RU2582277C1 - Method for testing strength of monolithic concrete building structures and anchor device for testing strength of monolithic concrete structures - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: group of inventions relates to testing concrete monolithic vertical building structures by separation with shearing. Disclosed is method for testing strength of concrete monolithic building structures by tearing with shearing drive piece concrete monolithic building structures by means of anchor device and measuring applied force of tearing, wherein anchor fixture attached to tube is fitted in assembly forms of monolithic building structures in area of cords that connect shields of formwork. Also described is anchor fixture for testing strength of concrete monolithic building structures.

EFFECT: lower labor input and higher accuracy of tests is achieved.

2 cl, 3 dwg

Description

The invention relates to the field of construction, in particular to testing concrete of monolithic vertical building structures by tearing with chipping.

Existing methods for testing concrete of building structures have their advantages and disadvantages, but one of the main - reference methods - are direct non-destructive tests, namely the method of separation with chipping. The modern method of implementing this method is based on a large number of intermediate operations that require additional labor, material resources and affect the accuracy of the results. The influence of these factors in most cases is difficult to evaluate. In this regard, the urgent task of finding new solutions for the implementation of the well-known separation method with chipping.

A test method is proposed, using a standard power device, used for the traditional method of tearing off with chipping, of concrete structure by means of an anchor device, which is installed during formwork in a technological hole in the place of passage of the strand to connect the formwork panels.

Known methods for testing concrete in a structure based on the use of an indirect relationship between the strength of concrete and the value of the local fracture force of concrete when an anchor device is torn out (tearing it off). These methods based on the use of special devices allow evenly increasing the force of the anchor located in concrete at a certain depth to load a fragment of concrete until separation. The recorded tear-off force is used to calculate the concrete strength in automatic or manual mode. As an anchor device, three types of anchor are traditionally used according to GOST 22690-88 “Concretes. Determination of strength by mechanical methods of non-destructive testing. " This is, firstly, the working rod fixed on the formwork before concreting and torn out during the required period of curing. The second and third types are working rods with an expanding cone and three segmented corrugated cheeks, which are installed in the structure immediately before the test. To do this, drill a hole for the selected anchor and install it.

The most common type of anchor is the second, used both when examining exploited structures, and when monitoring the quality of new construction in the process of building construction. The disadvantages of this method include a large amount of additional operations (it is required to determine the location of the reinforcing bars in the concrete body, to perform strictly vertical drilling to a certain depth). Accordingly, the quality of their performance affects the objectivity of the measurement results. At the same time, tests with an anchor of type II (and also type III) are not applicable in the early stages of concrete strength gain, due to the destructive effect of drilling and preparing a hole for an anchor, which can significantly affect the test results. Known devices for testing concrete using this type of anchor [1-6].

Anchor type I is practically not used due to the complexity and laboriousness of work on its installation or fixing on the formwork panels. The disadvantages of this method are the need to harm the deck of the shield to install the anchor, which in case of further use must be repaired, and that after the construction is made, the part of the anchor, for which the subsequent tearing device is mounted, protrudes above its surface. Moreover, due to the lack of preparatory measures characteristic of type II anchors, factors that may affect the final result (position of reinforcing bars in the concrete body, verticality and depth of the hole for the anchor), it is much smaller, which positively affects the measurement variations and their accuracy . Known devices for testing concrete, in which case you can use type I anchor [1-3, 7].

To date, the main changes in improving the cleavage method have been applied to the devices used (the use of electronic control units; devices that improve the quality of drilling holes, etc.), but not the type of anchors that remain standard according to GOST 22690-88.

The analysis of foreign experience [8, 9]. Known methods also include installing a pre-laid anchor in the concrete body by analogy with type I anchor according to GOST 22690. The main difference is the use of a support ring with the device that fixes the fracture zone at strictly defined boundaries.

In the 60s. XX century P. Kierkegaard-Hansen (Denmark) conducted research to determine the optimal test geometry, the possibility of testing in the "field" conditions using simpler (least labor-intensive) equipment and a high correlation between the ultimate tensile strength and compressive strength of the tested concrete designs. He improved the method developed by I.V. Wolf due to a number of innovations:

- determined the optimal parameters of the method, determined by the depth of monolithic of their type of anchor, the diameter of the rod end to be sealed and the diameter of the support ring;

- investigated the effect of reducing the diameter of the support ring. The support ring made it possible to reduce the scatter of the obtained values, the fracture surface received the shape of an ideal cone.

In 1975, Kaindl (Austria) introduced various modifications of tearing systems. Some of these included screens placed around the head of the shaft to exclude coarse aggregate from the fracture zone. The goal was to reduce the scatter of the obtained test values. But the screens are not widely used. Other modifications included the use of so-called “Compressible gaskets” to allow for a peel test without removing the formwork or to conduct tests deep in the structure. Information on the results of such tests is practically absent.

Based on these research materials, the modern standards of Europe and the USA are based: BS EN 12504-3: 2005 “Testing concrete in structures - Part 3:“ Determination of pull-out force ”(Part 3: Determination of tensile strength) ) and ASTM C900-06 "Standard test method for pullout strength of hardened concrete" ("Standard method for determining the hardened concrete tensile strength").

In addition to limiting the separation zone with cleaving to increase the accuracy of the results, the foreign design did not solve the main disadvantages of the test methods discussed above.

Closest to the claimed invention by technical nature are the method and the anchor device disclosed in the patent for invention RU No. 2271528 C1 (IPC G01N 3/00, publ. 10.03.2006) and selected as a prototype. This method has all the disadvantages when using both type I anchor and type II (III).

In the known method, the strength tests of concrete of building structures are carried out by tearing a piece of monolithic concrete of a structure with a power device by shearing by means of an anchor installed in a hole pre-drilled in monolithic concrete and measuring the detachment force, characterized in that a profile groove is drilled in the hole, and on the anchor fixture perform a protrusion corresponding to the location, shape and size of the bored profile groove. An anchor device for testing concrete of building structures contains an anchor with a threaded head at one end for connection to the rod, a working part at the other end, made in the form of an expandable and inverse cone, and a central cylindrical part, and characterized in that the central cylindrical part is made with flats , and the device is equipped with segments that fit the inverse cone, made with supporting collars with internal flanges for interfacing with the flanges of the central cylindrical part, at the end of the segments ying protrusions, the shape and size of which corresponds to the groove in the concrete boring hole.

An object of the invention is to improve the method for testing the strength of concrete of monolithic building structures and anchor devices by reducing the complexity and number of preparatory operations for direct tests, which also affect the accuracy of the results.

The specified result is achieved by the fact that in the method of testing the strength of concrete of monolithic building structures by tearing off with a power device a piece of concrete of a monolithic building structure by shearing with an anchor device and measuring the applied separation force, the anchor device mounted on the tube is pre-installed when installing the formwork of monolithic building structures in the zone of location of the cords connecting the formwork panels.

The indicated result is also achieved by the fact that in the anchor device for testing the strength of concrete of monolithic building structures, containing an anchor with a central cylindrical part and a working part, a thread is made at one end of the cylindrical part of the anchor to go to the coupling rod, and the working part is made of cylindrical the possibility of fixing on a tube and with a support platform for tearing a piece of concrete of monolithic building structures.

The proposed anchor device is installed during the installation of formwork of monolithic reinforced concrete walls, beams or columns together with a tube for the passage of reusable cords. When stripping structures, the strand is removed from the tube and reused. The tube, which previously serves as a spacer along with the anchor, remains in the concrete body. The technological holes remaining in the structure (wall, beam, etc.) are traditionally sealed with mortar, concrete or plastic plugs. In our case, the anchor fixture embedded in the concrete body allows us to evaluate its strength in this area by tearing with chipping.

For reasons of the uniqueness of the function of the formed technological hole during concrete work and the need to close it after removing the screed, it becomes possible to install the proposed type of anchor at the end of the plastic tube into the formwork to subsequently detach to evaluate the strength of concrete in the structure. Compared with the accepted methods and used anchors supplied with domestic devices GPNV-5, ONIKS-OS, POS-50MG4, as well as regulated by GOST 22690-88 and used abroad in the so-called LOK-TEST, the following advantages can be distinguished:

- eliminates the need for a special hole for the anchor in the formwork;

- the anchor is compatible with modern formwork systems (the design of the formwork panels often has openings for the passage of cords);

- measures (technological operations) for the repair of zones of damage from separation are combined with work on chasing holes;

- eliminates the appearance of additional zones of weakening of concrete from new breaks of pieces of concrete;

- preliminary control of the position of the anchor relative to the installed reinforcing bars in the body of the future design (as with type I anchors), which eliminates the cost of searching for them during subsequent tests and unnecessary rejection in case of unsuccessful breakouts (exposure of the reinforcement) due to the possible inaccuracy of non-destructive magnetic methods ;

- a fixed position of the anchor in the concrete body, including the depth of laying (as with type I anchors);

- lack of preparatory measures inherent to type II anchors (as for type I anchors), and, accordingly, factors that may affect the final result (position of reinforcing bars in the concrete body, verticality and depth of the hole for the anchor), which is positive in the end affects the variation of measurements and their accuracy;

- the method is applicable as in the early stages of concrete strength gain (as with type I anchors), because there is no harmful effect on drilling concrete and preparing a hole for an anchor; and during subsequent operation of a building or structure, as the anchor is located in the concrete body and does not protrude above the surface, unlike type I anchor. In the latter case, the hole with the anchor may not be hammered, but hidden, for example, only with a GVL sheet, while ensuring the possibility of subsequent tests. Thus, the proposed method has an unlimited range of applications in time;

- the ability to quickly install a large number of anchors while minimizing labor and material resources, which can be torn out during subsequent inspections of structures.

Anchor device is illustrated by drawings, where:

- in FIG. 1 is a diagram of an anchor for tearing with chipping (tearing);

- in FIG. 2 - installation diagram of the anchor in the formwork before concreting;

- in FIG. 3 is a diagram of the implementation of separation with chipping (tearing) a fragment of concrete.

An anchor device for testing the strength of concrete of monolithic building structures, containing an anchor 1 with a central cylindrical part 2 and a working part 3, is made in such a way that there is a thread 4 on one end of the cylindrical part of the anchor to go to the clutch rod 11, and the working part is cylindrical with the possibility of fixing on the tube 7 and with a supporting platform 5 for tearing off a piece of concrete of the vertical formwork panels 6 of monolithic building structures. Also, the anchor device for testing the strength of concrete of monolithic building structures contains a coupling bolt 8 for passage of reusable cords, a coupling nut 9, a bolt of transition 10 to the coupling rod 11, a device 12 for applying a tearing force, including a support ring of the device 13 for limiting the area of separation of concrete and the formation of the cone of destruction 14.

The test method is carried out in the following sequence: anchor 1 is pre-fixed when installing vertical formwork panels 6 of monolithic reinforced concrete walls, beams or columns together with a tube 7 for the passage of reusable strands of the coupling bolt 8, ensuring the spread of the formwork panels 6 with the coupling nut 9 and ensuring the design size constructed structures. When removing the structure, the coupling bolt 8 is removed from the tube and used again, and the tube 7 together with the anchor 1 remain in the concrete body. Then, when the test deadlines are reached, the transition bolt 10 is screwed into the anchor 1 onto the clutch rod 11, also fixed before the test. The device 12 for applying the separation force is installed on the controlled structure together with the support ring of the device 13 to limit the separation area of concrete and the formation of the fracture cone 14 formed during the test. As a result, the anchor device allows you to assess the strength of concrete in this area by the method of separation with chipping.

Designed parts: anchor 1 and transition bolt 10 should be made of steel with a hardness of at least 50HRC.

The calibration dependence between the indirect characteristic of the separation force (device readings) and the strength of concrete samples according to GOST 10180 should be established in accordance with GOST 22690. It is recommended to establish the calibration dependence:

- use at least 15 series of sample cubes according to GOST 10180 or at least 30 separate sample cubes;

- in each series additionally include at least three samples with a size of at least 300 × 300 × 300 mm;

- peel test with cleavage to be carried out one at a time on one of two (optional) side faces.

The inventive method of testing concrete with a new type of anchor can be widely used in the construction industry to determine the strength in vertical monolithic concrete and reinforced concrete products, because reduces the complexity of installing anchors, has simplicity, makes it possible to increase the number of tests at lower cost at modern high rates of concreting, so it meets the criterion of "industrial applicability".

The list of patents and copyright certificates by the method of separation with chipping (pulling) (A.S. - copyright certificate; P. - patent).

1. A.S. 169860. A device for testing the strength of artificial and natural stone materials / I.V. Wolf. - Publ. 1965.

2. A.S. 191873. A device for testing the strength of concrete in products and structures without destruction / B.G. Skramtaev, M.Yu. Leshchinsky. - Publ. 1967.

3. A.S. 920475. Device for mechanical testing of concrete / N.V. Belyaev, N.D. Lisov, L.S. Pavlov, S.Ya. Khomutchenko. - Publ. 1982.

4. P. RU 2212663 C2. Device for testing concrete / V.V. Gulunov, A.A. Pau, A.V. Gulunov, G.B. Gershkovich // Stroypribor LLC. - Publ. 2003.

5. P. RU 2271528 C1. Test method for concrete strength of building structures, a device for boring a profile groove, an anchor device for testing concrete of building structures, a power device for testing concrete of building structures, a conductor for drilling holes / B.A. Melnikov, V.A. Chebykin, G.A. Gubaidullin // LLC NPP INTERPRIBOR. - Publ. 2006.

6.P. RU 140181 U1. A device for determining the strength of concrete / G.A. Gubaidullin, S.M. Leonidov, E.V. Ilkaev // LLC NPP INTERPRIBOR. - Publ. 2014.

7. A.S. 51829. A method for testing the strength of concrete / I.V. Wolf. - Publ. 1937.

8. United States Patent 3,541,845. Method for testing the strength of the material of cast structures, particularly concrete structures / P. Kierkegaard-Hansen. - Publ. 1970.

9. United States Patent 3,861,201. Method and apparatus for early strength testing of in-place concrete / Franz Kaindl. - Publ. 1975.

Claims (2)

1. A method of testing the strength of concrete of monolithic building structures by tearing off with a power device chipping a piece of concrete of monolithic building structures by means of an anchor device and measuring the applied tensile strength, characterized in that the anchor device mounted on the tube is pre-installed during the installation of formwork of monolithic building structures in the zone the location of the cords connecting the formwork panels. 2. An anchor device for testing the strength of concrete of monolithic building structures, containing an anchor with a central cylindrical part and a working part, characterized in that a thread is made on one end of the cylindrical part of the anchor to go to the coupling rod, and the working part is made cylindrical with the possibility of fixing on a tube and with a support platform for tearing off a piece of concrete of monolithic building structures.

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