SU1717761A1 - Ferroconcrete structural member - Google Patents

Abstract

FIELD OF THE INVENTION The invention relates to construction, namely to long bearing elements. The purpose of the invention is to increase the bearing capacity of an element on torsional loads. The building reinforced concrete element consists of a concrete body 1 with an axial cavity 2 and has longitudinal reinforcement 3. On the inner surface of the axial cavity 2 there is a spiral rib 4, and in the walls 5 of the element with an axial cavity covering there is a metallic elastic helix 6 with a direction of winding opposite to the direction twisting the turns of the rib 4. Moreover, the pitch of the turns of the spiral 6 is equal to the pitch of the turns of the rib 4. 4 Il. w fe VI VI Os Figure 1

Description

The invention relates to the construction, in particular to long bearing elements, and can be used in the manufacture of reinforced concrete columns, beams, piles, power transmission towers and other structures subject to bending-twisting effects.

A prestressed reinforced concrete volume element is known, which includes a concrete body with an axial cavity made in it and a reinforcement cage.

The closest technical solution to the claimed object is a reinforced concrete support of a support comprising a concrete body with an axial cavity and reinforcement made in the form of a spiral mounted in the walls of the element.

The disadvantage of the known element is low bearing capacity due to the inefficient distribution of internal stresses from the effects of flexural-torsional forces, as a result of which zones with a stress-strain state of stretch-compression arise in the walls of the element, resulting in a decrease in concrete strength.

The purpose of the invention is to increase the bearing capacity of an element on torsional loads.

The goal is achieved by the fact that in a building reinforced concrete element comprising a concrete body with an axial cavity and reinforcement made in the form of a spiral installed in the walls of the element, a spiral rib is formed on the inner surface of the axial cavity, and the spiral in the walls of the element is installed with the direction of winding, opposite to the direction of twisting of the coil of the rib, and the pitch of the coils of the helix is equal to the pitch of the coil of the rib.

Figure 1 shows a building reinforced concrete element with a partial cut-out, in a perspective view; FIG. 2 is a section A-A in FIG. on fig.Z - building element in which the number of edges is equal to the number of its faces, longitudinal cut; figure 4 - section bb in fig.Z.

The building, reinforced concrete element consists of a concrete body 1 with an axial cavity 2 and a longitudinal reinforcement 3. On the inner surface of the axial cavity 2 there is a spiral rib 4, and in the walls 5 of the element with an axial cavity 2, there is a metallic elastic helix 6 with a winding direction opposite to the direction of tightening the coil of the rib 4. And step a

turns of the spiral 6 is equal to the pitch from the turns of the rib 4.

Making the rib 4 of the helical shape allows redistributing the internal stresses arising from the flexural-torsional effects on the element.

Step a turns of the spiral b, equal to the step with

ribs 4, allows you to compensate

helical lateral deformations

ribs 4 and reduce local tensile stresses near the free edge of rib 4 by covering the latter with coil 6 and the direction of twisting its turns opposite to the direction of twisting

4 rib turns.

To further increase the bearing capacity of the element by more uniform distribution of stresses over the cross section, the number of helical ribs 4 made on the inner surface of the axial cavity 2 and the spirals 6 installed in the walls 5 of the element can be equal to the number of faces of the element to be made.

In the proposed construction element, the thickness of each wall is assumed to be 1 / 4-1 / 25 the height of the cross section of the element, since this ensures the most efficient operation of the element.

The parameters of the helical edge must satisfy the conditions h 10h f,

b h f where h and b are respectively height and width

helical rib;

hf is the wall thickness of the element. These parameters of the rib 4 provide the most optimal joint operation of the walls 5 and the rib 4, which allows

as much as possible to redistribute internal stresses arising from bending-torsional effects on the element.

Building reinforced concrete element is made as follows.

A longitudinal reinforcement 3 and a helix 6 are installed in the form (not shown in the figures). Then a spiral-type core former (not shown in the figures) is installed inside the helix 6 and the concrete mix is laid. The element is kept in shape until concrete is set to temporal strength, after which it is disassembled and the core is removed, for example, by unscrewing.

The claimed building reinforced concrete element, for example a column, works in the frame of a multistory building as follows.

After the column is installed in its working position, external vertical and horizontal loads are transferred to it, which, as a result of their various combinations, cause longitudinal and transverse forces, bending and torsional moments. Moreover, under the influence of uneven or one-sided loading of floors, as well as special loads, such as seismic, flexural-torsional effects may prevail in the column. The spiral flow of main compressive stresses arising in the column is directed in accordance with the claimed element geometry along the helical rib 4. Compression of the rib 4 creates favorable conditions for the operation of the concrete rib 4 and relieves the walls 5 of the column. Under the influence of the spiral flow of the main tensile stresses in the walls 5 of the column in the spaces between the helical ribs 4, spatial cracks are formed in which spiral armature 6 enters into intensive work on the perception of the tensile forces. Thus, the torsion of the stress state of tension - compression, there is a uniform redistribution of internal forces between the spiral reinforcement 6, working for tension, and the helical edge 4, working compression. At the same time, occurring under the influence of torsional deplanation of the column cross sections due to

the presence of a helical rib 4 leads to tensile forces on the free face of the rib 4.

However, these forces are completely extinguished by the forces formed at the same time from helix 6 compressing a helical rib 4. The interaction of the helical rib 4 and helix 6 makes it possible to significantly increase the rigidity of the column, especially at the stage of its operation after the formation of cracks in the walls 5.

When the column has small torques, the large pitch of the helical rib 4 may not be sufficient to maintain the active interaction of the rib 4 with the spiral 6. Therefore, to ensure conditions for redistributing the internal forces, the spiral ribs 4 and the spiral 6 are made according to the number of edges of the element (column) .

Claims (1)

Invention Formula A building reinforced concrete element comprising a concrete body with an axial cavity and reinforcement made in the form of a spiral installed in the walls of the element, characterized in that, in order to increase the bearing capacity of the element for torsional loads, a spiral-shaped rib is made on the inner surface of the axial cavity the walls of the element are installed with the direction of twisting of the turns opposite to the direction of twisting of the turns of the rib, with the pitch of the turns of the spiral equal to the pitch of the turns of the rib.  B. ° - :; Ј2ЈЈ-. Aa . s s jl FIG 3