CN103940903A - Truss structured node damage detecting system and method - Google Patents

Abstract

The invention relates to a truss structured node damage detecting system and method, belonging to the technical field of structure detection. The truss structured node damage detecting system is characterized by comprising a data acquisition module, a data analysis module and a decision module, wherein the key technology is a jerk energy waveform averaging and normalizing curvature difference method based on a strain signal for truss node damage location in the data analysis module. The method is used for periodic detection for the truss structured node damage, and node damage is the most common damage type in the truss structure and is the chief culprit harming the truss structure; the system and the method have the advantages of high calculating speed, low cost, no demand of building structural finite element model, high noise resistance and the like, and have positive significance on safety service of the truss node in the engineering application.

Description

A kind of truss-frame structure Joint Damage detection system and method thereof

Technical field

The invention belongs to the structural damage detection technical field based on vibration, relate to the damage location of truss-frame structure node, specifically invented a damage positioning system regularly detecting for truss-frame structure node.

Background technology

Structural damage detection technology based on vibration is a kind of damage check technology that adopts global approach, in engineering structure safety detection, has broad application prospects.Structure Damage Identification based on vibration response signal time-domain analysis is one of them important branch, the vibratory response time series of this class methods Direct Analysis structure, need to not identify modal parameter based on vibration data, also avoid the impact on damage positioning result of uncertainty in the pilot process such as Modal Parameter Identification.In damage detecting method based on vibration, most critical is to build damage criterion with vibration information, detect damage in view of many construction damage positioning methods have adopted the index based on energy, and these damage positioning methods based on various " energy " are all obtained good effect; The present invention proposes the average normalization curvature difference method of the jerking movement degree energy waveform based on strain signal.Strain signal can obtain by foil gauge or fiber Bragg grating strain sensor, wherein fiber Bragg grating strain sensor have lightweight, super very thin, loss is low, chemical stability and anti-electromagnetic interference capability strong, adapt to the advantages such as low strain level, high-frequency range, support wavelength-division multiplex.

Truss-frame structure (grid structure) is the common structure type being widely used in all types of industries structure and engineering structure, many truss-frame structures are everlasting in extreme environment and are worked as steel purlin bridge construction, and Joint Damage (for example weld failure, bolt looseness) is the Major Diseases of steel truss structure.Existing document shows, the destruction of many steel constructions is to be caused by low-quality welding, and welding residual stress and weld defects etc. has fairly obvious effect in the brittle fracture accident of steel bridge, and the node of damage greatly reduces the earthquake resistibility of structure; Meanwhile, in the structure of in-service steel purlin, the loosening possibility even coming off of some high-strength bolts is also very large.Panel point is to the most important ingredient of truss-frame structure general safety, and the safety of node is the key of whole truss-frame structure safety; Once certain node failure, the truss rod of its periphery and the possibility of node failure just can increase thereupon, and then cause even disaster of structural failure.For example, document points out that the structural failure of Korea S Seongsu bridge is improper the causing of welding due to steel truss.If exist an effective method to detect in time the node state of steel truss structure, to find early the subtle change of node state, many disasters perhaps can be avoided.Therefore, to be applicable to the damage positioning method of truss-frame structure node significant in research.

Summary of the invention

In order to grasp in time the service state of panel point in truss-frame structure, invention provides a kind of truss-frame structure Joint Damage detection system, this system to comprise data acquisition module, data analysis module and three parts of decision-making module;

Wherein data collecting module collected is arranged in the strain-responsive signal of measuring point on all rod members of truss-frame structure minor structure to be measured and is stored in computing machine;

Damage positioning result is calculated and provided to the average normalization curvature difference method of data analysis module jerking movement degree energy waveform of the location of the truss-frame structure Joint Damage based on proposing by the strain signal of measuring point on rod member in all truss-frame structures that collect;

Decision-making module, according to the result of calculation of data analysis module, first shows the position that whether has abnormal measuring point and abnormal measuring point, if without abnormal measuring point, all safety of all panel points; If there is abnormal measuring point, must there be damage the panel point junction at truss rod two ends, abnormal measuring point place; Re-use physics lossless detection method the panel point at truss rod two ends, abnormal measuring point place is detected and determines that damage occurs in one end or two ends all have, finally injury region is keeped in repair.

The detecting step of truss-frame structure Joint Damage detection system is as follows:

Step 1: truss-frame structure to be measured is divided into several adjacent intervals, and each interval is called a minor structure, starts to detect one by one to the other end in order from one end of truss-frame structure;

Step 2, measuring point are arranged: a strain measuring point is arranged in the midpoint outside of each truss rod in truss minor structure to be measured, can use fiber-optic grating sensor or foil gauge test strain;

Step 3, data acquisition: in data acquisition module, while encouraging other certain panel point of truss minor structure to be measured with hand hammer, strain acquirement equipment gathers the strain signal at each truss rod measuring point place in minor structure to be measured, and the strain signal of truss rod measuring point is sent in computing machine;

Step 4: data analysis: the value of calculating the jerking movement degree energy JE of each measuring point place signal in data analysis module: truss rod in minor structure to be measured is numbered respectively to truss rod 1,2,3 ... M, supposes that (strain signal each loose some x) is x for the strain time series of the upper measuring point of truss rod k ₁, x ₂... x _n, the jerking movement degree energy JE that defines truss rod k measuring point place strain signal is as follows

${\mathrm{JE}}_k=\log \underset{i=1}{\overset{N-1}{\mathrm{\Σ}}}{\left(\frac{x_{i+1}-x_i}{\mathrm{\Δt}}\right)}^2---\left(1\right)$

Wherein JE _kbe jerking movement degree energy, log is common logarithm, and what N was strain signal counts; Adopt the lower value of calculating JE containing the strain-responsive of complete attenuation process of pulse excitation (or step excitation); After JE value on each measuring point is calculated, just can obtain jerking movement degree energy waveform by the value that connects these JE;

In step 5, data analysis module, calculate the curvature of jerking movement degree energy waveform: the curvature C of the jerking movement degree energy waveform of truss rod k measuring point place strain signal _k(1<k<M) be defined as follows

C _k＝JE _k-1-2JE _k+JE _k+1 (2)

Wherein JE _kit is the JE value of truss rod k measuring point place's strain;

C ₁and C _mcalculate based on following formula:

C ₁＝JE _M-2JE ₁+JE ₂ (3)

C _M＝JE _M-1-2JE _M+JE ₁ (4)

In step 6, data analysis module, calculate after the curvature value of the each measuring point in damage front and back, truss rod unit, the jerking movement degree energy waveform of strain-responsive is defined as follows in the curvature difference at truss rod k measuring point place

${\left(C_{\mathrm{\&Delta;}}^k\right)}_{\mathrm{rs}}={\left(C_{\mathrm{after}}^k\right)}_s-{\left(C_{\mathrm{before}}^k\right)}_r---\left(5\right)$

Wherein the curvature calculating according to the r group strain-responsive at truss rod k measuring point place before damage, the curvature calculating according to the s group strain-responsive at truss rod k measuring point place after damage;

The curvature difference in step 7, data analysis module, the strain signal (being one-time detection) before and after every a couple's damage being calculated be normalized, the poor maximal value of so each testing result mean curvature is 1, the curvature difference after normalization for

${\left(C_{\mathrm{\&Delta;}}^k\right)}_{\mathrm{rs}}^{*}={\left(C_{\mathrm{\&Delta;}}^k\right)}_{\mathrm{rs}}/\underset{k}{\max }\left[{\left(C_{\mathrm{\&Delta;}}^k\right)}_{\mathrm{rs}}\right]---\left(6\right)$

After repeated detection based on multi-group data in step 8, data analysis module, calculate the normalization curvature difference average μ of jerking movement degree energy waveform _kand be defined as damage criterion, define the damage criterion (DI) at truss rod k measuring point place _kas follows

${\left(\mathrm{DI}\right)}_k={\mathrm{\&mu;}}_k=\frac{1}{\mathrm{RS}}\underset{r=1}{\overset{R}{\mathrm{\&Sigma;}}}\underset{s=1}{\overset{S}{\mathrm{\&Sigma;}}}{\left(C_{\mathrm{\&Delta;}}^k\right)}_{\mathrm{rs}}^{*}---\left(7\right)$

Rule of thumb, RS >=10; The value of RS is the bigger the better, in actual use general desirable 20;

Step 9, the truss rod measuring point that damage criterion is more than or equal to threshold value δ in decision-making module are differentiated for abnormal measuring point,

Abnormal measuring point={ (DI) _k>=δ } (8)

Wherein δ is threshold value, and its damage positioning result based on strain-responsive data under harmless operating mode determines, δ be one than the jerking movement degree energy waveform normalization curvature difference average μ of harmless operating mode _kbigger value is to avoid reporting by mistake the appearance of measuring point;

Damage check result is: if without abnormal measuring point, survey the equal not damaged of all panel points in truss minor structure; If there is abnormal measuring point, the panel point at truss rod two ends, abnormal measuring point place must have damage, one end panel point of possible this truss rod has damage, and also the panel point at its two ends of possibility all has damage, and concrete degree of impairment need to be confirmed according to further local testing tool or method.

Truss-frame structure Joint Damage detection system and method thereof are equally applicable to the damage check of grid structure node, and concrete operation method is identical with truss-frame structure.

Beneficial effect of the present invention is, does not need to set up structural finite element model, can avoid the impact on damage check result of heavy structural finite element model modeling, correction and model error; The method of inventing, directly based on strain-responsive time series analysis, has also been avoided the impact of the uncertain pilot process such as Modal Parameter Identification on damage check result; And do not need interrecord structure excitation, before and after damage, the amplitude size of excitation does not affect testing result, but need be in identical Position input excitation before and after damage; The damage positioning method noise resisting ability of inventing is strong.The present invention is applicable to the regular detection of panel point damage, is also applicable to the damage check of grid structure node, and concrete operation method is identical with truss-frame structure.There is the advantages such as computing velocity finite element model, noise robustness fast, with low cost, that do not need to set up structure are strong; The safety of panel point is on active service and is had positive effect.

Brief description of the drawings

Fig. 1 system schematic of the present invention.

Fig. 2 process flow diagram of the present invention.

The average normalization curvature difference method computing module of the jerking movement degree energy waveform of Fig. 3 panel point damage location.

Fig. 4 steel purlin bridge and minor structure schematic diagram to be detected.

The strain signal example that Fig. 5 surveys.

The damage positioning result of the harmless operating mode of Fig. 6.

Fig. 7 damages the damage positioning result of operating mode 1.

Fig. 8 damages the damage positioning result of operating mode 2.

Fig. 9 damages the damage positioning result of operating mode 3.

Figure 10 damages the damage positioning result of operating mode 4.

The horizontal ordinate of Fig. 6～10 is truss rod measuring point numberings in truss minor structure to be measured, and ordinate is the poor average of normalization jerking movement degree energy waveform, if the ordinate of certain truss rod measuring point is more than or equal to threshold value 0.3, there is damage the panel point junction at its two ends.

Embodiment

The laboratory model of choosing the common Bailey beam formula steel purlin bridge of China carries out damage check as research object to its panel point, below in conjunction with accompanying drawing, technical scheme of the present invention is elaborated:

1) detected object

If Fig. 4 is the floor map of steel purlin, laboratory bridge model, the minor structure in selection figure in square frame is research object, to 12 bar number consecutivelies wherein, is designated as bar 1～12; Element number sequence does not affect result, but should remain unchanged before and after damage;

2) excitation

Vertically encourage this truss model at the place of point of excitation shown in Fig. 4 with hand hammer, do not need to record pumping signal;

3) damage operating mode: five test damage operating modes based in table 1 position damage truss-frame structure node default in this truss-frame structure; This test is simulated panel point damage by unscrewing the screw cap release bolt of truss rod one end on the bridge construction model of steel purlin; Study based on table.

The test damage operating mode of table 1 steel purlin bridge model

4) measuring point is arranged

Selective light fiber grating sensor monitor strain, at truss rod 1～12 mid point outer surface place respectively with 502 type bonding agents install a bare optical fibers and bare optical gratings sensor, by multiplexing fiber-optic grating sensor on optical fiber;

5) data acquisition

Adopt fiber Bragg grating (FBG) demodulator to carry out data acquisition based on LabVIEW software and graphic user interface, by the axial strain data real-time rendering of testing from fiber-optic grating sensor and be saved in computer, sample frequency is 1000Hz; As shown in Figure 5, choosing the strain-responsive in dashed rectangle in figure calculates;

6) definite threshold

The result of threshold value δ based on harmless operating mode determined: choose one group of strain vibratory response without damage structure as basis signal, add noise and obtain many groups of harmless strain-responsive signals under different noise levels; Repeated detection based on these signals can be damaged positioning result as shown in Figure 6, can definite threshold δ be therefrom 0.3;

7) truss-frame structure Joint Damage testing result

4 damage operating modes in the average normalization curvature difference method table 1 of the jerking movement degree energy waveform that employing the present invention proposes detect respectively, and net result is respectively as shown in Fig. 7～10; Therefrom known all testing results have all successfully been oriented abnormal measuring point, and must there be damage the panel point junction that goes out its two ends according to abnormal measuring point deducibility, and result is consistent with default damage;

8) conclusion

The damage check result of above single injury, poly-injury operating mode all show the average normalization curvature difference method of the jerking movement degree energy waveform of invented truss-frame structure Joint Damage location can be preferably for the damage location of truss-frame structure node.

Claims (3)

1. a truss-frame structure Joint Damage detection system, is characterized in that this system comprises data acquisition module, data analysis module and three parts of decision-making module;

Wherein data collecting module collected is arranged in the strain-responsive signal of measuring point on all rod members of truss-frame structure minor structure to be measured and is stored in computing machine;

Damage positioning result is calculated and provided to the average normalization curvature difference method of data analysis module jerking movement degree energy waveform of the location of the truss-frame structure Joint Damage based on proposing by the strain signal of measuring point on rod member in all truss-frame structures that collect;

Decision-making module, according to the result of calculation of data analysis module, first shows the position that whether has abnormal measuring point and abnormal measuring point, if without abnormal measuring point, all safety of all panel points; If there is abnormal measuring point, must there be damage the panel point junction at truss rod two ends, abnormal measuring point place; Re-use physics lossless detection method the panel point at truss rod two ends, abnormal measuring point place is detected and determines that damage occurs in one end or two ends all have, finally injury region is keeped in repair.

2. a kind of truss-frame structure Joint Damage detection system according to claim 1, is characterized in that detecting step is as follows:

Step 1: truss-frame structure to be measured is divided into several adjacent intervals, and each interval is called a minor structure, starts to detect one by one to the other end in order from one end of truss-frame structure;

Step 2, measuring point are arranged: a strain measuring point is arranged in the midpoint outside of each truss rod in truss minor structure to be measured, can use fiber-optic grating sensor or foil gauge test strain;

Step 3, data acquisition: in data acquisition module, while encouraging other certain panel point of truss minor structure to be measured with hand hammer, strain acquirement equipment gathers the strain signal at each truss rod measuring point place in minor structure to be measured, and the strain signal of truss rod measuring point is sent in computing machine;

Step 4: data analysis: the value of calculating the jerking movement degree energy JE of each measuring point place signal in data analysis module: truss rod in minor structure to be measured is numbered respectively to truss rod 1,2,3 ... M, supposes that (strain signal each loose some x) is x for the strain time series of the upper measuring point of truss rod k ₁, x ₂... x _n, the jerking movement degree energy JE that defines truss rod k measuring point place strain signal is as follows

${\mathrm{JE}}_k=\log \underset{i=1}{\overset{N-1}{\mathrm{\&Sigma;}}}{\left(\frac{x_{i+1}-x_i}{\mathrm{\&Delta;t}}\right)}^2---\left(1\right)$

Wherein JE _kbe jerking movement degree energy, log is common logarithm, and what N was strain signal counts; Adopt the lower value of calculating JE containing the strain-responsive of complete attenuation process of pulse excitation (or step excitation); After JE value on each measuring point is calculated, just can obtain jerking movement degree energy waveform by the value that connects these JE;

In step 5, data analysis module, calculate the curvature of jerking movement degree energy waveform: the curvature C of the jerking movement degree energy waveform of truss rod k measuring point place strain signal _k(1<k<M) be defined as follows

C _k＝JE _k-1-2JE _k+JE _k+1 (2)

Wherein JE _kit is the JE value of truss rod k measuring point place's strain;

C ₁and C _mcalculate based on following formula:

C ₁＝JE _M-2JE ₁+JE ₂ (3)

C _M＝JE _M-1-2JE _M+JE ₁ (4)

In step 6, data analysis module, calculate after the curvature value of the each measuring point in damage front and back, truss rod unit, the jerking movement degree energy waveform of strain-responsive is defined as follows in the curvature difference at truss rod k measuring point place

${\left(C_{\mathrm{\&Delta;}}^k\right)}_{\mathrm{rs}}={\left(C_{\mathrm{after}}^k\right)}_s-{\left(C_{\mathrm{before}}^k\right)}_r---\left(5\right)$

Wherein the curvature calculating according to the r group strain-responsive at truss rod k measuring point place before damage, the curvature calculating according to the s group strain-responsive at truss rod k measuring point place after damage;

The curvature difference in step 7, data analysis module, the strain signal (being one-time detection) before and after every a couple's damage being calculated be normalized, the poor maximal value of so each testing result mean curvature is 1, the curvature difference after normalization for

${\left(C_{\mathrm{\&Delta;}}^k\right)}_{\mathrm{rs}}^{*}={\left(C_{\mathrm{\&Delta;}}^k\right)}_{\mathrm{rs}}/\underset{k}{\max }\left[{\left(C_{\mathrm{\&Delta;}}^k\right)}_{\mathrm{rs}}\right]---\left(6\right)$

After repeated detection based on multi-group data in step 8, data analysis module, calculate the normalization curvature difference average μ of jerking movement degree energy waveform _kand be defined as damage criterion, define the damage criterion (DI) at truss rod k measuring point place _kas follows

${\left(\mathrm{DI}\right)}_k={\mathrm{\&mu;}}_k=\frac{1}{\mathrm{RS}}\underset{r=1}{\overset{R}{\mathrm{\&Sigma;}}}\underset{s=1}{\overset{S}{\mathrm{\&Sigma;}}}{\left(C_{\mathrm{\&Delta;}}^k\right)}_{\mathrm{rs}}^{*}---\left(7\right)$

Rule of thumb, RS >=10; The value of RS is the bigger the better, in actual use general desirable 20;

Step 9, the truss rod measuring point that damage criterion is more than or equal to threshold value δ in decision-making module are differentiated for abnormal measuring point,

Abnormal measuring point={ (DI) _k>=δ } (8)

Wherein δ is threshold value, and its damage positioning result based on strain-responsive data under harmless operating mode determines, δ be one than the jerking movement degree energy waveform normalization curvature difference average μ of harmless operating mode _kbigger value is to avoid reporting by mistake the appearance of measuring point;

Damage check result is: if without abnormal measuring point, survey the equal not damaged of all panel points in truss minor structure; If there is abnormal measuring point, the panel point at truss rod two ends, abnormal measuring point place must have damage, one end panel point of possible this truss rod has damage, and also the panel point at its two ends of possibility all has damage, and concrete degree of impairment need to be confirmed according to further local testing tool or method.

3. a kind of truss-frame structure Joint Damage detection system according to claim 1 and 2 and method thereof, is characterized in that, this system and method is equally applicable to the damage check of grid structure node, and concrete operation method is identical with truss-frame structure.