Static structures (e.g. – buildings) – Machine or implement
Patent
1989-12-11
1991-01-22
Wilson, Neill R.
Static structures (e.g., buildings)
Machine or implement
52693, 52732, E04C 330
Patent
active
049860518
DESCRIPTION:
BRIEF SUMMARY
This invention relates to roof trusses and beams for use therein.
BACKGROUND ART
It is a common present-day practice to prefabricate the frames of domestic dwellings, and other houses and buildings, and preassembled roof trusses are in frequent use. The transport and handling of timber roof trusses sometimes incurs damage thereto as they are somewhat unstable before on site erection in a roof. For this reason, as well as to reduce the cost and/or increase the strength, efforts have been made to produce metal roof trusses. A recently developed metal roof truss now in use is often preferred to its timer predecessors. However, it is of hollow section and a welding operation is included in its production.
DISCLOSURE OF INVENTION
A principal object of the invention is to provide a metal roof truss and a principal beam therefor which are superior in strength and cheaper in production cost as compared with conventional timber and metal beams and trusses.
In accordance with the invention there is provide a structural beam for use as an upper chord in a roof truss and composed of rolled form metal strip material having in cross-section a shape including a plurality of longitudinally extending integral portions, said beam comprising a first roof batten-fixing portion, a pair of parallel portions beneath and substantially perpendicular to said first portion and spaced apart less than the width of said first portion, and providing means for connection of said chord to the upper end of one or more spaced web members, a pair of inclined portions interconnecting the upper ends of respective ones of said parallel portions to adjacent lateral edges of said first portion, a flange portion having an outer return flange and extending outwardly at substantially right angles from the lower end of each of said parallel portions, and longitudinally extending reinforcing ribs formed in said first portion and in each of said inclined portions, the design of said beam being such that with the application of excessive load upon the beam in its use as an upper chord of a roof truss breakdown of substantially all of said portions of the cross-sectional shape occurs simultaneously.
BRIEF DESCRIPTION OF DRAWINGS
The invention will be described in more detail with reference to the accompanying drawings, in which:
FIGS. 1 and 2 show in side elevation two forms of roof trusses that may be achieved by the present invention;
FIG. 3 shows an enlargement of detail "A" shown in FIG. 1;
FIG. 4 shows an enlargement of detail "B" shown in FIG. 1;
FIG. 5 shows an enlargement of detail "C" shown in FIG. 1; and FIG. 6 is a section, drawn to scale of the beam constituting the upper chord of the truss.
BEST MODE OF CARRYING OUT THE INVENTION
The principal aim of the invention being to reduce the cost, and increase the strength, of a roof truss, the invention has evolved in the following manner. A conventional metal beam presently in use with roof trusses has been analysed and found to be constructed from 300 Mpa mild steel strip material of 230 mm width and 0.9 mm thickness. The conventional beam has been approved by government authority to be of adequate strength for roof trusses such as shown in FIGS. 1 and 2, wherein the upper chord 10 is constituted by the beam of this invention and is supported from a lower chord 11 by web members 12. When erected upon a building the lower chord 11 spans wall frames (not shown) and is fixed thereon so that a load carried upon the upper chords 10, which are intended as roof batten fixing portions for the roof, are subjected to axial compressive force as well as bending moment where engaged by the web members 12. However, with adequate design to sustain axial compressive strain derived from the intended use it has been found that the bending moment can be ignored if conventional spacing of webs 12 is adhered to. 300 Mpa mild steel strip material of the same width, viz. 230 mm, but of a thickness of 0.7 mm was folded along longitudinal lines to a great many different cross-sectional shapes in which uninter
REFERENCES:
patent: 3029914 (1962-04-01), Macomber
patent: 3541749 (1970-11-01), Troutner
patent: 3686819 (1972-08-01), Atkinson
patent: 4141191 (1979-02-01), Aarons
Meyer Dolph A.
Sardjono Wyatmodjo
LandOfFree
Roof truss and beam therefor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Roof truss and beam therefor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Roof truss and beam therefor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1547131