A low-frequency amplitude vibration excitation device for long-span bridges

Abstract

This invention belongs to the field of large-span bridge vibration excitation technology, and discloses a low-frequency, large-amplitude vibration excitation device for long-span bridges. This invention generates periodic vertical forces by controlling the direction and timing of water pump jets, providing a controllable vertical load to the bridge, thereby exciting large-amplitude vertical or torsional vibrations. By designing the water tank capacity, number of water pumps, nozzle diameter, and jet velocity, and employing a multi-nozzle parallel connection and phase control strategy, the jet force and water flow return force are optimized, significantly reducing system power, installation difficulty, and cost while achieving efficient excitation. Compared with existing technologies, this invention's low-frequency, large-amplitude vibration excitation device for long-span bridges does not require complex mechanical frequency tuning and actuators, is small in size, easy to assemble and disassemble, and has a flexible and adjustable control system that can quickly adapt to different vibration modes and frequency conditions of the bridge, demonstrating significant engineering application prospects and promotional value.

Description

Technical Field

[0001] This invention belongs to the field of large bridge vibration technology and relates to a low-frequency large-amplitude vibration excitation device for 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. Bridge damping, due to its complex influencing mechanism and its close relationship with amplitude, generally requires identification through field dynamic tests. Environmental excitation response amplitudes are small, and signal-to-noise ratios are low, limiting the identification of damping parameters to small amplitude conditions, and the accuracy of identification is difficult to guarantee. For small- to medium-span bridges, due to their relatively small mass and relatively high vibration frequency, the permissible amplitude is relatively small; therefore, commonly used excitation devices can easily excite the structure to generate the required amplitude. However, traditional excitation devices cannot be effectively used for low-frequency, large-amplitude vibration excitation of long-span bridges.

[0003] The vibration excitation equipment for dynamic testing of long-span bridges mainly includes eccentric inertial exciters, servo hydraulic exciters, electric exciters, spring-tuned mass exciters, and dynamically loaded excitation vehicles. Eccentric inertial exciters generate periodic inertial forces through rotating eccentric masses, thus forming excitation forces. However, under conditions requiring low frequencies and large excitation forces, a massive eccentric rotor is needed, rapidly increasing the total mass of the equipment, often reaching tens or even hundreds of tons, making transportation and installation difficult and costly. While 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 typically only provide single-point excitation, making it difficult to meet the needs of low-frequency large-amplitude vibration tests on long-span bridges. Mechanical vibration devices based on spring-tuned masses typically rely on springs for frequency tuning. For low-frequency applications, very long springs are required; for example, at a frequency of 0.1Hz, the spring deformation length is close to 25m, and the applicable frequency band is narrow, with insufficient multi-frequency excitation capability. Therefore, they are difficult to implement in engineering. In this case, inertial capacitive tuned mass devices can be used, but their structure is complex. The amplitude of bridge vibration is basically in the centimeter range when using dynamic loads such as moving vehicles or hopping vehicles, which cannot meet the requirements for large amplitude.

[0004] Therefore, in order to meet the requirements of low-frequency, multi-frequency, large amplitude, controllable frequency and lightweight equipment for dynamic testing of long-span bridges, it is necessary to develop a new type of excitation device that is simple in structure, light in weight, low in cost, has a wide range of applicable frequencies and high excitation efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a low-frequency, large-amplitude vibration excitation device for long-span bridges that is simple in construction, easy to assemble and disassemble, low in cost, highly efficient in excitation, has a wide range of excitation frequencies, and requires no complex mechanical frequency tuning or actuators. This device maximizes the jet reaction force and optimizes the water flow return force by rationally selecting nozzle size and jet velocity, and employing a multi-nozzle and phase control strategy. This significantly reduces the pump head and power requirements, eliminating the need for the pump to bear complex loads. By controlling the water flow direction and jet cycle, it accurately generates periodic vertical inertial forces, providing a controllable external vertical load to the bridge, thereby exciting large-amplitude vertical or torsional vibrations. This effectively overcomes the technical bottlenecks of traditional excitation equipment, which suffers from complex structure, heavy weight, low energy efficiency, insufficient low-frequency excitation capability, and inconvenient frequency tuning.

[0006] The technical solution of the present invention: A low-frequency large-amplitude vibration excitation device for a long-span bridge includes a water tank 1, water 2, a water pump 3, a water inlet 4, a vertical pipe 5, a horizontal pipe 6, a vertical pipe outlet 7, a horizontal pipe outlet 8, a sensor 9, a first data line 10, a controller 11, a second data line 12, and a control regulating valve 13. The water tank 1 is positioned on the bridge deck, typically at the section requiring the largest excitation mode displacement. For vertical displacement, it is placed in the central region of the bridge cross-section; for torsional displacement, it is symmetrically placed on both sides of the bridge cross-section. The water tank 1 is filled with water 2. The water pump 3 is placed inside the water tank 1. The water inlet 4 is located at the bottom of the water pump 3 and communicates with the water 2 inside the water tank 1. The horizontal pipe 6 is installed on both sides of the water pump 3, and the vertical pipe 5 communicates with the horizontal pipe 6. A control regulating valve 13 is installed between the vertical pipe 5 and the horizontal pipe 6. The vertical pipe outlet 7 and the horizontal pipe outlet 8 are connected. The inlet 8 is installed at the ends of the vertical pipe 5 and the horizontal pipe 6 respectively; the sensor 9 is set on the bridge and connected to the controller 11 through the first data line 10; the controller 11 is connected to the control regulating valve 13 through the second data line 12; after the water pump 3 is powered on, it draws in water 2 through the inlet 4 and accelerates it. According to the vibration period and phase of the excited mode, the water flow is controlled to flow through the vertical pipe 5 or the horizontal pipe 6 and sprayed out from the corresponding vertical pipe outlet 7 or the horizontal pipe outlet 8; the sensor 9 is installed on the bridge to monitor the movement signal of the bridge in real time and feeds it back to the controller 11 through the first data line 10. The controller 11 controls the rotation direction of the control regulating valve 13 through the second data line 12 to block the vertical pipe 5 or the horizontal pipe 6. The water 2 is regulated to spray out from the vertical pipe outlet 7 or the horizontal pipe outlet 8 at different times to achieve intermittent vertical excitation force.

[0007] When water 2 is sprayed upward from the vertical pipe outlet 7, it has a certain velocity from rest to vertical, and therefore acceleration. Its inertial force acts downward on the water tank 1 through the water pump 3, and this inertial force acts on the bridge through the water tank 1, thus providing a downward driving force for the bridge. When water 2 is sprayed horizontally from the horizontal pipe outlet 8, the horizontal inertial forces are basically symmetrically canceled out, meaning the resultant force in the horizontal direction is very small and will not excite lateral vibration of the bridge. Therefore, it is necessary to control the timing of water 2 spraying from the vertical pipe outlet 7 according to the vibration period and phase of the excitation mode, so that when the bridge vibrates downward, water 2 is sprayed from the vertical pipe outlet 7, providing a downward force to the bridge, doing positive work for the bridge, and exciting it to generate greater displacement and velocity. When the bridge moves upward, if water is still sprayed from the vertical pipe outlet 7, it will do negative work for the bridge and prevent the bridge from vibrating. To avoid this situation, water 2 needs to be sprayed from the horizontal pipe outlet 8, which will neither do positive nor negative work for the bridge.

[0008] The above scheme keeps the water pump 3 running continuously. By controlling the regulating valve 13 to block the vertical pipe 5 or the horizontal pipe 6, intermittent vertical excitation force is achieved. Since the low-frequency vibration period is relatively long, usually more than 3 seconds, the actual operation is relatively simple.

[0009] Furthermore, the horizontal pipe 6, the horizontal pipe outlet 8, and the control valve 13 are eliminated. The vertical pipe 5 is installed on both sides of the water pump 3, and the water pump 3 is directly controlled by the controller 11 to work intermittently. Water is only sprayed out intermittently from the vertical pipe outlet 7, thereby stimulating bridge vibration. This excitation method has a simpler structure, but requires the water pump 3 to have a sufficient response speed.

[0010] The beneficial effects of the present invention are as follows: (1) Compared with traditional spring-free eccentric inertial vibrators, servo hydraulic vibrators, electric vibrators and other excitation devices, the present invention generates a controllable reaction force to excite bridge vibration by jetting water, which can achieve lower frequency vibration excitation and significantly improves economy and ease of operation; (2) Compared with traditional spring-free excitation devices, the present invention does not require spring tuning. It achieves controllable jet excitation by controlling the regulating valve or water pump through the controller. It can directly perform frequency sweep or fixed frequency excitation, which is convenient to adjust, efficient, and has a wide frequency range, better meeting the low-frequency torsional vibration requirements of large-span bridges. (3) By designing the water tank capacity, number of water pumps, nozzle diameter and jet speed, and adopting a low-speed, high-flow pulse water spray scheme, the system power, installation difficulty and cost can be significantly reduced while improving system stability and achieving efficient excitation; (4) The low-frequency large-amplitude vibration excitation device for long-span bridges of the present invention has a compact structure and simple construction. It is easy and reliable to transport, arrange, install, disassemble and maintain. The control system is flexible and adjustable, and can quickly adapt to different vibration modes and vibration frequency conditions of the bridge. It has significant engineering application prospects and promotion value. Attached Figure Description

[0011] Figure 1 This is a structural diagram of a jet phase-controlled excitation device that uses a regulating valve to generate a controllable reaction force from the water pump's jet flow. Figure 2 This is a structural diagram of a jet phase-controlled excitation device that directly controls the water pump to generate a controllable reaction force. In the diagram: 1. Water tank, 2. Water, 3. Water pump, 4. Inlet, 5. Vertical pipe, 6. Horizontal pipe, 7. Vertical pipe outlet, 8. Horizontal pipe outlet, 9. Sensor, 10. First data line, 11. Controller, 12. Second data line, 13. Control regulating valve. Detailed Implementation

[0012] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0013] like Figure 1As shown, a low-frequency large-amplitude vibration excitation device for a long-span bridge, which utilizes a regulating valve to generate a controllable reaction force from a water pump jet, includes a water tank 1, water 2, a water pump 3, a water inlet 4, a vertical pipe 5, a horizontal pipe 6, a vertical pipe outlet 7, a horizontal pipe outlet 8, a sensor 9, a first data line 10, a controller 11, a second data line 12, and a control regulating valve 13. The water tank 1 is located at a suitable position on the bridge deck, typically at the section where the excitation mode displacement is greatest, and is filled with water 2. The water pump 3 is placed inside the water tank 1, with a water inlet 4 at the bottom. The horizontal pipe 6 is installed on both sides of the water pump 3, and the vertical pipe 5 communicates with the horizontal pipe 6. A control regulating valve 13 is installed between the vertical pipe 5 and the horizontal pipe 6 to adjust the water flow direction. The vertical pipe outlet 7 and the horizontal pipe outlet 8 are respectively installed at the ends of the vertical pipe 5 and the horizontal pipe 6. Sensor 9 is mounted on the bridge and connected to controller 11 via first data line 10; controller 11 is connected to control regulating valve 13 via second data line 12. Water pump 3 starts working after being powered on, drawing water in through inlet 4 and accelerating it, flowing through vertical pipe 5 or horizontal pipe 6, and being sprayed out through vertical pipe 5 and vertical pipe outlet 7 or horizontal pipe 6 and horizontal pipe outlet 8. When water is sprayed upwards above the water surface from vertical pipe outlet 7, its reaction force acts downwards on water tank 1 through water pump 3, and then on the bridge, providing downward driving force for the bridge. When water is sprayed horizontally from the horizontal pipe outlets 8 on the left and right sides submerged in water, the horizontal inertial forces almost symmetrically cancel each other out, that is, the horizontal forces are combined. The force is very small and will not excite lateral vibration of the bridge. Sensor 9 monitors the bridge motion signal in real time and feeds it back to controller 11 through the first data line 10. According to the vibration period and phase of the excitation mode, controller 11 controls the rotation direction of regulating valve 13 through the second data line 12 to block the horizontal pipe 6 or the vertical pipe 5. Water is regulated to spray out from the vertical pipe outlet 7 or the horizontal pipe outlet 8 at different times. Water 2 sprays out from the vertical pipe outlet 7, providing a downward force to the bridge, stimulating it to produce greater displacement and velocity, thereby stimulating the bridge to vibrate.

[0014] like Figure 2As shown, a low-frequency large-amplitude vibration excitation device for a long-span bridge that directly controls the water pump to generate a controllable reaction force includes a water tank 1, water 2, a water pump 3, a water inlet 4, a vertical pipe 5, a vertical pipe outlet 7, a sensor 9, a first data line 10, a controller 11, and a second data line 12. A water tank 1 is placed at a suitable location on the bridge deck and filled with sufficient water 2. A water pump 3 is placed inside the water tank 1. After the water pump 3 is powered on, it draws water in through the inlet 4 and accelerates it, flowing through the vertical pipe 5 and spraying it out through the outlet 7 of the vertical pipe. When the water sprays upward above the water surface from the outlet 7 of the vertical pipe, its reaction force acts downward on the water tank 1 through the water pump 3, and then on the bridge, providing a downward driving force for the bridge. The sensor 9 monitors the bridge's motion signal in real time and feeds it back to the controller 11 through the first data line 10. Based on the vibration period and phase of the excitation mode, the controller 11 controls the timing and speed of the water pump 3's spray through the second data line 12, adjusting the water to spray out from the outlet 7 of the vertical pipe at different times and at different speeds, providing a downward force to the bridge, stimulating it to produce greater displacement and velocity, thereby stimulating the bridge to vibrate.

[0015] The water tank 1 has sufficient strength, rigidity and water storage capacity. Taking into account factors such as transportation and storage costs, it can be used after necessary waterproofing treatment of the container.

[0016] The water 2 mentioned above is selected from water bodies that are widely available and inexpensive, such as river water or seawater, and the water tank 1 should always have a sufficient amount of water to meet the system's operating requirements.

[0017] The water pump 3 is selected according to the excitation target and the usage environment to ensure the continuity and stability of water spraying. If a variable frequency water pump is used, it is ensured that the frequency conversion time is short enough.

[0018] The inlet 4 is designed to meet the flow rate and pressure requirements of the system. It should be selected reasonably based on the system design flow rate and allowable flow velocity, and the flow capacity should meet the maximum working flow rate requirements.

[0019] The material type and size of the vertical pipe 5 or the horizontal pipe 6 meet the flow and pressure requirements, and the vertical pipe 5 can be slightly inclined to ensure smooth jet flow.

[0020] The cross-sectional shape and size of the vertical pipe outlet 7 or the horizontal pipe outlet 8 are not limited.

[0021] The sensor 9 has sufficient sensitivity and response speed to collect bridge vibration response signals and feed them back to the controller 11 via the first data line 10.

[0022] The type of the first data line 10 is not limited.

[0023] The controller 11 can accurately control parameters such as the jet timing and duty cycle of the control valve 13 or the water pump 3 to meet the needs of different bridge excitation conditions.

[0024] The second data line 12 should be selected reasonably according to the system power level and operating environment, and should have sufficient current carrying capacity, insulation performance and waterproof protection level to meet the long-term operation requirements of outdoor or humid environments.

[0025] The control valve 13 is an electric valve or solenoid valve with fast response characteristics. The controller 11 regulates the direction of the control valve 13, thereby adjusting the vertical or horizontal jet sequence and duration in real time, so that the jet duration matches the water flight time, realizing the synergistic superposition of jet reaction force and fall impact force, thereby significantly improving excitation efficiency and reducing system power requirements under low frequency conditions.

[0026] Parallel arrangement of multiple nozzles can reduce the size of a single nozzle and the corresponding pipe diameter while meeting the same excitation force, thereby reducing the system's structural dimensions and installation difficulty. At the same time, the arrangement of multiple nozzles is conducive to improving the uniformity of the jet flow field and enhancing the stability and controllability of the excitation force output. It has significant advantages in terms of structural adaptability, control performance, and engineering feasibility.

[0027] Two sets of devices can be arranged laterally along the bridge. These devices generate a downward driving force by alternately jetting water according to the period and phase of the target torsional mode vibration, thereby exciting the bridge's torsional vibration. To achieve the best excitation effect, the two sets of devices should be arranged as far as possible horizontally from the center of torsion.

[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 excitation device for long-span bridges, characterized in that, The low-frequency large-amplitude vibration excitation device for the long-span bridge includes a water tank (1), water (2), a water pump (3), an inlet (4), a vertical pipe (5), a horizontal pipe (6), a vertical pipe outlet (7), a horizontal pipe outlet (8), a sensor (9), a first data line (10), a controller (11), a second data line (12), and a control regulating valve (13). The water tank (1) is arranged on the bridge deck and is filled with water (2). The water pump (3) is placed inside the water tank (1). The inlet (4) is located at the bottom of the water pump (3) and is connected to the water (2) in the water tank (1). The horizontal pipe (6) is installed on both sides of the water pump (3), and the vertical pipe (5) is connected to the horizontal pipe (6). A control regulating valve (13) is installed between the vertical pipe (5) and the horizontal pipe (6). The vertical pipe outlet (7) and the horizontal pipe outlet (8) are respectively installed at the ends of the vertical pipe (5) and the horizontal pipe (6). The sensor (9) is installed on the bridge and connected to the controller (11) via the first data line (10). The controller (11) is connected to the control regulating valve (13) via the second data line (12). After the water pump (3) is powered on, it draws in water (2) through the inlet (4) and accelerates. According to the vibration period and phase of the excited mode, the water flows through the vertical pipe (5) or the horizontal pipe (6) and is sprayed out from the corresponding vertical pipe outlet (7) or the horizontal pipe outlet (8). The sensor (9) is installed on the bridge and monitors the movement signal of the bridge in real time. It is fed back to the controller (11) via the first data line (10). The controller (11) controls the rotation direction of the control regulating valve (13) via the second data line (12) to block the vertical pipe (5) or the horizontal pipe (6). The water (2) is sprayed out from the vertical pipe outlet (7) or the horizontal pipe outlet (8) at different times to achieve intermittent vertical excitation force.

2. The low-frequency amplitude vibration excitation device for long-span bridges according to claim 1, characterized in that, The horizontal pipe (6), the horizontal pipe outlet (8) and the control valve (13) are removed. The vertical pipe (5) is installed on both sides of the water pump (3). The water pump (3) is directly controlled by the controller (11) to work intermittently. Water is sprayed out intermittently only from the vertical pipe outlet (7), thereby stimulating the bridge to vibrate.

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