Presentation on Steel Fabrication work and Erection

of girder by Cantilever erection method.

By: Afroz A KapraGeneral Manager

P & R Infraprojects Ltd.Munger Ganga Bridge

Main codes to be used Sl

No.Item Code no. Item covered

1 Steel supply IS :2062 Steel plates

IS:1852 Rolled section

2 Fabrication IRS:B1 & IRC: WBC Fabrication & erection

3 Welding IRC: WBC Metal arc welding in steel

M-39 SAW welding – Wire & Flux

M-46 MIG welding

M-28 MMAW

IS:9595 Metal arc welding in carbon steel

IS:7307 (Pt-1) Approval test for welding procedures

IS: 7310 (Pt-1) Approval test for welders

4 UT of steel plates/ welding

SA 578/ 578M (ASTM) UT of plates

IS : 4225 UT of plates

IS:4260 UT of butt welds Continued…

Sl No.

Item Code no. Item covered

5 Riveting IS :1148 Specification of steel rivet bars

IS: 1149 Specification of High tensile steel rivet bars

IS: 1929 Specification for Hot forged steel rivets

6 Painting IS:9954 Surface preparation

IS: 5666 Specification for etch primer

IS:104 Specification for zinc chrome paints

IS: 2074 Red oxide zinc chrome paints

IS:2339 Specification for aluminum paints

IS:2590 Specification for aluminum

7 Erection IRS- B1 Erection of steel members

Steel Supply (IS: 2062)

• Earlier classification as Fe-410, Fe-490, Fe-570 etc. (410 is UTS in MPa)

• New classification is E-165, E-250, E-300, E-410, E-450 etc. (250 is yield stress in MPa)

• Grade of steel – A,B,C, D,E

• A, B, C grade is suitable for welding.

• Cutting plan to be prepared for minimum wastage of steel

• Steel history to be maintained for traceability of material

• Material test- (2 samples per heat)

Chemical analysis- Mechanical properties (a) Tensile strength

(b) Yield strength (c) % elongation (d) Initial bend diameter (e) Charpy V notch (for impact )

UT for lamination Z test for lamellar tearing (not specified in code) specially for higher thicknesses

Heat mark

Approvals required before Fabrication

• Approval of structural drawings• Approval of QAP by RDSO• Approval of erection scheme• Approval of layout and jigs • Approval of WPSS by RDSO• Approval of WPQR by RDSO• Approval of trial assembly by RDSO

Fabrication (IRS:B1-2001)

• Layout Full layout of span on template floor Template floor Should be perfectly level

Steel flooring desirable

Calibrated tape for measurement

• Jigs, master plates on fixture Master gussets – Reference gussets from layout from which jigs are made/ replaced after

sufficient use. Jigs - Device used in the mass production to locate the job as guide the toll for drilling (Joint jigs

& body jigs) Fixture – Holding the work in true shape during production

• Tolerances (IRS:B1-2001) Bores of bushes –

Initial tolerances - 0mm, 0.1mmRejection - -0mm, +0.4mmFor jigs from Master plates +0mm- 0.13mm

Layout platform

Camber layout

Master plates

Jig

Body jig

Fabrication of girder components(Sequence of activities )

Cutting of plates

Unloading & stacking of steelReceipt of steel

Plate straightening

Finishing of ends Fit up Welding

Drilling of Holes Marking

Finishing

Distortion correction

Painting & metalizingInspection

Workshop Layout

Workshop Layout• Satellite Image

• Plate unloading

Double sling system so that distortion can be checked during unloading.• Stacking

Place above the ground on platform / level bed

Proper drainage in stacking area

Different material storage in different stacks with color coding

Easily assessable.• Cutting Cutting in accordance with tolerances

up to 12mm – +3mm cutting allowance

12mm to up to 25mm +5mm cutting allowance

Above 25mm +7m cutting allowance Less distortion during cutting to be ensured through -

Two pug machine simultaneously

Discontinuous cutting

Hole in cutting lines (3 to 6 mm hole at 4mm spacing) Plasma Cutting

Low heat affected zone

High out put

Good for stainless steel CNC cutting (Computer numerical control)

High output /efficiency

Low wastage

Very useful in irregular cutting

•

Plate unloading

Double sling arrangement

Plate stacking

Cutting of plate by pug machine

Cutting by pug machine

CNC machine for plate cutting

CNC machine for plate cutting

• Straightening of plates

Extra rolled length of plates than requirement so that end bend part may be cut. Surface waviness or kinks are measured with the help of fishing cord and force applied on

opposite side.

• Finishing of ends of plates

Required dimensions are marked with the running punch line on both sides Plates are than ground to required size i.e. up to the half of the punch mark.

• Fit up (IS:9595- 1996)

The gap between edges and surfaces should not be more than 1.5mm. Tack weld shall be not less than the throat thickness/ lag length /root run. The Length of the track weld shall not be less than four times the thickness of the

thicker

part or 50mm whichever is smaller. Squareness of connections to be ensured.

Manual plate straightening

Plate straightening m/c

Edge finishing

Edge finish checking

Fit up

Fit-up of I-Section by machine

• Welding

Welding shall be carried out in accordance with approved welding procedure and approved welders by RDSO w.r.t WPSS.

WPSS consists of weld parameters, welding sequence etc. Parameters Current- Controls the rate at which wire melts. Excess current causes under cut. Voltage- Controls the shape of fusion zone. Higher voltage causes flater weld with

less penetration. Welding speed – Controls the weld bead size and penetration.

Run-in and Run- out should be ensured for proper quality. To prevent distortion, the measures such as proper welding sequence,

clamps, arresters, frames etc. should be used. Testso DPT to detect any crack, pin hole etc.o Micro etching to know the penetration deptho UT

Continued….

Welding continued

• Voltage fluctuation should be avoided for proper shape of weld• Proper pre heating of parent material (1500) and flux (2500 for 1 hr) should be ensured.

• Proper level of fixture should be ensured.

• Submerged Arc Welding (SAW) - To be used widely except short run where

ever possible -Wire and flux is used

• Gas Metal Arc Welding (GMAW) –

To be used in short run where ever SAW is not possible

CO2 or inert gas is used.

Horizontal welding is better than vertical welding

In case of vertical welding , work should be done from bottom to top

Proper positioning of job for equal leg length Spatters can be minimized by placing wire one inch to one and half inch out of gun

Wire spool for SAW welding

Flux

Oven for flux heating

Flux for SA welding

Fixture

Welding of I section

Frame to control distortion

Run in run out

Pre heating

Pre heating of box

Inside welding of box member

Seating for welding of box member

Outside welding of box

Go-No go guage for holes

DPT

Pin hole detected by DPT

Micro etching

Distortion correction Can be done manually by using jacks or by machines

Marking Punch marks for marking holes Diagonal cross check to be done Reference line to be transferred w.r.t. to web by making suitable

template. Right angle also can be use to check verticality between punch

marks

Drilling Job should be placed in level position before drilling . Level should

be checked by Sprit level at least at three locations. The drill bit should taken out frequently to allowed the chips to

come outDrill bit of good quality brand such as Adition to be used. The tip should be sharpened on daily basis. Timely replacement of drill bit, marker hole with sharp age

Manual distortion correction

Manual distortion correction

Distortion correction of box member

Distortion correction of I-Section by machine

Marking of member

Drilling by radial drill machine

Drilling by magnetic drill machine

Finishing of member

Finishing by end milling m/c

Sand blasting

Dry sand of size 600 micron to 1700 micron to be used

Air pressure should not be less then 4kg/cm2

Nozzle distance from surface to be 150 to 250mm.

Surface to be checked by standard comparator (Swedish standard

SIS 05 5900-1967). Painting should be started immediately after sand blasting to avoid rusting .

Metalizing May be with Aluminum or zinc Aluminum wire of 3.15mm dia with oxygen and LPG to be used Average of coating shall not less then 150micron. One coat of itch primmer shall by applied on metalizing surface. it is batter to do metalizing of light thickness first and then finishing with another coat to avoid rusting of naked sand blasted surface

Painting On metalized surface Yellow zing chrome one coat (30 micron min.) Aluminum paint one coat (20 to 22 micron) on member. Aluminum paint one coat (20 to 22 micron) after erection.On normal surface Yellow zing chrome one coat (30 micron min.) Red oxide one coat (30 micron min.) Aluminum paint one coat (20 to 22 micron) on member. Aluminum paint one coat (20 to 22 micron) after erection. Painting yard should be well isolated from blasting chamber to avoid dust etc. Permanent contact surfaces should be painted before assembling with one coat of yellow zinc chrome followed by one coat of red oxide.

Sand blasting

Sand for sand blasting

Sand blasting

Sand blasting of gusset plate

Metalizing of gusset plate

Etch primer

Checking of thickness by alcometer

Yellow zinc chrome primer

Al Paint

Launching of girdersTrial assembly Required for measurement of no load camber/dead load camber by RDSO 1st member has to be erected with nodal support method. Trial assembly should be erected on ground , inspected, dismantled and then

erected on piers (in case of Munger Bridge, trial assembly erected directly on piers with special approval of RDSO).

Each joint has to be support on trestles etc.

The erection of members may be done with the help of crane on ground or on top of girder.

Sequence of operation Foundation

Trestle erection

Grillage beam

Erection crane load test and commissioning

Erection of false span

Erection of erection crane on false span

Erection of trial assembly

Balance spans by cantilever erection method

Trial Assembly On Ground

Erection of Trial Span

Cantilever erection method

ERECTION SCHEME

Contd…..

ERECTION SCHEME

CANTILEVER ERECTION SCHEME

Link arrangement

Accessories required Link member

Link pin

Link plate

Buffer slab

Bearing slab

Vertical props

Hanging device

Every component is designed as per load.

Manufacture procedure of bearing / buffer slabs

Steel is forged steel with high yield capacity ( e.g. EN 19, BS- 970 etc.).

Ingot supply. Chemical and physical testing of material Forging Cooling UST Heat treatment Hardening Inspection for UST and hardening Machining Dimensional and UST check

Link member

Link pin

Link plate

Bearing slab

Hanging Device

750 T Jack & Traverser

Bearing & Buffer slab

Fixing of bearing & buffer slab

Anchoring arrangement

Temporary Bearing

Receiving bracket for landing of cantilever span

Receiving bracket for landing of cantilever span

Support of bottom member by hanging device

Load test of erection Crane

Cover plate for lifting of member

Procedure of erection To cater for erection stresses, strengthening of members is required by

designing the same.

Temporary bracings/posts to be used to take care erection stresses.

All temporary members/gudgets to be properly designed

After anchor span, link members and buffer/ bearing slabs are fixed to

start the next span erection.

Members are erected in a particular sequence with the help of hanging

device and continued.

Erection will be done with bolts and drifts in at least 50% of holes (40%

drifts and 60% bolts) initially and then replaced by rivets.

Link shortening to be provided to cater deflection for cantilever span.

Procedure of erection Previous penal to riveted before start of erection of next penal.

To ease out landing of span, receiving bracket may be used.

After landing immediate jacking of span to be done to release the stresses.

Edges of members to be protected during lifting by providing steel cover plates

etc.

Crane to be secured with top member properly.

At the time of lifting by crane, member should be secured properly with anti

slippage arrangement and released gradually.

Erection work should not be done during high wind.

Riveting• IS: 1148 for MS rivets & IS: 1149 for HTS rivets

• Dia of hole = Dia of rivet + 1.5mm (for rivets of dia < 25mm).

• Length of rivet = thickness of plates (grip length) + 1.5 x dia of rivet + thickness/ 8.

• Riveting by dolly and pneumatic hammer.

• Heating by coal furnace or induction heating.

• Heating in full length. Head shall be heated more particularly in long rivets

• Test of rivet (IS:1149) Dimensional check (IS:1929), Hot compression test & bend test at site. Chemical analysis, tensile test, bend test, shear test, head soundness

test .• Just like welders, riveters may also be tested for long rivets (not specified in

code)

• Painting of rivets to be done immediately with one coat of zinc chrome followed by red oxide to avoid rusting.

Dolly for riveting

Pneumatic hammer for riveting

At shake hand point

Erected members

Erected Joint

POT- PTFE Bearing

Safety precautions • “Safety first” rule to be observed

• Adequate safety measures for workmen like safety belt, helmet, gum boots

hand gloves, googles, shields , respiratory mask etc. to be used.

• Safety slogans and posters to be displayed at various locations.

• Equipments and machinery to be checked at stipulated frequency.

• Trial for material trolley, erection crane etc. should be done before taking in

use.

• Anti-slippage arrangements should be ensured for holding of members

during erection.

• Wire net should be used at the place of erection.

• One boat should be kept ready in water for emergency purpose.

• All inflammable objects like diesel. gases to be kept at safe place.

• Medical facilities such as doctor, ambulance ,medicine etc. should be

available at site along with phone nos. of hospital and doctors.

• Staff should be counseled and imparted safety training

Safety equipments

Practical problems faced during workItems Problem Solution/Recommendation

1. Steel supply 1. There are bends at the end of plates supplied by SAIL and it becomes very difficult to remove the same in higher thickness of plates such as 56mm, 63mm etc.

The problem was referred to Bhilai steel plant. The bend appears at the time of rolling. They started rolling more length and trimming of bend portion to have straight plate.

2. Surface of plates is rough on one side & smooth on another side.

This happens due to normalizing process (no effect on strength).

3. Mark in mid of thickness at edges has been found up to 2 to 3mm depth in plates of E-450 grade steel.

It is due to cutting of plates during rolling. 2 to 3 mm portion of plate should be removed.

4. Problem of lamination in thick plates i.e. more than 30mm specially in E-450 gr steel .

UT of plates should be done. Z test should also be conducted to identify lamellar tearing.

5. Fatigue load test Provision should be kept in agreement to check the steel against reversal of stresses (No provision in code)

2. Welding 1. Problem in welding of E-450 gr steel In code, no separate parameters provided for different grade of steel Parameters being fixed after doing trials.

Continued…..

Items Problem Solution/Recommendation

2. Welding 2 Inside SAW welding of box members Machines are available. However arrangement is required for movement of staff inside box for preheating , welding, cleaning etc. In house arrangement has been developed for this purpose.

3. RDSO approved welders for wire , flux & paints

1. There is problem getting the supply Approval of more welders by RDSO required .

4. Non availability of codal provision

Codes are silent are many issues such as 1. Penetration depth not defined for normal

penetration weld .

Min. depth to be achieved should be ascertained through trials.

2. Fabrication tolerances of members are not very clear .

Tolerances to be provided in code as given for plate girders and open web girders as a whole.

3. As per IRS-WBC, no concavity in weld profile is allowed. However it is not possible is SAW welding .

Proper weld thickness to be ensured in-spite of concave surface . Amendment in code required .