Method for testing strain of steel strand

Abstract

The invention provides a steel strand strain test method, which comprises the following steps that an optical fiber sensor is packaged in a central wire of a steel strand, and the two ends of the optical fiber sensor exceed the steel strand; pouring concrete outside the steel strand to form a concrete test piece; the concrete test piece is fixed to a fixing frame, the steel strand in the concrete test piece is connected with a stretching assembly, and the two ends of the optical fiber sensor are connected with a data collecting and analyzing device; the stretching assembly exerts pulling force on the steel strand, and the data collecting and analyzing device collects data of the optical fiber sensor and calculates the strain of the steel strand.

Description

Technical Field

[0001] The present application relates to the field of testing methods, and in particular to a testing method for strain of steel strands. Background Art

[0002] In traditional steel strand strain measurement, most of the methods are to grind the steel strands flat and coat the surface of the steel strands with epoxy resin, and then attach strain gauges around the steel strands for measurement. However, ordinary strain gauges will age in a humid and corrosive environment, which is not conducive to long-term monitoring. In addition, there is still a lack of convenient and quick devices for measuring the strain of steel strands in steel strands and concrete components.

[0003] The traditional steel strand pull-out test uses a reaction frame and a jack supporting device to pull the steel strand in the concrete to a certain displacement to obtain relevant data. At the same time, strain gauges need to be attached to the concrete surface to measure the concrete strain. This method of measuring strain is relatively traditional and cannot directly measure the strain of the steel strand. Summary of the invention

[0004] The purpose of the present application is to provide a test method for steel strand strain, which can be used for long-term direct measurement of the strain of steel strand.

[0005] The embodiment of the present application is implemented as follows:

[0006] In a first aspect, an embodiment of the present application provides a method for testing strain of a steel strand, comprising the following steps:

[0007] An optical fiber sensor is encapsulated in the central wire of the steel strand, and both ends of the optical fiber sensor extend beyond the steel strand;

[0008] pouring concrete outside the steel strand to form a concrete test piece;

[0009] The concrete specimen is fixed on a fixing frame, the steel strand in the concrete specimen is connected to a tensile assembly, and both ends of the optical fiber sensor are connected to a data acquisition and analysis device;

[0010] The tensile assembly applies tension to the steel strand, and the data acquisition and analysis device acquires data from the optical fiber sensor and calculates the strain of the steel strand.

[0011] In the above technical solution, the optical fiber sensor can be used to detect the deformation, and has the advantages of being not afraid of harsh environments, not being disturbed by environmental noise, and being resistant to electromagnetic interference. By encapsulating the optical fiber sensor in the central wire of the steel strand, the optical fiber sensor can be used for a long time to detect the deformation of the steel strand. Using the above test method, after the steel strand is cast in concrete to form a concrete specimen, and the two ends of the optical fiber sensor are connected to the data acquisition and analysis device, in the process of applying tension to the steel strand using the tensile component, the deformation of the steel strand will cause the signal fed back to the data acquisition and analysis device by the optical fiber sensor to change. The data acquisition and analysis device can calculate the strain of the steel strand through the signal fed back by the optical fiber sensor.

[0012] In some optional embodiments, the step of encapsulating the optical fiber sensor in the central wire of the steel strand comprises:

[0013] A through groove penetrating through both ends is arranged at the center wire of the steel strand, the optical fiber sensor is arranged in the through groove, and an adhesive is filled in the through groove and cured to encapsulate the optical fiber sensor in the through groove.

[0014] In the above technical solution, the through groove runs through both ends of the center wire, and the optical fiber sensor is arranged in the through groove. On the one hand, it can protect the optical fiber sensor, and on the other hand, it can extend the optical fiber sensor along the length direction of the center wire, thereby more accurately detecting the strain in the length direction of the steel strand after being subjected to tension. By filling the through groove with adhesive and curing it, the optical fiber sensor can be fixedly connected to the center wire as a whole, so as to better detect the strain of the center wire.

[0015] In some optional embodiments, the diameter of the central wire is in the range of 4 mm to 6 mm, the groove depth of the through groove is in the range of 2 mm to 3 mm, and the groove width is in the range of 2 mm to 3 mm.

[0016] In the above technical solution, the dimensions of the center wire and the through groove are within the above range, so that the through groove can be smaller in size while being able to accommodate the optical fiber sensor, thereby having less impact on the strength of the center wire, so that the test results can truly reflect the strain of the steel strand under tension.

[0017] In some optional embodiments, the step of connecting the optical fiber sensor to the data acquisition and analysis device includes: setting a protective cover at the end of the steel strand away from the fixed frame, and one end of the optical fiber sensor extends out of the steel strand and enters the protective cover; setting a jumper wire at the end of the protective cover away from the fixed frame, and connecting one end of the jumper wire to the steel strand and the other end to the data acquisition and analysis device.

[0018] In the above technical solution, since the optical fiber is led out from the end of the central wire, the situation where the optical fiber sensor is damaged at the end of the central wire can be effectively improved by setting a protective cover at the end of the steel strand away from the fixed frame. By setting a jumper at the end of the protective cover away from the fixed frame, the optical fiber sensor can be connected to the data acquisition and analysis device through the jumper, thereby realizing data transmission between the pipeline sensor and the data acquisition and analysis device.

[0019] In some optional embodiments, the concrete specimen is cast with a plurality of the steel strands, and all the optical fiber sensors are connected in series and then connected at both ends to the data acquisition and analysis device.

[0020] In the above technical solution, multiple steel strands are cast in the concrete specimen, and all the optical fiber sensors are connected in series, so that the measured strain includes the strain of the steel strands at multiple positions in the concrete specimen. Therefore, the test results can better reflect the strain that occurs when the steel strands are subjected to tension in the concrete.

[0021] In some optional embodiments, the stretching assembly includes a jack, a pull rod, and a first pad; and the test method includes:

[0022] One end of all the steel strands facing the fixing frame is connected to the first pad, one end of the pull rod is connected to the jack and the other end is connected to the first pad, and then the pull rod is pulled by the jack to apply tension to the steel strands.

[0023] In the above technical solution, by connecting one end of all steel strands to the first pad and then connecting the first pad and the jack through a pull rod, it is convenient to apply tension to multiple steel strands at the same time through a jack, and the tension on each steel strand is relatively uniform.

[0024] In some optional embodiments, the fixing frame includes a first support plate and a second support plate that are arranged opposite to each other, and the first support plate and the second support plate are connected by a support rod; the first support plate is provided with a first through hole, and the second support plate is provided with a second through hole; the jack is connected to the second support plate;

[0025] The test method includes: setting the concrete specimen on the side of the first support plate facing away from the second support plate, setting the jack on the side of the second support plate facing away from the first support plate, setting the first pad between the first support plate and the second support plate, passing the steel strand through the first through hole, passing the pull rod through the second through hole, and then applying tension to the steel strand by the tension assembly.

[0026] The fixing frame used in the above technical solution includes a first support plate and a second support plate that are arranged opposite to each other, and a support rod connecting the first support plate and the second support plate. When conducting the test, the concrete specimen is arranged on the side of the first support plate facing away from the second support plate, and the jack is arranged on the side of the second support plate facing away from the first support plate. Therefore, when the jack applies tension to the steel strand in the concrete specimen, the fixing frame is located between the jack and the concrete specimen, and the first support plate and the second support plate of the fixing frame will not be close to each other, so that after the steel strand is strained under the tension, the first pad can move between the first support plate and the second support plate.

[0027] In some optional embodiments, the fixing frame also includes a support arranged on the side of the first support plate facing away from the second support plate; the test method includes: placing the fixing frame at a position where the first support plate and the second support plate are relatively arranged in a horizontal direction, and then placing the concrete specimen on the support.

[0028] In the above technical solution, a support is provided on the side of the first support plate facing away from the second support plate. Then, during the test, the concrete specimen is placed on the support, which can support the concrete specimen and facilitate the application of horizontal tension to the steel strands in the concrete specimen.

[0029] In some optional embodiments, the data acquisition and analysis device includes a fiber optic moderator and a computer; the test method includes: connecting both ends of the fiber optic sensor to the fiber optic moderator, and then connecting the fiber optic moderator to the computer, the fiber optic moderator receiving and processing the signal from the fiber optic sensor, and then transmitting the processed signal to the computer to calculate the strain of the steel strand.

[0030] In the above technical solution, the signal from the optical fiber sensor can be processed by the optical fiber moderator, and a signal that can be processed by the computer can be obtained. The processed signal is then transmitted to the computer, and the computer calculates the strain of the steel strand. The strain of the steel strand can be automatically calculated, and the data processing process is more efficient and accurate.

[0031] In some optional embodiments, the data acquisition and analysis device includes a displacement meter and a pressure sensor, and the test method includes: setting the displacement meter at the end of the steel strand away from the tensile assembly to detect the displacement of the steel strand under the action of the tensile assembly; setting the pressure sensor at the end of the steel strand away from the tensile assembly to detect the tension applied to the steel strand.

[0032] In the above technical solution, during the test, a displacement meter is set at the end of the steel strand away from the tensile assembly, and the displacement between the steel strand and the concrete can be measured by the displacement meter to study the bonding performance between the steel strand and the concrete specimen. By setting a pressure sensor at the end of the steel strand away from the tensile assembly, the pull-out force on the steel strand can be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic diagram of a device used in the test method provided in the embodiments of the present application;

[0035] Figure 2 A schematic diagram of a tensile assembly and a concrete specimen installation and fixing frame provided in an embodiment of the present application;

[0036] Figure 3 Schematic diagram of the steel strand used in the test of this application;

[0037] Figure 4 is a schematic diagram of a central wire provided with an optical fiber sensor;

[0038] Figure 5 A cross-sectional view of a steel strand having a fiber optic sensor disposed on the center wire;

[0039] Figure 6 A schematic diagram of a fixing frame provided in an embodiment of the present application;

[0040] Figure 7 A schematic diagram of a pull rod provided in an embodiment of the present application connected to a first pad.

[0041] Icons: 101-jack; 102-pull rod; 103-second pad; 104-first pad; 105-fixed frame; 106-support; 107-first anchor; 108-first level; 110-protective cover; 111-third anchor; 112-second anchor; 113-second level; 114-displacement meter; 115-pressure sensor; 116-first support plate; 117-second support plate; 118-support rod; 201-fiber optic regulator; 202-computer; 301-concrete specimen; 401-first steel strand; 402-second steel strand; 403-third steel strand; 404-fourth steel strand; 501-center wire; 502-fiber optic sensor; 601-jumper. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0044] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0045] In the description of this application, it should be noted that the terms "center", "upper", "lower", "vertical", "horizontal", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the application is usually placed when in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0046] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0047] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0048] The present application provides a method for testing the strain of a steel strand. The equipment used is as follows: Figure 1 and Figure 2 As shown, it includes a concrete specimen 301, in which a steel strand is arranged, and a central wire 501 of the steel strand is encapsulated with an optical fiber sensor 502; it also includes a tensile component for applying tension, and a fixing frame 105 for mounting the concrete specimen 301 and the tensile component; it also includes a data acquisition and analysis device connected to the signal of the optical fiber sensor 502.

[0049] The steps of the test method provided in this application include:

[0050] S1: Encapsulate the optical fiber sensor 502 in the center wire 501 of the steel strand, and the two ends of the optical fiber sensor 502 extend beyond the steel strand. By encapsulating the optical fiber sensor 502 in the center wire 501, the signal fed back by the optical fiber sensor 502 can change with the strain generated by the center wire 501, thereby achieving the effect of detecting the strain of the steel strand. The two ends of the optical fiber sensor 502 extend beyond the steel strand, so that the steel strand can be more conveniently connected to the data acquisition device.

[0051] S2: pouring concrete outside the steel strand to form a concrete specimen 301.

[0052] S3: The concrete specimen 301 is fixed to the fixing frame 105, and then the steel strand in the concrete specimen 301 is connected to the tensile assembly, and the two ends of the optical fiber sensor 502 are connected to the data acquisition and analysis device. The concrete specimen 301 can be fixed to the fixing frame 105 first, and then the two ends of the optical fiber sensor 502 are connected to the data acquisition and analysis device; or the two ends of the optical fiber sensor 502 are connected to the data acquisition device first, and then the concrete specimen 301 is fixed to the fixing frame 105.

[0053] S4: Apply tension to the steel strands through the stretching assembly, collect data from the optical fiber sensor 502 through the data acquisition and analysis device, and calculate the strain of the steel strands.

[0054] In the test method provided in the present application, the optical fiber sensor 502 has the advantages of small size, no fear of harsh environment, no interference from environmental noise, anti-electromagnetic interference, integration of sensing and transmission, simple structure, and easy use, and also has the advantages of being able to perform high-precision absolute measurement and quasi-distributed digital measurement of the strain of the structure. Compared with other traditional monitoring methods (such as monitoring using magnetic flux sensors and pressure gauge sensors), the optical fiber sensor 502 is small in size and can be well coupled to the inside of the steel strand, realizing real-time monitoring of the steel strand that other sensors cannot achieve.

[0055] When the tensile component is used to apply tension to the steel strand, the deformation of the steel strand will cause the signal fed back by the optical fiber sensor 502 to the data acquisition and analysis device to change. The data acquisition and analysis device can calculate the strain of the steel strand through the signal fed back by the optical fiber sensor 502.

[0056] The optical fiber sensor 502 is encapsulated into the central wire 501 of the steel strand to measure the strain of the steel strand. The theoretical analysis method is as follows:

[0057] The optical fiber sensor 502 is encapsulated into the center wire 501 of the steel strand, and will deform as the stress of the steel strand changes. After the optical fiber sensor 502 is installed, pulse light is injected into the optical fiber sensor 502. When the optical signal is transmitted inside the optical fiber sensor 502, the optical fiber sensor 502 can generate scattered light inside the optical fiber sensor 502 according to the strain of the object being measured. The optical fiber sensor 502 transmits the scattered light back to the transmitting end for analysis. The device characterizes the reflected light with the change in the optical fiber frequency shift, and the size of the frequency shift change reflects the strain inside the structure. Therefore, the optical fiber sensor 502 can be used to detect the strain of the steel strand.

[0058] Further, in some embodiments, the step of encapsulating the optical fiber sensor 502 in the center wire 501 of the steel strand includes: setting a through groove running through both ends at the center wire 501 of the steel strand, setting the optical fiber sensor 502 in the through groove, filling the through groove with an adhesive and curing it to encapsulate the optical fiber sensor 502 in the through groove. Among them, the adhesive can be selected from epoxy resin, or other existing adhesives can be used. Further, the diameter of the center wire 501 is in the range of 4mm to 6mm, specifically 4mm, 5mm or 6mm, the groove depth of the through groove is in the range of 2mm to 3mm, specifically 2mm, 2.5mm or 3mm, and the groove width of the through groove is in the range of 2mm to 3mm, specifically 2mm, 2.5mm or 3mm. The center wire 501 and the through groove within this range can not only better accommodate the optical fiber sensor 502, but also will not cause a significant impact on the strength of the steel strand after the through groove is set.

[0059] For example, in one embodiment, Figures 3 to 5 As shown in FIG. 1 , the specific process of encapsulating the optical fiber sensor 502 into the center wire 501 includes: mechanically breaking up the steel strand, taking out the center wire 501, and then setting a through groove with a depth of 1.2 mm and a width of 1 mm in the longitudinal direction on the surface of the center wire 501. After wiping the through groove and the optical fiber sensor 502 clean with alcohol, the optical fiber sensor 502 is pasted into the through groove with a polymer adhesive while the center wire 501 is under load, and then epoxy resin is injected into the through groove and cured, and then the center wire 501 encapsulating the optical fiber sensor 502 is twisted with the side wires to form a steel strand with the optical fiber sensor 502.

[0060] Further, in some embodiments, the step of connecting the optical fiber sensor 502 to the data acquisition and analysis device includes: setting a protective cover 110 at the end of the steel strand away from the fixed frame 105, and one end of the optical fiber sensor 502 extends out of the steel strand and enters the protective cover 110; setting a jumper 601 at the end of the protective cover 110 away from the fixed frame 105, and connecting one end of the jumper 601 to the steel strand and the other end to the data acquisition and analysis device. In this embodiment, the optical fiber sensor 502 is led out from the end of the steel strand. In order to prevent the part of the end optical fiber sensor 502 extending out of the steel strand from being damaged, the protective cover 110 is used to encapsulate the end to protect the optical fiber sensor 502. The protective cover 110 is connected to the jumper 601 so that the optical fiber sensor 502 can be connected to the data acquisition and analysis device through the jumper 601. Among them, the protective cover 110 can be a steel pipe or other structural parts made of other materials.

[0061] Further, in some embodiments, the concrete specimen 301 is cast with multiple steel strands, and all the optical fiber sensors 502 are connected in series and then connected to a data acquisition and analysis device at both ends. Figure 1 As shown, four steel strands are cast in the concrete specimen 301, which are respectively recorded as the first steel strand 401, the second steel strand 402, the third steel strand 403 and the fourth steel strand 404. In this embodiment, the measured strain includes the strain of the steel strands at multiple positions in the concrete specimen 301. Therefore, the test results can better reflect the strain of the steel strands after being subjected to tension in the concrete, and further the bonding performance between the multiple steel strands and the concrete specimen 301 can be studied.

[0062] Further, in some embodiments, when performing the test method provided in the present application, the tension assembly used may include a jack 101, a pull rod 102, and a first pad 104. The corresponding test method includes: connecting one end of all steel strands facing the fixing frame 105 to the first pad 104, such as Figure 1 and Figure 7 As shown, one end of the pull rod 102 is connected to the jack 101 and the other end is connected to the first pad 104, and then the pull rod 102 is pulled by the jack 101 to apply tension to the steel strand. By connecting one end of all steel strands to the first pad 104, and then connecting the first pad 104 and the jack 101 by the pull rod 102, it is convenient to apply tension to multiple steel strands at the same time by one jack 101, and the tension on each steel strand is relatively uniform. Among them, the method of connecting the steel strand to the first pad 104 can be to anchor the steel strand on the first pad 104 by the first anchor 107 and the second anchor 112.

[0063] Of course, in other implementations, a jack 101 for applying tension may be provided corresponding to each steel strand.

[0064] In some embodiments, Figure 2 and Figure 6 As shown, when the test method provided in the present application is performed, the fixing frame 105 used includes a first support plate 116 and a second support plate 117. The first support plate 116 and the second support plate 117 are connected by a support rod 118; the first support plate 116 is provided with a first through hole, and the second support plate 117 is provided with a second through hole; the jack 101 is connected to the second support plate 117. The corresponding test method includes: setting the concrete specimen 301 on the side of the first support plate 116 facing away from the second support plate 117, setting the jack 101 on the side of the second support plate 117 facing away from the first support plate 116, setting the first pad 104 between the first support plate 116 and the second support plate 117, and passing the steel strand through the first through hole, passing the pull rod 102 through the second through hole, and then applying tension to the steel strand by the tension assembly. Further, one end of the pull rod 102 is anchored to the first pad 104 by an anchor.

[0065] Further, if Figure 1 As shown, a second pad 103 is further provided on the side of the jack 101 away from the fixing frame 105 , and one end of the pull rod 102 passes through the jack 101 and is anchored to the second pad 103 through a third anchor 111 .

[0066] Further, in some embodiments, the fixing frame 105 further includes a support 106 disposed on the side of the first support plate 116 facing away from the second support plate 117; the test method includes: placing the fixing frame 105 at a position where the first support plate 116 and the second support plate 117 are relatively disposed in a horizontal direction, and then placing the concrete specimen 301 on the support 106. By placing the concrete specimen 301 on the support 106, the concrete specimen 301 can be supported, thereby facilitating the application of horizontal tension to the steel strands in the concrete specimen 301. Further, whether the concrete specimen 301 is in horizontal contact with the tooling can be detected by placing the first level 108 on the first support plate 116 and the second level 113 on the first pad 104.

[0067] In some embodiments, the data acquisition and analysis device includes an optical fiber regulator 201 and a computer 202. The two ends of the optical fiber sensor 502 are connected to the optical fiber regulator 201. Specifically, the two ends of the optical fiber sensor 502 can be connected to the optical fiber regulator 201 through a jumper 601. The optical fiber regulator can process the signal from the optical fiber sensor 502 and obtain a signal that can be processed by the computer 202, and then transmit the processed signal to the computer 202, and the computer 202 calculates the strain of the steel strand. The corresponding test method includes: connecting the two ends of the optical fiber sensor 502 to the optical fiber regulator 201, and then connecting the optical fiber regulator 201 to the computer 202, and the optical fiber regulator 201 receives and processes the signal of the optical fiber sensor 502, and then transmits the processed signal to the computer 202 to calculate the strain of the steel strand.

[0068] Further, in some embodiments, Figure 1 As shown, the data acquisition and analysis device may also include a displacement meter 114 and a pressure sensor 115. The test method includes: setting the displacement meter 114 at the end of the steel strand away from the tensile assembly to detect the displacement of the steel strand under the action of the tensile assembly; setting the pressure sensor 115 at the end of the steel strand away from the tensile assembly to detect the tension exerted on the steel strand. During the test, the displacement meter 114 is set at the end of the steel strand away from the tensile assembly, and the displacement between the steel strand and the concrete can be measured by the displacement meter 114, which can be used to study the bonding performance between the steel strand and the concrete specimen 301. By setting the pressure sensor 115 at the end of the steel strand away from the tensile assembly, the pull-out force exerted on the steel strand can be measured.

[0069] Example 1

[0070] Please refer to Figure 1 The steel strand strain test method provided in one embodiment of the present application includes:

[0071] Step 1: First, mechanically break up the steel strand in the clockwise direction, take out the center wire 501, set a groove with a depth of 1.2mm and a width of 1mm on the surface of the center wire 501 in the longitudinal direction, wipe the groove and the optical fiber sensor 502 with alcohol, and then use a polymer adhesive to stick the optical fiber sensor 502 in the groove while the center wire 501 is under load, and then inject epoxy resin into the groove and solidify it to achieve encapsulation, and then twist the center wire 501 and the side wires that have encapsulated the optical fiber sensor 502 to form a steel strand with an optical fiber sensor 502. The optical fiber sensor 502 is led out at the end. In order to prevent the optical fiber sensor 502 from being damaged at the end of the steel strand, a protective sleeve 110 made of steel pipe is used to encapsulate the end of the steel strand and an external jumper 601 is connected so that the optical fiber sensor 502 can be connected to the optical fiber regulator 201. At this point, a steel strand with an optical fiber sensor 502 is completed.

[0072] Step 2: According to step 1, make another three steel strands with optical fiber sensors 502, put the four steel strands into the prefabricated template, and then cast the concrete specimen 301. After casting, wait until the concrete reaches the strength requirement, then remove the template to obtain the concrete specimen 301 with four steel strands encapsulated with optical fiber sensors 502.

[0073] Step 3: After the concrete specimen 301 is made, you can prepare for the steel hinge wire pull-out test. Find a test site, such as Figure 1 As shown, the fixing frame 105 is placed horizontally, and two supports 106 are set on the right side of the first support plate 116 of the fixing frame 105. Then the concrete specimen 301 is placed on the support 106, and the steel strand in the concrete specimen 301 is passed through the first through hole, and then the first anchor 107 is used to anchor one end of the steel strand to the first pad 104, so as to achieve the function of fixing the steel strand. Then the jack 101 and the second pad 103 are placed horizontally, and then the pull rod 102 is passed through the second pad 103, the jack 101 and the first pad 104 in sequence, and one end of the pull rod 102 is anchored to the first pad 104 by the second anchor 112, and the other end of the pull rod 102 is anchored to the second pad 103 by the third anchor 111.

[0074] Step 4: After the concrete specimen 301, the fixing frame 105 and the jack 101 are fixed, a level is placed on the first pad 104 and the first support plate 116 to detect whether the concrete specimen 301 is in horizontal contact with the fixing frame 105. If the bubble in the level is not in the center, a thin steel sheet can be added between the concrete specimen 301 and the first support plate 116 to achieve the purpose of leveling.

[0075] Step 5: At the end of the steel strand away from the jack 101, that is, Figure 1 The right ends of the steel strands are respectively installed with displacement meters 114 and pressure sensors 115, so as to measure the pull-out force on the steel strands and the relative displacement between the steel strands and the concrete specimen 301. In order to achieve the purpose of measuring the strain of multiple steel strands, the optical fiber sensors 502 in the four steel strands are connected in series through an optical fiber coupler, and then the jumpers 601 of the two steel strands at the right end are respectively connected to the input and output devices of the optical fiber demodulator, and the optical fiber demodulator is connected to the computer 202. After the equipment adjustment is completed, the oil pump of the jack 101 is started, and the pull-out test of the steel strand can be carried out, and the strain, displacement and pull-out force of the steel strand are respectively recorded at the computer 202 to complete the data required for the test measurement.

[0076] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A test method for steel strand strain, characterized in that: The steps include: An optical fiber sensor is encapsulated in the central wire of the steel strand, and both ends of the optical fiber sensor extend beyond the steel strand; pouring concrete outside the steel strand to form a concrete test piece; Fixing the concrete specimen on a fixing frame, connecting the steel strand in the concrete specimen to a tensile assembly, and connecting both ends of the optical fiber sensor to a data acquisition and analysis device; The tensile assembly applies tension to the steel strand, and the data acquisition and analysis device acquires data from the optical fiber sensor and calculates the strain of the steel strand.

2. The test method according to claim 1, characterized in that The steps of encapsulating the optical fiber sensor in the central wire of the steel strand include: A through groove penetrating through both ends is arranged at the center wire of the steel strand, the optical fiber sensor is arranged in the through groove, and an adhesive is filled in the through groove and cured to encapsulate the optical fiber sensor in the through groove.

3. The test method according to claim 2, characterized in that The diameter of the central wire is in the range of 4mm to 6mm, the groove depth of the through groove is in the range of 2mm to 3mm, and the groove width is in the range of 2mm to 3mm.

4. The test method according to claim 1, characterized in that: The steps of connecting the optical fiber sensor to the data acquisition and analysis device include: setting a protective cover at the end of the steel strand away from the fixed frame, and one end of the optical fiber sensor extends out of the steel strand and enters the protective cover; setting a jumper at the end of the protective cover away from the fixed frame, and connecting one end of the jumper to the steel strand and the other end to the data acquisition and analysis device.

5. The test method according to claim 1, characterized in that: The concrete specimen is cast with a plurality of the steel strands, and both ends of all the optical fiber sensors are connected in series and connected to the data acquisition and analysis device.

6. The test method according to claim 5, characterized in that The stretching assembly includes a jack, a pull rod and a first pad; the test method includes: One end of all the steel strands facing the fixing frame is connected to the first pad, one end of the pull rod is connected to the jack and the other end is connected to the first pad, and then the pull rod is pulled by the jack to apply tension to the steel strands.

7. The test method according to claim 6, characterized in that: The fixing frame comprises a first supporting plate and a second supporting plate which are arranged opposite to each other, and the first supporting plate and the second supporting plate are connected by a support rod; the first supporting plate is provided with a first through hole, and the second supporting plate is provided with a second through hole; the jack is connected to the second supporting plate; The test method includes: setting the concrete specimen on the side of the first support plate facing away from the second support plate, setting the jack on the side of the second support plate facing away from the first support plate, setting the first pad between the first support plate and the second support plate, passing the steel strand through the first through hole, passing the pull rod through the second through hole, and then applying tension to the steel strand by the tension assembly.

8. The test method according to claim 7, characterized in that: The fixing frame also includes a support arranged on the side of the first support plate facing away from the second support plate; the test method includes: placing the fixing frame at a position where the first support plate and the second support plate are relatively arranged in a horizontal direction, and then placing the concrete specimen on the support.

9. The test method according to any one of claims 1 to 8, characterized in that: The data acquisition and analysis device includes a fiber optic regulator and a computer; the test method includes: connecting the two ends of the fiber optic sensor to the fiber optic regulator, and then connecting the fiber optic regulator to the computer, the fiber optic regulator receiving the signal of the fiber optic sensor and processing it, and then transmitting the processed signal to the computer to calculate the strain of the steel strand.

10. The test method according to claim 9, characterized in that: The data acquisition and analysis device includes a displacement meter and a pressure sensor, and the test method includes: setting the displacement meter at the end of the steel strand away from the tensile assembly to detect the displacement of the steel strand under the action of the tensile assembly; setting the pressure sensor at the end of the steel strand away from the tensile assembly to detect the tension applied to the steel strand.

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