The role of cables in large span spatial structures: introduction of recent space structures with cables in Japan

Abstract

The use of cables as structural members in large-span spatial structures is increasing. One reason for this is that from an architectural design perspective, these cables are light and provide an expanded impression of space, while smoothly curving cables create soft outlines. A second reason is that from a structural design perspective, these cables provide for the well-defined transmission of forces and rational layout of members in a structural system where members can be arranged so as to make the best use of their individual material properties. Cables are used in a variety of ways. In cable structures they are used as tensile members, and they help control member stress and deformation of frame structures. They enable systems to be constructed for balancing entire structural frames, and by applying tension to these cables, structural members can be made resistant to compression. This paper reports, by introducing several fine examples constructed recently in Japan, on the role of cables in typical applications where they are used to control frame structure deformation and structural member stress, or to form systems that balance entire structural frames. In the Miyagi General Gymnasium, which was completed in April 1997, horizontal thrust generated at the base of the continuous gable frames forming the large ridge roof is absorbed by tie cables. The cables are laid out on planar gable frames at each end of the roof, and the thrust is transmitted to the gables through planar bracing frames attached to the lower edge of the roof. In this design, cables not only form the system, they also actively control member stresses as a result of the tension applied to them. This system provides the structure with a self-balancing space for the entire structural frame. In the Saitama Arena, which is due to be completed in March 2000, one edge of the roof (160 m) is supported by a 130 m beam–string–structure employing cables to control deformation in structural frames and stress in the members. This is achieved by applying a tension of 3000 tons to the cables, matching the typical load applied to cables used in bridges. This system also provides the arena with a dynamic atmosphere of tension. The Sapporo Dome, due to be completed in March 2001, employs a non-conventional design in which the edge-ring of the dome is cut along an arc and a 90 m span bridge girder is inserted to link the cut ends of the ring to form a partially open structure. This turns the open dome into a dynamically closed structure by introducing tension into cables arranged within the girder.