The construction of structures with a height of more than 25 m using sliding formwork is the most technologically complex process in construction. This type of construction is used for the construction of monolithic and prefabricated monolithic high-rise buildings, mainly industrial purposes. At the same time, the formwork system covers the entire constructed structure and rises up with jacks as concrete is carried out.
Pros and cons of sliding systems
The most promising and economically profitablely gliding formwork is used in construction to arrange a stiff nucleus for shafts of elevators, stairwells, wells for communications, as well as the construction of high chimneys, for various purposes for various purposes. For the construction of residential buildings with a large number of window and doorways, ceilings, embedded parts, such formwork is not recommended for such formwork.
Such restrictions are associated with both positive and negative aspects of its application:
The pluses include a high pace and a decrease in the cost of construction, the absence of joints, the function of overhauling the same kit for various architectural and planning solutions;
The disadvantages of the process of building ceilings and openings are ranked to the disadvantages, some “seasonality” associated with increasing the cost of work in winter, strict requirements for clear observance of process technology.
Technologically, the process of using sliding formwork requires high quality concrete, strict compliance with the work schedule and attract only highly qualified specialists for its implementation.
Using sliding formwork
But as a result of the use of this type of monolithic construction, the buildings receive better sound insulation, increased thermal and seismic -resistant properties, the range of architectural and planning solutions is expanding, for example, the creation of cone -shaped or hyperboloid structures.
Technology of the sliding method of monolithic construction
The main elements of the sliding system:
internal and outer unchanging structures of various sizes;
jack frames and rods;
suspended stage;
jacks or hydraulic systems;
connecting elements.
The shields are surrounded on all sides by the formwork beams that serve to ensure their immutability. The main load -bearing elements of the system are jack frames on which formwork shields are installed.
Shields experience all the pressure of the poured concrete. The stage are installed on the jack frames themselves, which take on the load of the working platform. The formwork jacks mounted on the jack frames, leaning on the rods freely raise the entire structure.
Important! The rods should have a load -bearing load by an order of magnitude larger than the acting on them.
The jacks use various designs:
manual,
hydraulic
Electric.
As a result of using a manual jack, its rods remain inside the structure and serve for reinforcement. In other types of jacks, the rods are not in contact with concrete and removed from the system after the end of work.
The technology of sliding formwork is based on phased, but continuous concreting.
The main stages of the installation of formwork and concreting:
installation of internal shields on the cone, then using spacers of external shields;
mounting jack frames taking into account the fact that the step depends on the free length of the wall, the carrying capacity of the jack;
Scientifics are hung on the brackets;
Before concreting, the jacks are charged with rods from 1 to 1/3 of the calculated length;
With concrete, up to ½ of the shield is filled with concrete, but not more than 70 cm, layers are laid with a thickness of ≈30cm;
concrete seal using vibrators or manually;
After grasping the concrete, the form rises by the jacks by ≈25 mm in one pass;
Each next layer of concrete mixture is poured only after the full laying of the previous one;
Further, after the full filling of the form, the calculated lifting speed is gradually achieved.
Important! In parallel, concreting is carried out reinforcing, leveling defects on a finished, but not yet completely frozen, concrete surface.
The sliding formwork method allows you to build a structure up to 4 m high per day and involves a round -the -clock mode of operation. The speed of rise depends on the time of setting the concrete layer, which should be determined in the laboratory conditions.
Creation technology
The height of the layers of concrete, in addition to the brand used, depends on:
the values of the calculated pressure on the shields;
the possibility of creating uniformity of the layer;
compliance with the condition of the without no effort of the constructed design.
For the possibility of creating interruptions in concreting, additives are introduced into the mixture, which slow down hardening. In the winter, on the contrary, to accelerate solidification, other additives and “warm” concreting can be used: use systems with electrical and infrared heating. To facilitate the process of leveling and sealing, plasticizing additives are used.
Technology for creating curved structures
A variety of sliding formwork, which allows you to build monolithic curved structures, is a horizontal-spelling formwork. The design of such a formwork makes it possible to have a highlighting concreting, due to the movement of the shields along the axis of the wall. The axial movement allows you to set a different slope of the surfaces that will turn out during concreting.
The component parts of horizontal-slipping formwork:
shields;
movement mechanism (two carts, beams);
tough frame with racks.
Moving mechanism and frame together make up a spatial frame. The horizontal system moves along the concrete wall along the rails or an electric ice if it is self -propelled, or using a mechanical drive with a non -self -propelled option. Concreting with a horizontally sliding method makes it possible to build buildings with a height of not more than 6 m and provides speed of 6-8 m/h.