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BUILDING EXTERIOR 63achieve a reasonable degree of physical and visual security. Althoughpedestrians can see through the glass panes between columns whenstanding directly in front of them, from oblique angles the columnedwallbecomes opaque.The architects’ goal ‘to create a building that possessed an unmistakableimage’ necessitated a creative approach to configuring the façade. 6 Severalsubtle geometric manipulations of the 17 m high columns transform apotentially repetitive façade into one comprising two columned planes,both angled inwards and one warped to achieve a dynamic visual effect.Beginning at the left-hand side of the embassy as seen from the street,vertical columns step back progressively from the pavement towardsthe entrance. To the right of the entrance, column bases lie on astraight-line between it and the corner of the building. However, theset-out line for the tops of the columns does not parallel the set-outline for their bases. From the right-hand corner of the building as seenfrom the street, the upper set-out line angles away from the columnbaseline below towards the street so that the top of the column closestto the entrance is located approximately 3 m in front of its base.This simple geometric variation between top and bottom set-out linescreates a warped surface, affecting the visual impact of the columnsprofoundly. As the eye moves relative to the columns, they also appearto move. An exquisite rough-chiseled finish to the white concretecolumns completes the structure’s positive visual contribution andreflects the embassy’s high quality design and construction.Structural scaleStructural scale strongly influences how exterior structure contributesaesthetically to a façade. The dimensions of structural members can lieanywhere on a continuum between the extremes of mesh-like finenessand massive monumentality. Several buildings, beginning with those utilizingsmall-scale structure, illustrate varied approaches to structural scale.Where steel is used most efficiently, in tension, members invariably fallinto the category of small scale – a consequence of sufficient strengthgained from minimal cross-sectional area. At the Cathédrale Nôtre Damede la Treille, Lille, a stainless steel rod-and-tube structure, reminiscent of aspider’s web, supports a new exterior nave wall (Figs 4.20 and 4.21). Thisdiaphanous steelwork contrasts with both the new post-tensioned stonearch needed to equilibrate the tension within the exposed steelwork, andthe cathedral’s original masonry structural elements. In this project, thedimensions of the exterior steel members were deliberately minimizedby pre-tensioning the steel. 7 Shadows from large structural members