Method for monitoring deflection change of long-span bridge

Abstract

The invention relates to the technical field of bridge detection, in particular to a monitoring method for deflection changes of a large-span bridge. Two layers of laser trackers are arranged on the bridge pier, the distance between the laser trackers and the target fixed on the bridge is monitored through the laser trackers, so that whether the bridge deforms or not is judged, the basic target is arranged, zero drift correction is conducted on the laser trackers, and the detected distance value is more accurate; by performing temperature compensation calculation on the first monitoring distance and the second monitoring distance, the influence of temperature change on the accuracy of laser ranging is avoided. According to the monitoring scheme, the bridge vibration response during typhoon can be monitored in real time, deflection accumulation caused by concrete creep can be monitored for a long time, data trend analysis can be performed for a long time, and the bridge rigidity degradation risk can be predicted.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge detection, and specifically to a method for monitoring the deflection change of a long-span bridge. Background Art

[0002] Long-span bridges (such as cable-stayed bridges and suspension bridges) are prone to deflection deformation under the action of long-term loads, environmental temperature changes, wind loads and traffic loads, which affects the structural safety. Therefore, it is necessary to monitor the deflection deformation of the bridge. Most traditional monitoring methods use sensors or total stations. Sensors are easily affected by the environment, easily damaged, and have high maintenance costs; total stations require manual operation, have poor real-time performance, and their accuracy is limited in bad weather; while the advantage of using image measurement is relatively high measurement accuracy, which can reach 0.1 mm, and at the same time has a high sampling rate. However, this method has high requirements for the cameras at the receiving end to ensure the measurement accuracy, and the image algorithm processing is relatively complex, which does not meet the requirements of high cost performance and convenient development. Summary of the Invention

[0003] The technical problem to be solved by the present invention is that the existing bridge deflection deformation monitoring methods are greatly affected by the environment, inaccurate in manual operation, and have relatively low cost performance.

[0004] The specific solution of the present invention to solve the above problems is as follows: A method for monitoring the deflection change of a long-span bridge, comprising the following steps: Step 1: Set an upper laser tracker and a lower laser tracker on the piers at both ends of the bridge, set a first target on both the left and right halves of the bridge, set a second target at the middle position of the bridge, and set reference targets at both ends of the bridge; Step 2: Align the upper laser trackers and lower laser trackers on both sides with the reference targets for self-calibration to correct the zero drift of the upper laser tracker and the lower laser tracker; Step 3: Obtain the distances between the corrected upper laser trackers on both sides and two adjacent first targets respectively, record them as the first initial distances, and obtain the distances between the corrected lower laser trackers on both sides and the second target, record them as the second initial distances; Step 4: Respectively track and measure the first targets on both sides with the corrected upper laser trackers on both sides to obtain the first monitoring distances in real time, and track and measure the second target with the corrected lower laser trackers on both sides to obtain the second monitoring distances in real time; Step 5: Perform temperature compensation calculation on the first monitoring distances and the second monitoring distances; Step 6: Calculate the difference between the compensated first monitoring distance and the first initial distance to obtain the first deformation value, and calculate the difference between the compensated second monitoring distance and the second initial distance to obtain the second deformation value; Step 7: Generate deflection curves of the first deformation value and the second deformation value varying with time, and set a deflection threshold. When the first deformation value or the second deformation value exceeds the deflection threshold, an alarm is triggered.

[0005] The present invention adopting the above technical solution, compared with the prior art, has the following beneficial effects: The present invention sets two layers of laser trackers on the bridge pier. By monitoring the distance between the laser tracker and the target fixed on the bridge, it is judged whether the bridge deforms. A basic target is set to correct the zero drift of the laser tracker, making the detected distance value more accurate. Through temperature compensation calculation for the first monitoring distance and the second monitoring distance, the accuracy of laser ranging affected by temperature change is avoided. The monitoring scheme of the present invention can monitor the vibration response of the bridge during typhoon in real time, monitor the deflection accumulation caused by concrete creep in the long term, conduct long-term data trend analysis, and predict the risk of bridge stiffness degradation.

[0006] As a preference, a further technical solution of the present invention is: In step 2: Detect the initial distances between the upper laser tracker and the lower laser tracker and the reference targets on both sides in advance. The upper laser trackers and the lower laser trackers on both sides respectively detect the measurement distances from the reference targets, calculate the difference between the measurement distance and the initial distance as the zero correction amount, and compensate the zero correction amount into the corresponding upper laser tracker and lower laser tracker.

[0007] The temperature compensation calculation in step 5 is specifically: ΔL = L0 * (P / P0) * (T0 + 273.15) / (T + 273.15), where L0 is the first monitoring distance or the second monitoring distance, P0 is the air pressure when obtaining the first monitoring distance or the air pressure when obtaining the first monitoring distance, T0 is the temperature when obtaining the first monitoring distance or the temperature when obtaining the first monitoring distance, P is the air pressure at the real-time monitoring moment, T is the temperature at the real-time monitoring moment, and ΔL is the first monitoring distance or the second monitoring distance after temperature compensation. Description of the Drawings

[0008] Figure 1 is the layout structure diagram of the embodiment of the present invention; Figure 2 is the laser detection position diagram of the embodiment of the present invention; In the figure: 1. Bridge; 2. Bridge pier; 3. Laser tracker; 4. Second target; 5. First target. Detailed Embodiments

[0009] The present invention will be further described below in conjunction with embodiments, and the purpose is only to better understand the content of the present invention. Therefore, the examples given do not limit the protection scope of the present invention.

[0010] See the appendix Figure 1-2 , an embodiment of the present invention discloses a method for monitoring the deflection change of a long-span bridge 1, including the following steps: Step 1: Set an upper laser tracker 3 and a lower laser tracker 3 on the piers 2 at both ends of the bridge 1. A plurality of upper laser trackers 3 and lower laser trackers 3 are set. Set a first target 5 on the left and right halves of the bridge 1, such as at the position of one-quarter span. Set a second target 4 at the middle position of the bridge 1, and set reference targets at both ends of the bridge 1; Set a controller as the control element for controlling the laser tracker 3; Step 2: Align the upper laser trackers 3 and lower laser trackers 3 on both sides with the reference targets for self-calibration to correct the zero drift of the upper laser tracker 3 and the lower laser tracker 3; In the laser tracker 3, due to reasons such as temperature change, power supply voltage fluctuation cooperation, and component aging, when the input signal is zero (theoretically the output should also be zero), the output deviates from the zero value. To solve the influence brought by the above zero drift, perform the following correction steps: Detect the initial distance L between the upper laser tracker 3 and the lower laser tracker 3 and the reference targets on both sides in advance by using a total station 初始 , and use each upper laser tracker 3 and lower laser tracker 3 on both sides to detect the measured distance L from the reference target respectively 测 , calculate the difference between the measured distance L of each laser tracker 3 测 and the initial distance L 初始 , the zero correction amount ΔL = L 测 −L 初始 , if the zero correction amount ΔL exceeds the allowable error (such as ±1 mm), store the zero correction amount ΔL as the zero correction amount of the current laser tracker 3; In subsequent real-time measurements, the zero correction amount is compensated into the corresponding upper laser tracker 3 and lower laser tracker 3, and all original data is automatically deducted by the zero correction amount ΔL; Step 3: Obtain the distances between the corrected upper laser trackers 3 on both sides and two adjacent first targets 5 respectively, and record them as the first initial distance L 初始1 , obtain the distances between the corrected lower laser trackers 3 on both sides and the second target 4, and record them as the second initial distance L 初始2 ; The first initial distance L 初始1 and the second initial distance L 初始2 refer to the distance values after zero correction; Step 4: Corresponding the corrected upper laser trackers 3 on both sides to track and measure the first targets 5 on both sides respectively, and obtain the first monitoring distance L1 in real time. The corrected lower laser trackers 3 on both sides track and measure the second target 4, and obtain the second monitoring distance L2 in real time; Step 5. Perform temperature compensation calculations on the first monitoring distance L1 and the second monitoring distance L2; specifically: ΔL1 = L1 * (P / P 01 ) * (T 01 + 273.15) / (T + 273.15), where L1 is the first monitoring distance, P 01 is the air pressure synchronously obtained when acquiring the first monitoring distance, T 01 is the temperature synchronously obtained when acquiring the first monitoring distance, P is the air pressure at the real-time monitoring moment, T is the temperature at the real-time monitoring moment, and ΔL1 is the first monitoring distance after temperature compensation; ΔL2 = L2 * (P / P 02 ) * (T 02 + 273.15) / (T + 273.15), where L2 is the second monitoring distance, P 02 is the air pressure synchronously obtained when acquiring the second monitoring distance, T 02 is the temperature synchronously obtained when acquiring the second monitoring distance, P is the air pressure at the real-time monitoring moment, T is the temperature at the real-time monitoring moment, and ΔL2 is the second monitoring distance after temperature compensation; Step 6. Calculate the difference between the compensated first monitoring distance ΔL1 and the first initial distance L 初始1 to obtain the first deformation value, and calculate the difference between the compensated second monitoring distance ΔL2 and the second initial distance L 初始2 to obtain the second deformation value; Step 7. The controller sends the first deformation value and the second deformation value to an external monitoring platform, generates deflection curves of the first deformation value and the second deformation value changing with time on the external monitoring platform, and sets a deflection threshold (static design value ±5%, dynamic vibration amplitude ±10%). When the first deformation value or the second deformation value exceeds the deflection threshold, an alarm is triggered, and the external monitoring platform gives an alarm or a pop-up window for reminder.

[0011] In the present invention, two layers of laser trackers 3 are provided on the bridge pier 2. By monitoring the distance from the laser tracker 3 to the target fixed on the bridge 1, it is judged whether the bridge 1 is deformed. A basic target is set to correct the zero drift of the laser tracker 3, making the detected distance value more accurate. By performing temperature compensation calculations on the first monitoring distance and the second monitoring distance, the accuracy of laser ranging affected by temperature changes is avoided. The monitoring scheme of the present invention can monitor the vibration response of the bridge 1 during typhoons in real time, monitor the deflection accumulation caused by concrete creep in the long term, perform long-term data trend analysis, and predict the risk of bridge 1 stiffness degradation.

[0012] The above are only the preferred and feasible embodiments of the present invention, and do not limit the scope of the rights of the present invention accordingly. Any equivalent changes made by using the content of the specification and the drawings of the present invention are included within the scope of the rights of the present invention.

Claims

1. A method for monitoring the deflection change of a long-span bridge, comprising the following steps: Step 1: An upper laser tracker and a lower laser tracker are set on the piers at both ends of the bridge, a first target is set on the left and right halves of the bridge, a second target is set in the middle of the bridge, and reference targets are set at both ends of the bridge; Step 2: Align the upper laser tracker and the lower laser tracker on both sides with the reference target, perform self-calibration, and correct the zero drift of the upper laser tracker and the lower laser tracker; Step 3: Obtain the corrected distances between the upper laser trackers on both sides and the two adjacent first targets, respectively, and record them as the first initial distances; obtain the corrected distances between the lower laser trackers on both sides and the second target, and record them as the second initial distances; Step 4: Use the corrected upper laser trackers on both sides to track and measure the first targets on both sides respectively, and obtain the first monitoring distance in real time; use the corrected lower laser trackers on both sides to track and measure the second targets, and obtain the second monitoring distance in real time; Step 5, performing temperature compensation calculation on the first monitoring distance and the second monitoring distance; Step 6: Calculate the difference between the compensated first monitoring distance and the first initial distance to obtain a first deformation value, and calculate the difference between the compensated second monitoring distance and the second initial distance to obtain a second deformation value; Step 7: Generate a deflection curve of the first deformation value and the second deformation value based on time changes, and set a deflection threshold. When the first deformation value or the second deformation value exceeds the deflection threshold, an alarm is triggered.

2. The method for monitoring the deflection change of a long-span bridge according to claim 1, characterized in that: In the step 2: the initial distances between the upper laser tracker and the lower laser tracker and the reference targets on both sides are detected in advance by a total station, the upper laser tracker and the lower laser tracker on both sides respectively detect the measured distances with the reference targets, and the difference between the measured distance and the initial distance is calculated as the zero point correction amount, and the zero point correction amount is compensated to the corresponding upper laser tracker and the lower laser tracker.

3. The method for monitoring the deflection change of a long-span bridge according to claim 1 is characterized in that: The temperature compensation calculation in step five is specifically as follows: ΔL=L0*(P / P0)*(T0+273.15) / (T+273.15), where L0 is the first monitoring distance or the second monitoring distance, P0 is the air pressure when the first monitoring distance is obtained or the air pressure when the first monitoring distance is obtained, T0 is the temperature when the first monitoring distance is obtained or the temperature when the first monitoring distance is obtained, P is the air pressure at the real-time monitoring moment, T is the temperature at the real-time monitoring moment, and ΔL is the first monitoring distance or the second monitoring distance after temperature compensation.

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