Erection Of Superstructure In Metro Viaduct
ERECTION OF SUPERSTRUCTURE
●
Erection
is done during night because road traffic is less and space required is
available.
●
Care
should be taken that work is done at least 6 m away from of electric wires and
poles.
●
There
should not be any traffic or anything prone to damage within swing area.
●
Cranes
are used to lift and place the structure. One crane is used for erecting pier
cap and two cranes for erecting U Girder
●
Location
of crane is decided upon following factors :
○
Size
and weight of superstructure.
○
Area
available free from utilities.
○
Boom
length and boom angle as decided by engineer.
○
Swing
Area.
○
Location
of trailer truck.
●
Crane
rests with its arms.
●
Steel
plates are kept below the arms so that load is transferred uniformly to ground
over larger area.
●
Counter
Weight is decided upon following factors :
○
Weight
of crane, boom, hook, chains, structure to be loaded.
○
Ground
reactions at all fours crane arms is calculated.
○
Moment
of all the forces is balanced about a point.
●
Boom
length and boom angle is decided upon load chart of the crane which is provided
by crane manufacturers.
●
Before
the erection once trial swinging is done without load, to check the alignment
and positioning.
●
Structure
is then lifted and placed.
○
Pier
cap on pier.
○
Girder
on pier cap.
●
Surveyors
play a important role in positioning the structure accurately as desired.
●
For
pier cap temporary steel support is given and stitching is done by pouring
concrete in the hollow region left.
Girders are rested on neoprene rubber pads
bolted with steel plates with structural glue applied on both surfaces for
shear load transferring.
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