Exchange House in detail
1 Ø 195.7 mm pipe with clevis 2 Bolts, six per bearing plate 3 Web plate
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floor system loads flow from the floor to the column /hangers, then to the arch, and finally down to the bearings. Realisation A high degree of dimensional control and craftsmanship during fabrication and erection was required to realise the structural details in an aesthetically consistent manner. To that end, SOM structural engineers provided highly detailed, fully-engineered structural connec tion details that were painstakingly coordinated with the architectural design. In contrast, the connections in a conventional steel building are typically designed and detailed by the steel fabricator, and the exact configuration of the details is often not fully understood during the architectural design process. SOM engineers worked collaboratively with both SOM archi tects and the steel fabricators early in the design process, prior to bid, to determine a comprehensive system of tolerances for fabrication and erection and to ensure that structural details allowed the necessary access and adjustment to correct for distor tions, movements and errors. Every detail was reviewed with the fabricator and erector, then modified as needed to optimise construction and maintenance. The tied arch was erected on temporary shores, with adjustable jacks at each hanger acting as columns during erection. The shores were sup ported on the plaza structure, which was capa ble of supporting the steel and metal deck struc ture (excluding the floor slab concrete) up to the eighth floor – the level which would complete the arch (Fig. 3.17). Upon completion of the arch and tie system, the shores were removed by jacking up the entire structure at the eight sup ports by 50 mm. This operation ensured that load was removed from all shores simultan eously and that the arch was uniformly loaded. The continuation of the hangers below the pri mary tie (to allow temporary support) was inten tionally expressed as a remnant of the construc tion process.
To a layperson, the simplicity of the structural concept and clarity of the detailing may belie the high degree of design and craftsmanship required to realise Exchange House. The para doxical – but now commonly accepted – convic tion of Mies van der Rohe that “less is more” could be amended in the case of Exchange House to “less is more work”. Indeed, the suc cess of Exchange House is a testament to the perseverance of the design team. The engineer ing goal of a minimum-material, well-propor tioned and hierarchical structure was comple mented by the sparsely elegant architectural expression that takes its form and beauty from the underlying hierarchical organisation of the building. Exchange House represents the suc cessful transformation of a difficult engineering challenge into architectural expression, and exemplifies the SOM tradition of building designs in which architects and structural engineers can, by working together, produce an elegant solution.
3.16 AIA Twenty-five Year Award The Broadgate Exchange House has been selected for the 2015 AIA Twenty-five Year Award. Recognis ing architectural design of enduring significance, the Twenty-five Year Award of the American Institute of Architects is conferred on a building project that has stood the test of time by embodying architectural excellence for 25 to 35 years. Proj ects must demonstrate excellence in function, in the distinguished exe cution of their original programme, and in the creative aspects of their statement by today’s standards. Other SOM projects that won this award were Lever House, New York City (1980), Air Force Academy Cadet Chapel, Colorado Springs (1996), John Hancock Center, Chicago (1999), Weyerhaeuser Cor porate Headquarters, Federal Way (2001) and Hajj Terminal at King Abdulaziz Airport, Jeddah (2010).
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