Structure for improving flutter stability of flat box girder and working method thereof

Abstract

The invention discloses a structure for improving flutter stability of a flat box girder and a working method thereof, the structure comprises a box girder body and tuyeres located at the two ends of the box girder body in the transverse direction of a bridge, the tuyeres are connected with the box girder body through linear driving mechanisms, and the linear driving mechanisms are used for driving the tuyeres to move in the transverse direction of the bridge. The working method comprises the following steps: monitoring the actual wind speed of a bridge location in real time; if the actual wind speed is smaller than the set threshold value, the linear driving mechanism drives the tuyeres to contract inwards in the transverse direction of the bridge; and if the actual wind speed is larger than the set threshold value, the linear driving mechanism drives the tuyeres to stretch outwards in the transverse direction of the bridge. According to the structure for improving the flutter stability of the flat box girder and the working method of the structure, the problem that in the prior art, a flat box girder structure is difficult to achieve good balance between the flutter stability and the vortex vibration performance is solved, and the pneumatic configuration of the flat box girder is actively controlled; and development and application of the flat box girder technology are promoted.

Description

Technical Field

[0001] The invention relates to the field of bridge engineering, and in particular to a structure for improving the flutter stability of a flat box girder and a working method thereof. Background Art

[0002] In contemporary building structures and traffic engineering designs, closed flat box girder designs are increasingly being used. However, as bridge spans continue to increase, the main beams become lighter, the natural frequency is low and densely distributed, and the torsion-bending frequency ratio is greatly reduced, making them more susceptible to flutter under the action of wind. Therefore, the study of flutter in large-span and ultra-large-span bridges is very important.

[0003] Flutter is a wind-induced vibration problem that needs to be considered during the design and construction of long-span bridge structures. Flutter instability refers to the phenomenon that the aerodynamic negative damping caused by the aerodynamic self-excitation force exceeds the structural damping under strong wind speeds, resulting in structural instability. Normally, at low wind speeds, the structure is in an air-stable state. As the wind speed increases, the change in the flutter derivative will gradually change the phase difference between the aerodynamic self-excitation force and the vibration state, and the airflow will change from dissipating structural energy to transmitting energy to the structure. After reaching a certain wind speed, the structural state will change to a dynamically unstable state, and flutter will occur. Flutter was first discovered in thin wings. It is a torsional divergent vibration or a combined bending and torsion divergent vibration, which is a manifestation of dynamic instability; the famous wind damage accident of the old Tacoma Bridge in the United States is a typical disaster caused by flutter instability. As far as bridge structures are concerned, the torsional effect of wider bridge decks is significant, and flutter stability should be guaranteed.

[0004] The box girder first appeared in the form of an integral box girder. From the perspective of aerodynamic shape, it can be divided into streamlined box girders with air nozzles and blunt box girders with cantilevers. However, the aerodynamic characteristics of this type of integral box girder (especially in terms of flutter stability) are difficult to break through the span limit of 2000m. At present, the effective way to improve the aerodynamic characteristics of the integral box girder is mainly to improve its aerodynamic stability by adding air nozzles, splitters, guide spoilers, central stabilizers, or changing the air permeability of the railings.

[0005] From the perspective of flutter control, slotting is the most effective way to suppress the flutter of integral box girders, which is a kind of aerodynamic control measure. The second-generation box girders introduced with central slotting are called split box girders. Compared with integral box girders, the flutter stability of slotted split box girders has been significantly improved, but the vortex-vibration performance has been significantly reduced. The reason is that slotting can easily cause vertical bending vortex-vibration. Insufficient vortex-vibration performance is one of the main reasons restricting the widespread application of split box girders.

[0006] In summary, the integral box girder in the existing technology has insufficient flutter stability, while the split box girder has insufficient vortex vibration performance, which has become one of the key technologies restricting the development of large-span bridges with flat box girder structures. Summary of the invention

[0007] The purpose of the present invention is to provide a structure for improving the flutter stability of a flat box girder and a working method thereof, so as to solve the problem in the prior art that it is difficult for the flat box girder structure to achieve a good balance between flutter stability and vortex vibration performance, to achieve active control of the aerodynamic configuration of the flat box girder, and to promote the development and application of flat box girder technology.

[0008] The present invention is achieved through the following technical solutions:

[0009] A structure for improving the flutter stability of a flat box girder comprises a box girder body and air nozzles located at both ends of the box girder body along the transverse direction of the bridge, wherein the air nozzles are connected to the box girder body via a linear drive mechanism, and the linear drive mechanism is used to drive the air nozzles to move along the transverse direction of the bridge.

[0010] In view of the problem that it is difficult for flat box girder structures in the prior art to achieve a good balance between flutter stability and vortex vibration performance, the present invention first proposes a structure for improving the flutter stability of flat box girder. Those skilled in the art should understand that the structure of the present application is a streamlined box girder with air nozzles in terms of aerodynamic shape, and the air nozzles are located at both ends of the box girder body along the transverse direction of the bridge; the transverse direction of the bridge in the present application refers to the line between the left and right sides based on the bridge section; the longitudinal direction of the bridge in the present application refers to the length direction of the bridge, which is perpendicular to the transverse direction of the bridge.

[0011] In the present application, the wind nozzle is connected to the box girder body through a linear drive mechanism, so the wind nozzle can be driven to move closer to and away from the box girder body in the transverse direction through the linear drive mechanism. When the present application is used specifically, the linear drive mechanism is controlled according to the actual wind speed: if the actual wind speed is less than the set threshold, the linear drive mechanism drives each wind nozzle to retract inward along the transverse direction of the bridge, so that the transverse inner end face of the wind nozzle is in contact with the transverse end face of the box girder body along the transverse direction of the bridge; at this time, the present application is consistent with the ordinary flat box girder in appearance, and will not increase the probability of vertical bending vortex vibration that may occur at low wind speeds, so it can maintain good vortex vibration performance. If the actual wind speed is greater than the set threshold, the linear drive mechanism drives each wind nozzle to extend outward along the transverse direction of the bridge, so that a spacing is formed between the wind nozzle and the box girder body in the transverse direction of the bridge, and it is automatically converted to a split box girder configuration, thereby improving the flutter stability of the bridge at high wind speeds.

[0012] It can be seen that the present application adopts the technical idea of ​​actively controlling the aerodynamic configuration of the flat box girder, abandoning the traditional research and development idea of ​​the prior art that can only passively improve the aerodynamic effect by adding auxiliary components to the outside of the box girder. It combines the aerodynamic performance advantages of the integral box girder and the split box girder, and can achieve a good balance between flutter stability and vortex-vibration performance. It can meet the vortex-vibration performance requirements of large-span bridges at low wind speeds and flutter stability at high wind speeds, which is beneficial to improving the driving comfort and safety of large-span bridges, and to a certain extent reduces bridge fatigue and extends the service life of bridges. It has a significant contribution to the technical development and promotion and application of large-span bridges.

[0013] It should be noted that the inventors of the present application discovered during the research process that not all cross-sectional forms of grooving stiffening beams can increase the critical flutter wind speed of the bridge. Among them, grooving of flat streamlined box beams has obvious flutter control effects. This is also the premise for the improvement and optimization based on the use of flat box beams with wind nozzles in the present application. The inventors also made creative efforts to discover this premise.

[0014] Furthermore, the linear drive mechanism includes a rack fixedly connected to the wind nozzle, a gear meshing with the rack, and a power device for driving the gear to rotate. The rack is slidably matched with the box girder body, and the axial direction of the rack is parallel to the transverse direction of the bridge.

[0015] In this solution, the power device drives the gear to rotate, driving the rack to make linear motion, and then driving the nozzle to make linear reciprocating motion, so as to realize the movement of the nozzle close to or away from the box beam body. Among them, the rack can be partially stored inside the box beam body and connected in a sliding fit, so as to ensure that the nozzle can shrink to fit the box beam body. In addition, the power device can be installed at any position on the box beam body and / or the nozzle, and the installation position can be flexibly set by technicians in this field according to specific working conditions. The power device and the gear can be transmitted through any existing transmission structure.

[0016] Furthermore, the rack is fixed on the square tube, and the square tube is slidably connected to the two ends of the box beam body along the transverse direction of the bridge, and the axial direction of the square tube is parallel to the transverse direction of the bridge. This solution provides an installation position for the rack through the square tube, and the square tube is slidably connected to the box beam body. When the rack moves, it drives the square tube to move synchronously. The square tube can be used to conveniently and quickly install the rack using its flat surface.

[0017] Further, the gear is arranged inside the box beam body and / or arranged at the end face of the box beam body along the transverse direction of the bridge. In addition, the installation position of the gear should ensure that it will not interfere with the contact between the air nozzle and the end face of the box beam body.

[0018] Furthermore, at least two racks are fixed to the upper and lower surfaces of the square tube, and each gear is meshed with a corresponding gear; all gears corresponding to each square tube are linked.

[0019] In this solution, for each square tube, at least four racks are fixed on it, and racks are provided on the upper and lower surfaces of the square tube. Each rack meshes with at least one gear, and all gears corresponding to each square tube rotate synchronously and in the same direction, thereby significantly improving the stability of the linear drive mechanism driving the nozzle to move.

[0020] Furthermore, the plurality of wind nozzles are symmetrically distributed in pairs along the vertical surface where the longitudinal center line of the bridge is located, and the two symmetrically distributed wind nozzles constitute a wind nozzle group; and the plurality of wind nozzle groups are evenly distributed along the longitudinal direction of the bridge.

[0021] In this solution, along the transverse direction of the bridge, the wind nozzles on the left and right sides and their matching linear drive mechanisms are symmetrical in pairs, which is more conducive to ensuring flutter stability.

[0022] Furthermore, along the longitudinal direction of the bridge, the spacing between two adjacent linear drive mechanisms is F: F = (8-10) × E; wherein E is the cross-sectional side length of the square tube.

[0023] Furthermore, the cross-sectional side length of the square tube is E: E=(0.3-0.5)×D; wherein D is the end face height of the box girder body along the transverse direction of the bridge.

[0024] The structure for improving the flutter stability of the flat box girder in the present application comprises:

[0025] Real-time monitoring of actual wind speed at the bridge location;

[0026] If the actual wind speed is less than the set threshold, the linear drive mechanism drives each wind nozzle to retract inwardly along the transverse direction of the bridge, so that the transverse inner end surface of the wind nozzle fits with the end surface of the box girder body along the transverse direction of the bridge;

[0027] If the actual wind speed is greater than a set threshold, the linear drive mechanism drives each wind nozzle to extend outward in the transverse direction of the bridge, so that a set distance is reached between the wind nozzle and the box girder body in the transverse direction of the bridge.

[0028] Furthermore, the set spacing is C: C = (0.1-0.15) × B; wherein B is the total width of the box girder body and the wind nozzles on both sides along the transverse direction of the bridge when the wind nozzles on both sides are retracted inward to fit with the box girder body.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] The present invention discloses a structure for improving the flutter stability of a flat box girder and a working method thereof, adopts a technical idea of ​​actively controlling the aerodynamic configuration of the flat box girder, abandons the traditional research and development idea of ​​the prior art that can only passively improve the aerodynamic effect by adding auxiliary components outside the box girder, combines the aerodynamic performance advantages of the integral box girder and the split box girder, can achieve a good balance between flutter stability and vortex-oscillation performance, can meet the vortex-oscillation performance requirements of long-span bridges at low wind speeds and flutter stability at high wind speeds, is beneficial to improving the driving comfort and safety of long-span bridges, and to a certain extent reduces bridge fatigue and prolongs the service life of the bridge, and has a significant contribution to the technical development and promotion and application of long-span bridges. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0032] Figure 1 It is a cross-sectional view of the air nozzle when it is contracted in a specific embodiment of the present invention;

[0033] Figure 2 It is a cross-sectional view of the tuyere when it is extended in a specific embodiment of the present invention;

[0034] Figure 3 It is a partial schematic diagram of the tuyere when it is extended in a specific embodiment of the present invention;

[0035] Figure 4 It is a distribution diagram of the linear drive mechanism in a specific embodiment of the present invention.

[0036] Marks and corresponding parts names in the attached drawings:

[0037] 1-square tube, 2-gear, 3-box beam body, 4-nozzle. DETAILED DESCRIPTION

[0038] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0039] Embodiment 1:

[0040] like Figures 1 to 4 A structure for improving the flutter stability of a flat box girder is shown, comprising a box girder body 3 and air nozzles 4 located at both ends of the box girder body 3 along the transverse direction of the bridge. The air nozzle 4 in this embodiment is a split structure with the box girder body 3, and the air nozzle 4 is connected to the box girder body 3 through a linear drive mechanism, and the linear drive mechanism is used to drive the air nozzle 4 to move along the transverse direction of the bridge.

[0041] The linear drive mechanism in this embodiment includes a rack fixedly connected to the wind nozzle 4, a gear 2 meshing with the rack, and a power device for driving the gear 2 to rotate. The rack is slidably matched with the box beam body 3, and the axial direction of the rack is parallel to the transverse direction of the bridge.

[0042] The rack is fixed on the square tube 1, and the square tube 1 is connected to both ends of the box beam body 3 by sliding along the transverse direction of the bridge, and the axial direction of the square tube 1 is parallel to the transverse direction of the bridge. The power equipment is arranged inside the box beam body 3 or at the end surface.

[0043] Preferably, at least two racks are fixed to the upper and lower surfaces of the square tube 1, and each gear 2 is meshed with a corresponding gear 2; all gears 2 corresponding to each square tube 1 are linked.

[0044] Preferably, the square tube 1 is a steel tube with a square cross-section; the square tube 1 is welded to the air nozzle 4 , and the rack is embedded in the surface of the square tube 1 .

[0045] In a more preferred embodiment, the square tube 1 is a hollow tube, and its top and bottom surfaces are both horizontal. The wall thickness of the square tube 1 should be determined according to the actual performance of the selected pipe material and the actual conditions such as the shape, size and weight of the nozzle. In addition, the power device can be implemented by a stepper motor or a servo motor.

[0046] In a more preferred embodiment, an inlet for the square tube 1 to enter is opened at the transverse end of the box beam body 3 .

[0047] In a more preferred embodiment, the total length of the square tube 1 should be appropriately longer than the maximum extension length of the square tube 1 to ensure that the square tube 1 is always partially slidably fitted inside the box beam body 3 .

[0048] Compared with the original flat box girder bridge, the present invention adds a retractable square tube 1 between the wind nozzle and the main beam of the bridge. At high wind speeds, the square tube 1 extends outward to form symmetrical grooves, which greatly increases the flutter critical wind speed of the flat box girder bridge, improves the flutter performance of the flat box girder bridge, improves driving safety and comfort, ensures the operational safety of the bridge, and extends the service life of the bridge.

[0049] Embodiment 2:

[0050] A structure for improving the flutter stability of a flat box girder. Based on Example 1, a plurality of wind nozzles 4 are symmetrically distributed in pairs along the vertical surface where the longitudinal center line of the bridge is located, and the two symmetrically distributed wind nozzles 4 constitute a wind nozzle group; and the plurality of wind nozzle groups are evenly distributed along the longitudinal direction of the bridge.

[0051] like Figure 3As shown, the cross-sectional side length of the square tube 1 is E: E=(0.3-0.5)×D; wherein D is the end face height of the box girder body 3 along the transverse direction of the bridge.

[0052] like Figure 4 As shown, along the longitudinal direction of the bridge, the spacing between two adjacent linear drive mechanisms is F: F = (8-10) × E; wherein E is the cross-sectional side length of the square tube 1. In this embodiment, the spacing between two adjacent linear drive mechanisms can be understood as the spacing between the center lines of two adjacent square tubes along the longitudinal direction of the bridge.

[0053] Embodiment 3:

[0054] Based on the structure for improving the flutter stability of the flat box girder described in Example 1 or 2, its operation is controlled as follows:

[0055] S1. Real-time monitoring of the actual wind speed at the bridge location;

[0056] S2. Compare the actual wind speed with the set threshold:

[0057] If the actual wind speed is less than the set threshold, the linear drive mechanism drives each nozzle 4 to retract inwardly along the transverse direction of the bridge, so that the transverse inner end surface of the nozzle 4 fits with the transverse end surface of the box girder body 3 along the transverse direction of the bridge. Figure 1 shown.

[0058] If the actual wind speed is greater than the set threshold, the linear drive mechanism drives each wind nozzle 4 to extend outward along the transverse direction of the bridge, so that along the transverse direction of the bridge, the wind nozzle 4 and the box girder body 3 reach a set distance. At this time, the state is as follows: Figure 2 and Figure 3 shown.

[0059] In this embodiment, the set threshold is 90%Y, where Y is the minimum flutter critical wind speed required for engineering safety.

[0060] In this embodiment, the set spacing is C: C = (0.1-0.15) × B; wherein B is the total width of the box girder body 3 and the air nozzles 4 on both sides along the transverse direction of the bridge when the air nozzles 4 on both sides are retracted inward to fit with the box girder body 3.

[0061] In order to verify the beneficial effects of the present application, in this embodiment, B=39.0m, D=2.0m, C=4000mm, E=700mm, F=6000mm are taken, and a segment model flutter test is carried out under the above specific parameters. The test results are shown in Table 1:

[0062] Table 1 Test results

[0063]

[0064] It can be seen from Table 1 that after the wind nozzle is extended, compared with the original cross-section main beam when the wind nozzle is contracted, the main beam flutter wind speed is increased by more than 20% at both 0° and ±3° attack angles. This proves that the technical means of deploying the wind nozzle under high wind speed conditions in this application has a significant effect. Therefore, according to the flutter test results of the main beam segment model of the flat box girder, the movable steel pipe and gear structures are added between the box girder and the wind nozzle, and the grooves are actively opened at high wind speeds, which can significantly improve the flutter stability of the flat box girder, while ensuring good vortex vibration performance at low wind speeds.

[0065] In addition, the applicant also took C=0.05×B and C=0.2×B to conduct flutter tests when the wind nozzle was extended. The test results showed that under these two conditions, the increase in the flutter wind speed of the main beam was less than 10%, which was significantly weaker than the improvement effect within the value range of (0.1~0.15)×B in this application.

[0066] It should be noted that, in this article, terms such as "include", "comprise" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In addition, the term "connected" used in this article can be directly connected or indirectly connected via other components without special explanation.

[0067] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A structure for improving the flutter stability of a flat box girder, comprising a box girder body (3), and air nozzles (4) located at both ends of the box girder body (3) in the transverse direction of the bridge, characterized in that: The air nozzle (4) is connected to the box girder body (3) via a linear drive mechanism, and the linear drive mechanism is used to drive the air nozzle (4) to move along the transverse direction of the bridge.

2. A structure for improving the flutter stability of a flat box beam according to claim 1, characterized in that: The linear drive mechanism comprises a rack fixedly connected to the nozzle (4), a gear (2) meshing with the rack, and a power device for driving the gear (2) to rotate; the rack is slidably matched with the box beam body (3), and the axial direction of the rack is parallel to the transverse direction of the bridge.

3. A structure for improving the flutter stability of a flat box beam according to claim 2, characterized in that: The rack is fixed on the square tube (1), and the square tube (1) is slidably connected to the two ends of the box beam body (3) along the transverse direction of the bridge, and the axial direction of the square tube (1) is parallel to the transverse direction of the bridge.

4. The structure for improving the flutter stability of a flat box beam according to claim 2, characterized in that: The gear (2) is arranged inside the box beam body (3), and / or is arranged at the end surface of the box beam body (3) along the transverse direction of the bridge.

5. The structure for improving the flutter stability of a flat box beam according to claim 3, characterized in that: At least two racks are fixed to the upper and lower surfaces of the square tube (1), and each gear (2) is meshed with a corresponding gear (2); all gears (2) corresponding to each square tube (1) are linked.

6. The structure for improving the flutter stability of a flat box beam according to claim 3, characterized in that: A plurality of the air nozzles (4) are symmetrically distributed in pairs along the vertical surface where the longitudinal center line of the bridge is located, and the two symmetrically distributed air nozzles (4) constitute an air nozzle group; and the plurality of the air nozzle groups are evenly distributed along the longitudinal direction of the bridge.

7. The structure for improving the flutter stability of a flat box beam according to claim 6, characterized in that: Along the longitudinal direction of the bridge, the spacing between two adjacent linear drive mechanisms is F: F=(8-10)×E; wherein E is the side length of the cross section of the square tube (1).

8. The structure for improving the flutter stability of a flat box beam according to claim 3, characterized in that: The cross-sectional side length of the square tube (1) is E: E=(0.3-0.5)×D; wherein D is the end face height of the box girder body (3) along the transverse direction of the bridge.

9. A working method for improving the flutter stability of a flat box girder according to any one of claims 1 to 8, characterized in that: include: Real-time monitoring of actual wind speed at the bridge location; If the actual wind speed is less than the set threshold, the linear drive mechanism drives each wind nozzle (4) to retract inwardly in the transverse direction of the bridge, so that the transverse inner end surface of the wind nozzle (4) fits with the end surface of the box girder body (3) in the transverse direction of the bridge; If the actual wind speed is greater than a set threshold value, the linear drive mechanism drives each wind nozzle (4) to extend outward in the transverse direction of the bridge, so that a set distance is achieved between the wind nozzle (4) and the box girder body (3) in the transverse direction of the bridge.

10. The working method according to claim 9, characterized in that: The set spacing is C: C = (0.1-0.15) × B; wherein B is the total width of the box girder body (3) and the air nozzles (4) on both sides along the transverse direction of the bridge when the air nozzles (4) on both sides are retracted inwards to fit with the box girder body (3).

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