Bridge monitoring system
- 产品详情
Bridge monitoring system
As a part of the transportation system, bridges play an important role in the development and evolution of human civilization. With the development of modern science and technology and the continuous growth of transportation demand, more and more bridges appear in people's vision. The cost of these bridges is often hundreds of millions or even billions of yuan, which has important strategic significance in transportation, military and social life. However, in the process of construction and use of bridges, due to the erosion of environment, harmful substances, vehicles, wind, earthquake, fatigue, human factors and other factors, as well as the continuous degradation of material properties, all parts of the structure have different degrees of fatigue and damage. If these damages can not be detected and maintained in time, they will affect the traffic safety and shorten the service life of the bridge, and even cause serious safety accidents. Therefore, the bridge monitoring system is an important measure of bridge safety.In the monitoring of bridges, the cable force is an important index to evaluate the health status of steel cable structures. At present, the construction monitoring and longterm monitoring measurement technologies of cable force mainly include: magnetic flux sensor measurement technology, hydraulic anchor cable force sensor, fiber Bragg grating anchor cable force sensor, string anchor cable force sensor.Measurement technology of magnetic flux sensor
1. Principle and application field of magnetic flux sensor
The magnetic flux sensor is based on the principle of magnetoelastic effect of ferromagnetic materials. That is, when the external mechanical load of ferromagnetic material changes, its internal magnetization (permeability) changes. The internal force of the component is measured by measuring the permeability change of the component made of ferromagnetic material. It can effectively measure the stress of cables and prestressed tendons. It is a non-destructive testing technology.
The magnetic flux sensor can be applied to the cable force test of cablestayed bridge, the cable force test of suspender and tie bar of tied arch bridge, the cable force test of suspension bridge, the cable force test of suspension structure, the tension test of tension member in tension structure, the tension test of external cable and prestressed reinforcement in prestressed concrete structure, and the anchor cable force test of geotechnical engineering, Test of ring anchor cable force in hydropower project.
2. Structure of magnetic sensorThe magnetic flux sensor consists of two copper coils, the primary coil and the secondary coil. When the primary coil is connected with a pulse current, it will generate an instantaneous current in the secondary coil due to the presence of an iron core. The current intensity and voltage generated by electromagnetic induction depend on the permeability of iron core material, and the permeability of iron core material is related to the stress state of iron core. The measurement is realized according to the relationship between induced voltage and stress.
3. Measurement system of magnetic flux sensor
The measurement system of magnetic flux sensor includes magnetic flux sensor, switch junction box, magnetoelastic instrument, monitoring and control computer or PLC controller, data acquisition and transmission card, data transmission line and pipe laying, instrument protection box, data management cloud server, client, etc.
Connection of magnetoelastic instrument and computer: it can communicate with computer through RS232 or 485rs. It can be wired or wireless to transmit signal.
Magnetic flux sensor monitoring system can be divided into offline monitoring system and online monitoring system. The off-line monitoring system needs to collect the cable force data manually on a regular basis; the online monitoring system can provide the bridge management department with the current operation status of the bridge in real time.
4. Characteristics of magnetic flux sensor
(1) The sensor is solid and water tight, suitable for long-term monitoring.
(2) When using, the sleeve is directly outside the component, which belongs to non-contact measurement, does not damage the structure, and does not need to change the length of the original component during installation.
(3) The sensor has low maintenance cost and long service life. Even if it is damaged, it is not necessary to dismantle the original structure, so as to make up the sensor on site.
(4) The sensor is easy to install and easy to detect.
5. Technical parameters
(1) Product model: QSM.CCTB Specification: inner diameter: 18mm ~ 270mm
(2) Measuring range: 0 ~ material yield stress.
(3) Large wiring length: 150m.
(4) Operating environment temperature: - 40 ~ 80 ℃.
(5) Measurement accuracy: ≤ 3% FS.
(6) Power supply: AC 110 ~ 240V, 60 / 50 Hz.
Hydraulic anchor cable force sensor
1. Measuring principle of hydraulic anchor cable force sensor
The liquid pressure in the elastic body cavity is used to sense the force exerted on it.
2. Structural composition
The sensor is mainly composed of guide ring, elastomer, special inert liquid and hydraulic transmitter. The special inert liquid fills the cavity of the elastomer compactly. The structure of the guide ring and the elastomer ensures that the pressure can be transferred to the special inert liquid. The hydraulic transmitter can accurately measure the pressure of the liquid in the elastic body cavity and convert it into current signal output. Through the calibration, the one-to-one correspondence between the external force and the current value is established, and the external pressure value is obtained from the measured current value in actual use.
3. Hydraulic anchor cable force sensor measurement system
The hydraulic sensor is used for on-site regular detection. The measuring instrument can be connected to read the output value directly.
When there are a large number of hydraulic sensors and long-term monitoring, online measurement system can be established. The measurement system includes hydraulic sensors, multi-channel measuring instruments, data acquisition software, data transmission line and other accessories.
The monitoring system can be composed of multi-channel measuring instrument, multiple hydraulic sensors and a set of measuring software.
Connection between measuring instrument and server: it can communicate with computer through RS232 or RS485, which can be wired connection or wireless signal transmission.
4. Features of hydraulic sensor
(1) The height of the sensor is small, and the height of the sensor is 50-100 mm;
(2) The zero drift is small and suitable for long-term monitoring;
(3) The influence of eccentric load is relatively small, which is suitable for installation on construction site;
(4) The structure is compact and simple;
5. Technical parameters of monitoring system
(1) Data acquisition mode: dynamic measurement, sampling frequency of single sensor is 8Hz;
(2) Maximum range: rated measuring force of sensor;
(3) Ambient temperature: - 40 ~ 80 ℃
(4) Measurement accuracy: ≤ 2% FS
(5) Measurement accuracy after 2 million fatigue tests: ≤ 2% FS
(6) Instrument power supply: AC 220 V
(7) Maximum wiring distance between sensor and instrument: ≤ 500m
6. Sensor installation method
When the hydraulic sensor is used for anchor cable, it is usually installed between two base plates in the anchor nut.
Fiber Bragg grating anchor cable force sensor
Fiber Bragg grating anchor cable force sensor is widely used in slope, bridge, water conservancy dam, etc. when the measured load acts on the fiber Bragg grating anchor cable force sensor, it will cause the deformation of the elastic cylinder and transfer to the fiber Bragg grating. According to the wavelength change of the fiber Bragg grating, the stress of the fiber Bragg grating can be changed. The optical signal is transmitted to the fiber Bragg grating analyzer through the optical cable, then the stress value can be measured and read out, and the total load value acting on the fiber grating anchor cable force sensor can be calculated.
Application
It is mainly used to measure and monitor the load and prestress loss of various anchors, anchor cables, rock bolts, pillars, supports in tunnels and underground caverns, and large prestressed reinforced concrete structures (bridges and dams, etc.).
Main performance indicators
(1) Grating wavelength range: 1510nm ~ 1590nm
(2) Measurement accuracy: 1% F.S
(3) Resolution: 0.1% F.S
(4) Temperature range: - 40 ~ + 80 ℃
String type anchor cable force sensor
String type anchor cable force sensor is mainly used to measure cable force of cable structure, load-bearing bridge, prestress, rock cable anchorage, dam cable anchorage, etc. As shown in the figure, the cable tension can be measured for a long time by installing the product between the anchor plate and the anchorage. If the product is placed at the tension end, the anchor cable gauge correction jack can also be used for cable tension construction control.
When installing and using, the following conditions shall be met as far as possible:
(1) Appropriate product size and range, try to make the diameter of the inner hole of the product consistent with the diameter of the anchor plate and the size of the anchorage.
(2) The anchor plate is flat and perpendicular to the cable force direction.
(3) The anchor plate is parallel to the surface of the anchorage.
(4) During installation, make the center of cable, anchor plate, anchor cable meter, anchorage and Jack coaxial as much as possible. When the above conditions can not be achieved, please add force buffer gasket at both ends of the product.