CN103792055B - A kind of impact load device that is applicable to small bridge quick diagnosis - Google Patents

Abstract

The invention discloses a bridge impact loading device, which comprises a bracket, a vertical guide rail arranged on the bracket, and a loading hammer arranged on the vertical guide rail, and a driving device connected with the loading hammer is also arranged on the bracket, and the driving device includes Motor, electromagnetic clutch, controller, counting sensor, drive shaft and traction rope wound on the drive shaft, the drive shaft is connected to the motor through the electromagnetic clutch, the load hammer is connected to the lower end of the traction rope, and the counting sensor is set The lower end of the bracket is used to detect the falling of the loading hammer and output the detected signal to the controller, and the controller controls the motor to drive the drive shaft to lift the loading hammer. The shock and vibration device of the present invention can generate a single-amplitude impact force (single shock), and has the advantage of generating a flat and consistent force spectrum, and there is no significant attenuation or zero-value region on the frequency spectrum.

Description

An impact load device suitable for rapid diagnosis of small and medium bridges

technical field

The invention relates to the fields of dynamic testing and safety evaluation of medium and small bridges in civil engineering and traffic engineering. The invention is a device for impact loading on small and medium bridges. The impact load generated has specific characteristics (large amplitude, wide frequency domain and single amplitude characteristics), which can realize the purpose of impact vibration testing and safety diagnosis of small and medium bridges .

Background technique

Bridge health diagnosis technology has developed rapidly in recent years. However, compared with long and large bridges, the health diagnosis of small and medium-sized bridges on national and provincial arterial roads and county and township roads has not received sufficient attention. As of the end of 2009, the total number of bridges in my country reached 594,600, including 552,800 small and medium bridges. Due to the limitations of funds, manpower, attention, etc., most small and medium-sized bridges have been in disrepair for a long time, and there are serious safety hazards. Therefore, it is an urgent scientific task to develop a fast, low-cost, and high-accuracy health diagnosis technology for small and medium bridges. Conventional environmental vibration tests for bridge health diagnosis can only provide modal parameters such as frequency and mode shape of the bridge, and it is difficult to provide very clear information for bridge health diagnosis engineering. Shock vibration testing is a new direction for the health diagnosis of small and medium-sized bridges. By observing the time history data of the impact force and the acceleration of important parts of the bridge during the shock vibration testing process, more detailed parameters such as the flexibility matrix of the structure can be identified, so as to achieve more accurate bridge safety diagnosis. Truck static load testing is a widely accepted field testing method for bridge engineers. Structural bearing capacity is an important indicator of structural safety. The truck static load test can effectively evaluate the bearing capacity of the bridge by loading different levels of the tested bridge and observing the corresponding displacement and strain data. The Ministry of Communications of my country's "Methods for Appraisal of Bearing Capacity of Old Highway Bridges" provides detailed regulations and explanations for the static load test method of trucks. The American Handbook of Condition Assessment of Highway Bridges (AASHTO) has similar instructions for static load tests on trucks. The truck static load test results are reliable, and it is a method specified in the code, so it is widely used in the evaluation of the bearing capacity of small and medium-sized bridges at home and abroad. In the determination of the dynamic characteristics of the bridge structure, it is necessary to excite the bridge through the sports car test, brake test and car jump test. The disadvantage is that the test is time-consuming, laborious and expensive, especially the bridge must be closed to traffic during the test, which affects traffic. Bridge managers are the least likely to see it.

Through the bridge flexibility matrix that can be identified by shock vibration, the deflection under any static load can be predicted, and then the verification coefficient of the bridge can be calculated according to the identification method of the old highway bridge bearing capacity of the Ministry of Communications, and a clear judgment of the bridge safety state can be obtained. It is feasible to simultaneously identify the dynamic and static characteristics of the structure through the shock vibration test, but the impact force required for identification of the flexibility matrix of the bridge must not only have a large amplitude, but also need a wide frequency domain, and the energy of the impact force must be uniform. Distributed in a wide frequency domain (for example, 0~100 Hz), otherwise the structural compliance matrix cannot be accurately identified in the signal analysis part, and the existing vibration device cannot meet the requirements of one impact, two impacts or multiple impacts Inconsistent and uneven force spectra will be generated, and the amplitude of the force spectrum will be attenuated by 30dB or more, especially at the resonance peak. Avoiding secondary shocks can obtain accurate analysis results, but the data obtained by multiple shocks is poor. The final analysis results are not reliable. Therefore, the current impact device cannot be applied to the impact vibration test, and the safety assessment of the bridge cannot be performed using the impact vibration theory. At present, the impact loading devices that can be applied to bridge testing are very limited. The most widely used is a simple hammering device (big hammer). However, the impact force generated by this hammering device is small and cannot effectively excite the The multi-order modes of the model lead to inaccurate identification of the structural flexibility matrix. Therefore, how to develop an effective impact loading device suitable for bridge safety diagnosis, to generate impact force with large amplitude and wide frequency range, and to avoid secondary impact has become a bottleneck restricting the development and application of small and medium bridge health diagnosis technology. question.

Contents of the invention

Aiming at the bottleneck problem in the health diagnosis of small and medium bridges introduced in the background technology section, the present invention discloses a loading device suitable for bridge vibration testing that can realize a single impact, thereby improving the accuracy and reliability of test analysis results.

In order to solve the problems of the technologies described above, the technical solution of the present invention is as follows:

A bridge impact loading device, comprising a bracket, a vertical guide rail arranged on the bracket, and a loading hammer arranged on the vertical guide rail, and a driving device connected to the loading hammer is also arranged on the bracket, and its characteristics in:

The driving device includes a motor, an electromagnetic clutch, a controller, a counting sensor, a drive shaft and a traction rope wound on the drive shaft, and the drive shaft is connected to the motor through the electromagnetic clutch, and The lower end of the traction rope is connected to the loading hammer, and the counting sensor is arranged at the lower end of the support to detect the falling of the loading hammer and output the detected signal to the controller, and the control The device controls the motor to drive the drive shaft to lift the loading hammer according to the output signal of the counting sensor.

Slide blocks are arranged at both ends of the loading hammer, the slide blocks are located on the guide rails, and an electric braking device for fixing the slide blocks on the guide rails is arranged on the slide blocks. The electric braking device includes: a guide rail clamping device, a spring energy storage device, a wedge sliding gear, and a piston. The electric braking device generates force electrically, and the wedge blocks clamped on both sides of the guide rail are applied to the contact surface, so as to clamp the guide rail and play the role of braking.

A force sensor and a rubber pad are arranged at the lower end of the loading hammer.

The loading device of the present invention adopts the electric motor to extract the heavy object and control the whole process of the falling, impact and rebound of the heavy object, and the generated impact force is provided by the acceleration generated by the free fall movement of the loading hammer. The structure of the whole device is simple and reasonable, and can meet the impact load required by the bridge vibration test. Since the impact force data needs to be used in the identification process of the structural flexibility matrix in the signal analysis part, a wireless load cell is installed on the lower end of the loading hammer, so that the time course data of the impact force generated can be recorded and wirelessly transmitted to the data acquisition computer . Loading hammers are variable loading weights that allow additional weight on the loading hammer to provide greater impact loads. When the loading hammer is lowered to the height in contact with the ground, a laser sensor is installed on the impact device, which can transmit the signal to the control circuit, and then the computer controls to send out an electric signal. After the brake device receives the electric signal, it is clamped on the guide rail by spring drive. The wedge blocks on both sides exert a force up to 9200N on the contact surface, thereby clamping the guide rail and playing the role of braking. The whole action process from sending an electric signal to braking takes a very short time. Due to the use of special materials and design, the brake device will not damage the guide rail, and the strong clamping force also ensures that there will be no relative movement between the slider and the guide rail, and the protection provided by the secondary impact of the loading hammer is avoided. The broadband characteristic of the impact force can be obtained by a flexible rubber pad under the force sensor. The flexible rubber pad produces a broadband that covers the frequency range of the mode of interest.

Beneficial effect

1. The impact vibration device of the present invention can generate a single-amplitude impact force (single impact), which has the advantage of generating a flat and consistent force spectrum, and there is no significant attenuation or zero value area on the spectrum diagram.

2. Utilize the impact vibration device announced by the present invention to produce the impact force with large amplitude and wide frequency domain and single amplitude characteristics, combined with the measured acceleration data, the flexibility matrix of the bridge can be accurately identified, and then the deflection of the bridge can be predicted, and the calibration correction can be calculated. test coefficient and bridge safety performance evaluation.

3. The present invention can combine multiple advanced sensors such as carbon fiber wireless sensing and FBG to quickly detect bridges.

4. The present invention can combine shock vibration theory and flexibility identification theory to predict the deflection of old bridges, it can replace the truck static load test specified in the code, and has the characteristics of convenience, low cost and high accuracy. Since there are many small and medium bridges in our country, the invented device has strong practicability and has broad application prospects in the rapid diagnosis of small and medium bridges.

Description of drawings

Fig. 1 is a structural schematic diagram of the device of the present invention.

Figure 2. Time history diagram of the resulting impact load.

Fig. 3 Spectrum diagram of the resulting impact load.

Among them: electromagnetic clutch 1, infrared sensor 2, electric brake 3, bracket 4, motor 5, controller 6, force sensor 7, rubber pad 8, loading hammer 9.

detailed description:

Below in conjunction with accompanying drawing, the present invention is described in detail:

As shown in Figure 1, the bridge impact loading device of the present invention includes a bracket 4, a vertical guide rail arranged on the bracket and a loading hammer 9 arranged on the vertical guide rail, and a force sensor 7 and a rubber pad 8 are arranged at the lower end of the loading hammer. Also be provided with motor 5, electromagnetic clutch 1, controller 6, the infrared sensor 2 that is used as counting sensor, drive shaft and the traction rope that is wound on the drive shaft on support, drive shaft is connected with motor by electromagnetic clutch, in traction rope The lower end is connected to the loading hammer 9, and the counting sensor is arranged at the lower end of the support to detect the falling of the loading hammer and output the detected signal to the controller. The controller controls the motor to drive the drive shaft to lift the loading hammer according to the output signal of the counting sensor. Slide blocks are arranged at both ends of the loading hammer, the slide blocks are located on the guide rail, and an electric brake device is arranged on the slide block. The electric brake device is an existing equipment and can be purchased directly.

The working principle of the loading device of the present invention is as follows: first, the motor lifts the loading hammer to a certain height (the required lifting height can be automatically judged according to the bridge type, that is, the required impact force), the motor stops working, the electromagnetic clutch is closed, and the driving The shaft is braked, and the loading hammer is fixed at the height to be determined. After the device is activated by the control button, the loading hammer will move down along the guide rail in a free-falling motion and produce an impact on the ground. After the loading hammer hits the bridge deck, The rebound rises in a short time, and when the loading hammer rebounds for the first time, the infrared sensor 2 located at the bottom of the impact device transmits the signal to the controller, and the motor is controlled by the controller, so that the motor can instantly lift the loading hammer, At the same time, the brake devices on both sides of the guide rail avoid the influence of the unfavorable factors of the secondary impact, that is, the primary impact process is completed.

Analysis of impact force characteristics of laboratory vibrator:

The shocking device of the present invention is subjected to an impact test on the surface of the structure. The impact force is as shown in Figure 2, and its impact force amplitude can reach 5t~17t. Fast Fourier transform is performed to it, and the frequency domain figure 3 of the impact force can be obtained. It was found to have broadband characteristics. The vibrating device of the present invention has large impact force, wide frequency range and no secondary impact, can fully stimulate the dynamic characteristics of the bridge, and realize the safety diagnosis of the bridge.

Claims (2)

1. An impact load device suitable for rapid diagnosis of small and medium-sized bridges, comprising a support, a vertical guide rail arranged on the support and a loading hammer arranged on the vertical guide rail, and a loading hammer connected to the loading rod is also arranged on the support. The hammer connection driving device is characterized in that: the driving device includes a motor, an electromagnetic clutch, a controller, a counting sensor, a drive shaft and a traction rope wound on the drive shaft, and the drive shaft passes through the The electromagnetic clutch is connected with the motor, and the loading hammer is connected at the lower end of the traction rope, and the counting sensor is arranged at the lower end of the support to detect the falling of the loading hammer and output the detected signal to The controller, the controller controls the motor to drive the drive shaft to lift the loading hammer according to the output signal of the counting sensor; sliders are arranged at both ends of the loading hammer, The slide block is located on the vertical guide rail, and an electric braking device is arranged on the slide block to fix the slide block on the vertical guide rail. 2. The impact loading device according to claim 1, characterized in that: a force sensor and a rubber pad are arranged at the lower end of the loading hammer.