e-mosty December 2017 MSS and Formwork Travellers | Page 13

This MSS model - AP - 2005 was used in:






Vila Pouca de Aguiar Viaduct (2016), Portugal –
Main contractor: Spie Batignolles Europe – a
motorway bridge with 60 m span between piers
Toxa Viaduct (2009), Spain – Main contractor:
U.T.E. Tecnosa + Sisocia + Cyopsa + extraco – high
speed railway bridges with 55 m span between
piers
Martixe Viaduct (2009), Spain – Main contractor:
U.T.E. Tecnosa + Sisocia + Cyopsa + extraco –
high speed railway bridges with 55 m span
between piers
Del Sar Viaduct (2011), Spain – Main contractor: –
Ferrovial S.A. – high speed railway bridges with
55 m span between piers
Esla Viaduct (2011), Spain – high speed railway
bridges with 55 m span between piers
V3 Viaduct (Venta de Baños) (2015), Spain – Main
contractor: Ferrovial S.A. – high speed railway
bridges with 55 m span between piers
On those viaducts MSS was supporting 280 kN/m of
concrete weight plus 60 kN/m of formwork weight,
with its supports 54 m apart (concreting span). All
those models could easily fly over 63 m distances
between piers (flying span).
After building bridges for the Spanish High-Speed
Train Line with 55 m span between deck piers but
with 54 m concreting span another challenge was
arriving – overcoming the mythic frontier of casting
70 m span in one stage.
2.5 MSS Design criteria for large spans
MSS must be designed to sustain the formwork and
the concrete load during pouring and must be able to
launch itself for the consecutive decks.
The capacity of a MSS is measured by:
 The admissible live load during pouring (but
including self-weight of the MSS and its form)
 The distance between concreting supports of
the MSS – concreting span
 The distance between launching supports of the
MSS – flying span
Although it could appear that the concreting span
would be the worst load combination case for a large
span MSS, in fact all launching stages can bring more
important stresses to the MSS structure and become
determinant for its design.
4/2017
In large spans, due to the reactions over central MSS
supports, the lower chords achieve very high shear
stresses during launching therefore MSS resistance
depends a lot on the flying span and the carried loads.
With the AP standard MSS, it is possible to build decks
with 80 m span between deck piers, if the construction
joint is at 1/4 th of the span (20 m) and the rear support is
placed 63 m behind the front pier (Figure 13: below -
Launching).
80.000
60.000 20.000
45.000
60.000 20.000
CONCRETING
63.000
80.000
17.000
LAUNCHING
Figure 13: Concreting and launching 80 m span viaduct
Any experienced MSS supplier can design one MSS for
very large spans (80 m -120 m, for ex.), the main
problem is not to design it, but to make a machine that
can be reused (if it is not possible to have it paid by
that project).
The bridge design engineers must be aware that the
state of the art of MSS engineering can provide them
any tool they may wish for designing multi-span large
bridges with larger spans that they are doing for the
moment.
In Spain this MSS model - AP2005 brought to the high-
speed railway bridge engineers more and more trust to
design their new bridges with larger and larger spans,
and they already are designing railway bridges with
68 m span between piers.