A large-span bridge flutter control device

Abstract

The utility model belongs to the field of bridge wind-induced vibration control technology discloses a large -span bridge flutter control device. The large -span bridge flutter control device mainly is by foundation, support, friction axle, friction band, high -strength cable and raft and is composed. Among them, the friction band is wound in the outer periphery of friction axle, and one end is connected with raft, and the other end is connected with bridge girder through high -strength cable. The friction band high -strength cable end tension and raft end tension ratio can be designed according to its winding angle and friction coefficient to greatly reduce the raft volume, and save the cost. When the bridge flutter, the friction band reciprocating friction energy consumption on the friction axle, suppresses bridge girder vibration. The large -span bridge flutter control device simple structure light -duty, loading and unloading are quick, and the cost is low, and it is stable and reliable, and the form is flexible and various, can greatly improve the bridge operation and construction state flutter performance, reduce static wind displacement, can be used as permanent or temporary bridge wind resistance measure.

Description

Technical Field

[0001] This utility model belongs to the field of bridge wind-induced vibration control technology, and relates to a flutter control device for long-span bridges. Background Technology

[0002] Long-span bridges may experience single-degree-of-freedom torsional or flexural-torsional coupled flutter in strong winds, therefore appropriate measures must be taken to ensure the bridge's flutter safety. Bridge flutter control or flutter performance improvement measures can be divided into three categories: structural measures, aerodynamic measures, and mechanical measures.

[0003] Structural measures primarily enhance flutter stability by increasing the overall stiffness of the bridge or the mass and moment of inertia of the main girder. Examples include increasing the torsional and bending stiffness of the main girder and optimizing the cable system layout. While these measures have a clear mechanism of action and can increase the critical flutter wind speed at the overall structural level, they significantly increase material usage and structural weight, leading to a sharp rise in project costs. Therefore, they are generally not the first-line method for flutter control in long-span bridges.

[0004] Aerodynamic measures primarily improve bridge flutter stability by adjusting the airflow characteristics around the bridge through modifications to the aerodynamic shape of the main girder cross-section. Common methods include installing wind deflectors, central stabilizing plates, deflectors, optimizing maintenance walkway railings, and creating central slots in the main girder. These methods can improve the bridge's wind resistance without significantly increasing structural mass and stiffness, and are therefore widely used in the design of long-span bridges. However, some aerodynamic structures may be expensive, complex to construct and maintain, and their applicability varies depending on different bridge cross-sections and wind angles of attack; their effectiveness needs to be verified through wind tunnel testing or numerical simulation. Furthermore, while some measures can improve flutter stability, they may adversely affect vortex-induced vibration; for example, central slots can induce or exacerbate vortex-induced vibration responses.

[0005] Mechanical measures mainly involve adding energy-dissipating and vibration-damping devices to the bridge structure to increase system damping and thus suppress wind-induced vibration. However, traditional mechanical devices are usually quite limited in their effectiveness in controlling flutter.

[0006] In summary, for long-span bridges, relying solely on structural or aerodynamic measures often fails to achieve a balance between engineering feasibility, economy, and safety. Furthermore, existing additional damping devices suffer from insufficient adaptability, complex engineering implementation, or high overall costs when addressing flutter instability. Therefore, there is an urgent need for an economical and practical flutter control device with a simple structure, reliable operating mechanism, and the ability to continuously and efficiently dissipate energy under very large static wind displacement conditions.

[0007] Based on the above background, this utility model proposes a flutter control device for long-span bridges, which can significantly increase the critical flutter wind speed of the bridge, reduce the amplitude, and ensure the wind resistance safety of the bridge. It also has the advantages of simple structure, safety and reliability, economy and efficiency, and strong engineering applicability. Utility Model Content

[0008] This invention proposes a control device for temporarily and significantly improving the flutter performance of long-span bridges. The device connects the bridge's main girder to the ground via cables. When the main girder experiences flutter, it undergoes vertical reciprocating motion relative to the ground. As the main girder moves upward, the cables drive a friction belt to slide along a friction axis, generating frictional force. The cables apply a downward tension to the main girder, performing negative work. When the main girder moves downward, the buoyancy of a floating block in the water causes the cables and friction belt to move in the opposite direction, preventing cable slack. This ensures that the cables remain taut and continuously dissipate energy during the next vibration cycle as the main girder moves upward, suppressing vibration and thus increasing the critical flutter wind speed, enhancing overall wind resistance. The device effectively suppresses flutter response without a complex control system, and its simple, reliable structure makes it suitable for engineering applications.

[0009] The technical solution of this utility model is as follows: A flutter control device for long-span bridges includes a foundation 1, a support 2, a friction shaft 3, a friction belt 4, a cable net 5, floats 6, high-strength cables 7, and anchor rings 8. The foundation 1 is placed underwater below the main girder of the bridge. The support 2 is fixed to the foundation 1. The friction shaft 3 is rigidly connected to the support 2. The friction belt 4 is spirally wound around the outer circumference of the friction shaft 3, with its spiral path forming a certain helical angle with the axis of the friction shaft 3, and both ends of the friction belt 4 have sufficiently long unwound sections. One end of the friction belt 4 is connected to the cable net 5, which is placed in the water and located above the friction shaft 3. The cable net 5 contains a number of floats 6. The other end of the friction belt 4 is connected to the lower end of the high-strength cables 7. The upper end of the high-strength cables 7 is suspended on anchor rings 8 at the bottom of the main girder of the bridge, or on anchor rings 8 on the main cable above the main girder of the bridge. The main cable can withstand vertical tension of hundreds or even thousands of tons, while the tension of a single anchor ring 8 at the bottom of the main girder of the bridge is typically in the tens of tons range. Optionally, after the support 2 and the friction shaft 3 are connected, the support 2 is fixed to the bottom plate of the main beam of the bridge; or the main cable is wrapped with a sleeve, the support 2 and the friction shaft 3 are removed, the friction strip 4 is directly wrapped around the sleeve, and the mass block is used to replace the cable net 5 and the float 6, and the lower end of the high-strength cable 7 is anchored to the foundation 1.

[0010] The foundation 1 can be an embedded foundation (permanent or similar to a temporary anchor) or a gravity foundation (such as a container filled with stones), which must be able to reliably withstand the tension of the cables. When the main girder of the bridge experiences a large lateral static wind displacement, the foundation 1 will also bear a significant horizontal load, so it must have sufficient horizontal bearing capacity.

[0011] The support 2 has sufficient strength, rigidity, durability and corrosion resistance, and its quantity, material, size, structure, installation position and installation direction are not limited; The friction shaft 3 has sufficient strength, rigidity, durability and wear resistance, and its size and material are not limited. The friction coefficient between the friction shaft 3 and the friction belt 4 is adjustable and can be reasonably selected according to the actual engineering conditions.

[0012] The friction belt 4 has sufficient strength, rigidity and wear resistance, and its material, size and form are not limited; the friction belt 4 has a certain degree of flexibility, can be smoothly and tightly wound on the friction shaft 3, and has a sufficient winding length to meet the vibration or large static wind displacement stroke of the bridge main beam.

[0013] The cable net 5 has sufficient strength and corrosion resistance, and its material, size, and form are not limited.

[0014] The float 6 is made of lightweight, low-density material with sufficient strength and rigidity. It can be made of hollow foam, hollow plastic, etc., and its size, structure, material, and quantity are not limited.

[0015] The high-strength cable 7 and anchor ring 8 have sufficient strength and rigidity, and their size, material type, and specifications are not limited.

[0016] When flutter occurs in long-span bridges, the main girder typically exhibits torsional vibration or flexural-torsional coupled vibration, with the vertical displacement amplitude on both sides of the main girder significantly greater than that at the centerline. To improve the ability to suppress flutter, flutter control devices for long-span bridges are symmetrically arranged in pairs on both sides of the main girder at sections with large vertical or torsional vibration displacements. Multiple sets can be installed along the longitudinal direction of the main girder.

[0017] The beneficial effects of this utility model are as follows: (1) This device can significantly improve the flutter critical wind speed of large-span bridges in both operational and construction states, reduce the amplitude, and significantly reduce the flutter critical wind speed requirement of the bridge itself, thereby significantly reducing the engineering cost of large-span bridges; (2) It has a simple structure, clear force distribution, lightweight structure, low cost, convenient disassembly and assembly, and is flexible and efficient; (3) The device relies on floats to achieve self-reset, is stable and reliable, and has both limiting and energy-consuming functions, which can effectively reduce the static wind displacement of the bridge; (4) The friction coefficient and number of windings between the friction shaft and the friction belt can be optimized as needed, which can significantly reduce the buoyancy requirement of the floats and save costs. Attached Figure Description

[0018] Figure 1 A schematic diagram of the structure of a flutter control device for long-span bridges; In the diagram: 1. Foundation, 2. Support, 3. Friction shaft, 4. Friction belt, 5. Cable net, 6. Buoy, 7. High-strength cable, 8. Anchor ring. Detailed Implementation

[0019] The specific embodiments of this utility model are further described below with reference to the accompanying drawings and technical solutions.

[0020] A flutter control device for long-span bridges is provided. Two flutter control devices are arranged as a group and symmetrically on both sides of the section where the flutter amplitude of the main beam of the bridge is large. Multiple groups can be set along the longitudinal direction of the main beam of the bridge.

[0021] The flutter control device for this long-span bridge is constructed as follows: Figure 1 As shown, the structure includes a foundation 1, a support 2, a friction shaft 3, a friction band 4, a cable net 5, floats 6, a high-strength cable 7, and an anchor ring 8. The foundation 1 is placed underwater below the main beam of the bridge; the support 2 is fixed to the foundation 1; the friction shaft 3 is rigidly connected to the support 2; the friction band 4 is spirally wound around the outer circumference of the friction shaft 3, with its spiral path forming a certain helical angle with the axis of the friction shaft 3, and both ends of the friction band 4 have sufficiently long unwound sections; one end of the friction band 4 is connected to the cable net 5, which is placed in the water and above the friction shaft 3, and the cable net 5 contains a number of floats 6 made of materials such as hollow foam; the other end of the friction band 4 is connected to the lower end of the high-strength cable 7; the upper end of the high-strength cable 7 is suspended from the anchor ring 8 at the bottom of the main beam of the bridge.

[0022] When the friction band 4 slides on the friction shaft 3, the tension ratio at both ends of the friction cable 4 increases exponentially with the product of the friction coefficient and the winding angle. Therefore, only a small amount of buoyancy from the hollow foam is needed to achieve a very large tension cable force at the end, thereby achieving efficient positioning and energy consumption.

[0023] Under strong winds, the main girder of the bridge experiences lateral, vertical, and torsional displacements relative to the ground, meaning that the suspension points on the main girder or main cable are displaced from the foundation 1. When the main girder moves vertically away from the foundation 1, the tension of the high-strength cable 7 increases. If this does not exceed the friction threshold, the device does not consume energy and only provides restraint. If it exceeds the friction threshold, the friction band 4 slides on the friction shaft 3 under the tension of the high-strength cable 7. Friction occurs between the friction shaft 3 and the friction band 4, consuming energy and suppressing the vibration of the main girder. When the main girder moves vertically closer to the foundation 1, the friction band 4 tends to loosen. Under the buoyancy of the hollow foam, the high-strength cable 7 drives the friction band 4 to slide in the opposite direction on the friction shaft 3, achieving repositioning. During this process, the friction between the friction shaft 3 and the friction band 4 is relatively small, so a small amount of hollow foam is not needed to provide sufficient buoyancy, ensuring that the high-strength cable 7 remains taut.

[0024] If there is no need for traffic beneath the bridge, flutter control devices for long-span bridges can serve as permanent flutter control measures to control various vibrations of the bridge (vortex-induced vibration, buffeting, galloping, vehicle vibration, and even earthquake-induced vibrations). If used only as a temporary flutter control measure, they can be quickly installed before extreme strong winds that may cause flutter risks to the bridge, and then easily disassembled or retracted after ensuring the bridge's wind resistance safety, thus meeting navigation conditions under normal weather conditions.

[0025] The above description is merely a preferred embodiment of this utility model and should not be considered as any limitation thereof. Any equivalent changes, modifications, or improvements made by those skilled in the art to the above embodiments when utilizing the technical solution of this utility model should be considered as falling within the protection scope of this utility model.

Claims

1. A flutter control device for long-span bridges, characterized in that, The flutter control device for the long-span bridge includes a foundation (1), a support (2), a friction shaft (3), a friction belt (4), a cable net (5), a float (6), a high-strength cable (7), and an anchor ring (8). The foundation (1) is placed on the bottom of the water below the main beam of the bridge. The support (2) is fixed on the foundation (1). The friction shaft (3) is rigidly connected to the support (2). The friction belt (4) is spirally wound around the outer circumference of the friction shaft (3), and its spiral path forms a spiral angle with the axis of the friction shaft (3). Both ends of the friction belt (4) have unwound sections. One end of the friction belt (4) is connected to the cable net (5) placed in the water and located above the friction shaft (3). The cable net (5) contains a float (6). The other end of the friction belt (4) is connected to the lower end of the high-strength cable (7). The upper end of the high-strength cable (7) is hung on the anchor ring (8) at the bottom of the main beam of the bridge or on the anchor ring (8) on the main cable above the main beam of the bridge.

2. The flutter control device for long-span bridges according to claim 1, characterized in that, After the support (2) and friction shaft (3) are connected, the support (2) is fixed on the bridge bottom plate; or the main cable is wrapped with a sleeve, the support (2) and friction shaft (3) are removed, the friction belt (4) is directly wrapped around the sleeve, and the mass block is used instead of the cable net (5) and the float (6).

3. The flutter control device for long-span bridges according to claim 1, characterized in that, The foundation (1) mentioned above adopts an embedded foundation or a gravity foundation.

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