e-mosty December 2017 MSS and Formwork Travellers | Page 11

 Radio control for all motion operations.
 Transformability to become a launcher of pre-
fabricated decks or pre-fabricated beams.
 In this bridge the innovations already used in A4
Motorway were: Capacity of hanging prefabricated deck segments
using span by span method.
 Minimal storing space when disassembled.
  Easy transportation overseas – all parts are
designed to be packed inside normal 40 feet
containers.
This case showed that the same MSS could be used
for longer continuous spans by placing the rear
support over the cantilever of previous span and the
front support on front pier. This way the total span,
between piers, could be 54 m.

Hanging from the main girder the pre-assembled
rebar beams during launching.
Having the front nose extended over the next pier
to allow the assembly of next support from the
nose.
The first innovation represented a gain of one/two
days compared to assembling the rebar beams in situ.
The second innovation removed the assembly of the
front support from the critical path by using the MSS
nose as a crane while other tasks were being done.
Until then the assembly of the front support was done
by using extra cranes and trucks or boats. In long
bridges such as Vasco da Gama these innovations
made possible an average construction cycle of one
week. Some spans were even done in five working
days.
In 2004, adding more capacities to the overhead MSS,
a new concept was presented gathering the following
principles:
 Maximum security.
 Capacity of unloading the trucks that feed the
materials to the MSS (rebar + pre-stressing
cables).
 Capacity of carrying the rebar and the pre-
stressing cables when launching.
 Full autonomy for assembling and disassembling
their own supports.
 Easy adaptation for different spans or girder
weights.
 Easy suspension of different shapes of formwork.
 Reversibility for parallel viaducts – i.e. the capacity
of building one side of the bridge in one direction
and coming back doing the other side in the
opposite direction.
 Minimal man power.
 Maximum of automation of all main tasks.
4/2017
The inclusion of so many features, when designing
these MSS, was done to give them have all the skills
required to optimize the costs for the first and
subsequent jobs, enabling the owners of such
machines to have more adaptable and versatile
machines and not one-job-only machine.
Obviously, the price of such overhead MSS, including
so many extra skills, may become a bit more
expensive for the first bridge than simpler MSS, but
that will be balanced because this MSS can be easily
reused in the following bridges, bringing larger savings
in the future.
The main goal of any construction company, when
choosing a MSS, is to find one autonomous MSS that
won’t bring expensive surprises such as needing extra
cranes, trucks or boats as well as the need of building
access roads in order that the MSS can work properly.
Often some inexperienced site engineers only look to
the initial price of the machine itself, disregarding the
necessary extra equipments and auxiliary works that
the chosen MSS will necessarily require. Once a wrong
choice has been taken there is no much left to the
constructor than to pay the extra bills.
A common extra cost arises when using a short nose
MSS supported on segments previously built by the
contractor over the piers to allow the MSS to use
simple slab supports over them, instead of steel
structures directly over the pier.
These preliminary segments are very expensive as
th ey require extra equipments to build them and it is
an obvious extra cost for a client that has bought a
machine that should have the formwork required for
the full length of the deck, and finally must pay for
extra equipments to build the segments over the
piers, what it is obviously a duplication of costs.