AU646030B2

AU646030B2 - Roof truss systems

Info

Publication number: AU646030B2
Application number: AU74352/91A
Authority: AU
Inventors: Ralph Eric Warner
Original assignee: PANTEX Pty Ltd
Current assignee: PANTEX Pty Ltd
Priority date: 1990-05-18
Filing date: 1991-04-12
Publication date: 1994-02-03
Anticipated expiration: 2011-04-12
Also published as: AU7435291A

Description

646030 COMMONWEALTH OF AUSTRALIA Patents Act 1952 Name of Applicant(s): Address of Applicant(s): .r 0

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Actual Inventor(s): Address for Service: COMPLETE SPECIFICATION PANTEX PTY LTD 15 HUNTINGTON STREET CLONTARF QLD 4019 RALPH ERIC WARNER CULLEN CO., Patent Trade Mark Attorneys, 240 Queen Street, Brisbane, Qld. 4000, Australia.

FOR THE INVENTION ENTITLED: ee r ROOF TRUSS SYSTEMS f The following statement is a full description of the invention including the best method of performing it known to us: 2 THIS INVENTION relates to building componentry and is particularly concerned with metal roof trusses and parts and accessories therefor.

Metal roof trusses are commonly manufactured from high tensile strength galvanized or zinc/aluminium steel sections which are welded together in an appropriate array to suit the required span and roof slope. A strengthening bracket is also welded at the intersection of the top and bottom chords as this is the region (known as the knee joint) 10 in which maximum forces are acting, and simple welds are 0 generally insufficient to provide the necessary strength at 0* this location in the structure. Welding of trusses is labour intensive, and causes damage to the stee oating which must be repaired with touch-up paint. Furthermore, it is sometimes 000 inconvenient for trusses to be transported in an assembled form because of their bulk.

In order to simplify the assembly of trusses, whether this takes place in a factory or on-site, it is obvious that a bolt-together truss would have considerable benefits.

It is therefore an object orf this invention to provide a more efficient system for a bolt-together truss than available in the prior art.

It is a further object of the invention to provide novel parts and accessories for use in the construction of such a truss.

Accordingly, one aspect of the present invention provides a knee joint plate for use in the construction of a 3 metal roof truss which is erected by bolting the componentry elements together, said knee joint plate having a pentagonal configuration wherein two adjacent edges, and an edge opposite thereto, include lips formed at right angles to the plate, on the same side thereof, said plate being suitable for bolting to either the left- or right-side knee joint of the truss.

Bolting can be effected by the provision of accurately located holes formed in the plane of the plate and in the lip which is adapted to lie adjacent the bottom chord of the truss.

The pentagonal configuration may be regular but it ao go is preferred for the lip-free edges to be substantially parallel with one another and this gives rise to an irregular :06 configuration. Furthermore, the lip free edges are preferably smaller in length than the two adjacent lipped edges, and the remaining lipped edge has the greatest length. Most preferably, the lip-free edges will be substantially

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commensurate in length with the breadth of the bottom chord so that a snug fitting may be made therewith. The plate is, furthermore, preferably symmetrical, about its mid point so that it is more convenient to use as either a left- or right- S" hand knee joint.

*e**a Particularly preferred dimensions for a knee joint plate for use in connection with a truss constructed from a standard ZED purlin profile (known in the industry as Z100) top and bottom galvanized steel chords, are as follows: length of lip free edges 80-100 mm length of adjacent lipped edges 220-235 mm length of longest edge 425-445 mm width of lip on adjacent lipped edges 15-25 mm width of lip on longest edge 30-40 mm In such a plate, the holes through which the bolts are passed for connecting it to the top and bottom chords are suitably located as follows: Two holes formed in the axis defining two symmetrical halves of the plate, one of which holes correlates with the mid axis of the top chord and its precise location depends upon the angle of slope of the top chord, and the other of which is located 45-50 mm from the longest edge on said axis;

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One hole formed 20-30 mm from a lip-free edge and 40-55 mm from the longest edge; One hole formed similarly to but adjacent the opposite lip-free edge; One hole formed in the longest lip located 90 mm from a lip free end and 20-25 mm from the plane of the plate; and 590* One hole formed similarly to but measured from the other lip free end.

For low pitch trusses, the lower of the two holes formed in the axis defining two symmetrical halves of the plate, is replaced by two symmetrically located holes offset from the axis towards the respective lip free ends of the plate. Only one of these holes will, in practice, be used depending upon whether the plate is used on the left or right side of the truss.

The holes are suitably 10.5-13.5 mm in diameter so as to snugly accommodate 10-13 mm diameter bolts of 15-25 mm in length. The bolts may be connected with nuts and flat washers or, most preferably, with flanged nuts and bolts.

Preferably, two stiffening ribs are suitably provided to strengthen the knee joint against downloads such as when the truss is required to support a tiled roof. These may take the form of depressions in the plate surface which can be formed by stamping or like means. A particularly preferred depression is an elongated channel havi:g a

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regularly curved surface.

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"In the knee plate with the dimensions mentioned

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above, a depression is located so as to extend at right angles oeo to the longest side, in each symmetrical half of the plate.

Each depression may have a depth of 5-10 mm, a width of about 15-20 mm and a length of 75-90 mm, and be located about 90-110 mm from the symmetrical axis of the plate, mid-way between the

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longest edge and the intermediate'length edge.

The knee-joint plate is suitably fabricated from Iv galvanized high tensile steel and its purpose is to strengthen the two critical regions of a truss while providing a simple 0* locator for fastening bolts.

The top edges, in'use, of the knee-joint plate are folded at right-angles to the main body of the plate to provide stiffening and to strengthen the bottom chord of the truss in the region where it has been weakened by removal of a notch and also to provide a stiffening rib for the top chord where it overhangs to support a roof eave.

The bottom edge of the plate is folded up to provide a stiffening element to the bottom chord at the region where the truss is attached to the wall fame.

The plate is preferably formed symmetrically so that the same plate shape can be used at each end of the truss. Two sizes of plate can generally be manufactured to accommodate a range of truss pitch angles from 15 to 260, being the most common pitches used.

According to another aspect of the invention, there is provided a metal roof truss comprising the following elements: a bottom chord, two top chords, a plurality of web members extending between top and bottom chords, a knee joint plate connecting each top chord to one of the ends of the bottom chord, as referred to 15 above, and a connector plate connecting the top chords together, wherein the elements are connected by bolts.

o Preferably the connector plate has a rectangular configuration wherein two opposing edges a go: include a flange formed at right angles to the plate, each of which flanges are on opposite sides of the plate, said connector plate being suitable for bolting to the intersecting top chords of a truss by the provision of three holes located in the plane of the plate. One of the holes is preferably located on a line which bisects 25 the plate in half from top to bottom, in the upper, in 0 situ, region of the plate, where the mid-axis of each top chord bisects the another. The two other holes are located in the upper, in use, quadrants of the plate, in symmetrical regions which align with the mid axis of each of the top chords.

The preferred rectangular dimensions of the connector plate are approximately 180 x 109 mm for a chord pitch and approximately 140 x 115 mm for a 260 chord pitch. The flanges preferably project about 25-35 mm.

The location of the hole positions will preferably be about 15-20 mm from the upper, in situ, h) jedge of the plate for the hole on the plate bisecting line. The remaining two hole locations will be determined by the degree of pitch and will be separated from one another by 130-140 mm and from the upper, in situ, edge of the plate by 35-45 mm, in the case of a chord pitch of between 15 and 20°, or 40-50 mm in the case of a chord pitch of between 20 and 26°.

The purpose of flanges on the connector plate is to stiffen the apex joint while allowing straight forward bolted connections at the apex. The lower, in use, flange also provides a strong base for crane lifting of the truss during installation. Two sizes of connector plate generally suit the common truss pitches in the range of 15-26°.

The web member preferably comprises a metal 15 channel section having substantially perpendicular flanges and holes, to enable connection, located on the mid-longitudinal axis thereof which are twenty to twentyfive mm from each end of the channel section.

Lipped channel may also be used for the web S' 20 members where stresses in these members are critical.

Preferably, the chord members have holes punched at predetermined locations along the centre line of their web to allow bolting through the web member and knee joint plate, and connector plate.

25 The metal chords and webs can be of any convenient section however ZED section chords and CHANNEL section webs are preferred. Conventional ZED sections used as purlins for the construction of low rise buildings such as houses, garages and sheds, such as ZED section Z10010, are particularly suitable. Similarly, suitable CHANNEL section webs are FRAMING CHANNEL section or the purlin section C10010. In both cases the cold formed sections should comply with AS1538.

The roof trusses of the invention obviate the need for specialist construction since they can be assembled by simple bolt connections through re-punched holes and thus provide an economical alternative to Sexisting pre-fabricated trusses. Additionally, the trusses do not suffer from load strain at the critical knee joints, as in the case of past attempts to produce bolted trusses, and they can be lifted into place by lifting means connected to the connector plate without the possibility of buckling or other damage occurring to the truss.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a side-elevation view of a knee joint plate according to the present invention; Figure 2 is a cross-section through A-A of Figure 1; Figure 3 is a cross-section through B-B of S 15 Figure 1; Figure 4 is a side-elevational view of an apex plate according to the present invention; S. Figure 5 is a cross-section through C-C of Figure 4; 20 Figure 6 is a side-elevational view of a web according to the present invention; Figure 7 is a cross-section through D-D of S: Figure 6; oo Figure 8 is a side-elevational view of a 25 further knee joint plate according to the present invention; Figure 9 is a cross-section through the mid point of the knee joint plate of Figure 8; and Figure 10 is a side-elevational view of a roof truss according to the present invention.

Referring firstly to Figures 1-3, there is illustrated a knee joint plate fabricated from 2.0 mm galvanized steel having a tensile yield strength of 450 MPa. The plate has two adjacent edges and an opposing edge formed with lips 10, 11, 12 extending at rightangles thereto. Lips 10 and 11 extend approximately V i mm from the plane of the plate and lip 12 extends by a S/ distance of approximately 35 mm. The approximate length of the plate is 435 mm and the width from the apex is approximately 155 mm. The widths at the non-lipped ends is approximately 90 mm.

Strengthening ribs 13, 13a are formed in the plate and are trough-shaped. They are approx 4 mately mm long and 18 mm wide, and have a radius of curvature, R, of approximately 12 mm (see Figure 3).

Holes 14, 15, 16 and 17 having a diameter of 12.5 mm are formed in the plane of the plate to enable bolts to be located therein for fixing to the chords of the truss. Holes 14, 15 and 17 are located approximately 48 mm up from the bottom of the plate so that they align with the mid-sectional axis of the bottom chord. Holes 14 and 16, or 15 and 16 depending on whether the ilate is 15 fitted to the bottom left or bottom right side of the truss, are aligned with the mid-sectional axis of either the left or right top chord. Holes 14 and 15 are located approximately 25 mm in from the non-lipped edges. The precise location of hole 16 will depend upon the pitch of 20 the top chord. For a pitch of 15-200, the hole 16 will be located approximately 40 mm from the apex of the plate.

Holes 19, 20 are also formed in the lip 12.

o These holes are located approximately 80 mm from each end 25 of the lip, and 22 mm from the plane of the plate. The purpose of these holes is to enable connection to the under surface of the bottom chord by means of bolts. The S• diameter of the holes is also 12.5 mm so that 12 mm x mm bolts with nuts and flat washers, or 12 mm x 20 mm flanged nuts, may be used.

Referring now to Figures 4 and 5, the connector plate is likewise fabricated from 2.0 mm galvanized steel having a tensile yield strength of 450 MPa. The plate measures approximately 180 x 109 mm and has flanges 21, 22 formed on opposing edgeF which protrude at right S. angles from the plane of the plate in opposing direction.

,Both flanges extend approximately 30 mm from the plate.

Holes 23, 24, 25 of 12.5 mm diameter, are accurately located in the face of the plate. Hole 25 is located 17 mm from the top of the plate on an axis which bisects the plate in two. Holes 23 and 24 are located so as to lie on the mid axis of each of the top chords and will therefore vary depending upon the chord slope angle.

For a chord slope angle of 15-20°, holes 23 and 24 will be approximately 40 mm from the top of the plate and 23 mm from each side, respectively.

Figures 6 and 7 illustrate a web member fabricated from 1.0 mm galvanized steel of yield strength 550 MPa. The web includes a mid-section 26 which measures 75 mm across, and two flanges 27, 28 each measuring 32 mm across and extending at right angles thereto. Holes 29, 30 are precisely located on the 15 longitudinal mid-axis of the web member, some 25 mm from 0 each end thereof. The holes measure 12.5 mm in diameter and accommodate 12 mm uolts with nut and washer fixtures S* or flanged nuts and bolts.

Figures 8 and 9 illustrate a knee joint pl4te similar to that depicted in Figures 1 and 2. The differences from the earlier embodiment are primarily in the number and location of the holes and strengthening ribs, and the length of the strengthening ribs- In g: particular it will be observed that there are seven holes 25 40, 41, 42, 43, 44, 45, 46. Holes 40, 41 and 42 are centered 50 mm up from the bottom of the plate, with I. holes 40 and 42 being coated 25 mm from the parallel edges and hole 41 being on the symmetrical line of the plate. Holes 43 and 44 are in line with the strengthening ribs 47, 48, 138 nun from the parallel edges, and centred 115 mm from the bottom of the plate. Holes 45 and 46 are located on the symmetrical line of the plate and are 120 mi and 140 mm, respectively, from the bottom of the plate.

The strengthening ribs 47, 48 have the same general configuration as depicted in Figures 1, 2 and 3 but are approximately 22 mm in width, 105 mm in length SA and 4.5 mm in depth.

1< At"- Plate washers 49, 50 are also located on the bottom lip 51, about holes 52, 53 formed therein.

Finally, reference is now made to Fiyure In this illustration, like reference numerals to those used in the previous drawings refer to like parts. This illustration depicts a truss suitable for the construction of a gable roof. The componentry parts are those shown in the previous drawings. The truss comprises a bottom chord 31 and two top chords 32, 33 interconnected by web members 34. Knee plates 35, 36 are located at each knee joint and fixed by 12 mm diameter x mm long bolts and nuts and washers. A connector plate 37 is locatel at the. intersection of the two top chords and is similarly fixed.

15 The web members are connected to the chords by S:.x bolts which extend through holes located on the centre axis of the top and bottom chords.

The truss thus described overcomes the problems of conventional welded constructions and the problems which arose when bolted constructions were attempted.

Whilst the above has been given by way of S. illustrative example of the invention, many modifications and variations may be made thereto by persons skilled in the art without departing from the broad scope and ambit 25 of the invention as herein set forth in the following claims.

Claims

1. A knee joint plate for use in the construction of a metal roof truss which is erected by bolting its componentry elements together, said knee joint plate having a pentagonal configuration wherein two adjacent edges, and an edge opposite thereto, include lips formed at right angles to the plate, on the same side thereof, said plate being suitable for bolting to either Jhe left- or right-side knee joint of the truss by the provision of holes formed in the plane of the plate and in the lip which, in situ, lies adjacent the bottom chord of the truss.

2. A knee joint plate as claimed in claim 1, wherein the lip free edges are substantially parallel 15 with one another and, in situ, extend perpendicular to the bottom chord. S.

3. A knee joint plate as claimed in claim 1 or claim 2, wherein the lip free edges are of equal length to one another and are substantially commensurate in length with the breadth of the bottom chord.

4. A knee joint plate as claimed in any one of claims 1-3, wherein t,'o said adjacent lipped edges are intermediate in length between the length of the edge opposite thereto and the lengths of the lip free edges.

5. A knee joint plate as claimed in any one of the preceding claims, w)erein the lip free edges are between 80 and 100 mm in length; the adjacent lipped edges are between 220 and 235 mm in length; and the remaining edge is between 425 and 455 mm in length.

6. A knee joint plate as claimed in any one of the preceding claims, wherein tie lip on the adjacent edges of the plate is between 15 and 25 mm in width and the lip on the longest edge is between 30 and 44 mm in width.

7. A knee joint plate as claimed in any one of the preceding claims, wherein either two holes are formed in the axis defining two symmetrical halves of the plate, A one of which holes correlates with the mid axis of the Stop chord and the other of which correlates with the mid 13 axis of the bottom chord; or one hole is formed in the axis defining two symmetrical halves of the plate, which hole correlates with the mid axis of the top chord, and two holes are symmetrically formed to opposing sides of said axis, which two holes correlate with the mid axis of the bottom chord; (ii) a hole is formed 20-30 mm from each lip-free edge and 40-55 mm from the edge connecting the lip-free edges; (iii) a hole is formed in the lip on the edge connecting the lip-free edges which is 70-90 mm from each lip-free edge and 20-25 mm from the plane of the plate.

8. A knee joint plate as claimed in any one of the preceding claims, and including strengthening ribs in the 1 plate surface. 15

9. A knee joint plate As claimed in claim 8, wherein there are two strengthening ribs in the form of channels having regularly curved surfaces, each of said channels extending substantially parallel to the lip free edges, and being symmetrically located with respect to one another in each half of the plate.

A knee joint plate as claimed in claim 9, wherein each channel is 5-10 mm in depth, 15-22 mm in width and 75-105 mm in length.

11. A metal roof truss comprising the following 25 elements: a bottom chord, two top chords, a plurality of web members extending b ,tweein the top and bottom chords. a knee joint plate connecting each top chord to one of the ends of the bottom chord, and a connector plate connecting the top chords together, wherein the elements are connected by bolts; said truss chb.,acterised in that the knee joint plate is as defined in any one of the preceding claims.

12. A metal roof truss as claimed in claim 11 wherein the connector plate has a rectangular configuration with two opposing edges including a flange formed at right angles to the plate, each of which o LL flanges are on opposite sides of the plate, there being u three holes located in the plane of the plate, one of 14 which holes is located on a line which bisects the plate in half from top to bottom, in the upper, in situ, region of the plate, where the mid-axis of each top chord bisects the other, and wherein the other two holes are located in the upper, in situ, quadrants of the plate, in symmetrical regions which align with the mid axis of each of the top chords of the roof truss.

13. A metal roof truss as claimed in Claim 11 or Claim 12, wherein said web members each comprise a metal channel section- having substantially perpendicular flanges and holes, to enable connection, located on the mid-longitudinal axis thereof which are twenty to twenty- five mm from each end of the channel section.

14. A metal roof truss as claimed in any one of 15 claims 11-13, wherein said chord members each include a web having a plurality of holes punched at predetermined locations along a longitudinal mid axis thereof to erable bolting to the said componentry elements.

15. A knee joint plate substantially as herein described with reference to Figures 1-3 of the S'accompanying drawings. DATED this 25Ah day of October 1993 PANTEX PTY LTD By their Patent Attorneys CULLEN CO. a a.