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

bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...

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 i ...

concrete bridge Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...

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 beam launcher, girder launcher, bridge building crane, and bridge-building machine, locally nicknamed the "Iron Monster") is a special-purpose mobile gantry crane used in bridge construction, specifically segmental ...

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 (constru ...

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 Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and maneuvered into place; examples include precast beam ...

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 reinforcing bar), known when massed as reinforcing steel or reinforcement steel, is a steel bar used as a Tension (physics), tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concr ...

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 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 Channel to Terminal Island. The bridge replaced the Gerald Desmond ...

Long Beach Long Beach is a city in Los Angeles County, California. It is the 42nd-most populous city in the United States, with a population of 466,742 as of 2020. A charter city, Long Beach is the seventh-most populous city in California. Incorporate ...

that replaced the

Gerald Desmond Bridge The 1968 Gerald Desmond Bridge was a through arch bridge that carried five lanes of Ocean Boulevard from Interstate 710 in Long Beach, California, west across the Back Channel to Terminal Island. The bridge was named after Gerald Desmond, a prom ...

, 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