U.S. patent application number 10/561185 was filed with the patent office on 2008-02-07 for an improved beam.
This patent application is currently assigned to Smorgon Steel LiteSteel Products Pty Ltd. Invention is credited to Ross John Bartlett, Ross Ian Dempsey, Alexander Noller, Russell Lambert Watkins, Keiji Yokoyama.
Application Number | 20080028720 10/561185 |
Document ID | / |
Family ID | 31954180 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080028720 |
Kind Code |
A1 |
Bartlett; Ross John ; et
al. |
February 7, 2008 |
An Improved Beam
Abstract
A hollow flange channel beam has a planar web with a pair of
narrow rectangular cross-section flanges extending along opposite
sides of said web and extending perpendicular to a face of said web
in the same direction. The section capacity is optimized when
Wf=(0.3)Db, Wf=(3.0)Df and WF=(30)t.
Inventors: |
Bartlett; Ross John;
(Beaudesert, AU) ; Dempsey; Ross Ian; (Calamvale,
AU) ; Watkins; Russell Lambert; (Coorparoo, AU)
; Noller; Alexander; (Springwood, AU) ; Yokoyama;
Keiji; (Funabashi, AU) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW, SUITE 300
WASHINGTON
DC
20005-3960
US
|
Assignee: |
Smorgon Steel LiteSteel Products
Pty Ltd
Port Melbourne
AU
|
Family ID: |
31954180 |
Appl. No.: |
10/561185 |
Filed: |
June 23, 2004 |
PCT Filed: |
June 23, 2004 |
PCT NO: |
PCT/AU04/00824 |
371 Date: |
March 1, 2007 |
Current U.S.
Class: |
52/846 |
Current CPC
Class: |
E04C 2003/0439 20130101;
E04C 3/292 20130101; E04C 3/07 20130101; E04C 2003/0473 20130101;
E04B 5/10 20130101; E04C 2003/0421 20130101; E04C 2003/023
20130101; Y10T 29/49634 20150115; E04C 2003/0413 20130101 |
Class at
Publication: |
52/726.2 |
International
Class: |
E04C 3/04 20060101
E04C003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 23, 2003 |
AU |
2003903142 |
Claims
1. A channel-shaped structural beam comprising: a planar elongate
web; and, hollow parallel sided flanges extending parallel to each
other perpendicularly from a plane of said web along opposite sides
thereof, said hollow flanges both extending in the same direction
away from one face of said web, said beam having a ratio of the
width of each said flange between opposite end faces thereof in a
direction perpendicular to said plane of said web and the depth of
said beam between opposite outer faces of said flanges in the ratio
of from 0.2 to 0.4.
2. The beam as claimed in claim 1 wherein the ratio of the width of
each said flange to the depth of said flange is in the range of
from 1.5 to 4.0.
3. The beam as claimed in claim 1 wherein the ratio of the width of
each said flange to the thickness of the web is in the range of
from 15 to 50.
4. The beam as claimed in claim 2 wherein the ratio of said width
of each said flange and the depth of each said flange is in the
range of from 2.5 to 3.5
5. The beam as claimed in claim 4 wherein the ratio of said width
of each said flange and said depth of each said flange is in the
range of from 2.8 to 3.2.
6. The beam as claimed in claim 1 wherein the ratio of the width of
each said flange to the depth of said beam may be in the ratio of
from 0.25 to 0.35.
7. The beam as claimed in claim 6 wherein the ratio of the width of
each said flange to the depth of said beam is in the range of from
0.28 to 0.32.
8. The beam as claimed in claim 3 wherein the ratio of the width of
the flange to the thickness of the web may be in the range of from
25 to 35.
9. The beam as claimed in claim 8 wherein the ratio of the width of
the flange to the thickness of the web is in the range of from 28
to 32.
10. The beam as claimed in claim 1 wherein said beam is
fabricated
11. The beam as claimed in claim 10 wherein said beam is fabricated
from high strength steel greater than 300 MPa.
12. The beam as claimed in claim 10 wherein said beam is fabricated
from stainless steel.
13. The beam as claimed in claim 1 wherein said beam is fabricated
from a planar web member with a hollow flange member continuously
welded along opposite sides of said web member, each said hollow
flange member having an end face lying substantially in the same
plane as an outer face of said web member.
14. The beam as claimed in claim 1 wherein said beam is fabricated
from a single sheet of steel.
15. The beam as claimed in claim 1 wherein said beam is fabricated
by a folding process.
16. The beam as claimed in claim 1 wherein said beam is fabricated
by a roll forming process.
17. The beam as claimed in claim 16 wherein free edges of said
hollow flanges are continuously seam welded to an adjacent web
portion to form closed hollow flanges.
18. The beam as claimed in claim 17 wherein said free edges of said
hollow flanges are continuously seam welded to said one face of
said web intermediate opposite edges of said web.
19. The beam as claimed in claim 17 wherein said free edges of said
hollow flanges are continuously seam welded along respective side
boundaries of said web.
20. The beam as claimed in claim 1 wherein said structural beam is
fabricated in a continuous cold rolling process.
21. The beam as claimed in claim 20 wherein said free edges of said
hollow flanges are continuously seam welded by a non-consumable
electrode welding process.
22. The beam as claimed in claim 14 wherein said free edges of said
hollow flanges are continuously seam welded by a consumable
electrode process.
23. The beam as claimed in claim 21 wherein said free edges of said
hollow flanges are continuously seam welded by a ERW process.
24. The beam as claimed in claim 1 wherein said structural beams
are fabricated from sheet steel having a corrosion resistant
coating.
25. The beam as claimed in claim 21 wherein said structural beams
are coated with a corrosion resistant coating subsequent to welding
of said free edges of said flanges.
26. The beam as claimed in claim 1 wherein said web includes
stiffening ribs.
27. The beam as claimed in claim 26 wherein the stiffening ribs
extend longitudinally of said web.
28. The beam as claimed in claim 26 wherein said stiffening ribs
extend transversely of said web.
29. The beam as claimed in claim 1 wherein each said flange
includes one or more longitudinally extending stiffening ribs.
Description
FIELD OF THE INVENTION
[0001] This invention is concerned with improvements in structural
beams.
[0002] The invention is concerned particularly, although not
exclusively, with a hollow flanged channel wherein opposed hollow
flanges along opposite sides of a web extend away from the web in
the same direction.
BACKGROUND OF THE INVENTION
[0003] Throughout history there has been an on-going quest by
engineers to develop cheaper and/or stronger structural members
such as beams or girders for all manner of structures including
buildings, bridges, ship structures, truck bodies and chassis,
aircraft and the like.
[0004] For several millennia timber was the primary source of
material for structural beams in buildings and bridges and the last
several centuries in particular have seen dramatic advancements
from timber to cast iron to wrought iron to mild steels and thence
to sophisticated steel alloys. Along with the advancement in
structural beam materials has gone improvements in fabrication
techniques and this, in turn, has permitted significant advances in
structural engineering. Throughout this period of change and
development in structural engineering, history has witnessed the
emergence of unique driving forces which have had a profound
influence on the nature and direction of these changes and
developments. These drivers have included labour costs, material
costs and, of more recent times, environmental issues.
[0005] United States Design Patents 27394 and 28864 illustrate
early forms of an I-beam and C-channel respectively while United
States Patent 426558 illustrates early forms of hollow flanged
beams, possibly made by a casting process.
[0006] Improvements in fabrication methods then led to structural
members of reduced mass whilst retaining structural performance.
U.S. Pat. No. 1,377,251 is indicative of a cold roll forming
process of a hollow flanged trough channel, while U.S. Pat. No.
3,199,174 describes a method of fabrication and reinforcement of
I-shaped beams by welding together separate strips of metal. U.S.
Pat. No. 4,468,946 describes a method for fabrication of a beam
having a lambda-shaped cross-section by bending a sheet of metal,
and U.S. Pat. No. 4,433,565 describes the manufacture by cold or
hot shaping of metal members having a variety of cross-sectional
shapes. U.S. Pat. No. 3,860,781 and Russian Inventor's Certificate
245935 both describe the automated fabrication of I-beams from
separate web, and flange strips fused together. U.S. Pat. No.
5,022,210 describes a milled timber beam having a solid central web
portion narrower than solid flanges extending along opposite sides
of the web.
[0007] Composite beam or truss structures fabricated from a
plurality of components are known to provide good strength to
weight ratios as illustrated in U.S. Pat. No. 5,012,626 which
describes an I-beam-like structure having planar flanges connected
to a transversely corrugated web. Other transversely corrugated web
beams are disclosed in U.S. Pat. Nos. 3,362,056 and 6,415,577, both
of which contemplate hollow flange members of rectangular
cross-section. Other transversely corrugated web beams with hollow
rectangular cross-section flanges are described in Australian
Patent 716272 and Australian Patent Application AU 1986-52906. A
method of fabrication of hollow flanged beams with corrugated webs
is disclosed in U.S. Pat. No. 4,750,663.
[0008] While the prior art is replete with structural members and
beams of widely varying configurations, a majority of such
structural members or beams have been designed with a specific end
use in mind although some are designed as general purpose beams to
replace say, a conventional hot rolled I-beam. U.S. Pat. No.
3,241,285 describes a hollow fabricated beam of thin austenitic
stainless steel which offers high strength to weight ratios and
lower maintenance costs than hot rolled I-beams in bridge building
applications. Another type of fabricated bridge girder known as the
"Delta" girder is described in AISC Engineering Journal, October
1964, pages 132-136. In this design, one or both of the flange
plates is stiffened by bracing plates extending the full length of
the beam on both sides between the flange plate(s) and the web.
[0009] U.S. Pat. No. 5,692,353 describes a composite beam
comprising cold rolled triangular hollow section flanges separated
by spaced wooden blocks for use as prefabricated roof and floor
trusses. United Kingdom Patent Application GB 2 093 886 describes a
cold rolled roofing purlin having a generally J-shaped
cross-section, while United Kingdom Patent Application GB 2 102 465
describes an I- or H-section beam rolled from a single strip of
metal. International Publication WO 96/23939 describes a C-section
purlin for use in a roof supporting building, and U.S. Pat. No.
3,256,670 describes a sheet metal joist having a double thickness
web with hollow flanges, the web and the flanges being perforated
to allow the joist to be incorporated into a cast concrete floor
structure.
[0010] U.S. Pat. No. 6,436,552 describes a cold roll formed thin
sheet metal structural member having hollow flanges separated by a
web member. This member is intended to function as a chord member
in a roof truss or floor joist.
[0011] The aforementioned examples of structural members or beams
represent only a small fraction of the on-going endeavours to
provide improvements in beams for a plethora of applications. The
present invention however, is specifically concerned with hollow
flanged beams of which an early example is described in United
States Patent 426558 mentioned earlier herein. The use of hollow
flanges to increase the flange section without adding mass is well
known in the art. Another early example of hollow flanged beams is
described in United States Patent 991603 in which the free edges of
triangular cross-section flanges are returned to the web without
welding to the web. Similar unwelded hollow flanged beams are
described in U.S. Pat. No. 3,342,007 and International Publication
WO 91/17328.
[0012] Hollow flanged I-beam-like structures, with fillet welded
connections between the flanges and the web are described in U.S.
Pat. No. 3,517,474 and Russian Inventor's Certificate 827723. An
extruded aluminium beam shown in Swedish Publication Number 444464
is formed with a ribbed planar web with hollow rectangular flanges
protruding from one web face, the hollow flanges being formed by
U-shaped extrusions which clip into spaced receiving ribs formed on
one face of the web.
[0013] U.S. Pat. No. 3,698,224 discloses the formation of H- and
I-beams and a channel section with hollow flanges by deforming
welded seam steel tubing to form a double thickness web between
spaced hollow flanges.
[0014] U.S. Pat. Nos. 6,115,986 and 6,397,550 and Korean Patent
Application KR 2001077017 A, describe cold roll formed thin steel
structural members having hollow flanges with a lip extending from
each flange being secured against the face of the web by spot
welds, rivets or clinches. The beams described in U.S. Pat. Nos.
6,115,986 and 6,397,550 are employed as wall studs which enable
cladding to be secured to the hollow flanges by screws or
nails.
[0015] British Patent No GB 2 261 248 describes hollow flanged
torsion resistant ladder stiles formed by extrusion or cold roll
forming.
[0016] U.S. Pat. No. 6,591,576 discloses a hollow flanged channel
shaped structural member with a cross-sectionally curved web shaped
by press forming to produce a longitudinally arcuate bumper bar
reinforcing member for a motor vehicle.
[0017] While most of the hollow flanged structural members
described above were fabricated with a closed flange with an
unfixed free edge or otherwise disclosed a fixed free edge by
welding or the like in a separate process, U.S. Pat. No. 5,163,225
described for the first time a cold rolling process wherein free
edges of hollow flanges were fixed to the edges of the web in an
in-line dual welding process. This beam was known as the "Dogbone"
(Registered Trade Mark) beam and possessed hollow flanges of
generally triangular cross-section. U.S. Pat. No. 5,373,679
describes a dual welded hollow flange "Dogbone" beam made by the
process of U.S. Pat. No. 5,163,225. Such was the performance for
price offered by these beams that a low mass thinner sectioned hot
rolled universal beam was introduced into the market to counter the
perceived threat to conventional universal beams of I- or
H-cross-section.
[0018] Further developments of the dual weld "Dogbone" process
described in U.S. Pat. No. 5,163,225 were disclosed in U.S. Pat.
No. 5,403,986 which dealt with the manufacture of hollow flange
beams wherein the flange(s) and the web(s) were formed from
separate strips of metal as distinct from a single strip of metal
in U.S. Pat. No. 5,163,225. A further development of the multiple
strip process for forming hollow flange beams was described in U.S.
Pat. No. 5,501,053 which taught a hollow flange beam with a slotted
aperture extending longitudinally of at least one flange to permit
telescopic engagement of a flange of one hollow flange beam within
a hollow flange of an adjacent beam for use in structural
applications as piling, walling, structural barriers or the
like.
[0019] A still further development of the dual welding "Dogbone"
process is described in Australian Patent 724555 and United States
Design Patent Des 417290. A hollow flange beam is formed as a
channel section to act as upper and lower chords of a truss beam
with a fabricated web structure secured in the channelled recess in
the chord members.
[0020] While generally superior to other hollow flange beams of
similar mass, the hollow flange "Dogbone" beams suffered a number
of limitations both in manufacture and in performance. In a
manufacturing sense, the range of sizes of "Dogbone" beams
available from a conventional tube mill was limited at a lower end
by the proximity of inner mill rolls and otherwise limited at a
larger end by the size of the roll stands. While "Dogbone" beams
generally exhibited increased capacity per unit mass or per unit
cost when compared to conventional "open" (unwelded) hollow flange
beams or conventional angle sections, I-beams, H-beams and
channels, they also exhibited a surprisingly high torsional
rigidity and thus a resistance to flexural (lateral) torsional
buckling over longer lengths. These hollow flange beams failed due
to a unique lateral distortional buckling mode of failure not found
in other similar products. Similarly, while the sloping inner
flange faces provided an excellent deterrent for avian and rodent
pests in some structural applications, the capacity for the flange
to resist local bearing failure was less than other beams such as
l-beams due to flange crushing. Additionally, special attachment
fittings were required because of the cross-sectional shape.
[0021] Conventionally, the selection of a structural beam for use
in a structure was usually made by an engineer after reference to
standard engineering tables to ascertain section efficiencies and
load bearing capacity in a range of readily available "standard"
beams such as laminated timber, hot rolled H-, L- or I-beams and
channels, cold rolled beams such as C-, Z-, J-shaped purlins or the
like. The higher the value of bending capacity per unit mass, the
more efficient the section. This value measures the performance per
unit cost thus allowing a comparison of cost efficiencies of
various beams by taking into account the cost per unit mass for
each product.
[0022] Where special performance requirements are demanded of a
beam, cost or cost efficiency may be governed by other factors and
often this is the impetus to design a special purpose beam for a
specific application. Otherwise, as the prior art so clearly
demonstrates, there has been and there continues to be an on-going
quest to produce more cost effective general purpose beams having
greater section efficiencies than widely used conventional general
purpose timber laminate beams, hot rolled I-, L- and H-beams, hot
rolled channels and cold rolled purlin beams of various
cross-sectional shapes. The fact that few, if any of the plethora
of prior art "improvements" has been adopted for widespread use is
probably due to an inability to combine both general cost
efficiency with general section efficiency.
[0023] The assignee of the present invention, is successor in title
to the "Dogbone" dual weld hollow flange beam inventions and has
conducted an exhaustive survey into actual costs of incorporating a
"Dogbone"-type beam into a structure with a view to designing a
hollow flange dual welded cold rolled general purpose beam which,
between manufacture, handling and transportation and ultimate
incorporation in a structure, was more cost effective in a holistic
sense than any of the prior art conventional general purpose beams
which otherwise overcame several recognized disadvantages in the
"Dogbone" beam, namely, connectivity and a capacity for flange
crushing with localized loads.
[0024] A conjoint research methodology was developed to measure the
individual product attribute utility for various beam profiles with
builders, engineers and architects. These key attributes were then
assigned values to produce a utility rating from which a customer
value analysis for various types of beams could enable a direct
comparison based on many product attributes other than merely
cost/unit mass and section efficiency. From this customer value
utility analysis, a range of dual welded hollow flange beam
configurations in both mild steel and thin gauge high strength
steel were devised as potential replacements for hot rolled steel
beams such as I- and H-beams and hot rolled channel as well as
laminated timber beams.
[0025] Among the many attributes considered in relation to hot
rolled steel beams, connectivity and cost of handling with cranes
were significant issues. U.S. Pat. No. 6,637,172, which describes a
clip to enable attachment to the flanges of hot rolled structural
beams, is indicative of the connectivity problems of such beams. As
far as timber was concerned, dwindling availability, length
availability, termites, straightness, and weather deterioration
were significant factors which adversely affected customer value
analyses.
[0026] Accordingly, it is an aim of the present invention to
overcome or alleviate at least some of the disadvantages of prior
art general purpose structural beams and to provide a structural
beam of greater overall customer utility than such prior art
general purpose structure beams.
SUMMARY OF THE INVENTION
[0027] According to one aspect of the invention there is provided a
channel-shaped structural beam comprising:
[0028] a planar elongate web; and,
[0029] hollow parallel sided flanges extending parallel to each
other perpendicularly from a plane of said web along opposite sides
thereof, said hollow flanges both extending in the same direction
away from said plane of said web, said beam characterized in that a
ratio of the width of each said flange between opposite end faces
thereof in a direction perpendicular to said plane of said web and
the depth of said beam between opposite outer faces of said flanges
is in the ratio of from 0.2 to 0.4.
[0030] Preferably, the ratio of the width of each said flange to
the depth of each said flange is in the range of from 1.5 to
4.00.
[0031] Suitably, the ratio of the width of the flange to the
thickness of the web is in the range of from 15 to 50.
[0032] If required, the ratio of said width of each said flange and
the depth of said flange is in the range of from 2.5 to 3.5.
[0033] Preferably, the ratio of said width of each said flange and
said depth of each said flange is in the range of from 2.8 to
3.2.
[0034] The ratio of the width of each said flange to the depth of
said beam may be in the ratio of from 0.25 to 0.35.
[0035] Preferably, the ratio of the width of each said flange to
the depth of said beam is in the range of from 0.28 to 0.32.
[0036] If required, the ratio of the width of the flange to the
thickness of the web may be in the range of from 25 to 35.
[0037] Preferably the ratio of the width of the flange to the
thickness of the web is in the range of from 28 to 32.
[0038] Suitably, said beam is fabricated from steel.
[0039] Preferably, said beam is fabricated from high strength steel
greater than 300 MPa.
[0040] If required, said beam may be fabricated from stainless
steel.
[0041] The beam may be fabricated from a planar web member with a
hollow tubular member continuously welded along opposite sides of
said web member to form hollow flanges, each said hollow flange
having an end face lying substantially in the same plane as an
outer face of said web member.
[0042] Preferably, said beam is fabricated from a single sheet of
steel.
[0043] If required, said beam may be fabricated by a folding
process.
[0044] Alternatively, said beam may be fabricated by a roll forming
process.
[0045] Suitably, free edges of hollow flanges are continuously seam
welded to an adjacent web portion to form closed hollow
flanges.
[0046] Said free edges of said hollow flanges may be continuously
seam welded to said one face of said web intermediate opposite
edges of said web.
[0047] Alternatively, said free edges of said hollow flanges may be
continuously seam welded along respective side boundaries of said
web.
[0048] Most preferably, said structural beam is fabricated in a
continuous cold rolling process.
[0049] Suitably, said free edges of said hollow flanges are
continuously seam welded by a non-consumable electrode welding
process.
[0050] Alternatively, said free edges of said hollow flanges are
continuously seam welded by a consumable electrode process.
[0051] Preferably, said free edges of said hollow flanges are
continuously seam welded by a high frequency electrical resistance
welding or induction welding process.
[0052] If required, said structural beams may be fabricated from
sheet steel having a corrosion resistant coating.
[0053] Alternatively, said structural beams may be coated with a
corrosion resistant coating subsequent to welding of said free
edges of said flanges.
[0054] If required, said flange may include one or more stiffening
ribs.
[0055] Suitably, said web may include stiffening ribs.
[0056] The stiffening ribs may extend longitudinally of said
web.
[0057] Alternatively, the stiffening ribs may extend transversely
of said web.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] In order that the present invention may be more fully
understood and put into practical effect, reference will now be
made to preferred embodiments of the invention illustrated in the
accompanying drawings in which:
[0059] FIG. 1 shows a typical configuration of a structural beam
according to the invention;
[0060] FIG. 2 shows schematically a cross-sectional view of the
hollow flange beam of FIG. 1;
[0061] FIG. 3 shows schematically an alternative embodiment of a
fabricated beam;
[0062] FIG. 4 shows a further embodiment of a fabricated beam;
[0063] FIG. 5 shows one configuration of a cold roll formed beam
according to the invention;
[0064] FIG. 6 shows an alternative configuration of a roll formed
beam according to the invention;
[0065] FIG. 7 shows graphically a comparison of section capacity
for HFC (Hollow flange channels) according to the invention; UB
(Hot rolled Universal beam of I-section), LUB (Low mass hot rolled
Universal beams of I-cross-section); PFC (Hot rolled channels), CFC
(Cold rolled C-sections), and HFB (Hollow flange beams of "Dogbone"
configuration i.e., triangular section flanges) where the effective
beam length=0;
[0066] FIG. 8 shows graphically the moment capacity of the same
sections where length=6.0 metres;
[0067] FIG. 9 shows schematically the configuration of a roll
forming mill;
[0068] FIG. 10 shows schematically a flower sequence for direct
forming a beam according to one aspect of the invention;
[0069] FIG. 11 shows schematically a flower sequence for forming
and shaping a beam according to another aspect of the
invention;
[0070] FIG. 12 shows schematically a cross-sectional view through
the seam roll region 17 of the welding station 12;
[0071] FIG. 13 shows schematically a cross-sectional view though
the squeeze roll region 18 welding station 12 at the point of
closure of the flanges;
[0072] FIG. 14 shows schematically a forming station;
[0073] FIG. 15 shows schematically a drive station;
[0074] FIG. 16 shows schematically a configuration of shaping rolls
in a shaping station;
[0075] FIGS. 17-21 illustrate the flexibility of beams according to
the invention;
[0076] FIG. 22 shows a hollow flanged beam with a reinforced flange
and a reinforced web; and
[0077] FIG. 23 shows an alternative embodiment of FIG. 22.
[0078] Throughout the drawings, where appropriate, like reference
numerals are employed for like features for the sake of
clarity.
DETAILED DESCRIPTION OF THE DRAWINGS
[0079] In FIG. 1, the beam 1 comprises a central web 2 extending
between hollow flanges 3 having a rectangular cross-section. The
opposite sides 4,5 of each flange 3 are parallel to each other and
extend away from web 2 in the same direction perpendicular to the
plane of web 2. End faces 6,7 of flanges 3 are parallel to each
other and end face 6 lies in the same plane as web 2.
[0080] FIG. 2 shows a cross-sectional view of the beam of FIG. 1 to
demonstrate the relationship between the width Wf of the flanges 3,
the depth Df of the flanges, the depth Db of the beam and the
thickness t of the steel from which the beam is fabricated.
[0081] In devising the shape of the hollow flange channel according
to the invention, advantage was taken of the capacity to employ
higher strength (350-500 MPa) steel than the 250-300 MPa grade
typically employed in current hot rolled beams. From the outset
this permitted the use of lighter gauge steels to create low mass
beams. A difficulty then confronted was the greater tendency of
light gauge cold rolled beams to undergo a variety of buckling
failure modes and this range of buckling failure modes in turn gave
rise to a selection of conflicting solutions in that while one
structural proposal reduced one failure mode it frequently
introduced another failure mode. For example, by shifting the mass
of the flanges away from the neutral axis of the beam differing
buckling modes of failure were introduced. With these conflicts in
mind, a hollow flange channel section as shown in FIGS. 1 and 2 was
devised as a chosen compromise and it has been determined that
optimum section efficiencies are obtained when
[0082] Wf=(0.3)Db,
[0083] Wf=(3)Df, and,
[0084] Wf=(30)t.
[0085] Although optimum sectional efficiencies are desirable, it is
recognized that there will be instances where some variation will
be required as a result of rolling mill constraints, end user
specific dimensional requirements and the like. In this context,
quite good section efficiencies can be retained with flange width
ratios in the ranges
[0086] Wf=(0.15-0.4)Db,
[0087] Wf=(1.5-4.0)Df, and,
[0088] Wf=(15-50)t.
[0089] FIG. 3 shows schematically a structural beam according to
the invention wherein the beam 1 is fabricated from separate web
and flange elements 2,3 respectively. Web 2 is continuously seam
welded along its opposite edges to radiussed corners 3a at the
junction between sides 5 and end faces 6.
[0090] Weld seam 8 may be formed in a continuous operation by high
frequency electrical resistance or induction welding.
Alternatively, in a semi-continuous operation, the weld seam 8 may
be formed utilizing a consumable welding electrode in a MIG, TIG,
SMAW, SAW GMAW, FCAW welding process laser or plasma welding or the
like. Where a semi-continuous consumable welding electrode process
is utilized, it is considered that a post welding rolling or
straightening process may be required to remove thermally induced
deformations. The continuous weld seam 8 is a full penetration weld
which creates an integrally formed planar web member 2 extending
between outer sides 4 of flanges 3.
[0091] Whilst semi-continuous fabrication is quite inefficient
compared with a continuous cold rolling process, it may be cost
efficient for a short run of a specially dimensioned non-standard
beam. In addition, fabrication of a beam from separate preformed
web and flange elements permits the use of elements of differing
thickness and/or strength. For example, such a beam may comprise
flanges of a thick high strength steel and a web of thinner lower
grade steel.
[0092] FIG. 4 shows an alternative process for fabrication of
discrete beam lengths by shaping the hollow flanged beam from a
single strip of metal by folding in a press brake or the like (not
shown).
[0093] Typically, a closed flange may be formed by progressively
folding side 5 relative to end face 7, then folding end face 7
relative to side 4 and then finally folding side 4 relative to web
2 until a free edge 5a contacts an inner surface 2a of the
channel-like beam so formed. A full penetration weld seam 8 is then
formed between free edge 5a and web 2 to form a unitary structure,
again with a continuous planar web member 2 extending between outer
sides 4 of flanges 3.
[0094] FIG. 5 shows one configuration of a beam according to the
invention when made by a continuous cold rolling process, which
process is preferred because of its high cost efficiency and the
ability to maintain small dimensional tolerances to produce beams
of consistent quality.
[0095] In this embodiment, the end faces 7 of hollow flanges 3 are
formed as radiussed curves. The section efficiency of this
configuration is inferior to a rectangular cross-section flange
although there may be applications for this cross-sectional
configuration.
[0096] Alternatively, it may be shaped further to form a flat end
face with radiussed curves.
[0097] A full penetration weld seam 8 is formed between the free
edges 5a of sides 5 and an inner surface 2a of web 2 by a high
frequency electrical resistance or induction welding process as
described generally in U.S. Pat. No. 5,163,225. The resultant beam
is an integrally formed member which relies upon the ability to
transmit load between outer flange sides 4 via a continuous web
element 2 extending therebetween.
[0098] FIG. 6 illustrates an alternative technique for forming a
cold rolled beam according to the invention.
[0099] In this embodiment a free edge 6a of end face 6 of hollow
flange 3 is welded to the radiussed junction 10 between web 2 and
side 5 by high frequency electrical resistance or induction welding
to form a full penetration weld seam 8 which effectively creates a
substantially continuous planar outer surface 2b of a load bearing
element comprising end faces 6 and web 2 whereby the load bearing
element extends between outer flange sides 4.
[0100] FIGS. 7 and 8 show respectively section capacity and moment
capacity in bending where L=6.0 metres. The lack of smoothness in
the curves for all but hot rolled channel sections arises from the
selection of a variety of web depths and flange widths which
manifests with overlapping values for each section on an increasing
mass based axis.
[0101] Based on a simple capacity vs. mass basis, it readily can be
seen that hot rolled universal beams (UB), low mass universal beams
(LUB) and hot rolled channels (PFC) are quite inferior to cold
rolled C-shaped purlin sections (CFC) and hollow flanged (HFB)
beams such as the "Dogbone" beam with triangular-shaped flanges and
the hollow flange channels (HFC) according to the present
invention.
[0102] The size ranges selected for the comparison are shown in
Table 1.
TABLE-US-00001 TABLE 1 Section Web (min) Web (max) HFC 125 mm 300
mm UB/LUB 100 mm 200 mm PFC 75 mm 250 mm CFC 100 mm 350 mm HFB 200
mm 450 mm
[0103] The graphs clearly illustrate the superior section capacity
of the HFC hollow flange channel over all other comparable beams
and exhibits superior moment capacity over longer lengths.
[0104] When the conjoint analysis ratings are then applied to the
sections evaluated, the attributes of the hollow flange channel
over the compared standard sections generate a utility rating which
is surprisingly superior to the UB and LUB hot rolled I-beams and
the HFB triangular hollow flange "Dogbone" beams.
[0105] For example, in the comparison of attribute values in Table
2 for UB hot rolled I-beams and HFC cold rolled channels according
to the invention, the aggregated utility scores for the HFC beam
were about 2.5 times that of the UB hot rolled I-beam at a 60%
price premium over the UB hot rolled beam.
TABLE-US-00002 TABLE 2 ATTRIBUTE CLASS ATTRIBUTE Options Price
Pre-Coatings Finishing Weld Appearance Beam Flange Length
Availability Inherent Services through beam Connectivity to
fixtures and fittings Connectivity to steel Connectivity to timber
Resources to handle.
[0106] Table 3 represents a utility value comparison with laminated
timber beams wherein the aggregate utility value of HFC hollow
flange channels according to the invention were about 2.5 times
that of the laminated timber beams.
TABLE-US-00003 TABLE 3 ATTRIBUTE CLASS ATTRIBUTE Options Price
Finishing Length Availability Beam Profile Inherent Termites Member
straightness Weather Deterioration
[0107] FIG. 9 shows schematically a typical configuration of a roll
forming mill which may be employed in the manufacture of hollow
flange beams according to the invention and as exemplified in FIGS.
5 and 6. Simplistically, the mill comprises a forming station 11, a
welding station 12 and a shaping station 13.
[0108] Forming station 11 comprises alternative drive stands 14 and
forming roll stands 15. Drive stands 14 are coupled to a
conventional mill drive train (not shown) but instead of employing
contoured forming rolls to assist in the forming process, plain
cylindrical rolls are employed to grip steel strip 16 in a central
region corresponding to the web portion of the resultant beam. The
forming roll stands 15 are formed as separate pairs 15a,15b each
equipped with a set of contoured rollers adapted to form a hollow
flange portion on opposite sides of the strip of metal 16 as it
passes through the forming station. As the forming roll stands
15a,15b do not require coupling to a drive train as in conventional
cold roll forming mills, forming roll stands 15a,15b are readily
able to be adjusted transversely of the longitudinal axis of the
mill to accommodate hollow flange beams of varying width.
[0109] When formed to a desired cross-sectional configuration, the
formed strip 16 enters the welding station 12 wherein the free
edges of respective flanges are guided into contact with the web at
a predetermined angle in the presence of a high frequency
electrical resistance or inductor welding (ERW) apparatus. To
assist in location of the flange edges relative to a desired weld
line, the formed strip is directed through seam guide roll stands
17 into the region of the ERW apparatus shown schematically at 17a.
After the flange edges and the weld seam line on the web are heated
to fusion temperature, the strip passes through squeeze roll stands
18 to urge the heated portions together to fuse closed flanges. The
welded hollow flange section then proceeds through a succession of
drive roll stands 19 and shaping roll stands 20 to form the desired
cross-sectional shape of the beam and finally through a
conventional turk's head roll stand 21 for final alignment and
thence to issue as a dual welded hollow flange beam 22 according to
the invention. The high frequency ERW process induces a current
into the free edges of the strip and respective adjacent regions of
the web due to a proximity effect between a free edge and the
nearest portion of the web. Because the thermal energy in the web
portion is able to dissipate bi-directionally compared with a free
edge of the flange, additional energy is required to induce
sufficient heat into the web region to enable fusion with the free
edge.
[0110] Hitherto it was found that by using conventional roll
forming techniques and an ERW process, the quantity of energy
required to heat the web portion to fusion temperature is such as
to cause the free edge of the flange to become molten and be drawn
outside a desired weld seam line. As a result of this strip edge
loss, the cross-sectional area of the flange was reduced
significantly and control of the strip edge into the weld point
became more difficult.
[0111] It has now been discovered that the aforementioned
difficulties can be overcome by aligning the free edge of the
flange with the intended weld line as it is heated and then urging
the free edge of the strip into contact with the heated web region
along a straight pathway in a direction corresponding to a desired
angle of incidence between the web portion and the region of flange
edge in the vicinity of the weld seam. This technique also confers
an additional advantage in that in the subsequent shaping process,
the weld seam is not stressed by shaping as the angle of incidence
between the web portion and the region of flange edge adjacent
thereto is chosen to correspond with a final cross-sectional web
shape. By guiding the free edge of the flange edge along this
predetermined trajectory, the "sweeping" effect caused by the
rotation of the flange in the squeeze rolls of the welding station
avoided the problem of inducing heat into an unnecessarily wide
path extending away from the desired weld line as the free edge
swept into alignment with the desired weld line.
[0112] The far greater control of the high frequency ERW process
has led to improved production efficiencies and significantly
improved manufacturing tolerances on the dual welded hollow flange
beams of the invention.
[0113] FIGS. 10 and 11 show typical flower shapes for the forming,
welding and shaping of hollow flange beams as illustrated in FIGS.
5 and 6 respectively. The flower shape leading to the configuration
shown in FIG. 6 is preferred in practice as there is less of a
tendency to accumulate mill coolant fluid in the channel between
the hollow flange sections in the region of the welding station.
Moreover, in the FIG. 6 configuration, visibility of the weld to
the mill operator is improved. The problems posed by accumulation
of mill coolant in the region of the flange seam welds may be
overcome by providing suction nozzles and/or mechanical or air
curtain wiper blades to keep the weld seams clear of coolant in the
induction region of the welding station.
[0114] Another alternative is to invert the section profile and
form the weld seam under the web outer surface.
[0115] A still further alternative is to operate the rolling mill
with the beam web oriented in a vertical or upright position.
[0116] FIG. 10 shows schematically the development of a hollow
flange in a cold roll forming operation by what is known as a
direct forming process through an entry point where the flat steel
strip 30 enters the mill and a final stage 10 at which edge welding
occurs. While not impossible to weld in a continuous cold roll
forming process, maintenance of weld stability and section shape is
very difficult. Direct formed hollow flange beams of this type may
be welded by a consumable electrode process either during the roll
forming process or subsequently utilizing automated or
semi-automated processes and/or low cost labour. With consumable
electrode welding processes, a post welding straightening process
is likely to be required to remove warping and local deformations
due to the greater heat input. Whether an automated, semi-automated
or manual welding process is employed, it is important to employ a
continuous weld seam to close the hollow flange formations in order
to maintain the greatest structural integrity of the beam so
formed.
[0117] In the embodiment illustrated, welding is effected at the
final stage illustrated and the subsequent processing through the
shaping section of a mill merely effects a straightening of any
warpage or deformations.
[0118] FIG. 11a shows a flower representing the progression of
planar steel strip 30 through the forming section of a cold roll
forming mill between an entry point through to the edge seam
alignment in the welding station just prior to entry into the
squeeze rolls of the mill where the free edges of the flanges are
brought into contact along the respective side boundaries of web
2.
[0119] FIG. 11b shows a flower progression from the squeeze roll
stand in the welding station through the shaping station to the
turk's head final straightening. During the shaping of the
initially closed flanges 3 as the profile progresses through the
shaping station, care is taken to avoid deformation of plastic
hinges in the immediate vicinity of the weld seams 8 to avoid
imposing stress on the weld seam itself such as to compromise the
structural integrity of the beam.
[0120] FIG. 12 shows schematically a seam roll stand 17 comprising
a support frame 35, a pair of independently mounted, contoured
support rolls 36,36a each journalled for rotation about aligned
rotational axes 37,37a and seam guide rolls 38,38a rotatably
journalled on respective inclined axes 39,39a. Seam guide rolls
38,38a serve to guide the free edges 16a,16b of strip 16 into
longitudinal alignment with a desired weld seam line as the shaped
strip 16 approaches the squeeze roll region of the welding
station.
[0121] FIG. 13 shows schematically the squeeze roll stand 18
comprising a cylindrical top roll 40 and a cylindrical lower roll
41 with contoured edges 41a, each of rolls 40,41 being rotatably
journalled about respective rotational axes 42,43. Squeeze rolls
44a,44b, rotatable about respective inclined axes 45a,45b are
adapted to urge the heated free edges 16a,16b of hollow flanges 3
into respective heated weld line regions along the opposed
boundaries of web 2 to effect fusion therebetween to create a
continuous weld seam.
[0122] The free edges 16a,16b are urged toward respective weld
lines in a linear fashion perpendicular to the respective
rotational axes 45a,45b of squeeze rolls 44a,44b without a
transverse "sweeping" action thereby maintaining stable induction
"shadows" or pathways on or at the desired position of the weld
seams between respective free edges 16a,16b and the opposed
boundaries of web 2.
[0123] FIG. 13a shows schematically in phantom an enlarged
perspective view of the relationship of the squeeze rolls 44a,44b
to upper and lower support rolls 40,41 as the free edges 16a,16b of
strip 16 are guided into fusion with the boundaries of web 2. In
the embodiment shown, lower support roll 41 is illustrated as
separately journalled roll elements, each with a contoured outer
edge 41a.
[0124] FIG. 14 shows schematically a shaping roll stand 50
comprising independent shaping roll stands 51 slidably mounted on a
mill bed 52. Roll stands 51 each support a complementary pair of
shaping rolls 53,54 to progressively impart shape to the outer edge
regions of steel strip 16 as illustrated generally by the forming
flower pattern illustrated in FIG. 11a.
[0125] As shown, shaping rolls 53,54 are undriven idler rolls.
[0126] FIG. 15 shows schematically a drive roll stand 60 which may
be employed with either of the forming station 11 or shaping
station 13 as shown in FIG. 9.
[0127] Drive roll stand comprises spaced side frames 61 mounted on
a mill bed 61a, the side frames 61 rotatably supporting upper and
lower driven shafts 62,63 on which are mounted cylindrical drive
rolls 64,65 respectively to engage the upper and lower surfaces of
the web portion 2 of a hollow flanged member as it is guided
through the forming and shaping regions of the cold rolling mill
shown generally in FIG. 9. Universal joints 66,67 couple driven
shafts 62,63 to output shafts 68,69 of a conventional mill drive
train (not shown).
[0128] If required, the roll stand 60 may be fitted with strip edge
rolls 70,71 to maintain alignment of strip 16 through the mill. The
edge rolls may be plain cylindrical rolls or they may be contoured
as shown. Rolls 70,71 are adjustably mounted on roll stands 61 to
accommodate hollow flange beams of varying widths.
[0129] FIG. 16 shows schematically a configuration of shaping rolls
in a shaping mill stand.
[0130] Shaping of the flanges 3 is effected by a respective shaping
roll set 75 positioned on each side of web 2. As shown, a flange 3
is subjected to shaping pressures from roller 76 mounted for
rotation on a horizontal axis 81, roller 77 mounted for rotation on
a vertical axis 82 and roller 78 mounted for rotation on an
inclined axis 83.
[0131] FIG. 17 illustrates one application of beams according to
the invention.
[0132] Where a greater load carrying capacity is required in a
location where a beam of greater width cannot be accommodated, a
pair of beams 90 can be secured back to back by any suitable
fasteners such as a spaced nut and bolt combination 91, a
self-piercing clench fastener or the like 92 or a self-drilling
self-tapping screw 93 through webs 90a. When installed, a support
bracket 94 for a utilities conduit 95 may be secured to flange 96
with a screw 97. Similarly, duct for cables may be formed by
securing a metal channel section 98 to a flange 99 by a screw 100
or the like to form a hollow cavity 101 to enclose electrical or
communications cables 102.
[0133] FIG. 18 shows a hollow flange channel 103 functioning as a
floorjoist. Floorjoint 103 is supported on another hollow flange
channel 104 functioning as a bearer. Timber flooring 105 is secured
to an upper flange 106 by a nail 107 or the like. Similarly, the
intersection of respective flanges 106,108 of hollow flange
channels is secured by an angle bracket 109 anchored by screws 110
to respective adjacent flanges 106,108.
[0134] FIG. 19 shows a composite structure 115 in the form of a
hollow flange channel 111 and an angle section 112 secured thereto
by a screw 113 or the like. Composite structure 115 thus can act as
a lintel-like structure to support a door or window opening in a
cavity brick structure whereby bricks 120 can rest upon angle
section 112 but otherwise be secured to the web 114 of channel 111
by a brick tie 116 having a corrugated portion 116a anchored in a
mortar layer 117 and a mounting tab 116b anchored to web 114 by a
screw 118.
[0135] FIG. 20 shows the formation of a cruciform joint between
hollow flange channels according to the invention.
[0136] In one embodiment, a hollow flange channel 120 may be
secured perpendicular to an outer face 121 of a similar sized
channel 122 by an angle bracket 123 secured to respective webs
124,125 by rivets, screws or any other suitable fasteners 126.
[0137] In another embodiment, a smaller hollow flange channel 127
is nestably located between the flanges 128 of channel 122 and is
secured therein by an angle bracket 129 attached to webs 125,130 of
channels 122,127 respectively by screws or other suitable fasteners
131.
[0138] Alternatively, adjacent flanges 128,132 of channels 122,127
respectively could be attached by an angle bracket 133 secured by
screws 134.
[0139] In a still further embodiment, adjacent flanges 128,132
could be secured by a screw-threaded fastener 135 extending between
flanges 128 and 132.
[0140] If required, the hollow interior 128a of the flanges may be
employed as ducting for electrical cables 138 or the like.
[0141] FIG. 21 shows yet another composite beam 140 wherein a
timber beam 141 is secured to an outer face of web 142 by mushroom
headed bolts 148 and nuts 144 to increase section capacity and/or
to provide a decorative finish.
[0142] It readily will be apparent to a person skilled in the art
that hollow flange channel beams according to the invention not
only provide an excellent moment capacity/mass per metre ratio
compared with other structural beams, they offer ease of
connectivity, ease of handling and flexibility in application which
greatly enhances "usability". Taking into account all of the
factors which contribute to an in situ installation value or cost,
hollow flange channel beams offer significant utility of up to 2.5
times conventional hot rolled beams and laminated timber beams and
have moment capacities that permit superior performances over
similar sized cold rolled open flange purlins over longer
lengths.
[0143] FIG. 22 shows an alternative embodiment of the hollow flange
beam according to the invention.
[0144] As illustrated, the beam is formed with longitudinally
extending alternating ribs 150 and troughs 151 to provide greater
resistance to longitudinal bending in web 2.
[0145] If required, flanges 3 may also have formed therein
longitudinally extending stiffening ribs 152.
[0146] FIG. 23 shows yet another embodiment of reinforced web
hollow flange beam according to the invention.
[0147] In this embodiment, transversely extending spaced ribs 153
provide greater resistance to transverse bending in web 2.
[0148] Throughout this specification and claims which follow,
unless the context requires otherwise, the word "comprise", and
variations such as "comprises" or "comprising", will be understood
to imply the inclusion of a stated integer or group of integers or
steps but not the exclusion of any other integer or group of
integers.
* * * * *