Note: Descriptions are shown in the official language in which they were submitted.
CA 02278650 1999-07-28
FLAT STRIP LAMELLA FOR REINFORCING BUILDING COMPONENTS AND
METHOD FOR PLACING A FLAT STRIP LAMELLA ON A COMPONENT
Description
The invention concerns a flat strip lamella for reinforcing
load-bearing or load-transmitting building components, which
is comprised of a composite structure of a plurality of
bendable or flexible reinforcing fibers aligned parallel to
each other and a binder matrix which joins the reinforcing
fibers to each other in a shear resistant manner, and which
can be attached facewise to the outer surface of the building
components by means of an adhesive. The invention further
concerns a process for application of this type of flat strip
lamella onto a building component.
Reinforcing lamellas of this type are known, for example, from
WO 96/21785. The therein disclosed reinforcing lamellas are
applied to longitudinally extending and/or flat surfaced
construction components. The reinforcing lamellas hardened
with a binder matrix of a Duroplast, in particular epoxy
resin, do not permit a bending with a small bending radius, so
that it is not possible to form a bowed reinforcement
extending over a corner of a construction component. Bowed
reinforcements or sheaths are necessary for example in order
to secure the connection or interrelation between the
compressive and tensile zones in steel reinforced concrete
girders or steel reinforced concrete T-beams and to avoid
stress and transverse fractures.
Beginning therewith the present invention is concerned with a
task of developing a flat strip lamella which can reinforce a
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construction component by extending over a corner thereof. A
further task of the invention is comprised in the development
of a process for the application of this type of flat strip
lamella to construction components.
For solving this task the combination of characteristics set
forth in claim 1 as well as 6 through 9 is proposed.
Advantageous embodiments and further developments of the
invention can be seen from the dependent claims.
l0
The inventive solution is based on the recognition, that the
bending flexibility of the flat strip lamellas is determined
primarily by the binder matrix. In order to be able to guide
the flat strip lamella also over bent construction component
outer surfaces and building component corners, it is proposed
in accordance with the invention, that the binder matrix be
comprised of a thermoplastic resin. This type of flat strip
lamella can be deformed by application of a local temperature
increase and then fitted to the outer surface contour of the
construction component to be reinforced. The glass transition
point of the employed thermoplastic resin is preferably above
100°C, while the melting point should begin above 160°C, in
order that a reliable manipulation is achieved. The local
heating of the flat strip lamella can be achieved on site with
the aid of a hot air gun.
For forming the binder matrix one can consider for example a
thermoplastic resin from the group consisting of polyolefins,
vinylpolymers, polyamide, polyester, polyoxymethylene,
polycarbonate and thermoplastic polyurethane and ionomers.
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The reinforcing fibers are preferably formed of carbon fibers,
which are characterized by a high modulus of elasticity. The
reinforcing fibers can however contain or be comprised of
aramid fibers, glass fibers, polypropylene fibers and the
like.
For application of the inventive longitudinally extending flat
strip lamella over a corner of a construction component to be
reinforced it is proposed in accordance with the invention
that the flat strip lamella is heated in the intermediate area
to be directed over the corner of the construction component
to a temperature above the glass transition point of the
thermoplastic binder, that it is bent in the heated condition
at an angle corresponding to that of the corner or edge angle
of the construction component, and that before or after
cooling it is adhered to the construction component over the
construction edge by means of a adhesive layer.
The inventive application of a thermoplastic binder matrix
makes it possible to apply the flat strip lamellas in the
pretensioned condition to a construction component outer
surface. The free ends of the flat strip lamellas which
project beyond the surface of the construction component to be
reinforced can, in their heated state, be drawn or stretched
with a tensioning element or be bent and fixed thereupon. The
tensioning elements can then be tensioned against each other
so that the flat strip lamella can be adhered to the
construction component outer surface in the pretensioned
condition. For tensioning of the tensioning elements a
tensioning mechanism can be provided spaced apart from the
construction component. The tensioning mechanism could also
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engage only at the free end of the .flat strip lamella, when
the other end is fixed to the construction component outer
surface~by a suitable tensioning element.
Further there exists with the inventive thermoplastic binder
matrix the possibility of pressing the free ends of the flat
strip lamella under the action of pressure and heat into a
wave or zigzag shape. To achieve a form-fitting anchoring,
the lamella ends deformed in this manner are introduced into a
recess in the construction component filled with adhesive, so
that the zigzag area fills with the pasty adhesive and after
hardening of the adhesive forms a form fitting connection.
The flat strip lamella with the inventive thermoplastic binder
matrix can additionally be employed for reinforcement of
column-shaped construction components. Therein the flat strip
lamella heated to a temperature above the glass transition
point of the binder matrix is wound in a spiral manner about a
column-shaped construction component of which the outer
surface is coated with fluid reaction adhesive and in this
wound state is cooled to room temperature with simultaneous
hardening of the adhesive. In order to avoid collection of
liquids below the flat strip lamella winding, it is
advantageous, when a separation is maintained between the
spiral windings of the flat strip lamella.
In order to improve the bond between the flat strip lamella
and the adhesive, such as epoxy resin, it can be advantageous,
when the flat strip lamella is freed of binder with
simultaneous exposure of the reinforcing fibers on the side to
be adhered, for example by roughening or grinding.
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In the following the invention will be described in greater
detail by reference to the embodiment shown in schematic
manner in the drawings. There is shown
Fig. la a top view of a section of a reinforcing lamella;
Fig. lb an enlarged representation of a section along
section line B-B of Fig. la;
Fig. 2 a section through a steel reinforced concrete T-beam
with bow-shaped bent reinforcing lamella;
Fig. 3 the one end of the reinforcing lamella, which can be
introduced into the recess in the construction
component according to section III of Fig. 2;
Fig. 4 a tensioning device for pretensioned application of
the reinforcing lamella to a construction component;
Fig. 5 a sectional side view of a column-shaped construction
component with a reinforcing lamella wound about in
spiral manner.
The flat strip lamellas 10 shown in the drawings are designed
for post reinforcement of construction components 12, such as
steel reinforced concrete structures and masonry structures.
They are secured at one of their face sides 14 against the
outer surface of the construction component with the aid of an
adhesive 16, preferably an epoxy resin, and supplementally
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anchored at their free ends 32, 34 to the construction
component 12 (Fig. 2).
The construction component 12 according to Fig. 2 is formed in
this example as a steel reinforced concrete T-beam, in which
the lamella 10 extends in a bow like manner over the cross
beam 22 of the construction component 12 and thereby is bent
over the corner edges 24 of the cross beam 22.
The flat strip lamella 10 has a composite structure of a
plurality of parallel aligned bendable or flexible reinforcing
f fibers 2 6 of carbon f fiber and of a binder matrix which j oins
the reinforcing fibers in a shear resistant manner, the binder
matrix being comprised of a thermoplastic resin. The
thermoplastic binder matrix 28 ensuxes that the flat strip
lamella is relatively stiff at temperatures of use and is
plastically deformable upon heating to a temperature above the
glass transition point. In order to initially guide the
longitudinally extending flat strip lamellas 10 over the
corners 24, they are heated in the intermediate area 30 to a
temperature above the glass transition point of the
thermoplastic binder matrix and plastically bent about the
edge angle, which may be rounded off, at approximately 90°.
This bend remains retained after the cooling to the
temperature of use.
In the illustrative embodiment shown in Fig. 2 the plastic
deformability under increased temperature of one end 32 of the
flat strip lamella is also taken advantage of in the anchoring
process. The bent-away end 32 is adhered to the construction
component 12 with an adhesive 16. At its other free end 34,
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the flat strip lamella exhibits a zigzag-shaped deformation,
with was produced under the action of pressure and heat. With
this end 34 the f-lat lamella 10 penetrates into an adhesive
filled recess 35 of the construction component 10 and forms a
form-fitting anchoring upon hardening of the adhesive in this
recess.
In the embodiment shown in Fig. 4 the free ends 36 of the
flat strip lamella 10 are drawn .in the heated, plastic
deformed condition upon drum-shaped tensioning elements 38 and
are anchored there. The tensioning elements 38 can, under the
influence of a suitable tensioning mechanism, be displaced in
the direction of the double arrow 39 towards each other so
that the flat strip lamella 10 is pretensioned during adhering
to the construction component 12 with the aid of the adhesive
16. If the pretensioning is maintained until the hardening of
the adhesive, one attains an improvement in the reinforcing
effect.
In the embodiment shown in Fig. 5 a flat strip lamella 10 is
wound in a spiral manner upon a column-shaped construction
component 12 and adhered thereto. In order to facilitate the
winding, the flat strip lamella is subjected to an elevated
temperature, so that during winding it can easily be brought
to its spiral shape.
In summary the following is to be concluded: The invention
concerns a flat strip lamella 10 for reinforcing load-bearing
or load-transmitting building components e.g. concrete, wood,
steel, natural stone or masonry. The flat strip lamella 10
has a composite structure consisting of a plurality of
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parallel aligned, bendable or flexible carrying fibers 26 and
a binding matrix 28 joining the carrying fibers to each other
and making them shear resistant. The lamella can-be attached
facewise to the surface of the building component to be
reinforced, using adhesive 16. In order to be able to bend
the flat strip lamella over corner edges of a building
component, it is proposed in accordance with the invention
that the binding matrix 28 consists of a thermoplastic resin
material.
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