RU2726031C1 - Bench for testing reinforced concrete elements for forcing at short-term dynamic load - Google Patents

Abstract

FIELD: test equipment.SUBSTANCE: invention relates to test equipment, namely to machines for testing concrete and reinforced concrete samples for forcing at impact loads. Test bench comprises a power floor on which a support base is rigidly fixed, vertical guides fixed on a support base, having cargo fall arresters, consisting of couplings bolted to vertical guides through rubber gaskets, load fixed on vertical guides, a sample, on top of which there is a force meter with a nozzle-damper. Nozzle-damper consists of two metal support plates and a set of rubber gaskets installed between them. Stand comprises a special support element, which is a collapsible metal frame and having fastening with turnbuckles and strings with nuts to the strata of the power floor, a clamping metal frame, which is two metal angles with stiffness ribs tightened by means of strings and nuts through rubber gaskets on vertical guides, and on the center of the tightening metal frame on top two angles with oval slots are attached, in which the rod is inserted the limiter of displacements, rod limit stop, bottom and top head of force meter. Experimental sample consists of plate and column part, its plate part rests on support element, and metal head of column part has cylindrical slots for installation of rod of movement limiter. Displacement limiter passes through the cylindrical holes in the angles on the tightening metal frame and is fixed in cylindrical grooves of the metal head of the column part of the experimental sample. Force meter is installed in lower head, which, in its turn, by means of cylindrical slot is installed on rod displacement limiter, and on top of force meter is put upper head, on which by means of annular slot installed attachment-damper, fixed by means of safety ropes to clamping metal frame. On each of four sides of the support element there are measuring sensors connected by cables to the measuring system.EFFECT: formation of a stressed-deformed state in an experimental sample working on forcing-out under impact-wave action and determining its support reaction taking into account the spatial nature of its occurrence.3 cl, 4 dwg

Description

The invention relates to testing equipment, and in particular to machines for testing concrete and reinforced concrete samples for bursting under shock loads.

Experimental tests of concrete and reinforced concrete elements for various types of dynamic loads are necessary to determine the properties of mass-produced, operated, or promising building structures, and to verify their design characteristics and quality.

In the prior art, for example, a bench for testing concrete and reinforced concrete elements for longitudinal central and eccentric short-term dynamic compression according to the invention patent RU 2315969, IPC G01N 3/30, publ. 01/27/2008. This stand includes vertical guides mounted on a support base, on which a traverse with a load is fixed with the possibility of vertical reciprocating movement, and a fastener for the lower end of the test sample. A head is mounted on the upper end of the test specimen, on which a force meter is mounted. On both sides of the test specimen, two hollow cylindrical nozzles are installed, each of which is fixedly connected to its respective vertical guide rail. In the cavity of each of the nozzles along the entire length to the stop with the possibility of torsion in two mutually opposite directions, a rod is placed. The free ends of the rods are fixedly connected to the head. The lower end of the test sample is provided with an additional support, by means of which it is fixedly mounted on the support base of the stand, and the support base is installed on the power floor. In addition, the stand is equipped with a plate for distributing stresses on the force floor, which is installed under the additional support, and the additional support is pinched on the support base by means of fixing angles. The design of the upper and lower attachment points of the test sample prevents horizontal displacement of the ends of the sample, but does not prevent their angular movement relative to their respective nodes. This stand allows testing concrete and reinforced concrete columns for central and eccentric compressive short-term dynamic effects and to create a stress-strain state close to the conditions of their operation with a hard version of fixing the bottom of the sample. The disadvantage of the stand is that it does not allow to test reinforced concrete elements for bursting under shock loads and to measure the support reaction.

In recent years, there is an increasing need to design reinforced concrete structures, which may be affected by intense short-term dynamic loads.

Such loads can occur when shockwaves are affected by structures due to explosions during accidents or terrorist attacks, natural or man-made disasters, due to the fall of a heavy load, etc. The resulting specific loads often cause significant structural damage, and even their complete or partial destruction, which can lead to personal injury and death, as well as damage to expensive equipment and, consequently, considerable material costs. Such loads are characterized by a sharp increase in the front, a short duration of action and the wave nature of the impact.

From literary sources (for example, Popov N.N., Rastorguev B.S. Dynamic calculation of reinforced concrete structures M., Stroyizdat, 1974, 207 pp.) It is known that a building structure can absorb a larger short-term dynamic load compared to static. This is due to a change in the physicomechanical characteristics of concrete and reinforcement compared with a static state. In the case of short-term dynamic loading, uneven development and a certain delay in deformations are observed in comparison with the results of static tests. That is, the physical processes occurring during short-term dynamic loading differ from the processes under static loading of the same element.

This requires a study of the behavior of reinforced concrete elements under short-term dynamic loads and the creation of appropriate testing equipment.

The closest known device adopted for the prototype is a test bench for building structures for the action of short-term dynamic compressive load according to the Eurasian patent for invention 027933 B1 Int. C1. G01M 7/08, G01N 3/303, publ. 09/29/2017.

According to the prototype, the stand contains a force floor on which the support base is rigidly fixed, a support for installing the test sample, containing the support plate mounted on the power floor, a support force meter, rigidly mounted on the support plate, vertical guides mounted on the support base, a beam with a load fixed on guides. The bench contains a head worn on the upper end of the test sample and the upper load cell. In addition, the stand contains two hollow cylindrical nozzles mounted horizontally on both opposite sides of the test sample and each of which is fixedly connected to a vertical guide. There are two rods located in the cavities of the respective cylindrical nozzles with the possibility of torsion in two directions, the free ends of which are motionlessly connected to the tip of the upper end of the test sample. The stand includes a metal ball mounted between the load meter and the lower end of the test sample. In this case, the lower end of the test sample is equipped with a head for installing the sample in it, based on the supporting load meter through a metal ball using a metal nozzle. On both opposite sides of the test sample, two further hollow cylindrical nozzles are additionally horizontally mounted, fixedly fixed by one side on vertical guides and also placed in the cavities of the corresponding cylindrical nozzles, the free ends of which are motionlessly connected to the tip of the lower end of the test sample. The force meter is mounted on the head through a plate rigidly fixed to the head with bolts, which is a replaceable structural element of the stand and consisting of a metal plate and a support ring rigidly fixed on it, by means of which the upper force meter is rigidly fixed to the plate. The support ring may be located in the center of the metal plate or offset horizontally relative to the center of the metal plate. A damper nozzle is mounted on the upper load cell, while the lower plate in the central part of the lower side is provided with a support ring, by means of which it is secured to the upper load cell. The bench allows testing of building structures for the action of a central, eccentric and oblique eccentric short-term dynamic compressive load and testing structures with reduced stiffness and increased flexibility, and also allows you to determine the support reaction. However, at this stand it is not possible to test the reinforced concrete elements for bursting under short-term dynamic loading, and it is also not possible to determine the support reaction, due to the fact that during burst tests it is not point but spatial in nature.

A new technical result, the achievement of which the proposed technical solution is aimed at, consists in the formation of a stress-strain state and determination of its support reaction taking into account the spatial nature of its occurrence in an experimental specimen working for punching under shock-wave action.

The technical result is achieved as follows.

The inventive stand contains a force floor on which the support base is rigidly fixed through the streams of the power floor, vertical guides mounted on the support base having load drop limiters consisting of couplings (clamps) bolted to the vertical guides through rubber gaskets. The load, mounted on vertical guides, has the possibility of vertical reciprocating movement, and with the help of which a short-term dynamic load is created on the experimental sample, on top of which a force meter with a damper nozzle is mounted, while the damper nozzle consists of two metal support plates and located between them a set of rubber gaskets. The damper nozzle serves to increase the duration of the load on the experimental sample and consists of two metal support plates and a set of rubber gaskets located between them. By changing the number of gaskets, you can adjust the duration of the load. By changing the weight of the load changes the magnitude of the load.

For the operation of the stand, an experimental sample is made, consisting of a slab and a column part, while the metal head of the column part has cylindrical grooves for installing the displacement limiter rod. To realize the possibility of restricting movements on the vertical guides of the pile driver, a coupling metal frame is installed at a certain level, which is two metal corners with stiffeners, tightened with cords and nuts through rubber gaskets on the vertical guides. From the top in the center of the coupling metal frame, two corners with oval slots are welded into which, in order to realize the possibility of limiting the movement, a rod limiter is inserted.

The force meter is installed in the lower head, in which there is a cylindrical groove on the bottom for installing a limiter on the rod. The upper head is put on top of the force meter, on which a damper nozzle is installed using an annular groove. The damper nozzle is secured to the tie-rod metal frame by means of safety ropes, in order to avoid falling during the test. The experimental sample of the slab part is based on a special support element, which is a collapsible metal frame. For fastening to the force floor and ensuring the absence of displacements of the supporting element during dynamic tests, fastenings with lanyards and bands with nuts through the streams of the power floor are provided.

Due to the fact that the support reaction when the load falls on the building structure has a spatial character and is distributed unevenly around the perimeter due to intolerance, hugs, displacements during installation, etc. it is necessary to have a set of measuring sensors distributed over each of the four sides of the support element. Measuring sensors are connected by cables to the measuring system. The readings of the measuring sensors in total give the values of the support reaction, and the analysis of the readings of each sensor separately allows you to get a picture of the distribution of the support reaction taking into account the spatiality of its occurrence.

Strain gauges can be used as measuring sensors.

In the inventive device, the used strain gauge sensor can be implemented, for example, prefabricated in four parts (one on each side of the support element), while each of the parts contains four measurement points distributed along the length. This strain gauge sensor has four working strain gages that are glued to the surface of the support element. To exclude a short to metal, insulating material is provided at the exit points of the working strain gages releases. A soldering pad is pasted nearby. All working strain gages are connected in series with wires. A non-deformable non-conductive pad is also glued to the support element, on which four compensation strain gages are located. All compensation strain gages are also serially connected by wires, and also have platforms for desoldering. Working strain gages and compensation strain gages on each side of the support element are a separate strain gauge sensor, they are combined in a half-bridge circuit and connected to the measuring system via a cable. For all strain gages, thermal insulation is provided.

The invention is illustrated by drawings.

In FIG. 1 shows a bench for testing concrete elements for bursting under short-term dynamic load. In FIG. 2 shows a support element and one of its sides with a strain gauge image for determining support reactions. In FIG. 3 shows a connection diagram of a strain gauge strain gauge sensor. In FIG. 4 shows a General view of the implemented stand for testing concrete elements for punching under short-term dynamic load.

The drawings show:

1 - power floor;

2 - vertical guides;

3 - supporting base;

4 - streams of power sex;

5 - experimental sample;

6 - supporting element;

7 - lanyards;

8 - bands with nuts;

9 - metal head of the column;

10 - rod - limiter movements;

11 - a metal frame;

12 - corner with oval slots;

13 - load meter;

14 - lower end of the load cell

15 - the upper tip of the load meter;

16 - nozzle-damper;

17 - safety ropes; 18-load;

19 - load drop limiters;

20 - working strain gages;

21 - insulating material;

22 - a platform for desoldering;

23 - wires;

24 - non-conductive pad;

25 - compensation thermistors;

26 - cables;

27 - thermal insulation;

28 - measuring system.

The presented stand for testing reinforced concrete elements for punching under short-term dynamic loading contains

power floor 1, on which the support base 3 is rigidly fixed through the streams 4 of the power floor 1,

vertical guides 2, mounted on a support base 3, having load drop limiters 19, consisting of couplings (clamps) bolted to the vertical guides through rubber gaskets,

a load 18, mounted on vertical guides 2, with the possibility of vertical reciprocating movement, with the help of which a short-term dynamic load is created on the experimental sample 5, on top of which a force meter 13 with a damper nozzle 16 consisting of two metal support plates and located between them is installed a set of rubber pads. At the same time, the stand design includes:

special supporting element 6, which is a collapsible metal frame and having fastenings by lanyards 7 and bands with nuts 8 to the streams of the power floor 1 for fixing to the power floor 1 and ensuring the absence of its displacements during dynamic tests.

a tightening metal frame 11 for realizing the possibility of restricting movements on the vertical guides of the pile rig, which is two metal corners with stiffeners, tightened with cords and nuts through rubber gaskets on the vertical guides, and two corners 12 with oval are attached from the top center of the fastening metal frame the slots into which the rod is inserted limiter displacement 10,

rod limiter 10,

lower 14 and upper 15 heads of the load meter 13.

Experimental sample 5 consists of a plate and column part, its plate part rests on a supporting element 6, and the metal head of the column part has cylindrical grooves for installing the rod of the movement limiter 10.

The rod displacement limiter 10 passes through cylindrical openings in the corners on the coupling metal frame 11, is fixed in cylindrical grooves in the metal head of the column part of the experimental sample 5 and serves to realize the possibility of restricting displacement.

The force meter 13 is installed in the lower head 14, which, in turn, is mounted on the rod using a cylindrical groove 10, and the upper head 15 is put on top of the force meter 13, on which the damper nozzle 16 is mounted using an annular groove, fixed with safety ropes 17 to the coupling metal frame 11.

On each of the four sides of the support element 6 are placed measuring sensors connected by cables 26 to the measuring system 28.

Strain gauges can be used as measuring sensors. For example, the used strain gauge sensors may have a design consisting of four working strain gages 20 glued to the surface of the support element 6, while insulating material 21 is provided at the exit points of the working strain gages 20, and a soldering pad is pasted 22. In this design, all workers the strain gages are connected in series with wires 23, and a non-deformable non-conductive pad 24 is also glued on the support element 6, on which there are four, connected in series by wires 23 on the desoldering pads 22, compensation strain gages 25, while the working 20 and compensation strain gages 25 are combined in a half-bridge circuit and connected to the measuring system via cable 26, while all strain gages are provided with thermal insulation 27.

The principle of operation of the stand is as follows: before testing the rod, the movement limiter 10 must be set to such a height from the bottom of the corners with oval slots 12 that it is necessary to limit the maximum deflections of the experimental sample 5 during the test. After applying the load, the rod limiter 10 will move down in the oval slots and will rest against the coupling metal frame 11, which due to its rigid attachment to the vertical guides 2 will limit the movement. Limiters of the fall of the load 19 must be set to the required elevation, to limit the movement of the load 18 during testing. If it is necessary to create an eccentricity of the dynamic load application, the rod displacement limiter 10 is not installed in the central cylindrical groove of the metal head of the column 9.

After connecting all the sensors to the measuring system 28, a test occurs. The load on the experimental sample 5 is transmitted by dropping the load 18 from a given height along the vertical guides 2.

The result of the load on the experimental sample is recorded by measuring sensors and transmitted via cables 26 to the measuring system 28.

Thus, the proposed technical solution allows testing reinforced concrete elements for punching under the action of short-term dynamic loads and determine the support reaction taking into account the spatial nature of its occurrence.

Claims (15)

1. Stand for testing reinforced concrete elements for punching under short-term dynamic load, containing power floor, on which the support base is rigidly fixed through the streams of the power floor, vertical guides mounted on a support base having load drop limiters consisting of couplings (clamps) bolted to vertical guides through rubber gaskets, a load secured on vertical guides, with the possibility of vertical reciprocating movement, by means of which a short-term dynamic load is created on the experimental sample, on top of which a force meter with a damper nozzle is mounted, while the damper nozzle consists of two metal support plates and located between them a set of rubber gaskets, characterized in that it contains a special supporting element, which is a collapsible metal frame and having fastenings with lanyards and bands with nuts to the streams of the power floor, a coupling metal frame, which is two metal corners with stiffening ribs, tightened with cords and nuts through rubber gaskets on vertical guides, and two corners with oval slots are attached to the center of the coupling metal frame from above, into which the limiter rod is inserted, rod limiter, lower and upper heads of the load meter, wherein the experimental sample consists of a plate and column part, its plate part rests on a support element, and the metal head of the column part has cylindrical grooves for mounting the displacement limiter rod, a movement limiter rod passes through cylindrical holes in the corners on the coupling metal frame and is fixed in the cylindrical grooves of the metal head of the column part of the experimental sample, the load meter is installed in the lower head, which, in turn, is installed with a cylindrical groove on the rod, a movement limiter, and the upper head is put on top of the load meter, on which a damper nozzle is mounted using the ring groove, fixed with safety ropes to the coupling metal frame , at the same time, on each of the four sides of the support element there are measuring sensors connected by cables to the measuring system. 2. The stand according to claim 1, characterized in that tensometric sensors are used as measuring sensors. 3. The stand according to claim 2, characterized in that the strain gauges consist of four working strain gages glued to the surface of the support element, while insulating material is provided at the exit points of the working strain gages, and a desoldering pad is glued nearby, all working strain gages are connected in series wires, and a non-deformable non-conductive pad is also glued to the support element, on which there are four, connected in series by wires on the desoldering pads, compensating strain gages, while the working and compensation strain gages are connected in a half-bridge circuit and connected to the measuring system by cable, while for all Strain gages provide thermal insulation.

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