Abstract:Although the primary objective on designing a structure is to support the external loads, the achievement of an optimal layout that reduces all costs associated with the structure is an aspect of increasing interest. The problem of finding the optimal layout for bridgelike structures subjected to a uniform load is considered. The problem is formulated following a theory on economy of frame structures, using the stress volume as the objective function and including the selection of appropriate values for statically indeterminate reactions. It is solved in a function space of finite dimension instead of using a general variational approach, obtaining near-optimal solutions. The results obtained with this profitable strategy are very close to the best layouts known to date, with differences of less than 2% for the stress volume, but with a simpler layout that can be recognized in some real bridges. This strategy could be a guide to preliminary design of bridges subject to a wide class of costs.

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ESPAÑA RESUMEN Conforme los indicios del deterioro ecológ ico se hacen más evidentes , la evaluación del impacto sobre el ambiente de las distintas actividades humanas se vuelve más insoslayable. Aquí se analiza el relativo m érito de distintas formulaciones del coste fisico de la construccion : energía incorporada, coste exerg ético y coste material; tambi én la estructura del cost e fisico agregado, incluyendo la valoración relativa de sus t érminos más significativos. Como ejemplos concretos, se evalúa la energía y la materia incorporada por distintas funciones constructivas según el material empleado (tierra, acero , ladrillo, hormigón) . Finalm ente , se extraen algunas conclusiones acerca de las caracteris ücas de una futura construcción "sostenible ".Fechade recepción: 2-X-OO 113-54

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