e-mosty September 2018 Vessels and Equipment Used for Bridge Construction | Page 44

Design and preparatory works
The construction process to assemble the cable-
stayed bridge section consisted of consecutive deck
sections lifts, by means of the balanced cantilever
method. Typical sections measured 20m long x 34.3m
wide x 2.7m high and the weights varied between
150t and 405t.
Using the strand jacks, the deck sections were lifted
and welded into position. Then the travellers moved
20m forward (the typical length of each section) for
the following deck section lifting manoeuvre.
Transport and lifting of the cabled sections -
equipment and operations
The lifting operations took place at the quay of
Cabezuela in Puerto Real, Cádiz. In order to lift the
deck sections, ALE designed four lifting travellers (two
per main pier) which were placed on the 52m-long
deck section that was previously installed, as this is
the minimum required length to install the lifting
trolleys.
Figure 3: Installation of travellers
These were moved by skidding along rail beams,
which were previously launched using two 500t
capacity skid shoes located on the central frame and
through the bogies (working at the back frame), into
position.
Figure 2: Traveller
Each lifting traveller comprises two longitudinal steel
lattices measuring 50m, which were transversely
separated one from the other by 20m. The traveller
was supported longitudinally onto the deck section in
its first 20m, leaving 30m of cantilevered lattice.
The rear support, working under tension, connected
to the bridge through pre-tensioned bars, whereas
the front part was working primarily in bending.
Note that the final deck section included a top precast
concrete slab. However, two different lifts were
performed at every stage: the first one for the steel
part of the section and the second one for the
concrete slabs.
The first lift was critical in terms of maximum weight
to lift, whereas the second one was critical in terms of
maximum overturning moment for the traveller.
Over these cantilever sections two transverse trolleys
were installed, including two 200t strand jacks each,
moved by means of a skidding system of 150t
capacity, which comprised flat skid beams and push -
pull units.
The trolleys allowed for both adjustment for the
location of the lifting units to the centre of gravity of
each section and adjusting the final location of the
section before welding the bridge.
3/2018
Figure 4: Lifting of a section