CN116067592A - Rapid diagnosis method for longitudinal bridge damage of prefabricated assembled girder bridge - Google Patents
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Abstract
The invention relates to the technical field of bridge health monitoring and detection, and particularly discloses a rapid diagnosis method for longitudinal bridge damage of a prefabricated assembled girder bridge, which comprises the following steps: collecting actual structural parameters of a bridge, and establishing a bridge finite element calculation model for calculating a theoretical strain influence line; strain measuring points are arranged at the longitudinal midspan positions of the two outer side beams and the middle beam of the prefabricated assembled beam, and a quasi-static loading test is carried out; extracting the strain of a beam bridge strain measuring point, and fitting and drawing a strain influence line; the total strain meter of the strain measuring points of the two outer beams is obtained; calculating the total strain meter change amplitude delta s of the two outer edge beam measuring points; and (3) establishing a delta S histogram of the two in the same coordinate axis, and comparing the delta S histogram with a qualitative diagnosis system of the longitudinal bridge damage to obtain a qualitative diagnosis result. The rapid diagnosis method for the longitudinal bridge damage of the prefabricated assembled girder bridge is loaded by adopting a quasi-static loading method, has short diagnosis time, does not interrupt traffic, improves economy, realizes rapid comprehensive diagnosis of the longitudinal bridge damage of the prefabricated assembled girder bridge, and improves diagnosis accuracy.
Description
Technical Field
The invention belongs to the technical field of bridge health monitoring and detection, and particularly relates to a rapid diagnosis method for longitudinal bridge damage of a prefabricated assembled girder bridge.
Background
The prefabricated assembled beam bridge has the advantages of quick construction, reliable quality, durability, environmental protection and the like, and is widely applied to bridge engineering in China. During the service period of the bridge, due to the comprehensive long-term effect of various natural environment factors, part of the bridge is gradually damaged and aged along with the increase of the service time, the bridge strength is reduced, the stress performance is reduced, the reliability is reduced, and the safety of pedestrians and driving can be seriously endangered. Liang Tizong bridge directional damage represented by concrete cracking, breakage and carbonization is an important factor endangering bridge safety, and rapid and accurate diagnosis of the damage is performed, so that the method is one of effective measures for ensuring bridge safety operation and avoiding bridge safety accidents.
The conventional damage diagnosis method for the service bridge is mainly a diagnosis method based on appearance investigation and a diagnosis method based on a load test. The diagnostic method based on appearance investigation is mainly characterized in that appearance diseases of the bridge are counted and analyzed according to engineering experience and subjective judgment of detection personnel, and then the technical condition grade of the bridge is assessed according to the highway bridge technical condition assessment standard by combining analysis results, and the diagnostic method has the following defects: the subjectivity is too strong, and the reliability of the diagnosis result is completely dependent on the richness of the related experience and knowledge of the detection personnel; the process is tedious, the operation is not simple and convenient, and the inspection of meticulous no dead angle is difficult to accomplish to some hidden positions of bridge structure. The diagnosis method based on the load test is a bridge damage diagnosis method widely adopted in bridge detection at present, and is more visual and objective than the diagnosis method of appearance investigation. The load test is divided into a static load test and a dynamic load test, wherein the static load test mainly adopts a graded loading method, external load basically equivalent to design load or use load is applied to the bridge structure, the change of the characteristics of deflection, stress, cracks, transverse distribution coefficients and the like of a control part and a control section of the bridge structure under the action of each level of test load is tested by utilizing a detection instrument, and an actual measurement value is compared with a theoretical calculation value of the structure under the action of corresponding load, so that the whole health condition of the bridge structure is diagnosed. The dynamic load test is mainly to test dynamic deflection, dynamic strain and modal parameters of each control part on a bridge structure by performing impulse test, driving, jumping, braking excitation or other excitation tests on the bridge structure, and then identify damaged parts of the structure through the modal parameters. The diagnosis method based on the load test mainly has the following defects: the traffic is closed for a long time in the implementation process of the diagnosis method, and the normal traffic is interfered; the diagnosis method has large loading capacity, adopts a step-by-step loading and unloading mode, causes the tedious and long time-consuming loading process and has poor economy; the diagnosis method is mainly used for diagnosing the whole health condition of the bridge, and has single diagnosis index, thicker diagnosis result and poor accuracy. The method is difficult to quickly and accurately diagnose the longitudinal damage of the prefabricated assembled girder bridge.
The method for diagnosing the damage of the prefabricated assembled beam bridge, which has the advantages of no traffic interruption, simple and quick operation and fine diagnosis result, has quick and good economy in the test process, has finer diagnosis result on the damage of the bridge, can provide reliable and effective basis for prolonging the service life of the bridge and formulating a maintenance scheme, and has remarkable social benefit.
Disclosure of Invention
The invention aims to provide a rapid diagnosis method for longitudinal bridge damage of a prefabricated assembled girder bridge, and overcomes the defect that the conventional diagnosis method is difficult to rapidly diagnose, position and quantitatively diagnose the longitudinal bridge damage of the prefabricated assembled girder bridge.
In order to achieve the above purpose, the invention provides a rapid diagnosis method for longitudinal bridge damage of a prefabricated assembled girder bridge, which comprises the following steps:
(1) Establishing a bridge finite element calculation model for calculating a theoretical strain influence line according to the bridge theoretical structural parameters;
(2) Strain measuring points A, E, C are respectively arranged in the longitudinal midspan of the two outer side beams and the middle beam of the prefabricated assembled beam bridge, and then a quasi-static loading test is carried out: the test loading vehicle uniformly runs along the bridge deck at a low speed from the bridge end to the bridge tail to apply a moving load to the girder bridge;
(3) Extracting the strain of the beam bridge strain measuring point under the action of a moving load, and fitting and drawing a strain influence line;
(4) The total strain meter of the two outer beam strain measuring points A, E is obtained, and the total strain meter is the total wrapping area between the strain influence line at the bridge structure measuring point and the abscissa axis under the action of moving load;
(5) Calculating the total strain meter change amplitude delta SA and delta SE of the measuring point A, E, wherein the total strain meter change amplitude is obtained by subtracting a theoretical total strain meter from the total strain meter obtained in the actual measurement in the step (4), and the theoretical total strain meter is the total envelope area between a theoretical strain influence line and an abscissa axis;
(6) And (3) establishing a delta S histogram of the two in the same coordinate axis, and comparing the delta S histogram with a qualitative diagnosis system of the longitudinal bridge damage to obtain a qualitative diagnosis result.
The invention provides a brand new concept on the basis of combining strain and influence lines, which shows a curve generated by the change of strain at a bridge structure measuring point along the action position of a moving load under the action of the load moving along the span direction 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 of the moving load at the corresponding measuring point at different coordinates. The total strain meter is a concept further put forward on the basis of the strain influence line, and refers to the total wrapping area between the strain influence line at the bridge structure measuring point and the abscissa axis under the action of moving load, and the calculation formula is as follows:
wherein L is the total span of the bridge; s is S Total (S) The total strain meter of the measuring point is shown as epsilon (x), and the strain influence line of the measuring point is shown as epsilon (x). The total strain meter is different from a general statics concept, is a function characteristic value reflecting the continuous response of the bridge structure strain obtained under the action of a longitudinal bridge moving load, and contains more structural information relative to a bridge static test amount. Therefore, the change of the total strain meter of the bridge measuring point can reflect the damage condition and the performance change condition of the beam body structure.
Preferably, in the method for rapidly diagnosing longitudinal bridge damage of a prefabricated assembled beam bridge, in the step (1), the finite element calculation model calculation is based on the following formula:
wherein epsilon (x) is a strain influence line of a k-number longitudinal beam, L is the total span of the bridge, EI is the section rigidity of the measuring point, L is the distance from the section of the measuring point to the bridge end, and y is the distance from the lower edge of the section of the measuring point to the neutral axis of the section; x is the distance between the acting position of the moving load F and the bridge end, alpha eta ki The actual transverse distribution coefficient of the k-shaped longitudinal beam.
From hooke's law, it can be seen that the section strain expression at B on a simply supported single beam at any length l from the beam end is as follows:
wherein L is simply supported single beam span, EI is the section rigidity of the measuring point, and y is the distance from the lower edge of the section of the measuring point to the neutral axis of the section; the prefabricated assembled bridge is a bridge structure which is generally composed of a plurality of longitudinal beams and transverse connection, and is different from a simple single-beam structure in that when a load F acts on the bridge structure, each longitudinal beam participates in bearing work to different degrees due to the transverse connection of the structure, and the strain influence line expression of the prefabricated assembled bridge needs to be considered when calculatingLet the transverse distribution coefficient alpha eta be considered ki A movable load F acts on the i-shaped beam of the prefabricated assembled beam bridge, and the load born by the i-shaped beam is F i ＝αη ii The load borne by the F and k beams is F k ＝αη ki F, obtaining a k-shaped beam B of the prefabricated assembled beam bridge of the actual engineering k The analysis formula of the strain influence line of the measuring point of the section is shown in the formula (1-2).
Preferably, in the method for rapidly diagnosing the longitudinal bridge damage of the prefabricated assembled girder bridge, the theoretical total strain meter expression of the measurement point of the section of the k-shaped girder is:
wherein L is the total span of the bridge, and EI is the section rigidity of the measuring point; l is the distance between the section of the measuring point and the bridge end, y is the distance between the lower edge of the section of the measuring point and the neutral axis of the section, x is the distance between the acting position of the moving load F and the bridge end, and alpha eta ki The actual transverse distribution coefficient of the k-shaped longitudinal beam.
Preferably, in the method for rapidly diagnosing the longitudinal bridge damage of the prefabricated assembled beam bridge, in the step (2), the loading path and the arrangement mode of the test loading vehicle are that the single-row vehicle is loaded under the normal loading path, and the three-axis loading vehicle or the four-axis loading vehicle is loaded, so that the loading efficiency is optimal, traffic is not interrupted, and the test data acquisition is facilitated.
Preferably, in the method for rapidly diagnosing the longitudinal bridge damage of the prefabricated assembled girder bridge, in the step (2), the uniform low speed of the test loading vehicle passes through the bridge deck along the center line of the bridge deck, wherein the uniform low speed is not more than 50% of the speed limit, and the lower the test loading vehicle is, the better the diagnostic effect is.
Preferably, in the method for rapidly diagnosing the longitudinal bridge damage of the prefabricated assembled bridge, in the step (3), a least square fitting method is adopted to draw a strain influence line.
Preferably, in the method for rapidly diagnosing the longitudinal bridge damage of the prefabricated assembled girder bridge, in the step (6), the diagnostic criteria of the qualitative diagnostic chart system of the longitudinal bridge damage in the step (6) are as follows:
when delta SA and delta SE are zero, prefabricating and assembling Liang Qiaoliang bodies to be in a nondestructive state;
ΔSA is negative, ΔSE is zero, and the outside Liang Shousun where the measurement point A is located;
Δsa is positive and Δse is zero, the side Liang Shousun adjacent to the outer beam where station a is located;
Δsa and Δse are positive, the middle beam is damaged;
Δsa is zero and Δse is positive, side Liang Shousun adjacent to the outer beam where point E is located;
when Δsa is zero and Δse is negative, point E is located outside Liang Shousun.
Preferably, in the method for rapidly diagnosing the longitudinal bridge damage of the prefabricated assembled girder bridge, the method further comprises the following steps:
(7) Dividing a damaged Liang Tice point strain influence line into n sections at equal intervals along a longitudinal bridge direction with c as a length, and obtaining section strain meters S of each section ii ；
(8) Calculating the change amplitude delta S of the interval strain meter ii The change amplitude of the interval total strain meter is obtained by subtracting the theoretical interval total strain meter from the interval strain meter obtained in the actual measurement in the step (7);
(9) According to the change amplitude delta S of the interval strain meter ii Positioning and quantifying damage, ΔS, to longitudinal bridge injury ii The interval with the largest absolute value is the position interval where the damage is located; when the damaged beam body is a loading beam, the damage degree of the damaged beam body is delta S ii Two times the absolute value; when the damaged beam body is a non-loaded beam, the damage degree of the damaged beam body is delta S ii Four times the absolute value.
Preferably, in the method for rapidly diagnosing longitudinal bridge damage of a prefabricated assembled beam bridge, in the step (7), the interval strain is m S ii The calculation formula is as follows:
wherein, I i The horizontal coordinate value of the middle position of the section i, c is the dividing length of each section of the measuring point strain influence line, epsilon i (x) For the test point interval i strain influence line expression，S i The section strain meter is the section strain meter of the measuring point strain influence line section i.
Preferably, in the method for rapidly diagnosing longitudinal bridge damage of a prefabricated assembled beam bridge, in the step (8), the interval strain meter change amplitude Δs ii The calculation formula is as follows:
wherein, I i The horizontal coordinate value of the middle position of the section i, c is the dividing length of each section of the measuring point strain influence line, and delta S ii The interval strain meter change amplitude of the interval i of the measuring point strain influence line is measured; epsilon ii (x) Actually measuring a strain influence line for a beam damage state measuring point interval i; epsilon i0 (x) And the theoretical strain influence line is the theoretical strain influence line of the beam body nondestructive state measurement point interval i.
Compared with the prior art, the invention has the following beneficial effects:
the rapid diagnosis method for the longitudinal bridge damage of the prefabricated assembled girder bridge is loaded by adopting a quasi-static loading method, overcomes the defects of long loading period and poor economy of a progressive static loading mode, has short diagnosis time and small influence on bridge traffic, can realize rapid diagnosis on the longitudinal bridge damage of the prefabricated assembled girder bridge, and improves the economy. The diagnosis method can realize the comprehensive diagnosis of the longitudinal damage of the prefabricated assembled girder bridge, improve the accuracy of the damage diagnosis of the prefabricated assembled girder bridge, provide reliable and effective basis for the extension of the service life of the bridge and the establishment of maintenance schemes, and have remarkable social and economic benefits.
Drawings
Fig. 1 is a schematic diagram of the arrangement and loading modes of the prefabricated assembled beam bridge measuring points in embodiment 1 of the present invention, and the dimension units are as follows: dm.
Fig. 2 is a qualitative diagnostic chart of the longitudinal bridge damage of the prefabricated assembled girder bridge in embodiment 1 of the present invention: (a) a beam body lossless state diagram; (b) a beam damaged condition; (c) B beam damage state diagram; (d) a beam body lossless state diagram; (e) D beam damage status diagram; (f) E-beam damaged condition.
Fig. 3 is a plot of strain influence lines by the rapid positioning and quantitative diagnosing method of longitudinal bridge damage of the prefabricated assembled girder bridge in embodiment 1 of the present invention.
Fig. 4 is a diagram showing the structure and dimensions of a prefabricated assembled bridge in mm in accordance with an embodiment of the present invention.
FIG. 5 is a diagram of a strain gauge point arrangement in an embodiment of the invention.
Fig. 6 is a schematic diagram of a moving load loading path in an application example of the present invention.
Fig. 7 is a theoretical and actual strain influence line of two sides Liang Cedian A, E of a bridge without damage in an application example of the present invention.
FIG. 8 is a qualitative diagnostic chart of the invention applied to the bridge without damage.
Fig. 9 is a theoretical and actual strain influence line of two sides Liang Cedian A, E of a beam bridge in a damaged state in an application example of the present invention.
Fig. 10 is a qualitative diagnosis chart of the damaged state of the beam bridge a in the application example of the present invention.
Fig. 11 is a theoretical and actual strain influence line of two sides Liang Cedian A, E in a damaged state of a beam bridge B in an application example of the present invention.
Fig. 12 is a qualitative diagnosis chart of the invention in the damaged state of the beam bridge B.
Fig. 13 is a theoretical and actual strain influence line of two sides Liang Cedian A, E of a beam bridge in a damaged state in an application example of the present invention.
Fig. 14 is a qualitative diagnosis chart of the damaged state of the bridge C-beam in the application example of the present invention.
Fig. 15 shows the variation amplitude (absolute value) of strain meters in each section in the damaged state of the bridge C-beam in the application example of the present invention.
Fig. 16 shows the change amplitude (absolute value) of strain meter in each section in the damaged state of the beam bridge a in the application example of the present invention.
Detailed Description
The following detailed description of specific embodiments of the invention is, but it should be understood that the invention is not limited to specific embodiments.
Example 1
The present embodiment is described with reference to a 5-piece prefabricated assembled girder bridge (see fig. 1) with a span of 40m, and each girder is named from an outer girder to an inner girder in sequence: the bridge deck center line loading system comprises an A beam, a B beam, a C beam, a D beam and an E beam, wherein the longitudinal midspan of the A beam, the C beam and the E beam is provided with 3 measuring points, and the C beam of the middle beam is a loading beam and the other four beams are non-loading beams as a loading vehicle runs along the bridge deck center line for loading.
The embodiment provides a rapid diagnosis method for longitudinal bridge damage of a prefabricated assembled girder bridge, which comprises the following steps:
(1) Establishing a bridge finite element calculation model for calculating a theoretical strain influence line according to the bridge theoretical structural parameters; the finite element calculation model calculation is based on the following formula:
wherein epsilon (x) is a strain influence line of a k-shaped longitudinal beam (any beam of a beam bridge), L is the total span of the bridge, EI is the section rigidity of a measuring point, L is the distance from the section of the measuring point to the bridge end, and y is the distance from the lower edge of the section of the measuring point to the neutral axis of the section; x is the distance between the acting position of the moving load F and the bridge end, alpha eta ki The actual transverse distribution coefficient of the k-number longitudinal beam;
(2) Strain measuring points A, E, C are respectively arranged at the midspan of the two side beams and the longitudinal bridge of the middle beam of the prefabricated assembled beam bridge, and then a quasi-static loading test is carried out: the test loading vehicle uniformly runs at low speed (50% of speed limit) along the center line of the bridge deck from the bridge end to the bridge tail to apply a moving load to the bridge;
(3) Extracting the strain of the beam bridge strain measuring point A, E, C under the action of a moving load, and fitting and drawing a strain influence line by adopting a least square method;
(4) The total strain meter of the two outer beam strain measuring points A, E is obtained, and the total strain meter is the total wrapping area between the strain influence line at the bridge structure measuring point and the abscissa axis under the action of moving load; the calculation formula is as follows:
wherein L is the total span of the bridge; s is S Total (S) The total strain meter of the measuring point is shown as epsilon (x), and the strain influence line of the measuring point is shown as epsilon (x);
(5) Calculating the total strain meter change amplitude delta SA and delta SE of the measuring point A, E, wherein the total strain meter change amplitude is obtained by subtracting the theoretical total strain meter from the total strain meter obtained in the step (4), and the theoretical total strain meter is the total envelope area between the theoretical strain influence line and the abscissa axis; the theoretical total strain meter expression of the section measuring point is:
wherein L is the total span of the bridge, and EI is the section rigidity of the measuring point; l is the distance between the section of the measuring point and the bridge end, y is the distance between the lower edge of the section of the measuring point and the neutral axis of the section, x is the distance between the acting position of the moving load F and the bridge end, and alpha eta ki The actual transverse distribution coefficient of the k-number longitudinal beam;
(6) Establishing a delta S histogram of the two in the same coordinate axis, and comparing the delta S histogram with a qualitative diagnostic chart system (see figure 2) of the longitudinal bridge damage to obtain a qualitative diagnostic result; FIG. 2 (a) shows a beam body lossless state diagram, wherein DeltaSA and DeltaSE are zero, and a prefabricated assembly Liang Qiaoliang body lossless state is shown; (b) A beam damage state diagram, wherein delta SA is negative, delta SE is zero, and the beam A (an outer beam where a measuring point A is positioned) is damaged; (c) B beam damage state diagram, delta SA is positive, delta SE is zero, B beam (side beam adjacent to outer beam where measuring point A is located) is damaged; (d) C beam damage state diagram, delta SA and delta SE are positive, C beam (middle beam) damage; (e) D beam damage state diagram, delta SA is zero, delta SE is positive, D beam (side beam adjacent to outer beam where measuring point E is located) is damaged; (f) E beam damage state diagram, delta SA is zero, delta SE is negative, E beam (outer side beam where measuring point E is located) is damaged;
(7) Dividing the damaged Liang Tice point strain influence line qualitatively diagnosed in the step (6) into n sections (see figure 3) at equal intervals along the longitudinal direction with c as the length, and obtaining the section strain meters S of each section ii Interval strain meter S ii The calculation formula is as follows:
wherein, I i The horizontal coordinate value of the middle position of the section i, c is the dividing length of each section of the measuring point strain influence line, epsilon i (x) S is a test point interval i strain influence line expression i Interval strain meters which are measuring point strain influence line intervals i;
(8) Calculating the change amplitude delta S of the interval strain meter ii The change amplitude of the interval total strain meter is obtained by subtracting the theoretical interval total strain meter from the interval strain meter obtained in the actual measurement in the step (7); ΔS ii The calculation formula is as follows:
wherein, I i The horizontal coordinate value of the middle position of the section i, c is the dividing length of each section of the measuring point strain influence line, and delta S ii The interval strain meter change amplitude of the interval i of the measuring point strain influence line is measured; epsilon ii (x) Actually measuring a strain influence line for a beam damage state measuring point interval i; epsilon i0 (x) The theoretical strain influence line is the theoretical strain influence line of the beam body nondestructive state measuring point interval i;
(9) According to the change amplitude delta S of the interval strain meter ii Positioning and quantifying damage, ΔS, to longitudinal bridge injury ii The interval with the largest absolute value is the position interval where the damage is located; when the damaged beam body is a loading beam, the damage degree of the damaged beam body is delta S ii Two times the absolute value; when the damaged beam body is a non-loaded beam, the damage degree of the damaged beam body is delta S ii Four times the absolute value.
Application example
Taking a certain seat of a 5-piece T-shaped bridge with a span of 40m as an example, the main parameters of the bridge are as follows: the span is 40m, the bridge width is 11.25m, and the T beam height is 2.5m. Material properties of T-beam: elastic modulus e=3.45×10 10 Pa, torsional modulus g=0.425 e=1.47×10 10 Pa, bulk density ρ=2500 Kg/m 3 Poisson ratio μ=0.2. Is arranged at the bridge fulcrum, 1/4 section, 2/4 section and 3/4 sectionThe diaphragm plate has the thickness of 0.2m and the height of 2.25m. T beams are numbered A through E, and the T beam dimensions are shown in FIG. 4. And diagnosing the nondestructive state, the damage of the A beam (30% of damage), the damage of the B beam (30% of damage) and the damage of the C beam (30% of damage) respectively.
And (3) utilizing finite element software Midas Civil modeling analysis, selecting a load path to be right above the C beam, setting up 801 equally-spaced nodes on the central line of the beam body, and simulating a mobile load in a mode of setting up single-point load on the nodes. By this method, the accuracy of the strain influence line obtained by numerical simulation on the axis of abscissa is 0.05m. The model built 7204 cells and 4005 nodes altogether for calculating the theoretical strain impact line.
The measuring point C and the measuring point A, E are respectively arranged on the middle beam and the two outer side beams of the midspan position of the bridge, as shown in fig. 5 and 6. A100 kN loading test vehicle is selected for loading at a low speed along the center line of the bridge deck by a quasi-static loading method, as shown in figure 6. Because the loading vehicle runs along the center line of the bridge deck to load, the middle beam C beam is a loading beam, and the other four beams are non-loading beams. Diagnosis was performed using the method provided in example 1.
1. Qualitative diagnosis of longitudinal bridge injury
(1) No damage state
The theoretical and actual strain influence lines of the side beam measuring points a and E are shown in fig. 7, and the total strain meter results of the measuring points a and E can be calculated as follows: finite element calculation theory results: SA (SA) Theory of ＝37.03(με.m)，SE Theory of =37.03 (με.m); the field actual measurement result of the inspector: SA (SA) Actual measurement ＝37.03(με.m)，SE Actual measurement ＝37.03(με.m)。
The total strain meter change amplitude of the side beam measuring points at two sides: Δsa=0.00%; Δse=0.00%. And (3) making a qualitative diagnosis chart of the longitudinal bridge damage of the prefabricated assembled girder bridge according to the total strain meter change amplitude of the side beam measuring points at two sides, as shown in figure 8. Diagnosis conclusion: the diagnosis result corresponds to fig. 2 (a), and the prefabricated assembled bridge is in an overall lossless state.
(2) A Beam damaged State
Two side beam measuring point A and measuring pointThe theoretical and actually measured strain influence lines of the point E are shown in fig. 9, and the total strain meter results of the point a and the point E can be calculated as follows, and the theoretical result is calculated by finite elements: SA (SA) Theory of ＝37.03(με.m)，SE Theory of =37.03 (με.m); the field actual measurement result of the inspector: SA (SA) Actual measurement ＝32.95(με.m)，SE Actual measurement ＝37.03(με.m)。
The total strain meter change amplitude of the side beam measuring points at two sides: Δsa= -11.02%; Δse=0.00%; and (5) making a qualitative diagnosis chart of the longitudinal bridge damage of the prefabricated assembled girder bridge according to the total strain meter change amplitude of the side beam measuring points at two sides, as shown in fig. 10. Diagnosis conclusion: the diagnosis result corresponds to fig. 2 (b), the prefabricated assembled beam bridge is damaged in the longitudinal direction, and the damaged beam is an a beam.
(3) B Beam damaged State
The theoretical and actual strain influence lines of the side beam measuring points a and E are shown in fig. 11, and the total strain meter results of the measuring points a and E can be calculated as follows: finite element calculation theory results: SA (SA) Theory of ＝37.03(με.m)，SE Theory of =37.03 (με.m); the field actual measurement result of the inspector: SA (SA) Actual measurement ＝40.33(με.m)，SE Actual measurement ＝37.03(με.m)。
The total strain meter change amplitude of the side beam measuring points at two sides: Δsa=8.93% and Δse=0.00%; and (3) making a qualitative diagnosis chart of the longitudinal bridge damage of the prefabricated assembled girder bridge according to the total strain meter change amplitude of the side beam measuring points at two sides, as shown in fig. 12. Diagnosis conclusion: the diagnosis result corresponds to fig. 2 (c), the prefabricated assembled beam bridge is damaged in the longitudinal direction, and the damaged beam is a B beam.
(4) C beam damaged state
Theoretical and actual measured strain influence lines of the side beam measuring points A and E are shown in FIG. 13, and theoretical results are calculated by finite elements: SA (SA) Theory of ＝37.03(με.m)，SE Theory of =37.03 (με.m); the field actual measurement result of the inspector: SA (SA) Actual measurement ＝38.31(με.m)，SE Actual measurement ＝38.31(με.m)。
The total strain meter change amplitude of the side beam measuring points at two sides: Δsa=3.47%; Δse=3.47%. And (4) making a qualitative diagnosis chart of the longitudinal bridge damage of the prefabricated assembled girder bridge according to the total strain meter change amplitude of the side beam measuring points at two sides, as shown in fig. 14. Diagnosis conclusion: the diagnosis result corresponds to fig. 2 (d), the prefabricated assembled beam bridge is damaged in the longitudinal direction, and the damaged beam is a C-beam.
2. Longitudinal bridge injury localization and quantitative diagnosis
And further carrying out positioning and quantitative diagnosis on the damage of the A beam and the damage of the C beam.
(1) C beam damage
The C beam was a load beam, and the equally divided interval C was 5m, and the strain influence line at the measuring point C was equally divided into 8 sections, as shown in table 1.
TABLE 1 dividing table for strain influence line interval (unit: m)
The calculated change amplitude of each section strain meter in the lossless state is shown in fig. 15, the section strain meter after the beam body is damaged is reduced compared with the section strain meter in the lossless state, the change amplitude is negative, the absolute value of the section strain meter change amplitude is shown in the figure, the section with the largest section strain meter change amplitude is shown as section 4, the change amplitude value is 18.85%, and the damage occurs on the loading beam, so that the diagnosis result is obtained as follows: the damage position in the longitudinal bridge direction is positioned in (15, 20) m, the damage degree is 18.85 percent multiplied by 2=37.64 percent, and the damage degree is consistent with the actual working condition.
(2) A beam damage
The a beam is a load beam, and the strain influence line is equally divided into 8 sections, as shown in table 1. The calculated change amplitude of the strain meter in each section in the lossless state is shown in fig. 16, which is the absolute value of the change amplitude of the strain meter in each section. As can be seen from the graph, the interval with the largest strain meter change width is interval 4, the change width value is 8.14%, and damage occurs on the unloaded beam. From this, the diagnostic result is: the damage position in the longitudinal bridge direction is positioned in (15, 20) m, the damage degree is 8.14 percent multiplied by 4=32.56 percent, and the damage degree is consistent with the actual working condition.
The foregoing descriptions of specific exemplary embodiments of the present invention are presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application to thereby enable one skilled in the art to make and utilize the invention in various exemplary embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.
Claims (9)
1. The rapid diagnosis method for the longitudinal bridge damage of the prefabricated assembled girder bridge is characterized by comprising the following steps of:
(1) Establishing a bridge finite element calculation model for calculating a theoretical strain influence line according to the bridge theoretical structural parameters;
(2) Strain measuring points A, E, C are respectively arranged in the longitudinal midspan of the two outer side beams and the middle beam of the prefabricated assembled beam bridge, and then a quasi-static loading test is carried out: the test loading vehicle uniformly runs along the bridge deck at a low speed from the bridge end to the bridge tail to apply a moving load to the girder bridge;
(3) Extracting the strain of the beam bridge strain measuring point under the action of a moving load, and fitting and drawing a strain influence line;
(4) The total strain meter of the two outer beam strain measuring points A, E is obtained, and the total strain meter is the total wrapping area between the strain influence line at the bridge structure measuring point and the abscissa axis under the action of moving load;
(5) Calculating the total strain meter change amplitude delta SA and delta SE of the measuring point A, E, wherein the total strain meter change amplitude is obtained by subtracting a theoretical total strain meter from the total strain meter obtained in the actual measurement in the step (4), and the theoretical total strain meter is the total envelope area between a theoretical strain influence line and an abscissa axis;
(6) And (3) establishing a delta S histogram of the two in the same coordinate axis, and comparing the delta S histogram with a qualitative diagnosis system of the longitudinal bridge damage to obtain a qualitative diagnosis result.
2. The method for rapid diagnosis of longitudinal bridge damage of a prefabricated assembled girder bridge according to claim 1, wherein in the step (1), the finite element calculation model calculation is based on the following formula:
wherein epsilon (x) is a strain influence line of a k-number longitudinal beam, L is the total span of the bridge, EI is the section rigidity of the measuring point, L is the distance from the section of the measuring point to the bridge end, and y is the distance from the lower edge of the section of the measuring point to the neutral axis of the section; x is the distance between the acting position of the moving load F and the bridge end, alpha eta ki The actual transverse distribution coefficient of the k-shaped longitudinal beam.
3. The rapid diagnosis method for longitudinal bridge damage of a prefabricated assembled girder bridge according to claim 1, wherein in the step (2), the test loading vehicle loads a single-row vehicle under a normal loading path in a loading path and an arrangement mode, and the three-axis loading vehicle or the four-axis loading vehicle loads.
4. The method for rapid diagnosis of longitudinal bridge damage of a prefabricated assembled girder bridge according to claim 1, wherein in the step (2), the test loading vehicle passes through the bridge deck along the center line of the bridge deck, and the uniform low speed is not more than 50% of the speed limit.
5. The rapid diagnosis method for longitudinal bridge damage of a prefabricated assembled girder bridge according to claim 1, wherein in the step (3), a least square fitting is adopted to draw a strain influence line.
6. The rapid diagnosis method for longitudinal bridge damage of a prefabricated assembled girder bridge according to claim 1, wherein in the step (6), the diagnosis standard of the qualitative diagnosis system for longitudinal bridge damage is:
when delta SA and delta SE are zero, prefabricating and assembling Liang Qiaoliang bodies to be in a nondestructive state;
ΔSA is negative, ΔSE is zero, and the outside Liang Shousun where the measurement point A is located;
Δsa is positive and Δse is zero, the side Liang Shousun adjacent to the outer beam where station a is located;
both Δsa and Δse are positive, the center sill is damaged;
Δsa is zero and Δse is positive, side Liang Shousun adjacent to the outer beam where point E is located;
when Δsa is zero and Δse is negative, point E is located outside Liang Shousun.
7. The method for rapid diagnosis of longitudinal bridge damage of a prefabricated assembled girder bridge according to claim 1, further comprising the steps of:
(7) Dividing the damaged Liang Tice point strain influence line into n sections at equal intervals along the longitudinal direction with c as the length, and obtaining section strain meters S of each section ii ；
(8) Calculating the change amplitude delta S of the interval strain meter ii The change amplitude of the interval total strain meter is obtained by subtracting the theoretical interval total strain meter from the interval strain meter obtained in the actual measurement in the step (7);
(9) According to the change amplitude delta S of the interval strain meter ii Positioning and quantifying damage, ΔS, to longitudinal bridge injury ii The interval with the largest absolute value is the position interval where the damage is located; when the damaged beam body is a loading beam, the damage degree of the damaged beam body is delta S ii Two times the absolute value; when the damaged beam body is a non-loaded beam, the damage degree of the damaged beam body is delta S ii Four times the absolute value.
8. The rapid diagnosis method for longitudinal bridge damage of prefabricated assembled girder bridge according to claim 7, wherein in the step (7), the interval strain meter S ii The calculation formula is as follows:
wherein, I i The horizontal coordinate value of the middle position of the section i, c is the dividing length of each section of the measuring point strain influence line, epsilon i (x) S is a test point interval i strain influence line expression i The section strain meter is the section strain meter of the measuring point strain influence line section i.
9. The rapid diagnosis method for longitudinal bridge damage of prefabricated assembled girder bridge according to claim 7, wherein in the step (8), the interval strain meter change amplitude Δs ii The calculation formula is as follows:
wherein, I i The horizontal coordinate value of the middle position of the section i, c is the dividing length of each section of the measuring point strain influence line, and delta S ii The interval strain meter change amplitude of the interval i of the measuring point strain influence line is measured; epsilon ii (x) Actually measuring a strain influence line for a beam damage state measuring point interval i; epsilon i0 (x) The strain influence line of the measurement point interval i in the nondestructive state of the beam body is the theoretical strain influence line.
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| CN116561860B (en) * | 2023-05-06 | 2023-10-27 | 中交第二公路勘察设计研究院有限公司 | Segment test piece design method suitable for staggered width splicing bridge model test |
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