SU49135A1 - The method of manufacturing reinforced concrete beams and the message to the reinforcement of its preliminary stresses - Google Patents

Description

Usually, iron-reinforced structures are concreted with layers immediately to their full height.

The proposed method for the manufacture of reinforced concrete beams consists in that the concreting of the compressed and stretched zone of the structure is carried out in two steps, and its preliminary stresses are communicated to the reinforcement.

In FIG. 1 and 5 are side views of a half-concreted beam; FIG. 2 and b - view of the beam from below; FIG. 3 - cross section of the beam; FIG. 4-view of a loaded, but still non-concrete beam.

The beam with the reinforcement laid is first concreted only at half the height subject to compressive stress. To connect the reinforcement with the concrete, the ends of the beam and some IO gaps to the length of the beam are concreted over the entire height (Fig. 1). After a known period of time, when the concrete acquires the necessary strength, the concrete beam is thoroughly applied to the load, sufficient to force in the iron the stresses close to the yield strength. In the loaded: the rest of the beam is concreted already at} this height. The unloading of the beam is also carried out on the acquisition of concrete {of the strength to be assembled.

In the prepared and unloaded beam, the stress in the compressed area of the working structure will be tensile. In the area of the valve, due to the stress in the iron caused by the preload, there will be compressive stresses.

In a working design, the stresses do not reach critical. Therefore, a beam prepared in this way, obviously, will not have static or even shrinking hair cracks.

A possible modification of the proposed method of manufacturing reinforced concrete beams is that a cross section is left in the concreted compressed zone (Fig. 5). When the concrete achieves a compressed zone of sufficient mechanical strength (after 7–9 days), the beams are placed in the clamps of the stretching machine (Fig. 6) and are stretched to produce stresses in iron close to the yield strength or temporary resistance. Compressed concrete, due to the presence of the cut, will not experience noticeable stretching. In the prestressing state, the stretching zone of the beam is concreted and in such a position the beam is maintained again for 7-9 days to give strength to the concrete; after that she can go into business.

The subject matter of the invention.

Claims (2)

1. A method of manufacturing reinforced concrete beams and providing the reinforcement with its prestressing, characterized in that at first only part of the beam is concreted and the reinforcement designed to work on stretching is left un-concreted for the most part of its length, then, after sufficient hardening of the concrete, the beam bend so that the non-concreted reinforcement is stretched, and concrete the rest of the beam, leaving it under load until the concrete has hardened in this part. 2. Modification of the method according to claim 1 ,. characterized in that in the concrete part of the beam concreted in the first step, a cross section is left and after the concrete is sufficiently cured of this part, the beam is stretched and then the second part is concrete, leaving the beam stretched to the required second part.