Summer Training Report

On

ANALYSIS AND DESIGN OF RAILWAY STEEL AND COCRETE BRIDGE

&

NON DESTRUCTIVE TESTING EQUIPMENTS USED FOR BRIDGE TESTING

At

RESEARCH DESIGN AND STANDARD OGANISATION(RDSO)

LUCKNOW

Submitted for Partial fulfilment of

Bachelor of Technology In CIVIL ENGINEERING

SUBMITTED TO- SUBMITTED BY-

DEPARTMENT OF CIVIL ENGINEERING VISHEK YADAV

GLA UNIVERSITY, MATHURA B. TECH ,4TH YEAR

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Summer Training ReportFrom 16-06-2014 to 21-07-2014

IN

Bridge and Structures Directorate

Of

Research Design & Standards Organization

Government of India-Ministry of Railways

Manak Nagar, Lucknow- 226011

Presented by:

VISHEK YADAV

(B.Tech, 4thyr)Roll N0- 111000166

GLA UNIVERSITY, MATHURA

PREFACE

This report has been prepared after getting different theoretical and practical

training in Bridge and Structures Directorate of RDSO from 16-06-2014 to 21-07-2014

in reference to my collage letter Training & Placement Officer for GLA

UNIVERSITY,MATHURA (UP). The training was divided in seven different sections of

the Directorate. They are Steel Bridge Unit-1, Steel Bridge Unit-2, Concrete Bridge Unit-

1, Concrete Bridge Unit-2, Testing Unit, Bridge Inspection Unit and Bridge & Flood Unit.

The process of training from my point of view was excellent for each section was very

useful for Civil Engineering Student with very limited re-sources and time schedule.

There are many things in the Directorate on each subject which can be learnt from

regular training and proper guidance.

A little knowledge which I could get from this training, I am trying to re-produce

some of them in following pages.

Any error in making deliberations may please be ignored.

DATE- 1-9-2014 Vishek Yadav

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SUBJECT INDEX

S.No. Description Page No.

1. Introduction 52. Bridges and Structures Directorate 6

3. Non Destructive Testing of Railway Bridges 7Introduction 8

Rebound Hammer 9

Ultrasonic Pulse Velocity Meter 9

Windsor Probe 10

Cut And Pull Out 11

Core Cutter 13

Permeability Tester 13

Video Borescope 14

Corrosion Analyser 15

Resistivity Meter 15

Acoustic Emission Technique 16

Digital Ultrasonic Distance Measuring Tester 16

4. Modernization of Bridge on Indian Railways 17

5. Design Steps of RC Precast Bridge Slab 20

6. Design of Pre–Stressed Concrete Railway Bridges

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7. Acknowledgement 24

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INTRODUCTION OF ORGANIZATION

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 Director General equivalent to General Manager of any

Zonal Railway. The Director General is assisted by an Additional Director General, Sr.

Executive Director and Executive Director, who are in charge of the 27 directorates. The

different directorates are Bridge and Structures, 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, Library & Publications and Defense Research. All the directorates except

Defense Research are located at RDSO in Lucknow.

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INTRODUCTION

OF

BRIDGES AND STRUCTURES DIRECTORATE

1. ABOUT 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. 01-06-1992 and the post had been subsequently re-designated as Executive Director (B&S).

2. FUNCTIONS:

(i) Evolving new standard designs of bridges (Steel, RCC, PSC and Composite etc.) for the latest loading standards.

(ii) Development of new loading standards as per the needs of Indian Railways.(iii) Speed clearance of new rolling stocks and locomotive for permitting it’s use on existing bridges.(iv) Design of platform shelters, microwave towers  and other structures of standard nature.(v) Formulation, updation and revision of Code of practices for the Design of Steel/RCC/PSC and

Arch Bridges as well as Sub-structure.(vi) Investigations and rehabilitation schemes of old bridges for running of heavier axle load trains.(vii) Inspection of welded plate girders and open web girders during their fabrication for use on the

Indian Railways.(viii) Study of structural characteristics of bridge girders. Effect on bridges due to train load including

longitudinal forces.(ix) Field trials and laboratory tests for validation of existing provisions and evolving new criteria for

design and strength assessment technique.(x) Preparation of manuals and guidelines on aspects related to inspection and maintenance of

bridges.(xi) Study of bridge hydraulics, scour and river training works.(xii) Represents Indian Railways in various committees of Bureau of Indian Standards and Indian

Road Congress.(xiii) Rendering consultancy services to the Zonal Railways concerning bridge structures in gauge

conversion project.(xiv) In house software development for analysis and design of bridges and other structures.

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MODERNIZATION OF BRIDGE ON INDIAN RAILWAYS

MODERNIZATION OF BRIDGES

Outline of this presentation

Identifying need for modernization.

Challenges in modernization.

Aspects of modernization.

Strategies for modernization of various aspects of bridges.

Brief Background of Indian Railways

World’s biggest railway under single management

Trains started on 16th April 1853 in India, now operations are over 150 years old

As on 31.03.2011:

o 64,460 route KMs.

o 7651 Million passengers annually.

o 926.43 Gross Million Tonnes of annual traffic.

Need for Modernization

Increasing axle loads

Carrying capacity of wagons being increased from 21.9 t to 25 t.

Dedicated Freight Corridor coming up.

Increasing speeds

Upgradation of speeds on existing tracks to 200 KMPH contemplated.

New tracks dedicated for high speed trains with speeds upto 350 KMPH being conceptualized.

Challenges in Modernization

Huge inventory of bridges.

Different ages

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Wide variety of types

Constructed to different loading standards

Huge network

Slow pace of adoption of technology.

Legacy of bridges

Total no. of bridges 1,33,160 No. of important bridges 720Major bridges 10,828 Minor bridges 1,21,612 Bridges more than 100 years old 27%

Number Of Bridges - Type Wise

ARCH BRIDGES ~ 19,500PG/OWG/ COMPOSITE ~ 15,500PSC BRIDGES ~ 700RCC BOX ~ 12,000RCC/ PSC SLABS ~ 34,000PIPES ~ 27,000OTHERS ~ 24,000

Inspection of Bridges and Record Keeping

Aim: Improve reliability of assets

Initiatives Taken

Use of Numerical rating system (NRS) for objective recording of condition of bridges.

On line recording of bridge inspections through Bridge Management System (BMS) in progress.

Guidelines for underwater inspection of bridges issued.

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DESIGN STEPS OF RC PRECAST BRIDGE SLAB

1. Analysis of Design : Calculation of

Effctive depth and Effective Span C/S area of Slab, Dead Load of Slab Super-Imposed Dead load (SIDL): Ballast (300mm & 400mm) & Track Live Load Dispersion of Live Load, CDA and Curvature effect Characteristic Loads and Design Load (with Load factor) Design Shear force and Design Bending Moment in ULS and SLS

2. Design of RC Precast Bridge Slab

ULTIMATE LIMIT STATE (ULS) : Calculation of Required Effective depth Required Main Reinforcement Local Bond Stress Anchorage Bond Stress Shear Reinforcement Ultimate Moment of Resistance

SERVICEABILITY LIMIT STATE (SLS) : Calculation of Design Crack width in Concrete Stresses in Concrete and Steel

Secondary Reinforcement

DESIGN OF PRE–STRESSED CONCRETE RAILWAY BRIDGES

1. Objective

To understand the basic concept of design of Prestressed Concrete Railway Bridges.

To use the provision of IRS:Concrete Bridge Code & IRS: Bridge Rule in design of Prestressed Concrete railwayBridge.

To equipped with the concept required for proof checking of design of Prestressed concrete girder.

2. BASICS OF PSC DESIGN

Pre-tension Vs Post-tension

Basic Prestress equation

Main component of design

Working stress Vs Limit State method

Serviceability Limit state Vs Ultimate Limit state

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Stages of Prestressing

Construction sequence

Pre-tensioning Method

Stage 1 Stage 2 Stage 3 Stage 4Tendons and reinforcement are positioned in the beam mould.

Tendons are stressed to about 70% of their ultimate strength.

Concrete is cast into the beam mould and allowed to cure to the required initial strength.

When the concrete has cured the stressing force is released and the tendons anchor themselves in the concrete.

Post-tensioning Method

Stage 1 Stage 2 Stage 3 Stage 4Cable ducts and reinforcement are positioned in the beam mould. The ducts are usually raised towards the neutral axis at the ends to reduce the eccentricity of the stressing force.

Concrete is cast into the beam mould and allowed to cure to the required initial strength.

Tendons are threaded through the cable ducts and tensioned to about 70% of their ultimate strength.

Wedges are inserted into the end anchorages and the tensioning force on the tendons is released. Grout is then pumped into the ducts to protect the tendons.

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3. BASIC PRESTRESSING EQUATION

Stress at top =P/A-P*e/Zt +MDL/Zt+MLL/Zt

Stress at bottom =P/A+P*e/Zt -MDL/Zt-MLL/Zt

4. Main component of design

Section

Loads

Calculation of Stress, Moment etc.

Comparison with Permissible stress , Moment of resistance etc.

Durability considerations

5. Working stress Vs Limit State method

Working stress method

Factor of safety is applied on stress only.

Area = Load / ( Stress / λ)

Limit state method

Factor of safety applied on load and stress both.

Area = (μ1 x Load ) /( stress / λ1)

6. Serviceability Limit state Vs Ultimate Limit state

Serviceability Limit state

deals with condition of the structure in service

Cracking

Deflection

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Maximum compression

Durability

7. Ultimate Limit state

Deals with the safety of the structure

Flexure

Shear

Torsion

8. Stages of Prestressing

As per IRS:CBC , The stages of prestressing shall be reduced to minimum, preferably not be more than two.

First stage of prestressing cater for Dead load of the structures only.

Second stage of prestressing counterbalances all forces other than Dead load.

Temporary prestressing may be done in between two stages to take care of forces arising during launching.

9. COSTRUCTION SEQUENCE

Construction sequence play a major role in the design.It effects the followiing aspects of the design

Loss due to prestress

Stages for checking the stress

Erection stresses

10. Modules of design

Data collection.

Section property.

Cable profile and properties.

Load calculation.

Bending Moment and Shear force calculation.

Prestress , Losses and effective prestress.

Stress check at transfer and serviceability

Check ultimate moment of resistance.

RAILWAY STEEL BRIDGE GIRDERS

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DESIGN STEP:

1. Dead Load

The D.L of structure is not known before it is designed. It is assumed or estimated on the basis of experience After designing, the assumed D.L is compared with actual D.L. if assumed D.L is less , then assumed D.L is revised and structure is redesigned.

2. Live Load

(i) EUDL

(a) BM: For Maximum forces in elements resisting bending (BC,TC) (App-II of BR)

(b) SF: For Maximum forces in elements resisting shear at section (end raker, diagonal, vertical) (App-II of BR)

(ii) Actual Axle load :- (App-I of BR)

3. LF: TF&BF

(App-VII of BR)-udl on stringer in long. Direction

4. WIND FORCES

On train &On structure

Depend upon the intensity of wind & Shape of structure.

Wind pressure=150kg/mm^2 (For loaded case) cl:2.11.2 of BR

WL=wind pressure*exposed area

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Exposed area= area of moving load + exposed area of truss members.

Full area of truss members on windward side +50% area of truss members on Leeward side.

5. SEISMIC FORCES

If the structure is situated in earthquake prone area. Seismic loads must be considered. Due to earthquake shocks the structure vibrates. The vibration can be resolved in three perpendicular direction – along length, width and height of the structure.

6. Truss analysis due to wind:

(i) Horizontal effect & Overturning effect (vertical effect).

Or

(ii) Horizontal bending of Top chord due to wind on top chord and moving load.

7. Truss analysis for all input Loads

Find out forces in each member

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NON DESTRUCTIVE TESTING OF RAILWAY BRIDGES

1.0 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.

2.1 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

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compressive strength of the concrete. 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.

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.

2.2 Ultrasonic Pulse Velocity Meter :

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

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

etc.

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.

There are three possible ways of measuring pulse velocity.

i) Direct transmission

ii) Semi direct transmission

iii) Indirect transmission (surface probing)

Direct Transmission

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Indirect Transmission

2.3 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.

Windsor Probe Instrument

2.4 Cut And Pull Out :

The principle behind pull out testing with CAPO test is thattest 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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2.5 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.

Core CutterIn 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.

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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).

2.6 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.

Permeability Tester

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

Quality of cover concrete Index kT (10-16 m2 )Very Bad 5 > 10Bad 4 1.0 - 10Normal 3 0.1 – 1.0Good 2 0.01 – 0.1Very Good 1 < 0.01

. 2.7 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.

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Video Borescope

3.0 CORROSION ASSESSMENT:

3.1 Corrosion Analyser :

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 andconcrete 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 - coppersulphate 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.

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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 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

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ACKNOWLEDGEMENT

I express my sincere gratitude to Executive Director/ Bridge & Structures,

Executive Director/Structures, all Directors of the Directorate along with Assistant

Engineers associated with this summer training for his proper guidance, useful

suggestions and timely treatment where ever required during the entire training. My best

wishes to Director General/RDSO for giving a chance for this summer training and know

about Indian Railways. My special thanks goes to Shri Srijan Tripathi /Director/Bridge and

Structures/SB-I and their team for designing the entire course in a very proper way

irrespective of their busy schedule of dally working.

Any suggestions for making this report better may please be forwarded to e-mail

ID vishek.yadav11@gmail.com.

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