A concrete dam deformation monitoring device based on magnetic grid sensing principle and installation method

Abstract

The application discloses a concrete dam deformation monitoring equipment based on a magnetic grid sensing principle and a mounting method, and solves the technical problem that traditional monitoring equipment and methods cannot simultaneously realize three-direction high-precision continuous monitoring. The equipment comprises a tensioning line, a movable rod, a first sliding block, a first sliding rail, a second sliding block, a second sliding rail, a water tank, a floating boat, a floating ball, a third magnetic grid ruler and a third magnetic head. The tensioning line is connected with the top of the movable rod, the bottom of the movable rod is connected with the first sliding block, the first sliding block is provided with the first magnetic head and is connected with the first magnetic grid ruler in the first sliding rail; the bottom of the first sliding rail is connected with the second sliding block, the second sliding block is provided with the second magnetic head and is connected with the second magnetic grid ruler in the second sliding rail; the water tank is communicated with an immovable point outside a dam body through a pipeline, the floating boat and the floating ball are placed in the water tank, and the top of the third magnetic grid ruler is connected with the floating ball. The application can simultaneously monitor the transverse river direction, the along-river direction and the vertical direction of the deformation of the concrete dam, and realizes comprehensive monitoring of the deformation of the concrete dam.

Description

Technical Field

[0001] This invention relates to the field of concrete dam deformation monitoring technology, specifically to a concrete dam deformation monitoring device and installation method based on the magnetic grating sensing principle. Background Technology

[0002] The safe and stable operation of dams is directly related to the safety of people and property downstream and the full realization of the benefits of water conservancy projects. With the rapid development of my country's water conservancy, especially in the development of hydropower resources in the west and the construction of flood control and disaster reduction systems, the scale of dam construction is constantly expanding, which places higher demands on their safety monitoring technology. Deformation monitoring is one of the core contents of dam safety monitoring. By monitoring the deformation of the dam body, abnormal deformation trends can be detected in a timely manner, the structural safety status can be assessed, and a scientific basis can be provided for the safe operation of the dam.

[0003] Traditional concrete dam deformation monitoring technologies, such as leveling, total station measurement, and GPS monitoring, each have their own advantages and disadvantages: leveling offers high accuracy but is cumbersome and inefficient; total station measurement is fast but greatly affected by environmental factors; GPS monitoring offers strong real-time performance but its accuracy may not meet requirements in certain situations; and tension line instruments can only monitor unidirectional or bidirectional deformation. With the rapid development of modern sensing, communication, and computer technologies, concrete dam deformation monitoring technology is moving towards higher precision, automation, and intelligence. In recent years, in particular, the application of new technologies such as 3D laser scanning, satellite remote sensing, fiber optic sensing, and artificial intelligence in dam deformation monitoring has provided new technical approaches for achieving continuous and accurate monitoring of the three-dimensional deformation of concrete dams. Therefore, researching new deformation monitoring equipment and methods for concrete dams adapted to complex environments is of great significance for improving the level of dam safety monitoring. Summary of the Invention

[0004] The purpose of this invention is to provide a concrete dam deformation monitoring device and installation method based on the magnetic grating sensing principle, so as to solve the technical problem that traditional monitoring devices and methods cannot simultaneously achieve three-dimensional high-precision continuous monitoring.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a concrete dam deformation monitoring device based on the magnetic grating sensing principle, comprising a tension wire, a movable rod, a first slider, a first slide rail, a second slider, a second slide rail, a water tank, a floating vessel, a buoy, a third magnetic grating ruler, and a third magnetic head. The tension wire is connected to the top of the movable rod, and the bottom of the movable rod is connected to the first slider. The first slider is equipped with a first magnetic head and is connected to the first magnetic grating ruler in the first slide rail. The bottom of the first slide rail is connected to the second slider, and the second slider is equipped with a second magnetic head and is connected to the second magnetic grating ruler in the second slide rail. When the tension wire deforms along the river or... When the magnetic head moves horizontally across the river, it slides across the magnetic scale, generating a magnetic signal, which is then converted into an electrical signal and output as a displacement signal. This allows the system to capture the horizontal deformation of the dam across and along the river. The water tank is connected to a stationary point outside the dam via a pipeline. The pontoon and buoy are placed inside the water tank. The top of the third magnetic scale is connected to the buoy. When the water depth changes, the buoy undergoes vertical displacement, causing the third magnetic scale to change. This causes the third magnetic head, fixed at the bottom of the water tank, to slide a certain distance on the third magnetic scale, generating a magnetic signal, which is then converted into an electrical signal and finally output as a displacement, thereby capturing the vertical deformation of the dam.

[0007] Furthermore, the first slide rail and the second slide rail are perpendicular to each other.

[0008] Furthermore, the first magnetic scale, the second magnetic scale, and the third magnetic scale are perpendicular to each other.

[0009] Furthermore, the water level in the tank is kept consistent with the water level at a fixed point outside the dam.

[0010] Furthermore, it also includes tension line protection pipes, which are installed at both ends of the tension line to protect it.

[0011] Furthermore, a hollow vertical rod is fixed inside the water tank, a third magnetic head is installed at the bottom of the vertical rod, and a third magnetic scale passes through the vertical rod. When the water depth changes, the third magnetic scale can move up and down inside the vertical rod.

[0012] Secondly, the present invention provides an installation method for a concrete dam deformation monitoring device based on the magnetic grating sensing principle, comprising the following steps:

[0013] Step 1: Before installation, perform a 3D scanning model of the concrete dam gallery to accurately obtain the internal structural dimensions and spatial distribution of the gallery. In combination with the dam deformation monitoring requirements, simulate the installation position of the tension line instrument in the model to ensure that the tension line can cover the key deformation monitoring area of ​​the dam and avoid obstacles.

[0014] Step 2: At the selected installation location, use high-precision drilling equipment to drill the installation holes for the embedded parts. The hole position deviation should be controlled within ±2mm. The hole depth should be determined according to the size of the embedded parts to ensure that the embedded parts are installed firmly.

[0015] Step 3: Install the tensioner housing, fix the housing to the corridor wall with the pre-embedded parts, and use a level to level it to ensure that the levelness error does not exceed 0.5mm / m;

[0016] Step 4: Install the second slide rail inside the box, and use a level to level it, ensuring that the horizontal error of the second slide rail does not exceed 0.5mm / m. At the same time, use a laser positioning device to ensure that the parallelism error of the two second slide rails is within 1mm.

[0017] Step 5: Install the second slider on the second slide rail, test the smoothness of the slider's movement to ensure there is no jamming, and then install the first slide rail above the second slider. Similarly, perform level calibration, and control the level error within 0.5mm / m.

[0018] Step 6: Install the first slider on the first slide rail and test its sliding performance. Then connect the bottom of the movable rod to the first slider and check the flexibility of the movable rod to move vertically up and down, ensuring that the movable rod moves vertically without obstruction.

[0019] Step 7: Install the tension line and lay it along the monitoring corridor. Fix both ends of the tension line to the fixed point on the bedrock of the dam abutment. Use vibration damping device at the fixing point to reduce the impact of external vibration on the tension line. When the tension line passes through the inside of each tension line instrument box, ensure that it is well connected to the top of the movable rod.

[0020] Step 8: Install the water tank, pontoon, and buoy. Fix the water tank in a suitable position on the tension line instrument box to ensure its stability. Connect the water tank to the fixed point outside the dam with a water pipe to ensure that the water pipe is unobstructed. Use the principle of communicating vessels to make the water head in the water tank consistent with the water head at the fixed point outside the dam. Put the pontoon and buoy into the water tank and check their floating status to ensure that they can float freely without tilting.

[0021] Step 9: Install the third magnetic scale and the third magnetic head. Fix the third magnetic head to the bottom of the water tank. Connect the top of the third magnetic scale to the float ball. Ensure that the verticality error of the magnetic scale does not exceed 0.5mm / m. Adjust the relative position of the third magnetic head and the third magnetic scale to ensure that the deformation can be accurately obtained when the float ball moves the third magnetic scale up and down.

[0022] Step 10: Perform overall debugging of the installed equipment, test the working performance of each part, including the accuracy of horizontal and vertical displacement measurement, to ensure that the equipment can work normally. Then install the tension line protection pipe to protect the tension line.

[0023] Furthermore, a certain pre-tension force needs to be applied during the installation of the tension line. The magnitude of the pre-tension force is determined by calculation based on the material and length of the tension line to ensure that the tension line is in a taut state without excessive stretching.

[0024] Based on the above technical solution, the embodiments of the present invention can produce at least the following technical effects:

[0025] This invention can simultaneously monitor the three-dimensional deformation of concrete dams—transverse, longitudinal, and vertical—achieving comprehensive monitoring of dam deformation. Compared to traditional monitoring equipment, it improves the comprehensiveness and accuracy of monitoring. The installation method employs 3D scanning modeling and high-precision installation technology, ensuring the accuracy and stability of the equipment installation and reducing the impact of installation errors on the monitoring results. Furthermore, the innovative installation location selection and fixing method improve the adaptability of the equipment within the concrete dam gallery. The monitoring data analysis method combines multiple technologies such as filtering, gross error identification, and neural networks, improving the accuracy and efficiency of data processing and enabling more accurate acquisition of the dam's three-dimensional deformation. Through finite element modeling and particle swarm optimization algorithms, instability risk assessment can be performed, enabling timely prediction of dam deformation and instability, providing strong support for the safe operation of the dam. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of the concrete dam deformation monitoring device of the present invention;

[0028] Figure 2 For the present invention Figure 1 Cross-sectional view along the middle I-I direction;

[0029] Figure 3 For the present invention Figure 1 Cross-sectional view along the middle II-II direction;

[0030] Figure 4 For the present invention Figure 1 Cross-sectional view along the middle III-III direction;

[0031] Figure 5 This is a schematic diagram of the installation method of the slope internal deformation monitoring equipment of the present invention;

[0032] Figure 6 This invention provides monitoring data of the concrete dam after river-direction deformation treatment.

[0033] Figure 7 This invention provides monitoring data of the transverse deformation of a concrete dam after treatment.

[0034] Figure 8 This invention provides monitoring data of the vertical deformation of a concrete dam after treatment.

[0035] Figure 9 This is a technical roadmap for assessing the deformation and instability risk of concrete dams according to the present invention.

[0036] In the diagram: 1. Tension line; 2. Movable rod; 3. First slider; 4. First slide rail; 5. Second slider; 6. Second slide rail; 7. Water tank; 8. Float; 9. Buoy; 10. Third magnetic scale; 11. Third magnetic head; 12. Tension line protection tube; 13. Pipeline. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0038] Example 1

[0039] like Figures 1-4 As shown, this embodiment provides a concrete dam deformation monitoring device based on the magnetic grating sensing principle, including tension wire 1, movable rod 2, first slider 3, first slide rail 4, second slider 5, second slide rail 6, water tank 7, floating boat 8, float 9, third magnetic grating ruler 10, and third magnetic head 11.

[0040] On the right side, tension line 1 is connected to the top of movable rod 2, and the bottom of movable rod 2 is connected to the first slider 3. The first slider 3 is equipped with a first magnetic head and is connected to the first magnetic scale in the first slide rail 4. The bottom of the first slide rail 4 is connected to the second slider 5, and the second slider 5 is equipped with a second magnetic head and is connected to the second magnetic scale in the second slide rail 6. When tension line 1 moves horizontally along or across the river, the magnetic head will slide across the magnetic scale, generating a magnetic signal, which is then converted into an electrical signal and outputs a displacement signal, thereby capturing the horizontal deformation of the dam in both the transverse and longitudinal directions.

[0041] On the left side, water tank 7 is connected to a stationary point outside the dam body through pipe 13, so that the water head remains the same. Using the principle of communicating vessels, when the dam body is raised or lowered vertically, the water depth in water tank 7 will change because the liquid level in water tank 7 must be consistent with the liquid level at the stationary point. The pontoon 8 and the float 9 are placed inside the water tank 7. The pontoon 8 is used to support the tension line 1, ensuring that the tension line 1 is stable at a certain height and preventing it from falling due to its own weight or stress relaxation. A vertical rod is fixed inside the water tank 7. The center of the vertical rod is hollow. The third magnetic head 11 is installed at the bottom of the vertical rod. The float 9 is connected to the third magnetic scale 10. The third magnetic scale 10 is embedded in this vertical rod and can move freely up and down. During measurement, the position of the third magnetic head 11 is fixed. The float 9 moves up and down due to the drop or rise of the liquid level, which drives the third magnetic scale 10 to move up and down. At this time, there will be a relative displacement between the third magnetic scale 10 and the fixed third magnetic head 11, generating a magnetic signal, which is converted into an electrical signal and finally output as a displacement amount, thereby capturing the vertical deformation of the dam.

[0042] In this embodiment, the first slide rail 4 and the second slide rail 6 are perpendicular to each other, and the first magnetic scale, the second magnetic scale and the third magnetic scale 10 are perpendicular to each other, respectively used to measure the deformation of the concrete dam along the river, across the river and vertically.

[0043] In this embodiment, a tension line protection tube 12 is also included. The material is PVC pipe. The tension line protection tube 12 is installed at both ends of the tension line 1 to protect the tension line 1.

[0044] Example 2

[0045] like Figure 5 As shown, this embodiment provides an installation method for a concrete dam deformation monitoring device based on the magnetic grating sensing principle, including a magnetic grating flexible triaxial tension wire instrument and tension wires, which are arranged in various elevation monitoring corridors of the concrete dam to measure the transverse, longitudinal, and vertical deformation of the dam. The method includes the following steps:

[0046] Step 1: Before installation, perform a 3D scanning model of the concrete dam gallery to accurately obtain the internal structural dimensions and spatial distribution of the gallery. In combination with the dam deformation monitoring requirements, simulate the installation position of the tension line instrument in the model to ensure that the tension line can cover the key deformation monitoring area of ​​the dam and avoid obstacles such as pipelines and equipment in the gallery.

[0047] Step 2: At the selected installation location, use high-precision drilling equipment to drill the installation holes for the embedded parts. The hole position deviation should be controlled within ±2mm. The hole depth should be determined according to the size of the embedded parts to ensure that the embedded parts are installed firmly.

[0048] Step 3: Install the tensioner housing, fix the housing to the corridor wall with the pre-embedded parts, and use a level to level it to ensure that the levelness error does not exceed 0.5mm / m;

[0049] Step 4: Install the second slide rail inside the box, and use a level to level it, ensuring that the horizontal error of the second slide rail does not exceed 0.5mm / m. At the same time, use a laser positioning device to ensure that the parallelism error of the two second slide rails is within 1mm.

[0050] Step 5: Install the second slider on the second slide rail, test the smoothness of the slider's movement to ensure there is no jamming, and then install the first slide rail above the second slider. Similarly, perform level calibration, and control the level error within 0.5mm / m.

[0051] Step 6: Install the first slider on the first slide rail and test its sliding performance. Then connect the bottom of the movable rod to the first slider and check the flexibility of the movable rod to move vertically up and down, ensuring that the movable rod moves vertically without obstruction.

[0052] Step 7: Install the tension wires and lay them out along the monitoring corridor. The two ends of the tension wires are fixed at fixed points on the bedrock of the dam abutment. The fixing points use special vibration damping devices to reduce the impact of external vibrations on the tension wires. A certain pre-tension force needs to be applied when installing the tension wires. The magnitude of the pre-tension force is determined by calculation based on the material and length of the tension wires to ensure that the tension wires are in a taut state without excessive stretching. When the tension wire body passes through the inside of each tension wire instrument box, ensure that it is well connected to the top of the movable rod.

[0053] Step 8: Install the water tank, pontoon, and buoy. Fix the water tank in a suitable position on the tension line instrument box to ensure its stability. Connect the water tank to the fixed point outside the dam with a water pipe to ensure that the water pipe is unobstructed. Use the principle of communicating vessels to make the water head in the water tank consistent with the water head at the fixed point outside the dam. Put the pontoon and buoy into the water tank and check their floating status to ensure that they can float freely without tilting.

[0054] Step 9: Install the third magnetic scale and the third magnetic head. Fix the third magnetic head to the bottom of the water tank. Connect the top of the third magnetic scale to the float ball. Ensure that the verticality error of the magnetic scale does not exceed 0.5mm / m. Adjust the relative position of the third magnetic head and the third magnetic scale to ensure that the deformation can be accurately obtained when the float ball moves the third magnetic scale up and down.

[0055] Step 10: Perform overall debugging of the installed equipment, test the working performance of each part, including the accuracy of horizontal and vertical displacement measurement, to ensure that the equipment can work normally. Then install the tension line protection pipe to protect the tension line.

[0056] Example 3

[0057] This embodiment provides a method for analyzing monitoring data, including:

[0058] (1) Monitoring data processing

[0059] By selecting a reference date and reference value, the deformation of the concrete dam in three directions—horizontal, longitudinal, and vertical—can be directly obtained from the measurement results of a concrete dam deformation monitoring device based on the magnetic grating sensing principle. Wavelet transform filtering is used to process the raw monitoring data in these three directions to remove noise interference. Wavelet transform has good time-frequency localization characteristics, effectively separating signal and noise. Specifically, by selecting appropriate wavelet basis functions and decomposition levels, the signal is decomposed and reconstructed to obtain the filtered signal. Density-based clustering (DBSCAN) is used to identify gross errors in the data. This algorithm calculates the density of data points, identifies low-density areas as gross errors, and removes these gross data, improving data reliability. The processed monitoring data is shown below. Figures 6-8 As shown.

[0060] (2) Risk assessment of deformation and instability of concrete dams

[0061] like Figure 9 As shown, a finite element model of a concrete dam is constructed based on measured triaxial deformation data. A particle swarm optimization algorithm is used to track and retrieve thermodynamic parameters. By comparing the calculated results of the finite element model with the measured data, the thermodynamic parameters are continuously adjusted to calibrate the finite element model. Based on the calibrated finite element model, the deformation of the concrete dam during construction, water impoundment, and operation is analyzed. The deformation development trend of the concrete dam under different working conditions is predicted, revealing the weak points and failure modes of the concrete dam, proposing criteria for deformation instability, and assessing the deformation instability risk of the concrete dam throughout its entire life cycle.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A concrete dam deformation monitoring device based on the magnetic grating sensing principle, characterized in that, The components include a tension wire (1), a movable rod (2), a first slider (3), a first slide rail (4), a second slider (5), a second slide rail (6), a water tank (7), a buoy (8), a float (9), a third magnetic scale (10), and a third magnetic head (11). The tension line (1) is connected to the top of the movable rod (2), and the bottom of the movable rod (2) is connected to the first slider (3). The first slider (3) is provided with a first magnetic head and is connected to the first magnetic scale in the first slide rail (4). The bottom of the first slide rail (4) is connected to the second slider (5). The second slider (5) is provided with a second magnetic head and is connected to the second magnetic scale in the second slide rail (6). When the tension line (1) moves horizontally along the river or across the river, the magnetic head slides across the magnetic scale, generates a magnetic signal, and then converts it into an electrical signal, outputting a displacement signal, thereby capturing the horizontal deformation of the dam in the river direction and along the river. The water tank (7) is connected to a stationary point outside the dam via a pipe (13). The floating boat (8) and the buoy (9) are placed inside the water tank (7). The top of the third magnetic scale (10) is connected to the buoy (9). When the water depth changes, the buoy (9) undergoes vertical displacement, which causes the third magnetic scale (10) to change. This causes the third magnetic head (11) fixed at the bottom of the water tank (7) to slide a distance on the third magnetic scale (10), generating a magnetic signal, which is converted into an electrical signal and finally output as a displacement, thereby capturing the vertical deformation of the dam. The first slide rail (4) and the second slide rail (6) are perpendicular to each other; The first magnetic grating ruler, the second magnetic grating ruler, and the third magnetic grating ruler (10) are perpendicular to each other; A hollow vertical rod is fixed inside the water tank (7). The third magnetic head (11) is installed at the bottom of the vertical rod. The third magnetic scale (10) passes through the vertical rod. When the water depth changes, the third magnetic scale (10) can move up and down inside the vertical rod.

2. The concrete dam deformation monitoring device based on the magnetic grating sensing principle according to claim 1, characterized in that, The water level in the water tank (7) is consistent with the water level at the fixed point outside the dam.

3. The concrete dam deformation monitoring device based on the magnetic grating sensing principle according to claim 1, characterized in that, It also includes tension line protection pipes (12), which are installed at both ends of the tension line (1) to protect the tension line (1).

4. The installation method of a concrete dam deformation monitoring device based on the magnetic grating sensing principle according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Before installation, perform a 3D scanning model of the concrete dam gallery to accurately obtain the internal structural dimensions and spatial distribution of the gallery. In combination with the dam deformation monitoring requirements, simulate the installation position of the tension line instrument in the model to ensure that the tension line can cover the key deformation monitoring area of ​​the dam and avoid obstacles. Step 2: At the selected installation location, use high-precision drilling equipment to drill the installation holes for the embedded parts. The hole position deviation should be controlled within ±2mm. The hole depth should be determined according to the size of the embedded parts to ensure that the embedded parts are installed firmly. Step 3: Install the tensioner housing, fix the housing to the corridor wall with the pre-embedded parts, and use a level to level it to ensure that the levelness error does not exceed 0.5mm / m; Step 4: Install the second slide rail inside the box, and use a level to level it, ensuring that the horizontal error of the second slide rail does not exceed 0.5mm / m. At the same time, use a laser positioning device to ensure that the parallelism error of the two second slide rails is within 1mm. Step 5: Install the second slider on the second slide rail, test the smoothness of the slider's movement to ensure there is no jamming, and then install the first slide rail above the second slider. Similarly, perform level calibration, and control the level error within 0.5mm / m. Step 6: Install the first slider on the first slide rail and test its sliding performance. Then connect the bottom of the movable rod to the first slider and check the flexibility of the movable rod to move vertically up and down, ensuring that the movable rod moves vertically without obstruction. Step 7: Install the tension line and lay it along the monitoring corridor. Fix both ends of the tension line to the fixed point on the bedrock of the dam abutment. Use vibration damping device at the fixing point to reduce the impact of external vibration on the tension line. When the tension line passes through the inside of each tension line instrument box, ensure that it is well connected to the top of the movable rod. Step 8: Install the water tank, pontoon, and buoy. Fix the water tank in a suitable position on the tension line instrument box to ensure its stability. Connect the water tank to the fixed point outside the dam with a water pipe to ensure that the water pipe is unobstructed. Use the principle of communicating vessels to make the water head in the water tank consistent with the water head at the fixed point outside the dam. Put the pontoon and buoy into the water tank and check their floating status to ensure that they can float freely without tilting. Step 9: Install the third magnetic scale and the third magnetic head. Fix the third magnetic head to the bottom of the water tank. Connect the top of the third magnetic scale to the float ball. Ensure that the verticality error of the magnetic scale does not exceed 0.5mm / m. Adjust the relative position of the third magnetic head and the third magnetic scale to ensure that the deformation can be accurately obtained when the float ball moves the third magnetic scale up and down. Step 10: Perform overall debugging of the installed equipment, test the working performance of each part, including the accuracy of horizontal and vertical displacement measurement, to ensure that the equipment can work normally. Then install the tension line protection pipe to protect the tension line.

5. The installation method of the concrete dam deformation monitoring equipment based on the magnetic grating sensing principle according to claim 4, characterized in that, When installing the tension line, a certain pre-tension force needs to be applied. The magnitude of the pre-tension force is determined by calculation based on the material and length of the tension line to ensure that the tension line is in a taut state without excessive stretching.

Images