Presentation on steel, fabrication & erection Munger Ganga Bridge

Presentation on Steel
Fabrication work and
Erection of girder by
Cantilever erection
method.
By: Afroz A Kapra
General 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

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, 0.1mm
Rejection - -0mm, +0.4mm
For jigs from Master plates +0mm- 0.13mm

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• Satellite Image

Presentation on steel, fabrication & erection Munger Ganga Bridge

• 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

Cutting of plate by pug machine

• 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.

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.
 Tests
o DPT to detect any crack, pin hole etc.
o Micro etching to know the penetration depth
o 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

Seating for welding of box member

 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 out
Drill 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

Distortion correction of box member

Distortion correction of I-Section by machine

Drilling by radial drill machine

Drilling by magnetic drill machine

 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.

Checking of thickness
by alcometer

Launching of girders
Trial 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

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

Fixing of bearing &
buffer slab

Receiving bracket for landing of cantilever span

Support of bottom member
by hanging device

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.

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

Practical problems faced during work
Items 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 .

Presentation on steel, fabrication & erection Munger Ganga Bridge

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Presentation on steel, fabrication & erection Munger Ganga Bridge