TECHNICAL FIELD

The present invention relates to a structural beam that has hollow flanges and to a method of manufacturing the beam.

BACKGROUND ART

Conventional structural beams, also referred to as universal beams, are I-shaped or H-shaped in transverse section and are used in a wide range of applications that require a load-bearing capacity. The applications include but are not limited to floor beams used in multi-story buildings, rafters in portal frame buildings, and bridge beams.

Conventional structural beams are made from a range of materials. Steel is a preferred material, with the beams typically being made from cold rolled steel, hot rolled steel I-sections, or I-sections fabricated from separate plates that are welded together.

One alternative to conventional structural beams is hollow flange beams. A

2010 thesis by Tharmarajah Anapayan submitted to the Queensland University of Technology describes hollow flange beams as“ cold-formed steel sections made of two torsionally rigid closed flanges and a slender web”

The present invention provides an alternative to the above-described conventional and hollow flange and other known beams.

The above references to the background art do not constitute an admission that the art forms a part of the common general knowledge of a person of ordinary skill in the art.

The above references to the background art are also not intended to limit the applications for the structural beam of the invention as disclosed herein. SUMMARY OF THE DISCLOSURE

According to the present invention there is provided a structural beam that includes a web and a pair of hollow flanges welded to the web, with each of the web and the flanges being made from a separate steel element, with the web extending into the hollow spaces defined by the flanges, and with the flanges being welded to the opposed faces of the web.

Forming the flanges as hollow flanges makes it possible to use post tension cables in the bottom flange (used in concrete and timber beams but not normally possible for steel). This is an advantage of the invention. There are other advantages of the beam structure of the invention that are described below.

The steel elements may be made from flat plate elements or from coiled strip/plate.

Each flange may be made from a flat steel plate that has been cold-formed into the flange shape.

Each flange may be made from coiled steel plate or strip that has been roll- formed into the flange shape.

The steel plate that forms the flanges may be any suitable thickness. In any given application, the thickness will be a function of factors such as the structural requirements for the beam, the flange shape, and the steel grade from which the beam is made.

The flange may be greater than 5 mm thick, more typically greater than 6 mm thick, and typically less than 16 mm thick.

The flanges may be formed into a required shape by any other suitable forming method.

The required shape of the flanges may be triangular-shaped in transverse cross- section.

A closed triangular flange is an advantage because it makes the beam cross- section much more stable against flexural -torsional buckling under major axis bending compared with an open flange I section beam. The flanges may be any other suitable shape in transverse cross-section. Other, although not the only other, options are square-shaped or circular-shaped in transverse cross-section.

The flanges may be the same size.

One flange may be larger than the other flange.

The extent to which the web penetrates into the hollow spaces defined by the flanges may be selected as required for a given set of beam requirements.

For example, this feature of selecting the extent of penetration of the web into the hollow spaces defined by the flanges makes it possible to vary the depth of the beam and produce a range of different depth beams from a single web.

By way of particular example with one embodiment, the applicant has found that increasing the beam depth from the minimum (i.e. flanges pushed hard against the web) to their maximum height makes it possible to vary the depth by 150 mm and increase the performance by 10%.

The web may be a solid web.

The web may have a plurality of openings along the length of the web to reduce weight.

The openings in the web may be in the form of a sinusoidal profile cut in the web which allows us to increase the web depth without increasing the amount of steel needed and only requiring a single cut.

The hollow flanges may be at least partly filled with a material.

The material may be concrete to improve the fire performance of the beam.

The material may be an elastomer or some other material to provide vibration damping, which can be an issue with long span floor beams.

The welds may be continuous welds.

The basic structure of the beam, i.e. forming the beam as three separate components assembled together as described above with the web extending into the hollow spaces defined by the flanges, makes it possible to optimise the properties of each component and, in particular, makes it possible to form the beam from relatively thick steel plate. This is an advantage in many applications. The web may be any suitable thickness. In any given application, the thickness will be a function of factors such as the structural requirements for the beam, the flange shape, and the steel grade from which the beam is made.

The web may be greater than 3 mm thick, typically 4 mm thick, typically greater than 5 mm thick, more typically greater than 6 mm thick, and typically less than 16 mm thick.

The beam may be any suitable depth, and the same factors that determine the web thickness are relevant to the depth.

The depth of the beam may be 500-1500 mm and typically 600-800 mm.

According to the present invention there is also provided the above-described beam when used as a floor beam of a multi-story building.

According to the present invention there is also provided a method of manufacturing the above-described structural beam that includes the steps of:

(a) forming a pair of hollow flanges from two separate steel elements; (b) positioning the flanges and the web together so that the opposite side edges of the web extend into the hollow spaces defined by the flanges; and

(c) welding the side edges of the flanges to the opposed faces of the web. Step (b) of the method may include adjusting the position of the web within the hollow spaces defined by the flanges and thereby varying the overall depth of the beam to a selected beam depth. The basic structure of the beam described above makes the depth variation possible. As a consequence, different depth beams can be produced without having to cut different-sized webs. This helps with stock standardisation and is an advantage of the invention on this basis.

Step (a) of the method may include cold bending two steel plates to form the pair of hollow flanges.

The method may include forming the flanges in step (a) so that the flanges and the web fit together with an interference fit.

Step (a) of the method may include roll-forming steel strip or plate to form the pair of hollow flanges.

Roll-forming step (a) may include unwinding steel strip or plate from a coil and passing the strip/plate through a series of roll-forming stations that progressively form the strip/plate into a flange shape and cutting the elongate roll-formed product into flanges of a required length.

Step (c) of the method may include forming continuous welds.

The method may include forming openings in the web to reduce the weight of the beam.

The method may include filling the hollow flanges with a material to improve selected properties of the beam.

The method may include pre-cambering the beam by jacking one or both of the flanges in or out to form a required camber prior to welding the flanges to the opposed faces of the web. As a consequence, it is not necessary to form a camber by the normal practice of profiling the web. This means that it is possible to carry stock rectilinear webs and then pre camber the webs in production rather than having to make the webs to order. This is a further advantage of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the invention, a specific embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings of which:

Figure 1 is a side view of one embodiment of a structural beam in accordance with the invention;

Figure 2 is an enlargement of the circled part of the beam shown in Figure 1 and Figure 3 is a transverse cross-section of the beam shown in Figure 1. DESCRIPTION OF EMBODIMENTS

The embodiment of the structural beam of the invention shown in the Figures includes a web 5 and a pair of hollow flanges 7 welded to the web 5. The web 5 extends into the hollow spaces defined by the flanges 7.

The web 5 includes a plurality of openings 19 in the form of a sinusoidal profile cut in the web at spaced intervals along the length of the web 5. The purpose of the openings 19 is to make it possible to increase the web depth without increasing the amount of steel needed using only one cut to create mirrored parts

The triangular flanges 7 support the web 5 and limit localise buckling. Analysis carried out by the applicant indicates that the beam is about 50% lighter than an equivalent conventional beam section.

The web 5 and the flanges 7 are each made from a separate steel element. By way of example, the flanges 7 may be made from flat plate elements or coiled strip/plate.

Specifically, the web 5 is formed by cutting a flat steel plate to a required size. In addition, each flange 7 is made by cold-bending a flat steel plate into the triangular shape shown in the Figures.

Alternatively, the flanges 7 may be manufactured in a continuous process rather than the batch cold-forming process described above.

The continuous process includes roll-forming steel strip or plate to form the flanges 7.

The roll-forming step includes unwinding steel strip or plate from a coil and passing the strip/plate through a series of roll-forming stations that progressively form the strip/plate into a flange shape and cutting the elongate roll-formed product into flanges 7 of the required length.

Each triangular-shaped flange 7 has a base 11 and two sides 13 that extend from the base 11 and converge towards each other. The longitudinal edges of the sides 13 of the flanges are welded to opposed faces 17 of the web 5.

The final assembly forms closed flanges 7. Closed triangular flanges 7 make the beam cross-section much more stable against flexural-torsional buckling under major axis bending compared with an open flange I-section beam.

Forming the beam so that the web 5 extends into the hollow spaces defined by the flanges 7 makes it possible to adjust the extent to which the web 5 penetrates the hollow spaces. As described above, this flexibility in production is an advantage of the invention.

The flanges 7 are welded to the opposed faces of the web 5. The welds are continuous welds. As described above, the basic structure of the beam, i.e. forming the beam as three separate components assembled together with the web 5 extending into the hollow spaces defined by the flanges 7, makes it possible to optimise the properties of each component and, in particular, makes it possible to form the beam from relatively thick steel elements. By way of example, the web 5 may be greater than 3 mm thick, typically greater than 4 mm thick, typically greater than 5 mm thick, more typically greater than 6 mm thick, and typically less than 16 mm thick. Moreover, the steel elements that forms the flanges 7 may be 5 mm or more thick, typically at least 6 mm thick. Moreover, the depth of the beam may be 500-1500 mm and typically 600-800 mm. These dimensions are particularly suitable for floor beams in multi-story buildings.

Filling the hollow flanges 7 with concrete provides an opportunity to improve the fire performance.

Putting an elastomer or some other material in the hollow flanges 7 provide an opportunity for vibration damping, which is an issue with long span floor beams.

One option for a manufacturing method for the beam includes the steps of:

(a) forming a pair of hollow flanges 7 from two separate steel elements - for example by the cold-forming and roll-forming options described above;

(b) positioning the flanges 7 and the web 5 together so that the opposite side edges of the web 5 extend into the hollow spaces defined by the flanges 7; and

(c) welding the side edges of the flanges 7 to the opposed faces 17 of the web 5.

Many modifications may be made to the embodiment of the beam described in relation to the Figures without departing from the spirit and scope of the invention.

By way of example, whilst the embodiment of the beam shown in the Figures includes triangular-shaped flanges 7, the invention is not confined to this arrangement and the flanges 7 may be by suitable cross-sectional profile.

In addition, it is not essential to the invention that the flanges 7 be the same size as shown in the Figures. There may be situations where it is advantageous from a structural viewpoint to form the flanges as different sized flanges 7. By way of further example, whilst the beam shown in the Figures includes openings 19 in the web 5, the invention is not confined to this arrangement and extends to arrangements in which the web 5 is a solid element.

In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” and variations such as“comprises” or“comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the end lap system and components of the end lap system as disclosed herein.