NON DESTRUCTIVE TESTING IN RAILWAY BRIDGES. INTRODUCTION Non – Destructive testing [NDT] is an activity to assess the variation from the design and

NON DESTRUCTIVE NON DESTRUCTIVE TESTINGTESTING

IN RAILWAY BRIDGESIN RAILWAY BRIDGES

INTRODUCTIONINTRODUCTION Non – Destructive testing [NDT] is an Non – Destructive testing [NDT] is an

activity to assess the variation from the activity to assess the variation from the design and monitor performance.design and monitor performance.

With the increasing number of structures With the increasing number of structures showing signs of distress a greater need is showing signs of distress a greater need is felt to apply more advance assessment felt to apply more advance assessment techniques and equipment in the bridge techniques and equipment in the bridge inspection.inspection.

This presentation focuses on the available This presentation focuses on the available techniques , and two nos case studies of techniques , and two nos case studies of NF Railway , where the NDT has been used NF Railway , where the NDT has been used successfully.successfully.

NDT TechniquesNDT TechniquesCompressive StrengthCompressive Strength Rebound Hammer Test, Windsor Rebound Hammer Test, Windsor

Probe Test , Core Test , Lok Test, Probe Test , Core Test , Lok Test, Capo Test Capo Test

Flexural StrengthFlexural Strength Break- Off TestBreak- Off Test

Direct Tensile StrengthDirect Tensile Strength Pull- Off TestPull- Off Test

HomogeneityHomogeneity Ultrasonic Pulse Velocity Test , Ultrasonic Pulse Velocity Test , Acoustic Emission Method , Pulse – Acoustic Emission Method , Pulse – echo method. Gamma- Ray echo method. Gamma- Ray Radiography , Endoscopy, Integrity Radiography , Endoscopy, Integrity Testing of PilesTesting of Piles

PermeabilityPermeability Initial Surface Absorption Test , Figg’s Initial Surface Absorption Test , Figg’s Air and Water Permeability TestAir and Water Permeability Test

NDT Techniques [… Contd]NDT Techniques [… Contd]

Chemical Composition Chemical Composition Wet Chemical Analysis for Total Wet Chemical Analysis for Total Chloride , Potential Measurement Chloride , Potential Measurement Technique for Chlorides, Technique for Chlorides, Determination Carbonation TestDetermination Carbonation Test

CracksCracks Ultrasound Pulse Velocity Test, Ultrasound Pulse Velocity Test, Acoustic Crack Detector , Dye Acoustic Crack Detector , Dye Penetration Test , X-Ray Radiography Penetration Test , X-Ray Radiography , Gamma Radiography , Gamma Radiography

NDT in NF Railway`NDT in NF Railway`

Of the above NDT techniques so detailed , Of the above NDT techniques so detailed , NF Railway has gained some experience NF Railway has gained some experience in the following techniques in the following techniques

A. Rebound Hammer TestA. Rebound Hammer Test

B. Core TestB. Core Test

C. Ultra Sound Pulse Velocity MethodC. Ultra Sound Pulse Velocity Method

D. Integrity Testing of PilesD. Integrity Testing of Piles

E. Chemical Analysis of the Concrete E. Chemical Analysis of the Concrete MaterialMaterial

NDT in NF RailwayNDT in NF Railway

The experienced so gained in the last The experienced so gained in the last two years on NF Railway shall be two years on NF Railway shall be explained in the remaining part of explained in the remaining part of the presentation using two nos case the presentation using two nos case studies of NF Railwaystudies of NF Railway

NDT in NF Railway --- Br No 40NDT in NF Railway --- Br No 40 Br No 40 is an Important Bridge on New Jalpaiguri Br No 40 is an Important Bridge on New Jalpaiguri

– New Bongaigaon section of NF Railway having – New Bongaigaon section of NF Railway having an span of 20 x 150 feet over Teesta River. Its an span of 20 x 150 feet over Teesta River. Its design discharge is 700000 cusecs. It has Cement design discharge is 700000 cusecs. It has Cement Concrete Well Foundation designed for BGML Concrete Well Foundation designed for BGML Standard with 30 Feet Well Dia and 100 feet Standard with 30 Feet Well Dia and 100 feet depth of well below HFL. The bridge was initially depth of well below HFL. The bridge was initially constructed as 13x150 feet spans . During 1988 constructed as 13x150 feet spans . During 1988 floods eastern approach was washed away and floods eastern approach was washed away and the bridge was extended by 7 spans of 150ft on the bridge was extended by 7 spans of 150ft on the east in 1975.the east in 1975.

For the last few years cracks were developing on For the last few years cracks were developing on Pier No. P1, P2 , P3 and P4.Pier No. P1, P2 , P3 and P4.

NDT in NF Railway --- Br No 40NDT in NF Railway --- Br No 40

PANORAMIC VIEW OF BRIDGE NO 40


ZIG ZAG CRACK PATTERN


CRACKS IN WELL CAP


SHOWING CASTING LIFT VARIATIONS


HORIZONTAL CRACKS FORMED DUE TO SEPERATION OF COLD JOINT IN COURSE OF TIME


CRACK MAGNIFIED


SEVERE VERTICAL CRACKS


CRACKS CONCENTRATION FROM DIFFERENT DIRECTIONS , RESULTING IN SEVERE DETERIORATION AT MEETING POINT

NDT in NF Railway --- Br No 40NDT in NF Railway --- Br No 40 These cracks were prominent in Piers P1, These cracks were prominent in Piers P1,

P2, P3 and P4.P2, P3 and P4. After this visual examination , certain After this visual examination , certain

points remained unansweredpoints remained unanswered It was not clear , as to what was the depth It was not clear , as to what was the depth

of these cracks?of these cracks? What was the resultant compressive What was the resultant compressive

strength of the concrete mass used in strength of the concrete mass used in Pier?Pier?

Whether the concrete has undergone any Whether the concrete has undergone any long term deterioration due to excessive long term deterioration due to excessive sulphur or chloride content?sulphur or chloride content?


In order to assess the above points it In order to assess the above points it was decided to undertake the was decided to undertake the following examinationsfollowing examinations

Ultrasonic Pulse Velocity TestUltrasonic Pulse Velocity Test Concrete Core extraction for Concrete Core extraction for

evaluation of compressive strengthevaluation of compressive strength Chemical Analysis to ascertain Chemical Analysis to ascertain

approximate mix proportions of approximate mix proportions of concreteconcrete


M/s S. K. Mitra and Associates of M/s S. K. Mitra and Associates of Kolkatta were entrusted the work, Kolkatta were entrusted the work, who carried out the same in March – who carried out the same in March – April 2003April 2003

Test Methods and the deductions on Test Methods and the deductions on the basis of the test results are the basis of the test results are explained in the following slides.explained in the following slides.

NDT in NF Railway --- Br No 40NDT in NF Railway --- Br No 40Ultrasonic Pulse Velocity TestUltrasonic Pulse Velocity Test

The aim of the Ultrasound pulse velocity test was The aim of the Ultrasound pulse velocity test was to identify weak locations possessing loss of to identify weak locations possessing loss of integrity , presence of void , quality of concrete integrity , presence of void , quality of concrete and depth of cracks which could not be and depth of cracks which could not be ascertained by visual inspection.ascertained by visual inspection.

The ultrasonic pulse is generated by an electro-The ultrasonic pulse is generated by an electro-acoustical transducer. When the pulse is induced acoustical transducer. When the pulse is induced in the concrete from a transducer, it undergoes in the concrete from a transducer, it undergoes multiple reflections at the boundaries of the multiple reflections at the boundaries of the different material phases within the concrete. A different material phases within the concrete. A complex system of stress waves is generated complex system of stress waves is generated which includes longitudinal , shear and surface which includes longitudinal , shear and surface waves. The receiving transducer detects the waves. The receiving transducer detects the longitudinal waves which is the fastest.longitudinal waves which is the fastest.


The velocity of an ultrasonic pulse through any The velocity of an ultrasonic pulse through any material depends upon its density , modulus of material depends upon its density , modulus of elasticity , presence of reinforcement steel and elasticity , presence of reinforcement steel and Poisson’s ratio.Poisson’s ratio.

The underlying principle of assessing the quality The underlying principle of assessing the quality of concrete is that comparatively higher velocities of concrete is that comparatively higher velocities are obtained when the quality of concrete in are obtained when the quality of concrete in terms of density , homogeneity and uniformity is terms of density , homogeneity and uniformity is good. In case of poorer quality , lower velocities good. In case of poorer quality , lower velocities are obtained.are obtained.

If there is a crack , void or flaw inside the If there is a crack , void or flaw inside the concrete which comes in the way of transmission concrete which comes in the way of transmission of the pulses, the pulse strength is attenuated of the pulses, the pulse strength is attenuated and lower velocities are obtained,and lower velocities are obtained,


TestTest Pulse Velocity by Pulse Velocity by Cross Probing Cross Probing [Km/sec][Km/sec]

Concrete Quality Concrete Quality Grading [IS Grading [IS 13311Part –I-1992]13311Part –I-1992]

11 Above 4.5Above 4.5 ExcellentExcellent

22 3.5 to 4.53.5 to 4.5 Good – Very GoodGood – Very Good

33 3.0 to 3.53.0 to 3.5 MediumMedium

44 Below 3.0Below 3.0 DoubtfulDoubtful

NDT in NF Railway --- Br No 40NDT in NF Railway --- Br No 40Ultrasonic Pulse Velocity Test-InterpretationsUltrasonic Pulse Velocity Test-Interpretations

There are two dimensions to the result There are two dimensions to the result interpretationinterpretation

First – General Quality Assessment of First – General Quality Assessment of Concrete- The velocity ranged fro 3.1 to Concrete- The velocity ranged fro 3.1 to 4.0 Km/sec. This indicates that 4.0 Km/sec. This indicates that quality of quality of concrete was good to very goodconcrete was good to very good

Second- Depth of Crack – It was assessed Second- Depth of Crack – It was assessed based on the velocity of propagated waves based on the velocity of propagated waves on both sides of the crack. on both sides of the crack. Crack Depth Crack Depth were found to be varying from 31mm were found to be varying from 31mm to 684 mm .to 684 mm .

NDT in NF Railway --- Br No 40NDT in NF Railway --- Br No 40Concrete Core ExtractionConcrete Core Extraction

The basic purpose to extract cores The basic purpose to extract cores was to evaluate directly the was to evaluate directly the compressive strength of concrete on compressive strength of concrete on the basis of cylinder strength and co-the basis of cylinder strength and co-relate it to conventional cube relate it to conventional cube strength.strength.

This gives fairly a good idea about This gives fairly a good idea about the compressive strength reached the compressive strength reached


CORE DRILLING IN OPERATION


CORE LOCATION AFTER DRILLING


5 Cores of 55mm Diameter were extracted.5 Cores of 55mm Diameter were extracted. To assess crushing strength , cores were trimmed To assess crushing strength , cores were trimmed

at the end and tested for voids and density also. at the end and tested for voids and density also. Prior to test , cores were capped with sulphur and Prior to test , cores were capped with sulphur and tested after soaking for 48 hourstested after soaking for 48 hours

Equivalent concrete cube strength was assessed Equivalent concrete cube strength was assessed as per IS 516-1959. The results obtained were as per IS 516-1959. The results obtained were found nearer to M-20 grade concrete.found nearer to M-20 grade concrete.

As per the completion plan , a mix proportion of As per the completion plan , a mix proportion of 1:3:6 is mentioned in the drawing for construction 1:3:6 is mentioned in the drawing for construction of pier , and the bed block and well cap was of pier , and the bed block and well cap was constructed using mix proportion of 1:2:4. constructed using mix proportion of 1:2:4. The The test results confirmed that the compressive test results confirmed that the compressive strength of the concrete is above the strength of the concrete is above the assumed value.assumed value.

NDT in NF Railway --- Br No 40NDT in NF Railway --- Br No 40Concrete Core Extraction- Test ResultsConcrete Core Extraction- Test Results

Sample Sample No No

Length Length [cm][cm]

% of Water % of Water AbsorptionAbsorption

Crushing Crushing Strength in Strength in N/sq mmN/sq mm

Eq Cube Eq Cube Strength in Strength in N/sq mmN/sq mm

C1C1 15.815.8 2.472.47 23.7823.78 29.229.2

C2C2 16.416.4 3.043.04 19.8319.83 24.824.8

C3C3 13.813.8 3.983.98 17.9117.91 22.3922.39

C4C4 1212 3.593.59 18.4018.40 23.0023.00

C5C5 14.614.6 4.964.96 18.5418.54 23.1723.17

NDT in NF Railway --- Br No 40NDT in NF Railway --- Br No 40Chemical AnalysisChemical Analysis

The aggregates of Cement Concrete The aggregates of Cement Concrete sample was separated from the sample was separated from the mortar mechanically and chemical mortar mechanically and chemical analysis of mortar portion of the analysis of mortar portion of the cement concrete was carried out cement concrete was carried out generally on the lines of ASTM C-85-generally on the lines of ASTM C-85-66.66.

PH value , Chloride content and the PH value , Chloride content and the Sulphate Content were analysed.Sulphate Content were analysed.

NDT in NF Railway --- Br No 40NDT in NF Railway --- Br No 40Chemical Analysis- Test ResultsChemical Analysis- Test Results

TestTest C1C1 C2C2 C3C3 C4C4 C5C5

PH at PH at 31Deg C 31Deg C

>10.>10.55

>10.5>10.5 >10.5>10.5 >10.5>10.5 >10.5>10.5

Chloride Chloride in PPMin PPM

247247 7474 2525 7474 9797

Sulphate Sulphate in PPMin PPM

30873087 40134013 34983498 51455145 57285728


As per IS 456 -2000 , the PH should not be less As per IS 456 -2000 , the PH should not be less than .Test results reveals that concrete is basic in than .Test results reveals that concrete is basic in nature and so no deterioration due to acidic nature and so no deterioration due to acidic nature was envisaged.nature was envisaged.

As per IS 456 – 2000 , the chloride content As per IS 456 – 2000 , the chloride content should be below 3000 ppm . In all the samples should be below 3000 ppm . In all the samples the Chloride content was found to be much below the Chloride content was found to be much below this this

The limiting value of the sulphate content is 4000 The limiting value of the sulphate content is 4000 ppm . In this case the sulphate content were ppm . In this case the sulphate content were found to be near or slightly more than the limiting found to be near or slightly more than the limiting value. As per IS 456-1978 , value. As per IS 456-1978 , higher values of higher values of sulphates can cause expansion and sulphates can cause expansion and disruption of concrete.disruption of concrete.


IS 456-2000 Clause 8.2.5.4 states that, IS 456-2000 Clause 8.2.5.4 states that, some aggregates containing particular some aggregates containing particular varieties of silica may be susceptible to varieties of silica may be susceptible to attack by alkalis originating from cement attack by alkalis originating from cement and other sources producing an expansive and other sources producing an expansive reaction which can cause cracking and reaction which can cause cracking and disruption of concrete.disruption of concrete.

Aggregates retrieved from the extracted Aggregates retrieved from the extracted core was subjected to aggregate reactivity core was subjected to aggregate reactivity test as per IS:2386 and the results test as per IS:2386 and the results ruled ruled out the possibility of Alkali- out the possibility of Alkali- Aggregate reactivity Aggregate reactivity

NDT in NF Railway --- Br No 40NDT in NF Railway --- Br No 40CONCLUSIONSCONCLUSIONS

Compressive Strength of Concrete was Compressive Strength of Concrete was found to be more than the design value.found to be more than the design value.

Crack depth was found to be varying Crack depth was found to be varying between 31mm to 684 mm between 31mm to 684 mm

Horizontal Cracks , noted in between the Horizontal Cracks , noted in between the lifts of casting in some cases were due to lifts of casting in some cases were due to cold joints formed during construction.cold joints formed during construction.

Higher sulphate content might have Higher sulphate content might have resulted in the cracks.resulted in the cracks.

NDT in NF Railway --- Br No 184NDT in NF Railway --- Br No 184 Br No 184 is a major bridge in Guwahati – Br No 184 is a major bridge in Guwahati –

Lumding section of NF Railway . This has span of Lumding section of NF Railway . This has span of 1x 12.20m and 3x 18.30m . The bridge was built 1x 12.20m and 3x 18.30m . The bridge was built between 1930-1935 . It is having well foundationsbetween 1930-1935 . It is having well foundations

Interestingly the bridge pier is of concrete with Interestingly the bridge pier is of concrete with one brick thick cladding all around the pier.one brick thick cladding all around the pier.

AEN/Lumding reported a hollow echoing sound AEN/Lumding reported a hollow echoing sound emanating from the piers peropheri , when the emanating from the piers peropheri , when the piers were struck by hammers at different points piers were struck by hammers at different points along the cross section and height of the along the cross section and height of the piers.Sectional Sr DEN imposed a restriction of 20 piers.Sectional Sr DEN imposed a restriction of 20 kmph over the bridge. The Division proposed kmph over the bridge. The Division proposed rebuilding of the bridge at an approximate cost of rebuilding of the bridge at an approximate cost of Rs 5.16 CroresRs 5.16 Crores


CBE’s inspection revealed that apart from CBE’s inspection revealed that apart from the usual weathering of the bricks , there the usual weathering of the bricks , there was no distress noticeable on the outer was no distress noticeable on the outer face of the piers where the hollow sounds face of the piers where the hollow sounds were coming fromwere coming from

CBE decided to carry out the NDT and CBE decided to carry out the NDT and have an insight into the bridge structural have an insight into the bridge structural behaviour before going for the complete behaviour before going for the complete rebuilding. rebuilding.


M/s S K Mitra & Associates were M/s S K Mitra & Associates were entrusted to carry out the NDT using entrusted to carry out the NDT using the following techniquesthe following techniques

Ultra sound pulse velocity testUltra sound pulse velocity test Core extraction and TestingCore extraction and Testing Chemical test to evaluate sulphate . Chemical test to evaluate sulphate .

Chloride content and PH valueChloride content and PH value

NDT in NF Railway --- Br No 184NDT in NF Railway --- Br No 184UPV TestUPV Test

MEASURING ULTRA SONIC PULSE VELOCITY


MEASURING PULSE VELOCITY


TestTest Pulse Velocity by Pulse Velocity by Cross Probing Cross Probing [Km/sec][Km/sec]

Concrete Quality Concrete Quality Grading [IS Grading [IS 13311Part –I-1992]13311Part –I-1992]

11 Above 4.5Above 4.5 ExcellentExcellent

22 3.5 to 4.53.5 to 4.5 Good – Very GoodGood – Very Good

33 3.0 to 3.53.0 to 3.5 MediumMedium

44 Below 3.0Below 3.0 DoubtfulDoubtful


Interestingly , the velocity of pulse ranged Interestingly , the velocity of pulse ranged from 0.668 to 1.45km/sec for Pier No 2 from 0.668 to 1.45km/sec for Pier No 2 and from 0.673 to 1.32 Km/sec for Pier No and from 0.673 to 1.32 Km/sec for Pier No P3P3

This placed the concrete quality as This placed the concrete quality as doubtful according to the UPVvalues as doubtful according to the UPVvalues as per IS:13311(Part I) per IS:13311(Part I)

Next Logical step was to carry out the Next Logical step was to carry out the Concrete Core Strength Tests and do the Concrete Core Strength Tests and do the Chemical Analysis.Chemical Analysis.

NDT in NF Railway --- Br No 184NDT in NF Railway --- Br No 184CONCRETE Core Cutter TestCONCRETE Core Cutter Test

CORE EXTRACTION IN PROGRESS


AFTER CORE EXTRACTION


Total 7 Nos cores of 50 mm dia were Total 7 Nos cores of 50 mm dia were extracted. Out of these , 2 Cores were extracted. Out of these , 2 Cores were extracted from the brick layer to assess extracted from the brick layer to assess the quality of the bricksthe quality of the bricks

In all cases , water absorption test was In all cases , water absorption test was carried out and strength determined as carried out and strength determined as per the procedure described in IS:516. To per the procedure described in IS:516. To assess crushing strength , cores were assess crushing strength , cores were trimmed at the end and tested for void trimmed at the end and tested for void and density.and density.


Sample Sample No No

Length Length [cm][cm]

% of Water % of Water AbsorptionAbsorption

Crushing Crushing Strength in Strength in N/sq mmN/sq mm

Eq Cube Eq Cube Strength in Strength in N/sq mmN/sq mm

C1C1 2020 6.46.4 7.857.85 9.819.81

C2C2 1916.41916.4 6.16.1 13.013.0 16.2516.25

C3C3 1818 6.76.7 11.011.0 13.7513.75

C4C4 1919 3.53.5 34.734.7 43.4043.40

C5C5 2020 5.05.0 18.318.3 22.9022.90


The results obtained were nearer to M15 , The results obtained were nearer to M15 , excepting in two cases where these were excepting in two cases where these were found nearer to M10 and M40 respectively.found nearer to M10 and M40 respectively.

Hence the quality of concrete was found to Hence the quality of concrete was found to be good in general be good in general

Concrete cores also displayed a lot of Concrete cores also displayed a lot of voids and honeycombing at the interface voids and honeycombing at the interface of the concrete core and brick cladding.of the concrete core and brick cladding.

NDT in NF Railway --- Br No 184NDT in NF Railway --- Br No 184Chemical AnalysisChemical Analysis

From the cores extracted , the From the cores extracted , the aggregate was separated from the aggregate was separated from the mortar mortar

From the chemical test result it was From the chemical test result it was concluded that , the concrete was concluded that , the concrete was basic in nature. Chloride and basic in nature. Chloride and Sulphate content of the concrete was Sulphate content of the concrete was well below the limit prescribed by well below the limit prescribed by IS456. IS456.

NDT in NF Railway --- Br No 184NDT in NF Railway --- Br No 184Condition Monitoring and Condition Monitoring and

Useful Life AssessmentUseful Life Assessment The results as obtained were conveyed to The results as obtained were conveyed to

Prof P. Banerjee of IIT-Powai. Pixel Prof P. Banerjee of IIT-Powai. Pixel Networks of Mumbai arranged for the site Networks of Mumbai arranged for the site visit and investigation of the bridge .visit and investigation of the bridge .

On 14On 14thth January 2004, Prof Banerjee visited January 2004, Prof Banerjee visited the site and . Two more cores were the site and . Two more cores were extracted from the bridge in his presence extracted from the bridge in his presence as requested by him.as requested by him.

He submitted his detailed report He submitted his detailed report afterwardsafterwards

NDT in NF Railway --- Br No 184NDT in NF Railway --- Br No 184CONCLUSIONS based on the NDT and CONCLUSIONS based on the NDT and

Prof Banerjee’s ReportProf Banerjee’s Report The hollow sound emanating form the pier The hollow sound emanating form the pier

was due to the voids and honeycombing was due to the voids and honeycombing formed at the face of pier and brick formed at the face of pier and brick cladding.cladding.

Lower pulse velocity was also due to the Lower pulse velocity was also due to the voids and honeycombing at the interfacevoids and honeycombing at the interface

Concrete Core was of fairly good quality Concrete Core was of fairly good quality and was found to be having sufficient and was found to be having sufficient strength to carry the present day loadingstrength to carry the present day loading

There was no deterioration due to acidity , There was no deterioration due to acidity , higher chloride content or higher sulphate higher chloride content or higher sulphate content.content.

NDT in NF Railway --- Br No 184NDT in NF Railway --- Br No 184CONCLUSIONS based on the NDT and CONCLUSIONS based on the NDT and

Prof Banerjee’s ReportProf Banerjee’s Report While calculating the strength of the While calculating the strength of the

bridge it was assumed that the brick bridge it was assumed that the brick cladding was not participating in any load cladding was not participating in any load sharing arrangement.sharing arrangement.

Hollow sound was not a cause of concern.Hollow sound was not a cause of concern. The Railway got confidence in the The Railway got confidence in the

structural integrity of the bridge and the structural integrity of the bridge and the rebuilding of the bridge was not rebuilding of the bridge was not considered necessaryconsidered necessary


The Cost of the NDT was Rs 1.6 Lakh and The Cost of the NDT was Rs 1.6 Lakh and the cost of Conditional monitoring by Prof the cost of Conditional monitoring by Prof Banerjee was Rs 2.5 LakhBanerjee was Rs 2.5 Lakh

The cost of rebuilding of the bridge was Rs The cost of rebuilding of the bridge was Rs 5.2 Crores.5.2 Crores.

Not only the NDT resulted in the huge Not only the NDT resulted in the huge saving , it also initiated an approach which saving , it also initiated an approach which is scientific , logical and extends beyond is scientific , logical and extends beyond the realms of judgments based solely on the realms of judgments based solely on the visual examinationsthe visual examinations

THANK YOUTHANK YOU

Documents

NON DESTRUCTIVE TESTING IN RAILWAY BRIDGES. INTRODUCTION Non – Destructive testing [NDT] is an activity to assess the variation from the design and