Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FORMWORK CONNECTING MEMBER
FIELD OF THE INVENTION
This invention relates generally to stay-in-place modular
formwork for creating concrete structures, and more particularly to
connecting members for use with such formwork.
BACKGROUND OF THE INVENTION
The use of modular formwork elements and members that
interconnect to create a stay-in-place formwork assembly or
structure into which concrete may be poured is well known in the
prior art. Typically, such modular formwork is manufactured from
lightweight plastic (such as PVC) or other lightweight materials in
order to minimize transportation costs and to facilitate the
assembly of a comparatively large section of formwork structure
prior to the pouring of the concrete. Examples of such modular
formwork, and of the methods for its use and application, are
provided in Canadian patent nos. 2215939, 2226497, and 2218600 to
Piccone. In formwork structures constructed of prior-known modular
formwork of this type, discrete inner and outer wall elements are
assembled together in end-to-end relationship and interconnected by
connecting members to create cells via the sliding engagement of
complementary terminal connectors that are present along the
longitudinal edges of the wall elements and connecting members.
The engagement between the connecting members and the wall elements
normally extends along the entire elongate (height) dimension of
the formwork.
Internal braces that extend between the connecting
members and supplementary engagement means on the inner surfaces of
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the wall elements may also be present. Such braces may similarly
be interconnected with the elements and members via a contiguous
sliding engagement of compatible engagement means. Since the
formwork is preferably thin (relative to the thickness of the
concrete structure) in order primarily to conserve material,
internal braces are particularly important in applications where it
is desired to prevent or limit outward distension of the central
portions of the wall elements (known as "pillowing") under the
weight of the concrete that is poured into the formwork assembly.
Thin sections of lightweight materials are (as is well known)
inherently susceptible to bending or flexing, but are generally
less susceptible to deformation under axial tension. The internal
braces of prior known formwork are themselves preferably
manufactured of thin, lightweight materials; accordingly, such
braces must generally extend at a relatively shallow angle relative
to the connecting member to which they are connected so as to
avoid excessive bending (such as might otherwise result from the
outward distension of the wall element to which the given brace is
also connected) .
It is also well known that concrete withstands
compressive forces well, but without reinforcement is not well
suited to withstand tensile forces. Accordingly, reinforcement
rods are conventionally set within concrete structures (whether or
not stay-in-place formwork is used in the construction of the
concrete structure) for strengthening purposes. To maximize the
effect that reinforcement rods of a given diameter and cluster
density may have on the prevention of excessive flexing in a
concrete structure (such as may be caused, for example, by wind
loading of the structure), it is generally preferable to set the
reinforcement rods relatively close to at least one surface of the
structure. If the rods cannot be located at or near the optimal
position for a given structure, then more rods or thicker rods (or
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both) need to be used; this, of course, increases overall cost.
Prior-known formwork connecting members and braces are
typically perforated to permit the placement of reinforcement rods
and to permit the cross-flow of concrete (between cells of the
formwork assembly) that is poured into the formwork assembly.
However, the attachment points between prior-known braces and
connecting members (which, as noted above, typically comprise a
sliding engagement of compatible engagement means) obstruct the
contiguity of such perforations. This makes it difficult or
impossible to place reinforcement rods at or near the optimal
placement position for a given structure. The attachment points
also limit the maximal overall dimensions of the perforations,
thereby limiting the maximal cross-flow of concrete from one
discrete cell of formwork assembly to another during the pouring of
concrete into the formwork assembly. Inadequacy in the cross-flow
of concrete may result in the bulging of one cell of formwork
assembly relative to another, which in turn may lead to undesirable
distortion in the concrete structure.
It is therefore an object of one aspect of the present
invention to provide a formwork connecting member that includes at
least one brace, but that is nevertheless suitably perforated to
permit the placement of reinforcement rods at or near the optimal
placement position for a given structure and to facilitate the
cross-flow of concrete.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention,
there is provided a formwork connecting member that includes an
elongate central portion that has terminal connectors located at
both longitudinal edges. The terminal connectors of the connecting
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a
member are adapted to mate slidingly with the complementary
terminal connectors that are present on the longitudinal edges of
the wall elements of known stay-in-place modular formwork, and
different terminal connectors may be selected to suit a given
modular formwork application. Preferably, the terminal connectors
of the connecting member (and the complementary terminal connectors
of the wall element) are selected so that the connectors of the
connecting member do not protrude, such that the connecting members
are not visible between the wall elements once they are assembled
in end-to-end relationship. This permits the entire connecting
member to be constructed of recycled material (or other lower-cost
materials) without adversely affecting the external aesthetic
quality of the resulting structure or wall.
The connecting member also includes at least one
associated elongate brace that depends from a point of connection
on the central portion that is offset from the terminal connectors.
The connection between the brace and the central portion may be
permanent (such that the brace at the point of connection is
integral with the central portion) or releasable (employing known
types of complimentary engagement means) depending, in part, upon
the physical characteristics of the material from which the
connecting member is constructed. In the preferred embodiments
described below that are manufactured of PVC plastic material, the
braces) at the point of connection is integral with the central
portion. The extent of the offset is dependent primarily upon the
particular application (relative to the size of the resulting
concrete structure, and relative to the position or function of the
connecting member within a given modular formwork system and as
between different formwork systems), and upon the material or
materials from which the connecting member is manufactured. In the
preferred embodiments described below that are manufactured of PVC
plastic material, the point of connection is offset far enough away
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from the nearest terminal connector to permit the brace to depend
at a comparatively shallow angle (preferably no more than about
60°, and most preferably about 45°) from the central portion so
as
. to limit flexing of the brace. In a typical commercial and
residential wall building application, the point of connection is
offset more than one inch from the nearest terminal connector.
The brace includes engagement means at its distal
longitudinal edge that are adapted to mate slidingly with the
supplementary engagement means that are present on the inner
surface of known wall elements. As noted previously, bracing
limits the "pillowing" of the central portion of the wall element
under the weight of the poured concrete. Both the central portion
and the associated brace (or braces) of the inventive connecting
member are perforated in a selected zone of perforation that
extends through the point of connection of the brace (or braces) to
facilitate the cross-flow of concrete and to permit the placement
of reinforcement rods at or near the optimal placement position for
a given structure. The ability to place the reinforcement rods at
or near the optimal placement position results not only in lower
material costs (due to the reduced need for reinforcement rods),
but also in a reduction in construction time because fewer or
thinner reinforcement rods need to be placed and those rods that do
need to be placed can be placed more easily. Placement of
reinforcement rods within a formwork structure generally involves
the insertion and tying in place of the rods to the formwork
structure before each given cell of formwork is completely closed
off. After the reinforcement rods are in place, a cell of formwork
assembly is closed off (usually by the sliding into place of a wall
element), and that cell of formwork assembly is then ready for the
pouring of concrete.
In typical commercial and residential wall building
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applications, the optimal position for reinforcement rods is about
one inch from at least one of the inner and outer surfaces of the
wall. This definition of optimal positioning is, in part,
determined with reference to government building regulations that
typically require a minimum of about % to one inch of concrete
cover over any reinforcement rods that may be present in order to
ensure that the reinforcing rods do not corrode as a result of
moisture seeping into the wall through minute cracks that may be
present in the concrete. It is noted that the government minimum
cover regulation to which reference is made is selected with
reference to traditional building practices (not involving the use
of stay-in-place formwork) and that concrete structures built using
stay-in-place formwork are inherently less susceptible to the
development of minute surface cracks because the formwork wall
elements at least partially protect the concrete from moisture,
temperature fluctuations, and other environmental variations. It
may accordingly be possible, for a typical commercial or
residential wall that is built using stay-in-place formwork, to
select an optimal position for the reinforcement rods that is
closer to the surface than one inch. However, current building
regulations would generally not allow for such positioning in a
typical commercial or residential wall.
In one embodiment of the invention, the connecting member
is configured to connect together two generally parallel rows of
wall elements of a known formwork assembly of the sort in which the
concrete (when poured) will communicate with the inner surface of
the wall elements of both of the parallel rows. In this
embodiment, at least one brace depends from a point of connection
on a first side of the central portion (relative to the
longitudinal mid-line of the central portion), and at least one
other brace depends from a point of connection on the other side of
the mid-line of the central portion. The braces of this embodiment
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do not extend across the mid-line of the central portion, but
instead each brace extends generally towards the supplementary
engagement means of the nearest wall element. The resulting
structure provides for the bracing of both of the parallel rows of
wall elements against the weight of the poured concrete (so as to
limit the distension of the central portions of the wall elements
of both rows). At the same time, excess use of materials (such as
would result from the extension of the braces across the mid-line)
is avoided.
In a similar embodiment of the invention, at least two
braces depend from at least two points of connection on each side
of the central portion (for a total of at least four braces
associated at at least four points of connection with the central
portion of the connecting member). Each braces extends towards the
supplementary engagement means of a different wall element, two of
which elements are associated in end-to-end relationship about each
of the terminal connectors of the connecting member. As in the
embodiment discussed immediately above, the braces of this
embodiment preferably do not extend across the mid-line of the
central portion so as to avoid the excess use of materials.
In another embodiment, two braces depend from each of two
points of connection, with one point of connection being on each
side of the mid-line (for a total of four braces associated at two
points of connection). As in the embodiment discussed above, each
of the four associated braces extend towards the supplementary
engagement means of a different wall element. This configuration
of braces into opposing pairs is preferable to the configuration in
which each brace has its own point of connection (as discussed
immediately above) in cases where the connecting member is made of
a comparatively flexible material (such as thin PVC) because the
tensile forces exerted upon the braces by the weight of the
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concrete on the wall elements will tend to balance out and limit
the distortion of the central portion. Distortions of the central
portion may lead to variations in the thickness of the resultant
wall or other concrete structure.
Embodiments of the inventive connecting member also have
application in the connection of two parallel rows of wall elements
of a known formwork assembly of the sort in which the concrete
(when poured) will communicate with the inner surface of the wall
elements of only one row, and in which a layer of insulating or
other material communicates with or sits adjacent the inner surface
of the wall elements of the other row. Since the insulation layer
of wall structures of this sort offers at least some measure of
resistance against distension under the weight of the poured
concrete of the central portion of the wall elements that are
adjacent the insulation layer (i.e. pillowing), it is not usually
necessary to brace these wall elements of the formork assembly.
Accordingly, inventive connecting members adapted for use with
known formwork assemblies of this type will typically include no
braces that extend to the wall elements on the insulation layer
side of the wall or structure. The various embodiments discussed
above (for use in non-insulated formwork assemblies) can be readily
adapted for use in insulated formwork assemblies by a person
skilled in the art. In order to conserve material from which the
inventive connecting member is made, the central portion may
include auxiliary perforations (in addition to the primary zone of
perforation) near the terminal connector that is adjacent the
insulation side of the formwork assembly. Such auxiliary
perforations are generally not intended for the placement of
reinforcement rods.
A suitable length and point of connection for the at
least one brace of any of the aforesaid embodiments may, of course,
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also be selected by a person skilled in the art having regard to
the discussion above so as to co-operate with convex or concave
wall elements, or wall elements having any other simple or complex
shape. Such wall elements may be used in situations where it is
desired to create a concrete structure having a scalloped
appearance (in the case of concave or convex wall elements) or some
other ornamental appearance.
Nibs, grooves, or other indentations or protrusions that
aid in holding a reinforcing rod in position during the tying of
the rod into place on the connecting member may be included within
individual perforations in the zone of perforation. The overall
elongate (height) dimension of individual perforations is selected
in part with reference to the material from which the connecting
member is manufactured, but in any event is selected to be
sufficiently large to permit the placement of reinforcement rods
that are of suitable dimension relative to the structure being
constructed. The longitudinal (width) dimension of individual
perforations may also be made discontinuous along their elongate
(height) dimension, especially in cases where the elongate (height)
dimension of individual perforations is relatively large, by the
inclusion of inward puckers that provide additional thickness to
the connecting member in regions that are adjacent the individual
perforations. This additional thickness limits possible vertical
pillowing along the elongate (height) dimension of the formwork.
Other forms and aspects of the invention will be
appreciated by those skilled in the art having reference to the
following detailed description of the preferred embodiments and to
the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
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In drawings that illustrate embodiments of the invention:
Figure 1 is a plan view of stay-in-place formwork in
accordance with the prior art;
Figure 2 is a frontal elevation of a connecting member in
accordance with the prior art;
Figure 3 is a plan view of a connecting member in accordance
with one embodiment of the invention;
Figure 4 is a frontal elevation of the connecting member of
Figure 3;
Figure 5 is a plan view of a connecting member in accordance
with another embodiment of the invention;
Figure 6 is a frontal elevation of the connecting member of
Figure 5;
Figure 7 is a plan view of stay-in-place formwork including
connecting members in accordance with embodiments of the invention.
Figure 8 is a plan view of stay-in-place formwork including
connecting members in accordance with embodiments of the invention,
and showing the location of placed reinforcement rods.
Figure 9 is a plan view of a connecting member in accordance
with one embodiment of the invention;
Figure 10 is a plan view of stay-in-place formwork including
connecting members in accordance with the embodiment of Figure 9.
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Figure 11 is a frontal elevation of a connecting member in
accordance with an embodiment of the invention;
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to Figure 1, there is illustrated one completed
cell of a PVC formwork assembly in accordance with the prior art.
The formwork assembly includes discrete wall elements 10 that are
assembled in end-to-end relationship to define a segment of an
inner or outer wall surface (12, 14) of the resulting structure.
The wall elements 10 are interconnected and held in spaced-apart
relationship by connecting members 16 via complementary terminal
connectors 18, 20 that are present respectively along the
longitudinal edges of the wall elements and connecting members.
Internal braces 22 extending between connecting members 16 and the
inner surface of wall elements 10 are similarly interconnected via
compatible attachment points and engagement means 24, 26 and 28,30
extending along the elongate dimension (height) of the braces,
members, and elements. As noted above, since the formwork is
constructed of thin PVC material, the attachment points 24 for the
braces 22 must be sufficiently offset from the nearest terminal
connector to limit bending of the brace 22 under the weight of the
poured concrete. In the prior art embodiment illustrated in Figure
1, the attachment points 24 are offset a sufficient distance from
terminal connectors 18, 20 to permit the braces 22 to depend at a
45° angle from the connecting member 16.
As seen in Figure 2, prior art connecting member 16
includes central perforations 32 to permit the cross-flow of
concrete between cells of the formwork assembly, and to permit the
placement of reinforcement rods (not shown). Auxiliary
perforations 34 are also present; these permit the cross-flow of
concrete, but are not suitably large to allow for the placement of
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of reinforcement rods. The presence of engagement means 24 along
the elongate dimension (height) of connecting member 16 limits the
longitudinal dimension (width) of the central perforations 32. As
discussed previously, this in turn makes it difficult or impossible
to place reinforcement rods at or near the optimal placement
position for a given structure. It also limits the maximal cross-
flow of concrete from one cell of formwork to another.
Figures 3 and 4 illustrate a connecting member 36 in
accordance with an embodiment of the present invention that is
suitable for connecting together two generally parallel rows of
wall elements of a known formwork assembly of the sort in which the
concrete (when poured) will communicate with the inner surface of
the wall elements of both of the parallel rows. Figures 5 and 6
illustrate a connecting member 38 in accordance with another
embodiment of the present invention that is suitable for connecting
together two parallel rows of wall elements of a known formwork
assembly of the sort in which the concrete (when poured) will
communicate with the inner surface of the wall elements of only one
row, and in which a layer of insulating or other material
communicates with or sits adjacent the inner surface of the wall
elements of the other row.
Connecting members 36 and 38 are manufactured of PVC
material and, as is best seen in Figures 3 and 5, the central
portions 40 and 42 (of connecting members 36 and 38 respectively)
are accordingly (given the relatively pliable nature of PVC
material) integral with braces 44 and 46 (of connecting members 36
and 38 respectively) at their points of connection 45 and 47 (of
connecting members 36 and 38 respectively). As noted previously,
the connection between the braces and the central portion of a
connecting member in accordance with the invention may be integral
or releasable depending upon the physical characteristics of the
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material from which the connecting member is constructed.
As best seen in Figures 4 and 6, the zones of perforation
48 and 50 (of connecting members 36 and 38 respectively) extend
through points of connection 45 and 47. As outlined previously,
this facilitates the cross-flow of poured concrete and permits the
placement of reinforcement rods at or near the optimal placement
position for a given structure.
A representative reinforcement rod 51 is shown cradled by
optional nib 52 in Figures 4 and 6. Auxiliary perforations 54
(intended primarily to conserve material) are shown in Figure 6, as
are ridges 56 that serve to locate the insulating material (shown
in Figure 7) adjacent one of the outer and inner wall surfaces.
Terminal connectors 20 and engagement means 30 of the sort
discussed above in relation to the prior art formwork assembly of
Figures 1 and 2 are also present on connecting members 36 and 38.
These connectors and engagement means cooperate with the formwork
system of Canadian patent no. 2218600. However, as previously
noted, different terminal connectors and engagement means may be
selected to suit other modular formwork systems or applications.
Figure 7 shows a segment of formwork assembly utilizing
connecting member 38, and Figure 8 shows a segment of formwork
assembly utilizing connecting member 36. The wall elements and
other formwork elements shown in Figures 7 and 8 correspond to the
prior art formwork system of Canadian patent no. 2218600. Figure 8
also illustrates the placement of reinforcement rods 51 at or near
the optimal placement position for a typical commercial or
residential wall structure.
Figures 9 and 10 illustrate a connecting member 58 having
shortened braces 60 dimensioned to cooperate with concave wall
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elements 62 that permit the construction of a wall structure having
a scalloped appearance. Apart from the presence of shortened
braces 60, connecting member 58 is otherwise the same as connecting
member 36.
Figure 11 illustrates a connecting member 64 in which the
longitudinal (width) dimension of perforations 66 is discontinuous
along their elongate (height) dimension due to the inclusion of
inward puckers 68 that provide additional thickness to one side of
the connecting member in regions adjacent the perforations.
Although the embodiment of Figure 11 shows puckers 68 on only one
side of connecting member 64, such puckers may of course be
included on both sides of a connecting member in accordance with
the invention.
As will be apparent to those skilled in the art in the
light of the foregoing disclosure, many alterations and
modifications are possible in the practice of this invention
without departing from the spirit or scope thereof. Accordingly,
the scope of the invention is to be construed in accordance with
the substance defined by the following claims.
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