Static structures (e.g. – buildings) – Compound curve structure – Geodesic shape
Patent
1995-09-01
1998-01-06
Canfield, Robert
Static structures (e.g., buildings)
Compound curve structure
Geodesic shape
52 811, 52639, 526521, 5274507, E04B 132, E04C 300
Patent
active
057041695
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention pertains to space trusses. More particularly, it pertains to structural truss arrangements composed of a plurality of stable modules which are efficiently interconnectible to define a truss system useful in diverse applications.
BACKGROUND OF THE INVENTION
While the present space truss has utility in structures of many kinds, it is described herein principally in the context of large span domes for which it first was conceived and developed. Following a description of the invention in that context, its application to other kinds of structures is discussed.
The owner of this invention (namely, Temcor of Carson, Calif., U.S.A.) has developed three kinds of light, strong, structurally efficient domes. In order of ascending range of spans practicable, they are the Geodesic Dome to which U.S. Pat. Nos. 3,026,651, 3,058,550, 3,063,519 and 3,194,360 are pertinent, the Polyframe Dome to which U.S. Pat. No. 3,909,994 is pertinent, and the Richter Dome to which U.S. Pat. Nos. 4,611,442 and 4,711,063, Canadian Patent 1,268,917 and U.K. Patent 2,194,735 are pertinent. The present space truss has utility in domes which use the design principles of Polyframe Domes.
As set forth in U.S. Pat. No. 3,909,994, the principal surface of a spherically curved dome, or that of a dome having other desired curvature, is triangulated over its surface to define triangular zones of substantially equal area, such zones being predominantly of preferably equilateral configuration. The dome surface is fully tiled by such triangular zones. The edges between adjacent zones in the actual dome are defined by structural strut members which preferably have cross-sections resembling those of I-beams. At the contiguous corners of the triangular zones, plural struts are interconnected at hub-like nodes; usually there are five or six struts connected at a node within the perimeter of the dome. The openings between the interconnected struts are closed by sheet metal closure panels which preferably are tensioned between the struts to which they are connected. The struts, node hubs and closure panels preferably are defined by similar metals which typically is aluminum.
Regardless of the structural system used to define them, domes are subject to varying extents to the troublesome phenomenon called "snap through." Snap through occurs when the loads on a dome become so great that the dome reverses curvature and becomes concave upwardly, rather than convex upwardly, over at least a portion of its area. Such loads can occur when natural loads, such a wind, snow or ice loads on the dome, when added to loads due to lights, scoreboards, sound equipment, climate control equipment, catwalks and the like suspended from the interior of the dome, reach critical levels. Snap through is a more serious problem in large diameter shallow (relatively low height) domes than it is in smaller diameter domes which are high relative to diameter. Shallow domes generally are preferred over higher domes. Domes become more resistant to snap through proceeding form the top of the dome to its perimeter where the dome structural elements are more vertical than they are at and adjacent to the top of the dome.
An obvious approach to preventing the occurrence of snap through in a dome is to make the structural members of the dome sufficiently strong to adequately resist and prevent snap through. That approach requires the use in the dome structure of struts of greater section modulus (i.e., depth) either throughout the dome or in the areas most susceptible to snap through. If stronger struts are used throughout the dome, substantial portions of the dome will be over-designed and the dome will be heavier and more costly than truly required to effectively deal with the problem of snap through. The use of stronger, i.e., deeper, struts can be confined to the portions of the dome which are most susceptible to snap through; that approach, however, has been found to require complicated and expensive hub structures at those places in the dome where stru
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Canfield Robert
Temcor
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