Large-span bridge wind-induced low-frequency torsional vibration control device

Abstract

The invention belongs to the technical field of bridge wind resistance, and discloses a large-span bridge wind-induced low-frequency torsional vibration control device which is mainly composed of a fixed pulley, a rope, a mass block, a spring and a damper or an actuator. Based on the characteristic that the two sides vertically vibrate in opposite phases during torsional vibration of a bridge girder, mass blocks are transversely and symmetrically arranged on the bridge girder in a stress mode of rope suspension and fixed pulley transmission, so that the mass blocks on the two sides are balanced in self weight in a static state, and the bearing capacity requirement of a spring or an actuator and the engineering cost are greatly reduced. Compared with a low-frequency torsional vibration control traditional passive measure, the strength, the length, the number and the cost of the spring are greatly reduced, and the static deformation of the spring is greatly reduced. Compared with a low-frequency torsional vibration control traditional active measure, the driving force and power consumption requirements of the actuator are greatly reduced, the weight is lighter, and the cost is lower. The device is also suitable for different-frequency torsional vibration control and torsional vibration excitation of other engineering structures, the function is powerful, and the application range is wide.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of vibration control, and relates to a wind-induced low-frequency torsional vibration control device for a large-span bridge. BACKGROUND

[0002] Large-span flexible bridges may experience significant torsional vortex vibration and buffeting under common wind loads, affecting the driving comfort and the fatigue characteristics of the bridge structure; under extreme wind conditions, torsional flutter or bending-torsional coupled flutter may occur, seriously threatening the safety of the bridge structure. For a bridge with a main span of more than 1,000 meters, especially a suspension bridge, the torsional vibration frequency may be lower than 0.2 Hz, such as the Strait of Messina Bridge in Italy (main span 3,300 m, minimum torsional frequency about 0.08 Hz), the 1915 Canakkale Bridge in Turkey (main span 2,023 m, minimum torsional frequency about 0.15 Hz), and the Zhangjingqiao Yangtze River Bridge in China (main span 2,300 m, minimum torsional frequency about 0.16 Hz).

[0003] Traditional tuned mass damper (TMD) is often used for bridge vibration control, and the relationship between the spring static deformation and the frequency is: δ = g / (2πf) 2 , where δ is the spring static deformation, g is the acceleration of gravity, and f is the frequency. When f = 0.2 Hz, δ ≈ 6.2 m; when f = 0.5 Hz, δ ≈ 1 m. Therefore, TMD is more suitable for high-frequency (e.g., > 0.5 Hz) vibration control of bridges. Due to the limitation of the vertical installation space of the bridge girder (usually < 4 m), it is difficult for a tensile spring TMD to achieve low-frequency control of the torsional vibration of a large-span bridge with a frequency lower than 0.2 Hz; although a compression spring can be installed and allows for greater deformation, the stability of the TMD is difficult to guarantee due to the torsional inclination of the bridge, so it is also difficult to apply to a frequency lower than 0.2 Hz. Although traditional active mass damper (AMD) can be used for wind-induced low-frequency lateral vibration control without the need for spring support, for wind-induced low-frequency torsional vibration of a large-span bridge, the actuator not only needs to provide driving force, but also usually needs to bear the weight of the mass, which requires a very high thrust of the actuator, and the actuator is huge in size and expensive. In addition, due to the limitation of the vertical space and installation conditions of the girder, it is difficult to arrange a large mass and large thrust actuator.

[0004] Aiming at the problem that the low-frequency torsional mode with a frequency below 0.2 Hz may occur vortex vibration, buffeting and flutter in the vertical space-limited interior of a large-span bridge main beam, a low-frequency torsional vibration control device with strong space adaptability, low cost and efficient and reliable vibration control is needed. Based on the characteristics of the vertical counter-phase vibration of the main beam on both sides of the bridge main beam during torsional vibration of the bridge main beam, a new control structure is designed, the horizontal space arrangement of the mass block in the interior of the bridge main beam is optimized, the high-strength light-weight rope is suspended and the low-friction damping large-diameter pulley is driven to avoid the stress mode in which all the gravity of the mass block is borne by the spring in the traditional TMD, only a small part of the gravity of the mass block is borne by the spring, thereby the spring strength requirement is significantly reduced, the low-frequency vibration of the large-tonnage mass block is tuned with shorter length and fewer springs (compared with the traditional TMD with the same mass block, the mass of the required spring can be reduced by at least one order of magnitude), and the installation of the spring and the mass block is no longer strictly limited by the limited vertical space in the interior of the main beam, the damping of the suspension transmission system can be adjusted in a large range, thereby the cost of the damper can be greatly reduced, and the low-frequency torsional vibration of the large-span bridge is efficiently controlled. Meanwhile, the damper can be replaced by an actuator, the spring is cancelled, the mass block is driven by the actuator to move in counter-phase resonance with the main beam, and the torsional vibration of the main beam is effectively controlled, and the mass block required at this time is smaller, and therefore the active control is more efficient. SUMMARY

[0005] Based on the above problems, the present application provides a large-span bridge wind-induced low-frequency torsional vibration control device.

[0006] The technical scheme of the present application is as follows:

[0007] A large-span bridge wind-induced low-frequency torsional vibration control device, comprising a fixed pulley, a rope, a first mass block, a second mass block, a first spring, a second spring and a damper; for a tuned mass damper device, two fixed pulleys are symmetrically installed on the end top plates on both sides of the bridge main beam at the section with the maximum vibration displacement, for supporting the horizontally arranged and tensioned rope; the two ends of the rope respectively suspend the first mass block and the second mass block; the upper ends of the first spring and the second spring are fixed to the end top plates in the interior of the bridge main beam, and the lower ends are respectively connected to the first mass block and the second mass block; the two ends of the damper are respectively connected to the mass block and the end top plate in the interior of the bridge main beam, for adjusting the damping and further adjusting the damping ratio of the large-span bridge wind-induced low-frequency torsional vibration control device. The first mass block and the second mass block are symmetrically arranged on both sides of the bridge main beam, the frequency is tuned through the first spring and the second spring, and the damping ratio is optimized through the damper, so that counter-phase resonance motion is generated during torsional vibration of the bridge main beam, and the tuning and control of the low-frequency torsional vibration are realized.

[0008] In the static equilibrium state, most of the gravity of the first mass and the second mass cancel each other out, and the first spring and the second spring only need to bear the small part of the gravity of the first mass and the second mass, thereby greatly reducing the load requirement of the first spring and the second spring, and the vibration frequency of the large-span bridge wind-induced low-frequency torsional vibration control device is no longer closely related to the static deformation of the first spring and the second spring, thereby greatly reducing the length, quantity and cost of the first spring and the second spring.

[0009] The damper in the large-span bridge wind-induced low-frequency torsional vibration control device is replaced by an actuator, and the first spring and the second spring are cancelled, at this time the tuned mass damper is converted into an active mass damper; when the main girder occurs torsional vibration, the acceleration directions of the first mass and the second mass are opposite, and the inertial forces generated thereby are also opposite, and the two form relative motion and excite system resonance, thereby realizing effective control of torsional vibration.

[0010] Further, the mass of the first mass and the second mass is the same or different.

[0011] Further, according to the actual situation, the first spring or the second spring in the large-span bridge wind-induced low-frequency torsional vibration control device is cancelled.

[0012] Further, the installation form of the first spring and the second spring is selected as vertical or horizontal arrangement according to the structural arrangement conditions.

[0013] Further, the actuator drives the main girder of the bridge to produce large torsional vibration, thereby identifying the modal frequency and modal damping ratio of the bridge under different amplitude conditions. By adjusting the output phase of the actuator, the bridge can also be excited to produce large torsional vibration, which is convenient for identifying the modal parameters under different amplitude conditions.

[0014] Further, the large-span bridge wind-induced low-frequency torsional vibration control device can also be suspended on a support installed inside the main girder of the bridge.

[0015] The large-span bridge wind-induced low-frequency torsional vibration control device is suitable for torsional vibration control of different vibration modes and frequencies of bridges and other engineering structures.

[0016] The beneficial effects of the present application are: (1) Compared with the traditional TMD, the mass blocks of the present application are symmetrically arranged on both sides of the bridge girder. When the bridge girder is subjected to torsional vibration, the two mass blocks generate inertia forces in opposite directions, thereby driving the tuned mass damper to vibrate. In the state of static equilibrium, the gravity of the two mass blocks is mostly counteracted by each other, and the spring only bears a small amount of gravity (even no gravity when tension-compression springs are used), which significantly reduces the spring load and strength requirements, thereby greatly reducing the spring length, quantity and cost; (2) Compared with the traditional TMD, the TMD of the present application does not need to rely on large deformation of the spring to achieve arbitrary low-frequency tuning, and the vertical space occupied by the spring is not limited, and the mass block size and material type are also not limited, which is more economically advantageous; (3) The damping of the tuned mass damper can be mainly provided by the friction of the fixed pulley, and the damping ratio can be adjusted by adjusting the friction characteristics of the pulley, thereby greatly reducing or even eliminating the independent damper, and significantly reducing the damping device and installation costs; (4) Compared with the traditional AMD, the gravity of the mass block of the present application does not need to be directly borne by the actuator, so the required driving force and power requirement of the actuator are smaller, and the price is lower; (5) The two types of devices are suitable for torsional vibration control of different vibration modes and frequencies of bridges and other engineering structures; (6) By adjusting the phase of the actuator output, the structure can also be excited to produce large torsional vibration, which is convenient for identifying modal parameters under different amplitude conditions. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a kind of control large span bridge wind induced low frequency torsional vibration's tuned mass damper.

[0018] Figure 2 It is a kind of control large span bridge wind induced low frequency torsional vibration's active mass damper.

[0019] In the figure: 1 fixed pulley, 2 rope, 3 first mass block, 4 second mass block, 5 first spring, 6 second spring, 7 damper, 8 actuator. DETAILED DESCRIPTION

[0020] The specific embodiments of the present application will be described in detail below in combination with the technical solutions and drawings.

[0021] As shown in Figure 1 and Figure 2 , the present application proposes a large-span bridge wind-induced low-frequency torsional vibration control device, which includes a fixed pulley 1, a rope 2, a first mass block 3, a second mass block 4, a first spring 5, a second spring 6 and a damper 7.

[0022] For the tuned mass damper device, two fixed pulleys 1 are symmetrically installed on the end top plates of the bridge girder at the positions of maximum vibration displacement, for supporting the horizontally arranged and tensioned rope 2; the two ends of the rope 2 are respectively suspended with a first mass block 3 and a second mass block 4; the upper ends of a first spring 5 and a second spring 6 are fixed on the end top plates in the bridge girder, and the lower ends are respectively connected with the first mass block 3 and the second mass block 4; the two ends of a damper 7 are respectively connected with the mass blocks and the end top plates in the bridge girder, for adjusting the damping and further adjusting the damping ratio of the wind-induced low-frequency torsional vibration control device of the long-span bridge. The first mass block 3 and the second mass block 4 are symmetrically arranged at the two sides of the bridge girder, and the system resonance is excited by the relative motion of the first mass block 3 and the second mass block 4 and the first spring 5 and the second spring 6, and the system energy is consumed, so as to realize the tuning and control of the arbitrary low-frequency torsional vibration.

[0023] In the static equilibrium state, most of the gravity of the first mass block 3 and the second mass block 4 is counteracted by each other, and the first spring 5 and the second spring 6 only need to bear the remaining small part of the gravity of the first mass block 3 and the second mass block 4, thereby greatly reducing the load requirement of the first spring 5 and the second spring 6, so that the vibration frequency of the wind-induced low-frequency torsional vibration control device of the long-span bridge is no longer closely related to the static deformation of the first spring 5 and the second spring 6, thereby greatly reducing the length, quantity and cost of the first spring 5 and the second spring 6.

[0024] When the first spring 5 and the second spring 6 are tension-compression springs, the mass of the first mass block 3 and the second mass block 4 can be the same. At this time, the load requirement of the first spring 5 and the second spring 6 is lower, and only needs to meet the conditions of the stiffness requirement of the tuned mass damper device and the allowable deformation being greater than the maximum amplitude of the first mass block 3 and the second mass block 4. In theory, the tuned mass damper device can realize arbitrary low-frequency (<0.01 Hz, even smaller) tuning.

[0025] From the engineering application point of view, the tension spring does not have the problem of compression stability, and is more practical. In the static equilibrium state, the first spring 5 and the second spring 6 jointly bear part of the gravity of the first mass block 3 and the second mass block 4, so as to ensure that the tuned mass damper device is always in an elastic tension state during vibration.

[0026] When the bridge girder is in torsional vibration, the acceleration directions of the first mass block 3 and the second mass block 4 are opposite, and the directions of the inertial forces generated thereby are also opposite, and the two form relative motion and excite system resonance, thereby consuming system energy and realizing effective control of the torsional vibration.

[0027] In the case of torsional vibration, the first spring 5 and the second spring 6 need to bear part of the gravity and the inertial force of the first mass block 3 and the second mass block 4. The maximum ratio of the inertial force to the gravity is expressed as (2πf) 2A / g, A is the amplitude of the first mass 3 and the second mass 4. The higher the frequency, the greater the amplitude, and the greater the inertial force. If f = 0.1 Hz, A = 0.5 m, then (2πf) 2 A / g is about 0.02. To ensure that the first spring 5 and the second spring 6 are always in tension in extreme cases, the initial tension thereof needs to be greater than the maximum inertial force that can occur. Therefore, for the above case, the dynamic carrying capacity of the first spring 5 and the second spring 6 only needs to reach about 0.05 times the gravity of the first mass 3 and the second mass 4 to meet the requirements. In contrast, in a conventional TMD, the spring not only bears the weight of the mass, but also bears its own gravity. Since a longer spring is required for low-frequency vibration, the spring gravity can even approach the mass gravity, resulting in extremely high strength requirements. Therefore, the wind-induced low-frequency torsional vibration control device for long-span bridges of the present application significantly reduces the strength requirements of the spring, effectively saving the cost of spring material and installation.

[0028] The type and size of the fixed pulley 1 are not limited, and it needs to have sufficient strength, stiffness and durability. In order to ensure that the vibration damping ratio of the tuned mass damper is not higher than the optimal damping ratio (usually in the range of 5%-8%, and the mass ratio to the bridge modal mass is related, the smaller the ratio, the smaller the optimal damping ratio. From the perspective of engineering application, the mass ratio to the bridge modal mass is usually not higher than 1%, otherwise the cost is higher and the engineering feasibility is poorer), the present application suggests taking two measures to minimize the energy consumption of the pulley during transmission: (1) the friction coefficient of the bearing of the fixed pulley 1 should be as small as possible; (2) the outer diameter of the fixed pulley 1 should be as large as possible (under the condition of a certain mass amplitude, the larger the outer diameter of the fixed pulley 1, the smaller the rotation angle of the bearing of the fixed pulley 1, and the lower the energy consumption). The damper 7 is used to adjust and optimize the optimal damping ratio of the tuned mass damper to achieve the best vibration control effect. The fixed pulley 1 is preferably arranged as far as possible on the outside of the main girder of the bridge. Under the same torsional amplitude and frequency conditions, the larger the distance between the fixed pulley 1, the greater the vertical acceleration and inertial force of the first mass 3 and the second mass 4, and the better the vibration control effect.

[0029] The material type of the rope 2 is not limited and needs to have sufficient stiffness and strength.

[0030] The masses of the first mass 3 and the second mass 4 can be the same or different and can be flexibly adjusted according to actual needs. The materials and forms of the first mass 3 and the second mass 4 are not limited and can adopt forms such as steel blocks, water tanks, sand tanks or concrete blocks. Steel blocks have high density and small volume, can save space, but have high cost; concrete blocks have low cost, but have small density, occupy large space; water tanks have the lowest cost and can flexibly change the mass by adjusting the water quantity, facilitating system frequency adjustment and parameter optimization. Since the tuned mass damper has small space limitation on the first mass 3 and the second mass 4, even if a water tank structure with a vertical dimension of meters is adopted, it can also meet the installation and working requirements.

[0031] The material, specification, number and length of the first spring 5 and the second spring 6 are not limited, and the stiffness thereof can be adjusted according to design requirements. Only the first spring 5 or the second spring 6 can be arranged according to actual conditions, or other materials or components with equivalent elastic characteristics can be used in replacement. The first spring 5 and the second spring 6 can be arranged vertically or horizontally according to structural arrangement conditions, and the installation position is not limited.

[0032] The type, specification, number, installation position of the damper 7 and the connection form thereof with the first mass block 3 and the second mass block 4 or the rope 2 are not limited, and can be selected flexibly according to actual requirements. When the frictional damping generated by the fixed pulley 1 is sufficient to meet the vibration control requirements, the damper 7 can not be arranged.

[0033] The damper 7 can also be replaced by an actuator 8, and the first spring 5 and the second spring 6 are cancelled, so that the device has an active control function, and the mass of the required mass block is smaller.

[0034] In addition, by using a suitable phase driving mode of the actuator 8, large amplitude torsional vibration of the bridge can also be actively excited, so that the modal parameters under different amplitude conditions can be identified. Therefore, the wind-induced low-frequency torsional vibration control device of the long-span bridge of the present application can be used for vibration reduction and excitation.

[0035] The wind-induced low-frequency torsional vibration control device of the long-span bridge of the present application can be directly suspended on the end top plate in the bridge main beam, and can also be suspended on the support installed in the bridge main beam, so that the influence on the local area of the end top plate in the bridge main beam can be reduced.

Claims

1. A device for controlling low-frequency wind-induced torsional vibration of a long-span bridge, characterized in that, The wind-induced low-frequency torsional vibration control device of the long-span bridge comprises fixed pulleys (1), ropes (2), first mass blocks (3), second mass blocks (4), first springs (5), second springs (6) and dampers (7); for the tuned mass damper device, two fixed pulleys (1) are symmetrically installed on the end top plates on the two sides of the bridge girder at the maximum vibration displacement section, for supporting the horizontally arranged and tensioned ropes (2); the two ends of the ropes (2) respectively suspend the first mass blocks (3) and the second mass blocks (4); the upper ends of the first springs (5) and the second springs (6) are fixed on the end top plates in the bridge girder, and the lower ends are respectively connected with the first mass blocks (3) and the second mass blocks (4); the two ends of the dampers (7) are respectively connected with the mass blocks and the end top plates in the bridge girder, for adjusting the damping and further adjusting the damping ratio of the wind-induced low-frequency torsional vibration control device of the long-span bridge.

2. The wind-induced low-frequency torsional vibration control device for long-span bridges according to claim 1, wherein The masses of the first mass blocks (3) and the second mass blocks (4) are the same or different.

3. The wind-induced low-frequency torsional vibration control device for long-span bridges of claim 1, wherein According to the actual situation, the first spring (5) or the second spring (6) in the wind-induced low-frequency torsional vibration control device of the long-span bridge is cancelled.

4. The wind-induced low-frequency torsional vibration control device for long-span bridges of claim 1, wherein The damper (7) in the wind-induced low-frequency torsional vibration control device of the long-span bridge is replaced by an actuator (8), and the first spring (5) and the second spring (6) are cancelled, so that the tuned mass damper device is converted into an active mass damper device; When the bridge girder is subjected to torsional vibration, the first mass blocks (3) and the second mass blocks (4) are driven by the actuator (8) to move in opposite phase resonance with the bridge girder, so that the torsional vibration of the bridge girder is effectively controlled.

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