Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
"HOLLOW FLANGE SECTION"
FIELD OF THE INVENTION
This invention relates to a hollow flange section and a method of
s making same. The invention also relates to a composite structural member
incorporating the hollow flange section.
BACKGROUND TO THE INVENTION
A diverse range of structural components have been developed in the
Io building industry over an extended number of years. The components
include joists, purlins, rafters and beams. Most of these components can be
formed in steel and include rolled hollow sections (R.S.), rolled steel joists
(RAJ), z-beams, C-sections and the like.
z-beams have been found useful in a wide range of applications
Is because of their relative ease of manufacture and structural efficiency in
load
bearing situations. Conventional z-beams (or universal beams) typically
consist of a pair of opposed parallel flanges joined by a single flat
intermediate web. In order to provide the required strength and resistance
to bending, the flanges are substantially thicker than the web.
2o Although useful, z-beams do have a number of disadvantages
including
(1 ) Exposed surface area to mass and strength ratios are high
which lead to increased costs for both corrosion protection and fire proofing;
(2) Flange widths to thickness ratios are generally limited to avoid
2s reductions in load bearing section capacity due to local buckling
considerations;
(3) Web widths to thickness ratios are generally limited to avoid
reductions in section load bearing capacity due to local buckling
considerations;
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(4) The hot rolling method of manufacture commonly used leads
to production of substantial mill scale and rust as well as providing a
limited
minimum thickness; and
(5) Prime painting during manufacture is not a practical
s proposition.
The applicants have developed an alternate structural member which
comprises a pair of hollow end sections and intermediate web characterised
in that each hollow end section is welded to the intermediate web so as to
form two weld lines or joins extending along the structural member. The
to structural member is described in detail in International Patent
Application
PCT/AU89/00313. This patent application also describes a number of prior
art structural members that are alternatives to conventional z-beams.
The known structural members are pre-formed and delivered to a
building site in set lengths. This can cause problems if long beams must be
is transported appreciable distances. There is advantage to providing modular
beams that can be more easily transported and assembled on-site.
A known approach to construction of composite structural members
is to knit together a number of beams welded to a pair of opposed angle
brackets at the top and bottom. In order to achieve sufficient strength a
2o complex web of struts and braces must be provided within each structural
member and between structural members.
An improved form of the basic design of a composite structural
member is disclosed in United States patent number 5644888 in the name
of Johnson. In the Johnson arrangement the angle brackets are replaced by
2s a hollow I-beam having a scalloped internal surface. The beams (or posts)
have complimentary surfaces that interlock with the 1-beam. The interfitting
elements form a complex post and brace structure. The disadvantage of the
Johnson arrangement is the complexity of the elements leads to expense in
manufacture and difficulty of assembly.
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An approach to solving this problem is the Davis truss described in
Australian Patent Numbers 230690 and 250131. The Davis truss is formed
from a CHS (circular hollow section) web that is captured between an
opposed parallet pair of decapitated coat hanger shaped flanges. The
s flanges are folded steel plate and therefore need to be particularly heavy
gauge in order to provide the required strength and resistance to skew. in
order to capture the web a lower portion of the CHS web is crushed so as to
form a neck which fits between the sides of the open mouth of the flange.
The Davis truss fails to achieve the properties necessary for an effective
to modular structural member.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a hollow flange
section useful in forming a composite structural member.
Is It is a further object of the invention to provide a composite structural
member incorporating the hollow flange section.
It is a yet further object to provide a method of making the hollow
flange section and composite structural member.
Further objects will be evident from the following description.
DISCLOSURE OF THE INVENTION
In one form, although it need not be the only or indeed the broadest
form, the invention resides in a hollow flange section comprising
a base member;
2s a pair of opposed cavity walls and a cavity base defining a cavity;
two opposing lateral support members extending from the base
member to the cavity walls such that each lateral support member forms an
enclosed volume with an adjoining one of the opposed cavity walls and an
adjoining portion of the base member;
wherein the cavity base and the base member form an integral
structure that resists skew deformation of the cavity.
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The cavity base may be a portion of the base member or may be a
separate element that is joined to the base member to form the integral
structure.
The enclosed volume may suitably be square or rectangular. In
s preference the lateral support members are linear and extend from the base
member at an angle to form enclosed volumes having a triangular cross-
section.
The angle between the base member and an adjoining lateral support
member is suitably in the range 20° to 45° and is most suitably
30°.
1o The cavity is suitably rectangular having parallel opposed walls and
an open mouth opposite the base. The size of the cavity is selected to suit
a web used to form a composite structural member.
In preference the hollow flange section comprises a unitary structure,
suitably manufactured of carbon steel.
Is The base member and the cavity base are preferably welded to form
an integral structure. The weld is preferably selected from the following :
high
frequency induction weld, metal inert gas weld, tungsten inert gas weld;
carbon dioxide shielded arc weld; atomic hydrogen gas weld, spot weld;
electron beam weld; laser weld or other suitable welding.
2o I n one form the lateral support members join the cavity walls at the top
of the cavity walls.
In another form the hollow flange section further comprises lugs
extending beyond an intersection of the lateral support member; and the
cavity walls. The lugs preferably terminate in a bead. In preference a
plurality
2s of apertures are formed in the lugs to facilitate fixing of a web to the
hollow
flange section for formation of a composite structural member.
In a further form, the invention resides in a process of forming a
hollow flange section comprising the steps of
passing a strip through a plurality of forming stations to successively
3o deform the strip to provide a cavity and a pair of substantially hollow
adjoining support volumes;
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further forming the deformed strip so that the base of the cavity
contacts a base member connecting the adjoining support volumes; and
welding the base of the cavity to the base member.
In preference the stations are roll forming stations.
s The process may suitably be performed in two phases. In the first
phase the strip is formed into a tube. In the second phase the tube is formed
into the hollow flange section.
The process may further include the step of forming lugs extending
beyond the adjoining support volumes. A further step of forming apertures
to in the lugs may also be included.
In a yet further form, the invention resides in a composite structural
member comprising
at least two opposed hollow flange sections, said hollow flange
sections comprising a base member; a pair of opposed cavity walls and a
is cavity base defrning a cavity; two opposing lateral support members
extending from the base member to the cavity walls such that each lateral
support member forms an enclosed volume with an adjoining one of the
opposed cavity walls and an adjoining portion of the base member; wherein
the cavity base and the base member are joined to form an integral structure
2o that resists skew deformation of the cavity; and
an intermediate web;
wherein the hollow flange sections are joined to opposing ends of the
intermediate web such that distal ends of the web are seated in a respective
cavity of the hollow flange section.
2s
BRIEF DETAILS OF THE DRAWINGS
To assist in understanding the invention preferred embodiments will
now be described with reference to the following figures in which
FIG 1 shows a perspective view of a first embodiment of a
3o hollow flange section;
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FIG 2 shows an end view of a composite structural
member
formed from an R.S.
web and a pair of
the flanges of FIG
1;
FIG 3 shows a perspective view of the composite
structural
member of FIG 2;
s FIG 4 shows a perspective view of a second embodiment
of
a hollow flange section;
FIG 5 shows an end view of a composite structural
member
formed from an R.S.
web and a pair of
the flanges of FIG
4;
FIG 6 shows a perspective view of the composite
structural
to member of FIG
5;
FIG 7 shows a flowchart of a roll forming process
for forming
the hollow flange
section;
FIG 8 shows an end view of a third embodiment
of a hollow
flange section;
is FIG 9 shows an end view of a fourth embodiment
of a hollow
flange section;
FIG 10 shows an end view of a fifth embodiment
of a hollow
flange section;
FIG 11 shows an end view of a sixth embodiment of a hollow
2o flange section;
FIG 12 shows an end view of a seventh embodiment of a hollow
flange section;
FIG 13 shows a graphical comparison of the bending capacity
of prior art joists compared to joists formed using hollow flange sections
2s according to the invention.
DETAILED DESCRIPTION OE,THE DRAWINGS
In the drawings, like reference numerals refer to like parts.
Referring to FIG 1 there is shown a hollow flange section 1 having a
3o base member 2 and opposing lateral support members 3. The lateral support
members 3 are separated by a cavity 4 having opposed cavity walls 5 and
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cavity base 6. The cavity base fi is welded to the base member 2. The lateral
support members 3, cavity walls 5 and base member 2 form opposing
enclosed volumes 7.
The cavity 4 is sized and shaped to receive web members for
s formation of a composite structural member as described in detail below with
reference to FIG 2.
The lateral support members 3 provide structural strength to the
flange 1 by supporting the cavity wails 5. The inventors have found that
between 20° and 45° is a suitable choice for the angle 6 between
the base
Io member 2 and the lateral support members 3. In the preferred embodiments
an angle of 30° is selected as being most appropriate. Smaller angles
do not
have sufficient enclosed volume to provide the required strength. Larger
angles require additional metal without improving performance.
A composite beam 8 can be formed by welding a web member 9
Is between opposing hollow flange sections 1, as shown in F1G 2. The flange
sections 1 are welded to the web 9 at 10. The resultant composite beam 8
can be used in situations previously requiring z-beams. The inventors have
conducted comparative tests between a conventional universal beam and
composite beams of the form shown in FIG 2. The following table shows that
2o equivalent strength is achieved at substantial reduction in mass.
Universal beam composite beam
material grade 300 plus grade 450
length 200mm 200mm
strength 1 1
2s mass 1 .81
Universal beam composite beam
material grade 300 plus grade 450
length 310mm 310mm
3o strength 1 1
mass 1 .77
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A composite structure incorporating the hollow flange section is shown
in FIG 3. The composite structure 11 comprises vertical beam members or
posts, such as 12, and inclined beam members or braces, such as 13,
assembled between a top flange 14 and a bottom flange 15. The beam
s members 11, 12 are welded to the flange sections 14, 15 in the manner
described above.
A substantial advantage of the composite structure of FIG 3 is the
reduced mass compared to prior art construction methods. Furthermore,
transport of components to a construction site is significantly easier since
the
Io structure can be assembled on-site rather than transported complete.
A further embodiment of a hollow flange section is shown in FIG 4.
The hollow flange section 21 comprises a base member 22 and opposing
lateral support. members 23. The lateral support members 23 are separated
by a cavity 24 having opposed cavity walls 25 and cavity base 26. The cavity
is base 26 is welded to the base member 22.
The cavity walls 25 extend beyond the lateral support members 23 to
provide lugs 27 terminating in beads 28. The lugs 27 facilitate mechanical
fixing of web 30 and flanges 21, as shown in FIG 5. Suitable forms of
mechanical fixing include TekT"" screws 31 and bolts 32. The hollow flange
2o section 21 may be made with pre-punched apertures to facilitate on-site
assembly of the structure 33 shown in FIG 6.
As with the embodiment of FIG 1 the lateral support members 23
provide support to the cavity walls 25 thereby giving structural strength to
the
flange 21. The combination of the lateral support members 23 and the weld
2s of the cavity base 26 to the base member 22 resists skew deformation of the
cavity 24.
The composite structure 33 has a similar construction to the
embodiment of FiG 3 and comprises vertical beam members or posts, such
as 34, and inclined beam members or braces, such as 35, assembled
3o between a top flange 36 and a bottom flange 37 The beam members 34, 35
are joined to the flange sections 36, 37 by bolts 38. For ease of assembly,
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apertures may be pre-formed in the flanges and beams.
The embodiments of FIG 1 and FIG 4 described above are
conveniently manufactured by roll forming a metal strip according to the
steps depicted in FIG 7. The step of forming a tube is optional since the
s hollow flange section can be formed directly from the strip. There may be
advantage in forming tube on a separate roll forming line prior to formation
of the hollow flange section.
After forming of the profile the base member and cavity base are
welded in a welding station. The formed hollow section then passes a
to finishing section where it is painted and cut to length, as required.
It will be appreciated that a different set of roll forming rollers will be
required for the embodiment of FIG 1 and the embodiment of FIG 4.
A third embodiment of the hollow flange section is shown in FIG 8.
This hollow flange section 40 can be conveniently formed by a similar
is process as described above. A flat strip or tube is rolled to form enclosed
volumes 41. The enclosed volumes are defined by the base member 42,
lateral support members 43 and cavity walls 44. The cavity 45 is defined by
the cavity base 46 and cavity walls 44. The cavity base 46 and base member
42 are welded at 47 to complete the hollow flange section. Other shapes for
2o the enclosed volume are also possible.
A fourth embodiment of the hollow flange section is shown in FIG 9.
The hollow flange section 50 is conveniently formed from a flat strip by the
process described above, although the optional step of tube forming is not
available. The flat plate is bent in a series of roll forming stations to tum
the
2s extremities over to form enclosed volumes 51: The enclosed volumes are
defined by the base member 52, lateral support members 53 and cavity walls
54. The cavity 55 is defined by the base member 52 and cavity walls 54.
Welds 56 complete the hollow flange section 50.
Welding of a terminating edge of a strip to a continuing face of a strip,
3o as required by weld 56 in FIG 9, has proven problematic. The preferred
method of welding two strip edges together is induction welding. However,
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induction welding is less successful for welding a strip edge to a strip face
due to dissipation of current and heat in the face. The inventors have solved
the problem by pre-heating the face.
The hollow flange section can also be formed from two components
s as shown in FIG 10. A hollow flange section 60 comprises a base
component 61 that is roll formed to make a base member 62 and lateral
support members 63. A separate cavity 64 is formed as a U section having
cavity walls 65 and cavity base 66. The base component 61 and cavity 64
are then welded at 67 to form the hollow flange section 60.
io Embodiments of the hollow flange section of FIG 4 can also be formed
from a flat plate. Two examples are shown in FIG 11 and FIG 12. In both
examples a flat plate is shaped in a series of roll forming stations and then
welded to complete a hollow flange section.
Composite structural components fabricated from two hollow flange
is sections and an interconnecting web provide better strength for mass
characteristics than existing components and therefore represent a
significant economic benefit for the building industry. The advantage of the
composite structural component is exemplified in FIG 13 which plots the
bending capacity of a standard joist and a joist utilizing the hollow flange
2o section for a range of standard joist sizes. As is clearly seen in the
plot, the
composite structural component always outperforms the conventional
component.
Throughout the specification the aim has been to describe the
preferred embodiments of the invention without limiting the invention to any
2s one embodiment or specific collection of features.
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