It is known from GB-A-2,207,934 to make cellular beams from a standard beam of the kind specified, that is a beam having an elongate web part having, at least at one of two opposite sides of the web part, a transversely extending head and/or foot part so that the beam is, for example, of L, T, I, U or Z shape in cross-section. Such a beam, of the kind specified, may be cut in a continuous line defining a series of equal length lines lying at alternate sides of, equally spaced from and parallel to, the centre line of the web, each adjacent pair of equal length lines having their closest ends joined by a further line that is twice the length of an equal line and that crosses and is inclined to the centre line of the web, alternate further the lines being at equal and opposite angles to the centre line of the web. The two halves of the beam thus made are then separated and moved relative to one another by a distance sufficient to juxtapose the equal length lines and thereafter the adjacent equal length line portions of the web are welded together. This produces a cellular beam having a web of one and a half times the depth of the web of the original beam of the kind specified, but having the same weight owing to the fact that there are now a series of hexagonal apertures in the web.

It is stated in GB-A-2,207,934 that such known cellular beams, referred to therein as castellated beams, have only been made with hexagonal or square apertures or castellations, and that square shapes are avoided since their structural performance is less than of hexagonal apertures. Even a beam having hexagonal apertures has a structural limit which is lower than it might be owing to the presence of the corners of the hexagonal apertures adjacent the upper and lower flanges of the beam.

GB-A-2,207,934 seeks to provide a method of producing cellular or castellated beams having apertures of other than hexagonal shapes. To this end a method is disclosed in which a first continuous cut is made along the web followed by a second cut made along the web on a path differing from the path of the first cut, the cuts being such as define rectilinear sections lying on alternate sides of the centreline of the web and at least partly curvilinear section joining the closest ends of the adjacent rectilinear sections. The thus cut portions are then separated. Thereafter, these portions are welded together in regions formed by juxtaposition of rectilinear sections of the two portions.

An object of the present invention is to provide a new and improved method of making a cellular beam.

According to one aspect of the present invention we provide a method of making a cellular beam comprising a plurality of apertures comprising the steps of taking a beam having a web and making a cut along the web to separate the web into two portions, each portion having joining parts lying on alternate sides of the longitudinal centre line of the web, separating said portions of the web and then joining said portions together in regions formed by juxtaposition of the joining parts of the two portions wherein said cut defines a first part of each aperture and, after separating said portions, at least one further cutting operation is performed to define a second part of each aperture to produce apertures of a desired shape when said portions are joined together.

The beam may be separated into said two portions by a single continuous separating cut made along the length of the web, wherein the cut may provide between each pair of adjacent joining portions a pair of ears, one ear projecting from one portion of the web and the other ear projecting from the other portion of the web.

After separating said portions, said ears may be separated from the portion of the web on which they project by said further cutting operation to define a second part of each aperture.

The portions may be joined by welding together said joining parts and then said ears may be separated from said portions by said at least one further cutting operation.

The at least one further cutting operation may be performed after said joining step.

The further cutting operation may form a plurality of circular apertures in the web between said joining parts.

The separating cut may comprise a plurality of spaced rectilinear sections disposed on one side of the longitudinal centre line of the web and a plurality of spaced second rectilinear sections disposed on the other side of the longitudinal centre line of the web and alternating longitudinally with the first plurality of rectilinear sections and between each pair of longitudinally adjacent rectilinear sections disposed on opposite sides of said centre line there being a first curvilinear section lying on an arc with a first curve, then a connecting section, normal to said arc, then a second curvilinear section lying on an arc of a second curve to which said connection section is also normal, and wherein the first arcs and seconds arcs are of opposite curvature.

The curves may be part circular or part elliptical.

When the curves are part elliptical, they may be disposed with their longer axis parallel to the centre line of the web or normal to the centre line of the web.

The separating cut may comprise a plurality of spaced rectilinear sections which may be of the same or, substantially the same, length disposed on one side of the longitudinal centre line of the web and a plurality of spaced second similar rectilinear sections disposed on the other side of the centre line of the web and alternating longitudinally with the first plurality of rectilinear sections and a first plurality of inwardly convex pairs of curvilinear sections, each section of said first plurality of pairs extending from opposite ends of the first rectilinear sections towards the next adjacent rectilinear section on the opposite side of said centre line and a second plurality of inwardly concave pairs of curvilinear sections, each section of said second plurality of pairs extending from opposite ends of the second rectilinear sections extending towards the next adjacent rectilinear section of said first set and a plurality of connecting sections extending between the ends of adjacent curvilinear sections which are distant from the rectilinear sections.

The first plurality of curvilinear sections lie on a sector of a circle which intersects the adjacent ends of the rectilinear sections on one side of the centre line and which is of a diameter equal to that of said circular cut which is made to remove said ears and at least part of said rectilinear parts of the first set and the second plurality of curvilinear sections lie on a sector of a circle which intersects the adjacent ends of the rectilinear sections on the other side of the centre line and which is of a diameter equal to that of said circular cut which is made to remove said ears and at least part of said rectilinear parts of the second set.

According to a second aspect of the invention, we provide a cellular beam where manufactured according to the method of the first aspect of the invention.

An example of the invention will now be described with reference to the accompanying drawings in which:- Figure 1 is a diagrammatic side view of a standard I-beam showing a cut made in accordance with the invention, Figure 2 is an end view of the section of Figure 1, Figure 3 is a diagrammatic view showing a stage in the manufacture of a cellular beam in accordance with the invention, and Figure 4 is a diagrammatic side view of a cellular beam made in accordance with the invention.

Referring to Figures 1 and 2 of the drawings a standard I-beam 10, which in the present example is hot-rolled, has a web 11 which is bounded at opposite ends by transversely extending foot and head flanges 12,13. The overall height of the beam, h, may be of any suitable value in accordance with the required height of the cellular beam to be made. If desired the beam may be of any desired shape and may have one or more flanges at opposite ends of the web and so may be of L, T, I, U Z or other shape. The web has a longitudinally extending centre line 14.

The web 11 is cut, for example by means of a suitable flame-cutting torch controlled by an appropriate machine which controls the path of the cut.

The cut follows the path indicated at 15 and as a result the web is separated into two portions 16,17. The two portions 16,17 are moved longitudinally relative to each other in order to juxtapose rectilinear joining parts 18 and 20 which are then fastened together in the region defined by joining parts 18,20, for example by welding, as shown at 22 to provide the section 23 as shown in Figure 3. A beam of an overall height D = 1.5 x h is achieved.

The cut along the path 15 thus defines a first part of each aperture, in the present example comprising part-circular portions 25,26,27,28. A further cutting operation comprising a second plurality of further, circular, cuts 24 of a diameter equal to the original overall height h of the I-beam 10 are then made to define a second part of each aperture. The circular cuts 24 lie on the same circumference as the part-circular portions resulting from the first cut as shown at 25,26,27,28, thus separating ear parts 29a, 29b, 29c, and 29d, from the web as well as forming the rectilinear parts 19,21 to form curvilinear parts all lying on the path of the part-circular portions 25,26,27,28. As a result of this plurality of further cuts 24, a final section, as shown in Figure 4, is achieved.

Referring now particularly to Figure 1 the first cut 15 comprises a first plurality of rectilinear sections which are parallel to the centre line 14 as indicated at 30 to provide the joining part 18, and rectilinear part 19 and a second plurality of rectilinear sections on the opposite side of the centre line 14 and parallel thereto as indicated at 31 to provide the joining part 20 and rectilinear part 21. Extending from opposite ends of the sections 30 are adjacently convex sections 32, 33 whilst extending from opposite ends of the sections 31 are adjacently concave sections 34,35. The ends of the sections 32 which are remote from the section 30 are connected to the end of the sections 35 remote from the sections 31 by transversely extending connecting sections 36 whilst similar free ends of the sections 33,34 are interconnected by transversely extending connecting sections 37. Sections 32,33,34,35 lie on a circle of the diameter h and the sections 36, 37 are normals to the circles upon which the sections 32, 35 and 33, 34, respectively lie.

Section 32 thus defines part-circular portion 26 and with section 36 defines ear 29c. Section 33 defines part-circular portion 28 and with section 37 defines ear 29a. Section 34 defines part-circular portion 25 and with section 37 defines ear 29d. Finally, section 35 defines part-circular portion 27 and with section 36 defines ear 29b.

If desired, the circles may be of different diameter to the diameter h described hereinbefore. The relationship between the diameter Do of the circles, the overall height D of the cellular beam, and the spacing S between the centres of the circles, may be such as to provide values of S/Do of approximately 1.25 and D/Do of approximately 1.5. However these values may be greater or lesser within accepted design limits of applicability.

Other shapes than circular may be provided, for example the curves may be elliptical and the longer axis of the ellipse may be parallel to the longitudinal centre line 14 or normal thereto or be disposed at any desired angle or angles thereto.

In the present specification"comprise"means"includes or consists of" and"comprising"means"including or consisting of.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.