Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MASONRY BRACKET, SYSTEM AND CONSTRUCTION METHOD
Field of the invention
The present invention concerns reinforcing devices for masonry walls. In
particular, the
reinforcing devices are brackets transferring stress such as shear forces
between masonry
courses. The brackets in the present invention are intended to be used in
masonry walls
comprising reinforcement.
Related art
In large buildings, masonry block walls are typically used as an infill for a
load bearing
framework. The load-bearing framework generally comprises a number of load-
bearing
steel and/or concrete columns and beams, between which panels of masonry
blockwork
are formed. Larger spans of masonry wall between the load-bearing columns, or
walls
with openings (e.g. for doors or windows) are more susceptible to forces
perpendicular to
the plane of the wall such as those exerted by wind. Excessive forces may
cause failures
in the structural integrity of the wall which can result in cracking or
failure.
It is therefore desirable to introduce reinforcing elements that have the
effect of
subdividing the masonry wall panel in to smaller sub panels and also
transferring wind
forces, transverse pressure differences, impacts or similar lateral loads to
the load bearing
framework. One common method of approaching this problem is to install
vertical steel
windposts within the masonry wall panel at intermediate points between the
load-bearing
columns. Such windposts typically extend from the bottom to the top of the
masonry
wall with a head portion and a foot portion secured to the beams or concrete
floor
slab/soffit of the framework. Windposts are typically large and cumbersome in
nature
making them difficult to install. Because of their cumbersome nature,
windposts are also
difficult to handle and are not desirable from a health and safety standpoint,
where good
practice and/or regulations require that building components carried by hand
be of
particular maximum manageable weights, typically 20kg or less. Windposts are
also
expensive, have significant procurement lead in times, and after installation,
quite often
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require further treatment to enhance their aesthetic, fire resistance, thermal
insulation
and/or acoustic properties.
Another method of subdividing a masonry wall panel into sub panels is to
provide a
horizontal reinforced concrete beam (known as a bond beam) that extends
between and
connects to adjacent load-bearing columns. Such bond beams are referred to in
patent
document GB2442543. The bond beam is typically housed within a hollowed
masonry
course within the masonry wall and is reinforced by one or more reinforcing
bars
("rebars") cast into the concrete. At least some of the hollowed masonry
blocks may
have a hole in the bottom that allows a masonry course connecting member to be
driven
into a perpend of a masonry course immediately below. The connecting member
allows
shear forces to be transferred between the courses concerned, effectively
tying adjacent
courses to the bond beam course, further enhancing the strength and cracking
resistance
of the masonry panel as a whole.
Once the rebar and connecting members are in place the hollowed masonry course
is
typically filled with concrete to form the bond beam. In such a bond beam, the
quantity
and location of the rebars is critical to the strength and bending moment
resistance of the
bond beam itself, and hence the characteristic design load of the wall.
Several devices
exist that can be used to locate a rebar within a concrete casting at one or
more specific
positions.
One such device is described in patent document U56629394 which discloses a
rebar
hanger for suspending rebars comprising a form hook for hooking on top of a
concrete
form, a first rebar hook for supporting a first rebar that extends away from
the lower end
of an inner section of the form hook and a second rebar hook for supporting a
second
rebar that extends downwardly and inwardly from the inner end of a brace.
Another such device is described in patent document U55907939 which discloses
a
reinforcing bar hanger comprising a pair of supporting arms contacting a
supporting
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block and vertically extending hanger members terminating in a rebar cradle
for receiving
and supporting a rebar to be positioned within the wall.
Alternatively for short spanning walls, the rebar can simply be positioned
within cleats or
similar securing brackets fixed to the load-bearing columns or within suitably
sized holes
formed in the supporting load bearing column. Either method would provide
sufficient
transfer of transverse forces between the rebar and the load bearing columns.
The rebar
can also be positioned by casting the bond beam in stages such that a bed of
concrete or
similar is placed to the appropriate height within the hollow of the block
before placing
the rebar. However this is more labour intensive and time consuming than
casting the
bond beam in a single pour. It may also introduce structural weaknesses into
the bond
beam if the separately cast sections do not fully knit together, or the rebar
is moved
laterally whilst the next layer of concrete is being placed and vibrated.
Summary of the invention
The present invention provides a masonry wall reinforcing bracket comprising
an
elongate inter-course stress transfer member, the stress transfer member
comprising a
rebar cradling feature. The stress transfer member may comprise a plate
operative to be
located within at least a perpend of a masonry wall. The stress transfer
member may act
for example to transfer shear stress between a bond beam and adjacent masonry
courses,
or to transfer stress between a bond beam and a vertically extending
reinforcing structure
built into the wall.
The bracket may further comprise a supporting member that protrudes
perpendicularly to
the length of the stress transfer member. The supporting member may comprise a
plate
operative to be located within a bed joint of the masonry wall. The supporting
member
may be a stabilising foot.
The present invention further provides a masonry wall tie bracket comprising:
a rebar
cradling feature for accommodating a rebar; and, an adaptor configured to
secure the
bracket to an elongate reinforcing member. Typically the adaptor may comprise
a socket
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for receiving an end of a vertical rebar or a spigot for inserting into the
top of a pillar within
the masonry wall. The pillar may be a steel column of any suitable section,
such as a box
section or other tubular or I or U section or solid.
In accordance with one embodiment of the present invention, there is provided
a masonry
system comprising: a wall reinforcing bracket comprising an elongate inter-
course stress
transfer member, a hollowed masonry block defining a bond beam cavity, and a
rebar
positioned within the bond beam cavity. The stress transfer member comprises a
supporting
member located in a bed joint, or a foot which rests on a floor of the bond
beam cavity, in either
case to provide a height alignment reference. The stress transfer member
further comprising a
rebar cradling feature supporting the rebar at a required location to allow it
to be cast into a
bond beam formed within the bond beam cavity.
Another embodiment provides a method of forming a masonry wall using the
masonry system
of the present invention, comprising the steps of locating the bracket such
that: I) at least part
of the stress transfer member protrudes into the bond beam cavity in a first
masonry course;
and, II) at least part of the stress transfer member protrudes into an
adjacent second masonry
course.
A still further embodiment provides a masonry structure comprising: a hollowed
masonry block
defining a bond beam cavity, a rebar positioned within the bond beam cavity,
and a wall tie
bracket. The wall tie bracket comprises: a) a first portion which protrudes
into the bond beam
cavity and which comprises a rebar cradling feature accommodating the rebar;
and, b) an
adaptor configured to secure the bracket to an end of an elongate reinforcing
member.
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Other preferred features of the present invention are as set out in the
dependent claims.
Illustrative embodiments of the invention are described below with reference
to the
drawings.
Brief description of the drawings
Figures 1 a to 1 e show a bracket embodying the present invention, the bracket
being
shown in relation to the surrounding masonry blockwork, rebars and rebar end
securing
cleats.
Figure 2 shows another form of bracket embodying the present invention.
Figures 3 and 3a show further brackets embodying the present invention where
the
brackets comprise cradling features located in different masonry courses.
Figures 3b and 3c are front and side views respectively of a yet further
bracket;
Figure 4 shows a cleat which may be used together with the masonry wall
reinforcing
brackets of the present invention.
Figures 5 and 6 are respectively front and side views of a cleat mounting
adaptor that
may be used together with brackets embodying the invention.
Figures 7a and 7b are side and front views respectively of a tie bracket of
the present
invention
Figure 7c is a vertical rebar cleat according to one aspect of the present
invention
Figures 8a and 8b show a vertical rebar being mounted into the tie bracket and
cleat of
Figures 7a-7c. =
Figures 9a and 9b show another tie bracket of the present invention.
Figure 10 shows the tie bracket of Figures 9a and 9b being inserted into a
vertical
reinforcement post.
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Detailed description
Referring to Figures la-le, the present invention provides a masonry wall
reinforcing
bracket 2 comprising an elongate stress transfer member 4 adapted and
configured to
extend between at least two courses 30 of masonry in use. The stress transfer
member 4
further comprises one or more rebar cradling features 6. The cradling feature
6 is
operative to support and locate a rebar 8 within a masonry wall 10, e.g. to
allow it to be
cast into a bond beam 12 formed within a course of hollowed masonry units 14.
The
bracket 2 is formed from a material that is stronger in tension and shear
compared to the
bond beam matrix material (i.e. concrete, usually) and mortar. Such a bracket
2 material
could be steel or another metal, or a metallic or non metallic composite
material.
As shown, the stress transfer member 4 extends between at least two
immediately
adjacent masonry courses 30, but it may in principle extend through any number
of
masonry courses 30. In use the stress transfer member may extend outwards to
one side
of the bond beam only. For example, a series of brackets may be provided
extending
from the bond beam into the adjacent masonry course alternately above and
below.
Alternatively, a central portion of the bracket may be embedded in the bond
beam in use,
with end portions projecting into adjacent masonry courses above and below the
bond
beam. The projecting portions may be symmetrically or asymmetrically disposed
with
respect to the reinforced concrete core of the bond beam. By having the stress
transfer
member 4 extending between adjacent masonry courses 30, shear forces applied
to the
wall 10 may be transferred between masonry courses 30 and more effectively
between
the masonry and the bond beam, to mitigate cracking and masonry course 30
separation,
ultimately dividing the wall 10 into sub-panels and increasing the
characteristic design
load of the wall 10.
Typically a masonry wall 10 is formed with bonded masonry whereby the perpends
22
between masonry units in one course 30 are offset horizontally from equivalent
perpends
22 in the adjacent masonry course 30. The stess transfer member 4 of the
bracket 2 in the
present invention extends at least into a perpend 22 or a specially formed
hole 16 in one
masonry course 30 and at least partially into a hollowed block 14 of an
adjacent masonry
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course 30. The bracket 2 and hollowed masonry block 14 form part of a combined
masonry system. The hollowed block 14 typically comprises a hole 16 in its
base
through which the stress transfer member 4 extends to protrude into the cavity
18 of the
hollowed masonry block 14 from below, as the hollow block is laid and
afterwards. The
open top of the cavity 18 allows the bracket to extend from within the
hollowed block
into the masonry course above. The part of the stress transfer member 4
extending into
the cavity 18 of the hollowed masonry block 14 comprises one or more rebar
cradling
features 6.
Once the stress transfer member 4 protrudes into the cavity 18, a rebar 8 may
then be
located within the rebar cradling feature 6. The present invention therefore
provides a
combined rebar cradling feature 6 and inter-masonry course stress transfer
mechanism
integrated into a single bracket 2. Personnel building a masonry wall 10
reinforced by a
rebar 8 therefore only have to incorporate into the masonry wall 10 a single
bracket 2 in
order to facilitate rebar 8 positioning and stress transfer between adjacent
masonry
courses 30. By having a single bracket 2 performing the functions of rebar
cradling and
stress transfer, the build time of a shear strengthened (or otherwise
strengthened) masonry
wall 10 and the number of building components required to form the wall 10 is
reduced,
which reduces overall building costs.
Typically, hollowed masonry blocks 14 are used to form part of a hollowed
masonry
course which houses one or more rebars 8 supported by one or more rebar
cradling
features 6 on one or more brackets 2 embodying the present invention. The
brackets 2
are typically distributed horizontally at the same vertical level along the
length of the wall
10, but may also be distributed at other locations throughout the wall 10. The
rebar 8
typically extends the full horizontal length of the masonry wall panel and
connects to the
end load-bearing columns 20 using one or more cleats 26 (see Fig. 4). Because
the rebar
8 and stress transfer member 4 are mechanically linked, transverse forces
applied to the
masonry panel are distributed through masonry courses 30 linked by the stress
transfer
member/s 4 to the rebar 8.
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The bracket 2 may also comprise a supporting member 28. Preferably the
supporting
member 28 protrudes perpendicularly to the length of the stress transfer
member 4 and is
typically intended to be located within a bed joint 24 of the masonry wall 10.
Such a
supporting member 28 when located in a bed joint 24 provides a height
alignment
reference for the bracket 2, and preferably acts as a foot for easy placement,
support and
lateral positioning of the bracket on top of an existing course 30 of blocks,
immediately
before the bracket is built into the blockwork. The foot 28 rests on the bed
joint 24
below, and the stress transfer member can be propped against the exposed
header face of
the most recently laid block, preferably being pressed into pre-applied mortar
(see Fig.
la). When the bracket 2 is in position, the one or more rebar cradling
features 6 are
located in alignment and at the correct uniform spacing from the bases of the
hollowed
masonry units 14 to support the one or more rebars 8 (Fig. 1c). Since any
further
brackets 2 along the length of the masonry wall 10 may also locate their
supporting
members 28 in the same bed joint 24, all the cradling features 6 may be
vertically aligned
with respect to one another providing a constant level distributed supporting
platform for
the one or more rebars 8.
Preferably the supporting member 28 and/or the stress transfer member 4 may
take the
form of plates that correspondingly allow the supporting member 28 to be
accommodated
within a bed joint 24, and the stress transfer member 4 to be accommodated
within a
perpend 22 of a masonry wall 10. The bracket 2 may be formed from a single
sheet or
strip of material thus allowing multiple brackets 2 to be made in a simple
manufacturing
process.
The bracket 2 also preferably comprises one or more apertures 32 in the stress
transfer
member 4 and/or the supporting member 28 that operate to allow masonry block
binding
material to pass through the bracket 2. By allowing masonry block binding
material,
typically mortar, to pass through the bracket 2, the bracket 2 is anchored
within the
structure of the masonry wall 10.
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Masonry walls 10 may in certain circumstances require vertically extending
reinforcement structures incorporated within or connected adjacent to the
masonry walls
10, for example, either side of a door or window to provide extra
reinforcement around
nominally weakened areas of the wall. Such structures are typically formed
from steel or
other metals or metal alloys. In principle, the vertical extending structures
may take any
form, but more typically take the form of vertical rebars 70 similar to the
horizontal
rebars 8 used in the aforementioned bond beam 12, or vertical reinforcement
pillars 78
typically formed from a hollow metal tubing. It is desirable in masonry walls
10 to
mechanically tie in and link the horizontal rebars 8 (thus the one or more
bond beams 12)
of a masonry wall 10 to the vertical reinforcement structures in order to
distribute the
shear forces acting upon one localised part of the wall to other parts of the
wall 10. The
present invention therefore further provides a masonry wall tie bracket 62
comprising a
first portion 64 with a rebar cradling feature 6 for accommodating a rebar 8
and a second
portion with an adaptor 66 configured to secure the bracket 62 to an elongate
reinforcing
member. The tie bracket 62 may transversely interlink and mechanically couple
the
horizontal rebars in the bond beam to one or more elongate vertical
reinforcement
structures/members, although in principle the adaptor 66 may be configured to
secure the
bracket 62 to other elongate reinforcing structures that are not vertical.
The following are illustrative examples of the present invention. The features
and
methods of any example or embodiment may be used in any compatible combination
or
permutation with those of any other example or embodiment described throughout
this
document.
The first example is a bracket 2 as shown in Figures lie for use in a bonded
masonry
wall 10. The bracket 2 in this example comprises a supporting member 28
wherein the
supporting member 28 is a stabilising foot attached to the bottom end of the
stress
transfer member 4. The stress transfer member 4 and the stabilising foot of
the bracket 2
in this example are respective limbs of a steel strip that has been bent into
an L shape.
Both the foot and the transfer member 4 comprise apertures 32 allowing masonry
block
binding material to pass through the bracket 2. It is however envisaged that
the foot or
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transfer member 4 of the bracket 2 may equally not comprise such apertures 32
in this
example.
The foot is located in a bed joint 24 beneath a first 'bottom' masonry course
30. When
the bottom masonry course 30 is being formed, the bracket 2 is placed within
the next
perpend 22 due to be formed between an existing laid block of the bottom
masonry
course 30 and the next adjacent block of the course 30 due to be laid. The
foot therefore
serves in use to allow the bracket 2 to stand or be propped against the most
recently laid
block whilst the next block of the bottom masonry course 30 is being laid.
When the bracket 2 is placed in this manner it is fully surrounded and
intimately
embedded within the masonry block binding material. This is in contrast to the
prior art
which requires the stress transfer member to be driven down into a perpend 22
of the
masonry course 30 below. Driving a member down into an already laid binding
material
is undesirable as, for example, anchoring holes or indentations formed in the
member are
not guaranteed to be completely filled by the binding material due to the
possible
formation of air gaps resulting from the driving action. Air gaps weaken the
perpend 22
as well as weakening the mechanical bond between the stress transfer member
and the
binding material. The problem is exacerbated by the fact that the binding
material in the
perpends 22 may have already set or cured to an undesirable extent at the time
the
brackets are driven into the perpends 22. This means that there cannot be any
substantial
delay between laying the course 30 containing these perpends 22, laying the
course 30 of
hollowed masonry units 14 and driving in the stress transfer members 4. The
same
problem does not arise with the reinforcing bracket 2 illustrated in this
example, which
can be built into the bottom course 30 at any time prior to laying of the bond
beam course
12, without adverse effect.
The stress transfer member 4 extends completely across the full depth of the
masonry
blocks of the bottom masonry course 30 and resides within a perpend 22
existing between
two blocks of the bottom course 30. The foot is accommodated in the bed joint
24
underneath a block of the bottom course 30.
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The stress transfer member 4 of the bracket 2 further extends upwards into a
second or
'bond beam' course 12 of the bonded masonry wall 10. The bond beam course 12
is
formed of hollowed masonry blocks 14 laid on top of the bottom course 30 with
a further
bed joint 24 in between. When the wall 10 around the bracket 2 is complete the
foot acts
to hold the bottom course 30 to the bond beam course 12 and any other
subsequent laid
course 30 mechanically linked by the stress transfer member 4.
The stress transfer member 4 protrudes through an aperture 16 in the base of a
hollowed
block 14 of the bond beam course 12 and into the cavity 18 formed from the
hollowed
centre of the hollowed block 14. The part of the stress transfer member 4 that
protrudes
into the cavity 18 of the hollowed block 14 comprises two rebar cradling
features 6. The
stress transfer member 4 of the bracket 2, in this example, also protrudes
into the perpend
22 of a course 30 immediately above the hollowed masonry course 14, although
it is
entirely feasible that a stress transfer member 4 may in principle vertically
extend through
any number of adjacently laid masonry courses 30.
Each rebar cradling feature 6 may be an inwardly recessed slot 34 with an
opening along
a long edge 38 of the stress transfer member 4. Each slot 34 may further
comprise a
retaining lip 36 serving to provide confinement of the rebar 8 in directions
traverse to the
wall 10. Each slot 34 is sized such that a rebar 8 may enter the slot 34 and
pass over the
retaining lip 36 into a retaining section of the slot 34. The slots 34 in this
example are
open into opposing long edges 38 of the stress transfer member 4 and are
separated
vertically along the length of the stress transfer member 4. Thus in this
example the
bracket 2 acts to cradle two rebars 8. Each slot 34 comprises a stopping edge
40 at the
inner end of the slot 34 opposite to the retaining lip 36 and opening. The
stopping edges
40 of the two slots 34 in this example therefore face in opposing directions.
Once both rebars 8 are located in the cradle features of the stress transfer
member 4, the
hollowed block 14 may be filled with a suitable material (e.g. concrete or
similar
cementatious material) to solidify in the hollowed block 14, cement the rebar
8 and
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bracket 2 in place, and form a compression resistant matrix in which the
rebars and mid-
portions of the brackets are embedded. The cradling features 6 are located
relative to the
supporting member 28 so that the rebars 8 are positioned at the correct
location within the
hollow of the bond beam course 14 as required according to the design of the
finished
bond beam.
The bracket 2 in this example is made from steel strip or sheet steel cut to
an elongate
rectangular shape. The foot is formed by simply bending the rectangle or strip
at one end
to make an L shape. By having the foot and stress transfer member 4 of the
bracket 2
formed from the same piece of steel, the bracket 2 may be formed cheaply and
simply.
Typically the steel has a thickness between 3 to 4 mm. The width of the
bracket 2 is
ideally not wider than the plan width of the masonry blocks so that when the
bracket 2 is
introduced into the masonry wall 10 structure it is hidden from the outside.
Preferably
the material of the bracket 2 does not occupy an excessive proportion of the
perpend 22
horizontal cross-section, so that sufficient binding material is present to
form a strong
mechanical bond with the bracket 2, and/or so that the bracket 2 does not form
a
significant plane of weakness in the perpend 22. At least the part of the
stress transfer
member 4 that extends through the hollowed block base aperture 16 has a width
that
allows a rebar 8 to be slid down between the inner sides of the hollowed block
14 and the
outer edge 38 of the shear transfer member 4 into the recessed slot opening/s.
The foot in this example protrudes outwardly from the stress transfer member 4
in a
single direction. This provides a clearly identifiable directional alignment
feature to the
bracket 2. When bricklayers are placing subsequent brackets 2 further along a
masonry
course 30, they may simply align the feet in the same direction as the
previously placed
brackets 2 such that the equivalent cradling slots 34 are correctly aligned
vertically and
horizontally with respect to each other, with corresponding slots all facing
in the same
direction.
Typically the widths of the foot and stress transfer member 4 are between 30
to 60 mm,
preferably 40mm. The length of the stress transfer member 4 is typically 500
to 700mm,
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preferably 610mm and the length of the foot is typically between 40 to 100mm,
preferably 70mm.
Following from the first example is a second example embodying the present
invention as
shown in Figure 2. Instead of a stabilising foot, the bracket 2 comprises one
or more
perpendicularly protruding supporting members 28 along its length, spaced from
the ends
of the stress transfer member 4.
The supporting members 28 in the second example are intended to be
accommodated
within a masonry wall bed joint 24. Similarly to the first example, the
supporting
members 28 in the second example provide height reference to the bracket 2,
which gives
corresponding height reference to the at least one rebar 8 located in the
supporting cradles
6 of the bracket 2.
Following from the previous examples is a third example embodying the present
invention as shown in Figure 3. In this example, brackets 2 (not shown)
similar to those
of the first example are utilised within the masonry wall 10. Some of the
brackets in this
example are extended length brackets 3 that comprise stress transfer members 4
that
extend into two hollowed masonry block courses 14. The stress transfer members
4 of
these extended length brackets 3 comprise at least two sets of rebar cradling
features 6
(two sets of one bar each, as shown), each cradling set located at different
positions along
the length of the shear transfer member 4 to coincide with the cavities of the
separate
hollowed masonry block courses 14. Thus the extended length brackets 3 are
intended to
engage with two sets of one or more rebars 8, each rebar 8 set being disposed
within a
different hollowed masonry course 14.
Such an extended length bracket 3 provides stress transferring mechanical
connection
between two sets of one or more rebars 8. Such a bracket 3 may be useful for
interconnecting rebars 8 running at different height levels, for example, when
one set of
rebars 8 cannot extend fully between adjacent load-bearing columns 20 due to
the
presence of an opening 42 in the masonry wall 10 such as a door or a window.
The
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extended length bracket 3 thus provides a means to interlink one or more
rebars 8 running
at height levels not horizontally inline with the wall opening 42 to one or
more rebars 8
interrupted by the opening 42. Figure 3a shows another extended length bracket
3 with
two sets A, B of rebar cradling features 6 and two cradling features in each
set. This can
be used for example to form a stress transfer connection between two bond
beams
positioned one above the other, each bond beam comprising two rebars. Parallel
bond
beams such as this may be used for example to support cantilevered loads
attached to a
wall, with load supporting frames or brackets spanning between and anchored to
the bond
beams. Of course, other numbers of sets of rebar cradling features and other
numbers of
rebar cradling features within each set can be provided as desired and to suit
different
purposes as required.
Figures 3b and 3c show another form of bracket 2a for use where the bond beam
is to be
tied into adjacent blockwork for stress transfer on one side only, e.g. where
the bond
beam forms a lintel above an opening such as for a window or door. The stress
transfer
member 4 is made shorter than that shown in Figures la-le and the rebar
cradling
features 6 are positioned relative to the foot 8 so that the foot 8 rests on
the floor of the
cavity 18 in the hollowed blocks so as to position the rebar cradling features
at the correct
height. The upper end of the stress transfer member 4 therefore extends into
the course
above, similarly to the example of Figures la-le, but no part of the bracket
2a extends
downwardly of the bond beam. To prevent the foot 8 of the bracket 2a from
being
incorrectly built into a bed joint in the manner of the bracket 2 (instead of
resting on the
base of the cavity 18 as intended) the end of the foot is split into two parts
with one part
8b being angled upwardly with respect to the other part 8b. The tips of the
parts 8a, 8b
are separated by a distance (e.g. 20mm) greater than the mortar joint
thickness (which is
typically lOmm). The foot is therefore too wide to be built into a mortar
joint.
In any of the previous examples there may also be included a cleat 26 which
mechanically joins an end of a rebar 8 to a load bearing column 20 (see
Figures le and 4).
The cleat 26 comprises a backplate 44 from which at least one rebar securing
feature 46
protrudes outwardly and acts as a pocket to secureably house the end section
of a rebar 8.
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A typical cleat rebar securing feature 46 would be a cylindrical tube as shown
in Figure 4.
The rebar is a sliding fit within the tube to allow longitudinal movement of
the rebar, e.g.
to accommodate thermal movement or shrinkage of the blockwork infill in the
load
bearing framework. Instead of the column 20, the baseplate may be secured by
suitable
fasteners to any other suitable load bearing structure, for example to provide
a bond beam
reinforced masonry infill similar to those described in our UK patent
specification nos.
2440531 and 2442543.
The back plate of the cleat 26, may have a hole 48 formed in line with the
bore of the
tube. The back plate hole 48 is sized such that the rebar 8 to be housed in
the securing
feature 46 may pass through the hole 48. In this manner, the entire cleat 26
may be fed
over the rebar 8. Because the rebar 8 may pass all the way through the cleat
26, the back
plate of the cleat 26 does not hinder the placement of the rebar 8 when being
manoeuvred
into its final operating position. Once the rebar 8 is located into its final
operating
position, the cleat 26 may then brought into contact and secured to the load
bearing
columns 20. The securing feature 46 of the cleat 26 protrudes outwardly from
the back
plate into the masonry wall 10 to an extent that it can secure the rebar 8
once the cleat 26
is secured to the column 20 and the rebar 8 is in its final operative
position.
A similar hole 50 may also be formed in the load bearing column 20 coinciding
with the
position of the back plate hole 48 to further facilitate lateral movement of
the rebar 8
when the rebar 8 is being placed into its final operative position. This is
advantageous,
for example, when a cleat 26 is already fixed to the load bearing column 20
before the
rebar 8 is in its final operative position. In this manner, the cleat 26 and
column 20 form
a cleating system.
Alternatively, the rebar can be provided in at least two separate lengths. An
end of each
length can be poked into a respective cleat pocket without the need to form a
hole in the
back plate 44 or in the column 20. The rebar ends are poked almost fully home,
merely
leaving a suitable clearance between the rebar end and the base of the pocket
to allow for
the anticipated relative movement. The remainder of the rebars can then be
manoeuvred
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into the bracket cradling features 6, e.g. over the retaining lips 36 and into
the retaining
sections of the slots 34. The lengths of the rebar sections are such that
their free ends
overlap in this position. The overlapping ends can be secured together by wire
ties or the
like, to hold them in the correct position whilst the bond beam concrete is
poured,
compacted and cured in the hollowed masonry block course 14. The length of the
overlap is made sufficient so that tensile stress in one section of
reinforcement can be
transmitted via shear stress at the interface to the surrounding cementitious
matrix and
then to the next section of reinforcement, without shear failure occurring
between the
matrix and the reinforcement ends (i.e. without the reinforcement ends pulling
out of the
cured cementitious mix). The length of overlap may be as specified in local
building
codes. For example 50x rebar diameter may be typical. The overlapping section
is
preferably placed away from regions of maximum rebar tensile stress, e.g. away
from the
region of maximum bending moment in the bond beam. Thus a rebar end overlap in
the
central region of its span should preferably be avoided in the case of a bond
beam
spanning a continuous blockwork infill wall subject to a uniform pressure
difference
between its inner and outer faces. Similarly the overlap should preferably be
placed away
from stress concentrations arising from nearby discontinuities in the
blockwork such as
those caused by openings in the blockwork. The overlap can be accommodated in
the
space between adjacent brackets, so that specially modified bracket rebar
cradling
feature/slot profiles are not needed.
Figures 5 and 6 show a mounting adaptor 52 for a cleat which in turn receives
rebar ends.
Thus the cleat may be as shown schematically in Figure 4. Preferably the cleat
is of the
kind for receiving a pair of rebar ends one above the other; generally as
shown in our UK
patent no. 2442543. The cleat mounting holes 18, 23 shown in that patent may
be
elongated transversely of the base plate rather than being generally circular
as shown.
This allows for increased adjustability when fixing the cleat to a load
bearing structure.
The adaptor 52 has a base plate 54 with four mounting holes 58 as shown, for
receiving
fasteners suitable for securing the adaptor to a load bearing structure. These
fasteners
may be, for example, bolts in the case of a steel structure or expansion bolts
in the case of
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a reinforced concrete load bearing pillar or wall slab. The mounting holes 58
are
elongated longitudinally of the base plate, to permit height adjustment of the
adaptor.
The mounting adaptor 52 further comprises a cleat receiving flange 56 welded
to and
extending perpendicularly from the base plate 54 at its longitudinal midline.
The cleat
receiving flange 56 has a pair of horizontally elongated mounting holes 60
suitably
spaced to receive fasteners (e.g. nuts and bolts) for securing the cleat to
it. Therefore the
mounting adapter 52 allows a bond beam containing blockwork wall to be built
alongside
and secured to a load bearing structure such as a pillar, column or wall slab;
ends of the
bond beam rebars being secured to the load bearing structure via the cleat and
mounting
adaptor. Where the blockwork wall continues away from the load bearing
structure in
either direction, a pair of cleats may be mounted back-to-back on either side
of the
receiving flange 52. These can thus receive rebars of a pair of bond beams
aligned end-
to-end. This contrasts with a masonry infill secured to a load bearing
structure to which
the cleat is directly mounted, in which the infill is in line with the load
bearing structure,
rather than to one side of it. The cleat and mounting adaptor can be combined
into a
unitary welded assembly, for example with tubular cleat pockets welded
directly to one
or both sides of the receiving flange 56.
Figures 7a and 7b show an example of a tie bracket 62 of the present invention
comprising a first elongated portion 64 similar to the stress transfer member
4 shown in
Figures la-e, 3 and 3a. The first portion 64 comprises one or more rebar
cradling features
6 similar to those described above and shown in Figures la-e, 3 and 3a, except
that the
retaining lip 36 is located at the top of the slot 34 so that the tie bracket
62 hangs from the
one or more horizontal rebars as shown in Figures 8a and 8b. The tie bracket
62 also
comprises a second elongated portion that acts as an adaptor 66 configured to
secure the
bracket 62 to an elongate reinforcing member. The adaptor 66 is nominally
disposed
beneath the first portion, and acts as a socket to sit on top of and house a
vertical rebar 70
as shown in Figures 8a and 8b. In principle, however the cradle retaining lip
36 may be
located at the bottom of the slot 34 and/or the adaptor 66 may extend upward
from the
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first portion to house the bottom of a vertical rebar. Typically the tie
bracket 62 is
formed from a rigid material such as steel or other metal.
The adaptor 66 as shown in Figures 7a-b and 8a-b comprises a cylindrical tube
adaptor
with a cylindrical hole 68 with a closed top end and an open bottom end. The
bottom end
opening of the tube and the internal diameter of the tube are sized to
accommodate a
vertical rebar 70 so that the adaptor 66 can be slid on to the vertical rebar
70 and form a
tight (close sliding) frt. When the tie bracket 62 has been located on to the
vertical rebar
70, the first portion 64 comprising the rebar cradling features 6 stands proud
from the top
end of the vertical rebar 70. In principle however, the tubular adaptor 66 may
be formed
from any suitable rigid material and may be of any cross-sectional shape that
fits a
vertical rebar 70. A cylindrical vertical rebar 70 and a cylindrical tubular
adaptor have the
advantage that once the adaptor is located upon the rebar, the tie bracket 62
can be rotated
about the longitudinal axis of the vertical rebar 70. Having the tie bracket
62 rotatable
about the rebar 70 and a generally flat transverse cross-section to the first
portion, allows
a person building the masonry wall 10 to lay the masonry bond beam blocks and
locate
the horizontal rebars 8 in position with the long dimensions of the tie
bracket 62
transverse cross-sections initially aligned longitudinally of the bond beam
cavity 18, for
ease of positioning the horizontal rebars 8 . Once the horizontal rebars 8 are
in position,
each tie bracket 62 is then simply rotated so that the rebar cradling features
6 can hook
over and hang the tie bracket 62 off the horizontal rebars 8.
Similarly to the brackets described previously, the first 64 and/or second
portion of the tie
bracket 62 may also comprise one or more apertures 32 that operate to allow
masonry
block binding/filling material to pass through the tie bracket 62 and thus
anchor the tie
bracket 62 within the structure of the masonry wall 10 and to the vertical
rebar 70. Once
the tie brackets 62 have been rotated into position over the horizontal rebars
8 as
described above, they are preferably shaken, vibrated or tapped downwardly to
ensure
close engagement with the horizontal rebars 8 and penetration of the
binding/filling
material such as wet concrete into the bracket apertures 32.
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The present invention also provides a vertical rebar cleat 72 which is shown
in Figure 7c.
The cleat 72 comprises a base plate 74 typically with fixing holes and an
outwardly
extending tubular portion 76. The tubular portion 76 is similar to that of the
adaptor 66 of
the tie bracket 62 and protrudes outwardly normal from the plane of the base
plate. The
tubular portion of the vertical rebar cleat 72 comprises cylindrical hole 68
that is sized to
accept and closely fit a vertical rebar 70. Typically, the cleat 72 is placed
upon and
affixed to a horizontal supporting structure that supports the masonry wall.
Preferably
the vertical rebar cleat 72 is sized in the plane of the base plate 74 to
allow the cleat 72 to
be fully accommodated within a vertical through-hole made within a masonry
block.
When used in a preferred method of constructing a masonry wall, the cleat 72
is
positioned so that the vertical through hole of a block in the first course of
masonry block
work sits over and surrounds the cleat 72. A vertical rebar 70 is then
inserted into the
tubular portion 76 of the vertical rebar cleat. Successive masonry block
courses are then
subsequently formed over the first masonry course, wherein the masonry block
of each
masonry course immediately above the rebar 70 comprises a through hole to
accommodate the vertical rebar 70.
For masonry walls 10 where the one or more horizontal bond beams 12 are to be
formed
within courses not immediately adjacent to the bottom masonry block course,
several
vertical rebars 70 may be required to be tied together to form a composite
vertical rebar
extending up to and into the bond beam masonry block course. Tying together
several
shorter rebars 70 rather than having a single long vertical rebar 70 extending
over
multiple masonry block courses is advantageous because a person building the
masonry
wall with a single long vertical rebar 70 will have difficulty sliding the
masonry blocks
with the vertical through holes over the rebar 70. The blocks would need to be
lifted up
and over the vertical rebar 70 so that the vertical though hole of the block
accommodated
the rebar 70. By successively tying one or more shorter vertical rebars 70
together, for
example no longer than the depth of 2 masonry courses, the person laying the
masonry
courses can place the blocks with the vertical through holes over the
shortened vertical
rebar 70 in a simpler manner and then, once the masonry block is in place, tie
another
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vertical rebar 70 to the existing rebar 70 so that the rebar 70 is extended on
a progressive
course by course basis.
Vertical rebars 70 may be tied together via a number of methods including
simple tying
using one or more wires or clips to form an overlap joint complying with
accepted
building regulations or practice, or by using joining brackets with two or
more connected
rebar accommodating tubular portions, similar to the adaptor 66 of the tie
bracket 62 in
Figures 7a-b. The tubular portions of such joining brackets may either be
located end on
or adjacent to each other, each tubular portion having respective open and
closed ends in
opposite configuration to the other tubular option so that the joining bracket
may
accommodate rebars 70 inserted into the joining bracket from opposite
directions.
In a preferred method of constructing a masonry wall 10 with one or more
horizontal
rebars 8 and one or more vertical rebars 70, the masonry wall 10 is nominally
built course
by course as described above. In each course, the masonry block/s in-line with
the
vertical rebars are threaded over the vertical rebars so that the rebars
protrude through the
vertical though holes of the blocks. Once the block is laid and the vertical
rebars protrude
through the through hole, other vertical rebars may be secured to the existing
vertical
rebars to form a composite extended rebar as described above. When the masonry
blocks
accommodating the vertical rebars are in place and any required vertical rebar
extensions
are attached, the block may be filled or bonded in accordance with the general
construction of the masonry course. For the adjacent masonry course 30
immediately
below the intended bond beam course 12, the vertical rebars 70 protruding into
the course
are designed or cut to end beneath the start of the subsequent bond beam
course 12.
Preferably the top end of the vertical rebars 70 stop within the block of the
masonry
course but may in principle extend into the bed joint 24. The adaptors 66 of
the tie
brackets 62 are then placed upon the end of the vertical rebars 70 so that the
tie brackets
62 securably engage the vertical rebars 70 such that the first portions 64 of
the tie
brackets 62 protrude into where the next bond beam masonry course is to be
laid. As
stated above, preferably the long dimension transverse cross-section of the
tie brackets 62
are initially aligned longitudinally of the bond beam cavity 18. Once the
adjacent
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masonry course below the bond beam course 12 is finished, the hollowed masonry
blocks
16 of the bond beam course 12 are laid upon abed joint 24, together with any
other shear
transfer brackets 2 according to the present invention as described above. The
hollowed
masonry blocks 16 of the bond beam course are as described above and
preferably
comprise a U-shaped longitudinal cavity. The masonry blocks immediately above
the tie
brackets 62 comprise a vertical through hole sized to accept and allow the tie
brackets 62
to protrude through the through hole into the cavity of the U-shaped masonry
blocks 14.
The vertical through hole may be similar to the hole 16 in the base of the
hollowed
masonry block 14 as described above, or any other suitable hole such as one
formed by
removing a portion of the base at one end of a hollowed masonry block 14.
Where the
vertical rebars extend upwardly from the bond beam, the open tops of the U-
blocks allow
the brackets 62 to pass upwardly from the bond beam space directly into the
hollow block
interiors in the course above. Alternatively the tie brackets 62 may be fitted
onto the
vertical rebars 70 after the hollowed masonry blocks 14 of the bond beam
course have
been put in place. Once all of the masonry blocks of the bond beam course 12
are in
position, the horizontal rebars 8 are located into the rebar cradling features
6 of the shear
transfer brackets 2 and the rebar cradling features 6 of the tie bracket 62
are hooked onto
the horizontal rebars 8 by lifting and rotating the tie bracket 62. The
vertical through
holes of the hollowed masonry blocks 14 and corresponding blocks of the
adjacent course
below are then backfilled with wet concrete. The longitudinal U shaped cavity
18 formed
by the hollowed masonry blocks 14 is then filled with concrete to form the
completed
bond beam 12.
Figures 9a and 9b show another example of tie bracket 62 similar to the tie
bracket 62
shown in Figures 7a-b and 8a-b. In this alternative version of the tie bracket
62, the
adaptor 66 is a spigot adapted to secure the tie bracket 62 to a vertical
reinforcing post or
pillar 78. Similarly to the tie bracket 62 shown in Figures 7a-b and 8a-b, the
first portion
64 of the tie bracket 62 shown in Figures 9a-b and 10 comprises rebar cradling
features 6
with retaining lips 36 at the top of the cradle 6 that operate to allow the
tie bracket 62 to
hang upon horizontal rebars 8. In this example of a tie bracket 62, the
adaptor is
configured to be located and housed within the hollow interior of a typically
tubular
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vertical reinforcing pillar 78, e.g. having a rectangular cross-section and a
corresponding
rectangular cross-sectioned inner hole. In principle however, a tie bracket 62
may be
adapted to be placed over the pillar in a similar fashion as the tie bracket
62 in Figure 7a-
b. The adaptor of the tie bracket 62 in the example shown in Figures 9a-b, as
further
shown in Figure 10, is inserted into the hollow interior of the vertical
reinforcing pillar
78. The tie bracket 62 may also comprise an at least partially circumferential
stopping lip
80 with at least one cross-sectional dimension greater than a corresponding
dimension of
the pillar hole. The adaptor 66 of the tie bracket 62 is inserted into the
pillar 78 until the
stopping lip 80 comes into contact with the top of the pillar 78.
Preferably, the cross sectional shape of the adaptor 66 may be made to fit
into a variety of
vertical reinforcing pillars 78. Where the cross-section of the adaptor 66
does not form a
close fit with the inner cross-section of the vertical pillar, spacing strips
82 may be
attached to the adaptor 66 of the tie bracket 62 by welding or any other
suitable fixing
method so that the adaptor 66 forms a close fit with the inner hole of the
vertical
reinforcing pillar 78.
A masonry wall 10 with one or more horizontal rebars 8 and vertical pillars 78
is
constructed in a similar manner to the preferred construction method of a
masonry wall
with vertical 70 and horizontal 8 rebars as detailed above. When constructing
a wall
10 with horizontal rebars 8 and vertical pillars 78 the masonry blocks of each
course must
have vertical through holes sized to accommodate the vertical pillars 78. The
top ends of
the pillars 78 finish below the hollowed blocks 14 of the bond beam 12 course,
either in
the course immediately beneath the bond beam 12 course or within the bed joint
24
between them. Each tie bracket 62 is fitted onto the end of its pillar 78 such
that at least
the first portions 64 of the tie brackets 62 protrude into the hollowed
masonry blocks 14.
Preferably, only the first portions 64 of the tie brackets 62 protrude through
into the
hollowed masonry blocks 14 of the bond beam 12 course, the stopping lips 80
residing
either in the bed joint 24 or within the vertical though hole of the adjacent
masonry
blocks below.
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Table of referenced features.
Reference Feature
2 Bracket
3 Extended length bracket
4 Stress transfer member
6 Rebar cradling feature
8 Rebar
Masonry wall
12 Bond beam
14 Hollowed masonry block
16 Hole in the base of a masonry block
18 Cavity
Load bearing columns
22 Perpends
24 Bed joint
26 Cleat
28 Supporting member
Adjacent masonry courses
32 Apertures
34 Slot
36 Retaining lip
38 Opposing long edges
Stopping edges
42 Opening
44 Back plate
46 Rebar securing feature
48 Back plate hole
Hole in load bearing column
52 Mounting adaptor
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54 Cleat base plate
56 Cleat receiving flange
58 Mounting holes
60 Elongate mounting holes
62 Tie bracket
64 Tie bracket first portion
66 Adaptor
68 Cylindrical hole
70 Vertical rebar
72 Vertical rebar cleat
74 Vertical rebar cleat base plate
76 Outwardly extending tubular portion
78 Vertical reinforcing post
80 Stopping lip
82 Spacing strips
23
