Movable Scaffolding System MSS
Content:
1. General
The STRUKTURAS MSS system is a modern Movable Scaffolding System used for cast in situ bridge and viaduct decks.?
The STRUKTURAS founder engineer Tore Gjolme is a pioneer in the field, with a history dating back to the creation of the first MSS in 1971. Constant engineering succession tradition raised a few generations of engineers filled with wisdom of the founder and supplementation of up to date digital tools.
STRUKTURAS engineering team is committed to quality and safety in every aspect of the working environment, because quality builds trust - trust builds business.
Hundreds of successfully executed projects globally showcase STRUKTURAS leadership and adaptability.
The STRUKTURAS MSS comes in underslung and overhead versions, which can be self-launching or not.
2. Underslung MSS system
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 by 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.?
STRUKTURAS MSS not only an intelligent and optimized engineering solution, but also competitive economically, because we estimate only as much as needed, not less, not more.
Main components?
Each underslung MSS normally consists of: a resistant steel structure, supporting brackets, suspension gallows, a set of working platforms and ladders, internal and external formwork, high resistance threaded bars, bolts, pin bolts and hydraulic systems that allow the MSS to be launched and formwork to be opened and closed, as well as making the necessary geometric adjustments. The MSS noses are hinged in relation to the main girders, making it possible to adjust to relatively small, fixed or variable plan view curvature radius.
Main components:
Underslung TT Deck Section MSS
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.
Main components
The main components of the underslung MSS solution adapted for double T sections are identical to the solution used for deck box sections, except in terms of the internal formwork, which is launched from one span to the next along with the MSS main structure. The transverse beams in this kind of MSS are normally equipped with a hinge so that they can partially rotate, making it easier to pass through the columns, which is not the common solution used in deck box sections.?
Main components:
Launching device?
Launching wagon?
The underslung MSS is equipped with three pairs of launching wagons with hydraulic jacks and teflon plates, 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 to reduce friction during MSS launching whenever this is necessary to ensure the stability of the columns.
Underslung self-launching MSS
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, which 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, making it possible for rebar assembly work to continue while the supporting brackets are being relocated.
Main components:
Underslung self-launching MSS is equipped with only two pairs of supporting brackets, instead of the three pairs used in current versions. The rear launching support makes it possible to keep the MSS rear suspended during concreting and launching until the center of gravity (COG) is positioned in front of the front column, ensuring the safety of the launching.
The underslung self-launching MSS solution is particularly suitable for the construction of decks located over water or 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 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.
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, which goes into a blockout 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 blockouts 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.
3. Overhead 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 where local conditions are more favourable to one or the other.
Main components (longitudinal view):
Overhead MSS normally has the advantage of being able to be assembled and dismantled behind the abutments, at an elevation close to ground level.?
The overhead MSS solution is normally equipped with a rebar cage transport system that includes electric winches and rails.
Overhead MSS typically consists of a resistant structure supported by the columns, from where the formwork is suspended. The resistant structure normally includes two main I-beams, a set of transverse beams and the noses and supports.?
When the solution is used for concreting box section decks, the internal formwork is identical to the internal formwork used in underslung MSS.
Main components (cross section):
Overhead Movable scaffolding System MSS
The main structure in overhead movable scaffolding may sometimes be made up of a single main girder aligned with the deck axis, instead of having a pair of main I-beams.?
In this case, overhead MSS only includes two noses, one front and one rear.
Main components:
Self-launching overhead MSS
The overhead MSS system can also be supplied in the self-launching version, which 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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4. Formwork
Internal formwork box section deck
The internal formwork in STRUKTURAS MSS is the same both for overhead MSS and underslung?MSS.
Main advantages:?
Important:?
In order to use the STRUKTURAS internal formwork system, it is necessary:?
Internal formwork transport trolley
The internal formwork transport trolley developed by STRUKTURAS is a simple solution that not only allows the panels to be transported effectively to the next span, but also assembles them in their final position, without the need to use cranes.
The transport trolley is equipped with motors and hydraulic jacks that allow it to carry out the different tasks it was designed for.
Internal formwork transport kinematics:
External formwork and cambering adjustment system
The panels in the external bottom formwork are made from a steel structure including U-profiles spaced in accordance with the capacity of the 21 mm plywood. Normally, the U-profiles are perforated to allow a wooden slat to be assembled next to them and thus facilitate the attachment of the plywood.
A set of adjustable screw jacks connecting the formwork to the transverse beams forms the cambering adjustment system, allowing the formwork to be adjusted to the deck transverse slope and compensating for the MSS deformations.
The web and wing external formwork is connected to the bottom formwork by bolts; it is also supported by adjustable struts that help keep the formwork steady and carry out the necessary adjustments.
Internal formwork TT section deck
The MSS internal formwork for TT-section decks is a foldable formwork connected to the bottom formwork by bolts, allowing it to be transported from one span to the next along with the MSS.?
In order to fold the underslung MSS internal formwork, the transverse beams are also folded, making it possible for the entire assembly to pass through the columns.?
A similar internal formwork solution is used at the overhead MSS.
Internal formwork folding kinematics:
The internal formwork is closed by reversing the opening sequence.??
5. Rebar transport and assembling
The use of electric winches on overhead MSS makes it possible to transport pre-assembled rebar cages, reducing crane usage time.?
The current pre-assembled rebar cage transport solution for underslung MSS normally uses cranes.
Rebar transport devices?
STRUKTURAS offers solutions for pre-assembled rebar transport from simple panels to the transport of the rebar cage full span.?
A tailor-made solution can be designed for each project.
6. Typical cycle
The formwork solutions specifically developed by STRUKTURAS for its MSS make it possible to optimise the relocation of MSS to the next span, leading to the execution of optimal cycles. Currently, the cycle duration varies between one and two weeks, depending on the complexity and size of the deck.
7. Project gallery
8. Safety and quality
More than 50 years of our experience in designing and supplying bridgebuilding equipment are leveraged by our commitment to keep focused on the high quality, simplicity and safety which results our solutions.?
A proper set of work platforms and ladders provides operators with safe access in carrying out all everyday tasks during span by span construction cycle.
The MSS steel structure is produced in CE-certified steel workshops. High risk components such as hydraulic systems, threaded bars and express rollers are manufactured by the world’s best and credible suppliers.
?9. Services
Our integrated services that ensures full Quality Control and Quality Assurance during all project cycle:
Equipment assembling, operation and dismantling
A professional team at your service.?
STRUKTURAS has teams specializing in planning, assembly, operation and dismantling of its MSS, allowing it to offer its clients turnkey solutions.?
By using our teams we are able to reduce costs for the client, given that this minimizes the use of auxiliary support equipment, such as cranes, forklifts, platforms, trucks, support towers, etc.
If you have any request, please do not hesitate to contact us:
Design Engineer
7 个月Insightful !!
Bridge Building Equipment at STRUKTURAS
1 年We develop MSS more than 50 years! I recommend this article to all bridge builders and designers to better understand versatility and productivity of MSS ??