GB2118589A

GB2118589A - Reinforced steel sections

Info

Publication number: GB2118589A
Application number: GB08210740A
Authority: GB
Inventors: Graeme Neville King
Original assignee: ROLL FORM IND Pty Ltd
Current assignee: ROLL FORM IND Pty Ltd
Priority date: 1982-04-13
Filing date: 1982-04-13
Publication date: 1983-11-02
Also published as: GB2118589B

Abstract

Steel sections (of lipped channel and Zed-sections) are provided with reinforcing struts which interconnect the junction of the web and a first flange with the second flange, and may connect the junction of the web and the second flange with the first flange to triangulate the section. The struts may be formed from wires, rods, straps or strips or may be pressed from the web and the struts may be provided in inclined pairs along the section. <IMAGE>

Description

SPECIFICATION Improvements in steel sections BACKGROUND OF THE INVENTION (1) Field of the Invention: THIS INVENTION relates to steel sections.

(2) Brief description of the prior art: High tensile, cold formed steel sections (e.g. lipped channel and Zed-sections) have been used for many years as industrial and domestic structural framing and support members.

Despite their ready acceptance in the market place, they have a number of well-recognised disadvantages.

Firstly, the inherent springiness of the sections, when used as supporting members, makes the sections unsuitable for applications such as floor joists where dynamic loads cause the floor to bounce or vibrate. To overcome this problem, large, heavy gauge sections have been proposed but these are generally uneconomical when compared with conventional wooden joists. Secondly, the limiting factor in the application of the sections for beams or pulins is usually the maximum allowed deflection, despite the high ultimate strength of such sections. Once again, the sections must be "over-designed" to remain within the deflection limits when the design load is applied. Thirdly, in many applications, only one flange is fully restricted, e.g. bolts, screws to roof sheeting or flooring.The other flange is generally only restrained at each end of a span where the section is attached to a cleat or bearer. When a load is applied to the section, the unrestrained flange tends to twist due both to the non-symmetrical cross-section of the steel section and to the non-alignment of the shear centre of the section with the loading axis, the latter being substantially through the centre of the steel section.

SUMMARY OF THE PRESENT INVENTION It is an object of the present invention to provide at least one reinforcing strut or like means to connect one flange or return flange to the web.

It is a preferred object that the reinforcing strut or the like connects the flange or return flange to the web at a point adjacent the junction of the web and the second flange.

It is a further preferred object to doubly triangulate the steel section to form a strong truss-like structure.

It is a still futher preferred object to provide a number of methods and means for carrying the invention into effect and which are simple and inexpensive.

Other preferred objects will become apparent from the following description.

In the broad aspect, the present invention resides in a steel section including: a web interconnecting a first flange and a second flange; and reinforcing means interconnecting said first flange to said web adjacent the junction of said second flange and said web.

Preferably, the first flange is provided with a return flange along its distal side and the reinforcing means is connected at one end, to either the first flange, the first return flange or the junction of the first flange and the first return flange.

Preferably the section further includes a second return flange on the second flange and the reinforcing means interconnects said second flange or second return flange to the web adjacent the junction of said first flange and said web.

Preferably the reinforcing means comprises reinforcing struts in the form of wires, rods, straps, strips or the like. The struts may be pressed from the web and may be provided with reinforcing ribs or flanges.

Preferably each strut includes two wire- or rod legs or two straps which are angularly inclined to each other and to the longitudinal axis of the section. The included angle between the legs or straps may be in the range 30 to 150 , more preferably 60 to 120 , most preferably 90 .

The struts may be alternated along the section with the apexes between the legs or straps provided adjacent the junction of the first flange and the web, and the junction of the second flange and the web respectively.

The struts may be welded, brazed, riveted, bolted, clinched, screwed or fixed by adhesives to the section.

In one preferred embodiment, the struts have a pair of lateral feet and the legs may be spaced apart to form a substantially linear apex portion, and the lateral feet and the apex portion are clamped to the section by tabs punched out of the section by a suitable metal-working tool. During the punching operation, the feet and apex portion are deformed or bent to engage the side edges of one or more respective tabs to prevent or reduce any sliding movement of the feet or apex portion along the section. The tabs may be wrapped around the feet or apex portion, but this is not essential to locate and restrain the struts.

BRIEF DESCRIPTION OF THE DRAWINGS To enable the invention to be fully understood, a number of preferred embodiments will now be described with reference to the accompanying drawings, in which: Figure 1 is a front view of a first embodiment of a lipped channel (or C-) section; Figure 2 is a sectional end view taken on line 2-2 on Fig. 1; Figure 3 is a sectional view of a portion of the section taken on line 3-3 on Fig. 2; Figure 4 is a sectional view of a further portion of the section taken on line 4-4 on Fig. 2; Figure 5 is a front perspective view of a second embodiment of a lipped channel section; Figure 6 is a front perspective view of a third embodiment of a lipped channel section; and Figure 7 is an end view of Fig. 6.

DETAILED DESCRIPTION OF THE PRE FERRED EMBODIMENTS Referring to Figs. 1 and 2, lipped channel (or C-) section 10 has a web 11 interconnecting a top flange 1 2 and bottom flange 13, the flanges being provided with top- and bottom return flanges 14, 1 5 respectively along their distal sides.

A series of reinforcing struts 16, 17, formed of high tensile (or mild steel) wire or rod, are provided at regular spaced intervals alternately along the C-section 10.

Before the struts 16, 1 7 are fixed in position in the C-section 10, each strut is formed with a pair of angularly inclined legs 1 8 connected by a substantially straight apex portion 1 9 which is arranged to lie along the junction of the web 11 and the top- or bottom flanges 12, 1 3. The inclined angle A between the legs may be in the range of 30"-150", more preferably 60" to 120 , most preferably 90". The distal ends of the legs 1 8 are provided with outwardly directed feet 20 which are substantially parallel to the apex portion 1 9.

The struts 16, 1 7 are snapped into position in the C-section 10. Each strut 1 6 has its apex portion 1 9 lying along the junction of the web 11 and bottom flange 1 3 and its feet 20 lying along the junction of the top flange 1 2 and top return flange 14, while each strut 1 7 has its apex portion 1 9 lying along the junction of the web 11 and top flange 1 2 and its feet 20 lying long the junction of the bottom flange 1 3 and bottom return flange 1 5. The feet 20 of adjacent struts 16, 1 7 are centred on a common transverse axis.

The apex portion 1 9 and the feet 20 are fixed to the C-section by tabs punched out of the web 11 and the top- and bottom flanges 12, 1 3 by a clinching tool (not shown).

Referring to Fig. 3, the clinching tool punches two spaced tabs 21 out of the top flange 1 2 for the struts.16 (or out of bottom flange 1 3 for the struts 17) and a third tab 22 out of top return flange 14 (or bottom return flange 1 5 respectively) to restrain each foot 20 in position. As the tabs 21, 22 are punched, the foot 20 is deformed into a substantially flattened W-shape as shown. Any tendency of any foot 20 to move along the Csection as a load is applied is resisted as the foot engages the respective side edges of the three tabs.

For example, if the applied load tended to move the foot 20 in Fig. 3 in the direction indicated by the arrow B, the side edges C of the tabs 21, 22 engage and/or dig into the foot 20 and restrain it against movement in the direction of the arrow. Similarly, movement of the foot 20 in the opposite direction is opposed by the opposide side edges of the tabs 21, 22.

Experimental work has shown that the feet display little, if any, tendency to pull out of the junction of the flanges 12, 1 3 and return flanges 14, 15 and so that tabs 21,22 do not have to wrap around the feet 20 but simply restrain the feet 20 against longitudinal movement in the C-section.

Referring now to Fig. 4, a pair of spaced tabs 23 are punched out of the web 11 and a third tab 24 punched out of the bottom flange 1 3 to restrain the apex portion 1 9 of the struts 1 6. (For the struts 17, the tabs 24 are punched out of the top flange 12.) As shown, the tabs 23 engage the struts at the junction of the apex portion 1 9 and a respective leg 18, while the tab 24 deforms the apex portion 1 9 into a substantially flattened W-shape (known as a "joggle"). In a similar manner to the feet 20, the apex portion 1 9 is restrained against longitudinal movement in the C-section 10 as a load is applied.

When the tabs 21. 22, 23, 24 are formed by the clinching tool, some of the galvanised coating on the C-section is "wiped" onto the edges of the tabs and resultant holes. This feature eliminates the need for later touchingup of the completed assembly with a suitable rust-resistant preparation. In addition, the holes provide suitable drain holes for any moisture which may enter the C-section. e.g.

when used as a structural member, thus eliminating the expensive and time-consuming operation of drilling suitable drain holes as are necessary in presently available C-sections when used in exposed conditions.

The bending of the apex portion 1 9 and feet 20 by their respective tabs, the resultant "joggle" in these components, and their engagement with the tabs (which bite into the wires) ensure that the struts 16, 1 7 are securely fixed in the C-section and will not move under design applied loads.

The relatively wide apex portion 1 9 and feet 20 ensure that each strut 16, 1 7 applies any load transmitted through it over a wide loading area, reducing the possibility of localized deformation of the C-section.

The web 11 is left clear for easy bolting at any position to the overlapped webs of similar C-sections and any reduction in strength of the web due to the holes left after the tabs are formed is more than compensated by the additional strength applied to the C-section by the struts 16, 1 7. Similarly, where the return flanges are weakened by the holes is where the maximum strength is gained in the Csection due to the inclusion of the struts.

As shown in Fig. 2, the C-section 10 is doubly triangulated. The first triangle is formed, by web 11, top flange 1 2 and strut 16, while the second triangle is formed by web 11, bottom flange 1 3 and strut 1 7. This means any tendency of the top or bottom flanges 12, 1 3 to twist is prevented or reduced as the flanges 12, 1 3 are fixed at both their junctions with the web 11 and their distal ends via the struts 16, 1 7. In addition, the portion of the C-section between the feet 20 of each strut 16, 1 7 is restrained from deflecting or springing when a load is applied due to the tensile strength of the legs 1 8 in each strut.Therefore, any deflection can only occur in the portions between the struts 16, 1 7 but the sum of these deflections will not exceed the maximum allowable deflection under the designed load. Finally, the sheer centre is effectively moved substantially towards the mid-point of the C-section and so into substantial alignment with the loading axis of the beam to further reduce any twisting movement on the beam.

The basic C-section 10 has now taken on the greater load carrying- and twist-resisting characteristics of a truss without the need for over designing the C-section or making the section uneconomic to manufacture.

Referring to Fig. 5, the wire struts 16a, 17a of the second embodiment are formed to a similar shape as the struts 16, 1 7 of the first embodiment with the exception that their respective apex portions 1 9a are continuously curved and not substantially flattened as in the first embodiment.

The struts 16a, 1 7a are positioned in the Csection 1 Oa in the manner hereinbefore described and their apex portions 1 9a and feet 20a are welded or brazed to the C-section 1 Oa to provide the desired triangulation of the section.

Figs. 6 and 7 show a third embodiment where the reinforcing struts 16b, 1 7b are formed from the material of the C-section 1 Ob. Each strut has a pair of straps 1 8b pressed from the web 11 b, with an undeformed portion of metal 1 9a between the pairs of straps 1 8b at their apexes. As shown in Fig. 7, the straps 1 8b are deformed out of the axis of the resultant slots 1 8c to enable the distal ends of the straps 1 8b to engage the top or bottom return flanges 14b, 15b and are welded, brazed or riveted thereto.

Preferably the distance between the straps 1 8b of adjacent struts 16b, 1 7b is greater than the length of the portion 1 9b between the straps 1 8b in a particular strut.

As with the C-sections 10, 1 Oa of the first and second embodiments, the C-section 1 Ob is doubly triangulated by the struts 1 6b. 17b.

If further strength is required, reinforcing ribs or flanges may be provided on the straps 1 8b to increase their strength.

In a further embodiment (not illustrated), the top- and bottom return flanges are rolled with a greater width than shown in Fig. 7.

Spaced longitudinal slits are cut in the return flanges intermediate their depth to form a series of spaced longitudinal straps along the section. The straps are bent out of the return flanges and inwardly towards the web and their free ends are welded or brazed to the junction of the opposite flange and the web, i.e. the straps formed out of the top return flange interconnect that return flange to the junction of the web and the bottom flange, and vice versa for the straps of the bottom return flange.

While lipped channel or C-sections have only been illustrated, similar reinforcing struts may be applied to Zed-sections, with the benefits of increased strength and resistance to twisting, as discussed previously.

By varying the thickness of the wire or rod (or the width of the straps), the included angle A between the legs or straps, and the spacing between the struts, a particular section can be tailored to be suitable for a wide range of applied loads and applications. For example, tests have shown that a particular C-section, which in its original form was not suitable for use as a floor joist, is now highly suitable in that application following the incorporation of the struts of the present invention.

While reference has only been made to steel sections, the invention may also be applied, with suitable modification, to aluminium sections or extrusions.

Various changes and modifications may be made to the methods and materials hereinbefore described to truss the steel sections without departing from the scope of the present invention.

Claims

1. A steel section including: a web interconnecting a first flange and a second flange; and reinforcing means interconnecting said first flange to said web at or adjacent the junction of said second flange and said web.

2. A steel section as claimed in Claim 1 and further including a first return flange on said first flange spaced from said web; and said reinforcing means includes a first strut having one end connected to said first flange, said first return flange or the junction of said first flange and said first return flange and the other end connected to said section at or adjacent the junction of said web and said second flange.

3. A steel section as claimed in Claim 2 and further including a second return flange on said second flange spaced from said web; and said reinforcing means includes a second strut having one end connected to said second flange, said second return flange or the junction of said second flange and said second return flange. the other end of said sec ond strut connected to said section at or adjacent the junction of said web and said first flange.

4. A steel section as claimed in Claim 3 wherein: each of said struts includes a pair of legs or straps which are angularly inclined to each other and to the longitudinal axis of said section; said first- and second struts being provided alternately along said section.

5. A section as claimed in Claim 4 wherein said first- and second struts are formed from steel wire or rod and include; a pair of angularly inclined legs interconnected by a substantially linear apex portion; an outwardly directed lateral foot on each leg substantially parallel to said apex portion; said apex portion and said lateral feet being clinched to said section by tabs deformed out of said web and said first and second flanges.

6. A section as claimed in Claim 5 wherein: during the puching operation to form said tabs, said apex portion and said lateral feet are deformed to engage the side edge of one or more respective tabs to prevent sliding movement of said apex portion or said lateral feet along said section.

7. A section as claimed in Claim 4 wherein said first- and second struts are formed from steel wire or rod and include: a pair of angularly inclined legs interconnected by a curved apex portion; an outwardly directed lateral foot on each leg; said apex portion and said lateral feet being welded or brazed to said section.

8. A section as claimed in Claim 4 wherein: said straps are punched out of said web and their free ends are welded or brazed to said first or second return flanges respectively.

9. A section as claimed in Claim 4 wherein: said straps are punched out of said first and second return flanges and then free ends are welded or brazed adjacent to the junction of said web and said second- and first-flanges respectively.

10. A section as claimed in Claim 8 or Claim 9 wherein: reinforcing flanges or. ribs are formed along said straps to increase their structural strength.

11. A section as claimed in any one of Claims 1 to 10 wherein said section is of substantially channel, C-, or Zed cross-section.

1 2. A steel section substalltially as hereinbefore described with reference to Figs. 1 to 4, or Fig. 5, or Figs. 6 and 7, of the accompanying drawings.