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Figure
4 : Example of primitive underslung MSS based on movable formwork tables system
2.2 Evolution of underslung MSS
The underslung MSS first evolved in the way that all parts of the outer form are carried by the supporting girders ( Main Girders - MG ) and are assembled in 2 longitudinal blocks - one left and one right - with the full length of the span rigidly fixed to the MG ( Figure 5 ).
These 2 blocks can be folded together with bracing elements and shifted outwards to allow the 2 MG to pass outside of the piers .
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The normal underslung MSS were very dependent on auxiliary cranes , telescopic platforms and trucks for installing the pier supports and the rebar . This dependence can significantly increase the cost of using those machines .
Therefore , when estimating the global cost of using these MSS it is necessary to consider the costs of using auxiliary trucks , cranes and telescopic platforms as well as the construction of supplementary roads to access the piers and some ground platforms under the MSS or around the piers .
Over water or in high bridges , this dependence and corresponding costs penalize and normally exclude those dependent MSS .
Commonly these extra options are not included in initial prices and can be supplied later as extra costs , being very annoying expensive surprises for the client .
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← Figure 5 : Underslung MSS schematic drawings with folded inside form and its respective movement towards the supporting brackets
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↑ Figure 6 : Underslung MSS – with foldable inside form and MG over supporting brackets
4 / 2017