U.S. patent application number 14/006279 was filed with the patent office on 2014-10-09 for beam and a method for reinforcing concrete slabs.
This patent application is currently assigned to Entek Pty Ltd. The applicant listed for this patent is Mark Allan Manning. Invention is credited to Mark Allan Manning.
Application Number | 20140298749 14/006279 |
Document ID | / |
Family ID | 46878548 |
Filed Date | 2014-10-09 |
United States Patent
Application |
20140298749 |
Kind Code |
A1 |
Manning; Mark Allan |
October 9, 2014 |
BEAM AND A METHOD FOR REINFORCING CONCRETE SLABS
Abstract
A beam for reinforcing a concrete slab, the beam including a
channel for receiving concrete mix therein, and the beam adapted to
receive at least one anchoring element such that the at least one
anchoring element protrudes into the channel, wherein the at least
one anchoring element is for engaging the concrete mix, such that
once the concrete mix hardens, the at least one element contributes
to engagement between the beam and concrete slab.
Inventors: |
Manning; Mark Allan; (North
Ryde, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Manning; Mark Allan |
North Ryde |
|
AU |
|
|
Assignee: |
Entek Pty Ltd
New South Wales
AU
|
Family ID: |
46878548 |
Appl. No.: |
14/006279 |
Filed: |
March 23, 2012 |
PCT Filed: |
March 23, 2012 |
PCT NO: |
PCT/AU2012/000307 |
371 Date: |
December 4, 2013 |
Current U.S.
Class: |
52/649.2 |
Current CPC
Class: |
E04C 3/293 20130101;
E04C 5/0645 20130101; E04B 5/40 20130101; E04C 5/06 20130101 |
Class at
Publication: |
52/649.2 |
International
Class: |
E04C 5/06 20060101
E04C005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2011 |
AU |
2011901064 |
Claims
1. A beam for reinforcing a concrete slab, the beam including a
channel for receiving concrete mix therein, and the beam adapted to
receive at least one anchoring element such that the at least one
anchoring element protrudes into the channel, wherein the at least
one anchoring element is for engaging the concrete mix, such that
once the concrete mix hardens, the at least one element contributes
to engagement between the beam and concrete slab.
2. A beam as claimed in claim 1, wherein the at least one anchoring
element is received through at least one hole in the beam.
3. A beam as claimed in claim 1, wherein the at least an anchoring
element is punched through the beam.
4. A beam as claimed in claim 1, wherein the channel includes a
base between two side walls, each side wall including and an
inwardly directed flange portion.
5. A beam as claimed in any one of the preceding claims, wherein
the beam has a substantially C-shaped cross sectional profile.
6. A beam as claimed in any one of the preceding claims, wherein
the at least one anchoring element protrudes from the underside of
the inwardly directed flange portions, toward the base of the
channel.
7. A beam as claimed in any one of the preceding claims, wherein
the at least one anchoring element is at least one screw, the
threaded portion of the at least one screw protruding into the
channel.
8. A beam as claimed in any one of the preceding claims, wherein
the inwardly directed flange portion is substantially L-shaped.
9. A beam as claimed in any one of the preceding claims, wherein
the inwardly directed flange portion is substantially C-shaped.
10. A beam as claimed in any one of the preceding claims, wherein
the beam is formed of two half parts.
11. A beam as claimed in any one of the preceding claims, wherein
the beam is formed of light gauge steel.
12. A system for reinforcing a concrete slab including: placing
formwork including at least one beam, the beam including: a channel
for receiving concrete mix therein such that a rib is formed in the
slab; and at least one element protruding into the channel for
engaging the concrete mix such that once the concrete mix hardens,
the beam is anchored to the slab.
13. A method for forming a concrete slab, the method including the
steps of: placing formwork including at least one beam, the beam
including: at least one channel for receiving concrete mix such
that a rib is provided in the slab; and, at least one anchoring
element protruding into the channel for engaging the concrete mix
such that once the concrete mix hardens, the beam is anchored to
the slab.
14. A method as claimed in claim 13, further including pouring
concrete mix into the formwork and allowing the mix to harden.
15. A method as claimed in claim 13 or 14 wherein placing formwork
includes fastening the at least one beam to an infill sheet.
16. A system for connecting an in-situ concrete slab to a light
gauge steel beam, wherein the slab includes a ribbed section, the
ribbed section being connected to the beam by one or more
connectors.
17. The system of point 16, wherein the steel beam section includes
top flanged portions, with the one or more shear connectors being
configured to connect the flanged portions to the in-situ
concrete
18. The system of any one of claim 16 or 17, wherein the system
further includes a metal infill sheet, the infill sheet being
connected to the slab by one or more connectors.
19. The system of any one of claims 17 to 18 wherein the connectors
are any one or a combination of steel screws, bolts, rivets, shear
studs or the like.
20. A beam as claimed in any one of claims 1 to 11, wherein two or
more of said beams are able to be fastened together.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to beams for reinforcing
concrete slabs, and methods of forming concrete slabs, in
particular ribbed concrete slabs.
DESCRIPTION OF THE BACKGROUND ART
[0002] The reference in this specification to any prior publication
(or information derived from it), or to any matter which is known,
is not, and should not be taken as an acknowledgment or admission
or any form of suggestion that the prior publication (or
information derived from it) or known matter forms part of the
common general knowledge in the field of endeavour to which this
specification relates.
[0003] Presently, in the field of construction, ribbed slabs are
used as one of the most efficient slab designs. This is typically
due to their utilisation of structural depth and reduction in
concrete weight, which is generally derived from the voids which
are formed between the ribbed beam elements. Permanent steel
(usually cold rolled) formwork systems, which act compositely is
with the in-situ concrete, also offer additional efficiencies due
to the designs using almost every component of the system both
before and after construction.
[0004] In the past, ribbed slabs have typically been constructed
using pre-cast or formed concrete beams with an in-situ slab infill
between, or by using composite structural steel formwork, which is
made from various cold rolled steel sheet profiles. The steel sheet
profile slabs are typically only one directional in their strength
characteristics.
[0005] However, the pre-cast concrete beams are typically heavy to
transport, crane lift intensive due to their weight, and also pose
significant safety concerns on site due to their size and weight.
Conventionally formed concrete ribs are expensive and generate a
lot of waste. Furthermore, structural steel formwork systems
generally do not adequately harness the composite slab efficiencies
of a true ribbed slab, which has its ribs spaced, according to one
example, at 1500 mm centres, which is far in excess of the typical
200 mm to 500 mm centres for standard one directional steel sheet
profiles.
[0006] Thus, the present invention seeks to substantially overcome,
or at least ameliorate, one or more disadvantages of existing
arrangements.
SUMMARY OF THE PRESENT INVENTION
[0007] In one broad form, the present invention provides a beam for
reinforcing a concrete slab, the beam including a channel for
receiving concrete mix therein and the beam adapted to receive at
least one anchoring element such that the at least one anchoring
element protrudes into the channel, wherein the at least one
anchoring element is for engaging the concrete mix, such that once
the concrete mix hardens, the at least one element contributes to
engagement between the beam and concrete slab.
[0008] In one form, the at least one anchoring element is received
through at least one hole in the beam.
[0009] Alternatively or additionally, the at least one anchoring
element is punched through the beam.
[0010] In another form, the channel includes a base between two
side walls, each side wall including and an inwardly directed
flange portion.
[0011] In a further form, the beam has a substantially C-shaped
cross sectional profile.
[0012] In one form, the at least one anchoring element protrudes
from the underside of the inwardly directed flange portions, toward
the base of the channel.
[0013] In another form, the at least one anchoring element is at
least one screw, the threaded portion of the at least one screw
protruding into the channel.
[0014] In one form, the inwardly directed flange portion is
substantially L-shaped.
[0015] In another form, the inwardly directed flange portion is
substantially C-shaped.
[0016] In one form, the beam is formed of two half parts.
[0017] In another form, the beam is formed of light gauge
steel.
[0018] In a further form, two or more of said beams are able to be
fastened together.
[0019] In another broad form, the present invention provides a
system for reinforcing a concrete slab including: [0020] placing
formwork including at least one beam, the beam including: [0021] a
channel for receiving concrete mix therein such that a rib is
formed in the slab; and [0022] at least one element protruding into
the channel for engaging the concrete mix such that once the
concrete mix hardens the beam is anchored to the slab.
[0023] In another broad form, the present invention provides a
method for forming a concrete slab, the method including the steps
of: [0024] placing formwork including at least one beam, the beam
including: [0025] at least one channel for receiving concrete mix
such that a rib is provided in the slab; and [0026] at least one
anchoring element protruding into the channel for engaging the
concrete mix such that once the concrete mix hardens, the beam is
anchored to the slab.
[0027] In another form, the method further includes pouring
concrete mix into the formwork and allowing the mix to harden.
[0028] In another form, placing formwork includes fastening the at
least one beam to an infill sheet.
[0029] In another broad form the present invention provides a
system for connecting an in-situ concrete slab to a light gauge
steel beam, wherein the slab includes a ribbed section, the ribbed
section being connected to the beam by one or more connectors.
[0030] In one form, the steel beam section includes top flanged
portions, with the one or more shear connectors being configured to
connect the flanged portions to the in-situ concrete
[0031] In one form, the system further includes a metal infill
sheet, the infill sheet being connected to the slab by one or more
connectors.
[0032] In another form, the connectors are any one or a combination
of steel screws, bolts, rivets, shear studs or the like.
[0033] It will be appreciated that the broad forms of the invention
may be used individually or in combination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] An example of the present invention will now be described
with reference to the accompanying drawings, in which:
[0035] FIG. 1A is a schematic diagram of an example plan view of a
system for connecting a slab to a beam;
[0036] FIG. 1B is a schematic diagram of an example cross-sectional
view (at 1) of the system of FIG. 1A;
[0037] FIG. 1C is a schematic diagram of an example cross-sectional
view (at 2) of the system of FIG. 1A;
[0038] FIG. 1D is a schematic diagram of example steel beam
profiles, which can be used with FIG. 1A.
[0039] FIG. 2A is a schematic diagram of another example plan view
of a system for connecting a slab to a beam;
[0040] FIG. 2B is a schematic diagram of an example cross-sectional
view (at 1) of the system of FIG. 2A;
[0041] FIG. 2C is a schematic diagram of an example cross-sectional
view (at 2) of the system of FIG. 2A;
[0042] FIG. 2D is a schematic diagram of example steel beam
profiles, which can be used with 25. FIG. 2A.
[0043] FIG. 3A is a schematic diagram of another example plan view
of a system for connecting a slab to a beam;
[0044] FIG. 3B is a schematic diagram of an example cross-sectional
view (at 1) of the system of FIG. 3A;
[0045] FIG. 3C is a schematic diagram of an example cross-sectional
view (at 2) of the system of FIG. 3A;
[0046] FIG. 3D is a schematic diagram of example steel beam
profiles, which can be used with FIG. 3A.
[0047] FIG. 4A is a schematic diagram of another example plan view
of a system for connecting a slab to a beam;
[0048] FIG. 4B is a schematic diagram of an example cross-sectional
view (at 1) of the system of FIG. 4A;
[0049] FIG. 4C is a schematic diagram of an example cross-sectional
view (at 2) of the system of FIG. 4A;
[0050] FIG. 4D is a schematic diagram of example steel beam
profiles, which can be used with FIG. 4A,
[0051] FIG. 5A is an example of the profile of a beam formed by two
half parts;
[0052] FIG. 5B is a schematic diagram of the profile one half part
of FIG. 5A;
[0053] FIG. 6A is a schematic diagram of a beam profile which may
be formed into a double beam profile by fastening two profiles
together, in this instance the two profiles are fastened together
by screw, rivet bolt or the like;
[0054] FIG. 6B is a schematic diagram of a beam profile which may
be formed into a double beam profile by fastening two profiles
together, in this instance the two profiles are fastened
welding;
[0055] FIG. 6C is a schematic diagram of a beam profile which may
be formed into a double beam profile by fastening two profiles
together, in this instance the two profiles are fastened welding or
crimping;
[0056] FIG. 6D is a schematic diagram of a beam profile which may
be formed into a double beam profile by fastening two profiles
together, in this instance the two profiles are fastened welding or
crimping;
MODES FOR CARRYING OUT THE INVENTION
[0057] FIGS. 1A to 1C show an example system for connecting a beam
to a slab and some example beam profiles.
[0058] In particular, the examples in the Figures show a concrete
slab 100 connected to a light gauge steel beam section 115. In this
particular example, the slab 100 is connected to the steel beam
section by one or more shear connectors 125 and 120 (anchoring
elements). The system described herein can include a ribbed slab
system incorporated in a typical structural flooring application,
including supporting elements.
[0059] Notably, the shear connector location is, in the examples
described herein, on top inwardly directed flanges of the steel
beam 115. This can allow for the connector 125 to act as both an
infill fastener and a concrete/steel beam shear connector.
[0060] As can be seen from Figures IA to IC, the steel beam section
115 includes sides and flanges where the preferred shear connector
125 location is on the top flanges, with additional shear
connectors 120 configured on the sides and bottom flange, in order
to connect the steel beam to the concrete slab 100.
[0061] The system described herein can also include a metal infill
sheet 130, where the infill sheet 130 can also be connected to the
slab 100 by one or more connectors (or anchoring elements) 125.
[0062] Thus, according to one particular example, steel roofing
screws can be used to secure the infill sheets to the top flange of
the steel beams. These screws can also act as the shear connectors
between the in-situ concrete within the beam/slab and the steel
beam itself. It will be appreciated, however, that many forms of
connectors such as rivets, bolts, shear studs, or the like, placed
through pre-drilled or punched holes, can also be used. In the
instance that the connectors (or anchoring elements) are punched
through the beam, the beam may have small indentations therein (or
other similar means) to encourage passage of the connectors through
the beam.
[0063] FIG. 1B also shows that in-situ concrete 135 can be used
with the system described herein. Furthermore, slab reinforcements
140 can also be used, and the system can include a zone 142 for
post-tensioning ducts and/or additional reinforcement, as required.
FIG. 1C shows that flashing 145, or void fillers, or formwork, can
be used between steel beam sections 115, as required. Notably, FIG.
1C shows the conventional formwork system at 150, and FIG. 1A also
shows that propping 155 can occur as required, where the number and
spacing of the propping lines can vary.
[0064] As can be seen in FIG. 1B, a typical `C` section purlin has
been used as the beam 115. However, it will be appreciated that the
gauge, size and profile may vary. Different example beam profiles
are shown in FIG. 1D (and for other examples described below, in
FIGS. 2D, 3D and 4D).
[0065] FIGS. 2A to 4D show variations of the example system
described herein.
[0066] In particular, FIG. 2C shows a variation including a steel
support beam 210 and shear studs 200, used as required. FIG. 3C
shows the steel support beam 210 including support angles 310, as
required. FIG. 4C shows the use of a wall support 410.
[0067] Notably, in this particular example, the slab 100 is a
concrete slab, and the shear connectors 125 and 120 can be steel
screw bolts, rivets, shear studs or the like. These features are
further described below.
[0068] The beam may also be formed of more than one part. For
example, two beams may be fastened together to provide a desired
profile (or "double beam" profile). FIG. 5A shows the profile of a
steel beam formed by two identical half parts 500, 501. A plate 503
is screw fastened to corresponding flanges 504, 505 of the two half
parts 500, 501 fastening them together. It will be appreciated that
the parts may be fastened together by other means and that the
joined parts need not be identical. FIG. 5B shows the profile of
one half part 500 from FIG. 5A. The advantage of using a double
beam profile is that it allows an increase the overall depth and
width of the section, which would otherwise not be possible using
commonly available steel coil widths. It will be appreciated that
the two half parts may be fastened together by other means, such
as, for example, welding, crimping or using screws rivets, bolts or
the like (See FIGS. 6A-6D).
[0069] It will further be appreciated that the presently described
system and method can utilise the inherent strength of the steel
formwork at all stages of the design life of the floor, from before
the pour of the in-situ concrete slab to the end of the design life
of the structure. Thus, the system and method described herein can
use the steel of the beams (ribs) both as formwork, but also as an
integral part of the reinforcement of the composite concrete ribbed
slab. Long term the steel shell of the rib acts as part (or all) of
the bottom longitudinal and the vertical shear reinforcement.
Transverse reinforcement may be required, and this can be achieved
via reinforcement placed within the in-situ concrete.
[0070] Some of the features of the beams and methods described
herein are further described below.
[0071] Full Composite Action
[0072] The slab ribs can gain full composite action due to the
designed connection of the metal infill to the steel beam section
and in-situ concrete. The connection also includes the detailing of
any additional shear connectors, as required by the design.
[0073] Thus, according to one particular example, the ribbed slab
composite action means that all of the steel beam section can be
included in the design calculations. This includes steel for shear,
bending, deflections and in some cases (depending on the profile)
fire reinforcement.
[0074] Furthermore, it will be appreciated that additional
reinforcement such as stressing wires/tendons, bar, mesh or fibre
reinforcement, and the like, may be added to the system, as
required by the design.
[0075] Increased Construction Capacity & Deflections
[0076] The steel beams can gain lateral restraint from the fixed
metal infill sheets and this restraint can allow the system to span
greater un-propped distances during construction (under wet
concrete). The continuity of the steel beams over supports (long
term or temporary) is also taken into account when calculating the
systems construction capacities and deflections.
[0077] Accordingly, commercially available structural steel
formwork can be used between the steel beams, such that the
structural steel formwork does not require propping and can span
easily with a relatively thin slab required. The steel beams (ribs)
in this example, are deeper than the structural steel formwork and
(usually) thicker, so they have a greater spanning capability
during construction, which can reduce propping distances compared
to standard structural steel formwork. Notably, the spanning
capability can be increased by the fact that the average concrete
depth over the net system is less than that of a standard
structural steel formwork system.
[0078] Light Gauge Steel Beams
[0079] As discussed herein, the light gauge steel beams connect to
the in-situ concrete slab and metal infill sheet via the shear
connectors, or anchoring elements.
[0080] The steel beams can be standard commercially available steel
"C" Purlins, or custom made steel sections, as required. Notably,
the use of custom made sections can improve the characteristics of
the system, but are not a necessary requirement.
[0081] The beams, according to one example, are formed from (but
not limited to) thin gauge galvanized steel. Furthermore, they can
be used to support the wet concrete slab over during the concrete
pour, and to act compositely with the slab long term.
[0082] It will be appreciated that by using a readily commercially
available section, the steel beams can be cost effective.
Furthermore, they are generally light and easy to handle.
[0083] Additionally, the steel beams can keep the thickness of the
slab over the infill sheets to a minimum, making the slab lighter.
Being deeper than the infill sheeting, they are able to, in one
example, span further too. It will be appreciated that this can
reduce the amount of temporary propping required during
construction.
[0084] Further still, the steel beams can also enable the metal
infill to maximize its spanning capability by shortening the
effective span of the infill. They act with the in-situ concrete
and the shear connectors to form a composite unit utilizing the
above-described materials.
[0085] Infill
[0086] The infill used can include any type of formwork, and in one
particular example is a commercially available structural steel
formwork (subject to detailed design), which can be used to span
the slab between steel beams during the concrete pour, and long
term. Thus, the infill used can be cost effective, light, and easy
to handle.
[0087] According to one particular example, the infill is able to
connect to the steel beams via the shear connectors. Thus, the
infill being connected (via the shear connectors) to the beams,
helps to restrain the top of the beams during the pouring of the
in-situ concrete slab.
[0088] Notably, it will be appreciated that the beams can be lined
next to each other such that there are only shear connectors in the
top flanges of each beam, and the system acts as a composite ribbed
slab, and infill is not required.
[0089] It will further be appreciated that the presently described
system may be implemented without the infill component.
[0090] Shear Connectors
[0091] The shear connectors keep the metal infill, steel beams, and
the in-situ concrete slab connected. It will be appreciated that
this can provide stability for a deck as a working platform. The
connectors can also restrain the top of the steel beam from
buckling during the concrete pour, and connect the in-situ concrete
to the beams in the hardened concrete state. Thus, they can be
large steel screws and may be placed anywhere on the top flanges of
the steel beam.
[0092] According to one example, the shear connectors can be
implemented as screws which act as both infill sheet fasteners and
composite action shear connectors. It will be appreciated that the
screw connectors may be substituted with bolts, rivets, shear studs
or the like located in pre-drilled, or pre-punched holes.
Additional screws, bolts, rivets, shear studs or the like may be
installed as required by the design.
[0093] Thus, the shear connectors can connect the infill to the
steel beams. During the concrete pour, the shear connectors can
enhance the buckling resistance of the top of the open beam.
Additionally, it will be appreciated that in the long term, the
connectors can connect the in-situ concrete slab to the steel beams
providing composite action between the concrete and steel.
[0094] As described, according to another particular example, the
shear connectors can be typically commercially available steel
screws. They may also take the form of commercially available
bolts, rivets, shear studs, or the like. Thus, they can be
implemented in a cost effective way, can be easy to attach and
require very little specialized equipment.
[0095] Accordingly, the shear connectors can be used to bring the
system all together, enabling the metal infill, steel beams and
in-situ concrete to act together as a unit during the various
design stages of a structure.
[0096] It will be appreciated that other anchoring elements may
also be used.
[0097] Flashing
[0098] In one example, folded steel flashing can be used to close
the space between the metal infill and a supporting surface.
Flashing can also provide sound and fire separation by setting down
the slab over load bearing and non load bearing walls (refer to the
Figures) for further system details.
[0099] Thus, the flashing can close off gaps at end supports to
control the flow of the in-situ concrete slab during the concrete
pour. The flashing can, in one example, keep the concrete from
pouring out the ends of the deck during a concrete pour.
[0100] Notably, commercially available flashing, void fillers,
formwork or variants thereof, can be used. Furthermore, flashing is
typically light weight, commercially available, easy to handle, and
cost effective.
[0101] Notably, any commercially available sheet metal may be used
for the flashing. It will be appreciated that void fillers or
formwork may also be used in place of steel flashing.
[0102] It will further be appreciated that the presently described
system may be implemented without the flashing component.
[0103] System Installation Procedure
[0104] According to particular examples, the system described
herein can be either partially assembled off site or fully
assembled on-site.
[0105] For the first case (partial off-site assembly) the light
gauge steel beams arrive on-site already connected to the metal
infill. These component sections are then laid out on the
supporting elements at the required centres. Alternate infill
sheets are then placed and fastened between the pre-assembled beam
elements. Steel flashing is then installed as required to close the
space between the infill sheets and the supporting structure.
[0106] For the second case (full on-site assembly), the light steel
beams and metal infill arrive on-site separately. The system is
installed by first placing the steel beams onto the supporting
elements at the required centres. The metal infill sheets are
fastened to the beam elements and, as with the first case, steel
flashing is then used to close the space between the infill sheets
and the supporting structure. The number, size and spacing of any
shear connectors, required to achieve full composite action, will
vary depending on the design. These connectors can be installed
either on or off site.
[0107] Installation of Temporary Propping
[0108] If required (depending on the spans, beam size and spacing),
temporary propping lines at the nominated centres can be installed
prior to installation. This propping will generally consist of (but
not limited to) standard propping frames and header beams.
[0109] Installation of Additional Reinforcement
[0110] Additional reinforcement, such as, for example, stressing
wires/tendons, bar, mesh or fibre reinforcement, may be added to
the system, as required by the design.
[0111] Placement of In-situ Concrete
[0112] According to one particular example, once the system and any
additional reinforcement is installed in-situ concrete is placed
over the slab deck at the required design thickness and allowed to
cure.
[0113] In its hardened state, the in-situ concrete interacts with
the shear connectors, so as to facilitate the transfer of internal
shear forces between the concrete, shear connectors and the light
gauge steel beams. This transfer of shear forces enables the slab
to act as a fully composite concrete/light gauged steel ribbed slab
system
[0114] Further Examples
[0115] According to one particular example, the system and method
described herein can maximise the composite actions between the
steel beams and the in-situ concrete above and within the beam
element. This composite action can be achieved through the
longitudinal shear connection detail of the steel beams to the
in-situ concrete and the metal infill sheeting. The connection
detail between the metal infill sheets and the steel beams is also
utilised during construction, which can also maximise the system's
un-propped span length.
[0116] Thus, in one particular example, the slab system can include
commercially available structural steel formwork (metal infill
sheets) spanning between the steel beam sections, which in
themselves also act as an integral part of the formwork system. A
reinforced in-situ concrete slab is poured over the deck, and can
act compositely with all elements of the formwork system. The
composite action can be achieved principally via the connection of
the metal infill sheets to the steel beams via steel screws, plus
any additional connectors between the beam and the in-situ slab as
required by the design. It will be appreciated that the screw
connectors may be substituted with bolts, rivets, shear studs or
the like.
[0117] It will be appreciated that many modifications will be
apparent to those skilled in the art without departing from the
scope of the present invention.
[0118] In the context of this specification, the word "comprising"
means "including principally but not necessarily solely" or
"having" or "including", and not "consisting only of". Variations
of the word "comprising", such as "comprise" and "comprises" have
correspondingly varied meanings.
* * * * *