CN111696103B - Constant-load linear mapping method of single-span simple girder bridge under uninterrupted traffic condition - Google Patents

Abstract

The invention discloses a constant load linear mapping method of a single-span simple girder bridge under the condition of no traffic interruption, and relates to the technical field of bridge state detection; the method comprises the following steps: data acquisition is carried out on each detection identification point; performing multi-scale wavelet decomposition on low frequency data in the acquired vertical dynamic displacement time-course curve to obtain a quasi-static component of the time-course curve; re-acquisition of t ₁ 、t ₂ Determining t by combining the position parameter of the identification point and the quasi-static component of the vehicle at the moment ₂ Moment vehicle load deflection effect; re-acquisition of t ₂ Instantaneous deflection of each detection mark point at moment and combining t ₂ And obtaining constant load deflection by the vehicle load deflection effect at the moment, thereby forming a constant load line shape of the bridge. The invention can realize the mapping of the constant load line shape of the bridge under the condition that the bicycle passes through the bridge, compared with the traditional/novel static deflection measuring method in the prior art, the invention does not need to seal traffic, has more flexible, simple and convenient and efficient detection, and greatly reduces the detection cost.

Description

Method for mapping the dead load alignment of a single-span simply supported beam bridge without interrupting traffic

Technical Field

The invention belongs to the technical field of bridge state detection, and in particular relates to a method for mapping the constant load line shape of a single-span simply supported beam bridge under the condition of non-interruption of traffic.

Background Art

In this industry, it is necessary to measure the alignment of bridges regularly to detect the stability and safety of bridges. This type of measurement is mainly static deflection measurement. In order to ensure the safety of testing personnel and avoid the influence of live load disturbance, it is necessary to use some measuring instruments to collect elevation data at different positions of the bridge when there is no vehicle load on the bridge, and use the corresponding deflection algorithm to obtain the deflection of the bridge. At present, the commonly used traditional methods for static deflection measurement include hanging hammer method, electronic displacement meter method, level measurement method, GPS positioning method, total station observation method, connecting pipe sensing technology, inclinometer measurement, static level system and other methods; with the continuous development of technology, a number of new static deflection measurement technologies have also been developed in recent years. These technologies mainly include radar interferometry measurement technology, three-dimensional laser scanning technology, optical fiber linear rapid measurement system, and close-range photogrammetry technology.

Taking the leveling method as an example, the implementation scheme of the traditional method of measuring the linear shape is briefly explained (refer to the "Implementation Rules for Bridge Alignment Detection" TNJC/SSXZ/01-02/07): Step 1: Mark the specific positions of the abutments and piers on the bridge deck with chalk. For the longitudinal linear mapping of the bridge deck structure with beam span structure, arch and cable tower structure, it is advisable to arrange the measuring points along the longitudinal section of the bridge, divide the bridge axis and the three side lines of the upstream and downstream edge lines of the carriageway, and conduct closed leveling measurement in accordance with the requirements of the second-class engineering leveling measurement. The measuring points should be arranged on the cross-section of the span of the bridge span or bridge deck structure. Step 2: Set up the precision level on a smooth road surface and level it, erect the tower ruler at the measurement position, and use the elevation of the leveling point near the route as the benchmark. Record the elevation reading of the measurement point in m. The principle of leveling measurement is shown in Figure 1. Step 3: Continuously measure all measuring points and close them with the leveling point. Step 4: Calculate the elevation of each point on the bridge deck, and draw a longitudinal line diagram of the bridge deck structure using the position and elevation of each point.

Although many methods have been developed for bridge deflection measurement, all of them belong to static deflection measurement of bridges and cannot be applied when the bridge is open to traffic. Therefore, traffic needs to be closed. This process involves approval, newspaper announcements and traffic broadcasts, as well as the cooperation of multiple parties such as road maintenance personnel, traffic police, and maintenance departments. This will result in high time, personnel and economic costs, which is not conducive to the flexible, efficient and low-cost measurement requirements.

Summary of the invention

In view of this, an object of the present invention is to propose a method for constant load linear mapping of a single-span simply supported beam bridge without interrupting traffic, so as to solve the problem that the static deflection measurement of the bridge in the prior art requires closure of traffic, which is not conducive to the requirements of flexible, efficient and low-cost measurement.

In some illustrative embodiments, the method for mapping the constant load linear shape of the single-span simply supported beam bridge without interrupting traffic includes: setting a plurality of detection identification points in sequence along the span direction of the bridge, and obtaining a vertical dynamic displacement time-history curve of each detection identification point when a single vehicle passes through the bridge; performing multi-scale wavelet decomposition on the low-frequency data in each vertical dynamic displacement time-history curve to obtain a quasi-static component of the vertical dynamic displacement time-history curve; obtaining position parameters of the vehicle at time _t1 and time _t2 , combining the position parameters of each detection identification point and the quasi-static component of the vertical dynamic displacement time-history curve to perform calculations to determine the vehicle load deflection effect at time _t2 ; obtaining the instantaneous deflection of each detection identification point at time _t2 , combining the vehicle load deflection effect at time _t2 to perform calculations to obtain the constant load deflection of the bridge, and connecting lines based on the constant load deflections of the bridge to form its constant load linear shape.

In some optional embodiments, the multi-scale wavelet decomposition specifically uses the sym7 wavelet function.

In some optional embodiments, before obtaining the position parameters of the vehicle at time _t1 and time _t2 , the method includes: obtaining video data of a single vehicle passing through a bridge, wherein the video data is synchronized with the vertical dynamic displacement time-history curve; obtaining the position parameters of the vehicle at time _t1 and time _t2 specifically includes: extracting first image data at time _t1 and second image data at time _t2 based on the video data; performing geometric feature recognition on the vehicle in the first image data and the second image data, respectively, to determine the centroid of the vehicle in the first image data and the second image data; and determining the position parameters of the vehicle in the first image data and the second image data based on the determined relative position of the centroid of the vehicle and the bridge.

In some optional embodiments, the calculation is performed in combination with the position parameters of each detection mark point and the quasi-static component of the vertical dynamic displacement time history curve to determine the vehicle load deflection effect at time _t2 , specifically including: determining the ratio _Ni of the vehicle load deflection effect at time t1 to the vehicle load deflection effect at time _t2 according to the position parameters of the vehicle at time _t1 and time _t2 and the position parameters of _each detection mark point; determining the vehicle load deflection effect at time _t2 according to the following formula:

为t₂时刻第i个检测标识点的车辆荷载挠度，

为t₂时刻第i个检测标识点相对于t₁时刻的车辆荷载挠度变化量。in,

is the vehicle load deflection of the i-th detection mark point at time _t2 ,

is the change in vehicle load deflection of the i-th detection mark point at time _t2 relative to time _t1 .

对上述各检测标识点的位置参数进行无量纲化处理，令

当x_i＜a₁时，根据如下公式确定所述t₁时刻的车辆荷载挠度效应与t₂时刻的车辆荷载挠度效应比N_i：In some optional embodiments, the determining of the ratio Ni of the vehicle load deflection effect at time _t1 to the vehicle load deflection effect at time _t2 according to the position parameters of the vehicle at time _t1 and time _t2 and the position parameters of each detection mark point _specifically includes: determining the horizontal distance _a1 of the vehicle from the first end of the bridge and the horizontal distance _b1 of the vehicle from the second end of the bridge at time _t1 , the horizontal distance _a2 of the vehicle from the first end of the bridge and the horizontal distance _b2 of the vehicle from the second end of the bridge at time _t2 , and the horizontal distance _xi of the i-th detection mark point from the first end of the bridge; performing dimensionless processing on the above position parameters at time _t1 and time _t2 , and setting

The position parameters of the above detection points are dimensionless, and

When x _i ＜a ₁ , the ratio _Ni of the vehicle load deflection effect at time t ₁ to the vehicle load deflection effect at time t ₂ is determined according to the following formula:

When a ₁ ＜ _xi ＜a ₂ , the ratio _Ni of the vehicle load deflection effect at time t ₁ to the vehicle load deflection effect at time t ₂ is determined according to the following formula:

When x _i > a ₂ , the ratio _Ni of the vehicle load deflection effect at time t ₁ to the vehicle load deflection effect at time t ₂ is determined according to the following formula:

为t₁时刻第i个检测标识点的车辆荷载挠度。Among them, _n1 is the position parameter of the vehicle at time _t1 after dimensionless processing, _n2 is the position parameter of the vehicle at time _t2 after dimensionless processing, _mi is the position parameter of the i-th detection mark point after dimensionless processing,

is the vehicle load deflection of the i-th detection mark point at time _t1 .

In some optional embodiments, the step of obtaining the instantaneous deflection of each detection mark point at time _t2 specifically includes: performing geometric feature recognition on each detection mark point in the second image data at time _t2 to determine the centroid of each detection mark point; and determining the instantaneous deflection of each detection mark point at time _t2 based on the relative position between the determined centroid of the detection mark point and the bridge.

In some optional embodiments, the calculation is performed in combination with the vehicle load deflection effect at time _t2 to obtain the constant load deflection of the bridge, and a line is connected based on the constant load deflection of the bridge to form its constant load line shape, specifically including: determining the constant load deflection of each detection mark point at time _t2 according to the instantaneous deflection of each detection mark point at time _t2 and the vehicle load deflection effect at time _t2 ; and forming the constant load line shape of the bridge according to the constant load deflections of each detection mark point.

In some optional embodiments, determining the constant load deflection of each detection mark point at time _t2 according to the instantaneous deflection of each detection mark point at time t2 and the vehicle load deflection effect _{at time t2 specifically} includes: calculating and determining the constant load deflection of each detection mark point according to the following formula:

为t₂时刻第i个检测标识点的瞬时挠度，

为t₂时刻第i个检测标识点的车辆荷载挠度。Where, y ₀ ( _xi ) is the dead load deflection of the ith detection mark point,

is the instantaneous deflection of the ith detection mark point at time _t2 ,

is the vehicle load deflection of the i-th detection mark point at time _t2 .

In some optional embodiments, the multiple detection identification points are set in sequence along the span direction of the bridge, specifically including: setting a mid-span measuring point at the center of the bridge, and setting multiple other measuring points equidistant on both sides with the mid-span measuring point as the center; the _t1 is the initial measurement moment, and the _t2 moment is the moment when the vehicle load produces the maximum deflection at the mid-span measuring point.

In some optional embodiments, multiple other measuring points are set equidistantly on both sides with the mid-span measuring point as the center, specifically including: the other measuring points are set with the mid-span measuring point as the center, and are distributed at eighth points or sixteenth points according to the length of the span.

Compared with the prior art, the present invention has the following technical advantages:

The bridge constant load linear mapping method of the present invention adopts the bridge dynamic deflection measurement technology, which can realize the mapping of the bridge constant load linear shape under the condition of a single vehicle passing through the bridge. Compared with the traditional/new static deflection measurement method in the prior art, the present invention does not need to close traffic, and the detection is more flexible, simple and efficient, and the detection cost is greatly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the measurement principle of a level meter in the prior art;

FIG2 is a flow chart of a method for mapping a constant load line in an embodiment of the present invention;

3 is a schematic diagram of the relationship between the vehicle and the bridge at any time within a time period t according to an embodiment of the present invention;

FIG4 is a schematic diagram of a theoretical deflection curve of a bridge in the absence of vehicles according to an embodiment of the present invention;

FIG5 is a schematic diagram of the relationship between the vehicle and the bridge at time _t1 in an embodiment of the present invention;

FIG6 is a schematic diagram of the relationship between the vehicle and the bridge at time _t2 in an embodiment of the present invention;

7 is a detailed flow chart of an example of a method for mapping a constant load line in an embodiment of the present invention;

FIG8 is a deflection curve of a bridge under deadweight in a verification example in an embodiment of the present invention;

FIG9 is an original displacement time history curve of the 5# measuring point in the verification example in an embodiment of the present invention;

10 is a dynamic component of the original displacement time history curve of the 5# measuring point in the verification example in an embodiment of the present invention;

11 is a quasi-static component of the original displacement time history curve of the 5# measuring point in the verification example in an embodiment of the present invention;

FIG12 is a key frame image at time _t1 in a verification example in an embodiment of the present invention;

FIG13 is a key frame image at time _t2 in a verification example in an embodiment of the present invention;

FIG. 14 is a constant load line shape of a bridge obtained in a verification example in an embodiment of the present invention.

DETAILED DESCRIPTION

The following description and the accompanying drawings fully demonstrate the specific embodiments of the present invention so that those skilled in the art can practice them. Other embodiments may include structural, logical, electrical, process and other changes. The examples represent possible changes only. Unless explicitly required, separate components and functions are optional, and the order of operation may vary. The parts and features of some embodiments may be included in or replace the parts and features of other embodiments. The scope of the embodiments of the present invention includes the entire scope of the claims, and all available equivalents of the claims. In this article, these embodiments of the present invention may be represented individually or collectively by the term "invention", which is only for convenience, and if more than one invention is actually disclosed, it is not intended to automatically limit the scope of the application to any single invention or inventive concept.

The term "bridge alignment" refers to the line connecting the elevations of the longitudinal sections of the bridge, usually represented by a diagram. Usually, the coordinate system is defined first, with the support at one end of the bridge as the coordinate origin, the support and the direction of the bridge as the X-axis, and the vertical upward as the Y-axis. The line connecting the vertical displacements of each section of the bridge is the bridge alignment.

The term "dead load" refers to the dead weight of the bridge structure.

The term "dead load alignment" refers to the change in geometric shape caused by the dead weight of the structure.

The term "live load deflection effect" refers to the deflection effect caused by loads such as vehicles, temperature, and wind. For this application, due to the short inspection time, environmental conditions such as temperature and wind are basically unchanged, so the impact on the deflection change is extremely low and can be ignored. Therefore, the live load deflection effect in this application mainly considers the vehicle load deflection effect.

It should be noted that the various technical features in the embodiments of the present invention can be combined with each other without conflict.

The embodiment of the present invention discloses a method for mapping the linear shape of a single-span simply supported beam bridge under constant load without interrupting traffic. Specifically, as shown in FIG2 , FIG2 is a flow chart of the method for mapping the linear shape of a single-span simply supported beam bridge under constant load without interrupting traffic in the embodiment of the present invention; the method for mapping the linear shape of a single-span simply supported beam bridge under constant load without interrupting traffic includes:

Step S11, sequentially setting a plurality of detection mark points along the span direction of the bridge, and obtaining a vertical dynamic displacement time history curve of each of the detection mark points when a single vehicle passes through the bridge;

Step S12, performing multi-scale wavelet decomposition on the low-frequency data in each of the vertical dynamic displacement time history curves to obtain a quasi-static component of the vertical dynamic displacement time history curve;

Step S13, obtaining the position parameters of the vehicle at time _t1 and time _t2 , combining the position parameters of each detection mark point and the quasi-static component of the vertical dynamic displacement time history curve to calculate and determine the vehicle load deflection effect at time _t2 ;

Step S14, obtain the instantaneous deflection of each detection mark point at time _t2 , calculate it in combination with the vehicle load deflection effect at time _t2 , obtain the constant load deflection of the bridge, and connect the constant load deflections of the bridge to form its constant load line shape.

The bridge constant load linear mapping method of the present invention adopts the bridge dynamic deflection measurement technology, which can realize the mapping of the bridge constant load linear shape under the condition of a single vehicle passing through the bridge. Compared with the traditional/new static deflection measurement method in the prior art, the present invention does not need to close traffic, and the detection is more flexible, simple and efficient, and the detection cost is greatly reduced.

In step S11 of the embodiment of the present invention, the detection identification points can be specifically selected from detection identification plates, or natural identification points with obvious texture features on the bridge to be tested; during nighttime detection, luminous identification can be laid out as detection identification points. The position distribution of the detection identification points set should cover the entire span of the bridge to be tested, which is conducive to the subsequent acquisition of a relatively complete constant load linear shape of the entire bridge to be tested. Among them, for the bridge to be tested, the number of detection identification points set can be selected according to the length of the bridge span. The more the number of layouts, the higher the accuracy of the obtained constant load linear shape, but the higher the requirements for measuring instruments and computing equipment; on the other hand, when setting the detection identification points, they can be laid out equidistantly, which is conducive to obtaining a constant load linear shape that changes smoothly and accurately, and avoiding abnormal mutation problems in a certain section.

Preferably, the detection marking points can be set by setting multiple detection marking points equidistantly along the longitudinal direction of the bridge; wherein the detection marking points include marking points located at the starting position of the bridge and marking points at the end position of the bridge, and the number of detection marking points does not exceed 33 at most.

Furthermore, the detection identification point can first be set at the mid-span measuring point of the bridge, and then multiple other measuring points equidistantly set on both sides with the mid-span measuring point as the center. The other measuring points cover the starting position and the end position of the bridge, and are arranged with 8-point, 10-point, and 16-point points.

In step S11 of the embodiment of the present invention, the vertical dynamic displacement time history curve of each detection mark point when a single vehicle passes through the bridge is obtained. Specifically, the video data of the vehicle passing through the bridge and the vertical dynamic displacement time history curve of each detection mark point during the entire period t when the single vehicle passes through the bridge can be obtained synchronously through the bridge deflection detector. The video data should include the bridge, the vehicle and each detection mark point throughout the whole process.

The vertical dynamic displacement time history curve of each detection mark point refers to the change in vertical displacement of each detection mark point caused by the displacement of the vehicle on the bridge within time t;

Furthermore, the applicant found that the vertical dynamic displacement time history curve of the detection mark point is a time-related sequence, which can be decomposed into different frequency bands by discrete wavelet transform. For example, in the field of health monitoring, some scholars have proposed to use wavelet multi-scale analysis to separate the measured historical information of bridge structure response into transient and slow-changing information, where the deflection effect caused by temperature is in the low frequency band, corresponding to the slow-changing information, and the deflection effect caused by vehicle load is in the high frequency band, corresponding to the transient information. The multi-scale wavelet decomposition can effectively distinguish the two. In the method adopted in this application, due to the short test time, only the deflection changes within a range of less than one vehicle driving cycle (time t) are recorded, and the influence of temperature and constant load on the deflection has not changed. The vertical dynamic displacement is mainly caused by the vehicle load. At this time, the data is subjected to wavelet decomposition, and the low-frequency data obtained is the quasi-static deflection effect of the vehicle load, and the high-frequency data is the vibration effect caused by the vehicle movement, which can be removed as noise to eliminate the secondary influence of vehicle movement on the change of bridge deflection. The main influence of vehicle load on the change of bridge deflection is mainly considered, which is conducive to improving the accuracy of the subsequent bridge line shape. Therefore, based on the multi-scale analysis method, the vertical dynamic displacement time-history curve of each detection mark point measured can be decomposed and the characteristics of the expression signal can be reconstructed.

Therefore, in step S12 of the embodiment of the present invention, multi-scale wavelet decomposition is performed on the low-frequency data in the vertical dynamic displacement time-history curve of each detection identification point to obtain the quasi-static component of the vertical dynamic displacement time-history curve of each detection identification point. In this step S12, the low-frequency data of the vertical dynamic displacement time-history curve of each detection identification point is continuously decomposed to filter out the high-frequency data therein, so as to improve the accuracy of the change in the bridge deflection effect caused by the vehicle load.

Among them, wavelet multi-scale analysis is used to analyze the test data. The specific process includes: selecting a suitable orthogonal wavelet basis as the wavelet function; selecting a suitable decomposition layer number J and performing wavelet transform on the noisy low-frequency signal to decompose it into J layers; using the approximation coefficients decomposed into J layers to reconstruct the quasi-static component of the signal as the change in bridge deflection caused by vehicle load.

Furthermore, the wavelet function of the present application may use the Symlet wavelet function, which is an approximately symmetrical wavelet function proposed by Ingrid Daubechies, usually expressed as symN (N = 2, 3, ..., 8). The symN wavelet function has good regularity and symmetry, and can reduce the phase distortion when analyzing and reconstructing the signal to a certain extent. In some other embodiments, the present application may also use other wavelet functions.

Preferably, the present application selects the wavelet basis function sym7, which is decomposed into 7 layers and then reorganized to obtain the quasi-static component Δw(t, x _i ) and dynamic component of the load-deflection effect, where t is the acquisition time (i.e., the time t when the above-mentioned vehicle passes through the bridge), i=1, 2…n, and n is the number of detection identification points.

In step S13 of the embodiment of the present invention, the position parameters of the vehicle at time _t1 and time _t2 are obtained, and the position parameters of each detection mark point and the quasi-static component of the vertical dynamic displacement time history curve are combined for calculation to determine the vehicle load deflection effect at time t2; wherein, time _t1 and time _t2 can be two different times selected within the time t when the vehicle passes through the bridge. Generally, time _t2 is after time _t1 .

The position parameters of the vehicle at time _t1 and time _t2 in this embodiment can be respectively captured and extracted from the collected video data, namely, the first image data at time _t1 and the second image data _at time _t2 ; then the position parameters of the vehicle can be determined by analyzing the relative position relationship between the vehicle and the span of the _bridge in the image data; wherein, the centroid of the vehicle can be determined by the detection experience of the measurement/analysis personnel, and the position parameters of the centroid with respect to the bridge can be determined; or the geometric centroid of the vehicle can be determined by image feature extraction. The video data used can be obtained in the above steps.

Preferably, the present application obtains the position parameters of the vehicle at time _t1 and time _t2 , specifically including: extracting the first image data at time _t1 and the second image data at time _t2 respectively based on the video data; performing geometric feature recognition on the vehicle in the first image data and the second image data respectively, and determining the centroid of the vehicle in the first image data and the second image data; determining the position parameters of the vehicle in the first image data and the second image data according to the relative position between the determined centroid of the vehicle and the bridge. Among them, since the present application is only for the case of a single vehicle, it is only necessary to identify the vehicle in the key frame image according to the color, shape, size and other information of the vehicle. Specifically, the centroid recognition of the vehicle can be achieved by using the open source code in opencv and the principle of background difference to identify the centroid of the vehicle. In some other embodiments, the centroid of the vehicle can be identified by other digital image processing methods, such as feature extraction, SVM classification, deep learning, etc.

In some embodiments, the position parameters of each detection mark point can also be detected and obtained in the same manner as the position parameters of the above-mentioned vehicle, or when setting the detection mark point, its center is used as its centroid, that is, the position parameters of the detection mark point are known quantities and do not need to be measured.

The step S13 combines the position parameters of each detection mark point and the quasi-static component of the vertical dynamic displacement time history curve to calculate and determine the vehicle load deflection effect at time _t2 , specifically including: determining the ratio Ni of the vehicle load deflection effect at time _t1 to the vehicle load deflection effect at time _t2 according to the position parameters of the vehicle at time _t1 and time _t2 and the position parameters of each detection mark _point ; determining the vehicle load deflection effect at time _t2 according to the following formula:

为t₂时刻第i个检测标识点的车辆荷载挠度，

为t₂时刻第i个检测标识点相对于t₁时刻的车辆荷载挠度变化量。in,

is the vehicle load deflection of the i-th detection mark point at time _t2 ,

is the change in vehicle load deflection of the i-th detection mark point at time _t2 relative to time _t1 .

为例，具体表示t₂时刻第i个检测标识点的位置x_i上的车载荷载挠度，即t₂时刻第i个检测标识点的车载荷载挠度，其它与与“x_i”相关参数，与上述理解相同，在此不再赘述。In the embodiment of the present invention, "xi _" represents the horizontal position of the i-th detection mark point relative to the bridge. In some embodiments, it can be expressed in specific coordinates relative to the bridge.

For example, it specifically represents the vehicle load deflection at the position _xi of the ith detection mark point at time _t2 , that is, the vehicle load deflection at the ith detection mark point at time _t2 . Other parameters related to " _xi " are the same as the above understanding and will not be repeated here.

可通过提取检测标识点的竖向动态位移时程曲线的准静态分量在t₂时刻和t₁时刻的车辆荷载挠度变化量得到。Among them, in the above calculation,

It can be obtained by extracting the vehicle load deflection change at time _t2 and time _t1 from the quasi-static component of the vertical dynamic displacement time history curve of the detection mark point.

FIG3 shows a schematic diagram of the relationship between the vehicle and the bridge at any time within a time period t in an embodiment of the present invention; FIG4 is a schematic diagram of the deflection curve of the bridge in the absence of a vehicle in an embodiment of the present invention; FIG5 is a schematic diagram of the relationship between the vehicle and the bridge at time _t1 in an embodiment of the present invention; FIG6 is a schematic diagram of the relationship between the vehicle and the bridge at time _t2 in an embodiment of the present invention. Among them, Def1 is the bridge constant load deflection line, Def2 is the bridge instantaneous deflection line at time _t1 , and Def3 is the bridge instantaneous deflection line at time _t2 ; among them, the bridge constant load deflection schematic diagram of FIG4 is used in conjunction with FIG5 and FIG6, so that those skilled in the art can understand the state of the bridge when there is no vehicle, at time _t1 and at time _t2 , so as to understand the present application more quickly.

对上述各检测标识点的位置参数进行无量纲化处理，令

当x_i＜a₁时，根据如下公式确定所述t₁时刻的车辆荷载挠度效应与t₂时刻的车辆荷载挠度效应比N_i：3 to 6 , the method of determining the ratio _Ni of the vehicle load deflection effect at time _t1 to the vehicle load deflection effect at time _t2 according to the position parameters of the vehicle at time _t1 and time _t2 and the position parameters of each detection mark point specifically includes: determining the horizontal distance _a1 of the vehicle from the first end of the bridge and the horizontal distance _b1 of the vehicle from the second end of the bridge at time _t1 , the horizontal distance _a2 of the vehicle from the first end of the bridge and the horizontal distance _b2 of the vehicle from the second end of the bridge at time _t2 , and the horizontal distance _xi of the i-th detection mark point from the first end of the bridge; performing dimensionless processing on the position parameters at time _t1 and time _t2 , and setting

The position parameters of the above detection points are dimensionless, and

When x _i ＜a ₁ , the ratio _Ni of the vehicle load deflection effect at time t ₁ to the vehicle load deflection effect at time t ₂ is determined according to the following formula:

When a ₁ ＜ _xi ＜a ₂ , the ratio _Ni of the vehicle load deflection effect at time t ₁ to the vehicle load deflection effect at time t ₂ is determined according to the following formula:

When x _i > a ₂ , the ratio M of the vehicle load deflection effect at time t ₁ to the vehicle load deflection effect at time t ₂ is determined according to the following formula:

Among them, _n1 is the position parameter of the vehicle at time _t1 after dimensionless processing, _n2 is the position parameter of the vehicle at time _t2 after dimensionless processing, and _mi is the position parameter of the i-th detection identification point after dimensionless processing.

Specifically, referring to FIG. 3 for example, when the vehicle travels to point D of the bridge, according to the material mechanics theory, the deflection curve equation of the single-span simply supported beam under concentrated load can be solved as follows:

For the AD segment, the deflection curve equation is:

For the DB segment, the deflection curve equation is:

Where F represents the vehicle load, a and b represent the positions of the vehicle load as shown in the figure, E is the elastic modulus, I is the moment of inertia of the main beam section, and l is the span.

和

之间的换算关系(即t₁时刻的车辆荷载挠度效应与t₂时刻的车辆荷载挠度效应比N_i)，然后以N_i和

通过计算获得t₂时刻的车辆荷载挠度；该计算方式无需考虑车辆荷载F、弹性模量E和主梁截面惯性矩I，从而可以降低本申请对于部分数据参数的获取难度，实现本方案测绘方法的可行性和高效性。The applicant found that the above two formulas can be used to solve

and

The conversion relationship between (i.e., the ratio of the vehicle load deflection effect at time _t1 to the vehicle load deflection effect at time _t2 , _Ni ), and then _Ni and

The vehicle load deflection at time _t2 is obtained by calculation; this calculation method does not need to consider the vehicle load F, elastic modulus E and main beam section moment of inertia I, thereby reducing the difficulty of obtaining some data parameters in this application and realizing the feasibility and efficiency of the surveying and mapping method of this scheme.

In some optional embodiments, the step of obtaining the instantaneous deflection of each detection mark point at time _t2 specifically includes: performing geometric feature recognition on each detection mark point in the second image data at time _t2 to determine the centroid of each detection mark point; and determining the instantaneous deflection of each detection mark point at time _t2 according to the relative position between the determined centroid of the detection mark point and the bridge.

In some optional embodiments, the calculation is performed in combination with the vehicle load deflection effect at time _t2 to obtain the constant load deflection of the bridge, and lines are connected based on the constant load deflection of the bridge to form its constant load line shape, specifically including: determining the constant load deflection of each detection mark point at time _t2 according to the instantaneous deflection of each detection mark point at time _t2 and the vehicle load deflection effect at time _t2 ; forming the constant load line shape of the bridge according to the constant load deflections of each detection mark point.

In some embodiments, the constant load linear shape of the bridge is formed according to the constant load deflection of each detection mark point, and a coordinate system is established according to the constant load deflection of each detection mark point, and then the constant load deflection of each detection mark point in the coordinate system is connected to form the constant load linear shape of the bridge. Preferably, before determining the vehicle load and the relative position of each detection mark point relative to the bridge, a coordinate system is established with the end points of the bridge, so that the vehicle load and the relative position of each detection mark point relative to the bridge are determined based on the coordinate system, and then there is no need to establish a separate coordinate system later.

Determining the constant load deflection of each detection mark point at time _t2 according to the instantaneous deflection of each detection mark point at time t2 and _{the vehicle load deflection effect at time t2 specifically} includes: calculating and determining the constant load deflection of each detection mark point according to the following formula:

为t₂时刻第i个检测标识点的瞬时挠度，

为t₂时刻第i个检测标识点的车辆荷载挠度。Where, y ₀ ( _xi ) is the dead load deflection of the ith detection mark point,

is the instantaneous deflection of the ith detection mark point at time _t2 ,

is the vehicle load deflection of the i-th detection mark point at time _t2 .

In some embodiments, the multiple detection identification points are set in sequence with equal intervals along the span direction of the bridge, specifically including: setting a mid-span measuring point at the center of the bridge, and setting multiple other measuring points with equal intervals on both sides with the mid-span measuring point as the center; time _t2 is selected as the time when the vehicle load produces the maximum deflection at the mid-span measuring point. At this time, the deflection of the bridge is also the largest, and the obtained constant load linear shape of the bridge is more accurate and more intuitive.

In order to facilitate those skilled in the art to quickly understand the technical solution of the present application, the detailed steps and derivation process of the present application are elaborated in detail herein, as shown in FIG7 , which is a detailed flow chart of the preferred solution in an embodiment of the present invention.

Step 1: Data collection. The BJQN-X bridge deflection detector is used to collect the main beam vibration video data and multi-point vertical dynamic displacement time history curves under the condition of single vehicle traffic.

Step 2: Decomposition of vehicle load deflection effect. Perform multi-scale wavelet decomposition on the vertical dynamic displacement time history data of the detection mark point (i.e., vertical dynamic displacement time history curve) to obtain quasi-static components and dynamic components. The quasi-static component is taken as the main effect of load deflection and is taken as the deflection change Δw(t, _xi ).

Step 3: Select time _t1 and time _t2 , and determine the change in the vehicle load deflection at time t2 relative to the deflection at time _t1 for each detection mark point;

Among them, the time _t1 is preferably zero (i.e., t=0), and the time _t2 is preferably the time when the bridge produces the maximum deformation under the action of the vehicle load. By taking the "zero" time as _t1 , the difficulty of selecting the time _t1 can be reduced, which is conducive to directly determining the change in the overall vehicle load deflection of each detection mark point at the time t2 relative to the deflection at the time t1 after determining the time _t2 .

挠度变化量Δw_max对应的时刻作为t₂。Specifically, according to the principle of material mechanics, the mid-span measurement point can be used.

The time corresponding to the deflection change Δw _max is taken as t ₂ .

In this application, the measuring point can be arranged in the middle of the span, that is, the 1/2 position, and the other measuring points can be arranged according to the requirements of equal division points. The eighth or sixteenth points can be selected according to the length of the span.

曲线中，找到Δw_max，和与它对应的时刻t₂，即为桥梁在车载作用下，产生最大变形的时刻。At the mid-span point

In the curve, find Δw _max and the corresponding time t ₂ , which is the time when the bridge produces the maximum deformation under the action of the vehicle load.

Step 4: Obtain key frame vehicle position information from video data. For the measurement video, extract the key frame images at the initial measurement time _t1 and the maximum mid-span deformation time _t2. Use digital image processing methods to perform vehicle recognition on the key frame images _t1 and _t2. Use the vehicle centroid position to characterize the vehicle position, and obtain the coordinates _a1 and _a2 of the vehicle position along the bridge at time _t1 and _t2 , respectively.

Among them, the formula in this application is applicable to the deflection conversion when a vehicle passes through a bridge, so there is no need to recognize the license plate. It is only necessary to identify the vehicle in the key frame image based on the vehicle's color, shape, size and other information.

The open source code in OpenCV is used to implement the vehicle identification. The background difference principle can be used to identify the vehicle; wherein, the use of the open source code in OpenCV to implement the vehicle geometric feature identification in this application is a common method in the art and will not be repeated here.

Step 5: Solve for the deflection effects due to vehicle loads

到跨中测点产生最大位移的时刻t₂，仪器检测到的荷载挠度效应的准静态分量

是各测点相对于t₁时刻的挠度变化量，应该等于实际车辆荷载挠度效应与初始挠度效应的差值，即：The dynamic deflection of the marked points on the beam is measured when traffic is open. At the beginning of the measurement (time _t1 ), the vehicle has caused the initial deflection of the marked points on the bridge.

At the time _t2 when the maximum displacement occurs at the mid-span measuring point, the quasi-static component of the load-deflection effect detected by the instrument is

is the change in deflection of each measuring point relative to time _t1 , which should be equal to the difference between the actual vehicle load deflection effect and the initial deflection effect, that is:

As shown in Figure 3, according to the material mechanics theory, the deflection curve equation of a single-span simply supported beam under concentrated load can be solved as follows:

For the AD segment, the deflection curve equation is:

For the DB segment, the deflection curve equation is:

Where F represents the vehicle load, a and b represent the positions of the vehicle load as shown in the figure, E is the elastic modulus, I is the moment of inertia of the main beam section, and l is the span.

和

之间的换算关系。定义t₁时刻车辆位置为a₁、b₁，t₂时刻车辆位置为a₂、b₂；其中，第i个检测标识点距桥梁第一端的水平距离x_i；According to equations (2) and (3), we can solve

and

The conversion relationship between them. Define the vehicle position at time t ₁ as a ₁ , b ₁ , and the vehicle position at time t ₂ as a ₂ , b ₂ ; where the horizontal distance from the i-th detection mark point to the first end of the bridge is x _i ;

n为标识点个数In order to make it dimensionless,

n is the number of identification points

和

可以由式(2)表达，令二者的比值为比例系数N_i，经过公式推导得到：When x _i ＜a ₁ ,

and

It can be expressed by formula (2), and the ratio of the two is set as the proportional coefficient _Ni . The formula is derived as follows:

和

可以由式(2)、式(3)表达，令二者的比值为比例系数N_i，经过公式推导得到：When a ₁ ＜ _xi ＜a ₂ ,

and

It can be expressed by formula (2) and formula (3), and the ratio of the two is set as the proportional coefficient _Ni . After formula derivation, we get:

和

可以由式(3)表达，令二者的比值为比例系数N_i，经过公式推导得到：When x _i ＞a ₂ ,

and

It can be expressed by formula (3), and the ratio of the two is set as the proportional coefficient _Ni . The formula is derived as follows:

代入式(1)，经过换算可以得到but

Substituting into formula (1), we can get

Step 6: Extract the instantaneous line shape of the bridge from the video data. Extract a single frame image at time _t2 from the video data, perform digital image processing on the frame image, extract the identification points and convert them to obtain the instantaneous line shape of the bridge.

The identification point can be a regular black and white circle, and the centroid of the identification point can be extracted using _o pencv programming. Among them, using the open source code in _o pencv to implement the geometric feature recognition of the identification point in this application is a common method in this field and will not be repeated here.

(i＝1，2…n，n为标识点的个数)。The centroid coordinates of the marking points are identified by the above method, and the pixel coordinates of the center point of each sign are obtained, which are converted into actual coordinate values according to the scale factor. The line connecting point A and point B of the support is taken as the X-axis (the positive direction is from point A to point B), and the vertical upward direction is the positive direction of the Y-axis. The y value of each point is the instantaneous deflection at time _t2.

(i=1, 2…n, n is the number of identification points).

Step 7: Subtract the change in deflection from the instantaneous deflection to obtain the dead load deflection y ₀ ( _xi )

仅考虑恒载挠度效应y₀(x_i)和车辆荷载效应

因此可以近似的认为恒载挠度可以通过下式求得：The instantaneous deflection includes the effects of constant load deflection, temperature deflection, creep deflection, and vehicle load. The deflection effects caused by temperature and creep are long-period effects and can be ignored in the short-term measurement used in this patent.

Only the dead load deflection effect y ₀ ( _xi ) and vehicle load effect are considered

Therefore, it can be approximately considered that the dead load deflection can be obtained by the following formula:

Step 8: Connect the constant load deflections at multiple points to obtain the constant load line shape.

Connecting the y ₀ ( _xi ) of each identification point and matching it with the X and Y coordinate axes, we can get the constant load line shape.

The following is a calculation example of the present application method:

The constant load deflection of a real bridge is not easy to obtain, the indoor test factors are controllable, and the theoretical calculation and test methods are relatively easy to implement. Therefore, this method is verified on a single-span test beam. A steel ruler is used to simulate a simple beam, a sign is placed at the eighth point of the simple beam, and a weight is used to simulate a trolley to demonstrate the implementation process of this patented method.

1) Acquisition of initial linear shape: In order to verify the accuracy of the algorithm, the initial linear shape is measured at the beginning of the experiment.

As shown in Figure 8, the parameters of each point are shown in the following table:

2) Step 1: Data collection when the vehicle passes

Use weights to simulate a small car, pass it on a simple beam, and collect multi-point dynamic deflection data and videos.

3) Step 2: Decomposition of load-deflection effects

The wavelet basis function sym7 is selected this time. After being decomposed into 7 layers, the quasi-static component Δw(t, _xi ) and dynamic component of the load-deflection effect are reorganized respectively, where t is the acquisition time and i=1, 2…9 is the number of identification points.

点)为例，图9为5#测点的原始位移时程曲线，图10为解耦重构后的荷载动态分量和准静态分量时程曲线Δw(t，x_i)。Take the mid-span measuring point (point 5#, i.e.

Taking the 5# measuring point as an example, FIG9 is the original displacement time history curve of the 5# measuring point, and FIG10 is the time history curve Δw(t, _xi ) of the dynamic component and the quasi-static component of the load after decoupling and reconstruction.

挠度变化量Δw_max对应的时刻t₂ 4) Step 3: Find the mid-span measuring point

The time _t2 corresponding to the deflection change Δw _max

Analysis of the quasi-static component displacement time history curve of the 5# measuring point shows that the maximum displacement is 19.43 mm, which is the maximum deformation caused by the 5# measuring point at t = 43.0076 s (the trolley (100 g weight) acts on the mid-span), as shown in Figure 11. It can be seen that the time _t2 corresponding to the deflection change Δw _max of the mid-span measuring point is 43.0076 s.

5) Step 4: Obtain key frame vehicle position information from video data

The key frame images at the initial time _t1 and the time _t2 of the maximum deformation in the middle of the span are shown in Figures 12 and 13. Through the method of digital image processing, the key frame images at _t1 and _t2 are used to identify the vehicle, and the vehicle position is characterized by the position of the vehicle centroid. The pixel coordinates _a1 and _a2 of the vehicle position along the bridge relative to the support at time _t1 and _t2 are obtained respectively. Since the ratio is used in step 5, there is no need to convert the actual coordinates. Among them, _a1 at time _t1 is 251.746; _a2 at time _t2 is 514.002.

6) Step 5: Solve for the deflection effect caused by vehicle load

计算结果如下表所示： _a1 , _a2 and _xi are known, and _n1 , _n2 , _mi are obtained according to the formula. Substituting them into formulas (4), (5) and (6), we can obtain _Ni in turn. According to formula (7), we can calculate

The calculation results are shown in the following table:

Note: Theoretically, when _xi is 0, L, _Ni is 0. However, in the test, the coordinates of the signboards at 0, L will change with the deformation of the simple beam and cannot be accurately equal to 0, L. Therefore, the corresponding value of _Ni in the test is not 0.

7) Step 6: Extracting the instantaneous alignment of the bridge from the video data

Extract a single frame image at time _t2 from the video data, perform digital image processing on the frame image, extract the identification points and convert them to obtain the instantaneous line shape of the bridge.

Instantaneous deflection value at time _t2 (mm)

8) Step 7: Subtract the change in deflection from the instantaneous deflection to obtain the constant load deflection y ₀ ( _xi )

The dead load deflection is obtained according to formula (8).

Deflection value of dead load at each point (mm)

9) Step 8: Constant load line

The constant load line shape is shown in Figure 14.

10) Verification:

Comparing y ₀ ( _xi ) and y ⁰ ₀ ( _xi ) as shown in the table, the results show that the method given in the present application can effectively map the constant load line shape under vehicle traffic conditions with high accuracy.

Verify the dead load deflection value of each point (mm)

Those skilled in the art will also appreciate that the various illustrative logic blocks, modules, circuits, and algorithmic steps described in conjunction with the embodiments herein can all be implemented as electronic hardware, computer software, or a combination thereof. In order to clearly illustrate the interchangeability between hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above around their functions. Whether such functions are implemented as hardware or software depends on specific applications and the design constraints imposed on the entire system. A skilled person can implement the described functions in an alternative manner for each specific application, but such implementation decisions should not be interpreted as departing from the scope of protection of the present disclosure.

Claims (8)

1. A method for mapping the constant load alignment of a single-span simply supported beam bridge without interrupting traffic, characterized by comprising: A plurality of detection mark points are sequentially set along the span direction of the bridge, and a vertical dynamic displacement time history curve of each detection mark point is obtained when a single vehicle passes through the bridge; Performing multi-scale wavelet decomposition on low-frequency data in each of the vertical dynamic displacement time history curves to obtain a quasi-static component of the vertical dynamic displacement time history curve; Acquire video data of a bicycle passing through a bridge, wherein the video data is synchronized with the vertical dynamic displacement time history curve; Acquiring the position parameters of the vehicle at time _t1 and time _t2 specifically includes: extracting first image data at time _t1 and second image data at time _t2 respectively based on the video data; performing geometric feature recognition on the vehicle in the first image data and the second image data respectively to determine the centroid of the vehicle in the first image data and the second image data; determining the position parameters of the vehicle in the first image data and the second image data according to the determined relative position between the centroid of the vehicle and the bridge; The vehicle load deflection effect at time t2 is determined by combining the position parameters of each detection mark point and the quasi-static component of the vertical dynamic displacement time history curve, specifically including: determining the ratio Ni of the vehicle load deflection effect at time _t1 to the vehicle load deflection effect at time _t2 according to the position parameters of the vehicle at time _t1 and time _t2 and the position parameters of _each detection mark _point ; determining the vehicle load deflection effect at time _t2 according to the following formula:

in,

is the vehicle load deflection of the i-th detection mark point at time _t2 ,

is the change in vehicle load deflection of the i-th detection mark point at time _t2 relative to time _t1 ; The instantaneous deflection of each detection mark point at time _t2 is obtained, and the vehicle load deflection effect at time _t2 is combined for calculation to obtain the constant load deflection of the bridge, and the constant load deflection of the bridge is connected to form its constant load line shape. 2. According to the constant load linear mapping method of claim 1, it is characterized in that the multi-scale wavelet decomposition specifically selects the sym7 wavelet function. 3. The method for mapping the constant load linear shape according to claim 1, characterized in that the step of determining the ratio Ni of the vehicle load deflection effect at _{time t1} to the vehicle load deflection effect at time _t2 according to the position parameters of the vehicle at time t1 and time _t2 and the position parameters of each detection mark point _specifically comprises: Determine the horizontal distance _a1 and the horizontal distance _b1 from the vehicle to the first end of the bridge and the second end of the bridge at time _t1 , the horizontal distance _a2 and the horizontal distance _b2 from the vehicle to the first end of the bridge and the second end of the bridge at time _t2 , and the horizontal distance x _i from the i-th detection mark point to the first end of the bridge; The above position parameters at time _t1 and time _t2 are dimensionless, and

The position parameters of the above detection points are dimensionless, and

When x _i ＜a ₁ , the ratio _Ni of the vehicle load deflection effect at time t ₁ to the vehicle load deflection effect at time t ₂ is determined according to the following formula:

When a ₁ ＜ _xi ＜a ₂ , the ratio _Ni of the vehicle load deflection effect at time t ₁ to the vehicle load deflection effect at time t ₂ is determined according to the following formula:

When x _i > a ₂ , the ratio _Ni of the vehicle load deflection effect at time t ₁ to the vehicle load deflection effect at time t ₂ is determined according to the following formula:

Among them, _n1 is the position parameter of the vehicle at time _t1 after dimensionless processing, _n2 is the position parameter of the vehicle at time _t2 after dimensionless processing, _mi is the position parameter of the i-th detection mark point after dimensionless processing,

is the vehicle load deflection of the i-th detection mark point at time _t1 . 4. The method for mapping the linear shape of a constant load according to claim 1, wherein the step of obtaining the instantaneous deflection of each detection mark point at time _t2 specifically comprises: Performing geometric feature recognition on each detection mark point in the second image data at time _t2 to determine the centroid of each detection mark point; According to the determined relative position between the centroid of the detection mark point and the bridge, the instantaneous deflection of each detection mark point at time _t2 is determined.

5. The method for mapping the constant load line shape according to claim 4 is characterized in that the calculation is performed in combination with the vehicle load deflection effect at time _t2 to obtain the constant load deflection of the bridge, and the constant load line shape of the bridge is formed by connecting lines based on the constant load deflection of the bridge, specifically comprising: Determine the dead load deflection of each detection mark point according to the instantaneous deflection of each detection mark point at time _t2 and the vehicle load deflection effect at time _t2 ; The constant load line shape of the bridge is formed according to the constant load deflection of each detection mark point. 6. The method for mapping the linear shape of a constant load according to claim 5, characterized in that the method of determining the constant load deflection of each detection mark point at time _t2 according to the instantaneous deflection of each detection mark point at time _t2 and the vehicle load deflection effect at time _t2 specifically comprises: The constant load deflection of each detection mark point is calculated and determined according to the following formula:

Where, y ₀ (χ _i ) is the dead load deflection of the i-th detection mark point,

is the instantaneous deflection of the ith detection mark point at time _t2 ,

is the vehicle load deflection of the i-th detection mark point at time _t2 . 7. The method for mapping the constant load linear shape according to claim 1 is characterized in that the multiple detection identification points are sequentially set along the span direction of the bridge, specifically comprising: A mid-span measuring point is set at the center of the bridge, and a plurality of other measuring points are set at equal distances on both sides with the mid-span measuring point as the center; The time t1 is the initial time of measurement; Time t2 is the moment when the vehicle load produces the maximum deflection at the mid-span measuring point. 8. The method for mapping the linear shape of a constant load according to claim 7 is characterized in that a plurality of other measuring points are set equidistantly on both sides with the mid-span measuring point as the center, specifically including: The other measuring points are centered on the mid-span measuring point and are distributed at eighth or sixteenth points according to the length of the span.

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