Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a method
of casting reinforced concrete floors of the
ribbed or troughed type using per~nanent form-
work and the par*s and form-work used in the
casting of such floors.
Floors of the ribbed or troughed type
are formed by laying out the area to be floored
with form-work arranged to receive the concrete
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when poùred. Such form-work normally rests upon
a supporting structure such a~ walls,~beams or a
combination of both to support the span of the
floor. The base of each of the troughs which
when filled with concrete form the ribs of the
floors in some forms of construction consists
of a concrete plank, the trough being formed by
each of the longitudinal edges of the form-work
used to position the shallower part of the floor
resting on an edge of the ~ank. Such conerete
planks must be stiffened by the pro~ision of
reinforcing rods and carry some or ~11 of the
steel reinforcement req~ired in the trough~
In forming auch concrete plank~ and setting the
associated reinforcing metal in the plank, the
metal reinforce~ent must be held accurately in
position by some form of support system. It
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is not possible to locate the edges of the
form-work used to form the shallow part of the
floor accurately on the appropriate edge of the
plank so as to give a flush fit. Furthermore
each plank must be prepared with the correct
dimensions and steelwork for a particular floor
loadi~g. It is thus impossible to carry an
inventory of standard planks, and it is normal ~,
to cast planks against orders for a particular ~
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floor in a particular building. It i9 therefore s
impossible to accommodate any changes in design
at the last moment or any changes in site
dimen-sions. The concrete planks being made of
pre-cast concrete are subject to damage on site ;
or during transport to the site as the material
is not resistant to impact. Concrete also tend~
to spall in a fire~
We have n~w devised a composite plank
which can be used in a troughed or ribbed flooring
system to directly support the form-work which can
be made in standard lengths no matter what loading
~ ~ and which, in addition9 increases the fire
- ~ resistance of the flooring and reduces the risk
of damage due to impact before and after
installation, This composite plank is also~shaped
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to receive the edge of the form-work so as to
provide a flush fitting and position the form- .
work edge positively on the edge of the plank~ ,
Our invention also provides a new method of
forming a troughed or ribbed floor utilising
the composite plank of the pre~ent invention .
in which all or a substantial part of the
reinforcing steel other than that required to
proYide the necessary stiffening of the
composite plank to remain rigid between temporary
supp~s, is placed in position after the form-
: work and planks are assembled together on site.
The composite plank of our invention
therefore consists of a skin o~ fibre reinforced .
: 15 osment forming an open trough with a flat bottom
and vertical or substantially vertical sides :into which at least the metal rein~orcement .
necessary to maintain the plank rigid acros~
temporary supports is placed and held in place
by concrete cast around that portion of the
: :
. metal reinforcement that lies within the con~
: -fine3 of the trough~ We prefer to use a skin :
of 5 to 10 mm thickness of cement which has ~ :
been reinforced with alkali resistant glass :
fibre such as that sold under the trade name
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"Cem-~IL" by Fibreglass Limited. In casting
the concrete within the skin of fibre reinforced
cement we prefer to arrange the casting such
that a longitudinal channel is formed at the
upper part of each wall ofthe skin, between
the wall and the concrete. The concreta between
the channels is preferably cast so as to be ~
raised above the top of the walls of the fibre d
reinforced skin. The channel thus formed
provides an opening into which a suitably
shaped longitudinal edge of the form-work which
is to rest on the composite plank can be slotted.
This enables such form-work to be positively
positioned in place. The longitudinal edges ~;
of the for~-work are preferably the lower edges ~
o~ the walls of inverted troughs, the hollow i
space formed between the walls of the trough
facing the area beneath the floor being cast.
The fibre rein~orced skin, because
of its increased impact resistance, provides a
protection against the kind of damage l1kely ~rS
to be experienced by an unprotected concrete
planX resulting in either the need for remedial
work or an unsatisfactory finish to the u~der-
side of the floor. In our preferred embodiment
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alkali resistant glas4 fibre is used as the s,
reinforcing material as this material can be
readily incorporated into the cement ma-trix
when spraying a mixture of glass fibre in
chopped form and cement onto a m~uld shaped
to that desired ~or the skins for the composite ,
plank. .The skins may also be made by forming
a flat sheet and shapin~ it on a former while l ~
still in the green or uncured state. It is js
10 ' possible by the use o~ these techniques to
produce articles with a skin thickness in the
range 5 to 10 mm which, when cured, can be
readily handled and delivered to where concrete
- - is to be ca-~t. Below.a skin thicknes~ ~f 5 mm
; 15 problems may be experienced in forming a
atisfactory edge to the cha~nel which ~ to .
receive the sultably shaped edge of the ~orm-
- work and, at thicknesses above 10 mm, the quantity
of glass fibre needed even at levels o~ the order
of 5~ renders the final product unattractive .
because of cost. At thicknesses in the range
.5 to lO mm adequate impact strength and an :
adequate increase in fire re~istance i~ obtained ~ ~
. of the order of several hours over that which ~ .
would be obtained with a concrete plan~ not ~
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provided with an outer skin Or glass fibre
reln~orced cement. Organic ~ibres such as
polypropylene fibres can also be used but such
material does not have the same degree of fire
resistance. Asbestos fibre, while usable, is
tending to become unacceptable in exposed
situations within buildings because of health
hazards. It is not so con~enient to use in
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forming relati~ely thin skinned articles with
a high impact strength. We prefer to use as
the metal reinforcement to be held in place in
the composite plank, an assembly of steel wire
or rod in which two rods are plàced along the
trough spaced apart from one another and a
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further rod spaced abo~e and betwe~n them and
held in place relative to the rirst tw~ rods by
a serie~ of inverted V-shaped trus~es arranged
along the length of the trough. An arrangement
such as this enables any load on the plank to
be tran~ferred along the plank and give the
necessary rigidity or stiffness to enable the
planks to be used with the minimu~ of temporary
; supports. In the absence of this metal re-
inforcement the pla~k~ would require temporary
support6 at perhaps a maxi~um Or 1 metre inter~al-.
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The oomposite plank Or our inventio~ can ~pan ¦:,
at least 2 metres betw~*n temporary s~pports
and accept the load of site installed metal j~
reinforcement and concrete ~hile the concrete
is curing. -
Our in~ention also includes a method :
` of ~orming a ribbed or trough~d $kor in which a .
: plurality of composite planks as described above
are laid on temporary supports with a space ~
between them, and the space between them is ,
then filled with form-work arranged so that their
longitudinal edges re~t in channels along the
: edges o~ the composite planks, metal reinforcement
~: : . is mounted on the planks and form-work and
finally concrete iB poured into place to cast
the floor~
One form of our inventlon will now .
be described with reference to the aocompanying
drawings in which:-
~igure 1 is a part-ser~onalside ~iew
o~ a composite plank according to the invention; ~ .
~: Figure ~ ls a cross-sectional viewsubstantially taken ~rom the line 2-2 in
Figure 1;:
Figure 3 is a cross-sectional view
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of a portion of a floor before the concrete is
cast and the remaining metal reinforcement
provided;
Figure 4 is a fragmentary perspective ! ~'
- . 5 view corresponding to part of Figure 3 showing
an inverted trough engaged in the channel formed ~
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in the plank; and
~igure 5 is a fragmentary perspective
view showing another type of form-work mounted
across a pair of planks. . ~'s
The composite plank P in the preferred
form shown in ~igures 1 and 2 ~omprises a fibre ~
: reinrorced cement outer skin 1 which is in the i;
~orm of an elongated trough, with side walls 2 .
: 15 and 3, and base 4 forming a container in which .
a matal reinforcement assembly 5 is placed~
This assembly comprises two steel rods 6 and 7
placed along the base 4 and which are inter- .
connected with a ~rther rod 8 by a series o~
inverted V-shaped trusses 9 which are welded
- ~ at contact points to the rods 6~ 7 and 8. ~
This interconnected structure thus formed .
maintains the rigidity of the plank. The
rods 6 and 7 and the portions of the trusses
adjacent these rods are covered wlth concrete.
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The concrete covering 10 is cast so as to leaYe
two longitudinal channels or slots 11 and 12 at
each side of the plank into which the longitudinal
edges of form-work can be slotted.
,5 The overall arrangement of a floor
is shown in Figure 3 and the method of casting
; a floor will now be described with reference to
that drawing~ Three planks P as in ~igures 1
and 2 are shown. These planks would be placed
where the span is acceptable from wall to wall
in the area to be ~loored. If necessary
temporary supports can be provided to reduce
the span. The spacing between the planks is
adJusted to allow the related edges 13 of
permanent form-work F to be ~itted ~nto the
- longitudinal channels provided along the sldes
of the planks so as to give ~irtually a flush
fit at the contact point between the outer ed~e
of the wall of the channel and the bottom
surface of the form ~rork. The form-work F
forms voids V, and is preferably made o~ glass
fibre reinforced cement. The use of this
material for the form-work and the outer ~kin
of the composite planXs means that ths inter-
connectlng parts of the planks and form-work
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can be accurately formed e~-~though they are
relatively thin. 5uch part~ either could not
be formed easily in concrete or, if formed,
would be very vulnerable to damage both before
, 5 and during installation. Once the form-work
and planks have bsen assembled as shown in
Figure 3, the remaining metal reinforcement
required for the particular floor loading is
placed-and concrete cast to form the floor in
a manner well known to those practised in the
art of forming floors.
Figure 4 indicates a continuous
- uniform section or trough unit Fr for th0 form-
work, while Figure 5 indicates that by pro~iding
form-work with spaced ralsed portions R it is
possible to form a solid transverse stiffening
rib in the space ~ without any specially shaped
additlon}l form-work being required.
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