Continuous beam bridge different span loading load test method

Abstract

The present application relates to the technical field of bridge quality detection, especially to a continuous beam bridge different span loading load test method, comprising the following steps: determining a control section on the continuous beam bridge; measuring the axle load and the wheelbase of the test vehicle; calculating and analyzing the interval area of the calculated bending moment change effect function with the moving vehicle; analyzing and calculating the interval area of the measured bending moment change effect function with the moving vehicle; comparing the ratio of the interval area of the calculated bending moment change effect function with the moving vehicle and the interval area of the measured bending moment change effect function with the moving vehicle through the calibration coefficient to determine whether the bearing capacity requirement is met. The continuous beam bridge different span loading load test method can effectively reduce the arrangement of measuring points and the need for test vehicles, and quickly and accurately judge the bearing capacity state of the bridge by calculating the bending moment change effect function with the moving vehicle and the measured bending moment change effect function with the moving vehicle.

Description

Technical Field

[0001] This invention relates to the field of road and bridge quality testing technology, and in particular to a method for loading tests on continuous beam bridges with varying spans. Background Technology

[0002] my country is a major bridge-building nation with numerous newly built and existing bridges, most of which are continuous beam bridges. Some of these bridges have been in operation for a long time, resulting in severe material aging and significant reduction in cross-sectional stiffness. Whether old or new, both bridges require precise and effective assessments to determine their condition and load-bearing capacity. Traditional load testing calculates the ratio of the internal forces or deformations at the control section under the test load to the internal forces or deformations under the load used for load capacity assessment. This yields the test load efficiency. The test load is then applied to designated locations on the bridge, and parameters such as static displacement and static strain at the test section are measured to evaluate the bridge's performance and serviceability.

[0003] Traditional load tests can provide a direct assessment of the load condition, and the results are relatively accurate and reliable. However, they require a large number of vehicles, including many loading vehicles, and the simultaneous occurrence of load tests takes a long time. The entire process requires traffic closure, numerous measurement points, and consumes considerable time and testing costs. Finding vehicles on-site is difficult, the load weights may not perfectly match the calculated loads, and the vehicle placement locations vary depending on different working conditions, resulting in too much randomness and low comparability of repeated test data. Furthermore, different software programs can produce theoretical data with some discrepancies, and the algorithm based on multiplying the test load by the influence line cannot accurately reflect the actual condition. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a method for loading tests on continuous beam bridges with varying spans. This method effectively reduces the need for measuring points and test vehicles. Furthermore, by calculating the effect function of bending moment as a function of moving vehicles and comparing it with the measured effect function of bending moment as a function of moving vehicles, the bearing capacity of the bridge can be quickly and accurately determined.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The method for loading tests on continuous beam bridges with varying spans includes the following steps:

[0007] 1) Determination of the control section: Determine a control section on a continuous beam bridge;

[0008] 2) Measurement of test vehicle data: Measure the axle load and wheelbase of the test vehicle;

[0009] 3) Establishment of the effect function of bending moment variation with moving vehicle: Based on the influence line curve of the bending moment of the control section and the axle load and number of axles of the test vehicle, calculate and analyze the effect function of bending moment variation with moving vehicle for any section, and calculate and analyze the area of ​​the interval of the effect function of bending moment variation with moving vehicle through integration.

[0010] The expression for the effect function of the calculated bending moment at any cross section varying with the moving vehicle is:

[0011]

[0012] Where Xp is the distance from the rear axle of the test vehicle to the origin of the bridge, X is the expression for the influence line of the bending moment calculated at any cross section, X is the coordinate of any cross section, Z1 is the rear axle distance, Z2 is the rear axle distance, P1 is the first rear axle load, P2 is the second rear axle load, and P3 is the front axle load.

[0013] 4) Establishment of the effect function of measured bending moment changing with moving vehicles:

[0014] A1: Determine the stiffness of the control section;

[0015] A2: Arrange one or more strain gauges in the control section;

[0016] A3: Drive the test vehicle from the beginning of the bridge to the end of the bridge, and calculate the effect function of the measured bending moment changing with the moving vehicle based on the data analysis of steps A1 and A2. Calculate the area of ​​the interval of the effect function of the measured bending moment changing with the moving vehicle through integral analysis.

[0017] 5) Assessment of bearing capacity: Place the area of ​​the calculated bending moment variation effect function with moving vehicles and the area of ​​the measured bending moment variation effect function with moving vehicles in the same coordinate system. By comparing the integral area of ​​the calculated bending moment variation effect function with the measured bending moment variation effect function with moving vehicles, determine whether the continuous beam bridge meets the bearing capacity requirements.

[0018] Further, in step 3), the establishment of the influence line curve of the calculated bending moment of the control section includes the following steps:

[0019] B1: Measure the individual spans and the total span of the bridge, and measure the location of the control section;

[0020] B2: Based on the data obtained in step B1 and the expression for the influence line influence factor, determine the influence line influence factor for each bridge span;

[0021] B3: Based on the data obtained in step B2 and the expression for the influence line of the calculated bending moment of any cross section, determine the influence line of the calculated bending moment of the cross section.

[0022] Furthermore, when analyzing the influence line of the calculated bending moment of the control section on the corresponding bridge span, the position of the control section on the corresponding bridge span is determined, and the influence lines of the calculated bending moment of the control section on both ends of the corresponding bridge span are analyzed respectively.

[0023] Furthermore, in step A3, the test vehicle is ensured to pass slowly and at a constant speed from the bridgehead to the bridge tail.

[0024] Furthermore, in step A1, the stiffness of the control section is calculated based on the bridge span length and concrete grade coefficient.

[0025] Furthermore, the strain gauge acquires signals via a high-speed data acquisition device.

[0026] Furthermore, the verification coefficient is 1. When the ratio of the area of ​​the calculated bending moment variation effect function with respect to the area of ​​the measured bending moment variation effect function with respect to the moving vehicle is less than 1, the bearing capacity of the bridge meets the requirements.

[0027] The beneficial effects of this invention are:

[0028] 1. By obtaining the influence line curve of bending moment at any cross-section using the axle load and wheelbase of the test vehicle, the effect function of bending moment variation with moving vehicle at any cross-section is obtained. This allows the determination of the effect function of calculated bending moment variation with moving vehicle at the control section. In actual testing, stress gauges are placed at the control section, and the test vehicle is driven from the bridgehead to the bridge abutment. By measuring the stress gauge data and the stiffness of the control section, the effect function of measured bending moment variation with moving vehicle at the control section is determined. The integral area ratio of the effect function of bending moment variation with moving vehicle at the control section and the effect function of measured bending moment variation with moving vehicle at the measured section effectively reduces the need for measuring points and test vehicles. Furthermore, by comparing the effect function of calculated bending moment variation with moving vehicle and the effect function of measured bending moment variation with moving vehicle at the measured section, the bearing capacity state of the bridge can be quickly and accurately determined, overcoming the limitations of using the influence line multiplied by the theoretical load as an evaluation algorithm.

[0029] 2. Since the applied load acts on the entire bridge, each control section of the bridge has a fixed calculated bending moment effect function as a function of the change of the bending moment with the moving vehicle. Therefore, by placing strain gauges at a certain control section, the actual bending moment effect function as a function of the change of the bending moment with the moving vehicle at that control section can be detected, thereby reducing the number of control sections and strain gauges required.

[0030] 3. The test vehicle passes over the bridge at a constant and slow speed to ensure that there is no acceleration during the test vehicle's operation, thus avoiding the influence of acceleration and load, which could lead to deviations in the test results.

[0031] 4. When testing the effect function of the actual bending moment of the control section changing with the moving vehicle, only one vehicle is needed as the load, without interrupting traffic, reducing testing time, and facilitating repeated testing, thus reducing randomness in the test process. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the test vehicle loading method for a continuous beam bridge with varying spans according to an embodiment of the present invention.

[0033] Figure 2 This is a diagram showing the arrangement of strain gauges at the control section of a continuous beam bridge with varying spans, according to an embodiment of the present invention.

[0034] Figure 3 This is a curve showing the effect of calculated bending moment on the change of moving vehicle on the load test method for a continuous beam bridge with different spans according to an embodiment of the present invention.

[0035] Figure 4 This is a curve showing the effect of measured bending moment on moving vehicle variation in a continuous beam bridge differential load test method according to an embodiment of the present invention.

[0036] Figure 5 This is a comparison of the bending moment effect function curves as a function of moving vehicles in the load test method for continuous beam bridges with varying spans according to one embodiment of the present invention.

[0037] In the figure, 1-test vehicle, z1-rear wheelbase, z2-front wheelbase, p1-first rear axle load, p2-second rear axle load, p3-front axle load, 2-bridge, L1-first span, L2-second span, L3-third span, L-total span, 2-bridge, 21-control section, 3-strain gauge. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] The method for loading tests on continuous beam bridges with varying spans includes the following steps:

[0042] 1) Determination of the control section: A control section 21 is determined on the continuous beam bridge 2. In this embodiment, the bridge being tested is a three-span continuous beam bridge with equal cross-section and equal span. The control section 21 is located at the mid-span of the side span.

[0043] 2) Measurement of test vehicle 1 data: The axle load and wheelbase of test vehicle 1 were measured. In this implementation, the selected test vehicle 1 is a three-axle truck, where the first rear axle load p1 = the second rear axle load p2 = 150kN, the front axle load p3 = 70kN, the rear wheelbase z1 = 1.35m, and the front wheelbase z2 = 3.6m.

[0044] 3) Establishment of the effect function of bending moment variation with moving vehicle: Based on the influence line curve of the bending moment of control section 21 and the axle load and number of axles of test vehicle 1, the effect function of bending moment variation with moving vehicle is calculated and analyzed. The area of ​​the interval of the effect function of bending moment variation with moving vehicle is calculated and analyzed by area integration.

[0045] The expression for the effect function of the calculated bending moment at any cross section varying with the moving vehicle is as follows:

[0046] ①

[0047] Where Xp is the distance from the rear axle of the test vehicle to the bridge origin, and the bridge origin is the bridgehead with coordinates (0, 0). This is the expression for the influence line of bending moment calculation for any cross section. X is the coordinate of any cross section, with coordinates (x.0). Z1 is the rear axle distance, Z2 is the rear axle distance, P1 is the first rear axle load, P2 is the second rear axle load, and P3 is the front axle load.

[0048] The expression for the influence line of the calculated bending moment at any cross section is:

[0049] ②0≤X P ≤L1: ③L1≤X P ≤L-L3: ④L-L3≤X P ≤L:

[0050] Where L is the total span, L1 is the span of span #1, L2 is the span of span #2, L3 is the span of span #3, a1 and a2 are the influence factors of the influence line of span #1, b1 and b2 are the influence factors of the influence line of span #2, and c1 and c2 are the influence factors of the influence line of span #3.

[0051] From the expression for the effect function of the calculated bending moment on the moving vehicle at any cross section, it can be seen that the effect function of the calculated bending moment on the moving vehicle at control section 21 is related to the first rear axle load p1, the second rear axle load, the front axle load, the rear wheelbase, the front wheelbase of test vehicle 1, and the influence line curve of the calculated bending moment at control section 21. The expression for the effect function of the calculated bending moment on the moving vehicle at control section 21 can be obtained by multiplying the expression for the influence line of the calculated bending moment at control section 21 by the applied load. The area of ​​the interval of the effect function of the calculated bending moment on the moving vehicle is calculated and analyzed by area integration.

[0052] The establishment of the influence line for the calculated bending moment of the control section includes the following steps:

[0053] B1: Measure the individual spans and the total span of bridge 2. In this embodiment, the first span L1 = the second span L2 = the third span L3 = 30m, and the total span L = 90m.

[0054] B2: Determine the influence factor of each bridge span based on the data from step B1, and derive the analytical expression of the influence line;

[0055] B3: Based on the location of the control section in the corresponding bridge span and the analytical expression of the influence line, determine the influence of the control section on each bridge span, and establish the influence line of the calculated bending moment of the control section.

[0056] From formulas ②-④, it can be seen that the expression for the influence line of the calculated bending moment at any cross-section is determined by the influence line influence factor. The influence line influence factor for each bridge span is related to the first span L1, the second span L2, the third span L3, and the total span L. In step B1, the spans and the total span of bridge 2 are measured. The influence line influence factor for each bridge span is calculated using B2. Based on the influence line influence factor in B2, the influence of the control section on each span of the bridge is determined, and the calculated bending moment influence line for the control section is established.

[0057] When analyzing the influence line of the calculated bending moment of the control section 21 on the corresponding bridge span, the position of the control section 21 on the corresponding bridge span is determined, and the influence line of the calculated bending moment of the control section 21 on both ends of the corresponding bridge span is analyzed respectively.

[0058] Let x = L1 / 2. According to formulas ②-④, in this embodiment, the expression for the influence line of the calculated bending moment of the control section 21 is:

[0059]

[0060] Based on the influence line expression for the calculated bending moment at control section 21, and the axle load and number of axles of test vehicle 1, the effect function of the calculated bending moment varying with the moving vehicle is obtained, as follows: Figure 3 As shown.

[0061] 4) Establishment of the effect function of measured bending moment varying with moving vehicles: The establishment of the effect function of measured bending moment varying with moving vehicles includes the following steps:

[0062] A1: The stiffness of the control section 21 is determined. The stiffness of the control section 21 is calculated based on the span length of bridge 2 and the concrete grade coefficient. In this embodiment, the concrete grade of the bridge is C50, and the elastic modulus is 3.45 × 10⁻⁶. 4 MPa, the stiffness of the control section 21 is calculated to be 5.02362 × 10 MPa. 7 kN.m 2 .

[0063] A2: One or more strain gauges 3 are arranged on the control section, as shown in the strain gauge arrangement diagram. Figure 2 As shown.

[0064] A3: Drive test vehicle 1 from one end of the bridge to the other, ensuring that test vehicle 1 passes through the bridge at a constant and slow speed. This constant and slow speed ensures that the test vehicle experiences no acceleration during operation, avoiding the influence of acceleration and load, which could lead to deviations in the test results. Based on the data analysis of steps A1 and A2, calculate the effect function of the measured bending moment changing with the moving vehicle. Then, calculate the area of ​​the interval of the effect function of the measured bending moment changing with the moving vehicle using area integration analysis. In this embodiment, a dynamic strain gauge measurement system is used.

[0065] Only one vehicle is needed as a loading vehicle, which does not require traffic interruption, reduces testing time, and facilitates repeated testing, reducing randomness in the testing process.

[0066] The effect function of measured bending moment changing with moving vehicle is as follows: Figure 4 As shown.

[0067] 5) Assessment of bearing capacity: The ratio of the area of ​​the calculated bending moment variation effect function with respect to the area of ​​the measured bending moment variation effect function with respect to the moving vehicle is compared with the verification coefficient to determine whether the bearing capacity requirements are met.

[0068] In this embodiment, the verification coefficient is 1. The bridge's bearing capacity meets the requirement when the ratio of the area under the calculated bending moment effect function as a function of moving vehicles to the area under the measured bending moment effect function as a function of moving vehicles is less than 1. The comparison curves of the area under the calculated bending moment effect function as a function of moving vehicles and the area under the measured bending moment effect function as a function of moving vehicles are shown below. Figure 5 As shown.

[0069] This invention obtains the effect function of bending moment variation with moving vehicle at any cross-section by measuring the axle load and wheelbase of test vehicle 1 and the influence line curve of bending moment at any cross-section. This allows for the determination of the effect function of calculated bending moment variation with moving vehicle at control section 21. In actual testing, stress gauges are placed at control section 21, and test vehicle 1 is driven from the bridgehead to the bridge abutment. By measuring the data from stress gauges 3 and the stiffness of the control section, the effect function of measured bending moment variation with moving vehicle at control section 21 is determined. The integral area ratio of the effect function of bending moment variation with moving vehicle at control section 21 and the effect function of measured bending moment variation with moving vehicle at control section 21 provides a direct, accurate, and comprehensive assessment of whether the bearing capacity of bridge 1 meets the requirements, overcoming the limitations of using the influence line multiplied by the theoretical load as an evaluation algorithm. Since the applied load acts on the entire bridge, each control section of the bridge has a fixed effect function of calculated bending moment variation with moving vehicle. Therefore, by placing strain gauges at a certain control section, the effect function of actual bending moment variation with moving vehicle at that control section can be detected, thus reducing the number of control sections and strain gauges required.

Claims

1. A method for loading tests on continuous beam bridges with varying spans, characterized in that, Includes the following steps: 1) Determination of control section: A control section is determined on the continuous beam bridge, which is a multi-span coupled continuous beam bridge. The load test method of continuous loading between spans is adopted, that is, a single triaxial test loading vehicle completes the load test method of continuous loading between spans. The control section is the key section of the continuous beam bridge with coupled load between spans. The location of the control section is set at the mid-span of the side span. 2) Measurement of data from the three-axle test loading vehicle: Measure the axle load and wheelbase of the three-axle test loading vehicle; 3) Establishment of the effect function of bending moment variation with moving vehicle: Based on the influence line curve of the bending moment of the control section and the axle load and number of axles of the three-axle test loading vehicle, calculate and analyze the effect function of bending moment variation with moving vehicle of any section, and calculate and analyze the area of ​​the interval of the effect function of bending moment variation with moving vehicle through integration. The expression for the effect function of the calculated bending moment at any cross section varying with the moving vehicle is: Where Xp is the distance from the rear axle of the triaxial test loading vehicle to the bridge origin. This is the expression for the influence line of bending moment calculation for any cross section. X is the coordinate of any cross section, Z1 is the rear axle distance, Z2 is the front axle distance, P1 is the first rear axle load, P2 is the second rear axle load, and P3 is the front axle load. In step 3), the establishment of the influence line curve for the calculated bending moment of the control section includes the following steps: B1: Measure the individual spans and the total span of the bridge, and measure the location of the control section; B2: Based on the data obtained in step B1 and the expression for the influence line influence factor, determine the influence line influence factor for each bridge span; B3: Based on the data obtained in step B2 and the expression for the influence line of the calculated bending moment of any cross section, determine the influence line of the calculated bending moment of the control section; When analyzing the influence line of the calculated bending moment of the control section on the corresponding bridge span, the position of the control section on the corresponding bridge span is determined, and the influence lines of the calculated bending moment of the control section on both ends of the corresponding bridge span are analyzed respectively. 4) Establishment of the effect function of measured bending moment changing with moving vehicles: A1: Determine the stiffness of the control section; A2: Arrange one or more strain gauges in the control section; A3: Drive the three-axle test loading vehicle from the beginning of the bridge to the end of the bridge. Calculate the effect function of the measured bending moment changing with the moving vehicle based on the data analysis of steps A1 and A2. Calculate the area of ​​the interval of the effect function of the measured bending moment changing with the moving vehicle through integral analysis. 5) Evaluation of bearing capacity: Place the area of ​​the calculated bending moment variation effect function with moving vehicle and the area of ​​the measured bending moment variation effect function with moving vehicle in the same coordinate system. By comparing the area of ​​the calculated bending moment variation effect function with moving vehicle and the area of ​​the measured bending moment variation effect function with moving vehicle, determine whether the continuous beam bridge meets the bearing capacity requirements. The verification coefficient is 1. When the ratio of the area of ​​the calculated bending moment variation effect function with respect to the moving vehicle to the area of ​​the measured bending moment variation effect function with respect to the moving vehicle is less than 1, the bearing capacity of the bridge meets the requirements. The ratio is the ratio of the area of ​​the calculated bending moment variation effect function with respect to the moving vehicle to the area of ​​the measured bending moment variation effect function with respect to the moving vehicle under the loading scenario of different spans of a continuous beam bridge.

2. The method for loading test of continuous beam bridges with varying spans according to claim 1, characterized in that: In step A3, ensure that the triaxial test loading vehicle passes slowly and uniformly from the bridgehead to the bridge tail.

3. The method for loading test of continuous beam bridges with varying spans according to claim 1, characterized in that: In step A1, the stiffness of the control section is calculated based on the bridge span length and concrete grade coefficient.

4. The method for loading test of continuous beam bridges with varying spans according to claim 1, characterized in that: The strain gauge acquires signals via a high-speed data acquisition device.

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