Patent Application
20160138285
The invention relates to the field of reinforcing supporting structures, preferably by attaching a surface reinforcement, in particular by introducing force into the surface reinforcement.
Methods for increasing the supporting resistance of existing supporting structures, typically reinforced concrete components, have already been used for many years. This often takes place by means of an additional reinforcement attached on the surface. Reinforcements which are predominantly adhesively bonded on the surface and are composed of fiber composite materials have become largely accepted here. The effectiveness of said surface reinforcement is normally limited by the maximum force which can be transmitted from the concrete to the reinforcement.
A very wide variety of methods for improving the transmission of force from the supporting structure to the surface reinforcement are known. A widespread method consists in introducing fiber bundles into a bore in the supporting structure and anchoring said fiber bundles there and in spreading or fanning out an end of the fiber bundle protruding over the surface and in adhesively bonding same on the surface. The surface reinforcement can subsequently then be adhesively bonded onto the reinforced supporting framework surface. Alternatively, the surface reinforcement can first of all also be adhesively bonded onto the supporting framework surface such that, when an anchor consisting of a fiber bundle is then attached, the protruding end of said fiber bundle is adhesively bonded onto the surface of the surface reinforcement. In the case of surface reinforcements having a plurality of layers, it is frequently recommended, for better transmission of force, to spread the anchor between the woven fabric layers.
The effectiveness of this measure has been demonstrated experimentally, but remains limited for various reasons.
Firstly, the potential area of fracture in the vicinity of the surface is pierced by each anchor only at one location (in the shaft). The resistance of said potential area of fracture is therefore increased only to a limited extent. Secondly, the transmission of force from those fibers of the fiber bundle which are spread on the surface to the fibers of the woven fabric is not optimum. The very thin fiber composite material formed on the surface by the fibers of the fiber bundle can be substantially loaded only in the tension direction. When subjected to a compressive load, the fiber composite material buckles, and when subjected to a shearing and bending load, only very low forces can be transmitted.
Therefore, only the fibers lying approximately in the tension direction of the surface reinforcement are completely effective. Said fibers make up only a small part of the cross section of the fiber bundle and cover only a small part of the width of the surface reinforcement.
A further disadvantage of the known method consists in that that end of the fiber bundle which protrudes over the surface is spread on the surface itself and therefore protrusions cause protruding deformations on the surface, which can firstly interfere with the visual appearance of a structure, but secondly may also cause technical disadvantages. For example, elevations in an otherwise flat surface may result in water, in particular rain water, or snow, and also dirt, accumulating at said elevations and impairing the long-term effect.
It is therefore the object of the present invention to provide an arrangement and a method, according to which the introduction of force into a surface reinforcement is intended to be improved.
It is furthermore the object of the present invention to improve the transmission of force by fiber bundles which are attached to a supporting framework, in particular into a surface region or into a region in the vicinity of the surface.
It has surprisingly been found that this object can be achieved by means of an arrangement as claimed in claim 1.
Accordingly, the essence of the invention is an arrangement comprising a supporting structure with a surface consisting of one or more faces, wherein a bore runs from at least one face into an inner region of the supporting structure, and said bore is filled with an adhesive and with a portion of a fiber bundle projecting beyond said bore, wherein, on the at least one face from which the bore runs into an inner region of the supporting structure, the supporting structure is provided with at least one groove which extends from the bore in at least one direction on the surface, and the projecting part of the fiber bundle is at least partially located in the at least one groove and is fastened therein with the adhesive.
An element or a part of an element which is exposed to forces is designated the supporting structure here. The supporting structure is typically a structure or a constituent part of a structure, for example a plate, a covering, a wall, a pillar, a rib, a beam or the like. The supporting structure is typically composed here of concrete, in particular of reinforced concrete, but may also be composed of bricks or other building stones, of wood, of steel or of other materials and also of any combinations of said materials. The structures are typically building construction and underground construction structures, such as houses, bridges, tunnels, barrages, sports installations, etc.
The fiber bundle is a loose arrangement of substantially uniformly directed individual fibers or filaments, in particular of carbon, glass, basalt, aramid, steel or other inorganic or organic materials. The fibers are preferably carbon fibers. The thickness of the fiber bundle is dependent on the region of use and on the forces which are intended to be transmitted by the fiber bundle. If the fiber bundle consists of carbon fibers, said fiber bundle comprises in particular 1,000 to 50,000 individual fibers which in each case themselves have a diameter within the range of 5 to 10 μm. A typical fiber bundle preferably has a cross-sectional area of 20 to 70 mm2, in particular of 25 to 40 mm2.
The fiber bundle is attached to the supporting structure typically by a bore which serves for receiving a portion of the fiber bundle being provided, in a first step, at the desired location. The bore can be provided here using any means, wherein such means are very well known to a person skilled in the art. The dimensions of the bore arise from the thickness and the length of the fiber bundle and the thickness and length arise in turn from the requirements imposed on the arrangement according to the invention. A suitable bore typically has a diameter of 1 to 5 cm, in particular of 1.5 to 3 cm, and a depth of 5 to 30 cm, in particular of 7 to 20 cm.
In a further step, one or more grooves are provided starting from the bore or from the entry point of the bore into the surface of the supporting structure. The grooves can also be provided using any means, for example using an angle grinder.
The groove or the grooves is or are dimensioned here in such a manner that said grooves, in the entirety thereof, can receive the fiber bundle which, in the event of a plurality of grooves being present, can be divided up into individual fiber strands. The number and arrangement of the grooves is dependent here on the region of use of the arrangement according to the invention.
After the bore and the at least one groove are provided, the fiber bundle is inserted into bore and groove and adhesively bonded therein. For this purpose, first of all an adhesive is placed into the bore and into the at least one groove. The fiber bundle, which has been impregnated previously preferably with a resin, is then placed into the bore in such a manner that a portion of the fiber bundle projects beyond the bore. During the course of attaching the arrangement according to the invention to a supporting framework, that portion of the fiber bundle which projects beyond the bore generally also projects beyond the surface of the supporting structure. That portion of the fiber bundle which, however, is located in a groove in the mounted arrangement then no longer projects beyond the surface of the supporting structure, as a result of which a uniform and smooth surface can be ensured.
Said projecting portion of the fiber bundle is at least partially inserted into the groove provided with adhesive, or is uniformly divided up into a number of fiber strands corresponding to the number of grooves and inserted into the grooves. The entire fiber bundle or all of the fiber strands is or are generally preferably inserted into one or more grooves such that the fiber bundle does not project beyond the surface of the supporting structure at any point. After the fiber bundle is inserted into the at least one groove, the fiber bundle can be held down therein. Adhesive running out of the drill hole or out of the groove is subsequently removed or is distributed uniformly in the region of the surface affected by the arrangement. If, after the fiber bundle is inserted, there are still cavities in the bore or in the at least one groove, said cavities can be filled with adhesive.
The introduction of the fiber bundle into the bore takes place in particular with a needle-like object. For better guidance with the needle-like object, a clamp, a cable connector or the like, on which the needle-like object can be hooked, can be attached to the fiber bundle.
The impregnation of the fiber bundle with a resin before being inserted into bore and groove has the advantage that the entire fiber bundle can be wetted with resin, even in the inner region. In order to ensure optimum adhesion between fiber bundle and supporting structure, the resin for the impregnation of the fiber bundle has in particular the same chemical basis as the adhesive for fastening the fiber bundle in bore and groove. In particular, both the resin and the adhesive are epoxy resin compositions. It is possible for the adhesive and the resin to be the same composition, wherein, in the case of the resin, the viscosity is typically set somewhat lower than in the case of the adhesive, which, in turn, serves for better wetting of the fibers.
Both in the case of the adhesive for fastening the fiber bundle into bore and groove and in the case of the resin for the possible impregnation of the fiber bundle, use is preferably made of a two-pack epoxy resin composition. Suitable epoxy resin compositions are commercially available from Sika Schweiz AG, for example under the trade name Sikadur®.
The adhesive bonding points on the supporting structure are preferably clean, dry and free from dust and grease. Suitable cleaning measures or preliminary treatments may be used depending on the materials of which the supporting structure is composed.
The arrangement according to the invention can be attached to a supporting structure for different purposes. In particular, the arrangement itself serves as a reinforcement for the supporting structure and/or serves as an anchor or as an anchorage for a surface reinforcement attached to the supporting structure.
If the arrangement serves as an anchorage for a surface reinforcement attached to the supporting structure, said arrangement preferably has a plurality of grooves which extend along the surface from the bore. In this case, the number of grooves per bore is preferably 2 to 16, in particular 6 to 10. The grooves are arranged here in particular in a circular manner and at regular intervals around the bore. In particular, the grooves are arranged in a circular sector around the bore, wherein the circular sector preferably has a center point angle of 60 to 360°. The arrangement of the grooves is generally aligned in accordance with the load direction of the surface reinforcement which is adhesively bonded via the arrangement according to the invention to the supporting structure as an anchor or anchorage. In particular, the grooves in this case spread out in the tension direction of the surface reinforcement.
In a further embodiment, the arrangement itself can serve for reinforcing a supporting structure. In this case, in particular, a plurality of the described arrangements are attached at regular intervals to a supporting structure. Also in this case, the arrangement according to the invention can have a plurality of grooves, as described previously. The arrangement in this case preferably has a second bore which runs into an inner region of the supporting structure, wherein the second bore can be located on the same face or on another face of the surface. The at least one groove runs here from the inlet location of the one bore, i.e. the first bore, along the surface of the supporting structure toward the inlet location of the second bore; the two bores are therefore connected to each other in the surface region of the supporting structure via the at least one groove.
If the two bores are not located on the same face of the surface of the supporting structure, i.e. if, for example, one or more edges or corners are therefore located between the faces, the at least one groove also runs over said edges or corners.
If the two bores are located on mutually averted faces of a supporting structure, it is possible for the two bores to be connected to each other in the extension of the respective bore axes thereof.
For example, this is the case if the arrangement according to the invention is intended to be attached in the region of the end side of a wall which is free-standing at least on one side. In this case, the two bores can be provided by the wall being bored through at one point. A groove is then provided in particular in such a manner that said groove connects the inlet location and the outlet location of the bore in the wall to each other beyond the end side. The outlet location of the one bore in the wall constitutes the inlet location of the second bore.
Also in the case of such a use of the arrangement according to the invention, a surface reinforcement can be attached to the surface of the supporting structure.
Irrespective of the structure of the arrangement according to the invention, the surface reinforcement is preferably attached in such a manner that said surface reinforcement covers that portion of the fiber bundle which runs on the surface of the supporting structure in at least one groove and the bore or the inlet location of the bore into the surface as a whole and is adhesively bonded over said entire region to the surface of the supporting structure.
Lamellas or woven fabrics which run along the surface of a supporting structure and are adhesively bonded thereto, in particular over the full surface area, are particularly suitable as the surface reinforcement. Suitable lamellas include in particular uni-directionally fiber-reinforced plastics flat ribbon lamellas. The fiber reinforcement customarily takes place by means of carbon fibers, but, as in the case of the fiber bundle, can also take place by means of glass, basalt or aramid. In particular, an epoxy resin matrix serves as the plastics matrix. Equally suitably, a plastics matrix can be based on polyurethane, vinyl esters, polyacrylate or other compositions which have structural properties. Suitable fiber-reinforced plastics flat ribbon lamellas are commercially available from Sika Schweiz AG, for example under the trade name Sika® CarboDur®.
An, in particular uni-directional, carbon fiber woven fabric is preferably suitable as the woven fabric, wherein said woven fabric can also be composed of glass fibers, basalt fibers or aramid fibers. In contrast to the fiber-reinforced plastics flat ribbon lamellas, the woven fabric is typically not applied to the surface already in a cured plastics matrix, but rather is provided with a curable composition before or after attachment to the surface. The curable composition is in particular an epoxy resin composition, wherein polyurethane or polyacrylate could also be used here.
A suitable woven fabric is in particular a carbon fiber woven fabric, as is commercially available from Sika Schweiz AG, for example under the designation SikaWrap®.
Preferably, two-pack epoxy resin compositions, as are commercially available from Sika Schweiz AG, for example under the trade name Sikadur®, are used both as the plastics matrix for the fiber-reinforced plastics flat ribbon lamellas and for the adhesive bonding of said plastics matrix or of the woven fabric to the supporting structure.
As already described previously, it is possible for the fiber bundle to run in the at least one groove over edges and/or corners which connect different faces of the surface of the supporting structure to one another. If an edge is involved here, said edge preferably has a rounded portion in the interior of the groove. The radius of the rounded portion is in particular approximately 0.5 to 10 cm, in particular 1 to 5 cm.
The rounded portion of the edge protects the fiber bundle which is placed into bore and groove, as a result of which fewer breakages of the fibers occur and an improved transmission of force is possible. Irrespective of the respective embodiment of the present invention, all edges of the supporting structure over which a groove with fiber bundle is intended to run are generally preferably rounded within the groove.
Furthermore, it is also possible for the transition from the bore into the groove also to have a rounded portion in accordance with the preceding description.
The arrangement according to the invention and a method for application thereof are typically used in the reinforcement of existing supporting structures, for example in the case of renovation, repair or in the case of earthquake reinforcement attached retrospectively to supporting structures. If the supporting structure is a reinforced concrete structure, the reinforcement takes place, for example, wherever the steel reinforcement is inadequate or where the latter has incurred damage due to an unforeseen event.
A method according to the invention for reinforcing a supporting structure with a surface consisting of one or more faces accordingly comprises the following steps:
According to the preceding description of the arrangement according to the invention, the method may comprise further steps. In particular, the fiber bundle is impregnated with a resin before being introduced into the bore and inserted into the at least one groove.
If a surface reinforcement is provided on the supporting structure, the method furthermore comprises a step of attaching a surface reinforcement to the surface of the supporting structure, wherein a surface reinforcement, in particular a lamella or a woven fabric, is attached over that portion of the fiber bundle which has been fastened in the groove by means of adhesive and is adhesively bonded to the surface of the supporting framework at least in the region of that portion of the fiber bundle which has been fastened in the groove by means of adhesive.
Exemplary embodiments of the invention are explained in more detail with reference to the drawings. Identical elements are provided with the same reference signs in the various figures. Of course, the invention is not limited to exemplary embodiments which are shown and described.
In the drawings:
Only the elements essential for direct comprehension of the invention are shown in the figures.
Irrespective of the above-described embodiments, that portion of the fiber bundle which is located in the bore constitutes in particular one of the two loose ends of the fiber bundle. The other loose end of the fiber bundle constitutes that part of the fiber bundle which projects beyond the bore or which is located in the groove or the grooves and is fastened there.
In another, less preferred embodiment, it is also possible to fold over a fiber bundle, in particular in the region of the center thereof or geometric center of gravity thereof, and thus to place the two loose ends of the fiber bundle one above the other. The fiber bundle is then introduced into the bore, preferably by the folded end, and the two loose ends are placed into the groove or divided up between a plurality of grooves. In both cases, that portion of the fiber bundle which is located in the bore is in each case in particular approximately the same length as that portion which projects beyond the bore.
Arrangements as are shown in
An embodiment of the arrangement according to the invention as shown in
A further embodiment of the invention is shown in
An embodiment of the present invention, in which there are also two bores which are connected to each other in the extension of the bore axes thereof is illustrated in
One possible application of the arrangement shown in
A similar embodiment as in
In general and in particular also with regard to the embodiments of the invention, as are shown in
The groove 5 runs here over a respective edge 8 which connects the two faces 2a and 2c or 2c and 2b of the surface of the supporting framework to each other, and said one edge 8 has a rounded portion 9 in the interior of the groove 5.
Exemplary embodiments which will explain the described invention in more detail are cited below. Of course, the invention is not limited to these described exemplary embodiments.
Concrete cubes with an edge length of 20 cm were produced as test pieces, wherein concrete from the same batch was used for all the cubes. The concrete cubes were stored for 28 days at 23° C. and 50% relative air humidity. The concrete cubes were ground on one side in order to free them from cement slurry. A bore with a diameter of 20 mm and a depth of 100 mm was provided in the center of the treated face. Two concrete cubes were left without a bore. Starting from the bore 8 grooves were provided in each case uniformly around the bore in the concrete cubes with an angle grinder. The grooves had a width of 5 mm and a depth of 5 mm and extended over a length of 8 cm. The angle between the grooves was in each case 45°. In the case of four concrete cubes, only five grooves were in each case provided in a semicircular manner. The edges at the transition from the bore into the grooves were slightly rounded. No grooves were provided in the case of two cubes. The concrete cubes were subsequently repeatedly cleaned on the machined surface and in the interior of the bore with compressed air and a brush and thus substantially freed from dust.
Sikadur®-330, commercially available from Sika Schweiz AG, was applied to the machined surface of the concrete cubes without the bore with an average layer thickness of approx. 1 mm by means of a notched trowel. In the case of the concrete cubes with a bore, the bore was filled from below upward, and also the grooves were filled with Sikadur®-330. Care had to be taken here to ensure that no air remained enclosed in the bore.
A fiber bundle of a length of 20 cm and a fiber cross-sectional area of approximately 25 mm2 was completely impregnated with Sikadur® 300 from Sika Schweiz AG with the aid of a paint brush. Subsequently, a cable connector was attached to a loose end of the impregnated fiber bundle and firmly tightened and cut to size. With the aid of a knitting needle which was hooked onto the cable binder, the fiber bundle was introduced into the bore as far as the stop. The protruding end of the fiber bundle was divided up into fiber strands, wherein the number of fiber strands had to correspond to that of the previously provided grooves, and the fiber strands were placed into the grooves. In the case of the concrete cubes without grooves, the protruding end of the fiber bundle was uniformly fanned out and spread over the machined surface of the concrete cube.
On the machined surface of the concrete cube, Sikadur®-330 was then distributed uniformly over the grooves with the fiber bundle, and therefore the entire machined surface was covered with sufficient adhesive.
A prepared woven fabric composed of SikaWrap® 300 C NW (width 20 cm, length 180 cm) was laminated in the region of the final 20 cm of the loose ends thereof with Sikadur®-300 by means of a paint roller. A laminated loose end was placed onto the machined face of the concrete cube and pressed on there with a paint roller. Sikadur®-330 was applied over the attached woven fabric by means of a notched trowel. The woven fabric was folded in a loop, and the other loose and laminated end was placed onto the same location of the concrete cube such that the two ends of the woven fabric came to lie one above the other. The woven fabric was pressed on in turn with the paint roller. Excess adhesive was removed from the test piece with a spatula of the width of the concrete cube.
The test pieces produced in such a manner were left for 7 days at 23° C. and 50% relative air humidity so that the adhesive could cure. Test pieces with fiber bundles made from glass fibers with a fiber cross-sectional area of approximately 25 mm2 were also produced in the same manner.
Two identical test bodies of each type were produced in each case. The results of the measurements represent the mean value of the measurements on the two identical test pieces.
The combined tension and shear resistance of different test pieces was measured in accordance with ISO 527-4/EN 2561 at a measurement speed of 2 mm/min at 23° C. and a relative air humidity of 50%.
The combined tension and shear resistance of the adhesive bond was tested by the loop formed by the SikaWrap-300C NW woven fabric being placed around a steel tube connected to the movable frame of the test machine. The concrete cube was connected to the fixed frame of the test machine via a steel tie-bar placed thereon and threaded rods.
| Number | Date | Country | Kind |
|---|---|---|---|
| 13170879.4 | Jun 2013 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/061915 | 6/6/2014 | WO | 00 |
