Note: Descriptions are shown in the official language in which they were submitted.
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PANELS FOR THE MANUFACTURE OF CIRCULAR ABOVE-GROUND
TANKS, MOULD, AND ASSOCIATED MANUFACTURING METHOD
The invention relates to prefabricated reinforced
concrete panels for the manufacture of circular above-
ground tanks, a mould for the production of the said
product, and a method of manufacturing the said
product. In particular, the panels are flat, with
horizontal ribs containing holes for the passage of
pre-stressing cables; said holes are made by inserting
into the mould, before casting, a flexible pipe whose
length is such that when the mould closes, the ends of
the pipe are compressed and it curves, taking on an arc
shape with the same radius as the tank.
A known type of above-ground tank is made by joining a
number of panels with a straight section which are
placed side by side, coupled and tightened by pre-
stressing cables wound round the tanks, the said cables
usually being fitted on the outside of the panel, in
ducts formed in the horizontal ribbing of the panels.
However, this system presents the disadvantage that the
pre-stressing cables are exposed to atmospheric agents
unless a further cable protection operation is
performed, which typically involves filling the seating
in which they are housed with mortar.
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This mortar filling operation considerably increases
production time and therefore labour costs.
The tanks thus obtained are also more difficult to
dismantle if required.
Equally, it is inconvenient to make cable passages in
this kind of panel, as it would be very difficult to
insert cables dozens of metres long into a passage
which is bent at an angle at the joint between each
panel and the next.
lo Curved panels for the construction of circular tanks
are also known, in which holes for the passage of pre-
stressing cables are formed in the horizontal ribbing.
Panels of this kind, described, for example, in
European patent 0514583 by the same Applicant, present
the advantage of good cable protection and easy
insertion because of the curved configuration of the
holes.
The curved shape, however, requires more complex and
therefore more expensive moulds, and the manufacturing
process is more laborious as regards the laying and
compacting of the concrete.
The main purpose of this invention is to eliminate the
problems mentioned above by offering improved panels
which allow fast, easy insertion of pre-stressing
cables without the difficulties presented by known
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panels.
The invention also relates to the manufacturing method
and associated mould. These tasks, and these and other
purposes, are achieved by a product made of reinforced
concrete in accordance with the characterising part of
the annexed claims.
Further advantages of the invention will clearly emerge
from the description of a preferred, but not the only
method of manufacturing the product in accordance with
the invention, which is supplied by way of example but
not of limitation, with reference to the annexed
figures in which:
~ figures 1 to 3 are the plan view, cross-section, and
front view respectively of a panel in accordance with
the invention;
~ figure 4 is the plan view of a further embodiment
panel in accordance with the invention;
~ figure 5 is the vertical cross-section of a detail of
the panel;
~ figure 6 is the horizontal cross-section at a joint;
figures 7 to 10 are the plan view, cross-section,
front view and side view respectively of the end
panel in a tank made with the products in accordance
with the invention;
~ figures 11, 12 and 13 are the plan view, cross-
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section and front view respectively of an assembled
tank;
figures 14a and 14b schematically illustrate in
cross-section a mould for the manufacture of the
panels in accordance with the invention, such mould
being shown open and closed respectively.
With reference to figures 1 to 4, the panel in
accordance with the invention presents a flat wall 1,
with vertical stiffening ribs 2 and horizontal
stiffening ribs 3 located on the outer side.
This flat configuration facilitates manufacturing
operations.
At the sides the panel is shaped with "male" and
"female" contours shown as 4 and 5 respectively
(fig.6), to form a joint which provides a secure
connection between adjacent panels.
Holes are formed in horizontal ribs 3, each of which
holes constitutes a passage for the pre-stressing
cables.
The characteristic feature of the invention is that the
panels are flat, and the holes designed for the passage
of the cables are curved to an arc shape having the
same radius as the tank.
This configuration involves the least possible strain
on the product, and therefore the greatest possible
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reduction in steel reinforcement.
The invention therefore combines the advantages of flat
panels, which are compact and easy to manufacture, and
curved panels, in which the cables can easily be
inserted.
The method of manufacturing these panels involves
making the said holes by installing flexible tubular
elements in the mould in a position corresponding with
the ribbing; the length of the said tubular elements is
greater than the distance between the walls of the
mould, so that when the mould is closed, the pressure
exerted on the tube curves it to the required extent.
Figure 14 shows a mould designed for the manufacture of
the panels in accordance with the invention.
This mould comprises a back wall 6, a front wall 7 and
a pair of side walls 8 and 9; the latter can be
installed with different inclinations to give the sides
of the panel the inclination required by the radius of
the tank to be assembled.
A number of pairs of pegs 10 are fixed to side walls 8
and 9 at the horizontal ribs of the panel, and the same
number of flexible tubular elements 11, destined to
constitute the passage for the pre-stressing cables,
are fitted onto the said pegs before the mould is
closed.
The length of tubular elements 11 is greater than the
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internal width of the mould, so that when the mould
closes the side walls move together and compress
tubular element 11 lengthwise into an arc shape; the
longer the tubular element, the more accentuated the
arc.
A simple calculation therefore suffices to determine
the length of tubular element 11 so that the closing of
the mould crushes it to such an extent as to produce
the required radius, in particular a radius equivalent
lo to that of the tank.
The pegs will preferably be slightly inclined towards
the outer wall of the panel, to ensure that the tubular
element bends in the right direction.
The sides of the mould can also advantageously be made
with adjustable inclination, in order to produce panels
with the side edges arranged radially in relation to
the centre of the tank.
The process in accordance with the invention therefore
comprises the following stages:
insertion of a flexible tubular element, of the same
length as an arc which presents a radius equal to the
radius of the tank and a chord equal to the width of
the panel, into a mould with mobile sides, on a pair
of pegs fitted to the sides at the horizontal ribs of
the panel;
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approach of the mobile sides until the mould closes,
so that the said flexible tubular element takes on
the arc shape required;
installation of reinforcement and laying of concrete
concrete shaving;
curing and removal of finished product.
The invention thus devised could form the subject of
numerous modifications and variations, all of which
fall within the ambit of the invention concept.
Thus horizontal ribs 3 may be straight, or, if required
by the width of the panels, may be curved as shown in
fig. 4. In practice, any materials or dimensions can be
used, as required.
