A method for testing and evaluating the lateral stiffness of small box girder bridges

Abstract

The invention discloses a method for testing and evaluating the lateral stiffness of a small box girder bridge, and belongs to the field of bridge structure safety detection. The method comprises the following steps: a deflection sensor collects deflection values ​​of measuring points based on a loading process of a loading vehicle; a longitudinal bridge deflection influence line of each measuring point is obtained based on the deflection values ​​of the measuring points and an information matrix of the loading vehicle; an interpolation method is adopted based on the longitudinal bridge deflection influence line to obtain a transverse bridge deflection influence line of the small box girder bridge; and a stiffness evaluation is performed based on the transverse bridge deflection influence line of the small box girder bridge to obtain a stiffness evaluation result.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge structure safety detection, and in particular relates to a method for testing and evaluating the lateral stiffness of a small box girder bridge. Background Art

[0002] In bridge construction, there are many small and medium span bridges, accounting for a large proportion. Among them, small box girder bridges, as one of the main bridge types of small and medium span bridges, have been rapidly developed and widely used at home and abroad in recent years. As a key hub in transportation, bridge structures play a vital role. However, due to the influence of factors such as internal material aging or external loads, bridges will be damaged to varying degrees, resulting in a reduction in bridge stiffness. In daily operations, this is manifested in certain deformations of box girder bridges and multiple cracks in the beam body. The reduction in stiffness directly affects the bearing capacity, stability and service life of the bridge. Timely detection of the parts where stiffness reduction occurs has important practical significance and social value for subsequent load-bearing assessment, maintenance and treatment.

[0003] At present, when obtaining stiffness, the test method mainly focuses on the distribution law of bending stiffness in the longitudinal direction of the bridge, and pays less attention to the stiffness change and distribution in the transverse direction of the bridge. Transverse stiffness is crucial to the stability of the overall structure of the bridge. Sufficient transverse stiffness can effectively resist the effects of transverse loads and wind loads, maintain the stability of the bridge structure, and reduce structural deformation and vibration. Good transverse stiffness can ensure the uniform distribution of loads inside the bridge structure and reduce local stress concentration, thereby ensuring the safe operation of the bridge.

[0004] The detection methods for the stiffness of small box girder bridges are mainly divided into dynamic method and static method. The dynamic response and static response of the bridge are obtained by the detection instrument. The data are combined with the data processing algorithm and formula calculation to evaluate the stiffness of the bridge. Based on the static response of the bridge, Li Chunliang et al. judged the degree of damage and damage location of the bending stiffness at any position of the bridge by the deflection value of each point of the bridge when the vehicle was parked at the key position of the bridge. Based on the dynamic response of the bridge, Qi Xingjun et al. measured the fundamental frequency of the bridge, compared the measured fundamental frequency with the theoretical fundamental frequency of the bridge, and obtained the approximate value of the static load deflection verification coefficient of the bridge, thereby evaluating the overall stiffness of the bridge. However, these methods do not consider the distribution state of the transverse stiffness and cannot be used to evaluate the transverse stiffness of the small box girder bridge. Therefore, it is necessary to improve the detection method for obtaining the stiffness of the bridge. Design a special measuring point position, use the vehicle load to obtain the longitudinal bridge deflection influence line of the bridge, and fit the transverse deflection influence line of the bridge through the interpolation algorithm. The difference between the transverse deflection influence lines of the measuring points at different time intervals can be used to determine the location of stiffness damage in the transverse section of the bridge. It has a good application prospect in bridge performance evaluation. Therefore, it is of great significance to study a test and evaluation method for the lateral stiffness of small box girder bridges. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a method for testing and evaluating the lateral stiffness of a small box girder bridge to solve the problems existing in the above prior art.

[0006] To achieve the above object, the present invention provides a method for testing and evaluating the lateral stiffness of a small box girder bridge, comprising:

[0007] The deflection sensor collects the deflection value of the measuring point based on the loading process of the loading vehicle;

[0008] Based on the deflection value of the measuring point and the information matrix of the loaded vehicle, the longitudinal bridge deflection influence line of each measuring point is obtained;

[0009] Based on the longitudinal bridge deflection influence line, an interpolation method is used to fit the transverse bridge deflection influence line of the small box girder bridge;

[0010] The stiffness evaluation result is obtained by performing stiffness evaluation based on the transverse deflection influence line of the small box girder bridge.

[0011] Optionally, before collecting the deflection value of the measuring point, the deflection sensor is also deployed, and the deployment process of the deflection sensor includes:

[0012] At the mid-span section of the bridge, two deflection measuring points are arranged on the bottom surface of each small box girder;

[0013] At the quarter span section of the bridge, one deflection measuring point is arranged on the bottom surface of each small box girder;

[0014] At the one-eighth span section of the bridge, a deflection measuring point is arranged on the bottom surface of each small box girder;

[0015] In the cross section of the bridge support, two deflection measuring points are arranged on the bottom surface of each small box girder;

[0016] At the same time, radar speed meters are arranged at the quarter span and mid-span of the bridge.

[0017] Optionally, the process of collecting data based on the loading process sensor of the loading vehicle includes:

[0018] The loading vehicle moves along the longitudinal direction of the bridge from one end edge to the other end edge of the bridge to complete one longitudinal bridge loading;

[0019] Then the loading position moves along the transverse bridge to the other end. Each time the loading position moves along the transverse bridge, it continues to move along the longitudinal bridge direction until it reaches the edge of the bridge in the longitudinal bridge direction to complete the secondary longitudinal bridge loading.

[0020] After completing the secondary longitudinal loading, observe the readings of the radar speed meter at the quarter span and the mid-span of the bridge. When the readings of the speed meter at the mid-span and the quarter span differ by less than 5%, the data collected by the sensor is valid.

[0021] Optionally, the Tikhonov regularization method is used to identify the influence line of the longitudinal bridge deflection; wherein the expression for identifying the influence line of the longitudinal bridge deflection is:

[0022]

[0023] Where P is the influence coefficient vector of the longitudinal bridge deflection influence line, R is the deflection response vector collected by the deflection sensor, C is the loaded vehicle information matrix, λ is the regularization coefficient, and K is the regularization matrix.

[0024] Optionally, the process of obtaining the influence line of the transverse deflection of the small box girder bridge includes:

[0025] Based on the first longitudinal bridge loading and the second longitudinal bridge loading, two deflection influence lines at the same transverse position are obtained, and the average value of the two deflection influence lines is calculated to obtain the final longitudinal bridge deflection influence line of the current measuring point;

[0026] The influence coefficients of the longitudinal deflection influence lines of the two deflection measurement points of the mid-span section and the support section of the bridge are averaged to obtain the longitudinal deflection influence lines of the mid-span section and the support section;

[0027] The transverse deflection influence line of the small box girder bridge is obtained by fitting the longitudinal deflection influence lines of the support section, one-eighth span section, one-quarter span section and mid-span section.

[0028] Optionally, the stiffness assessment process includes:

[0029] The benchmark influence line is obtained based on the first fitting of the transverse deflection influence line of the small box girder bridge;

[0030] After half a year, the loading test is carried out again on the test cross section to obtain the current lateral deflection influence line;

[0031] Obtaining a deflection influence coefficient difference of each measuring point based on the reference influence line and the current lateral deflection influence line;

[0032] When the difference in the deflection influence coefficient on both sides of the fixed horizontal coordinate changes alternately between positive and negative, the stiffness decreases.

[0033] Optionally, the criterion for judging the stiffness reduction also includes: the change range of the slope of the deflection influence line of the current measuring point on both sides of the stiffness reduction area is higher than that of the rest.

[0034] Optionally, the expression for the difference in deflection influence coefficients of each measuring point on the cross section is:

[0035]

[0036] Where i is the lateral loading point on the same cross section, m is the number of lateral loading points, and x isi represents the position coordinates of the lateral loading point i on the same section, s 1 (x i ) 基 It represents the expression of the reference transverse deflection influence line of the first test section fitted in the first test, s 1 (x i ) is the expression of the transverse deflection influence line of the measuring point on the first test section fitted half a year later, Δs 1 (x i ) represents the difference function of the deflection influence coefficient at different lateral positions of the measuring points on the first test section, and n represents the number of test sections.

[0037] Compared with the prior art, the present invention has the following advantages and technical effects:

[0038] The present invention adopts the measures of symmetrically arranging sensors at the bottom of the cross-section beam and loading the vehicle load twice at the same speed on the same lane, thereby improving the accuracy of the influence line data, having little impact on traffic during the test, and causing no new damage to the bridge;

[0039] The lateral deflection influence line fitting method of the present invention has a strict theoretical basis. The lateral response relationship is obtained through the longitudinal bridge deflection influence line, which can locate the lateral stiffness drop. The data obtained under the special sensor layout method and vehicle loading design scheme can ensure that the structure has high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0041] Figure 1 This is a flow chart of a method for testing and evaluating the lateral stiffness of a small box girder bridge according to an embodiment of the present invention;

[0042] Figure 2 It is a schematic diagram of the positions of displacement sensors in the mid-span section and the section at the support according to an embodiment of the present invention;

[0043] Figure 3 A schematic diagram of the positions of the quarter-section and one-eighth-section displacement sensors according to an embodiment of the present invention;

[0044] Figure 4 A loading vehicle simulated by an embodiment of the present invention;

[0045] Figure 5 A schematic diagram of the longitudinal bridge loading position of an embodiment of the present invention;

[0046] Figure 6A schematic diagram of a transverse bridge loading position according to an embodiment of the present invention;

[0047] Figure 7 This is a schematic diagram of an assembled small box girder bridge according to an embodiment of the present invention, wherein: Figure 7 (a) is the front view. Figure 7 (b) is a side view;

[0048] Figure 8 The following is a comparison chart of the working conditions of the embodiment of the present invention, where: Figure 8 (a) is a schematic diagram of the influence line of the transverse bridge deflection at the bottom of the No. 3 beam in the mid-span. Figure 8 (b) is a schematic diagram of the difference in influence coefficient of the transverse deflection influence line of the bottom of beam No. 3 in the front and rear mid-span of the stiffness damaged beam;

[0049] Fig. 9 This is a comparison chart of indicators under working condition 2 of an embodiment of the present invention, where: Fig. 9 (a) is a schematic diagram of the influence line of the transverse bridge deflection at the bottom of the No. 3 beam in the mid-span. Fig. 9 (b) is a schematic diagram of the difference in influence coefficient of the transverse deflection influence line of the bottom of beam No. 3 in the front and rear mid-span of the stiffness damaged beam;

[0050] Fig.10 This is a comparison chart of indicators under three working conditions of an embodiment of the present invention, where: Fig.10 (a) is a schematic diagram of the influence line of the transverse bridge deflection at the bottom of the No. 4 beam in the mid-span. Fig.10 (b) is a schematic diagram of the difference in influence coefficients of the transverse deflection influence line at the bottom of beam No. 4 in the front and rear mid-span of the stiffness damaged beam. DETAILED DESCRIPTION

[0051] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0052] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0053] Embodiment 1

[0054] like Figure 1As shown, in this embodiment, a method for testing and evaluating the transverse stiffness of a small box girder bridge is provided. The present invention arranges displacement sensors at the designed position, so that the loading vehicle loads the bridge according to a specific scheme, obtains the corresponding deflection response data, and then solves the longitudinal deflection influence line. Then, the cubic spline difference formula is introduced to fit the transverse deflection influence line of the small box girder bridge. The transverse deflection influence line obtained at different times is used to make a difference with the reference influence line to realize the transverse stiffness evaluation of the small box girder bridge. The method is simple to operate, has a single data type, and has a small data transmission error. It is suitable for the detection of transverse stiffness damage in small box girder bridges and can realize the qualitative evaluation of transverse stiffness. Specifically, the following steps are included: the deflection sensor collects the deflection value of the measuring point based on the loading process of the loading vehicle; the longitudinal deflection influence line of each measuring point is obtained based on the deflection value of the measuring point and the information matrix of the loading vehicle; the transverse deflection influence line of the small box girder bridge is fitted by the interpolation method based on the longitudinal deflection influence line; the stiffness evaluation is performed based on the transverse deflection influence line of the small box girder bridge to obtain the stiffness evaluation result.

[0055] Before collecting the deflection value of the measuring point, the deflection sensor is also arranged. The arrangement process of the deflection sensor includes step 1:

[0056] Step 1. Sensor layout method for small box girder bridge

[0057] For the collection of deflection data of small box girder bridges, deflection sensors are used, and the mid-span section, quarter-span section, one-eighth span section and section at the support of the bridge are taken as test sections. At the mid-span section of the bridge, two deflection measuring points are arranged on the bottom surface of each small box girder, and the measuring points are symmetrically distributed on the bottom center line of each small box girder, and the longitudinal positions of the measuring points in the mid-span section remain consistent; at the quarter-span section of the bridge, one deflection measuring point is arranged on the bottom surface of each small box girder, and the measuring point is located at the bottom center line of each small box girder, and the longitudinal positions of the measuring points remain consistent; at the one-eighth span section of the bridge, one deflection measuring point is arranged on the bottom surface of each small box girder, and the measuring point is located at the bottom center line of each small box girder, and the longitudinal positions of the measuring points remain consistent; in the section at the support of the bridge, two deflection measuring points are arranged on the bottom surface of each small box girder, and the measuring points are symmetrically distributed on the bottom center line of each small box girder, and the longitudinal positions of the measuring points are consistent with each other, and the lateral positions are consistent with the measuring points at the mid-span section. The layout positions of bridge displacement sensors are as follows: Figure 2 , Figure 3 At the same time, radar speed meters are arranged at the quarter span and the middle span of the bridge to record the vehicle speeds as the vehicles pass through one by one.

[0058] The process of data collection by the sensor during the loading process of the loading vehicle includes: the loading vehicle moves along the longitudinal direction of the bridge from one edge of the bridge to the other edge of the bridge to complete a longitudinal loading; then the loading position moves along the transverse direction of the bridge to the other end, and each time the loading position moves along the transverse direction of the bridge, it continues to move along the longitudinal direction of the bridge to complete the secondary longitudinal loading of the bridge when it reaches the edge of the bridge in the longitudinal direction; after completing the secondary longitudinal loading of the bridge, observe the readings of the radar speedometers at the quarter span and the mid span of the bridge. When the readings of the speedometers at the mid span and the quarter span differ by less than 5%, the data collected by the sensor is valid. The specific implementation process includes step 2:

[0059] Step 2. Loading small box girder bridge vehicles

[0060] A three-axle truck was selected as the loading vehicle. At the beginning of the test, the vehicle started loading from the left end near the edge of the road, and gradually moved along the longitudinal direction of the bridge to the other end of the bridge, and ended at the right edge. After that, the loading position moved along the transverse direction of the bridge to the other end. Each transverse movement distance s was half of the wheelbase. After each movement, it continued to move along the longitudinal direction of the bridge to the other end of the bridge, and ended at the right edge. During the loading process, the same transverse position was loaded twice. The longitudinal loading position of the vehicle is as follows: Figure 5 , Figure 6 As shown. After each loading is completed, the next loading will start after an interval of 5 minutes. During the loading process, observe the speedometer readings. If the difference between the speedometer readings at the mid-span and the quarter-span is within 5%, the data obtained by the sensor can be used as valid data. When the difference between the speedometer readings at the mid-span and the quarter-span is greater than 5%, reloading is required.

[0061] Step 3. Identification of the influence line of the longitudinal deflection of the small box girder bridge

[0062] During the entire loading process, the deflection values ​​of the main beam mid-span section, quarter-span section, eighth-span section and support section measuring points are collected after each loading. The load of each axle of the loaded vehicle is defined as M i When a loaded vehicle passes through the bridge, the deflection sensors at the corresponding measuring points will collect a series of responses R. The response equation can be written in matrix form as follows:

[0063] R=CP (1)

[0064] Where R is the deflection response vector collected by the deflection sensor, P is the influence coefficient vector of the longitudinal bridge deflection influence line, and C is the loaded vehicle information matrix. The form of C is as follows:

[0065]

[0066] M is the vehicle axle weight, k is the number of axles, b is the number of bridge response collection points, and a is the number of influence line coefficients. For the sensor response equation, the vehicle load matrix is ​​known, and the structural response vector can be measured by installing sensors. However, the actual measured structural response vector R is usually subject to fluctuations caused by factors such as dynamic impact, rough road surface, environmental noise, and measurement errors. Direct solution will result in large errors, so the existence and stability of the solution to the equation are satisfied by limiting the solution space, and the Tikhonov regularization method is used to identify the influence line, and its expression is as follows:

[0067]

[0068] Where P is the influence coefficient vector of the longitudinal bridge deflection influence line, R is the deflection response vector collected by the deflection sensor, C is the loaded vehicle information matrix, λ is the regularization coefficient, and K is the regularization matrix.

[0069] The influence coefficient vector P that minimizes the sum of the squares of the two norms is selected as the optimal solution to the complete influence line equation.

[0070] The process of obtaining the transverse deflection influence line of a small box girder bridge includes: obtaining two deflection influence lines at the same transverse position based on the first longitudinal bridge loading and the second longitudinal bridge loading, averaging the two deflection influence lines to obtain the final longitudinal deflection influence line of the current measuring point; averaging the influence coefficients of the longitudinal deflection influence lines of the two deflection measuring points of the mid-span section and the section at the support of the bridge to obtain the longitudinal deflection influence lines of the mid-span section and the section at the support; fitting the longitudinal deflection influence lines of the section at the support, the one-eighth span section, the one-quarter span section and the mid-span section to obtain the transverse deflection influence line of the small box girder bridge. The specific implementation process includes step 4:

[0071] Step 4. Fitting the influence line of the transverse deflection of the small box girder bridge

[0072] The longitudinal bridge deflection influence lines of each measuring point obtained are sorted out.

[0073] Firstly, for a certain measuring point, since two longitudinal bridge loading tests were carried out at the same transverse position, the influence coefficients of the two deflection influence lines obtained at the same transverse position were averaged and taken as the final longitudinal bridge deflection influence line of the measuring point.

[0074] Then, there are two deflection measurement points on the bottom surface of each small box girder at the mid-span section and the support section. The deflection influence line of the two deflection measurement points is averaged to find the influence coefficient, and the deflection influence line at the center line of the bottom of the beam is fitted. In this way, for the support section, one-eighth span section, one-quarter span section and mid-span section, there is only one longitudinal bridge deflection influence line at the center line of the bottom of each box girder under each lane loading.

[0075] Finally, for the test section, each beam bottom has different longitudinal influence lines, with the same longitudinal position coordinates and different influence coefficients. The influence coefficient of the influence line of a certain measuring point at the same section is recorded. The interpolation method is used to fit the transverse deflection influence line of the small box girder bridge, and the cubic spline interpolation formula is introduced to fit the transverse deflection influence line expression of the same measuring point at different transverse positions.

[0076] The stiffness evaluation process includes: obtaining the reference influence line based on the first fitted transverse deflection influence line of the small box girder bridge; fitting the current transverse deflection influence line by loading the test cross section again after half a year; obtaining the difference in deflection influence coefficient of each measuring point based on the reference influence line and the current transverse deflection influence line; when the difference in deflection influence coefficient on both sides of the fixed horizontal coordinate changes alternately between positive and negative, the stiffness decreases. The specific implementation process includes step 5:

[0077] Step 5. Stiffness evaluation based on the influence line of the transverse deflection of the small box girder bridge

[0078] The state evaluation of the lateral stiffness of the small box girder bridge is carried out according to the lateral deflection influence line of the fitted measuring point. For each measuring point on a test cross section, the lateral deflection influence line fitted by the first test is used as the benchmark, and a loading test is carried out every six months. The lateral deflection influence line fitted by the measuring point is subtracted from the first benchmark influence line to obtain a deflection influence coefficient difference Δs with the lateral coordinate x as the independent variable. n (x i ) is a function of the dependent variable, and then it is transferred into the MATLAB program to draw the image. The difference function of the deflection influence coefficient of each measuring point on the cross section is shown in Formula 3:

[0079]

[0080] Where i is the lateral loading point on the same cross section, m is the number of lateral loading points, and x is i represents the position coordinates of the lateral loading point i on the same section, s 1 (x i ) 基 It represents the expression of the reference transverse deflection influence line of the first test section fitted in the first test, s 1 (x i ) is the expression of the transverse deflection influence line of the measuring point on the first test section fitted half a year later, Δs 1 (x i ) represents the difference function of the deflection influence coefficient at different lateral positions of the measuring points on the first test section, and n represents the number of test sections.

[0081] Determine the decrease in stiffness: This is done by observing the difference in the deflection influence coefficients of each measuring point on the test section. When the difference in the deflection influence coefficients on both sides of a fixed horizontal coordinate changes alternately between positive and negative, this indicates that the stiffness near the horizontal position has decreased. In addition, the slope of the deflection influence line of the measuring point on both sides of the stiffness decrease area changes more than the rest.

[0082] Based on the above specific implementation process, this embodiment uses a numerical example to calculate the full-bridge test conditions.

[0083] In this numerical example, a 30m span prefabricated small box girder bridge is simulated. The prefabricated small box girder bridge model consists of 5 main beams, which are named 1-5 main beams and 1-4 hinge joints in order from left to right. Assuming that the mass distribution of each main beam is consistent, the main beam cross section and the bridge model are as follows: Figure 7 As shown, Figure 7 (a) is the front view. Figure 7 (b) is a side view. The dimensions of the loaded vehicle are as follows: Figure 4 As shown, load according to the loading process described in step 2.

[0084] In this implementation, the stiffness reduction of the small box girder bridge is set to multiple working conditions. Taking the mid-span section as an example, the section stiffness reduction is 25%, 35%, and 45%, respectively, as shown in Table 1. These working conditions are simulated in the finite element, and the corresponding loading and calculation are performed according to the above steps. The front and rear influence lines at the bottom of the small box girder bridge are as follows: Figure 8 As shown, Figure 8 (a) is a schematic diagram of the influence line of the transverse bridge deflection at the bottom of the No. 3 beam in the mid-span. Figure 8 (b) is a schematic diagram of the difference in influence coefficient of the transverse deflection influence line of the bottom of the No. 3 beam in the middle of the stiffness damaged beam before and after. The difference in influence coefficient before and after the same measuring point is as follows Fig. 9 As shown, Fig. 9 (a) is a schematic diagram of the influence line of the transverse bridge deflection at the bottom of the No. 3 beam in the mid-span. Fig. 9 Middle (b) is a schematic diagram of the difference in influence coefficient of the transverse deflection influence line at the bottom of beam No. 3 in the front and rear mid-span of the stiffness damaged beam.

[0085] Table 1

[0086]

[0087] In the evaluation of the lateral stiffness of small box girder bridges, Figure 8 It can be seen that the front and rear deflection influence lines at the bottom of beam 3 intersect at the transverse coordinate of 6.58, and the difference in the deflection influence coefficient on both sides of the transverse coordinate 6.58 changes alternately between positive and negative, indicating that stiffness damage occurs at this position, which is very close to the transverse coordinate of the position where stiffness damage occurs at hinged joint No. 2 in the middle of the first span of the working condition; Fig. 9It can be seen that the front and rear deflection influence lines at the bottom of beam 3 intersect at the transverse coordinate of 6.58. The difference in the deflection influence coefficient on both sides of the transverse coordinate 6.58 changes alternately between positive and negative. Stiffness damage occurs at this position. Figure 8 , the stiffness damage position is the same, the damage degree is different, and the difference in influence coefficient is greater, which is consistent with the conditions of working condition 2; Fig.10 (a) is a schematic diagram of the influence line of the transverse bridge deflection at the bottom of the No. 4 beam in the mid-span. Fig.10 (b) is a schematic diagram of the difference in the influence coefficient of the transverse deflection influence line of the bottom of the No. 4 beam in the front and rear mid-span of the stiffness damaged beam. Fig.10 It can be obtained that the front and rear deflection influence lines at the bottom of beam 4 intersect at the transverse coordinate of 9.72. The difference in the deflection influence coefficient on both sides of the transverse coordinate 9.72 changes alternately between positive and negative. Stiffness damage occurs at this position, which is consistent with the conditions of working condition 3. Figure 8 , Fig. 9 By comparison, it can be seen that the above method can be used to determine whether stiffness damage occurs in the transverse direction of the bridge at different measuring points.

[0088] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for testing and evaluating the lateral stiffness of a small box girder bridge, characterized in that: The following steps are involved: The deflection sensor collects the deflection value of the measuring point based on the loading process of the loading vehicle; Based on the deflection value of the measuring point and the information matrix of the loaded vehicle, the longitudinal bridge deflection influence line of each measuring point is obtained; The Tikhonov regularization method is used to identify the influence line of the longitudinal bridge deflection. The expression for identifying the influence line of the longitudinal bridge deflection is: In the formula, is the influence coefficient vector of the longitudinal bridge deflection influence line, is the deflection response vector collected by the deflection sensor, To load the vehicle information matrix, is the regularization coefficient, is the regularization matrix; Based on the longitudinal bridge deflection influence line, an interpolation method is used to fit the transverse bridge deflection influence line of the small box girder bridge; The process of obtaining the influence line of the transverse deflection of a small box girder bridge includes: Based on the first longitudinal bridge loading and the second longitudinal bridge loading, two deflection influence lines at the same transverse position are obtained, and the average value of the two deflection influence lines is calculated to obtain the final longitudinal bridge deflection influence line of the current measuring point; The influence coefficients of the longitudinal deflection influence lines of the two deflection measurement points of the mid-span section and the support section of the bridge are averaged to obtain the longitudinal deflection influence lines of the mid-span section and the support section; Based on the longitudinal deflection influence lines of the support section, one-eighth span section, one-quarter span section and mid-span section, the transverse deflection influence line of the small box girder bridge is obtained by fitting. A stiffness evaluation is performed based on the transverse deflection influence line of the small box girder bridge to obtain a stiffness evaluation result; Wherein, before collecting the deflection value of the measuring point, the deflection sensor is also arranged, and the arrangement process of the deflection sensor includes: At the mid-span section of the bridge, two deflection measuring points are arranged on the bottom surface of each small box girder; At the quarter span section of the bridge, one deflection measuring point is arranged on the bottom surface of each small box girder; At the one-eighth span section of the bridge, a deflection measuring point is arranged on the bottom surface of each small box girder; In the cross section of the bridge support, two deflection measuring points are arranged on the bottom surface of each small box girder; At the same time, radar speed guns were installed at the quarter span and mid span of the bridge; The process of collecting data based on the loading process sensor of the loading vehicle includes: The loading vehicle moves along the longitudinal direction of the bridge from one end edge to the other end edge of the bridge to complete one longitudinal bridge loading; Then the loading position moves along the transverse bridge to the other end. Each time the loading position moves along the transverse bridge, it continues to move along the longitudinal bridge direction until it reaches the edge of the bridge in the longitudinal bridge direction to complete the secondary longitudinal bridge loading. After completing the secondary longitudinal loading, observe the readings of the radar speed meter at the quarter span and the mid-span of the bridge. When the readings of the speed meter at the mid-span and the quarter span differ by less than 5%, the data collected by the sensor is valid.

2. The method for testing and evaluating the lateral stiffness of a small box girder bridge according to claim 1 is characterized in that: The stiffness assessment process includes: The benchmark influence line is obtained based on the first fitting of the transverse deflection influence line of the small box girder bridge; After half a year, the loading test is carried out again on the test cross section to obtain the current lateral deflection influence line; Obtaining a deflection influence coefficient difference of each measuring point based on the reference influence line and the current lateral deflection influence line; When the difference in the deflection influence coefficient on both sides of the fixed horizontal coordinate changes alternately between positive and negative, the stiffness decreases.

3. The method for testing and evaluating the lateral stiffness of a small box girder bridge according to claim 2 is characterized in that: The criteria for judging the decrease in stiffness also include: the change in the slope of the deflection influence line of the current measuring point on both sides of the stiffness decrease area is higher than that of the rest.

4. The method for testing and evaluating the lateral stiffness of a small box girder bridge according to claim 2 is characterized in that: The expression of the difference of deflection influence coefficient of each measuring point on the cross section is: In the formula, is the lateral loading point of the same cross section, is the number of lateral loading points, Indicates the lateral loading point of the same section The location coordinates of It represents the expression of the reference transverse deflection influence line of the first test section fitted in the first test, is the expression of the lateral deflection influence line of the measuring point on the first test section fitted half a year later, It represents the difference function of the deflection influence coefficient at different lateral positions of the measuring point on the first test section, Indicates the number of test sections.

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