linkage and the mechanical behaviour are examined. Two series of tests were carried out, with specimens formed by four bars supported reciprocally around the proposed linkage. In the first case, the bars had their ends simply resting on the base and in the second one displacement was restricted at their ends. Theoretical analysis and the experimental tests results are also included. The tests make it possible to define the failure patterns of the different elements of the linkages, bars or bolts. The theoretical models and the experimental results show that the proposed reciprocal linkages are highly effective. Tests of plane scissor meshes were also carried out using reciprocal linkages, showing a very significant reduction in their displacements.

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Resumenuando Frei Otto afirmó, con motivo de la Expo de Sevilla 1992, que una Exposición Universal es una oportunidad para hacer experimentos y mostrar caminos para el futuro, habían transcurrido casi 150 años desde la celebración de la primera Exposición Universal en Londres. Durante este largo período las Expos adoptaron un papel fundamental como lugar de ensayo de nuevos materiales y tipologías estructurales, constituyendo verdaderas fuentes de innovación que, vertiendo sus experiencias en edificaciones gestadas al margen de las mismas, se fueron erigiendo como componente intrínseco de la historia de los sistemas estructurales arquitectónicos. El presente artículo aporta una visión sintética de algunas de las principales aportaciones estructurales de las Exposiciones Universales, condensando la amplitud que supone el análisis de un período tan largo y fructífero de desarrollo estructural en cinco categorías básicas: prueba y error, fantasía y utopía, gérmenes tipológicos, el conjunto tipológico, generación normativa y producción científica.Palabras clave: arquitectura, estructura, Exposiciones Universales, pabellones de exposición, tipos estructurales Abstract:When, on the occasion of Expo Seville 1992, Frei Otto declared that a World Expo is an opportunity to experiment and show the ways to the future, almost 150 years had gone by since the first World Fair held in London. Over the course of this long period, the World Expos took on a leading role as testing grounds for new structural materials and typologies; moreover, thanks to the fact that the experiences garnered in the World Expos were then applied to buildings that were created beyond them, they have become veritable sources of innovation that have risen to the forefront as an intrinsic component in the history of architectural structural systems. This paper offers a synthetic vision of some of the structural contributions of the World Expos, distilling the scope of an analysis of such a large and fruitful period of structural development into five basic categories: trial and error, fantasy and utopia, typological seeds, the typological set, generation of codes and scientific production.