RU2782378C1 - Reinforced concrete element in the form of a stand for compression testing - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to the field of construction and can be used in the manufacture of a reinforced concrete element in the form of a rack for testing central and eccentric compression. The reinforced concrete element in the form of a rack includes concrete and a reinforcing cage, consisting of a working longitudinal reinforcement and transverse reinforcement. The reinforced concrete element is equipped with U-shaped structures for reinforcing the head of the element, to which removable cantilever structures are attached with the help of a bolted connection. Each U-shaped reinforcement structure is made of two steel plates with holes, welded at an angle of 90° to a solid section steel plate parallel to each other, and round steel tubes located between the steel plates with holes and connecting their holes. Each detachable cantilever structure is made in the form of a steel square tube, welded along the perimeter to the base steel console plate, provided with holes located outside the connection area with the square tube, which correspond to the holes on the steel plates of the U-shaped reinforcement structure.

EFFECT: providing the possibility of testing on press equipment without the use of additional equipment; the possibility of loading an element with an eccentricity of the application of an external load that goes beyond the section of the element; reduction of deformability of the upper and lower parts of the reinforced concrete element (heads); implementation of a uniform distribution of the applied external load over the surface of the sample; ensuring reliable anchoring of the working longitudinal reinforcement.

4 cl, 8 dwg

Description

The invention relates to the field of construction and can be used in the manufacture of a reinforced concrete element in the form of a rack for testing central and eccentric compression.

Known building element in the form of a rack containing a concrete core and a spatial frame, consisting of a coaxial central spiral wound around the longitudinal rods, and four spirals of circular cross-section located at the corners and wound around the grouped longitudinal rods. /Patent RU 178561, IPC E04C 3/36 (2006.01). Building element in the form of a rack. Krishan A.L., Chernyshova E.P., Sabirov R.R., Astafieva M.A., Appl. Federal State Budgetary Educational Institution of Higher Education "Magnitogorsk State Technical University named after V.I. G.I. Nosov": 10/20/2017, published: 04/09/2018, Bull. №10/[1] - prototype.

The disadvantages of the known design are the impossibility of loading the element with the eccentricity of the external load application, which goes beyond the section of the element, as well as the increased deformability of the upper and lower parts of the reinforced concrete element (heads).

The technical result of the invention is:

- the possibility of testing on standard testing machines (press equipment) without the use of additional equipment;

- loading of an element with an eccentricity of the application of an external load that goes beyond the section of the element;

- reduction of deformability of the upper and lower parts of the reinforced concrete element (heads);

- uniform distribution of the applied external load over the surface of the test sample;

- increasing the reliability of the anchoring of the working longitudinal reinforcement;

- reduction of time for the preparatory and testing process during the compression test of a reinforced concrete element in the form of a rack.

The specified technical result in the implementation of the invention is achieved by the fact that in a well-known reinforced concrete element in the form of a rack, including concrete and a reinforcing cage, consisting of a working longitudinal reinforcement and transverse reinforcement, characterized in that it is equipped with U-shaped structures for reinforcing the head of the element, to to which, by means of a bolted connection, removable cantilever structures are attached, while the U-shaped reinforcement structure is made of two steel plates with holes welded at an angle of 90 ° to a solid section steel plate parallel to each other, and round steel tubes located between the steel plates with holes and interconnecting their holes; the detachable cantilever structure is made in the form of a steel square tube, welded along the perimeter to the base steel plate of the console, provided with holes located outside the connection area with the square tube, which correspond to the holes on the steel plates of the U-shaped reinforcement structure.

The cross section of the element can be square or rectangular.

The transverse reinforcement is made in the form of clamps and segments of rods or brackets.

The causal relationship between the set of features and the technical result is as follows.

The possibility of loading an element with an eccentricity of applying an external load that goes beyond the section of the element makes it possible to use standard testing machines (pressing equipment) for testing reinforced concrete elements with an extended range of eccentricities that cannot be applied without additional equipment.

The use of a U-shaped reinforcement design reduces the deformability of the element heads and allows uniform transfer of the load to the element.

Welding of the working longitudinal reinforcement to the elements of the U-shaped reinforcement structure makes it possible to ensure its reliable anchoring.

All this together helps to reduce the preparation time for experimental work on the elements of load-bearing structures operating in central and eccentric compression.

In FIG. 1 and FIG. 2 shows a U-shaped reinforcement structure: 1 - steel plate with holes; 2 – solid steel plate; 3 - a sleeve made of a steel pipe of circular cross section; 4 - welded fillet weld.

In FIG. 3 and FIG. 4 shows the reinforcing cage of an element with a U-shaped reinforcement structure (element concrete is not shown): 1 - steel plate with holes; 2 – solid steel plate; 3 - a sleeve made of a steel pipe of circular cross section; 5 - working longitudinal reinforcement S; 6 - working longitudinal reinforcement S` 7 - transverse reinforcement (clamps); 8 - transverse reinforcement in the form of brackets or segments of rods.

In FIG. 5 and FIG. 6 shows a three-dimensional model of a reinforced concrete element prepared for testing in the form of a rack (concrete of the element is conventionally not shown): 1 - steel plate with holes; 2 – solid steel plate; 3 - a sleeve made of a steel pipe of circular cross section; 5 - working longitudinal reinforcement S; 6 - working longitudinal reinforcement S` 7 - transverse reinforcement (clamps); 9 - removable cantilever structure; 10 - steel bolts; 11 - steel nuts.

In FIG. 7 and FIG. 8 shows a removable cantilever design: square pipe - 12; console base steel plate - 13.

Concrete is not shown in the figures.

A reinforced concrete element in the form of a post includes a reinforcing cage containing a working longitudinal reinforcement S - 5, a working longitudinal reinforcement S` - 6, transverse reinforcement (clamps) - 7, transverse reinforcement in the form of brackets or segments of rods - 8 and a U-shaped structure reinforcement, made of two steel plates with holes - 1, welded at an angle of 90 ° to a steel plate of a solid section - 2 parallel to each other, and bushings from a steel pipe of round section - 3, located between the steel plates with holes - 1 and connecting between their holes.

The removable cantilever structure - 9 is made in the form of a steel square pipe - 12, attached by a fillet weld along the perimeter to a part of the base steel plate of the console - 13, the other part of which is provided with holes. The location of the holes in the base steel plate of the console - 13 correspond to the holes on the steel plates of the U-shaped reinforcement structure. Removable cantilever structure - 9 is installed to a concreted reinforcing frame with a U-shaped reinforcement structure on a rigid cement-sand mortar and attached to a reinforced concrete element by means of steel bolts - 10, passed through the holes of the base steel plate of the console, the holes of the steel plates of the U-shaped reinforcement structure, round steel pipe bushings - 3 of the U-shaped reinforcement structure, and steel nuts - 11.

The reinforced concrete element in the form of a post consists of a reinforcing cage, in which the working longitudinal reinforcement S - 5 and the working longitudinal reinforcement S` - 6 are made of reinforcing steel of class A400÷A600, transverse reinforcement (clamps) 7, transverse reinforcement in the form of brackets or segments of rods 8 are made of reinforcing steel of class A240 or B500; and a U-shaped reinforcement structure (Fig. 1, 2), the elements of which are made of carbon structural steel. The materials used have high tensile and compressive strength, which makes it possible to provide the required strength of the reinforced concrete element in the form of a rack. The outer part of the rods of the working longitudinal reinforcement S and S` - 5 and 6, respectively, is located at a distance of at least 20 mm and at least half the diameter of the rod from the edge of the section of the manufactured element [2]. At smaller distances, it will not be possible to ensure the safety of the rods of the working longitudinal reinforcement S and S` - 5 and 6, respectively, from environmental influences (including in the presence of aggressive influences). Transverse reinforcement (clamps) 7 and transverse reinforcement in the form of brackets or segments of rods 8 at one face are located along the height of the element with a step of no more than 15 multiples of the largest diameter of the working longitudinal reinforcement S and S` - 5 and 6, respectively. This is necessary to hold the longitudinal rods in the design position and secure them from lateral buckling in any direction [2]. The working longitudinal reinforcement S and S` - 5 and 6, respectively, in its design position is welded to steel plates with holes 1 and a solid steel plate 2, respectively, which provides reliable anchoring for the working longitudinal reinforcement S and S` - 5 and 6, respectively. The presence in the reinforced concrete element of a U-shaped reinforcement structure, consisting of two steel plates with holes 1 and a steel plate of solid section 2 connected to each other by means of a welded fillet weld 4, makes it possible to reduce the deformability of the upper and lower parts of the reinforced concrete element (heads), to carry out a uniform distribution applied external load on the sample surface. Uniform distribution of the load is carried out from the removable cantilever structure 9 through a layer of cement-sand mortar to the U-shaped structure of the element reinforcement. Inside the U-shaped reinforcement structure, bushings made of a steel pipe of circular cross section 3 are installed, allowing you to fix a removable cantilever structure 9 on a reinforced concrete element, which allows you to load the element during the test with an eccentricity of the application of an external load that goes beyond the section of the element (Fig. 5, 6) . Concrete is not shown in the figures.

Information confirming the possibility of carrying out the invention to obtain the above technical result.

A reinforced concrete element in the form of a rack is made as follows: first, the reinforcing cage of the element, the U-shaped reinforcement structure and the removable cantilever structure are made. Two steel plates with holes 1 are welded at an angle of 90° to a solid steel plate 2 by means of a fillet weld 4 (Fig. 1 node A), forming a U-shaped product. Further, the working longitudinal reinforcement S - 5 and the working longitudinal reinforcement S` - 6, fixed in the design position, are welded to the plates of the manufactured U-shaped reinforcement structure. Then bushings from a steel pipe of circular cross section - 3, designed to pass steel bolts 10 through the element, are welded to steel plates with holes 1, centering the holes in the plates with the holes of the bushings. After that, the device of transverse reinforcement (clamps) is performed in place 7. In places where the device of closed clamps is impossible, but there is a possibility of loss of stability of the working longitudinal reinforcement, transverse reinforcement is installed in the form of brackets or segments of rods 8. Holes of bushings from a steel pipe of circular cross section 3 filled with mounting foam or a wooden plug to prevent filling with concrete during the concreting process, while maintaining the possibility of passing steel bolts 10 through these holes to secure the removable cantilever structure. After that, the manufactured reinforcing cage with a U-shaped reinforcement structure (Fig. 3, 4) is placed in a pre-prepared formwork, and the sample is concreted. After 2-3 days, the element is stripped. There is a set of concrete strength within 28 days during hardening in normal natural conditions.

Removable cantilever structure - 9 is made by welding around the perimeter of a square pipe - 12, made of steel plates connected to each other by a fillet weld, to the base steel plate of the console - 13 with holes by a fillet weld. The seams are made using automatic or semi-automatic welding, which is important for obtaining a reliable high-quality connection. The size of the overhang of a square pipe - 12 is determined by the value of the required eccentricity of the application of external force. The width and height of a square pipe - 12 are equal to the size of the height of the section of a reinforced concrete element in the form of a rack. The thickness of the plates for a square pipe - 12 and the base steel plate of the console - 13 with holes is selected by calculating the strength, rigidity and stability according to the current regulatory documents [3]. The thickness of the plates for a square pipe - 12 is taken equal to 8 ÷ 15 mm, the base steel plate of the console - 13 with holes - 20 ÷ 30 mm. The width of the base steel plate of the console - 13 with holes exceeds the width of the square pipe - 12 to create a welded joint with the required leg of the seam. The calculation of a welded joint with fillet welds is performed on the action of a moment in a plane perpendicular to the plane of the weld location [3]. The sequence of manufacturing the reinforcing cage of an element with a U-shaped reinforcement structure or a removable cantilever structure does not matter.

The holes in the plates of the U-shaped reinforcement structure and the base steel plate of the console - 13 of the removable console structure are made of the same diameter and located in such a way that they are aligned when applied. This is necessary to pass steel bolts 10 through these holes to secure the removable cantilever structure 9. The number of holes in the plates is determined by the number of bolts, which is selected according to the design force perceived by one bolt in the connection, for shear, crushing, tension and acting force [3].

The cantilever structure is installed to a concreted reinforcing cage with a U-shaped reinforcement structure on a hard cement-sand mortar, and is kept in this position for a day. Then, bolts with washers - 10 are installed in the holes made in the U-shaped reinforcement structure and the base steel plate of the console - 13 of the removable cantilever structure, and the connection is fixed by sequentially tightening all steel nuts - 11. Next, the reinforced concrete element is set to the design position in accordance with given eccentricity. Prior to testing, the position of the reinforced concrete element is checked vertically in two planes, the position of the cantilever structures relative to the sample body - the reinforced concrete element. In this case, it is necessary to ensure the coaxiality of the upper and lower consoles with the body of the sample - a reinforced concrete element.

Thus, a reinforced concrete element is proposed in the form of a rack for compression tests, which makes it possible to load the element with an eccentricity of the application of an external load that goes beyond the cross section of the element; reduce the deformability of the upper and lower parts of the reinforced concrete element (heads); to carry out a uniform distribution of the applied external load over the surface of the sample of the reinforced concrete element; ensure reliable anchoring of the working longitudinal reinforcement.

Example. Reinforced concrete element in the form of an eccentric compression test stand with an external force application eccentricity of 300 mm.

The height of the reinforced concrete element in the form of a rack is 1 m. The class of concrete in terms of axial compressive strength is B40.

The working longitudinal reinforcement S is made of two rods with a diameter of 22 mm class A400, the working longitudinal reinforcement S` - two rods with a diameter of 12 mm class A400, transverse reinforcement (clamps) and transverse reinforcement in the form of brackets or segments of rods - with a diameter of 8 mm class A240 with a step element height 160 mm.

To prevent the destruction of concrete in the heads of the reinforced concrete element, steel U-shaped reinforcement structures were installed, which ensure uniform transfer of the load to the concrete, and also serve to fix the cantilever structure on the reinforced concrete element, for which holes for ∅25 mm bolts are made in their plates. For bolts of normal accuracy, holes are made 1 mm larger than the diameter of the bolt. The U-shaped reinforcement structure is shown in Fig. 1 and 2. Round steel tube bushings are made with an inner diameter of 34 mm.

The U-shaped reinforcement structure consists of two steel plates 240×200×10mm in size with six holes ∅25mm and one solid section plate with dimensions 200×190×10 mm. Plates with holes are connected to a solid section plate by means of a fillet welded joint at an angle of 90° - a “P”-shaped joint (node A in Fig. 1). Connection symbol according to [GOST 5264-80] - U6. The structural elements of the prepared edges of the parts to be welded and the weld, as well as their geometric parameters, are given in Table 40 [GOST 5264-80]. Bushings made of round steel pipe are installed between the plates with holes to protect the working bolts from concreting for subsequent applications.

The working longitudinal reinforcement S is welded to the plate with holes in its design position. The connection is made in accordance with the requirements of [GOST 14098-91], Table 18 of which indicates the geometric characteristics of this type of welded joint.

The removable cantilever structure is an integral part of the reinforced concrete element for compression testing. It is a square pipe 200×200×12 mm in size, attached to the base steel plate of the console with holes 500×250×20 mm in size with a fillet weld with a 13 mm leg by welding along the profile perimeter (Fig. 7 and 8). In the base steel plate of the console with holes, six holes ∅25 mm were made, providing connection by means of a bolted connection with the U-shaped reinforcement structure of the reinforced concrete element head. The design of the square pipe is made of steel plates 12 mm thick (Fig. 7).

The calculation of a removable cantilever structure was made using the standards [3] as a reinforced concrete element bent in one of the main planes. The section is selected based on the required value of the section modulus according to the assortment [GOST 30245-94]. Since the cantilever structure is removable, the calculation was made for the maximum bending moment that occurs during testing of the samples.

The calculation of a welded joint with fillet welds was made for the action of a moment in a plane perpendicular to the plane of the weld location in accordance with the manual [Manual for the calculation and design of welded joints in steel structures (to chapter SNiP II-23-81)] and standards [3]. The section by which the calculation of the welded joint for a given combination of steel, welding wire and welding method is determined in accordance with Table 2 [Manual for the calculation and design of welded joints in steel structures (to chapter SNiP II-23-81)] and is - according to weld metal.

As a result of the test, it was found that the breaking load on the reinforced concrete element in the form of a rack is 21.2 tons. The experiment was carried out in the Branch Research Laboratory of the Department of Reinforced Concrete Structures of the Samara State Technical University (Samara) in 2010-2011.

The proposed technical solution for a reinforced concrete element in the form of a rack was used during experimental work in the Branch Research Laboratory of the Department of Reinforced Concrete Structures of the Samara State Technical University (Samara).

Sources of information

1. Patent RU 178561, IPC E04C 3/36 (2006.01). Building element in the form of a rack. Krishan A.L., Chernyshova E.P., Sabirov R.R., Astafieva M.A., Appl. Federal State Budgetary Educational Institution of Higher Education "Magnitogorsk State Technical University named after V.I. G.I. Nosov": 10/20/2017, publ. 04/09/2018, Bull. No. 10.

2. SP 63.13330.2018. Concrete and reinforced concrete structures. Basic provisions. SNiP 52-01-2003 (with Amendment No. 1). – M.: Ministry of Construction of Russia. – 2018 – 119 p.

3. SP 16.13330.2017. Steel structures. Updated edition of SNiP II-23-81* (as amended, with Amendment No. 1). - M.: Ministry of Construction of Russia, 2019. - 145 p.

Claims (4)

1. Reinforced concrete element in the form of a rack, including concrete and a reinforcing cage, consisting of working longitudinal reinforcement and transverse reinforcement, characterized in that it is equipped with U-shaped structures for reinforcing the head of the element, to which removable cantilever structures are attached by means of a bolted connection, wherein each U-shaped reinforcement structure is made of two steel plates with holes, welded at an angle of 90° to a solid steel plate parallel to each other, and round steel tubes located between the steel plates with holes and connecting their holes; each detachable cantilever structure is made in the form of a steel square tube, welded along the perimeter to the base steel plate of the console, provided with holes located outside the connection area with the square tube, which correspond to the holes on the steel plates of the U-shaped reinforcement structure. 2. Reinforced concrete element in the form of a rack according to claim 1, characterized in that the cross section of the element is made square or rectangular. 3. Reinforced concrete element according to claim 1, characterized in that the transverse reinforcement is made in the form of clamps and segments of rods. 4. Reinforced concrete element according to claim 1, characterized in that the transverse reinforcement is made in the form of clamps and brackets.

Images