CN115683035B - A method for measuring strain modal parameters of a beam structure - Google Patents
A method for measuring strain modal parameters of a beam structureInfo
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- CN115683035B CN115683035B CN202211297849.0A CN202211297849A CN115683035B CN 115683035 B CN115683035 B CN 115683035B CN 202211297849 A CN202211297849 A CN 202211297849A CN 115683035 B CN115683035 B CN 115683035B
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Abstract
The invention discloses a strain modal parameter measurement method of a beam structure, which comprises the following steps of determining a signal generation point in the beam structure; the method comprises the steps of defining signal sampling points in signal generating points, constructing a serial full-bridge structure at the signal sampling points, configuring a calculation model according to the serial full-bridge structure, obtaining output signals of the test sampling points, and calculating strain modal parameters of the beam structure. According to the technical scheme, the strain modal parameters of the beam structure under different working conditions can be accurately identified and measured, the accuracy of identification and measurement results can be improved, the measured modal parameters are closer to the actual conditions, and nonlinear errors caused by abrupt structural changes can be effectively avoided.
Description
Technical Field
The invention relates to the field of bridge health monitoring, in particular to a strain modal parameter measurement method of a beam structure.
Background
With the rapid development of modern industry, highways and railways in China, particularly the development of the industries of travelling frames, steel and beam structures, more and more buildings and other fields are built by adopting beam structures, and the beam structures are often the first choice, even the only choice, of key structures of national key engineering projects. At present, common detection methods for damage identification and vibration fatigue of a beam type structure comprise ultrasonic detection, infrared detection, acoustic emission, natural potential detection, impact echo detection and the like, and the detection methods can be used for detecting the appearance and structural part characteristics of the beam type structure.
The damage judgment of key structural components and nodes of the beam structure is difficult to reflect through the detection method, so that the structural damage judgment method is a technical scheme for carrying out systematic and comprehensive evaluation on the health condition, the safety degree, the residual life and the like of the whole structure of the building of the beam structure, and the technical scheme is used for obtaining the natural frequency, the damping and the corresponding structural mode shape of a structural system through the strain mode parameter identification, the measurement and the processing of the beam structure, so that a scientific means is provided for the damage identification and the structural health monitoring of the beam structure.
Disclosure of Invention
In order to achieve the above purpose, the application provides a method for measuring strain modal parameters of a beam structure, which comprises the following steps:
Determining a signal generation point in the beam structure;
designating a signal sampling point in the signal generating point;
Building a serial full-bridge structure at the signal sampling point, and configuring a calculation model according to the serial full-bridge structure;
obtaining an output signal of a test sampling point, and calculating strain modal parameters of the beam structure;
The method for constructing the serial full-bridge structure comprises the steps of arranging resistance strain gauges on the surfaces of four directions of a beam, forming four groups of bridge arms through the resistance strain gauges, and defining the four groups of bridge arms as a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm.
The first bridge arm is formed by connecting a strain gauge arranged on the top surface of the beam and a strain gauge arranged on the right surface of the beam end to form a bridge;
the second bridge arm is formed by connecting two constant value resistors with the same resistance value as the first bridge arm in an end-to-end manner;
The third bridge arm is formed by connecting one strain gauge arranged on the left side of the beam and one strain gauge arranged on the bottom surface of the beam end to form a bridge;
the fourth bridge arm is formed by connecting two constant value resistors with the first bridge arm or the third bridge arm and the like in an end-to-end mode to form a bridge.
Further, the serial full-bridge structure means that the bridge arms of the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm are connected end to form a serial bridge.
Further, the resistance strain gauge is arranged to be a constant resistance with a strain gauge arranged along the length direction of the beam structure and externally connected with the constant resistance.
The calculation model further comprises a variable voltage source, an impact hammer, a dynamic strain signal amplifier and a data processing system;
the variable voltage source is used for supplying power to the serial full-bridge structure;
the impact force hammer is used for hammering at a signal generation point and providing hammering excitation for the serial full-bridge structure;
The dynamic strain signal amplifier is used for amplifying the strain response generated by the structure under hammering excitation;
the data processing system is connected with the circuit output of the serial full-bridge structure and is used for calculating a calculation model corresponding to the output quantity input of the full-bridge structure so as to calculate and obtain the recognition result of each direction.
Further, obtaining output signals of the test sampling points comprises obtaining resistance parameters of four groups of resistance strain gauges, bridge voltage of a Wheatstone circuit and sensitivity coefficients of the strain gauges, wherein the resistance parameters also comprise a beam structure right surface resistance R R, a beam structure left surface resistance R L, a beam structure top surface resistance R T and a beam structure bottom surface resistance R B;
the output voltage of the full-bridge strain gauge is calculated in the following way:
Wherein, U B is the bridge voltage of the Wheatstone circuit, U 0 is the output voltage of the full-bridge strain gauge, R is the resistance of the strain gauge, and DeltaR is the variation of the strain gauge resistance.
The strain modal parameters comprise longitudinal strain of each surface of the beam structure, and the calculation mode is as follows:
wherein epsilon is the longitudinal strain of each surface of the beam structure, and the value of epsilon is the sum of the strain responses of the four surfaces of the beam structure.
Further, the output signal of the test sampling point refers to:
a strain signal generated by hammering excitation of an impact hammer at a signal generation point of a beam structure;
the strain signal has been amplified by a dynamic strain signal amplifier.
In one of the beam structures 9 signal generating points are arranged, said 9 signal generating points being evenly distributed in the beam structure.
According to the invention, the strain modal parameters of the beam structure under different working conditions can be accurately identified and measured, the accuracy of identification and measurement results is improved, the modal parameters are closer to the actual conditions, and nonlinear errors caused by abrupt structural changes are effectively avoided.
Drawings
FIG. 1 is a step diagram of a beam structure strain modal parameter measurement method provided according to an embodiment of the invention;
FIG. 2 is a schematic diagram of a tandem full bridge configuration provided in accordance with an embodiment of the present invention;
fig. 3 is a schematic diagram of a point location of an electrical resistance strain gauge according to an embodiment of the present invention.
Detailed Description
The following describes in detail the specific implementation of the present invention with reference to the drawings accompanying the specification.
The invention is used for detecting the characteristics of key structural components of a beam structure, a resistance strain gauge is arranged at a designated position on the surface of the key structural components to form a multi-surface serial combination, and the multi-surface serial combination is matched with a variable voltage source, an impact hammer, a dynamic signal amplifier and a data acquisition system to acquire amplified signals after strain response and calculate strain modal parameters.
FIG. 1 provides a step diagram of a method for measuring strain modal parameters of a beam structure, which comprises the following steps:
Step S100, determining a signal generation point in a beam structure;
In the method provided by the application, nine hammering points are determined on the beam as signal generation points, and 9 signal generation points are evenly distributed in the beam structure as shown in fig. 3.
Step S110, signal sampling points are specified in the signal generating points:
In the signal generating point provided in step S100, a point is selected as a signal sampling point, and as shown in fig. 3, a 2 nd point is selected as a signal sampling point, and the serial full bridge is laid out at the signal sampling point.
Step S120, a serial full-bridge structure is built at a signal acquisition position, and a calculation model is configured according to the serial full-bridge structure;
The beam structure built in the step is a serial full-bridge structure, firstly, four groups of resistance strain gauges are arranged on the surfaces of the four directions of the beam, four groups of bridge arms are formed by the four groups of resistance strain gauges, and the four groups of bridge arms are defined as a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm;
the first bridge arm is formed by connecting a strain gauge arranged on the top surface of the beam and a strain gauge arranged on the right surface of the beam end to form a bridge;
the second bridge arm is formed by connecting two constant value resistors with the same resistance value as the first bridge arm in an end-to-end manner;
The third bridge arm is formed by connecting one strain gauge arranged on the left side of the beam and one strain gauge arranged on the bottom surface of the beam end to form a bridge;
the fourth bridge arm is formed by connecting two constant value resistors with the first bridge arm or the third bridge arm and the like in an end-to-end mode to form a bridge.
When the transverse section of the beam structure is quadrilateral, the first surface is a right surface, the third surface is a top surface, the second surface and the fourth surface are a left surface and a bottom surface respectively, namely, the first resistance strain gauge, the third resistance strain gauge, the second resistance strain gauge and the fourth resistance strain gauge are longitudinally arranged in parallel with the beam structure in the right surface, the left surface, the top surface and the bottom surface.
As shown in FIG. 2, the serial full bridge structure comprises a first bridge arm, a third bridge arm, a left bridge arm and a bottom bridge arm, wherein the first bridge arm is formed by sequentially connecting two longitudinal resistance strain gauges on the right surface and the top surface in series; and connecting the constant value resistors with external equal resistance values end to form a second bridge arm and a fourth bridge arm, and connecting the bridge arms of the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm end to form a serial bridge.
In practical application, the longitudinal material properties of each surface of the beam structure have non-uniformity, and the strain influence of each surface is different due to the difference of the longitudinal material properties, so that the position where the strain gauge is arranged is designed in the application, namely, the strain gauge and the constant value resistor with external equal resistance are arranged at the center positions of four surfaces in the middle of the beam structure along the length direction of the structure to form a multi-bridge arm serial full bridge, namely, the arrangement of the resistance strain gauge means that the strain gauge and the constant value resistor with external equal resistance are arranged on each bridge arm along the length direction of the beam structure to form the resistance strain gauge.
The strain gauge can reflect the surface deformation of the tested piece, and the strain influence difference of the surface material is reduced by the arrangement mode of the position of the strain gauge, so that nonlinear errors caused by abrupt structural changes are effectively avoided.
The operation method for arranging the strain gauge can be used for adhering and fixing the strain gauge on the surface of the beam structure.
After the serial full-bridge structure is determined, a calculation model is continuously configured, and the calculation model further comprises a variable voltage source, an impact hammer, a dynamic strain signal amplifier and a data processing system;
the variable voltage source is used for supplying power to the serial full-bridge structure;
The impact force hammer is used for providing hammering excitation for the serial full bridge structure so as to generate a strain signal;
The dynamic strain signal amplifier is used for amplifying a strain signal generated by the structure under hammering excitation so as to improve the accuracy of identification and measurement results and enable the measured modal parameters to be closer to the actual conditions;
the data processing system is connected with the circuit output of the serial full-bridge structure and is used for calculating a calculation model corresponding to the output quantity input of the full-bridge structure so as to calculate and obtain the recognition result of each direction.
Step S130, obtaining an output signal of a test sampling point, and calculating strain modal parameters of the beam structure;
Fig. 3 is a schematic diagram of the distribution positions of the resistance strain gauges, where nine hammering points are determined on the beam, and in the present application, the sequence of using the impact force hammer to hammer different hammering points is designed, and sampling is performed at the 2 nd point, so as to implement measurement and identification of one row and one column of the strain frequency response function matrix of the beam structure, and the measurement and identification are used for measuring strain modal parameters of the beam under different working conditions.
In this step, the resistance parameters, wheatstone circuit bridge pressure, sensitivity coefficients of the strain gauges, and the like of the four sets of resistance strain gauges are acquired, and in the strain gauge arrangement, as shown in fig. 2, the beam structure right face R R is arranged longitudinally along the beam structure, the beam structure left face R L is arranged longitudinally along the beam structure, the beam structure top face R T is arranged longitudinally along the beam structure, and the beam structure bottom face R B is arranged longitudinally along the beam structure.
The output voltage of the full-bridge strain gauge is calculated in the following way:
wherein U B is the bridge voltage of the Wheatstone circuit, U 0 is the output voltage of the full-bridge strain gauge, R is the resistance of the strain gauge, and DeltaR is the variation of the strain gauge resistance;
this calculation can be written as: Wherein K is the sensitivity coefficient of the strain gauge;
The calculation method of the output voltage can be modified as follows: Wherein epsilon is the sum of the strain responses of the four surfaces of the beam structure, and epsilon 1、ε2、ε3 and epsilon 4 are the longitudinal strain responses measured on the four surfaces of the beam structure respectively;
Epsilon 1＝εT1;ε2＝εR1;ε3＝εB1;ε4＝εL1;
the modal parameters comprise longitudinal strain of each surface of the beam structure, and the calculation mode is as follows:
where ε is the sum of the strain responses of the four faces of the beam structure and ε 1、ε2、ε3 and ε 4 are the longitudinal strain responses measured on the four faces of the beam structure, respectively.
Output voltage:
The deformation is as follows:
from epsilon=epsilon 1+ε2+ε3+ε4:
In this step, the exact strain response value of the structure is identified by the full bridge as input to a row or column of the responsive frequency conversion function matrix.
The method provided by the invention can accurately identify and measure the strain modal parameters of the beam structure under different working conditions, can improve the accuracy of identification and measurement results, has the measured modal parameters closer to the actual conditions, and can effectively avoid nonlinear errors caused by structural abrupt changes.
The above disclosure is only a few specific embodiments of the present invention, but the present invention is not limited thereto, and any changes that can be thought by those skilled in the art should fall within the protection scope of the present invention.
Claims (6)
1. The method for measuring the strain modal parameter of the beam structure is characterized by comprising the following steps of:
Determining a signal generation point in the beam structure;
Designating a signal sampling point in the signal generating point;
Building a serial full-bridge structure at the signal sampling point, and configuring a calculation model according to the serial full-bridge structure;
Obtaining an output signal of the signal sampling point, and calculating a strain modal parameter of the beam structure;
The series-connection type full-bridge structure comprises four groups of bridge arms, wherein the four groups of bridge arms are defined as a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm, the bridge arms where the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm are arranged are connected end to form a series-connection type bridge, the resistance strain gauges are arranged along the length direction of the beam structure and are externally connected with fixed value resistors of the resistance values, the positions where the strain gauges are arranged are the central positions of four surfaces in the middle of the beam structure, the four surfaces are right side surfaces, top surfaces, left side surfaces and bottom surfaces, the longitudinal two resistance strain gauges on the right side surfaces and the top surfaces are sequentially connected in series to form the first bridge, and the longitudinal two resistance strain gauges on the left side surfaces and the bottom surfaces are sequentially connected in series to form the third bridge arm;
the output signal of the signal sampling point is calculated based on longitudinal strain responses measured by four surfaces of the beam structure;
the first bridge arm is formed by connecting a strain gauge arranged on the top surface of the beam and a strain gauge arranged on the right surface of the beam end to form a bridge;
The second bridge arm is formed by connecting two fixed-value resistors which are connected in series and have the same resistance value as the first bridge arm in an end-to-end manner;
the third bridge arm is formed by connecting a strain gauge arranged on the left side of the beam and a strain gauge arranged on the bottom surface of the beam end to form a bridge;
The fourth bridge arm is formed by connecting two fixed value resistors which are connected in series and have the resistance values of the first bridge arm or the third bridge arm and the like in an end-to-end mode to form a bridge.
2. The method of claim 1, wherein the computing model further comprises a variable voltage source, an impact force hammer, a dynamic strain signal amplifier, and a data processing system;
The variable voltage source is used for supplying power to the serial full-bridge structure;
The impact force hammer is used for hammering at a signal generation point and providing hammering excitation for the serial full-bridge structure;
The dynamic strain signal amplifier is used for amplifying the strain response generated by the structure under hammering excitation;
The data processing system is connected with the circuit output of the serial full-bridge structure and is used for calculating a calculation model corresponding to the output quantity input of the full-bridge structure so as to calculate and obtain the identification result of each direction.
3. The method of claim 1, wherein the obtaining the output signal of the signal sampling point comprises:
Acquiring resistance parameters of the four groups of resistance strain gauges, bridge voltage of a Wheatstone circuit and sensitivity coefficients of the strain gauges, wherein the resistance parameters also comprise a beam structure right resistance R R, a beam structure left resistance R L, a beam structure top resistance R T and a beam structure bottom resistance R B;
the calculation mode of the output voltage of the full bridge structure is as follows:
,
Wherein, the For the wheatstone circuit bridge voltage,The output voltage of the full-bridge strain gauge, R is the resistance of the strain gauge,Is the amount of change in gauge resistance.
4. The method for measuring strain modal parameters as set forth in claim 3, wherein the strain modal parameters include longitudinal strain of each surface of the beam structure by the following calculation method:
,
wherein ɛ is the sum of the strain responses of the four faces of the beam structure, ɛ 1、ɛ2、ɛ3 and ɛ 4 are the longitudinal strain responses measured on the four faces of the beam structure, respectively, and K is the sensitivity coefficient of the strain gauge.
5. The method of claim 1, wherein the output signal of the signal sampling point is:
a strain signal generated by hammering excitation of an impact hammer at a signal generation point of a beam structure;
the strain signal is amplified by a dynamic strain signal amplifier.
6. A method of measuring strain modal parameters according to claim 1, characterized in that 9 signal generating points are provided in one of the beam structures, the 9 signal generating points being evenly distributed in the beam structure.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104457681A (en) * | 2014-09-18 | 2015-03-25 | 合肥工业大学 | Girder structure dynamic deflection monitoring method based on strain mode |
| CN110031085A (en) * | 2019-04-19 | 2019-07-19 | 大连理工大学 | A kind of Damage Assessment Method sensor and Structural Damage Identification based on favour stone full-bridge principle |
| CN114720029A (en) * | 2022-03-11 | 2022-07-08 | 中国航发沈阳发动机研究所 | Load measuring device and method of multi-element pull rod structure |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105547205B (en) * | 2015-12-10 | 2018-03-30 | 苏州大学 | Method for measuring position of neutral axis of engineering structure by using modal strain |
| CN110793603B (en) * | 2019-10-31 | 2021-03-19 | 中南大学 | Combined bridge type coupler multi-element multi-directional load measuring system and decoupling method |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104457681A (en) * | 2014-09-18 | 2015-03-25 | 合肥工业大学 | Girder structure dynamic deflection monitoring method based on strain mode |
| CN110031085A (en) * | 2019-04-19 | 2019-07-19 | 大连理工大学 | A kind of Damage Assessment Method sensor and Structural Damage Identification based on favour stone full-bridge principle |
| CN114720029A (en) * | 2022-03-11 | 2022-07-08 | 中国航发沈阳发动机研究所 | Load measuring device and method of multi-element pull rod structure |
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