METAL ROOF TRUSS
FIELD OP THE INVENTION
The present invention relates generally to a metal roof
truss and relates particularly, though not exclusively, to
a method of forming a metal roof truss and its components
including elongate stiffening webs and chord members.
This application has been divided out of patent applicatio
No.718/K0LNP/2003.
SUMMARY OP THE INVENTION
According to one aspect of the present invention there is
provided a metal roof truss comprising:
a lower chord member at opposing ends being connected
to respective of a pair of upper chord members; and
a plurality of elongate compression webs at opposing
ends being connected to the lower chord member and one of
the upper chord members, respectively, the compression
webs and said chord members each being of a channel
section profile, one or more of the compression webs at
opposing ends being configured wherein opposing flanges of
said compression web are cut or otherwise preformed to
engage the lower chord member and/or said one of the upper
chord members whilst a protruding end web portion of said
compression web is mounted flush with a corresponding web
of said chord member.
It has been found that this engagement or contact of the
flanges of the compression web with the upper or lower
chord member increases the structural performance of the
roof truss.
Preferably, the lower and upper chord members together
with the plurality of compression webs are arranged in the
same plane.

Preferably, the chord members and the compression webs are
of a substantially identical sectional profile. More
preferably the chord members and the compression webs
include a web and an opposing pair of flanges each having
a free edge portion turned inwardly of the chord member or
compression web.
Preferably at least one of the flanges of the lower chord
member at its opposing ends is cut or otherwise preformed
to engage or contact respective of the upper chord
members.
Preferably the chord members and/or the compression webs
are in sectional profile asymmetric wherein one of the
opposing flanges is of a reduced height compared to the
other of said flanges. More preferably, a pair of the
chord members and/or compression webs are designed to
interlock with one another to form a closed section. In
one embodiment the web and/or the flanges of the chord
members and/or the compression webs include a
longitudinally extending stiffening rib.
Preferably interconnected of the chord members and the
compression webs include preformed holes which are
mutually aligned for fixing of the roof truss. More
preferably the chord members and the compression webs are
fixed together via one or more fasteners which engage the
preformed and aligned holes. Fasteners commercially
available in Australia under the trade mark TRUSSTITE are
particularly suited.

Preferably, the pair of upper chord members are at an
upper end connected to one another with an apex plate.
More preferably the apex plate is elongate and at least
one of its opposing longitudinal edges includes a
stiffening flange. In one embodiment the stiffening flange
includes a lip formed orthogonal to the apex plate and the
apex plate is fixed to the chord members via a plurality
of apex fasteners.
According to another aspect of the present invention there
is provided a method of forming a plurality of elongate
stiffening webs and/or chord members of a metal roof
truss, said method comprising the steps of:
forming one or more pairs of opposing notches in
elongate strip metal; and
roll forming the elongate strip metal to form said
stiffening webs and/or chord members continuous with one
another and of a channel section profile.
Preferably, the pair of opposing notches provide a
frangible connection at the juncture of the stiffening
webs and/or chord members, the frangible connection
permitting separation of said webs and/or chord members
after roll forming. Generally the frangible connection is
provided at the juncture of a web of adjoining of the webs
and/or the chord members. More preferably the separation
is effected by manipulation only without cutting or
separation tools.
Preferably said step of forming the notches involves
punching or stamping the strip metal.

Preferably the method also comprises pre-forming fastener
holes in opposing ends of the stiffening web and/or the
chord member. More preferably the fastener holes are
prepunched in a web of the channel section profile.
According to a further aspect of the present invention
there is provided a method of forming a metal roof truss,
said method comprising of steps of:
providing processing means and printing means being
arranged to operatively communicate with one another;
inputting design information to the processing means
wherein the metal roof truss configuration and fixing
details are calculated; and
printing at least the fixing details on components of
the metal roof truss.
Preferably the fixing details are printed on the component
of the roof truss to which the detail applies. More
preferably the fixing details are printed on elongate
stiffening webs and/or chord members of the metal roof
truss.
Preferably, printing of the fixing details involves ink-
jet printing on strip metal from which the roof, truss
component is thereafter to be roll formed.
Preferably, the inputting of design information involves
inputting dimensional and loading data pertaining to a
building structure on which the metal roof truss is to be
erected.

According to yet another aspect of the present invention
there is provided a method of forming a metal roof truss,
said method comprising the steps of:
providing processing means to which design
information is inputted for the calculation of the roof
truss configuration, and means for notching metal strip
from which components of the metal roof truss are to be
roll formed, said notching means being arranged, to
operatively communicate with the processing means, and
notching the metal strip utilising the notching means
wherein opposing pairs of notches are formed in the metal
strip, said pairs of notches defining a frangible
connection between adjacent components of the metal roof
truss and being shaped dependent on the roof truss
configuration.
According to yet a further aspect of the present invention
there is provided an apparatus for forming a metal roof
truss, said apparatus comprising:
processing means to which design information is
inputted for the calculation of the roof truss
configuration; and
means for notching metal strip from which components
of the metal roof truss are to be roll formed, said
notching means being arranged to operatively communicate
with the processing means wherein opposing pairs of
notches are formed in the metal strip, said pairs of
notches defining a frangible connection between adjacent
components of the metal roof truss and being shaped
dependent on the roof truss configuration.
Generally the adjacent components include one or more
elongate stiffening webs and/or chord members.

Preferably, the apparatus also comprises a roll former
operatively coupled to the notching means whereby the
prenotched metal strip is roll formed into a channel
section profile.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to achieve a better understanding of the nature
of the present invention a preferred embodiment of a metal
roof truss together with the various other aspects of the
invention will now be described, by way of example only,
with reference to the accompanying drawings in which;
Figure 1 is a perspective view of a metal roof truss;
Figure 2 is an exploded perspective view of the metal
roof truss of Figure 1;
Figure 3 is front and rear detailed views; of a web to
chord connection of the roof truss of Figure 1;
Figure 4 is front and rear detailed views of a heel
connection of the metal roof truss of Figure 1;
Figure 5 is a perspective view of pre-notched strip
steel of roof truss components prior to roll forming;
Figure 6 is a perspective view of an apex plate of
the metal roof truss of Figure 1; and
Figure 7 is a block flow diagram of the general
process steps involved in forming a metal roof truss
according to an embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in Figure 1 there is a metal roof truss 10
comprising a lower chord member 12 at opposing ends being
connected to respective of a pair of upper chord members
14 and 16. The metal roof truss 10 also comprises a
plurality of elongate stiffening webs such as 18 and 2 0

which at opposing ends are connected to the lower chord
member 12 and one of the upper chord members 14
respectively. In this example one of the stiffening webs
is a compression web 18 whereas the other stiffening web
is a tension web 20. The metal roof truss 10 of this
embodiment is shaped generally triangular wherein adjacent
ends of the upper chord members 14 and 16 are connected at
an apex connection 22. Opposite ends of the upper chord
members 14 and 16 are connected to opposing ends of the
lower chord member 12 at respective heel connection such
as 24. However, it should be appreciated that the metal
roof truss configuration may vary from that described
whilst remaining within the ambit of the invention, for
example the bottom chord may include more than one chord
member and similarly the pair of upper chord members may
be extended to multiple chords.
As shown in Figure 2 the lower and upper chords 12 to 16
together with the stiffening webs such as 18 and 20 are
cold roll formed from strip steel into a channel section
profile including a web 26 and an opposing pair of flanges
such as 28 and 30. The flanges 28 and 30 include free edge
portions which are turned inwardly toward one another. The
bottom and top chords 12 to 16 together with the
stiffening webs 18 and 20 are fabricated from relatively
light gauged strip steel typically of a thickness of
0.75mm such as that commercially available in Australia.
According to one aspect of the invention opposing ends of
the stiffening webs such as 18 and 20 are configured
wherein opposing flanges such as 28 and 3 0 of the
respective stiffening web 18 or 20 engage the lower chord
12 and one of the upper chords such as 14.

This is best illustrated in Figure 3 where according to
one embodiment the engagement or contact of the flanges
such as 28 and 3 0 of the compression web 18 increases the
structural performance of the roof truss 10. The lower and
upper chords 12 to 16 together with the stiffening web
such as 18 and 20 are arranged in the same plane and the
respective webs such as 2 6 of the stiffening webs such as
18 and the chord members such as 12 are flush with one
another. Importantly, the flanges such as 28 and 3 0 of the
compression webs 18 are at opposing ends cut or otherwise
preformed to engage or contact the lower and upper chords
12 and 14, respectively. The "depth" to which the flanges
such as 28 and 30 are cut is dictated by the orientation
of the stiffening web relative to the chord member such as
18 and 12 respectively.
The stiffening webs such as 18 and 2 0 and the lower or
upper chord members 12 to 16 include preformed holes such
as 32 and 34 which are mutually aligned for fixing of the
roof truss 10. Screw fasteners such as those commercially
available in Australia under the trade mark TRUSSTITE
which have a relatively coarse thread, engage the aligned
holes such as 32 or 34 so as to fix the stiffening web to
the lower chord 18 and 20 respectively. The aligned holes
such as 32 and 34 are generally prepunched in the strip
steel from the chord member such as 12 or stiffening web
18 is roll formed.
As shown in Figure 4 the opposing flanges such as 2 8 and
30 of the upper chord member 14 are similarly preformed at
one end to form the heel connection 24. The flanges 28 and
3 0 are cut or otherwise preformed at opposing ends of the

upper chord member 14 wherein the flanges 28 and 3 0 engage
or contact the lower chord 12. The lower and upper chords
12 and 14 also include preformed and mutually aligned
holes such as 38 which is engaged by a TRUSSTITE or other
fastener for fixing of the lower and upper chords 12 and
14. The engagement or contact of the flanges 28 and 30 of
the upper chord 14 with a corresponding flange such as 28
of the lower chord 12 further increases the structural
performance of the roof truss 10. The "depth" to which the
flanges 2 8 and 3 0 of the upper chord 14 or 16 are cut or
otherwise preformed is dictated by the configuration of
the roof truss 10 and in particular the angle of the upper
chord member 14 or 16 relative to the lower chord 12.
The channel section chords 12 to 16 and stiffening webs
such as 18 and 20 of this embodiment are asymmetric in
sectional profile. One of the opposing flanges such as 28
is of a reduced height compared to the other of said
flanges such as 3 0 wherein a pair of channel section
chords or webs such as 12 or 18 are designed to interlock
with one another to form a chord or stiffening web of a
closed section. The chords 12 to 16 and/or stiffening webs
18 and 2 0 may include one or more longitudinally extending
stiffening ribs. Preferably, the stiffening ribs are
formed in the web such as 2 6 of the channel section.
According to another aspect of the invention there is a
method of forming elongate stiffening webs such as 18 and
20 and/or chord members such as 12 to 16. As shown in
Figure 5 this embodiment of the method involves preforming
one or more pairs of opposing notches such as 36 and 38 in
elongate strip steel 40. The pair of opposing notches such
as 36 and 38 provide a frangible connection at the

juncture of, in this example, adjacent stiffening webs
such as 18 and 20. The preformed opposing notches 36 and
3 8 are shaped so that:
i) the adjacent stiffening webs 18 and 20 of this
embodiment can, after roll forming of the section, be
separated by manipulation or by repeated bending of the
adjacent webs 18 and 20;
ii) opposing flanges such as 28 and 3 0 of the; respective
stiffening web 18 or 20 contact the lower chord 12 or
upper chord 14 or 16 when the roof truss 10 is erected.
In this example the opposing notches such as 36 and 38
extend part way into the web such as 2 6 of the
corresponding stiffening web 18 or 20. Thus, the web 26 is
sufficiently weakened at the juncture of the stiffening
webs 18 and 20 to allow separation of the stiffening webs
18 and 20. However, the frangible connection is
sufficiently strong to retain the connection between
adjacent metal roof components such as the stiffening webs
18 and 20 during roll forming. Therefore, the various
components of the metal roof truss such as the stiffening
webs 18 and 20 can be fabricated as a "string". For
example, the stiffening webs such as 18 and 2 0 together
with the other stiffening webs of the roof truss 10 can be
fabricated as a single "string" and separated prior to
erection of the metal roof truss 10. Similarly, for
relatively small trusses the upper and lower chords such
as 12 to 16 may be linked in a "string". This increases
the speed at which the metal roof truss components can be
fabricated, reduces the risk of losing components, and
facilitates the erection of the metal roof truss such as
10.

The prenotched chords such as 12 to 16 and stiffening webs
18 and 2 0 may also be preholed to facilitate subsequent
assembly. In this instance fastener holes such as 32 and
3 4 are formed in opposing ends of the respective
stiffening webs such as 18 and 22 together with mutually
aligned fastener holes formed in this example in the
bottom chord 12. The fastener holes such as 32 and 34 are
prepunched in the web such as 26 of the respective roof
truss component either before, after, or during
prenotching of the strip steel such as 40. The prenotched
and preholed strip 40 is then cold roll formed into the
channel section depicted in Figure 2. The roll former is
relatively low cost and "dumb" whereas the prenotching and
preholing of the strip steel is to be effected with a
relatively high degree of precision. This ensures that on
fixing and erection of the metal roof truss such as 10 the
flanges such as 28 and 3 0 of for example the stiffening
webs 18 and 20 bear against the lower and upper chords 12
and 14 respectively.
Figure 6 illustrates an apex plate 42 to be included in
the apex connection 22. The apex plate 42 is elongate and
includes a stiffening flange 44 along one of its
longitudinal edges. The stiffening flange 44 isdefined by
a lip which is bent at right angles to the apex plate 42.
The apex plate 42 is screwed or otherwise fixed to the
webs of adjoining top chords 14 and 16. The apex plate 42
is oriented generally horizontally with the stiffening
flange 44 located between the top chords 14 and 16 and
directed inwardly of the roof truss 10. The apex plate 42
is suited to a range of apex connections up to an angle of
around 40 degrees. The apex plate 42 includes a plurality
of preformed holes such as 46 arranged for fixing of the

apex plate 42 to the upper chords 14 and 16 and the webs
such as 20.
Figure 7 is a block flow diagram of the various steps
involved in design and fabrication of a metal roof truss
such as that described in the preceding paragraph. The
general steps involved in forming the metal roof truss 10
are as follows:
i) design information is inputted to a processor which
is configured to output control information to a
prenotching and preholding apparatus;
ii) strip steel is fed to the prenotching and preholing
apparatuses which form the strip steel according to
the control information from the processor;
iii) fixing details generated and outputted by the
processor are printed on the prenotched and preholed
strip steel; and
iv) the strip steel is roll formed in a conventional
relatively low cost roll former.
The fixing details are preferably printed on the component
such as the chord 12 or stiffening web 16 to which the
detail applies. For example, the stiffening web 18 may
include the fixing details or instructions wherein it
requires two fasteners at each end to be secured to the
appropriately designated upper and lower chord.
Additionally, the roof truss component may include post-
assembly validation information for checking by a third
party. The marking of components is also intended to
assist with the design integrity of the roof truss and the
speed at which it is assembled.

The processor includes software which operates in a CAD
"environment" and determines the preferred configuration
of the metal roof truss depending on the dimensional and
loading data pertaining to the building structure.
Additionally, the program accurately determines the
prenotching and preholing requirements dependent on the
relative angles of the various roof truss components. This
is particularly important in ensuring that, for example,
the flanges of the stiffening webs contact the upper and
lower chords.
Those skilled in the art will appreciate that the
invention described herein is susceptible to variations
and modifications other than those specifically described.
For example, the sectional profile of the stiffening webs
and/or chord members may vary provided the structural
advantages of the opposing flanges engaging the chord
members are achieved. The prenotching of the strip steel
may vary provided a frangible connection is provided
between adjacent components, such as stiffening webs, of
the metal roof truss.
All such variations and modifications are to be considered
with the scope of the present invention the nature of
which is to be determined from the foregoing description.
In the preceding summary of the invention, except where
the context requires otherwise due to express language or
necessary implication, the word "comprising" is used in
the sense of "including", i.e. the features specified may
be associated with further features in various embodiments
of the invention.

WE CLAIM:
1. A metal roof truss comprising:
a lower chord member at opposing ends being
connected to respective of a pair of upper chord members;
and
a plurality of elongate compression webs at
opposing ends being connected to the lower chord member
and one of the upper chord members, respectively, the
compression webs and said chord members each being of a
channel section profile, one or more of the compression
webs at opposing ends being configured wherein opposing
flanges of said compression web are cut or otherwise
preformed to engage the lower chord member and/or said one
of the upper chord members whilst a protruding end web
portion of said compression web is mounted flush with a
corresponding web of said chord member.
2. A metal roof truss as defined in claim 1 wherein the
lower and upper chord members together with the plurality
of compression webs are arranged in the same plane.
3. A metal roof truss as defined in claim 1 or 2 wherein
the chord members and the compression webs are of a
substantially identical sectional profile.
4. A metal roof truss as defined in any one of the
preceding claims wherein the chord members and the
compression webs include a web and an opposing pair of
flanges each having a free edge portion turned inwardly of
the chord member or compression web.

5. A metal roof truss as defined in claim 4 wherein the
flanges of the lower chord member at its opposing ends is
cut or otherwise preformed to engage or contact respective
of the upper chord members.
6. A metal roof truss as defined in any one of the
preceding claims wherein the chord members and/or the
compression webs are in sectional profile asymmetric
wherein one of the opposing flanges is of a reduced height
compared to the other of said flanges.
7. A metal roof truss as defined in any one of the
preceding claims wherein a pair of the chord members
and/or compression webs are designed to interlock with one
another to form a closed section.
8. A metal roof truss as defined in any one of the
preceding claims wherein the web and/or the flanges of the
chord members and/or the compression webs include a
longitudinally extending stiffening rib.
9. A metal roof truss as defined in any one of the
preceding claims wherein interconnected of the chord
members and the compression webs include preformed holes
which are mutually aligned for fixing of the roof truss.
10. A metal roof truss as defined in claim 9 wherein the
chord members and the compression webs are fixed together
via one or more fasteners which engage the preformed and
aligned holes.
11. A metal roof truss as defined in any one of the
preceding claims wherein the pair of upper chord members

are at an upper end connected to one another with an apex
plate.
12. A metal roof truss as defined in claim 11 wherein the
apex plate is elongate and at least one of its opposing
longitudinal edges includes a stiffening flange.
13. A metal roof truss as defined in claim 12 wherein the
stiffening flange includes a lip formed orthogonal to the
apex plate and the apex plate is fixed to the chord
members via a plurality of apex fasteners.
14. A method of forming a plurality of elongsLte
stiffening webs and/or chord members of a metal roof
truss, said method comprising the step of:
forming one or more pairs of opposing notches in
elongate strip metal; and
roll forming the elongate strip metal to form said
stiffening webs and/or chord members continuous with one
another and of a channel section profile.
15. A method as defined in claim 14 wherein the pair of
opposing notches provide a frangible connection at the
juncture of the stiffening webs and/or chord members, the
frangible connection permitting separation of said webs
and/or chord members after roll forming.
16. A method as defined in claim 15 wherein the frangible
connection is provided at the juncture of a web of
adjoining of the webs and/or the chord members.

17. A method as defined in claim 15 wherein the
separation is effected by manipulation only without
cutting or separation tools.
18. A method as defined in any one of claims 14 to 17
wherein said step of forming the notches involves punching
or stamping the strip metal.
19. A method as defined in any one of claims 14 to 18
also comprising pre-forming fastener holes in opposing
ends of the stiffening web and/or the chord member.
20. A method as defined in claim 19 wherein the fastener
holes are prepunched in a web of the channel section
profile.
21. A method of forming a metal roof truss, said method
comprising the steps of:
providing processing means and printing means being
arranged to operatively communicate with one another;
inputting design information to the processing means
wherein the metal roof truss configuration and fixing
details are calculated; and
printing at least the fixing details on components of
the metal roof truss.
22. A method as defined in claim 21 wherein the fixing
details are printed on the component of the roof truss to
which the detail applies.
23. A method as defined in claim 22 wherein the fixing
details are printed on elongate stiffening webs and/or
chord members of the metal roof truss.

24. A method as defined in any one of claims 21 to 23
wherein printing of the fixing details involves ink-jet
printing on strip metal from which the roof truss
component is thereafter to be roll formed.
25. A method as defined in any one of claims 21 to 24
wherein the inputting of design information involves
inputting dimensional and loading data pertaining to a
building structure on which the metal roof truss is to be
erected.
26. A method of forming a metal roof truss, said method
comprising the steps of:
providing processing means to which design
information is inputted for the calculation of the roof
truss configuration, and means for notching metal strip
from which components of the metal roof truss are to be
roll formed, said notching means being arranged to
operatively communicate with the processing means; and
notching the metal strip utilising the notching means
wherein opposing pairs of notches are formed in the metal
strip, said pairs of notches defining a frangible
connection between adjacent components of the metal roof
truss and being shaped dependent on the roof truss
configuration.
27. A method as defined in claim 26 wherein the adjacent
components include one or more elongate stiffening webs
and/or chord members.
28. An apparatus for forming a metal roof truss, said
apparatus comprising:

processing means to which design information is
inputted for the calculation of the roof truss
configuration; and
means for notching metal strip from which components
of the metal roof truss are to be roll formed, said
notching means being arranged to operatively communicate
with the processing means wherein opposing pairs of
notches are formed in the metal strip, said pairs of
notches defining a frangible connection between adjacent
components of the metal roof truss and being shaped
dependent on the roof truss configuration.
29. An apparatus as defined in claim 28 wherein the
adjacent components include one or more elongate
stiffening webs and/or chord members.
30. An apparatus as defined in claim 28 or 29 also
comprising a roll former operatively coupled to the
notching means whereby the prenotched metal strip is roll
formed into a channel section profile.

A metal roof truss comprising:
a lower chord member at opposing ends being
connected to respective of a pair of upper chord members; and a plurality of elongate compression webs at opposing ends being connected to the lower chord member and one of the upper chord members, respectively, the compression webs and said chord members each being of a
channel section profile, one or more of the compression webs at opposing ends being configured wherein opposing flanges of said compression web are cut or otherwise
preformed to engage the lower chord member and/or said one of the upper chord members whilst a protruding end web portion of said compression web is mounted flush with a
corresponding web of said chord member.