Suspended Structures Suspended structures are used for long-span roofs. They are most effective if the curvature is compatible with spatial design objectives, and the horizontal thrust is resisted by a compression ring or by infrastructures, such as grandstands. Suspended cables effectively resist gravity load in tension, but are unstable under wind uplift and uneven loads. Under its own weight a cable assumes the funicular shape of a catenary (Latin for chain line). Under load uniformly distributed horizontally, the funicular will be parabolic; under point load the funicular is a polygon. Thus, without some means of stabilizing, cables assume different shapes for each load. Furthermore, under wind uplift suspended cables tend to flutter. Several means can be used to stabilize cables for variable loads and wind uplift. Among them are stabilizing cables, anticlastic (saddle-shaped) curvature, described later, and ballast weight. However, in seismic areas ballast weight would increase the mass and thus lateral loads. 1
Suspended roof with compression ring to absorb lateral thrust
2
Suspended roof with grandstands to resist lateral thrust
3
Catenary funicular under cable self weight
4
Parabolic funicular under horizontally distributed load
5
Polygon funicular under point load
6
Deformed roof under point load
7
Deformed roof under uneven load (snow at one side, for example)
8
Roof subject to wind uplift
9
Roof with convex stabilizing cables to resist uplift and uneven loads
10
Dead load to resist uplift and reduce deformation under uneven load
14-11
HORIZONTAL SYSTEMS
Tensile Resistant