2. BRIDGE INSPECTION
SYSTEMATIC OBSERVATION OF
CONDITION AND BEHAVIOUR OF
VARIOUS COMPONENETS/ PARTS
OF A BRIDGE IS CALLED BRIDGE
INSPECTION
3. AIMS OF BRIDGE
INSPECTION
To assess structural soundness and
fitness for use
To identify trouble at the earliest stage
To keep a systematic record of
condition and behaviour (data bank)
To plan repair and rehabilitation
strategy and programme
4. SCHEDULE OF INSPECTION
BRIDGE INSPECTOR
Steel girders including bearings of girders >
12.2m – once in 5 years
Welded girder – initial inspection after 1 year of
installation, than once in 3 years
Composite girder – 1 year and subsequently 5
years
Overstressed girders – at least once in a year
Early steel girder – Floor System– once in a year
: rest-once in 5 years.
Steel work, rivet testing, weld test etc.
5. Schedule Of Inspection
AEN/DEN (Bridge)
Scrutinize – register sent by BRI
Inspect Bridges referred to him
Bridges call for inspection
All overstressed bridges – camber loss
10% test check of BRIs work
Dy. CE/Bridges
Scrutinize bridge inspection register
Inspect Bridges referred to him or call for
inspection
6. BEARINGS
ROLE OF BEARINGS
Transmission of Forces from
superstructure to substructure
Vertical
Horizontal
To permit movement
Translation
Rotation
9. INSPECTION OF BEARINGS
The longitudinal alignment - straight
and central to base plates.
The girders - symmetrically placed
No cavity/ gap between base plate and
bed block
Bearings are free to move in the
designed manner
10. INSPECTION OF BEARINGS
contd.
Check the condition of location strip and
guide strip or shearing of rivets
The anchor bolts - in proper position
and intact. Look for any bend or
shearing of bolt
Uniform seating of rollers & bearing
strip check with feeler gauge
14. INSPECTION OF BEARINGS
contd.
All fittings of rocker and roller- Sound
and proper
Free movement of bearings and
condition of grease
check both ends of girder are in same
level.
15. CAMBER
Camber in steel truss girder is provided
upward amount being equal to
deflection of girder under design load
during fabrication and erection so that
girder under full load, truss shall be in
horizontal plane (nominal shape).
Steel plate girders of span 12.2m,
18.3m & 24.4m span (either welded
construction or rivetted construction)
are not provided with camber
16. PRESTRESSING
Prestressing of open web steel girder of
track bridge is predeforming of
members during fabrication and
erection of girder to ensure girder
under full design load shall be in
nominal shape to minimise
deformation stresses.
17. MEASURE CAMBER
During technical inspection, camber is
checked at every panel point of bottom
chords of both truss with the help of dumpy
level or precision level, which will facilitate
the inspection officials to understand the
structural condition.
As far as possible camber observations are
required to be taken at the ambient
temperature mentioned in the stress sheet.
Graph in different colour.- Dead Load Camber
18. INSPECTION OF STEEL
SUPERSTRUCTURE
Check the Camber
Loss of camber/Sagging due to
Heavy overstressing
Loss of cross section
Increased load/fatigue
Overstressing of joint
Play between holes and rivets
19. LOSS OF CAMBER
IF loss of Camber observed –
Impose SR of 30 KMPH
Investigate in detail-loose rivets,
corrosion, distortion
Measure stress in critical members by
Faraday Palmer Stress Recorder or
Strain Gauges
Check for frozen bearings
20. INSPECTION OF STEEL
SUPERSTRUCTURE contd.
DISTORTION
Plate girder
Top flange- comp member
Web plate near bearings-stress
concentration
Top lateral bracing – excessive
vibration
21. INSPECTION OF STEEL
SUPERSTRUCTURE contd.
DISTORTION
Open web girder
Top chord – insufficient restraints
Diagonal web member – made of flat in
mid span
Bottom chord member – if not braced
properly
Top lateral/ portal bracing - If not braced
properly
Frozen bearings
22. DISTORTION -CHECK
Distortion can be checked visually as
well as by a piano wire stretched
between panel points over the
members
Sometimes web member i.e. diagonal,
vertical and end rakers in through
girder bridges are hit by moving loads
due to shifting of load in wagons,
particularly ODC. Hence, these
members should be checked at 1.2
meters above rail level for any damage.
23. RIVETS
3 groups:
stitch rivets are driven to form a member.
These rivets are driven in workshop and
mostly do not become loose in service life
of girder upto 80 to 100 years
rivets at joints connecting members. These
rivets transfer the load from member to
joint. Tend to become loose after 40 to 50
years.
rivets connecting top and bottom lateral
bracings including sway and portal
bracings tend to become loose on account
of vibrations.
24. TESTING FOR LOOSE
RIVETS
Testing of rivets by rivet hammer chips
off the paint film, making rivet head
steel exposed to environment leading to
corrosion of rivet heads
During technical inspection rivets should
be tested at the critical locations
Inspect Rivets for loose rivets
rivet testing once in 5 years
25. LOOSE RIVET–CRITICAL LOCATION
PLATE/COMPOSITE GIRDER
Web plate to flange angle at end of
girders
Bearing stiffener
Splice rivets of flanges
Bracing and cross frame connection
26. LOOSE RIVET –CRITICAL LOCATION
OPEN WEB GIRDERS
Rail bearer – cross girder connections
Cross girder – panel point gussets
Panel point main gussets
Top/bottom lateral bracings
27. CORROSION
Inspect for corrosion/loss of section
Critical locations
Under wooden sleepers
Formation of water pocket due to
construction
Places where dust accumulate
In vicinity of drainage system
Area directly affected by diesel loco fumes
28. CORROSION- PAINTING
The inspecting officials should clearly
indicate the following during inspection:
i) Major portion of steel work require
only cover coat painting and at some
locations patch painting.
ii) Steel girder requires complete
painting.
iii) Only patch painting.
iv) Paint in good condition, hence no
painting is required.
29. FATIGUE
Fatigue Cracks
Fatigue is the tendency of metal to fail
at lower stress level when subjected to
cyclic loading
Fatigue is becoming important because
of growing volume of traffic at greater
speeds and higher axle loads.
30. LOCATION-FATIGUE CRACK
Critical locations of cracking;
i) Ends of diagonal members near middle of
the span due to reversal of stresses.
ii) Sharp edges at cut notch in stringer
flanges at connections with cross girders.
iii) Top flange plates or flange angles of plate
girders or rail bearers especially below the
sleepers.
31. LOCATION-FATIGUE CRACK
iv) Roots of channel and angles on
account of rolling defects.
v) Corrosion pits at any location in
tension member. Joints where heavy
shear is transmitted.
To arrest the crack propagation, a hole
should be drilled at the end of the crack
in plate and cover material is provided
with rivets.
42. Maintenance of Steel superstructures
Inspection and recording
Cleaning and greasing of bearings
Protective painting system for steel
structures
Replacement of loose rivets or repair to
weld joint
Strengthening of steel superstructure
Replacement of corroded rivets
43. Painting
Steel girders are prone for corrosion
Where humidity > 60%
In coastal areas
Bridge across creek
Bridge surrounded by chemical industry.
Type of traffic
Public nuisance
44. Painting
Surface preperation
Use emery paper , wire brush, scrappers
With power tools
Blast cleaning – sand or grit
Flame cleaning – oxy-acetylene flame
(not to be done on plates with
thickness<10mm)
Luke warm water – 2% detergent
45. Painting
No severe corrosion
Priming coat
Heavy coat of ready mixed paint red lead
priming to IS 102 or
One coat of Zink cromate priming to IS 104
followed by red oxide zink crome priming to IS
2074 or
Two coat of Zink cromate red oxide primer to
IRS P31
Finishing coat
Two cover coats of red oxide paint to IS 123
46. Painting
Severe corrosion
Priming coat
Two coats of red lead priming to IS 102
Finishing
Two coats of aluminium paint to IS 2339
Above also recommended for open web girders in
all cases due to better and longer life.
All floor and top bracing system in electrified
areas with epoxy painting
47. Paint life
Paint red lead - 4 months
Paint red oxide – 1 year
Aluminium
When paste & oil not mixed – 1 year
When mixed – 4 months
Red lead dry paint – No time limit
48. Time lag between paints
Surface prep and Primer – 24 hours
Primer coat and first finishing coat – 7
days
First fininshing coat and 2nd fininshing
coat –7 days
49. Epoxy painting
Should be done for
Flooring system ( cross girder and rail bearer) in
open web girders
Top flange plate of plate girder and underslung
girder
Top bracing system in open web girders in
electrified areas
Steel girders subjected to salt spray
50. Epoxy painting
Remove oil/grease using petrolium hydrocarbon
solvent ( IS 1745)
Prepare the surface by sand blasting
Primer coat – Epoxy zinc phosphate primer
to 60 micron min. ( RDSO M&C/PCN-102/ 86)
Intermediate coat – One coat of micaceous iron
oxide to 100 micron . ( RDSO M&C/PCN-103/ 86)
Finishing coat - two coats of polyurethane
aluminium to 40 micron. ( RDSO M&C/PCN-110/
88)
51. Metallising
Should be done for
Flooring system ( cross girder and rail bearer) in
open web girders
Top flange plate of plate girder and underslung
girder
Top bracing system in open web girders in
electrified areas
Steel girders subjected to salt spray
52. Metallising
Zinc chrome primer to IS 104
Two coat of aluminium paint to IS2339
Min thickness of metal coating 115 micron
Surface preparation crucial
Final cleaning by chilled iron grit G24.
Final surface roughness as per IS 5909.
Aluminium to be sprayed as per BS1475
53. Renewal of loose rivets
Slight slackness does not cause loss of
strength
Renewal should be done only when in groups
All hand loose rivets which have lost 50% of
head
All hammer loose rivets where corrosion has
set in bet head and plate
In end stiffeners where hammer loose rivets
> 30%
54. Renewal of loose rivets
Use only pneumatic rivetting
Not > 10% rivets should be cut at a joint at a
time
Preferably drill a rivet out than use a rivet
buster
Rivet to be heated to white hot
Rivet to be driven and snap removed within
20 sec. After leaving fire
Length
Snap head – L= G +1.5 D +1 mm for every 4mm of grip
Counter sunk – L= G + 0.5 D +1 mm for every 4mm of grip
59. 2 3 4 5 6 7 8
HORIZONTAL LEG OF ANGLE MISSING
DUE TO ACUTE CORROSSION
3' 4' 5' 6' 7'
OHE OHE
VIEW A-A
ADDITIONAL
COVER PLATE
60. CORRODED BOTTOM
FLANGE ANGLE WITH
MISSING LEG BOTTOM SPLICE PLATE
INTACT BOTTOM FLANGE
ANGLE
NEW ANGLES WELDED
TO PROVIDE BOTTOM
FLANGE AREA
CORRODED BOTTOM
FLANGE ANGLE WITH
MISSING LEG BOTTOM SPLICE PLATE
INTACT BOTTOM FLANGE
ANGLE
NEW ANGLES WELDED
TO PROVIDE BOTTOM
FLANGE AREA
CORRODED BOTTOM
FLANGE ANGLE WITH
MISSING LEG BOTTOM SPLICE PLATE
INTACT BOTTOM FLANGE
ANGLE
NEW ANGLES WELDED
TO PROVIDE BOTTOM
FLANGE AREA
BOTTOM SPLICE PLATE
INTACT BOTTOM FLANGE
ANGLE
NEW ANGLES WELDED
TO PROVIDE BOTTOM
FLANGE AREA
INTACT BOTTOM FLANGE
ANGLE
NEW ANGLES WELDED
TO PROVIDE BOTTOM
FLANGE AREA
NEW ANGLES WELDED
TO PROVIDE BOTTOM
FLANGE AREA
