Cables, Rods, Castings & Machined Components
The use of tensile elements — primarily steel cables and rods — is a design strategy to dematerialize structure and enhance the transparency of building facades. Compression elements are frequently minimized or eliminated, and when present, are crafted from cast and machined components for an elegant expression of exposed structure. The fittings and components that tie these structural members together are similarly crafted.
Bridge engineer and builder John A. Roebling first manufactured wire rope in the United States during the 1840’s. These materials ultimately found their way into the vernacular of architecture through stunning works such as Mathew Nowicki’s Dorton Arena in 1952 and Eero Saarinen’s Ingalls Rink at Yale University in 1958. Structural glass facade designers have since embraced these same tensile materials as a means to minimize the structural profile of support systems. Wire rope composition, material type, finishes and end terminations are all important considerations in specifying these materials, which are available from a relatively limited number of manufacturers and specialty fabricators. Enclos has put many of these manufacturers through its rigorous qualification process, resulting in several exceptional vendor/partners that have successfully provided materials on various projects incorporating structural glass facade technologies.
The use of steel rods as a substitute for cables in the design of structural glass facades was a practice borrowed from the yacht racing industry, and popularized by I.M. Pei’s Louvre Pyramid in Paris. Rods are most commonly fabricated from ASTM A316 stainless steel because of the material’s combination of strength and corrosion resistance. In high-load applications, or when extremely thin profiles are desired, additional high strength stainless options exist. Rod terminations are often custom designed and refined, with the intent of minimizing or eliminating exposed threads, turnbuckle or other tensioning mechanisms. Rod fabrication typically involves slipping the end fittings over the rod and upsetting the rod ends through a process called cold-heading. Alternately, equally elegant threaded fittings have also been developed. Depending upon the design of a structure, cable systems can have significant advantages over rod systems, particularly with respect to cost. However, the refined appearance of a rod system is worth a premium to many clients.
Casting is an ancient process with a storied history in the construction industry, including the increase of low cost materials during the Industrial Revolution. Castings were used later to spectacular affect in the Gerberettes and components for the Center Georges Pompidou by architects Richard Rogers and Renzo Piano.
The casting of structural components demand a high level expertise in both the design and fabrication process. Cast nodes for the space frame structure on the Jacob K. Javits Convention Center in New York, for example, were famously discovered during construction to contain cracks, requiring the disassembly of nearly half of its structure and a project delay of almost two years. An intimate knowledge of the materials and processes of casting is critical to the development and implementation of a custom cast structural component. Among components appropriate for casting are spiders and glass-fixing devices, spacer struts and anchor assemblies. Various options for material and finish must be considered depending upon component design application.
In many respects, structural glass facade technologies are more closely akin to the automotive industry than conventional building construction: both are highly engineered and built to extreme tolerances, and their exposure adds an important visual element to system components. Despite the widespread pursuit of building facade transparency, many designers choose to express exposed structure in dramatic fashion, often at the expense of transparency. These factors and considerations combine to make machined components a frequent and effective choice. Enclos designs custom components or specifies off-the-shelf parts as appropriate, sourcing both from our network of vendor/partners.