CN109839440B - Bridge damage positioning method based on static vehicle test - Google Patents

Bridge damage positioning method based on static vehicle test Download PDF

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CN109839440B
CN109839440B CN201910213384.8A CN201910213384A CN109839440B CN 109839440 B CN109839440 B CN 109839440B CN 201910213384 A CN201910213384 A CN 201910213384A CN 109839440 B CN109839440 B CN 109839440B
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damage
bridge
vehicle
axis vehicle
frequency
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CN109839440A (en
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贺文宇
任伟新
王佐才
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Hefei University of Technology
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Hefei University of Technology
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Abstract

The invention discloses a bridge damage positioning method based on static vehicle test, which is characterized by comprising the following steps of: the method comprises the steps that a single wireless acceleration sensor is installed on a two-axis vehicle to form movable testing equipment, the two-axis vehicle is gradually placed at different positions of a bridge to be tested, dynamic response of the two-axis vehicle and the bridge system under environmental excitation is obtained, frequency spectrum analysis is carried out on the dynamic response through Fourier transform to obtain corresponding frequency, system frequency change curves of the two-axis vehicle at different positions before and after damage are compared, and the damage position of the bridge is determined. The method is convenient to implement, high in efficiency and intuitive in result, and effectively solves the problems that a large number of test sensors are needed, the test is troublesome and the data processing difficulty is high in the traditional damage positioning method.

Description

Bridge damage positioning method based on static vehicle test
Technical Field
The invention relates to the field of beam structure monitoring and detection, in particular to a bridge damage positioning method based on static vehicle test, and the identification result can be used for evaluating the safety state of a bridge.
Background
The bridge is a key junction in traffic engineering. In the subsequent service process, the bridge is eroded by various complex environments, such as typhoons, earthquakes, floods, corrosion, explosion and the like, and the continuously increased vehicle load and traffic flow repeatedly act for a long time. The materials are aged and fatigued, damages are accumulated continuously, the performance is degraded gradually, and then huge hidden dangers are brought to the safe operation of the bridge structure, so that the necessity and the urgency of state monitoring and damage identification in the operation process of the bridge structure are highlighted.
At present, health monitoring of bridge structures has become an important subject of research of civil engineering workers, and the most critical and difficult problem is identification of damage to the structures. The use of changes in structural dynamic characteristics and dynamic response resulting from damage to identify damage has received considerable attention in the civil engineering industry. In general, these power-based impairment recognition methods can be categorized into two broad categories depending on whether a model is needed: one is a finite element model-based method and the other is a model-free method. For the first method, it is usually necessary to build a finite element model of the bridge according to the design drawing as a reference for damage identification. However, the actual civil engineering structure is often in a complex environment, the finite element modeling difficulty is high, and the uncertainty of the result is also high. The second method, a model-free damage identification method, does not depend on a model, does not need to establish a complex structural model, thereby reducing the calculation workload and avoiding the errors caused by modeling. The damage identification method based on the power can be classified into a direct method and an indirect method according to the position of a sensor for acquiring signals; in the direct method, a sensor acquires the dynamic response of the bridge, which belongs to the traditional method, and usually needs a large number of sensors, so that the field workload is huge, the data processing is complex, and the implementation is inconvenient; in the indirect method, the sensors collect the dynamic response of the vehicles on the bridge, and the damage identification can be carried out through the signals collected by the sensors which are installed on the vehicles individually, so that the method is convenient to implement, has a wide application prospect, and needs a complex signal processing means.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a bridge damage positioning method based on static vehicle testing, which determines the damage position of a bridge by testing the frequency of two-axis vehicles gradually placed at different positions of the bridge so as to solve the problems that the traditional method needs a finite element model, is inconvenient to implement, has high data processing difficulty and needs a large number of sensors.
The invention adopts the following technical scheme for solving the technical problems:
the invention relates to a bridge damage positioning method based on static vehicle test, which is characterized in that: the method comprises the steps that a single wireless acceleration sensor is installed on a two-axis vehicle to form movable testing equipment, the two-axis vehicle is gradually placed at different positions of a bridge to be tested, dynamic response of the two-axis vehicle and the bridge system under environmental excitation is obtained, frequency spectrum analysis is carried out on the dynamic response through Fourier transform to obtain corresponding frequency, system frequency change curves of the two-axis vehicle at different positions before and after damage are compared, and the damage position of the bridge is determined.
The method for positioning the damage of the bridge based on the static vehicle test is also characterized by comprising the following steps of:
step 1, selecting a two-axis vehicle, placing a single wireless acceleration sensor on the two-axis vehicle to form a movable testing device, and determining the mass M of the two-axis vehicle according to the following principle:
principle one: the frequency of a two-axis vehicle-bridge system can be measurably different from the frequency of a bridge, and the mass ratio of the vehicle to the bridge is required to be not less than 1%;
step 2, according to the wheel base L of the two-axle vehicletThe bridge to be tested with the length of L is divided into N intervals at equal intervals, and the method comprises the following steps: l ist=L/N;
Step 3, placing the two-axis vehicle in each section of the bridge step by step for testing to obtain the dynamic response of the two-axis vehicle-bridge system under the environment excitation;
step 4, carrying out frequency spectrum analysis on the obtained dynamic response through Fourier transform, and identifying frequency;
and 5, calculating a damage positioning index DLI according to system frequency changes of the vehicle at different positions before and after the damage, and determining the damage position of the bridge.
The beam structure damage positioning method based on the standing vehicle test is also characterized in that the damage position of the bridge is determined according to the following mode:
testing before damage: gradually arranging the two-axis vehicle in N intervals, forming a two-axis vehicle-bridge system before damage in each interval, and obtaining N first-order frequencies related to the two-axis vehicle-bridge system before damage through detectionWherein the superscript u represents the intact state, the subscript i represents the interval number, and the subscript i is 1,2, … N;
testing after damage: performing post-damage test by the same method as the pre-damage test, and detecting to obtain N first-order frequencies F of the post-damage two-axis vehicle-bridge systemi dThe superscript d indicates the damage status;
then, the relative frequency difference FD of each section before and after the damageiCharacterized by formula (1):
frequency difference curvature FDCiCharacterized by formula (2):
definition of injury localization index DLIiAs characterized by formula (3):
by using injury location indicator DLIiAs ordinate, with interval N as abscissa, draw DLIicurve-N, DLIiThe interval where the peak value in the-N curve is located is the damage interval.
The method comprises the steps that a single wireless acceleration sensor is installed on a two-axis vehicle, the two-axis vehicle is gradually placed at different positions of a bridge to be tested, the dynamic response of a two-axis vehicle-bridge system under environmental excitation is obtained, then, frequency spectrum analysis is carried out through Fourier transform, corresponding frequencies are obtained, system frequency change curves of the two-axis vehicle at different positions before and after damage are drawn, and the damage position of the bridge is determined; compared with the prior art, the invention has the beneficial effects that:
1. according to the invention, a single acceleration sensor is adopted for testing, and the problems of large equipment quantity and workload, inconvenience in implementation and high difficulty in the testing process caused by the fact that a plurality of sensors need to be arranged on the structure in the testing process are solved by moving the position of the two-axis vehicle.
2. The method well utilizes the characteristics of frequency change and damage position correlation of the two-axis vehicle-bridge system, the damage is positioned through frequency testing, the signal processing is carried out in the whole process by adopting the traditional classical Fourier transform, the data analysis process is simple, and the positioning efficiency is greatly improved only according to the first-order frequency.
3. The method only needs to test the system frequency of the two-axis vehicle placed at different positions of the bridge before and after damage, does not need to establish a finite element model, and has better applicability compared with the traditional method needing the finite element model.
Drawings
FIG. 1 is a schematic view of a procedure for lesion localization using the method of the present invention;
FIG. 2 is a simple beam model;
FIG. 3 is a typical dynamic response of a randomly excited simple beam;
FIG. 4 is a spectral plot of a typical dynamic response of a randomly excited simple beam;
FIG. 5 shows the positioning result of a single-damage simply supported beam;
FIG. 6 shows the positioning results of a double-damaged simply supported beam;
FIG. 7 is a two-span continuous beam model;
FIG. 8 shows the positioning results of a single-damage two-span continuous beam;
figure 9 shows the results of a double lesion two-span continuous beam positioning.
Detailed Description
Referring to fig. 1, in the method for positioning a bridge damage based on a stationary vehicle test in this embodiment, a single wireless acceleration sensor a is mounted on a two-axis vehicle a to form a movable test device, the two-axis vehicle is gradually placed at different positions of a bridge to be tested, dynamic responses of the two-axis vehicle and a bridge system under environmental excitation are obtained, frequency spectrum analysis is performed on the dynamic responses through fourier transform to obtain corresponding frequencies, and system frequency change curves of the two-axis vehicle at different positions before and after damage are compared to determine a damage position of the bridge.
In a specific embodiment, as shown in fig. 1, a bridge damage positioning method based on a stationary vehicle test is performed according to the following steps:
step 1, selecting a two-axis vehicle a, placing a single wireless acceleration sensor A on the two-axis vehicle a to form movable testing equipment, and determining the mass M of the two-axis vehicle a according to the following principle: principle one: the frequency of the two-axis vehicle-bridge system can be measurably different from the frequency of the bridge, and the mass ratio of the vehicle to the bridge is required to be not less than 1%.
Step 2, according to the wheel base L of the two-axle vehicle atThe bridge to be tested with the length of L is divided into N intervals at equal intervals, and the method comprises the following steps: l ist=L/N。
And step 3, placing the two-axis vehicle a in each section of the bridge step by step for testing, wherein the test of the two-axis vehicle a in the section 1, the section 2, the section i, the section N-1 and the section N of the bridge is shown in the figure 1, and the dynamic response of the two-axis vehicle-bridge system under the environmental excitation is obtained.
And 4, carrying out frequency spectrum analysis on the obtained dynamic response through Fourier transform, and identifying the frequency.
And 5, calculating a damage positioning index DLI according to system frequency changes of the vehicle at different positions before and after the damage, and determining the damage position of the bridge.
After the two-axis vehicle is still, the frequency of a two-axis vehicle-bridge system formed by the two-axis vehicle and the bridge changes, and the change of the frequency at the damage position is obviously different from that at other positions; therefore, in the present embodiment, the position of the bridge damage is determined as follows:
testing before damage: gradually arranging the two-axis vehicle in N intervals, forming a two-axis vehicle-bridge system before damage in each interval, and obtaining N first-order frequencies F related to the damage of the two-axis vehicle-bridge system before damage through detectioni uWherein, the superscript u represents the intact state, the subscript i represents the interval number, and the subscript i is 1,2, … N.
Testing after damage: performing post-damage test in the same manner as the pre-damage test, and detecting to obtain N data of the post-damage two-axis vehicle-bridge systemFirst order frequency F after injuryi dAnd the superscript d indicates the damage status.
Then, the relative frequency difference FD of each section before and after the damageiCharacterized by formula (1):
frequency difference curvature FDCiCharacterized by formula (2):
definition of injury localization index DLIiAs characterized by formula (3):
by using injury location indicator DLIiAs ordinate, with interval N as abscissa, draw DLIicurve-N, DLIiThe interval where the peak value in the-N curve is located is the damage interval.
Example 1:
FIG. 2 shows a simple beam having a length of 20m and an elastic modulus of 7.5X 1010N/m2Density of 2.7X 103kg/m3The cross section is a square section, the side length is 0.2m, and the cross section is divided into 30 intervals at equal intervals. The method adopts a numerical simulation means, and is divided into 20 plane Euler beam unit simulations, wherein the sampling frequency is 100Hz, and the time is 200 s. And calculating the dynamic response of the beam by a Newmark-beta method by adopting random excitation. The present embodiment considers the following two conditions:
(1) single damage condition: interval 17, the section stiffness is reduced to 70% of the original value;
(2) double damage working condition: interval 12, the section stiffness is reduced to 80% of the original value; in the interval 20, the section stiffness is reduced to 75% of the original value.
An identification step:
s1: selecting a two-axle vehicle a with the mass of 50 kg;
s2: setting 30 parking positions of the two-axis vehicle, wherein the parking positions are distributed at equal intervals;
s3: selecting a single wireless acceleration sensor, and placing the single wireless acceleration sensor on a two-axis vehicle to form movable test equipment;
s4: gradually placing the two-axis vehicle in each interval of the bridge, forming a two-axis vehicle-equal section beam system in each interval, and obtaining the dynamic response of the two-axis vehicle-bridge system under the environmental excitation, wherein the typical acceleration dynamic response is shown in fig. 3;
s5: performing spectrum analysis on the obtained dynamic response through Fourier transform, wherein a typical spectrogram is shown in FIG. 4, the peak value is obvious, and the frequency is identified;
s6: and calculating a damage positioning index DLI and determining the damage position of the bridge. The positioning results under the single damage condition and the double damage condition are shown in fig. 5 and fig. 6, respectively.
Example 2:
the length of each span of the two-span continuous beam cantilever beam shown in fig. 7 is 15m, other parameters, solving methods and identification processes are the same as those of the cantilever beam in the embodiment 1, and two working conditions are considered as well:
(1) single damage condition: section 23, the section stiffness is reduced to 80% of the original value;
(2) in the double damage condition, the section stiffness is reduced to 70% of the original value in the interval 10, and the section stiffness is reduced to 75% of the original value in the interval 23. The positioning results under the single damage condition and the double damage condition are shown in fig. 8 and fig. 9, respectively.
The embodiment 1 and the embodiment 2 verify that the method adopts a single acceleration sensor for testing, measures a plurality of system frequencies by moving the positions of the two-axis vehicle, and can effectively realize damage positioning by the constructed positioning indexes; the invention effectively solves the problems of large equipment quantity, high data processing difficulty, requirement of a finite element model and the like in the test process of the traditional damage identification method.

Claims (2)

1. A bridge damage positioning method based on standing vehicle test is characterized by comprising the following steps: installing a single wireless acceleration sensor on a two-axis vehicle to form movable testing equipment, gradually placing the two-axis vehicle at different positions of a bridge for testing, obtaining dynamic response of the two-axis vehicle and the bridge system under environmental excitation, performing frequency spectrum analysis on the dynamic response through Fourier transform to obtain corresponding frequency, comparing system frequency change curves of the two-axis vehicle at different positions before and after damage, and determining the damage position of the bridge according to the following mode:
testing before damage: gradually arranging the two-axis vehicles in N intervals, forming a two-axis vehicle-bridge system before damage in each interval, and obtaining N first-order frequencies F related to the damage of the two-axis vehicle-bridge system before damage through detectioni uWherein, the superscript u represents an undamaged state, the subscript i represents an interval number, and the subscript i is 1,2, … N;
testing after damage: performing post-damage test by the same method as the pre-damage test, and detecting to obtain N post-damage first-order frequencies F related to the post-damage two-axis vehicle-bridge systemi dThe superscript d indicates the damage status;
then, the relative frequency difference FD of each section before and after the damageiCharacterized by formula (1):
frequency difference curvature FDCiCharacterized by formula (2):
definition of injury localization index DLIiAs characterized by formula (3):
by using injury location indicator DLIiAs a ordinateWith the interval N as the abscissa, the DLI is drawnicurve-N, DLIiThe interval where the peak value in the-N curve is located is the damage interval.
2. The method for positioning the damage of the bridge based on the static vehicle test as claimed in claim 1, which comprises the following steps:
step 1, selecting a two-axis vehicle, placing a single wireless acceleration sensor on the two-axis vehicle to form a movable testing device, and determining the mass M of the two-axis vehicle according to the following principle:
principle one: the frequency of a two-axis vehicle-bridge system can be measurably different from the frequency of a bridge, and the mass ratio of the vehicle to the bridge is required to be not less than 1%;
step 2, according to the wheel base L of the two-axle vehicletThe bridge to be tested with the length of L is divided into N intervals at equal intervals, and the method comprises the following steps: l ist=L/N;
Step 3, placing the two-axis vehicle in each section of the bridge step by step for testing to obtain the dynamic response of the two-axis vehicle-bridge system under the environment excitation;
step 4, carrying out frequency spectrum analysis on the obtained dynamic response through Fourier transform, and identifying frequency;
and 5, calculating a damage positioning index DLI according to system frequency changes of the vehicle at different positions before and after the damage, and determining the damage position of the bridge.
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CN111397821A (en) * 2020-04-03 2020-07-10 暨南大学 Bridge structure damage positioning method based on cross correlation of axle signals

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