The 32m cab, top mast sections and temporary works
were constructed at T4's cargo area, and moved across the Southern runway
by SPMT's (self propelled modular trailers) to T3 during the night to
minimise disruption. Three jacking towers were assembled and erected
around the cab and mast sections, and after test 'overloads' proved
successful, the structure commenced jacking on January 21st 2005 to
allow the first section to be added, then progressively jacked up over
the weeks using a strand jacking system, adding the other sections as
it gained height. On March 6th 2005, the structure achieved its maximum
height of 87m tall.
The jacking procedure is weather reliant, and therefore the wind speeds
were observed very carefully during this period, 12.5 metres/second
being the maximum allowed speed to safely 'jack', and the 'down' time
was fortunately kept to a minimum due to favourable weather conditions.
A satellite GPS was set up to monitor the masts upright plumb position
during jacking, and any adjustments required, were made by tweaking
the diagonal guy strand jacks.
The temporary works, jacking towers and lifting jacket were dismantled
to make way for the now completed base building around the bottom section
of the tower, and is currently being fitted out with electrical switch
gear, external glass panels and internal partition walling etc.
The temporary support guys have all been removed and replaced with the
permanent guys which have undergone a series of stressing cycles to
allow them to ‘bed in’ and remove any residual stress within
the inner layers of the cables. The GPS was again used to monitor the
masts position during the sequence of stressing procedures
A link bridge to the existing Terminal 3, Pier 5 structure will be erected
to allow access to the control tower, and foundation piling is ongoing.
The £50 million air traffic control tower is more than double
the height of the existing tower,
and
will offer controllers uninterrupted 360º views of aircraft on
the airfield including the new Terminal 5.
