Automatic mass center moving mechanism for improving flutter performance of large-span bridge
By designing an automatic center-of-gravity movement mechanism on long-span bridges and using a counterweight gear and planetary gear system to adjust the position of the center of gravity, the problem of bridge flutter control under extreme wind conditions was solved, and flutter performance and safety were improved without changing the aerodynamic shape and structural system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA RAILWAY MAJOR BRIDGE RECONNAISSANCE & DESIGN INSTITUTE CO LTD
- Filing Date
- 2026-04-28
- Publication Date
- 2026-07-07
AI Technical Summary
Existing technologies struggle to effectively control flutter performance without altering the aerodynamic shape and structural system of long-span bridges, especially since the influence of the center of mass location on the critical flutter wind speed is not fully utilized under extreme wind conditions.
An automatic center of mass movement mechanism is designed. Using a system of counterweight gears, planetary gears, and traction racks, the center of mass position is automatically adjusted by the torsion angle of the main beam, thereby moving the center of mass in the direction of the incoming flow and enhancing the flutter control effect.
It can effectively adjust the position of the bridge's center of gravity under any wind conditions, improve flutter performance, ensure structural safety, avoid the high cost and space limitations of mechanical measures, and does not affect aerodynamic performance.
Smart Images
Figure CN122105958B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of vibration suppression technology in bridge wind engineering. Background Technology
[0002] Long-span bridges are increasingly used in cross-sea engineering, facing complex and variable natural conditions, especially extreme weather events such as typhoons. Methods to improve flutter control in long-span bridges typically include aerodynamic measures, mechanical measures, and structural system optimization. Aerodynamic measures are only effective within specific wind angles of attack and low wind speed ranges, and their wind-induced vibration control effect is often limited. Mechanical measures, which increase the damping ratio of the long-span bridge system, are also inefficient in flutter control and costly. Furthermore, the limited space within the beams of long-span bridges makes it difficult to meet the vertical movement requirements of traditional mechanical measures within the narrow beams. The structural system is mainly related to factors such as the system's mass, damping ratio, and stiffness, but is often determined by design parameters and construction costs. Meanwhile, for flutter, a form of wind-induced vibration, the position of the center of mass plays a crucial role in the flutter critical wind speed. In bridge wind engineering, when the center of mass moves forward towards the direction of the flow, the flutter critical wind speed increases significantly; conversely, when the center of mass moves away from the direction of the flow, the flutter critical wind speed decreases. Adjusting the center of mass can effectively improve the flutter performance of a bridge, but this improvement only works when the center of mass is moved in the direction of the incoming flow. Furthermore, the lift moment coefficient of long-span bridge sections often increases with the angle of attack. Summary of the Invention
[0003] To further improve the flutter performance of bridge sections without altering the original aerodynamic shape and structural system, this invention proposes an automatic center-of-gravity (COG) movement mechanism for enhancing the flutter performance of long-span bridges. This mechanism automatically adjusts the COG position towards the direction of the incoming flow based on the torsional angle of the main girder, thereby achieving effective control under any wind conditions.
[0004] The technical solution adopted in this invention is: an automatic center of mass movement mechanism for improving the flutter performance of long-span bridges, comprising: a fixed bearing, a counterweight gear, a planetary gear, a traction rack, and a mass block;
[0005] The counterweight gear is a gear structure with a large mass counterweight at the lower end, and the counterweight gear is set at the centroid of the bridge box girder through the fixed bearing.
[0006] The planetary gears include: a first planetary gear and a second planetary gear that have the same mass, shape and mass distribution; the first planetary gear and the second planetary gear are symmetrically arranged on both sides of the counterweight gear and mesh with it;
[0007] The traction rack is slidably mounted on the bridge box girder along the transverse direction of the bridge, and the traction rack meshes with the first planetary gear and the second planetary gear.
[0008] The mass block includes a first mass block and a second mass block that have the same mass, shape and mass distribution; the first mass block and the second mass block are respectively disposed at both ends of the traction rack.
[0009] The technical solution for improving the above-mentioned basic structure further includes: a first traction rack mounting base and a second traction rack mounting base; the traction rack includes: a first traction rack and a second traction rack;
[0010] On the bridge box girder, the first traction rack mounting seat and the second traction rack mounting seat are symmetrically arranged on both sides of the counterweight gear. The first traction rack mounting seat and the second traction rack mounting seat are respectively provided with a first slide groove and a second slide groove arranged in the transverse direction of the bridge.
[0011] The first traction rack is disposed in the first groove of the first traction rack mounting seat, the first traction rack meshes with the first planetary gear, and the first mass block is disposed at the end of the first traction rack facing the outside of the bridge.
[0012] The second traction rack is disposed in the second groove of the second traction rack mounting seat, the second traction rack meshes with the second planetary gear, and the second mass block is disposed at the end of the second traction rack facing the outside of the bridge.
[0013] In this preferred embodiment, the purpose of using two traction racks is to address the need for a counterweight gear with the largest possible radius, considering the center of gravity offset. Using two traction racks positioned on either side of the counterweight gear facilitates installation and avoids conflicts with the installation position of the central counterweight gear. This embodiment proposes a specific technical solution where the traction racks are slidably arranged along the transverse direction of the bridge box girder. Planetary gears drive the traction racks to move within a groove, thereby causing the mass block to move laterally.
[0014] A preferred technical solution for the above improvement is that the first mass block is disposed in the first groove of the first traction rack mounting seat; and the second mass block is disposed in the second groove of the second traction rack mounting seat.
[0015] Another preferred technical solution to the above-mentioned improvement scheme is as follows: the first traction rack is disposed in the first groove of the first traction rack mounting seat; the second traction rack is disposed in the second groove of the second traction rack mounting seat; the first mass block at the end of the first traction rack is located outside the first groove; the second mass block at the end of the second traction rack is located outside the second groove; the distance between the first mass block and the first groove, and the distance between the second mass block and the second groove are both greater than the distance by which the first mass block and the second mass block move synchronously towards the oncoming flow side when the bridge is subjected to the action of the oncoming wind from one side.
[0016] A further preferred technical solution is that the radius of the gear structure of the counterweight gear (2) and the size of the mass block are set according to the following algebraic relationship:
[0017]
[0018] in, This represents the expected centroid offset for optimal flutter performance, obtained from actual wind tunnel tests. The static wind torsion angle of the main beam at the target wind speed; The radius of the counterweight gear (2); the forward movement distance of the first mass block and the second mass block is ; The equivalent mass of each linear mass block; The mass of the main beam per meter.
[0019] A further preferred technical solution is that the total mass of the fixed bearing, the counterweight gear, the first planetary gear, the second planetary gear, the traction rack, and the mass block does not exceed 10% of the dead load of the long-span bridge.
[0020] This preferred solution can control the total mass of the automatic center of mass movement mechanism provided by the present invention while satisfying the purpose of the present invention, so that it does not significantly amplify the constant load.
[0021] A further preferred technical solution includes: a viscous oil damper; the viscous oil damper is disposed between the fixed bearing and the counterweight gear.
[0022] By installing a viscous oil damper on the counterweight gear, the oscillation of the counterweight gear under high-frequency random loads can be suppressed, further ensuring that the "counterweight gear-planetary gear" system only undergoes relative motion under static wind torque.
[0023] A further preferred technical solution is that both the first traction rack and the second traction rack are arranged with their teeth facing upwards.
[0024] A further preferred technical solution is that the first planetary gear and the second planetary gear are both mounted on the bridge box girder via fixed shafts; the fixed bearing and the fixed shaft are mounted on the bridge box girder by means of being mounted on each transverse diaphragm or transverse beam of the main beam.
[0025] In practical applications, multiple sets of the automatic center of gravity moving mechanism provided by this invention need to be installed on the main beam along the longitudinal direction of the bridge. By setting each set of fixed bearings and fixed shafts on different transverse diaphragms or beams of the main beam, the application of multiple sets of the automatic center of gravity moving mechanism provided by this invention on long-span bridges can be realized without the need for a continuous arrangement along the span direction.
[0026] A more preferred technical solution is that the fixed bearing, the first planetary gear, and the second planetary gear are all made of materials with high rigidity, high strength, and light weight.
[0027] Compared with the prior art, the advantages of the present invention are as follows:
[0028] For long-span bridges, horizontal airflow typically causes the main girder to rotate around its centroid at a positive angle of attack, and this angle of torsion gradually increases with wind speed. The automatic center of mass movement mechanism for improving the flutter performance of long-span bridges provided by this invention converts the static torsional displacement of the main girder into translational motion of a mass block using a counterweight gear, planetary gear, and traction rack mounted on a fixed bearing. The counterweight gear, with its large mass at its lower end, ensures that its center of gravity is precisely below the fixed bearing. In windless conditions and without extreme eccentric live loads, the average torsion angle of the main girder is close to 0, and the automatic center of mass movement mechanism remains stationary. In windy conditions, the lift moment causes the bridge box girder to rotate. The counterweight gear, under the influence of gravity and supported by the fixed bearing, remains in its original position. The rotation of the bridge box girder causes the planetary gear to rotate around the counterweight gear, simultaneously causing the traction rack to translate in the direction of the airflow. The mass block connected to the end of the traction rack moves synchronously towards the airflow side, thus shifting the center of mass forward.
[0029] The automatic center of mass moving mechanism for improving the flutter performance of long-span bridges provided by this invention can remain stationary when the bridge is at rest, with the center of mass of the cross-section still at the center position, without affecting the aerodynamic performance. When the bridge is subjected to the action of an oncoming wind from one side, it will deflect under the action of the lift moment. The automatic center of mass moving mechanism will move the center of mass in the direction of the oncoming wind according to the deflection amplitude, thereby improving the flutter performance of the bridge structure and ensuring structural safety. Attached Figure Description
[0030] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0031] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention applied to a long-span bridge.
[0032] Figure 2 This is a schematic diagram illustrating the working principle of an embodiment of the present invention.
[0033] In the diagram: 1. Fixed bearing; 2. Counterweight gear; 31. First planetary gear; 32. Second planetary gear; 41. First traction rack; 42. Second traction rack; 51. First mass block; 52. Second mass block; 6. Bridge box girder. Detailed Implementation
[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0035] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.
[0036] like Figure 1 As shown in the figure, this embodiment provides an automatic center of mass movement mechanism for improving the flutter performance of long-span bridges, including: a fixed bearing 1, a counterweight gear 2, a first planetary gear 31, a second planetary gear 32, a traction rack, and a mass block.
[0037] Among them, the counterweight gear 2 is a gear structure with a large mass counterweight at the lower end, and the counterweight gear 2 is set at the center of the bridge box girder 6 through the fixed bearing 1.
[0038] The first planetary gear 31 and the second planetary gear 32 are symmetrically arranged on both sides of the counterweight gear 2 and mesh with it.
[0039] The traction rack is slidably mounted on the bridge box girder 6 along the transverse direction of the bridge, and meshes with the first planetary gear 31 and the second planetary gear 32.
[0040] The mass block includes a first mass block 51 and a second mass block 52 of the same mass, which are respectively disposed at the two ends of the traction rack.
[0041] For the counterweight gear 2, as Figure 2 As shown, the purpose of the counterweight gear 2 is to ensure that the counterweight gear 2 is absolutely stationary relative to the inertial coordinate system and does not move with the main beam. This ensures that when the main beam rotates clockwise around its centroid under the action of aerodynamic lifting torque, the first planetary gear 31 and the second planetary gear 32 fixed on the bearing rotate clockwise synchronously, driving the traction rack to move towards the windward side, thereby shifting the center of mass forward.
[0042] In this embodiment, a low-friction precision bearing is used as the fixed bearing 1. The counterweight gear 2 is connected to the main beam through the low-friction precision bearing, but there is no rigid connection between them, allowing for unrestrained relative motion. The lower end of the counterweight gear 2 has a large-mass counterweight, ensuring that the overall center of gravity falls precisely below the fixed bearing 1. In this embodiment, a viscous oil damper is also provided for the counterweight gear 2. The viscous oil damper is located between the fixed bearing 1 and the counterweight gear 2 to suppress the oscillation of the counterweight gear 2 under high-frequency random forces, ensuring that the "counterweight gear-planetary gear" system only undergoes relative motion under static wind torque.
[0043] Regarding the number of traction racks, this embodiment preferably includes: a first traction rack 41 and a second traction rack 42. The specific installation method is as follows: on the bridge box girder 6, a first traction rack mounting seat and a second traction rack mounting seat are symmetrically arranged on both sides of the counterweight gear 2. The first traction rack mounting seat and the second traction rack mounting seat are respectively provided with a first sliding groove and a second sliding groove arranged transversely along the bridge. The first traction rack 41 is disposed in the first sliding groove of the first traction rack mounting seat, and the first traction rack 41 meshes with the first planetary gear 31. A first mass block 51 is disposed at the end of the first traction rack 41 facing outwards from the bridge. The second traction rack 42 is disposed in the second sliding groove of the second traction rack mounting seat, and the second traction rack 42 meshes with the second planetary gear 32. A second mass block 52 is disposed at the end of the second traction rack 42 facing outwards from the bridge.
[0044] In this preferred embodiment, the purpose of setting two traction racks is as follows: considering the center of gravity offset, it is necessary to use the largest possible radius of the counterweight gear 2. The method of setting two traction racks on both sides of the counterweight gear 2 makes the mechanism easier to install and avoids conflict with the installation position of the middle counterweight gear 2.
[0045] Regarding the positional relationship between the mass blocks and the traction rack mounting base, the first mass block 51 and the second mass block 52 can be respectively positioned in the first groove of the first traction rack mounting base and the second groove of the second traction rack mounting base; alternatively, the first traction rack 41 and the second traction rack 42 can be respectively positioned in the first groove of the first traction rack mounting base and the second groove of the second traction rack mounting base, with the first mass block 51 at the end of the first traction rack 41 and the second mass block 52 at the end of the second traction rack 42 located outside the first groove and the second groove, respectively. Furthermore, the distance between the first mass block 51 and the first groove, and the distance between the second mass block 52 and the second groove, are both greater than the distance that the first mass block 51 and the second mass block 52 would move synchronously towards the oncoming flow side when the bridge is subjected to an incoming wind from one side. , .
[0046] In this embodiment, both the first traction rack 41 and the second traction rack 42 are arranged with their teeth facing upwards.
[0047] For the materials of fixed bearing 1, first planetary gear, and second planetary gear, materials with high rigidity, high strength, and light weight are preferred.
[0048] The method for determining the radius of the counterweight gear 2 and the size of the mass block is as follows: For long-span bridges, the horizontal flow direction usually causes the main beam to rotate clockwise around the centroid, and the torsion angle gradually increases with the increase of wind speed. To determine the optimal centroid offset for flutter performance based on actual wind tunnel tests, the static wind torsion angle of the main beam at the target wind speed is set as follows: According to the principle of mechanical transmission, the forward movement distance of the first mass block 51 and the second mass block 52 is... ,in Let be the radius of the counterweight gear 2. Based on torque balance, the equivalent mass of the mass block per meter can be determined. and expected centroid offset Mass per meter of main beam The radius of the counterweight gear 2 and still wind twist angle The algebraic relationship between them is:
[0049]
[0050] The radius and mass block size of the counterweight gear 2 are set according to the above algebraic relationship.
[0051] In practical applications, multiple sets of the automatic center of gravity moving mechanism provided in this embodiment should be used and installed at multiple locations along the longitudinal direction of the long-span bridge. Specifically, multiple transverse diaphragms or beams of the main beam are selected as carriers, and multiple sets of this embodiment are installed. The fixed bearing 1 and the fixed shaft of the planetary gear in each set are installed on the same transverse diaphragm or beam, without the need for continuous arrangement along the span direction.
[0052] Considering that the mass blocks do not significantly amplify the dead load, preferably, the total mass of the multiple sets of this embodiment installed on the long-span bridge should not exceed 10% of the dead load of the long-span bridge.
[0053] The working principle of this embodiment is as follows:
[0054] (1) Static state
[0055] In windless conditions and without extreme eccentric live loads, the average torsional angle of the main beam is close to 0, and the automatic center of mass moving mechanism does not move, thus maintaining the horizontal balance of the bridge.
[0056] (2) Working status
[0057] like Figure 2 As shown, under the lifting torque generated by the incoming flow, the bridge box girder 6 rotates. The counterweight gear 2 remains in its original position under the influence of gravity and the support of the fixed bearing 1. The rotation of the bridge box girder 6 will drive the first planetary gear 31 and the second planetary gear 32 to rotate around the counterweight gear 2. At the same time, it will further drive the first traction rack 41 and the second traction rack 42 to translate in the direction of the incoming flow. The first mass block 51 connected to the end of the first traction rack 41 and the second mass block 52 connected to the end of the second traction rack 42 move synchronously towards the side of the incoming flow, thereby achieving the effect of moving the center of mass forward.
[0058] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
[0059] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.
[0060] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0061] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. An automatic center-of-gravity movement mechanism for improving the flutter performance of long-span bridges, characterized in that, include: Fixed bearing (1), counterweight gear (2), planetary gear, traction rack, mass block; The hammer gear (2) is a gear structure with a large mass hammer at the lower end. The hammer gear (2) is set at the centroid of the bridge box girder (6) through the fixed bearing (1). The planetary gears include: a first planetary gear (31) and a second planetary gear (32) with the same mass, shape and mass distribution; the first planetary gear (31) and the second planetary gear (32) are symmetrically arranged on both sides of the counterweight gear and mesh with it. The traction rack is slidably arranged on the bridge box girder (6) along the transverse direction of the bridge, and the traction rack meshes with the first planetary gear (31) and the second planetary gear (32); The mass blocks include a first mass block (51) and a second mass block (52) that have the same mass, shape and mass distribution; the first mass block (51) and the second mass block (52) are respectively disposed at both ends of the traction rack.
2. The automatic centroid movement mechanism for improving the flutter performance of long-span bridges as described in claim 1, characterized in that, It also includes: a first traction rack mounting seat and a second traction rack mounting seat; the traction rack includes: a first traction rack (41) and a second traction rack (42). On the bridge box girder (6), the first traction rack mounting seat and the second traction rack mounting seat are symmetrically arranged on both sides of the counterweight gear (2). The first traction rack mounting seat and the second traction rack mounting seat are respectively provided with a first groove and a second groove arranged in the transverse direction of the bridge. The first traction rack (41) is disposed in the first groove of the first traction rack mounting seat, the first traction rack (41) meshes with the first planetary gear (31), and the first mass block (51) is disposed at the end of the first traction rack (41) facing the outside of the bridge. The second traction rack (42) is disposed in the second groove of the second traction rack mounting seat, the second traction rack (42) meshes with the second planetary gear (32), and the second mass block (52) is disposed at the end of the second traction rack (42) facing the outside of the bridge.
3. The automatic centroid movement mechanism for improving the flutter performance of long-span bridges as described in claim 2, characterized in that, Both the first traction rack (41) and the second traction rack (42) are arranged with the teeth facing upwards.
4. The automatic centroid movement mechanism for improving the flutter performance of long-span bridges as described in claim 3, characterized in that, The first mass block (51) at the end of the first traction rack (41) is located outside the first chute; the second mass block (52) at the end of the second traction rack (42) is located outside the second chute; the distance between the first mass block (51) and the first chute, and the distance between the second mass block (52) and the second chute are both greater than the distance by which the first mass block (51) and the second mass block (52) move synchronously toward the oncoming flow side when the bridge is subjected to the action of the oncoming wind from one side.
5. The automatic centroid movement mechanism for improving the flutter performance of long-span bridges as described in any one of claims 1 to 4, characterized in that, The radius of the gear structure of the counterweight gear (2) and the size of the mass block are set according to the following algebraic relationship: in, This represents the expected centroid offset for optimal flutter performance, obtained from actual wind tunnel tests. The static wind torsion angle of the main beam at the target wind speed; The radius of the counterweight gear (2); the forward movement distance of the first mass block (51) and the second mass block (52) is... ; The equivalent mass of each linear mass block; The mass of the main beam per meter.
6. The automatic center of mass movement mechanism for improving the flutter performance of long-span bridges as described in claim 5, characterized in that, The total mass of the fixed bearing (1), the counterweight gear (2), the first planetary gear (31), the second planetary gear (32), the traction rack, and the mass block shall not exceed 10% of the dead load of the long-span bridge.
7. The automatic centroid moving mechanism for improving the flutter performance of long-span bridges as described in claim 6, characterized in that, Also includes: A viscous oil damper; the viscous oil damper is disposed between the fixed bearing and the counterweight gear.
8. The automatic centroid movement mechanism for improving the flutter performance of long-span bridges as described in claim 7, characterized in that, The first planetary gear (31) and the second planetary gear (32) are both mounted on the bridge box girder (6) via a fixed shaft; the fixed bearing (1) and the fixed shaft are mounted on the bridge box girder (6) by means of being mounted on each transverse diaphragm or transverse beam of the main beam.
9. The automatic centroid moving mechanism for improving the flutter performance of long-span bridges as described in claim 8, characterized in that, The fixed bearing (1), the first planetary gear (31), and the second planetary gear (32) are all made of materials with high rigidity, high strength, and light weight.