Strukturas MSS
Movable Scaffolding System - MSS
The Strukturas MSS system is a modern movable scaffolding system used for cast in-place bridges and viaducts decks.
Engineer Tore Gjolme, who founded Strukturas in 1991, developed the MSS concept while working as an engineer for Olav Opedal AS, a company in the AKER group that specializes in mechanical engineering. The first MSS developed in this way was used by the company in Norway in 1971.
The idea of movable scaffolding arose after the use of prestressed technology became generalized and Strukturas has contributed
greatly to its development over the last 30 years.
The Strukturas movable scaffolding system (MSS) comes in underslung and overhead versions, which can be self-launching or not.
Underslung MSS Deck box section
The Underslung MSS solution is currently used in the construction of the decks on road and railway bridges and viaducts, with spans normally varying between 20 m and 70 m.
Concreting each box section span using Underslung MSS can be done in one or more stages, depending on the deck design.
The versatility of the Underslung MSS solution makes it possible to be used on decks with a variable plan view radius and up to minimum of 250 m to 300 m.
The search for simple yet effective solutions has guided the work done by Strukturas over its many years in existence
Underslung MSS Deck TT section
The Underslung MSS is also used to concrete deck TT sections, in which case concreting spans of around 45 m in length is commonplace.
When using this type of solution, the internal formwork is transported together with the main MSS structure and this is opened and closed by a specific hydraulic system.
To allow the MSS two halves to pass through the columns, minimizing their transverse side shift and consequently the length of the supporting brackets, the transverse beams of the MSS joining the main girders are foldable.
The underslung MSS can be easily adapted to different deck sections and different span lengths, as well as to variable curvature radius, both vertical and horizontal.
Underslung self-launching MSS
The underslung self-launching MSS solution is particularly suitable for the construction of decks located over water. Moreover they are suitable when the columns are very high, making it difficult, if not impossible, to use mobile cranes positioned at ground level.
Because the supporting brackets are moved suspended from the main girders and the front noses, this MSS solution is harder to use when the plan radius of curvature is small. This is because it requires the introduction of an angle between the main girders and the front noses, making it difficult for the transport bogie to pass.
Launching wagon
The underslung MSS is equipped with three pairs of launching wagons with hydraulic jacks and Teflon plates. It is also designed to carry out the opening and closing of the two MSS halves and for its longitudinal movement.
Apart from the current solution using Teflon plates in the launching wagons, Strukturas also has solutions using express rollers or wheels. They are used to reduce friction during MSS launching whenever this is necessary to ensure the stability of the columns.
In the current versions of underslung MSS, mobile cranes are used to relocate the supporting brackets on the columns in the different spans.
With the MSS self-launching version, cranes are not needed for relocating the supporting brackets. Because the MSS is equipped with a specific device for carrying out this operation.
The supporting brackets are suspended from a transport bogie. It moves them along the main girders and the noses with the aid of electric winches included in the system.
The front nose is long enough to rest on the next column, while the back nose is short.
During relocation of the supporting brackets, the main girders rest on the front column through a temporary support. It is making it possible for rebar assembly work to continue while the supporting brackets are being relocated.
Main support:
Underslung MSS normally transmits its front reactions to the columns through the supporting brackets.
The supporting brackets are equipped with a steel corbel on their lower extremities. They go into a block-out left in the columns. To ensure the stability of the pair of brackets, these are connected to each other by prestressed threaded bars, pushing them against the column.
Whenever block-outs cannot be left in the columns, alternative solutions working by friction are used. Suspending the brackets from the column or transmitting the reactions to the foundations through struts.
The rear reactions are transmitted to the tip of the deck concreted in the previous stage, through a suspension gallows.
Overhead movable scaffolding system (MSS)
Overhead MSS is another movable scaffolding system solution that is also suitable for concreting box or double T deck sections.
Both MSS solutions are similar. But one solution can have advantage over the other in some situations. For example where local conditions are more favorable to one or the other.
Self-launching overhead MSS
The overhead MSS system can also be supplied in the self-launching version. It means that the actual MSS can relocate its supports on the columns of the next span without the need to use a crane.
Main support:
The MSS main supports are designed in each case to adjust to the geometry of the columns. In each project and the way the reactions should be transmitted to the concrete.
Strukturas has extensive experience in designing different support configurations for overhead MSS.
The most common support solution consists of assembling support legs directly on the column. In which case the legs are connected to the concrete using embedded anchors.
Other solutions less frequently used have profiles passing through the column walls, collar friction or even precast concrete legs which become lost inside the deck structure.
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If you wish to see more detailed and visual information about the Strukturas movable scaffolding systems (MSS) – you can download the full catalogs on the link below: