The optimal use of any bridge construction equipment requires a close cooperation between the bridge designers and the equipment suppliers as happened in the bridge shown in Figure 8 .
Pier supports for underslung MSS are sometimes complex due to the piers shape .
In Figure 6 - right - the pier is a single column and the piers supports are made of two brackets that can transfer horizontal loads from side to side through the pier compensating each other .
In Figure 8 the pier is made of 2 different piles and a more complicated solution to hold the brackets was necessary because the pile-piers cannot resist horizontal actions . Supplementary horizontal connections had to be used to connect both piles equilibrating horizontal loads from both pier supports .
Almost everything can have an engineering solution , but in bridge construction the simplest solutions are the cheapest and faster to use . Therefore , it is very important in the preliminary work to optimize the superstructure design regarding the construction equipment .
Underslung MSS apparently look easier to use but their efficiency depends a lot on the design of the abutments and of the piers so that the machines can be used in all bridge spans and can be fully assembled on the first span .
Complex pier supports such as shown in Figure 8 take a lot of work and time to install increasing the bridge cost .
2.3 Overhead MSS
Some construction companies started using main girders of beam launchers to launch and support formworks for casting decks “ in situ ” using flexible suspensions such as dywidag bars . These were the first overhead MSS .
This preliminary use of existing launchers as Main Girders for MSS , also created the common mistake of calling LG – Launching Girders as Movable Scaffolding Systems - MSS .
As we can see in Figure 9 , using dywidag bars as main suspensions implicates that they had to be placed vertically , which has serious limitations on the suspended formwork design and its continuous adjustment when building viaducts with large longitudinal and transversal slopes changing along the length of the viaduct .
2.4 Evolution of AP MSS
AP Bridge Construction Systems started designing and supplying MSS in 1993 / 1994 with specific equipment designed for motorway bridges in Portugal . The first two were made for A4 motorway ( Porto – Amarante ).
One of those two and another three similar new ones were used for Vasco da Gama bridge construction in Lisbon ( 1995-1996 ). Vasco da Gama ’ s South Viaduct had 88 spans of 45 m with cast in situ decks .
Their weight was about 250 kN / m and as it is shown in Figure 10 the required distance between MSS supports was 46 m due to the bridge expansion joints concreting 54 m at once , 45 m between piers plus 9 m of cantilever ahead of front pier .
Figure 9 : Launcher with suspended formwork using individual modules and dywidag bars as suspensions
4 / 2017
Figure 10 : Vasco da Gama Bridge – rear support location at construction joint