CN104569157A - Defect detection method of pre-stress structure - Google Patents

Abstract

The invention discloses a defect detection method of a pre-stress structure. The defect detection method comprises the following steps: stimulating a pulse load outside a channel to be detected to obtain reflection speed signals on the two sides of a stimulating point; carrying out analysis treatment on the reflection speed signals; carrying out fractional order Fourier transform on the reflection speed signals and calculating a fractional order region amplitude ratio; and analyzing an obtained result. Compared with the prior art, in the defect detection method of the pre-stress structure, a fractional order Fourier transform amplitude ratio of a signal is utilized to reflect inner defects of the structure; the result accuracy is high, namely all detection results are analyzed by a computer, so that influences caused by subjective factors or manual factors are avoided; the accuracy risk that a technicist judges whether the channel to be detected has defects or not is avoided; the accuracy is high and the objectivity is strong; and meanwhile, the detection time is shortened, the detection efficiency is improved and the application prospect is very large.

Description

The defect inspection method of prestressed structure

Technical field

The invention belongs to technical field of information processing, particularly relate to prestress passage compactness of grouting detection method.

Background technology

Along with the quickening of urbanization process, building, as one of important indicator weighing urban economy strength, makes prestressing technique become an indispensable important technology of urban construction.Prestressing technique is when building is built, and to be on active service performance to improve structure, and in the compressive stress that construction period applies in advance to structure, structure during one's term of military service pre-compression stress can the tension that causes of all or part of counteracting load, avoids structural failure.Before Engineering Structure Component bears external load, to the reinforcing bar in tension module, apply compressive pre-stress, improve the rigidity of component, postpone the time that crack occurs, increase the permanance of component.For physical construction, its implication is for make it produce stress in advance, and its benefit to improve the rigidity of structure own, and the elastic strength obviously can improving tension module is done in minimizing vibration and elastic deformation like this, makes resistance originally stronger.

Before structure bears external load, in advance compressive stress is applied to the tensile region under its outer load effect, prestressed structure is referred to as with the structural shape improving the performance that structure uses, be usually used in xoncrete structure, before xoncrete structure bearing load, in advance pressure is applied to it, concrete in tension zone internal force during its outer load effect is made to produce compressive stress, in order to offset or to reduce the tension that external load produces, structure is made not produce crack in the condition of normal use or split more late.And the advantage of prestressed reinforced concrete construction is based upon deformed bar and concrete (concrete) coheres on complete basis, the mechanical characteristic good by means of it and tensile property are used widely, particularly in large span or heavy load structure, and do not allow in the structure of cracking, prestressing technique also becomes better and approaching perfection day by day.

Along with the high speed development of Chinese engineering construction, prestress passage (comprising pipeline, duct etc.) slip casting structure is widely used, and the squeezing quality of its reserved passageway is the problem that people pay close attention to always.Prestressed structure relies on the ground tackle of component ends that the prestressing force of steel strand wires is passed to concrete, makes it produce compressive pre-stress; Finally in duct, be pressed into grout, make prestress wire and concrete component form entirety.Because slip casting leakiness causes steel strand wires corrosion in corrugated tube, cause the prestress of bridge bearing beam slab to lose in advance, foreshorten to 1/10th of designed life the actual life of bridge.Therefore in xoncrete structure, the quality of passage slip casting effect directly affects security and the serviceable life of whole prestressed reinforced concrete construction, and prestress passage slip casting effect is mainly evaluated by grouting quality packing.For the prestress effect of guarantee beam body and the permanance of structure, and avoid moisture to invade and corrosion steel bundle, in prestress beam hole pipeline, full water mud must be pressed.In theory, according to grouting process and quality control method, the packing of slip casting can be ensured preferably, but because channel blockage, injecting paste material, grouting method are improper or the reason such as human negligence easily causes passage grouting quality defect, i.e. slip casting leakiness.When passage grouting quality exists serious problems, buildings can be made in use quality accidents to occur.Therefore, adopt advanced Dynamic Non-Destruction Measurement to detect the overall grouting quality of the pipeline of prestressed structure, significant to the quality condition of objective evaluation structure.

At present, for the ultrasound examination of bridge prestress pipeline compactness of grouting, main signal processing method is based on the total length velocity of wave analysis of time domain and the spectrum analysis based on frequency domain, the analysis of total length velocity of wave extracts signal when walking, then velocity of wave is calculated, according to velocity of wave size divided rank, graduation evaluation structure grouting quality; Spectrum analysis is then carry out Fourier transform to signal, that signal is converted to frequency-region signal by time-domain signal, the Assessment of Changes grouting quality at observation signal frequency peak, these two kinds of methods often combine the judgement carrying out defect size and position, but these two kinds of methods receive the subjective factor impact of people in actual applications, the standard that the grade classification being mainly reflected in velocity of wave is not determined, spectrum information is complicated and changeable, and the experience accumulation also needing testing staff a large amount of could improve the accuracy judged.Therefore, a kind of newly intuitively can identify that the method that defect in structure exists urgently is released.

At present, the defect inspection method of traditional detection prestressed structure mainly contains ground penetrating radar method and sound velocity method (Zhu Xian, maintain the achievements of one's predecessors in garden. the applied research of ground penetrating radar in road quality Non-Destructive Testing [J]. and coal field geology and exploration, 2002,30 (5): 47-51.), due to intensive reinforcing bar interference-limited, it uses radar method, and sound velocity method is mainly by the micro-judgment whether defectiveness of technician, is subject to the impact of people's subjective factor and makes judged result inaccurate.

Due to above-mentioned defect inspection method Problems existing, thus the defects detection result of prestressed structure remains to be discussed, so the defect inspection method studying the higher prestressed structure of a kind of accuracy of detection is imperative.

Summary of the invention

For the problems referred to above that prior art exists, the defect inspection method that the object of this invention is to provide a kind of prestressed structure is to detect bridge pipeline whether existing defects, and conclusion objective reality, without the need to judging with artificial experience.

In order to realize foregoing invention object, the technical solution used in the present invention is:

A defect inspection method for prestressed structure, comprises the steps:

Step a) at the outer excitation pulse load of passage to be measured, obtains the reflection rate signal of shot point both sides;

Step b) by step a) gained reflection rate signal carry out analyzing and processing;

Step c) Fourier Transform of Fractional Order is carried out to reflection rate signal, calculate its fractional order territory Amplitude Ration;

Steps d) to step c) acquired results analyzes.

Preferably, step concrete operations a) are: apply impulse load in the center of bridge beam slab outer wall passage to be measured, subsequently with the reflection rate signal of signal receiving sensor difference received pulse shot point both sides.

More preferably, the pumping signal adopted when applying impulse load is the pulse signal in 10 cycles, and centre frequency is 100kHz.

More preferably, the distance reflecting rate signal extraction point and pulse excitation point is 5 ~ 10cm; Be preferably 5cm.

Preferably, step b) concrete operations be: utilize MATLAB software just step a) gained reflection rate signal carry out two-dimensional search, obtain the three-dimensional plot of the Fourier Transform of Fractional Order reflecting rate signal thus, the range value of three-dimensional plot is Fourier Transform of Fractional Order value, and transverse axis is p; More preferably, if the p value that in three-dimensional plot, the peak-peak point of amplitude is corresponding is optimum p value.

Preferably, step c) concrete operations be: set p value as the conversion order of Fourier Transform of Fractional Order, in MATLAB, p rank Fourier Transform of Fractional Order is carried out to step a gained reflection rate signal, obtain its fractional order amplitude spectrum, extract fractional order territory highest amplitude point and time amplitude point of reflection rate signal, calculate Amplitude Ration.

Preferably, to the formula that reflection rate signal carries out Fourier Transform of Fractional Order be:

$\begin{array}{c}{X}_p\left(u\right)={\∫}_{-\∞}^{+\∞}\mathrm{\χ}\left(t\right)B_{\mathrm{\α}}(t,u)\mathrm{dt}\\ =\left\{\begin{array}{cc}\sqrt{\frac{1-\mathrm{j\ωt}\left(\mathrm{\α}\right)}{2\mathrm{\π}}}{\∫}_{-\∞}^{+\∞}\mathrm{\χ}\left(t\right)\exp \left[j\frac{t^2+u^2}{2}\cot \left(\mathrm{\α}\right)-\mathrm{jtu}\csc \left(\mathrm{\α}\right)\right]\mathrm{dt},& \mathrm{\α}\≠\mathrm{n\π}\\ \mathrm{\χ}\left(t\right),& \mathrm{\α}=2\mathrm{n\π}\\ \mathrm{\χ}(-t),& \mathrm{\α}=(2n\±1)\mathrm{\π}\end{array}\right.---\left(1\right)\end{array}$

Wherein, the function that χ (t) is pumping signal, B _α(t, u) is the kernel function of p rank Fourier Transform of Fractional Order, and dt is the unit time;

In the fractional order amplitude spectrum obtained, horizontal ordinate is fractional order territory u, and ordinate is fractional order amplitude.

More preferably, kernel function B _αthe computing formula of (t, u) is:

$B_{\mathrm{\α}}(t,u)=\left\{\begin{array}{cc}\sqrt{\frac{1-j\cot \left(a\right)}{2\mathrm{\π}}}\exp [j\frac{t^2+u^2}{2}\cot \left(\mathrm{\α}\right)-\mathrm{jtu}\csc \left(\mathrm{\α}\right)],& \mathrm{\α}\≠\mathrm{n\π}\\ \mathrm{\δ}(t-u),& \mathrm{\α}=2\mathrm{n\π}\\ \mathrm{\δ}(t+u),& \mathrm{\α}=(2n\±1)\mathrm{\π}\end{array}\right.---\left(2\right)$

Wherein, δ (u+t), δ (u-t) are coordinate translation formula, and n is integer, ɑ=p pi/2, and p is the order of Fourier Transform of Fractional Order.

It should be noted that, function (the Michaels J E that χ (t) is pumping signal, Lee S J, Croxford A J, et al.Chirpexcitation of ultrasonic guided waves [J] .Ultrasonics, 2013,53 (1): 265-270.), be specially:

χ (t)=-10*sin (2* π * freq*t) * (1-cos (2* π * freq*t/10)) (3) wherein, freq=100000Hz.

Preferably, steps d) concrete operations be: according to step c) acquired results analyzes, and to judge in passage whether existing defects.

More preferably, steps d) criterion is: when the fractional order territory Amplitude Ration of shot point both sides signal is unequal, passage to be measured is part slip casting; When signal fractional order territory, shot point both sides Amplitude Ration is equal, passage to be measured is empty slip casting (namely compactness of grouting is 0%) or full slip casting (namely compactness of grouting is 100%); When the empty slip casting of further judgement or full slip casting, the reflection rate signal incident wave amplitude of empty slip casting is much larger than the reflection rate signal incident wave amplitude of full slip casting.

Compared with prior art, the advantage of the defect inspection method of prestressed structure provided by the invention is: carry out reflect structure inherent vice with signal Fourier Transform of Fractional Order Amplitude Ration, result precision is high, namely testing result is all analyzed by computer, avoid the impact of subjective factor or human factor, having evaded technician relies on experience to judge the risk of the passage to be measured whether correctness of existing defects, accuracy is high, objectivity is strong, save detection time simultaneously, improve detection efficiency, have great application prospect.

Accompanying drawing explanation

Fig. 1 a to be passage compactness of grouting be 0% finite element model schematic diagram;

Fig. 1 b to be passage compactness of grouting be 30% local finite meta-model schematic diagram;

Fig. 1 c to be passage compactness of grouting be 50% local finite meta-model schematic diagram;

Fig. 1 d to be passage compactness of grouting be 70% local finite meta-model schematic diagram;

Fig. 1 e to be passage compactness of grouting be 100% local finite meta-model schematic diagram;

Fig. 2 is the pumping signal schematic diagram of the applying of the defect inspection method of prestressed structure provided by the invention;

Fig. 3 to be passage compactness of grouting that the defect inspection method of prestressed structure provided by the invention gathers in pumping signal shot point A side be 0% model reflection rate signal schematic diagram;

Fig. 4 is that the defect inspection method of prestressed structure provided by the invention reflects rate signal three-dimensional FRFT treatment effect figure to the finite element model that passage compactness of grouting is 0%;

Fig. 5 is that the defect inspection method of prestressed structure provided by the invention reflects rate signal two dimension FRFT treatment effect figure to the finite element model that passage compactness of grouting is 0%;

Fig. 6 is the reflection rate signal fractional order thresholding schematic diagram that the defect inspection method of prestressed structure provided by the invention extracts;

Fig. 7 is the reflection rate signal fractional order territory Amplitude Ration schematic diagram of each finite element model of defect inspection method of prestressed structure provided by the invention;

Fig. 8 is the signal excitation of the defect inspection method of prestressed structure provided by the invention and receiving position and reflecting interface particular location schematic diagram;

Wherein, 1 is signal excitation point; 2 is defect reflection interface; 3 is bottom reflection interface; A is signal extraction point A, i.e. shot point A side; B is signal extraction point B, i.e. shot point B side.

Embodiment

In order to further understanding can be had to the present invention, below in conjunction with accompanying drawing, model and embodiment, the present invention is further elaborated.

In order to verify correctness of the present invention, now set up finite element model and defect inspection method according to prestress result provided by the invention detects its compactness of grouting.The present invention is to set up the finite element model of 5 bridge beam slabs, it should be noted that, the quantity of finite element model is not fixed, can require the passage compactness of grouting of bridge to be measured according to concrete engineering and determine: according to the physical parameter design finite element model of bridge to be measured, model height L is 900mm, width H is 300mm, in model, inside diameter of bel R2 is 100mm, corrugated tube wall thickness is 2.5mm, bar diameter R1 is 15mm, and the compactness of grouting that each finite element model is corresponding is respectively 0%, 30%, 50%, 70%, 100%; Apply pumping signal at finite element model outer wall, obtain reflection rate signal; And p rank Fourier Transform of Fractional Order is carried out to reflection rate signal, obtain its fractional order amplitude spectrum; The fractional order territory Amplitude Ration chosen in fractional order amplitude spectrum is compared, obtains a result; Step is as follows:

(1) Selection Model material, sets up the finite element model that passage compactness of grouting is 0%;

As shown in Figure 1, according to the passage compactness of grouting C of injecting cement paste elastic modulus E separately in passage in concrete body, concrete body in bridge to be measured and passage, density p and Poisson ratio υ and setting, in ANSYSLS-DYNA software, set up passage compactness of grouting finite element model; Wherein, the concrete of concrete body to be intensity be C50, pipeline is PVC corrugated tube, and injecting cement paste is M42.5 type cement, and material parameter is as shown in table 1:

Table 1

(2) apply pumping signal at finite element model outer wall, extract the reflection rate signal of finite element model shot point A side;

In the finite element model obtained step (1) in ANSYSLS-DYNA software, on the left of concrete body, outer wall respective channel center applies impulse load (i.e. pumping signal), as shown in Figure 2, the reflection rate signal of pulse excitation point A side is extracted subsequently in LS-prepost, reflection rate signal (X-Y scheme) when Acquisition channel compactness of grouting is 0%, as shown in Figure 3, in figure, horizontal ordinate is the time, and ordinate is speed; It should be noted that the pumping signal of employing is the pulse signal in 10 cycles, centre frequency is 100kHz, and the distance that reflection rate signal extracts point and pulse excitation point is 5cm.

(3) utilize software MATLAB that the reflection rate signal of step (2) gained finite element model shot point A side is converted to three-dimensional plot, obtain optimum p value;

The reflection rate signal of shot point A side (ɑ, u) plane in MATLAB software is carried out two-dimensional search, and search point, according to sampling time and sampling interval setting, sets search point as 1ms/1 μ s=1000 at this; Hunting zone is fractional order cycle, i.e. a p=0 to 4, then the scouting interval of p is 4/1000=0.004; As shown in Figure 4, obtain by MATLAB the three-dimensional plot of Fourier Transform of Fractional Order reflecting rate signal, namely calculate the range value in (ɑ, u) plane and obtain its peak-peak point, if p value corresponding to peak-peak point is optimum p value; Wherein, ɑ=p pi/2.

(4) p rank Fourier Transform of Fractional Order is carried out to the reflection rate signal of finite element model shot point A side;

Choose optimum p value, the optimum p value of this finite element model is 1.23, carries out p rank Fourier Transform of Fractional Order, obtain its fractional order amplitude spectrum, as shown in Figure 5 in MATLAB to reflection rate signal; Definition X _pu () is the fractional order amplitude of the p rank Fourier Transform of Fractional Order of step (4) gained reflection rate signal, its computing formula is:

$\begin{array}{c}{X}_p\left(u\right)={\∫}_{-\∞}^{+\∞}\mathrm{\χ}\left(t\right)B_{\mathrm{\α}}(t,u)\mathrm{dt}\\ =\left\{\begin{array}{cc}\sqrt{\frac{1-\mathrm{j\ωt}\left(\mathrm{\α}\right)}{2\mathrm{\π}}}{\∫}_{-\∞}^{+\∞}\mathrm{\χ}\left(t\right)\exp \left[j\frac{t^2+u^2}{2}\cot \left(\mathrm{\α}\right)-\mathrm{jtu}\csc \left(\mathrm{\α}\right)\right]\mathrm{dt},& \mathrm{\α}\≠\mathrm{n\π}\\ \mathrm{\χ}\left(t\right),& \mathrm{\α}=2\mathrm{n\π}\\ \mathrm{\χ}(-t),& \mathrm{\α}=(2n\±1)\mathrm{\π}\end{array}\right.---\left(1\right)\end{array}$

Wherein, the function that χ (t) is pumping signal, B _α(t, u) is the kernel function of p rank Fourier Transform of Fractional Order, and dt is the unit time; In the fractional order amplitude spectrum obtained, horizontal ordinate is fractional order territory u, and ordinate is fractional order amplitude.

Kernel function B _αthe computing formula of (t, u) is:

$B_{\mathrm{\α}}(t,u)=\left\{\begin{array}{cc}\sqrt{\frac{1-j\cot \left(a\right)}{2\mathrm{\π}}}\exp [j\frac{t^2+u^2}{2}\cot \left(\mathrm{\α}\right)-\mathrm{jtu}\csc \left(\mathrm{\α}\right)],& \mathrm{\α}\≠\mathrm{n\π}\\ \mathrm{\δ}(t-u),& \mathrm{\α}=2\mathrm{n\π}\\ \mathrm{\δ}(t+u),& \mathrm{\α}=(2n\±1)\mathrm{\π}\end{array}\right.---\left(2\right)$

Wherein, δ (u+t), δ (u-t) are coordinate translation formula, and n is integer, ɑ=p pi/2, and p is the order of Fourier Transform of Fractional Order.

Below to B _α(t, u) method for solving is briefly described:

According to selected p value, after bringing the solution formula of formula ɑ=p pi/2 and kernel function into, obtain B _α(t, u), χ (t) is known again, be specially: χ (t)=-10*sin (2* π * freq*t) * (1-cos (2* π * freq*t/10)) (3), then obtain X by Fourier Transform of Fractional Order formula _p(u).

(5) the fractional order territory Amplitude Ration of the reflection rate signal of finite element model shot point A side is calculated;

Extract fractional order territory highest amplitude point a1 and time amplitude point a2 of the reflection rate signal in Fig. 6 with Origin software, calculate the a1/a2 of finite element model shot point A side, the fractional order territory Amplitude Ration of the reflection rate signal namely in finite element model shot point A side.

(6) extract the reflection rate signal of finite element model shot point B side, data processing is carried out to it;

According to the operation of step (2) ~ (5), data processing after the reflection rate signal of extraction finite element model shot point B side, calculates shot point B side a1 '/a2 '.

(7) set up compactness of grouting be respectively the finite element model of 30%, 50%, 70%, 100% and detect, carry out interpretation of result;

According to the operation of step (1) ~ (6), set up compactness of grouting respectively and be the finite element model of 30%, 50%, 70%, 100% and detect, operation steps does not repeat them here; Each finite element model is detected and calculates obatained score rank Amplitude Ration and compare, as shown in Figure 7.

Below the reflection rate signal of shot point A side is calculated, verify its waveform component correctness;

As shown in Figure 8, if the length of pumping signal shot point (i.e. outer wall respective channel center on the left of concrete body) distance defect interface is L in finite element model ₁, in finite element model, the length of pumping signal shot point distance floor interface is L ₂, then pumping signal is transmitted to defect interface time t by shot point can be calculated ₁with the travel-time t of floor interface reflection wave ₂, by t ₁and t ₂contrast with the flaw echo composition on Fig. 3 and Bottom echo composition corresponding time, verify that whether the reflection rate signal that method provided by the invention obtains is correct, its computing formula is:

$t_1=\frac{2L_1}{V_l}---\left(4\right)$

$t_2=\frac{2L_2}{V_l}---\left(5\right)$

Wherein, V _lrepresent longitudinal wave velocity in concrete, be specially:

$V_l=\sqrt{\frac{E(1-v)}{\mathrm{\ρ}(1+v)(1-2v)}}---\left(6\right)$

In above-mentioned formula, elastic modulus E, density p and Poisson ratio υ in table 1, L again ₁=0.505m, L ₂=0.9m, can calculate t ₁=(2.15e-4) s, t ₂=(5.12e-4) s, after contrasting with penstock reflection ripple in Fig. 3 (Pipeline reflection wave) or bottorm echo (Bottom reflection wave), confirm that waveform component is correct, method therefor can be used to detect prestressed structure whether defectiveness.

Interpretation of result

As shown in Figure 8, when model be empty slip casting (namely compactness of grouting is 0%) and full slip casting (namely compactness of grouting is 100%) time, signal fractional order territory, shot point both sides Amplitude Ration is equal, when model is part slip casting, the fractional order territory Amplitude Ration of shot point both sides signal is unequal, according to this testing result, we can analyze by carrying out detection to the passage of bridge beam slab to be measured, thus to identify in bridge beam slab to be measured whether defective existence.

Embodiment 1

Below to detect bridge beam slab mock-up, the concrete of the concrete body of this beam slab model to be intensity be C50, pipeline is PVC corrugated tube, and injecting cement paste is M42.5 type cement, long 10 meters of beam slab, xsect is high 1.6 meters, wide 0.15 meter, 0.05 meter, aperture, without presetting defect, elastic modulus E, density p and Poisson ratio υ in table 1, wherein, the L measured ₁=0.05, L ₂=0.15, detecting step is as follows:

(1) apply pumping signal at bridge beam slab mock-up outer wall, receive with receiving sensor and extract the reflection rate signal of mock-up shot point A side;

On the left of the concrete body of bridge beam slab mock-up, outer wall respective channel center applies impulse load (i.e. pumping signal), use the reflection rate signal of signal receiving sensor received pulse shot point A side subsequently, namely obtain the reflection rate signal of this bridge beam slab mock-up; It should be noted that the pumping signal of employing is the pulse signal in 10 cycles, centre frequency is 100kHz, and the distance that reflection rate signal extracts point and pulse excitation point is 5cm.

(2) utilize software MATLAB that the reflection rate signal of step (1) gained mock-up shot point A side is converted to three-dimensional plot, obtain optimum p value;

The reflection rate signal of shot point A side (ɑ, u) plane in MATLAB software is carried out two-dimensional search, and search point, according to sampling time and sampling interval setting, sets search point as 1ms/1 μ s=1000 at this; Hunting zone is fractional order cycle, i.e. a p=0 to 4, then the scouting interval of p is 4/1000=0.004; Obtain by MATLAB the three-dimensional plot of Fourier Transform of Fractional Order reflecting rate signal, namely calculate the range value in (ɑ, u) plane and obtain its peak-peak point, if p value corresponding to peak-peak point is optimum p value; Wherein, ɑ=p pi/2.

(3) p rank Fourier Transform of Fractional Order is carried out to the reflection rate signal of mock-up shot point A side;

Choose optimum p value, in the present embodiment, optimum p value is 2.54, in MATLAB, carry out p rank Fourier Transform of Fractional Order to the reflection rate signal of shot point A side, obtains its fractional order amplitude spectrum; Definition X _pu () is the fractional order amplitude of the p rank Fourier Transform of Fractional Order of the reflection rate signal of step (4) gained shot point A side, its computing formula is:

$\begin{array}{c}{X}_p\left(u\right)={\∫}_{-\∞}^{+\∞}\mathrm{\χ}\left(t\right)B_{\mathrm{\α}}(t,u)\mathrm{dt}\\ =\left\{\begin{array}{cc}\sqrt{\frac{1-\mathrm{j\ωt}\left(\mathrm{\α}\right)}{2\mathrm{\π}}}{\∫}_{-\∞}^{+\∞}\mathrm{\χ}\left(t\right)\exp \left[j\frac{t^2+u^2}{2}\cot \left(\mathrm{\α}\right)-\mathrm{jtu}\csc \left(\mathrm{\α}\right)\right]\mathrm{dt},& \mathrm{\α}\≠\mathrm{n\π}\\ \mathrm{\χ}\left(t\right),& \mathrm{\α}=2\mathrm{n\π}\\ \mathrm{\χ}(-t),& \mathrm{\α}=(2n\±1)\mathrm{\π}\end{array}\right.---\left(1\right)\end{array}$

Wherein, the function that χ (t) is pumping signal, is specially χ (t)=-10*sin (2* π * freq*t) * (1-cos (2* π * freq*t/10)), freq=100000Hz, B _α(t, u) is the kernel function of p rank Fourier Transform of Fractional Order, and dt is the unit time; In the fractional order amplitude spectrum obtained, horizontal ordinate is fractional order territory u, and ordinate is fractional order amplitude.

Kernel function B _αthe computing formula of (t, u) is:

$B_{\mathrm{\α}}(t,u)=\left\{\begin{array}{cc}\sqrt{\frac{1-j\cot \left(a\right)}{2\mathrm{\π}}}\exp [j\frac{t^2+u^2}{2}\cot \left(\mathrm{\α}\right)-\mathrm{jtu}\csc \left(\mathrm{\α}\right)],& \mathrm{\α}\≠\mathrm{n\π}\\ \mathrm{\δ}(t-u),& \mathrm{\α}=2\mathrm{n\π}\\ \mathrm{\δ}(t+u),& \mathrm{\α}=(2n\±1)\mathrm{\π}\end{array}\right.---\left(2\right)$

Wherein, δ (u+t), δ (u-t) are coordinate translation formula, and n is integer, ɑ=p pi/2, and p is the order of Fourier Transform of Fractional Order.

Below to B _α(t, u) method for solving is briefly described:

According to selected p value, after bringing the solution formula of formula ɑ=p pi/2 and kernel function into, obtain B _α(t, u), χ (t) is known again, obtains X by Fourier Transform of Fractional Order formula _p(u).

(4) the fractional order territory Amplitude Ration of the reflection rate signal of mock-up shot point A side is calculated;

Extract fractional order territory highest amplitude point a1 and time amplitude point a2 of the reflection rate signal of shot point A side with Origin software, calculate the a1/a2 of mock-up shot point A side, i.e. the fractional order territory Amplitude Ration of the reflection rate signal of mock-up shot point A side.

(5) extract the reflection rate signal of mock-up shot point B side, data processing is carried out to it;

According to the operation of step (2) ~ (4), data processing after the reflection rate signal of extraction mock-up shot point B side, calculates shot point B side a1 '/a2 '.

Embodiment 1 gained testing result is in table 2.

Embodiment 2

The defect that the difference of the present embodiment and embodiment 1 is only to preset in the bridge beam slab model to be measured selected be a segment length is 0.6 meter, compactness of grouting is the defect of 80%.

Embodiment 2 gained testing result is in table 2.

Embodiment 3

The defect that the difference of the present embodiment and embodiment 1 is only to preset in the bridge beam slab model to be measured selected be a segment length is 0.6 meter, compactness of grouting is the defect of 20%.

Embodiment 3 gained testing result is in table 2.

Table 2

	Optimum p value	a1/a2	a1’/a2’
				Embodiment 1	2.54	1.0955	1.0955
Embodiment 2	2.75	1.0573	1.0648
				Embodiment 3	1.73	1.0456	1.0557

The Amplitude Ration calculated in his-and-hers watches 2 is analyzed, and analytic process is: in embodiment 1, A side is equal with the numerical value of a1/a2 and the a1 '/a2 ' of B side, is judged to be zero defect; In embodiment 2, A, B two Fourier Transform of Fractional Order Amplitude Ration of side data are unequal, are judged to be defectiveness; In embodiment 3, A, B two Fourier Transform of Fractional Order Amplitude Ration of side data are unequal, are judged to be defectiveness.

In order to embody objectivity of the present invention and advantage, with ground penetrating radar method and sound velocity method, the bridge beam slab model in embodiment 1 ~ 3 being detected below, and contrasting with embodiment 1 ~ 3 acquired results, the results are shown in Table 3; Wherein, ground penetrating radar method and sound velocity method are prior art, refer to document (Zhu Xian, maintain the achievements of one's predecessors in garden. the applied research of ground penetrating radar in road quality Non-Destructive Testing [J]. and coal field geology and exploration, 2002,30 (5): 47-51.), do not repeat at this.

Table 3

In sum, relative to prior art, the defect inspection method of prestressed structure provided by the invention compares by after the Amplitude Ration of computer calculate fractional order territory, and accuracy is high, and objectivity is strong, has great application prospect.

Finally be necessary described herein: above embodiment is only for being described in more detail technical scheme of the present invention; can not be interpreted as limiting the scope of the invention, some nonessential improvement that those skilled in the art's foregoing according to the present invention is made and adjustment all belong to protection scope of the present invention.

Claims (10)

1. a defect inspection method for prestressed structure, is characterized in that, comprises the steps:

Step a) at the outer excitation pulse load of passage to be measured, obtains the reflection rate signal of shot point both sides;

Step b) step a gained reflection rate signal is carried out analyzing and processing;

Step c) Fourier Transform of Fractional Order is carried out to reflection rate signal, calculate its fractional order territory Amplitude Ration;

Steps d) to step c) acquired results analyzes.

2. the defect inspection method of prestressed structure according to claim 1, it is characterized in that, step concrete operations a) are: apply impulse load in the center of bridge beam slab outer wall passage to be measured, subsequently with the reflection rate signal of signal receiving sensor difference received pulse shot point both sides.

3. the defect inspection method of prestressed structure according to claim 2, it is characterized in that the pumping signal adopted when applying impulse load is the pulse signal in 10 cycles, centre frequency is 100kHz.

4. the defect inspection method of prestressed structure according to claim 2, is characterized in that: the distance that reflection rate signal extracts point and pulse excitation point is 5 ~ 10cm; Be preferably 5cm.

5. the defect inspection method of prestressed structure according to claim 1, it is characterized in that, step b) concrete operations be: utilize MATLAB software just step a) gained reflection rate signal carry out two-dimensional search, obtain the three-dimensional plot of the Fourier Transform of Fractional Order reflecting rate signal thus, the range value of three-dimensional plot is Fourier Transform of Fractional Order value, and transverse axis is p.

6. the defect inspection method of prestressed structure according to claim 1, it is characterized in that, step c) concrete operations be: set p value as the conversion order of Fourier Transform of Fractional Order, in MATLAB, p rank Fourier Transform of Fractional Order is carried out to step a gained reflection rate signal, obtain its fractional order amplitude spectrum, extract fractional order territory highest amplitude point and time amplitude point of reflection rate signal, calculate Amplitude Ration.

7. the defect inspection method of prestressed structure according to claim 1, is characterized in that, formula reflection rate signal being carried out to Fourier Transform of Fractional Order is:

$\begin{array}{c}{X}_p\left(u\right)={\∫}_{-\∞}^{+\∞}\mathrm{\χ}\left(t\right)B_{\mathrm{\α}}(t,u)\mathrm{dt}\\ \left\{\begin{array}{cc}\sqrt{\frac{1-\mathrm{j\ωt}\left(\mathrm{\α}\right)}{2\mathrm{\π}}}{\∫}_{-\∞}^{+\∞}\mathrm{\χ}\left(t\right)\exp \left[j\frac{t^2+u^2}{2}\cot \left(\mathrm{\α}\right)\mathrm{jtu}\csc \left(\mathrm{\α}\right)\right]\mathrm{dt},& \mathrm{\α}\≠\mathrm{n\π}\\ \mathrm{\χ}\left(t\right),& \mathrm{\α}=2\mathrm{n\π}\\ \mathrm{\χ}(-t),& \mathrm{\α}=(2n\±1)\mathrm{\π}\end{array}\right.\end{array}---\left(1\right)$

Wherein, the function that χ (t) is pumping signal, B _α(t, u) is the kernel function of p rank Fourier Transform of Fractional Order, and dt is the unit time; In the fractional order amplitude spectrum obtained, horizontal ordinate is fractional order territory u, and ordinate is fractional order amplitude.

8. the defect inspection method of prestressed structure according to claim 7, is characterized in that, kernel function B _αthe computing formula of (t, u) is:

$B_{\mathrm{\α}}(t,u)=\left\{\begin{array}{cc}\sqrt{\frac{1-j\cot }{2\mathrm{\π}}}\exp [j\frac{t^2+u^2}{2}\cot \left(\mathrm{\α}\right)-\mathrm{jtu}\csc \left(\mathrm{\α}\right)],& \mathrm{\α}\≠\mathrm{n\π}\\ \mathrm{\δ}(t-u),& \mathrm{\α}=2\mathrm{n\π}\\ \mathrm{\δ}(t+u),& \mathrm{\α}=(2n\±1)\mathrm{\π}\end{array}\right.---\left(2\right)$

Wherein, δ (u+t), δ (u-t) are coordinate translation formula, and n is integer, ɑ=p pi/2, and p is the order of Fourier Transform of Fractional Order.

9. the defect inspection method of prestressed structure according to claim 1, is characterized in that, steps d) concrete operations be: according to step c) acquired results analyzes, and to judge in passage whether existing defects.

10. the defect inspection method of prestressed structure according to claim 9, is characterized in that, steps d) criterion is: when the fractional order territory Amplitude Ration of shot point both sides signal is unequal, passage to be measured is part slip casting; When signal fractional order territory, shot point both sides Amplitude Ration is equal, passage to be measured is empty slip casting or full slip casting; When the empty slip casting of further judgement or full slip casting, the reflection rate signal incident wave amplitude of empty slip casting is much larger than the reflection rate signal incident wave amplitude of full slip casting.。