Method for diagnosing damage of precast assembled beam bridge in longitudinal direction

Abstract

The present application relates to the technical field of bridge health monitoring and detection, and discloses a prefabricated assembled beam bridge longitudinal damage rapid diagnosis method, which comprises the following steps: collecting actual structure parameters of a bridge, establishing a bridge finite element calculation model for calculating a theoretical strain influence line; arranging strain measuring points at the longitudinal midspan of the two outer side beams and the middle beam of the prefabricated assembled beam, and performing a pseudo-static loading test; extracting the strain of the beam bridge strain measuring points, fitting and drawing a strain influence line; calculating the total strain meters of the two outer side beam strain measuring points; calculating the total strain meter change amplitude ΔS of the two outer side beam measuring points; establishing a ΔS column chart of the two in the same coordinate axis, and comparing with a longitudinal damage qualitative diagnosis graph system to obtain a qualitative diagnosis result. The prefabricated assembled beam bridge longitudinal damage rapid diagnosis method has the advantages of short diagnosis time, no interruption of traffic, improved economy, realization of rapid comprehensive diagnosis of the prefabricated assembled beam bridge longitudinal damage, and improved diagnosis accuracy.

Description

Technical Field

[0001] This invention belongs to the field of bridge health monitoring and detection technology, and specifically relates to a rapid diagnosis method for longitudinal damage in precast assembled beam bridges. Background Technology

[0002] Precast assembled beam bridges offer advantages such as rapid construction, reliable quality, durability, and environmental friendliness, and are widely used in bridge engineering in my country. During their service life, due to the combined long-term effects of various natural environmental factors, some bridges gradually deteriorate and age, leading to reduced strength, decreased load-bearing capacity, and reduced reliability. In severe cases, this can even endanger pedestrian and vehicular safety. Longitudinal damage to the beam structure, represented by concrete cracking, breakage, and carbonation, is a significant factor jeopardizing bridge safety. Rapid and accurate diagnosis of this damage is one of the effective measures to ensure safe bridge operation and prevent bridge accidents.

[0003] Currently, the commonly used damage diagnosis methods for bridges in service are mainly based on visual inspection and load testing. Visual inspection-based methods rely on the engineering experience and subjective judgment of inspectors to statistically analyze the bridge's external defects. The analysis results are then combined with the highway bridge technical condition assessment standards to evaluate the bridge's technical condition level. This method has the following drawbacks: it is too subjective, and the reliability of the diagnostic results depends entirely on the inspector's experience and knowledge; the process is cumbersome and inconvenient, and it is difficult to conduct a thorough and comprehensive inspection of some hidden parts of the bridge structure. Load testing-based methods are currently the most widely used bridge damage diagnosis method in bridge inspection, offering greater intuitiveness and objectivity than visual inspection methods. Load testing is divided into static load testing and dynamic load testing. Static load testing mainly uses a graded loading method, applying external loads to the bridge structure that are roughly equivalent to the design load or service load. Testing instruments are used to measure the changes in deflection, stress, cracks, and lateral distribution coefficient of the control parts and sections of the bridge structure under each level of test load. The measured values ​​are compared with the theoretical calculation values ​​under the corresponding loads to diagnose the overall health condition of the bridge structure. Dynamic load testing mainly involves pulsation testing, vehicle driving, jumping, braking, or other excitation tests on the bridge structure to test the dynamic deflection, dynamic strain, and modal parameters of various control parts of the bridge structure. The modal parameters are then used to identify the damaged areas of the structure. The diagnostic method based on load testing has the following main shortcomings: it requires prolonged traffic closure, which disrupts normal traffic; the large loading volume and the graded loading and unloading method make the loading process cumbersome, time-consuming, and uneconomical; and while it mainly diagnoses the overall health condition of the bridge, the diagnostic indicators are limited, resulting in coarse and inaccurate diagnostic results. The above methods are insufficient for the rapid and accurate diagnosis of longitudinal damage in precast assembled beam bridges.

[0004] This study proposes a method for diagnosing damage to precast assembled beam bridges that is non-disruptive to traffic, easy and quick to operate, and provides detailed diagnostic results. The experimental process is rapid and economical, and the results are more precise. This method can provide a reliable and effective basis for extending the service life of bridges and formulating maintenance plans, thus having significant social benefits. Summary of the Invention

[0005] The purpose of this invention is to provide a rapid diagnostic method for longitudinal damage in precast assembled beam bridges, overcoming the shortcomings of existing diagnostic methods that are difficult to quickly diagnose, locate, and quantify longitudinal damage in precast assembled beam bridges.

[0006] To achieve the above objectives, this invention provides a rapid diagnosis method for longitudinal damage of precast assembled beam bridges, comprising the following steps:

[0007] (1) Based on the theoretical structural parameters of the bridge, a finite element calculation model of the bridge is established to calculate the theoretical strain influence line;

[0008] (2) Strain measuring points A, E, and C are arranged at the mid-span of the two outer beams and the middle beam of the precast assembled beam bridge, and then a pseudo-static loading test is carried out: the test loading vehicle moves at a constant low speed along the bridge deck from the end of the bridge to the end of the bridge to apply a moving load to the beam bridge.

[0009] (3) Extract the strain at the strain measurement points of the beam bridge under the action of moving load, and fit and draw the strain influence line;

[0010] (4) Calculate the total strain meters at strain measuring points A and E on the two outer beams. The total strain meters is the total envelope area between the strain influence line at the bridge structure measuring point and the horizontal axis under the action of moving load.

[0011] (5) Calculate the total strain meter variation range ΔSA and ΔSE at measuring points A and E. The total strain meter variation range is the total strain meter measured in step (4) minus the theoretical total strain meter. The theoretical total strain meter is the total envelope area between the theoretical strain influence line and the horizontal axis.

[0012] (6) Establish ΔS bar charts for both on the same coordinate axis, compare them with the longitudinal bridge damage qualitative diagnosis charts, and obtain the qualitative diagnosis results.

[0013] 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 strain at a measuring point on the bridge structure as the position of the moving load changes under the action of a load moving along the span of the bridge structure. The abscissa of the strain influence line is the position coordinate value of the moving load along the span of the bridge structure, and the ordinate is the strain value at the measuring point corresponding to the moving load at different coordinates. Total strain meters is a further concept proposed based on the strain influence line, referring to the total envelope area between the strain influence line at the measuring point of the bridge structure and the abscissa axis under the action of a moving load. The calculation formula is:

[0014]

[0015] In the formula, L is the total span of the bridge; S 总 Let ε(x) be the total strain in meters at the measuring point, and ε(x) be the strain influence line at the measuring point. Total strain in meters differs from the general statics concept; it is a characteristic value of a function reflecting the continuous strain response of a bridge structure under longitudinal moving loads. Compared to static measurements of bridges, it contains more structural information. Therefore, changes in the total strain in meters at bridge measuring points are more effective in reflecting the damage status and performance changes of the bridge structure.

[0016] Preferably, in the above-mentioned rapid diagnosis method for longitudinal bridge damage of precast assembled beam bridges, in step (1), the finite element calculation model is calculated based on the following formula:

[0017]

[0018] In the formula, ε(x) is the strain influence line of longitudinal beam k, L is the total span of the bridge, EI is the stiffness of the measuring point section, l is the distance from the measuring point section to the bridge end, y is the distance from the lower edge of the measuring point section to the neutral axis of the section; x is the distance between the location of the moving load F and the bridge end, αη ki This is the actual transverse distribution coefficient of longitudinal beam k.

[0019] According to Hooke's Law, the expression for the cross-sectional strain at a point B, any distance l from the beam end, on a simply supported beam is as follows:

[0020]

[0021] In the formula, L is the span of a simply supported single beam, EI is the stiffness of the measuring point section, and y is the distance from the lower edge of the measuring point section to the neutral axis of the section. Precast assembled beam bridges are generally beam bridge structures composed of multiple longitudinal beams and transverse connections. Unlike simply supported single beam structures, when a load F is applied, the transverse connections of the structure cause each longitudinal beam to participate in the load-bearing work to varying degrees. Therefore, the transverse distribution coefficient αη needs to be considered when calculating the strain influence line expression for precast assembled beam bridges. ki A moving load F is applied to beam i of a precast assembled beam bridge. The load borne by beam i is F. i =αη ii The load borne by beam F, k is F k =αη ki F, yielding beam B of the actual precast assembled beam bridge. k The analytical expression for the strain influence line at the measuring point of the section is given in formula (1-2).

[0022] Preferably, in the above-mentioned rapid diagnosis method for longitudinal damage of precast assembled beam bridges, the theoretical total strain meter expression for the measuring point of beam section k is:

[0023]

[0024] In the formula, L is the total span of the bridge, EI is the stiffness of the measuring point section; l is the distance from the measuring point section to the bridge end, y is the distance from the lower edge of the measuring point section to the neutral axis of the section, x is the distance between the location of the moving load F and the bridge end, and αη ki This is the actual transverse distribution coefficient of longitudinal beam k.

[0025] Preferably, in the above-mentioned rapid diagnosis method for longitudinal bridge damage of precast assembled beam bridge, in step (2), the loading path and arrangement of the test loading vehicle is a single row of vehicles under the 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 is conducive to the collection of test data.

[0026] Preferably, in the above-mentioned rapid diagnosis method for longitudinal bridge damage of precast assembled beam bridge, in step (2), the test loading vehicle passes through the bridge deck at a uniformly low speed along the center line of the bridge deck. The uniformly low speed means no more than 50% of the speed limit, and the lower the speed, the better the diagnostic effect.

[0027] Preferably, in the above-mentioned rapid diagnosis method for longitudinal bridge damage of precast assembled beam bridge, in step (3), the least squares method is used to fit and draw the strain influence line.

[0028] Preferably, in the above-mentioned rapid diagnosis method for longitudinal bridge damage of precast assembled beam bridges, in step (6), the diagnostic criteria for the qualitative diagnosis system of longitudinal bridge damage are as follows:

[0029] When ΔSA and ΔSE are zero, the precast assembled beam bridge body is in an undamaged state;

[0030] When ΔSA is negative and ΔSE is zero, the outer beam at measuring point A is damaged.

[0031] When ΔSA is positive and ΔSE is zero, the side beam adjacent to the outer beam where measuring point A is located is damaged;

[0032] When ΔSA and ΔSE are positive, the middle beam is damaged;

[0033] When ΔSA is zero and ΔSE is positive, the side beam adjacent to the outer beam where measuring point E is located is damaged;

[0034] When ΔSA is zero and ΔSE is negative, the outer beam at measuring point E is damaged.

[0035] Preferably, the above-mentioned rapid diagnosis method for longitudinal damage of precast assembled beam bridges further includes the following steps:

[0036] (7) Divide the strain influence line of the measuring points of the damaged beam into n intervals with length c along the longitudinal direction of the bridge, and calculate the interval strain in meters S for each interval. ii ;

[0037] (8) Calculate the range of strain per meter change ΔS ii The variation range of the total strain meter in the interval is the interval strain meter measured in step (7) minus the theoretical total strain meter in the interval;

[0038] (9) Based on the variation range ΔS of the strain meter in the interval ii Longitudinal bridge damage was located and quantified, ΔS iiThe interval containing the maximum absolute value is the location interval of the damage; when the damaged beam is a loaded beam, the degree of damage to the damaged beam is ΔS. ii Twice the absolute value; when the damaged beam is an unloaded beam, the degree of damage to the damaged beam is ΔS. ii Four times the absolute value.

[0039] Preferably, in the above-mentioned rapid diagnosis method for longitudinal bridge damage of precast assembled beam bridges, in step (7), the interval strain meter S ii The calculation formula is as follows:

[0040]

[0041] 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) is the expression for the strain influence line of the measuring point interval i, S i Let be the interval strain in meters of the strain influence line interval i at the measuring point.

[0042] Preferably, in the above-mentioned rapid diagnosis method for longitudinal bridge damage of precast assembled beam bridges, in step (8), the range of strain meter variation ΔS ii The calculation formula is as follows:

[0043]

[0044] In the formula, l i Let 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 ΔS be the x-coordinate of the midpoint of interval i. ii ε represents the range of strain variation in interval i of the strain influence line at the measuring point; ii (x) represents the influence line of the measured strain at the measuring point interval i of the beam damage state; ε i0 (x) represents the theoretical strain influence line of the measurement point interval i in the undamaged state of the beam.

[0045] Compared with existing technologies, the present invention has the following advantages:

[0046] The present invention provides a rapid diagnosis method for longitudinal damage in precast assembled beam bridges. This method employs a quasi-static loading method, overcoming the shortcomings of step-by-step static loading, such as long loading cycles and poor economic efficiency. It offers a short diagnosis time, minimal impact on bridge traffic, and enables rapid diagnosis of longitudinal damage in precast assembled beam bridges, thus improving economic efficiency. The diagnostic method of this invention can achieve a comprehensive qualitative, locational, and quantitative diagnosis of longitudinal damage in precast assembled beam bridges, improving the accuracy of damage diagnosis. This provides a reliable and effective basis for extending the service life of bridges and formulating maintenance plans, resulting in significant social and economic benefits. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the layout of measuring points and loading method of the precast assembled beam bridge in Embodiment 1 of the present invention. The unit of measurement is dm.

[0048] Figure 2 The following are the qualitative diagnostic diagrams of longitudinal bridge damage in the precast assembled beam bridge in Embodiment 1 of the present invention: (a) diagram of undamaged beam body; (b) diagram of damage state of beam A; (c) diagram of damage state of beam B; (d) diagram of undamaged beam body; (e) diagram of damage state of beam D; (f) diagram of damage state of beam E.

[0049] Figure 3 This is a diagram showing the influence of the strain line on the method for rapid location and quantitative diagnosis of longitudinal damage in precast assembled beam bridges in Embodiment 1 of the present invention.

[0050] Figure 4 This is a diagram showing the structure and dimensions of a prefabricated assembled beam bridge in an application example of the present invention. The dimensions are in mm.

[0051] Figure 5 This is a diagram showing the arrangement of strain measurement points in an application example of the present invention.

[0052] Figure 6 This is a schematic diagram of the moving load loading path in an application example of the present invention.

[0053] Figure 7 The theoretical and measured strain influence lines of measuring points A and E on both sides of the beam in the application example of this invention are shown.

[0054] Figure 8 This is a qualitative diagnostic diagram of a beam bridge without damage in an application example of the present invention.

[0055] Figure 9 The theoretical and measured strain influence lines of measuring points A and E on both sides of the beam in the damaged state of beam A in the application example of this invention are shown.

[0056] Figure 10 This is a qualitative diagnostic diagram of the damage state of beam A in a beam bridge in an application example of the present invention.

[0057] Figure 11 The theoretical and measured strain influence lines of measuring points A and E on both sides of beam B in the damage state of beam B in the application example of the present invention are shown.

[0058] Figure 12 This is a qualitative diagnostic diagram of the damage state of beam B in a beam bridge in an application example of the present invention.

[0059] Figure 13 The theoretical and measured strain influence lines of measuring points A and E on both sides of beam C in the application example of this invention are shown.

[0060] Figure 14 This is a qualitative diagnostic diagram of the damage state of beam C in a beam bridge in an application example of the present invention.

[0061] Figure 15 The absolute value represents the variation of strain meters in each interval under the damage state of beam C in the beam bridge in the application example of this invention.

[0062] Figure 16 The absolute value represents the variation range of strain meters in each interval under the damage state of beam A in the beam bridge in the application example of this invention. Detailed Implementation

[0063] 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.

[0064] Example 1

[0065] Taking a 40m span, 5-piece precast precast beam bridge as an example (see...) Figure 1 In this embodiment, each main beam is named sequentially from the outer edge beam to the inner edge beam: beam A, beam B, beam C, beam D, and beam E. Three measuring points are arranged at the mid-span of beams A, C, and E. Since the loading vehicle travels along the center line of the bridge deck, beam C is the loading beam, and the other four beams are non-loading beams.

[0066] This embodiment provides a rapid diagnosis method for longitudinal bridge damage in precast assembled beam bridges, including the following steps:

[0067] (1) Based on the theoretical structural parameters of the bridge, a finite element calculation model of the bridge is established to calculate the theoretical strain influence line; the finite element calculation model is based on the following formula:

[0068]

[0069] In the formula, ε(x) is the strain influence line of longitudinal beam k (any beam of the beam bridge), L is the total span of the bridge, EI is the stiffness of the measuring point section, l is the distance from the measuring point section to the bridge end, y is the distance from the lower edge of the measuring point section to the neutral axis of the section; x is the distance between the location of the moving load F and the bridge end, αη ki This represents the actual transverse distribution coefficient of longitudinal beam k.

[0070] (2) Strain measuring points A, E, and C are arranged at the mid-span of the two side beams and the middle beam of the precast assembled beam bridge in the longitudinal direction, and then a pseudo-static loading test is carried out: the test loading vehicle moves at a uniform low speed (50% of the speed limit) along the center line of the bridge deck from the end of the bridge to the end of the bridge to apply a moving load to the beam bridge.

[0071] (3) Extract the strain at strain measurement points A, E, and C of the beam bridge under moving load, and use the least squares method to fit and draw the strain influence line;

[0072] (4) Calculate the total strain meters at strain measuring points A and E on the two outer beams. The total strain meters is the total envelope area between the strain influence line at the bridge structure measuring point and the horizontal axis under the moving load. The calculation formula is:

[0073]

[0074] In the formula, L is the total span of the bridge; S 总 Let ε(x) be the total strain at the measuring point in meters, and let ε(x) be the strain influence line at the measuring point.

[0075] (5) Calculate the total strain meter variation ranges ΔSA and ΔSE at measuring points A and E. The total strain meter variation range is the total strain meter measured in step (4) minus the theoretical total strain meter. The theoretical total strain meter is the total envelope area between the theoretical strain influence line and the horizontal axis. The expression for the theoretical total strain meter at the cross-section measuring point is:

[0076]

[0077] In the formula, L is the total span of the bridge, EI is the stiffness of the measuring point section; l is the distance from the measuring point section to the bridge end, y is the distance from the lower edge of the measuring point section to the neutral axis of the section, x is the distance between the location of the moving load F and the bridge end, and αη ki This represents the actual transverse distribution coefficient of longitudinal beam k.

[0078] (6) Establish ΔS histograms for both on the same coordinate axis, and compare them with the longitudinal bridge damage qualitative diagnosis system (see Figure 2 This leads to a qualitative diagnosis. Figure 2 (a) Undamaged state diagram of the beam body, ΔSA and ΔSE are zero, indicating the undamaged state of the precast assembled beam bridge body; (b) Damaged state diagram of beam A, ΔSA is negative and ΔSE is zero, indicating damage to beam A (the outer beam where measuring point A is located); (c) Damaged state diagram of beam B, ΔSA is positive and ΔSE is zero, indicating damage to beam B (the side beam adjacent to the outer beam where measuring point A is located); (d) Damaged state diagram of beam C, ΔSA and ΔSE are positive, indicating damage to beam C (the middle beam); (e) Damaged state diagram of beam D, ΔSA is zero and ΔSE is positive, indicating damage to beam D (the side beam adjacent to the outer beam where measuring point E is located); (f) Damaged state diagram of beam E, ΔSA is zero and ΔSE is negative, indicating damage to beam E (the outer beam where measuring point E is located).

[0079] (7) Divide the strain influence lines of the damaged beam measuring points identified in step (6) into n intervals along the longitudinal direction with a length of c at equal intervals (see...). Figure 3 ), calculate the interval strain in meters S for each interval. ii , interval strain meters S ii The calculation formula is as follows:

[0080]

[0081] 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) is the expression for the strain influence line of the measuring point interval i, S i Let the interval strain in meters be the interval i of the strain influence line at the measuring point;

[0082] (8) Calculate the range of strain per meter change ΔS ii The variation range of the total strain in meters in the interval is the interval strain in meters measured in step (7) minus the theoretical total strain in meters in the interval; ΔS ii The calculation formula is as follows:

[0083]

[0084] In the formula, l i Let 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 ΔS be the x-coordinate of the midpoint of interval i. ii ε represents the range of strain variation in interval i of the strain influence line at the measuring point; ii (x) represents the influence line of the measured strain at the measuring point interval i of the beam damage state; ε i0 (x) represents the theoretical strain influence line of the measuring point interval i in the non-destructive state of the beam, i.e., the theoretical strain influence line.

[0085] (9) Based on the range of strain meter variation ΔS ii Longitudinal bridge damage was located and quantified, ΔS ii The interval containing the maximum absolute value is the location interval of the damage; when the damaged beam is a loaded beam, the degree of damage to the damaged beam is ΔS. ii Twice the absolute value; when the damaged beam is an unloaded beam, the degree of damage to the damaged beam is ΔS. ii Four times the absolute value.

[0086] Application examples

[0087] 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 4Diagnostic tests were performed on four working conditions: no damage, A beam damaged (30% damage), B beam damaged (30% damage), and C beam damaged (30% damage).

[0088] 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.

[0089] Measuring points C and A and E are respectively arranged on the middle beam and the two outer side beams at the mid-span of the beam bridge. Figure 5 and Figure 6 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 6 As shown. Since the loaded vehicle travels along the centerline of the bridge deck, beam C is the loaded beam, and the other four beams are unloaded beams. The method provided in Example 1 is used for diagnosis.

[0090] 1. Qualitative diagnosis of longitudinal bridging damage

[0091] (1) No damage state

[0092] The theoretical and measured strain influence lines of measuring points A and E on both side beams, as shown below. Figure 7 As shown, the total strain meters at measuring points A and E can be calculated separately as follows: Finite element calculation theoretical results: SA 理论 =37.03 (με.m), SE 理论 = 37.03 (με.m); On-site measurement results by testing personnel: SA 实测 =37.03 (με.m), SE 实测 =37.03 (με.m).

[0093] The variation range of total strain meters at the measuring points on both side beams: △SA = 0.00%; △SE = 0.00%. Based on the variation range of total strain meters at the measuring points on both side beams, a qualitative diagnostic diagram of longitudinal damage to the precast assembled beam bridge can be drawn, such as... Figure 8 As shown. Diagnostic conclusion: The diagnostic results are consistent with... Figure 2 (a) Correspondingly, the precast assembled beam bridge is in an overall undamaged state.

[0094] (2) Damage state of beam A

[0095] The theoretical and measured strain influence lines of measuring points A and E on both side beams, as shown below. Figure 9As shown, the total strain meters at measuring points A and E can be calculated separately as follows, based on the finite element method theoretical results: SA 理论 =37.03 (με.m), SE 理论 = 37.03 (με.m); On-site measurement results by testing personnel: SA 实测 =32.95 (με.m), SE 实测 =37.03 (με.m).

[0096] The variation range of total strain meters at the measuring points on both sides of the beam is: △SA = -11.02%; △SE = 0.00%. Based on the variation range of total strain meters at the measuring points on both sides of the beam, a qualitative diagnostic diagram of longitudinal damage to the precast assembled beam bridge can be drawn, such as... Figure 10 As shown. Diagnostic conclusion: The diagnostic results are consistent with... Figure 2 (b) Correspondingly, the precast assembled beam bridge suffered longitudinal bridge damage, and the damaged beam was beam A.

[0097] (3) Damage status of beam B

[0098] The theoretical and measured strain influence lines of measuring points A and E on both side beams, as shown below. Figure 11 As shown, the total strain meters at measuring points A and E can be calculated separately as follows: Finite element calculation theoretical results: SA 理论 =37.03 (με.m), SE 理论 = 37.03 (με.m); On-site measurement results by testing personnel: SA 实测 =40.33 (με.m), SE 实测 =37.03 (με.m).

[0099] The variation range of total strain meters at the measuring points on both sides of the beam is: △SA = 8.93%, △SE = 0.00%. Based on the variation range of total strain meters at the measuring points on both sides of the beam, a qualitative diagnostic diagram of longitudinal damage to the precast assembled beam bridge can be drawn, such as... Figure 12 As shown. Diagnostic conclusion: The diagnostic results are consistent with... Figure 2 (c) Correspondingly, the precast assembled beam bridge suffered longitudinal bridge damage, and the damaged beam was beam B.

[0100] (4) Damage status of C-beam

[0101] The theoretical and measured strain influence lines of measuring points A and E on both side beams, as shown below. Figure 13 As shown, the theoretical results of the finite element calculation are: SA 理论 =37.03 (με.m), SE 理论 = 37.03 (με.m); On-site measurement results by testing personnel: SA 实测 =38.31 (με.m), SE 实测 =38.31 (με.m).

[0102] The variation range of total strain meters at the measuring points on both side beams: △SA = 3.47%; △SE = 3.47%. Based on the variation range of total strain meters at the measuring points on both side beams, a qualitative diagnostic diagram of longitudinal damage to the precast assembled beam bridge can be drawn, such as... Figure 14 As shown. Diagnostic conclusion: The diagnostic results are consistent with... Figure 2 (d) Correspondingly, the precast assembled beam bridge suffered longitudinal bridge damage, and the damaged beam was beam C.

[0103] 2. Longitudinal bridging damage localization and quantitative diagnosis

[0104] Further localization and quantitative diagnosis of A-beam and C-beam damage were performed.

[0105] (1) C-beam damage

[0106] Beam C is the loaded beam. The equal interval c is taken as 5m. The strain influence line of measuring point C is divided into 8 intervals at equal intervals, as shown in Table 1.

[0107] Table 1. Strain Influence Line Interval Division Table (Unit: m)

[0108]

[0109] The calculated strain variation in meters in each interval under the relatively undamaged condition is as follows: Figure 15 As shown, the strain gauge length of the damaged beam is lower than that of the undamaged beam, and the change is negative. The figure shows the absolute value of the change in strain gauge length. It can be seen from the figure that the interval with the largest change in strain gauge length is interval 4, with a change value of 18.85%. Since the damage occurred on the loaded beam, the diagnosis result can be concluded that the longitudinal bridge damage location is within (15,20)m, and the damage degree is 18.85%×2=37.64%, which is consistent with the actual working condition.

[0110] (2) A-beam damage

[0111] Beam A is a loaded beam, and its strain influence line is divided into 8 equally spaced intervals, as shown in Table 1. The calculated strain variation in meters in each interval under the condition of near-undamaged stress is as follows: Figure 16 As shown in the figure, the absolute values ​​of the strain meter variation range are displayed in intervals. It can be seen from the figure that the interval with the largest strain meter variation range is interval 4, with a variation range of 8.14%, and since the damage occurred on an unloaded beam, the diagnostic result can be concluded as follows: the longitudinal bridge damage location is within (15, 20) m, and the damage degree is 8.14% × 4 = 32.56%, consistent with the actual working conditions.

[0112] 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 longitudinal damage in precast assembled beam bridges, characterized in that, Includes the following steps: (1) Based on the theoretical structural parameters of the bridge, a finite element calculation model of the bridge is established to calculate the theoretical strain influence line; (2) Strain measuring points A, E, and C are arranged at the mid-span of the two outer beams and the middle beam of the precast assembled beam bridge, respectively, and then a pseudo-static loading test is carried out: the test loading vehicle moves at a constant low speed along the bridge deck from the end of the bridge to the end of the bridge to apply a moving load to the beam bridge. (3) Extract the strain at the strain measurement points of the beam bridge under the action of moving load, and fit and draw the strain influence line; (4) Calculate the total strain meters at the strain measurement points A and E of the two outer beams. The total strain meters is the total envelope area between the strain influence line at the bridge structure measurement point and the horizontal axis under the action of moving load. (5) Calculate the total strain meter variation at measuring points A and E. , The variation range of the total strain meter is the total strain meter measured in step (4) minus the theoretical total strain meter, where the theoretical total strain meter is the total envelope area between the theoretical strain influence line and the horizontal axis. (6) Establish the two on the same coordinate axis The bar chart, compared with the longitudinal bridge damage qualitative diagnosis chart, yields the qualitative diagnosis results; The diagnostic criteria for the longitudinal bridge damage qualitative diagnostic system are as follows: and When the value is zero, the precast assembled beam bridge body is in an undamaged state; For negative When the value is zero, the outer beam where measuring point A is located is damaged; For positive When the value is zero, the side beam adjacent to the outer beam where measuring point A is located is damaged; and When both are in positive position, the central beam is damaged; Zero When the value is positive, the side beam adjacent to the outer beam where measuring point E is located is damaged; Zero When the value is negative, the outer beam at measuring point E is damaged; (7) Divide the influence line of strain at the measuring points of the damaged beam into n intervals with length c along the longitudinal direction, and calculate the interval strain in meters for each interval. ; (8) Calculate the range of strain per meter in the interval. The range of variation of the interval strain meters is the interval strain meters measured in step (7) minus the theoretical total interval strain meters; (9) Based on the range of strain meters To locate and quantify longitudinal bridge damage, The interval containing the maximum absolute value is the location interval of the damage; when the damaged beam is a loaded beam, the degree of damage to the damaged beam is... Twice the absolute value; When the damaged beam is an unloaded beam, the degree of damage to the damaged beam is: Four times the absolute value.

2. The rapid diagnosis method for longitudinal damage of precast assembled beam bridges according to claim 1, characterized in that, In step (1), the finite element calculation model is calculated based on the following formula: In the formula, for Strain influence line of longitudinal beam No. 1 L The total span of the bridge EI For the cross-sectional stiffness of the measuring point, l y is the distance from the measuring point section to the bridge end, and y is the distance from the lower edge of the measuring point section to the neutral axis of the section. x For moving loads F The distance between the point of action and the end of the bridge. for k Actual transverse distribution coefficient of longitudinal beam No.

1.

3. The rapid diagnosis method for longitudinal damage of precast assembled beam bridges according to claim 1, characterized in that, In step (2), the loading path and arrangement of the test loading vehicle are as follows: a single row of vehicles is loaded under the positive load path, and a three-axle or four-axle heavy-duty vehicle is used for loading.

4. The method for rapid diagnosis of longitudinal damage in precast assembled beam bridges according to claim 1, characterized in that, In step (2), the test loading vehicle passes through the bridge deck along the center line of the bridge deck, and uniform low speed means no more than 50% of the speed limit.

5. The rapid diagnosis method for longitudinal damage of precast assembled beam bridges according to claim 1, characterized in that, In step (3), the least squares method is used to fit and draw the strain influence line.

6. The rapid diagnosis method for longitudinal damage of precast assembled beam bridges according to claim 1, characterized in that, In step (7), the interval strain meter The calculation formula is as follows: In the formula, l i For interval i The x-coordinate value of the middle position, c The length of each interval of the strain influence line at the measuring point is determined. Let i be the expression for the strain influence line of the measurement point interval i.

7. The rapid diagnosis method for longitudinal damage of precast assembled beam bridges according to claim 1, characterized in that, In step (8), the range of strain meters is... The calculation formula is as follows: In the formula, l i For interval i The x-coordinate value of the middle position, c The length of each interval of the strain influence line at the measuring point is determined; The influence line of measured strain in interval i of the beam damage state measurement point; The strain influence line of the measuring point interval i in the undamaged state of the beam is the theoretical strain influence line.

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