AU5842199A - Improvements relating to trusses - Google Patents

Description

WO 00/15921 PCT/AU99/00771 -1 IMPROVEMENTS RELATING TO TRUSSES This invention relates generally to trusses and methods of manufacturing the same. 5 Trusses currently in use generally comprise assemblies having top and bottom chords interconnected by a series of webs which are interconnecting members with different cross sections. Traditionally trusses are manufactured using different materials (i.e. steel and timber) or materials of the same type but of different dimensions for the structural elements being the webs, trusses and connection plates. A roof truss for example, is generally 10 triangular in shape with a series of webs extending between the bottom chord and the two top chords. In a parallel chord truss the top and bottom chords are generally parallel to one another with the webs extending therebetween in an inclined fashion. A varentl truss includes parallel top and bottom chords with the webs extending between them in a vertical fashion. Trusses may be formed from timber structural elements connected together to form 15 the truss. The various elements may be secured together using nail plates or the like. Other forms of trusses may utilise a combination of timber and metal structural elements. In the manufacture of such trusses the various components need first to be manufactured and thereafter assembled together. A major disadvantage of such trusses is that assembly can be relatively complicated and time consuming. 20 One object according to one aspect of the present invention is to provide an improved truss which alleviates one or more of the aforementioned disadvantages. Another object according to another aspect of the present invention is to provide an 25 improved method of manufacturing a truss. According to one aspect of the present invention there is provided a truss which includes two elongated generally channel shaped members which are adapted to be assembled together to form the truss. The channel shaped members may for example be generally C 30 shaped. Each channel shaped member includes two end flanges, a channel web extending WO 00/15921 PCT/AU99/00771 -2 therebetween and, in a preferred embodiment return flanges at the free end of each end flange the return flanges extending towards one another. The channel shaped members are preferably configured such that in the assembled position the members are arranged so that the channel webs are spaced apart from one another the end flanges at respective ends of the 5 channel shaped members being in abutting relation. In the preferred form, the return flanges of each member are in abutting relation with respective portions of the channel webs of the other member. Each channel web has a plurality of apertures therein which are disposed in spaced relation along the channel web, the space between adjacent apertures forming truss webs. The truss when viewed in cross section is a hollow generally box-shaped structure. 10 Preferably, the end flange of one member at one end nests within the other member and the end flange of the other member at the other end nests within the first mentioned member. 15 In one form, the apertures may be generally triangular in shape with the apexes of adjacent apertures being disposed towards opposite end flanges of each member. The adjacent sides of adjacent apertures may be generally parallel to one another so that the truss webs formed by the space between the adjacent apertures are inclined with respect to the longitudinal axis of the members and extend generally in direction between the end flanges. 20 In another form of the invention, the apertures are generally square or rectangular in shape, and the adjacent sides of adjacent apertures are generally parallel to one another so that the truss webs formed by the space between the adjacent apertures are at right angles with respect to the longitudinal axis of the members and extend generally in direction between the 25 end flanges. Preferably, the sides of the apertures have flared portions which extend from the surface of the channel webs so that the truss webs are generally C-shaped when viewed in cross-section. Preferably, the flared portions extend inwardly from each channel web when 30 in the assembled position.

WO 00/15921 PCT/AU99/00771 -3 Preferably, when the members are in the assembled position the channel shaped members are secured to another. The members may be, for example, secured by stakes formed in the return flanges connecting the return flanges to the channel web of the other channel shaped member. In addition to or as an alternative the members may be secured 5 through the adjacent end flanges. The members may in addition to or alternatively be secured together by welding, rivets etc. According to another aspect of the present invention there is provided a method of producing a boxed truss includes the steps of, forming two channel shaped members each 10 member including two end flanges and a channel web extending therebetween assembling the members together so that the structural members are nested together with the end flanges at respective ends of the channel shaped members being in abutting relation, and forming a plurality of apertures in each channel web, the apertures being disposed in spaced relation therealong. 15 In a preferred form, the members include return flanges at the free end of each end flange the return flange extending towards one another, the return flanges of each of the members being in abutting relation with respective portions of the channel webs of the other member. 20 Preferably, the channel shaped members are roll formed using any suitable roll forming technique. Preferably, the apertures are punched and flared. Preferably, the members are staked together and this procedure may be effected using a conventional staking roll former. In one embodiment the apertures of the opposing sections may be off set so that 25 the web of one side supports the unsupported flange of the other side. The truss according to a preferred form of the present invention has the advantage that it is formed from two substantially similar elements only and the truss chords and webs are formed from the same element. The truss chords are defined by the double thickness of the 30 two abutting end flanges when the channel members are assembled together. This compares WO 00/15921 PCT/AU99/00771 -4 with existing trusses which comprise at least four elements. Existing trusses require additional end bearing support in the form of a concentration of vertical web members, but in the present invention the ends can be unpunched - without introducing additional members and connection means. 5 The fabrication process can be reduced to roll forming, punch and flare and roll forming the stakes. Accordingly, the process can be a fully continuous operation producing completed product at the speed of the roll former. 10 No jig is required to hold the assembled components in place until fixing as the finished product is both positioned and held in place until staked by the staking roll former. The webs may be formed by the punching out of holes in the channel webs and are strengthened by the flaring of the holes. The flare forms the webs into "C" like section. 15 The staking of the two sections provides a resistance to warping causing an increase in torsion. The staking of the two sections provides a resistance to the sliding of one flange along the other. Furthermore, the web, flange and web/flange connector are all formed from the one piece of material which creates increased web to chord joint rigidity, creates increased torsional resistance of the truss. The webs supporting the top and bottom chords can be 20 symmetrical and in line which resists twisting effects from eccentric loading applied to the top chord. A high strength to weight ratio is achieved because of no connectors/welding of components. As well as increasing the strength to weight ratio, the web integration with the chord material has the benefit of increasing overall stiffness. This can be compared with traditional (on timber trusses) connection using knuckle plates which are strong axially but 25 not in bending moment. Preferred embodiments of the invention will be hereinbefore described with reference to the accompanying drawings. 30 Figure 1 is a schematic perspective view of a truss according to the present invention; WO 00/15921 PCT/AU99/00771 -5 Figure 2 is a schematic end elevation of the truss shown in Figure 1 but which does not show the flaring in the apertures; Figure 3 is a schematic perspective view of one of the structural members forming the 5 truss; Figure 4 is a cross-sectional view taken along the line X - X in Figure 3; Figure 5 is a schematic side elevation of a modified form of truss; and 10 Figure 6 is a schematic side elevation of a further modified form of truss. Referring to the drawings there is shown a truss generally indicated at 10 comprising two generally "C" channel shaped structural members 12 and 14 each having two end flanges 15 16, 17, 18 and 19 and a channel web 21 and 22 extending therebetween. Each end flange further includes a return flange 23, 24, 25 and 26 at the free end thereof, the end flanges extending towards one another. The structural members are assembled together to form a generally box shaped member with one structural member nesting other structural member so that the channel webs are spaced apart from one another the end flanges at respective ends 20 of the channel shaped members being in abutting relation, the return flanges of each member being in abutting relation with respective portions of the channel webs of the other member. Each channel web 21 and 22 has a plurality of apertures 30 therein which are disposed in spaced relation along the channel web. 25 As shown in Figures 1 and 3 the apertures 30 are generally triangular in shape with the apexes of adjacent apertures being disposed towards opposite end flanges of each member and the adjacent sides of adjacent apertures are generally parallel to one another so that the truss webs 40 formed by the space between the adjacent apertures are inclined with respect to the longitudinal axis of the members and extend generally in direction between the end 30 flanges. As best seen in Figures 1, 3 and 4 the sides of the apertures 30 have flared WO 00/15921 PCT/AU99/00771 -6 portions 32. With reference to the truss shown in Figure 5 all the single section punchings in one orientation and from one side, for each of manufacturing, allows the apex of one penetration 5 to coincide with the base of the other channel penetration when boxed. This orientation causes the webs to be diametrically opposed from one side to the other. This orientation is beneficial in resisting bearing loads from internal supporting walls when the truss is used in two or multiple span applications, because the reinforced apex can withstand greater loadings than the base portion. Any point load in proximity of the reinforced apex will be resisted 10 by the increased bearing stiffness due to the combination of adjacent apex points causing a smaller effective length of base plate portions either side. When the apex and base portions are in similar orientation when viewed from the side of the truss (Figure 1), the base plate section acts to resist the action of a point load and may in some circumstances need a stiffening bracket to be fitted to withstand the load. This bracket will be required at a far 15 greater load in the previous arrangement. With reference to Figure 6, the truss is comprised of a series of uni oriented penetrations both sides. The advantage of this arrangement is that there is a distinct difference in loading capacity from the top to the bottom of the beam. The top is suited to 20 resisting combined bending and compression loading, the bottom is best suited to resisting bearing loads from internal supports, so that the truss orientation with the top side up gives the better design strength capacity in certain applications such as for floors. The channel shaped members are secured to one another by means of stakes 33. 25 To manufacture the truss, metal which may for example be steel coil is roll formed into two similar channel shaped members 12 and 14. The members are then punched with a series of apertures 30. Alternatively, the apertures may be punched before roll forming. The apertures 30 are then flared (the punch and flare could be carried out in the same process 30 or in subsequent processes). One channel spaced member is then inverted so that it nests WO 00/15921 PCT/AU99/00771 -7 into the other. Each channel member has one flange smaller in overall width by twice its thickness than the other flange, so that it nests inside the larger flange of the mating channel whose smaller flange in turn nests inside the layer flange of the first channel. The two members are then staked together through the double thickness of the return flanges 23, 24, 5 25, 26 at the web 21 and 22. Finally, it is to be understood that the various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.

Claims (11)

1. A boxed truss which includes two elongated structural members which are adapted to be assembled together to form the truss, each structural member including, when viewed in 5 section or profile a generally channel shaped member including two end flanges and a channel web extending therebetween, the structural members being configured such that in the assembled position the structural members are nested together so that the channel webs are spaced apart from one another the end flanges at respective ends of the channel shaped members being in abutting relation, each channel web having a plurality of apertures therein 10 which are disposed in spaced relation along the channel web, the space between adjacent apertures forming truss webs.

2. A boxed truss according to claim 1 further including return flanges at the free end of each end flange the return flanges extending towards one another, the return flanges of each 15 member being in abutting relation with respective portions of the channel webs of the other member.

3. A boxed truss according to claim 1 or claim 2, wherein the apertures are generally triangular in shape with the apexes of adjacent apertures being disposed towards opposite end 20 flanges of each member and said adjacent sides of adjacent apertures being generally parallel to one another so that the truss webs formed by the space between the adjacent apertures are inclined with respect to the longitudinal axis of the members and extend generally in direction between the end flanges. 25

4. A boxed truss according to claim 1, claim 2 or claim 3 wherein the sides of the apertures have flared portions.

5. A boxed truss according to any preceding claim wherein in the assembled position the channel shaped members are secured to another. 30 WO 00/15921 PCT/AU99/00771 -9

6. A boxed truss according to claim 4 wherein the members are secured by stakes formed in the return flanges.

7. A method of producing a boxed truss includes the steps of, forming two channel 5 shaped members each member including two end flanges and a channel web extending therebetween assembling the members together so that the structural members are nested together with the end flanges at respective ends of the channel shaped members being in abutting relation, and forming a plurality of apertures in each channel web, the apertures being disposed in spaced relation therealong. 10

8. A method according to claim 7 wherein the members include return flanges at the free end of each end flange the return flange extending towards one another, the return flanges of each of the members being in abutting relation with respective portions of the channel webs of the other member. 15

9. A method according to claim 7 or 8 wherein the channel shaped members are roll form.

10. A method according to claim 7, 8 or 9 wherein the apertures are punched and flared. 20

11. A method according to any one of claims 7 to 10 wherein the two members are staked together.