SU93070A1 - A method of manufacturing prestressed concrete beams - Google Patents

Description

The introduction of prestressed reinforced concrete structures, which, as compared with conventional reinforced concrete structures, are more sophisticated in both technical and economic terms, encounters great difficulties, mainly because of the complex manufacturing technology.

Structures with preserved adhesion of reinforcement to concrete (as a type of concrete) are limited to small spans and for small design loads, and therefore the economic effect from their use is small. A much greater economic effect can be achieved with large spans, which, in turn, requires special complex and expensive fittings for tensioning the reinforcement.

Refusal of the latter led to the type of structures with deliberate violation of the reinforcement adhesion to concrete.

In addition to the complexity of the preparation of these structures, the latter are significantly inferior in technical terms. On the basis of numerous experiments, we came to the conclusion that the adhesion must be restored by injecting the solution into the cavities of the reinforcement beams. It is quite obvious that it is not feasible to restore the complete adhesion of the reinforcement to the concrete by injecting special measures taken in advance to ensure the impossibility of such adhesion under tension.

Methods are known for the manufacture of prestressed structures that are intermediate in comparison with the methods of manufacturing the above types of structures. This includes, for example, the manufacture of beams with the location of the reinforcement in the gutters of previously prepared concrete elements, followed by the incorporation of gutters with mortar or concrete. A method has also been proposed in which the beam is concreted without an extended zone, which is concreted after tensioning the reinforcement. This method has not, however, become widespread due to practical flaws and due to its substantial shortcomings.

The method of the present invention also provides for the manufacture of beams without a stretched zone (without lower parts) and KVV dobetonirov after tension. Feature

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The proposed method consists in that the beams without lower rims (shelves) are placed in pairs by upper shelves one to the other and the reinforcement of the shelves of each pair is tensioned by means of connecting the reinforcement using concreted parts of the beams as a tension frame.

In this way, the manufacture not only maintains the correct principle for the implementation of the pre-stressed structure, but considerably simplifies both the process of tensioning the reinforcement and the design of the tensioning devices.

A schematic drawing explains the process of making beams. FIG. 1 shows the beams in the first stage of production (without an extended zone); in fig. 2 is a section along the ax, FIG. one; in fig. 3 and 4 are the same beams in the second stage of manufacture (after de-tinting the stretched zone); in fig. 5-beams in finished form.

In the 1st stage the part is concreted

beams L without bottom flange (without stretched zone, fig. D and 2).

At the same time, two beams of the same span and section are made and concreted, which are located in the horizontal position with upper shelves to each other. Using concreted parts of beams as a skeleton, production of reinforcement.

Tightening reinforcement, a state of individual rods or of several rods connected in a bundle, bends around the lower edge of the concrete section and is provided at the ends with clamps.

Captures can be carried out on one of the Known Tits. The grippers are mounted in tension E, with which the valve is tensioned to a predetermined voltage.,

Tensioning devices are placed at the ends of the beams with one or two sides. In the first case, the valve has the form of a ring; in the second case consists of two j iacTKoB.