Static structures (e.g. – buildings) – Openwork; e.g. – truss – trellis – grille – screen – frame – or... – Truss with unitary chord and web; e.g. – sheet metal
Patent
1994-09-02
1996-07-16
Friedman, Carl D.
Static structures (e.g., buildings)
Openwork; e.g., truss, trellis, grille, screen, frame, or...
Truss with unitary chord and web; e.g., sheet metal
527291, 527295, 527317, E04C 316
Patent
active
055355692
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to elongate structural members for use in load bearing frames comprising a reticulation of such members joined each to each. The inventive structural members are well adapted, but not exclusively so, for use in triangulated frames, that is to say frames wherein the rigidity of the frame as a whole results from the triangular arrangement of the members rather than from the rigidity of the joints between members.
The invention is concerned with members that are cold-formed from sheet metal, but, within that limitation has several aspects, namely the nature of the members themselves, the method of manufacture of the members, and the nature of joints between members in a frame. The invention also extends to structural frames assembled from members and/or utilizing joints in accordance with the relevant aspects of the invention.
BACKGROUND ART
Prior known elongate structural members that are cold-formed from sheet metal, for example, by rolling, folding or pressing a metal strip, have typically been essentially channel, Z or I sectioned. That is to say, they have usually comprised a web with flanges projecting from the edges of the web. The original strip which may, for example, be steel strip coated with zinc or an alloy of aluminium and zinc, is necessarily relatively thin, say two or three millimetres thick, to render it cold-formable, but the resultant light weight structural members are suitable for use in structures subjected to relatively modest stresses. For example, they find widespread use as the structural members of wall frames and roof trusses in dwellings, sheds, small commercial buildings and the like.
DISCLOSURE OF THE INVENTION
When the flanges of such structural members are subjected to axial compression, either directly or as a result of bending loads on the member, failure frequently originates from buckling of the flange's free edge remote from the web. Of course, other modes of failure may occur, for example the sudden collapse of a member functioning as a strut, if an adventitious bending lead causes displacement of a center portion of the member due to rotation thereof about the shear point of the member's section.
Generally speaking, the design of structural members becomes more exacting and critical as the thickness of the metal decreases. The lighter the gauge of the sheet metal the more likely is a catastrophic, progressive type failure originating in the unintended or excessive deflection of a small part of the section. On the other hand, it is desired to reduce the metal thickness as much as possible so as to reduce the material cost and the weight of the member.
Therefore, an object of the present invention is to provide a structural member of the kind under discussion that is made from light gauge sheet metal, no more than 1.2 mm thick, and which has a greater lead bearing capacity and is more stable under lead than conventional members of equivalent weight per unit length.
The building industry in respect of domestic housing and like buildings is very competitive and every effort is made to contain costs, both in regard to the structural members used and in the erection of prefabricated or other frames made from them. Thus, it is desirable that the members be suitable for manufacture by automatic and quick production processes, that their design be such that efficient use of material is achieved and that they lend themselves to simple on-site assembly by relatively unskilled labour.
Thus, another object of the invention is to provide a light gauge, cold-formed, sheet metal structural member that meets those desiderata.
The invention consists in a cold-formed, sheet metal, elongate structural member having a metal thickness not exceeding 1.2 millimetres, comprising a substantially planar web having two longitudinally extending edges, a first hollow flange extending along one edge and projecting laterally to both sides of the web, and a second hollow flange extending along the other and projecting laterally to one side only of the web.
REFERENCES:
patent: 518645 (1894-04-01), Crittenden
patent: 991603 (1911-05-01), Brooks
patent: 3083794 (1960-04-01), Stovall
patent: 3404496 (1968-10-01), Ballard
patent: 3646725 (1972-03-01), Troutner
patent: 3785108 (1974-01-01), Satchell
patent: 4881355 (1989-11-01), Bosl et al.
Field Peter R.
Golledge Brad F.
Hunt Peter J.
Seccombe Campbell J.
BHP Steel (JLA) Pty Ltd.
Friedman Carl D.
Jersen David
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