SU1172729A1 - Method of manufacturing prestrained ferroconcrete structure - Google Patents

Abstract

METHOD FOR PRODUCING A prestressed concrete structures, vklyuchayush, s molding violation reinforcement engagement with anticorrosive coating with concrete possessing strength 1 - YuUovgo project marks hardening and the tension reinforcement in concrete, characterized in that, in order to reduce the force when debonding, the latter is carried out by shifting the reinforcement in the longitudinal direction relative to the concrete, first in one direction and then in the opposite direction by equal distances of 40-60% of the required elongation fittings under tension.

Description

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Fig. A The invention relates to the construction, namely the manufacture of prestressed structures, primarily from cellular concrete. The purpose of the invention is to reduce the force in the event of adhesion failure. The essence of the method is. that, in a newly formed product, reinforcing rods with a corrosion-resistant coating are shifted relative to the concrete first to one and then to the opposite side by equal distances 40-60 / 0 from the required elongation under tension. In this case, a channel is formed in the concrete due to the cut-off and obstruction of the concrete, which is not yet strong, with protruding parts of the PERIODIC profile of the reinforcement. FIG. 1-3 shows the formation of a channel in concrete of an early age. FIG. 1 is a schematic representation of a reinforcing bar of a periodic profile molded into concrete. The reef spacing (outlines) is denoted by t, and their thickness is b. For reliable clutch failure, i.e. cutting the concrete, and compacting it between the reefs, the rod must be moved in young concrete in the longitudinal direction by an amount equal to the spans between the reefs, i.e. t-b differences. h, l reinforcement of classes A-IV-A-VI, which is produced with a diameter of 10-32 mm of reefs 7 (at f 10 mm) - 10 mm (at f 32 mm), and the thickness of reefs 1 (at 5 10 mm) - 2 mm (at f 32 mm). Thus, 5ln 6-8 mm, i.e. in order to violate the adhesion of the rod, it is sufficient to move the concrete in the longitudinal direction to the 6th r.iM, depending on the diameter of the rod itself. Ultimate elongation lR --JiLll (lK - g CK. Where k. Is the length of the structure; Ea is the modulus of elasticity of reinforcement equal for class A-IV 2.0 X 10 kN / cm. The magnitude of the limiting elongation is 16.2 mm, respectively at the same time, the displacement amount (5 for debonding at 40% of elongation is 6.48 mm, and at 60% 9.72 mm. Thus, at minimum reinforcement diameters (10 mm), a movement of 40% of g is sufficient, and at maximal diameters (32 mm) - 60% of Af. This guarantees not only the cutting of concrete in the areas between the reefs, but also the entry of all the reefs of the reinforcement into the area Reefs formed by adjacent reefs. This eliminates the formation of under-cuts of concrete, which may occur due to deviations in the size of reinforcement from nominal. When moving 35% from the elongation of reinforcement, there are under-cuts of concrete (Fig. 2). 10 mm, having Zmii 6 mm, when moving by the value of 35% of the DC or 16.2X0, 67 mm, the concrete section will be not cut, since S Sr. Conversely, it is impractical to take the magnitude of the displacement larger, since extra work is performed while the effect is unchanged. According to the proposed method, an effort is made to disrupt the adhesion of the reinforcement to the concrete, not the greater force required to fipTnHa ppn pmatiya to be used for cutting and placing the concrete along the perimeter of the rod, which is equal to the product of the cut surface / product of the perimeter S by the length of the rod concrete resistance to shear at an early age s. The shear strength of concrete, for example, for cellular concrete, is taken as Ry. 0.2R-0.0005R2 (where R is the compressive strength of concrete at an early age, is not more than 10% of the concrete grade. According to the prototype, the force for breaking the reinforcement of a periodic profile with concrete is not less than that at which the rod is brought to large plastic deformations in order to ensure the elongation of the rod along the entire length of the structure by 6-8 mm. The required force is equal to the product of the reinforcement cross-section area and the relative yield strength of the reinforcement N Fa-5 (1.1. For rod p 10 mm from reinforcing steel of class A-LV (Pd 00.785 cm2, S 3.14 cm, 60 kN / cm2) in The structures are 6 m long, made of cellular concrete with the M50 strength (R 0.5 kN / cm) force for disrupting the adhesion of the proposed method Mlax 18.60 kN, NKIW 1.88 kN, and prototype N 47.1 kN. Reinforcing rods coated with an anticorrosive composition are placed in the formwork, then the product is molded, then, with concrete gaining 5% of the brand, a channel is formed by displacing the rebar against the concrete, first to one and then to the opposite side for the same distance. constituting 50% of elongation required under tension. At the end of the heat treatment and cooling of the product, the reinforcement is strained on the concrete.

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Claims (1)

METHOD FOR PRELIMINARY REINFORCED CONCRETE, including molding, malfunctioning of reinforcement with an anticorrosive coating with concrete having a strength of 1-10% of its design grade, hardening and tensioning of reinforcement on concrete, characterized in that, in order to reduce stress in case of adhesion failure, the latter is carried out by shifting the reinforcement in the longitudinal direction relative to concrete, first in one, and then in the opposite direction, at equal distances of 40-60% of the required elongation of the reinforcement under tension.