POSTTENSIONED AND SHAPED HYPAR SPACE-TRUSSES

This paper describes a kind of innovative posttensioned and shaped hyp ar space truss characterized by an economical fabrication and construc tion process. The hypar truss, assembled initially in a planar square layout on the ground, is posttensioned at the short bottom chords at o ne diagonal. As a result, the top chords become curved and thereby a n onzero Gaussian curvature surface of a hypar space truss is shaped. A distinguishing feature of posttensioned and shaped hypar trusses, comp ared 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 scaffold ing. The essential aspects of shape formation are discussed and a smal l-scale posttensioned and shaped hypar is formed in this paper. Result s of experiment and nonlinear finite-element analysis indicate that, e ven within the yield limit of the members, a planar square layout can be deformed to a significant hypar shape by the proposed shape formati on method. Potentially, this procedure can offer economies over tradit ional construction methods.