Efficient measurement method for bridge deflection at target detection wheel track

Abstract

The application provides a high-efficiency measurement method for deflection of a bridge at a wheel trace of a target detection vehicle, three prisms are installed on a top plate of a common truck carriage of a rear axle double-wheel type in three positions of left, right and middle front, one range finder is installed under a bottom plate of the carriage at a gap of the rear axle double-wheel type to prepare a target detection vehicle, three intelligent total stations automatically track the three prisms on the target detection vehicle running on the bridge at an ultra-low speed and synchronously measure coordinates of the three prisms, initial coordinates of a midpoint of a wheel trace of the rear axle double-wheel type are calculated according to the measured data and geometric relations, the distance data measured by the range finder is aligned with the total station measurement data according to a time stamp, a cross slope of the bridge at the rear axle is calculated, the initial coordinates are corrected by replacing the corresponding data measured by the range finder with the distance from the ground measured under the static corresponding cross slope to count the influence of the side tilt moment and remove the influence of the running vibration, and the bridge deflection of the midpoint of the wheel trace of the rear axle double-wheel type of the target detection vehicle is obtained by comparing the corrected coordinates with a high-precision three-dimensional curved surface model of the bridge.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering measurement technology, specifically relating to an efficient method for measuring bridge deflection at the wheel tracks detected by a target. Background Technology

[0002] Bridge deflection, as a key indicator reflecting the stress state and deformation characteristics of a bridge, is a primary criterion for assessing its load-bearing capacity and structural health. Currently, bridge deflection measurement methods are mainly classified into four categories: traditional contact methods, optical geometric methods, photoelectric imaging methods, and sensor-based indirect inversion methods. Traditional contact methods directly measure structural deformation through physical contact, recording displacement via dial gauge mechanical contacts or electromagnetic induction using a low-level displacement meter (LVDT). The advantages are simple principle and reliable data; the disadvantages are the need for scaffolding and low sampling efficiency, making them suitable for static measurements on small and medium-sized bridges where scaffolding can be erected. Optical geometric methods use levels or total stations and geometric trigonometric principles for long-distance non-contact measurements. The advantages are long measurement range and high accuracy; the disadvantages are that they often require road closures and cannot be used for dynamic deflection measurements, making them suitable only for situations with a limited number of measurement points. Photoelectric imaging methods are based on image processing, photoelectric sensors, and modern computing. Deformation measurement using machine vision algorithms includes photoelectric image-based deflectometers, machine vision video displacement methods, and collimated laser displacement methods. Advantages include high precision, non-contact operation, high sampling frequency, and support for multi-point synchronization. Disadvantages include a trade-off between field of view and accuracy, high equipment cost, and sensitivity to ambient light. These methods are suitable for dynamic load testing and short- to medium-term vibration monitoring of bridges. Indirect sensor inversion measures physical quantities such as structural strain, tilt angle, and acceleration, and then calculates deflection using mechanical or mathematical models. Methods include GPS / BeiDou differential positioning, millimeter-wave radar interferometry, tiltmeter integration, fiber optic grating (FBG) strain inversion, and accelerometer quadratic integration. Advantages include independence from reference standards and all-weather operation. Disadvantages include reliance on complex models and calibrations, the need for periodic algorithm calibration, and relatively lower accuracy. These methods are suitable for long-term health monitoring of ultra-long-span bridges. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an efficient method for measuring the deflection of a bridge at the wheel track detection point on a target.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: 1. Prepare a target detection vehicle. Install three total station prisms at three positions on the left, right, and front center of the roof of a regular truck with a single rear axle and two wheels. Install a rangefinder under the floor of the truck bed at the gap between the two wheels on both sides of the rear axle to form a target detection vehicle. The positions of the left and right prisms are geometrically directly related to the midpoint of the wheel tracks on both sides of the rear axle. The prism at the front center is located on the perpendicular line from the midpoint of the line connecting the left and right prisms to facilitate the calculation of the longitudinal and transverse slopes of the truck bed roof. To prevent the total station from missing or crossing targets during automatic tracking, the prism at the front center is significantly higher. Place the target detection vehicle with the verified rear axle load and tire pressure on a rigid platform with an adjustable lateral slope. Measure the distance from the ground measured by the rangefinders on both sides under different lateral slopes and form a corresponding dataset. This dataset, measured under static conditions, takes into account the effect of the lateral tilting moment caused by the lateral slope.

[0005] 2. Set up three intelligent total stations at a station with unobstructed line of sight to the rear of the measurement range, complete the relevant settings, connect and control the three intelligent total stations with a computer, and after turning on the automatic tracking mode, each total station aims at one of the three prisms on the roof of the target detection vehicle traveling at an ultra-low speed of about 2 km / h on the bridge surface, and synchronously measures its coordinates at the frequency provided by the total station. Calculate the initial coordinates of the midpoint of the wheel tracks of the target detection vehicle's two rear axles on both sides of the bridge surface based on the measurement data and geometric relationships. The cross slope of the vehicle roof surface calculated by the intelligent total station from the coordinates of the left and right prisms is actually the sum of the bridge surface cross slope and the lateral tilt moment cross slope. The lateral tilt moment cross slope is due to the pressure of the suspension on both sides. The roll moment is caused by the difference in shrinkage and tire deformation, and is positively correlated with the bridge deck cross slope, but its value is smaller than the bridge deck cross slope. The roll moment cross slope can be obtained by using the ground clearance data measured by the rangefinder under the double wheel gap of the rear axle on both sides. However, the measurement data is affected by vehicle driving vibration. By aligning the ground clearance data measured by the rangefinder with the measurement data of the total station according to the timestamp, the bridge deck cross slope at the rear axle of the target detection vehicle can be calculated. In order to take into account the influence of the roll moment caused by the bridge deck cross slope and remove the influence of vehicle driving vibration, the distance from the ground at the double wheel gap of the rear axle on both sides of the vehicle floor measured by the target detection vehicle under the static corresponding cross slope condition is used to replace the corresponding data measured by the rangefinder to correct the initial coordinates.

[0006] 3. By comparing the discrete corrected coordinate points with the high-precision three-dimensional curved surface model of the bridge deck, the bridge deck deflection at the midpoint of the wheel tracks of the two rear axles of the target detection vehicle can be obtained.

[0007] The beneficial effects of this invention are as follows: 1. This invention transforms bridge deflection measurement from directly measuring the deflection at a limited number of points on the bottom of the beam to indirectly estimating the bridge deck deflection at the wheel track by measuring the coordinates of a prism on a bridge deck target detection vehicle. An intelligent total station in automatic tracking mode measures and calculates the coordinates of two measuring points every 0.3 seconds, easily meeting measurement requirements. The coordinate measurement accuracy of the intelligent total station is at the millimeter level, the distance measuring instrument's measurement accuracy is at the millimeter level, and the accuracy of the three-dimensional curved surface model of the bridge deck used as a reference is also at the millimeter level. Therefore, the calculated bridge deck deflection at the wheel track is also at the millimeter level.

[0008] 2. The deflection measurement method of the present invention may measure the combined deflection of the longitudinal beam and the transverse bridge deck. For example, the bridge deck deflection measured in the outer lane of the middle span of a large cantilever box girder bridge is the combined deflection. To understand the proportion of longitudinal and transverse deflection, the deflection of the longitudinal beam can be measured at the box girder ribs, and the deflection of the transverse bridge deck can be measured at the pier supports.

[0009] 3. With the measurement of the bridge deck's millimeter-level three-dimensional curved surface model as a reference no longer difficult, the bridge deck deflection measurement method of the present invention can be applied to almost all vehicular bridge decks, such as cast-in-place box girder continuous beam bridges, long-span prestressed concrete cable-stayed bridges, precast assembled multi-beam bridges, and planar irregular bridges at the junctions of grade-separated lanes. The deflection measurement method of the present invention can be used to find the area of ​​maximum deflection on the entire bridge deck. Attached Figure Description

[0010] Figure 1 This is a rear view showing the mounting position of the prism and rangefinder of the target detection vehicle of the present invention. Figure 2 This is a side view of the mounting position of the prism and rangefinder of the target detection vehicle of the present invention. Figure 3 Top view of the prism mounting position of the target detection vehicle of the present invention. Figure 4 This is a schematic diagram showing the installation position of the rangefinder under the floor of the vehicle body according to the present invention. In the diagram: 1. Left prism, 2. Right prism, 3. Front center prism, 4. Left rangefinder, 5. Right rangefinder, 6. Midpoint of the left double-wheel contact wheel tracks, 7. Midpoint of the right double-wheel contact wheel tracks.

Claims

1. An efficient method for measuring bridge deflection at the wheel tracks detected by a target, characterized in that... The following equipment and steps are as follows: Three prisms are installed on the roof of a regular truck bed with two rear axles at three positions: left, right, and front center. A rangefinder is installed under the floor of the truck bed at the gap between the two rear axles to prepare a target detection vehicle. Three intelligent total stations are used to automatically track the three prisms on the target detection vehicle traveling at ultra-low speed on the bridge surface and simultaneously measure their coordinates. The initial coordinates of the midpoint of the wheel tracks of the two rear axles are calculated based on the measurement data and geometric relationships. The distance data measured by the rangefinders is aligned with the measurement data of the total station according to the timestamp to calculate the cross slope of the bridge surface at the rear axle. The ground clearance measured under the static corresponding cross slope is used to replace the corresponding data measured by the rangefinders to correct the initial coordinates. The corrected coordinates are compared with the high-precision three-dimensional curved surface model of the bridge surface to obtain the bridge surface deflection at the midpoint of the wheel tracks of the two rear axles of the target detection vehicle.

2. The three prism positions according to claim 1, characterized in that: The positions of the left and right prisms are geometrically related to the midpoint of the wheel tracks on both sides of the rear axle. The prism in the front center is located on the perpendicular line from the midpoint of the line connecting the left and right prisms.

3. The automatic tracking measurement using three intelligent total stations as described in claim 1, characterized in that: Connect and control three intelligent total stations using a computer. After activating the automatic tracking mode, each total station aims at one of the three prisms on the roof of the target detection vehicle traveling at ultra-low speed on the bridge surface and synchronously measures its coordinates at the frequency provided by the total station. Calculate the initial coordinates of the midpoint of the wheel tracks of the target detection vehicle's two rear axles on both sides of the bridge surface based on the measurement data and geometric relationships.

4. The method for correcting initial coordinates by replacing the corresponding data measured by the rangefinder with the ground clearance measured under a static cross slope, as described in claim 1, is characterized in that: The target testing vehicle with the verified rear axle load and tire pressure is placed on a rigid platform with an adjustable lateral slope. The distances from the ground measured by the rangefinders on both sides under different slopes are measured and corresponding datasets are generated. This dataset, measured under static conditions, takes into account the effect of the lateral tilting moment generated by the slope.

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