Technical Field

The present invention relates essentially to the construction industry, specifically to a method of production of flight of stairs, the main load-carrying structure of the stairs.

Background Art

For the construction of presently known flights of stairs, wood, metal, and reinforced concrete beams are used. In order to obtain the shape of reinforced concrete flight of stairs, wood formworks are used: wood planks, beams, particleboards, pressed paper. The shape of flights of stairs built out of profiled metal sheets may be straight- lined or angular but not streamlined because it is impossible to roll large profiled metal sheets. (SU1765327, 12.11.1990).

The main disadvantage of the presently known method of construction of reinforced concrete flight of stairs is that the assembling of formworks is time-consuming. Practically, it is impossible to produce the flights of stairs having graceful and streamlined shapes when using planks or wood fibreboard. If an arched three-dimensional flight of stairs was produced by means of wood form work, the external surface of the flight of stairs is angular; therefore, it is impossible to obtain a regular geometric shape. Smoothing out the shape irregularities of the arched three-dimensional flight of stairs produced by means of the wood formwork would result in very high labour and material costs. The load-carrying capacity of presently known reinforced concrete flights of stairs depends on the following two components: concrete and reinforcement; consequently, large-dimensional flights of stairs have a very large cross-section. When the flight of stairs has a very large cross-section and is very long, the whole structure appears very massive, its shape graceless; such flight of stairs transfers heavy loads to the base.

Summary of Invention The purpose of the present invention is to provide a technique for the production of the flight of stairs, the main load-carrying structure. Production of the flight of stairs by using inexpensive materials and at low labour costs. Reduction of the production and assembling time. Reduction of the cross-section and self-weight of the flight of stairs. At very low labour costs, production of flights of stairs having light, streamlined, graceful and regular geometrical and three-dimensional shapes. Increase the load carrying capacity of the flight of stairs without increasing its cross-section and self-weight. Application of the structure of flight of stairs for any purpose and in any complex and aggressive environments. Providing maximum durability of the flight of stairs.

The main characteristic of the present invention is that the frame of the flight of stairs, which consists of frame, treads, and landings, is built out of the following components: out of stay-in-place metal formworks; out of stay-in-place metal formworks including concrete; out of stay-in-place metal formworks including reinforcement and concrete; out of one external stay-in-place metal form work including reinforcement and concrete; out of external removable metal formworks including reinforcement and concrete; out of external removable and internal stay-in- place metal formworks including reinforcement and concrete; out of external and internal stay-in-place metal formworks including reinforcement and concrete; out of internal stay-in-place metal formworks including reinforcement and concrete.

For the production of the flight of stairs, formworks are used. For the production of the frame, removable metal formworks are assembled, reinforcement is placed, concrete mix is poured, and, after concrete has cured to a required strength, the said metal formworks are removed. For the production of the frame, removable and/or stay-in-place internal and/or external metal formworks are assembled, reinforcement is placed, concrete mix is poured, and, after concrete has cured to a required strength, the removable metal formworks are stripped, and stay-in-place internal and/or external metal formworks are left in place.

Brief Description of Drawings

A better understanding of the invention will result from the following description of the flight of stairs with reference to the following drawings:

Figure 1 (a-d). The flight of stairs, the frame of which is build out of stay-in- place metal formworks, without reinforcement and without concrete: a) - Perspective view; b) - Top view; c) - Side view; d) - Cross-section A

Figure 2 (a-d). The flight of stairs, the frame of which is build out of stay-in- place metal formworks, without reinforcement, including concrete: a) - Perspective view; b) - Top view; c) - Longitudinal section B; d) - Cross-section C

Figure 3 (a-d). The flight of stairs, the frame of which is build out of stay-in- place metal formworks, including reinforcement and concrete: a) - Perspective view; b) - Top view; c) - Longitudinal section E; d) -

Cross-section D

Figure 4 (a-d). The flight of stairs, the frame of which is build out of removable metal formworks, including reinforcement and concrete: a) - Perspective view; b) - Top view; c) - Longitudinal section G; d) - Cross-section F

Figure 5 (a-d). The flight of stairs, the frame of which is build out of removable metal formworks, one stay-in-place metal formwork, including reinforcement and concrete: a) - Perspective view; b) - Top view; c) - Longitudinal section I; d) - Cross-section H

Figure 6 (a-d). The flight of stairs, the frame of which is build out of external stay-in-place or removable metal formworks and internal stay-in-place metal formworks, including reinforcement and concrete: a) - Perspective view; b) - Top view; c) - Longitudinal section K; d) - Cross- section J.

Description of the Preferred Embodiments

Figure 1 (a-d) shows the flight of stairs, the frame of which is build out of stay- in-place metal formworks, without reinforcement and without concrete. For this structure, only stay-in-place metal formworks (1) are fabricated and assembled. Considering the purpose, length, and cross-section of the flight of stairs, the load- carrying capacity depends on only one component of load-carrying capacity: stay-in- place metal formworks (1). The structure of the flight of stairs shown in Figure 1 (a-d), compared to that of the flights of stairs shown in Figure 2 (a-d) - Figure 6 (a-d), is light and is used in the light construction buildings (light construction base and wall, wood floors).

Figure 2 (a-d) shows the flight of stairs, the frame of which is build out of stay- in-place metal formworks, without reinforcement, including concrete. Considering the purpose, length and cross-section of and other impacts on the structure, once metal formworks (1) have been assembled, concrete mix (2) of appropriate density, structure and class is poured on the whole flight of stairs. The load-carrying capacity of this structure depends on the following two components of load-carrying capacity: stay- in-place metal formworks (1) and concrete (2). This type of flight of stairs is often used when the flight of stairs is secured into walls of the staircase because this structure includes concrete (2) and, compared to the flight of stairs shown in Figure 1 (a-d), is more stable and has a higher load-carrying capacity. The flight of stairs shown in Figure 2 (a- d) mostly is used when the flight of stairs is secured into walls of the staircase. Figure 3(a-d) shows the flight of stairs, the frame of which is build out of stay-in-place metal formworks including reinforcement and concrete. The production and assembling of this structure, compared to that of the flights of stairs shown in Figure 1 (a-d) and Figure 2 (a-d), is more complicated. Once formworks (1) have been assembled, reinforcement (3) or metal bars (3) of appropriate properties and geometrical characteristics are embedded, depending on the purpose, length and cross-section of and loading and other impacts on the flights of stairs. Once the formworks (1) and reinforcements (3) of the flight of stairs have been assembled, concrete mix (2) of appropriate density, structure, and class is poured on the structure. The load- carrying capacity of this flight of stairs depends on the following three components of load-carrying capacity: stay-in-place metal formworks (1), reinforcement (3) and concrete (2). By the load-carrying capacity, this structure, compared to the conventional reinforced concrete flights of stairs, is stronger and it is used mostly for production of large-dimensional flights of stairs. This flight of stairs is mounted in space because it has sufficiently solid bearing and end points and is not dependant on the dimensions of the staircase. The shape of this type of flight of stairs is streamlined; this type of flight of stairs may be of any three-dimensional shape.

Figure 4 (a-d) shows the flight of stairs, the frame of which is build out of removable metal formworks including reinforcement and concrete. Concrete (2) and reinforcement (3) of the flight of stairs are prerequisite because the formworks (1) are stripped; thus, the metal formwork (1), as the third load-carrying component, does not act. The technique for production of this flight of stairs structure is the same as in the case of the flight of stairs shown in Fig. 3 (a-d). For the production of this flight of stairs, the formworks are used only for forming the shape of beams; these formworks are thin and have low class and geometrical characteristics because after complete curing of concrete (2), the metal formworks (1) are removed from the flight of stairs. The curing time of concrete mix (2) of the flight of stairs depends on the concrete (b) density, structure and class, and exposure class, if necessary. This flight of stairs structure is used mostly in the open space when the stairs are intended for use outdoors where it will affected directly by atmospheric factors (rain, sun, frost etc.).

Figure 5 (a-d) shows the flight of stairs, the frame of which is build out of removable metal formworks, one stay-in-place metal formwork including reinforcement and concrete. In order to obtain thin and streamlined shape, the inner or outside part of the flight of stairs is produced by means of removable formworks (1) and one stay-in- place stainless steel formwork of appropriate thickness and height, considering the purpose, length, and cross-section of the flight of stairs. The load-carrying capacity depends on three load-carrying capacity components; therefore, there is the same possibility to produce shapes of the flight of stairs (large dimensions, streamlined and light shape) and achieve the resistance against the direct impact of atmospheric factors (rain, sun, frost etc.).

Figure 6 (a-d) shows the flight of stairs, the frame of which is build out of external stay-in-place or removable metal formworks, internal stay-in-place metal formworks including reinforcement or without reinforcement, including concrete or without concrete. The technique for production of this flight of stairs structure is the same as in the case of the flights of stairs shown in Figure 1 (a-d) - Figure 5 (a-d). The flight of stairs has internal stay-in-place metal formworks (I ¹ ). The flight of stairs characterised in that, comprising external stay-in-place metals formworks, (1) and internal stay-in-place metal formworks (I ¹ ), it has a very high load-carrying capacity because the load-carrying capacity depends on the following four components: external stay-in-place metal formworks (1), internal stay-in-place metal formworks (I ¹ ), reinforcement (3) and concrete (2). This structure has the highest load-carrying capacity of all aforementioned flight of stairs structures. If the flight of stairs is intended for use outdoors under exposure to the atmospheric factors, the external metal formworks (1) are removed and internal metal formworks (I ¹ ) only are left at place. In order to increase the load-carrying capacity and produce a light and streamlined shape of the flight of stairs, the internal stay-in-place metal formworks (I ¹ ) are used, considering the purpose, length and loads and other impacts. If the flight of stairs will be exposed to the atmospheric factors, the internal metal formworks (I ¹ ) should be made of a corrosion-resistant metal and have appropriate geometrical characteristics and be of appropriate class depending on atmospheric impact. If the flight of stairs will be covered by waterproof treads, the internal stay-in-place metal formworks (I ¹ ) should be fabricated of a metal non-resistant to corrosion. The number and thickness of the internal stay-in-place metal formworks (I ¹ ) depends on the purpose, length and cross- section of and loading and other impacts on the flight of stairs. The length and of this flight of stairs and the form of the cross-section may vary.

Depending on the shape, purpose, length and cross-section of and loads and other impacts on the flight of stairs, the metal formworks are fabricated of a metal sheet 1 - 30 mm thick. The thickness of the sheet of metal formworks depends on a selected structure of flight of stairs. The geometrical characteristics and class of the metal formworks depends on the shape, purpose, length and cross-section of and loads and other impacts on the flight of stairs. The use of concrete and reinforcement for the flight of stairs is a prerequisite, if the metal formworks are to be removed and when there are no internal metal formworks. Depending on the shape, purpose, length and cross-section of and loads and other impacts on the flight of stairs, the use of reinforcement and concrete is not required if the metal formworks are produced.

The metal formworks for flights of stairs may be produced from the metal sheet either in the shop floor or at the site of assembling. As the metal sheet is rolled easily, metal elements of formworks may be fabricated of regular and streamlined or three- dimensional shape, at low labour costs. The technique for the assembling of metal formworks is very simple (Lego principle). Each element of the formwork bears a number from 1 to n; numbers carries out the assembling of elements consecutively. Internal stiffening metal strips and metal formworks are pressed against each other; depending on the shape of the beam, elements are connected by spot, continuous, or other weld seams. The principle of assembling of the beam is not declared: assembling may be performed from 1-n or n-1, depending on which option is more convenient. The assembling of the flight of stairs may be carried out from the first tread of from the last one, i.e. starting at the base of the flight of stairs or at the end of the flight of stairs. The assembling of metal formwork elements may without performed from 1-n or n-1 depending on the flight of stairs structure [Figure 1 (a-d) - Figure 6 (a-d)] connected by spot, continuous or other weld seams. Once the metal formworks have been assembled, depending on the structure [Figure 1 (a-d) - Figure 6 (a-d)], the flight of stairs is reinforced and concrete mix is poured. The finish of metal stay-in-place formworks (flights of stairs) is optional. By other technique, concrete is covered by metal cohesive materials, filler or plaster and painted by conventional paint (for wall of ceiling), or is daubed by a metal daub and painted by paint for metal. Once the metal formworks have been stripped, the flight of stairs is covered by filler or plaster and painted by an appropriate paint depending on exploitation conditions.