e-mosty December 2017 MSS and Formwork Travellers | Page 16

2.5.1.2 Design requirements for the MSS
construction joints, instead of 1/5 th , considering the
concreting span of at 63 m, 58.5 m and finally 54 m.
The initial design of the MSS was done considering
that the construction joint would be at 1/5 th of the
span, with 14 m cantilever ahead of the pier, and the
MSS should have a front support on the span pier and
a rear support over the cantilever, 63 m behind
(Figure 18).
These calculations were done taking into
consideration the reduction of the MSS length and
self-weight as well as corresponding reactions.
After a global cost analysis for pre-stressing +
concrete + MSS final cost, the client finally decided to
use 1/4 th of the span joints and it was achieved a 9 m
shorter MSS with 54 m concreting span (Figure ), what
became a cheaper global solution to build the viaduct
shown in Figure 20.
The MSS was then designed with a total length of
148 m considering a concrete span of 63 m (Figure
18). This MSS configuration allowed it to perform
70 m span between concrete piers.
Meanwhile, the engineer who designed the bridge
performed some calculations using 1/4 th of the span
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Figure 18: MSS 148 m long with 63 m concreting span
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Figure 19: MSS 139 m long with 54 m concreting span
2.5.1.3 Relevance of the construction joint location
The global cost studies made for Viaduct do Engano
brought very important conclusions concerning the
interaction between the bridge design and the
construction equipment design for large span
viaducts.
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in the end, there was a total save of about 150.000 €
to the client.
A very important conclusion is that the location of the
construction joint may have a big impact on the final
bridge cost showing that it is worth giving it high
relevance during bridge design.
The gain of weight in the MSS steel girder was about
70 tones by lowering its concreting span and
consequently reduce the total length of 9 m, what
corresponded to around 300.000 €.
The increase in pre-stressing steel due to this solution
for the whole bridge was only half of that amount but
Figure 20: Overall view of the Engano Viaduct with the MSS at the last span
4/2017