EP3234277B1 - Process for providing pre-stressed constructions and elements by sma tensionning elements and a construction and element fitted with such sma tensionning elements - Google Patents
Process for providing pre-stressed constructions and elements by sma tensionning elements and a construction and element fitted with such sma tensionning elements Download PDFInfo
- Publication number
- EP3234277B1 EP3234277B1 EP15817138.9A EP15817138A EP3234277B1 EP 3234277 B1 EP3234277 B1 EP 3234277B1 EP 15817138 A EP15817138 A EP 15817138A EP 3234277 B1 EP3234277 B1 EP 3234277B1
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- component
- tension
- tension element
- shape memory
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- 229910018195 Ni—Co—Ti Inorganic materials 0.000 description 1
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- 229910052748 manganese Inorganic materials 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- UNASZPQZIFZUSI-UHFFFAOYSA-N methylidyneniobium Chemical compound [Nb]#C UNASZPQZIFZUSI-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
- C22C38/105—Ferrous alloys, e.g. steel alloys containing cobalt containing Co and Ni
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
- E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
- E04B1/02—Structures consisting primarily of load-supporting, block-shaped, or slab-shaped elements
- E04B1/04—Structures consisting primarily of load-supporting, block-shaped, or slab-shaped elements the elements consisting of concrete, e.g. reinforced concrete, or other stone-like material
- E04B1/06—Structures consisting primarily of load-supporting, block-shaped, or slab-shaped elements the elements consisting of concrete, e.g. reinforced concrete, or other stone-like material the elements being prestressed
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/08—Members specially adapted to be used in prestressed constructions
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G21/00—Preparing, conveying, or working-up building materials or building elements in situ; Other devices or measures for constructional work
- E04G21/12—Mounting of reinforcing inserts; Prestressing
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
- E04G23/0225—Increasing or restoring the load-bearing capacity of building construction elements of circular building elements, e.g. by circular bracing
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G21/00—Preparing, conveying, or working-up building materials or building elements in situ; Other devices or measures for constructional work
- E04G21/12—Mounting of reinforcing inserts; Prestressing
- E04G2021/127—Circular prestressing of, e.g. columns, tanks, domes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49616—Structural member making
- Y10T29/49623—Static structure, e.g., a building component
- Y10T29/49632—Metal reinforcement member for nonmetallic, e.g., concrete, structural element
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49826—Assembling or joining
- Y10T29/49863—Assembling or joining with prestressing of part
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49826—Assembling or joining
- Y10T29/49863—Assembling or joining with prestressing of part
- Y10T29/49865—Assembling or joining with prestressing of part by temperature differential [e.g., shrink fit]
Definitions
- This invention relates to a method for creating tensioned components in new constructions (cast in situ on the construction site) or in prefabrication, as well as for the subsequent reinforcement of existing structures or, more generally, of any components.
- Tension elements made of shape memory alloys often referred to by experts as shape memory alloy profiles or SMA profiles for short, are applied to the structure for the subsequent application of tension. This subsequent tensioning can also be used to attach extensions to an existing structure under prestress.
- the invention also relates to a structure or component that was created or subsequently reinforced using this method, or to which extensions were docked using this method.
- shape memory alloys based on steel in the form of tension elements or tension rods are used to generate the prestress.
- Prestressing a structure generally increases its usability by reducing existing cracks, preventing cracks from forming altogether, or causing them to only occur under higher loads.
- Such prestressing is already used today to strengthen concrete parts against bending or to strap supports, for example, to increase axial loads or to increase shear.
- Tesla's new "Gygafactory" battery factory in Nevada, USA is to be the largest factory in the world, with 1 million m 2 of manufacturing space, namely two floors of 500,000m 2 each. (The largest factory to date of the aircraft manufacturer Boeing in Everett in the state of Washington, USA, covers a total of 400,000m 2 ).
- concrete blocks measuring 20m x 5m are laid in a row.
- prestressing components made of concrete or other building materials is pipes for liquid transport and silos or tank containers, which are tied around to create prestressing.
- round steel bars or cables are inserted into the concrete or building material for prestressing or subsequently fixed externally to the surface of the component on the tension side.
- Anchoring and force introduction from the prestressing element into the concrete is complex with all of these known methods.
- the anchoring elements (anchor heads) are very expensive.
- the prestressing steels or cables must also be protected against corrosion by means of a coating. This is necessary because conventionally used steels are not corrosion-resistant.
- prestressing cables are inserted into the concrete, they must be protected against corrosion with a lot of effort using cement mortar, which is injected into the sheathing pipes.
- external prestressing is also achieved using fiber composite materials that are bonded to the surface of concrete or to a structure or component. In this case, Fire protection is often very complex because the adhesives have a low glass transition temperature.
- Corrosion protection is the reason why a minimum cover of around 3cm between the steel inserts in traditional concrete must be maintained. As a result of environmental influences (namely CO2 and SO2 in the air), carbonation takes place in the concrete. Because of this carbonation, the basic environment in the concrete (pH 12) drops to a lower value, i.e. to a pH of 8 to 9. If the internal reinforcement is in this carbonated range, the corrosion protection of conventional steel is no longer guaranteed. The 3cm thick cover of the steel guarantees corrosion resistance for the internal reinforcement over a service life of the structure of around 70 years. When using the new shape memory alloy, carbonation is much less critical because the new shape memory alloy is much more corrosion resistant than conventional structural steel. As a result of the prestressing of a concrete part, or Mortar closes cracks and the penetration of harmful substances is greatly reduced.
- WO 2014/166003 A2 and WO96/12588 A1 each disclose generic methods for constructing prestressed structures or components.
- the object of the present invention is therefore to create a method for prestressing new structures and components of all kinds for reinforcement, optionally to improve the serviceability or the fracture state of the structure or component, to ensure more flexible use of the building for subsequent cantilevered extensions, or to increase the durability and fire resistance of the structure or component. It is also an object of the invention to specify a structure and a component which has prestressing or reinforcements produced using this method.
- the object is initially achieved by a method for creating prestressed structures or components made of concrete or other materials using tension elements made of a shape memory alloy, whether for new structures and components or for reinforcing existing structures and components, which is characterized in that at least one tension element made of a steel-based shape memory alloy of polymorphic and polycrystalline structure, which can be brought from its state as martensite to its permanent state as austenite by increasing its temperature, is placed on the structure or component in the form of a flat steel or is placed freely on it, or this tension element is guided around at least one corner, with one or more end anchors penetrating the structure or component, or the tension element wraps around a structure or component one or more times as a band, in which case the two ends of the tension element are either connected to one another in a tensile manner or are each separately connected to the structure or component with one or more end or intermediate anchors that penetrate the structure or component, or the tension element overlaps or crosses one or more times for clamping, and that
- a structure or component created according to this method, which is characterized in that it has at least one tension element made of a shape memory alloy, which runs along the outside of the structure or component or is freely extending on the structure or component and is connected to it by means of end anchors or additionally an adhesive bond, or the structure or component is completely enclosed by the tension element as a band, wherein the two end regions of the tension element are end-anchored or connected in a tensile force-locking manner, and the tension element is permanently prestressed by heat input.
- buildings can be effectively prestressed retrospectively and components such as balcony cantilevers, balcony parapets, pipelines, etc. can be dimensioned thinner. This makes the components lighter and more economical to use.
- shape memory alloys SMA
- SMA shape memory alloys
- SMA shape memory alloys
- SMA shape memory alloys
- the dominant crystal structure of shape memory alloys (SMA) depends on their temperature on the one hand, and on the external stress - be it tension or pressure - on the other. At high temperatures, it is an austenite, and at low temperatures it is a martensite.
- SMA shape memory alloys
- the shape memory alloys (SMA) are stable within a type-specific temperature range, i.e. their structure does not change within certain limits of mechanical stress. For applications in the construction industry in outdoor areas, the ambient temperature fluctuation range of -20°C to +60°C is assumed. Within this temperature range, a shape memory alloy (SMA) used here should not change its structure.
- the transformation temperatures at which the structure of the Shape memory alloy (SMA) changes can vary considerably depending on the composition of the shape memory alloy (SMA). The transformation temperatures are also load-dependent. As the mechanical load on the shape memory alloy (SMA) increases, its transformation temperatures also increase.
- shape memory alloy (SMA) is to remain stable within certain load limits, these limits must be paid close attention to. If shape memory alloys (SMA) are used for structural reinforcement, in addition to the corrosion resistance and relaxation effects, the fatigue quality of the shape memory alloy (SMA) must also be taken into account, especially when the loads vary over time. A distinction is made between structural fatigue and functional fatigue. Structural fatigue concerns the accumulation of microstructural defects as well as the formation and propagation of surface cracks until the material finally breaks. Functional fatigue, on the other hand, is the result of the gradual degradation of either the shape memory effect or the damping capacity due to microstructural changes in the shape memory alloy (SMA). The latter is associated with the modification of the stress-strain curve under cyclic loading. The transformation temperatures are also changed.
- Shape memory alloys based on iron Fe, manganese Mn and silicon Si are suitable for absorbing permanent loads in the construction sector, whereby the addition of up to 10% chromium Cr and nickel Ni gives the SMA a similar corrosion behavior to that of rust-proof steel.
- carbon C, cobalt Co, copper Cu, nitrogen N, niobium Nb, niobium carbide NbC, vanadium nitrogen VN and zirconium carbide ZrC can improve the shape memory properties in various ways.
- a shape memory alloy (SMA) made of Fe-Ni-Co-Ti shows particularly good properties, which absorbs fracture stresses of up to 1000 MPa, is highly resistant to corrosion and whose upper temperature for conversion to the austenite state is approx. 100 - 250°C.
- the Prestress (recovery stress) for this alloy is typically 40-50% of the breaking load.
- the present reinforcement system makes use of the properties of shape memory alloys (SMAs) and those of a shape memory alloy (SMA) based on steel that is significantly more corrosion-resistant than structural steel, because such shape memory alloys (SMAs) are significantly less expensive than SMAs made of nickel-titanium (NiTi), for example.
- SMAs shape memory alloys
- the shape memory alloys (SMAs) based on steel are used in the form of flat steels.
- this process involves attaching a flat steel made of a shape memory alloy, or SMA flat steel, to a structure or component and anchoring it in the structure at its end. If necessary, the flat steel is also anchored in between. Additional bonding makes sense for safety reasons.
- the SMA flat steel is then heated using electricity. The heating softens the adhesive, but this is not a problem because the adhesive hardens again when it cools down and can guarantee safety in the final state. This leads to a contraction of the SMA flat steel and therefore causes a prestress on the structure or component. The prestressing forces are introduced into the structure or component at the end areas of the SMA flat steel via end anchors.
- the two ends of the flat steel 1 can either be connected to each other in a tensile manner or can be connected to the building or component 2 separately with one or more end anchors 4 which penetrate into the building or component 2, or can be connected to the building or component 2 once or several times for clamping. Intermediate anchors 12 can of course also be used.
- the flat steel 1 is then contracted as a result of an active and controlled heat input with heating means and generates a permanent tensile stress and accordingly a permanent prestress on the structure or the component 2.
- electrical connections 3 are present so that the flat steel can be subjected to an electrical voltage which induces a current flow through it.
- a suitable adhesive 18 can be introduced between the flat steel and the structure or component for additional bonding, for example on an epoxy or PU basis.
- tension elements with a rough surface at least on the side facing the bond are used to improve the adhesive bond.
- the end anchorage can also be used only to generate a prestressing force and a safety reserve can be designed so that the breaking load of the tension elements is introduced into the structure or component solely through the hardened bond.
- end anchors and additional bonding are used, the end anchors or any intermediate anchors can be removed after the tension elements have contracted for reasons of space or aesthetic reasons.
- the end anchor can also be dimensioned so that it only has to withstand the pre-tension of the tension element as a result of heating plus a reserve force.
- the additional bond provided by the bonding offers additional safety, as the risk of explosive flaking is greatly reduced if the tension element is damaged. This is important for personal protection, especially when passers-by can be close to the structure, as is the case in urban areas.
- a tension element 1 in the form of a flat steel is guided around two corners 5 of a cantilevered concrete slab 2.
- it is firmly connected to the concrete slab 2 by means of several end anchors 4.
- the tension element 1 or flat steel can be anchored at the end or additionally anchored in between, or its tensile force can be introduced to the structure by means of an adhesive bond, or the force can be introduced via a combination of mechanical anchors and an adhesive bond.
- the Figure 3 shows an application in which a tension element 1 in the form of an SMA flat steel was wrapped around a component. Because the flat steel is first guided around one end of the cylindrical component, such as a column, more than once as a band and then wraps the cylindrical component upwards as a band along a helical line and also wraps the component several times at the upper end in an overlapping manner, a strong end anchor is hardly necessary anymore. The contraction of the flat steel band causes it to jam at the two rings 10 formed at the ends, and the contraction also causes a very strong constriction of the component over the entire wrapping, which substantially stabilizes it and protects it from cracking. This application by means of a wrap can also be used to reinforce cement or other pipes.
- the Figure 4 shows an application on a large silo 11 with a diameter of many meters as a liquid container, whether made of concrete or steel segments.
- several tension elements 1 are looped around the entire structure at a certain distance from each other, connected with their overlapping end areas in a force-locking manner and then contracted by heat input, so that a firm and permanent pre-stressed strapping is created, which strengthens the structure considerably.
- the Figure 5 shows an application to a timber construction.
- Timber constructions with vertical supports 15 and beams 16 supported on them are widespread, with the beams 16 and supports 15 being connected by means of special steel connector elements 14 are screwed or nailed together.
- the steel connector elements 14 are connected to each other as shown with crossing tension elements 1 in the form of SMA profiles, whereby the end anchoring is carried out by means of bolts which penetrate the steel connector elements and SMA profiles. The penetration is carried out by pre-drilling the SMA profile and the steel connector element and then inserting a nail or screw connection through these two elements into the wood. Heat is then introduced and the SMA profiles contract and brace the wooden structure to a previously unknown level of stability.
- the end anchors of the flat steel can be realized in many different designs. In the Figures 6 to 9 Examples of this are shown.
- the Figure 6 shows a variant in which the end areas 6 of the flat steel have a toothing in their surface area.
- Two flat steels 1 can be placed on top of each other in such a way that their toothing interlocks, creating a claw and thus a tight connection.
- This connection can be secured by means of a band wrap or a screw connection, but it cannot come loose as long as it is under tension.
- this connection can also be used if the two identically designed end areas of a single flat steel come to lie on top of each other by enclosing a component.
- the Figure 7 shows an example where a connection is designed in such a way that the two flat steels run towards each other with the top and bottom sides lying in the same plane, thus creating a flush transition.
- a helical gear is implemented, which can also be secured by means of a screw connection or by means of a wrapping band.
- the Figure 8 shows a connection in which the ends of the flat steels to be connected to each other are formed into open hooks, whereby in the example shown the flat steel coming from the left has three such hooks 13, each with a recess between the hooks 13.
- Two identical hooks 13, in the example shown curved upwards instead of downwards, engage in the two recesses thus formed at the ends of the flat steel coming from the right.
- FIG. 9 shows a further connection in which the end regions 6 of the flat steels are formed into two barbs of equal strength which fit together in a form-fitting manner, whereby the connection can also be secured with a screw connection as shown, for example as shown by means of a connection at two points at each of which a screw 8 or a bolt passes through the two flat steels and these are ultimately clamped together by means of a lock nut 9.
- connection of the end regions of the flat steels can therefore generally be achieved by interlocking and claw-locking on the overlapping sides of the end regions 6. However, they can also simply be mechanically connected to one another at the overlapping points using one or more screws 8 in a tensile manner, with the penetrating screws 8 being tightened with a lock nut 9.
- Another anchoring option is to wrap at least one flat steel 1 made of a shape memory alloy as a band around a component 7 so that the band overlaps over an area, after which a voltage is applied between electrical contacts at the end regions of the band so that the flat steel 1 heats up as a result of its electrical resistance and is converted from its state as martensite to a permanent state as austenite. This causes a permanent confinement of the component 7.
- a structure or component equipped with such an SMA flat steel always has at least one tension element 1 in the form of a flat steel made of a shape memory alloy, which runs along the outside of the structure or component and is connected to it by means of end anchors 4.
- the structure or component 7 can be designed as in Figure 3 or 4 shown be completely enclosed or wrapped by one or more flat steels 1, wherein the two end areas of the flat steels 1 are connected in a tensile manner, and the flat steel(s) 1 are permanently prestressed by heat input.
- the wraps can also form overlapping areas, so that the flat steel 1 causes a permanent constriction of the component 7 after heat input and contraction and the overlapping areas 10 generate a sufficient static friction force to maintain the constriction.
- SMA shape memory alloy
- the SMA flat steel is placed on a concrete structure in any direction, but mainly in the direction of tension, and anchored to the same at the end.
- the SMA flat steel is then heated using electricity, which causes the SMA flat steel to shorten.
- the shortening causes a prestress and the forces are introduced directly into the concrete structure or component via the end anchors, or in the case of wrapping even over the entire length of the steel profile.
- the heating of the SMA flat steels 1 is advantageously carried out electrically by setting up a resistance heater by applying a voltage to the heating cables 3, as in Figure 1 shown so that the SMA flat steel or the SMA flat steel strip 1 heats up as a current conductor. Because with long SMA flat steel or strips, heating by means of electrical resistance heating would take too long and then too much heat would be introduced into the concrete, several power connections are set up along the length of the SMA flat steel or strip. The SMA flat steel can then be heated in stages by applying a voltage to two adjacent heating cables, and then to the next two which are adjacent, and so on, until the entire SMA flat steel is brought to the austenitic state.
- the batteries must be connected in series. The number, size and type of batteries must be selected accordingly so that the required current (amperes) and voltage (volts) can be called up, and the energy supply must be regulated by a control system so that at the push of a button - tailored to a specific flat steel length and thickness - exactly the right
- the flat steel is under voltage for a certain period of time and the necessary current flows. In the case of long flat steels of several meters, heating can be carried out in stages by providing power connections after certain sections, where the voltage can then be applied. In this way, the necessary heat can be applied section by section - one section after the other over the entire length of a flat steel, in order to finally bring the entire length into the austenitic state.
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Description
Diese Erfindung betrifft ein Verfahren zur Erstellung von gespannten Bauteilen in Neukonstruktionen (in situ auf der Baustelle gegossen) oder in der Vorfabrikation sowie für die nachträgliche Verstärkung von bestehenden Bauwerken oder ganz allgemein von irgendwelchen Bauteilen. Dabei werden Zugelemente aus Formgedächtnis-Legierungen, unter Fachleuten oft als Shape-Memory-Alloy-Profile oder kurz SMA-Profile bezeichnet, zum nachträglichen Anlegen einer Spannung an das Bauwerk angelegt. Mit diesem nachträglichen Spannen können auch Anbauten an ein bestehendes Bauwerk unter Vorspannung angebracht werden. Zusätzlich betrifft die Erfindung auch ein Bauwerk oder Bauteil, das unter Anwendung dieses Verfahrens erstellt oder nachträglich verstärkt wurde resp. an welches Anbauten nach diesem Verfahren angedockt wurden. Als Besonderheit werden hierzu für die Erzeugung der Vorspannung Formgedächtnis-Legierungen auf der Basis von Stahl in Form von Zugelemente bzw. Zugstäben eingesetzt.This invention relates to a method for creating tensioned components in new constructions (cast in situ on the construction site) or in prefabrication, as well as for the subsequent reinforcement of existing structures or, more generally, of any components. Tension elements made of shape memory alloys, often referred to by experts as shape memory alloy profiles or SMA profiles for short, are applied to the structure for the subsequent application of tension. This subsequent tensioning can also be used to attach extensions to an existing structure under prestress. In addition, the invention also relates to a structure or component that was created or subsequently reinforced using this method, or to which extensions were docked using this method. As a special feature, shape memory alloys based on steel in the form of tension elements or tension rods are used to generate the prestress.
Eine Vorspannung eines Bauwerks erhöht allgemein dessen Gebrauchstauglichkeit, indem existierende Risse verkleinert werden, die Rissbildung überhaupt verhindert wird oder diese erst bei höheren Lasten auftritt. Eine solche Vorspannung wird bereits heute zur Verstärkung gegen das Durchbiegen von Betonteilen oder zur Umschnürung beispielsweise von Stützen zur Erhöhung der Axialbelastung resp. zur Schubverstärkung verwendet. Die neue Batteriefabrik "Gygafactory" von Tesla in Nevada, USA soll die grösste Fabrik weltweit werden, mit 1 Mio. m2 Fabrikationsfläche, nämlich zwei Stockwerke von je 500'000m2. (Die bisher grösste Fabrik des Flugzeugbauers Boeing in Everett im Gliedstaat Washington, USA, umfasst insgesamt 400'000m2). Für das Fundament der "Gygafactory" werden Betonblöcke von 20m x 5m aneinander gereiht verlegt. Jeder solche Betonblock wird später eine von Hunderten von Säulen tragen (
Eine weitere Anwendung der Vorspannung von Bauteilen aus Beton oder anderen Baustoffen sind Rohre für Flüssigtransporte und Silos resp. Tankbehälter, welche zur Erzeugung einer Vorspannung umschnürt werden. Zur Vorspannung werden im Stand der Technik Rundstähle oder Kabel in den Beton oder das Baumaterial eingelegt oder nachträglich extern auf der Oberfläche des Bauteils auf der Zugseite fixiert. Die Verankerung und Krafteinleitung aus dem Vorspannelement in den Beton ist bei all diesen bekannten Methoden aufwändig. Für die Verankerungselemente (Ankerköpfe) fallen hohe Kosten an. Bei externer Vorspannung gilt es, die Vorspannstähle resp. -kabel zusätzlich mittels einer Beschichtung gegen Korrosion zu schützen. Das ist deswegen nötig, weil herkömmlich verwendete Stähle nicht korrosionsfest sind. Werden die Vorspannkabel in den Beton eingelegt, so müssen sie mit viel Aufwand mittels Zementmörtel, welcher mittels einer Injektion in die Hüllrohre eingebracht wird, gegen Korrosion geschützt werden. Eine externe Vorspannung wird im Stand der Technik auch mit Faserverbundwerkstoffen erzeugt, welche auf die Oberfläche von Beton oder auf eine Bauwerk oder Bauteil aufgeklebt werden. In diesem Fall ist der Brandschutz oftmals sehr aufwändig, da die Klebstoffe eine tiefe Glasübergangstemperatur aufweisen.Another application of prestressing components made of concrete or other building materials is pipes for liquid transport and silos or tank containers, which are tied around to create prestressing. In the current state of the art, round steel bars or cables are inserted into the concrete or building material for prestressing or subsequently fixed externally to the surface of the component on the tension side. Anchoring and force introduction from the prestressing element into the concrete is complex with all of these known methods. The anchoring elements (anchor heads) are very expensive. With external prestressing, the prestressing steels or cables must also be protected against corrosion by means of a coating. This is necessary because conventionally used steels are not corrosion-resistant. If the prestressing cables are inserted into the concrete, they must be protected against corrosion with a lot of effort using cement mortar, which is injected into the sheathing pipes. In the current state of the art, external prestressing is also achieved using fiber composite materials that are bonded to the surface of concrete or to a structure or component. In this case, Fire protection is often very complex because the adhesives have a low glass transition temperature.
Der Korrosionsschutz ist der Grund dafür, dass im traditionellen Beton eine minimale Überdeckung der Stahleinlagen von ca. 3cm eingehalten werden muss. Infolge von Umwelteinflüssen (namentlich CO2 und SO2 in der Luft) findet im Beton eine Karbonatisierung statt. Wegen dieser Karbonatisierung fällt das basische Milieu im Beton (pH-Wert 12) auf einen tieferen Wert, das heisst auf einen pH-Wert von 8 bis 9. Liegt die Innenbewehrung in diesem karbonatisierten Bereich, so ist der Korrosionsschutz des herkömmlichen Stahls nicht mehr gewährleistet. Die 3cm starke Überdeckung des Stahls garantiert entsprechend einen Korrosionswiderstand für die Innenbewehrung über eine Lebensdauer des Bauwerks von ca. 70 Jahren. Beim Verwenden der neuartigen Formgedächtnis-Legierung ist die Karbonatisierung wesentlich weniger kritisch, da die neuartige Formgedächtnis-Legierung im Vergleich zu gewöhnlichem Baustahl eine deutlich höhere Korrosionsbeständigkeit aufweist. Infolge der Vorspannung eines Beton-Teils resp. Mörtels werden Risse geschlossen und entsprechend wird das Eindringen von Schadstoffen stark reduziert.Corrosion protection is the reason why a minimum cover of around 3cm between the steel inserts in traditional concrete must be maintained. As a result of environmental influences (namely CO2 and SO2 in the air), carbonation takes place in the concrete. Because of this carbonation, the basic environment in the concrete (pH 12) drops to a lower value, i.e. to a pH of 8 to 9. If the internal reinforcement is in this carbonated range, the corrosion protection of conventional steel is no longer guaranteed. The 3cm thick cover of the steel guarantees corrosion resistance for the internal reinforcement over a service life of the structure of around 70 years. When using the new shape memory alloy, carbonation is much less critical because the new shape memory alloy is much more corrosion resistant than conventional structural steel. As a result of the prestressing of a concrete part, or Mortar closes cracks and the penetration of harmful substances is greatly reduced.
Die Aufgabe der vorliegenden Erfindung ist es daher, ein Verfahren zum Vorspannen von neuen Bauwerken und Bauteilen aller Art für die Verstärkung zu schaffen, wahlweise zwecks Verbesserung der Gebrauchstauglichkeit oder des Bruchzustandes des Bauwerks oder Bauteils, zum Gewährleisten einer flexibleren Nutzung des Gebäudes für nachträgliche auskragende Anbauten, oder zur Erhöhung der Dauerhaftigkeit sowie des Brandwiderstandes des Bauwerks oder Bauteils. Weiter ist es eine Aufgabe der Erfindung, ein Bauwerk und ein Bauteil anzugeben, welches unter Anwendung dieses Verfahren erzeugte Vorspannungen oder Verstärkungen aufweist.The object of the present invention is therefore to create a method for prestressing new structures and components of all kinds for reinforcement, optionally to improve the serviceability or the fracture state of the structure or component, to ensure more flexible use of the building for subsequent cantilevered extensions, or to increase the durability and fire resistance of the structure or component. It is also an object of the invention to specify a structure and a component which has prestressing or reinforcements produced using this method.
Die Erfindung wird durch die beigefügten Ansprüche definiert. Die Aufgabe wird zunächst gelöst von einem Verfahren zum Erstellen von vorgespannten Bauwerken oder Bauteilen aus Beton oder anderen Materialen mittels Zugelementen aus einer Formgedächtnis-Legierung, sei es von neuen Bauwerken und Bauteilen oder für die Verstärkung von bestehenden Bauwerken und Bauteilen, das sich dadurch auszeichnet, dass mindestens ein Zugelement aus einer Formgedächtnis-Legierung auf Stahlbasis von polymorpher und polykristalliner Struktur, welche durch Erhöhung ihrer Temperatur aus ihrem Zustand als Martensit auf ihren bleibenden Zustand als Austenit bringbar ist, in Form eines Flachstahls auf das Bauwerk oder Bauteil aufgelegt oder an dieses frei verlaufend angelegt wird oder dieses Zugelement um wenigstens eine Ecke geführt ist, wobei eine oder mehrere Endverankerungen in das Bauwerk oder Bauteil eindringen, oder aber das Zugelement ein Bauwerk oder Bauteil ein- oder mehrmals als Band umschlingt, wobei in diesem Fall die beiden Enden des Zugelementes entweder zugkraftschlüssig miteinander verbunden werden oder je gesondert mit einer oder mehreren End- oder Zwischenverankerungen, die in das Bauwerk oder Bauteil eindringen, mit demselben verbunden werden, oder aber sich das Zugelement ein oder mehrmals für eine Verklemmung überlappt oder kreuzt, und dass sich das Zugelement infolge eines anschliessenden aktiven und gesteuerten Wärmeeintrages mit Heizmitteln kontrahiert und eine permanente Zugspannung erzeugt und entsprechend eine permanente Vorspannung sowie eine Restzugkraft bis zur Bruchlast des Zugelementes auf das Bauwerk oder das Bauteil erzeugt.The invention is defined by the appended claims. The object is initially achieved by a method for creating prestressed structures or components made of concrete or other materials using tension elements made of a shape memory alloy, whether for new structures and components or for reinforcing existing structures and components, which is characterized in that at least one tension element made of a steel-based shape memory alloy of polymorphic and polycrystalline structure, which can be brought from its state as martensite to its permanent state as austenite by increasing its temperature, is placed on the structure or component in the form of a flat steel or is placed freely on it, or this tension element is guided around at least one corner, with one or more end anchors penetrating the structure or component, or the tension element wraps around a structure or component one or more times as a band, in which case the two ends of the tension element are either connected to one another in a tensile manner or are each separately connected to the structure or component with one or more end or intermediate anchors that penetrate the structure or component, or the tension element overlaps or crosses one or more times for clamping, and that the tension element contracts as a result of a subsequent active and controlled heat input with heating means and a permanent Tensile stress is generated and accordingly a permanent prestress as well as a residual tensile force up to the breaking load of the tension element is generated on the structure or the component.
Die Aufgabe wird des Weiteren gelöst von einem Bauwerk oder Bauteil, erstellt nach diesem Verfahren, das sich dadurch auszeichnet, dass es mindestens ein Zugelement aus einer Formgedächtnis-Legierung aufweist, das längs der Bauwerks- oder Bauteilaussenseite verläuft oder am Bauwerk oder Bauteil frei verlaufend angelegt ist und mit demselben mittels Endverankerungen oder zusätzlich einer Verklebung verbunden ist, oder das Bauwerk oder Bauteil vollständig vom Zugelement als Band umschlossen ist, wobei die beiden Endbereiche des Zugelementes endverankert oder zugkraftschlüssig verbunden sind, und das Zugelement durch Hitzeeintrag permanent vorgespannt ist.The object is further achieved by a structure or component, created according to this method, which is characterized in that it has at least one tension element made of a shape memory alloy, which runs along the outside of the structure or component or is freely extending on the structure or component and is connected to it by means of end anchors or additionally an adhesive bond, or the structure or component is completely enclosed by the tension element as a band, wherein the two end regions of the tension element are end-anchored or connected in a tensile force-locking manner, and the tension element is permanently prestressed by heat input.
Mit der Neuentwicklung können Bauwerke nachträglich wirksam vorgespannt werden und entsprechend können auch Bauteile wie Balkonauskragungen, Balkonbrüstungen, Rohrleitungen etc. dünner dimensioniert werden. Die Bauteile werden dadurch leichter und wirtschaftlicher in der Verwendung.With the new development, buildings can be effectively prestressed retrospectively and components such as balcony cantilevers, balcony parapets, pipelines, etc. can be dimensioned thinner. This makes the components lighter and more economical to use.
Anhand der Zeichnungen wird das Verfahren beschrieben und erklärt. Es werden Anwendungen beim Neubau resp. bei der Vorfabrikation sowie Anwendungen für die nachträgliche Verstärkung von bestehenden Bauwerken, egal aus welchem Baumaterial, sowie spezielle auch von Betonkonstruktionen und anderen Bauteilen beschrieben und erläutert.The process is described and explained using drawings. Applications for new construction or prefabrication as well as applications for the subsequent reinforcement of existing buildings, regardless of the building material, as well as special applications for concrete structures and other components are described and explained.
- Figur 1:Figure 1:
- Einen Beton-Träger oder eine Beton-Platte, gegossen auf der Baustelle oder im Vorfabrikationswerk, mit aufgelegtem, endverankerten Zugelement in Form eines SMA-Flachstahl aus einer Formgedächtnis-Legierung und allenfalls einer zusätzlichen Verklebung;A concrete beam or a concrete slab, cast on the construction site or in the prefabrication plant, with an applied, end-anchored tension element in the form of an SMA flat steel made of a shape memory alloy and, if necessary, an additional bonding;
- Figur 2:Figure 2:
- ein Beton-Bauteil das an drei Seiten von einem Zugelement in Form eines flachen SMA-Flachstahls umschlossen ist;a concrete component which is enclosed on three sides by a tension element in the form of a flat SMA flat steel;
- Figur 3:Figure 3:
- Ein zylinderförmiges Bauteil, das von einem SMA-Flachstahl umschlungen ist, unter Bildung von überlappenden Bereichen;A cylindrical component wrapped by an SMA flat steel, forming overlapping areas;
- Figur 4:Figure 4:
- Ein Silo das mit umschlingenden Zugelementen in Form von SMA-Bandstählen eingeschnürt ist;A silo that is tied up with tension elements in the form of SMA strip steel;
- Figur 5:Figure 5:
- Eine Holzbau-Konstruktion mit über das Kreuz verspannter Zugelemente aus SMA-Profilen zur Erhöhung der Stabilität der Konstruktion;A timber construction with cross-braced tension elements made of SMA profiles to increase the stability of the construction;
- Figur 6:Figure 6:
- Eine Verbindung zweier mit ihren Endbereichen überlappender Zugelemente durch Verkrallung;A connection of two tension elements overlapping at their end areas by claw engagement;
- Figur 7:Figure 7:
- Eine Variante einer Verkrallung von Endbereichen eines SMA-Flachstahls mit aussen bündigem Übergang;A variant of a claw connection of end areas of an SMA flat steel with a flush transition on the outside;
- Figur 8:Figure 8:
- Eine weitere Variante einer Verkrallung von Endbereichen eines SMA-Flachstahls mit aussen bündigem Übergang, zusätzlich gesichert mittels querender Schraub-Bolzen;Another variant of a claw connection of end areas of an SMA flat steel with a flush transition on the outside, additionally secured by means of transverse screw bolts;
Zunächst muss das Wesen von Formgedächtnis-Legierungen [engl. Shape Memory Alloy (SMA)] verstanden werden. Es handelt sich um Legierungen, die eine bestimmte Struktur aufweisen, die wärmeabhängig veränderbar ist, jedoch nach einer Wärmeabfuhr wieder in ihren Ausgangszustand zurückkehrt. Wie andere Metalle und Legierungen, enthalten Formgedächtnis-Legierungen (SMA) mehr als eine Kristallstruktur, sind also polymorph und somit polykristalline Metalle. Die dominierende Kristallstruktur der Formgedächtnis-Legierungen (SMA) hängt einerseits von ihrer Temperatur ab, andrerseits von der von aussen wirkenden Spannung - sei es Zug oder Druck. Bei hoher Temperatur handelt es sich um einen Austenit, und auf der tiefen Temperatur um einen Martensit. Das Besondere an diesen Formgedächtnis-Legierungen (SMA) ist, dass sie ihre initiale Struktur und Form nach Erhöhen der Temperatur in die hohe Temperaturphase wieder annehmen, auch wenn sie zuvor in der tiefen Temperaturphase deformiert wurden. Dieser Effekt kann ausgenutzt werden, um Vorspannkräfte in Baustrukturen zu applizieren.First, the nature of shape memory alloys (SMA) must be understood. These are alloys that have a specific structure that can be changed depending on the heat, but that return to their original state after heat has been removed. Like other metals and alloys, shape memory alloys (SMA) contain more than one crystal structure, so they are polymorphic and thus polycrystalline metals. The dominant crystal structure of shape memory alloys (SMA) depends on their temperature on the one hand, and on the external stress - be it tension or pressure - on the other. At high temperatures, it is an austenite, and at low temperatures it is a martensite. The special thing about these shape memory alloys (SMA) is that they return to their initial structure and shape after the temperature is increased to the high temperature phase, even if they were previously deformed in the low temperature phase. This effect can be used to apply prestressing forces in building structures.
Wenn keine Wärme künstlich in die Formgedächtnis-Legierung (SMA) eingebracht oder aus ihr abgeführt wird, so befindet sie sich auf der Umgebungstemperatur. Die Formgedächtnis-Legierungen (SMA) sind innerhalb eines artspezifischen Temperaturbereichs stabil, das heisst ihre Struktur ändert sich innerhalb von gewissen Grenzen der mechanischen Belastung nicht. Für Anwendungen in der Baubranche im Aussenbereich wird der Schwankungsbereich der Umgebungstemperatur von -20°C bis +60°C vorausgesetzt. Innerhalb dieses Temperaturbandes sollte also eine Formgedächtnis-Legierung (SMA), die hier zum Einsatz kommt, ihre Struktur nicht verändern. Die Transformations-Temperaturen, bei denen sich die Struktur der Formgedächtnis-Legierung (SMA) ändert, kann je nach Zusammensetzung der Formgedächtnis-Legierung (SMA) beträchtlich variieren. Die Transformationstemperaturen sind auch lastabhängig. Mit steigender mechanischer Belastung der Formgedächtnis-Legierung (SMA) steigen auch ihre Transformationstemperaturen. Wenn die Formgedächtnis-Legierung (SMA) innerhalb gewisser Belastungsgrenzen stabil bleiben soll, so ist diesen Grenzen grosse Beachtung zu schenken. Werden Formgedächtnis-Legierungen (SMA) für Bauverstärkungen eingesetzt, so muss nebst der Korrosionsbeständigkeit und den Relaxationseffekten auch die Ermüdungsqualität der Formgedächtnis-Legierung (SMA) berücksichtigt werden, besonders wenn die Lasten über die Zeit variieren. Dabei unterscheidet man zwischen der strukturellen Ermüdung und der funktionellen Ermüdung. Die strukturelle Ermüdung betrifft die Akkumulation von mikrostrukturellen Defekten wie auch die Formation und die Ausbreitung von Oberflächen-Rissen, bis das Material letztendlich bricht. Die funktionelle Ermüdung hingegen ist die Folge der graduellen Degradation entweder des Formgedächtnis-Effektes oder der Dämpfungskapazität durch auftretende mikrostrukturelle Veränderungen in der Formgedächtnis-Legierung (SMA). Das Letztere ist verbunden mit der Modifikation der Spannungs-Dehnungskurve unter zyklischer Belastung. Die Transformations-Temperaturen werden dabei ebenfalls verändert.If no heat is artificially introduced into or removed from the shape memory alloy (SMA), it is at the ambient temperature. The shape memory alloys (SMA) are stable within a type-specific temperature range, i.e. their structure does not change within certain limits of mechanical stress. For applications in the construction industry in outdoor areas, the ambient temperature fluctuation range of -20°C to +60°C is assumed. Within this temperature range, a shape memory alloy (SMA) used here should not change its structure. The transformation temperatures at which the structure of the Shape memory alloy (SMA) changes can vary considerably depending on the composition of the shape memory alloy (SMA). The transformation temperatures are also load-dependent. As the mechanical load on the shape memory alloy (SMA) increases, its transformation temperatures also increase. If the shape memory alloy (SMA) is to remain stable within certain load limits, these limits must be paid close attention to. If shape memory alloys (SMA) are used for structural reinforcement, in addition to the corrosion resistance and relaxation effects, the fatigue quality of the shape memory alloy (SMA) must also be taken into account, especially when the loads vary over time. A distinction is made between structural fatigue and functional fatigue. Structural fatigue concerns the accumulation of microstructural defects as well as the formation and propagation of surface cracks until the material finally breaks. Functional fatigue, on the other hand, is the result of the gradual degradation of either the shape memory effect or the damping capacity due to microstructural changes in the shape memory alloy (SMA). The latter is associated with the modification of the stress-strain curve under cyclic loading. The transformation temperatures are also changed.
Für das Aufnehmen von dauerhaften Lasten im Bausektor eignen sich Formgedächtnis-Legierungen (SMA) auf der Basis von Eisen Fe, Mangan Mn und Silizium Si, wobei die Zugabe von bis zu 10% Chrom Cr und Nickel Ni das SMA zu einem ähnlichen Korrosionsverhalten bringt wie rostfeier Stahl. In der Literatur findet man, dass die Zugabe von Kohlenstoff C, Kobalt Co, Kupfer Cu, Stickstoff N, Niobium Nb, Niobium-Karbid NbC, Vanadium-Stickstoff VN und Zirkonium-Karbid ZrC die Formgedächtnis-Eigenschaften in verschiedener Weise zu verbessern vermögen. Besonders gute Eigenschaften zeigt eine Formgedächtnis-Legierung (SMA) aus Fe-Ni-Co-Ti, welche Bruchspannungen bis zu 1000 MPa aufnimmt, hoch resistent gegen Korrosion ist, und deren obere Temperatur zur Überführung in den Zustand eines Austeniten ca. 100 - 250°C beträgt. Die Vorspannung (recovery stress) beträgt bei dieser Legierung üblicherweise 40-50% der Bruchlast.Shape memory alloys (SMA) based on iron Fe, manganese Mn and silicon Si are suitable for absorbing permanent loads in the construction sector, whereby the addition of up to 10% chromium Cr and nickel Ni gives the SMA a similar corrosion behavior to that of rust-proof steel. In the literature it can be found that the addition of carbon C, cobalt Co, copper Cu, nitrogen N, niobium Nb, niobium carbide NbC, vanadium nitrogen VN and zirconium carbide ZrC can improve the shape memory properties in various ways. A shape memory alloy (SMA) made of Fe-Ni-Co-Ti shows particularly good properties, which absorbs fracture stresses of up to 1000 MPa, is highly resistant to corrosion and whose upper temperature for conversion to the austenite state is approx. 100 - 250°C. The Prestress (recovery stress) for this alloy is typically 40-50% of the breaking load.
Das vorliegende Verstärkungssystem macht sich die Eigenschaften von Formgedächtnis-Legierungen (SMAs) zunutze, und jene einer Formgedächtnis-Legierung (SMA) auf der Basis von im Vergleich zu Baustahl wesentlich korrosionsbeständigerem Stahl, weil solche Formgedächtnis-Legierungen (SMAs) wesentlich preiswerter sind als etwa SMAs aus Nickel-Titan (NiTi). Die Formgedächtnis-Legierungen (SMAs) auf Stahlbasis werden in Form von Flachstählen eingesetzt.The present reinforcement system makes use of the properties of shape memory alloys (SMAs) and those of a shape memory alloy (SMA) based on steel that is significantly more corrosion-resistant than structural steel, because such shape memory alloys (SMAs) are significantly less expensive than SMAs made of nickel-titanium (NiTi), for example. The shape memory alloys (SMAs) based on steel are used in the form of flat steels.
Im Grundsatz wird nach diesem Verfahren ein Flachstahl aus einer Formgedächtnis-Legierung, kurz ein SMA-Flachstahl, an ein Bauwerk oder ein Bauteil angelegt und mit seinen Endbereichen in demselben verankert. Allenfalls wird der Flachstahl bei Bedarf auch zwischenverankert. Eine zusätzliche Verklebung macht aus Sicherheitsgründen Sinn. Dann erfolgt die Erhitzung des SMA-Flachstahls durch Stromzufuhr. Infolge der Erhitzung wird der Kleber aufgeweicht, dies ist jedoch unproblematisch, da der Kleber bei der Abkühlung wieder nachhärtet und die Sicherheit im Endzustand garantieren kann. Dies führt zu einer Kontraktion des SMA-Flachstahls und bewirkt entsprechend eine Vorspannung auf das Bauwerk oder Bauteil. Die Vorspannkräfte werden an den Endbereichen des SMA-Flachstahls über Endverankerungen in das Bauwerk oder Bauteil eingeleitet.In principle, this process involves attaching a flat steel made of a shape memory alloy, or SMA flat steel, to a structure or component and anchoring it in the structure at its end. If necessary, the flat steel is also anchored in between. Additional bonding makes sense for safety reasons. The SMA flat steel is then heated using electricity. The heating softens the adhesive, but this is not a problem because the adhesive hardens again when it cools down and can guarantee safety in the final state. This leads to a contraction of the SMA flat steel and therefore causes a prestress on the structure or component. The prestressing forces are introduced into the structure or component at the end areas of the SMA flat steel via end anchors.
Bei der Vorfabrikation von Stahlbetonbauteilen, beispielsweise Balkon- oder Fassadenplatten oder Rohren, an welchen die neuartigen SMA-Stahlprofile angelegt und vorgespannt werden, bieten sich weitere Vorteile. Dank Vorspannung dieser vorfabrizierten Betonbauteile, können die Querschnitte des Bauteils reduziert werden. Da das Bauteil infolge interner Vorspannung rissfrei ausgebildet ist, liegt viel mehr Schutz gegen Chlorid-Eindringung resp. Karbonatisierung vor. Das heisst, solche Bauteile werden nicht nur leichter sondern viel widerstandsfähiger und entsprechend dauerhafter. Die Erfindung kann auch angewendet werden, um ein Bauwerk für den Brandfall besser zu schützen, wozu die direkte Kontraktion der SMA-Flachstähle durch Wärmeeintrag zunächst bewusst unterlassen wird. In einem Brandfall aber ziehen sich die angebauten SMA-Flachstähle durch die Hitzeeinwirkung des Brandes zusammen. Eine Gebäudehülle aus Beton, welche mit SMA-Flachstählen verstärkt wurde, generiert somit im Brandfall automatisch eine Vorspannung und dadurch eine Verbesserung des Brandwiderstandes. Das Bauwerk wird im Brandfall sozusagen rundum zusammengeklammert und wird viel später einstürzen, wenn überhaupt. Weitere Einsatzgebiete:
- Verbinden von Rohrleitungen beispielsweise aus Stahl oder Guss.
- Bei Erdbeben- oder Windsicherungen bei Holzfachwerken werden die Zugelemente diagonal an den Ecken durchgreifend durch die Stahlverbinder befestigt (genagelt oder geschraubt).
- Unterschiedliche Fixierungen: auf Holz genagelt oder verschraubt, auf Stahl geschraubt oder genietet, auf Beton oder Mauerwerk mechanische verankert.
- Connecting pipes made of steel or cast iron, for example.
- For earthquake or wind protection of timber trusses, the tension elements are attached diagonally at the corners through the steel connectors (nailed or screwed).
- Different fixations: nailed or screwed to wood, screwed or riveted to steel, mechanically anchored to concrete or masonry.
Im Kern geht es also um ein Verfahren zum Erstellen von vorgespannten Betonbauwerken oder Bauteilen 4 wie in
In
Die
Die
Die
Die Endverankerungen der Flachstähle können in vielerlei Ausführungen realisiert werden. In den
Die Verbindung der Endbereiche der Flachstähle kann also generell realisiert sein, indem auf den sich überlappenden Seiten der Endbereiche 6 diese formschlüssig ineinandergreifen und sich verkrallen. Sie können aber auch einfach an den Überlappungsstellen bloss durch eine oder mehrere Schrauben 8 mechanisch zugkraftschlüssig miteinander verbunden werden, wobei die durchdringenden Schrauben 8 mit einer Kontermutter 9 verspannt werden. Eine weitere Möglichkeit der Verankerung bietet an, indem mindestens ein Flachstahl 1 aus einer Formgedächtnis-Legierung als Band um ein Bauteil 7 geschlungen wird, sodass sich das Band über einen Bereich überlappt, wonach mittels zwischen elektrischen Kontakten an den Endbereichen des Bandes eine Spannung angelegt wird, sodass sich der Flachstahl 1 infolge seines elektrischen Widerstandes erhitzt und von seinem Zustand als Martensit in einen bleibenden Zustand als Austenit überführt wird. Dadurch wird eine permanente Umschnürung des Bauteils 7 bewirkt.The connection of the end regions of the flat steels can therefore generally be achieved by interlocking and claw-locking on the overlapping sides of the
Eine mit einem solchen SMA-Flachstahl ausgerüstetes Bauwerk oder Bauteil weist in jedem Fall mindestens eine Zugelement 1 in Form eines Flachstahls aus einer Formgedächtnis-Legierung auf, der längs der Bauwerks- oder Bauteilaussenseite verläuft und mit demselben mittels Endverankerungen 4 verbunden ist. Alternativ kann das Bauwerk oder Bauteil 7 wie in
Bei einem Wärmeeintrag kontrahiert die Legierung nämlich dauerhaft in ihren Ursprungszustand zurück. Werden die SMA-Flachstähle also auf die Temperatur für den Zustand als Austenit erhitzt, so nehmen sie ihre ursprüngliche Form an und behalten diese bei, auch unter Last. Der erzielte Effekt ist mit diesen Formgedächtnis-Legierungen (SMA) ist eine Vorspannung auf das Bauwerk oder ausgerüstete Bauteil, wobei sich diese Vorspannung gleichmässig bzw. linear über die gesamte Länge des Profils aus einer Formgedächtnis-Legierung erstreckt.When heat is introduced, the alloy contracts permanently back to its original state. If the SMA flat steels are heated to the temperature for the austenite state, they take on their original shape and retain it, even under load. The effect achieved with these shape memory alloys (SMA) is a prestress on the structure or equipped component, whereby this prestress extends evenly or linearly over the entire length of the shape memory alloy profile.
Für eine nachträgliche Verstärkung wird der SMA-Flachstahl in beliebigen Richtungen, hauptsächlich aber in Zugrichtung auf ein Beton-Bauwerks aufgelegt und mit demselben endseitig verankert. Dann werden die SMA-Flachstähle mittels Elektrizität erhitzt, was zur Verkürzung dieser SMA-Flachstähle führt. Die Verkürzung bewirkt eine Vorspannung und die Kräfte werden über die Endverankerungen direkt in das des Beton-Bauwerks oder Bauteil eingeleitet, oder im Falle von Umwicklungen sogar über die ganze Länge des Stahlprofils.For subsequent reinforcement, the SMA flat steel is placed on a concrete structure in any direction, but mainly in the direction of tension, and anchored to the same at the end. The SMA flat steel is then heated using electricity, which causes the SMA flat steel to shorten. The shortening causes a prestress and the forces are introduced directly into the concrete structure or component via the end anchors, or in the case of wrapping even over the entire length of the steel profile.
Bei der Vorfabrikation von Stahlbetonbauteilen, beispielsweise Balkon- oder Fassadenplatten oder Rohren, auf welche die neuartigen SMA-Flachstähle aufgelegt und vorgespannt werden, bieten sich weitere Vorteile. Dank Vorspannung dieser vorfabrizierten Betonbauteile können die Querschnitte des Bauteils reduziert werden. Da das Bauteil infolge interner Vorspannung rissfrei ausgebildet ist, liegt viel mehr Schutz gegen Chlorid-Eindringung resp. Karbonatisierung vor. Das heisst, solche Bauteile werden nicht nur leichter sondern viel widerstandsfähiger und entsprechend dauerhafter.There are further advantages to the prefabrication of reinforced concrete components, such as balcony or facade panels or pipes, onto which the new SMA flat steels are placed and prestressed. Thanks to the prestressing of these prefabricated concrete components, the cross-sections of the component can be reduced. Since the component is crack-free as a result of internal prestressing, there is much more protection against chloride penetration. Carbonation occurs. This means that such components are not only lighter but also much more resistant and therefore more durable.
Die Erhitzung der SMA-Flachstähle 1 erfolgt vorteilhaft elektrisch durch Errichtung einer Widerstandheizung, indem eine Spannung an die angelegten Heizkabel 3 angelegt wird, wie in
- 11
- Zugelement, FlachstahlTension element, flat steel
- 22
- Bauwerk, BauteilBuilding, component
- 33
- Elektrische AnschlüsseElectrical connections
- 44
- EndverankerungenEnd anchors
- 55
- EckenCorners
- 66
- Endbereich des Zugelementes bzw. FlachstahlsEnd area of the tension element or flat steel
- 77
- Bauteil, auskragendComponent, cantilevered
- 88th
- Schraubescrew
- 99
-
Kontermutter zu Schraube 8Lock nut for
screw 8 - 1010
- Ringe, überlappende BereicheRings, overlapping areas
- 1111
- Silosilo
- 1212
- ZwischenverankerungIntermediate anchoring
- 1313
- Haken an den Ende der FlachstähleHooks on the end of the flat steel
- 1414
- Stahl-VerbinderelementeSteel connectors
- 1515
- Trägercarrier
- 1616
- Balkenbar
- 1717
- Bolzen zu Haken 13Bolt to hook 13
- 1818
- Klebstoffadhesive
Claims (15)
- Method for constructing prestressed structures or components (2) made of concrete or other materials by means of tension elements (1) made of a shape memory alloy, whether for new structures and components or for reinforcing existing structures and components, characterised in that at least one tension element (1) made of a shape memory alloy based on steel of polymorphic and polycrystalline structure, which can be brought from its state as martensite to its permanent state as austenite by increasing its temperature, is in the form of a flat steela) placed on the structure or component (2) orb) is applied freely to the structure or component, orc) this tension element (1) is guided around at least one corner (5),i) wherein in variants a) to c) one or more end anchors (4) penetrate into the structure or component (2), or elsed) the tension element (1) wraps around a structure or component (2) one or more times as a band, whereby in this caseand that the tensile element (1) contracts as a result of a subsequent active and controlled heat input with heating agents and generates a permanent tensile stress and correspondingly generates a permanent pre-tension and a residual tensile force up to the breaking load of the tensile element (1) on the structure or the component (2).ii) the two ends of the tension element (1) are either connected to each other in a tension-locking manner oriii) each separately connected to the structure or component (1) by one or more end (4) or intermediate (12) anchorages which penetrate the structure or component, oriv) the tensile element (1) overlaps or crosses once or several times for jamming,
- Method for creating prestressed structures or components by means of tension elements (1) made of a shape memory alloy according to claim 1, characterised in that the tension elements (1) are used in strip form, and in that bolts crossing the tension elements are additionally used when creating anchorages by overlapping or crossing the strip-shaped tension elements.
- Method for producing prestressed structures or components by means of tension elements (1) made of a shape memory alloy according to claim 1, characterised in that at least one straight tension element (1) is placed on a wall of a structure or on the outside of a component (2), and its two end regions are firmly connected to the structure or component (2) by one or more end anchors (4) by these end anchors (4) penetrating into the structure or component (2), and then a voltage U is applied to the end regions of the tension element (1) by means of electrical contacts (3), so that the tension element (1) heats up as a result of its electrical resistance and is converted from its state as martensite to a permanent state as austenite, so that the tension element (1) exerts a permanent tensile stress and a residual tensile force up to the breaking load of the tension element (1) on the structure or component (2) and this is introduced into the latter (2) at the end anchorages (4).
- Method for constructing prestressed structures or components by means of tension rods made of a shape memory alloy according to claim 1, characterised in that at least one tension element (1) is placed on the outside of a structure or on the outside of a component (2) with one or more bends (5), and its two end regions (6) are firmly connected to the structure or component (2) by means of one or more end anchorages (4) or additional intermediate anchorages (12), by these end anchorages (4) penetrating into the structure or component (2), and then a voltage is applied to the end regions (6) of the flat steel by means of electrical contacts, so that the flat steel (1) heats up as a result of its electrical resistance and is converted from its state as martensite to a permanent state as austenite, so that it exerts a permanent tensile stress around the enclosed part of the structure or component (2), as well as a residual tensile force up to the breaking load of the tensile element (1), and this is introduced into the latter at the end anchorages (4).
- Method for producing prestressed structures or components by means of tension elements made of a shape memory alloy according to claim 1, characterised in that at least one tension element (1) is wrapped around a component (7) so that the two ends of the tension element (1) overlap and are mechanically connected to one another in a tensile force-locking manner, after which a voltage is applied to the end regions of the tension element (1) by means of electrical contacts, so that the tension element (1) heats up as a result of its electrical resistance and is converted from its state as martensite to a permanent state as austenite, so that the tension element (1) causes a permanent constriction of the component (7).
- Method for producing prestressed structures or components by means of tension rods made of a shape memory alloy according to claim 5, characterised in that the two ends of the tension element (1) are mechanically connected to one another in a tensile force-locking manner by interlocking on the overlapping sides of the end regions (6) and interlocking with one another.
- Method for producing prestressed structures or components by means of tension rods made of a shape memory alloy according to claim 5, characterised in that the two ends of the tension element (1) are connected to each other in a mechanically tension-locking manner by connecting them to each other by means of at least one screw (8) passing through them at the overlapping point or, in the case of an interlocking connection, by means of end hooks (13) with a bolt (17) passing through them.
- Method for producing prestressed structures or components by means of tension rods made of a shape memory alloy according to claim 1, characterised in that at least one tension element (1) is looped as a strip around a component (7) so that the latter overlaps over a region, after which a voltage is applied by means of electrical contacts between the end regions of this flat steel strip, so that the flat steel heats up as a result of its electrical resistance and is converted from its state as martensite to a permanent state as austenite, so that the strip causes a permanent necking of the component (7) and the overlapping region generates sufficient static friction force to maintain the necking.
- Method according to one of claims 1 to 8, characterised in that the anchoring to the structure or component is effected by means of one or more of the following fastening means, depending on the load-bearing base of the same: Dowels, expansion dowels, nails, anchors, adhesive anchors, cement-filled anchors, or by means of riveting or screwing,
- Method according to one of claims 1 to 8, characterised in that, in addition to the final anchoring of the tension elements (1) to the structures or components, the tension elements (1) are bonded to the supporting base of the structures or components with an epoxy- or PU-based adhesive (18), wherein tension elements are used which have a rough surface on at least one of their sides to improve the adhesive bond.
- Method according to one of the preceding claims, characterised in that the end anchoring of the tension element (1) is designed only for the prestressing force, including a safety reserve, so that the introduction of the breaking load of the tension element (1) into the structure or component takes place solely by means of the hardened bonding by means of adhesive (18).
- Method according to claim 10, characterised in that the end anchoring of the tension elements (10) is removed after the adhesive (18) of the bonding has hardened.
- A structure or component constructed according to one of the methods according to claims 1 to 12, characterised in that it comprises at least one tension element (1) which extends along the outside of the structure or component or is applied freely to the structure or component and is connected thereto by means of end anchors (4) or additionally by bonding by means of adhesive (18), or the structure or component (2) is completely enclosed by the tension element (1) as a strip, wherein the two end regions of the tension element (1) are end-anchored or connected in a tension-locking manner, and the tension element (1) is permanently prestressed by the application of heat.
- Structure or component according to claim 13, characterised in that it has at least one tension element (1) which runs around one or more bends (5) along the outside of the structure or component (2) and is connected to the same at least by means of end anchorages (4) or additionally by means of intermediate anchorages (12).
- Structure or component according to claim 13, characterised in that it has at least one tension element (1) which wraps around the component (7) several times as a band and forms overlapping areas, so that it causes a permanent constriction of the component (7) after the application of heat and the overlapping areas (10) generate sufficient static friction force to maintain the constriction.
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CH01980/14A CH710538B1 (en) | 2014-12-18 | 2014-12-18 | Method for creating prestressed structures or components by means of tension elements made of shape memory alloys and building or component equipped therewith. |
PCT/EP2015/079607 WO2016096737A1 (en) | 2014-12-18 | 2015-12-14 | Method for producing prestressed structures and structural parts by means of sma tension elements, and structure and structural part equipped therewith |
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CA2971244C (en) | 2023-02-21 |
CN107407100A (en) | 2017-11-28 |
US10246887B2 (en) | 2019-04-02 |
WO2016096737A1 (en) | 2016-06-23 |
KR20170125321A (en) | 2017-11-14 |
US20170314277A1 (en) | 2017-11-02 |
CN107407100B (en) | 2020-02-21 |
CA2971244A1 (en) | 2016-06-23 |
CH710538B1 (en) | 2018-09-28 |
KR102445949B1 (en) | 2022-09-20 |
EP3234277A1 (en) | 2017-10-25 |
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