Note: Descriptions are shown in the official language in which they were submitted.
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Constructional Wall Element
The present invention relates to constructional wall elements
for use in the construction of exterior walls of buildings.
More particularly, the invention relates to such elements
which have an inner concrete panel, an outer cladding panel
securely connected thereto, rigid thermal insulation on the
outer surface of the concrete slab, and a gap between the
outer panel and the insulation, which gap communicates with
the atmosphere through an air passageway.
Such elements may be pre-fabricated off-site and usually
comprise a relatively thick concrete inner slab, which may
serve to form an air and moisture vapour barrier, and to
carry structural items such as window frames. The insulation
reduces heat loss from the building, and the air gap, which
is vented to the atmosphere through the passageway, acts to
equalize pressure differences between the inner and outer
sides of the outer panel thus avoiding or reducing the forces
that the outer panel is subjected to in service. The outer
panel is usually a relatively thin panel which serves to shed
rain, to protect the insulation material that may be inter-
posed between the inner slab and outer cladding panel, and to
provide the outer surface of the wall with an aesthetically
attractive or decorative appearance. With these constructional
elements, owing to ~he differences in the natures and
properties of the inner and outer panels, there is a tendency
for the panels to become subjected to certain mechanical
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stresses owing to relative movement between the inner and
outer panels, e.g. stress due to differential thermal
expansion, and, as the outer cladding panel is normally the
more fragile of the two panels, this has resulted in a
tendency for the outer cladding panel to become fractured,
before or after placement of the element in position on the
side of a building. ThiS has been very undesirable as it
spoils the aesthetic or decorative appeal of the cladding
panel, and interferes with the element's performance. Also
this fracturing may require the repairing or replacing of the
cladding panel or of the whole element, and presents the risk
of portions of the fractured panel becoming detached and
falling from some height from the side of the building, with
risk of the falling pieces causing injury to persons or
property. The reasons behind the fracture of the cladding
panel have not in the past always been readily apparent or
fully understood, and various proposals have been made for
arrangements for securely attaching the cladding panel to the
concrete inner panel.
It has now been found that the incidence of fracturing of the
cladding panels owing to relative movement between the panels
can be at the least considerably reduced by supporting the
cladding panel on the inner concrete panel in such manner that
the two panels can readily bow relative to one another.
The present invention provides a constructional wall element
comprising an inner reinforced concrete panel, a rigid layer
of thermal insulation over the outer surface of the concrete
panel and affixed thereto, a rigid decorative outer panel
extending over the layer of insulation, spaced apart anchors
fixing the outer panel to the inner panel, the arrangement of
the anchors permitting relative bowing of the inner and outer
panels to a bowed position in which one panel is smoothly
bowed relative to the other panel, a gap being present for
circulation of air between the outer panel and the insulation
layer, and a passageway through which the gap communicates
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with the atmosphere, the wall element being in the form of a
transportable unit and having means on its rear surface
whereby it can be attached on a building structure.
In the preferred form which is hereinafter described, the
element has four anchors which rigidly connect the inner and
outer panels together at anchoring points each located
inwardly from the edge of one panel, typically inwardly from
the edge of the cladding panel, at approximately the same
distance from the centre of the panel, there is spacing
between the panels, and, in the central region, the panels are
free to move towards or away from one another, whereby, as
will readily be appreciated, one panel can readily become
smoothly bowed independently of the other panel by becoming
deflected out of its own general plane at central and
peripheral regions spaced from the anchoring points.
More than one cladding panel may be supported on a common
concrete inner panel, each cladding panel being attached to
the inner panel by an arrangement of anchors permitting
relative
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bowing between the cladding panels and the inner panel.
In the accompanying drawings, which illustrate an embodiment
of the invention:
Figure 1 is a front view of a constructional wall element
provided on its front surface with eight marble slabs as
cladding panels;
Figure 2 is a sectional view along the line 2-2 of Figure 1
through the element and part of window frames above and below
the panel;
Figure 3 is an enlarged sectional view of part of the element
taken along the line 3-3 of Figure l;
Figure 4 is a rear view of the element on a smaller scale than
Figure 1, taken along the line 4-4 of Figure 2 and showing
columns from which the element is supported; and
Figure 5 is a perspective view of forms being used during the
construction of the element.
Referring to the drawings in greater detail, in Figure 4, two
vertical columns 2 support a steel spandrel beam 4 horizontally
between them. The beam 4 has flanged upper and lower edges 6
and can be welded to the columns 2. The vertical columns 2 and
the steel spandrel beam 4 are part of a building (not shown).
The beam 4 is conventional in building construction and need not
be further discussed. A wall element 8 is mounted on the beam 4.
Referring to Figure 2, the element 8 is mounted at the outer
side 10 of the beam 4. The means for mounting the element 8 will
be discussed in more detail below. The element 8 is constructed
with flanged upper and lower edges 16, which extend rearwardly
from the element. After the element 8 is mounted on the beam 4,
an inner surface 12 of the beam 4 and the flanges 6 are coated
with an insulating sprayed fire-proofing material 14, for
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example, an asbestos-based material.
The fire-proofing material 14 contacts the flanges 16 of the
element 8, leaving a cavity 18 between an inner surface 20 of
the element 8 and the outer surface 10 of the beam 4. The
ends of the flanges 16 are cut away at 17 to allow for the
columns 2 (see Figure 4).
The element 8 includes an inner precast reinforced concrete
panel-form slab 22. Usually, it is desired to provide a layer
of thermal insulation between the outer cladding panel 28 and
the 51ab 22, and in the example shown in the drawings, the slab
22 is bonded to a rigid layer of thermal insulation 24. A
spacing 26 is provided between the insulation layer 24 and an
outer cladding panel 28.
In the example shown in the drawings, there are eight cladding
panels 28 supported on a common concrete slab 22. Each cladding
panel is connected securely to the inner panel 18 by four
anchors 30 which, in the as-manufactured condition of the wall
element, maintain the panels 28 parallel to the slab 22. In
the example illustrated in Figure 3, each anchor 30 consists of
a pin having a headed end 32 and threaded end 34. The
threaded end 34 of each pin is embedded securely in the concrete
slab 22. From the slab 22, each pin extends through the
insulation layer 24 and into a dovetail hole 36 in the inner
surface of the cladding panel 28. Each hole 36 contains a filler
38, such as epoxy resin, which secures the panel 28 to the pin.
The pins constituting anchors 30 can withstand any force on the
cladding panel normal to the element 8 that is encountered by
the element in use. Other types of anchor may of course be
employed. In the example shown in the drawings, the weight of
each cladding panel is carried principally by a steel rod 40
embedded in a concrete projection 42 of the slab 22, this
projection extending through a circular hole 44 in the
insulation layer 24 and into a hole 46 in the inner surface of
the cladding panel 28. Between the end of the rod 40 and the
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bottom of the hole 44 there is a readily compressible buffer
48, e.g. of neoprene rubber, and between the inner surface of
panel 28 and the outer end of the projection 42 there is a
resiliently compressible pad 50 e.g. of foamed or expanded
polystyrene or of rubber. The buffer 48 and the pad 50 serve
to reduce the shock if the panel 28 is in its central region
forced rearwardly towards the slab 22 by, for example, a gust
of wind.
The positions of the rigid anchor pins 30 and of the central
rods 40 on the panels 28 are illustrated in Figure 1. It will
be noted that the anchors 30 are each located inwardly from the
edge of the panel 28 and each at the same or approximately the
same distance from the rod 40 at the centre of the panel. As
will be readily appreciated, the arrangement of the rod 40
lodging in the hole 44 is intended to permit the central regions
of the panel 28 and the slab 22 to move towards or away from
one another in the direction normal to the general plane of the
wall element 8 and the spacing 26 between the inner side of the
panel 28 and the outer side of the slab 22 permits similar
deflection of the panel 28 and of the slab 22 relative to one
another in the direction normal to the plane of element 8 not
only in the central region adjacent the rod 40 but also at the
edges and the peripheral regions of the panel 28 spaced from
the rigid anchors 30. In this manner, the slab 22 and the
panel 28 may bow relative to one another by deflection of the
central and peripheral portions spaced from the anchors 30 out
of their original general planes with the whole of one panel
being bowed smoothly, in a continuous smooth curve, through the
central portion of the panel being deflected inwardly or
outwardly of its original plane and with the edge regions of
the panel being deflected in a correspondingly opposite
direction, i.e. outwardly if the central region deflects
inwardly, so that a smoothly concavely bowed curve is obtained,
or inwardly if the central region deflects outwardly so that
a smoothly convexly bowed curve is the result.
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The spacing between the inner face of the cladding panel 28 and
the slab 22 may be occupied by resiliently compressible
material e.g. the expanded plastic pad 50, as this will readily
yield and not interfere with the kinds of inward movement of
portions of the panel referred to above.
The arrangement of the invention is applied with particular
advantage in the case of relatively thin, fragile or brittle
cladding panels of natural stone e.g. marble, granite, or slate,
or of glass. It can also be employed with cladding panels made
from concrete or stainless steel, if desired, although with
these materials there is normally less tendency for fracture of
the cladding panel and conventional wall element structures may
be equally effective or may in some instances be preferable.
In the particular embodiment illustrated, the eight rectangular
cladding panels 28, which in the particular example illustrated
are intended to be of marble, are arranged edge to edge in two
horizontal rows. Between the marble panels 28 are spaces 52
which may for example be approximately 3/8 inch wide. These
spaces 52 are preferably sealed with a suitable caulking material
54, for example, a polysulfide sealant, to prevent ingress of
rain through the spaces 52. Marble-to-marble joints between the
constructional element 8 illustrated and adjacent elements
(not shown) are also approximately 3/8 inch in width and sealed
with a suitable caulking material. In addition, spaces
between the element illustrated and adjacent elements (not shown),
along the edges of the insulation layer 24 and the concrete slab
22, are sealed with a suitable caulking material in order to
prevent any moisture from passing through said spaces and also
to seal off the cavity 18 between the inner surface 20 of the
element and the spandrel beam 4. The sealed cavity 18 acts as
an insulator. As shown in Figure 2, adjacent to the top and
bottom of the element 8 are window frames 56 and 58 respectively.
Any gap between the top frame 56 and the adjacent cladding
panels 28 is sealed with a suitable caulking material at 60.
However, the upper surface 62 of the bottom frame 58 is spaced
below the spacing 26, leaving an unsealed opening 64 that
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connects the spacing 26 to the ambient air. The opening 64
ensures that, under steady state conditions, the pressure of
the air present in the spacing 26 will be substantially equal
to the pressure of the ambient air. Furthermore, the upper
surface 62 of the bottom frame 58 is sloped downward and
outward from the insulation layer 24 of the element 8 so that
water collected or formed in the spacing 26 can drain away
through the opening 64.
The element 8 is supported from the beam 4 near six points
64-69, indicated in Figure 4. The actual means of support are
well known to those skilled in the art and need not be
described in detail. Suitable examples are shown in 1971 Form
No. 30791 published by the Mo-Sai Institute, Inc. and entitled
"Precast Concrete with Exposed Aggregate". The present address
of the Mo-Sai Institute is c/o David W. Evans and Associates,
110 Social Hall Avenue, Salt Lake City, Utah, U.S.A. 84111. At
the points 64,66, near its upper corners, the element 8 is
restrained vertically as well as horizontally normal to the
element. At the point 65, near the centre of its upper edge,
the element 8 is restrained horizontally in all directions.
Near the lower edge, at the points 67, 69 near its corners, and
at the point 68 near the centre of its lower edge, the element
8 is restrained horizontally normal to the panel. Other types
of restraints can be employed so long as they permit differential
movements of the element and beam due to variations in
temperature, concrete shrinkage and building deflections.
As shown in Figure 5, the element 8 may be manufactured using a
mold 70 which can be made of wood, steel, precast concrete or
other suitable material. First the marble panels 28 are placed
edge to edge (with approximately 3/8 inch spaces between them)
face down in the mold 70. The pins 30 and the rod 40 can be
affixed to each panel 28 either before or after the panels are
placed in the mold 70. Next, spacers 72, which can be rubber
strips, are laid crosswise on the upper surfaces of the marble
panels 28, the thickness of the spacers 72 defining the spacing
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26. The spacers 72 extend through slots 74 in the side walls
of the mold 70. A compressible pad 50 is placed around the rod
40 of each panel 28. Then, the insulation layer 24 is laid on
the spacers 72 with the anchor pins 30 penetrating the insulation
layer 24, and with each rod 40 passing through its corresponding
circular hole 44 which is pre-cut in the insulation layer 24. A
grid of reinforcing steel (not shown) is placed over the upper
surface of the insulation layer 24. The grid is designed in
the usual way to reinforce the concrete. Concrete is then
poured onto the upper surface of the insulation layer 24 and
around the reinforcing grid to form the slab 22. The
compressible pad 50 of each panel 28 covers the end of each hole
44 and prevents the concrete from running into the spacing gap
26. The concrete flows into each hole 44 in the insulation
layer 24, thus on setting the projection 42 in which each rod
40 becomes embedded. The number of spacers 72 required depends
on the size of the element 8, the strength of the insulation
layer 24 and the weight of the concrete slab 22. The concrete,
in setting, adheres or binds itself to the insulation layer 24.
After the concrete is set, the panel is removed from the mold 70.
The spacers 72 can be removed by pulling on them longitudinally
either before or after the element 8 is removed from the mold,
leaving the spacing 26 between the marble panels 28 and the
insulation layer 24.
As stated above, due to the fact that the spacing 26 is ventilated
through opening 64, under steady state conditions, the pressure
of the air in the spacing 26 is substantially equal to the
pressure of the ambient air. This is advantageous as under
steady state conditions the pressure on either side of the
cladding panel 28 will be the same, and there will then be no
resultant air pressure force acting normally on the cladding panel
28 and all forces normal to the element 8 will be taken by the
concrete slab 22. Thus, the facing sheet need only be designed
to withstand forces during unsteady state conditions, which
occur due to a sudden change in wind suction or wind pressure.
Another advantage of ventilated spacing 26 is that, under steady
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state conditions, moisture on the outer surface of the cladding
panels 28 or on joints between the panels 28 will not seep
through to the spacing 26 because there is no pressure
differential across the panels 28 or joints. Thus, under
steady state conditions, rain falling against the outer surface
of a cladding panel will not penetrate the panel because the
pressure on both sides of the cladding panel is the same. Thus,
the cladding panel in combination with the ventilated spacing
26 acts as a rainscreen. Any moisture that collects in the
spacing 26 can form droplets that will drain out of the spacing
through the opening 64 at the bottom. The spacing 26 should be
sufficiently wide that water will drain away rather than form a
film across the spacing. If the spacing were so narrow that
water ~ould form a film across it, a film of water might block
the spacing and thereby defeat its purpose with respect to
pressure equalization.
Merely by way of illustration it may be mentioned that in one
example of an element as illustrated in the accompanying
drawings, the anchor pins 30 are each located approximately one-
fifth of the length of the marble cladding panel 28 from an edgethereof and approximately one-fifth of the width of the panel
from another edge thereof, the spacing 26 has a thickness
between about 1/4 inch to 2 inches. The thermal insulation
layer 24 when present, preferably has a thickness between about
1/2 inch to 3 inches. The thickness of the insulation layer
depends on the thermal conductivity of the particular type of
insulation used, on the insulation requirements of the
particular building where the panel is to be used, on the
rigidity or strength of the insulation used and on the thickness
required for the precast concrete slab 22. The insulation used
in the embodiment illustrated is expanded polystyrene, the marble
panels 28 having a thickness between about 3/4 inches to 1 1/2
inches. Whenever marble is used as a cladding panel 28 in an
element according to the present invention, it preferably has a
thickness between about 3/4 inches to 3 inches.
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Various types of anchors can be used to support the cladding
panel 28 in accordance with the invention. The panel can be
attached to virtually any building structure having sufficient
strength to support it. Modifications within the scope of the
attached claims will readily occur to those skilled in the
art.
