ndt report summer training @rdso

RESEARCH DESIGN AND STANDARDS ORGANIZATION (RDSO)

CIVIL ENGINEERING DEPARTMENT |SRMCEM , LUCKNOW i

INTRODUCTION TO THE ORGANISATION

Figure 1 Logo Of RDSO

The Research Design and Standards Organization (RDSO) is an ISO- 9001 certified

organization under the Ministry of Railways, Government of India, which functions as a

technical adviser and consultant to the Railway Board, the Zonal Railways, the Railway

Production Units, RITES and IRCON International in respect of design and standardization

of railway equipment and problems related to construction, operation and maintenance.

The RDSO is headed by a Director General who ranks with a General Manager of a Zonal

Railway. The Director General is assisted by an Additional Director General and 23 Sr.

Executive Directors and Executive Directors, who are in charge of the 27 directorates:

Bridges and Structures, the Centre for Advanced Maintenance Technology (CAMTECH),

Carriage, Geotechnical Engineering, Testing, Track Design, Medical, EMU & Power Supply,

Engine Development, Finance & Accounts, Telecommunication, Quality Assurance,

Personnel, Works, Psycho-Technical, Research, Signal, Wagon Design, Electric Locomotive,

Stores, Track Machines & Monitoring, Traction Installation, Energy Management, Traffic,

Metallurgical & Chemical, Motive Power and Library & Publications. All the directorates

except Defence Research are located in Lucknow.

Main Focus of the organisation:

RDSO is the sole R&D organisation of Indian Railways and functions as the technical

advisor to Railway Board Zonal Railways and Production Units and performs the following

important

Functions:


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Development of new and improved designs.

Development, adoption, absorption of new technology for use on Indian Railways.

Development of standards for materials and products specially needed by Indian

Railways.

Technicalinvestigation, statutory clearances, testing and providing consultancy

services.

Inspection of critical and safety items of rolling stock,locomotives, signalling&

telecommunication equipment and track components.

RDSO multifarious activities have also attracted attention of railway and non-railway

organisations in India and abroad.

Motivation in choosing the organisation:

To develop safe, modern and cost effective Railway technology complying with

Statutory and Regulatory requirements, through excellence in Research, Designs

and Standards and Continual improvements in Quality Management System to cater

to growing demand of passenger and freight traffic on the railways.

Summary of work that I have performed:

I have learnt about design methodology of PSC bridges, slab, box girders, I

girders, 2I girders, R.C.C box Culvert, components of bridges. inspection and Non-

Destructive Testing Equipments for Railway Bridges.


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INTRODUCTION TO BRIDGE AND STRUCTURES DIRECTORATE

Bridges & Structures Directorate was formed in April, 1986 by carving it out from Civil

Design Directorate. Subsequently Bridges & Flood (B&F) wing, which had earlier been

working under Research Directorate, was brought under Director Standards (B&S) with

effect from April, 1987. Research (B&S) unit, along with functions of field trials and bridge

laboratory was also brought under Director Standards (B&S) w.e.f. 01-6-92 and the post had

been subsequently re-designated as Executive Director (B&S).

Evolving new standard designs of bridges (Steel, RCC, PSC and Composite etc.) for

the latest loading standards.

Development of new loading standards as per the needs of Indian Railways.

Speed clearance of new rolling stocks and locomotive for permitting it's use on

existing bridges.

Design of platform shelters, microwave towers? and other structures of standard

nature.

Formulation, updating and revision of Code of practices for the Design of

Steel/RCC/PSC and Arch Bridges as well as Sub-structure.

Investigations and rehabilitation schemes of old bridges for running of heavier trains.

Inspection of welded plate girders and open web girders during their fabrication for

use on the railways.

Study of structural characteristics of bridge girders. Effect on bridges due to train load

including longitudinal forces.

Field trials and laboratory tests for validation of existing provisions and evolving new

criteria for design and strength assessment technique.

Preparation of manuals and guidelines on aspects related to inspection and

maintenance of bridges.


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Study of bridge hydraulics, scour and river training works.

Represent Indian Railways in various committees of Bureau of Indian Standards and

Indian Road Congress.

Rendering consultancy services to the Zonal Railways concerning bridge structures in

gauge conversion project.

In house software development for analysis and design of bridges and other

structures.

Proof checking of designs of bridges submitted by consultants through Zonal

Railways.

Developing list of competent manufacturers of girder bridges and bearings.

Any other function assigned by Railway Board

Details of Company:

Organisation Name: Research Design And Standards Organization (RDSO)

Guide Name: Shri. Srijan Tripathi

Designation: Director / B&S / SB-1

Contact No. : 9794 863 399

E-mail : [email protected]


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CHAPTER 1: INTRODUCTION

There are about 1, 20,000 bridges of different type with varying spans on Indian Railways. As

on date approx 40% of the bridges are over 100 years old and 60% bridge are 80 years old and

have already completed their codal life. With the introduction of 25 t loading, HM loading and

DFC loading the maintenance/rehabilitation effort for the bridges is being increased regularly.

To meet the challenge it has been continuously striving to get knowledge from international

market. Various types of projects in this context has also been undertaken some of them are

acoustic emission, under water inspection, non distractive testing, instrumentation of bridges

etc. The present method of bridge inspection is mostly visual and is not capable to assess

hidden defects in structure, if any. For Railway bridges, particularly steel, fatigue is the

principle mode of failure and may lead to crack growths. There was a need to develop a

suitable technique for monitoring fatigue crack and its growth.

NDT survey is relatively quick, easy to use, cheap and give a general indication of the required

property of the Structure (concrete). It is often worthwhile to perform Non-Destructive

Testing (NDT) techniques as compared to other methods involving greater expense,

preparation or damage .The choice of particular NDT method depends upon the property of

concrete to be observed such as strength, corrosion, crack monitoring etc. Though there are

some limitations of these test methods. Even then subsequent testing of structure will largely

depend upon the results of preliminary testing done with the appropriate NDT technique.

NDT techniques not only provide fair idea about the relative strength and overall quality of

concrete in structure but also help in deciding whether more rigorous tests like load testing,

core drilling etc. at selected location are required or not. The objective of a non- destructive

test is to obtain an estimate of the required property of material by measuring certain

parameters which are empirically related to its strength.

Now a day’s different type of NDT equipments are available for condition assessment of

bridges and structures. Some of them have been procured by RDSO. I have got training

regarding the following NDT Instruments.


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Purpose of Non-destructive Tests:

The non-destructive evaluation techniques are being increasingly adopted in concrete

structures for the following purposes:

(i) Estimating the in-situ compressive strength

(ii) Estimating the uniformity and homogeneity

(iii) Estimating the quality in relation to standard requirement

(iv) Identifying areas of lower integrity in comparison to other parts

(v) Detection of presence of cracks, voids and other imperfections

(vi) Monitoring changes in the structure of the concrete which may occur with time

(vii) Identification of reinforcement profile and measurement of cover, bar diameter, etc.

(viii) Condition of pre-stressing/reinforcement steel with respect to corrosion

(ix) Chloride, sulphate, alkali contents or degree of carbonation

(x) Measurement of Elastic Modulus

(xi) Condition of grouting in pre-stressing cable ducts

From the discussions on various non-destructive test methods given hereunder, it will be

apparent that each method have some strengths and some weaknesses. Therefore, the prudent

approach would be to use more than one method in combination so that the strength of one

compensates the weakness of the other.

Types of Non Destructive Tests:

According to their use, non-destructive equipment can be grouped as under:

i) Strength estimation of concrete

ii) Corrosion assessment and monitoring

iii) Detecting defects in concrete structure

iv) Laboratory tests


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CHAPTER 2 : NDT FOR STRENGTH ASSESMENT OF CONCRETE

1. Rebound Hammer

This method is based on the principle that the rebound of an elastic mass depends on the

hardness of the surface against which the mass impinges. Rebound Hammer consists of a

spring-controlled mass that slides on a plunger within a tubular housing. When the plunger

is pressed against the surface of the concrete, the spring controlled mass rebounds and the

extent of such rebound depends upon the surface hardness and, therefore, the rebound is

related to the compressive strength of the concrete. The rebound value is read along a

graduated scale and is designated as the " rebound number". The compressive strength cab

be read directly from the graph provided on the body of the hammer. Depending upon the

impact energy, these are classified into four types i.e. N, L, M and P. Type N test hammer

having impact energy of 2.2 N-m and are suitable for grades of concrete from M15 to M45.

Type P is suitable for grades of concrete below M15. Type L test hammer is suitable for

lightweight concrete or small and impact sensitive part of the structure. Type M test hammer

is generally recommended for heavy structure and mass concrete.

Figure 2 Rebound Hammer

for taking a measurement , the hammer should be held at right angle to the surface of the

structure. the test can thus be conducted horizontally on vertical surfaces or vertically

upwards or downwards on horizontal surfaces . if the situation so demands , the hammer can

be held at intermediate angles also, but in each case, the rebound hammer will be different(


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up to certain extent ) for the same concrete. it is necessary that the test hammer is frequently

calibrated and checked against the test anvil to ensure reliable results.

The rebound hammer method provides a convenient and rapid indication of the compressive

strength of concrete by means of establishing a suitable correlation between the rebound

number and the strength of concrete. Rebound hammer directly gives the average

compressive strength of the tested location. The compressive strength is in N/mm2. Unit is

inter changeable to R, Q, psi and Kg/cm2.

Figure 3 Using Rebound Hammer

the rebound number increases as a strength increases but it is also influenced by a number of

other factors like type of cement and concrete; surface condition and moisture content ,age of

concrete and extent of carbonation on concrete surface . as such the estimation of strength of

concrete by rebound hammer method cannot be considered to be very accurate and probable

accuracy of prediction of concrete strength in a structure is ± 25 %. If the relationship

between rebounding number and compressive strength can be checked by test on core

samples obtained from the structure of standard specimens made with the same concrete

materials and mix proportion then the accuracy of the result and confidence there on are

greatly increased . it can then be used with greater confidence for differentiating between the

questionable and acceptable parts of a structure or for relative comparison between two

different structures.

2. Ultrasonic Pulse Velocity Meter :


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This is based on the principle that the velocity of an ultrasonic pulse through any material

depends upon the density, modules of elasticity and Poisson’s ratio. Comparatively higher

velocity is obtained when concrete quality is good in terms of density, uniformity,

homogeneity,

Figure 4 Ultrasonic pulse Velocity Meter

Pulse Velocity measurements can be used to assess the homogeneity of concrete,

presence of cracks, voids etc., quality of concrete relative to standards requirements.

Ultrasonic pulse velocity measurements are influenced by surface condition, moisture

content, temperature of concrete, path length, shape and size of member and

presence of reinforcing bars. The method is complex and requires skill to obtain

usable results, which can often provide excellent information regarding condition of

concrete.

using the special equipment the ultrasonic pulse is produced by a transducer held in

contact with one surface of concrete members Under test .after traversing a known

path length (L) in the concrete, the pulse of vibration is converted into an electrical

signal by the second transducer held in contact with the other surface of the concrete

members at the predetermined place and an electric timing circuit enables the

transmit time(T) of the pulse to be measured. the pulse velocity is given by

V = 𝐿

𝑇 in km/sec.


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There are three possible ways of measuring pulse velocity.

i) Direct transmission

ii) Semi direct transmission

iii) Indirect transmission (surface probing)

out of the three methods , the direct transmission method is considered to be the best.

Once the ultrasonic pulse impinges on the surface of the material, the maximum energy is

propagated at right angles to the face of the transmitting transducer, and best results are

therefore obtained when the receiving transducer is placed on the opposite face of the

concrete member. This is called “Direct Transmission” or “Cross Probing”. In many

situations, the two opposite faces of the structural member may not be accessible for

measurements. In such cases, the transmitting and receiving transducers are placed on the

same face of the concrete member. This is called “Surface Transmission”. “Surface

transmission” is not so efficient as “Direct Transmission”, because the signal produced at the

receiving transducer has an amplitude of only 2 to 3 % of that produced by “Cross Probing”,

and the test results may vary from 5 to 20% depending upon the quality of concrete under

test.

In view of inherent variability in the test results, sufficient number of readings are taken by

dividing the structural member under test in suitable grid markings of 30x30cm and in some

cases even smaller. Each junction point of the grid becomes a point of observation.

Table 1 Guidelines for assessing condition of concrete based on pulse velocity

Since actual values of the pulse velocity obtained depend on a number of parameters, any

criterion for assessing the quality of concrete on the basis of pulse velocity as given in the

above table can be considered as satisfactory only to a general extent. However, when the


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comparison is made amongst different parts of the structure, which have been built at the

same time with similar materials, construction practices and supervision, the assessment of

quality becomes more meaningful and reliable.

The assessment of compressive strength of concrete from ultrasonic pulse velocity values is

not adequate because the statistical confidence of the correlation between the ultrasonic pulse

velocity and the compressive strength of the concrete is not very high. Ultrasonic Pulse

Velocity test can also be used for measuring depth of crack.

Figure 5 Mechanism for pulse velocity

3. Windsor Probe:

Windsor Probe Test is based on penetration of hardened concrete. ASTM, C 803-82 has

standardized this equipment/test procedure. The underlying principle of this penetration

resistance technique is that for standard test conditions, the penetration of probe into the

concrete is inversely proportional to the compressive strength of the concrete. In other words,

larger the expose length of the probe, greater the compressive strength of concrete.

Figure 6 Using Windsor probe

This equipment consists of a power-activated gun or driver unit, hardened alloy probe, loaded


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art-ridge and a measuring instrument such as depth gauge etc. The probes are 6.35mm in

diameter and 79.5mm in length. Larger diameter probes (7.94mm) are also available for

testing lightweight concrete. Probe is threaded in to the probe-driving head and fired into the

concrete using a template. The driver utilizes a standard power cartridge. The power level can

be reduced when testing low strength concrete by locating the probe at a fixed position within

the driver barrel. Two types of templates are provided with the equipment e.g. single probe

template and a three probe triangular template. Exposed length of probe is correlated to the

compressive strength of concrete.

The Windsor Probe is basically a hardness tester and provides an excellent means of

determining the relative strength of concrete in the same structure or relative strengths in

different structures. The test is not expected to determine the absolute values of strength of

concrete in the structure. The method may be used to assess the uniformity of in-situ

concrete, to delineate zones or regions of poor quality or deteriorated concrete in the structure

and to indicate changes with time in characteristics of concrete, when forms and shoring may

be removed.

The precision of Windsor probe measurement has been found to vary with the maximum size

of aggregates in concrete. The penetration of the probe in to the concrete is affected by the

hardness of the aggregates. Therefore, it is desirable to prepare separate calibration curve for

the type of aggregate used in the concrete under investigation. There are requirements of

minimum edge distance, probe spacing and member thickness. If the minimum recommended

dimensions are not complied with, there can be danger of splitting of members. The

penetration technique is considered almost non-destructive as the damage to concrete made

by 6 mm probes is only local, which has to be made good. The test has the advantage over

rebound hammer test as the measurement is made not on the surface of the concrete but in

depth .

4. Cut And Pull Out :

The principle behind pull out testing with CAPO test is that test equipment designed to a

specific geometry will produce pull out forces that closely correlate to the compressive

strength of concrete. This correlation is achieved by measuring the force required to pull a

steel ring embedded in the concrete, against a circular counter pressure placed on the

concrete surface concentric with the ring.


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5. Core Cutter :

This is the most reliable method for checking the compressive strength of concrete. But this

is not a purely NDT but comes under partially destructive test. This can be used for bigger

size members where partial destruction of concrete due to core cutting does not disturb the

stability of the member.

Figure 8 Core Cutter

In this method, a core size of 50mm or 70mm dia. is taken out from the member using

diamond bits. The length to core dia. ratio shall be normally between 1.0 to 2.0

(preferably 2.0). The core dia. shall be at least three times the nominal maximum size

of the aggregate. The location for taking out the sample should be decided so that it

does not have any reinforcement.

Figure 7 Cut and Pull Out


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The core will be tested for compressive strength and at least three cores shall be tested for

acceptable accuracy. Tests should be conducted as per IS : 516-1959, IS : 1199 – 1959 & IS :

456 – 2000.

6. Permeability Tester:

The permeability tester is a measuring instrument which is suitable for the determination of

the air permeability of cover concrete by a non destructive method. The permeability tester

permits a rapid and non-destructive measurement of the quality of the cover concrete with

respect its durability.

Significance of permeability in addition to compressive strength in accessing quality of

concrete has become more important due to increase instances of corrosion in reinforce

cement concrete. The rate at which the air from concrete cover me extracted is a measure of

permeability of concrete .this method can be used to access the resistance of concrete to

carbonation, penetration of aggressive ions and quality of grout in post tension ducts.

It operates under vacuum and can be used at the building site and also in the laboratory. the

essential features of the method of measurement are a two Chamber vacuum cell and pressure

regulator which ensures an air flow at right angles to the surface and into the inner chamber.

Dry Surface without cracks should be selected for test .it should we ensured that inner

chambers should not be located above the reinforcement bar. pressure loss is calibrated from

time to time and after a large change in temperature and pressure. 3 to 6 measurements of

electrical resistance of the concrete and its mean value is taken for the measurement of

coefficient of permeability . this test permits the calculation of the permeability Coefficient

kT on the basis of theoretical model.

In case of dry concrete, the results in good agreement with the laboratory methods, such as

Oxygen permeability , capillary suction, chloride penetration and others .

Quality of cover concrete Index kT (10-16 m2 )

Very Bad 5 > 10

Bad 4 1.0 - 10

Normal 3 0.1 – 1.0

Good 2 0.01 – 0.1


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Very Good 1 < 0.01

Table 2 The quality class of the cover concrete is determined from kT

The humidity, a main influence on the permeability, is compensated by additional measuring

the electrical resistance ρ of the concrete .with kT and ρ the quality class is obtained from a

nomogram.

7. Video Borescope :

Those who are familiar with maintenance procedures know that there are three types of

maintenance in any facility: preventive maintenance, corrective maintenance and predictive

maintenance. We normally follow established procedures in each of these types, since each

one targets a different aspect of maintenance. Borescope inspections are an integral part of

procedures for preventive maintenance, along with such routine tasks.

Figure 9 Video Borescope Instrument


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CHAPTER 3 CORROSION ASSESSMENT

1. CORROSION ANALYZER :

Corrosion analyzer is based on electro chemical process to detect corrosion in the

reinforcement bar of the structure. The instrument measures the potential and the

electrical resistance between the reinforcement and the surface to evaluate the

corrosion activity as well as the actual condition for the cover layer during testing.

The electrical activity of the steel reinforcement and concrete leads them to be

considered as one half of weak battery cell with the steel acting as one electrode

and concrete as electrolyte. The name half cell surveying derives from the fact that

the one half of the battery cell is considered to be the steel reinforcing bar and the

surrounding concrete. The electric potential of a point on the surface of steel

reinforcing bar can be measured comparing its potential with that of copper -

copper sulphate reference electrode on the surface. In field it is achieved by

connecting a wire from one terminal of a voltmeter to the reinforcement and another

wire to the copper sulphate reference electrode.

Figure 10 Corrosion Analyser

This risk of corrosion is evaluated by means of the potential gradient obtained. The

higher the gradient, the higher risk of corrosion. ASTM C – 876 prescribes a half


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potential method for detection of reinforcement corrosion. The results can be

interpreted based on the following table.

Half-cell potential (mV) relative to copper-copper sulphate electrode

% chance of corrosion activity

< -200 mV Initial Phase – There is a greater than 90% probability that corrosion activity not taking place

-200mV to – 350mV Transient Phase – corrosion activity

uncertain Table 3 Corrosion Evaluation

2. RESISTIVITY METER:

The corrosion of steel in concrete is an electro-chemical process, which generates a

flow of current and can dissolve metals. The lower the electrical resistance, the more

readily the corrosion current flows through the concrete and the greater is the

probability of corrosion. The limits of possible corrosion are related with resistivity as

under: -

With 12 kcm ………… corrosion is improbable

With = 8 to 12 kcm ………… corrosion is possible

With 8 kcm……… corrosion is fairly certain

where, (rho) = resistivity

Resistivity Meter is used to measure the electrical resistance of the cover concrete.

With the graphical display of the major values, it is possible to determine the spots in

the concrete structure where corrosion may occur. The combination of resistance

measurement by Resistivity Meter and potential measurement by Resistivity Meter

Corrosion Analyzing Instrument (described below) furthermore improves the

information about the corrosion condition of the rebar.


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CHAPTER 4 NDT FOR DETAILS OF REINFORCEMENT STEEL

1. PROFOMETER

Profometer is a portable battery operated equipment used for measuring the depth of cover

concrete , location and size of the steel reinforcement embedded in concrete. The equipment

is useful for investigating the structures where drawings are not available .the equipment

consist of data logger , diameter probe and calibration blocks. The equipment has sufficient

memory store the scanned data. The meter needle is zeroed and the probe moved over the

concrete surface and rotated to obtain a maximum reading and this position correspond to the

location of reinforcement bar. It is used for (a) measuring concrete cover (b) detecting

reinforcing bar (c) determine bar size and direction .

In heavily reinforced section, however, the effect of secondary reinforcement cannot be

eliminated completely . Nevertheless, this equipment give fair idea about average thickness

of cover with maximum duration of ± 5 mm .

Figure 11 Using Profometer


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CHAPTER 5 NDT FOR LOCATING CRACK AND ITS GROWTH

1. Crack Detection Microscope

Figure 12 Crack Detection Microscope

This is the pocket size equipment used crack width measurement of concrete member,

masonry and other type of structures. for measurement of crack width a simple small hand-

held microscope having graduated scale marked on the lens known as "crack comparer" may

be used. where greater accuracy of measurement of crack is required. transducer or

extensometer or strain gauges can be used.

Depth of crack can be measured either by Pulse Velocity Technique (ASTM C-597) OR by

taking cores from concrete. Continuous monitoring and recording of crack movements for 24

hours maybe required for separating cracks caused due to temperature effects from that due to

o load effects.

2. Eddy Current Meter:

Eddy current metre to predominantly used in detecting the cracks in the metal structures.

availability of cracks disrupt the flow of eddy current. Availability of cracks disrupt the flow

of eddy current this disruption is measured to know the Flaws/Cracks/Voids etc. Eddy current

meter can be used in the field for detection of Flaws/Cracks/Voids in the metal structures

i.e. Steel girder bridges, FOB's etc. in the field.


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Figure 13 Eddy Current Meter

3. Infrared Imagery

Figure 14 Infrared thermal imager . source: www.w-nexco-usa.com

Infrared is an energy similar to visible light but with a longer wavelength. Infrared energy is

invisible to the human eye, however, while visible light energy is emitted by objects only at a

very high temperature, infrared energy is emitted by all objects at average temperatures.

Since, thermal imagers sense infrared energy which varies with temperature of objects image

generator provider a thermal signature of these objects. this image cannot be displayed on

standard video monitor. infrared energy from object a focus by optics onto an infrared detector.

The infrared information is then passed to sensor electronics for image processing. The signal

processing circuitry translates infrared detector data into an image that can be viewed on a

standard video monitor.

The Thermographer measures the temperature of a target. you have to put the proper data into

the camera in order to get accurate temperature measurements. this means that setting up your

camera before an inspection is important.


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The thermal imager uses IR Fusion technology, which simultaneously captures both a digital

photo as well as infrared image and fuses them together making it easier to identify features

and taking the mystery out of IR image analysis. simply scroll through the different viewing

modes to better identify trouble areas in full IR thermal, picture - in - picture or automatic

blend visual and thermal imagers.

Switch on the camera. Insert the 2gb memory card, allows users to save more than 3000 screen

images or 1200 IR fusion images. focus the lens at target by manually rotating lens until the

image is in focus . Press the Level and Span button to automatically set the cameras

temperatures level and span. Press the same button again to properly scale the image .press and

hold the same button until the IR fusion blend level control box appears on the display screen.

Tap the Trigger button to retain settings. Tap the Trigger button once to pause the live image.

Press and hold the trigger button for 2 seconds to save the image.

4. Acoustic Emission Technique:

Figure 15. Acoustic Emission Technique . Source www.idinspections.com

Introduction:

Present system of visual inspection of bridge is not capable to detect the smaller crack and

cracks developed on hidden location of various Bridge members. Therefore, a need is felt to

develop Non Destructive Techniques which can overcome the problems. Acoustic Emission

Technique has potential to detect cracks in early stage and can monitor its growth.

Fundamental:

Acoustic emission are elastic waves which are generated due to Rapid release of energy from

the location within the material under stress. Acoustic emission signal is recorded placing

sensors on the surface of the material. The acoustic emission signals observed on bridge


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members indicate the presence of crack and analysis of signal provide the valuable information

about the location of crack and its growth.

Instrumentation:

6 channel SPARTAN 2000 systems

6 channel MISTRAS 2001 system

Sensors ranging from 30 kHz to 300 kHz

Pc and connecting cables

Procedure:

Sensors are fixed on which members at different location and are connected to AE

system through cables.

Running trains are used as external force to make the crack active.

AE signals are recorded in AE system for further analysis.

Different time history correlation graph are produced using AE parameters such as

amplitude, counts, rise time, energy, duration and hits.

Noise due to other sources are eliminated by using at post software.

Concentration of AE signals are observed and the required crack location and its

activity is observed using above graphs analysis.

Advantages:

It can detect the location of cracks in structure.

It can help in checking progressive growth of crack in bridge structure.

It can help in checking the effectiveness of retrofitting / repair to bridge.

It can help in maintaining fatigue performance of bridge structure.

It can help in checking the quality of weld and fabricated structure.


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CHAPTER 6 DIGITAL ULTRASONIC DISTANCE MEASURING TESTER

Figure 16 DIGITAL ULTRASONIC DISTANCE MEASURING TESTER

There is a large population of Concrete/ Steel bridges on Indian Railways. Sometimes it is

very difficult to measure unreachable second point of the girder length of the bridges with

the help of measuring tape. Digital Ultrasonic Measuring Tool is a measuring device that

can carry several measuring operations such as the length, surface area and volume of

unreachable surfaces with the use of ultrasonic waves. Its measuring angle is 0.6 metres to

20 metres. On switching the unit it is automatically in the operation mode "Length

Measurement" and measurements can be recorded.

During the measuring procedure ,a Laser indicated (7- point laser) is also activated, which

indicates if the unit is pointed at the desired target Surface. The laser points are arranged

circular and outline the measured surface. If the ambient light conditions are too bright , the

visibility can be increased by using the laser spectacles.

The running Period of the conical expanding Ultrasonic waves used for measurement of

distance. The respective measuring surface is Marked by the laser indicator. The

measurements can only be carried out on targets with even and smooth surface .

It can be used to measure the distance of unreachable points. It directly give the surface area

and volume of a rectangular structures by measuring the required dimensions.


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CHAPTER 7 TESTING OF SLEEPERS (AT B&S LAB)

Growing scarcity of Timber suitable for making wooden Bridge sleepers has prompted

Railways to explore alternative materials. It was decided to develop an alternative to the

wooden sleepers in collaboration with R&DE (Engineers)/ Pune. Prototype sleepers have

been developed and tested under static and dynamic conditions. ME during his review

meeting at R D S O on desire that impact test on FRP sleepers should be conducted to assess

its performance during derailment .

Static load test on sleeper helps in verifying the design and structural properties and the

behaviour of the sleeping under condition of static loading. The sweeper is required to

withstand applied loads without being excessively deformed/severely compressed for safety

considerations.

Impact test measures the resistance of FRP sleepers to shock. This test is intended to observe

the behaviour of the sleepers under consideration which stimulate the derailment of wagons

in case of accidents. The sleeper is required to withstand such loads without being severely

damaged for safety considerations.

Objective:

I. To assess structural integrity of sleeper.

II. To ensure your absence of void, dry patches, resin rich areas and de-lamination inside

sleeper.

Type of test performed on sleeper in B&S lab.

I. Static load test : To assess adequacy of design.

Performs on centre of rail on both sides of sleeper.

II. Impact test: To assess shock absorption capacity of sleeper i.e. To assess its

performance against derailment forces.


CIVIL ENGINEERING DEPARTMENT |SRMCEM , LUCKNOW xxv

STATIC LOAD TEST:

The test were carried out on both ends of three sleepers. Test sleeper was placed on test floor

under the reaction frame. A mild steel plate of 260 X 220 mm size was placed on rail seat

position of the sleeper. Another m s plate of larger size was kept over the plates projecting

out of the sleeper's width. On this plate two dial gauges were fixed on both side of the sleeper

to measure deflection under the applied load.

A remote controlled hydraulic Jack of 100 t capacity was used for application of static load

on sleeper. To ensure the accuracy of applied load, a pre-calibrated compression proving ring

was placed between the hydraulic Jack and the sleeper, the gap between the sleeper and

proving ring was filled up by cast iron blocks and steel packing plates. The centre of

hydraulic Jack, proving ring and test sleeper was aligned with the help of plumb bob, to

ensure precise application of the test load.

The maximum test load applied after 500 kN, in increment of load at 50 kN / min, starting

from 50 kN . The maximum applied load 500 kN was sustained for 5 minutes. Development

of cracks and deflection of sleepers was observed and noted after each increment of load.

Static load test was carried out on three sleepers.

Figure 17 Loading arrangement of Testing of Composite Sleeper

Acceptance criteria

No crack should be developed on the surface.


CIVIL ENGINEERING DEPARTMENT |SRMCEM , LUCKNOW xxvi

Deflection of sleeper at test locations should be minimum to extent possible.

IMPACT TEST :

Sleeper was placed on two nos. Bearing plates at an inclination of 30º , under a loco wheel

approx. Weight 500 kg, hanged on the test frame. The wheel was tied with one end of a wire

rope and the other end of the wire rope is attached with the lifting and pulling machine. The

lifting and pulling machine is used to keep the wheel at desired height and sudden drop of

the position of the wheel and location strike of sleeper was aligned before drop. The wheel

was position at the height of 75 cm from the edge of sleeper and drop freely by releasing the

lever of pulling machine on both ends of the sleeper at two locations i.e. 200 mm away from

sleeper end and 294 mm away from the centre line of the rail towards the centre of sleepers.

Impact test was carried out on the same three static load tested sleepers and the wheel was

dropped twice at each location tested.

Figure 18 Impact Test on FRP Sleeper

Acceptance criteria:

Only recess should form.

No cracks, splitting should appear on the surface of sleeper.


CIVIL ENGINEERING DEPARTMENT |SRMCEM , LUCKNOW xxvii

REFERENCES

Websites :

1. www.w-nexco-usa.com

2. www.idinspections.com

3.www.rdso.indianrailways.gov.in

Articles:

1. "Draft Provisional Specification For Composite Sleeper", page no. 13 -14,RDSO .

2. "Guidelines For Inspection, Maintenance And Rehabilitation Of Concrete Bridges", page

no. 2-10, RDSO.