RU2770963C2 - Method for tensioning reinforcement by the electrothermal method - Google Patents

Abstract

FIELD: building.

SUBSTANCE: when implementing the method for tensioning reinforcement by the electrothermal method in the manufacture of reinforced concrete products, the reinforcement is placed in a mould, a fixed stopper with a grip and a movable grip are secured thereon at a distance from the ends, followed by connecting terminals to the reinforcement, defining the part of the reinforcement subjected to the greatest stretching during the operation of the reinforced concrete product, in order to heat this part of the reinforcement. The movable grip is then moved to the design reference mark in order to stretch the reinforcement, and the terminals are removed. After cooling, the mould is filled with concrete, wherein after the concrete reaches 75% of the strength, the fixed stopper with a grip and the movable grip are removed.

EFFECT: ensured tensioning of reinforcement in reinforced concrete products.

1 cl, 2 dwg

Description

The invention relates to construction and can be used for the manufacture of prestressed concrete products.

There is a known "Method of manufacturing a pre-stressed reinforced concrete beam", when the sections of the reinforcing bars that should be tucked in for pre-tensioning or compression are left bare and, after the concrete has gained sufficient strength, with the help of couplings screwed onto the reinforcing bars, the reinforcement is pre-compressed in sections of the reinforcement compressible from external load and pre-stretching - on stretched ones, while in the zone of action of the preliminary compressive stress in the reinforcement, which has adhesion to concrete, the latter is not subjected to pre-stretching. (Patent of the Russian Federation No. 2170312 "Method of manufacturing a prestressed reinforced concrete beam" by R.L. Mailyan, D.R. Mailyan. Published on 10.07.2001)

The disadvantage of this technology for the manufacture of prestressed reinforced concrete beams is the difficulty of connecting the reinforcement with couplings, it is difficult to mechanize the twisting of the couplings, the inability to control the quality of the tension of the reinforcement, the complexity and the fact that the work on twisting the couplings must be carried out from below the structure - a violation of safety, the presence of couplings leads to an increase in the protective layer, leads to a heavier structure and an increase in price. In prestressed reinforced concrete, it is desirable that all reinforcement branches along their entire length work synchronously, but the presence of couplings cannot contribute to this, couplings increase the cost of the reinforced concrete structure and reduce its reliability.

The closest, in our opinion, is the electrothermal method of tensioning the reinforcement, when the reinforcing bars heated with the help of an electric current are stretched, fixed in rigid stops, which prevent the reinforcement from shortening during cooling (A.K. Tretyakov, M.D. Rozhnenko “Reinforcing and concrete work "M." Higher School "1982 p 86)

The disadvantage of this method is the heating of the reinforcement along its entire length, high energy costs, the end parts of the reinforcement, which are not involved in elongation and compression when the load on the reinforced concrete product changes, also experience prestressing and so that they do not move from their places, they are anchored, which complicates work and increase cost.

The purpose of the invention is to create a reinforced concrete product with uneven prestressing along the reinforcing bars.

This goal is achieved by the fact that only that part of the reinforcement that is subjected to the greatest stretching is subjected to heating and stretching.

The invention is illustrated by drawings Fig-1 1 - armature, 2 - fixed stopper with armature grip - 1, 3 - terminal connecting armature-1 with electric wire - 4, 5 - terminal connecting armature-1 with electric wire - 6, 7 - armature grip- 1 which can move to the right to tension the reinforcement - 1 (that part of the reinforcement that is subjected to the greatest tension during the operation of the reinforced concrete product), 8 - a hole for the movement of the gripper - 7 with a terminal - 5, 9 - a mold pallet, 10-11-12-sides forms. Fig-2 1 - reinforcement, 13 - concrete. (ready product)

The proposed invention works as follows: voltage is applied to terminals 3 and 5, after heating the armature-1 at a distance between terminals 3-5, the armature is heated to the design value (this is usually 400-500 degrees and the time is from 1 to 3 minutes) . Then the armature grip - 7 moves to the right to the design mark, is fixed (the driving mechanism is not shown in the drawing), terminals 3 and 5 are disconnected, the armature cools down and the form is filled with concrete. After the concrete gains 75% of its strength, the fixed stop - 2 and the armature grip - 7 release the armature, the residual tension is transferred to the ends of the armature. If the reinforcement is straight and protected from corrosion by a protective layer of concrete, then windows should be left in the protective layer to detach the stoppers.

The advantages of the proposed invention: - no need to heat the entire reinforcement - saving electricity, saving reinforcement blanks - the reinforcement is prepared with a shorter length than the concrete product itself, and then when heated, it lengthens to the design value, the diameter of the reinforcement at its ends does not change - better setting with concrete, the tensioning process is faster than with the traditional method, the ends of the reinforcement securely fix it (they are not stretched) and there is no need to anchor them, with this method of tensioning the reinforcement there is no bending of the reinforced concrete product in the opposite direction, if the reinforcement is protected by a layer of concrete, then to release it from the terminals and stoppers, windows should be left in a protective layer and then concreted.

Claims (1)

The method of tensioning reinforcement by the electrothermal method in the manufacture of reinforced concrete products, characterized in that the reinforcement is placed in a mold, a fixed stopper with a grip and a movable grip are fixed on it at a distance from its ends, followed by connecting terminals to the reinforcement, limiting the part of the reinforcement subject to the greatest tension during operation reinforced concrete product, to heat this part of the reinforcement, after which the movable grip is moved to the design mark for stretching the reinforcement and the terminals are removed, and after cooling, the mold is filled with concrete, upon reaching 75% of the strength, the fixed stopper with the grip and the movable grip are removed.

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