Strand with sensor

Abstract

The present invention relates to a strand for applying stress to concrete, the strand having a diameter ranging from 1 mm to 100 mm and a tensile strength of more than 1500 MPa, wherein the strand comprises at least three strand elements, the at least three strand elements including at least one central strand element, at least one intermediate strand element and at least one outer strand element, wherein at least one additional strand element is a sensor, and the sensor is the intermediate strand element.

Description

[0001] This invention relates to a strand for applying stress to concrete, the strand having a diameter ranging from 1 mm to 100 mm and a tensile strength exceeding 1500 MPa.

[0002] The strand comprises at least three strand elements, including at least one central strand element, at least one intermediate strand element, and at least one outer strand element.

[0003] At least one additional strand element is a sensor, and the sensor is an intermediate strand element. The invention further relates to a measurement method using strands according to the invention.

[0004] Prestressed concrete is a form of concrete that is compressed by applying tension to enhance its resistance to tensions it will experience during service. Prestressed concrete thus includes pre-tensioned concrete and / or post-tensioned concrete. For pre-tensioned concrete, tension is applied before the concrete is poured, while for post-tensioned concrete, tension is applied after the concrete is poured and / or after it has hardened.

[0005] Tension can thus be applied specifically using steel strands or wires (especially steel or synthetic wires).

[0006] However, this means that during the pouring, curing, or service life of a concrete structure, there may be temperature or force variations beyond specifications, which can be harmful and the service life may be difficult or impossible to estimate.

[0007] Therefore, it is desirable to monitor the forces applied to concrete and / or the temperature of the concrete to avoid the aforementioned problems and ensure the quality and / or integrity and / or durability of stressed concrete structures. In practice, this invention can help identify potentially harmful out-of-specification temperature or force variations during the pouring, curing, or service life of a concrete structure, and aid in estimating its service life. Furthermore, this invention can, for example, help control concrete shrinkage and / or creep, detect fires, monitor strand integrity and / or tensile strength, regulate strain, detect overloads, trigger and / or schedule maintenance work and / or inspections, record the strain history of the structure and / or its reinforcing elements, and especially obtain estimates of effective life or service time.

[0008] This is made possible by the strand according to the invention, i.e., the strand for applying stress to concrete, having a diameter ranging from 1 mm to 100 mm and a tensile strength exceeding 1500 MPa.

[0009] The strand comprises at least three strand elements, including at least one central strand element, at least one intermediate strand element, and at least one outer strand element.

[0010] At least one other strand element is a sensor, and the sensor is an intermediate strand element.

[0011] The strand according to the invention can thus be a group of two or more filaments, strands, or cords. At least two filaments, strands, or cords of the strand can be twisted together, for example, at a given strand twist pitch, preferably only one given strand twist pitch.

[0012] In the context of this invention, the strand element can thus be, for example, any other component including the sensor, such as a filament, strand, or wire.

[0013] The strand according to the invention thus comprises inner strand elements, outer strand elements, and intermediate strand elements. The inner strand elements are thus located inside the strand and / or preferably at the center of the strand, and are therefore surrounded by other strand elements, which may therefore be outer strand elements. On the other hand, in the sense of the invention, the outer strand elements are located on the outward-facing outer side of the strand, and are therefore in contact with the periphery of the strand. Furthermore, one or more inner strand elements located at the center of the strand or alternatively opposite one or more other outer strand elements may be one or more central strand elements. In the sense of the invention, intermediate strand elements may thus be located between one or more inner strand elements or central strand elements on one side and one or more outer strand elements on the other side.

[0014] The strands according to the present invention may include at least three strand elements, wherein the at least three strand elements include at least one central strand element, at least one intermediate strand element, and at least one outer strand element.

[0015] At least one other strand element is a sensor, and the sensor is an intermediate strand element. The position of the sensor according to the invention thus contributes to more accurate and / or reliable measurements, as well as helps to minimize the impact on the mechanical properties of the strand.

[0016] The strands according to the invention can have tensile strengths, for example, higher than 500 MPa, higher than 1700 MPa, preferably higher than 1800 MPa, preferably higher than 1900 MPa, preferably higher than 2000 MPa, and more preferably between 1800 MPa and 4000 MPa. This can help allow for, for example, structural reinforcement and ease of installation.

[0017] In one embodiment, the strands according to the invention may include a central strand element. This can help to make such strands more stable and / or prevent strand deformation, especially when using a larger number of strand elements. In fact, with more than five strand elements, the strand configuration may become unstable, and the central strand element can stabilize such a configuration by blocking the central position and thus preventing other strand elements from moving to the central position.

[0018] In one embodiment of the invention, the strands may have a maximum breaking load, for example, higher than 190 kN, preferably higher than 195 kN, preferably higher than 200 kN, preferably higher than 220 kN, more preferably between 192 kN and 600 kN, more preferably between 195 kN and 350 kN, and more preferably between 200 kN and 10000 kN. This can help allow, for example, structural reinforcement and ease of installation.

[0019] In one embodiment of the invention, the strands may include non-steel strand elements, such as, for example, synthetic filaments or synthetic fibers, such as, for example, polyethylene (PE), polypropylene (PP), aramid, polyester, polycarbonate, polyamide (PA), aramid and / or polyoxymethylene (POM) filaments and / or carbon fiber and / or glass fiber. In one embodiment of the invention, the strands may include steel strand elements, particularly, for example, coated or uncoated steel wires and / or steel cords, which may be groups of wires preferably stranded at steel cord pitches, more preferably only one steel cord pitch. In one embodiment of the invention, the strands may include both non-steel strand elements and steel strand elements. In another embodiment of the invention, the strands may thus comprise, for example, a majority of steel strand elements and / or a majority of non-steel strand elements. Preferably, in the sense of the invention, the non-steel strand elements and / or steel strand elements are distinct from the sensor. This can help allow, for example, structural reinforcement and ease of installation. In one embodiment of the invention, the central strand element and the outer strand elements may be steel strand elements. Furthermore, the strands according to the invention may preferably not include Z-shaped steel wires and / or steel wires with high vanadium content. The high vanadium content can thus be >0.15%, preferably >1%, and even more preferably >4%.

[0020] In one embodiment of the invention, the strands may comprise, for example, 2, 3, 7, 3×1+6, 1+6+12, or 7×7 strand elements, particularly steel strand elements and / or non-steel strand elements. This can help allow such strands to be made, for example, more flexible, especially as the number of strand elements increases. Strands with 1+6 strand elements, particularly steel strand elements, according to the invention are thus preferred.

[0021] In one embodiment of the invention, the strand may comprise or consist of n-1, n-2, n-3, or n-4 strand elements, which are non-steel strand elements and / or steel strand elements, where n is the total number of strand elements in the strand. In such cases, the remaining strand elements of the strand may preferably be, for example, sensors. This can help to allow, for example, accurate and / or reliable measurements and / or measurements of multiple parameters and / or measurements using different methods and / or ensure redundancy.

[0022] In one embodiment of the invention, the outer strand elements may be helical, and / or the center strand element may be substantially straight. Two or more outer strand elements may be wound together, for example, with a given strand twist pitch, preferably only one given strand twist pitch. On the other hand, one or more inner strand elements and / or the center strand element may be substantially straight. Preferably, the outer strand elements may thus be wound together in a helical manner, more preferably, for example, wound together in a helical manner around one or more inner strand elements and / or the center strand element. In the sense of the invention, substantially straight may therefore preferably mean not wound with at least one given twist pitch. This can help to allow for greater stability of such strands and / or avoid strand deformation.

[0023] In one embodiment of the invention, the sensor may be selected, for example, from: optical sensors, conductivity sensors, optical fibers, glass fibers, coaxial cables, carbon elements, copper or copper alloy wires. In one embodiment of the invention, the sensor may be, in particular, a strain sensor and / or a temperature sensor. In one embodiment of the invention, the sensor may be configured to compensate for strain measurements based on temperature data. In one embodiment of the invention, a single sensor may measure both strain and temperature, or two different sensors may measure temperature on one hand and strain on the other. In one embodiment of the invention, the sensor may be, in particular, a fiber Bragg grating sensor or an optical fiber. This can help allow, for example, accurate and / or reliable measurements and / or measurements of multiple parameters and / or measurements using different methods and / or ensure redundancy.

[0024] In one embodiment of the invention, the sensor can be straight or helical. The sensor can thus be helically wound with another outer strand element, more preferably, for example, helically wound around one or more inner strand elements and / or a central strand element. The sensor can also be straight, preferably located, for example, between one or more central strand elements and one or more outer strand elements. This can help allow for greater stability of such strands and / or prevent strand deformation. This can also help allow, for example, accurate and / or reliable measurements and / or measurements of multiple parameters and / or measurements using different methods and / or ensure redundancy.

[0025] In one embodiment of the invention, the sensor may be coated with at least one polymer or include at least one polymer sheath. In one embodiment of the invention, the material selected for the polymer coating and / or the polymer sheath comprises or consists of at least one of the following: polyvinyl chloride (PVC), glass fiber reinforced polymer, polyester, polyimide, polyethylene (PE), polypropylene (PP), thermoplastic elastomer, thermoplastic polyester elastomer, or high-density polyethylene (HDPE). This can help allow for accurate and / or reliable measurements, and avoid damage to the sensor. In one embodiment of the invention, the sensor may be externally coated with polyester, polyimide, or glass fiber reinforced polymer, thereby helping to improve the mechanical interlocking of the sensor with at least one other strand element. This can help allow, for example, accurate and / or reliable measurements. In one embodiment of the invention, the sensor may be externally coated with PVC, polyethylene (PE), high-density polyethylene (HDPE), polypropylene (PP), thermoplastic elastomer, or thermoplastic polyester elastomer, thereby helping to reduce lateral forces, especially lateral forces from mechanical interlocking, and / or minimize the risk of damage to the sensor. In one embodiment of the invention, the sensor may be externally coated with a polymer material having a Vickers hardness (e.g., measured using a DURAMIN-10 AC tester and an indentation time of 10 seconds) between 1 HV0.01 and 10 HV0.01, preferably between 2 HV0.01 and 8 HV0.01, more preferably between 3 HV0.01 and 7 HV0.01, and even more preferably between >3.5 HV0.01 and <6.5 HV0.01). This can help improve the mechanical interlocking of the sensor with at least one other strand element. Furthermore, this can help allow for, for example, accurate and / or reliable measurements.

[0026] In one embodiment of the invention, at least two additional strand elements may be sensors and / or both sensors may be intermediate strand elements. In another embodiment, the two sensors may preferably be located, for example, on opposite sides of the strands and / or adjacent to each other, more preferably forming an angle between 100° and 200° and / or between 10° and 90°. In another embodiment, one sensor may be a central strand element. This can help allow, for example, accurate and / or reliable measurements and / or measurements of multiple parameters and / or measurements using different methods and / or ensuring redundancy. In another embodiment, a strand element serving as a sensor, preferably a strain sensor, may be an intermediate strand element serving as a sensor, which can be mechanically interlocked to at least one strand element in another strand element, and a second strand element serving as a sensor, preferably a temperature sensor, may be not mechanically interlocked to at least one strand element in another strand element. This can help allow, for example, accurate and / or reliable measurements and / or measurements of multiple parameters, especially strain and / or temperature.

[0027] In one embodiment of the invention, the intermediate strand element serving as a sensor can be secured to at least one of the other strand elements using an adhesive and / or by a softening polymer coating or polymer sheath. In one embodiment, at least some, preferably all, of the center strand element, intermediate strand element, and outer strand elements are secured to each other, preferably by an adhesive and / or by a softening polymer coating or polymer sheath. In one embodiment, the intermediate strand element serving as a sensor can be secured to at least one of the other strand elements using an adhesive and / or by a softening polymer coating or polymer sheath and / or by a mechanical interlock. In one embodiment, the mechanical interlock can be particularly used, for example, to secure the sensor, serving as an intermediate strand element, to at least three of the other strand elements and / or to at least three of the other strand elements. The mechanical interlock can thereby, for example, help to minimize or reduce lateral forces and / or reduce the need for adhesives and / or other compounds to be used, which may affect and / or interfere with the mechanical properties of the strands. This can also help to allow for accurate and / or reliable measurements, for example, by minimizing deviations and avoiding damage to the sensor. The ratio of the sensor's diameter to the diameter of the outer strand element with the smallest diameter can thus preferably be >0.180, preferably >0.185, more preferably >0.190, even more preferably <0.250, and / or between >0.180 and <0.250. This can help improve mechanical interlocking and / or can also help with accurate and / or reliable measurements. In one embodiment of the invention, the diameter of the strand element (especially steel strand element) is between 2 mm and 10 mm, preferably between 3 mm and 7 mm, and / or the diameter of the sensor as the strand element is between 0.8 mm and 1.5 mm, preferably >0.9 mm and <1.3 mm. This can also help improve mechanical interlocking and / or can also help with accurate and / or reliable measurements. In one embodiment of the invention, the diameter of the inner strand element can be more than 3% larger than the diameter of the smallest outer strand element, and / or can be more than 3% larger than the diameter of each of the outer strand elements. This can help allow the inner strand element to support the strands. The strands according to the invention can thus be obtained, for example, in the following manner. The sensor, as a strand element, can be introduced into the strands at two different steps in the production process, namely during stranding or during lubrication and coating.

[0028] When the sensor is introduced during stranding, this can preferably be done before the subsequent heat treatment.

[0029] On the other hand, when a sensor is introduced during the lubrication and coating process, this requires opening the strands and closing them again before applying grease and coating.

[0030] In both cases, rapid closure of the strands is crucial to ensure that the strand element (especially steel strand elements) does not loosen its grip on the sensor upon introduction (particularly during initial introductions that may only involve short lengths), and to guarantee that the sensor remains securely positioned at the designated point and does not skip to another point. Once the strands are under tension, this can lead to, for example, damage to the sensor.

[0031] The supply and guidance of the sensor can be achieved, for example, through the following:

[0032] - A strand opener, which may be a rotating plate having a specified number of holes of appropriate diameter and positioned for the required number of strand elements and / or for sensors to be introduced into the strand.

[0033] - A supply system for weight balancing of the sensor, adapted to hold the sensor spool and ensure proper tension of the sensor when it is introduced into the strands, and adapted to rotate freely and smoothly around the strands, especially in the absence of sudden movement (e.g., by using counterweights to balance the mass).

[0034] - Synchronizing the supply and introduction of the sensor with the direction of twisting of the strand elements (twist direction) and the distance traveled by a strand element to twist 360° (twist pitch) allows the sensor to be positioned as an intermediate strand element in a designated gap. This strand opener can be integrated with the supply device and can be used as a synchronization and propulsion unit for the rotating portion of the supply system. Furthermore, a strand closeer can be used, which can be, for example, a loop or any other element that brings the strand elements back close to each other to reclose the strands, thereby positioning it as close as possible to the outlet of the strands from the supply system, so that the sensor is properly clamped and placed as quickly as possible. Therefore, the invention further relates to a method for producing strands, comprising, for example:

[0035] - Use the stock line opener to open the stock lines.

[0036] - The sensor, which is a strand element, is supplied using a feeder suitable for free and smooth rotation around the strand.

[0037] - Use a strand closure device to close the strand.

[0038] And / or the supply and introduction of the sensor are synchronized with the direction in which the strands of the wire element are twisted and the distance that a strand of the wire element takes to twist 360°. As a result, the sensor may thus undergo some twisting.

[0039] The invention further relates to a rope comprising, for example, two or more strands according to the invention. In one embodiment, this can be used to anticipate, for example, one or more sensors between the strands of the rope.

[0040] The present invention further relates to a measurement method,

[0041] in

[0042] During the pouring of concrete structures, and / or

[0043] During the curing of concrete structures, and / or

[0044] During the lifespan of a concrete structure, the strands according to the invention can be used directly or indirectly (i.e., including, for example, via reflected wavelengths) to measure at least one parameter selected from: force and / or strain and / or temperature; and / or

[0045] The measurement can be performed continuously along the length of the sensor or at discrete intervals along the length of the sensor. In the context of this invention, the measurement can be performed at discrete intervals along the length of the sensor, which is particularly relevant, for example, when using a fiber Bragg grating sensor, because in such cases, the measurement can be performed, for example, at a Bragg grating pre-defined along the length of the sensor at discrete intervals. It is also possible for the sensor to include multiple measurement segments pre-defined along the length of the sensor at discrete intervals. This can also help allow for accurate and / or reliable measurements and avoid damage to the sensor. It can also help ensure the quality and / or integrity and / or durability of stressed concrete structures.

[0046] Example :

[0047] The following is a comparison of different strands according to the present invention.

[0048] Using an Instron 8803 servo-hydraulic testing system (300kN limit), force was recorded as a function of deformation in micro-strain (1 / 1,000,000) at a test speed of 12.5kN / min in force-controlled measurements. The strand was secured to the machine head and frame with wedges via two identical standard cylinders. One or more sensors, which are fiber optic, fiber Bragg grating sensors, were connected to an interrogator BG-Scan 90X from FBGS Technologie GmBH, Germany, which then converted the wavelength into micro-strain.

[0049] Figure 1A comparison between two strands according to the invention is shown. The first strand A (dashed line) is a strand with 6+1 steel strand elements, wherein the outer steel strand elements have a diameter of 5.2 mm, and the sensor is a middle strand element and an optical fiber, preferably a fiber Bragg grating sensor, which has an external polyethylene coating, particularly a high-density polyethylene coating, and has a diameter of 0.9 mm. The central steel strand element thus has a diameter of 5.4 mm. The ratio of the sensor diameter to the diameter of the outer strand element with the smallest diameter is <0.180, i.e., 0.173. The second strand B (thick line) is a strand with 6+1 steel strand elements, wherein the outer steel strand elements have a diameter of 5.2 mm, and the sensor is a middle strand element and an optical fiber, preferably a fiber Bragg grating sensor, which has an external glass fiber reinforced polymer coating and has a diameter of 1 mm. The central steel strand element thus has a diameter of 5.4 mm. Therefore, the ratio of the sensor's diameter to the diameter of the outer strand element with the smallest diameter is >0.180, or 0.192. All other parameters are the same.

[0050] The graphs of the measured and thus recorded force / microstrain curves show that the measured strain of sensor B (higher, thicker line) is closer to the applied and / or calculated strain (thinner line) than the strain of sensor A (lower, dashed line). This can contribute to more accurate measurements.

[0051] Figure 2 A comparison between two strands according to the invention is shown. The first strand A (dashed line) is a strand with 6+1 steel strand elements, wherein the outer steel strand elements have a diameter of 5.2 mm, and the middle strand element is a sensor and optical fiber, preferably a fiber Bragg grating sensor, which is fixed to at least one of the other strand elements with adhesive. The central steel strand element thus has a diameter of 5.4 mm. The second strand B (thick line) is a strand with 6+1 steel strand elements, wherein the outer steel strand elements have a diameter of 5.2 mm, and the sensor is a middle strand element and optical fiber, preferably a fiber Bragg grating sensor, which is fixed to at least one of the other strand elements by mechanical interlocking, and / or wherein the mechanical interlocking is used to fix the sensor as an intermediate strand element to at least three of the other strand elements and / or between at least three of the other strand elements. The central steel strand element thus has a diameter of 5.4 mm. All other parameters are the same.

[0052] The graphs of the measured and thus recorded force / microstrain curves show that, compared to the strain of sensor A (higher dashed line), the measured strain of sensor B (lower thicker line) is closer to the applied and / or calculated strain (thinner line). This can contribute to more accurate measurements.

[0053] Figure 3 A comparison between two different locations of a sensor in a strand having 6+1 steel strand elements is shown. The first sensor A (dashed line) is the middle strand element and optical fiber, preferably a fiber Bragg grating sensor according to the invention, which is mechanically interlocked. The second sensor B (thick line) is the outer strand element, which is the sensor and optical fiber, preferably a fiber Bragg grating sensor, fixed to at least one of the other strand elements by adhesive. The ratio of the sensor diameter to the diameter of the outer strand element with the smallest diameter is thus <0.180, i.e., 0.173 in both cases, and all other parameters are the same.

[0054] The graphs of the measured and thus recorded force / microstrain curves show that the strain measured by sensor A (higher dashed line) is more reliable than that measured by sensor B (lower thicker line) because, if any, it slightly overestimates the strain compared to the applied and / or calculated strain (thin line), while sensor B, on the other hand, may underestimate the strain. This can contribute to more reliable measurements.

[0055] Figure 4 A schematic representation of a strand having 6+1 steel strand elements (C) and two different positions of the sensor is shown. The first sensor A is the intermediate strand element according to the invention. The second sensor B is a sensor serving as an outer strand element. The intermediate strand element as sensor A can thus be mechanically interlocked to at least one of the other strand elements, and / or the mechanical interlock is used to fix the sensor as the intermediate strand element to at least three of the other strand elements and / or between at least three of the other strand elements. On the other hand, the outer strand element as the sensor can be fixed to at least one of the other strand elements with adhesive.

Claims

1. A strand for applying stress to concrete, said strand having a diameter ranging from 1 mm to 100 mm and a tensile strength exceeding 1500 MPa. The strand comprises at least three strand elements, including at least one central strand element, at least one intermediate strand element, and at least one outer strand element. At least one other strand element is a sensor, and the sensor is an intermediate strand element.

2. The strand according to claim 1, The strands described herein have a tensile strength of more than 500 MPa, preferably more than 1800 MPa, preferably more than 1900 MPa, preferably more than 2000 MPa, and more preferably between 1800 MPa and 4000 MPa.

3. The strand according to claim 1 or 2, The strands described herein have a maximum breaking load of more than 190 kN, preferably more than 195 kN, preferably more than 200 kN, preferably more than 220 kN, more preferably between 192 kN and 600 kN, more preferably between 195 kN and 350 kN, and more preferably between 200 kN and 10000 kN.

4. The strand according to any one of the preceding claims, The strands include non-steel strand elements, and / or the strands include steel strand elements and / or most steel strand elements and / or most non-steel strand elements, and / or the strands do not include Z-shaped wires and / or wires with high vanadium content.

5. The strand according to any one of the preceding claims, The strands comprise 2, 3, 7, 3×1+6, 1+6+12, or 7×7 strand elements, particularly steel strand elements and / or non-steel strand elements, and / or the diameter of the steel strand elements is between 2 mm and 10 mm, preferably between 3 mm and 7 mm, and / or the diameter of the sensor serving as a strand element is between 0.8 mm and 1.5 mm, preferably >0.9 mm and <1.3 mm, and / or the ratio of the sensor diameter to the diameter of the outer strand element with the smallest diameter is >0.180, preferably >0.185, further preferably >0.190, even further preferably <0.250, and / or between >0.180 and <0.250, and / or the diameter of the inner strand element is more than 3% larger than the diameter of the smallest outer strand element, and / or more than 3% larger than the diameter of each of the outer strand elements.

6. The one according to any one of the preceding claims, Wherein n-1, n-2, n-3, or n-4 strand elements are steel filaments or steel cords and / or non-steel filaments, where n is the total number of strand elements, and / or wherein the central strand element and the outer strand element can be steel strand elements.

7. The strand according to any one of the preceding claims, The outer strand element is helical, and / or the central strand element is straight.

8. The strand according to any one of the preceding claims, The sensor is selected from: optical sensor, conductivity sensor, optical fiber, glass fiber, coaxial cable, copper or copper alloy wire, and / or the sensor is a strain sensor and / or a temperature sensor, and / or the sensor is configured to compensate for strain measurement based on temperature data, and / or one of the sensors measures both strain and temperature, or two different sensors measure temperature on one hand and strain on the other hand, and / or the sensor is a fiber Bragg grating sensor or optical fiber.

9. The strand according to any one of the preceding claims, The sensor described therein is either straight or spiral-shaped.

10. The strand according to any one of the preceding claims, The sensor is coated with at least one polymer or includes at least one polymer sheath, and / or the material selected for the polymer coating and / or polymer sheath comprises or is composed of at least one of the following: PVC, glass fiber reinforced polymer, polyester, polyimide, PE, PP, thermoplastic elastomer, thermoplastic polyester elastomer, or HDE, and / or the sensor is externally coated with polyester, polyimide, or glass fiber reinforced polymer, and / or the sensor is externally coated with PVC, polyethylene (PE), high-density polyethylene (HDPE), polypropylene (PP), thermoplastic elastomer, or thermoplastic polyester elastomer, and / or the sensor is capable of being externally coated with a polymer material having a Vickers hardness between 1HV0.01 and 10HV0.01, preferably between 2HV0.01 and 8HV0.01, more preferably between 3HV0.01 and 7HV0.01, and even more preferably between >3.5HV0.01 and <6.5HV0.

01.

11. The strand according to any one of the preceding claims, At least two other strand elements are sensors and / or both sensors are intermediate strand elements, the two sensors preferably located on opposite sides of the strands and / or adjacent to each other, more preferably formed at an angle between 100° and 200° and / or at an angle between 10° and 90°.

12. The strand according to any one of the preceding claims, The intermediate strand element serving as a sensor can be fixed to at least one of the other strand elements by adhesive and / or by a softening polymer coating or polymer sheath, and / or at least some, preferably all, of the central strand element, intermediate strand element, and outer strand elements are preferably fixed to each other by adhesive and / or by a softening polymer coating or polymer sheath, and / or the intermediate strand element serving as a sensor is fixed to at least one of the other strand elements by adhesive and / or by a softening polymer coating or polymer sheath and / or by mechanical interlocking, and / or the mechanical interlocking is used to fix the sensor serving as an intermediate strand element to at least three of the other strand elements and / or fix it between at least three of the other strand elements.

13. A method for producing strands according to any one of claims 1 to 12, wherein the method comprises: - Use the stock line opener to open the stock lines. - The sensor, as a strand element, is supplied using a feeder suitable for free and smooth rotation around the strand. - Use a strand closure device to close the strand. And / or the supply and introduction of the sensor are synchronized with the direction in which the strands are twisted and the distance traveled by which a strand is twisted 360°.

14. A rope for applying stress to concrete, The rope comprises two or more strands as described in claims 1 to 12.

15. A measurement method, in During the pouring of concrete structures, and / or During the curing of concrete structures, and / or During the service life of a concrete structure, the strands according to claims 1 to 12 or the rope according to claim 14 are used to measure at least one parameter selected from: force and / or strain and / or displacement and / or temperature; and / or The measurements are performed either continuously along the length of the sensor or at discrete intervals along the length of the sensor.

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