Posttensioned and Shaped Hypar Space Trusses
This paper describes a kind of innovative posttensioned and shaped hypar space truss characterized by an economical fabrication and construction process. The hypar truss, assembled initially in a planar square layout on the ground, is posttensioned at the short bottom chords at one diagonal. As a result, the top chords become curved and thereby a nonzero Gaussian curvature surface of a hypar space truss is shaped. A distinguishing feature of posttensioned and shaped hypar trusses, compared with conventional metal trusses, is that the shape formation and erection is completed by a simple posttensioning process, rather than by the traditional techniques involving the use of cranes and scaffolding. The essential aspects of shape formation are discussed and a small-scale posttensioned and shaped hypar is formed in this paper. Results of experiment and nonlinear finite-element analysis indicate that, even within the yield limit of the members, a planar square layout can be deformed to a significant hypar shape by the proposed shape formation method. Potentially, this procedure can offer economies over traditional construction methods.