Research on GPS bridge deformation monitoring technology?

What are the methods of bridge monitoring and measurement based on GPS technology? How to take the exam? Please read the article edited by Zhong Da Consulting Company.

1 deformation monitoring

The so-called deformation monitoring refers to the use of relevant measuring instruments and methods to record the movement of mine strata and surface, dams, slopes, surface subsidence, surface deformation and so on. In the form of data or images, as the basic data to analyze its safety, and make a scientific and reasonable explanation to predict and predict the development trend and speed of deformation. According to the scope of deformation monitoring, it can be divided into three categories: engineering construction and local deformation research, regional deformation research and global deformation research.

However, no matter what kind of deformation monitoring, its detection principles and methods are similar, and the monitoring contents can be basically divided into the following categories: First, in order to accurately predict the ground subsidence and take timely protective measures, it is necessary to periodically observe the ground deformation and effectively grasp the basic laws of ground recovery and subsidence; Second, geotechnical buildings, such deformation monitoring is mainly based on different structures to develop different deformation monitoring content; Three, industrial and civil buildings, this kind of deformation monitoring mainly includes vertical displacement, horizontal displacement, dynamic deformation monitoring, building itself inclined crack monitoring and building foundation uniform settlement. The main significance of deformation monitoring is to study the deformation law, analyze and predict the deformation, verify the structural design, feedback the construction quality and evaluate the safety state of the building.

At present, the methods and technologies of deformation monitoring mainly include four categories: First, the ground photogrammetry technology has its limitations. Due to the reduction of the resolution of photographic equipment, the monitoring range is small and the accuracy is low. However, with the vigorous development of digital photography technology and the gradual maturity of real-time photography technology, ground photogrammetry technology has ushered in new development opportunities; Second, special measurement methods such as tilt measurement, collimation measurement and static leveling are not within the traditional measurement range of deformation monitoring in civil engineering.

Thirdly, geodesy, which is the most commonly used traditional method, mainly completes the deformation measurement through leveling, edge measurement, angle measurement and other related technologies. Geodetic survey has a high precision and has formed a relatively perfect theory and method, but there are also many defects such as low survey efficiency, low degree of mechanization and modernization, heavy task and great difficulty in large-scale engineering survey. Fourthly, the new technology of deformation monitoring. The popularization and application of new technology has always been the direct driving force to improve the monitoring level. In recent years, computer tomography, laser scanning and InSAR technology have become emerging technologies for deformation monitoring. Although some technologies are not mature enough, they have greatly improved the monitoring accuracy and reduced the monitoring difficulty.

2 bridge deformation monitoring

Bridge health monitoring has become an important means to prevent the instability of bridge structure, especially the deformation monitoring in the process of bridge operation, which is of great significance. The main contents of bridge monitoring include the following aspects:

(1) deformation monitoring of bridge tower, in which the main observation contents include the observation of the overall inclination of tower column, the observation of the expansion and contraction of inclined tower column, the observation of tower column disturbance and the observation of horizontal displacement at the top of tower column.

(2) Plane displacement monitoring of bridge, external factors such as vehicle load and wind load will cause the displacement of bridge foundation, so the monitoring content of bridge deck displacement is horizontal displacement perpendicular to the bridge axis.

(3) pier deformation monitoring, including vertical displacement monitoring and horizontal displacement monitoring.

(4) Monitoring the deflection of the bridge deck. Under the action of external load, the vertical displacement along the bridge axis, that is, deflection, will directly affect the traffic safety of the bridge deck and the service life of the bridge.

There are many methods of bridge deformation monitoring, such as photogrammetry, total station observation, leveling, suspension, special deflection meter observation, GPS measurement and so on. The monitoring methods of horizontal displacement include traverse method, angle measurement method, baseline method, intersection method and GPS measurement method; The monitoring methods of vertical displacement include precision leveling, static leveling, trigonometric leveling and GPS measurement.

As can be seen from the above introduction, GPS measurement can be carried out in all aspects of bridge deformation monitoring, and its high synchronization, high precision, convenience and reliability determine the bright future of GPS technology in bridge deformation monitoring.

3 GPS deformation monitoring technology based on bridge monitoring

The full name of GPS is GlobalPositioningSystem, that is, Global Positioning System, which consists of three parts: user receiving equipment, ground monitoring part and space part. The user accepts the equipment, that is, the GPS signal receiver, and calculates the time, speed, altitude, latitude and longitude of the geographical location of the equipment through a series of steps such as signal capture, data acquisition and data processing. The ground control system consists of monitoring station, ground antenna and main control station. The space part consists of 3 spare satellites and 2 1 working satellite, which are evenly distributed on 6 orbital planes and 20,200 kilometers away from the ground.

The principle of GPS positioning measurement is based on data code (D code), ranging code (C/A code, P code) and carrier signal transmitted by GPS satellites. The basic principle of pseudo-range measurement is based on space rear intersection. Suppose at a certain moment t, the spatial distance from point P to three satellites is (), and the spatial coordinates of the satellites are (√ ([_ _] [_ _]).

Among them: the correction of receiver clock error; Used for satellite clock error correction, tropospheric delay correction and ionospheric delay correction.

The principle of carrier phase measurement is based on the L-band carrier of GPS satellite and two kinds of high-frequency signals of the carrier. Assuming that the phase of the satellite at this moment is _ _ d _ dd _ _ _, and the phase variation is, the basic expression of the carrier phase measurement principle is:

Where: is an integer week, __D_Dd___

There are two main measurement methods of GPS technology in bridge deformation monitoring, one is determination positioning method, and the other is relative positioning method. GPS static relative positioning method is a linear combination technology of phase observation and carrier phase observation. Assuming that two receivers and satellites M and N are observed synchronously in time and time respectively, the following phase angles are obtained:

Based on the carrier phase, the GPSPTK mode sets up a GPS receiver at the reference station to receive the satellite signals, and at the same time transmits the observed values and coordinates to the mobile station. The mobile station sets up a measurement point to receive the reference station information and satellite signals, and at the same time, uses the differential technology to process the information to realize real-time positioning and give the coordinates of the point to be measured.

The above research on GPS bridge deformation monitoring technology was collected by Zhong Da Consulting Company.

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