The Importance of Online Monitoring of Bridge Vibration Frequency and Vibration Size-Instrument Network

In recent years, with the increasing number of large buildings and the application of high technology, building health monitoring is developing towards integration, automation, digitization, and intelligence. Bridge vibration monitoring is a necessary monitoring content, monitoring the frequency and magnitude of bridge vibration, which is of great significance for the safety and health of bridges.

The spectral characteristics of bridge acceleration response data under free vehicle and environmental load excitation show significant differences between the periods with and without vehicles on the bridge. The time history and frequency spectrum of the bridge acceleration response when a vehicle is on the bridge are shown in Figure 3-4. The vibration energy of 2-4Hz has the advantage, and the low-frequency vibration components of the bridge are almost submerged by the response of the vehicle excitation. The peak of the low-frequency vibration frequency spectrum is not obvious, and there is a peak at non structural frequency points; Figure 3-5 shows the time history and frequency spectrum of the bridge acceleration response when there is no vehicle on the bridge. The vibration energy of 2-4Hz is greatly reduced, and the low-frequency vibration energy below 1Hz dominates, with obvious spectral peaks.

By conducting similar analyses on a large amount of monitoring data, the following conclusions can be drawn:

1) Vehicles add mass to bridges, resulting in a shift in the peak frequency spectrum of natural frequencies.

2) The forced vibration of bridges caused by vehicle excitation will have a significant impact on the small low-frequency vibration of bridges due to the high energy and limited current collection accuracy and sampling frequency, manifested as a shift in the peak frequency spectrum at the frequency points of low-frequency vibration.

3) There are significant differences in the frequency spectrum characteristics of bridges when different vehicles ride on them, and the natural frequency point positions are unstable.

4) The reliability and accuracy of modal recognition using data containing a large number of vehicle periods will inevitably decrease.

Vibration and acceleration characteristics (frequency, amplitude, acceleration, velocity, damping, vibration acceleration level) detection in bridges. As a professional research and manufacturing enterprise of acceleration sensors, it is recommended to use piezoelectric ceramic crystal vibration acceleration sensors with lower noise and higher sensitivity in the acceleration monitoring scheme of bridges. Two products, 374A-0.25 and 374A-0.5, are recommended for online monitoring;

Product Overview of 374A Seismic Sensor:

374A series acceleration sensorIt is an acceleration sensor designed specifically for detecting ultra-low frequency and low-frequency vibrations in large buildings, infrastructure, and earthquake detection applications; Its characteristic is to output a low-noise and high amplitude signal through a sensing mechanism, with excellent measurement resolution. Both ceramic crystals and quartz crystals can be used in the design of seismic acceleration sensors, with ceramic crystals having higher output efficiency than quartz crystals. The 374A product uses ceramic crystals as sensitive components, which provides better signal quality and low-frequency response characteristics. It also has a built-in low-noise signal modulator, resulting in high resolution. In order to achieve measurement results, seismic acceleration sensors are usually used together with gain amplifiers and power signal modulators. This accelerometer uses laser welding to firmly weld the stainless steel shell and the joint together; The shell isolation, internal shielding, and controllable impact of external environment (including RF, EMI, ESD, and overload) and misoperation on the product ensure its repeatability and long-term stability.

374A seismic sensorFeatures:

·Ultra-low frequency response

·Top out connector

·High sensitivity

·Metal welding seal

·Shell isolation

·EMI/RFI shielding

Application of 374A seismic sensor:

·Building vibration monitoring

·Earthquake detection

·Bridge monitoring

·Research on Infrastructure Vibration