Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to an adaptable truss construction useful for
roof
trusses, wall studs, beams, lintels and floor joists and relates to novel
diagonal bracing
members used in said truss constructions. More specifically, the improved
truss
construction finds particular application in metallic light-weight structural
framing
systems and modular concrete forming.
(ii) Description of the Related Art
Open-web floor joists and roof rafters having wooden upper and lower wooden
chords joined at equispaced intervals by V-shaped metal diagonals are known.
The truss
construction has the advantage over solid wooden joists and rafters of
permitting utilities
such as plumbing, electrical wiring and ventilation ductwork to freely pass
through open
spaces in the trusses, whilst using up to thirty percent less material.
Light-weight structural framing systems comprised of solid metal channel and I-
beam studs and top and bottom horizontal tracks and bridging channels joined
by sheet
metal angle brackets and gussets using sheet metal screws or by tack welds are
also
known. The webs of the channel and I-beam joists are closed, necessitating the
costly
drilling or cutting of the webs by skilled workmen to allow utilities to pass
through.
E. J. W. Ragsdale, in U.S.patent number 1,924,881 discloses an open trussed
girder having hollow chords of generally channel form and three-sided hollow
web
members secured to the inner sides of said hollow chords portion by means of
integral
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extensions. The integral extensions are bent to fit against the corresponding
walls of the
hollow chords.
U.S. patent 3,152,671 issued to A. M. Mallory, Jr. teaches structural truss
members having C-shaped angular chord members carrying protruding end
attachment
plates. One embodiment describes truss members provided with upper and lower
spans,
each span comprising a plurality of segmental chords. The latter are C-shaped
in cross
section longitudinally disposed in end to end abutment to form the upper and
lower linear
spans of the trusses.
In U.S. Patent No, 5,761,873 issued to J. Slater, there is disclosed a web,
beam
and frame system for a building structure. The system comprises the load
bearing
members, i.e. beams, wherein each beam is assembled to include a pair of
hollow metal
chords of equal outer cross-section, and a metal web shaped to provide a pair
of jigs
which pre-locate the chords parallel to one another. Each web has a plurality
of holes for
installation of the fasteners therethrough and into the chords.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide novel metal truss
structures,
particularly for roof trusses, wall studs, beams, lintels and floor joists.
It is a further objective of the present invention to provide metal truss
structures
which may be rapidly and cost effectively assembled either at a factory
installation or at
a construction site.
In its broadest embodiment, the invention comprises at least two spaced-apart
elongate metal chord tubes having a U-shaped, open-sided cross-section which
chord
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tubes are interconnected by means of bracing members having particularly
angled
configurations and wherein said bracing members define a generally U-shaped
cross-
section having inwardly extending curved lips formed along the upper edges of
the side
walls thereof.
More particularly, the invention extends to a metal truss comprising a pair of
parallel, spaced apart, generally U-shaped elongate chord members each having
a
longitudinal axis, a plurality of alternating diagonal bracing members
securedly fastened
by means of fasteners within said chord members at predetermined intervals and
angles,
said diagonal bracing members having a generally U-shaped section consisting
of a
central web and depending side arms, each said side arm having an inwardly
extending
bent or curved lip portion, along the distal edges thereof, and said elongate
chord
members being maintained by said diagonal bracing members in a reinforced,
fixed,
rigid, spatial relationship one to another.
A more specific embodiment of the invention includes a metal roof truss
comprising a triangular array of parallel, spaced apart, generally U-shaped,
elongate
chord tube members and a plurality of bracing members alternatively positioned
between
and securely affixed by means of fasteners within said chord tubes, said
bracing members
being positioned between said chord members in a vertical orientation or a
diagonal
orientation, said bracing members having a generally U-shaped section and
forming
along the length of both side arms thereof at the outermost distal portion of
said side
arms, an inwardly extending bent or curved lip portion, said elongate chord
members
being maintained by said bracing members in a reinforced, fixed, rigid,
spatial
relationship one to another.
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In order to attain mechanical strength and transverse rigidity, in particular
resistance to deflection for floor joists and roof trusses, the diagonal
bracing members
preferably are bevelled and truncated at their ends and positioned in abutment
at junctions
of adjacent members within the chord tube channels.
A preferred embodiment of the invention for horizontal metal trusses, such as
floor joists, lintels and beams, comprises two spaced-apart parallel elongate
chord tubes
each having a U-shaped cross-section with a central web and depending side
walls
defining a longitudinal channel therebetween, with said longitudinal slots in
opposed
relation, a plurality of elongate bracing members each having a generally U-
shaped cross-
section with side walls terminating in inwardly bent or curved lips formed
along the distal
edges thereof, said elongate bracing members each having parallel bevelled end
surfaces
with a shallow blunt bearing surface perpendicular to the end surface at
opposite ends
thereof, said plurality of elongate bracing members being alternately
diagonally disposed
in a zigzag pattern between the chord tubes with the opposite ends of the
bracing
members inserted into the longitudinal slots of the chord tubes in abutment
with the
chord tube central webs and with the blunt bearing surfaces of adjacent
elongate bracing
members in abutment with each other, and fasteners for securing the bracing
members
to the elongate chord tubes.
Preferably, the fasteners are selected from spot welds, self tapping screws,
rivets,
and nut and bolt assemblies. The most preferred fastener would be a spot weld.
Advantageously, in providing in combination an open-ended , U-shaped chord
tube together with bracing members having a generally U-shaped cross-section
defining
an inwardly extending lip along the distal edge portion of the side walls of
the bracing
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member, the fasteners may be easily placed to secure said bracing members
within said
chord members, thus facilitating ease and thus cost effectiveness of
fabrication.
Furthermore, the metal trusses of the invention having diagonal bracing
members with
bevelled end surfaces and shallow blunt bearing surfaces in abutment with
adjacent
5 bracing members display unexpectedly high mechanical strength and rigidity
with
resistance to lateral deflection.
Description of the Drawings
The metal trusses of the invention and the related building system will now be
discussed by way of example, having reference to the accompanying drawings in
which:
Figure 1 is an elevational view of the overall building system of the present
invention showing an embodiment of truss construction;
Figure 2 is an enlarged, perspective view of a of a metal roof truss as used
in the building system of Figure 1;
Figure 3 is an enlarged elevational view of a wall stud as used in the
building system of Figure 1;
Figure 4 is an enlarged perspective view of a floor joist as used in the
building system of Figure 1;
Figure 5 is a detailed perspective view of an embodiment of bracing
member of the present invention;
Figure 6 is a perspective view of a preferred embodiment of the bracing
member of the present invention;
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Figure 7 is a side elevation of a floor truss incorporating the bracing
member shown in Figure 6;
Figure 8 is an enlarged elevation of the abutting bracing members shown
in Figure 7;
Figure 9 is a section taken along line 9 - 9 of Figure 6;
Figure 10 is an enlarged perspective view of the bracing member shown in
Figure 6;
Figure 11 is a side elevation thereof;
Figure 12 is a top plan view thereof;
Figure 13 is an end elevation taken at the left of Figure 10; and
Figure 14 is an end elevation taken at the right of Figure 10.
Descri,~tion of the Preferred Embodiment
Having reference to the accompanying drawings, there is generally depicted in
Figure 1 an overall building system 10 utilizing an embodiment of the bracing
members
12, 13 of the present invention. More specifically, the building system
illustrated
comprises roof trusses 14, wall studs 16 and floor joists or beams 18, which
may be
assembled at a factory or transported to a building site for assembly.
As typified in Figure 2, the metal roof truss 14 consists of formed, rolled or
extruded chord tubes 20, 22, 24 said chord tubes having a generally U-shaped
or channel-
shaped, open-ended cross-section. The chord tubes 20, 22, 24, are arranged in
a
conventional, triangular configuration being interconnected, reinforced and
secured in a
predetermined spacial relationship by means of bracing members 13, to be
described,
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positioned within the chord channels 26 and affixed therein by fasteners 28.
More
specifically, the bracing members 13 are orientated either as vertical members
30 or
diagonal members 32 in a predetermined spacial relationship and angularity. It
is to be
noted that the central vertical bracing member 30a is positioned at the apex
of the
triangle and the diametrically opposed, adjacent diagonal bracing members 32a
abut at
the base of the central vertical bracing member 30a. Sequentially positioned
diagonal
bracing members 32 and vertical bracing members 30 abut one another at either
upper
or lower chord tubes 20, 22 24 as exemplified in the aforementioned drawing.
As typified in Figure 3, the wall stud 16 consists of formed rolled or
extruded
parallel metal chord tubes 20, 22 having an open-ended, U-shaped cross-section
interconnected by means of a diagonal bracing member 12 positioned within the
chord
channels 26 and secured therein by means of fasteners 28. It is to be noted
that for the
wall studs 16 it is not a requirement that the diametrically opposed diagonal
bracing
members 12 abut one another within the chord channels 26 because the requisite
codes
for mechanical strength, torsional rigidity and deflection are less than for
roof trusses and
floor joists.
The floor joist 18 of the invention as depicted in Figure 4 consists,
similarly to
the wall stud 16, of parallel metal chord tubes 20, 22, having an open-ended,
U-shaped
cross-section interconnected by means of zigzag diagonal bracing members or
struts 12
positioned and secured within the chord channels 26 by fasteners 28.
In Figure 5, the bracing member 12 of the invention which may be used in wall
studs 16 is of an open-ended, generally U-shaped or channel-shaped cross-
section and
defines, along the length of the distal edges of side walls 34, an inwardly
extending, bent
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or curved lip 36 which provides reinforcement to said bracing member 12.
Although a
curved lip flange 36 is illustrated, it will be understood that lip 36 can be
an inwardly
extending flange perpendicular to or at an acute angle to side walls 34.
With reference now to Figures 6 - 8 and Figures 10 - 14, a preferred bracing
member 13 is illustrated wherein side walls 50 having inwardly facing flange
lips 52 are
reversely bevelled at opposite ends 54, 56 to define parallel bevelled end
surfaces 58, 60
respectively at a predetermined angle to the long axis of the bracing member
substantially
equal to the oblique angle defined between the bracing members 13 and chord
tubes 20,
22, shown in Figure 4.
The acute ends of bracing members 13 are truncated transversely to the end
surfaces 58, 60 to form shallow, blunt bearing surfaces 62, 64 perpendicular
to the said
end surfaces 58, 60. Apertures 65, 66 preferably are formed at ends 54, 56 to
facilitate
assembly with rivets or nuts and bolts.
Figures 7 and 8 illustrate the assembly of bracing members in a joist, lintel
or
beam 18 in an alternating or zigzag pattern. Each bracing member 13 abuts the
adj acent
bracing member 13 at opposing faces 64 at their lower ends 56 and at opposing
faces 62
at their upper ends 54 within the channel slots defined between side walls 68
of upper
chord 20 and between side walls 70 of lower chord 22. The end surfaces 58, 60
of the
bracing members 13 are in abutment with the interior surfaces of the webs 72,
74 of
chords 20, 22 respectively. It has been found that the provision of shallow
abutting faces
at the junction of the adjacent bracing members 13 in the trusses surprising
increases the
load capacity of the trusses with a minimum of fastening means at apertures
65, 66.
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The fasteners may be selected from self tapping metal screws, rivets, spot
welds
or nuts and bolts, or clinching. As is evident in the art, should rivets or
nut and bolt
assemblies be utilized, suitable holes must be formed in the chord tubes and
correspondingly in the bracing members for receiving the fasteners 28 (Figure
4).
In order to provide additional rigidity to the metal joist trusses, a block of
wood
or the like 40 (Figure 4) preferably is inserted at the outer ends of one or
both of the
chord tubes 20, 22.
Typical wall stud trusses 16 are formed of 18 to 26 gauge galvanized steel
chord
tubes, preferably 18 to 20 gauge for structural load-bearing walls and 20 to
26 gauge for
non-loading-bearing walls, 1.5" wide and from 3/4" to 2" deep interconnected
by 16 to
18 gauge galvanized steel bracing members 4" to 12" long at a diagonal angle
of 45°
using steel self tapping screws, rivets or by welds or by a nut and bolt
assembly. Floor
joist, lintels and beams 18, of the same material, preferably have an upper
compression
chord tube larger than the lower tension chord tube, e.g. 1.5" x 2.5" to 7.5"
upper chord
tube and 1.5" x 1.5" to 3" lower chord tube, typically 3.5" x 1.5" upper and
lower chord
tubes. Roof trusses may be fabricated of 1.5" x 1.5" upper and lower chord
tubes, 2.5"
x 2.5" upper and lower chord tubes, or 3.0" x 1.5" upper and lower chord
tubes,
depending upon the truss length and anticipated loading.
The present invention provides a number of important advantages. A floor
assembly consisting of the joist assembly shown in Figure 7 comprised of 16
gauge 1.5"
x 7" upper chord, 18 gauge 1.5" x 1.5" lower chord, joined by abutting 18
gauge 1.5" x
1.5" bracing members, all galvanized steel, the joists, at 18" lateral spacing
for 12' length,
supported a load of 2000 kilograms with a maximum deflection of only 4 mm.
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The trusses can be assembled in a factory by the use of mechanical connectors
or
by spot welding through the open side walls, or the trusses can be assembled
at the
building site by semi-skilled workmen. The trusses are suitable for use as
roof trusses,
studs, floor joists or lintels in conventional building construction, or for
use as beams in
combination with floor jacks in modular building construction for supporting
concrete
forms. The strength and rigidity of the joists with minimum vertical
deflection makes the
truss members particularly suited for concrete forming.
The open chord and bracing members permit the installation of services such as
electrical wiring and plumbing and the open concept facilitates installation
of ducting for
furnace and air conditioning systems.
It will be understood that modifications can be made in the embodiment of the
invention illustrated and described herein without departing from the scope
and purview
of the invention as defined by the appended claims.
