Reyaz Report 2

SUMMER TRAINING REPORTSubmitted in partial fulfillment for the award of degree of b.tech

Training report on

FABRICATION OF 12.2 M SPANCOMPOSITE STEEL GIRDER-WELDED TYPE

North Eastern Railway Bridge Workshop(Gorakhpur Division)

1st June -30th June 2015

SUBMITTED BY SUPERVISORREYAZ AHMAD MR. VIKRMA PRASADB.TECH , 4th yr SENIOR SECTION ENGINEER

BRIDGE WORKSHOP, GORAKHPUR CANTT

INTEGRAL UNIVERSITYINDUSTRIAL TRAINING AT RAILWAY BRIDGE WORK SHOP

ACKNOWLEDGEMENTS

I owe my profound gratitude to my project guide Mr. Vikrma

Prasad who took keen interest on my project work and guided

me all along till the completion of my project work.

The success and final outcome of this project required a lot of

guidance and assistance from many people of the Bridge

workshop and I am extremely fortunate to have got all this all

along the completion of this project work.

Whatever I have done is only due to such guidance and

assistance and I would not forget to thank them.

Finally, I gratefully acknowledge my family members and

my friends for their love, support and constant encouragement

during the study.

REYAZ AHMAD

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NORTH EASTERN RAILWAY

The North Eastern Railway is one of the seventeen railway zones in

India. It is headquartered at Gorakhpur and comprises Lucknow and

Varansi divisions as well as reorganized Izzatnagar division.

The North eastern railway was formed on 14 april 1952 by combining

two railway systems the Oudh and trihut railway and Assam railway

and the Canpore-Achnera section of the Bombay, Baroda and Central

India Railway.

NER has 3.042.46 route km with 486 stations. NER primarily serves

the areas of Uttar Pradesh , Uttarakhand & western districts of Bihar.

It has also the longest platform in the world at Gorakhpur Railway

station about 1.3 km in length by combining the platforms 1 &2.

As Gorakhpur is the headquarter of the NER zone therefore it have all

the construction sites i.e. from steel bridges workshop to concrete

yard.

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Table of ContentsAcknowledgements…………………………………………………2 About North Eastern Railway……………………………………….3 Table of Contents……………………………………………………4

• INTRODUCTION• Girder……………………………………………………6• Types of Girder………………………………………….6• Advantages of using steel for Girders…………………..7• Composite steel girder…………………………………..7

• SPECIFICATIONS • Steel ……………………………………………………..9• Concrete……………………………………………….....9• Drilling………………………………………………….10• Rivets and Riveting …………………………………….10

• LAYOUT OF COMPOSITE STEEL GIRDER• General…………………………………………………..11• Design drawings of Girder………………………………11• Part List………………………………………………….18• Shipping List…………………………………………….19

• FABRICATION OF JOB• General…………………………………………………..20

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• Items requiring attention before fabrication of girder….21• Tested steel of required quality………………………….21• Manufacture……………………………………………..22• Templates ……………………………………………….22• Cutting of plates…………………………………………22• Flattening and Straightening…………………………….24• Planning and shearing…………………………………...24• Jig and fixture making…………………………………..25• Tack Assembling of job………………………………....26

• Tack welding……………………………………...26• Important checks for tack welding………………..27

• Saw Welding…………………………………………….28• Inspection of Weld………………………………………30

• Micro etching test…………………………………30• Visual Test………………………………………...31• Weld Gauge ………………………………………31• DPT test…………………………………………...32

• Initial Assembling of job………………………………..35• Drilling and Sub punching……………………………....36

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1.INTRODUCTION

• GIRDER

A girder is a support beam used in construction. It is the main horizontal support of a structure which supports smaller beams.

Girders often have an I-beam cross section for strength but may also have a box shape, Z shape and other forms. A girder is commonly used many times in the building of bridges, and planes.

A girder bridge, in general is a bridge that utilizes girders as the means of supporting the deck.

• TYPE OF GIRDERS

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• A Rolled Steel Girder is a girder that has been fabricated by rolling a blank cylinder of steel through a series of dies to create the desired shape. These create standardized I-beam and wide flange beam shapes up to 100 feet in length.

• A Plate Girder is a girder that has been fabricated by welding plates together to create the desired shape. The fabricator receives large plate of steel in the desired thickness, then cuts the flanges and web from the plate in the desired length and shape. Plate girders can be used for spans between 10 meters and more than 100 meters. Stiffeners are occasionally welded between the compression flange and the web to increase the strength of girder.

• A Box Girder or “tub girder” is, as the name suggests, a box shape. They consist of two vertical webs, short top flanges on top of each web, and a wide bottom flange connecting the webs together. A box girder in particularly resistant to torsion and, while expensive, are utilized in situations where a standard girder might succumb to torsion or toppling effects.

2.SPECIFICATIONS

2.1. STEEL

• IS:2062 , Quality “B” Grade Designation E250 (Fe 410 W) fully killed and normalized/controlled cooled, Plates less than 12mm thick need not be normalized/controlled-cooled.

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• IS:2062 , Quality “C” Grade Designation E250 (Fe 410 W) fully killed and normalized/controlled cooled, ensuring impact properties at (-) 200 C or (-) 400 C shall be used for sub-zero temperature areas for welded/riveted girders subjected to Railway loading. Plates less than 12mm thick need not be normalized/controlled-cooled.

• Steel for bolts shall conform to property class 4.6 or 6.6 as specified in IS:1367 accordingly,

• Steel for drifts shall be in accordance with IS:1875 for forged quality steel or IS:7283 for hot rolled bars.

• Steel for rivets shall comply with the requirement of IS:1148 for hot rolled rivet bars for general structural purposes and IS:1149 for high tensile steel rivet bars for high strength structural purposes.

2.2 CONCRETE

• All RCC work to be done as per IRC-21

• C.C mix for substructure M-35 and for superstructure M35.

• All structural steel shall conform to IS: 2062-2006 grade ‘B’

• All RCC work shall be of concrete mix M-35 and reinforcement bars shall conform to IS: 1786-1985 of minimum grade Fe-415.

2.2. DRILLING

• The bores of bushes shall initially have a tolerance of -0mm, 0.1mm. The tolerance shall be checked from time to time and

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when the bores exceed a tolerance of, -0mm, +0.4mm, the bushes shall be rejected. Tolerances for checking jigs from master plates shall be +0mm-0.13mm.

2.4. RIVETS AND RIVETING

• The rivet holes shall be 1.5 mm greater than the diameter of the rivet bars used. The rivets shall be made to IS:1929.

• Rivets when driven shall completely fill the holes, have the heads concentric with the shanks and shall be in full contact with the surface. Driven rivets when struck 12 sharply on the head with the 110-gm. rivet testing hammer shall be free from movement or vibration.

3.LAYOUT OF COMPOSITE STEEL GIRDER

3.1. GENERAL

• Layout is drawing of complete structure on full scale. Normally half span is drawn on a leveled smooth floor.

• Nominal as well as camber layout will be drawn on the floor.

• Length of the members will be kept as per camber layout. However the for main gussets will be fabricated using nominal layout.

3.2. DESIGN DRWAING OF CWG

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Here CWG stands for composite steel girder. Its design drawings includes the elevation , top and cross sectional plan & also the front and back frame

FABRICATION OF CWG

4.1. GENERAL

The fabrication of steel girder bridges is being done by various

Railway Workshops as well as through trade. The fabrication is governed by the provisions of:

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i) Indian Railway Standard specification for fabrication and erection of steel girder bridges and locomotive turn-tables (B1-2001).

ii) Indian Railway Standard Code of Practices for metal arc welding for structural steel bridges carrying rail cum road or pedestrian traffic (Adopted 1972 Revised 2001).

The officials associated with fabrication work should have thorough understanding of both the codes i & ii. However, these guidelines have been prepared for helping the field engineers associated with execution of the fabrication work through trade. It has been tried to cover various aspects which require close attention of the field engineers for ensuring quality of the fabrication work. These guidelines are just to facilitate and not to supersede the two codes. All engineers associated with fabrication are advised to understand the provision of IRS B1-2001 and Welded Bridge Code and take help from these guidelines. Book published by RETS IRICEN “Steel Structure Fabrication for Railways” is also a very good guide for the Engineer incharge of fabrication. The workshop engineer of contractors should also have good understanding of various provisions of above Railway codes and other related codes.

4.2. ITEMS REQUIRING ATTENTION BEFORE FABRICATION OF GIRDER:

Inspection of Layout on template floor – Field engineer has to ensure that the Template floor is level. Nominal and camber layout are drawn with the calibrated steel tape. The certificate of calibration from a

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authorized agency should be kept in record. For squareness, diagonal measurement are also checked. It should be remembered that tape

4.3. TESTED STEEL OF REQUIRED QUALITY

• IS:2062-2011 GR.-B0 FULLY KILLED AND NORMALIZED FOR WELDED GIRDERS SUBJECTED TO RAILWAY LOADING

(If Service Temp. does not fall below 0 degree C ).

- PLATES LESS THAN 12mm THICK NEED NOT BE NORMALIZED.

- PLATES MORE THAN 12mm THICK SHOULD BE NORMALIZED AND ULTRASONICALLY TESTED.

• IS:2062 GR.-C FULLY KILLED AND NORMALIZED – FOR WELDED/ GIRDERS SUBJECTED TO RAILWAY LOADING

(If Service Temp. fall below 0 degree C ).

- PLATES LESS THAN 12mm THICK NEED NOT BE NORMALIZED.

- PLATES MORE THAN 12MM THICK SHOULD BE NORMALIZED AND ULTRASONICALLY TESTED.

4.4. MANUFACTURE

The whole work shall be representative of the highest class of workmanship. The greatest accuracy shall be observed in the design, manufacture and erection of every part of the work to ensure that all

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parts will fit accurately together on erection. The whole of work to be erected complete and pieces marked to place

4.5. TEMPLATES

• The templates through out the work shall be of steel. The template shall be used for marking of cutting material and as well as profile machining for girders of railway loading. • Templates shall be used for marking of drilling holes in steel structures other than girder of Railway loadings.

In case where actual materials from a bridge have been used as templates for drilling similar pieces the Inspecting Officer will decide whether they are fit to be used as part of the finished structure

4.6. CUTTING OF PLATES

• Plates are cut into desired length using …………

• ordinary oxy-acetylene cutting torch• pug cutting machine• profile cutting machine• Galloting shear machine (faster but for plates up to 10mm

thickness)

• Angles are cut into desired length using …………

• shaper machine

• shearing and punching machine

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• circular saw profile cutting machine

• Cutting allowance …………

• 3mm up to 12mm thick plates• 6mm for than 12mm thick plates

• After cutting it should be ensured that all the edges are clean, reasonably square and true.

Use of multi-head flame cutting machine having multiple oxy acetylene torches is desirable for higher productivity and reducing the distortion due to cutting operation. Plasma-arc cutting method can also be employed. This process offers less heat input causing less distortion.

4.7. FLATTENING AND STRAIGHTENING

All steel materials, plates, bars and structural shall have straight edges, flat surfaces and be free from twist. If necessary, they shall be cold

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straightened or flattened by pressure before being worked or assembled unless they are required to be of curvilinear form. Pressure applied for straightening or flattening shall be such as it would not injure the material and adjacent surfaces or edges shall be in close contact or at uniform distance throughout.

Flattening and straightening under hot condition shall not be carried out unless authorized and approved by the Inspecting Officer

4.8. PLANNING AND SHEARING

• Except where otherwise indicated, cutting of all plates and sections shall be affected by shearing or sawing. All edges shall be clean, reasonably square and true. Wherever possible the edges shall be cut in a shearing machine, which will take the whole length of the plate in one cut.

• Should be inspection find it necessary, the cut edges shall be ground afterwards.

• Planning or machining of the edges or surface shall be carried out when so specified in the contract drawings or where specifically ordered by the Engineer. Where machining is specified, the plates or all sections shall be cut in the first instance to such a size so as to permit not less than 3mm of metal being removed from each sheared edge or end, in the case of plates or sections of 12mm or less in thickness and not less than 6mm of metal being removed in the case of plates and sections exceeding 12mm in thickness.

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The butting ends of all booms and struts where spliced shall be faced in an end milling machine after members have been completely fabricated. In the case of compression members the face shall be machined so that the faces are at right angle to the axis of the members and the joint when made, will be in close contact throughout. At the discretion of the Inspecting Officer, a tolerance of 0.4mm may be permitted at isolated places on the butting line.

4.9. JIG AND FIXTURE MAKING

• Jigs are the device used in the mass production of standard jobs for drilling holes without marking. Jig is the member with drilled holes of one component, so that by placing this jig over the component, holes can be drilled in the component

• For guiding the drilling toll and to prevent oversizing holes of jig, bushes or reffules are provided over the jigs. The internal dia. Of bushes should be within tolerance –0.0mm to +0.1mm. When the bores exceed a tolerance of -0.0mm to +0.4mm, the bushes shall be rejected.

• For every working jig, one master plate should be fabricated. This master plates is used only for checking the working jigs. Tolerance for checking jigs from master plates shall be +0.0mm to -0.13mm.

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4.10. TACK ASSEMBLY OF JOB

Steel sections after cutting to required size and straightening will be brought to this process for temporary assembly with tack welding to form a member so that it will be placed in fixture will be placed over tack assembly member and prepared for saw welding.

4.10.1. TACK WELDINGTACK Welding is to be done by AC Welding transformer set as on following-• Electrode:- 4 mm dia: Type- A2, 4212X• CLASS- IRS-M-28/2002• Current :- AC• Current IN (amp.) :- 180 (approximate)• Arc Voltage (v) :- 80 (approximate)

4.10.2. IMPORTANT CHECKS FOR TACK WELDING

i) Check that top & bottom flange plate are perfectly perpendicular with reference to web throughout the length of I Section.

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ii) Check the squareness i.e. 900 angle between flange & web of top

and bottom flange plate to avoid out of squares flanges.

iii) Check with filler gauge throughout the length of top & bottom flange connection for uniform contact throughout the web plate.

4.11. SAW WELDING

Fillet welding 6mm to 10 mm Welding is to be done by automatic submerged arc welding machine as on following approximate)-• 4 mm copper coated wire class-IRS- M-39 / 2001 is used.• FLUX Class- IRS- M-39 / 2001is used.• Current IN :- DC• Current IN (amp.) :- 500 to 600• Arc Voltage (v) :- 32 to 34• Wire feed speed (m/mm) :- 2.550 to 3.200• Travel Speed of SAW (m/mm) :- 0.475 to 0.375

• Thorough cleaning of tack welded member should be done with appropriate tool like wire brush, before shifting for full welding. Minimum width of 75mm throughout the length shall be cleaned to ensure that the surface is free from dust, mill scale, grease, oil and paint to ensure sound quality of weld.

ii) Full welding shall be carried out in flat position with SAW process as per sequence mentioned in WPSS/WPQR using manipulator/special welding fixture.iii) The sequence of welding shall be shown in WPSS/WPQR marked as 1, 2, 3 & 4 in the order of welding

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Submerged arc welding

Welded construction work shall be carried out generally in accordance with the provisions of Indian Railway Standard Welded Bridge Code and subject to further specifications given in the following paragraphs.

• All welds should be done by submerged-arc welding process either fully automatic or semi-automatic. Carbon di oxide welding or manual metal-arc welding may be done only for welds of very short runs or of minor importance or where access of the locations of weld do not permit automatic or semi-automatic welding.

• Except for special types of edge preparation, such as single and double „U‟ single and double „J‟ the fusion edges of all the plates which are to be joined by welding may be prepared by using mechanically controlled automatic flame cutting equipment and then ground to a smooth finish. Special edge preparation should be made by machining or gouging.

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• Welding procedures:- The welding procedure shall be such as to avoid distortion and minimize residual shrinkage stresses. Properly designed jigs should be used for assembly. The welding techniques and sequence, quality, size of electrodes, voltage and current required shall be as prescribed by manufacturers of the material and welding equipment.

• For fabrication of welded composite girders, channel shear connectors shall be welded on top flange plate prior to assembly of I-section. This facilitates correction of any distortion of flange plate developed during the welding of channel shear connectors.

4.12. INSPECTION OF WELD

• MACRO ETCHING TEST

Macro etch testing allows the tester to see a cross section of the weld,

and see the arrangement of the grains in the parent metal and the weld

material. This is known as its Macrostructure. Its can also show up

defects such as porosity, inclusions and poor fusion. You need minimal

equipment to perform a macro etch test. Firstly, it involves cutting a

sample from the welded joint. Cold cutting methods are best for this,

such as a bandsaw.

Then the surface needs to be polished. File away any burrs and rough

marks, then use progressively finer grades of emery until a smooth even

polish is obtained.

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• VISUAL TEST

Fatigue cracks on webs were reported in DOT reportsbut couldn’t indentify by visual inspection induced by vibration of lateral bracing due to differential deflection of girders

• WELD GAUGE

• To measure fillet welds place irregular curve edge flush to horizontal toe of weld so the straight edge is in line with the horizontal member.

• To measure weld throat thickness place the 45° angle end flush to the horizontal and vertical members. Loosen the thumb screw and slide the pointer until it touches the face of the weld.

• DYE PENETRANT TESTING (DPI)

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Dye Penetrant Inspection (DPI) – Liquid Penetrant Inspection

(LPI) – Liquid Penetrant Testing (PT)

ECE Global Inspection Services offers a complete line of surface

examination techniques including Liquid Penetrant and Magnetic

Particle NDT applications and techniques. The application of these

testing methods by experienced technicians has been proven to give

reliable information as to the shape and length of different defects that

are open to surface.

This can be very important when indications are noted and additional

resources and techniques are needed to assess the overall condition of

your component (e.g. Phased Array Ultrasonic Testing).

Many of the technicians employed by ECE Global are multi-disciplined

and able to apply the other NDT disciplines that may be necessary to

fully determine the suitability of the component for service.

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Dye Penetrant Inspection (DPI), also called Liquid Penetrant Inspection

(LPI) or Liquid Penetrant Testing(PT),

is a widely applied and low-cost inspection method used to locate

surface-breaking defects in all non-porous materials (metals, plastics, or

ceramics). For applications where a greater sensitivity to smaller defects

is required, the fluorescent penetrant method is preferred.

The Penetrant may be applied to all non-ferrous materials and ferrous

materials, but for inspection of ferrous components magnetic-particle

inspection may be preferred for its subsurface detection capability.

Commonly, DPI is used to detect cracks, surface porosity, lack of

penetration in welds and defects resulting from in-service conditions

(e.g. fatigue cracks of components or welds) in castings, forgings, and

welding surface defects.

1. Section with a normally not visible surface-breaking crack.

2. Penetrant is applied to the surface.

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3. Excess Penetrant is removed.

4. Developer is applied, rendering the crack visible.

The effectiveness of this method relies on many factors including the

training/skill of the technician, how clean the part is, and the procedure

that is being used to perform the test. DPI is a relatively cost effective

method, considering the amount of training required, and the cost of

materials used. DPI can be used in both manufacturing and in-service

inspections. As with other inspection methods, DPI requires that a

known defect standard has been defined using standard parameters. Thus

indications can be compared to with defined allowable limits.

• INITIAL ASSEMBLY OF JOB

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All the surfaces which will be in permanent contact shall be throughly cleaned by grinding to remove paint, mill scale, dust etc. One coat of read lead to IS:102 or zinc chrome red oxide priming to IS:2074 should be applied immediately after cleaning.

• DRILLING AND SUB PUNCHING

All holes shall be drilled but the Contractor may, if he/she so prefers sub- punch them to a diameter 6mm less than that of finished holes, e.g. a punched hole which is to be drilled out to 25mm in diameter shall not exceed 19mm in diameter at the die end. When the rivet holes are to be sub-punched, they shall be marked with a centre punch and made with a nipple punch or preferably, shall be punched in a machine in which the position of the hole is automatically regulated. The punching shall be so accurate that when the work has been put together before drilling, a gauge 1.5mm less in diameter than the size of the punched holes can be passed easily through all the holes.

• MAKING OF JOINTS

• Cleaning of permanent contact surfaces:- Surfaces which will have permanent contact shall be removed of paints and mill scale down to bare metal, clean and dried and immediately a coating of zinc chrome red oxide priming to IS:2074 shall be applied. Care shall be taken to

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see that all burrs are removed and no surface defects exist before the parts are assembled

• Bolting and Drifting:

Only barrel drifts shall be used in erection. They may be used for drawing light members into position; but their use on heavy members shall be restricted to securing them in their correct position. Any apparent error in shop work, which prevents the assembling and fitting up of the parts by the proper use of these drifts, shall be investigated immediately.

• SITIFFENERS

• Stiffeners are required where factored concentrated loads or reactions exceed the factored Compressive (vertical) resistance of the plate girder web.

• Failure due to concentrated loads can be as local buckling of the web in the region where it joins the flange, or overall buckling of the web throughout its depth

• TRANSVERSE STIFFENERS

If a girder has insufficient strength (web local yielding or web crippling) to support concentrated point loads then a pair of transverse stiffeners can be added to the web to transfer the concentrated force to the web.

BEARING STIFFENERS

• Bearing stiffeners are placed over the end bearings of welded plate girders and over the intermediate bearings of continuous welded plate girders.

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• They consist of two or more plates placed on both sides of the web.

• RIVETING

• BOLTS NUTS AND WASHERS

Bolts, Nuts and Washers shall be in accordance with the following specifications:

• Black hexagonal bolts to IS:6639 and Nuts to IS:1363.

• Precision and turned bolts with nuts and hexagonal screws to IS:1364.

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• Plain washers to IS:2016 and IS:5369.

• Spring washers - IS:3063.

• Taper washers - IS:5372 and IS:5374.

Manufacture, workmanship, Marking, Packing etc. for Bolts and Nuts shall comply with the requirements of IS:1367.

• Where the head and nuts bear on timber, square washers having the length of each side not less than three diameters of the bolt and the thickness not less than one quarter of the diameter shall be provided. Steel, wrought iron or malleable cast iron taper washers shall also be provided for al heads and nuts bearing on bevelled surfaces.

• For black bolts a clearance (difference in diameter) of 1.5mm for all sizes of bolts shall be allowed.

• Where turned bolts are required they shall be carefully turned and shall be parallel throughout the barrel. Holes for turned bolts should be 1mm undrilled in shop and should be reamed at site to suit the diameter of the turned bolts.

• FINAL ASSEMBLY OF JOB• RIVETTING SECTION

• Details of rivet checking to be maintained as per rivet checking register (item no.-2 of appendix-i of b1-2008.

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• FINAL ASSEMBLY SECTION

• Final finishing of length, profile, notches etc.

• Fixing of fitting for site connections.

• All the defects should be rectified

• Final check & inspection.

• Final assembly includes acurate machining of end profile of component.

• All the members should be correctly marked before dispatch to fecilitate easier erection.

• INSPECTION OF THE WORK DONE

The work shall be temporarily erected complete at the Contractor‟s Works for inspection by the Inspecting Officer, with the exception of such rivetting as has to be done at site, so that accuracy of fit and perfection of workmanship may be assured. The work shall be put together with sufficient numbers of parallel drifts or turned bolts or both to bring the pieces into place. When so erected all holes left to be filled at site shall be so fair that a parallel gauge turned to a diameter

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0.8mm less than that of the hole, of a length equal to the depth of the hole, can be passed through them without difficulty.

• FINAL SETTING OF STUD

Studs are the shear reinforcements provided on the top portion of girder. It can be in the form of a I section that is welded on the top of it. Studs play an important role in case of composite steel girders. At the time of erection with concrete they bind up with the reinforcements provided and increase the load bearing capacity of girder.

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• OILING, PAINTING AND METALLIZING

• No part of the work shall be painted or coated, packed or dispatched, until it has been finally inspected and approved by the Inspecting Officer. Dry Film Thickness shall be measured by elcometer or any other approved method.

• When so specified by the Purchaser, the whole of the work except machined surfaces shall be given protective coating using one of the systems of painting or metalizing given in clauses.

• Prior to the application of protective coating , the surface of work shall be carefully prepared removing mill- scale, rust, etc. using wire brushes, sand or grit blasting as stipulated and approved by the Purchaser.

• For locations where the girders are subjected to salt spray such as in close vicinity of the sea and/or over creeks etc. the protective coating by metallizing with sprayed aluminium followed by painting as per painting schedule given below may be applied:

(i) One coat of etch primer to IS:5666.

(ii) One coat of zinc chrome primer to IS:104 with the additional proviso that zinc chrome to be used in the manufacture of primer shall conform to type 2 of IS:51.iii) Two coats of aluminium paint to IS:2339 brushing or spraying as required. One coat shall be applied before the fabricated steel work leaves the shop. After the steel work is erected at site, the second

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finishing coat shall be applied after touching up the primer and the finishing coat if damaged in transit.

• For locations where girders are exposed to corrosive environment i.e. flooring system of girders in all cases, girders in industrial, suburban or coastal areas etc., protective coating by metallizing followed by painting or by painting using epoxy based paints as per the following painting schedule may be applied:

I) SURFACE PREPARATION

a) Remove oil/grease from the metal surface by using petroleum hydrocarbon solvent to IS:1745

b) Prepare the surface by sand or grit blasting to Sa 2-1/2 to IS:9954 i.e. near white metallic surface.

(II) PAINTING

(a) Primer Coat

Apply by brush/airless spray two coats of Epoxy Zinc Phosphate primer to RDSO Specification No. M&C/PCN/102/86 to 60 microns min, dry film thickness( DFT) giving sufficient time gap between two coats to enable the first coat of primer to hard dry

(b) Intermediate Coat

Apply by brush/ airless spray one coat of Epoxy Micaceous Iron Oxide paint to RDSO Specification No. M&C/PCN/103/86 to 100 microns minimum

DFT of 100 and allow it to hard dry.

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(c) Finishing CoatApply by brush/airless spray two coats of polyurethane aluminium finishing to RDSO Specification No. M&C/PCN-110/88 for coastal locations or polyurethane red oxide (red oxide to ISO 446 as per IS:5) to RDSO Specification M&C/PCN- 109/88 for other locations to 40 microns minimum DFT giving sufficient time gap between two coats to enable the first coat to hard dry. The finishing coats to be applied in shop and touched after erection if necessary

• PRECAUTIONS DURING FABRICATION

DOs-

• Use proper fixtures and clamps to hold the members firmly at desired location while welding. The clamps and fixtures must be strong enough to prevent any distortion of the member while cooling of the welding joint. The clamps and fixtures are only to be removed when the joint is cooled to ambient temperature.

• Do the welding work in a warm and dry place so that rain water or other atmospheric elements may not come in contact while welding is in progress.

• While welding in very cold weather pre-heat the material before welding and apply post heating to prevent the weld joint from rapid cooling and develop stress raiser due to sudden contraction.

• Cross level of bearing plates in the welded plate girders should be checked properly for proper sitting over bed plate.

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• Drilling of holes through approved set of jig particularly long members should be ensured. No fabrication should be done with unapproved jig.

• Proper edge finishing with grinding/ special attention in top chord compression members butting by end milling should be carried out

• Application of paint on permanent contact surface should be ensured after proper surface preparation visual inspection is very important tool.

• The plates should be perfectly horizontal while drilling the holes to ensure horizontal verticality of holes.

• Consistency of weld quality is higher in Submerged Arc Welding Process and chances of human errors are also eliminated. Therefore, welding of the girders should be done by SAW process. Whenever not possible then only CO2 welding or MMAW may be adopted if provided in app. WPSS.

DONT’S

• Use of pitted/ corroded material should not be done because it gives rise to concentration of stresses and results in poor fatigue strength.• Do not hammer the distorted joints for rectification. It may lead to the development of cracks and failure of the joints.

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Reyaz Report 2

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