Wind vibration monitoring and intelligent vibration reduction protection device for split three-box girder of long-span bridge

Abstract

The application discloses a large-span bridge separated three-box girder wind vibration monitoring and intelligent damping protection device, which comprises four sets of wind speed and direction instruments, a plurality of acceleration sensors, an acquisition box, a central control system and four sets of suction / blowing systems. The central control system collects the data of the four sets of wind speed and direction instruments and the plurality of acceleration sensors in real time, determines the wind field condition of the maximum acceleration position and the static or vibration state of the three-box girder, judges whether the vibration amplitude exceeds the standard allowable value if the three-box girder vibrates, controls the operation of the four sets of suction / blowing systems, and feeds back the collected wind speed signals and vibration signals in real time, forms a closed-loop control, and stops until the gap flow main frequency power spectrum density amplitude and the real-time vibration amplitude are less than the allowable value. The device has the advantages of simple structure and can effectively prevent / control the vortex-induced vibration of the separated three-box girder structure.

Description

Technical Field

[0001] This invention belongs to the field of wind-induced vibration prevention and control of engineering structures, specifically involving a wind vibration monitoring and intelligent vibration reduction protection device for a long-span bridge with a separated three-box girder. Background Technology

[0002] Engineering requirements have placed higher demands on the span of main girders in long-span bridges. The separated three-box girder section, due to its large ultimate span and superior flutter stability, is being widely used, such as the Xihoumen and Taoyaomen road-rail bridges currently under construction, whose main girders all employ this section. As bridge spans increase, the main girder structure becomes more flexible, with reduced stiffness and damping, making it more sensitive to wind loads and prone to wind-induced vibrations. While the separated three-box girder section improves the flutter stability of the main girder, it is more sensitive to vortex-induced vibrations. In low-wind-speed environments, the upper and lower shear layers interact in the gaps between the box girders, forming large-scale vortices that detach alternately. When the frequency of vortex shearing approaches the frequency of a certain order of the main girder's array, vortex-induced vibration occurs. After vortex-induced vibration occurs, the vortex shearing location shifts from the downstream gap to the upstream gap. Furthermore, structural vibration also enhances the instability of the unilateral shear layer, inducing vibration-induced vortices that maintain the structure's vortex-induced response. Vortex-induced vibration can damage the main girder structure itself, impairing its durability and safety. Therefore, reducing wind loads and wind-induced vibrations is a crucial aspect of the design process for separated three-box girder bridges with long spans. Current main control measures include mechanical damping control and aerodynamic control. The former controls wind-induced vibration by altering the inherent characteristics of the structure, such as damper control. The latter controls wind-induced vibration by stabilizing the surrounding flow field, such as active air intake control.

[0003] Traditional active suction and blowing control schemes for single box girders (such as the patent application with publication number CN113235398A) cannot be effectively applied to separated three box girders because: (1) The main working principle is to delay the interaction between the upper and lower shear layers by blowing air on the leeward side, thereby suppressing the Karman vortex in the wake and the vortex-induced vibration induced by it. For separated three box girders, the shedding of Karman vortices in the gaps (especially the downstream gaps) is the main cause of vortex-induced vibration. Although the airflow blown out by the forward and reverse air acceleration units can suppress the directional vortex, it will directly act on the downstream box girder of the separated three box girder, increasing the aerodynamic force on the downstream box girder; (2) When the seasons change and the monsoon wind direction at the bridge site reverses, the unsteady vortex in the gaps will increase. The position changes. Traditional solutions are difficult to identify the location of unstable gap flows and cannot meet control requirements. If control is applied to steady gap flows, gap flow instability will be amplified, increasing the probability of vortex-induced vibration. (3) When gap vortices induce vortex-induced vibration in the structure, the location of alternating shedding vortices will also change. Traditional solutions cannot accurately monitor the complex wind field of the three-box girder and implement effective control. (4) Structural vibration will lead to enhanced instability of the unilateral shear layer, generating vibration-induced vortices on the upper and lower walls of the box girder. Traditional solutions cannot suppress such vortices. Therefore, the active suction and blowing control scheme for single-box girder based on flow direction vortex suppression cannot effectively monitor the complex wind field at the site of the separated three-box girder bridge, and it is even more difficult to effectively prevent and control its vortex-induced vibration. Summary of the Invention

[0004] Based on the above shortcomings, the purpose of this invention is to provide a wind vibration monitoring and intelligent vibration reduction protection device for separated three-box girder bridges with long spans. This device is used to monitor the complex wind field and vibration displacement of the three-box girder structure at the bridge site of a separated three-box girder bridge with a long span, and to prevent / control its vortex-induced vibration under specific wind fields. This solves the problem that the existing technology cannot effectively monitor the complex wind field at the bridge site of a separated three-box girder bridge, and it is even more difficult to effectively prevent and control its vortex-induced vibration.

[0005] The technical solution adopted in this invention is as follows: A wind vibration monitoring and intelligent vibration reduction protection device for a long-span bridge with a separated three-box girder, comprising four sets of anemometers, multiple acceleration sensors, a data acquisition box, a central control system, and four sets of suction / blowing systems. Anemometer A is located at the wind nozzle position on the windward edge box girder, anemometer B is located at the vertical center of the windward web of the middle box girder, anemometer C is located at the vertical center of the leeward web of the middle box girder, and anemometer D is located at the wind nozzle position on the leeward edge box girder. Anemometers A / D are used to monitor the incoming wind field, wind speed, and wind direction. Instruments B / C are used to monitor unstable wind fields in the gaps. Multiple acceleration sensors are respectively set at key nodes and points of maximum deflection of the three box girders to obtain the maximum axial deflection of the three box girders. Each of the two edge box girders is equipped with a suction / blowing system, and the middle box girder has two suction / blowing systems. Each suction / blowing system includes a fan, multiple blowing holes, multiple suction holes, and connecting pipes. Powered by the fan, gas is drawn in through the suction holes, accelerated, and blown out through the blowing holes via the connecting pipes. At the lowest edge of the windward bottom plate of the windward edge box girder, and close to the leeward side of the windward edge box girder... Multiple air inlets and air outlets are arranged sequentially and at intervals along the web of the girder, with the airflow direction of each air inlet and air outlet perpendicular to the windward bottom plate wall. At the lowest edge of the leeward bottom plate of the leeward edge box girder and close to the windward web of the leeward edge box girder, multiple air inlets and air outlets are arranged sequentially and at intervals along the web of the girder, with the airflow direction of each air inlet and air outlet perpendicular to the leeward bottom plate wall. On both sides of the bottom plate of the intermediate box girder and close to the web of the girder, multiple air inlets and air outlets are arranged sequentially and at intervals along the web of the girder, with the airflow direction of each air inlet and air outlet perpendicular to the bottom plate wall. The central control system collects data from four sets of anemometers and multiple accelerometers in real time to determine the wind field conditions at the location of maximum acceleration, including information on incoming wind direction, wind speed, and wind angle of attack. It also determines whether the three box girders are stationary or vibrating. If the three box girders vibrate, the central control system will determine whether the vibration amplitude exceeds the allowable value specified in the standard, and then control the operation of the four sets of air intake / blowing systems. It also provides real-time feedback of the collected wind speed and vibration signals to form a closed-loop control until the amplitude of the interstitial flow power spectral density and the real-time vibration amplitude of the three box girders are less than the allowable value.

[0006] Furthermore, the distance between the two sets of suction / blowing systems of the intermediate box girder is no greater than the height of the intermediate box girder.

[0007] Furthermore, the air intake is equipped with a filter and a dehumidifier, and the air outlet is equipped with a dehumidifier.

[0008] Furthermore, if the wind speed is less than the critical wind speed for vortex-induced vibration and the acceleration of the three box girders is less than the allowable value specified in the standard, the central control system will not take any measures or will shut down the operating air intake / blowing system.

[0009] If the wind speed is close to the critical wind speed of vortex-induced vibration or is within the wind speed range of vortex-induced vibration, but the acceleration value of the three box girders is still less than the allowable value specified in the code, the vortex-induced vibration prevention scheme shall be adopted, and the steps are as follows;

[0010] S11: The central system analysis module loads the data collected by the anemometers B / C, and through power spectral density analysis, obtains the dominant frequency of the flow in each gap and the corresponding power spectral density amplitude to determine the region where the unsteady gap flow is located. If the unsteady gap flow is located in the upstream gap, the suction / blowing system in the windward side box is activated. If the unsteady gap flow is located in the downstream gap, the suction / blowing system on the leeward side of the intermediate box girder is activated. If the unsteady gap flow exists in both the upstream and downstream gaps, the suction / blowing systems in both the windward side box and the leeward side of the intermediate box girder are activated simultaneously.

[0011] S12: By activating the suction / blowing system, the spanwise correlation of shear layer interactions in the gap weakens, and the spanwise scale of alternating shedding vortices decreases, resulting in a reduction in the time-averaged and pulsating velocities of the gap flow. This weakens the energy of the alternating shedding vortices in the gap, and the amplitude of the power spectral density of the gap flow's dominant frequency decreases accordingly. At this time, the central control system processes the unsteady gap flow wind speed signal transmitted by the anemometers B / C in real time and performs power spectral analysis on the obtained wind speed signal. If the analysis results still contain a prominent dominant frequency, the central control system issues an early warning message and the power spectral density analysis results and uploads them to the host computer for alarm. At the same time, the central control system gradually increases the fan power of the activated blowing / suction system until the prominent dominant frequency disappears.

[0012] S13: Then the central control system gradually reduces the fan power of the activated suction / blowing system, thus preventing vortex-induced vibration of the bridge.

[0013] If the acceleration value of the three box girders is greater than the allowable value in the specification, the vortex vibration control scheme is adopted, and the steps are as follows: S21: The central control system loads the data collected by the wind speed and direction instrument B / C, performs power spectral density analysis on the wind speed data, obtains the power spectral density map of each gap flow, and determines the region where the unsteady gap flow is located based on whether there are harmonic frequencies.

[0014] S22: The central control system activates the intake / blowing system on the leeward side of the upstream box girder and the intermediate box girder to control the vortex energy of the unsteady gap flow and reduce its spanwise scale. At the same time, for the large-scale unilateral vortex induced by the vortex-induced vibration of the three box girders, the central control system increases the power of the intake / blowing system fan to accelerate the dissipation of the large-scale flow vortex into a small-scale vortex, thereby weakening the self-excitation force of the vortex vibration of the three box girders, reducing the amplitude of the vortex-induced vibration, and reducing the spanwise scale and energy of the vibration-induced vortex, thereby weakening the amplitude of the vortex-induced vibration.

[0015] S23: The central control system processes the collected real-time acceleration signal. If the real-time amplitude value of the three box girder is still greater than the allowable value of the specification, the central control system continues to increase the power of the blower of the already started air intake / blowing system, and further controls the energy of the alternating falling vortex and vibration-induced vortex to suppress the amplitude of vortex-induced vibration until the real-time vibration amplitude of the three box girder structure is less than the allowable value of the specification.

[0016] S24: The central control system gradually reduces the power of the blower in the activated air intake / blowing system, thereby controlling the vortex-induced vibration of the bridge.

[0017] Advantages and beneficial effects of the present invention: The device of the present invention has the advantage of simple structure and can effectively prevent / control vortex-induced vibration of a split three-box girder structure. The device of the present invention can disrupt the correlation of the shear layer about to enter the gap of the three box girders, suppress the scale of spanwise vortices, thereby weakening the shedding of gap vortices in the split three box girders, and thus ultimately preventing the occurrence of vortex-induced vibration; and can also disrupt the large-scale vibration-induced vortices induced by the vibration of the three box girders, and can also disrupt the spanwise correlation of alternating shedding vortices in the gap flow field of the three box girders, thereby ultimately suppressing vortex-induced vibration. Attached Figure Description

[0018] Figure 1 A simplified diagram of the equipment layout at the key cross-section;

[0019] Figure 2 A schematic diagram of a spanwise air intake and blowing control system for vibration reduction and protection of a separated three-box girder bridge;

[0020] Figure 3 A schematic diagram showing the division of the air intake / blowing system in a separated three-box girder vibration reduction and protection system for a long-span bridge;

[0021] Figure 4 A schematic diagram of the uncontrolled flow field around a separated three-box girder bridge when it is stationary;

[0022] Figure 5 A schematic diagram of the flow field around the cross-section of a separated three-box girder under the vortex-induced vibration prevention scheme;

[0023] Figure 6 A virtual outline of the controlled gap flow field of a separated three-box girder under a vortex-induced vibration prevention scheme;

[0024] Figure 7 A schematic diagram of the uncontrolled flow field around a separated three-box girder bridge during vortex-induced vibration.

[0025] Figure 8 This is a schematic diagram of the flow field around the controlled section of a separated three-box girder under the vortex-induced vibration control scheme.

[0026] Figure 9 This is a schematic diagram of the vortex-induced vibration control principle of the vibration reduction and protection device of the present invention.

[0027] Among them, 1. Windward edge box girder, 2. Middle box girder, 3. Leeward edge box girder, 4. Anemometer A, 5. Anemometer B, 6. Anemometer C, 7. Anemometer D, 11. Accelerometer, 12. First suction / blowing system, 13. Second suction / blowing system, 14. Third suction / blowing system, 15. Fourth suction / blowing system, 18. Suction port, 19. Blowing port, 20. Connecting pipe. Detailed Implementation

[0028] The invention will be further illustrated below with an example from the attached drawings of a long-span dual-purpose road-rail bridge in Southwest my country.

[0029] Example 1:

[0030] like Figure 1-3As shown, a wind-induced vibration monitoring and intelligent vibration reduction protection device for a long-span bridge with a separated three-box girder includes four sets of anemometers and wind direction meters, multiple acceleration sensors, a data acquisition box, a central control system, and four sets of suction / blowing systems. Anemometer A4 is located at the wind nozzle position of the windward edge box girder 1, anemometer B5 is located at the vertical center of the windward web of the middle box girder 2, and anemometer C... 6 is located at the vertical center of the leeward web of the middle box girder; anemometer D7 is located at the nozzle of the leeward edge box girder 3; anemometers A / D are used to monitor the incoming wind field; anemometers B / C are used to monitor the unstable wind field at the gap; multiple acceleration sensors 11 are respectively set at key nodes and points of maximum deflection of the three box girders to obtain the maximum axial deflection of the three box girders; the windward edge box girder 1 is equipped with a first suction / blowing system 12; the leeward edge box girder 3 is equipped with a fourth suction / blowing system 15; the middle box girder is equipped with a second suction / blowing system 13 and a third suction / blowing system 14. Each suction / blowing system includes a fan, multiple blowing holes 18, multiple suction holes 19, and connecting pipes 20. Powered by the fan, gas is drawn in through the suction holes 18 and accelerated out through the blowing holes 18 via the connecting pipes 20; in the windward edge box girder 1... Multiple air-blowing holes and air-inhaling holes of the first air-blowing system 12 are arranged sequentially and at intervals along the longitudinal direction of the leeward web of the leeward edge box girder at the lowest edge of the leeward bottom plate. The airflow direction of each air-blowing hole and air-inhaling hole is perpendicular to the wall of the leeward bottom plate. Multiple air-blowing holes and air-inhaling holes of the fourth air-blowing system 15 are arranged sequentially and at intervals along the longitudinal direction of the leeward edge box girder 3 at the lowest edge of the leeward bottom plate. The airflow direction of each air-blowing hole and air-inhaling hole is perpendicular to the wall of the leeward bottom plate. Multiple air-blowing holes and air-inhaling holes of the second air-blowing system 13 and the third air-blowing system 14 are arranged sequentially and at intervals along the longitudinal direction of the bottom plate on both sides of the bottom plate of the middle box girder and at the position close to the web. The airflow direction of each air-blowing hole and air-inhaling hole is perpendicular to the bottom plate wall. Each air-inhaling hole is equipped with a filter screen and a dehumidifier, and each air-blowing hole is equipped with a dehumidifier. Furthermore, the distance between the second suction / blowing system 13 and the third suction / blowing system 14 is not greater than the height of the intermediate box girder;

[0031] like Figure 4 As shown, when the suction / blowing system is closed, in the upstream gap, the shear layer intermittently impacts the leading edge wall of the intermediate box girder, and the vortex energy in the recirculation zone formed in the gap is low. In the downstream gap, alternating vortices will form, and when the vortex frequency approaches the structure's natural frequency, vortex-induced vibration of the three box girders will be induced.

[0032] The central control system collects data in real time from four sets of anemometers and multiple accelerometers to determine the wind field conditions at the location of maximum acceleration, including incoming wind direction, wind speed, and angle of attack. It also determines whether the three box girders are stationary or vibrating. If vibration occurs, the central control system checks if the vibration amplitude exceeds the permissible limit and then controls the operation of the four suction / blowing systems. It provides real-time feedback of the collected wind speed and vibration signals, forming a closed-loop control system, until the interstitial flow power spectral density amplitude and real-time vibration amplitude of the three box girders are below the permissible limits. The central control system has a data caching function, which can identify the critical wind speed for vortex-induced vibration of the three box girders based on long-term monitoring data—that is, the incoming wind speed under different wind directions when the structural amplitude of the three box girders just reaches the permissible limit.

[0033] If the wind speed is less than the critical wind speed for vortex-induced vibration and the acceleration of the three box girders is less than the allowable value specified in the standard, the central control system will not take any measures or will shut down the operating air intake / blowing system; if the wind speed is close to the critical wind speed for vortex-induced vibration or is within the wind speed range for vortex-induced vibration, but the acceleration value of the three box girders is still less than the allowable value specified in the standard, the vortex-induced vibration prevention scheme will be adopted, and the steps are as follows.

[0034] S11: The central system analysis module loads the data collected by the anemometers B / C, and through power spectral density analysis, obtains the dominant frequency of the flow in each gap and the corresponding power spectral density amplitude to determine the region where the unsteady gap flow is located. If the unsteady gap flow is located in the upstream gap, the suction / blowing system in the windward side box is activated. If the unsteady gap flow is located in the downstream gap, the suction / blowing system on the leeward side of the intermediate box girder is activated. If the unsteady gap flow exists in both the upstream and downstream gaps, the suction / blowing systems in both the windward side box and the leeward side of the intermediate box girder are activated simultaneously.

[0035] S12: By activating the suction / blowing system, the spanwise correlation of shear layer interactions in the gap weakens, and the spanwise scale of alternating shedding vortices decreases, resulting in a reduction in the time-averaged and pulsating velocities of the gap flow. This weakens the energy of the alternating shedding vortices in the gap, and the amplitude of the power spectral density of the gap flow's dominant frequency decreases accordingly. At this time, the central control system processes the unsteady gap flow wind speed signal transmitted by the anemometers B / C in real time and performs power spectral analysis on the obtained wind speed signal. If the analysis results still contain a prominent dominant frequency, the central control system issues an early warning message and the power spectral density analysis results and uploads them to the host computer for alarm. At the same time, the central control system gradually increases the fan power of the activated blowing / suction system until the prominent dominant frequency disappears.

[0036] S13: Then the central control system gradually reduces the fan power of the activated suction / blowing system, thus preventing vortex-induced vibration of the bridge.

[0037] If the acceleration value of the three box girders is greater than the allowable value in the specification, the vortex vibration control scheme is adopted, and the steps are as follows: S21: The central control system loads the data collected by the wind speed and direction instrument B / C, performs power spectral density analysis on the wind speed data, obtains the power spectral density map of each gap flow, and determines the region where the unsteady gap flow is located based on whether there are harmonic frequencies.

[0038] S22: The central control system activates the intake / blowing system on the leeward side of the upstream box girder and the intermediate box girder to control the vortex energy of the unsteady gap flow and reduce its spanwise scale. At the same time, for the large-scale unilateral vortex induced by the vortex-induced vibration of the three box girders, the central control system increases the power of the intake / blowing system fan to accelerate the dissipation of the large-scale flow vortex into a small-scale vortex, thereby weakening the self-excitation force of the vortex vibration of the three box girders, reducing the amplitude of the vortex-induced vibration, and reducing the spanwise scale and energy of the vibration-induced vortex, thereby weakening the amplitude of the vortex-induced vibration.

[0039] S23: The central control system processes the collected real-time acceleration signal. If the real-time amplitude value of the three box girder is still greater than the allowable value of the specification, the central control system continues to increase the power of the blower of the already started air intake / blowing system, and further controls the energy of the alternating falling vortex and vibration-induced vortex to suppress the amplitude of vortex-induced vibration until the real-time vibration amplitude of the three box girder structure is less than the allowable value of the specification.

[0040] S24: The central control system gradually reduces the power of the blower in the activated air intake / blowing system, thereby controlling the vortex-induced vibration of the bridge.

[0041] like Figure 5 As shown, when the third suction / blowing system on the leeward side of the intermediate box girder is activated, the blowing airflow can weaken the curling of the lower shear layer, causing it to directly impact the windward wall of the downstream box girder, preventing it from interacting with the upper shear layer and generating alternating shedding vortices that induce vortex-induced vibrations in the structure. The suction airflow can alter the spanwise correlation of the alternating shedding vortices, reducing the spanwise scale of the alternating shedding vortices in the gaps.

[0042] like Figure 6 As shown, air is drawn in through the intake port, passes through the ventilation pipe, and is accelerated by the fan before being blown out through the exhaust port. The staggered intake and exhaust airflows can disrupt the spanwise correlation of alternating detached vortices in the gap flow field during vortex-induced vibration of the structure, reduce the size of alternating detached vortices in the gap, and lower the time-averaged and pulsating velocity of the gap flow. This greatly reduces the pulsating pressure on the surface of the separated three-box girder structure and significantly reduces the lift on the box girder surface.

[0043] like Figure 7 As shown, when the structure experiences vortex-induced vibration, alternating shedding vortices transfer from the downstream gap to the upstream gap, and large-scale vibration-induced vortices appear on both sides of the separated three-box girder structure. The alternating shedding vortices in the upstream gap and the vibration-induced vortices on both sides of the structure work together to maintain the vortex-induced vibration of the structure.

[0044] like Figure 8 As shown, when the first suction / blowing system 12 and the third suction / blowing system 14 on the leeward side of the central control system's windward edge box girder 1 and the middle box girder 2 work together, the blowing airflow of the windward edge box girder 1 can weaken the upward curling of the shear layer, preventing it from interacting with the upper shear layer to form alternating shedding vortices. Simultaneously, the suction airflow of the windward edge box girder 1 can weaken the spanwise correlation of the alternating shedding vortices in the upstream gap, further weakening their energy. The blowing airflow on the leeward side of the middle box girder 2 can disrupt large-scale vibration-induced vortices, breaking them into smaller vortices and accelerating their dissipation. Meanwhile, the suction airflow on the leeward side of the middle box girder 2 can reduce the scale of the vibration-induced vortices flowing towards them, further weakening the vortex energy. Therefore, the vortex energy maintaining the vortex-induced vibration of the structure is weakened, thereby reducing the aerodynamic self-excited force acting on the box girder structure and reducing the amplitude of the vortex-induced vibration.

[0045] The wind field surrounding the separated three-box girder structure is complex, and the alternating shedding vortices that induce vortex-induced vibration exhibit multi-regional characteristics as the angle of attack changes. Therefore, real-time monitoring of the incoming wind speed at multiple regions and measurement points is necessary to prevent vortex-induced vibration. By comparing and analyzing the critical wind speed for vortex-induced vibration obtained from long-term monitoring data, the central control system automatically determines whether to adopt a vortex-induced vibration prevention / control scheme. Because the alternating shedding vortices that induce vortex-induced vibration exhibit multi-regional characteristics, the central system, after determining to adopt a vortex-induced vibration prevention scheme, can determine the gaps containing highly unstable unsteady vortices based on real-time data provided by the wind speed sensors at the intermediate box girder, and implement precise control. Furthermore, when vortex-induced vibration occurs, the device can determine whether to adopt a vortex-induced vibration control scheme based on whether the maximum axial deflection of the bridge exceeds the allowable value specified by the central control system. Management personnel can also manually shut down the intake / blowing system based on information provided by the central control system. For a split three-box girder structure, the strong blowing airflow generated by the suction / blowing system, if directly acting on the gap flow field, will greatly increase the turbulence of the downstream flow field and worsen the stress condition of the downstream box girder. Therefore, when implementing the control system of this device, the suction and blowing pipes are perpendicular to the bottom wall of each box girder. In the vortex-induced vibration prevention scheme, the correlation of the shear layer in the gap about to enter the three box girders can be disrupted, and the scale of spanwise vortices can be suppressed, thereby weakening the shedding of vortices from the gaps of the split three box girders, and ultimately preventing the occurrence of vortex-induced vibration. In the vortex-induced vibration control scheme, both the large-scale vibration-induced vortices induced by the vibration of the three box girders and the spanwise correlation of alternating shed vortices in the gap flow field of the three box girders can be disrupted, thereby ultimately suppressing vortex-induced vibration.

Claims

1. A wind-induced vibration monitoring and intelligent vibration reduction protection device for a long-span bridge with a separated three-box girder, comprising four sets of anemometers, multiple acceleration sensors, a data acquisition box, a central control system, and four sets of suction / blowing systems, characterized in that: Anemometer A is located at the wind nozzle of the windward edge box girder; anemometer B is located at the vertical center of the windward web of the middle box girder; anemometer C is located at the vertical center of the leeward web of the middle box girder; and anemometer D is located at the wind nozzle of the leeward edge box girder. Anemometers A and D are used to monitor the incoming wind field, while anemometers B and C are used to monitor the unstable wind field at the gaps. Multiple acceleration sensors are respectively installed at key nodes and points of maximum deflection of the three box girders to obtain the maximum axial deflection of the three box girders. Each of the two edge box girders is equipped with one suction / blowing system, and the middle box girder is equipped with two suction / blowing systems. Each air intake / exhaust system includes a fan, multiple air intake holes, multiple air intake holes, and connecting pipes. Powered by the fan, gas is drawn in through the air intake holes, accelerated, and blown out through the air intake holes via the connecting pipes. Multiple air intake holes and air intake holes are arranged sequentially at intervals along the span of the windward side of the box girder, adjacent to the leeward side of the box girder. The airflow direction of each air intake hole and air intake hole is perpendicular to the windward side wall. Similarly, multiple air intake holes and air intake holes are arranged sequentially at intervals along the span of the leeward side of the box girder, adjacent to the windward side of the box girder. The airflow direction of each air intake hole and air intake hole is perpendicular to the leeward side wall. Multiple air intake holes and air intake holes are arranged sequentially at intervals along the span of the bottom plate of the intermediate box girder, adjacent to the web. The airflow direction of each air intake hole and air intake hole is perpendicular to the bottom plate wall. The central control system collects data from four sets of anemometers and multiple accelerometers in real time to determine the wind field conditions at the location of maximum acceleration, including information on incoming wind direction, wind speed, and wind angle of attack. It also determines whether the three box girders are stationary or vibrating. If the three box girders vibrate, the central control system will determine whether the vibration amplitude exceeds the allowable value specified in the standard, and then control the operation of the four sets of air intake / blowing systems. It also provides real-time feedback of the collected wind speed and vibration signals to form a closed-loop control until the amplitude of the interstitial flow power spectral density and the real-time vibration amplitude of the three box girders are less than the allowable value.

2. The wind vibration monitoring and intelligent vibration reduction protection device for a long-span bridge with a separated three-box girder as described in claim 1, characterized in that: The distance between the two sets of suction / blowing systems of the intermediate box girder is no greater than the height of the intermediate box girder.

3. The wind vibration monitoring and intelligent vibration reduction protection device for a long-span bridge with a separated three-box girder as described in claim 2, characterized in that: The air intake is equipped with a filter and a dehumidifier, and the air outlet is equipped with a dehumidifier.

4. A wind-induced vibration monitoring and intelligent vibration reduction protection device for a long-span bridge with a separated three-box girder, as described in any one of claims 1-3, characterized in that: If the wind speed is less than the critical wind speed for vortex-induced vibration and the acceleration of the three box girders is less than the allowable value specified in the standard, the central control system will not take any measures or shut down the operating air intake / blowing system. If the wind speed is close to the critical wind speed of vortex-induced vibration or is within the wind speed range of vortex-induced vibration, but the acceleration value of the three box girders is still less than the allowable value specified in the code, the vortex-induced vibration prevention scheme shall be adopted, and the steps are as follows; S11: The central system analysis module loads the data collected by the anemometers B / C, and through power spectral density analysis, obtains the dominant frequency of the flow in each gap and the corresponding power spectral density amplitude to determine the region where the unsteady gap flow is located. If the unsteady gap flow is located in the upstream gap, the suction / blowing system in the windward side box is activated. If the unsteady gap flow is located in the downstream gap, the suction / blowing system on the leeward side of the intermediate box girder is activated. If the unsteady gap flow exists in both the upstream and downstream gaps, the suction / blowing systems in both the windward side box and the leeward side of the intermediate box girder are activated simultaneously. S12: By activating the suction / blowing system, the spanwise correlation of shear layer interactions in the gap weakens, and the spanwise scale of alternating shedding vortices decreases, resulting in a reduction in the time-averaged and pulsating velocities of the gap flow. This weakens the energy of the alternating shedding vortices in the gap, and the amplitude of the power spectral density of the gap flow's dominant frequency decreases accordingly. At this time, the central control system processes the unsteady gap flow wind speed signal transmitted by the anemometers B / C in real time and performs power spectral analysis on the obtained wind speed signal. If the analysis results still contain a prominent dominant frequency, the central control system issues an early warning message and the power spectral density analysis results and uploads them to the host computer for alarm. At the same time, the central control system gradually increases the fan power of the activated blowing / suction system until the prominent dominant frequency disappears. S13: Then the central control system gradually reduces the fan power of the activated suction / blowing system, thus preventing vortex-induced vibration of the bridge. If the acceleration value of the three box girders exceeds the allowable value specified in the code, a vortex-induced vibration control scheme shall be adopted, and the steps are as follows: S21: The central control system loads the data collected by the wind speed and direction instrument B / C, performs power spectral density analysis on the wind speed data, obtains the power spectral density map of each gap flow, and determines the region where the unsteady gap flow is located based on whether there are harmonic frequencies. S22: The central control system activates the intake / blowing system on the leeward side of the upstream box girder and the intermediate box girder to control the vortex energy of the unsteady gap flow and reduce its spanwise scale. At the same time, for the large-scale unilateral vortex induced by the vortex-induced vibration of the three box girders, the central control system increases the power of the intake / blowing system fan to accelerate the dissipation of the large-scale flow vortex into a small-scale vortex, thereby weakening the self-excitation force of the vortex vibration of the three box girders, reducing the amplitude of the vortex-induced vibration, and reducing the spanwise scale and energy of the vibration-induced vortex, thereby weakening the amplitude of the vortex-induced vibration. S23: The central control system processes the collected real-time acceleration signal. If the real-time amplitude value of the three box girder is still greater than the allowable value of the specification, the central control system continues to increase the power of the blower of the already started air intake / blowing system, and further controls the energy of the alternating falling vortex and vibration-induced vortex to suppress the amplitude of vortex-induced vibration until the real-time vibration amplitude of the three box girder structure is less than the allowable value of the specification. S24: The central control system gradually reduces the power of the blower in the activated air intake / blowing system, thereby controlling the vortex-induced vibration of the bridge.

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