Falsework
Encyclopedia
Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
to support spanning or arched structures in order to hold the component in place until its construction is sufficiently advanced to support itself. Falsework also includes temporary support structures for formwork
Formwork
Formwork is the term given to either temporary or permanent molds into which concrete or similar materials are poured. In the context of concrete construction, the falsework supports the shuttering moulds.-Formwork and concrete form types:...
used to mould concrete to form a desired shape and scaffolding
Scaffolding
Scaffolding is a temporary structure used to support people and material in the construction or repair of buildings and other large structures. It is usually a modular system of metal pipes or tubes, although it can be from other materials...
to give workers access to the structure being constructed.
BS 5975:1982 (British code of practice for falsework) defines falsework as: Any temporary structure used to support a permanent structure while it is not self-supporting.
History
Timber
Timber may refer to:* Timber, a term common in the United Kingdom and Australia for wood materials * Timber, Oregon, an unincorporated community in the U.S...
. To compensate for timber shortages in different regions and to rationalize labor and material usage, new systems were developed.
The major developments include the design of connection devices (coupler), transitions to other spanning beams such as steel pipes or profiles or reusable timber beams, and adjustable steel props. In 1935 W.A. de Vigier designed an adjustable steel prop which revolutionized many aspects of the construction industry including to support slab formwork, wall formwork, trench sheeting and falsework.
During the same period many different scaffolding systems were being developed around the world. These consisted of welded frames that could be slotted or clipped together to form access or support towers. The reduction in construction time and complexity led to reduced labor costs and required less skill in assembly.
Further developments have made scaffolding
Scaffolding
Scaffolding is a temporary structure used to support people and material in the construction or repair of buildings and other large structures. It is usually a modular system of metal pipes or tubes, although it can be from other materials...
systems even easier to use. Stronger systems have been introduced that either incorporate horizontal restraints (via lacers, ties, or braces) at more levels or use stronger tubes or connections. Materials from which falsework systems are manufactured have also diversified from traditional steel and timber to aluminum components.
In the UK, BS 5975 gives recommendations for the design and use of falsework on construction sites. It was first introduced by the British Standards Institute in March 1982 and was then revised in March 1996. The code is currently under revision again, a draft copy was released in late 2007, and the new version of the code is expected in the summer of 2008. The new revisions bring the code up to date with methodology developed in the new CDM 2007 regulations and also the requirements of the new European codes EN 12811-1:2003 Temporary works equipment - Part 1: Scaffolds, and EN 12812:2004, Falsework - Performance requirements and general design.
In modern roadway construction
- Fabrication: Metalworkers fabricate a falsework section from pipe and beams.
- Erection: A section is lifted to a vertical position with the assistance of two forklift operators.
- Placement: The section is guided in to position by a ground crew.
- Completed Falsework: Decking and some formswork has been added.
Here we see the use of modern pipe-column falsework, this to support the formswork for a post-tensioned reinforced concrete flyover connector for the Eastern span replacement of the San Francisco-Oakland Bay Bridge
Eastern span replacement of the San Francisco-Oakland Bay Bridge
The eastern span replacement of the San Francisco – Oakland Bay Bridge has been under construction since 2002. Originally scheduled to open in 2007, it is now scheduled to open to traffic in 2013 at an estimated cost of $6.3 billion....
. When the supports are complete, wood beams and plywood or reusable metal forms will be placed, reinforcing and tenon conduits added, and concrete poured. After curing and any tenon tensioning, wedges will be removed and forms and falsework disassembled.