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Expansion Joints |
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Maintenance
Manual of Strip Seal
PURPOSE:-
Expansion Joint and its components
are continually exposed to natural
element, eg. Temperature changes,
rain, snow, moisture, ozone, carbon
dioxide and ultra violet rays and
elements that are introduced by humans
like Traffic impact, chemical influences
such as Industrial pollutants and
de-icing salts. The combined effect
of these elements on the joint component
is a steady and unavoidable deterioration
process.
That
is why regular inspection and maintenance
are vital measures for a long life
span of expansion joint system.
Inspection
of Expansion Joints at site is required
from time to time to ascertain the
performance of the joints. Periodic
nominal maintenance of joints shall
be carried out in order to ensure
better performance and longer life
of joints. The joints are required
to be inspected at an interval of
one year for the first five years
and at an interval of 2 years thereafter.
However, the joints shall also be
examined carefully after unusual
occurrences like heavy traffic,
earthquake, cyclones and battering
from debris in high floods.
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ELEMENTS
OF MAINTENANCE:
The followings
are recommended maintenance elements
and actions which are considered necessary
to monitor and upkeep the joints:
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Debris
accumulation in the joint gaps,
if any. :- The maintenance shall
be preceded by careful cleaning
of the expansion joints to permit
free movement avoiding incompressible
clogging of the joint due to
debris accumulation. All accumulated
foreign objects shall be cleaned
either by pressurized air or
by water jet. It is to be noted
that high water pressure (above
100 bar ) or heated water (above
25 degree C) shall not be used.
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Riding
comfort over the Joints. :-
The alignment of the joints
is a helpful indicator for the
general behavior of the Superstructure
and Substructure concerning
movements as tilting rotation
etc. In general, the deviation
of the alignment can cause a
reduction of driving comfort
for the vehicles or can have
a negative influence on the
joint system as a whole.
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Especially
two points required to be inspected
with care are: |
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The
alignment in transverse
direction (referring the
joint)
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The
vertical alignment measured
along longitudinal direction
with respect to the level
of adjacent road surface.
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The
alignment in transverse direction
shall be measured with a 4 m straight
edge. The deviation between the joint
and straight edge should not be more
than 5mm. The vertical alignment measured
along longitudinal direction with
respect to the level of adjacent road
surface should not be more than 3%.
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Measurement
of Movement :-
During maintenance
at site, measurements are required
to be taken and documented to compute
its movement and rotation values in
relation to their design values to
ascertain whether the performance
of joint are satisfactory. To ascertain
maximum movement, measurement should
be taken once during peak winter (early
morning) and once during peak summer
(afternoon) and corresponding atmospheric
temperature should be recorded. The
recorded value of movement shall be
compared with design values.
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Measurement
of Dimensions :-
Overall dimensions
of the joints are required to be measured
and compared with the actual dimensions
to ascertain any excessive stress
or strain on the joints.
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Evidence
of Locked in Condition :-
If any movable
or rotating part of a joint is found
to be in locked -in / jammed condition,
necessary rectification measure shall
be taken immediately. Distribution
of width of surface gaps (if any)
provided to accommodate movement should
be checked over the length of joint.
Any abnormal variation of surface
gap width over the length of the joint
and / or the distribution of the gap
width beyond the design limits, if
detected, the joint should be thoroughly
checked for the locked-in condition
in order to detect mechanical obstruction
and possible remedial measures should
be taken immediately.
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Evidence
of Corrosion :-
The condition of corrosion protection
shall be checked carefully. Early
detected and repaired damages will
certainly avoid expensive repairs
on a later date. If corrosion of any
part of exterior exposed steel surface
of the joint is detected, following
measures may be taken. In addition,
the root cause of defect should be
searched and proper action should
be taken to avoid recurrence of the
problem.
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Condition
of the Adjacent Bridge Structure :-
The Bridge structure adjacent to the
Joint shall be examined for the following
common defects, which may lead to
further damage of the joint. If damages
are detected they must be repaired
as soon as possible to avoid further
source of damage.
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Condition
of the Sealing Elements :-
The condition of the Elastomeric unit/
seals shall be carefully inspected
to uncover possible defects like loose,
torn, split, cracked, damaged or cut
etc.
If
any one of the above defects appears,
remedial action should be taken the
degree of which depends on the present
defects. In general, following remedial
action should be taken:
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Water
Tightness / Evidence of Leakage :-
Leakage of water together with temperature
and chemical reaction might be a reason
for following damages beside an unpleasant
appearance:
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If
evidence of leakage is detected remedial
actions must be taken by replacing
the seal element or applying sealing
element as per the instruction of
the joint manufacturer or tightening
of the loose component depending upon
the cause of the leakage.
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Evidence
of Noise :-
Abnormal rollover noises generated
by the joint under traffic load can
be regarded as the indicator for the
condition of the joint and also for
the adjacent bridge structure. Abnormal
noise may be caused by loosened and
/ or damaged joint components, loosened
bolts, metal to metal contact due
to damage of joint components.
If
such an abnormal noise is noticed,
the origin of noise should be probed
first and depending upon that, remedial
works shall be taken up by tightening
the loose fixing and / or replacing
the damaged components.
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Visible
Damage of the Joint Components :-
Any visible damage of joint component,
welded and bolted connections as well
as connection of joint with bridge
structure if detected during inspection,
proper remedial measures should be
taken immediately in consultation
with the joint supplier.
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Results
& Actions :-
The results
of every inspection have to be recorded
in the inspection report and shall
be classified in each case into the
following types of action:
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No action.
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Further measurements / long-term
monitoring or design analysis
needed (e.g. considering extreme
temperatures / exposures, variation
of loads etc.). Actions to be
outlined in a report.
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Minor
repair works e.g. cleaning, repainting
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Repair or replacement of entire
joint or components of the joints.
Actions to be outlined in a
report. In case of defects where
the cause of necessary actions
cannot be determined by the
inspecting person or the responsible
bridge engineer, the Expansion
Joint manufacturer should be
consulted.
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