Method for prestressing and reinforcing structures or structural parts by means of wire strands or wire cables made of a shape memory alloy (SMA), and structure or structural part produced according to this method
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-05
- Publication Date
- 2026-08-13
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Figure EP2026053094_13082026_PF_FP_ABST
Abstract
Description
Applicant: re-ferAG Riedmattli 9 CH-6423 Seewen Inventor: Daniel Schmidig, 6440 Brunnen (CH) Julien Michels, 8032 Zurich (CH) Method for prestressing and reinforcing structures or components using wire strands or wire ropes made of a shape memory alloy (SMA), as well as a structure or component manufactured according to this method
[0001] This invention primarily relates to structures or components made of concrete, cement, and mortar, and a method for prestressing and reinforcing them using shape memory alloys (SMAs). However, other materials to be reinforced are also conceivable, such as plastic, clay, loam, or calcium silicate brick. The method is suitable for creating prestressed components both for new constructions, i.e., 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. The invention also relates to a structure or component that has been created or subsequently reinforced using this method, or to which extensions have been attached using this method. A special feature is the use of shape memory alloys based on steel in the form of tension elements for generating the prestress.
[0002] First, the nature of shape memory alloys (SMAs) must be understood. These are alloys that exhibit a specific structure which changes depending on temperature, but contracts to a permanent initial state after the application of heat. Like other metals and alloys, shape memory alloys (SMAs) contain more than one crystal structure; they are polymorphic and therefore polycrystalline metals. The dominant crystal structure of shape memory alloys (SMAs) depends on both their temperature and the external stress applied—whether tensile or compressive. At high temperatures, the structure is austenite, and at low temperatures, it is martensite.The special feature of these shape memory alloys (SMAs) is that they regain and retain their initial structure and shape after being raised 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.
[0003] If no heat is artificially introduced into or removed from the shape memory alloy (SMA), it remains at ambient temperature. Shape memory alloys (SMAs) are stable within a specific temperature range, meaning their structure does not change within certain limits of mechanical stress. For outdoor construction applications, an ambient temperature range of -20°C to +60°C is assumed. Within this temperature range, a shape memory alloy (SMA) used in this context should therefore not change its structure. The transformation temperatures at which the structure of the shape memory alloy (SMA) changes can vary considerably depending on its composition. These transformation temperatures are also load-dependent.As the mechanical stress on a shape memory alloy (SMA) increases, so do its transformation temperatures. If the shape memory alloy (SMA) is to remain stable within certain load limits, these limits must be carefully observed. When shape memory alloys (SMA) are used for structural reinforcement, in addition to corrosion resistance and relaxation effects, the fatigue properties of the shape memory alloy (SMA) must also be considered, especially when loads vary over time. A distinction is made between structural fatigue and functional fatigue. Structural fatigue involves the accumulation of microstructural defects as well as the formation and propagation of surface cracks until the material ultimately fails.Functional fatigue, on the other hand, results from 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 a modification of the stress-strain curve under cyclic loading. The transformation temperatures are also altered in this process.
[0004] Shape memory alloys (SMAs) based on iron (Fe), manganese (Mn), and silicon (Si) are suitable for withstanding permanent loads in the construction sector. The addition of up to 10% chromium (Cr) and nickel (Ni) can make the SMA more resistant to corrosion. Literature indicates 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 shape memory properties in various ways. A shape memory alloy (SMA) made of Fe-Mn-Si-Cr-Ni exhibits particularly good properties, withstanding fracture stresses up to 850 MPa and an upper temperature range of 100–300°C for transitioning to the austenitic state. The recovery stress for this alloy is typically 300–400 MPa.
[0005] Currently, tension elements made of shape-memory alloys, often referred to by experts as shape-memory alloy profiles or SMA profiles for short, are used to apply tension to a structure after construction. This subsequent tensioning also allows for the attachment of extensions to an existing structure under prestress. Prestressing a structure generally increases its serviceability by reducing existing cracks, preventing crack formation altogether, or delaying cracking until it occurs under higher loads. Such prestressing is already used today to reinforce concrete components against deflection, for earthquake-resistant reinforcement of concrete and masonry, or for encasing columns, for example, to increase axial load capacity or shear strength.
[0006] Another application of prestressing components made of concrete or other building materials is in pipes for liquid transport and silos or tanks, which are clamped to create prestress. In current technology, prestressing is achieved by embedding round steel bars or cables in the concrete or building material, or subsequently by mechanically stretching and fixing them externally on the surface of the component through elastic deformation. This creates a prestressing force in the anchorage. The force transmission from the prestressing element into the concrete is complex with all these known methods. High costs are incurred for the anchorage elements (anchor heads) and the tensioning process. With external prestressing, the prestressing steel bars or cables must also be protected against corrosion by means of a coating.If the prestressing cables are embedded in concrete, they must be protected against corrosion with considerable effort using cement mortar, which is injected into the sheathing tubes. In current technology, external prestressing is also achieved using fiber-reinforced composites, which 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.
[0007] The required corrosion protection is the reason why a minimum concrete cover of approximately 3 cm is necessary for the steel reinforcement in traditional concrete. Due to environmental influences, particularly CO2 and SO2 in the air, carbonation gradually occurs in the concrete. This carbonation causes the alkaline environment in the concrete, with a pH value of 12, to decrease over time to a pH value of 8 to 9. If the internal reinforcement is located in this carbonated zone, the corrosion protection of the conventional steel is no longer guaranteed. The 3 cm concrete cover therefore ensures corrosion resistance for the internal reinforcement over the building's service life of approximately 70 years. When using the innovative shape memory alloy, carbonation is significantly less critical, as this alloy exhibits higher corrosion resistance compared to conventional structural steel.As a result of the prestressing of a concrete component or mortar, cracks are closed and the penetration of pollutants is greatly reduced.
[0008] Square and round columns, containers, or pipe sections made of such materials are typically reinforced with reinforcing elements, either for structural reasons or due to the material's low inherent tensile strength, which can lead to cracking. In addition to axially oriented, straight reinforcing elements, radial reinforcements such as spiral reinforcements, stirrups, or meshes are also used. The reinforcing elements must always be adapted to the shape of the structure.
[0009] Steel reinforcements must be pre-bent accordingly, while meshes made of fiberglass and similar materials can be formed directly on site due to their low rigidity. Steel reinforcements are fitted with rolled / pressed-on ribs or threads. The surface is part of the element and serves for subsequent bonding with the surrounding, load-bearing matrix of the building structure. This bond is crucial, as the reinforcement element would otherwise be unable to exert any force on the building structure and would be useless.
[0010] Other ways to create this bond include bonding. This allows fibers, flat lamellar profiles, or nets to be effectively connected to the substrate, even if they do not create a mechanical interlock through their shape.
[0011] In the construction industry today, ribbed bars, smooth bars, small fibers for fiber-reinforced concrete, and lamellae made of shape memory alloys (SMA) are common. These products can be used not only as simple reinforcement elements but also prestressed by heating. After installation, they contract permanently due to heat input, thus creating a permanent prestress. For structural elements with special shapes or rounded surfaces, i.e., for radial reinforcement, SMA ribbed bars, lamellae, or thin, smooth bars with a thickness of approximately 0.6 mm or more have been used. The ribbed bars create an interlocking bond with the structural element via their ribbed surface, while the other products are mechanically connected to the substrate via end anchors or bonded to it.Ribbed steel offers optimal load-bearing capacity because it creates a bond along its entire length and is easy to handle with mortar, concrete, etc.
[0012] WO2016 / 096737 A1 discloses the method of prestressing structures using shape memory alloy (SMA) steels. Specifically, this document also discloses a method for constructing prestressed concrete structures or components to achieve reinforcement using tension elements made of an SMA alloy, for example, in the form of flat bars of such a shape memory alloy. This method applies to new structures and components as well as to the reinforcement of existing structures made of concrete, stone, or other building materials. For this purpose, at least one flat bar made of a shape memory alloy with a polymorphic and polycrystalline structure, which can be brought from its martensite state to its permanent austenite state by increasing its temperature, is first placed or fitted onto the structure or component. This placement or fitting can also be performed around corners or completely encompass or wrap around a component.One or more end anchors penetrate deep into the structure or component. If the flat steel bar encircles a structure or component one or more times, the two ends of the flat steel bar can either be connected to each other by a tensile bond, or each can be connected separately to the structure or component by one or more end anchors that penetrate it, or they can cross one or more times for clamping. Intermediate anchors can, of course, also be used. The flat steel bar is then contracted by active and controlled heat input using heating elements, generating a permanent tensile stress and, consequently, a permanent prestress on the structure or component.
[0013] In principle, this process involves attaching a flat steel bar made of a shape memory alloy, or SMA flat steel bar, to a structure or component and anchoring its ends within it. If necessary, the flat steel bar may also be anchored at intermediate points. Additional bonding is advisable for safety reasons. The SMA flat steel bar is then heated by applying an electric current. This heating softens the adhesive, but this is not a problem because the adhesive re-hardens upon cooling, ensuring safety in the final state. The heating causes the SMA flat steel bar to contract, thereby creating a prestress on the structure or component. These prestressing forces are transferred into the structure or component at the ends of the SMA flat steel bar via end anchors.
[0014] Further advantages arise during the prefabrication of reinforced concrete components, such as balcony or facade panels or pipes, to which the SMA steel profiles are attached 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 due to internal prestressing, it offers significantly greater protection against chloride penetration and carbonation. This means that such components are not only lighter but also much more resistant and therefore more durable.
[0015] Other areas of application: Connecting pipes, for example made of steel or cast iron. For earthquake or wind bracing of timber trusses, the tension elements are attached diagonally at the corners, passing through the steel connectors (nailed or screwed). Different fixing methods: nailed or screwed to wood, screwed or riveted to steel, mechanically anchored to concrete or masonry.
[0016] The primary problem with such SMA flat bars is that they can only be bent around their transverse axis, which makes handling difficult. Furthermore, without additional measures, they are highly exposed to environmental influences (corrosion, fire, etc.). Moreover, without complex additional measures, there is no bond between the SMA flat bars and the supporting structure. The problem with SMA rib bars is similar: they can only be adapted to the required shape by prior bending. Adjusting and bending the bars on-site requires heavy equipment and other aids for temporary fixation to the substrate. When used in new structures, the reinforcement elements must be prepared with millimeter precision beforehand to ensure a correct fit, for example, into the concrete formwork. This approach is not feasible for subsequent reinforcement.The other products mentioned are also somewhat inflexible and too rigid to be easily attached to the structure. Prestressing products with low inherent stiffness would be preferable. They would need to be flexible and easily adaptable to specific structural shapes. At the same time, however, bonding with the substrate should be ensured, and the product should have a certain cross-sectional area to transmit sufficiently high forces. Unfortunately, ribs can no longer be effectively pressed onto thin rods, wires, or fibers, as a certain ribbing size is necessary to interact with the concrete aggregate for a tight interlock.
[0017] It is therefore the object of the present invention to provide a method by which structures or components can be prestressed without a distinct prestressing direction. Furthermore, the invention relates to structures or components prestressed in this manner.
[0018] This problem is solved by a method for prestressing and reinforcing existing or newly constructed structures or components according to claim 1. Furthermore, the problem of an existing or newly constructed structure or component according to claim 11 and a use according to claim 14 is solved. Advantageous embodiments of the invention are described in the dependent claims.
[0019] The solution lies in using SMA wire strands, or a rope made of such SMA wire strands. Ropes consist of many twisted fibers or individual steel wires or wire strands. A rope made of SMA wire strands offers three advantages: 1) a sufficiently large overall cross-section for sufficient tensile forces, 2) a structured surface due to the special, spiral direction of the individual fibers or wires, 3) flexibility in all directions and therefore great flexibility in application. 4) No anchors are needed to bear any loads. Only fixing elements for installation are necessary, but these are not designed to bear any tensile forces.
[0020] The present reinforcement system utilizes the properties of shape memory alloys (SMAs), and preferably those of a shape memory alloy (SMA) based on steel that is more corrosion-resistant than structural steel, because such shape memory alloys (SMAs) are significantly less expensive than, for example, nickel-titanium (NiTi) SMAs. Steel-based shape memory alloys (SMAs) have so far only been used in the form of flat or ribbed steels. In the following, "SMA" refers to both the singular and plural forms.
[0021] The figures also illustrate such SMA wire strands in the form of ropes, and their application for bracing and reinforcing structures or components is described and explained.
[0022] It shows: Figure 1a: a parallel winding / stranding of two wire strands each, for the production of a twisted wire rope; Figure 1b: a parallel winding / stranding of three wire strands, open to the production of a twisted wire rope; Figure 2: a left and right winding of a wire strand each, opened up, and running centrally and straight inside it another wire strand, for the production of a twisted wire rope; Figure 3: A cylindrical concrete column with a threaded SMA wire rope wrapping for its tensioning and reinforcement, and a grouting of the wrapping indicated by dashed lines; Figure 4: The cylindrical concrete column according to Figure 3 in cross-section, with the grouting of the wrapping; Figure 5: An enlarged section of a component with an open recess / hollow with internal SMA wire rope wrapping or a linear SMA wire rope configuration; Figure 6: A wire rope loop with a safety sleeve; Figure 7: A wire rope loop with two safety clamps; Figure 8: A wire rope end with a screw-on stopper element; Figure 9: A wire rope end with an attached end steel eyelet to be tensioned on it; Figure 10: The wire rope end according to Figure 9 with the end steel eyelet attached and fully tensioned on it; Figure 11: A representation of the electrical heating of an SMA wire rope wound around a bolt to transform it from its state as martensite to its permanent state as austenite; Figure 12: A representation of the electrical heating of an SMA wire rope formed into a secured loop and placed around a screw, to transform the SMA wire rope from its state as martensite to its permanent state as austenite; Figure 13: An SMA wire rope with untangled wire strands at the end; Figure 14: An SMA wire rope with wire strands gathered into a ball at the end; Figure 15: A pressing device for crimping onto SMA wire ropes End termination elements; Figure 16: A concrete pipe with a helically arranged SMA wire rope wrapping cast into it for tensioning and reinforcement; Figure 17: A sub-reinforcement for a concrete floor-ceiling slab, with sheathing tubes placed over it in a conventional manner, containing initially loose tension rods, before the application of the top reinforcement and the concreting, as a conventional technology; Figure 18: One end or front of a concrete floor-ceiling slab with sheathing tubes protruding from it and a hydraulic press attached to one sheathing tube for prestressing and subsequent anchoring of the tension rods located therein to this front, as conventional technology; Figure 19: A cross-section through a concrete floor-ceiling slab produced using the present method, with an SMA wire strand laid in it before concreting, to achieve a subsequent permanent prestressing effect after the concrete has hardened due to heat input and thus contraction of the SMA wire strand.
[0023] The invention is not limited to wrappings, although this is one of its main focuses. Other applications are conceivable and possible, such as flat or planar configurations, as well as applications requiring special shapes that deviate from wrappings. For example, an SMA wire rope made of a few to many stranded SMA wire strands can be bent in any direction, even curved multiple times along its length in any direction in space, unlike, say, an SMA flat steel bar, which can only be bent perpendicular to its direction of travel. This gives the applications of SMA wire ropes enormous and previously unheard-of flexibility. Such applications are suitable for new construction as well as for the subsequent reinforcement / renovation of structures or components. For new construction, the SMA wire strand or SMA wire rope is embedded directly into the newly created load-bearing matrix, e.g., concrete.No additional layer of mortar is necessary.
[0024] For production, Fe-SMA can easily be hot-rolled down to a diameter of at least 5 mm and then cold-drawn down to a diameter of 1 mm, although subsequent heat treatment, e.g., annealing at approximately 800-1000°C for 2 hours, is necessary, according to publication M. Shaverdi SMAR 2024.
[0025] In this context, a strand is understood to be a (single) wire. Strands are woven, wound, twisted, braided, or twisted together with at least one other strand to form a wire rope. An "SMA strand" is a (single) SMA wire. An "SMA wire rope" is understood to be a wire rope containing at least one SMA strand. Here, the terms "strand" and "wire strand" are used synonymously. An SMA wire rope made of two or three SMA strands proves advantageous. This results in an attractive winding shape with a high degree of surface texturing. The height of the winding is called the lay length, and this results in different twist shapes. A lay length of approximately 9 x 0 of the wire strand(s) is suitable, for example. During stranding, the wire must be plastically deformed; otherwise, it would simply spring back apart. Therefore, the wire is bent more sharply and experiences greater elongation at the outer radii.A 0.3 mm wire is suitable for the production of SMA stranded wires and SMA wire ropes. The pre-stretched SMA wire must not be overstretched, otherwise the memory effect could be weakened or even lost. If it needs to be treated by solution annealing for approximately 2 hours at 800-1000°C to relieve stress on the structure, then pre-stretching the finished stranded wire after production would be necessary. For example, an SMA wire rope can be produced from 3 x 0.3 mm SMA wire strands. This then achieves a total cross-sectional area of approximately 21 mm². 2The wires have a diameter of approximately 6.5 mm and a lay length of 54 mm. They can be wound in the same direction, meaning all are wound in the same direction, or in opposite directions. Figure 1a shows such a parallel winding of the SMA wire strands 24, while Figure 1b shows them with the twist open. When the thin SMA wires 24, which are very flexible in all directions, are pulled together as shown, they lie close to each other and form a tightly twisted SMA wire rope 15, which is itself flexible in all directions. It is also conceivable that at least one wire strand consists of an SMA shape memory alloy and is combined, i.e., stranded, with wire strands made of other materials.
[0026] Figure 2 shows a left-hand and a right-hand winding of a wire strand 24, exposed, with another wire strand 25 running centrally and straight within them, for the production of a twisted wire rope. Here, too, the wire strands will snuggle together due to the tight twisting and form a tight, closed, flexible SMA wire rope. It is understood that such a wire rope, whether with or without one or more central straight wires 25, can also be twisted with a multitude of surrounding wire strands 24, and thus SMA wire ropes of varying thicknesses and therefore strengths can be produced. The more wire strands 24 such an SMA wire rope has, the stiffer it will be with respect to its flexibility.
[0027] Figure 3 shows a cylindrical concrete column 14 with a threaded SMA wire rope wrapping for tensioning and reinforcement. The SMA wire rope 15 is secured at its starting point to the concrete column 14, here with a radially penetrating bolt 16 that passes through a loop 17 formed from the SMA wire rope 15. From this point, the SMA wire rope 15 is wound clockwise around the concrete column 14 along a threaded line until it reaches the lower edge of the column 14. There, it is anchored as at its starting point. These anchors primarily serve to simplify handling during installation and do not necessarily have a structural function. Only when this wrapping is applied to the concrete support 14 and completely embedded in a hardened mortar, is the SMA wire rope 15 transformed from its state as martensite to its permanent state as austenite by the application of heat.This heating of the strands or the SMA wire rope 15 can be achieved by applying electrical clamps – for example, at both ends. The resulting current heats the SMA wire rope 15, causing it to contract. Due to the rigid bond with the mortar, this contraction is prevented, and the SMA wire rope 15 exerts a radial force on the concrete column 14, constricting it and creating tension and reinforcement. Electrical insulation of any other internal reinforcement using plastic components or a coating is always necessary when using electrical heating. Alternatively, heat can be applied using a gas burner. Anchoring can also be achieved by simply embedding the SMA strand or the DMA wire rope 15 in mortar over a certain distance. Then the middle, exposed part of the SMA strand or SMA wire rope 15 is heated with a radiant heater or gas burner, thus creating a pre-tension force.The power transmission via these SMA strands or SMA wire ropes is only needed at the end in certain cases. The pretension is, for example, 350 N / mm. 2 and is introduced directly into the object at the end anchorages. However, all additional loads that pass through these, for example 350 N / mm², are not affected. 2 extend beyond the point of possible breakage of the SMA strand or SMA wire rope, for example around 700 N / mm² 2 The forces are transferred via the bond with the mortar / concrete. Finally, the wrapping is mortared in place, as indicated by the dashed lines. It is important that in the final state, the SMA strands or SMA wire ropes 15 are always completely embedded in the load-bearing matrix. Concrete compression struts can also be reinforced in the same way.
[0028] Figure 4 shows a cross-section of this cylindrical concrete support 14 according to Figure 3. The wrapping has tightly fitted itself to the concrete support 14 and constricts it firmly, and a layer of mortar 18 has been applied to this wrapping, which completely covers the wrapping with mortar and thus also protects it from the elements.
[0029] Figure 5 shows an enlarged section of a component where an internal SMA wire rope wrapping or linear SMA wire rope configuration can be seen through a recess in the mortar. Figure 5 shows a concrete column 14 as the building structure, but it could be any other structure as well. The SMA wire rope 15 consists of a multitude of SMA wire strands, which here have parallel turns that are tightly twisted or twisted / stranded together. This gives the SMA wire rope 15 a sufficient external structure that firmly grips the wrapped or surrounding concrete or mortar. The entire SMA wire wrapping or linear SMA wire rope configuration is surrounded by a layer of concrete or embedded in a layer of mortar 18 to provide a protective layer for the SMA wire rope 15. Such recesses / recesses can also be deliberately placed, e.g.At both ends of the SMA wire rope 15, or at intermediate points, connections are made to serve as points for (electrical) heating. A voltage source is attached to the SMA wire rope 15 to convert it from its martensite state to its permanent austenite state, thereby generating a prestressing force in the structure or component. After the heating process, the resulting recesses / holes are preferably filled with mortar or other materials.
[0030] Figure 6 shows a loop 1 made from an SMA wire rope 15, designed to be attached to a bolt, hook, or other retaining element. This retaining element should ideally be adapted to the inner curve of the loop 1 so that the loop 1 fits snugly around it. To prevent the loop 1 from coming loose, it is secured with a clamping sleeve 2, in which the end section of the supplied wire rope 15 overlaps. For this purpose, the clamping sleeve 2 is equipped with a radially penetrating set screw with an Allen key, acting as a clamping screw 3, allowing the passing wire ropes 15 to be tensioned within it.
[0031] Figure 7 shows a further tensioning of two parallel SMA wire ropes 15 by means of two clamping elements 4, each of which has a U-shaped steel bracket 5, both leg ends of which are provided with external threads onto which clamping nuts 6 can be screwed.
[0032] Figure 8 shows a cylindrical end element 7 with a longitudinally or axially recessed channel 8 for precisely receiving the end section of an SMA wire rope 15. To prevent the end from splaying, such an end element 7 is placed laterally onto the wire rope 15, after which it is clamped in this end element 7 or stopper element 7 by means of a radially penetrating setscrew 9. Alternatively, the ends of the wire ropes can also be secured by means of crimping heads or a crimp. It is also possible to anchor the strand ends or wire rope ends by bonding them in high-strength resins or cementitious materials, in particular UHPC / UHPCFRC (ultra-high-performance fiber-reinforced concrete / ultra-high-performance fiber-reinforced cementitious composite).
[0033] Figure 9 shows a wire rope 15 with an end piece 22 that can be screwed onto an end section. This end piece 22 forms a steel eyelet 10 at its end. An inner clamping sleeve 11 has a continuous slot in its longitudinal direction and tapers very slightly conically on the outside towards the front to an increased diameter. First, an outer clamping sleeve 21 with an external hexagon 12 and an internal cone is placed onto the end section of the wire rope 15, and then this outer clamping sleeve 21 is pushed forward over the slightly conical inner clamping sleeve 11. The cones fit together. The end piece 22 with the steel eyelet 10 can be screwed into the outer clamping sleeve 21 by means of the nut 13 and the threaded section 23 firmly connected to it.By drawing the two parts together, the outer clamping sleeve 21 presses against the inner clamping sleeve 11, which tightly constricts the continuous SMA wire rope 15, so that the end piece 22 with the steel eyelet 10 is tensile-resistant and connected to the end of the wire rope 15. Figure 10, shown below Figure 9, shows this end piece 22 in its fully screwed-together state.
[0034] Figure 11 illustrates the electrical heating of an SMA wire rope 15 wound around a bolt 19 to transform it from its martensitic state to its permanent austenitic state. A clamp is applied to each end of the SMA wire rope 15, which protrudes from the hardened mortar, and a voltage source is connected between the two clamps, ensuring a sufficiently strong current flows through the SMA wire rope 15. This transforms the wire rope from its martensitic to its austenitic state, causing it to contract in length and subsequently retain this state permanently. A structure or component wrapped with the wire rope is then tensioned and reinforced accordingly. The protruding end piece can then be cut off.
[0035] Figure 12 shows another illustration of the electrical heating of an SMA wire rope 15 formed into a secured loop 1 and placed around a screw 20, to transform the SMA wire rope 15 from its martensite state to its permanent austenite state. The loop 1 is secured here with two clamping elements 4, with the end of the SMA wire rope 15 again protruding from the mortar / concrete / component.
[0036] The SMA strand or SMA wire rope is embedded in a load-bearing matrix, e.g. in concrete or mortar.
[0037] To improve its integration into the concrete or mortar, or the load-bearing matrix, the strand or SMA wire rope 15 can also be "untwisted" at the end, as shown in Figure 13. The individual strands 24 thus wedge themselves more securely into the concrete when the wire rope 15 is subjected to tensile force. It is also possible to crimp the end of the wire rope 15 to form a coil 26, which acts as a kind of anchor head, as shown in Figure 14.
[0038] Figure 15 shows a crimping device 27 with crimpable end termination elements 28 next to it. An end termination element 28 can be slipped over the ends of a wire rope and crimped together. This greatly simplifies the handling of wire ropes on site.
[0039] Finally, Figure 16 shows a concrete pipe with a helical SMA wire rope wrapping cast into it, thus concealing it, for tensioning and reinforcement. Such reinforcement can be applied within the concrete of the pipe, either by casting it in during production or by subsequent wrapping or adding turns to the outside of the finished concrete pipe. Compared to an unreinforced concrete pipe, this tensioned concrete pipe is far more stable and significantly better protected against breakage.
[0040] In particular, the following applications can be noted: 1. Wrapping of concrete columns / Z-pillars for subsequent reinforcement: The concrete column cross-sections can be square, round, or oval. The concrete surface is roughened, and the corners of square columns are rounded. This can preferably be done by hydromechanical removal or by mechanical "peeling" with a chisel hammer, followed by sandblasting. The roughened concrete is then wrapped with one or more SMA wire ropes made of SMA strands. Plastic or other material anchors are used at the beginning and end of each SMA wire rope to secure the wire rope ends to the structure. The SMA wire ropes are then permanently tensioned by applying heat, and finally, a layer of mortar is applied. 2. Helical reinforcements for cement or concrete pipes These can also be other thin-walled containers, round, oval, or rectangular, or other three-dimensional shapes, for example, well troughs. Such reinforcements are suitable for new constructions as well as for prefabricated components that are critical to cracking, such as those used for water pumping or as water reservoirs. 3. Prestressed components made of concrete, clay, brick, or sand-lime brick. Products with SMA strand or SMA wire rope reinforcement. These components may be cement fiber pipes, drainage pipes, 3D shaped bodies or domes made of concrete or components, or channel-shaped and arched roofs made of concrete or components, each wrapped by one or more SMA wire strands 24, 25 or by one or more wire ropes 15 made therefrom. 4. Prestressed clay floors, fired clay, brick or sand-lime brick products with SMA strand or SMA wire rope reinforcements Any object made of materials that are not, or not sufficiently, resistant to tensile stress can be suitable for wrapping and tensioning with SMA strands or SMA wire ropes made from them. The SMA strands or SMA wire ropes are wrapped around the objects and tensioned in suitable directions where tensile forces are to be absorbed. A single SMA strand or wire rope can also be wrapped around an object like the outermost layers of a ball of yarn, with alternating directions. The heating then leads to an all-around constriction of the object, which gives it enormous dimensional stability. Embedding the SMA strand(s) or wire rope(s) in a load-bearing matrix, e.g., in concrete or mortar, results in effective force transmission into the object being reinforced.
[0041] Another interesting application involves prestressing concrete floor / ceiling slabs 32. Conventionally, such prestressing is achieved, for example, by inserting wires made of conventional prestressing steel into sheathing tubes 30, which are then embedded in the floor / ceiling slab along the bending moment path. The sheathing tubes 30 separate the prestressing steel 29 from the concrete and form a protective shell. Figure 17 shows a lower reinforcement 31 on formwork for a floor and / or ceiling slab, over which four such sheathing tubes 30 containing stranded prestressing wires have been laid – four in a first direction and four more in a direction perpendicular to it. The upper reinforcement is then added, followed by the pouring of the concrete.
[0042] After the concrete has hardened, one end of the tension wires 29 is anchored externally, and the other end of the wires 29 is subjected to tensile stress by means of a hydraulic press 33, as shown in Figure 18. The deformation of the wires 29, corresponding typically to a few parts per thousand elongation, generates a tensile force or prestressing force in the wires 29, which is transferred via the deflection and the external force application points, i.e., via the anchors 34, into the supporting structure or into the concrete 32. For the prestressing process to be successful, it is therefore necessary that there is no bond between the wire and the concrete matrix. Even the friction of the wire against the sheathing ducts 30 during tensioning leads to a loss in the prestressing force. The slab bends slightly upwards and is prestressed.The sheathing tubes 30 are filled with injected cement or mortar or other filling material to prevent the ingress of air and water and thus protect the prestressing steel from corrosion, apart from the form and force interlock mediated by the filling between the prestressing steel and the concrete.
[0043] With the present concept of embedding the SMA strand or SMA wire rope in a load-bearing matrix, e.g., in concrete or mortar, prestressing can be significantly simplified. SMA wire strands can be cast directly into the load-bearing matrix in any direction – depending on the structural requirements – for example, into the concrete 32 along a sub-reinforcement. Figure 19 shows such an embedded SMA wire rope 15 in a cross-section through a concrete floor and / or ceiling slab. After the concrete 32 has hardened, the SMA wire rope 15(s) are prestressed by the application of heat. They transfer the forces directly to the adjacent concrete 32 via their surfaces, thus creating prestress in the entire floor / ceiling slab 32. No hydraulic presses or sheathing tubes are required. Accordingly, filling the sheathing tubes is also unnecessary.Furthermore, there are no friction losses as described in the previous section. Point anchors are no longer necessary, as the surface structure of the SMA strands 15 is designed to interlock with the hardened concrete 32, ensuring the transfer of forces into it. Anchors, if used at all, serve only the purpose of installation or temporary fixation. Moreover, the SMA wire strands 15 are protected from fire and corrosion by being directly embedded in the concrete. It goes without saying that this SMA wire rope system is also suitable for any other building structures, including beams, cantilevers, balconies, canopies, etc. It is suitable for reinforcement in bridge construction, building construction, civil engineering, geotechnical engineering, etc. Even specially shaped and unusual architectural designs can be efficiently prestressed with this SMA wire rope system. The SMA strands, or rather...SMA wire ropes, like conventional tendons, can also be integrated into structural materials other than concrete.
[0044] The problem described at the outset is solved in particular by the subject matter of the invention according to the following sections or any combination of these following sections:
[0045] Method for prestressing and reinforcing existing or newly constructed structures or components, characterized in that at least one SMA wire strand 24 made of a shape memory alloy or at least one SMA wire rope 15 containing at least two wire strands 24, wherein at least one wire strand consists of a shape memory alloy, is embedded in a load-bearing matrix, or that at least one SMA wire strand 24 made of a shape memory alloy or at least one SMA wire rope 15 containing at least two wire strands 24, wherein at least one wire strand consists of a shape memory alloy, is embedded in a load-bearing matrix, such that after the load-bearing matrix has hardened by increasing the temperature, the shape memory alloy is brought from the martensite state to a permanent austenite state, and thus, as a result of the induced contraction force – thanks to the mutually twisting,The windings are positively connected to the hardened load-bearing matrix – a force transmission and prestressing force is generated between the SMA wire strand (24) or the SMA wire rope (15) and the structure or component.
[0046] Methods for prestressing and strengthening existing or newly constructed structures or components according to section
[0045] , characterized in that the supporting matrix is cement-bound.
[0047] Methods for prestressing and strengthening existing or newly constructed structures or components according to one of the preceding sections
[0045] or
[0046] , characterized in that the load-bearing matrix is formed from concrete or mortar.
[0048] Methods for prestressing and strengthening existing or newly constructed structures or components according to one of the preceding sections
[0045] to
[0047] , characterized in that the SMA strand 24 or the SMA wire rope 15 is untangled at the end to improve the integration into the supporting matrix.
[0049] Methods for prestressing and strengthening existing or newly constructed structures or components according to one of the preceding sections
[0045] to
[0048] , characterized in that at least one SMA wire strand 24 made of a shape memory alloy or at least one SMA wire rope 15 containing at least two wire strands 24, wherein at least one wire strand consists of a shape memory alloy, is wound around the structure or component in a suitable direction and is brought from the martensite state to a permanent austenite state by increasing the temperature, and thus a prestress is generated on the structure or component as a result of the induced contraction force, and / or at least one SMA wire strand 24 made of a shape memory alloy or at least one SMA wire rope 15 containing at least two wire strands 24, wherein at least one wire strand consists of a shape memory alloy, wherein the SMA wire strand 24 or the SMA wire rope 15 is wound around the structure or component to be newly erected before the The structural material is arranged, inserted, or attached in such a way that it is ordered, placed, or fitted.that it is embedded in a load-bearing matrix formed by the structural material, or, in the case of an existing structure or component, the SMA wire strand 24 or the SMA wire rope 15 is arranged, inserted, or attached in such a way that it is embedded in an applied load-bearing matrix, and after the load-bearing matrix has hardened, the shape memory alloy is brought from the martensite state to a permanent austenite state by increasing the temperature, and thus a prestress is generated on the structure or component as a result of the induced contraction force.
[0050] Procedure according to one of the preceding sections
[0045] to
[0049] , characterized in that at least one SMA wire strand 24 made of a shape memory alloy or at least one SMA wire rope 15 containing at least two wire strands 24, wherein at least one wire strand consists of a shape memory alloy, is arranged, inserted, or attached to a concrete slab or structure of a building or component before concreting, and the shape memory alloy of the SMA wire strand (24) or the SMA wire rope (15) is brought from the martensite state to a permanent austenite state after the concrete has hardened by increasing the temperature, and thus, as a result of the induced contraction force – thanks to the mutually twisting windings positively connected with the hardened concrete – a force transmission and prestressing force is exerted between the SMA wire strand (24) or the SMA wire rope (15) and the building. or component is produced.
[0051] Method for prestressing and reinforcing existing or newly constructed structures or components, characterized in that at least one SMA wire strand 24 made of a shape memory alloy or at least one SMA wire rope 15 containing at least two wire strands 24, wherein at least one wire strand consists of a shape memory alloy, is wound around the structure or component in a suitable direction and is brought from the state as martensite to a permanent state as austenite by increasing the temperature, and thus a prestress is generated on the structure or component as a result of the induced contraction force.
[0052] Methods for prestressing and strengthening existing or newly constructed structures or components according to section
[0051] in combination with one of the preceding sections
[0045] to
[0050] .
[0053] Methods for prestressing and strengthening existing or newly constructed structures or components according to one of the preceding sections
[0045] to
[0052] , characterized in that at least one SMA wire strand 24 made of a shape memory alloy or at least one SMA wire rope 15 containing at least two wire strands 24, wherein at least one wire strand consists of a shape memory alloy, is wound around the structure or component in a suitable direction and is brought from the state as martensite to a permanent state as austenite by increasing the temperature, and thus a prestress is generated on the structure or component as a result of the induced contraction force.
[0054] Procedure according to one of the preceding sections
[0045] to
[0053] , characterized in that one or more SMA wire strands 24 or SMA wire ropes 15 are wound completely, partially or multiple times around a structure or a component in a suitable direction or in several suitable directions or also in directions changing direction.
[0055] Procedure according to one of the preceding sections
[0045] to
[0054] , characterized in that structures or components made of concrete, cement, mortar, plastic, clay, loam or masonry are wrapped by means of at least one (preferably flexible) SMA wire strand 24 or by means of at least one SMA wire rope 15 made of at least two SMA wire strands 24 wound around themselves, wherein these are placed directly into the structure or component or attached to it in a load-bearing matrix and, thanks to the mutually twisting windings that are positively connected to the structure or component, a force transmission is generated between the individual SMA wire strands 24 or SMA wire ropes 15 and the structure or component.
[0056] Procedure according to one of the preceding sections
[0045] to
[0055] , characterized in that the wrapping with an SMA wire rope 15 is made from two or more individual SMA wire strands 24 which are wound helically and in opposite directions to each other around a third, centrally running core wire strand 25, which increases the flexibility and pliability of the SMA wire rope 15 thus created compared to a single SMA wire with a comparable solid cross-sectional area and at the same time creates a wound, twisted surface.
[0057] Procedure according to one of the preceding sections
[0045] to
[0056] , characterized in that several SMA wire strands 24 or SMA wire ropes 15 of the same or different diameter are used for wrapping the component or structure.
[0058] Procedure according to one of the preceding sections
[0045] to
[0057] , characterized in that the ends of the SMA wire strands 24, 25 or SMA wire ropes 15 are anchored by means of end anchoring elements to bolts 19 or screws 20 which penetrate into the structure or component in a tensile-locking manner.
[0059] Procedure according to one of the preceding sections
[0045] to
[0058] , characterized in that the heat input for increasing the temperature is carried out by means of an applied electrical voltage to generate a resistance heating of the SMA wire strand 24, 25 or the SMA wire rope 15, wherein current clamps are applied section by section in stages and the sections in between are heated, or the current clamps are applied to both ends of the SMA wire strand 24, 25 or the SMA wire rope 15 and the heating takes place over the entire length of the SMA wire strand 24, 25 or the SMA wire rope 15 in one go.
[0060] Procedure according to one of the preceding sections
[0045] to
[0059] , characterized in that the connection of the current terminals to the SMA wire strand 24, 25 or the SMA wire rope 15 is carried out via recesses in the concrete, cement, mortar, plastic, clay, loam, sand-lime brick or the supporting matrix, to which these current terminals can be attached.
[0061] Procedure according to one of the preceding sections
[0045] to
[0060] , characterized in that the current terminals are attached to both end pieces of the inserted SMA wire strand 24, 25 or the SMA wire rope 15, which protrude from the structure or component or from the supporting matrix respectively.
[0062] Procedure according to one of the preceding sections
[0045] to
[0061] , characterized in that the heat input for increasing the temperature in the SMA wire strand 24, 25 or in the SMA wire rope 15 is carried out by means of an electric radiant heater or heating fan or by means of a gas burner.
[0063] Procedure according to one of the preceding sections
[0045] to
[0062] , characterized in that the heat input for increasing the temperature in the inserted SMA wire strand 24, 25 or the inserted SMA wire rope 15 is carried out by means of electric resistance heating, radiant heater, heating fan or flame by heating the entire structure or component.
[0064] Procedure according to one of the preceding sections
[0045] to
[0063] , characterized in that the strand or the SMA wire rope is embedded in a supporting matrix.
[0065] Procedure according to one of the preceding sections
[0045] to
[0064] , characterized in that the strand or the SMA wire rope is embedded in concrete or mortar.
[0066] An existing or newly constructed structure or component, characterized in that it is braced by one or more SMA wire strands 24, 25 or by one or more SMA wire ropes 15 made therefrom, embedded in a load-bearing matrix, or that it is braced by at least one SMA wire strand (24) made of a shape memory alloy or by at least one SMA wire rope (15) containing at least two wire strands (24), wherein at least one wire strand consists of a shape memory alloy, wherein the at least one SMA wire strand (24) or the at least one SMA wire rope (15) is embedded in a load-bearing matrix.
[0067] Existing or newly constructed building or component according to section
[0066] , characterized in that the supporting matrix is cement-bound.
[0068] Existing or newly constructed building or component according to one of the preceding sections
[0066] or
[0067] , characterized in that the supporting matrix is formed from concrete or mortar.
[0069] Existing or newly constructed building or component according to one of the preceding sections
[0066] to
[0068] , characterized in that it is completely, partially or multiple times wrapped by one or more SMA wire strands 24, 25 or by one or more SMA wire ropes 15 produced therefrom in a suitable direction or in several suitable directions or also direction-changing directions and is tensioned by the application of heat.
[0070] Existing or newly constructed building or component according to one of the preceding sections
[0066] to
[0069] , characterized in that the structure or component is a cement fiber pipe, a drainage pipe, a 3D shaped body or a dome made of concrete or components or a channel-shaped or arched roof made of concrete or components, and these products are each completely, partially or multiple times wrapped by one or more SMA wire strands 24, 25 or by one or more SMA wire ropes 15 made therefrom in a suitable direction or in several suitable directions or also direction-changing directions and are tensioned by the application of heat and subsequently the SMA wire strands 24, 25 or wire ropes 15 are covered by mortar or a covering of other material.
[0071] Existing or newly constructed building or component, characterized in that it is completely, partially or multiple times wrapped by one or more SMA wire strands 24, 25 or by one or more SMA wire ropes 15 produced therefrom in a suitable direction or in several suitable directions or also directions changing direction and is tensioned by heat input.
[0072] Existing or newly constructed building or component according to section
[0071] in any combination with any of the preceding sections
[0066] to
[0070] .
[0073] Existing or newly constructed building or component according to one of the preceding sections
[0066] to
[0072] , characterized in that the structure or component is a cement fiber pipe, a drainage pipe, a 3D shaped body or a dome made of concrete or components, or a channel-shaped or arched roof made of concrete or components, and these products are each completely, partially or multiple times wrapped by one or more SMA wire strands 24, 25 or by one or more SMA wire ropes 15 made therefrom in a suitable direction or in several suitable directions or also direction-changing directions and are tensioned by heat input and subsequently the SMA wire strands 24, 25 or wire ropes 15 are covered by mortar or a covering of other material.
[0074] Existing or newly constructed building or component according to a method in accordance with one of the sections
[0045] to
[0073] .
[0075] Use of at least one SMA wire strand 24 made of a shape memory alloy or at least one SMA wire rope 15 containing at least two wire strands 24, wherein at least one wire strand is made of a shape memory alloy, for prestressing and reinforcing existing or newly constructed structures or components, wherein the at least one SMA wire strand (24) or the at least one SMA wire rope (15) is embedded in a load-bearing matrix.
[0076] Use according to section
[0075] in a method according to any of the preceding sections
[0045] to
[0065] .
[0077] Use according to section
[0075] or
[0076] in an existing or newly constructed building or component according to one of the preceding sections
[0066] to
[0074] ,
[0078] The subject matter of the invention according to one of the preceding sections
[0045] to
[0077] , wherein the component is a floor and / or ceiling panel.
[0079] The subject matter of the invention according to one of the preceding sections
[0045] to
[0078] , wherein the SMA wire strand (24) or SMA wire strands (24) or the SMA wire rope (15) or the SMA wire ropes (15) are not installed in the same or the same encompassing sheathing tubes. Number index 1 loop of SMA wire rope 2 clamping sleeves 3 Allen screws 4 clamping elements 5 steel brackets 6 nuts 7 Stopper element 8 Channel in the axial direction of the stopper element 9 clamping screw 10 steel eyelets 11 Inner clamping sleeve with outer cone 12 hexagonal 13 Hexagon with external thread extension 14 Cylindrical concrete column 15 SMA wire rope 16 bolts 17 loops 18 Mortaring 19 anchor bolts 20 anchoring screws 21 External clamping sleeve with internal cone 22 End element with steel eyelet, external thread on end element SMA wire strand Straight SMA wire strands Ball of SMA wire strands Pressing device Finishing elements Steel tension rods sheathing tube Forearm Concrete floor / ceiling slab Hydraulic press for pre-tensioning the steel tension rods Pre-anchored steel tension rods with cast-in sheath tubes 30
Claims
Patent claims 1. Method for prestressing and strengthening existing or newly constructed structures or components, characterized in that at least one SMA wire strand (24) made of a shape memory alloy or at least one SMA wire rope (15) containing at least two wire strands (24), wherein at least one wire strand consists of a shape memory alloy, is embedded in a load-bearing matrix.
2. Method for prestressing and reinforcing existing or newly constructed structures or components according to claim 1, characterized in that at least one SMA wire strand (24) made of a shape memory alloy or at least one SMA wire rope (15) containing at least two wire strands (24), wherein at least one wire strand consists of a shape memory alloy, is wound around the structure or component in a suitable direction and is brought from the state as martensite to a permanent state as austenite by increasing the temperature, and thus a prestress is generated on the structure or component as a result of the induced contraction force.
3. A method for prestressing and reinforcing existing or newly constructed structures or components according to one of the preceding claims, characterized in that at least one SMA wire strand (24) made of a shape memory alloy or at least one SMA wire rope (15) comprising at least two wire strands (24), wherein at least one wire strand consists of a shape memory alloy, wherein the SMA wire strand (24) or the SMA wire rope (15) is arranged, inserted, or attached in a newly constructed structure or component before the application of the structural material such that it is embedded in a load-bearing matrix formed by the structural material, or in the case of an existing structure or component, the SMA wire strand (24) or the SMA wire rope (15) is arranged, inserted, or attached such that it is embedded in a load-bearing matrix formed by the structural material.it is embedded in an applied load-bearing matrix, and after the load-bearing matrix has hardened, the shape memory alloy is brought from the state of martensite to a permanent state of austenite by increasing the temperature, and thus a prestress is generated on the structure or component as a result of the induced contraction force.
4. A method according to one of the preceding claims, characterized in that at least one SMA wire strand (24) made of a shape memory alloy or at least one SMA wire rope (15) containing at least two wire strands (24), wherein at least one wire strand consists of a shape memory alloy, is arranged, inserted, or attached to a concrete slab or structure of a building or component before concreting, and the shape memory alloy of the SMA wire strand (24) or the SMA wire rope (15) is brought from the martensite state to a permanent austenite state after the concrete has hardened by increasing the temperature, and thus, as a result of the induced contraction force – thanks to the mutually twisting coils positively connected with the hardened concrete – a force transmission and prestressing force is exerted between the SMA wire strand (24) or the SMA wire rope. (15) and is produced in the building or component.
5. Method according to one of the preceding claims, characterized in that one or more SMA wire strands (24) or SMA wire ropes (15) are wound completely, partially or multiple times around a structure or a component in a suitable direction or in several suitable directions or also in directions changing direction.
6. Method according to one of the preceding claims, characterized in that structures or components made of concrete, cement, mortar, plastic, clay, loam or masonry are wrapped by means of at least one SMA wire strand (24) or by means of at least one SMA wire rope (15) made of at least two SMA wire strands (24) wound around themselves, wherein these are placed directly into the structure or component or attached to it in a load-bearing matrix and a force transmission is generated between the individual SMA wire strands (24) or SMA wire ropes (15) and the structure or component thanks to the mutually twisting windings that are positively connected to the structure or component.
7. Method according to one of the preceding claims, characterized in that the wrapping with an SMA wire rope (15) is carried out from two or more individual SMA wire strands (24) which are wound helically and in opposite directions to each other around a third, centrally running core wire strand (25), which increases the flexibility and pliability of the SMA wire rope (15) thus produced compared to a single SMA wire with a comparable solid cross-sectional area and at the same time creates a wound, twisted surface.
8. Method according to one of the preceding claims, characterized in that several SMA wire strands (24) or SMA wire ropes (15) of the same or different diameters are used for wrapping the component or structure.
9. Method according to one of the preceding claims, characterized in that the heat input for increasing the temperature is carried out by means of an applied electrical voltage to generate a resistance heating of the SMA wire strand (24, 25) or the SMA wire rope (15), wherein current clamps are applied section by section in stages and the sections in between are heated, or the current clamps are applied to both ends of the SMA wire strand (24, 25) or the SMA wire rope (15) and the heating takes place over the entire length of the SMA wire strand (24, 25) or the SMA wire rope (15) in one go.
10. Method according to one of the preceding claims, characterized in that it is applied to a floor and / or ceiling slab.
11. Existing or newly constructed structure or component, characterized in that it is tensioned by at least one SMA wire strand (24) made of a shape memory alloy or by at least one SMA wire rope (15) containing at least two wire strands (24), wherein at least one wire strand consists of a shape memory alloy, wherein the at least one SMA wire strand (24) or the at least one SMA wire rope (15) is embedded in a load-bearing matrix.
12. Existing or newly constructed building or component according to claim 11, characterized in that it is completely, partially or multiple times wrapped by one or more SMA wire strands (24, 25) or by one or more SMA wire ropes (15) produced therefrom in a suitable direction or in several suitable directions or also direction-changing directions and is tensioned by heat input.
13. Existing or newly constructed component according to claim 11 or 12, characterized in that it is a floor and / or ceiling slab.
14. Use of at least one SMA wire strand (24) made of a shape memory alloy or at least one SMA wire rope (15) containing at least two wire strands (24), wherein at least one wire strand is made of a shape memory alloy, for prestressing and reinforcing existing or newly constructed structures or components, wherein the at least one SMA wire strand (24) or the at least one SMA wire rope (15) is embedded in a load-bearing matrix.
15. Use according to claim 14 for prestressing and reinforcing a floor and / or ceiling panel.