Page 33 - TT Magazine Feb-Mar 2019

INFRASTRUCTURE

Arc Welding (GMAW). To ensure an error-
free welding - Magnetic Particle Testing, Dry
Penetration Testing and Ultra Sonic Testing
were deployed. A specialized Beam making
CMM Machine from Italy is used for the
first time in India for fabrication of Box and
I-Sections using Submerged Arc Welding
(SAW) procedure. A blasting gun was used
to achieve the surface roughness of SA 2½
before applying paint. The Intermediate and
final spray coatings are performed in a highly
controlled climatic chamber with spray guns.
Assembly: Thereafter these fabricated
sections were moved to the assembly shop
where they installed on their designated
beds. They are guided to their correct
positions through jacking and welded
by GMAW process. These segments are
arranged in a sequence and sent for the
vertical assembly using horizontal lifters.
After installation of the top and bottom used for moving the steel truss over the
girders, the final Truss Bridge Dimension
Design Chambers are examined thoroughly pillars. Two sets of steel cable strands were
and approved to complete the fit out. A anchored to the end cross beams of the
Nose is fabricated and fitted on the first Truss and hauled by hydraulic jacks. The
truss before launching it on the piers. Truss slides over the Launching Bearing
with the help of Sliding Plates, which were
Launching: While determining the
methodology of erecting the steel trusses inserted at one end and taken out at the
on pillars, engineers had two choices — other, thereby moving the Truss towards its
lift the spans with floating cranes or erect desired position. In order to limit the required
them with a launching truss. And they have launching forces, the superstructure was
to decide based on which option would be
proved more practical and economical.
After weighing the pros and cons, the
HCC team came-up with a solution of
pulling the steel trusses with a set of jacks
and winches on the pillars. This eliminated
the need to enter the river, which was
often turbulent during monsoons. Besides,
it also ensured safer working conditions,
precluded the mobilisation of giant setup
on either side of the river having a width
of 4.8 km and accelerated the pace of
the project. The strategy is a testimony
of the company’s value engineering, an
important feature of the globally-practiced
‘Lean Construction’ that is changing the
way projects are executed from design to
construction.
A 1000 tonnes hydraulic jacks and strand
jacks linked with the substructures were

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