A tuned mass inertia damper for suppressing low-frequency vortex-induced vibration of long-span bridges

Abstract

The present invention belongs to the technical field of wind-induced vibration control of bridges. Aiming at the problems that traditional tuned mass dampers for controlling low-frequency vortex-induced vibrations have springs that are too long, too heavy, and too expensive, a tuned mass inertia damper for suppressing low-frequency vortex-induced vibrations of large-span bridges is provided. A small-mass, large-diameter rotor is introduced to greatly improve the equivalent mass of the vibration system; thereby greatly shortening the spring length, improving the spring stiffness, and further greatly reducing the spring's own weight, static elongation or compression, and cost; the stretch spring can be designed and processed to have a specified initial stress, thereby further reducing its static elongation under the weight of the mass body, saving installation space; the mass body material, structure and layout form are not limited, so the cost is greatly reduced compared with the traditional tuned mass damper; the clear height inside the box-shaped main beam of a large-span bridge is generally higher than 3m, and the damper can reach a low-frequency level of 0.1Hz after optimized design, providing an efficient and practical means for vortex-vibration control of a kilometer-class main span bridge.

Description

Technical Field

[0001] The invention belongs to the technical field of wind-induced vibration control of bridges, and relates to a tuned mass inertia damper for suppressing low-frequency vortex-induced vibration of a long-span bridge. Background Art

[0002] Some large-span cable-supported bridges have experienced large vortex-induced vibrations (abbreviated as vortex-induced vibrations) during operation, such as the Xihoumen Bridge, Humen Bridge, Yingwuzhou Bridge, Dahaidong Bridge, Deer Isle Bridge, and Fred Hartman Bridge. In fact, the vortex-induced vibrations of large-span bridges are mainly vertical bending vibrations, and no obvious torsional vortex-induced vibrations have been reported. Bridge vortex-induced vibrations will have adverse effects on the bridge structure itself and the drivers and passengers on the bridge, and may even cause social panic. Therefore, it is necessary to prevent the occurrence of bridge vortex-induced vibrations or control their amplitude within an acceptable range. The main beams of large-span cable-supported bridges with a main span of one kilometer usually adopt truss sections or closed (open) box beams. Truss main beam sections generally do not cause vortex-induced vibrations. The main beams of bridges that experience vortex-induced vibrations generally adopt box beam sections, and the main beam height is generally in the range of 3-5m.

[0003] Low-order vertical bending modes of long-span bridges are more prone to vortex vibration, and their frequencies are generally low (<0.2Hz, even lower than 0.1Hz). Traditional tuned mass dampers (TMDs) are an effective means of controlling vortex vibrations of some bridges (with frequencies greater than 0.25Hz), but are difficult to use for vortex vibration control with modal frequencies lower than 0.2Hz. The reasons are as follows: (1) Under the weight of the mass, the static extension or compression of the spring is g / ω. 2 (m), where g is the acceleration due to gravity (usually 9.8 m / s 2), ω is the traditional TMD design circular frequency (basically consistent with the bridge vortex vibration frequency). For example, when the bridge vortex vibration is controlled at a frequency of 0.2Hz and 0.1Hz, the static extension (or compression) of the spring is 6.2m and 24.8m respectively. Therefore, for low-frequency vibration control occasions, the length, mass, cost and installation cost of the spring will increase significantly. For example, for the 0.1Hz working condition, the self-mass of the traditional TMD spring (circular cross-section steel) may reach more than 2 times the mass of the mass body, so it is no longer feasible. Moreover, due to the large length and stretching length of the spring itself, it cannot be directly suspended vertically or supported inside the main beam. (2) The weight of the traditional TMD mass body is large. Even if it is calculated as 0.5% of the modal mass of the controlled object, it may reach hundreds of tons or even hundreds of tons. If several modes are controlled, the weight may increase nearly linearly with the control order. Therefore, it is also a "burden" for the bridge, and once installed, it will be difficult to disassemble. (3) Traditional TMD mass bodies are generally made of steel, and the price per ton of TMD system is basically more than RMB 50,000, so the cost can easily reach tens of millions or even hundreds of millions of yuan. (4) Due to the small stiffness of traditional TMD springs, the mass body has a large stroke and cannot be placed inside the main beam. Hanging it under the main beam will also affect the appearance of the bridge, and there are safety risks, which will not be accepted by owners and the public. Therefore, the existing traditional tuned mass damper is generally only used in bridge vortex vibration control occasions with a frequency higher than 0.25Hz.

[0004] In summary, it is necessary to propose a more advanced, lower-frequency, and more economical low-frequency vortex-vibration control device for large-span bridges through comprehensive and in-depth research. Summary of the invention

[0005] The present invention proposes a tuned mass inertia damper for suppressing low-frequency vortex-induced vibrations of long-span bridges. In view of the low frequency of vertical vortex-induced vibrations of long-span cable-supported bridges, the difficulty of installing traditional TMDs directly inside the main beams and the high cost, several improvements are made to traditional TMDs to make them more applicable at a lower frequency, more economical in cost, more convenient and practical to use. The tuned mass inertia damper of the present invention has the following features: on the basis of using a tension spring to vertically suspend the mass body, a rotor is introduced that can provide a large equivalent mass during the vibration of the tuned mass damper. Compared with traditional TMD, the mass of the suspended mass body can be greatly reduced, thereby greatly reducing the spring strength, and then reducing the spring wire diameter, number of coils and mass, significantly improving the spring stiffness, and greatly reducing the static elongation of the spring, which can ultimately greatly reduce the project cost; using a spring with initial pressure to suspend the mass body can further reduce the static elongation of the spring, so that the tuned mass inertia damper can be installed inside the main beam and provide enough space for its vibration as much as possible; the material of the mass body is not limited, and concrete blocks and water tanks can be used (temporary water injection and drainage can be used according to needs to achieve the goal of not bringing additional load to the bridge at ordinary times) The cost can be reduced by an order of magnitude from the tens of millions to the millions of yuan compared to the traditional TMD of the same tonnage, which significantly improves the market competitiveness. The mass body arrangement of the vibration control system is not limited, and its bottom is as flush as possible with the bottom of the spring to reduce the vertical space occupation. It can also be arranged in a frame type and the rotor is arranged inside the frame to reduce the space required for installation. The rotor is arranged on both sides of the mass body or inside the frame-type mass body, without occupying additional vertical space, making the layout of the tuned mass inertia damper more compact and significantly reducing the space required for installation.

[0006] The technical solution of the present invention:

[0007] A tuned mass inertia damper for suppressing low-frequency vortex vibration of a long-span bridge comprises a linear tension spring 1, a mass body 2, a high-strength frame 3, a high-strength thin rope 4, a rotor 5, a bearing 6, a bearing support 7 and a damper 8; the tuned mass inertia damper is a symmetrical structure, one end of the linear tension spring 1 is suspended below the top plate inside the main beam, and the other end is fixed on the mass body 2 for suspending the mass body 2; the high-strength frame 3 is a semi-I-shaped structure, which is fixed on the mass body 2; the top plate and A high-strength thin rope 4 is fixed between the bottom plates, and the high-strength thin rope 4 is sleeved outside the rotor 5. The high-strength thin rope 4 drives the rotor 5 to rotate when the mass body 2 moves vertically; the bearing 6 is used to support the central axis at both ends of the rotor 5, and allows the rotor 5 to rotate freely and reduce friction as much as possible; the bearing support 7 fixed on the bottom plate inside the main beam is used to support and fix the bearing 6; the damper 8 is connected to the top plate or bottom plate of the main beam at one end, and connected to the mass body at the other end, providing additional damping for the tuned mass inertia damper. For low-frequency vibration, driven by the high-strength thin rope 4, the rotor 5 can provide an equivalent mass of dozens or even hundreds of times its own physical mass to the tuned mass inertia damper due to its own mass distribution characteristics (the diameter of the part wrapped by the high-strength thin rope 4 is relatively small, and most of the mass is distributed at a position far away from the rotation center, and the rotor 5 structure is not limited) and rigid rotation. Therefore, when the system is not in operation, the linear tension spring 1 mainly bears the deadweight of the mass body 2, instead of all the mass being borne by the spring like in the traditional TMD system, which can greatly reduce the strength of the spring and greatly reduce the spring wire diameter. In addition, compared with the traditional TMD, in order to achieve the same frequency, the introduction of the rotor equivalent mass leads to an increase in the system mass, which greatly increases the spring stiffness of the new system, thereby greatly reducing the number of spring coils. Therefore, the deadweight of the linear tension spring 1 and the static elongation under the deadweight of the mass body 2 are greatly reduced; the linear tension spring 1 can be designed and processed to have a specified initial stress, thereby further reducing its static elongation, saving installation space, and through the reasonable arrangement of other components, the tuned mass inertia damper can be installed inside the main beam; according to the frequency of a certain modal vortex-induced vibration of the bridge and the installation space inside the main beam of the bridge, the parameters of the linear tension spring 1, the size and mass of the mass body 2, and the size and mass of the rotor 5 are designed, and the resonance energy absorption principle is used to transfer the vibration energy of the bridge to the mass body 2 and the rotor 5, and the damper 8 is used to dissipate the total energy of the system, thereby suppressing the vertical (arranged in the transverse center position of the main beam) or torsional (arranged on both sides of the main beam near the edge position) vortex vibration of the bridge.

[0008] The material of the linear tension spring 1 is steel or a high-strength and low-elastic modulus polymer material, the cross-section is circular or rectangular, and the cross-section is solid, hollow or open; the linear tension spring 1 has a set initial compression force, and only when the tension reaches a certain value, the linear tension spring 1 begins to stretch and deform, thereby greatly reducing the static elongation of the linear tension spring 1 caused by the deadweight of the mass body 2, thereby leaving as much up and down vibration space as possible for the mass body 2 inside the main beam, thereby improving the vibration control efficiency.

[0009] The mass body 2 can be made of steel like a traditional tempered damper, or it can be made of more economical concrete slabs, beams, blocks or water tanks. The water tank can store water as needed, or it can be temporarily filled with water when vortex vibration occurs, and the water can be released when the vortex vibration disappears, thereby reducing the weight of the damper under normal conditions of the bridge. Advantages of the water tank: low cost, easy to adjust the deadweight (water inlet and outlet are set at the top and bottom respectively); when not in operation, the water is released without bringing additional load to the bridge.

[0010] The bottom of the mass body 2 is as flush as possible with the bottom end of the linear tension spring 1, that is, the mass body 2 is arranged within the vertical range of the linear tension spring 1, which is different from the traditional TMD mass body 2 being arranged below the linear tension spring 1. This can ultimately leave as much upward and downward vibration space as possible for the mass body 2 inside the main beam.

[0011] The high-strength thin rope 4 is divided into two sections, the upper end of the upper section and the lower end of the lower section are respectively fixed to the top plate and the bottom plate of the high-strength frame 3, and the upper and lower sections are both wrapped around the central axis of the rotor 5 for several turns. The lower end of the upper section and the upper end of the lower section are fixed on the central axis of the rotor 5, so that there is no relative sliding between the high-strength thin rope 4 and the central axis of the rotor 5, and the rotational displacement can be effectively transmitted.

[0012] The physical mass of the rotor 5 itself is relatively small, and the specific form is not limited. Under normal working conditions, the diameter of the winding part of the high-strength thin rope 4 is minimized as much as possible, and the mass is distributed as far away from the rotation center as possible, similar to the shape of a hub; the rotor 5 can be arranged on both sides of the mass body 2, or after changing the arrangement form of the mass body 2 to a frame type, it can be arranged inside the frame of the mass body 2, thereby reducing the area required for installation; the arrangement position and form of the rotor 5 are not limited.

[0013] The bearing 6 has strong durability, strong load-bearing capacity and a friction coefficient as small as possible.

[0014] The bearing support rod 7 has high rigidity, strong load-bearing capacity and high stability.

[0015] The damping linearity provided by the damper 8 is good, the damping changes little under different amplitudes, and the working state is stable.

[0016] The tuned mass inertia damper uses the resonance energy absorption principle to transfer the vibration energy of the bridge to the mass body 2 and the rotor 5, and uses the damper 8 to dissipate the total energy of the system, thereby suppressing the vertical (arranged in the transverse center of the main beam) or torsional (arranged on both sides of the main beam near the edge) vortex vibration of the bridge.

[0017] The beneficial effects of the present invention are as follows: (1) By introducing a rotor with a small winding diameter, most of the mass distributed on the periphery, and a small physical mass, the equivalent mass of the vibration system can be greatly improved; (2) The spring wire diameter, number of turns, and length are greatly shortened, and the spring stiffness is increased, thereby greatly reducing the spring deadweight, static elongation or compression, and finally realizing a low-frequency, low-cost damper within a small installation and vibration range; (3) The tension spring can be designed and processed with a specified initial stress, thereby further reducing its static elongation, saving installation space, maximizing the vibration space, and improving vibration control efficiency; (4) The mass body arrangement material and structural form are not limited, and low-cost concrete beams or even water tanks (quick temporary mass addition) can be used. , so the cost is greatly reduced compared with the traditional TMD; (5) The mass body 2 is arranged within the vertical range of the linear tension spring 1, which can save vertical arrangement space and improve the vibration control efficiency; (6) The rotor can be arranged on both sides of the mass body, or after changing the mass body arrangement form to a frame type, it can be arranged inside the mass body frame, thereby reducing the plane area required for installation; (7) According to the characteristics that the net height inside the large-span box-shaped main beam is generally higher than 3m, the damper system structure is optimized and designed to meet the requirements of controlling the vibration frequency of 0.1Hz; (8) The damper system can not only suppress the vertical vortex vibration of the bridge (arranged in the horizontal center position of the main beam), but also suppress the torsional vortex-induced vibration through reasonable arrangement (arranged on both sides of the main beam near the edge). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural diagram of a tuned mass inertia damper for suppressing low-frequency vortex-induced vibration of a long-span bridge;

[0019] Figure 2 It is a partial enlarged view of the high-strength frame 3 and the high-strength rope 4.

[0020] In the figure: 1 linear tension spring, 2 mass body, 3 high-strength frame, 4 high-strength thin rope, 5 rotor, 6 bearing, 7 bearing support rod, 8 damper; DETAILED DESCRIPTION

[0021] The following is a detailed description of the specific implementation of the present invention in combination with the technical scheme and the accompanying drawings, but the implementation of the present invention is not limited thereto:

[0022] like Figure 1As shown, a tuned mass inertia damper for suppressing low-frequency vortex-induced vibration of a long-span bridge comprises a linear tension spring 1 suspended below the top plate inside the main beam, a mass body 2, a high-strength frame 3, a high-strength thin rope 4, a rotor 5, a bearing 6, a bearing support 7 fixed to the bottom plate inside the main beam, and a damper 8; the linear tension spring 1 is used to suspend the mass body 2, and can be designed and processed to have a specified initial stress, which can further reduce the static elongation of the linear tension spring 1 caused by the deadweight of the mass body 2; the high-strength frame 3 is fixed on the mass 2, and is used to tension the high-strength thin rope 4, so that the high-strength thin rope 4 drives the rotor 5 to rotate when the mass body 2 moves vertically; the high-strength thin rope 4 is divided into two sections, the upper and lower ends of the upper and lower sections are respectively fixed to the top of the high-strength frame 3 The plate and the bottom plate, the upper and lower sections are both wrapped around the rotor 5 axis for several turns, and the lower and upper ends of the upper and lower sections are fixed on the rotor 5 axis, so that there is no relative sliding between the high-strength thin rope 4 and the rotor 5 axis, and the rotational displacement can be effectively transmitted; the diameter of the rotor 5 part wrapped by the high-strength thin rope 4 is relatively small, and most of the mass is distributed at a position far away from the rotation center, which can provide an equivalent mass of dozens or even hundreds of times its own physical mass to the tuned mass inertia damper; the bearing 6 is used to support the rotor 5 and allow the rotor 5 to rotate freely and reduce friction as much as possible; the bearing support 7 is used to support and fix the bearing 6; the two ends of the damper 8 are respectively connected to the top plate or bottom plate of the main beam and the mass body, providing additional damping for the tuned mass inertia damper. According to the frequency of a certain modal vortex-induced vibration of the bridge and the internal installation space of the bridge main beam, the parameters of the linear tension spring 1, the size and mass of the mass body 2, and the size and mass of the rotor 5 are designed. The vibration energy of the bridge is transferred to the mass body 2 and the rotor 5 by using the resonance energy absorption principle, and the damper 8 is used to dissipate the total energy of the system, thereby suppressing the vertical (arranged in the transverse center position of the main beam) or torsional (arranged at the edge positions on both sides of the main beam) vortex vibration of the bridge.

[0023] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any equivalent changes, modifications or evolutions made by those skilled in the art to the above examples using the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A tuned mass inertia damper for suppressing low-frequency vortex-induced vibration of a long-span bridge, characterized in that: The tuned mass inertia damper comprises a linear tension spring (1), a mass body (2), a high-strength frame (3), a high-strength thin rope (4), a rotor (5), a bearing (6), a bearing support (7) and a damper (8); the tuned mass inertia damper is a symmetrical structure, one end of the linear tension spring (1) is suspended below the top plate inside the main beam, and the other end is fixed on the mass body (2) for suspending the mass body (2); the high-strength frame (3) is a semi-I-shaped structure, which is fixed on the mass body (2); the top plate and the bottom plate of the high-strength frame (3) are fixedly connected. A high-strength thin rope (4) is provided, and the high-strength thin rope (4) is sleeved outside the rotor (5). When the mass body (2) moves vertically, the high-strength thin rope (4) drives the rotor (5) to rotate; the bearing (6) is used to support the central axis at both ends of the rotor (5), and allows the rotor (5) to rotate freely and reduce friction as much as possible; the bearing support (7) fixed on the bottom plate inside the main beam is used to support and fix the bearing (6); one end of the damper (8) is connected to the top plate or bottom plate of the main beam, and the other end is connected to the mass body, providing additional damping for the tuned mass inertia damper; The material of the linear tension spring (1) is steel or a high-strength, low-elastic modulus polymer material, the cross-section is circular or rectangular, and the cross-section is solid, hollow or open; the linear tension spring (1) has a set initial compression force, and only when the tension reaches a certain value, the linear tension spring (1) begins to stretch and deform; The bottom of the mass body (2) is as flush as possible with the bottom end of the linear tension spring (1), that is, the mass body (2) is arranged within the vertical range of the linear tension spring (1); The high-strength thin rope (4) is divided into two sections, the upper end of the upper section and the lower end of the lower section are respectively fixed to the top plate and the bottom plate of the high-strength frame (3), and the upper and lower sections are both wound around the central axis of the rotor (5) for several turns. The lower end of the upper section and the upper end of the lower section are fixed to the central axis of the rotor (5), so that relative sliding does not occur between the high-strength thin rope (4) and the central axis of the rotor (5), and the rotation displacement can be effectively transmitted; the diameter of the part of the rotor (5) wound by the high-strength thin rope (4) is relatively small, and most of the mass is distributed at a position far from the rotation center.

2. The tuned mass inertia damper according to claim 1, characterized in that: The mass body (2) is made of steel, concrete slabs, beams, blocks or water tanks.

3. The tuned mass inertia damper according to claim 1 or 2, characterized in that: The rotor (5) is arranged on both sides of the mass body (2), or after the arrangement form of the mass body (2) is changed to a frame type, it is arranged inside the frame of the mass body (2).

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