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MARKET AT POLA DE SIERO [ 1929-1930 l
The market at Pola de Siero is indisputably lldefonso Sánchez del Río Pisón's most origina l work, a pioneer structure both for the compos ition of its architecture and its contribution to the development of large-scale reinforced concrete roofs. lts roof, with its ground leve l springing, defines the entire space enclosed by the building in one fe ll swoop. lt thus constitutes a "modern ist" approach to architectural space whose precedent, in this sole respect, was the dome over Centennial Hall built at Wroclaw, Poland to a design authored by Max Berg and engineers Willi Gehler and Günther Trauer. The building plan is an isosceles right-angle triangle, w ith the main fa<;:ade defined by the 100-metre long hypotenuse. lts volume is generated by the intersection of two perpendicular paraboloid cy lindri ca l barrel vaults, each of whose long axes is parallel to one of the two sides of the triangle. This spatial arrangement is remarkably simil ar to the stone ribbecl vau lts devisecl by Medieval master builders for Gothic cathedrals. The ingenuity of the clesign of this reinforcecl concrete ribbed roof, however, lies in the underlying geometry, wh ich sets it apart from Middle Age predecessors. The choice oí this shape enabled its author both to position ali the supports on the peri meter and to use his unique structura l design system, wh ich eschewed the complexity of dimensioning continuous surfaces by fragmenting the area to be roofed with arched ribs and filling the gaps between them with thin reinforced concrete severies. The result was a wholly open plan building covering an area of 3 000 square metres. One of the most origina l features of the roof is its diagonal arch wh ich, positioned at the intersection between the two barrel vaults, absorbs the imbalanced thrust generated by the unsymmetrical triangular plan. By adapting the shape of this (50-metre span) arch to the funicular load curve, Sánchez del Río generated a doub le intersection arch w ith a variable cross-section. That avo ided the change in geometry inherent in a single arch and the radical change in roof volume that such a so lution wou ld have entai led. Sánchez del Rio's ingenious arrangement was the fruit of an in-depth understanding of stab ility, acquired in his pursuit of the ability to build large reinforced concrete roofs without engaging in the sort of comp lex engineering that not on ly deviated widely from the simplicity of graph ic static design, but which in the nineteen twenties was neither wiclespread nor fully developed. As noted above, the three large reinforced concrete roofs that pioneered the modernist thin concrete shell venture were co ncluded in 1930. Although the spatial structure for the Pola de Siero market consists of thick arched ribs and no continuous shell-like member, it constituted a milestone in the development of large reinforced concrete roofs when this material was still in the earl iest stages of its international development.
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llDEfONSO SÁNCHEZ DEL RÍO PISÓN EL INGENIO DE UN LEGADO
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