Research ArticleDamage Identification of Piles Based onVibration Characteristics

Xiaozhong Zhang12 Wenjuan Yao1 Bo Chen2 and Dewen Liu3

1 Department of Civil Engineering Shanghai University Shanghai 200072 China2 School of Architectural Engineering Quzhou University Quzhou Zhejiang 324000 China3 College of Civil Engineering Kunming Southwest Forestry University Yunnan 650000 China

Correspondence should be addressed to Wenjuan Yao zhangxiaozhong126com

Received 19 June 2014 Accepted 25 July 2014 Published 17 November 2014

Academic Editor Dimitrios G Aggelis

Copyright copy 2014 Xiaozhong Zhang et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

A method of damage identification of piles was established by using vibration characteristics The approach focused on theapplication of the element strain energy and sensitive modals A damage identification equation of piles was deduced using thestructural vibration equation The equation contained three major factors change rate of element modal strain energy damagefactor of pile and sensitivity factor ofmodal damageThe sensitivemodals of damage identificationwere selected by using sensitivityfactor of modal damage firstly Subsequently the indexes for early-warning of pile damage were established by applying the changerate of strain energyThen the technology of computational analysis of wavelet transformwas used to damage identification for pileThe identification of small damage of pile was completely achieved including the location of damage and the extent of damageIn the process of identifying the extent of damage of pile the equation of damage identification was used in many times Finallya stadium project was used as an example to demonstrate the effectiveness of the proposed method of damage identification forpiles The correctness and practicability of the proposed method were verified by comparing the results of damage identificationwith that of low strain test The research provided a new way for damage identification of piles

1 Introduction

In practical engineering the quality of piles was influencedby various factors including the conditions of geotechnicalengineering structural design construction quality and thesurrounding environment As a result the problems of pilersquosquality could not be easily found and the accidents weredifficult to deal Due to the imperceptibility and complex-ity of pile foundation and the limitations of the existingidentification methods there are numerous veiled issueson theories and practices of pile damage detection [1ndash4]Therefore an early detection of the crack damage of pilefoundation and quick formulation of relevant preventionmeasures has become challenging topics for each evaluatoron structural health Regarding the pile quality problems inthe construction a variety of detection technologies havebeen developed in the past 50 years Chen [5] researchedthe application of core drilling method to test pile damage

but this method was not able to accurately judge the fractureand the development of piles foundation in service Xiao[6] established the method of application using ultrasonictransmission method in detecting the defects of piles Liuet al [7] applied the low strainmethod to detect the defects ofpiles Wu et al [8] proposed an approach to test the damageof foundation piles with a combination of applications ofcore drilling method ultrasonic transmission method andlow strain integrity testingThe demonstrated results verifiedthe reliability of the technology to identify the damageof piles The above studies are all related to bridges orbuildings under constructionHowever due to the restrictionof superstructure of built bridges or buildings the usual piletesting methods are not fully applicable to determine theintegrality of pile foundation Johnson and Rausche [9] andLuo et al [10] successively proposed to use the low straindual velocitymethod ultraseismicmethod and equal seismic

Hindawi Publishing Corporatione Scientific World JournalVolume 2014 Article ID 150516 8 pageshttpdxdoiorg1011552014150516

2 The Scientific World Journal

methods in detecting damage of the pile foundation inservice In 1995 Japanese researchers explored to apply holecamera technology to roughly determine the degree of cracksand damage of the foundation piles in southern Hyogo ofpostearthquake period but they did not achieve good resultsfor various reasons [11] In 2009 Yuan et al [12] determinedthe integrality of the bridge piles in service by collectingdisplacement signals in the condition that horizontal impactload was integrated with static loading Qi in 2012 achievedaccurate detection results by applying full-bore wall imagingtechnology in detecting damage of the pile foundation inservice [13] However in this process certain damage wasoccurred when the cores of piles were drilling In order toweaken the influence on test signal of foundation pile whichwas caused by flat-slab superstructure Zhang and Tian [14]used wavelet analysis method to eliminate the interferencesignal and applied wavelet analysis technology to detect theintegrality of high-pile

Dong et al [15] proposed a damage detection methodbased on both the changes in strain mode shape and changesin resonant frequency The difference between the damagedand undamaged structures was calculated by considering theindex Δ120601

119894that is given by

Δ120601119894= (

120596119906

119894

120596119889

119894

)

2

120601119889

119894minus 120601119906

119894 (1)

where 120596119906119894and 120596

119889

119894are the pulsations of the 119894th mode for the

undamaged and damaged structures 120601119906119894and 120601

119889

119894are respe-

ctively the 119894th strain mode shape of the undamaged anddamaged structures It was demonstrated that the index Δ120601

119894

was more sensitive to the damage severity when comparedwith the similar index calculated by displacement eigenparameter

Another damage detection method focused on the decr-ease of modal stain energy between two structural degrees offreedom This technique was proposed by Stubbs et al [1617] For a Bernoulli-Euler beam a damage index was given toidentify the damage in beams

The mode strain energy was performed by Parloo et al[18] for the identification of various damages in the I-40highway bridge inNewMexico It was shown that themethodwas not capable of achieving an efficient and robust detectionof small damage due to measurement noise

Alvandi and Cremona [19] used the strain energymethodfor damage detection not only in beam but also in civilengineering structures with experimental data They showedthat the strain energy method presented the best stabilityagainst disturbing signals Even if the strain energy methodappeared to be more efficient than other tested methods inthe complex and simultaneous damage case they indicatedthat the detection of two damages in the structures can bemore difficult and a specific procedure should be appliedThesame conclusions were reported by authors if the damage waslocated near supports or joints

Fan and Qiao [20] presented a strain energy basedidentification method to identify damage of plate-type struc-tureTheproposedmethodwas response-based identificationtechnique which required modal frequencies and curvature

mode shapes before and after damage However the bendingstiffness of the elements in the structures was assumed tobe constant in this study while in other structures it willbe no longer a constant in the real progress So study onstrain energy identification method should be a promisingsubject for the development of the real-time structural healthmonitoring system in the future

Yao and Zhang [21] have established a sensitive identi-fication method for fracture damage identification of pilesBut they only proposed the method theoretical derivation isnot very tight and there is no test to verify So in this paperthe theory of damage identification was derived rigorouslyon the basis of result of [21] In addition to this numericalmethods and experimental approachwere employed to verifythe proposed method

In summary scientists have done a series of studieson structural damage detection with strain energy methodand they have achieved certain research results Howeverregarding the damage detection in the pile foundation of thestructure in service the work is conducted in the exploratorystage and arduous efforts and further researches are neededbefore it can be much useful in engineering practicesParticularly for the small initial crack damage detection ofpile foundation it needs further theoretical analysis andexploration in practice Taking full advantages of the naturalfrequency on integral damage identification the sensitivity ofthe element modal strain energy method on small injuriesdetection and the efficient local analysis of Time domainand frequency domain of wavelet analysis an identificationmethod for locating the small injure of pile and measuringdamage severity was established in this paper of whichthe correctness and efficiency were also demonstrated byengineering application examples

2 Basic Theory

21 Eigenvalue Equation of Structural Vibration with Frac-ture Damage The general cause of fracture damage isthe decrease in local stiffness of the structure Thereforeaccording to the perturbation theory the structural vibrationeigenvalue equation is as follows [22]

[(119870 + Δ119870) minus (120582119894+ Δ120582119894)119872] (120601

119894+ Δ120601119894) = 0 (2)

where

Δ119870 =

119899

sum

119895=1

Δ119870119895= minus

119899

sum

119895=1

120572119895119870119895

(0 le 120572119895le 1)

Δ120582119894= Δ1205962

119894= 120601119879

119894Δ119870120601119894

(3)

119872 119870 represent respectively the mass matrix and stiffnessmatrix 120601

119894represents the 119894th ordermodal vector 120582

119894represents

the eigenvalue of 119894th modal of the vibration system 120582119894=

1205962

119894= (2120587119891)

2 Δ119870 represents changes of structural stiffness120572119895represents 119895th element damage factor of the structure

119870119895represents structural stiffness matrix of the 119895th element

before damage 119899 represents the total number of elements ofthe structure Expand (2) and then finish structural vibration

The Scientific World Journal 3

eigenvalue equation (2) of the structure can be expressed asfollows

120601119879

119894Δ119870120601119894+ 120575119894120601119879

119894119870120601119894+ 120601119879

119894Δ119870Δ120601

119894+ 120575119894120601119879

119894119870Δ120601119894= 0 (4)

where 120575119894= minusΔ120582

119894120582119894is change rate of structure eigenvalue

which ismainly used to determine sensitivity of the 119894thmodalon structural damage detection Therefore it is called modaldamage sensitivity factor

22 Identification Equation of Structural Damage Accordingto the energy balance theory the released elastic strainenergy was changed into plastic strain energy and surfaceenergy when pile cracks occur which stimulates the crackpropagation thus causing the decrease in structural strain inthe macroscopic level As a result (4) can be expressed in theform of the strain energy For piles structures define the 119895thelement strain energy of 119894th modal as follows

MSE119894119895= 120601119879

119894119870119895120601119894

MSE119889119894119895= (120601119889

119894)119879

119870119889

119895120601119889

119894= (1 minus 120572

119895) (120601119889

119894)119879

119870119895120601119889

119894

(5)

where the superscript ldquo119889rdquo represents the damaged structureAccording to the above formulas we can get

120601119879

119894119870120601119894=

119899

sum

119895=1

120601119879

119894119870119895120601119894=

119899

sum

119895=1

MSE119894119895= MSE

119894

120601119879

119894Δ119870120601119894=

119899

sum

119895=1

120601119879

119894Δ119870119895120601119894= minus

119899

sum

119895=1

120572119895120601119879

119894119870119895120601119894

= minus

119899

sum

119895=1

120572119895MSE119894119895

(6)

Ignore second-order or more high-end items we can get

120601119879

119894119870Δ120601119894=

119899

sum

119895=1

120601119879

119894119870119895Δ120601119894

=

119899

sum

119895=1

[(120601119889

119894)119879

119870119895120601119889

119894minus 120601119879

119894119870119895120601119894+ (120601119889

119894)119879

Δ119870119895120601119889

119894]

=

119899

sum

119895=1

[(1 minus 120572119895) (120601119889

119894)119879

119870119895120601119889

119894minus 120601119879

119894119870119895120601119894]

=

119899

sum

119895=1

(MSE119889119894119895minusMSE

119894119895)

120601119879

119894Δ119870Δ120601

119894=

119899

sum

119895=1

120601119879

119894Δ119870119895Δ120601119894= minus

119899

sum

119895=1

120572119895120601119879

119894119870119895Δ120601119894

= minus

119899

sum

119895=1

120572119895(MSE119889

119894119895minusMSE

119895)

(7)

Substitute (6) and (7) into (4) and (4) can be expressed asfollows

120575119894sdotMSE119889

119894=

119899

sum

119895=1

(120572119895sdotMSE119889

119894119895) (8)

where MSE119889119894= sum119899

119895=1MSE119889119894119895represent the total strain energy

of the 119894th modal of injured structureFormula (8) is equation of structural damage identifica-

tion which is composed by modal damage sensitivity factormodal strain energy of injured structure and the elementdamage factor Due to the sensitivity of strain energy on smalldamage [20] and the high accuracy and easy measurementof the modal damage sensitivity factor [23] (8) can be usedto accurately identify the damage severity of structurersquos smallinjuries

120575119894is the indicator used to determine the modal sensitivity

on structural damage the larger the value of 120575119894is the

more sensitive the modal identification on structural damageis and vice versa Therefore we can select the modal forstructural damage identification according to factor 120575

119894 while

in practical application a certain threshold value is set basedon the environment and damage situation of the structurethe efficient mode appears when the actual threshold value isgreater than the set one

23 Calculation of Element Modal Strain Energy For thepile structure in the case that element is sufficiently smallelement modal strain energy can be represented by theformula as follows

MSE119894119895= 120601119879

119894119870119895120601119894=1

2int

119887119895+1

119887119895

(EI)119895 (1205972120601119894

1205971199112)

2

119889119911

MSE119889119894119895= (1 minus 120572

119895) (120601119889

119894)119879

119870119895120601119889

119894=1

2int

119887119895+1

119887119895

(EI)119889119895(1205972120601119889

119894

1205971199112)

2

119889119911

(9)

(EI)119895and (EI)119889

119895represent respectively the structural flexural

rigidities of 119895th element before and after damage 119887119895and 119887119895+1

represent 119911 coordinates of node 119895 and node 119895 + 1In experimental modal analysis the flexural rigidity (EI)119889

119895

is unknown while in the case of small injury it can be sub-stituted by flexural rigidity before injury ((EI)

119895) Considering

that the selected elements are relatively small so the flexuralrigidity (EI)

119895of the 119895th element can be approximated as a

constant which can be put outside of the integral sign So (9)can be rewritten as follows

MSE119894119895=

1

2(EI)119895int

119887119895+1

119887119895

(1205972120601119894

1205971199112)

2

119889119911 (10)

MSE119889119894119895=

1

2(EI)119895int

119887119895+1

119887119895

(1205972120601119889

119894

1205971199112)

2

119889119911 (11)

4 The Scientific World Journal

(12059721206011198941205971199112)2 in (11) can be replaced by the mean value of (12060110158401015840

119894119895)2

and (12060110158401015840

119894(119895+1))2 so (11) can be expressed as follows

MSE119894119895=1

4(EI)119895[(12060110158401015840

119894119895)2

+ (12060110158401015840

119894(119895+1))2

] (119887119895+ 119887119895+1

) (12)

Similarly (13) can be rewritten as follows

MSE119889119894119895=1

4(EI)119895[(120601119889

119894119895)10158401015840

]

2

+ [(120601119889

119894(119895+1))10158401015840

]

2

(119887119895+ 119887119895+1

)

(13)

where (12060110158401015840119894119895)2 (12060110158401015840119894(119895+1)

)2 [(120601119889119894119895)10158401015840]2 and [(120601

119889

119894(119895+1))10158401015840]2 can be got

by measuring displacement mode shapes

24 Determination of Damage Location The difference valuebetween the element modal strain energies before and afterdamage will be set as the original signal of injury

119891119895 (119911) = MSE119889

119894119895minusMSE

119894119895 (14)

The signal119891119895(119911)was firstly fitted by cubic spline interpolation

and then transformed by wavelet function for transformcoefficients which can be used to detect the damage location

119863119868119894119895= 119862(119886 119887)

119894119895 (15)

119862(119886 119887)119894119895

represents the transformation coefficient of 119895thelement in which ldquo119886rdquo is the scale parameter and ldquo119887rdquo isthe time parameter 119863119868

119894119895represents the location index of

damaged element So index119863119868119894119895can be used to determine the

damaged element specifically the larger value of index 119863119868119894119895

is the bigger possibility of a damaged 119895th element isIn order to reduce the impact of random noise from the

test mode shapes multiorder efficient modals are used todiagnose structural damage location

119863119868119895=

1

119873sum

119898

119863119868119894119895 (16)

where 119873 is the number of selected efficient modals Inpractical applications a given threshold value of 119863119868

119895can be

used to determine whether there is a damage or not in thestructure

25 Calculation of Damage Severity After damaged elementis determined formula (8) will be applied to calculate thedegree of element damage The element damage factor 120572

119895

can be used to represent the damage severity If there is onlyone location of damage which is assumed in 119896 element then120572119895= 0 (119895 = 119896) only 120572

119896= 0 Equation (8) can be expressed

120572119896=120575119894sdotMSE119889

119894

MSE119889119894119896

(17)

If there are multiple locations of damage assuming that thereare 119898 elements (119896

1 1198962 119896

119898) damaged (119898 le 119899) then 119898

number of efficient modes (1199021 1199022 119902

119898) are needed for the

calculation Therefore using the equation set which consists

of 119898 equations the corresponding damage factor 120572 can besolved The equation set is as follows

120575 sdotMSED = 120572 sdotMSEDD (18)

where

120575 = [12057511990211205751199022

1205751199023

sdot sdot sdot 120575119902119898]

MSED =

[[[[[[[[[[[

[

MSE1198891199021

MSE1198891199022

MSE1198891199023

MSE119889119902119898

]]]]]]]]]]]

]

120572 = [12057211989611205721198962

1205721198963

sdot sdot sdot 120572119896119898]

MSEDD

=

[[[[[[[[[

[

MSE11990211198961

MSE11990221198961

MSE11990231198961

sdot sdot sdot MSE1199021198981198961

MSE11990211198962

MSE11990221198962

MSE11990231198962

sdot sdot sdot MSE1199021198981198962

MSE11990211198963

MSE11990221198963

MSE11990231198963

sdot sdot sdot MSE1199021198981198963

MSE1199021119896119898

MSE1199022119896119898

MSE1199023119896119898

sdot sdot sdot MSE119902119898119896119898

]]]]]]]]]

]

(19)

119901 represents the number of measured modals 119898 representsthe number of damaged elements If 119901 lt 119898 extended modalwhich extracted by experimental modal expansion technique[24] can be applied in the calculation

3 Example Verification

31 Overview of Project Natural hollowed filling piles andartificial hollowed filling piles were used in the foundationconstruction of Ouhai Sports Center Stadium with effectivepile length ranging from 4m to 30m diameter range from600mm to 1000mm and C25 of pile concrete strengthTotally there were 129 piles used in the project according tothe verification results of low strain detection and excavation96 of the damage occurred at 74m from the top of number71 pileThe length of number 71 pile is 21m and its diameter is1mThe actual damage of number 71 pile is shown in Figure 1Figure 1(b) is the ultrasonic strain curve of the pile

32 Mode Measurement Using Top Acceleration and Deflec-tions of the Pile Typical accelerometer was attached on thestructure at the top of the pile (Figure 2) The accelerationand deflection of the pile were obtained from the datacollected by the accelerometer (Figure 3) Figure 3 is theacceleration response from 163 second to 171 second usingultrasonic technology Figure 4 is the top defection usingdisplacement sensor Figure 4 shows the first five ordermodalshapes derived for sensors Mode shapes (actual modal of thepile) and frequencies were derived by the acceleration anddeflection (Table 1)

The Scientific World Journal 5

(a) On-site excavation detection

Location SYYTP ID 71 R 700mm V 350mS Date 2010-8-2

000 525 1050 1575 2100

1000m

(b) Detection of low strain

Figure 1 The actual damage of pile

Figure 2 Typical accelerometer attachment

0

002

004

006

008

163 164 165 166 167 168 169 170 171

Acce

lera

tion

(g)

Time (s)

minus008

minus006

minus004

minus002

Figure 3 Acceleration response of sensor

0

05

1

15

0 10 20 30 40

Mag

nitu

de

Distance (m)

Series 1Series 2Series 3

Series 4Series 5

minus1

minus05

Figure 4 Mode shapes derived by sensors

33 Finite Element Modeling Applying finite element soft-ware ANSYS we establish finite element model of soil-pileinteraction for number 71 pile (Figure 5(a)) according tothe design drawings According to actual damage on thenumber 71 pile the pile model of the cracks was establishedat 74 meters from the top of the pile with crack depthaccounting for 96 of the diameter of pile foundation(Figure 5(b)) The element type of pile foundation model isSOLID45The nonlinear spring element COMBIN139 is usedto simulate pile-soil interaction In order to establish a finiteelement computation model which is more consistent withthe environment of actual engineering situation the modelupdating technology was used to improve the finite elementmodel based on the measured data

6 The Scientific World Journal

(a) Before damage (b) After damage

Figure 5 Finite element model of pile-soil interaction

0

005

01

015

02

025

03

035

04

045

05

1 2 3 4 5 6 7 8 9 10

The r

ate o

f cha

nge

Mode

Figure 6 The change rate of the natural frequency

005

115

225

335

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101

106

111

116

121

DI

Elementsminus15

minus1

minus05

Figure 7 The DI of each element calculated by efficient modal

34 Selection of EfficientMode The change rate of the naturalfrequencies before and after damage is shown in Figure 6 andTable 1 and the efficient frequency threshold is set as 120575

119894ge

04 As Figure 6 shows mode 1 and mode 4 are the efficientmodes of damage case

35 Damage Location Identification Information function isestablished using the changes of element strain energy beforeand after damage andwavelet transform is used to determinethe parameters (119863119868) for the damage location Efficient modal119863119868119895is shown in Figure 7 By setting the threshold (119863119868 gt 2)

it can be clearly determined that crack damage occurred inthe elements from 55 to 59 which is very identical with theactual damage location The identification results of damagelocation are shown in tables The identification error is 3which proves the accuracy advantage of damage locationidentification method

36 Identification of Injury Severity Element damage factor120572 is calculated by applying (18) and the results are shownin Table 2 As shown in Table 2 the result of actual injury isvery close to that of calculated injury with identification errorby 62 which proves that the method of damage severityidentification has a higher accuracy

4 Conclusions

This paper firstly selected efficient modes for damage identi-fication by applying the change rate of eigenvalues and thenit established an accurate method for small damage iden-tification based on the application of sensitivity of elementmodal strain energy to small structural injury and efficientlocal analysis capabilities of wavelet analysis The efficiencyand accuracy of the proposed method were verified through

The Scientific World Journal 7

Table 1 Calculated natural frequencies from the FE model

ModeThe experimental

monitoringfrequencies

The calculatednatural frequencies Difference ()

1 1940 1932 0412 3035 2997 1253 6835 6805 0444 6983 6944 0565 7883 7852 039

Table 2 Results of damage identification

Actualinjury

Low strainmethoderror

Newmethoderror

Damage location 74m 671m93 708m43Damage severity 96 Small damage 10262

identifying small cracks damage of the pile used in the OuhaiSports Center The conclusions are as follows

(1) Fracture identificationmethod proposed in this papercan effectively and accurately identify the fracturedamage location for the hidden structures in service

(2) The proposed method can effectively identify andquantify the fracture damage severity for the hiddenstructures in service providing an important refer-ence for the assessment of fracture damage

(3) The method presented in this paper provided anew approach for damage identification of concealedstructure

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is one of research projects financed by HunanProvince Research Center for Safety Control Technology andEquipment of Bridge Engineering (Changsha University ofScience amp Technology) The number of research projects is13KC05

References

[1] H W Zhou W T Weng and Y Wang ldquoSeveral methods ofthe bridge pile testingrdquo Highway and Transportation Research(Applied Technology Edition) vol 4 pp 222ndash225 2012

[2] X L Han Y X Han and X M Tang ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 6 pp 105ndash107 2001

[3] H Y Chai M G Liu and S W Bai ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 5 pp 624ndash628 2003

[4] C H Zhang J L Zhang J H Xie et al ldquoThe multi-reflectedwave analysis on the low strain integrity testing of pile founda-tionrdquo Journal of Xiamen University Natural Science vol 3 pp214ndash216 2005

[5] Y M Chen ldquoGot method drills in pile foundation inspectionabout the application analysisrdquo Construction and Design forProject vol 7 pp 129ndash131 2011

[6] C X Xiao ldquoApplication of ultrasonic transmission method todetecting integrity of large-diameter bored cast-in-place pilesrdquoRock and Soil Mechanics supplement 1 pp 169ndash171 2003

[7] F C LiuWWang Z S Zhang andWQ Liu ldquoWave analysis ofpile foundation low strain detection and determination of pilebody integrityrdquo Port Engineering Technology vol 2 pp 46ndash482012

[8] H QWu R Y Ma L Y Huang J Peng and L Chen ldquoGeneralapplication and analysis of several detection methods in theengineering foundation pilesrdquoConcrete vol 4 pp 119ndash121 2012

[9] M Johnson and F Rausche ldquoLow strain testing of piles utilizingtow acceleration signardquo Stress Wave vol 3 pp 859ndash869 1996

[10] X Luo H Haya T Inaba T Shiotani and Y Nakanishi ldquoDam-age evaluation of railway structures by using train-induced AErdquoConstruction and Building Materials vol 18 no 3 pp 215ndash2232004

[11] X S Hao ldquoOutline of on-the-spot investigation on the earth-quake occurring in the south of hyogo prefecture Japan onJanuary 171995rdquo Recent Developments in World Seismology vol7 pp 12ndash16 1995

[12] W C Yuan F Cui and Q W Zhang ldquoCurrent research anddevelopment of structural health monitoring and conditionassessment for bridgesrdquo Journal of Tongji University vol 2 pp184ndash188 1999

[13] Y Z Qi ldquoHole wall imaging technology in old bridge pilefoundation inspectionrdquo Highway vol 3 pp 16ndash19 2012

[14] Y Zhang and S Z Tian ldquoApplication of wavelet analysis inhigh-piledwharf pile integrity testingrdquo Journal ofWaterway andHarbor vol 2 pp 163ndash168 2012

[15] C Dong P Zhang andW F T Huang ldquoThe sensitivity study ofthe modal parameters of a cracked beamrdquo in Proceeding of the12th International Modal Analysis Conference vol 1 pp 98ndash1041994

[16] N Stubbs J Kim and K Topole ldquoAn efficient and robustalgorithm for damage localization in offshore platformsrdquo inProceedings of the ASCE 10th Structures Congress vol 1 pp 543ndash546 1992

[17] N Stubbs J Kim and C Farrar ldquoField verification of anondestructive damage localization and severity estimationalgorithmrdquo in Proceedings of the 13th International ModalAnalysis Conference vol 1 pp 210ndash218 Nashville Tenn USA1995

[18] E Parloo P Guillaume and M Van Overmeire ldquoDamageassessment using mode shape sensitivitiesrdquoMechanical Systemsand Signal Processing vol 17 no 3 pp 499ndash518 2003

[19] A Alvandi and C Cremona ldquoAssessment of vibration-baseddamage identification techniquesrdquo Journal of Sound and Vibra-tion vol 292 no 1-2 pp 179ndash202 2006

[20] W Fan and P Qiao ldquoA strain energy-based damage severitycorrection factor method for damage identification in plate-type structuresrdquoMechanical Systems and Signal Processing vol28 pp 660ndash678 2012

[21] W Yao and X Zhang ldquoFracture damage identification of pileusing element strain energymethod based on sensitivemodalsrdquo

8 The Scientific World Journal

in Proceedings of the 13th International Conference on Fracturepp 2372ndash2380 Beijing China June 2013

[22] L J Hadjileontiadis E Douka and A Trochidis ldquoFractaldimension analysis for crack identification in beam structuresrdquoMechanical Systems and Signal Processing vol 19 no 3 pp 659ndash674 2005

[23] H Hu C Wu andW-J Lu ldquoDamage detection of circular hol-low cylinder using modal strain energy and scanning damageindex methodsrdquo Computers and Structures vol 89 no 1-2 pp149ndash160 2011

[24] J-H Zhang Y-H Liu and J-S Wang ldquoStudy on radiatednoise of engine oil sump by experimental modal expansiontechniquerdquo Transactions of CSICE (Chinese Society for InternalCombustion Engines) vol 23 no 6 pp 532ndash535 2005

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

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Navigation and Observation

International Journal of

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DistributedSensor Networks

International Journal of

2 The Scientific World Journal

methods in detecting damage of the pile foundation inservice In 1995 Japanese researchers explored to apply holecamera technology to roughly determine the degree of cracksand damage of the foundation piles in southern Hyogo ofpostearthquake period but they did not achieve good resultsfor various reasons [11] In 2009 Yuan et al [12] determinedthe integrality of the bridge piles in service by collectingdisplacement signals in the condition that horizontal impactload was integrated with static loading Qi in 2012 achievedaccurate detection results by applying full-bore wall imagingtechnology in detecting damage of the pile foundation inservice [13] However in this process certain damage wasoccurred when the cores of piles were drilling In order toweaken the influence on test signal of foundation pile whichwas caused by flat-slab superstructure Zhang and Tian [14]used wavelet analysis method to eliminate the interferencesignal and applied wavelet analysis technology to detect theintegrality of high-pile

Dong et al [15] proposed a damage detection methodbased on both the changes in strain mode shape and changesin resonant frequency The difference between the damagedand undamaged structures was calculated by considering theindex Δ120601

119894that is given by

Δ120601119894= (

120596119906

119894

120596119889

119894

)

2

120601119889

119894minus 120601119906

119894 (1)

where 120596119906119894and 120596

119889

119894are the pulsations of the 119894th mode for the

undamaged and damaged structures 120601119906119894and 120601

119889

119894are respe-

ctively the 119894th strain mode shape of the undamaged anddamaged structures It was demonstrated that the index Δ120601

119894

was more sensitive to the damage severity when comparedwith the similar index calculated by displacement eigenparameter

Another damage detection method focused on the decr-ease of modal stain energy between two structural degrees offreedom This technique was proposed by Stubbs et al [1617] For a Bernoulli-Euler beam a damage index was given toidentify the damage in beams

The mode strain energy was performed by Parloo et al[18] for the identification of various damages in the I-40highway bridge inNewMexico It was shown that themethodwas not capable of achieving an efficient and robust detectionof small damage due to measurement noise

Alvandi and Cremona [19] used the strain energymethodfor damage detection not only in beam but also in civilengineering structures with experimental data They showedthat the strain energy method presented the best stabilityagainst disturbing signals Even if the strain energy methodappeared to be more efficient than other tested methods inthe complex and simultaneous damage case they indicatedthat the detection of two damages in the structures can bemore difficult and a specific procedure should be appliedThesame conclusions were reported by authors if the damage waslocated near supports or joints

Fan and Qiao [20] presented a strain energy basedidentification method to identify damage of plate-type struc-tureTheproposedmethodwas response-based identificationtechnique which required modal frequencies and curvature

mode shapes before and after damage However the bendingstiffness of the elements in the structures was assumed tobe constant in this study while in other structures it willbe no longer a constant in the real progress So study onstrain energy identification method should be a promisingsubject for the development of the real-time structural healthmonitoring system in the future

Yao and Zhang [21] have established a sensitive identi-fication method for fracture damage identification of pilesBut they only proposed the method theoretical derivation isnot very tight and there is no test to verify So in this paperthe theory of damage identification was derived rigorouslyon the basis of result of [21] In addition to this numericalmethods and experimental approachwere employed to verifythe proposed method

In summary scientists have done a series of studieson structural damage detection with strain energy methodand they have achieved certain research results Howeverregarding the damage detection in the pile foundation of thestructure in service the work is conducted in the exploratorystage and arduous efforts and further researches are neededbefore it can be much useful in engineering practicesParticularly for the small initial crack damage detection ofpile foundation it needs further theoretical analysis andexploration in practice Taking full advantages of the naturalfrequency on integral damage identification the sensitivity ofthe element modal strain energy method on small injuriesdetection and the efficient local analysis of Time domainand frequency domain of wavelet analysis an identificationmethod for locating the small injure of pile and measuringdamage severity was established in this paper of whichthe correctness and efficiency were also demonstrated byengineering application examples

2 Basic Theory

21 Eigenvalue Equation of Structural Vibration with Frac-ture Damage The general cause of fracture damage isthe decrease in local stiffness of the structure Thereforeaccording to the perturbation theory the structural vibrationeigenvalue equation is as follows [22]

[(119870 + Δ119870) minus (120582119894+ Δ120582119894)119872] (120601

119894+ Δ120601119894) = 0 (2)

where

Δ119870 =

119899

sum

119895=1

Δ119870119895= minus

119899

sum

119895=1

120572119895119870119895

(0 le 120572119895le 1)

Δ120582119894= Δ1205962

119894= 120601119879

119894Δ119870120601119894

(3)

119872 119870 represent respectively the mass matrix and stiffnessmatrix 120601

119894represents the 119894th ordermodal vector 120582

119894represents

the eigenvalue of 119894th modal of the vibration system 120582119894=

1205962

119894= (2120587119891)

2 Δ119870 represents changes of structural stiffness120572119895represents 119895th element damage factor of the structure

119870119895represents structural stiffness matrix of the 119895th element

before damage 119899 represents the total number of elements ofthe structure Expand (2) and then finish structural vibration

The Scientific World Journal 3

eigenvalue equation (2) of the structure can be expressed asfollows

120601119879

119894Δ119870120601119894+ 120575119894120601119879

119894119870120601119894+ 120601119879

119894Δ119870Δ120601

119894+ 120575119894120601119879

119894119870Δ120601119894= 0 (4)

where 120575119894= minusΔ120582

119894120582119894is change rate of structure eigenvalue

which ismainly used to determine sensitivity of the 119894thmodalon structural damage detection Therefore it is called modaldamage sensitivity factor

22 Identification Equation of Structural Damage Accordingto the energy balance theory the released elastic strainenergy was changed into plastic strain energy and surfaceenergy when pile cracks occur which stimulates the crackpropagation thus causing the decrease in structural strain inthe macroscopic level As a result (4) can be expressed in theform of the strain energy For piles structures define the 119895thelement strain energy of 119894th modal as follows

MSE119894119895= 120601119879

119894119870119895120601119894

MSE119889119894119895= (120601119889

119894)119879

119870119889

119895120601119889

119894= (1 minus 120572

119895) (120601119889

119894)119879

119870119895120601119889

119894

(5)

where the superscript ldquo119889rdquo represents the damaged structureAccording to the above formulas we can get

120601119879

119894119870120601119894=

119899

sum

119895=1

120601119879

119894119870119895120601119894=

119899

sum

119895=1

MSE119894119895= MSE

119894

120601119879

119894Δ119870120601119894=

119899

sum

119895=1

120601119879

119894Δ119870119895120601119894= minus

119899

sum

119895=1

120572119895120601119879

119894119870119895120601119894

= minus

119899

sum

119895=1

120572119895MSE119894119895

(6)

Ignore second-order or more high-end items we can get

120601119879

119894119870Δ120601119894=

119899

sum

119895=1

120601119879

119894119870119895Δ120601119894

=

119899

sum

119895=1

[(120601119889

119894)119879

119870119895120601119889

119894minus 120601119879

119894119870119895120601119894+ (120601119889

119894)119879

Δ119870119895120601119889

119894]

=

119899

sum

119895=1

[(1 minus 120572119895) (120601119889

119894)119879

119870119895120601119889

119894minus 120601119879

119894119870119895120601119894]

=

119899

sum

119895=1

(MSE119889119894119895minusMSE

119894119895)

120601119879

119894Δ119870Δ120601

119894=

119899

sum

119895=1

120601119879

119894Δ119870119895Δ120601119894= minus

119899

sum

119895=1

120572119895120601119879

119894119870119895Δ120601119894

= minus

119899

sum

119895=1

120572119895(MSE119889

119894119895minusMSE

119895)

(7)

Substitute (6) and (7) into (4) and (4) can be expressed asfollows

120575119894sdotMSE119889

119894=

119899

sum

119895=1

(120572119895sdotMSE119889

119894119895) (8)

where MSE119889119894= sum119899

119895=1MSE119889119894119895represent the total strain energy

of the 119894th modal of injured structureFormula (8) is equation of structural damage identifica-

tion which is composed by modal damage sensitivity factormodal strain energy of injured structure and the elementdamage factor Due to the sensitivity of strain energy on smalldamage [20] and the high accuracy and easy measurementof the modal damage sensitivity factor [23] (8) can be usedto accurately identify the damage severity of structurersquos smallinjuries

120575119894is the indicator used to determine the modal sensitivity

on structural damage the larger the value of 120575119894is the

more sensitive the modal identification on structural damageis and vice versa Therefore we can select the modal forstructural damage identification according to factor 120575

119894 while

in practical application a certain threshold value is set basedon the environment and damage situation of the structurethe efficient mode appears when the actual threshold value isgreater than the set one

23 Calculation of Element Modal Strain Energy For thepile structure in the case that element is sufficiently smallelement modal strain energy can be represented by theformula as follows

MSE119894119895= 120601119879

119894119870119895120601119894=1

2int

119887119895+1

119887119895

(EI)119895 (1205972120601119894

1205971199112)

2

119889119911

MSE119889119894119895= (1 minus 120572

119895) (120601119889

119894)119879

119870119895120601119889

119894=1

2int

119887119895+1

119887119895

(EI)119889119895(1205972120601119889

119894

1205971199112)

2

119889119911

(9)

(EI)119895and (EI)119889

119895represent respectively the structural flexural

rigidities of 119895th element before and after damage 119887119895and 119887119895+1

represent 119911 coordinates of node 119895 and node 119895 + 1In experimental modal analysis the flexural rigidity (EI)119889

119895

is unknown while in the case of small injury it can be sub-stituted by flexural rigidity before injury ((EI)

119895) Considering

that the selected elements are relatively small so the flexuralrigidity (EI)

119895of the 119895th element can be approximated as a

constant which can be put outside of the integral sign So (9)can be rewritten as follows

MSE119894119895=

1

2(EI)119895int

119887119895+1

119887119895

(1205972120601119894

1205971199112)

2

119889119911 (10)

MSE119889119894119895=

1

2(EI)119895int

119887119895+1

119887119895

(1205972120601119889

119894

1205971199112)

2

119889119911 (11)

4 The Scientific World Journal

(12059721206011198941205971199112)2 in (11) can be replaced by the mean value of (12060110158401015840

119894119895)2

and (12060110158401015840

119894(119895+1))2 so (11) can be expressed as follows

MSE119894119895=1

4(EI)119895[(12060110158401015840

119894119895)2

+ (12060110158401015840

119894(119895+1))2

] (119887119895+ 119887119895+1

) (12)

Similarly (13) can be rewritten as follows

MSE119889119894119895=1

4(EI)119895[(120601119889

119894119895)10158401015840

]

2

+ [(120601119889

119894(119895+1))10158401015840

]

2

(119887119895+ 119887119895+1

)

(13)

where (12060110158401015840119894119895)2 (12060110158401015840119894(119895+1)

)2 [(120601119889119894119895)10158401015840]2 and [(120601

119889

119894(119895+1))10158401015840]2 can be got

by measuring displacement mode shapes

24 Determination of Damage Location The difference valuebetween the element modal strain energies before and afterdamage will be set as the original signal of injury

119891119895 (119911) = MSE119889

119894119895minusMSE

119894119895 (14)

The signal119891119895(119911)was firstly fitted by cubic spline interpolation

and then transformed by wavelet function for transformcoefficients which can be used to detect the damage location

119863119868119894119895= 119862(119886 119887)

119894119895 (15)

119862(119886 119887)119894119895

represents the transformation coefficient of 119895thelement in which ldquo119886rdquo is the scale parameter and ldquo119887rdquo isthe time parameter 119863119868

119894119895represents the location index of

damaged element So index119863119868119894119895can be used to determine the

damaged element specifically the larger value of index 119863119868119894119895

is the bigger possibility of a damaged 119895th element isIn order to reduce the impact of random noise from the

test mode shapes multiorder efficient modals are used todiagnose structural damage location

119863119868119895=

1

119873sum

119898

119863119868119894119895 (16)

where 119873 is the number of selected efficient modals Inpractical applications a given threshold value of 119863119868

119895can be

used to determine whether there is a damage or not in thestructure

25 Calculation of Damage Severity After damaged elementis determined formula (8) will be applied to calculate thedegree of element damage The element damage factor 120572

119895

can be used to represent the damage severity If there is onlyone location of damage which is assumed in 119896 element then120572119895= 0 (119895 = 119896) only 120572

119896= 0 Equation (8) can be expressed

120572119896=120575119894sdotMSE119889

119894

MSE119889119894119896

(17)

If there are multiple locations of damage assuming that thereare 119898 elements (119896

1 1198962 119896

119898) damaged (119898 le 119899) then 119898

number of efficient modes (1199021 1199022 119902

119898) are needed for the

calculation Therefore using the equation set which consists

of 119898 equations the corresponding damage factor 120572 can besolved The equation set is as follows

120575 sdotMSED = 120572 sdotMSEDD (18)

where

120575 = [12057511990211205751199022

1205751199023

sdot sdot sdot 120575119902119898]

MSED =

[[[[[[[[[[[

[

MSE1198891199021

MSE1198891199022

MSE1198891199023

MSE119889119902119898

]]]]]]]]]]]

]

120572 = [12057211989611205721198962

1205721198963

sdot sdot sdot 120572119896119898]

MSEDD

=

[[[[[[[[[

[

MSE11990211198961

MSE11990221198961

MSE11990231198961

sdot sdot sdot MSE1199021198981198961

MSE11990211198962

MSE11990221198962

MSE11990231198962

sdot sdot sdot MSE1199021198981198962

MSE11990211198963

MSE11990221198963

MSE11990231198963

sdot sdot sdot MSE1199021198981198963

MSE1199021119896119898

MSE1199022119896119898

MSE1199023119896119898

sdot sdot sdot MSE119902119898119896119898

]]]]]]]]]

]

(19)

119901 represents the number of measured modals 119898 representsthe number of damaged elements If 119901 lt 119898 extended modalwhich extracted by experimental modal expansion technique[24] can be applied in the calculation

3 Example Verification

31 Overview of Project Natural hollowed filling piles andartificial hollowed filling piles were used in the foundationconstruction of Ouhai Sports Center Stadium with effectivepile length ranging from 4m to 30m diameter range from600mm to 1000mm and C25 of pile concrete strengthTotally there were 129 piles used in the project according tothe verification results of low strain detection and excavation96 of the damage occurred at 74m from the top of number71 pileThe length of number 71 pile is 21m and its diameter is1mThe actual damage of number 71 pile is shown in Figure 1Figure 1(b) is the ultrasonic strain curve of the pile

32 Mode Measurement Using Top Acceleration and Deflec-tions of the Pile Typical accelerometer was attached on thestructure at the top of the pile (Figure 2) The accelerationand deflection of the pile were obtained from the datacollected by the accelerometer (Figure 3) Figure 3 is theacceleration response from 163 second to 171 second usingultrasonic technology Figure 4 is the top defection usingdisplacement sensor Figure 4 shows the first five ordermodalshapes derived for sensors Mode shapes (actual modal of thepile) and frequencies were derived by the acceleration anddeflection (Table 1)

The Scientific World Journal 5

(a) On-site excavation detection

Location SYYTP ID 71 R 700mm V 350mS Date 2010-8-2

000 525 1050 1575 2100

1000m

(b) Detection of low strain

Figure 1 The actual damage of pile

Figure 2 Typical accelerometer attachment

0

002

004

006

008

163 164 165 166 167 168 169 170 171

Acce

lera

tion

(g)

Time (s)

minus008

minus006

minus004

minus002

Figure 3 Acceleration response of sensor

0

05

1

15

0 10 20 30 40

Mag

nitu

de

Distance (m)

Series 1Series 2Series 3

Series 4Series 5

minus1

minus05

Figure 4 Mode shapes derived by sensors

33 Finite Element Modeling Applying finite element soft-ware ANSYS we establish finite element model of soil-pileinteraction for number 71 pile (Figure 5(a)) according tothe design drawings According to actual damage on thenumber 71 pile the pile model of the cracks was establishedat 74 meters from the top of the pile with crack depthaccounting for 96 of the diameter of pile foundation(Figure 5(b)) The element type of pile foundation model isSOLID45The nonlinear spring element COMBIN139 is usedto simulate pile-soil interaction In order to establish a finiteelement computation model which is more consistent withthe environment of actual engineering situation the modelupdating technology was used to improve the finite elementmodel based on the measured data

6 The Scientific World Journal

(a) Before damage (b) After damage

Figure 5 Finite element model of pile-soil interaction

0

005

01

015

02

025

03

035

04

045

05

1 2 3 4 5 6 7 8 9 10

The r

ate o

f cha

nge

Mode

Figure 6 The change rate of the natural frequency

005

115

225

335

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101

106

111

116

121

DI

Elementsminus15

minus1

minus05

Figure 7 The DI of each element calculated by efficient modal

34 Selection of EfficientMode The change rate of the naturalfrequencies before and after damage is shown in Figure 6 andTable 1 and the efficient frequency threshold is set as 120575

119894ge

04 As Figure 6 shows mode 1 and mode 4 are the efficientmodes of damage case

35 Damage Location Identification Information function isestablished using the changes of element strain energy beforeand after damage andwavelet transform is used to determinethe parameters (119863119868) for the damage location Efficient modal119863119868119895is shown in Figure 7 By setting the threshold (119863119868 gt 2)

it can be clearly determined that crack damage occurred inthe elements from 55 to 59 which is very identical with theactual damage location The identification results of damagelocation are shown in tables The identification error is 3which proves the accuracy advantage of damage locationidentification method

36 Identification of Injury Severity Element damage factor120572 is calculated by applying (18) and the results are shownin Table 2 As shown in Table 2 the result of actual injury isvery close to that of calculated injury with identification errorby 62 which proves that the method of damage severityidentification has a higher accuracy

4 Conclusions

This paper firstly selected efficient modes for damage identi-fication by applying the change rate of eigenvalues and thenit established an accurate method for small damage iden-tification based on the application of sensitivity of elementmodal strain energy to small structural injury and efficientlocal analysis capabilities of wavelet analysis The efficiencyand accuracy of the proposed method were verified through

The Scientific World Journal 7

Table 1 Calculated natural frequencies from the FE model

ModeThe experimental

monitoringfrequencies

The calculatednatural frequencies Difference ()

1 1940 1932 0412 3035 2997 1253 6835 6805 0444 6983 6944 0565 7883 7852 039

Table 2 Results of damage identification

Actualinjury

Low strainmethoderror

Newmethoderror

Damage location 74m 671m93 708m43Damage severity 96 Small damage 10262

identifying small cracks damage of the pile used in the OuhaiSports Center The conclusions are as follows

(1) Fracture identificationmethod proposed in this papercan effectively and accurately identify the fracturedamage location for the hidden structures in service

(2) The proposed method can effectively identify andquantify the fracture damage severity for the hiddenstructures in service providing an important refer-ence for the assessment of fracture damage

(3) The method presented in this paper provided anew approach for damage identification of concealedstructure

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is one of research projects financed by HunanProvince Research Center for Safety Control Technology andEquipment of Bridge Engineering (Changsha University ofScience amp Technology) The number of research projects is13KC05

References

[1] H W Zhou W T Weng and Y Wang ldquoSeveral methods ofthe bridge pile testingrdquo Highway and Transportation Research(Applied Technology Edition) vol 4 pp 222ndash225 2012

[2] X L Han Y X Han and X M Tang ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 6 pp 105ndash107 2001

[3] H Y Chai M G Liu and S W Bai ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 5 pp 624ndash628 2003

[4] C H Zhang J L Zhang J H Xie et al ldquoThe multi-reflectedwave analysis on the low strain integrity testing of pile founda-tionrdquo Journal of Xiamen University Natural Science vol 3 pp214ndash216 2005

[5] Y M Chen ldquoGot method drills in pile foundation inspectionabout the application analysisrdquo Construction and Design forProject vol 7 pp 129ndash131 2011

[6] C X Xiao ldquoApplication of ultrasonic transmission method todetecting integrity of large-diameter bored cast-in-place pilesrdquoRock and Soil Mechanics supplement 1 pp 169ndash171 2003

[7] F C LiuWWang Z S Zhang andWQ Liu ldquoWave analysis ofpile foundation low strain detection and determination of pilebody integrityrdquo Port Engineering Technology vol 2 pp 46ndash482012

[8] H QWu R Y Ma L Y Huang J Peng and L Chen ldquoGeneralapplication and analysis of several detection methods in theengineering foundation pilesrdquoConcrete vol 4 pp 119ndash121 2012

[9] M Johnson and F Rausche ldquoLow strain testing of piles utilizingtow acceleration signardquo Stress Wave vol 3 pp 859ndash869 1996

[10] X Luo H Haya T Inaba T Shiotani and Y Nakanishi ldquoDam-age evaluation of railway structures by using train-induced AErdquoConstruction and Building Materials vol 18 no 3 pp 215ndash2232004

[11] X S Hao ldquoOutline of on-the-spot investigation on the earth-quake occurring in the south of hyogo prefecture Japan onJanuary 171995rdquo Recent Developments in World Seismology vol7 pp 12ndash16 1995

[12] W C Yuan F Cui and Q W Zhang ldquoCurrent research anddevelopment of structural health monitoring and conditionassessment for bridgesrdquo Journal of Tongji University vol 2 pp184ndash188 1999

[13] Y Z Qi ldquoHole wall imaging technology in old bridge pilefoundation inspectionrdquo Highway vol 3 pp 16ndash19 2012

[14] Y Zhang and S Z Tian ldquoApplication of wavelet analysis inhigh-piledwharf pile integrity testingrdquo Journal ofWaterway andHarbor vol 2 pp 163ndash168 2012

[15] C Dong P Zhang andW F T Huang ldquoThe sensitivity study ofthe modal parameters of a cracked beamrdquo in Proceeding of the12th International Modal Analysis Conference vol 1 pp 98ndash1041994

[16] N Stubbs J Kim and K Topole ldquoAn efficient and robustalgorithm for damage localization in offshore platformsrdquo inProceedings of the ASCE 10th Structures Congress vol 1 pp 543ndash546 1992

[17] N Stubbs J Kim and C Farrar ldquoField verification of anondestructive damage localization and severity estimationalgorithmrdquo in Proceedings of the 13th International ModalAnalysis Conference vol 1 pp 210ndash218 Nashville Tenn USA1995

[18] E Parloo P Guillaume and M Van Overmeire ldquoDamageassessment using mode shape sensitivitiesrdquoMechanical Systemsand Signal Processing vol 17 no 3 pp 499ndash518 2003

[19] A Alvandi and C Cremona ldquoAssessment of vibration-baseddamage identification techniquesrdquo Journal of Sound and Vibra-tion vol 292 no 1-2 pp 179ndash202 2006

[20] W Fan and P Qiao ldquoA strain energy-based damage severitycorrection factor method for damage identification in plate-type structuresrdquoMechanical Systems and Signal Processing vol28 pp 660ndash678 2012

[21] W Yao and X Zhang ldquoFracture damage identification of pileusing element strain energymethod based on sensitivemodalsrdquo

8 The Scientific World Journal

in Proceedings of the 13th International Conference on Fracturepp 2372ndash2380 Beijing China June 2013

[22] L J Hadjileontiadis E Douka and A Trochidis ldquoFractaldimension analysis for crack identification in beam structuresrdquoMechanical Systems and Signal Processing vol 19 no 3 pp 659ndash674 2005

[23] H Hu C Wu andW-J Lu ldquoDamage detection of circular hol-low cylinder using modal strain energy and scanning damageindex methodsrdquo Computers and Structures vol 89 no 1-2 pp149ndash160 2011

[24] J-H Zhang Y-H Liu and J-S Wang ldquoStudy on radiatednoise of engine oil sump by experimental modal expansiontechniquerdquo Transactions of CSICE (Chinese Society for InternalCombustion Engines) vol 23 no 6 pp 532ndash535 2005

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

The Scientific World Journal 3

eigenvalue equation (2) of the structure can be expressed asfollows

120601119879

119894Δ119870120601119894+ 120575119894120601119879

119894119870120601119894+ 120601119879

119894Δ119870Δ120601

119894+ 120575119894120601119879

119894119870Δ120601119894= 0 (4)

where 120575119894= minusΔ120582

119894120582119894is change rate of structure eigenvalue

which ismainly used to determine sensitivity of the 119894thmodalon structural damage detection Therefore it is called modaldamage sensitivity factor

22 Identification Equation of Structural Damage Accordingto the energy balance theory the released elastic strainenergy was changed into plastic strain energy and surfaceenergy when pile cracks occur which stimulates the crackpropagation thus causing the decrease in structural strain inthe macroscopic level As a result (4) can be expressed in theform of the strain energy For piles structures define the 119895thelement strain energy of 119894th modal as follows

MSE119894119895= 120601119879

119894119870119895120601119894

MSE119889119894119895= (120601119889

119894)119879

119870119889

119895120601119889

119894= (1 minus 120572

119895) (120601119889

119894)119879

119870119895120601119889

119894

(5)

where the superscript ldquo119889rdquo represents the damaged structureAccording to the above formulas we can get

120601119879

119894119870120601119894=

119899

sum

119895=1

120601119879

119894119870119895120601119894=

119899

sum

119895=1

MSE119894119895= MSE

119894

120601119879

119894Δ119870120601119894=

119899

sum

119895=1

120601119879

119894Δ119870119895120601119894= minus

119899

sum

119895=1

120572119895120601119879

119894119870119895120601119894

= minus

119899

sum

119895=1

120572119895MSE119894119895

(6)

Ignore second-order or more high-end items we can get

120601119879

119894119870Δ120601119894=

119899

sum

119895=1

120601119879

119894119870119895Δ120601119894

=

119899

sum

119895=1

[(120601119889

119894)119879

119870119895120601119889

119894minus 120601119879

119894119870119895120601119894+ (120601119889

119894)119879

Δ119870119895120601119889

119894]

=

119899

sum

119895=1

[(1 minus 120572119895) (120601119889

119894)119879

119870119895120601119889

119894minus 120601119879

119894119870119895120601119894]

=

119899

sum

119895=1

(MSE119889119894119895minusMSE

119894119895)

120601119879

119894Δ119870Δ120601

119894=

119899

sum

119895=1

120601119879

119894Δ119870119895Δ120601119894= minus

119899

sum

119895=1

120572119895120601119879

119894119870119895Δ120601119894

= minus

119899

sum

119895=1

120572119895(MSE119889

119894119895minusMSE

119895)

(7)

Substitute (6) and (7) into (4) and (4) can be expressed asfollows

120575119894sdotMSE119889

119894=

119899

sum

119895=1

(120572119895sdotMSE119889

119894119895) (8)

where MSE119889119894= sum119899

119895=1MSE119889119894119895represent the total strain energy

of the 119894th modal of injured structureFormula (8) is equation of structural damage identifica-

tion which is composed by modal damage sensitivity factormodal strain energy of injured structure and the elementdamage factor Due to the sensitivity of strain energy on smalldamage [20] and the high accuracy and easy measurementof the modal damage sensitivity factor [23] (8) can be usedto accurately identify the damage severity of structurersquos smallinjuries

120575119894is the indicator used to determine the modal sensitivity

on structural damage the larger the value of 120575119894is the

more sensitive the modal identification on structural damageis and vice versa Therefore we can select the modal forstructural damage identification according to factor 120575

119894 while

in practical application a certain threshold value is set basedon the environment and damage situation of the structurethe efficient mode appears when the actual threshold value isgreater than the set one

23 Calculation of Element Modal Strain Energy For thepile structure in the case that element is sufficiently smallelement modal strain energy can be represented by theformula as follows

MSE119894119895= 120601119879

119894119870119895120601119894=1

2int

119887119895+1

119887119895

(EI)119895 (1205972120601119894

1205971199112)

2

119889119911

MSE119889119894119895= (1 minus 120572

119895) (120601119889

119894)119879

119870119895120601119889

119894=1

2int

119887119895+1

119887119895

(EI)119889119895(1205972120601119889

119894

1205971199112)

2

119889119911

(9)

(EI)119895and (EI)119889

119895represent respectively the structural flexural

rigidities of 119895th element before and after damage 119887119895and 119887119895+1

represent 119911 coordinates of node 119895 and node 119895 + 1In experimental modal analysis the flexural rigidity (EI)119889

119895

is unknown while in the case of small injury it can be sub-stituted by flexural rigidity before injury ((EI)

119895) Considering

that the selected elements are relatively small so the flexuralrigidity (EI)

119895of the 119895th element can be approximated as a

constant which can be put outside of the integral sign So (9)can be rewritten as follows

MSE119894119895=

1

2(EI)119895int

119887119895+1

119887119895

(1205972120601119894

1205971199112)

2

119889119911 (10)

MSE119889119894119895=

1

2(EI)119895int

119887119895+1

119887119895

(1205972120601119889

119894

1205971199112)

2

119889119911 (11)

4 The Scientific World Journal

(12059721206011198941205971199112)2 in (11) can be replaced by the mean value of (12060110158401015840

119894119895)2

and (12060110158401015840

119894(119895+1))2 so (11) can be expressed as follows

MSE119894119895=1

4(EI)119895[(12060110158401015840

119894119895)2

+ (12060110158401015840

119894(119895+1))2

] (119887119895+ 119887119895+1

) (12)

Similarly (13) can be rewritten as follows

MSE119889119894119895=1

4(EI)119895[(120601119889

119894119895)10158401015840

]

2

+ [(120601119889

119894(119895+1))10158401015840

]

2

(119887119895+ 119887119895+1

)

(13)

where (12060110158401015840119894119895)2 (12060110158401015840119894(119895+1)

)2 [(120601119889119894119895)10158401015840]2 and [(120601

119889

119894(119895+1))10158401015840]2 can be got

by measuring displacement mode shapes

24 Determination of Damage Location The difference valuebetween the element modal strain energies before and afterdamage will be set as the original signal of injury

119891119895 (119911) = MSE119889

119894119895minusMSE

119894119895 (14)

The signal119891119895(119911)was firstly fitted by cubic spline interpolation

and then transformed by wavelet function for transformcoefficients which can be used to detect the damage location

119863119868119894119895= 119862(119886 119887)

119894119895 (15)

119862(119886 119887)119894119895

represents the transformation coefficient of 119895thelement in which ldquo119886rdquo is the scale parameter and ldquo119887rdquo isthe time parameter 119863119868

119894119895represents the location index of

damaged element So index119863119868119894119895can be used to determine the

damaged element specifically the larger value of index 119863119868119894119895

is the bigger possibility of a damaged 119895th element isIn order to reduce the impact of random noise from the

test mode shapes multiorder efficient modals are used todiagnose structural damage location

119863119868119895=

1

119873sum

119898

119863119868119894119895 (16)

where 119873 is the number of selected efficient modals Inpractical applications a given threshold value of 119863119868

119895can be

used to determine whether there is a damage or not in thestructure

25 Calculation of Damage Severity After damaged elementis determined formula (8) will be applied to calculate thedegree of element damage The element damage factor 120572

119895

can be used to represent the damage severity If there is onlyone location of damage which is assumed in 119896 element then120572119895= 0 (119895 = 119896) only 120572

119896= 0 Equation (8) can be expressed

120572119896=120575119894sdotMSE119889

119894

MSE119889119894119896

(17)

If there are multiple locations of damage assuming that thereare 119898 elements (119896

1 1198962 119896

119898) damaged (119898 le 119899) then 119898

number of efficient modes (1199021 1199022 119902

119898) are needed for the

calculation Therefore using the equation set which consists

of 119898 equations the corresponding damage factor 120572 can besolved The equation set is as follows

120575 sdotMSED = 120572 sdotMSEDD (18)

where

120575 = [12057511990211205751199022

1205751199023

sdot sdot sdot 120575119902119898]

MSED =

[[[[[[[[[[[

[

MSE1198891199021

MSE1198891199022

MSE1198891199023

MSE119889119902119898

]]]]]]]]]]]

]

120572 = [12057211989611205721198962

1205721198963

sdot sdot sdot 120572119896119898]

MSEDD

=

[[[[[[[[[

[

MSE11990211198961

MSE11990221198961

MSE11990231198961

sdot sdot sdot MSE1199021198981198961

MSE11990211198962

MSE11990221198962

MSE11990231198962

sdot sdot sdot MSE1199021198981198962

MSE11990211198963

MSE11990221198963

MSE11990231198963

sdot sdot sdot MSE1199021198981198963

MSE1199021119896119898

MSE1199022119896119898

MSE1199023119896119898

sdot sdot sdot MSE119902119898119896119898

]]]]]]]]]

]

(19)

119901 represents the number of measured modals 119898 representsthe number of damaged elements If 119901 lt 119898 extended modalwhich extracted by experimental modal expansion technique[24] can be applied in the calculation

3 Example Verification

31 Overview of Project Natural hollowed filling piles andartificial hollowed filling piles were used in the foundationconstruction of Ouhai Sports Center Stadium with effectivepile length ranging from 4m to 30m diameter range from600mm to 1000mm and C25 of pile concrete strengthTotally there were 129 piles used in the project according tothe verification results of low strain detection and excavation96 of the damage occurred at 74m from the top of number71 pileThe length of number 71 pile is 21m and its diameter is1mThe actual damage of number 71 pile is shown in Figure 1Figure 1(b) is the ultrasonic strain curve of the pile

32 Mode Measurement Using Top Acceleration and Deflec-tions of the Pile Typical accelerometer was attached on thestructure at the top of the pile (Figure 2) The accelerationand deflection of the pile were obtained from the datacollected by the accelerometer (Figure 3) Figure 3 is theacceleration response from 163 second to 171 second usingultrasonic technology Figure 4 is the top defection usingdisplacement sensor Figure 4 shows the first five ordermodalshapes derived for sensors Mode shapes (actual modal of thepile) and frequencies were derived by the acceleration anddeflection (Table 1)

The Scientific World Journal 5

(a) On-site excavation detection

Location SYYTP ID 71 R 700mm V 350mS Date 2010-8-2

000 525 1050 1575 2100

1000m

(b) Detection of low strain

Figure 1 The actual damage of pile

Figure 2 Typical accelerometer attachment

0

002

004

006

008

163 164 165 166 167 168 169 170 171

Acce

lera

tion

(g)

Time (s)

minus008

minus006

minus004

minus002

Figure 3 Acceleration response of sensor

0

05

1

15

0 10 20 30 40

Mag

nitu

de

Distance (m)

Series 1Series 2Series 3

Series 4Series 5

minus1

minus05

Figure 4 Mode shapes derived by sensors

33 Finite Element Modeling Applying finite element soft-ware ANSYS we establish finite element model of soil-pileinteraction for number 71 pile (Figure 5(a)) according tothe design drawings According to actual damage on thenumber 71 pile the pile model of the cracks was establishedat 74 meters from the top of the pile with crack depthaccounting for 96 of the diameter of pile foundation(Figure 5(b)) The element type of pile foundation model isSOLID45The nonlinear spring element COMBIN139 is usedto simulate pile-soil interaction In order to establish a finiteelement computation model which is more consistent withthe environment of actual engineering situation the modelupdating technology was used to improve the finite elementmodel based on the measured data

6 The Scientific World Journal

(a) Before damage (b) After damage

Figure 5 Finite element model of pile-soil interaction

0

005

01

015

02

025

03

035

04

045

05

1 2 3 4 5 6 7 8 9 10

The r

ate o

f cha

nge

Mode

Figure 6 The change rate of the natural frequency

005

115

225

335

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101

106

111

116

121

DI

Elementsminus15

minus1

minus05

Figure 7 The DI of each element calculated by efficient modal

34 Selection of EfficientMode The change rate of the naturalfrequencies before and after damage is shown in Figure 6 andTable 1 and the efficient frequency threshold is set as 120575

119894ge

04 As Figure 6 shows mode 1 and mode 4 are the efficientmodes of damage case

35 Damage Location Identification Information function isestablished using the changes of element strain energy beforeand after damage andwavelet transform is used to determinethe parameters (119863119868) for the damage location Efficient modal119863119868119895is shown in Figure 7 By setting the threshold (119863119868 gt 2)

it can be clearly determined that crack damage occurred inthe elements from 55 to 59 which is very identical with theactual damage location The identification results of damagelocation are shown in tables The identification error is 3which proves the accuracy advantage of damage locationidentification method

36 Identification of Injury Severity Element damage factor120572 is calculated by applying (18) and the results are shownin Table 2 As shown in Table 2 the result of actual injury isvery close to that of calculated injury with identification errorby 62 which proves that the method of damage severityidentification has a higher accuracy

4 Conclusions

This paper firstly selected efficient modes for damage identi-fication by applying the change rate of eigenvalues and thenit established an accurate method for small damage iden-tification based on the application of sensitivity of elementmodal strain energy to small structural injury and efficientlocal analysis capabilities of wavelet analysis The efficiencyand accuracy of the proposed method were verified through

The Scientific World Journal 7

Table 1 Calculated natural frequencies from the FE model

ModeThe experimental

monitoringfrequencies

The calculatednatural frequencies Difference ()

1 1940 1932 0412 3035 2997 1253 6835 6805 0444 6983 6944 0565 7883 7852 039

Table 2 Results of damage identification

Actualinjury

Low strainmethoderror

Newmethoderror

Damage location 74m 671m93 708m43Damage severity 96 Small damage 10262

identifying small cracks damage of the pile used in the OuhaiSports Center The conclusions are as follows

(1) Fracture identificationmethod proposed in this papercan effectively and accurately identify the fracturedamage location for the hidden structures in service

(2) The proposed method can effectively identify andquantify the fracture damage severity for the hiddenstructures in service providing an important refer-ence for the assessment of fracture damage

(3) The method presented in this paper provided anew approach for damage identification of concealedstructure

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is one of research projects financed by HunanProvince Research Center for Safety Control Technology andEquipment of Bridge Engineering (Changsha University ofScience amp Technology) The number of research projects is13KC05

References

[1] H W Zhou W T Weng and Y Wang ldquoSeveral methods ofthe bridge pile testingrdquo Highway and Transportation Research(Applied Technology Edition) vol 4 pp 222ndash225 2012

[2] X L Han Y X Han and X M Tang ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 6 pp 105ndash107 2001

[3] H Y Chai M G Liu and S W Bai ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 5 pp 624ndash628 2003

[4] C H Zhang J L Zhang J H Xie et al ldquoThe multi-reflectedwave analysis on the low strain integrity testing of pile founda-tionrdquo Journal of Xiamen University Natural Science vol 3 pp214ndash216 2005

[5] Y M Chen ldquoGot method drills in pile foundation inspectionabout the application analysisrdquo Construction and Design forProject vol 7 pp 129ndash131 2011

[6] C X Xiao ldquoApplication of ultrasonic transmission method todetecting integrity of large-diameter bored cast-in-place pilesrdquoRock and Soil Mechanics supplement 1 pp 169ndash171 2003

[7] F C LiuWWang Z S Zhang andWQ Liu ldquoWave analysis ofpile foundation low strain detection and determination of pilebody integrityrdquo Port Engineering Technology vol 2 pp 46ndash482012

[8] H QWu R Y Ma L Y Huang J Peng and L Chen ldquoGeneralapplication and analysis of several detection methods in theengineering foundation pilesrdquoConcrete vol 4 pp 119ndash121 2012

[9] M Johnson and F Rausche ldquoLow strain testing of piles utilizingtow acceleration signardquo Stress Wave vol 3 pp 859ndash869 1996

[10] X Luo H Haya T Inaba T Shiotani and Y Nakanishi ldquoDam-age evaluation of railway structures by using train-induced AErdquoConstruction and Building Materials vol 18 no 3 pp 215ndash2232004

[11] X S Hao ldquoOutline of on-the-spot investigation on the earth-quake occurring in the south of hyogo prefecture Japan onJanuary 171995rdquo Recent Developments in World Seismology vol7 pp 12ndash16 1995

[12] W C Yuan F Cui and Q W Zhang ldquoCurrent research anddevelopment of structural health monitoring and conditionassessment for bridgesrdquo Journal of Tongji University vol 2 pp184ndash188 1999

[13] Y Z Qi ldquoHole wall imaging technology in old bridge pilefoundation inspectionrdquo Highway vol 3 pp 16ndash19 2012

[14] Y Zhang and S Z Tian ldquoApplication of wavelet analysis inhigh-piledwharf pile integrity testingrdquo Journal ofWaterway andHarbor vol 2 pp 163ndash168 2012

[15] C Dong P Zhang andW F T Huang ldquoThe sensitivity study ofthe modal parameters of a cracked beamrdquo in Proceeding of the12th International Modal Analysis Conference vol 1 pp 98ndash1041994

[16] N Stubbs J Kim and K Topole ldquoAn efficient and robustalgorithm for damage localization in offshore platformsrdquo inProceedings of the ASCE 10th Structures Congress vol 1 pp 543ndash546 1992

[17] N Stubbs J Kim and C Farrar ldquoField verification of anondestructive damage localization and severity estimationalgorithmrdquo in Proceedings of the 13th International ModalAnalysis Conference vol 1 pp 210ndash218 Nashville Tenn USA1995

[18] E Parloo P Guillaume and M Van Overmeire ldquoDamageassessment using mode shape sensitivitiesrdquoMechanical Systemsand Signal Processing vol 17 no 3 pp 499ndash518 2003

[19] A Alvandi and C Cremona ldquoAssessment of vibration-baseddamage identification techniquesrdquo Journal of Sound and Vibra-tion vol 292 no 1-2 pp 179ndash202 2006

[20] W Fan and P Qiao ldquoA strain energy-based damage severitycorrection factor method for damage identification in plate-type structuresrdquoMechanical Systems and Signal Processing vol28 pp 660ndash678 2012

[21] W Yao and X Zhang ldquoFracture damage identification of pileusing element strain energymethod based on sensitivemodalsrdquo

8 The Scientific World Journal

in Proceedings of the 13th International Conference on Fracturepp 2372ndash2380 Beijing China June 2013

[22] L J Hadjileontiadis E Douka and A Trochidis ldquoFractaldimension analysis for crack identification in beam structuresrdquoMechanical Systems and Signal Processing vol 19 no 3 pp 659ndash674 2005

[23] H Hu C Wu andW-J Lu ldquoDamage detection of circular hol-low cylinder using modal strain energy and scanning damageindex methodsrdquo Computers and Structures vol 89 no 1-2 pp149ndash160 2011

[24] J-H Zhang Y-H Liu and J-S Wang ldquoStudy on radiatednoise of engine oil sump by experimental modal expansiontechniquerdquo Transactions of CSICE (Chinese Society for InternalCombustion Engines) vol 23 no 6 pp 532ndash535 2005

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

4 The Scientific World Journal

(12059721206011198941205971199112)2 in (11) can be replaced by the mean value of (12060110158401015840

119894119895)2

and (12060110158401015840

119894(119895+1))2 so (11) can be expressed as follows

MSE119894119895=1

4(EI)119895[(12060110158401015840

119894119895)2

+ (12060110158401015840

119894(119895+1))2

] (119887119895+ 119887119895+1

) (12)

Similarly (13) can be rewritten as follows

MSE119889119894119895=1

4(EI)119895[(120601119889

119894119895)10158401015840

]

2

+ [(120601119889

119894(119895+1))10158401015840

]

2

(119887119895+ 119887119895+1

)

(13)

where (12060110158401015840119894119895)2 (12060110158401015840119894(119895+1)

)2 [(120601119889119894119895)10158401015840]2 and [(120601

119889

119894(119895+1))10158401015840]2 can be got

by measuring displacement mode shapes

24 Determination of Damage Location The difference valuebetween the element modal strain energies before and afterdamage will be set as the original signal of injury

119891119895 (119911) = MSE119889

119894119895minusMSE

119894119895 (14)

The signal119891119895(119911)was firstly fitted by cubic spline interpolation

and then transformed by wavelet function for transformcoefficients which can be used to detect the damage location

119863119868119894119895= 119862(119886 119887)

119894119895 (15)

119862(119886 119887)119894119895

represents the transformation coefficient of 119895thelement in which ldquo119886rdquo is the scale parameter and ldquo119887rdquo isthe time parameter 119863119868

119894119895represents the location index of

damaged element So index119863119868119894119895can be used to determine the

damaged element specifically the larger value of index 119863119868119894119895

is the bigger possibility of a damaged 119895th element isIn order to reduce the impact of random noise from the

test mode shapes multiorder efficient modals are used todiagnose structural damage location

119863119868119895=

1

119873sum

119898

119863119868119894119895 (16)

where 119873 is the number of selected efficient modals Inpractical applications a given threshold value of 119863119868

119895can be

used to determine whether there is a damage or not in thestructure

25 Calculation of Damage Severity After damaged elementis determined formula (8) will be applied to calculate thedegree of element damage The element damage factor 120572

119895

can be used to represent the damage severity If there is onlyone location of damage which is assumed in 119896 element then120572119895= 0 (119895 = 119896) only 120572

119896= 0 Equation (8) can be expressed

120572119896=120575119894sdotMSE119889

119894

MSE119889119894119896

(17)

If there are multiple locations of damage assuming that thereare 119898 elements (119896

1 1198962 119896

119898) damaged (119898 le 119899) then 119898

number of efficient modes (1199021 1199022 119902

119898) are needed for the

calculation Therefore using the equation set which consists

of 119898 equations the corresponding damage factor 120572 can besolved The equation set is as follows

120575 sdotMSED = 120572 sdotMSEDD (18)

where

120575 = [12057511990211205751199022

1205751199023

sdot sdot sdot 120575119902119898]

MSED =

[[[[[[[[[[[

[

MSE1198891199021

MSE1198891199022

MSE1198891199023

MSE119889119902119898

]]]]]]]]]]]

]

120572 = [12057211989611205721198962

1205721198963

sdot sdot sdot 120572119896119898]

MSEDD

=

[[[[[[[[[

[

MSE11990211198961

MSE11990221198961

MSE11990231198961

sdot sdot sdot MSE1199021198981198961

MSE11990211198962

MSE11990221198962

MSE11990231198962

sdot sdot sdot MSE1199021198981198962

MSE11990211198963

MSE11990221198963

MSE11990231198963

sdot sdot sdot MSE1199021198981198963

MSE1199021119896119898

MSE1199022119896119898

MSE1199023119896119898

sdot sdot sdot MSE119902119898119896119898

]]]]]]]]]

]

(19)

119901 represents the number of measured modals 119898 representsthe number of damaged elements If 119901 lt 119898 extended modalwhich extracted by experimental modal expansion technique[24] can be applied in the calculation

3 Example Verification

31 Overview of Project Natural hollowed filling piles andartificial hollowed filling piles were used in the foundationconstruction of Ouhai Sports Center Stadium with effectivepile length ranging from 4m to 30m diameter range from600mm to 1000mm and C25 of pile concrete strengthTotally there were 129 piles used in the project according tothe verification results of low strain detection and excavation96 of the damage occurred at 74m from the top of number71 pileThe length of number 71 pile is 21m and its diameter is1mThe actual damage of number 71 pile is shown in Figure 1Figure 1(b) is the ultrasonic strain curve of the pile

32 Mode Measurement Using Top Acceleration and Deflec-tions of the Pile Typical accelerometer was attached on thestructure at the top of the pile (Figure 2) The accelerationand deflection of the pile were obtained from the datacollected by the accelerometer (Figure 3) Figure 3 is theacceleration response from 163 second to 171 second usingultrasonic technology Figure 4 is the top defection usingdisplacement sensor Figure 4 shows the first five ordermodalshapes derived for sensors Mode shapes (actual modal of thepile) and frequencies were derived by the acceleration anddeflection (Table 1)

The Scientific World Journal 5

(a) On-site excavation detection

Location SYYTP ID 71 R 700mm V 350mS Date 2010-8-2

000 525 1050 1575 2100

1000m

(b) Detection of low strain

Figure 1 The actual damage of pile

Figure 2 Typical accelerometer attachment

0

002

004

006

008

163 164 165 166 167 168 169 170 171

Acce

lera

tion

(g)

Time (s)

minus008

minus006

minus004

minus002

Figure 3 Acceleration response of sensor

0

05

1

15

0 10 20 30 40

Mag

nitu

de

Distance (m)

Series 1Series 2Series 3

Series 4Series 5

minus1

minus05

Figure 4 Mode shapes derived by sensors

33 Finite Element Modeling Applying finite element soft-ware ANSYS we establish finite element model of soil-pileinteraction for number 71 pile (Figure 5(a)) according tothe design drawings According to actual damage on thenumber 71 pile the pile model of the cracks was establishedat 74 meters from the top of the pile with crack depthaccounting for 96 of the diameter of pile foundation(Figure 5(b)) The element type of pile foundation model isSOLID45The nonlinear spring element COMBIN139 is usedto simulate pile-soil interaction In order to establish a finiteelement computation model which is more consistent withthe environment of actual engineering situation the modelupdating technology was used to improve the finite elementmodel based on the measured data

6 The Scientific World Journal

(a) Before damage (b) After damage

Figure 5 Finite element model of pile-soil interaction

0

005

01

015

02

025

03

035

04

045

05

1 2 3 4 5 6 7 8 9 10

The r

ate o

f cha

nge

Mode

Figure 6 The change rate of the natural frequency

005

115

225

335

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101

106

111

116

121

DI

Elementsminus15

minus1

minus05

Figure 7 The DI of each element calculated by efficient modal

34 Selection of EfficientMode The change rate of the naturalfrequencies before and after damage is shown in Figure 6 andTable 1 and the efficient frequency threshold is set as 120575

119894ge

04 As Figure 6 shows mode 1 and mode 4 are the efficientmodes of damage case

35 Damage Location Identification Information function isestablished using the changes of element strain energy beforeand after damage andwavelet transform is used to determinethe parameters (119863119868) for the damage location Efficient modal119863119868119895is shown in Figure 7 By setting the threshold (119863119868 gt 2)

it can be clearly determined that crack damage occurred inthe elements from 55 to 59 which is very identical with theactual damage location The identification results of damagelocation are shown in tables The identification error is 3which proves the accuracy advantage of damage locationidentification method

36 Identification of Injury Severity Element damage factor120572 is calculated by applying (18) and the results are shownin Table 2 As shown in Table 2 the result of actual injury isvery close to that of calculated injury with identification errorby 62 which proves that the method of damage severityidentification has a higher accuracy

4 Conclusions

This paper firstly selected efficient modes for damage identi-fication by applying the change rate of eigenvalues and thenit established an accurate method for small damage iden-tification based on the application of sensitivity of elementmodal strain energy to small structural injury and efficientlocal analysis capabilities of wavelet analysis The efficiencyand accuracy of the proposed method were verified through

The Scientific World Journal 7

Table 1 Calculated natural frequencies from the FE model

ModeThe experimental

monitoringfrequencies

The calculatednatural frequencies Difference ()

1 1940 1932 0412 3035 2997 1253 6835 6805 0444 6983 6944 0565 7883 7852 039

Table 2 Results of damage identification

Actualinjury

Low strainmethoderror

Newmethoderror

Damage location 74m 671m93 708m43Damage severity 96 Small damage 10262

identifying small cracks damage of the pile used in the OuhaiSports Center The conclusions are as follows

(1) Fracture identificationmethod proposed in this papercan effectively and accurately identify the fracturedamage location for the hidden structures in service

(2) The proposed method can effectively identify andquantify the fracture damage severity for the hiddenstructures in service providing an important refer-ence for the assessment of fracture damage

(3) The method presented in this paper provided anew approach for damage identification of concealedstructure

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is one of research projects financed by HunanProvince Research Center for Safety Control Technology andEquipment of Bridge Engineering (Changsha University ofScience amp Technology) The number of research projects is13KC05

References

[1] H W Zhou W T Weng and Y Wang ldquoSeveral methods ofthe bridge pile testingrdquo Highway and Transportation Research(Applied Technology Edition) vol 4 pp 222ndash225 2012

[2] X L Han Y X Han and X M Tang ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 6 pp 105ndash107 2001

[3] H Y Chai M G Liu and S W Bai ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 5 pp 624ndash628 2003

[4] C H Zhang J L Zhang J H Xie et al ldquoThe multi-reflectedwave analysis on the low strain integrity testing of pile founda-tionrdquo Journal of Xiamen University Natural Science vol 3 pp214ndash216 2005

[5] Y M Chen ldquoGot method drills in pile foundation inspectionabout the application analysisrdquo Construction and Design forProject vol 7 pp 129ndash131 2011

[6] C X Xiao ldquoApplication of ultrasonic transmission method todetecting integrity of large-diameter bored cast-in-place pilesrdquoRock and Soil Mechanics supplement 1 pp 169ndash171 2003

[7] F C LiuWWang Z S Zhang andWQ Liu ldquoWave analysis ofpile foundation low strain detection and determination of pilebody integrityrdquo Port Engineering Technology vol 2 pp 46ndash482012

[8] H QWu R Y Ma L Y Huang J Peng and L Chen ldquoGeneralapplication and analysis of several detection methods in theengineering foundation pilesrdquoConcrete vol 4 pp 119ndash121 2012

[9] M Johnson and F Rausche ldquoLow strain testing of piles utilizingtow acceleration signardquo Stress Wave vol 3 pp 859ndash869 1996

[10] X Luo H Haya T Inaba T Shiotani and Y Nakanishi ldquoDam-age evaluation of railway structures by using train-induced AErdquoConstruction and Building Materials vol 18 no 3 pp 215ndash2232004

[11] X S Hao ldquoOutline of on-the-spot investigation on the earth-quake occurring in the south of hyogo prefecture Japan onJanuary 171995rdquo Recent Developments in World Seismology vol7 pp 12ndash16 1995

[12] W C Yuan F Cui and Q W Zhang ldquoCurrent research anddevelopment of structural health monitoring and conditionassessment for bridgesrdquo Journal of Tongji University vol 2 pp184ndash188 1999

[13] Y Z Qi ldquoHole wall imaging technology in old bridge pilefoundation inspectionrdquo Highway vol 3 pp 16ndash19 2012

[14] Y Zhang and S Z Tian ldquoApplication of wavelet analysis inhigh-piledwharf pile integrity testingrdquo Journal ofWaterway andHarbor vol 2 pp 163ndash168 2012

[15] C Dong P Zhang andW F T Huang ldquoThe sensitivity study ofthe modal parameters of a cracked beamrdquo in Proceeding of the12th International Modal Analysis Conference vol 1 pp 98ndash1041994

[16] N Stubbs J Kim and K Topole ldquoAn efficient and robustalgorithm for damage localization in offshore platformsrdquo inProceedings of the ASCE 10th Structures Congress vol 1 pp 543ndash546 1992

[17] N Stubbs J Kim and C Farrar ldquoField verification of anondestructive damage localization and severity estimationalgorithmrdquo in Proceedings of the 13th International ModalAnalysis Conference vol 1 pp 210ndash218 Nashville Tenn USA1995

[18] E Parloo P Guillaume and M Van Overmeire ldquoDamageassessment using mode shape sensitivitiesrdquoMechanical Systemsand Signal Processing vol 17 no 3 pp 499ndash518 2003

[19] A Alvandi and C Cremona ldquoAssessment of vibration-baseddamage identification techniquesrdquo Journal of Sound and Vibra-tion vol 292 no 1-2 pp 179ndash202 2006

[20] W Fan and P Qiao ldquoA strain energy-based damage severitycorrection factor method for damage identification in plate-type structuresrdquoMechanical Systems and Signal Processing vol28 pp 660ndash678 2012

[21] W Yao and X Zhang ldquoFracture damage identification of pileusing element strain energymethod based on sensitivemodalsrdquo

8 The Scientific World Journal

in Proceedings of the 13th International Conference on Fracturepp 2372ndash2380 Beijing China June 2013

[22] L J Hadjileontiadis E Douka and A Trochidis ldquoFractaldimension analysis for crack identification in beam structuresrdquoMechanical Systems and Signal Processing vol 19 no 3 pp 659ndash674 2005

[23] H Hu C Wu andW-J Lu ldquoDamage detection of circular hol-low cylinder using modal strain energy and scanning damageindex methodsrdquo Computers and Structures vol 89 no 1-2 pp149ndash160 2011

[24] J-H Zhang Y-H Liu and J-S Wang ldquoStudy on radiatednoise of engine oil sump by experimental modal expansiontechniquerdquo Transactions of CSICE (Chinese Society for InternalCombustion Engines) vol 23 no 6 pp 532ndash535 2005

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

The Scientific World Journal 5

(a) On-site excavation detection

Location SYYTP ID 71 R 700mm V 350mS Date 2010-8-2

000 525 1050 1575 2100

1000m

(b) Detection of low strain

Figure 1 The actual damage of pile

Figure 2 Typical accelerometer attachment

0

002

004

006

008

163 164 165 166 167 168 169 170 171

Acce

lera

tion

(g)

Time (s)

minus008

minus006

minus004

minus002

Figure 3 Acceleration response of sensor

0

05

1

15

0 10 20 30 40

Mag

nitu

de

Distance (m)

Series 1Series 2Series 3

Series 4Series 5

minus1

minus05

Figure 4 Mode shapes derived by sensors

33 Finite Element Modeling Applying finite element soft-ware ANSYS we establish finite element model of soil-pileinteraction for number 71 pile (Figure 5(a)) according tothe design drawings According to actual damage on thenumber 71 pile the pile model of the cracks was establishedat 74 meters from the top of the pile with crack depthaccounting for 96 of the diameter of pile foundation(Figure 5(b)) The element type of pile foundation model isSOLID45The nonlinear spring element COMBIN139 is usedto simulate pile-soil interaction In order to establish a finiteelement computation model which is more consistent withthe environment of actual engineering situation the modelupdating technology was used to improve the finite elementmodel based on the measured data

6 The Scientific World Journal

(a) Before damage (b) After damage

Figure 5 Finite element model of pile-soil interaction

0

005

01

015

02

025

03

035

04

045

05

1 2 3 4 5 6 7 8 9 10

The r

ate o

f cha

nge

Mode

Figure 6 The change rate of the natural frequency

005

115

225

335

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101

106

111

116

121

DI

Elementsminus15

minus1

minus05

Figure 7 The DI of each element calculated by efficient modal

34 Selection of EfficientMode The change rate of the naturalfrequencies before and after damage is shown in Figure 6 andTable 1 and the efficient frequency threshold is set as 120575

119894ge

04 As Figure 6 shows mode 1 and mode 4 are the efficientmodes of damage case

35 Damage Location Identification Information function isestablished using the changes of element strain energy beforeand after damage andwavelet transform is used to determinethe parameters (119863119868) for the damage location Efficient modal119863119868119895is shown in Figure 7 By setting the threshold (119863119868 gt 2)

it can be clearly determined that crack damage occurred inthe elements from 55 to 59 which is very identical with theactual damage location The identification results of damagelocation are shown in tables The identification error is 3which proves the accuracy advantage of damage locationidentification method

36 Identification of Injury Severity Element damage factor120572 is calculated by applying (18) and the results are shownin Table 2 As shown in Table 2 the result of actual injury isvery close to that of calculated injury with identification errorby 62 which proves that the method of damage severityidentification has a higher accuracy

4 Conclusions

This paper firstly selected efficient modes for damage identi-fication by applying the change rate of eigenvalues and thenit established an accurate method for small damage iden-tification based on the application of sensitivity of elementmodal strain energy to small structural injury and efficientlocal analysis capabilities of wavelet analysis The efficiencyand accuracy of the proposed method were verified through

The Scientific World Journal 7

Table 1 Calculated natural frequencies from the FE model

ModeThe experimental

monitoringfrequencies

The calculatednatural frequencies Difference ()

1 1940 1932 0412 3035 2997 1253 6835 6805 0444 6983 6944 0565 7883 7852 039

Table 2 Results of damage identification

Actualinjury

Low strainmethoderror

Newmethoderror

Damage location 74m 671m93 708m43Damage severity 96 Small damage 10262

identifying small cracks damage of the pile used in the OuhaiSports Center The conclusions are as follows

(1) Fracture identificationmethod proposed in this papercan effectively and accurately identify the fracturedamage location for the hidden structures in service

(2) The proposed method can effectively identify andquantify the fracture damage severity for the hiddenstructures in service providing an important refer-ence for the assessment of fracture damage

(3) The method presented in this paper provided anew approach for damage identification of concealedstructure

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is one of research projects financed by HunanProvince Research Center for Safety Control Technology andEquipment of Bridge Engineering (Changsha University ofScience amp Technology) The number of research projects is13KC05

References

[1] H W Zhou W T Weng and Y Wang ldquoSeveral methods ofthe bridge pile testingrdquo Highway and Transportation Research(Applied Technology Edition) vol 4 pp 222ndash225 2012

[2] X L Han Y X Han and X M Tang ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 6 pp 105ndash107 2001

[3] H Y Chai M G Liu and S W Bai ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 5 pp 624ndash628 2003

[4] C H Zhang J L Zhang J H Xie et al ldquoThe multi-reflectedwave analysis on the low strain integrity testing of pile founda-tionrdquo Journal of Xiamen University Natural Science vol 3 pp214ndash216 2005

[5] Y M Chen ldquoGot method drills in pile foundation inspectionabout the application analysisrdquo Construction and Design forProject vol 7 pp 129ndash131 2011

[6] C X Xiao ldquoApplication of ultrasonic transmission method todetecting integrity of large-diameter bored cast-in-place pilesrdquoRock and Soil Mechanics supplement 1 pp 169ndash171 2003

[7] F C LiuWWang Z S Zhang andWQ Liu ldquoWave analysis ofpile foundation low strain detection and determination of pilebody integrityrdquo Port Engineering Technology vol 2 pp 46ndash482012

[8] H QWu R Y Ma L Y Huang J Peng and L Chen ldquoGeneralapplication and analysis of several detection methods in theengineering foundation pilesrdquoConcrete vol 4 pp 119ndash121 2012

[9] M Johnson and F Rausche ldquoLow strain testing of piles utilizingtow acceleration signardquo Stress Wave vol 3 pp 859ndash869 1996

[10] X Luo H Haya T Inaba T Shiotani and Y Nakanishi ldquoDam-age evaluation of railway structures by using train-induced AErdquoConstruction and Building Materials vol 18 no 3 pp 215ndash2232004

[11] X S Hao ldquoOutline of on-the-spot investigation on the earth-quake occurring in the south of hyogo prefecture Japan onJanuary 171995rdquo Recent Developments in World Seismology vol7 pp 12ndash16 1995

[12] W C Yuan F Cui and Q W Zhang ldquoCurrent research anddevelopment of structural health monitoring and conditionassessment for bridgesrdquo Journal of Tongji University vol 2 pp184ndash188 1999

[13] Y Z Qi ldquoHole wall imaging technology in old bridge pilefoundation inspectionrdquo Highway vol 3 pp 16ndash19 2012

[14] Y Zhang and S Z Tian ldquoApplication of wavelet analysis inhigh-piledwharf pile integrity testingrdquo Journal ofWaterway andHarbor vol 2 pp 163ndash168 2012

[15] C Dong P Zhang andW F T Huang ldquoThe sensitivity study ofthe modal parameters of a cracked beamrdquo in Proceeding of the12th International Modal Analysis Conference vol 1 pp 98ndash1041994

[16] N Stubbs J Kim and K Topole ldquoAn efficient and robustalgorithm for damage localization in offshore platformsrdquo inProceedings of the ASCE 10th Structures Congress vol 1 pp 543ndash546 1992

[17] N Stubbs J Kim and C Farrar ldquoField verification of anondestructive damage localization and severity estimationalgorithmrdquo in Proceedings of the 13th International ModalAnalysis Conference vol 1 pp 210ndash218 Nashville Tenn USA1995

[18] E Parloo P Guillaume and M Van Overmeire ldquoDamageassessment using mode shape sensitivitiesrdquoMechanical Systemsand Signal Processing vol 17 no 3 pp 499ndash518 2003

[19] A Alvandi and C Cremona ldquoAssessment of vibration-baseddamage identification techniquesrdquo Journal of Sound and Vibra-tion vol 292 no 1-2 pp 179ndash202 2006

[20] W Fan and P Qiao ldquoA strain energy-based damage severitycorrection factor method for damage identification in plate-type structuresrdquoMechanical Systems and Signal Processing vol28 pp 660ndash678 2012

[21] W Yao and X Zhang ldquoFracture damage identification of pileusing element strain energymethod based on sensitivemodalsrdquo

8 The Scientific World Journal

in Proceedings of the 13th International Conference on Fracturepp 2372ndash2380 Beijing China June 2013

[22] L J Hadjileontiadis E Douka and A Trochidis ldquoFractaldimension analysis for crack identification in beam structuresrdquoMechanical Systems and Signal Processing vol 19 no 3 pp 659ndash674 2005

[23] H Hu C Wu andW-J Lu ldquoDamage detection of circular hol-low cylinder using modal strain energy and scanning damageindex methodsrdquo Computers and Structures vol 89 no 1-2 pp149ndash160 2011

[24] J-H Zhang Y-H Liu and J-S Wang ldquoStudy on radiatednoise of engine oil sump by experimental modal expansiontechniquerdquo Transactions of CSICE (Chinese Society for InternalCombustion Engines) vol 23 no 6 pp 532ndash535 2005

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

6 The Scientific World Journal

(a) Before damage (b) After damage

Figure 5 Finite element model of pile-soil interaction

0

005

01

015

02

025

03

035

04

045

05

1 2 3 4 5 6 7 8 9 10

The r

ate o

f cha

nge

Mode

Figure 6 The change rate of the natural frequency

005

115

225

335

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101

106

111

116

121

DI

Elementsminus15

minus1

minus05

Figure 7 The DI of each element calculated by efficient modal

34 Selection of EfficientMode The change rate of the naturalfrequencies before and after damage is shown in Figure 6 andTable 1 and the efficient frequency threshold is set as 120575

119894ge

04 As Figure 6 shows mode 1 and mode 4 are the efficientmodes of damage case

35 Damage Location Identification Information function isestablished using the changes of element strain energy beforeand after damage andwavelet transform is used to determinethe parameters (119863119868) for the damage location Efficient modal119863119868119895is shown in Figure 7 By setting the threshold (119863119868 gt 2)

it can be clearly determined that crack damage occurred inthe elements from 55 to 59 which is very identical with theactual damage location The identification results of damagelocation are shown in tables The identification error is 3which proves the accuracy advantage of damage locationidentification method

36 Identification of Injury Severity Element damage factor120572 is calculated by applying (18) and the results are shownin Table 2 As shown in Table 2 the result of actual injury isvery close to that of calculated injury with identification errorby 62 which proves that the method of damage severityidentification has a higher accuracy

4 Conclusions

This paper firstly selected efficient modes for damage identi-fication by applying the change rate of eigenvalues and thenit established an accurate method for small damage iden-tification based on the application of sensitivity of elementmodal strain energy to small structural injury and efficientlocal analysis capabilities of wavelet analysis The efficiencyand accuracy of the proposed method were verified through

The Scientific World Journal 7

Table 1 Calculated natural frequencies from the FE model

ModeThe experimental

monitoringfrequencies

The calculatednatural frequencies Difference ()

1 1940 1932 0412 3035 2997 1253 6835 6805 0444 6983 6944 0565 7883 7852 039

Table 2 Results of damage identification

Actualinjury

Low strainmethoderror

Newmethoderror

Damage location 74m 671m93 708m43Damage severity 96 Small damage 10262

identifying small cracks damage of the pile used in the OuhaiSports Center The conclusions are as follows

(1) Fracture identificationmethod proposed in this papercan effectively and accurately identify the fracturedamage location for the hidden structures in service

(2) The proposed method can effectively identify andquantify the fracture damage severity for the hiddenstructures in service providing an important refer-ence for the assessment of fracture damage

(3) The method presented in this paper provided anew approach for damage identification of concealedstructure

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is one of research projects financed by HunanProvince Research Center for Safety Control Technology andEquipment of Bridge Engineering (Changsha University ofScience amp Technology) The number of research projects is13KC05

References

[1] H W Zhou W T Weng and Y Wang ldquoSeveral methods ofthe bridge pile testingrdquo Highway and Transportation Research(Applied Technology Edition) vol 4 pp 222ndash225 2012

[2] X L Han Y X Han and X M Tang ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 6 pp 105ndash107 2001

[3] H Y Chai M G Liu and S W Bai ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 5 pp 624ndash628 2003

[4] C H Zhang J L Zhang J H Xie et al ldquoThe multi-reflectedwave analysis on the low strain integrity testing of pile founda-tionrdquo Journal of Xiamen University Natural Science vol 3 pp214ndash216 2005

[5] Y M Chen ldquoGot method drills in pile foundation inspectionabout the application analysisrdquo Construction and Design forProject vol 7 pp 129ndash131 2011

[6] C X Xiao ldquoApplication of ultrasonic transmission method todetecting integrity of large-diameter bored cast-in-place pilesrdquoRock and Soil Mechanics supplement 1 pp 169ndash171 2003

[7] F C LiuWWang Z S Zhang andWQ Liu ldquoWave analysis ofpile foundation low strain detection and determination of pilebody integrityrdquo Port Engineering Technology vol 2 pp 46ndash482012

[8] H QWu R Y Ma L Y Huang J Peng and L Chen ldquoGeneralapplication and analysis of several detection methods in theengineering foundation pilesrdquoConcrete vol 4 pp 119ndash121 2012

[9] M Johnson and F Rausche ldquoLow strain testing of piles utilizingtow acceleration signardquo Stress Wave vol 3 pp 859ndash869 1996

[10] X Luo H Haya T Inaba T Shiotani and Y Nakanishi ldquoDam-age evaluation of railway structures by using train-induced AErdquoConstruction and Building Materials vol 18 no 3 pp 215ndash2232004

[11] X S Hao ldquoOutline of on-the-spot investigation on the earth-quake occurring in the south of hyogo prefecture Japan onJanuary 171995rdquo Recent Developments in World Seismology vol7 pp 12ndash16 1995

[12] W C Yuan F Cui and Q W Zhang ldquoCurrent research anddevelopment of structural health monitoring and conditionassessment for bridgesrdquo Journal of Tongji University vol 2 pp184ndash188 1999

[13] Y Z Qi ldquoHole wall imaging technology in old bridge pilefoundation inspectionrdquo Highway vol 3 pp 16ndash19 2012

[14] Y Zhang and S Z Tian ldquoApplication of wavelet analysis inhigh-piledwharf pile integrity testingrdquo Journal ofWaterway andHarbor vol 2 pp 163ndash168 2012

[15] C Dong P Zhang andW F T Huang ldquoThe sensitivity study ofthe modal parameters of a cracked beamrdquo in Proceeding of the12th International Modal Analysis Conference vol 1 pp 98ndash1041994

[16] N Stubbs J Kim and K Topole ldquoAn efficient and robustalgorithm for damage localization in offshore platformsrdquo inProceedings of the ASCE 10th Structures Congress vol 1 pp 543ndash546 1992

[17] N Stubbs J Kim and C Farrar ldquoField verification of anondestructive damage localization and severity estimationalgorithmrdquo in Proceedings of the 13th International ModalAnalysis Conference vol 1 pp 210ndash218 Nashville Tenn USA1995

[18] E Parloo P Guillaume and M Van Overmeire ldquoDamageassessment using mode shape sensitivitiesrdquoMechanical Systemsand Signal Processing vol 17 no 3 pp 499ndash518 2003

[19] A Alvandi and C Cremona ldquoAssessment of vibration-baseddamage identification techniquesrdquo Journal of Sound and Vibra-tion vol 292 no 1-2 pp 179ndash202 2006

[20] W Fan and P Qiao ldquoA strain energy-based damage severitycorrection factor method for damage identification in plate-type structuresrdquoMechanical Systems and Signal Processing vol28 pp 660ndash678 2012

[21] W Yao and X Zhang ldquoFracture damage identification of pileusing element strain energymethod based on sensitivemodalsrdquo

8 The Scientific World Journal

in Proceedings of the 13th International Conference on Fracturepp 2372ndash2380 Beijing China June 2013

[22] L J Hadjileontiadis E Douka and A Trochidis ldquoFractaldimension analysis for crack identification in beam structuresrdquoMechanical Systems and Signal Processing vol 19 no 3 pp 659ndash674 2005

[23] H Hu C Wu andW-J Lu ldquoDamage detection of circular hol-low cylinder using modal strain energy and scanning damageindex methodsrdquo Computers and Structures vol 89 no 1-2 pp149ndash160 2011

[24] J-H Zhang Y-H Liu and J-S Wang ldquoStudy on radiatednoise of engine oil sump by experimental modal expansiontechniquerdquo Transactions of CSICE (Chinese Society for InternalCombustion Engines) vol 23 no 6 pp 532ndash535 2005

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

The Scientific World Journal 7

Table 1 Calculated natural frequencies from the FE model

ModeThe experimental

monitoringfrequencies

The calculatednatural frequencies Difference ()

1 1940 1932 0412 3035 2997 1253 6835 6805 0444 6983 6944 0565 7883 7852 039

Table 2 Results of damage identification

Actualinjury

Low strainmethoderror

Newmethoderror

Damage location 74m 671m93 708m43Damage severity 96 Small damage 10262

identifying small cracks damage of the pile used in the OuhaiSports Center The conclusions are as follows

(1) Fracture identificationmethod proposed in this papercan effectively and accurately identify the fracturedamage location for the hidden structures in service

(2) The proposed method can effectively identify andquantify the fracture damage severity for the hiddenstructures in service providing an important refer-ence for the assessment of fracture damage

(3) The method presented in this paper provided anew approach for damage identification of concealedstructure

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is one of research projects financed by HunanProvince Research Center for Safety Control Technology andEquipment of Bridge Engineering (Changsha University ofScience amp Technology) The number of research projects is13KC05

References

[1] H W Zhou W T Weng and Y Wang ldquoSeveral methods ofthe bridge pile testingrdquo Highway and Transportation Research(Applied Technology Edition) vol 4 pp 222ndash225 2012

[2] X L Han Y X Han and X M Tang ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 6 pp 105ndash107 2001

[3] H Y Chai M G Liu and S W Bai ldquoNumerical analysis ofwave propagation in platform-pile systemrdquo Chinese Journal ofGeotechnical Engineering vol 5 pp 624ndash628 2003

[4] C H Zhang J L Zhang J H Xie et al ldquoThe multi-reflectedwave analysis on the low strain integrity testing of pile founda-tionrdquo Journal of Xiamen University Natural Science vol 3 pp214ndash216 2005

[5] Y M Chen ldquoGot method drills in pile foundation inspectionabout the application analysisrdquo Construction and Design forProject vol 7 pp 129ndash131 2011

[6] C X Xiao ldquoApplication of ultrasonic transmission method todetecting integrity of large-diameter bored cast-in-place pilesrdquoRock and Soil Mechanics supplement 1 pp 169ndash171 2003

[7] F C LiuWWang Z S Zhang andWQ Liu ldquoWave analysis ofpile foundation low strain detection and determination of pilebody integrityrdquo Port Engineering Technology vol 2 pp 46ndash482012

[8] H QWu R Y Ma L Y Huang J Peng and L Chen ldquoGeneralapplication and analysis of several detection methods in theengineering foundation pilesrdquoConcrete vol 4 pp 119ndash121 2012

[9] M Johnson and F Rausche ldquoLow strain testing of piles utilizingtow acceleration signardquo Stress Wave vol 3 pp 859ndash869 1996

[10] X Luo H Haya T Inaba T Shiotani and Y Nakanishi ldquoDam-age evaluation of railway structures by using train-induced AErdquoConstruction and Building Materials vol 18 no 3 pp 215ndash2232004

[11] X S Hao ldquoOutline of on-the-spot investigation on the earth-quake occurring in the south of hyogo prefecture Japan onJanuary 171995rdquo Recent Developments in World Seismology vol7 pp 12ndash16 1995

[12] W C Yuan F Cui and Q W Zhang ldquoCurrent research anddevelopment of structural health monitoring and conditionassessment for bridgesrdquo Journal of Tongji University vol 2 pp184ndash188 1999

[13] Y Z Qi ldquoHole wall imaging technology in old bridge pilefoundation inspectionrdquo Highway vol 3 pp 16ndash19 2012

[14] Y Zhang and S Z Tian ldquoApplication of wavelet analysis inhigh-piledwharf pile integrity testingrdquo Journal ofWaterway andHarbor vol 2 pp 163ndash168 2012

[15] C Dong P Zhang andW F T Huang ldquoThe sensitivity study ofthe modal parameters of a cracked beamrdquo in Proceeding of the12th International Modal Analysis Conference vol 1 pp 98ndash1041994

[16] N Stubbs J Kim and K Topole ldquoAn efficient and robustalgorithm for damage localization in offshore platformsrdquo inProceedings of the ASCE 10th Structures Congress vol 1 pp 543ndash546 1992

[17] N Stubbs J Kim and C Farrar ldquoField verification of anondestructive damage localization and severity estimationalgorithmrdquo in Proceedings of the 13th International ModalAnalysis Conference vol 1 pp 210ndash218 Nashville Tenn USA1995

[18] E Parloo P Guillaume and M Van Overmeire ldquoDamageassessment using mode shape sensitivitiesrdquoMechanical Systemsand Signal Processing vol 17 no 3 pp 499ndash518 2003

[19] A Alvandi and C Cremona ldquoAssessment of vibration-baseddamage identification techniquesrdquo Journal of Sound and Vibra-tion vol 292 no 1-2 pp 179ndash202 2006

[20] W Fan and P Qiao ldquoA strain energy-based damage severitycorrection factor method for damage identification in plate-type structuresrdquoMechanical Systems and Signal Processing vol28 pp 660ndash678 2012

[21] W Yao and X Zhang ldquoFracture damage identification of pileusing element strain energymethod based on sensitivemodalsrdquo

8 The Scientific World Journal

in Proceedings of the 13th International Conference on Fracturepp 2372ndash2380 Beijing China June 2013

[22] L J Hadjileontiadis E Douka and A Trochidis ldquoFractaldimension analysis for crack identification in beam structuresrdquoMechanical Systems and Signal Processing vol 19 no 3 pp 659ndash674 2005

[23] H Hu C Wu andW-J Lu ldquoDamage detection of circular hol-low cylinder using modal strain energy and scanning damageindex methodsrdquo Computers and Structures vol 89 no 1-2 pp149ndash160 2011

[24] J-H Zhang Y-H Liu and J-S Wang ldquoStudy on radiatednoise of engine oil sump by experimental modal expansiontechniquerdquo Transactions of CSICE (Chinese Society for InternalCombustion Engines) vol 23 no 6 pp 532ndash535 2005

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

8 The Scientific World Journal

in Proceedings of the 13th International Conference on Fracturepp 2372ndash2380 Beijing China June 2013

[22] L J Hadjileontiadis E Douka and A Trochidis ldquoFractaldimension analysis for crack identification in beam structuresrdquoMechanical Systems and Signal Processing vol 19 no 3 pp 659ndash674 2005

[23] H Hu C Wu andW-J Lu ldquoDamage detection of circular hol-low cylinder using modal strain energy and scanning damageindex methodsrdquo Computers and Structures vol 89 no 1-2 pp149ndash160 2011

[24] J-H Zhang Y-H Liu and J-S Wang ldquoStudy on radiatednoise of engine oil sump by experimental modal expansiontechniquerdquo Transactions of CSICE (Chinese Society for InternalCombustion Engines) vol 23 no 6 pp 532ndash535 2005

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of