Low-frequency large-amplitude vibration transmission device for long-span bridges

Abstract

The present application belongs to the technical field of large bridge excitation, and discloses a low-frequency large-amplitude vibration transmission device for a large-span bridge. Two mass bodies are arranged along the transverse direction or the longitudinal direction of the bridge to realize gravity self-balancing, and the stroke requirement of an actuator and the gravity requirement of the mass bodies are greatly reduced by introducing a differential diameter turntable. The inertia force generated by the up-down acceleration and deceleration reverse vibration of the two mass bodies driven by the actuator provides an additional load for the bridge, so as to excite large torsional or vertical vibration of the bridge. The present application has the advantages of simple structure, convenient disassembly and assembly, low cost, various forms, high transmission efficiency, wide excitation frequency, no need of spring frequency modulation, and wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of large bridge vibration technology, and relates to a low-frequency large-amplitude vibration of long-span bridges. Background Technology

[0002] Modal parameters of bridges are key indicators characterizing the dynamic properties of a structure, among which the damping ratio has a significant impact on the wind resistance and seismic performance of bridges. Due to the complex mechanisms by which bridge damping affects the structure and its close relationship with vibration amplitude, it generally requires identification through field dynamic tests. The small amplitude and low signal-to-noise ratio of environmental excitation responses to bridges make accurate identification of damping parameters difficult. Using dynamic load excitations such as moving vehicles or vehicle bounces results in highly random excitations and very limited bridge vibration amplitudes, leading to significant dispersion in the identification results.

[0003] Currently, the vibration excitation equipment used in bridge dynamic testing mainly includes eccentric inertial exciters, servo hydraulic exciters, and electric exciters. For small- and medium-span bridges, due to their relatively small mass and relatively high vibration frequency, the allowable amplitude is relatively small. Therefore, these traditional excitation devices can conveniently excite the structure to generate the required amplitude. However, under low-frequency and high-force excitation conditions, eccentric inertial exciters require a massive eccentric rotor, rapidly increasing the total mass of the equipment, often reaching tens or even hundreds of tons, making transportation and installation difficult and costly. Although servo hydraulic and electric exciters can achieve a certain range of frequency adjustment, their output excitation force is limited under low-frequency conditions, and they can usually only form single-point excitation, making it difficult to meet the needs of low-frequency large-amplitude vibration tests for large-span bridges. Some excitation devices rely on spring-mass systems for frequency tuning, requiring precise matching between spring stiffness and oscillator mass. When there is a deviation between the tuning frequency and the target frequency, the excitation efficiency is low. For lower vibration frequencies, a large number of springs are required, and the device is huge, increasing the cost of equipment manufacturing, transportation, installation, and commissioning. Therefore, these devices are difficult to use effectively for low-frequency large-amplitude vibration excitation of long-span bridges.

[0004] Therefore, in order to meet the excitation requirements of low frequency, multiple frequency, large amplitude, controllable frequency, unsuitable mass, and unsuitable actuator stroke in torsional and vertical dynamic tests of long-span bridges, it is necessary to develop a transmission device with a simple structure, light weight, low cost, wide applicable frequency, and high working efficiency. Summary of the Invention

[0005] This invention provides a device that is simple in construction, easy to assemble and disassemble, low in cost, highly efficient in excitation, has a wide range of excitation frequencies, requires no spring frequency adjustment, and achieves gravity self-balancing through reasonable arrangement of the mass body along the transverse or longitudinal direction of the bridge. By introducing a differential diameter turntable, the travel requirements of the actuator and the weight requirements of the mass body are significantly reduced. The actuator does not need to bear the weight of the mass body. The actuator drives the mass body to vibrate up and down, accelerating and decelerating to generate inertial force to provide an external load for the bridge, thereby exciting the bridge to undergo large-scale torsional or vertical vibration. This device overcomes the technical difficulties of traditional large-scale excitation equipment, which is complex in structure, bulky, expensive, has low low-frequency efficiency, and is complicated in frequency adjustment.

[0006] The technical solution of this invention: A low-frequency large-amplitude vibration transmission device for long-span bridges includes a base 1, a support 2, a bearing 3, a rotating shaft 4, a turntable 5, a first high-strength flexible cable 6, a mass 7, a first fixed pulley 8, a second high-strength flexible cable 9, a third high-strength flexible cable 10, a connecting plate 11, a fourth high-strength flexible cable 12, a second fixed pulley 13, and an actuator 14. The base 1 is laid flat on the bridge deck; the support 2 is fixedly installed on the base 1; the bearing 3 is installed on the top of the support 2; the rotating shaft 4 is supported by the bearing 3; the turntable 5 is fixed on the rotating shaft 4; one end of the first high-strength flexible cable 6 is wound around the turntable 5 to suspend the mass 7, and the other end passes over the first fixed pulley 8 installed on the top of the base 1. One end of the second high-strength flexible cable 9, which is in a horizontal position, is connected to the other end of the second high-strength flexible cable 9, which is connected to the first high-strength flexible cable 6 of another set of low-frequency large-amplitude vibration transmission devices for large-span bridges. The second high-strength flexible cable 9 connects the two sets of low-frequency large-amplitude vibration transmission devices for large-span bridges into one unit. One end of the third high-strength flexible cable 10 is wound and fixed on the rotating shaft 4, and the other end is connected to the top surface of the connecting plate 11. One end of the fourth high-strength flexible cable 12 is wound and fixed on the rotating shaft 4, and the other end passes around the second fixed pulley 13 installed on the top of the base 1 and is connected to the bottom surface of the connecting plate 11. The actuator 14 is supported on the base 1 at the bottom and connected to the bottom surface of the connecting plate 11 at the top. By driving the connecting plate 11 in opposite phases through the actuators 14 of the two sets of low-frequency large-amplitude vibration transmission devices for large-span bridges that are far apart, the two mass bodies 7 are driven to vibrate in opposite directions, thereby exciting the large-span bridge to generate low-frequency large-amplitude vibration.

[0007] Another form: The actuator 14 is arranged only on one side of the low-frequency large-amplitude vibration transmission device for long-span bridges. The turntable 5, the third high-strength flexible cable 10, the connecting plate 11, the fourth high-strength flexible cable 12, the second fixed pulley 13 and the actuator 14 are removed from the low-frequency large-amplitude vibration transmission device for long-span bridges on the other side. Only one end of the first high-strength flexible cable 6 is retained, which is wrapped around the rotating shaft 4 to suspend the mass body 7, and the other end is wrapped around the first fixed pulley 8 and connected to the second high-strength flexible cable 9.

[0008] The material, shape, and size of the base 1 are not limited, but it has sufficient strength, rigidity, anti-slip and anti-overturning capabilities. The bottom surface of the base 1 is made of rubber material with the highest possible coefficient of friction.

[0009] The material, shape, size, and construction form of the bracket 2 are not limited, but it has sufficient strength and rigidity, and its construction form is easy to assemble and disassemble.

[0010] The material and size of the bearing 3 are not limited, but it has sufficient strength and rigidity, and the coefficient of friction is as small as possible.

[0011] The material and size of the rotating shaft 4 are not limited, but it has sufficient strength and rigidity, and can be made of steel pipe or aluminum pipe, etc.

[0012] The material, size, structure, and quantity of the turntable 5 are not limited, but it has sufficient strength and rigidity. The ratio of its diameter to the diameter of the rotating shaft 4 is optimized as needed, and its position on the rotating shaft 4 is determined as needed.

[0013] The materials, shapes, and sizes of the first high-strength flexible cable 6, the second high-strength flexible cable 9, the third high-strength flexible cable 10, and the fourth high-strength flexible cable 12 are not limited, but they are required to have sufficient strength and tensile stiffness. Their area is reasonably determined according to the tension they are subjected to, and they are generally wound around the corresponding rotating shaft 4 or turntable 5 1-2 times to meet the displacement requirements.

[0014] The mass body 7 has sufficient gravity, and its material, shape, and size are not limited. It can be made of steel blocks, concrete blocks, or water tanks, etc. The mass bodies 7 on the two sets of low-frequency large-amplitude vibration transmission devices for long-span bridges are basically equal in mass.

[0015] The materials, dimensions, and quantities of the first fixed pulley 8 and the second fixed pulley 13 are not limited, but they are required to have sufficient strength and rigidity, a low coefficient of friction, a large pulley diameter, a small rotation angle of the fixed pulley under the same linear displacement conditions, less frictional energy consumption, and higher excitation efficiency.

[0016] The material, shape, and size of the connecting plate 11 are not limited, but it has sufficient strength and rigidity.

[0017] The specifications, quantity, and arrangement of the actuators 14 are not limited, and they can meet the driving force and amplitude requirements of the excitation system. In cases where the driving force is not large and the frequency is low, artificial excitation can also be used instead.

[0018] If vertical vibration is to be excited, two sets of low-frequency large-amplitude vibration transmission devices for long-span bridges are arranged at different longitudinal sections of the bridge. The arrangement principles are: (1) the difference in vertical displacement between the two positions in the excitation target mode should be as large as possible; (2) the longitudinal distance should be as small as possible.

[0019] The beneficial effects of the present invention are as follows: (1) Compared with the traditional excitation device without spring tuning, the weight of the mass body no longer needs to be directly borne by the actuator. Instead, the gravity self-balancing is achieved by symmetrically arranging the mass bodies on both sides, which greatly reduces the output force requirement of the actuator and greatly improves the economy; (2) Compared with the traditional excitation device with spring tuning, the actuator directly drives the mass body to perform forced vibration, which no longer requires spring tuning. The structure is greatly simplified, and the actuator can directly achieve frequency sweep excitation. Therefore, frequency tuning is more convenient and efficient, and the frequency range is not limited, which meets the needs of arbitrary torsion or vertical modal large vibration excitation on the site of large-span bridges; (3) Using a large-diameter turntable to suspend the mass body can greatly increase the acceleration and inertial force of the mass body to reduce the gravity requirement of the mass body; using a small-diameter rotating shaft to connect the actuator can give full play to the advantage of the large driving force output of the actuator and avoid the large increase in cost caused by the large stroke; and the bidirectional cable structure ensures that the actuator can work throughout the entire cycle, which greatly improves the working efficiency while avoiding the introduction of new mass bodies. (4) The device has a reasonable structural design, simple construction, diverse forms, and is economical and practical. It is easy to operate, reliable and efficient in transportation, installation, disassembly, storage and working condition switching, and has broad application prospects. Attached Figure Description

[0020] Figure 1 This is a structural diagram of a low-frequency large amplitude excitation device for a long-span bridge, which is a type of actuator-driven balanced mass body. Figure 2 This is a structural diagram of another type of low-frequency large-amplitude excitation device for long-span bridges, which uses an actuator to drive a balanced arrangement of mass bodies. In the diagram: 1. Base, 2. Support, 3. Bearing, 4. Rotating shaft, 5. Turntable, 6. First high-strength flexible cable, 7. Mass body, 8. First fixed pulley, 9. Second high-strength flexible cable, 10. Third high-strength flexible cable, 11. Connecting plate, 12. Fourth high-strength flexible cable, 13. Second fixed pulley, 14. Actuator. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0022] like Figure 1As shown, a low-frequency large-amplitude vibration transmission device for a long-span bridge includes a base 1, a support 2, a bearing 3, a rotating shaft 4, a turntable 5, a first high-strength flexible cable 6, a mass 7, a first fixed pulley 8, a second high-strength flexible cable 9, a third high-strength flexible cable 10, a connecting plate 11, a fourth high-strength flexible cable 12, a second fixed pulley 13, and an actuator 14. The base 1 is laid flat on the bridge deck; the support 2 is fixedly installed on the base 1; the bearing 3 is installed on the top of the support 2; the rotating shaft 4 is supported by the bearing 3; the turntable 5 is fixed on the rotating shaft 4; one end of the first high-strength flexible cable 6 is wound around the turntable 5 to suspend the mass 7, and the other end passes over the first fixed pulley 8 installed on the top of the base 1. The first end of the second high-strength flexible cable 9 is connected to the second high-strength flexible cable 6, which is in a horizontal position. The other end of the second high-strength flexible cable 9 is connected to the first high-strength flexible cable 6 of another set of low-frequency large-amplitude vibration transmission devices for large-span bridges. The second high-strength flexible cable 9 connects the two sets of low-frequency large-amplitude vibration transmission devices for large-span bridges into one unit. One end of the third high-strength flexible cable 10 is wound and fixed on the rotating shaft 4, and the other end is connected to the top surface of the connecting plate 11. One end of the fourth high-strength flexible cable 12 is wound and fixed on the rotating shaft 4, and the other end passes around the second fixed pulley 13 installed on the top of the base 1 and is connected to the bottom surface of the connecting plate 11. The actuator 14 is supported on the base 1 at the bottom and connected to the bottom surface of the connecting plate 11 at the top. By driving the connecting plate 11 in opposite phases through the actuators 14 of the two sets of low-frequency large-amplitude vibration transmission devices for large-span bridges that are far apart, the two mass bodies 7 are driven to vibrate in opposite directions, thereby exciting the large-span bridge to generate low-frequency large-amplitude vibration.

[0023] The low-frequency amplitude vibration transmission device for long-span bridges can be further simplified based on actual site conditions and available resources to reduce testing costs. Two sets of low-frequency amplitude vibration transmission devices for long-span bridges should be positioned with sufficient distance between them on the bridge deck; placing them together would cause them to fail. When used to excite vertical vibration, the two sets of low-frequency amplitude vibration transmission devices for long-span bridges should be arranged at different cross-sectional positions along the longitudinal direction of the bridge. The vertical displacement difference corresponding to the target vibration mode should be maximized, and the longitudinal spacing should be minimized. This should be determined by comprehensively considering various factors, and the devices should be arranged as centrally as possible along the transverse direction of the bridge deck.

[0024] Specifically, if the connecting plate 11, the fourth high-strength flexible cable 12, and the second fixed pulley 13 are removed, the actuator 14 can be directly connected to the third high-strength flexible cable 10 to induce vibration. However, because the third high-strength flexible cable 10 can only be subjected to tension and not compression, the actuator 14 only pulls the third high-strength flexible cable 10 to perform work for half a cycle. By using the connection method provided by this invention, the actuator 14 is guaranteed to perform work for the entire cycle, significantly improving efficiency.

[0025] Specifically, if the turntable 5, the third high-strength flexible cable 10, the connecting plate 11, the fourth high-strength flexible cable 12, and the second fixed pulley 13 are eliminated, and the first high-strength flexible cable 6 is directly wound around the rotating shaft 4 to suspend the mass 7, with the top of the actuator 14 directly connected to the mass 7, the low-frequency large-amplitude vibration transmission device for long-span bridges can also operate. However, this presents two difficulties: firstly, the mass of the mass 7 needs to be significantly increased; secondly, the stroke of the actuator 14 needs to be significantly increased (the unidirectional stroke may reach meters or even more). Both of these aspects will significantly increase the cost of the device. Therefore, the solution provided by this invention optimizes the diameter ratio of the rotating shaft 4 to the turntable 5, significantly reducing the experimental cost.

[0026] Specifically, the vibration excitation device can still operate if the first fixed pulley 8 is removed. However, because the top of the turntable 5 is relatively high above the bridge deck (possibly exceeding 3m, or even higher), the enormous horizontal tension of the first high-strength flexible cable 6 and the second high-strength flexible cable 9 will generate a very large overturning moment. Taking other measures to ensure that the low-frequency large-amplitude vibration transmission device of a long-span bridge has sufficient anti-overturning safety requires a huge investment. With the solution of this invention, the overturning moment can be basically ignored (if the first high-strength flexible cable 6 and the second high-strength flexible cable 9 are close enough to the bridge deck).

[0027] In particular, if the main beam of the bridge has a central slotted section, a simplified scheme similar to the one described above can be adopted, in which the bearing 3, the shaft 4, and the actuator 14 are arranged on the crossbeam between the slots, and the mass body 7 is suspended below the bridge deck.

[0028] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any equivalent changes, modifications, or variations made by those skilled in the art to the above examples using the technical solutions of the present invention shall still fall within the scope of the technical solutions of the present invention.

Claims

1. A low-frequency amplitude vibration transmission device for long-span bridges, characterized in that, The low-frequency large-amplitude vibration transmission device for the long-span bridge includes a base (1), a support (2), a bearing (3), a rotating shaft (4), a turntable (5), a first high-strength flexible cable (6), a mass (7), a first fixed pulley (8), a second high-strength flexible cable (9), a third high-strength flexible cable (10), a connecting plate (11), a fourth high-strength flexible cable (12), a second fixed pulley (13), and an actuator (14). The base (1) is laid flat on the bridge deck; the support (2) is fixedly installed on the base (1); the bearing (3) is installed on the top of the support (2); the rotating shaft (4) is supported by the bearing (3); the turntable (5) is fixed on the rotating shaft (4); one end of the first high-strength flexible cable (6) is wound around the turntable (5) to suspend the mass (7), and the other end passes around the first fixed pulley (8) installed on the top of the base (1) and is connected to one end of the second high-strength flexible cable (9) which is in a horizontal state; the second high-strength flexible cable (9) is connected to the first fixed pulley (8) installed on the top of the base (1); the second high-strength flexible cable (9) is connected to the first fixed pulley (8) installed on the top of the base (1), and the second high-strength flexible cable (9) is connected to the first fixed pulley (8) installed on the top of the base (1). The other end of the flexible cable (9) is connected to the first high-strength flexible cable (6) of another set of low-frequency large-amplitude vibration transmission devices for large-span bridges. The second high-strength flexible cable (9) connects the two sets of low-frequency large-amplitude vibration transmission devices for large-span bridges into one unit. One end of the third high-strength flexible cable (10) is wound and fixed on the rotating shaft (4), and the other end is connected to the top surface of the connecting plate (11). One end of the fourth high-strength flexible cable (12) is wound and fixed on the rotating shaft (4), and the other end passes around the second fixed pulley (13) installed on the top of the base (1) and is connected to the bottom surface of the connecting plate (11). The actuator (14) is supported on the base (1) at the bottom and connected to the bottom surface of the connecting plate (11) at the top. The connecting plate (11) is driven in opposite phase by the actuators (14) of the two sets of low-frequency large-amplitude vibration transmission devices for large-span bridges that are far apart, thereby driving the two mass bodies (7) to vibrate in opposite directions and exciting the large-span bridge to generate low-frequency large-amplitude vibration.

2. The low-frequency amplitude vibration transmission device for long-span bridges according to claim 1, characterized in that, The actuator (14) is arranged on one side of the low-frequency large-amplitude vibration transmission device for the long-span bridge. The turntable (5), the third high-strength flexible cable (10), the connecting plate (11), the fourth high-strength flexible cable (12), the second fixed pulley (13) and the actuator (14) are removed from the low-frequency large-amplitude vibration transmission device for the long-span bridge on the other side. Only one end of the first high-strength flexible cable (6) is retained to be wound around the rotating shaft (4) to suspend the mass body (7), and the other end is connected to the second high-strength flexible cable (9) after passing around the first fixed pulley (8).

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