HK1094016B - An improved beam - Google Patents

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 is optimised when Wf =(0.3)Db, Wf=(3.0)Df and WF=(30)t.

Description

Improved beam

Technical Field

The present invention relates to improvements in structural beams.

The invention is particularly, although not exclusively, concerned with a hollow flange channel in which hollow flanges along opposite sides of a web extend away from the web in the same direction.

Background

Throughout history, engineers have sought to develop cheaper and/or stronger structural components such as beams or trusses for all forms of structure including buildings, bridges, ship structures, truck body chassis, aircraft, and the like.

Wood has been the primary source of material for structural beams in buildings and bridges for thousands of years, particularly over the last centuries, with a growing progress from wood to cast iron to wrought iron to mild steel and further to complex steel alloys. Manufacturing techniques have also improved with advances in structural beam materials, which in turn has made significant advances in engineering possible. Throughout this period of change and development in structural engineering, history has witnessed the emergence of a unique driving force that has profound effects on nature and the direction of these changes and developments. These drivers include labor costs, material costs, and environmental concerns in the more recent years.

Us design patents 27394 and 28864 illustrate early forms of i-beams and C-channel beams, respectively, while us 426558 illustrates an early form of hollow i-beams (bent beams) that may be manufactured by casting.

Advances in manufacturing methods have thus resulted in structural members having reduced mass while maintaining structural performance. Us 1,377,251 describes a cold roll forming process for hollow flange underpads, and us 3,199,174 describes a process for manufacturing and reinforcing i-beams by welding separate metal strips together. Us patent 4,468,946 describes a method of manufacturing beams having a Λ -shaped cross-section by bending a metal strip and us patent 4,433,565 describes a method of cold or hot forming metal members having various cross-sectional shapes. Both U.S. patent 3,860,781 and russian certificate of invention 245935 describe automated manufacture of i-beams from separate web and fused-together flange strips. Us patent 5,022,210 describes a milled wooden beam having a solid central beam web portion which is narrower than solid flanges extending along opposite sides of the beam web.

Composite beam or truss structures made from multiple components are known to provide good strength to weight ratio as described in U.S. patent 5,012,626, which describes an i-beam structure having planar flanges connected to transverse corrugated beam webs. Other transverse corrugated webs are described in U.S. Pat. nos. 3,362,056 and 6,415,577, which contemplate hollow flange members of rectangular cross-section. Other transverse corrugated webs with hollow flanges of rectangular cross section are described in australian patent 716272 and australian patent application AU 1986-52906. A method of manufacturing hollow i-section beams with corrugated web is described in us patent 4,750,663.

While the prior art implies a variety of different configurations of structural members and beams, most of these structural members or beams are designed for the intended end-use specific application, although some are designed as universal beams to replace conventional hot rolled i-beams. Us patent 3,241,285 describes a hollow fabricated beam of thin chromium nickel stainless steel that provides high strength for weight ratio and lower maintenance cost than hot rolled i-beams in bridge construction applications. Another type of fabricated bridge truss, known as a "delta" truss, is described in the Journal of AISC engineering (aiscinginening Journal) at 10.1964, pages 132-136. In this design, one or both of the flange plates are reinforced by a support plate extending on both sides over the full length of the spar between the flange plate and the spar web.

Us patent 5,692,353 describes a composite beam comprising cold rolled triangular hollow flanges separated by spaced apart blocks of wood, which is used as prefabricated roof and floor. United kingdom patent GB 2093886 describes a cold rolled roof purlin having a generally J-shaped cross-section, and british patent GB 2102465 describes a beam of I or H-shaped cross-section rolled from a single metal strip. International publication WO 96/23939 describes a C-section purlin for supporting the roof of a building and us patent 3,256,670 describes a metal sheet joist with hollow flanges having a double thickness web, the web and flanges being perforated to allow the joist to be incorporated into a cast concrete floor structure.

U.S. patent 6,436,552 describes a cold-rolled thin sheet metal structural member having hollow flanges separated by beam web members. The member is intended to act as a chord member in a roof truss or floor joist.

The foregoing examples of structural members or beams reflect only a small portion of the continuing efforts to provide improved beams for use in more applications. In particular, however, the present invention relates to hollow i-section steel, an example of which was previously described in us patent 426558. The use of i-section steel to increase i-section without adding mass is well known in the art. Another previous example of a hollow i-section is described in us patent 991603 in which the free edges of the triangular cross-section flanges are folded back into the web without being welded to the web. Similar unwelded hollow I-beams are described in U.S. Pat. No. 3,342,007 and International patent publication No. WO 91/17328.

U.S. patent 3,517,474 and russian certificate 827723 describe hollow flange i-steel structures with fillet welded connections between the flanges and the web. Extruded aluminium beams described in swedish patent publication No. 444464 are formed with ribbed planar beam webs and hollow rectangular flanges extending from one web face, the hollow flanges being formed from U-shaped extrusions which are captured in spaced receiving ribs formed on one face of the beam web.

U.S. Pat. No. 3,698,224 discloses forming H and I beams and channel sections with hollow flanges by deforming welded steel tubes to form a double thickness web between spaced hollow flanges.

U.S. patents 6,115,986 and 6,397,550 and korean patent application KR2001077017A describe cold-rolled thin steel structural members having hollow flanges with flanges extending from each flange being secured against the face of the beam web by spot welding, riveting or clamping. The beams described in us patent 6,115,986 and 6,397,550 are used for wall studs which allow the cladding to be secured to the hollow flange by screws or nails.

GB 2261248 describes hollow flange anti-twist ladder side plates formed by extrusion or cold roll forming.

U.S. patent 6,591,576 describes a hollow flange web-forming structural member with a web bent in cross-section by press forming to produce a longitudinally curved bumper bar reinforcement member for an automotive vehicle.

Although most hollow flange structural members described above are manufactured in a separate process by welding or the like from closed flanges with unsecured free edges or otherwise disclosed secured free edges, U.S. patent 5,163,225 describes for the first time a cold rolling process in which the free edges of the hollow flanges are secured to the edges of the web in an in-line double welding process. The beam is referred to as a "Dogbone" (registered trade mark) beam and has hollow flanges of generally triangular cross-section. U.S. patent 5,373,679 describes a double welded hollow flange "Dogbone" beam made by the method of U.S. patent 5,163,225. Because of the cost/performance ratio provided by these beams, lightweight thinner section hot rolled utility beams are introduced into the market to counter the pre-challenge of conventional utility beams of I or H cross-section.

A further development of the double weld "Dogbone" method described in U.S. patent 5,163,225 is described in U.S. patent 5,403,986, which relates to the manufacture of hollow i-section steel in which the flange(s) and web(s) are formed from separate metal strips, unlike the single metal strip in U.S. patent 5,163,225. A further development of the multi-strip method of forming hollow i-section steel is described in us patent 5,501,053 which teaches a hollow i-section steel with a slot extending longitudinally in at least one flange to allow the flanges of one hollow i-section steel to be nested in the hollow flanges of an adjacent beam for structural applications such as piling, wall building, structural barriers and the like.

Still further developments of the double weld "Dogbone" method are described in australian patent 724555 and us design patent Des 417290. A hollow I-steel is formed into channel sections for use as the upper and lower chords of a truss beam, and a fabricated beam web structure is secured in a channel in the chord member.

Although generally superior to other hollow i-beams of similar quality, the hollow flange "Dogbone" beam encounters many limitations in terms of manufacturing and performance. In terms of manufacture, the "Dogbone" beam obtained from a conventional tube mill is limited in size range by the access of the inner rolls at the lower end and by the size of the roll stand at the larger end on the other hand. Although "Dogbone" beams typically have increased resistance per unit mass or cost compared to conventional "open (unwelded)" hollow i-section steel or conventional angular section, i-beam, H-beam and channel beams, they also have surprisingly high torsional stiffness and therefore resist bending (lateral) torsional buckling over longer lengths. These hollow i-beams fail due to a unique lateral deformation buckling failure mode not found in other similar products. Similarly, while the inclined inner flange faces provide good deterrence to birds and rodent pests in some structural applications, the flanges are less tolerant to localized bearing damage than other beams such as i-beams due to flange fragmentation. In addition, special connection joints are required due to the cross-sectional shape.

Traditionally, structural beams for a structure are typically selected by engineers, after reference to standard engineering tables to determine section efficiency and load bearing capacity, within the range of readily available "standard" beams, such as laminated wood panels, hot rolled H, L or I-beams and channel beams, cold rolled beams such as C, Z, J purlins, and the like. The higher the bending load force per unit mass, the more effective the cross section. This value measures the performance per unit cost, thus allowing the cost efficiencies of various beams to be compared by considering the cost per unit mass of each product.

Cost or cost effectiveness is subject to other factors when particular performance requirements are placed on the beam, and this is often the impetus for a dedicated beam designed for a particular application. Additionally, as the prior art so clearly demonstrates, there has been and continues to be a continuing need to produce more cost effective universal beams having greater cross-sectional efficiencies than the widely used conventional universal laminated timber beams of various cross-sectional shapes, hot rolled I, L and H-beams, hot rolled channel beams and cold rolled purlin beams. The fact that there are few examples in the large number of prior art "developments" that are suitable for widespread use is likely due to the inability to combine overall cost efficiency and overall cross-sectional efficiency at the same time.

The assignee of the present invention is the successor to the title of the "Dogbone" double welded hollow i-section invention and has made a thorough investigation into the actual cost of incorporating a "Dogbone" type beam into a structure with a view to designing a hollow flange double welded cold rolled universal beam that is more cost effective overall than any of the prior art conventional universal beams that additionally overcome several of the drawbacks recognized in "Dogbone" beams, namely, connectivity and flange crush resistance under localized loading, in the middle of manufacturing, handling, transporting, and ultimately incorporating into a structure.

Joint analysis methodologies are proposed for builders, engineers, and architects to evaluate individual product quality utilities for various beam profiles. These key qualities are then assigned to produce utility grades from which customer value analysis of various beams can be directly compared based on many product qualities, not just cost/unit mass and section efficiency. From this customer value utility analysis, double welded hollow I-beam constructions in the mild steel and thin gauge high strength steel range were designed as potential replacements for hot rolled steel beams such as I and H beams, and hot rolled channel beams, as well as laminated wood plate beams.

Among the many qualities considered with respect to hot rolled steel beams, connectivity and the cost of crane operation are important aspects. Us patent 6,637,172, which teaches a clamp capable of being attached to the flanges of a hot rolled structural beam, addresses the problem of the connectivity of such beams. As far as wood is concerned, problems of reduced availability, length availability, termites, straightness and weather deterioration are important factors which negatively affect the analysis of the customer value.

It is therefore an object of the present invention to overcome or alleviate at least some of the disadvantages of the prior art universal structural beams and to provide a structural beam having greater overall customer utility than the prior art universal structural beams.

Disclosure of Invention

According to an aspect of the present invention, there is provided a channel structural beam comprising:

a planar elongate web; and

spaced hollow rectangular cross-section flanges extending perpendicularly from the inner surface of the web parallel to one another along opposite side margins thereof, the hollow flanges all extending in the same direction away from the inner surface of the web to form a longitudinally extending grooved recess of the inner surface of the beam and a substantially planar surface extending between the opposite outer edges of the beam on the outer surface of the beam opposite the inner surface of the beam, the beam being characterized in that the web region extending between the spaced hollow flanges comprises a single layer of metal of substantially uniform thickness; and

a ratio of a width of each of the hollow flanges between opposing outer surfaces thereof measured in a direction perpendicular to the outer surfaces of the beam to a height Db of the beam between opposing outer surfaces of the hollow flanges measured in a direction parallel to the outer surfaces of the beam is in a range of 0.25-0.35, and wherein a ratio of the width of each of the hollow flanges to a height of each of the hollow flanges is in a range of 1.5-4.0.

Suitably, the ratio of the width of each said hollow flange to the thickness of the web is in the range 15 to 50.

If desired, the ratio of the width of each of the hollow flanges to the height of each of the hollow flanges is in the range of 2.5-3.5.

Preferably, the ratio of the width of each of the hollow flanges to the height of each of the hollow flanges is in the range of 2.8-3.2.

The ratio of the width of each of the hollow flanges to the height of the beam may be in the ratio of 0.25 to 0.35.

Preferably, the ratio of the width of each of the hollow flanges to the height of the beam is in the range 0.28-0.32.

The ratio of the width of each said hollow flange to the thickness of the web may be in the range 25 to 35 if desired.

Preferably, the ratio of the width of each said hollow flange to the thickness of the web is in the range 28-32.

Suitably, the beam is made of steel.

Preferably, the beam is made of high strength steel greater than 300 MPa.

The beams may be made of stainless steel, if desired.

The beam may be manufactured from a planar beam web member with hollow tubular members continuously welded along opposite sides of the beam web member to form hollow flanges, each of the hollow flanges having an end face lying substantially in the same plane as the outer face of the beam web member.

Preferably, the beam is made of a single-layer steel plate.

The beam may be manufactured by a folding process, if desired.

Alternatively, the beam may be manufactured by a roll forming process.

Suitably, the free edges of the hollow flanges are continuously welded to adjacent web portions to form closed hollow flanges.

The free edges of the hollow flanges may be continuously welded to the one face of the web intermediate the opposite edges of the web.

Alternatively, the free edges of the hollow flanges may be welded along respective side margins of the web.

Most preferably, the structural beam is manufactured in a continuous cold rolling process.

Suitably, the free edges of the hollow flanges are continuously welded by a non-consumable welding process.

Alternatively, the free edges of the hollow flanges are continuously welded by a consumable electrode process.

Preferably, the free edges of the hollow flanges are continuously welded by a high frequency resistance welding or induction welding process.

The structural beam may be made of steel plate with a corrosion-resistant coating, if desired.

Alternatively, the structural beam may be coated with an anti-corrosive coating.

Each of the hollow flanges may include one or more reinforcing ribs, if desired.

Suitably, the web may comprise a plurality of stiffening ribs.

The reinforcing rib may extend in a longitudinal direction of the web.

Alternatively, the reinforcing rib may extend transversely of the web.

Drawings

For a more complete understanding of the present invention, and to the accomplishment of the same, reference is now made to the preferred embodiments of the invention, illustrated in the accompanying drawings, in which:

FIG. 1 illustrates one exemplary configuration of an exemplary structural beam according to the present invention;

FIG. 2 schematically illustrates a cross-sectional view of the hollow I-beam of FIG. 1;

FIG. 3 schematically illustrates an alternative embodiment of the finished beam;

FIG. 4 shows yet another embodiment of a finished beam;

FIG. 5 shows one configuration of a cold-rolled beam according to the present invention;

FIG. 6 shows an alternative configuration of a cold-rolled formed beam according to the present invention;

FIG. 7 graphically illustrates a comparison of the section bearing forces of HFC (hollow flange channel beam), UB (hot rolled universal beam of I-section), LUB (light hot rolled universal beam of I-section), PFC (hot rolled channel beam), CFC (cold rolled C-section) and HFB (hollow I-steel of Dogbone construction, i.e. triangular section flange) of the present invention at an effective beam length of 0;

figure 8 graphically illustrates the instantaneous bearing force of the same section at a length of 6.0 meters;

FIG. 9 schematically shows a configuration of a roll forming mill;

FIG. 10 schematically illustrates a flow sequence for directly forming a beam in accordance with an aspect of the present invention;

FIG. 11 schematically illustrates a flow sequence for forming and shaping a beam according to another aspect of the present invention;

FIG. 12 schematically shows a cross-section through the stitch roll area 17 of the welding station 12;

FIG. 13 schematically shows a cross-sectional view through nip roll zone 18 of station 12 at the point of closure of the flange;

FIG. 14 schematically shows a forming station;

FIG. 15 schematically shows a drive stage;

FIG. 16 schematically illustrates the configuration of the shaping rollers in the planing forming station;

FIGS. 17-21 illustrate the flexibility of a beam according to the present invention;

FIG. 22 shows a hollow I-beam with reinforcing flanges and reinforcing beam webs; and

fig. 23 shows an alternative embodiment of fig. 22.

In all figures, the same reference numerals are used for the same features as appropriate for clarity.

Detailed Description

In fig. 1, a beam 1 comprises a central spar 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 the web 2 in the same direction perpendicular to the plane of the web 2. The end faces 6, 7 of the flanges 3 are parallel to each other and the end face 6 lies in the same plane as the web 2.

Fig. 2 shows a cross-sectional view of the beam of fig. 1 to illustrate the relationship between the width Wf of the flanges 3, the height Df of the flanges, the height Db of the beam and the thickness t of the steel from which the beam is made.

In designing the shape of the hollow flange channel beam of the present invention, taking into account the advantage of the bearing capacity, steels with greater strength (350-500MPa) than the 250-300MPa class strength typically used for current hot rolled beams are used. This allows for the use of lighter gauge steel from the outset to produce a lighter weight beam. The problem then faced is that light gauge cold rolled beams tend to withstand more various bending failure modes and this range of bending failure modes in turn leads to conflicting solution options as although one structural proposal reduces one failure mode, it often introduces another failure mode. For example, by moving the body of the flange away from the neutral axis of the beam, different bending failure modes will be introduced. In view of these conflicts, the cross-section of the hollow flange channel section shown in fig. 1 and 2 is designed as a selected compromise and is determined to be satisfactory when

Wf＝(0.3)Db

Wf ═ 3 Df, and

Wf＝(30)t

the best cross-sectional efficiency is obtained.

While optimal cross-sectional efficiency is desirable, it should be recognized that some variation is required due to rolling mill limitations, end-user dimensional requirements, and the like. In this context, the flange width ratio can be maintained very well in the following range for very good section efficiency

Wf＝(0.15-0.4)Db

Wf ═ (1.5-4.0) Df, and

Wf＝(15-50)t。

figure 3 shows schematically a structural beam according to the invention, in which the beam 1 is manufactured from separate web and flange parts 2,3, respectively. The web 2 is continuously seam welded along its opposite edges to the radius corner 3a of the junction between the side face 5 and the end face 6.

The weld 8 may be formed in a continuous operation by high frequency resistance or induction welding. Alternatively, the weld bead 8 may be formed in a semi-continuous operation using a consumable welding electrode (consumable welding electrode) during MIG, TIG, SMAW, SAW GMAW, FCAW welding processes, laser or plasma welding, or the like. In the case of a semi-continuous consumable welding electrode process, it is contemplated that a post-weld rolling or straightening process is required to eliminate heat-induced distortion. The continuous weld 8 is a full penetration weld which results in an integrally formed planar beam web member 2 extending between the outer sides 4 of the flanges 3.

Although semi-continuous manufacturing is less efficient than continuous cold rolling processes, it is cost effective for short term operation of non-standard beams of a particular size. In addition, manufacturing the beam from separately prefabricated beam web and flange members allows the use of members of different thicknesses and/or strengths. For example, such a beam may include a thick high strength steel flange and a thinner lower grade steel web.

Figure 4 shows an alternative method of manufacturing discrete beam lengths by forming hollow i-section steel from a single strip of metal by folding in a plate bender or similar device (not shown).

Typically, the closure flange is formed by progressively folding the side 5 relative to the end 7, then folding the end 7 relative to the side 4, and finally folding the side 4 relative to the web 2 until the free edge 5a contacts the inner surface 2a of the channel beam so formed. A full penetration weld 8 is then formed between the free edge 5a and the web 2 to form a unitary structure, and has a continuous planar web member 2 extending between the outer sides 4 of the flanges 3.

Figure 5 shows one configuration of the beam of the present invention when manufactured by a continuous cold rolling process, which is preferred due to its high cost efficiency and the ability to maintain small dimensional tolerances to produce a beam of consistent quality.

In this embodiment the end faces 7 of the hollow flanges 3 are formed with a radius curvature. Although there may be applications for this cross-sectional configuration, the cross-sectional efficiency of the configuration is lower than that of a rectangular cross-sectional flange.

Alternatively, the end face 7 may be further shaped to form a flat end face with a radius curvature.

A full penetration weld 8 is formed between the free edge 5a of the side 5 and the inner surface 2a of the web 2 by a high frequency resistance or induction welding process generally described in U.S. patent 5,163,225. The resulting beam is an integrally formed member which relies on the ability to transfer loads between the outer flange sides 4 through the continuous beam web member 2 extending therebetween.

Fig. 6 illustrates an alternative technique for forming the cold rolled beam of the present invention.

In this embodiment, the free end 6a of the end face 6 of the hollow flange 3 is welded by high frequency resistance or induction welding to the radius blend 10 between the web 2 and the side face 5 to form a full penetration weld 8, which effectively creates a substantially continuous flat outer surface 2b of the load bearing member comprising the end face 6 and the web 2, whereby the load bearing member extends between the outer flange side faces 4.

Fig. 7 and 8 show the section resistance and the instantaneous bending resistance at L-6.0 m, respectively. The lack of smoothness in the curves for almost hot rolled channel sections is due to the selection of various web heights and flange widths, which suggests an overlap value for each section on the axis based on added mass.

Based on a simple basis of bearing force versus mass, it can be easily seen that hot rolled Universal Beams (UB), Light Universal Beams (LUB) and hot rolled channel beams (PFC) are significantly lower than cold rolled C-shaped purlin section (CFC) and Hollow Flange (HFB) beams such as "Dogbone" beams with triangular flanges and hollow flange channel beams (HFC) according to the present invention.

The size ranges selected for comparison are shown in table 1.

TABLE 1

Cross section of	Beam web (min)	Beam web (max)
			HFC	125mm	300mm
UB/LUB	100mm	200mm
			PFC	75mm	250mm
CFC	100mm	350mm
			HFB	200mm	450mm

The graph clearly shows the excellent cross-sectional resistance of the HFC hollow flange channel beam over all other comparative beams and the excellent instantaneous resistance over a longer length.

When joint analysis grading is applied to the sections being evaluated, the quality of the hollow flange trough beam over the comparative standard section produced a utility grade that was surprisingly higher than UB and LUB hot rolled I-beams and HFB triangular hollow flange "Dogbone" beams.

For example, in comparing the quality values for UB hot rolled I-beams and HFC cold rolled trough beams of the present invention in Table 2, the cumulative utility score for HFC beams at a price 60% higher than UB hot rolled I-beams is approximately 2.5 times that for UB hot rolled I-beams.

TABLE 2

Quality classification	Quality of product
		Options for	Price precoat
Dressing	Welding appearance beam flange

	Length availability
		Inherent of	Resources mastered by connectivity of beam service to fixture and fitting to connectivity of steel to connectivity of wood

Table 3 shows the cumulative utility value for the HFC hollow flange channel beam according to the present invention compared to the utility value for a laminated plank beam, which is approximately 2.5 times that of the laminated plank beam.

TABLE 3

Quality classification	Quality of product
		Option trimming	Price length availability beam profile
Inherent of	Weather deterioration of termite members

Figure 9 schematically illustrates one typical configuration of a roll former that may be used to manufacture the hollow i-section of the present invention, which is illustrated in simplified form in figures 5 and 6, and which includes a forming station 11, a welding station 12 and a planing station 13.

The forming station 11 includes an alternating drive station 14 and a forming roller frame 15. The drive table 14 is connected to a conventional mill drive train (not shown) but instead assists the forming process with a forming roll which is used to clamp the steel strip 16 in a central region corresponding to the web portion of the finished beam. The forming roll stand 15 is formed as a separate pair 15a, 15b, 15a, 15b each equipped with a set of forming rolls adapted to form hollow flange portions on opposite sides of the metal strip 16 as it passes through the forming station. When the forming roll stands 15a, 15b do not need to be connected to the drive train as in a conventional cold roll forming mill, the forming roll stands 15a, 15b can be easily adjusted transverse to the longitudinal axis of the mill to accommodate hollow i-beams of various widths.

When the desired cross-sectional configuration is formed, the forming strip 16 enters the welding station 12 where the free edges of the respective flanges are directed to contact the web at a predetermined angle in the presence of a high frequency resistance or induction welding (ERW) device. To assist in the positioning of the flange edges relative to the desired weld line, the forming strip is guided by means of a slot guide roller stand 17 to the region of the ERW device shown schematically at 17 a. After the flange edges and weld lines on the web are heated to a melting temperature, the tape is passed through an extrusion roller stand 18 to force the heated portions to fuse together into a closed flange. The welded hollow flange section then proceeds and continues through drive roll stand 19 and planing roll stand 20 to form the desired cross-sectional shape of the beam and finally through a conventional turn's head roll stand 21 for final calibration to produce a double welded hollow i-beam 22 according to the present invention. The high frequency ERW process introduces current into the free edge of the strip and the respective adjacent regions of the web due to proximity effects between the free edge and the nearest portion of the web. Since the thermal energy in the web portion can be dissipated in both directions compared to the free edges of the flanges, additional energy is required to introduce sufficient heat into the web area to enable fusing of the free edges.

It has heretofore been found that by using conventional roll forming techniques and the ERW process, the amount of energy required to heat the web portion to the melting temperature causes the free edges of the flanges to melt and be drawn out of the desired weld line. As a result, the tape edge is lost, the cross-sectional area of the flange is significantly reduced and it becomes more difficult to control the tape edge into the weld.

It has now been found that the aforementioned difficulties can be overcome by aligning the free edges of the flanges with the intended weld line as it is heated and then urging the free edges of the strip into contact with the heated web region in a straight path in a direction corresponding to the desired angle of attack between the web portion and the region of the flange edges in the vicinity of the weld. This technique has the additional advantage that during subsequent planing, the weld is not pinched by the planing when the angle of attack between the web portion adjacent thereto and the region of the flange edge is selected to correspond to the final cross-sectional web shape. By guiding the free edges of the flange edges along this predetermined trajectory, the "sweeping" effect caused by the rotation of the flanges in the squeeze rollers of the welding station avoids the problem of introducing heat into an unnecessarily wide path away from the desired weld line as the free edges are swept into alignment with the desired weld line.

The greatly enhanced control of the high frequency ERW process results in improved production efficiency and improved manufacturing tolerances for the double welded hollow i-section of the present invention.

Fig. 10 and 11 show exemplary flow configurations for forming, welding and planing the hollow i-section shown in fig. 5 and 6, respectively. The flow pattern that results in the configuration shown in fig. 6 is preferred in practice because there is less tendency for rolling mill coolant fluid to accumulate in the troughs between the hollow flange sections in the region of the weld station. Also, in the configuration of fig. 6, visibility to the rollerblade weld is improved. The problems caused by the accumulation of rolling mill coolant in the flange weld zone can be overcome by providing suction nozzles and/or mechanical curtains or air curtain wipers to keep the weld free of coolant in the lead-in zone of the welding station.

Another option is to reverse the cross-sectional profile and form a weld under the outer surface of the spar web.

Yet another option is to operate the mill with the spar web of the spar oriented in a vertical or upright position.

Fig. 10 schematically illustrates the formation of hollow flanges in a cold roll forming operation, referred to as the direct forming process of the final stage 10 where the edge welding occurs and the entry point into the mill through the flat strip 30. Although welding can be performed in the continuous cold-roll forming process, maintenance of welding stability and sectional shape is very difficult. Hollow i-section steels of this type that are directly formed can be welded by a consumable electrode process during the roll-forming process or subsequently using an automated or semi-automated process and/or during inexpensive labor. With consumable electric welding processes, a post-weld straightening process is likely to be required to eliminate warping and localized deformation due to large heat inputs. Regardless of which of automated, semi-automated, or manual welding processes are used, it is important to close the hollow flange structure with a continuous weld in order to maintain maximum structural integrity of the beam so formed.

In the embodiment shown, the welding is effected at the final stage shown and the subsequent straightening of any warping or deformation is effected only by the operation of planing the section through the rolling mill.

Fig. 11a shows a flow path representing the progression of a profiled section of a flat steel strip 30 through a cold-forming mill between the entry point to the edge seam in the welding station just before entering the pinch rolls of the mill where the free edges of the flanges meet along the respective side boundaries of the web 2.

Fig. 11b shows the progression from the pinch roll stand in the welding station through the planing station to final straightening of the turn's head. During the beginning of the planing of the closing flange 3 when said profile passes through the planing station, care needs to be taken to avoid deformation of the plastic hinges in the vicinity of the weld 8, to avoid exerting stresses on the weld itself so as to compromise the structural integrity of the beam.

Fig. 12 schematically shows a weld roll stand 17 comprising a support frame 35, a pair of independently mounted shaped support rolls 36, 36a, each of the shaped support rolls 36, 36a being mounted for rotation about an aligned axis of rotation 37, 37a, and a seam guide roll 38, 38a rotatably mounted on a respective inclined shaft 39, 39 a. The seam guide rollers 38, 38a serve to guide the free edges 16a, 16b of the strip 16 into longitudinal alignment with the desired weld seam line as the shaved strip 16 approaches the pinch roller area of the welding station.

Fig. 13 schematically shows a squeeze roll stand 18 comprising an upper cylindrical roll 40 and a lower cylindrical roll 41 with a profiled edge 41a, each of the rolls 40, 41 being rotatably mounted about a respective axis of rotation 42, 43. The squeeze rollers 44a, 44b rotatable about respective tilt axes 45a, 45b are adapted to urge the heated free edges 16a, 16b of the hollow flanges 3 along opposite margins of the web 2 to respective heated weld line regions to effect fusion therebetween to produce a continuous weld.

The free edges 16a, 16b are urged towards the respective weld line in a linear manner perpendicular to the respective axes of rotation 45a, 45b of the squeeze rollers 44a, 44b without a lateral "sweeping" action, thereby maintaining a stable incoming "shadow" or path between the respective free edges 16a, 16b and the opposite edge of the beam web 2 at the desired location or position of the weld seam.

Figure 13a shows schematically in a simulation an enlarged perspective view of the squeeze rollers 44a, 44b and the upper and lower support rollers 40, 41 as the free edges 16a, 16b of the strip 16 are guided into fusion with the boundaries of the spar web 2. In the illustrated embodiment, the lower support roller 41 is shown as separately mounted roller members, each having a shaped outer edge 41 a.

Fig. 14 schematically shows a planing roller housing 50 comprising a separate planing roller housing 51 slidably mounted on a mill bed 52. Each roll stand 51 supports a pair of complementary planing rolls 53, 54 to progressively impart shape to the outer edge regions of the steel strip 16, which are generally illustrated by the forming flow diagram shown in figure 11 a.

As shown, the planing rollers 53, 54 are idle rollers that are not driven.

Fig. 15 schematically shows a drive roller housing 60 that may be used with the forming table 11 or the planing table 13 shown in fig. 9.

The drive roll stand includes spaced side frames 61 mounted on a rolling mill bed 61a, the side frames 61 rotatably supporting upper and lower driven shafts 62, 63 on which cylindrical drive rolls 64, 65 are respectively mounted to engage the upper and lower surfaces of the web portion 2 of the hollow flange member as it is guided through the forming and planing zone of the cold rolling mill generally shown in fig. 9. Universal joints 66, 67 connect the driven shafts 62, 63 to output shafts 68, 69 of a conventional mill drive train (not shown).

If desired, the roll stand 60 may be provided with edge rolls 70, 71 to maintain alignment of the strip 16 passing through the mill. The edge rollers may be flat cylindrical rollers or they may have the shape as shown. The rollers 70, 71 are adjustably mounted to the roller frame 61 to accommodate hollow i-beams of various widths.

Figure 16 schematically shows the configuration of the planing rollers in the planing mill stand.

The planing of the flanges 3 is effected by respective planing rollers 75 located on each side of the web 2. As shown, the flanges 3 are subjected to planing pressure from a roller 76 and a roller 77 and a roller 78, the roller 76 being mounted for rotation on a horizontal axis 81, the roller 77 being mounted for rotation on a vertical axis 82, the roller 78 being mounted for rotation on a tilting axis 83.

Figure 17 shows one application of a beam according to the invention.

In the event that greater load bearing capacity is required where larger width beams cannot be accommodated, a pair of beams 90 may be secured back-to-back by any suitable fastener, such as spaced nut and screw combinations 91, self-piercing clamp fasteners or similar fasteners 92 or self-drilling self-tapping screws 93 through the beam web 90 a. When installed, brackets 94 for utility pipes 95 may be secured to flanges 96 with screws 97. Similarly, a hollow cavity 101 may be formed for enclosing a cable or communication cable 102 by securing a metal channel section 98 to the flange 99 with screws 100 or the like to form a conduit for the cable.

Figure 18 shows a hollow flange channel beam 103 for use as a floor joist. The floor joist 103 is supported on another hollow flange channel beam 104 which acts as a support base. Wood flooring 105 is secured to upper flanges 106 by nails 107 or the like, and similarly the intersection of each flange 106, 108 of the hollow flange channel beam is secured to the respective adjacent flange 106, 108 by angle brackets 109 anchored by screws 110.

Figure 19 shows a hollow flange channel beam 111 and a composite structure 115 in the form of an angle section 112 secured thereto by screws 113 or the like. The composite structure 115 may thus be used as a lintel-shaped structure to support a door or window opening in an air-brick structure whereby the brick 120 may rest on the angle section 112 but is otherwise secured to the spar web 114 of the channel beam 111 by a brick band 116 having a corrugated portion 116a anchored in a mortar bed 117 and a mounting tab 116b anchored to the spar web 114 by screws 118.

FIG. 20 illustrates the formation of a cruciform joint between hollow flange trough beams of the present invention.

In one embodiment, the hollow flange trough beams 120 may be secured perpendicular to the outer faces 121 of similarly sized trough beams 122 by angle brackets 123 secured to each of the webs 124, 125 by rivets, screws, or any other suitable fasteners.

In another embodiment, a smaller hollow flange channel beam 127 is nested between the flanges 128 of the channel beam 122 and secured therein by angle brackets 129 attached to the webs 125, 130 of the channel beams 122, 127, respectively, by screws or other suitable fasteners 131.

Alternatively, the adjacent flanges 128, 132 of the trough beams 122, 127, respectively, may be connected by angle brackets 133 secured by screws 134.

In yet another embodiment, adjacent flanges 128, 132 may be secured by a threaded fastener 135 extending between flanges 128 and 132.

The hollow interior 128a of the flange may be used for carrying cables 138 or the like, if desired.

Fig. 21 shows yet another composite beam 140 in which a wood beam 141 is secured to the outside of the spar web 142 by mushroom-head screws 148 and nuts 144 to increase cross-sectional resistance and/or provide decorative finishing.

It will be apparent to those skilled in the art that the hollow flange channel beams according to the present invention not only provide superior instantaneous force/mass per meter ratio compared to other structural beams, but they also provide ease of connection, ease of operation and flexibility of application which greatly enhances "usability". Considering all factors contributing to in-situ installation value or cost, hollow flange channel beams provide significant utility up to 2.5 times that of conventional hot rolled and laminated plank beams, and have instantaneous bearing capacity that allows superior performance over similar sized cold rolled open flange purlins over longer lengths.

Fig. 22 shows an alternative embodiment of a hollow i-section according to the invention.

As shown, the beam is formed with longitudinally extending alternating ribs 150 and recesses 151 to provide greater resistance to longitudinal bending in the beam web 2.

The flanges 3 may also have longitudinally extending strengthening ribs 152 formed therein, if desired.

FIG. 23 shows yet another embodiment of a reinforcing beam web hollow I-beam according to the present invention.

In this embodiment, the laterally extending spacer ribs 153 provide greater resistance to lateral bending in the spar web 2.

In this specification and the 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.

Claims (25)

1. A channel beam, comprising:

a planar elongate web; and

spaced hollow rectangular cross-section flanges extending perpendicularly from the inner surface of the web parallel to one another along opposite side margins thereof, the hollow flanges all extending in the same direction away from the inner surface of the web to form a longitudinally extending grooved recess of the inner surface of the beam and a planar surface extending between the opposite outer edges of the beam on the outer surface of the beam opposite the inner surface of the beam, the beam being characterized in that the web region extending between the spaced hollow flanges comprises a single layer of metal of uniform thickness; and

a ratio of a width of each of the hollow flanges between opposing outer surfaces thereof measured in a direction perpendicular to the outer surfaces of the beam to a height of the beam (Db) between opposing outer surfaces of the hollow flanges measured in a direction parallel to the outer surfaces of the beam is in a range of 0.25-0.35, and

wherein the ratio of the width of each of the hollow flanges to the height of each of the hollow flanges is in the range of 1.5-4.0.

2. The beam defined in claim 1, wherein the ratio of the width of each of the hollow flanges to the height of each of the hollow flanges is in the range of 2.5-3.5.

3. The beam defined in claim 2, wherein the ratio of the width of each of the hollow flanges to the height of each of the hollow flanges is in the range of 2.8-3.2.

4. The beam defined in claim 1, wherein the ratio of the width of each hollow flange to the height of the beam is in the range of 0.28-0.32.

5. The beam defined in claim 1, wherein the ratio of the width of each hollow flange to the thickness of the beam web is in the range of 15-50.

6. The beam defined in claim 5, wherein the ratio of the width of each hollow flange to the thickness of the beam web is in the range of 25-35.

7. The beam defined in claim 6, wherein the ratio of the width of each hollow flange to the thickness of the beam web is in the range of 28-32.

8. The beam of claim 1, wherein the beam is made of steel.

9. The beam of claim 8, wherein the beam is fabricated from high strength steel greater than 300 MPa.

10. The beam of claim 8, wherein the beam is made of stainless steel.

11. The beam of claim 1, wherein the beam is fabricated from a single layer of steel sheet.

12. The beam of claim 11, wherein the beam is manufactured by a folding process.

13. The beam defined in claim 11, wherein the beam is manufactured by a roll-forming process.

14. The beam defined in claim 13, wherein the free edges of the hollow flanges are continuously welded to adjacent beam web portions to form closed hollow flanges.

15. The beam defined in claim 14, wherein the free edges of the hollow flanges are continuously welded to the inner surface of the spar web intermediate opposite edges of the spar web.

16. The beam defined in claim 14, wherein the free edges of the hollow flanges are welded along respective side margins of the web.

17. The beam defined in claim 16, wherein the free edges of the hollow flanges are continuously welded by a non-consumable electric welding process.

18. The beam defined in claim 16, wherein the free edges of the hollow flanges are continuously welded by a consumable electrode process.

19. The beam defined in claim 16, wherein the free edges of the hollow flanges are continuously welded by a resistance or induction welding process.

20. The beam according to claim 8, wherein the structural beam is made of steel sheet with a corrosion resistant coating.

21. The beam defined in claim 8, wherein the structural beam is coated with a corrosion resistant coating.

22. The beam of claim 1, wherein the web includes a plurality of reinforcing ribs.

23. The beam defined in claim 22, wherein the reinforcing ribs extend in a longitudinal direction of the web.

24. The beam defined in claim 22, wherein the stiffening ribs extend transversely of the web.

25. The beam defined in claim 1, wherein each of the hollow flanges includes one or more longitudinally extending reinforcing ribs.