Cable-stayed cable damping test test quick unloading device, test system and test method

Abstract

The application discloses a kind of cable damping test test quick unloading device, test system and test method.The device includes cable clamp assembly, force transmission top rod, sleeve, locking piece and connecting piece, cable clamp assembly is equipped with transmission hole, one end of force transmission top rod is inserted with transmission hole, the other end is axially movably contained in sleeve, locking piece is detachably connected between force transmission top rod and sleeve;System includes exciter, displacement sensor, control module and the device;Method includes determining exciter installation position to avoid vibration mode node, connect exciter with cable, collect vibration signal, apply excitation force to stable vibration, remove locking piece to make force transmission top rod separate from transmission hole, enter free attenuation, collect data and identify damping ratio.The application realizes the instantaneous cut-off of excitation force by pulling out locking piece, unloading is fast, disturbance is small, and the precision and repeatability of damping test are improved.

Description

Technical Field

[0001] This invention relates to the field of cable-stayed bridge damping testing technology, and in particular to a rapid unloading device, testing system and testing method for cable-stayed bridge damping testing. Background Technology

[0002] In cable-stayed bridge damping tests, the forced vibration-free decay method is typically used to identify the structural damping characteristics. This involves using a vibrator to bring the cable-stayed bridge to a stable vibration state, then removing the external excitation to allow it to enter a free decay process. Existing bridge vibration devices usually employ a motor / manual traction of a steel wire rope to excite the cable-stayed bridge. In this case, the steel wire rope is under tension, and the corresponding unloading method is to directly disconnect the motor / manual excitation from the steel wire rope. This presents the following technical problems: (1) Uncontrollability of unloading time. Existing tests rely on manual operation or simple mechanical release methods, which are not fast enough and it is difficult to accurately control the unloading time. This results in large differences in the initial vibration state (such as amplitude and phase) between different tests, affecting the initial conditions of free decay and leading to low comparability and accuracy of test results.

[0003] (2) The unloading process is prone to introducing additional disturbances. Traditional unloading methods are prone to generating lateral disturbances or additional excitations during operation. The unloading process is prone to introducing additional disturbances, thereby disrupting the original vibration state of the cable and affecting the authenticity of the free decay response, resulting in low test accuracy.

[0004] (3) Uncontrollable disconnection of force transmission path. Most existing unloading devices remove the connection between the motor excitation (manual excitation) and the wire rope, lacking a mechanism to quickly and stably disconnect the excitation force transmission path, resulting in a delayed or incomplete unloading process.

[0005] (4) The device is complex to adjust and has poor repeatability. It is difficult to adapt to the test requirements of different modes and different installation positions. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a simple and quick unloading device for cable damping test.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: In a first aspect, the present invention provides a rapid unloading device for a stay cable damping test, comprising a cable clamp assembly, a force transmission rod, a sleeve, a locking member, and a connecting member. The cable clamp assembly is used to connect to the stay cable and has a transmission hole. One end of the force transmission rod is inserted into the transmission hole, and the other end is axially movable and accommodated in the sleeve. The locking member is detachably connected between the force transmission rod and the sleeve to restrict their movement. The connecting member is used to connect the sleeve and the vibrator. When the locking member is removed, the force transmission rod moves axially relative to the sleeve to disengage from the transmission hole.

[0008] As a further improvement to the above technical solution, a rapid rebound component is also included. The rapid rebound component includes an elastic element, a first base, and a second base. The first base is installed at one end of the force-transmitting rod near the transmission hole, and the second base is installed on the sleeve. The elastic element is connected between the first base and the second base to give the force-transmitting rod a tendency to retract into the sleeve.

[0009] As a further improvement to the above technical solution, the force-transmitting push rod is provided with a through hole, the sleeve is provided with an adjustment hole, and the locking member is a pin-type structure. The locking member passes through both the adjustment hole and the through hole to restrict the relative movement between the force-transmitting push rod and the sleeve.

[0010] As a further improvement to the above technical solution, the cable clamp assembly includes two clamping blocks, each clamping block having a groove. The grooves on the two clamping blocks are joined together to accommodate the stay cable. The two clamping blocks are locked together by bolts, and the transmission hole is located on one of the clamping blocks.

[0011] Secondly, the present invention provides a cable-stayed bridge damping test system, including a vibrator, a displacement sensor, and a control module, and also includes the aforementioned rapid unloading device. The vibrator is connected to the connecting member and is used to apply excitation force to the cable-stayed bridge. The displacement sensor is used to collect the vibration response signal of the cable-stayed bridge. The control module is connected to the vibrator and the displacement sensor respectively.

[0012] Thirdly, the present invention provides a test method based on the above-mentioned cable-stayed bridge damping test system, comprising: The installation position of the exciter is determined based on the order of the target test mode to avoid mode shape nodes; The vibrator is connected to the cable-stayed bridge via the rapid unloading device. The vibration response signal of the stay cable is acquired by the displacement sensor; By applying an excitation force consistent with the target modal frequency through a vibrator, the cable-stayed cable achieves stable forced vibration. Remove the locking component to disengage the force transmission rod from the transmission hole, and the cable-stayed cable enters free damping vibration; Data on free decaying vibrations are collected using displacement sensors. The damping ratio of the stay cable is identified based on the free decay vibration data.

[0013] As a further improvement to the above technical solution, multiple displacement sensors are provided, respectively arranged at three positions L / 7, L / 9, and L / 11 of the stay cable, where L is the length of the stay cable; the method further includes: selecting sensor signals from the multiple displacement sensors that do not fall within the stagnation point region of the vibration mode as signals for damping ratio identification, based on the target modal order, specifically including: When testing modes 6-8 or 13-15, avoid measuring point L / 7. When testing modes 8-10 or 17-19, avoid measuring at L / 9. When testing the 10th to 12th or 20th modes, avoid the L / 11 measurement point.

[0014] As a further improvement to the above technical solution, the sleeve is provided with a plurality of adjustment holes arranged sequentially along the axial direction. The number of adjustment holes is determined according to the difference in the modal order of the cable to be tested. If it is necessary to switch from the i-th mode to the j-th mode for testing, the number of adjustment holes is set to ji and they are evenly arranged along the axial direction of the sleeve.

[0015] As a further improvement to the above technical solution, the connecting component is a height adjusting bolt. One end of the height adjusting bolt is threadedly connected to the sleeve, and the other end is threadedly connected to the vibrator. Before connecting the vibrator and the height adjusting bolt, the process includes: making a large-range coarse adjustment by selecting adjustment holes at different positions, and then making a small-range fine adjustment by rotating the height adjusting bolt. After that, the vibrator is connected to the height adjusting bolt.

[0016] As a further improvement to the above technical solution, the step of determining the exciter installation position according to the order of the target test mode includes: for higher-order modes, installing the exciter at or near the antinode of the mode shape.

[0017] Compared with the prior art, the advantages of the present invention are as follows: This invention employs a plug-in cable clamp assembly in conjunction with a force-transmitting rod, using a locking element as the sole detachable connecting component to restrict their relative movement. When the locking element is removed, the force-transmitting rod can rapidly move along the sleeve axis and disengage from the transmission hole, thereby achieving instantaneous and clean disconnection of the force transmission path between the exciter and the stay cable. This solves the problems of delayed unloading and easy introduction of lateral disturbances in existing wire rope traction methods. Simultaneously, because the removal of the locking element is simple and without delay, the unloading time can be precisely controlled, ensuring the consistency of the initial conditions for free decay. Furthermore, the entire device consists only of a cable clamp, a force-transmitting rod, a sleeve, a locking element, and a connecting element, making it simple in structure and easy to operate. It can adapt to stay cables of different diameters and different exciter installation positions without complex adjustments, significantly improving the repeatability and accuracy of damping tests.

[0018] Furthermore, the cable damping test method provided by this invention achieves high-precision and high-repeatability testing of multi-mode damping ratios by installing the exciter at the antinode of the target mode, employing a dual height adjustment mechanism to achieve precise alignment between the exciter and the cable, utilizing a combination of multiple measuring points and dynamically selecting effective signals based on the modal order, and relying on a rapid unloading device to instantaneously cut off the force transmission path. This method effectively avoids the excitation failure problem caused by the exciter being located at a mode node, solves the signal loss problem caused by a single measuring point falling into the stagnation region, and eliminates the additional disturbances caused by traditional unloading methods. Attached Figure Description

[0019] The invention will now be described in more detail with reference to embodiments and the accompanying drawings. Figure 1 This is a schematic diagram of the rapid unloading device for cable damping test in Embodiment 1 of the present invention.

[0020] Figure 2 This is a schematic diagram of the cable-stayed bridge damping test system of Embodiment 2 of the present invention.

[0021] Figure 3 This is a simplified flowchart illustrating the cable damping test method of Embodiment 3 of the present invention.

[0022] Figure 4 This is a schematic diagram showing the antinodes and stagnation points of the i-th and j-th mode shapes of the cable in Embodiment 3 of the present invention.

[0023] The labels in the diagram represent: 1. Cable clamp assembly; 101. Transmission hole; 102. Groove; 11. Clamping block; 2. Force transmission rod; 3. Sleeve; 31. Adjustment hole; 4. Locking component; 5. Connecting component; 6. Cable; 7. Vibrator; 81. Elastic element; 82. First base; 83. Second base; 9. Damper. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0025] like Figure 2 As shown, a damper 9 is installed on the stay cable 6 to simulate the vibration reduction effect in actual engineering. The quick unloading device of this invention is connected to the vibrator 7 and the stay cable 6 at the position on the side of the damper 9. During the test, an excitation force is applied through the vibrator 7, causing the stay cable 6 and the damper 9 to vibrate. After unloading, the free decay signal is collected, which can identify the damping characteristics of the stay cable system after the damper is installed. It should be noted that the damper 9 is not a necessary component of this invention, and this device is also applicable to the damping test of stay cables without dampers installed.

[0026] Example 1 Figure 1 An embodiment of a rapid unloading device for cable-stayed bridge damping testing according to the present invention is shown.

[0027] The fast unloading device for cable damping test in this embodiment includes a cable clamp assembly 1, a force transmission rod 2, a sleeve 3, a locking component 4, and a connecting component 5.

[0028] The cable clamp assembly 1 is used to fix and hold the cable 6, and a transmission hole 101 is provided on the cable clamp assembly 1. One end of the force transmission rod 2 is inserted into the transmission hole 101 to form a plug-in fit, and the other end of the force transmission rod 2 is axially movable and accommodated inside the sleeve 3. The locking member 4 is detachably connected between the force transmission rod 2 and the sleeve 3, and restricts the relative axial movement between the two under load. One end of the connecting member 5 is fixedly connected to the sleeve 3, and the other end is used to connect to the vibrator 7.

[0029] When the locking element 4 is removed, the force transmission rod 2 and the sleeve 3 are no longer restricted by the locking element 4, and the force transmission rod 2 can move axially relative to the sleeve 3, thereby causing the end of the force transmission rod 2 to disengage from the transmission hole 101 of the cable clamp assembly 1.

[0030] The vibrator 7 transmits the excitation force to the stay cable 6 through the connector 5, sleeve 3, locking member 4, force transmission rod 2, and cable clamp assembly 1, causing the stay cable 6 to generate stable forced vibration. At this time, the locking member 4 undertakes the function of transmitting axial load, ensuring that the force transmission rod 2 and the cable clamp assembly 1 are always in the plugged state.

[0031] When it is necessary to allow the stay cable 6 to enter free damping vibration, the operator pulls out the locking piece 4. Once the locking piece 4 is removed, the constraint between the force transmission rod 2 and the sleeve 3 is removed, and the force transmission rod 2 can move freely axially within the sleeve 3. Guided by the sleeve 3, the force transmission rod 2 quickly retracts axially, and its end completely disengages from the transmission hole 101 of the cable clamp assembly 1. At this point, the mechanical connection between the exciter 7 and the stay cable 6 is completely severed, and the stay cable 6 is no longer subjected to any external excitation, and vibrates freely damping only under its own damping.

[0032] The core of this rapid unloading device lies in its ability to quickly unload the excitation force. Once the locking piece 4 is pulled out, the constraint between the force transmission rod 2 and the sleeve 3 is immediately released. Under the action of gravity or inertia, the force transmission rod 2 instantly retracts and disengages from the cable clamp assembly 1. The entire unloading process is completed in a very short time without any mechanical delay. The device has a simple overall structure, is easy to operate, and has good repeatability, meeting the stringent requirements for unloading speed and consistency in laboratory scaled-down model cable multimodal damping tests.

[0033] This embodiment also includes a rapid rebound assembly, which comprises an elastic element 81, a first base 82, and a second base 83. The first base 82 is fixedly installed on the end of the force-transmitting rod 2 near the transmission hole 101, and the second base 83 is fixedly installed on the sleeve 3 by bolts. The elastic element 81 is preferably a spring, with two springs arranged on both sides of the force-transmitting rod 2. One end of each spring is connected to the first base 82, and the other end is connected to the second base 83. In the loaded state (i.e., when the locking member 4 is inserted), the force-transmitting rod 2 is fixed by the locking member 4, and the springs on both sides are in a stretched or compressed energy-storing state. When the locking member 4 is manually pulled out, the elastic potential energy stored in the springs on both sides is released simultaneously, instantly driving the force-transmitting rod 2 to rapidly retract along the axial direction of the sleeve 3, giving the force-transmitting rod 2 a tendency to actively retract into the sleeve 3, thereby accelerating the complete disengagement of the end of the force-transmitting rod 2 from the transmission hole 101. The use of symmetrically arranged springs on both sides not only provides greater driving force but also ensures that the force-transmitting rod 2 is subjected to balanced force and moves smoothly, avoiding jamming due to uneven loading. This rapid rebound component enables the unloading process to be actively driven by the spring rather than passively relying on gravity or inertia, achieving a faster unloading response speed: once the locking element 4 is removed, the elastic potential energy is immediately converted into kinetic energy, and the force transmission rod retracts in a very short time, ensuring a complete physical separation between the vibrator and the cable without any mechanical delay; at the same time, the driving force of the spring is uniform and repeatable, ensuring the consistency of unloading conditions in multiple tests and avoiding incomplete separation caused by friction or jamming. It is particularly suitable for laboratory multimodal damping tests with stringent requirements for the initial conditions of free decay.

[0034] In this embodiment, the force-transmitting rod 2 has a through hole, the sleeve 3 has an adjustment hole 31, and the locking member 4 is a pin-type structure, preferably an unloading pin. The locking member 4 passes through both the adjustment hole 31 and the through hole to restrict the relative movement between the force-transmitting rod 2 and the sleeve 3. Multiple adjustment holes 31 are provided, arranged sequentially along the axial direction of the sleeve 3 to form multiple discrete positions, used to achieve a wide range of coarse adjustments to the height of the rapid unloading device. The connecting member 5 is a height-adjusting bolt, which is threaded to the sleeve and also threaded to the groove on the top of the vibrator 7, and fixed with a nut. Small-range continuous fine adjustments can be made by rotating the height-adjusting bolt, thereby achieving precise adjustment of the device height. In this way, coarse and fine adjustments work together to form a dual height adjustment mechanism: First, based on the target installation position of the exciter 7 (e.g., avoiding the mode nodes of a certain mode or approaching the antinodes), a suitable adjustment hole 31 on the sleeve 3 is selected, and the locking member 4 is inserted into the adjustment hole 31 and the through hole of the force transmission rod 2 to complete a large-range coarse height adjustment; then, the height adjustment bolt is rotated for fine adjustment, so that the exciter 7 and the cable 6 achieve the optimal excitation alignment. The dual adjustment structure ensures both the ability to quickly adapt to different modes and different installation positions, and achieves precise alignment between the exciter 7 and the cable 6. Under load, the locking member 4 simultaneously performs the functions of locking the height and transmitting the excitation force. When unloading is required, the locking member 4 is simply pulled out, and the force transmission rod 2 can be disengaged by the drive of the rapid rebound component, while the height adjustment bolt remains connected to the exciter 7, facilitating quick reset for the next test. In actual operation, the operator pre-selects the adjustment hole 31 according to the target modal order, makes a coarse adjustment and then fine-tunes the height adjustment bolt. The whole process does not require disassembling other parts, has high repeatability and positioning accuracy, and significantly improves the efficiency and consistency of multimodal damping test.

[0035] In this embodiment, the cable clamp assembly 1 includes two clamping blocks 11, each with a groove 102. The grooves 102 on the two clamping blocks 11 are aligned to form a clamping hole that conforms to the shape of the stay cable 6, used to accommodate and clamp the stay cable 6. The two clamping blocks 11 are bolted through and locked, so that the cable clamp assembly 1 is firmly fixed at a predetermined position on the stay cable 6. A transmission hole 101 is formed on one of the clamping blocks 11 for insertion and engagement with the end of the force transmission rod 2. This split clamping block structure facilitates installation and removal at any position on the stay cable 6, and the bolt tightening force can adapt to stay cables of different diameters, ensuring a firm clamping and preventing slippage. During installation, the two clamping blocks 11 are first placed on both sides of the stay cable 6, so that the grooves 102 fit against the surface of the stay cable 6, and then the bolts are tightened to make the clamping blocks 11 hold the stay cable 6 tightly. After the cable clamp assembly 1 is fixed, the end of the force transmission rod 2 is inserted into the transmission hole 101, and the locking piece 4 is inserted to complete the loading preparation. Since the transmission hole 101 is located on the clamp block 11, the excitation force acts directly on the cable clamp assembly 1 through the force transmission rod 2, and is then transmitted to the stay cable 6. The force transmission path is short and the stiffness is high. During rapid unloading, the force transmission rod 2 disengages from the transmission hole 101, and the cable clamp assembly 1 remains fixed on the stay cable 6, without imposing any additional constraints on the stay cable 6.

[0036] Example 2 like Figure 2 As shown in the figure, this embodiment discloses a cable-stayed bridge damping test system.

[0037] The cable-stayed bridge damping test system of this embodiment includes a vibrator 7, a displacement sensor (not shown in the figure), a control module (not shown in the figure), and the quick unloading device described in Embodiment 1. The output end of the vibrator 7 is connected to the connector 5 (i.e., height adjustment bolt) of the quick unloading device. The vibrator 7 is used to apply an adjustable excitation force to the cable-stayed bridge 6. The displacement sensor is arranged at a suitable position on the cable-stayed bridge 6 (e.g., at the mid-span or near the end) to collect the vibration response signal of the cable-stayed bridge 6 in real time during forced vibration and free decay processes, which is usually a displacement, velocity, or acceleration time history signal. The control module is connected to the vibrator 7 and the displacement sensor respectively. Its functions include: controlling the output frequency and amplitude of the vibrator 7 so that the excitation force frequency is consistent with the frequency of the target test mode; receiving the vibration signal collected by the displacement sensor in real time, and displaying, storing, or preliminarily processing the signal. In the actual test, the installation position of the vibrator 7 is first determined according to the target modal order, and the vibrator 7 is connected to the cable-stayed bridge 6 through the quick unloading device. Then, the control module controls the exciter 7 to apply an excitation force at a specific frequency, driving the stay cable 6 to achieve steady-state forced vibration. Once the vibration stabilizes, the operator manually pulls out the locking piece 4 of the quick-release device (or performs the pull-out action according to the prompt signal given by the control module), instantly cutting off the excitation force transmission path, and the stay cable 6 immediately enters free-dampening vibration. The displacement sensor transmits the vibration signal of the entire process to the control module, which can further calculate the damping ratio of the stay cable system based on the free-dampening waveform.

[0038] This testing system organically combines a rapid unloading device with automatic control and signal acquisition modules, realizing a streamlined operation from excitation and unloading to data acquisition, significantly improving the repeatability and accuracy of damping tests. Because the unloading process involves almost no additional disturbance, and the control module can accurately record vibration data before and after unloading, it is particularly suitable for high-precision identification of multi-mode damping ratios of stay cables in a laboratory environment.

[0039] Example 3 This embodiment discloses a test method for cable damping test, which adopts the cable damping test system in Embodiment 2.

[0040] like Figure 3 As shown, the test method of the cable-stayed bridge damping test system in this embodiment includes: (1) Determine the installation position of the exciter according to the order of the target test mode to avoid the mode node.

[0041] The installation position of the exciter 7 is determined based on the order of the target test mode. For example... Figure 4 As shown, the mode shapes of cable 6 have several stagnation points distributed along the length direction (e.g., Figure 4 P2 is a stationary point with zero amplitude) and antinodes (such asFigure 4 In the diagram, P1 represents the antinode (the point with the largest amplitude). X1 represents the i-th mode shape, and X2 represents the j-th mode shape. If the exciter 7 is installed near a stagnation point, that mode will be difficult to excite effectively; conversely, if it is installed at or near an antinode, the maximum response can be obtained with the minimum excitation force. Therefore, for lower-order modes, it is necessary to ensure that the exciter 7 avoids the mode shape nodes; for higher-order modes (e.g., the 10th and above), the mode shapes are more complex and the number of stagnation points increases, so the exciter 7 should preferably be installed at or near an antinode of that mode shape to ensure excitation efficiency.

[0042] (2) Connect the vibrator 7 to the cable 6 via the quick unloading device.

[0043] The exciter 7 and the stay cable 6 are connected by a quick unloading device. In this embodiment, the sleeve 3 of the quick unloading device is provided with multiple adjusting holes 31 arranged sequentially along the axial direction, and the connecting part 5 is a height adjusting bolt. First, according to the target height of the exciter 7 determined in step one, the adjusting hole 31 at the corresponding position on the sleeve 3 is selected, and the locking part 4 (pin) is inserted through both the adjusting hole 31 and the through hole on the force transmission rod 2 to complete a large-range coarse height adjustment; then, the height adjusting bolt, which serves as the connecting part 5, is rotated to perform small-range continuous fine adjustments, so that the exciter 7 and the stay cable 6 achieve precise excitation alignment. The number of adjusting holes 31 can be set according to the difference in the order of the modes to be tested. For example, when it is necessary to switch from the i-th mode to the j-th mode, the number of adjusting holes 31 is set to ji and evenly arranged along the axial direction of the sleeve 3, so that the discrete gears match the mode switching requirements.

[0044] (3) The vibration response signal of the cable 6 is collected by the displacement sensor.

[0045] In this embodiment, multiple displacement sensors are arranged at three positions: L / 7, L / 9, and L / 11 of the stay cable 6, where L is the length of the stay cable 6. During the test, based on the target modal order, the sensor signal that does not fall within the mode stagnation region is selected as the valid signal from the signals of the multiple displacement sensors for subsequent damping ratio identification. The specific selection rules are as follows: avoid the L / 7 measuring point when testing modes 6-8 or 13-15; avoid the L / 9 measuring point when testing modes 8-10 or 17-19; and avoid the L / 11 measuring point when testing modes 10-12 or 20. Through this multi-measuring point combination and dynamic selection strategy, it can be ensured that there is at least one valid measuring point for each mode within the first 20 modal test range, thereby completely acquiring the free decay response signal of each mode.

[0046] (4) Apply an excitation force consistent with the target modal frequency through the exciter 7 to make the cable 6 achieve stable forced vibration.

[0047] The control module controls the vibrator 7 to apply an excitation force consistent with the target modal frequency, enabling the stay cable 6 to reach a stable vibration state. Simultaneously, the control module receives vibration signals collected by the displacement sensor in real time, assisting operators in determining whether the vibration has reached a steady state and issuing an unloading prompt at the optimal moment.

[0048] (5) Remove the locking piece 4 to disengage the force transmission rod 2 from the transmission hole, and the cable 6 enters free damping vibration.

[0049] Once the vibration stabilizes, the operator manually pulls out the locking piece 4 according to the prompt signal output by the control module. Once the locking piece 4 is removed, the constraint between the force transmission rod 2 and the sleeve 3 is immediately released. Simultaneously, the elastic potential energy stored in the elastic element 81 of the rapid rebound assembly is released instantaneously, driving the force transmission rod 2 to rapidly retreat along the axial direction of the sleeve 3, causing its end to instantly disengage from the transmission hole 101 of the cable clamp assembly 1. At this point, the force transmission path between the vibrator 7 and the stay cable 6 is completely cut off, and the stay cable 6 immediately enters a state of free damped vibration. The entire unloading process is actively driven by the elastic element, completed in a very short time, and without any lateral impact or additional excitation.

[0050] (6) Collect free decay vibration data through displacement sensors.

[0051] During the free decay process of cable 6, the displacement sensor at the selected effective measuring point in step (3) continuously collects the vibration response signal, and the control module records and stores the pre-selected effective measuring point signal. Since the sensor avoids the stagnation area, the amplitude of the collected free decay signal is large enough and the signal-to-noise ratio is high.

[0052] (7) Identify the damping ratio of cable 6 based on free decay vibration data.

[0053] Finally, based on the collected free decay vibration data, the control module or external processing equipment uses methods such as the logarithmic decay method or the half-power bandwidth method to identify the damping ratio of the stay cable 6. For a stay cable system equipped with a damper 9, this damping ratio represents the system's damping characteristics after the damper is installed, and can be used to evaluate the damper's vibration reduction effect.

[0054] The test method of this embodiment has the following technical effects: First, it unloads quickly, achieving instantaneous unloading through active driving of the elastic element 81, ensuring the purity of the initial conditions for free decay; Second, it minimizes disturbance, avoiding the additional excitation caused by traditional manual operation; Third, the dual height adjustment mechanism (coarse adjustment of discrete holes plus fine adjustment of height adjustment bolts) combined with the correspondence between the number of adjustment holes and the difference in modal order can flexibly adapt to different modes and different exciter installation positions, achieving rapid switching of operating conditions; Fourth, the combination of multiple measurement points ensures that each order has an effective signal available in multi-mode testing, significantly improving the integrity and reliability of multi-mode damping testing.

[0055] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A rapid unloading device for cable-stayed bridge damping testing, characterized in that, The device includes a cable clamp assembly (1), a force transmission rod (2), a sleeve (3), a locking member (4), and a connecting member (5). The cable clamp assembly (1) is used to connect with the stay cable (6). The cable clamp assembly (1) is provided with a transmission hole (101). One end of the force transmission rod (2) is inserted into the transmission hole (101), and the other end is axially movable and accommodated in the sleeve (3). The locking member (4) is detachably connected between the force transmission rod (2) and the sleeve (3) to restrict their movement. The connecting member (5) is used to connect the sleeve (3) and the vibrator (7). When the locking member (4) is removed, the force transmission rod (2) moves axially relative to the sleeve (3) to disengage from the transmission hole (101).

2. The rapid unloading device for cable-stayed bridge damping testing according to claim 1, characterized in that, It also includes a rapid rebound assembly, which includes an elastic element (81), a first base (82) and a second base (83). The first base (82) is mounted on one end of the force transmission rod (2) near the transmission hole (101), and the second base (83) is mounted on the sleeve (3). The elastic element (81) is connected between the first base (82) and the second base (83) to give the force transmission rod (2) a tendency to retract into the sleeve (3).

3. The rapid unloading device for cable-stayed bridge damping testing according to claim 1, characterized in that, The force-transmitting rod (2) has a through hole, and the sleeve (3) has an adjustment hole (31). The locking member (4) is a pin-type structure. The locking member (4) passes through both the adjustment hole (31) and the through hole to restrict the relative movement of the force-transmitting rod (2) and the sleeve (3).

4. The rapid unloading device for cable-stayed bridge damping testing according to claim 1, characterized in that, The cable clamp assembly (1) includes two clamping blocks (11), each clamping block (11) having a groove (102). The grooves (102) on the two clamping blocks (11) are joined together to accommodate the stay cable (6). The two clamping blocks (11) are locked together by bolts. The transmission hole (101) is located on one of the clamping blocks (11).

5. A cable-stayed bridge damping testing system, comprising an exciter (7), a displacement sensor, and a control module, characterized in that, It also includes the rapid unloading device according to any one of claims 1 to 4, wherein the vibrator (7) is connected to the connector (5) for applying excitation force to the cable (6); the displacement sensor is used to collect the vibration response signal of the cable (6); and the control module is connected to the vibrator (7) and the displacement sensor respectively.

6. A test method based on the cable-stayed bridge damping test system according to claim 5, characterized in that, include: The installation position of the exciter (7) is determined according to the order of the target test mode to avoid the mode shape nodes; The vibrator (7) is connected to the cable (6) via the quick unloading device. The vibration response signal of the cable (6) is acquired by the displacement sensor; By applying an excitation force consistent with the target modal frequency through the exciter (7), the cable-stayed cable (6) achieves stable forced vibration; Remove the locking member (4) to disengage the force transmission rod (2) from the transmission hole (101), and the cable (6) enters free damping vibration; The displacement sensor collects free decay vibration data. The damping ratio of the cable (6) is identified based on the free decay vibration data.

7. The test method according to claim 6, characterized in that, Multiple displacement sensors are provided and arranged at three positions L / 7, L / 9 and L / 11 of the stay cable (6), where L is the length of the stay cable (6); the method further includes: selecting sensor signals that do not fall in the mode stagnation region from the signals of multiple displacement sensors as signals for damping ratio identification according to the target modal order, specifically including: When testing modes 6-8 or 13-15, avoid measuring point L / 7. When testing modes 8-10 or 17-19, avoid measuring at L / 9. When testing the 10th to 12th or 20th modes, avoid the L / 11 measurement point.

8. The test method according to claim 7, characterized in that, The sleeve (3) is provided with a plurality of adjustment holes (31) arranged sequentially along the axial direction. The number of adjustment holes (31) is determined according to the difference in the modal order of the cable (6) to be tested. If it is necessary to switch from the i-th mode to the j-th mode for testing, the number of adjustment holes (31) is set to ji and they are evenly arranged along the axial direction of the sleeve (3).

9. The test method according to claim 8, characterized in that, The connector (5) is a height adjustment bolt. One end of the height adjustment bolt is threaded to the sleeve (3), and the other end is threaded to the vibrator (7). Before connecting the vibrator (7) and the height adjustment bolt, the following steps are also included: making a large-range coarse adjustment by selecting the adjustment hole (31) at different positions, and then making a small-range fine adjustment by rotating the height adjustment bolt. After that, the vibrator (7) is connected to the height adjustment bolt.

10. The test method according to claim 6, characterized in that, The step of determining the installation position of the exciter (7) according to the order of the target test mode includes: for higher order modes, installing the exciter (7) at or near the antinode of the mode shape.

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