|Title of Invention||
CHANNEL-SHAPED STRUCTURAL BEAM
|Abstract||A hollow flange channel beam has a pianar 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 is optimised when Wf =(0.3)Db, Wf=(3.0)Df and WF=(30)t.|
|Full Text||FIELD OF THE INVENTION
This invention is concerned with improvements in structural beams.
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
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 andlhe like,
For several millennia timber was the primary source of material for structural beams in buildings and bridges andthe 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 pone improvements in fabrication techniques and this, in turn, has permitted significant advances in structural engineering. Throughoutthis 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 ofihese changes and developments. These drivers have included labour costs, material costs and, Dfmore recenttimes, environmental issues.
United States Design Patents 27394 and 28864 illustrate early forms of an I-beam and C-channei respectively while United States Patent 42B558 illustrates eariy forms of hollowflanged beams, possibiy made by a casting process.
Improvements in fabrication methods then led to structural members of reduced mass whilst retaining structural performance. United States Patent 1,377,251 is indicative of a cold roll tormina Drocess of s
hollow flanged trough channel, while United States Patent 3,199,174 describes a method of fabrication and reinforcement of (-shaped beams by welding together separate strips of metal. United States Patent 4,468,946 describes a method for fabrication of a beam having a lambda-shaped cross-section by bending a sheet of metal, and United States Patent 4,433,565 describes the-manufacture by cold or hot shaping of metal members having a variety of cross-sectional shapes. United States Patent 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. United States Patent 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.
Composite beam or truss structures fabricated from a plurality of components are known to provide pood strength to weight ratios as illustrated in United States Patent 5,012,626 which describes an I-beam-like structure having planarfianges connected to a transversely corrugated web. Other transversely corrugated web beams are disclosed in United States Patents 3,362,056 and £,415,577, both of which contemplate hollow flange membprs of rectangular cross-section. Dthertransversely corrugated web beams with hollow rectangular cross-section flanges are described in Australian Patent716272 and Australian Patent Application AU 1986-52906. A method of fabrication of hollow f ianged beams with corrugated webs is disclosed in United States Patent4,750,653.
While the prior art is replete with structural members and beams of widely varying configurations, a majority of such structural members of 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 l-beam. United States Patent3,241,285 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.
United States Patent 5,692,353 describes a composite beam comprising cold rolled triangular hollow section flanges separated by spaced woodenblocks for use as prefabricated roof and floor trusses. United Kingdom Patent Application GB 2 093 886 describes a cold rolled roofing puriin 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 WO96/23939 describes a C-section purlin for use in a roof supporting building, and United States Patent 3,256,670 describes a sheet metal joist having -a double thickness web with hollowfianges, the web and the flanges being perforated to allow the joist to be incorporated into a cast concrete floor structure.
United States Patent 6,436,552 describes a cold roll formed thin sheet metal structural member having hollow Hanges separated by a web member. This member is intended to function as a chord member in a roof truss orfloor joist.
The aforementioned examples of structural members or beams represent only a small fraction of the on-going endeavours io 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 Hange section without adding mass is well known in the art. Another early example Df hollow Hanged beams is described in United States Patent 991603 in which theHree edgesof triangular cross-section Hanges are returned to the web without weldingtothe web. Similar unwelded hollowHanged beams are described in United States Patent3,342,007 and International Publication WO 91 /17328.
HDIIOW flanged I-beam-like structures, with fillet welded connections between the flanges and the web are described in United States Patent 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 lace, the hollow flanges being-formed by U-shaped extrusions which clip into spaced receiving ribs formed on one face of "the web,
United States Patent 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.
United States Patents 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 United States Patents 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.
British Patent 'No GB 2 261 248 describes hollow flanged torsion resistant iadder stiles formed :by extrusion or cold Tollforming.
United States Patent '5,591/576 discloses a hollow flanged channel shapedstructural member with a cross-sectionaliy curved web shaped by press forming to produce a longitudinally arcuate bumper :bar reinforcing memberf or a motor vehicle.
While most of the holiowfiangedstructural members describedabove were fabricated with a closed flange with anunfixed free edge or otherwise disclosed a fixed free edge by welding or the like in a separate process, United States Patent 5,163,225 described forthe first time a cold Tolling process wherein free edges of hollowflanges were fixed to the edges ofthe web in an in-line dual welding process, This :beam was 'known as the '"Dogbone" (Registered Trade Mark) beam and possessed holiow flanges of generally triangular cross-section. United States Patent 5,373,679 describes a dual welded hollowflange "Dogbone" beam made by the process of United States Patent 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.
further developments of the dual weld "Dogbone" process described in United States Patent 5,163,225 were disclosed in United States Patent 5,403,986 which dealt with the manufacture of hollow flange beams wherein the ftange(s) and the web(s) were formed -from separatestrips of metal as distinct from a single strip of metal in United States Patent 5,163,225. A further development of the multiple strip process for forming hollowflange beams was described in United States Patent 5,501,053 which taught a hollowflange 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.
A still further development of the dual welding "Dogbone" process is described in Australian Patent724555 and UnitedStates Design Patent Des417290. A hollowflange beam is formed as a channel section to act as upper and lower chords of a truss beam with a fabricated web structuresecured in the channelled recess in the chord members.
While generaliy superiorto otherhollowfiange beiams.of'similar mass, the hollowflange "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 ats 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 flangebeams or conventional angle sections, l-rbeams, H-beams and channels, they also exhibited a surprisingly high torsional rigidity and thus a resistance to fiexural (iateral)torsional buckling over longer -lengths. These hollow flange beams failed due to a unique lateral distortional buckling mode of failure not found in other simllar products. Similarly, while the sloping inner flange faces provided an excellent deterrentfor 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 I-beams due to "flange crushing. Additionally, special attachment fittings were required because of the cross-sectional shape.
Conventionally, the selection of a structural beam for use in a structure was usually made :by an engineer after reference tostandard engineering tablesto 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 orthe like. The higherthe value ofbending capacity perunit mass, the more efficientthe section.This value measures the performance per unit cost thus allowing a comparison of cost efficiencies of various beams bytaking into account the cost per unit mass tor each product.
Where -special performance requirements are demanded of a beam, cost or costefficiency may :be governed by otherf actors and often this is the impetus to design a special purpose beam for a specific application. Otherwise,as the priorartso clearly demonstrates, there has beenand there continues to be an on-going questto produce more cost'effective general purpose beams having greater section efficiencies than widely used conventional general purpose timber laminate beams, hot rolled I-, 1-and H-beams, hot rolled channels and cold Tolled purlin beams of various cross-sectional shapes. The fact that -few, if any Df the plethora of prior art "improvements" has been adopted for widespread use is probably due.toan inability to combine bothgeneral cost efficiency with general Bection efficiency.
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 beanrinto-a structure-with a viewlo designing a hollow flange dual welded cold rolled general purpose beam which, between manufacture, handling and transportation andultimate 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, nameiy, connectivity and a capacity forflange crushing with localized loads,
A conjoint research methodology was developed to measure the individual product attribute utility for various beam profiles with builders,engineers.and architects. Thesekey attributes were then assigned valueslo 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 otherthan merely cost/unit mass and section efficiency. Fromthis customer valueutility analysis, a range of dual welded hollow flangebeam configurations in both mild steelandthin gauge high strength steel were devised as potential replacements for hot rolled steel beams such as I- and H-beamsand hot rolled channel as well as laminated limber beams.
Among the many attributes considered in relation to hot rolled steel :beams, connectivity and cost of handling with cranes were significant issues. United States Patent 6,637,172, which describes a clip lo -enable attachment to the flanges of hot rolled structural :beams, :is indicative of the connectivity problems of such beams,, As 1ar as limber was concerned, dwindlingavailability,lengthavailability,lermites,straightness and weather deterioration were significant factors which adversely affected customer value analyses,
Accordingly, it is an aim of thepresent inventionto 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 According to one aspect of "the invention there is provided 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 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 from0.2 to 0,4..
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.
Suitably, the ratio of the width of the flange to the thickness of the web is in the range of from 15 to 50.
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 to3:5.
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.
The ratio of the width of each said flange to the depth of said beam may be in the ratio offrom'D.25 to 0.35.
Preferably, the ratio of the width of eachsaid flange to the depth of said beam is in the range of from 0.28 to0.32.
lf required, the ratio of the width of the flange to the thickness of the web may be in the range of from 25 to35.
Preferably the natiosof thewidth oftheflange^tothe-thickness of the web ;is.in the range of from 28 to 32.
Suitably, said beam is fabricated from steel.
Preferably, said beam is fabricated from high strength steel greaterthan 30.0 MPa.
If required, said beam may be fabricated from stainless steel.
The beam may be fabricated from a planar web member with a hollowtubular member continuously welded along opposite sides ofsaid web membertoform hollDwflanges, each said hollowtlange having an end face lying substantially in the same plane as an outerface of said web member.
Preferably, said beam is fabricated f rom a single sheetofsteel.
If required, said beam may be fabricated by:a folding process.
Alternatively, said beam may be fabricated by a roll forming process.
Suitably, free edges of hollow flanges are continuously seam welded to an adjacent web portion to form closed hollow flanges.
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.
Alternatively, said free -edges of said hollow flanges may be continuously seam welded along respective side boundaries of said web.
Most preferably, said structural beam is fabricated in a continuous cold rolling process.
Suitably, said free edges of said hollow flanges are continuously seam welded by a non-consumable electrode welding process. Alternatively, said free edges of said hollow flanges are continuously seam welded by a consumable electrode process.
Preferably, said free -edges of said hollow flanges are continuously seam welded :by a highfrequency electrical resistance weldingor induction welding process.
If required, said structural beams-maybefabricated from sheet steel having a corrosion resistant coating.
Alternatively, said -structural beHms may :be -coated with a corrosion resistant coating subsequent to welding of said free edges of said flanges.
If required, said flange may include one or more stiffening ribs. Suitably, said web may include stiffening ribs. The stiffening ribs may extend longitudinally of said web. Alternatively, the stiffening ribs may extend transversely of said web.
BRIEF DESCRIPTION OF THE DRAWINGS 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:-
FIG. 1 shows a typical configuration of a structural beam
according to the invention;
FIG..2 shows schematically a cross-sectional view of the hollow flange beam of FIG. 1;
FIG.3 shows schematically an alternative embodiment of a fabricated beam;
FIG. A shows a further embodiment of a fabricated beam;
FIG. 5 shows one configuration of a cold roll formed beam according to the invention;
FIG..6 shows an alternative configuration of a roll formedbeam according to the invention;
FIG.7 shows graphically a comparison of section capacity for HFC (Hollow flange channels) according to the invention; UB (Hot rolled Universal:beam of (-section), LUB (Low mass hot rolled Universal:beams of I- cross-section); PFC (Hot rolled channels), CFC (Cold rolled C-sections),and HFB (Hollowfiange beams of "Dogbone" configuration i.e., triangular section flanges) where the effective :beam length =0;
FIG. B shows graphically the moment capacity of the same sections where -length =6.0 metres;
FIG. 9 shows sohematioally the configuration of a roll forming mill;
FIG. 1.0 shows -schematically a flower sequence for direct forming ;abeam according to one aspect of the invention;
FIG, 11 shows schematically atlowersequence for forming and shaping a beam according to another aspect of the invention;
FIG. 1.2 shows schematically a cross-sectional view through the seam roll region 17 of the welding station 12;
FIG. 13 shows schematically a cross-sectional view thoughthe squeeze roll region 18 welding station 12 at the point of closure of the flanges;
FIG. 14 shows schematically a forming station;
FIG, 15 shows schematically a drive station;
FIG. 16 shows schematically a configuration of shaping rolls in
a shaping station;
FIGS, 17-21 illustrate the flexibility of beams according to the invention;
FIG. 22 shows a hollow fianged beam with a reinforced flange and a reinforced web; and
FIG. 23 shows an alternative embodiment of FIG. 22.
Throughout "the drawings, where appropriate, like reference numerals are employed for like features for the sake of clarity.
DETAILED DESCRIPTION OF THE DRAWINGS
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 web2 in the same direction perpendicular to the plane of web2. End faces 6,7 of flanges 3 are parallel to each other and end face 6 lies in the same planeas web 2.
RIG.2 shows a cross-sectional view of thebeam 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 ;steeif rom which the beam is fabricated.
In devising the shape of the hollowfiange channel accordingto the. invention, advantage was taken of the. capacity to employ higher strength (350-500 'MPa) steelthan the 250-300 MRa grade typically employed in current hot rolledbeams. From the outset this permitted theuse 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 ofbuckling 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 ^frequently introduced anotherfaiiure 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 hollowfiange 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
Wf = (0.3)Db,
Wf = (3)Df, and,
Wf = (30)t,
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
Wf = (0.15-0.4)Db,
Wf = (1.5-4.0)Df,and,
Wf = (15-50)t.
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 3aat the junction between sides 5 and end faces 6.
Weld seam 8 may be formed in a continuous operation by high frequenofelectrioal resistance or induction welding. Alternatively, in a semi-continuous operation, the weld seam8 may be formed utilizing a consumable weiding electrode in a MIG, TIG, SMAW, SAW GMAW.'FCAW welding process laser or plasma welding or the like. Where a semi-continuous consumable weiding 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 B is a full penetration weld which creates an integrally formed planar web member 2 extending between outer sides 4 of flanges 3.
Whilst semi-continuousfabrication is quite inefficient compared with a continuous cold-rolling process,-it may be cost efficient-tor 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.
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).
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 weid 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.
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.
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 Teetangular cross section flange although 1here may be applications for this cross-sectional configuration.
Alternatively, it may be shaped further to form e fiat end face with radiussed curves.
A full penetration weld seam B 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 United States Patent 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.
FIG. 6 illustrates an alternative technique forforming a cold rolled beam according to the invention.
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.
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.
Based on a simple capacity vs. mass basis, it readiiy 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 Oshaped purlin sections (CFC) and hollow flanged (HFB) beams such as the "Dogbone" beam with triangular-shaped flanges and the hollow flange channels (HFC) according ID the present invention.
The size Tanges -selected for 1he comparison are shown in Table 1.
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 iengths.
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.
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 3 represents ;a utility value comparison withlaminated limberbeams wherein "the aggregate utility value of HFC hollow flange channels according to the invention were about 2.5 times that of the laminated timberbeams.
FIG.9 shows schematicallya typical configurationof 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.
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 rollforming 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
When formed to a desired cross-sectional configuration, the formed -strip 16 enters the weiding station 12 wherein the free edges of respective flanges are guided into contact with the webat a predetermined angle in the presence of © high frequency electrical resistance or inductor weldin§*(!ER'W)=appapatus, T:o-;assist;:infQoation'ofthei;iange-'eidgesTeiative 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 alignmentand 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.
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.
It has now been discovered that the aforementioned difficulties can be overcome by aligning the free edge of the flange with the intended weid 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 offiangeedge 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 adjaoentt hereto is ohosen to correspond withafinal cross-sectional web shape. By guiding the free edge of the flange sdge along this predetermined trajectory, the "sweeping" effect caused by the rotation of the flange in the squeeze rolls of the weiding 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 weid line.
The far greater control of the highfrequencyERW process has led to improved production efficiencies and significantly improved manufacturing tolerances on the dual welded hollow flange beams of the invention.
FIGS. 10 and 11 show typicalflower shapes for the forming, welding and shaping of holiow 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 weid 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 Dr air curtain wiperblades to keep the weld seams clear of coolant in the induction region of the welding station.
Another alternative is to invert the section profile and form the weld seam under the web outer surface.
A still further alternative is to operate the rolling mill with the beam web oriented in a vertical or upright position.
FIG. 10 shows schematically the development of a holiow 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 3D enters the mill :and a final stage 10 at which edge welding occurs. While not impossible tD weld in a continuous cold roll forming process, maintenance of weld stability :and section shape is very difficult, Direct-formed hollowf lange :beams of this type way 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 iikeiy 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 holiow flange formations in order to maintain the greatest structural integrity of the beam so formed.
in the embodiment illustrated, welding is effected at the final stage illustrated-and thesubsequent prooessingthrough the shapingsection of a mill merely effects a straightening of any warpage or deformations.
FIG. 11 a shows s fiower representing the progression of planar steel strip 3D through the forming section of a coid roll forming mil! between
an entry point through/to the edge seam alignment in the weiding station just prior to entry into the squeeze rolis of the mil! where the'free edges of the flanges are brought into contact along the respective side boundaries of web 2.
FIG. 11b shows a flower progression from the squeeze roll stand in the welding station through the shaping station to the lurk's head final straightening. During the shaping of the initially closed flanges3 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,
FIG. 1.2 shows schematically a.seam roll stand 17 comprising a support-frame 35, -a pair of independently mounted, contoured support rolls 36,36a each journalledfor rotation about.aiigned rotational axes 37,37a and seam guide rolls '3B,38a rotatabiy journalled on respective inclined axes 3S,39a. Seam puide rolis 38,38eserveto guide the free edges 16a,15b of strip 16 into longitudinal alignment with s desired weld seam line as the shaped strip 16 approaches thesqueeze roll region of the welding station. FIG. 13 shows sshematically the squeeze roll stand 18 comprising acylindrical top roll 40 -and &cylindrical lower roll 41 with contoured edges 41:a, Bach of rolis 4041 being rotatably journalledabout respective rotational axes 42,43. Squeeze rolls 44a,44b, rotatabie about respective inclined axes45a,45bare adaptedto urge the -heated free edges 15a,'16b of holiowflanges 3 into respective heated weld line regions along the opposed boundaries of web 2 to effect fusion therebetween to create a continuous weld seam.
Thefree edges 1Ba,16b are urged toward respective weid lines in a linear fashion perpendicular to the respective rotational axes45a,45b Df squeeze rolls 44aT44b without -s transverse '-'sweeping" ^action thereby maintaining stable induction 'shadows'" or pathways on or at the desired position of the weld seams between respective free edges 15a, 15b and the opposed boundaries of web2.
FIG, 13a shows schematically in phantom an enlarged perspective view of the relationship Df thesqueeze rolls 44a,44b to upper and lower support rolls 4041 as the free edges 16a,"l6b of strip 16 are guided into-fusion with theboundaries of web.2. In.the embodiment shown, lower support roll 41 is Illustrated..as separately journalled roll elements, each witha contoured outer-edge41a.
FIG. 14 shows schematically a shaping roll stand 50 comprising independent shaping roll stands51 siidably mounted on a mill.bed 52. Roll stands 51 each support a complementary pair Df shaping rolls 53,54 to progressively impartshape to the outer edge regions of steel strip 16 as illustrated generally by'the forming'flower pattern illustrated in FIG. 11a. As shown, shaping rolls 53,54 areundriven idler rolls. FIG. 15 shows schematically a drive roll stand 60 whichmaybe employed with either of the forming station 11 or shaping station 1.3as shown in FIG.9.
Drive roll stand comprises spaced side frames 51 -mounted on a mill bed -61a, the side -frames B1 rotatably supporting upper and lower driven shafts 62,63 on -which are mounted cylindrical drive rolls 54,65
respeotively toengage 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).
If required, the roll stand 60 may be fitted with stripedge rolis 70,71 to maintain alignment of strip 16 through the mill. Theedge rolls -may beplain cylindrical rolis or they may be contoured as shown. Rolls 70,71 are adjustably mounted on roll stands 61 to accommodate hollowfiange.beams of varying widths.
FIG.16-shows sehematieally B eonfigurafion of shaping rolis-in a shaping mill stand.
Shaping of the flanges3 is effected by a respective shaping roll set 75 positioned on each side of web 2. As shown, afiange 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.
FIG. 17 illustrates one application of beams according to the invention.
Where a greater load carrying capacity is required in a location wherea 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 orthe like 92 ora self-drillingself-tapping screw 93'through webs 90a, When installed, a support bracket 94fora utilities conduit 95 may be securedto-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 orthe like to forma hollow cavity 1.01 to enclose electrical orcommunications cables 102.
FIG. 1B shows a hollow flange channel 103 -functioning as a floor joist Floor joint 103 is supported on another hollowflange channel 104 functioning as a :bearer. Timber flooring 1.05 is secured to an upperflange 1D6:bya nail 107 orthe like, Similarly,the intersection.of respective flanges 106,108 of hollow flange channels is sesuned -.by an angle bracket 109 anchored by screws 110 to respective adjacent flanfes 1.06,108.
'FIG. 19 shows a composite structure 115 in 1he '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 canactasa 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 lab 116b anchored to web 114 by a screw 118.
FIG 20 shows the tormation of a cructform joint -between holiowtiange channels according to the invention.
In one embodiment, a hollowflange channel 120 may be secured perpendicularto 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 c-ther suitable fasteners 126.
In another embodiment, a smaller hollowflange channel127 is nestabiy located between the flanges 12B 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.
Alternatively, adjacent flanges 126,132 of channels 122,1.27 respectively could be attached by an angle bracket 133 secured by screws 134.
In a still further embodiment, adjacent flanges 1.28,132 could be -secured by a screw-threaded fastener 135 -extending between flanges 128 and 132.
If required, the hollow interior 128a of the flanges may be employed as ducting for electrical cables 136 orthe like.
FIG. 21 shows yet another composite beam 140 wherein a limber beam 141 is secured to an -outer face of web 142 by mushroom headed.bolts 148 and nuts 144 to increase section capacity and/onto provide a decorative finish,
It readily will be apparent to a person skilled in the art that hollowflange channel beams according to the invention not only provide an excellent moment -capacity/mass per metre ratio compared with other structural bsarns, 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, hollowflange 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 coid rolled open flange purlins over longer lengths.
FIG 22-shDws-an-alternative embodiment of the hollowflange beam according to the invention.
As Illustrated, the beam is formed with longitudinally extending alternating ribs 150 and troughs 151 to provide greater resistance ID
longitudinal bending in web 2.
If required, flanges 3 may also have formed therein longitudinally extending stiffening ribs 152.
FIG. 23 shows yet another embodiment of reinforced web hollow flange beam according to the invention.
In this-embodiment, transversely extending spaced ribs 1.53 provide greater resistance to transverse bending in web 2.
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.
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 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 in the ratio of from 0.2 to 0.4.
2. A 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. A 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. A 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. A 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. A 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. A 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. A 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. A beam as claimed in claim 1 wherein said beam is fabricated from steel.
11. A beam as claimed in claim 10 wherein said beam is fabricated from high strength steel greater than 300 MPa.
12. A beam as claimed in claim 10 wherein said beam is fabricated from stainless steel.
13. A 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. A beam as claimed in claim 1 wherein said beam is fabricated from a single sheet of steel.
15. A beam as claimed in claim 1 wherein said beam is fabricated by a folding process.
16. A beam as claimed in claim 1 wherein said beam is fabricated by a roll forming process.
17. A beam as claimed in claim 16 wherein free edges of hollow flanges are continuously seam welded to an adjacent web portion to form closed hollow flanges.
18. A 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. A 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. A beam as claimed in claim 1 wherein said structural beam is fabricated in a continuous cold rolling process.
21. A 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. A beam as claimed in claim 14 wherein said free edges of said hollow flanges are continuously seam welded by a consumable electrode process.
23. A beam as claimed in claim 21 wherein said free edges of said hollow flanges are continuously seam welded by a ERW process.
24. A beam as claimed in claim 1 wherein said structural beams are fabricated from sheet steel having a corrosion resistant coating.
24. A 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.
25. A beam as claimed in claim 1 wherein said web having stiffening ribs.
26. A beam as claimed in claim 26 wherein the stiffening ribs extend longitudinally of said web.
27. A beam as claimed in claim 26 wherein said stiffening ribs extend transversely of said web.
28. A beam as claimed in claim 1 wherein each said flange having one or more longitudinally extending stiffening ribs.
|Indian Patent Application Number||223/DELNP/2006|
|PG Journal Number||34/2009|
|Date of Filing||12-Jan-2006|
|Name of Patentee||SMORGON STEEL LITESTEEL PRODUCTS PTY. LTD.|
|Applicant Address||650 LORIMER STREET, PORT MELBOURNE, VICTORIA 3207, AUSTRALIA.|
|PCT International Classification Number||E04C 3/04|
|PCT International Application Number||PCT/AU2004/000824|
|PCT International Filing date||2004-06-23|