A movable scaffolding system (MSS) is a special-purpose self-launching form used in

bridge A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, whi ...

construction, specifically

prestressed Prestressed concrete is a form of concrete used in construction. It is substantially prestressed ( compressed) during production, in a manner that strengthens it against tensile forces which will exist when in service. Post-tensioned concreted is ...

concrete bridge Concrete bridges are a type of bridge, constructed out of concrete. They started to appear widely in the early 20th century. History file:First concrete bridge in Britain.jpg, Homersfield Bridge, England, cast iron reinforced, constructed 1869 ...

s with segments or spans that are cast in place. The movable scaffolding system is used to support a form while the concrete is cured; once the segment is complete, the scaffold and forms are moved to the end of the new segment and another segment is poured. While superficially similar, movable scaffolding systems should not be confused with

launching gantry A launching gantry (also called bridge building crane, and bridge-building machine) is a special-purpose mobile gantry crane used in bridge construction, specifically segmental bridges that use precast box girder bridge segments or precast girders ...

machines, which also are used in

segmental bridge A segmental bridge is a bridge built in short sections (called segments), i.e., one piece at a time, as opposed to traditional methods that build a bridge in very large sections. The bridge is made of concrete that is either cast-in-place (constr ...

construction. Both feature long girders spanning multiple bridge spans which move with and temporarily support the work, but launching gantry machines are used to lift and support precast bridge segments and bridge girders, while movable scaffolding systems are used for cast-in-place construction.

Operation and design

An MSS is generally used instead of a launching gantry to minimize the number of joints, since the cast in place segments typically are longer than precast segments. Once several bridge piers are complete, support brackets are attached to adjacent piers and the main parallel girders of the MSS are lifted in place to support the scaffold and concrete forms. Jacks are used to raise the girders and forms and the concrete is poured for the segment (or span) after

rebar Rebar (short for reinforcement bar or reinforcing bar), known when massed as reinforcing steel or steel reinforcement, is a tension device added to concrete to form ''reinforced concrete'' and reinforced masonry structures to strengthen and aid ...

is placed. After the concrete has cured and the tendons have been tensioned, the jacks are lowered and the MSS girders are launched to bridge the next span. This process is repeated until the bridge is complete. Both overhead (forms suspended from support girder(s) above the bridge deck level) and underslung (forms supported by support girder(s) below bridge deck level) MSS are available.

History

MSS construction was developed in the 1960s in Europe; the first bridge built with a MSS was the in Germany, completed in 1959. The first bridge constructed with a MSS in California was the

Long Beach International Gateway The Long Beach International Gateway, originally known as the Gerald Desmond Bridge Replacement, is a cable-stayed bridge that carries six lanes of Interstate 710 and a bicycle/pedestrian path in Long Beach, California, west across the Back Ch ...

Long Beach Long Beach is a coastal city in southeastern Los Angeles County, California, United States. It is the list of United States cities by population, 44th-most populous city in the United States, with a population of 451,307 as of 2022. A charter ci ...

that replaced the Gerald Desmond Bridge, completed in 2020.

References

External links

* {{cite web , url=https://www.bridgetech-world.com/blogs/the-bridge-club/movable-scaffolding-systems-mss-introduction , title=Introduction to Movable Scaffolding Systems (MSS) , author=Rosignoli, Marco , website=bridgetech World Civil engineering Construction equipment