Formwork

The purpose of the formwork is to generally realize with concrete but also with Pisé of the works to the definite forms. The formwork is a provisional, useful structure to maintain material in place, while waiting for its catch then its hardening

History

The principle of the formwork is already very old, the principal current techniques of placement of the concrete were already employed for the casting in place and the manufacture of blocks containing dried ground reinforced by vegetable fibers. Fault of mechanical resistance and means of lifting only the heavy panels were lacking. Later the use of allied lime to a mixture of sand, gravels and stones will make it possible to constitute a genuine concrete sometimes reinforced by fasten metal. The form wood was very early related to the cheap construction since the realization of walls per casting in this summary mould allowed the use of the most various materials, sometimes of recovery.

Since more than one century architecture knew a true innovation, and that unquestionably comes from materials and the techniques used. The appearance of the concrete and more particularly of the reinforced concrete made it possible architects such as Le Corbusier to revolutionize the world of construction by creating new spaces and new forms.

The mechanical properties of the concrete and its malleability in a fresh state gave place to new forms of constructions and constructive novel methods. At the time of its implementation, the concrete is in a pasty state, and, subjected to its actual weight, requires a mould to give him its form then to maintain it in place, until it reached its phase of autostability. The formwork constitute the essential tool of the placement of the concrete. The realization of a formwork, supply or the manufacture of this material, the casting of the concrete, the completions on which the quality of the formwork has a fundamental influence. All these elements take part for nearly sixty percent in the appreciation brought by the company of carcass work heavy castings in the construction of a work. This proportion illustrates well the fundamental importance of a formwork and its design in the saving in a process of construction.

The industry of civil engineering remains very active in the search for new processes, and the techniques evolve/move constantly. That made it possible to improve profitability by a reduction of unit times and implementation. As example, of beginning of the year 70, one thought that the method of construction of the floors using prédalles was most economic. The marketing of formwork boxes or modular made it possible economically to rehabilitate the floors run in place. The evolution of the material of formwork also relates to the taking into account of the safety of paid by the integration of protection collective (footbridges, railing, scales….)

Types of formwork

We will distinguish three principal types from formwork

  1. horizontal formwork (for the realization of floor) generally supported by a proping

  2. vertical formwork (for the realization of veils or posts)
  3. " moules" (for the realization of parts prefabricated)

The formwork differ according to materials and the techniques employed, we usually find:

  • Panels manuportables (skin of plywood formwork bakelized on metal framework)
  • Formwork paperboard (for the posts)
  • modular metal Forms ((standard NF-P-93-350))
  • Formwork out of plastics (panels manuportable)
  • traditional Formwork out of wooden of fir tree (small plank)
  • traditional Formwork out of plywood bakelized
  • Formwork resin and glass fiber
  • Formworks sacrifice (Prédalles vats steel .....)
  • Formwork " outil" metal (special manufacture)
  • architectonic Skins

Choice of the formwork

The elements has to take into accounts for the choice of a type of formwork are:

  • Economic: Compromise durability/damping

  • the adaptation to the forms envisaged and the modularity
  • the simplicity of implementation and adjustment
  • the availability in the company or on the market of the hiring
  • the weight of the formwork, requiring or not means of lifting
  • the safety of paid at the time of the phases of formwork, reinforcements and concretings
  • the facing have to obtain (concrete rough, neat, coating, lasuré, architectonic.)
  • possible specifications of the contract

Points has to supervise at the time of the formwork

  • Stability: and in particular the wind-bracing

  • deformations due to pushed concrete
  • Quality of the facings: reduction of the arrows, bullage limited, sealing (little escape of milt)
  • Adjustment: horizontality and verticality
  • Safety Protection, footbridge of service, scales, railing

Case of the formwork great height

For the realization of constructions great height (piles of bridge, silos, chimneys, antennas, turns…) it will be implemented of the specific techniques such as for example:

  • climbing formwork

  • car-climbing formwork
  • formwork semi-grampants
  • slip formworks

Casing vertical panels

Definition (standard NF-P-93-350) : “ the casing vertical panels or form are formwork tools which, coupled face to face, make it possible to carry out walls.

They are often inserted in a train of forms during the cycles of construction, and can be equipped with spillplates, under rise and extensions. A cycle is a complete series of operations and situations following one another in a pre-determined sequence, which renews in a indentic way. They constitute a work station and must as a tool car-ensure the safety of the people. ”

See too

Bonds Internet

  • PERISHED current - the magazine of formwork and propings

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