This paper presents a simple strategy in order to search for the ideal shape of a generic variable section beam through algorithm-aided design; the latter makes it possible to interconnect the morphological requirements dictated by all the disciplines that contribute to the architectural / structural composition. At this aim, a specific optimization procedure is codified by Grasshopper software. The search for the minimum middle rise of the beam is posed as a single-objective optimization problem, while suitable architectural/geometrical constraints are considered for gaining the optimal shape. The dimensions and characteristics of the beam are taken from an existing structure (nowadays demolished), the BRAZIL PAVILION at the OSAKA Expo (1970) designed by Paolo Mendes da Rocha. The structure was characterized by an important structural span, that was covered by adopting advanced technological methods, shapes and materials.