Friction loss testing device based on electromagnetic elastic absolute stress sensor

Abstract

The utility model discloses a friction loss testing device based on an electromagnetic elastic type absolute stress sensor, which comprises a prestressed steel beam, a prestressed test beam, an electromagnetic elastic type absolute stress sensor and a magnetoelastic cable force demodulation device, the electromagnetic elastic type absolute stress sensors are fixedly arranged outside the prestressed pipeline, at least one set of electromagnetic elastic type absolute stress sensors are arranged at the first end of the prestressed pipeline, at the second end of the prestressed pipeline and between the two ends of the prestressed pipeline, and the multiple sets of electromagnetic elastic type absolute stress sensors are used for conducting multi-point-position prestress detection on the prestressed steel beam. The comprehensiveness and the fineness of prestress data acquisition can be improved; the electromagnetic elastic type absolute stress sensor is fixed outside the prestressed pipeline and is not in contact with the steel beam, when the prestressed steel beam is tensioned or grouted, the electromagnetic elastic type absolute stress sensor cannot be additionally pressed and damaged, meanwhile, a grouting material and a beam body pouring material cannot affect the sensor, and the detection precision can be ensured.

Description

Technical Field

[0001] This utility model belongs to the field of measurement and relates to friction loss testing technology, and in particular to a friction loss testing device based on an electromagnetic spring-type absolute stress sensor that can be used in bridge engineering. Background Technology

[0002] In building construction, such as bridge engineering, prestressing friction loss is one of the main components of prestress loss in post-tensioned prestressed concrete beams. Its appropriate value not only affects the deformation of prestressed concrete members but also the durability and load-bearing capacity of the structure. Furthermore, insufficient estimation of prestress loss can lead to a lower actual compressive stress reserve in the concrete, which is one of the main causes of web cracking and mid-span deflection in large-span prestressed concrete continuous box girders.

[0003] Traditional methods for calculating prestressed friction loss in engineering mainly refer to relevant bridge design specifications. Although these specifications provide some suggested ranges, prestressed friction loss is also related to material properties, the type of prestressed steel strands, and the type of anchorage. Construction quality, tensioning process, and environment are also factors that closely affect prestressed friction loss. In actual engineering projects, prestressed ducts made of different materials have significantly different friction coefficients, making it difficult to accurately calculate prestressed friction loss.

[0004] The inventor is aware of a method for detecting friction loss, namely the resistance strain gauge method. Although this method can improve the accuracy of prestressed friction loss calculation to a certain extent, it still has shortcomings: (1) The resistance strain gauge is fixed on the prestressed steel strand. When the prestressed steel strand bends in the pipe, it will squeeze the resistance strain gauge. Not only will the measurement data be inaccurate, but it may even damage the resistance strain gauge, resulting in a large error in the friction loss calculation; (2) The resistance strain gauge is generally only fixed to the anchoring end and tensioning end of the prestressed steel strand. It cannot simulate the stress condition of the prestressed steel strand under real working conditions. The measurement data lacks representativeness and has poor accuracy. Utility Model Content

[0005] The purpose of this invention is to provide a friction loss testing device based on an electromagnetic spring-type absolute stress sensor, which can simulate the real friction conditions of prestressed steel strands in building engineering. At the same time, it adopts a multi-point in-situ measurement method, which can collect data in detail and calculate friction loss with high accuracy. It can solve the problems of inaccurate measurement data and large friction loss calculation error in the traditional friction loss detection technology.

[0006] To achieve the above objectives, this utility model provides the following solution:

[0007] This utility model provides a friction loss testing device based on an electromagnetic spring-type absolute stress sensor, comprising:

[0008] Prestressed steel strands;

[0009] A prestressed test beam, which has a prestressed duct through which the prestressed steel strands pass;

[0010] An electromagnetic spring-type absolute stress sensor is fixedly installed outside the prestressed duct, and at least one set of the electromagnetic spring-type absolute stress sensor is installed at the first end, the second end, and between the two ends of the prestressed duct, so that when the prestressed steel strand is in the tensioning stage, the prestressed steel strand can be detected at multiple points by multiple sets of the electromagnetic spring-type absolute stress sensor.

[0011] The magnetoelastic force demodulation device is communicatively connected to all of the aforementioned electromagnetic spring-type absolute stress sensors.

[0012] In some embodiments, at least one corner is provided between the two ends of the prestressed duct, and at least one set of electromagnetic spring-type absolute stress sensors is provided on both sides of any one of the corners.

[0013] In some embodiments, at least one set of electromagnetic spring-type absolute stress sensors is provided at any of the corners of the prestressed duct.

[0014] In some embodiments, the prestressed ducts are arranged symmetrically along their length within the prestressed test beam.

[0015] In some embodiments, the first and second ends of the prestressed duct are both straight segments, and at least three corners are provided between the first and second ends of the prestressed duct, and any one of the corners is a rounded corner.

[0016] In some implementations, any two adjacent corners are connected by a straight line segment.

[0017] In some embodiments, tensioning devices are provided at both ends of the prestressed duct, and the tensioning devices are used to tension the prestressed steel strands at both ends; or, the tensioning device is provided at one end of the prestressed duct and the anchoring device is provided at the other end, the anchoring device is used to anchor one end of the prestressed steel strand and the tensioning device is used to tension the other end of the prestressed steel strand.

[0018] In some embodiments, the prestressed test beam is integrally cast outside the prestressed duct.

[0019] In some embodiments, the prestressed steel strand is a prestressed steel wire bundle.

[0020] In some embodiments, the magnetoelastic force demodulation device is a magnetoelastic instrument.

[0021] In some embodiments, the magnetoelastic device is communicatively connected to each of the electromagnetic spring-type absolute stress sensors via a data cable.

[0022] The present invention achieves the following technical advantages over the prior art:

[0023] The friction loss testing device based on electromagnetic spring-type absolute stress sensors proposed in this invention features a novel and reasonable structure. By installing at least one set of electromagnetic spring-type absolute stress sensors at the first, second, and both ends of the prestressed duct, in-situ prestress values ​​at multiple locations during the tensioning stage of the prestressed steel strand can be directly obtained. This allows for more refined data acquisition and accurate acquisition of the prestress distribution during the tensioning stage, simulating the actual friction conditions of prestressed steel strands in building engineering, thus improving the accuracy of prestress friction loss calculation. Furthermore, the electromagnetic spring-type absolute stress sensors are installed outside the prestressed duct, avoiding contact with the prestressed steel strands inside. This prevents the prestressed steel strands from squeezing or damaging the sensors during the tensioning or grouting stages. Simultaneously, the grouting material and beam casting material do not affect the electromagnetic spring-type absolute stress sensors during grouting or casting, ensuring the accuracy of the measurement data and improving the accuracy of prestress friction loss calculation. Compared to existing technologies, this effectively reduces experimental errors and significantly improves the accuracy of friction loss calculation.

[0024] This invention employs a method of detecting the absolute stress distribution of prestressed steel strands by installing electromagnetic spring-type absolute stress sensors at multiple points on the prestressed duct. This method can obtain accurate prestress distribution during the prestressing stage of the prestressed steel strands. It can not only meet the high-precision friction testing requirements of short-span prestressed test beams, but also be applicable to the friction testing requirements of large-span prestressed test beams. It solves the problem that commonly used prestressed friction loss calculation methods in engineering have inaccurate friction coefficients and insufficient accuracy in calculating friction loss for large-span prestressed beams. It has broad application prospects in bridge engineering and other fields. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is an overall schematic diagram of a friction loss testing device based on an electromagnetic spring-type absolute stress sensor, as shown in one or more embodiments of the present invention.

[0027] In the figure, the attached figures are labeled as follows:

[0028] 100. Friction loss testing device based on electromagnetic elastic absolute stress sensor;

[0029] 1. Prestressed steel strands;

[0030] 2. Prestressed test beam;

[0031] 3. Prestressed duct; 31. First end; 32. Second end; 33. Corner;

[0032] 4. Electromagnetic spring-type absolute stress sensor;

[0033] 5. Magnetic elastic force demodulation equipment;

[0034] 6. Data cable. Detailed Implementation

[0035] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0036] The purpose of this invention is to provide a friction loss testing device based on an electromagnetic spring-type absolute stress sensor, which can simulate the real friction conditions of prestressed steel strands in building engineering. At the same time, it adopts a multi-point in-situ measurement method, which can collect data in detail and calculate friction loss with high accuracy. It can solve the problems of inaccurate measurement data and large friction loss calculation error in traditional friction loss detection technology.

[0037] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] like Figure 1As shown, this embodiment provides a friction loss testing device 100 based on an electromagnetic spring-type absolute stress sensor, which includes a prestressed steel strand 1, a prestressed test beam 2, an electromagnetic spring-type absolute stress sensor 4, and a magnetic spring-type cable force demodulation device 5. A prestressed pipe 3 is formed inside the prestressed test beam 2 for the prestressed steel strand 1 to pass through. The electromagnetic spring-type absolute stress sensor 4 is fixedly installed outside the prestressed pipe 3. At least one set of electromagnetic spring-type absolute stress sensors 4 is installed at the first end 31, the second end 32, and between the two ends (i.e., between the first end 31 and the second end 32) of the prestressed pipe 3. All electromagnetic spring-type absolute stress sensors 4 are arranged along the length extension direction of the prestressed pipe 3 to test the friction loss of the prestressed steel strand 1. During the tensioning stage, multiple sets of electromagnetic spring-type absolute stress sensors 4 are used to perform multi-point prestress detection on the prestressed steel strand 1. Compared with the existing method of only collecting prestress data at both ends of the prestressed steel strand 1, this method improves the comprehensiveness and accuracy of prestress data acquisition. Furthermore, the electromagnetic spring-type absolute stress sensors 4 are fixedly installed outside the prestressing duct 3 and do not contact the prestressed steel strand 1. During the tensioning process of the prestressed steel strand 1, they will not cause additional pressure or damage to the electromagnetic spring-type absolute stress sensors 4. Simultaneously, the grouting material and beam casting material will not affect the electromagnetic spring-type absolute stress sensors during grouting or casting, further improving the prestress detection accuracy of the electromagnetic spring-type absolute stress sensors 4 on the prestressed steel strand 1. The aforementioned magnetic elastic cable force demodulation device 5 is communicatively connected to all electromagnetic spring-type absolute stress sensors 4 to receive and process the detection data from each sensor 4 in a timely manner.

[0039] In some embodiments, a straight section can be used between the two ends of the prestressed duct 3, that is, the entire prestressed duct 3 is a straight pipe structure. However, considering that in real construction projects, such as bridge construction projects, the prestressed duct 3 in the prestressed beam is mostly a curved pipe, in order to increase the simulation realism of the tensioning condition of the prestressed steel strand 1, it is preferable to adopt a curved pipe design for the prestressed duct 3, that is, at least one bend 33 is provided between the first end 31 and the second end 32 of the prestressed duct 3. The bend 33 is the main friction generation area of ​​the prestressed steel strand 1 during the tensioning stage. In order to improve the realism and refinement of the prestress data acquisition of the prestressed steel strand 1, it is preferable to provide at least one set of electromagnetic spring-type absolute stress sensors 4 on both sides before and after any bend 33.

[0040] In some implementations, to further improve the accuracy and precision of the prestress data acquisition for the prestressed steel strand 1, in addition to installing electromagnetic spring-type absolute stress sensors 4 on both sides before and after any corner 33, at least one set of electromagnetic spring-type absolute stress sensors 4 can also be installed on the outside of each corner 33. Generally, the more numerous and denser the electromagnetic spring-type absolute stress sensors 4 are arranged on the prestressed duct 3, the higher the precision of the data acquisition.

[0041] In some embodiments, the prestressed duct 3 is preferably arranged symmetrically in the prestressed test beam 2 along its own length direction to further increase the simulation realism of the tensioning condition of the prestressed steel strand 1.

[0042] In some embodiments, preferably, both the first end 31 and the second end 32 of the prestressed duct 3 are straight sections, and at least three bends 33 are provided between the first end 31 and the second end 32 of the prestressed duct 3, and any one of the bends 33 is a rounded bend 33. For example Figure 1 As shown, the first end 31 and the second end 32 of the prestressed duct 3 are both straight segments, and four corners 33 are provided between the first end 31 and the second end 32, making the entire prestressed duct 3 a symmetrical "U" shape. The number and distribution of corners 33 in the prestressed duct 3 are not limited to... Figure 1 As shown, adjustments can be made adaptively to simulate different prestressed beam conditions according to different test requirements. It should be noted that the above... Figure 1 The prestressed test beam 2 shown can be used as a standalone full-span test beam; alternatively, it can be a portion of a full-span test beam, i.e., the full-span test beam consists of N (N is an integer and not less than 2) sections. Figure 1 The prestressed test beam 2 shown is arranged continuously in a certain pattern, for example, Figure 1 The prestressed test beam 2 shown is a periodic unit structure within the full-span test beam. In summary, Figure 1 The prestressed test beam 2 shown is only a structural example. In practical applications, its length and internal pipe configuration can be flexibly adjusted.

[0043] in addition, Figure 1 The prestressed test beam 2 shown contains a prestressed duct 3, which includes a straight section and four corner curved sections. This can be used to simulate the flat bending condition of the top slab tendons and to study the influence of the turning angle and radius on the duct friction. In addition, other tests can be conducted by adjusting the shape of the prestressed duct 3 within the prestressed test beam 2. For example, the prestressed duct 3 can be used to simulate the bottom slab closure tendons by using a straight section instead of a curve; the prestressed duct 3 can be composed of a straight section and two corner curved sections to simulate the web tendons; and the prestressed duct 3 can be a horizontal duct arranged at the bottom of the beam to simulate stress-balanced tendons.

[0044] In some embodiments, any two adjacent bends 33 of the prestressed duct 3 are connected by straight segments, with straight segments connecting the front and rear sides of each bend 33, and the straight segments being tangent to the ends of adjacent bends 33. The straight segments of the prestressed duct 3 facilitate the fixing of electromagnetic spring-type absolute stress sensors 4. Generally, it is preferred that the electromagnetic spring-type absolute stress sensors 4 be fitted onto the outside of the prestressed duct 3 and reinforced with fixing methods including, but not limited to, adhesive or pipe clamps, thereby enabling in-situ detection of the prestressed duct 3 by each electromagnetic spring-type absolute stress sensor 4. "The electromagnetic spring-type absolute stress sensors 4 are fixedly installed on the outside of the prestressed duct 3" means that the relative positions of the electromagnetic spring-type absolute stress sensors 4 and the prestressed duct 3 are fixed, and the fixing methods include both detachable (e.g., pipe clamp fixing) and non-detachable (e.g., adhesive, welding).

[0045] In some embodiments, tensioning devices may be selectively installed at both ends of the prestressed duct 3. These devices simultaneously tension both ends of the prestressed steel strand 1 to prepare for data acquisition by the electromagnetic spring-type absolute stress sensor 4. Alternatively, a tensioning device may be installed at one end of the prestressed duct 3, and an anchoring device at the other end. The anchoring device anchors one end of the prestressed steel strand 1, while the tensioning device tensions the other end. The specific tensioning method can be flexibly selected according to actual experimental requirements. During tensioning, the tension force of the prestressed steel strand 1 can be controlled by using a hydraulic pressure gauge and the elongation of the steel strand bundle.

[0046] In some embodiments, the prestressed test beam 2 is generally a concrete test beam, preferably cast integrally with the prestressed duct 3. Generally, a prestressed duct 3 of the corresponding shape is prepared first, and an electromagnetic spring-type absolute stress sensor 4 is fixed at the corresponding detection position of the prestressed duct 3. Then, a prestressed test beam 2 of the corresponding material and shape is cast outside the prestressed duct 3.

[0047] In some embodiments, the prestressed steel strand 1 may be a prestressed steel strand bundle.

[0048] In some embodiments, the magnetic elastic force demodulation device 5 can be a magnetic elastic instrument. The magnetic elastic instrument can not only demodulate the output signals of each electromagnetic elastic absolute stress sensor 4, but also acquire signals and output effective prestress measurement values. The magnetic elastic instrument is a conventional finished product, and its specific structural composition and working principle will not be described in detail here.

[0049] In some implementations, the magnetoelastic device can be wirelessly connected to each electromagnetic spring-type absolute stress sensor 4, or it can be wiredly connected to each electromagnetic spring-type absolute stress sensor 4 via a data cable 6.

[0050] The following is a detailed explanation of the testing process and principle of the friction loss testing device 100 based on the electromagnetic elastic absolute stress sensor described in this scheme:

[0051] like Figure 1 As shown, this is a tensioning configuration where one end of the prestressed steel strand 1 is tensioned and the other end is anchored. Correspondingly, the first end 31 of the prestressed duct 3 corresponds to the tensioning end of the prestressed steel strand 1, and the second end 32 corresponds to the anchoring end of the prestressed steel strand 1. Electromagnetic elastic absolute stress sensors 4 are installed on the prestressed duct 3 at the first end 31, the second end 32, the mid-span position between the two ends, and before and after any corner 33. During the tensioning stage of the prestressed steel strand 1, the magnetoelastic instrument collects and records the signals from all the electromagnetic elastic absolute stress sensors 4, thereby directly obtaining the refined prestress distribution of the prestressed steel strand 1 during the tensioning stage, and then calculating the measured prestress friction loss value of the prestressed steel strand 1. The magnetoelastic instrument uses a mature technology for calculating the friction loss value, which will not be elaborated here.

[0052] After completing the tensioning of each stage of the prestressed steel strand 1, the measured values ​​of the prestress distribution of the prestressed steel strand 1 are recorded, and finally the refined prestress friction loss is obtained.

[0053] In practice, the electromagnetic spring-type absolute stress sensor 4 should be calibrated under indoor load and temperature conditions beforehand. This calibration ensures the accuracy and reliability of the electromagnetic spring-type absolute stress sensor 4 under actual operating conditions. Simultaneously, the materials used for calibration of the prestressed steel strand 1 and prestressed duct 3 should be consistent with those used in the tension friction test. Furthermore, temperature calibration of the prestressed steel strand 1 and prestressed duct 3 should be performed within the actual operating temperature range to reduce the impact of temperature on the tension friction test of the prestressed steel strand 1.

[0054] In addition, it should be noted that the tensioning of the prestressed steel strand 1 should be carried out after the concrete curing of the prestressed test beam 2 has reached the required age. During tensioning, the tensioning prestress is controlled by the oil pressure gauge and the elongation of the steel strand. The effective stress detection values ​​at all measuring points of the electromagnetic spring-type absolute stress sensor 4 are recorded at each tensioning stage.

[0055] The friction loss testing device 100 based on the electromagnetic spring-type absolute stress sensor described in this scheme, by densely distributing the electromagnetic spring-type absolute stress sensors 4 at multiple points outside the prestressing duct 3, can directly obtain the in-situ prestressing values ​​at multiple locations of the prestressed steel strand 1 during the tensioning stage, which is beneficial to improving the accuracy of prestressing friction loss calculation. Moreover, since the electromagnetic spring-type absolute stress sensors 4 are installed outside the prestressing duct 3 and do not contact the prestressed steel strand 1 inside the duct 3, it avoids the compression or damage to the electromagnetic spring-type absolute stress sensors 4 during the tensioning or grouting stages. Simultaneously, the grouting material will not affect the electromagnetic spring-type absolute stress sensors during the grouting process. Furthermore, the electromagnetic spring-type absolute stress sensors 4 have a metal protective shell, so the beam pouring material (such as concrete) will not affect the structure and performance of the electromagnetic spring-type absolute stress sensors during the test beam pouring process. In summary, this design helps to ensure the accuracy of the measurement data from the electromagnetic spring-type absolute stress sensors 4, thereby improving the accuracy of the prestressing friction loss calculation for the prestressed steel strand 1, and effectively reducing experimental errors compared to existing technologies. In practical applications, sensor connection cables are also protected against water and pressure, for example, by adding conduit to the outside of the connection cable.

[0056] In addition, this scheme uses electromagnetic spring-type absolute stress sensors 4 installed at multiple points on the prestressed duct 3 to detect the absolute stress distribution of the prestressed steel strand 1. This method can obtain accurate prestress distribution during the tensioning stage of the prestressed steel strand, thereby achieving refined testing of friction loss. It can not only meet the high-precision friction testing requirements of short-span prestressed test beams, but also be applicable to the friction testing requirements of large-span prestressed test beams. It solves the problem that the friction coefficient of commonly used prestressed friction loss calculation methods in engineering is inaccurate, and the calculation accuracy of friction loss for large-span prestressed beams is insufficient. It has broad application prospects in bridge engineering and other fields.

[0057] This utility model uses specific examples to illustrate its principles and implementation methods. The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the idea of ​​this utility model. In summary, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A friction loss testing device based on an electromagnetic spring-type absolute stress sensor, characterized in that, include: Prestressed steel strands (1); A prestressed test beam (2) has a prestressed duct (3) inside for the prestressed steel strand (1) to pass through; An electromagnetic spring-type absolute stress sensor (4) is fixedly installed outside the prestressed pipe (3), and at least one set of the electromagnetic spring-type absolute stress sensor (4) is installed at the first end (31), the second end (32) and between the two ends of the prestressed pipe (3) so that when the prestressed steel strand (1) is in the tensioning stage, the prestressed steel strand (1) can be prestressed at multiple points by multiple sets of the electromagnetic spring-type absolute stress sensor (4). The magnetoelastic force demodulation device (5) is communicatively connected to all the electromagnetic spring-type absolute stress sensors (4).

2. The friction loss testing device based on an electromagnetic spring-type absolute stress sensor (4) according to claim 1, characterized in that, At least one bend (33) is provided between the two ends of the prestressed duct (3), and at least one set of electromagnetic spring-type absolute stress sensors (4) is provided on both sides of any bend (33).

3. The friction loss testing device based on an electromagnetic spring-type absolute stress sensor (4) according to claim 2, characterized in that, At least one set of electromagnetic spring-type absolute stress sensors (4) is provided at any of the corners (33) of the prestressed duct (3).

4. The friction loss testing device based on an electromagnetic spring-type absolute stress sensor (4) according to claim 2 or 3, characterized in that, The prestressed duct (3) extends along its own length and is arranged symmetrically on the left and right sides within the prestressed test beam (2).

5. The friction loss testing device based on an electromagnetic spring-type absolute stress sensor (4) according to claim 4, characterized in that, The first end (31) and the second end (32) of the prestressed duct (3) are both straight segments. At least three corners (33) are provided between the first end (31) and the second end (32) of the prestressed duct (3), and any one of the corners (33) is a rounded corner (33).

6. The friction loss testing device based on an electromagnetic spring-type absolute stress sensor (4) according to claim 5, characterized in that, Any two adjacent corners (33) are connected by a straight line segment.

7. The friction loss testing device based on an electromagnetic spring-type absolute stress sensor (4) according to any one of claims 1 to 3, characterized in that, Both ends of the prestressed duct (3) are equipped with tensioning devices, which are used to tension the prestressed steel strand (1) at both ends; or, one end of the prestressed duct (3) is equipped with the tensioning device and the other end is equipped with an anchoring device, which is used to anchor one end of the prestressed steel strand (1) and the tensioning device is used to tension the other end of the prestressed steel strand (1).

8. The friction loss testing device based on an electromagnetic spring-type absolute stress sensor (4) according to any one of claims 1 to 3, characterized in that, The prestressed test beam (2) is integrally cast outside the prestressed duct (3).

9. The friction loss testing device based on an electromagnetic spring-type absolute stress sensor (4) according to any one of claims 1 to 3, characterized in that, The prestressed steel strand (1) is a prestressed steel strand bundle.

10. The friction loss testing device based on an electromagnetic spring-type absolute stress sensor (4) according to any one of claims 1 to 3, characterized in that, The magnetoelastic force demodulation device (5) is a magnetoelastic instrument.

Images