Combined identification method for damage of main beam and hinge joint of fabricated plate girder bridge

Abstract

The invention belongs to the field of structural safety detection, and discloses an assembly type plate girder bridge girder and hinge joint damage combined identification method, which comprises the following steps: (1) converting latitude and longitude coordinates of a test loading vehicle position obtained by GNSS-RTK into bridge coordinates; (2) determining the moving time range of the test loading vehicle between two influence coefficients; (3) converting the time domain bridge response into a space domain; (4) identifying the influence surface of each main beam; (5) calculating a hinge joint damage index; (6) identifying the hinge joint damage of the fabricated plate girder bridge; (7) calculating a main beam rigidity degradation index; and (8) identifying the rigidity degradation of the main girder of the fabricated plate girder bridge. According to the invention, the influence surface can be recognized according to the real-time position information of the test loading vehicle and the response of each piece of beam of the multi-girder bridge, and the effective positioning of the hinge joint damage of the plate girder bridge and the effective quantification of the girder damage are realized based on the actually measured influence surface. The method has good potential in subsequent engineering application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of structural safety detection, and relates to a joint identification method for hinge joint and main beam damage of an assembled slab girder bridge based on influence surface field testing. TECHNICAL BACKGROUND

[0002] The assembled slab girder bridge is widely used in the global medium and small span bridges due to the advantages of convenient construction, clear force transmission and beautiful appearance. However, in the long-term service process, the hinge joint of the assembled slab girder bridge will be damaged due to the coupling influence of environmental erosion, material aging and long-term load effect, and the main beam will produce multiple diseases such as white separation, water seepage, cracking and corner dropping. If these diseases cannot be found in time and reinforcement is completed, the assembled slab girder bridge will eventually collapse due to insufficient bearing capacity of single slab. Therefore, the damage diagnosis of the bridge hinge joint and the main beam is crucial to the safe operation of the multi-beam bridge.

[0003] The current damage detection technology of the assembled slab girder bridge has the following technical bottlenecks: in the aspect of hinge joint damage detection, the traditional non-destructive testing methods (including optical interference method, electromagnetic detection method and acoustic emission method) can realize local defect positioning, but cannot effectively represent the influence of hinge joint damage on its force transmission performance. The damage method based on vibration mode and modal is easily affected by the operating environment and other factors, and the detection result has large discreteness; in the aspect of main beam stiffness degradation evaluation, the existing technology mainly estimates the overall stiffness of the single beam, and lacks effective means suitable for the stiffness evaluation of each main beam in the assembled slab girder bridge.

[0004] In recent years, the diagnostic load test method based on the movement of a single test loading vehicle has developed rapidly. The bridge response time history caused by the diagnostic load test contains important performance parameters of the bridge: influence surface. The influence surface can reflect the lateral and longitudinal mechanical properties of the bridge and is widely used in bridge damage identification. However, the current damage identification method of the assembled slab girder bridge based on the influence surface still has the following problems: the influence surface is regarded as an important indicator reflecting the performance of the bridge, but the mapping relationship between the performance change of the assembled multi-beam bridge and the influence surface change has not been established; the existing stiffness evaluation methods are mainly for ideal simply supported single beams, and the damage identification method for the stiffness of each main beam in the multi-beam bridge is insufficient; the existing damage identification methods are mainly for a certain specific damage type, and the main beam and hinge joint damage in the assembled slab girder bridge jointly affect the load lateral distribution of the bridge, and there is a lack of joint identification method for multiple damage types. SUMMARY

[0005] The purpose of the present application is to provide a joint identification method for main beam and hinge joint damage of an assembled slab girder bridge, so as to solve the series of problems existing in the current damage identification method of the multi-beam bridge, realize the effective early identification of the main beam and hinge joint damage of the multi-beam bridge, and provide guidance for bridge reinforcement and management.

[0006] The technical solution of this invention: A method for joint identification of damage to the main girder and hinge joint of a prefabricated slab girder bridge, comprising the following steps: Step 1: Identify the influence surfaces of each main girder segment based on bridge response and GNSS-RTK synchronous positioning data from the test loading vehicle. (1) Convert the latitude and longitude coordinates of the test loading vehicle obtained by GNSS-RTK into bridge coordinates. It is approximately assumed that the latitude and longitude coordinates of GNSS-RTK are located on a plane. The latitude and longitude coordinates are converted into bridge coordinates in a plane coordinate system with meters as the unit through affine transformation. The affine transformation formula is: (1); in, and The longitude and latitude of the test vehicle at a specific moment are obtained by GNSS-RTK. u and v It refers to the transverse and longitudinal positions of the bridge deck test loading vehicle; a 1~ a 6 is the affine parameter, which is obtained by inversion formula (1) based on the least squares method through at least 3 sets of determined mapping relationships between bridge surface coordinates and latitude and longitude coordinates; (2) After completing the affine transformation, if the spatial resolution of the target influence coefficient is d According to the i Bridge coordinates and the corresponding time t i = i / f ( f (For the GNSS-RTK sampling frequency), determine the test loading vehicle at the... k and( k +1) Time range of movement between influence coefficients : (2); in, p It is the distance between the origin of the bridge coordinate system and the longitudinal coordinate of the first influence coefficient; (3) If the GNSS-RTK and bridge response sampling are synchronized, the bridge response in the time domain can be expressed by the following formula. Convert to spatial domain : (3); in, mean This represents calculating the average value; x j Representing the j The location of each influence coefficient point; (4) After the spatiotemporal coordinate transformation of the bridge response, the original data is preprocessed by eliminating outlier data and correcting residual response. Based on the bridge response data The bridge response vector R is constructed, and the influence coefficient is identified based on the influence surface inversion algorithm, thereby obtaining the measured influence surface of each main girder. ; Step 2, Identify hinge joint damage in prefabricated slab girder bridges based on measured influence surfaces: (5) Based on the influence surfaces identified from the measured data and their theoretical reference values, a hinge joint damage index based on multiple influence surfaces is constructed. j Hinge joint damage index of root beam Expressed as: (4); in, x It tests the longitudinal coordinates of the bridge. y It is the horizontal coordinate. It is the first j The influence surface of the field test corresponding to the beam sensor. It is the first j The theoretical influence surface corresponding to the beam sensor, calculated by the finite element model; (6) Based on the hinge damage index Locate the damaged hinge joint, if from i From the beam to the first j Damage index of beam hinge joint If the change is less than 20%, it indicates that from the [missing information]... i From the beam to the first j The hinge joint between the beams is undamaged. If from... m From the beam to the first n Damage index of beam hinge joint A change greater than 20% indicates that from m From the beam to the first n The hinge joint between the beams was damaged; Step 3: Identify damage to the main beam of the prefabricated slab girder bridge based on measured influence surfaces: (7) Through the first j Field test influence surface of sensors on the root main beam Impact of reference theory By comparing the double integrals, the stiffness degradation index of the main beam is calculated. : (5); (8) The stiffness degradation of the main girder of the prefabricated slab girder bridge is judged by the stiffness degradation index. If If the value is greater than 1, it proves that the actual stiffness of the beam is greater than the theoretical value. j The beam was not damaged; if If the actual stiffness of the slab beam is less than the theoretical value, the 1st j The slab beam is damaged.

[0007] Advantages of the present application: 1. The present application establishes a field test method combined with real-time tracking of the test loading vehicle position, proposes a space-time synchronization method of bridge response and test loading vehicle position information, and can convert the time-domain bridge response time history into bridge response related to position; compared with the previous simplification of the test loading vehicle as uniform motion, the speed change of the loading vehicle can be considered, so that the spatial position of the test loading vehicle can be determined more accurately, and the bridge influence surface identification can be realized more accurately.

[0008] 2. Based on the analysis of the transverse and longitudinal mechanical properties of the multi-beam bridge, the relationship between the influence surface and the hinge joint shear stiffness and the bending stiffness of each main beam is established, and the hinge joint damage index and the stiffness degradation index are proposed accordingly. Compared with the existing single damage index, the method of the present application can realize effective positioning of the hinge joint damage of the multi-beam bridge while completing the quantitative analysis of the main beam damage. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 The flowchart of the method of the present application is shown in the figure; Figure 2 The cross-sectional view of the prefabricated slab beam bridge to be tested in Example 1 of the method of the present application is shown in the figure; Figure 3 The top view of the prefabricated slab beam bridge to be tested in Example 1 of the method of the present application is shown in the figure; Figure 4 The test loading vehicle used in Example 1 of the method of the present application is shown in the figure; Figure 5 The GPS-RTK receiver installed in Example 1 of the method of the present application is shown in the figure; Figure 6 The basic situation of the test bridge in Example 1 of the method of the present application is shown in the figure; Figure 7 The strain influence surface identified in Example 1 of the method of the present application is shown in the figure; Figure 8 Some influence coefficient values in the strain influence surface identified in Example 1 of the method of the present application are shown in the figure; Figure 9 The hinge joint damage identification result when the test loading vehicle is driving on the 11th main beam in Example 1 of the method of the present application is shown in the figure; Figure 10 The hinge joint damage identification result when the test loading vehicle is driving on the 13th main beam in Example 1 of the method of the present application is shown in the figure; Figure 11 The main beam damage result of the prefabricated slab beam bridge based on the measured influence surface in Example 1 of the method of the present application is shown in the figure; Figure 12 This is the on-site inspection result of the main beam damage in Embodiment 1 of the method of the present invention. Detailed Implementation

[0010] The invention will now be described in further detail with reference to the accompanying drawings and a real bridge example.

[0011] The prefabricated slab girder bridge damage identification method of the present invention consists of three steps: "identifying the influence surface based on the GNSS-RTK positioning of the test loading vehicle and the bridge response data synchronously", "identifying the hinge joint damage of the prefabricated slab girder bridge based on the measured influence surface", and "identifying the main beam damage of the prefabricated slab girder bridge based on the measured influence surface". The specific implementation method has been given above. The following example illustrates the usage and features of the invention.

[0012] Example 1: Damage Identification Case of Prestressed Hollow Slab Beam Bridge To verify the effectiveness of the proposed method, this embodiment presents a damage identification example for a hollow slab beam bridge. The hollow slab bridge to be tested has a span of 22 m and a deck width of 17 m. The superstructure consists of sixteen precast hollow slabs. Strain gauges were installed at the mid-span of each beam to collect strain time history data at a sampling frequency of 100 Hz. The west-side support of the bridge was set as the starting position for the test vehicle. The main girders were numbered from 1 to 16 from south to north. The basic information of the bridge to be tested is described in [link to relevant documentation]. Figure 2 and Figure 3 A crane with a total weight of 60 tons was selected as the test loading vehicle. This vehicle has five axles, each weighing 12 tons. The distances between the front axle and the subsequent axles are 2.75m, 1.85m, 1.65m, and 2m, respectively. The specific geometric dimensions of the test loading vehicle are shown in [reference needed]. Figure 4 A vehicle-mounted GNSS-RTK with a sampling frequency of 20Hz was installed on the roof of the test vehicle to determine its real-time position. For details on the GPS-RTK deployment, please refer to [link to details]. Figure 5 The apparent defects of the bridge under test are shown in the following figures. Figure 6 .

[0013] Based on the multi-main beam response caused by the test loading vehicle, the real-time position of the vehicle, and the vehicle's size and weight information, according to the formula... The bridge response was transformed into the spatial domain, and the strain influence surfaces of 16 main girders were identified based on the proposed algorithm. The identification results are shown below. Figure 7 Some influence coefficient values ​​can be found in [the table]. Figure 8 The identification results show that the strain influence coefficient reaches its maximum value near the deployed strain gauges, and when the sensor is installed on the north side of the bridge, the influence coefficient on the south side is almost zero, and vice versa. This indicates that there may be potential damage near the central hinge joint of the bridge, affecting the lateral transfer of load.

[0014] Based on the impact area identified on-site, the hinge joint damage index formula is used. Calculate the hinge joint damage index. Taking the test loading vehicle traveling on beams 11 and 13 as an example, the calculation results show that the hinge joint damage index does not change significantly from beam 9 to beam 16. Figure 9 However, the change in the damage index of the hinge joint between beams 8 and 9 exceeded 20%. Figure 10 On-site inspection revealed a significant relative displacement between the two main beams, consistent with the damage index detection results, thus proving the effectiveness of the hinge joint damage identification method of this invention.

[0015] Based on the impact surfaces identified on-site, the stiffness degradation index of each main beam was calculated. The result is as follows Figure 11 As shown, the results indicate that the stiffness degradation index of most main beams is less than 1, indicating that their stiffness is greater than the theoretical stiffness; however, the damage index of beams 11 and 13 is greater than 1, especially beam 11, whose actual stiffness is close to half of the theoretical value. (On-site inspection) Figure 12 The discovery of severe water seepage and transverse cracks in beam No. 11, consistent with the stiffness degradation index identification results, proves the accuracy of the main beam stiffness degradation identification method of this invention. Compared with existing single damage indexes, the method of this invention can effectively locate hinge joint damage in multi-beam bridges while simultaneously completing a quantitative analysis of main beam damage.

Claims

1. A method for joint identification of damage to the main beam and hinge joint of a prefabricated slab girder bridge, comprising the following steps: Step 1: Identify the influence surfaces of each main girder segment based on bridge response and GNSS-RTK synchronous positioning data from the test loading vehicle. (1) Convert the latitude and longitude coordinates of the test loading vehicle obtained by GNSS-RTK into bridge coordinates. It is approximately assumed that the latitude and longitude coordinates of GNSS-RTK are located on a plane. The latitude and longitude coordinates are converted into bridge coordinates in a plane coordinate system with meters as the unit through affine transformation. The affine transformation formula is: （1）； in, and The longitude and latitude of the test vehicle at a specific moment are obtained by GNSS-RTK. u and v It refers to the transverse and longitudinal positions of the bridge deck test loading vehicle; a 1~ a 6 is the affine parameter, which is obtained by inversion formula (1) based on the least squares method through at least 3 sets of determined mapping relationships between bridge surface coordinates and latitude and longitude coordinates; (2) After completing the affine transformation, if the spatial resolution of the target influence coefficient is d According to the i Bridge coordinates and the corresponding time t i = i / f ( f (For the GNSS-RTK sampling frequency), determine the test loading vehicle at the... k and( k +1) Time range of movement between influence coefficients : （2）； in, p It is the distance between the origin of the bridge coordinate system and the longitudinal coordinate of the first influence coefficient; (3) If the GNSS-RTK and bridge response sampling are synchronized, the bridge response in the time domain can be expressed by the following formula. Convert to spatial domain : （3）； in, mean This represents calculating the average value; x j Representing the j The location of each influence coefficient point; (4) After the spatiotemporal coordinate transformation of the bridge response, the original data is preprocessed by eliminating outlier data and correcting residual response. Based on the bridge response data The bridge response vector R is constructed, and the influence coefficient is identified based on the influence surface inversion algorithm, thereby obtaining the measured influence surface of each main girder. ; Step 2, Identify hinge joint damage in prefabricated slab girder bridges based on measured influence surfaces: (5) Based on the influence surfaces identified from the measured data and their theoretical reference values, a hinge joint damage index based on multiple influence surfaces is constructed. j Hinge joint damage index of root beam Expressed as: （4）； in, x It tests the longitudinal coordinates of the bridge. y It is the horizontal coordinate. It is the first j The influence surface of the field test corresponding to the beam sensor. It is the first j The theoretical influence surface corresponding to the beam sensor, calculated by the finite element model; (6) Based on the hinge damage index Locate the damaged hinge joint, if from i From the beam to the first j Damage index of beam hinge joint If the change is less than 20%, it indicates that from the [missing information]... i From the beam to the first j The hinge joint between the beams is undamaged. If from... m From the beam to the first n Damage index of beam hinge joint A change greater than 20% indicates that from m From the beam to the first n Hinge joint damage occurred between the beams; Step 3: Identify damage to the main beam of the prefabricated slab girder bridge based on measured influence surfaces: (7) Through the first j Field test influence surface of sensors on the root main beam Impact of reference theory By comparing the double integrals, the stiffness degradation index of the main beam is calculated. : （5）； (8) The stiffness degradation of the main girder of the prefabricated slab girder bridge is judged by the stiffness degradation index. If If the value is greater than 1, it proves that the actual stiffness of the beam is greater than the theoretical value. j The beam was not damaged; if If the value is less than 1, it proves that the actual stiffness of the beam is less than the theoretical value. j The beam was damaged.

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