RU30372U1 - Reinforced concrete beam - Google Patents

Abstract

Reinforced concrete beam, consisting of concrete and high-strength bar reinforcement, subjected to pre-stretching in the stretched zone and pre-compression in the compressed zone, characterized in that the beam in the longitudinal direction has a stepped profile, and the tensile reinforcement breaks in the span in accordance with the diagram of materials.

Description

REINFORCED CONCRETE BEAM

The utility model relates to construction and can be used as truss and floor beams of buildings.

Reinforced concrete beams are known with prestressed reinforcement extending over the entire length of the beam (See, for example, Baykov V.N., Sigalov E.E. Reinforced concrete structures. - M .: Stroyizdat, 1991. - S. ISOIS 1,385-387,409-412) .

The closest technical solution is a typical Reinforced Concrete can with a span of 12 m with allelic belts with pre-stretched reinforcement stretched over the entire length of the beam (see Reinforced concrete coating beams. Series 1.462.1 - 1/88 in. 1, 2 - BSP12-4A beam -VI. M.: CIT. - 1988).

In all existing solutions, prestressed reinforcement is stretched from one end of the beam to the other, which leads to a large overspending of materials and an excess supply in less loaded sections of the beams.

In order to eliminate this major drawback and significantly reduce the consumption of high-strength steel, as well as concrete, a new structural solution is proposed in which the beam has a stepped profile that allows breaking off the tensile material in the span in accordance with the plot of the materials. Also, the solution allows you to get as close to the beam of equal resistance.

The utility of the utility model consists in the fact that a reinforced concrete beam consisting of concrete and a high-strength rod gfmatura is subjected to preliminary stretching in the stretched zone and preliminarily compresses in the compressed zone, while in the longitudinal direction it has a stepped profile, and the tensile reinforcement breaks into span in accordance with the plot of materials.

I Illllfll ll m., ... r T

iil

-L 2 Z

MKII 04C3 / 20

In the proposed solution, unlike the standard one, combined prestressing is adopted, in which the high-strength reinforcement of the stretched zone is subjected to pre-tension stretching, and of the compressed zone to preliminary compression. This will not only increase the crack resistance of the stretched zone, but also increase the stresses in the reinforcement of the compressed zone before the destruction of the compressed concrete to Rsc + or gp.

In the proposed solution, breaks of high-strength longitudinal reinforcement of class A-VI are provided for in both compressed and expanding zones.

The utility model is illustrated in the drawing, where

FIG. 1 - profile of reinforced concrete beams;

FIG. 2 - diagrams of moments of external and internal forces;

FIG. 3 - dimensions of the concrete section of the reinforced concrete beam and its reinforcement in section AA;

FIG. 4 - the same, in the context of BB;

FIG. 5 - the same, in the context of CC;

FIG. 6 - the same, in the context of DD;

FIG. 7 - the location of the floor in a steel formwork;

FIG. 8 is a diagram of reinforcement tension.

Reinforced concrete beam 1 has concrete ledges 2, creating a step profile 5.

The torn off prestressed matra 3 and 4 are anchored in concrete ledges of 2 beams 1 having a stepped profile. The preliminary tensile forces from the jack to the reinforcement 3 are transmitted through inventory rods 5, and the preliminary compression forces are transmitted in the same way, but through rigid inserts. Anchoring of prestressed reinforcement; probe; carried out by collet clamps 6.

The stability of reinforcing bars during pre-needle compression is ensured by their binding with a knitting wire 7 in the places of inflection to

/ J, / 7 transverse reinforcement 8, and the entire reinforcing cage as a whole - focusing on the walls 9 and the bottom 10 of the steel form - formwork.

Beams are fabricated in the usual manner — assembly of the fabric frame, its installation and fastening in the formwork, u) pressure-free tension and compression of the reinforcement with the transfer of reactive forces to the stands of the stand or to the ends of the power form) decks, concrete beams, transfer of the Unit voltage from the reinforcement to concrete upon reaching concrete transmission strength; beam formwork.

To obtain specific technical and economic data of the proposed solution and comparison with standard beams, the latter are redesigned in accordance with the specified proposal.

For comparison, a typical pre-stressed reinforced concrete beam of I-section with parallel belts series 1.462.1 - 1/88 (beam BSP-12-4A-G) was developed by Promstroyproekt and EIIZhB. The longitudinal reinforcement of a typical beam is constant over the entire length. The main working prestressed fittings are 4020 A-VI.

Evaluation of the effectiveness of the use of reinforcement can be performed by determining a coefficient equal to the ratio of the area of the diagram of moments from external forces 11 in FIG. 2 to the area of the plot of materials 12 for the proposed beam and 13 for the typical one in the same FIG. (diagrams of moments of internal forces) - t | Am / Avn In an ideal beam of equal resistance, this ratio is 1. In real beams, it is less than 1. With its decrease, the efficiency of using beam materials, in particular reinforcement, decreases.

In typical reinforced concrete beam 1 BSP-12-4AU1, as well as in other reinforced concrete beams with parallel faces and with prestressed gfmatura, the cross section of which along the beam is constant, the coefficient of efficiency of the use of reinforcement is minimal, in the considered beam, 58. Its value can be significantly increased with

breaks of pre-stressed reinforcement in the span of beams having a stepped profile.

In the beam with rims u) of the single prestressed reinforcement in the stretched and compressed zones (Fig. 1), the coefficient is 8, and in the beam with the breaks of the prestressed mat only in the stretched zone, 77.

Compared to the standard solution, the consumption of longitudinal high-strength full-time reinforcement for mats in stretched and compressed zones decreases by 12.5%, and when the mats breaks only in the stretched zone - by 9%. The total consumption of longitudinal gfmatura in both solutions is reduced by 18 ... 21% (see table).

Technical and economic indicators of prestressed beams with a span of 12 m offered and typical with the same height of the beams (89 cm) and design

load (39 kN / m).

,

Table

Claims (1)

Reinforced concrete beam, consisting of concrete and high-strength bar reinforcement, subjected to pre-stretching in the stretched zone and pre-compression in the compressed zone, characterized in that the beam in the longitudinal direction has a stepped profile, and the tensile reinforcement breaks in the span in accordance with the diagram of materials.