RU2059052C1 - Reinforced concrete column - Google Patents

Abstract

FIELD: civil engineering, particularly reinforced concrete building members carrying static and dynamic compression loads. SUBSTANCE: reinforced column has reinforcing spirals inscribed in column cross sections and placed close to one another. The spirals are interconnected with crosswise link-clamps. The clamps are made of steel strips and installed on external surface of end spirals in a pitch providing coincide operation of all spirals. Erection lengthwise reinforcing bars with 235 - 390 MPa yield strength are installed inside spirals preferentially with tacking to the spirals. These reinforcing bars are intended for reliable stopping the spirals in design position, particularly in concreting. Lengthwise high-strength reenforcing bars of not less than 500 MPa yield strength are installed along lengthwise column axis inside spirals and in closed areas between the spirals. The reinforced bars are attached to the spirals preferentially with twisted wires. EFFECT: increased bearing capacity and deformability of the reinforced columns. 2 cl, 3 dwg

Description

 The invention relates to construction, in particular to reinforced concrete building elements, perceiving compressive static and dynamic loads.

 Known reinforced concrete building element [1] reinforced with a helical spiral with filling the core with dispersively reinforced concrete.

 The disadvantages of this element are the relatively small bearing capacity and deformability of the reinforced concrete element.

Closest to the invention is a reinforced concrete building element comprising a helical spiral [2]
The disadvantages of this element are the low bearing capacity and deformability of the element.

 The purpose of the invention is the increase of the bearing capacity and deformability of reinforced concrete building elements that perceive compressive static and dynamic loads.

 The goal is achieved in that a reinforced concrete column containing a reinforcing cage formed by longitudinal rods connected by spiral reinforcement and having mounting longitudinal reinforcement is provided with at least two additional reinforcing cages, all the cages are located adjacent to each other and are connected by transverse connections strip clamps. In addition, the goal is achieved by the fact that the column is equipped with additional longitudinal reinforcement made of high-strength steel, placed inside the reinforcing frames and in closed areas formed by adjacent reinforcing frames.

 Figure 1 presents a reinforced concrete column, a cross section; in FIG. 2 same side view; figure 3 diagrams of "stress relative deformation" (σ-ε) obtained as a result of experimental studies.

 The reinforced concrete column (Fig. 1) contains reinforcing spirals 1 inscribed in a cross section and adjacent to each other, which are interconnected by transverse ties-clamps 2. The clamps 2 are made of strip steel and are installed on the outer surface of the extreme spirals with a certain pitch along the length columns (figure 2).

 Inside the space 3, limited by reinforcing spirals 1, mounted longitudinal mounting reinforcement 4 with fastening, mainly on tacks, to the spirals. Mounting longitudinal reinforcement 4 has a yield strength of 235-390 MPa (class A-1 A-III) and is intended for reliable fixation of spirals 1 in the design position, in particular during concreting. The location of the mounting longitudinal reinforcement 4 is selected, as a rule, 2-4 rods inside each spiral ring with a uniform distribution around the circumference.

 An additional longitudinal high-strength reinforcement 6 with a yield strength of at least 500 MPa (class A-IV A-VI wire B-II). High-strength reinforcement 6 is attached to reinforcing spirals 1, mainly on wire twists. In addition, another fixing method can be used that does not impair the strength and deformation characteristics of this reinforcement (in particular, welded methods, such as tacking, are not allowed).

 Reinforcement with a yield strength of less than 500 MPa cannot be used in this case, since it has insufficient deformability corresponding to the yield strength (about 0.2-0.5%), and its introduction will not lead to an increase in the deformability and bearing capacity of the column.

 It should be noted that the longitudinal high-strength reinforcement 6 can simultaneously play the role of mounting longitudinal reinforcement 4, while the latter can be eliminated. The effect of such a solution will obviously be to reduce the consumption of fittings. However, it must be borne in mind that it will be necessary to fasten the coils of the spirals 1 to the longitudinal high-strength reinforcement 6, while welding methods are excluded, since they lead to a decrease in the strength and deformation properties of high-strength steels.

 The column reinforcing bar thus mounted is filled with concrete (items 3, 5 and 7).

 Reinforced concrete column works as follows.

 With the perception of compressive static or dynamic load, the column begins to deform. Upon reaching longitudinal relative deformations of about 0.2, concrete located outside the cage begins to collapse. Concrete inside the spirals 1 (space 3) continues to absorb the load, as it deforms in cramped conditions, since the spirals prevent lateral deformations, creating a cage effect. Concrete in the closed areas 5 between the spirals is also deformed under constrained conditions, since it turns out to be "surrounded" on all sides by turns of contacting spirals, and the clamps 2 prevent the spirals from moving relative to each other.

 Thus, unlike one inscribed spiral, most of the cross-section of the column operates in confined spaces. The diagram of the deformation of a reinforced concrete column reinforced with one spiral inscribed into the cross section without clamps (prototype) is shown in figure 3, position 8.

The determining condition for the operation of the proposed column at the transcendental stage of deformation (Fig. 3, position 9 of the σ-ε diagram of a column consisting of four spirals 1 without clamps 2) is to ensure that the percentage of the volume content of clamps (M _x ) is equal to or greater than the percentage of the volume content of spirals (M _cp ), i.e. the condition M _x ≥M _cp must be satisfied _. Otherwise, the clamps break at relative strains 0.6 0.8 the column loses its bearing capacity, while the falling branch is not realized on the σ-ε diagram (Fig. 3, position 10). It is important to note that the clamps 2 to some extent contribute to the creation of a cage effect for areas 7 of the cross section of the reinforced concrete column, which are limited on one side by turns of spirals 1, and on the other (near the free surface) by clamps 2. This also increases the bearing capacity of the column.

 The step of the clamps 2 should be chosen so that the compatibility of all spirals in the cross section of the column is ensured (approximately equal to the diameter of one spiral).

 With further deformation of the column, the relative longitudinal deformations reach 0.8 1.3% (Fig. 3, position 11), the turns of the reinforcing spirals 1 enter the stage of fluidity, however, the destruction of reinforced concrete does not yet occur, since the introduced high-strength reinforcement 6 with such compression deformations retains bearing capacity (its stability is preserved, obviously, due to concrete).

 In this case, the forces are redistributed from concrete to high-strength reinforcement, while the coils of the spirals are not yet destroyed, therefore, the concrete works in the conditions of volumetric stress state and continues to absorb the load. Due to this, the efforts increase, and the deformability of reinforced concrete increases to 1.1-1.5 at maximum bearing capacity (figure 3, position 12).

With further loading, the σ-ε diagram descends to the descending branch, the coils of the reinforcing spirals break, intense deformation and destruction of concrete and high-strength reinforcement occurs 6. The longitudinal relative deformations at the time of fracture are about 4
Thus, the energy intensity of the deformation of the reinforced concrete column (the area under the σ-ε diagram) due to the increase in deformability and the increase in maximum stresses (Fig. 3) significantly increased. Consequently, the bearing capacity of the reinforced concrete column increased.

The technical and economic efficiency of the invention consists in increasing the bearing capacity and deformability of reinforced concrete building elements that perceive compressive static and dynamic loads, due to:
the use of three or more reinforcing spirals inscribed in the cross section, combined by clamps, which provides a large (in comparison with the prototype) cross-sectional area, working in conditions of volumetric stress state;
introducing additional longitudinal high-strength reinforcement, which ensures the redistribution of forces from concrete to reinforcement and increase the deformability of concrete in the cage.

Claims (2)

 1. REINFORCED CONCRETE COLUMN, comprising a reinforcing cage formed by longitudinal rods connected by spiral reinforcement and having mounting longitudinal reinforcement, characterized in that it is provided with at least two additional reinforcing cages, all the frames are located adjacent to each other and are connected by transverse stainless steel band clamps.  2. The column according to claim 1, characterized in that it is provided with additional longitudinal reinforcement made of high-strength steel, placed inside the reinforcing cages and in closed areas formed by adjacent reinforcing cages.

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