Strain influence line based rapid damage diagnosis method for transverse direction of precast assembly beam bridge

Abstract

The application relates to the technical field of bridge test detection, and particularly discloses a prefabricated assembled beam bridge transverse damage rapid diagnosis method based on strain influence lines, which comprises the following steps: arranging two strain measuring points on a to-be-detected prefabricated assembled beam bridge; applying a moving load to the span direction of the prefabricated assembled beam bridge by adopting a quasi-static loading mode; extracting the strain of the two measuring points under the action of the moving load; and fitting and drawing a strain influence line; calculating the total envelope area S between the strain influence line of the bridge measuring point and the transverse coordinate axis 总 , then calculating the change amplitude of the total envelope area i ; and qualitatively diagnosing the prefabricated assembled beam bridge transverse damage according to the measuring point i . The prefabricated assembled beam bridge transverse damage rapid diagnosis method can comprehensively diagnose the prefabricated assembled beam bridge transverse damage, and improves the accuracy of the damage diagnosis result. The method has the advantages of short diagnosis time, uninterrupted traffic and the like, can rapidly diagnose, reduces the test cost, and improves the economy.

Description

Technical Field

[0001] This invention relates to the field of bridge testing and inspection technology, and in particular to a rapid diagnostic method for transverse damage in precast assembled beam bridges based on strain influence lines. Background Technology

[0002] Precast assembled beam bridges, as a common bridge structure, are widely used in bridge engineering in my country. During their service life, due to the combined effects of various natural environmental factors over a long period, some bridges gradually deteriorate and age, resulting in reduced strength, decreased load-bearing capacity, and reduced reliability. In severe cases, this can even endanger pedestrian and vehicular safety. For precast assembled beam bridges, lateral damage reduces the overall integrity of the bridge, affects the lateral distribution of loads, and in severe cases, can even cause single-beam stress conditions, causing the load-bearing beam to exceed the design load, thus affecting bridge safety. Relevant data shows that lateral connection defects in precast assembled beam bridges first manifest as damage to the diaphragms. Only when the diaphragms are severely damaged will damage occur in the cast-in-place wet joint sections. Therefore, the diagnosis of lateral bridge damage mainly focuses on the damage status of the diaphragms. However, current technologies cannot achieve rapid and accurate qualitative diagnosis of lateral damage in precast assembled beam bridges, making it difficult to quickly locate the damage position and quantify the degree of damage. This undoubtedly increases the difficulty of bridge maintenance and repair.

[0003] Currently, several commonly used diagnostic methods exist in bridge inspection: visual inspection, expert experience-based diagnosis, design code-based methods, reliability analysis, health monitoring system-based methods, and load testing. Each of these methods has its limitations. Visual inspection is highly dependent on human factors, time-consuming, and easily influenced by the subjective opinions of the investigators. Furthermore, the investigation process is often superficial, overlooking important components that are invisible to the naked eye. Expert experience-based diagnosis is time-consuming, requiring extensive documentation and coordination, making it inconvenient and uneconomical for small to medium-sized precast beam bridges. Design code-based methods are challenging for bridges with long service lives, as comprehensive data may be lacking, making detailed and thorough diagnosis difficult. The main problems with reliability analysis are: in reality, the factors affecting reliability are quite complex, and further theoretical research is needed to comprehensively study the impact of various factors on structural damage. The main problems with assessment methods based on bridge health monitoring systems are: first, they require substantial financial investment and are only applicable to bridges with particularly complex structures and of significant importance; second, they lack comprehensive indicators, making it difficult to reflect the relationship between the local and the overall structure; and third, the complexity of the structural system presents a contradiction between the fineness of structural system division and computational costs, leading to difficulties in diagnosing bridge damage. The main problems with load testing are: first, bridge engineering reports and crude inspection methods cannot reflect the true condition of the bridge, and hastily conducting load tests can easily cause structural damage; second, the test results are immediate and cannot dynamically reflect the bridge's safety status, which is a limitation for large and complex bridges that require real-time reflection of their condition; and third, with economic development and significant traffic pressure, closing traffic for load tests would result in substantial economic losses. None of these diagnostic methods can achieve rapid, accurate qualitative diagnosis, location, and quantitative analysis of transverse damage in precast assembled beam bridges. Summary of the Invention

[0004] The purpose of this invention is to provide a rapid diagnostic method for transverse damage of precast assembled beam bridges based on strain influence lines, enabling rapid and accurate qualitative diagnosis, localization, and quantitative analysis of transverse damage in precast assembled beam bridges.

[0005] To achieve the above objectives, this invention provides a rapid diagnosis method for transverse damage of precast assembled beam bridges based on strain influence lines, comprising the following steps:

[0006] (1) Two strain measuring points are arranged on the precast assembled beam bridge to be tested. One measuring point C is located on the loaded beam, and the other measuring point A is located on the unloaded beam. The measuring points are arranged at the section with the maximum bending moment, i.e. the section with the maximum strain. The loaded beam refers to the beam where the moving load is applied.

[0007] (2) Apply a moving load to the precast assembled beam bridge in the span direction using a quasi-static loading method. Extract the two measuring points under the moving load and use the "least square method" or "moving average method" to fit and draw the strain influence line. The horizontal axis of the strain influence line is the position coordinate value of the moving load along the bridge structure span, and the vertical axis is the strain value at the measuring point corresponding to the moving load at different coordinates.

[0008] (3) Calculate the total envelope area S between the strain influence line of the bridge measuring point and the horizontal axis. 总 Then calculate the change in the total envelope area ΔS. i The calculation formula is as follows:

[0009]

[0010] In the formula, L is the total span of the bridge, and ε i (x) represents the measured strain influence line, ε0(x) represents the theoretical strain influence line, and ΔS i The change in the total envelope area of ​​measurement point i;

[0011] (4) Based on the two measuring points ΔS i Qualitative diagnosis of transverse bridge damage in precast assembled beam bridges is performed, with the diagnostic criteria being: ΔS C and ΔS A When ΔS is zero, the transverse diaphragms of the beam bridge are undamaged; C For positive values, ΔS A When the value is negative, the transverse diaphragm at the mid-span of the beam bridge is damaged; ΔS C Negative value, ΔS A When the value is positive, the transverse diaphragm on the side of the beam bridge is damaged.

[0012] In this invention, the strain influence line is a novel concept proposed based on the combination of strain and influence lines. It represents a curve showing the change in strain at a measuring point on the bridge structure as the moving load changes with the position of the moving load under the action of a load moving along the span direction of the bridge structure. Transverse damage in precast assembled beam bridges primarily manifests as damage to the transverse diaphragms. Only when the transverse diaphragm damage is relatively severe will damage occur in the cast-in-place section of the wet joint. Therefore, the diagnosis of transverse damage mainly focuses on diagnosing the damage condition of the transverse diaphragms.

[0013] Preferably, in the above-mentioned rapid diagnosis method for transverse damage of precast assembled beam bridge, in step (1), the two strain measuring points are located at the middle position of the span of the precast assembled beam bridge.

[0014] Preferably, in the above-mentioned rapid diagnosis method for transverse bridge damage of precast assembled beam bridge, the pseudo-static loading method in step (2) is as follows: the loading vehicle travels at a uniform low speed along the center line of the bridge deck from the end of the bridge to the end of the bridge to complete the entire loading process. The uniform low speed refers to no more than 50% of the speed limit. The lower the speed, the better the diagnostic effect.

[0015] Preferably, in the above-mentioned rapid diagnosis method for transverse damage of precast assembled beam bridges, the loading path and arrangement are as follows: single-row loading under positive load path, with three-axle or four-axle heavy-duty vehicles for loading, which has the best loading efficiency, does not interrupt traffic, and facilitates the collection of test data.

[0016] Preferably, in the above-mentioned rapid diagnosis method for transverse damage of precast assembled beam bridge, in step (3), the theoretical strain influence line ε0(x) is obtained by modeling and finite element calculation.

[0017] Preferably, in the above-mentioned rapid diagnosis method for transverse damage of precast assembled beam bridges, in step (4), two measuring points ΔS are established on the same coordinate axis. i Bar chart, ΔS i By comparing the bar chart with the qualitative diagnostic chart of the injury, a qualitative diagnostic result can be obtained.

[0018] Preferably, the above-mentioned rapid diagnosis method for transverse damage of precast assembled beam bridges also includes the localization and quantitative diagnosis of transverse damage in precast assembled beam bridges, with specific steps including:

[0019] S1. Divide the influence lines of the beam measuring points obtained in step (2) into n intervals with length c along the longitudinal direction, and calculate the envelope area S between the influence lines of each interval and the horizontal axis. ii ;

[0020] S2. Calculate the difference ΔS between the envelope area of ​​each interval of the damaged beam and the envelope area in the undamaged state. ii ;

[0021] S3. Plot the difference curve of the envelope area of ​​the measurement point interval, use the peak position of the difference curve for local diagnosis, and use the change range of the peak of the difference curve for quantitative diagnosis.

[0022] In the transverse damage localization and quantitative diagnosis of prefabricated assembled beam bridges of the present invention, the smaller the c value and the larger the n value, the better the diagnostic effect.

[0023] Preferably, in the above-mentioned rapid diagnosis method for transverse damage of precast assembled beam bridges, in step S1, the envelope area S ii The calculation formula is as follows:

[0024]

[0025] In the formula, l iLet ε be the x-coordinate of the midpoint of interval i, c be the length of each interval division of the strain influence line at the measuring point, and ε be the x-coordinate of the midpoint of interval i. i (x) represents the strain influence line of the measuring point interval i, S ii Let be the envelope area of ​​the strain influence line interval i at the measuring point.

[0026] Preferably, in the above-mentioned rapid diagnosis method for transverse damage of precast assembled beam bridges, in step S2, the difference ΔS ii The calculation formula is as follows:

[0027]

[0028] In the formula, l i Let ε be the x-coordinate of the midpoint of interval i, c be the length of each interval division of the strain influence line at the measuring point, and ε be the x-coordinate of the midpoint of interval i. ii (x) represents the expression for the strain influence line of the measuring point interval i under the beam damage state, ε i0 (x) is the expression for the strain influence line of the measuring point interval i in the non-destructive state of the beam (the theoretical strain influence line of interval i), ΔS ii Let be the difference between the envelope area of ​​the strain influence line interval i at the measuring point and the envelope area under the undamaged state.

[0029] Preferably, in the above-mentioned rapid diagnosis method for transverse damage of precast assembled beam bridges, in step S3, the location where the peak value of the curve showing the difference in the envelope area of ​​the measuring point interval appears is the location of the damaged transverse diaphragm.

[0030] Preferably, in the above-mentioned rapid diagnosis method for transverse damage of precast assembled beam bridges, in step S3, the change range of the damage degree is proportional to the change range of the peak value of the difference curve of the interval envelope area, with a ratio of 1:4, and the damage degree is quantitatively diagnosed by using the change range of the peak value of the difference curve.

[0031] The aforementioned rapid diagnostic method for transverse damage in precast assembled beam bridges is used for rapid qualitative, locational, or quantitative diagnosis of transverse diaphragm damage in normally operating precast assembled beam bridges, old bridges, or dangerous bridges.

[0032] Compared with existing technologies, the present invention has the following advantages:

[0033] The present invention provides a rapid diagnosis method for transverse damage in precast assembled beam bridges. This method applies a moving load using a quasi-static loading approach and, based on strain influence lines, achieves a comprehensive qualitative, locational, and quantitative diagnosis of transverse damage in precast assembled beam bridges, thus improving the accuracy of the damage diagnosis results. It features short diagnosis time, non-disruption of traffic flow, minimal impact on bridge traffic, rapid diagnosis of transverse damage, reduced testing costs, and improved economic efficiency, making it of significant importance and practical value. Attached Figure Description

[0034] Figure 1This is a flowchart of the rapid qualitative diagnosis method for transverse damage of precast assembled beam bridges in Embodiment 1 of the present invention.

[0035] Figure 2 The following is a qualitative diagnostic diagram of transverse damage to the precast assembled beam bridge in Embodiment 1 of the present invention: (a) diagram of the undamaged state of the transverse diaphragm of the beam bridge; (b) diagram of the damaged state of the transverse diaphragm at the mid-span of the beam bridge; (c) diagram of the damaged state of the transverse diaphragm on one side of the beam bridge.

[0036] Figure 3 The diagram shows the structure and dimensions of the prefabricated assembled beam bridge in Example 1 of this invention. The dimensions are in mm.

[0037] Figure 4 This is a diagram showing the arrangement of strain measurement points in Embodiment 1 of the present invention.

[0038] Figure 5 This is a schematic diagram of the loading position of the moving load in Embodiment 1 of the present invention.

[0039] Figure 6 The theoretical and measured strain influence lines of measuring point A on the side beam and measuring point C on the middle beam when the transverse diaphragm of the example beam bridge in Embodiment 1 of the present invention is damaged.

[0040] Figure 7 This is a qualitative diagnostic diagram of damage to a single-sided transverse diaphragm in an example beam bridge in Embodiment 1 of the present invention.

[0041] Figure 8 The theoretical and measured strain influence lines of measuring point A on the side beam and measuring point C on the middle beam are shown in Example 1 of the present invention when the transverse diaphragm at the mid-span of the beam bridge is damaged.

[0042] Figure 9 This is a qualitative diagnostic diagram of damage to the mid-span transverse diaphragm of the example beam bridge in Embodiment 1 of the present invention.

[0043] Figure 10 This is a flowchart of the method for rapid location and quantitative diagnosis of transverse damage in a precast assembled beam bridge in Embodiment 2 of the present invention.

[0044] Figure 11 This is a diagram showing the influence of the strain line on the method for rapid location and quantitative diagnosis of transverse damage in precast assembled beam bridges in Embodiment 2 of the present invention.

[0045] Figure 12 The theoretical and measured strain influence lines of measuring point C in the middle beam when the transverse diaphragm 2 on one side of the beam bridge is damaged in Embodiment 2 of the present invention.

[0046] Figure 13 The difference ΔS is the area of ​​the interval envelope of measuring point C in the middle beam when the transverse diaphragm 2 on one side of the beam bridge is damaged in Embodiment 2 of the present invention. ii .

[0047] Figure 14This is the theoretical and measured strain influence line of the measuring point C in the middle beam when the transverse diaphragm 3 in the mid-span of the example beam bridge in Embodiment 2 of the present invention is damaged.

[0048] Figure 15 The difference ΔS is the area of ​​the interval envelope of measuring point C in the middle beam when the mid-span transverse diaphragm 3 of the example beam bridge in Embodiment 2 of the present invention is damaged. ii . Detailed Implementation

[0049] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0050] Example 1

[0051] A rapid qualitative diagnosis method for transverse damage in precast assembled beam bridges based on strain influence lines, with the diagnostic flowchart shown below. Figure 1 As shown, it includes the following steps:

[0052] (1) Two strain measuring points are arranged at the mid-span of the precast assembled beam bridge to be tested, one measuring point C is located on the middle beam and the other measuring point A is located on the side beam;

[0053] (2) The quasi-static loading method was used to apply the moving load. The test loading vehicle moved at a constant low speed along the center line of the bridge deck from the end of the bridge to the end of the bridge to complete the entire loading process. The middle beam was the loading beam. The strain of measuring points C and A under the action of the moving load was extracted. The strain influence line was plotted by fitting the "least square method". The strain influence line represents a curve generated by the change of the strain at the measuring point of the bridge structure with the position of the moving load under the action of the load moving along the span of the bridge structure. The horizontal axis of the strain influence line is the position coordinate value of the moving load along the span of the bridge structure, and the vertical axis is the strain value at the measuring point corresponding to the moving load at different coordinates.

[0054] (3) Calculate the total envelope area S between the strain influence line of the bridge measuring point and the horizontal axis. 总 Then calculate the change in the total envelope area ΔS. i The calculation formula is as follows:

[0055]

[0056]

[0057] In the formula, L is the total span of the bridge, ε(x) is the strain influence line at the measuring point, and ε i (x) represents the measured strain influence line, ε0(x) represents the theoretical strain influence line, and ΔS i The change in the total envelope area of ​​measurement point i;

[0058] (4) Based on the two measuring points ΔS iQualitative diagnosis of transverse damage to precast assembled beam bridges: Establish two measuring points ΔS on the same coordinate axis. i Bar chart, ΔS i Bar chart comparison of qualitative diagnosis of injury (see) Figure 2 This leads to a qualitative diagnosis. Figure 2 (a) shows the undamaged state of the transverse diaphragm of the beam bridge, ΔS C and ΔS A (a) is zero, indicating no damage to the transverse diaphragm of the beam bridge; (b) is a damage diagram of the transverse diaphragm at mid-span of the beam bridge, ΔS C For positive values, ΔS A When the value is negative, the mid-span transverse diaphragm of the beam bridge is damaged; (c) is a diagram showing the damage status of a single-sided transverse diaphragm of the beam bridge, ΔS C Negative value, ΔS A When the value is positive, the transverse diaphragm on one side of the beam bridge is damaged.

[0059] Taking a 40m span, 5-piece T-beam bridge as an example, after consulting design literature, its main parameters are as follows: span 40m, bridge width 11.25m, T-beam height 2.5m. The material properties of the T-beams are: elastic modulus E = 3.45 × 10⁻⁶. 10 Pa, torsional modulus G = 0.425E = 1.47 × 10 10 Pa, bulk density ρ = 2500 kg / m³ 3 Poisson's ratio μ = 0.2. Transverse diaphragms are installed at the bridge supports, 1 / 4 section, 2 / 4 section, and 3 / 4 section. The diaphragm thickness is 0.2m and the height is 2.25m. T-beams are numbered from A to E; T-beam dimensions are shown below. Figure 3 Diagnostic tests were performed for two working conditions: damage to the mid-span diaphragm 3 and damage to the unilateral diaphragm 2.

[0060] Modeling and analysis were performed using the finite element software Midas Civil. The load path was selected directly above beam C. 801 nodes were established at equal intervals along the beam's centerline, and moving loads were simulated by applying single-point loads to these nodes. Using this method, the strain influence line obtained from the numerical simulation achieved an accuracy of 0.05m on the horizontal axis. The model consisted of 7204 elements and 4005 nodes, used to calculate the theoretical strain influence line.

[0061] Measuring points C and A are respectively arranged on the middle beam and the side beam at the mid-span of the beam bridge, such as... Figure 4 , Figure 5 As shown. A 100kN loading test vehicle was selected and subjected to a quasi-static loading method, with uniform low-speed loading along the centerline of the bridge deck, as follows. Figure 5 As shown. Since the loading vehicle travels along the centerline of the bridge deck, beam C in the middle is the loaded beam, and the other four beams are unloaded beams.

[0062] (1) Damage to one side of the diaphragm

[0063] The theoretical and measured strain influence lines of measuring point A on the side beam and measuring point C on the middle beam, such as... Figure 6 As shown. Finite element calculation results: SA 理论 =37.03 (με.m), SC 理论 = 30.19 (με.m); On-site measurement results by testing personnel: SA 实测 =37.92 (με.m), SC 实测 =28.84 (με.m). Variation in the total envelope area of ​​the measuring points on the side beams and middle beams: △SA = 2.42%; △SC = -4.46%. Based on the variation in the total envelope area of ​​the measuring points on the side beams and middle beams, a qualitative diagnostic diagram of transverse damage for precast assembled beam bridges can be drawn, such as... Figure 7 As shown. The test results are consistent with... Figure 2 (c) Correspondingly, the precast assembled beam bridge suffered transverse bridge damage, and it was damage to a single side of the transverse diaphragm.

[0064] (2) Damage to the mid-span diaphragm

[0065] The theoretical and measured strain influence lines of measuring point A on the side beam and measuring point C on the middle beam, such as... Figure 8 As shown. Finite element calculation results: SA 理论 =37.03 (με.m), SC 理论 = 30.19 (με.m); On-site measurement results by testing personnel: SA 实测 =34.58 (με.m); SC 实测 =34.42 (με.m). Variation in the total envelope area of ​​the measuring points on the side beams and middle beams: ΔSA = -6.62%, ΔSC = 14%; Based on the variation in the total envelope area of ​​the measuring points on the side beams and middle beams, a qualitative diagnostic diagram of transverse damage for precast assembled beam bridges can be drawn, such as... Figure 9 As shown. The test results are consistent with... Figure 2 (b) Correspondingly, the precast assembled beam bridge suffers transverse bridge damage, which is damage to the mid-span transverse diaphragm.

[0066] Example 2

[0067] A rapid and quantitative diagnosis method for transverse damage in precast assembled beam bridges based on strain influence lines, with a diagnostic flowchart as follows: Figure 10 As shown, it includes the following steps:

[0068] S1. Same as steps (1) and (2) in Example 1, obtain the strain influence line of the measuring point;

[0069] S2. Divide the strain influence line of the beam measuring points into n intervals along the longitudinal direction with a length of c at equal intervals (see...). Figure 11Let each interval be named as: interval 1, interval 2, interval 3... interval n, and calculate the area S of the envelope between the influence line of each interval and the horizontal axis. ii The calculation formula is as follows:

[0070]

[0071] In the formula, l i Let ε be the x-coordinate of the midpoint of interval i, c be the length of each interval division of the strain influence line at the measuring point, and ε be the x-coordinate of the midpoint of interval i. i (x) represents the strain influence line of the measuring point interval i, S ii Let i be the envelope area of ​​the strain influence line interval i at the measuring point;

[0072] S3. Calculate the difference ΔS between the envelope area of ​​each interval of the damaged beam and the envelope area in the undamaged state. ii The calculation formula is as follows:

[0073]

[0074] In the formula, l i Let ε be the x-coordinate of the midpoint of interval i, c be the length of each interval division of the strain influence line at the measuring point, and ε be the x-coordinate of the midpoint of interval i. ii (x) represents the expression for the strain influence line of the measuring point interval i under the beam damage state, ε i0 (x) is the expression for the strain influence line of the measuring point interval i in the non-destructive state of the beam (the theoretical strain influence line of interval i), ΔS ii The difference between the envelope area of ​​the strain influence line interval i at the measuring point and the envelope area under the undamaged state;

[0075] S4. Plot the curve of the difference in the envelope area of ​​the measurement point interval. Use the peak position of the curve of the difference in the envelope area of ​​the interval for local diagnosis. The location of the peak is the location of the damaged diaphragm. The change in the degree of damage is proportional to the change in the peak value of the curve of the difference in the envelope area of ​​the interval, with a ratio of 1:4. Use the change in the peak value of the difference curve for quantitative diagnosis.

[0076] Taking a 40m span, 5-segment T-beam bridge from Example 1 as an example, with the same bridge parameters as in Example 1, diagnoses were performed for two conditions: 80% damage to the mid-span diaphragm 3 and 80% damage to a single-sided diaphragm 2. Measuring point C was placed at the mid-span of the bridge beam, with the same loading method as in Example 1.

[0077] (1) Damage to diaphragm 2

[0078] Under quasi-static loading, strain influence lines are plotted by extracting strain at measuring point C and fitting the strain, as shown below. Figure 12 As shown in Table 1, the span of the precast assembled beam bridge is 40m. In this calculation example, the equal division interval c is taken as 5m, and the strain influence line of the measuring point is divided into 8 intervals at equal intervals.

[0079] Table 1. Strain Influence Line Interval Division Table (Unit: m)

[0080]

[0081] Based on the difference ΔS of the area of ​​the interval envelope ii The calculation formula yields the strain meter difference curves for each interval between the measured state and the undamaged state at measuring point C, as shown in the figure. Figure 13 As shown in the figure, the peak value of the strain gauge difference curve at measuring point C is located in interval 2, with a peak value of -0.508. Furthermore, due to the finite element analysis showing that the diaphragm 2 is 40% damaged, the peak value of the difference curve at measuring point C is -0.191. Therefore, the diagnostic result can be concluded that the damaged diaphragm is located within (5, 10) m, and the degree of damage is...

[0082] (2) Damage to diaphragm 3

[0083] Under quasi-static loading, strain influence lines are plotted by extracting strain at measuring point C and fitting the strain, as shown below. Figure 14 As shown in the table. Similarly, the strain influence lines are divided into 8 equally spaced intervals, as shown in Table 1. The difference in the area envelope of each interval, ΔS... ii The calculation formula yields the strain meter difference curves for each interval between the measured state and the undamaged state at measuring point C, as shown in the figure. Figure 15 As shown. The peak value of the strain gauge difference curve at measuring point C is located in interval 4, with a peak value of 1.380. Furthermore, due to the finite element analysis showing that diaphragm 3 is 40% damaged, the peak value of the difference curve at measuring point C is 0.515. Therefore, the diagnostic result can be concluded that the damaged diaphragm is located within (15, 20) m, and the degree of damage is...

[0084] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A rapid diagnosis method for transverse damage of precast assembled beam bridges based on strain influence lines, characterized in that, Includes the following steps: (1) Two strain measuring points are arranged on the precast assembled beam bridge to be tested, one measuring point C is located on the loaded beam, and the other measuring point A is located on the unloaded beam; (2) Apply a moving load to the span direction of the precast assembled beam bridge using a quasi-static loading method, extract the strain of the two measuring points under the moving load, and use the least squares method or the moving average method to fit and draw the strain influence line. (3) Calculate the total envelope area between the strain influence line of the bridge measuring point and the horizontal axis. Then calculate the change in the total envelope area. The calculation formula is as follows: In the formula, L is the total span of the bridge. For the measured strain influence line, This is the theoretical strain influence line. For measuring points i The range of change in the total envelope area; (4) Based on the two measuring points Qualitative diagnosis of transverse damage to precast assembled beam bridges is performed, and the diagnostic criteria are as follows: and When the value is zero, the transverse diaphragms of the beam bridge are undamaged; For positive values When the value is negative, the transverse diaphragm at the mid-span of the beam bridge is damaged; Negative values When the value is positive, the transverse diaphragm on the side of the beam bridge is damaged; It also includes the location and quantitative diagnosis of transverse damage to precast assembled beam bridges, with specific steps including: S1. Divide the influence lines of the beam measuring points obtained in step (2) into n intervals with length c along the longitudinal direction, and calculate the envelope area between the influence lines of each interval and the horizontal axis. ; S2. Calculate the difference between the envelope area of ​​each interval of the damaged beam and the envelope area under the undamaged state. ; S3. Plot the difference curve of the envelope area of ​​the measurement point interval, and use the peak position of the difference curve for local diagnosis. The change in the degree of damage is proportional to the change in the peak value of the difference curve of the envelope area of ​​the interval, with a ratio of 1:

4. Use the change in the peak value of the difference curve for quantitative diagnosis.

2. The rapid diagnosis method for transverse damage of precast assembled beam bridges according to claim 1, characterized in that, In step (1), the two strain measuring points are located at the middle of the span of the precast assembled beam bridge.

3. The rapid diagnosis method for transverse damage of precast assembled beam bridges according to claim 1, characterized in that, In step (2), the pseudo-static loading method is as follows: the loading vehicle travels at a uniform low speed along the center line of the bridge deck from the end of the bridge to the end of the bridge to complete the entire loading process. The uniform low speed means not exceeding 50% of the speed limit.

4. The rapid diagnosis method for transverse damage of precast assembled beam bridges according to claim 1, characterized in that, In step S1, the envelope area The calculation formula is as follows: In the formula, l i For interval i The x-coordinate value of the middle position, where c is the length of each interval of the strain influence line at the measuring point. For the measurement point interval i Strain influence line The range of strain influence lines at the measuring points i The envelope area.

5. The rapid diagnosis method for transverse damage of precast assembled beam bridges according to claim 1, characterized in that, In step S2, the difference The calculation formula is as follows: In the formula, l i For interval i The x-coordinate value of the middle position, where c is the length of each interval of the strain influence line at the measuring point. The expression for the strain influence line of the measuring point interval i under the damage state of the beam is given. Here is the expression for the strain influence line of the measuring point interval i in the non-destructive state of the beam. Let be the difference between the envelope area of ​​the strain influence line interval i at the measuring point and the envelope area under the undamaged state.

6. The rapid diagnosis method for transverse damage of precast assembled beam bridges according to claim 1, characterized in that, In step S3, the location where the peak of the curve of the difference in the envelope area of ​​the measuring point interval appears is the location of the damaged diaphragm.

7. The rapid diagnosis method for transverse damage of precast assembled beam bridges according to any one of claims 1 to 6, characterized in that, The diagnostic method is used for rapid qualitative, locational, or quantitative diagnosis of diaphragm damage in precast assembled beam bridges, old bridges, or dangerous bridges in normal operation.

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