A dynamic weighing method for bridges based on strain area

Abstract

This invention relates to a dynamic weighing method for bridges based on strain area, belonging to the technical field of dynamic weighing in bridge engineering. The bottom position of the mid-span section of the bridge is selected as the sensor measuring point. Through actual bridge vehicle tests, data from each dynamic strain sensor is extracted, and the bridge strain influence surface corresponding to the measuring point is calibrated. An equation system is established by assuming the theoretical strain area and the measured strain area are equal. A solution equation system is established for each selected test point, and an error function is constructed to solve for the total weight of the vehicle under test. The equation system corresponding to the minimum error function value is determined; the total weight of the vehicle in this equation system is the actual total weight of the vehicle.

Description

Technical Field

[0001] This invention relates to a dynamic weighing method for bridges based on strain area, belonging to the field of dynamic weighing technology for bridges in bridge engineering. Background Technology

[0002] In recent years, my country's highway bridge construction has developed rapidly, with small and medium-sized bridges accounting for over 90% of all bridges. With the increasing number of vehicles and growing transportation demand, overloading incidents are frequent, leading to bridge performance degradation and even collapse. There is an urgent need for a convenient and efficient weighing system to monitor and control vehicle loads on bridges.

[0003] There are two main methods for controlling heavy vehicles on highway bridges. One method involves burying strip sensors under the road surface. When a vehicle passes over, the pressure on the strip is converted into an electrical signal by the sensor, thus achieving the purpose of weighing. However, this method requires excavating the road surface, and the strip sensors lack durability, degrading in performance after repeated compaction. The other method is dynamic bridge weighing. Dynamic bridge weighing systems treat the bridge structure as a "scale," measuring the bridge's dynamic response over time by installing sensors such as dynamic strain gauges at different measuring points at the bottom of the bridge. This allows for the identification of vehicle weight. Dynamic weighing offers advantages such as not disrupting traffic, causing no damage to the road surface, high durability, and low cost. Furthermore, the test data can be used to monitor the health of the bridge, facilitating its management and maintenance.

[0004] Currently, the Moses algorithm is the primary algorithm used for dynamic weighing of bridges. This method collects dynamic strain information when vehicles cross the bridge. By using vehicles of known weight to cross the bridge and collecting information, the influence line of the bridge can be calculated. The dynamic strain signal is approximately equal to the superposition of the product of the bridge influence line and the load value. Based on this principle, the theoretical value is compared with the measured value, and the least squares principle is used to identify the vehicle weight. However, the traditional Moses algorithm is only suitable for one-dimensional structures, i.e., single-lane single-vehicle traffic. When the bridge deck is wide, using only the influence line of a single beam for calculation will lead to a large identification error, and it is not suitable for multi-vehicle traffic conditions. Summary of the Invention

[0005] This invention provides a dynamic weighing method for bridges based on strain area to address the above-mentioned problems.

[0006] A dynamic weighing method for bridges based on strain area, comprising the following steps:

[0007] S1. The bottom position of the mid-span section of the bridge is determined as the sensor measuring point. The number of dynamic strain sensors corresponding to the main beam are arranged along the transverse direction of the bridge to collect the dynamic strain response of the bridge when vehicles cross the bridge. S2. Through actual bridge vehicle tests, extract data from each dynamic strain sensor and calibrate the bridge strain influence surface corresponding to the measuring point; the influence surface is a spatial function corresponding to the bridge deck position, and each measuring point corresponds to a strain influence surface function; S3. Establish a coordinate system with the geometric center of the bridge deck as the origin, the transverse direction as the x-axis, and the longitudinal direction as the y-axis. The bridge deck has lanes; within each lane, select points at regular intervals along the x-axis and determine their coordinates. For any given point, after obtaining the coordinates, extract the corresponding strain influence line from the influence surface of each measuring point. Then, integrate the strain influence line to calculate the strain area. Let the total weight of the vehicle to be tested be m, then This represents the theoretical strain area; S4. Conduct vehicle bridge crossing test: When the vehicle under test actually crosses the bridge, the strain time-domain curve of the vehicle from the moment it enters the bridge to the moment it exits the bridge is collected from the sensor measuring points located at different positions on the bridge surface in step S1. The strain area is calculated by integrating the strain time-domain curve of each measuring point. S5. Based on the theoretical strain area obtained in step S3 and the measured strain area obtained in step S4, establish a set of equations. For each selected location point, establish a set of solution equations. S6. For the system of equations established for each location point in step S5, construct an error function to solve for the total weight of the vehicle under test; determine the system of equations corresponding to the minimum error function value, at which point the total weight of the vehicle in the system of equations is the actual total weight of the vehicle.

[0008] The bridge dynamic weighing method based on strain area described in this invention sets the number of lanes as follows: n Shares; respectively marked as Lane; The number of vehicles distributed horizontally at the same time is also... The total weight of the vehicles is recorded according to their positions on the lane. , The sensor measurement points within each lane range are numbered as follows: Then the lane The location point number is , road The location point number is , Sensor number is , Indicates the vehicle is traveling at position point At that time, from the sensor The integral area of ​​the influence line taken from the influence surface at the measuring point. express The area under the integral of the strain time-domain curve measured by the sensor. Based on the above definition, the following system of equations can be established:

[0009] Total available A system of equations.

[0010] The bridge dynamic weighing method based on strain area described in this invention includes step S6 as follows: Constructing the error function using the least squares method , Indicates the first R Error function of a system of equations The statement is as follows:

[0011] In order to obtain Find the extreme value of , set the partial derivative to zero, and obtain the following formula:

[0012] For each error function The corresponding solutions can be obtained from all of them. , get Substitute the values ​​into the error function to calculate the error. ,make At this time, G corresponds to , which is the actual total weight of each vehicle under test.

[0013] In the bridge dynamic weighing method based on strain area described in this invention, step S3 involves selecting position points at a certain interval along the x-axis and determining the coordinates of the position points. The interval between the coordinates of the selected position points is no greater than 10cm.

[0014] Beneficial effects This invention, by combining the calibration influence surface and considering the lateral distribution of loads on the bridge, utilizes collected dynamic strain information and an algorithm based on strain area to accurately identify the total weight of vehicles under multi-lane, multi-vehicle traffic conditions. Compared to traditional bridge dynamic weighing systems based on the Moses algorithm, this invention eliminates the need for axle sensors, using only strain sensors to obtain the total vehicle weight. This reduces the damage to road pavement caused by axle sensor installation, making the system simpler, more economical, and easier to apply in engineering projects. Furthermore, it is applicable to multi-lane, multi-vehicle traffic conditions, expanding the application scope of bridge dynamic weighing systems and providing crucial data for structural safety assessments and overload management. Attached Figure Description

[0015] Figure 1 The flowchart of the bridge dynamic weighing method based on strain area of ​​the present invention is shown below. Figure 2 This is a schematic diagram of the sensor measuring point arrangement used in the strain area-based bridge dynamic weighing method of the present invention. Figure 3 This is a schematic diagram of the calibration influence surface in the strain area-based bridge dynamic weighing method of the present invention; Figure 4 This is a schematic diagram showing the location point setting of a two-lane bridge in the strain area-based dynamic weighing method for bridges of the present invention. Detailed Implementation

[0016] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] A dynamic weighing method for beam bridges based on strain area is used to monitor the lateral position and total weight of vehicles crossing the bridge. The specific implementation steps include: Step S1: Determine the bottom of the mid-span section of the bridge as the sensor measuring point, such as... Figure 2 As shown, a number of dynamic strain sensors corresponding to the main beam are arranged along the transverse direction of the bridge to collect the dynamic strain response of the bridge when vehicles cross it. Step S2: Through actual bridge vehicle tests, extract data from each dynamic strain sensor and calibrate the bridge strain influence surface corresponding to the measuring point. The influence surface is a spatial function corresponding to the bridge deck position, and each measuring point corresponds to a strain influence surface function; Step S3: Establish a coordinate system with the geometric center of the bridge deck as the origin, the transverse direction as the x-axis, and the longitudinal direction as the y-axis. The bridge deck has lanes. Within each lane, select points at regular intervals along the x-axis and determine their coordinates. For any given point, after obtaining the coordinates, extract the strain influence line corresponding to the coordinates from the influence surface of each measuring point. Then, integrate the strain influence line to calculate the strain area. Let the total weight of the vehicle to be tested be m, then This represents the theoretical strain area.

[0018] Step S4: When the vehicle under test actually crosses the bridge, the sensors at each measuring point collect strain data of the entire time process from the vehicle entering the bridge to exiting the bridge. The strain area is calculated by integrating the strain data collected at each measuring point. ; This represents the measured strain area; Step S5: Based on the theoretical strain area and measured strain area Establish a system of equations to solve the problem. The unknown in the system of equations is the total weight m of the vehicle under test. A system of equations can be established for each location point. Step S6: For the system of equations established at each location point, construct an error function to solve for the total weight m of the vehicle under test. Substitute the obtained m into the error function; find the system of equations that minimizes the error function value. At this time, the total weight m of the vehicle under test in the system of equations is the actual total weight of the vehicle.

[0019] Step S1 further includes the following: First, determine the sensor measurement points. Dynamic data is collected using dynamic strain sensors. To obtain the maximum dynamic response, the dynamic strain sensors are typically placed at the bottom of each beam. The number of strain sensor measurement points needs to be selected based on the number of lanes on the bridge deck. Assuming the number of lanes is n, the minimum number of sensor measurement points should be [number missing]. Sensor measuring points should be distributed as evenly as possible along the transverse direction of the bridge. Taking a simply supported composite box girder concrete bridge as an example, such as... Figure 2 As shown, in order to obtain larger sensor measurement values, strain measurement points should be arranged at the mid-span position of the bottom of the beam.

[0020] Step S2 further includes the following: This algorithm requires calibrating the actual influence surface of the bridge, which is difficult to obtain in practice. However, during actual testing, because the distribution of discrete points in the transverse and longitudinal directions of the bridge is relatively regular, data from test points can be collected first, and then the actual influence surface of the bridge can be fitted using a surface fitting method. For example... Figure 3 The diagram shown is a shape representation of the affected surface. The specific method is as follows: In step S2, an actual bridge test is set up, in which the vehicle travels along different lateral positions on the bridge surface, and the response of the sensor is collected when the vehicle crosses the bridge. The influence line of the measuring point corresponding to each lateral position of the bridge is obtained by mathematical method. The influence lines obtained from different lateral positions are combined according to coordinates to fit the influence surface of the entire bridge.

[0021] The steps are as follows: 1) Select a heavy-duty calibrated vehicle with known vehicle weight and axle load (generally, the total weight of the vehicle should not be less than 20 tons). 2) Select the lateral position of the vehicle's travel along the bridge surface and assign lateral position coordinates. The spacing between lateral positions shall not exceed 1m. 3) Make the calibrated vehicle travel along the designated lateral position. When traveling, try to make the center line of the front of the vehicle coincide with the designated lateral position line. Maintain a constant speed and do not exceed 15km / h during the travel. 4) The vehicle travels along a certain lateral position, and the sensor at the measuring point collects strain data in real time. The Moses algorithm can be used to calibrate the strain influence lines of different measuring points corresponding to this lateral position coordinates. 5) Repeat step 4) to obtain the strain influence lines of all the different measuring points corresponding to the defined lateral position coordinates; 6) Combine the influence lines corresponding to each measuring point according to their lateral coordinates, and fit the influence surface of the entire bridge using a surface fitting method. The influence surfaces of different measuring points can be obtained through the above calibration method.

[0022] Steps S3, S4, and S5 further include the following: A coordinate system is established with the geometric center of the bridge deck as the origin, the transverse direction as the x-axis, and the longitudinal direction as the y-axis. The bridge deck has lanes. Within each lane, points are selected at regular intervals along the x-axis to determine their coordinates. For any given point, after obtaining the coordinates, the strain influence line corresponding to the coordinates can be extracted from the influence surface of each measuring point. Then, the strain area is calculated by integrating the strain influence line. Assuming the number of lanes on the bridge is n Marked sequentially as If a lane has a number of vehicles distributed laterally, then the number of vehicles distributed laterally is also [number missing]. n The total weight of the vehicles is recorded according to their positions on the lane. Within each lane, points are selected at regular intervals along the x-axis to determine their coordinates. Theoretically, smaller intervals between coordinates result in more accurate calculations, but this increases the number of equations and computation time. Here, an interval of 10mm is chosen. The points within each lane are numbered as follows: Then the lane The location point number is ,Lane The location point number is Because the existence of lane markings limits the vehicle's driving position to a certain range, and the vehicle's effect on the bridge is equivalent to a load along the vehicle's centerline, the possible lateral positions of the vehicle in the algorithm will be limited to a certain range. Figure 4 A schematic diagram showing the location of the two-lane bridge.

[0023] The sensor number is recorded as , Indicates the vehicle is traveling at position point At that time, from the sensor The integral area of ​​the influence line taken from the influence surface at the measuring point. express The integral area of ​​the strain time-domain curve measured by the sensor yields the following equation: Total available A system of equations.

[0024] Step S6 further includes the following: Constructing the error function using the least squares method , Indicates the first R Error function of a system of equations Then we have the following formula:

[0025] In order to obtain Find the extreme value of , set the partial derivative to zero, and obtain the following formula:

[0026] For each error function The corresponding solutions can be obtained from all of them. , get Substitute the values ​​into the error function to calculate the error. ,make At this time, G corresponds to , which is the actual total weight of each vehicle under test.

[0027] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A dynamic weighing method for bridges based on strain area, characterized in that: The steps are as follows: S1. The bottom position of the mid-span section of the bridge is determined as the sensor measuring point. The number of dynamic strain sensors corresponding to the main beam are arranged along the transverse direction of the bridge to collect the dynamic strain response of the bridge when vehicles cross the bridge. S2. Through actual bridge vehicle tests, extract data from each dynamic strain sensor and calibrate the bridge strain influence surface corresponding to the measuring point. S3. Establish a coordinate system with the geometric center point of the bridge deck as the origin; Within the lane area defined by the bridge deck, location points are set and their coordinates are determined. The strain influence lines corresponding to the coordinates of the location points are extracted from the bridge strain influence surface corresponding to each measurement point. The strain area is obtained by integrating the strain influence line. S4. Conduct vehicle bridge crossing test: When the vehicle under test actually crosses the bridge, the sensor measuring points located at different positions on the bridge surface in step S1 are used to collect strain data of the vehicle from the moment it enters the bridge to the moment it exits the bridge. The strain area is calculated by integrating the strain in the time domain of each measuring point. S5. Based on the theoretical strain area obtained in step S3 and the measured strain area obtained in step S4, establish a set of equations. For each selected location point, establish a set of solution equations. S6. For the system of equations established for each location point in step S5, construct an error function to solve for the total weight of the vehicle under test; determine the system of equations corresponding to the minimum error function value, at which point the total weight of the vehicle in the system of equations is the actual total weight of the vehicle.

2. The bridge dynamic weighing method based on strain area according to claim 1, characterized in that: The number of lanes set is n Shares; respectively marked as Lane; The number of vehicles simultaneously distributed laterally along the lane is also... n The total weight of the vehicles is recorded according to their positions on the lane. , Determine the location points within each lane range. N One, then lane The location point number is recorded as ,Lane The location point number is recorded as ; Sensor number is ; Indicates the vehicle is traveling at position point , i =1,2,⋯, n ; j =1,2,⋯, N At that time, from the sensor The integral area of ​​the influence line taken from the influence surface at the measuring point. l =1,2,3,⋯, m ; express The area of ​​integration of the strain time-domain curve measured by the sensor; Based on the above definition, the following system of equations can be established: 。 3. The bridge dynamic weighing method based on strain area according to claim 2, characterized in that: Step S6 is as follows: Constructing the error function using the least squares method , Indicates the first R Error function of a system of equations The statement is as follows: In order to obtain Find the extreme value of , set the partial derivative to zero, and obtain the following formula: For each error function The corresponding solutions can be obtained from all of them. , get Substitute the values ​​into the error function to calculate the error. ,make At this time, G corresponds to , which is the actual total weight of each vehicle under test.

4. The bridge dynamic weighing method based on strain area according to claim 1, characterized in that: The specific steps for S3 are as follows: S3-1. Establish a coordinate system with the geometric center point of the bridge deck as the origin, the transverse direction of the bridge as the x-axis, and the longitudinal direction of the bridge as the y-axis. S3-2. The bridge deck has lanes. Within each lane, select points at certain intervals along the x-axis and determine the coordinates of the points. S3-3. For the location points obtained in S3-2, after obtaining the coordinates through any location point, extract the strain influence line corresponding to the coordinates from the influence surface of each measuring point. S3-4. Integrate the strain influence line to obtain the strain area. Let the total weight of the vehicle to be tested be m, then This represents the theoretical strain area.

5. The bridge dynamic weighing method based on strain area according to claim 4, characterized in that: The distance between the coordinates of the selected location points in step S3-2 is no greater than 10cm.

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