Device and method for measuring axial tensile strain of concrete at low temperature

Abstract

The invention discloses a low-temperature concrete axial tensile strain measuring device and method, and relates to the technical field of building structure testing devices.The low-temperature concrete axial tensile strain measuring device comprises a low-temperature box, a strain measuring structure and a temperature control structure, a testing section of a test piece is located in the low-temperature box, the low-temperature box is provided with an inlet, and the inlet is used for being communicated with an external low-temperature medium source; the temperature control structure is used for controlling the temperature in the low-temperature box, the strain measurement structure is arranged on a test piece, and the strain measurement structure is used for measuring the strain of axial tension of the test piece. The temperature in the low-temperature box can be accurately controlled through the temperature control structure, so that the concrete test piece can be always in a target low-temperature state within the measurement time, and the strain measurement structure can be used for accurately measuring the deformation of the measurement section under the action of the low-temperature axial load.

Description

Technical Field

[0001] The invention relates to the technical field of building structure test devices, and in particular to a device and method for measuring axial tensile strain of concrete at low temperature. Background Art

[0002] The measurement of axial tensile strain of concrete at low temperature generally involves exposing the concrete in a low temperature state to the air for measurement. However, due to the heat exchange between the low temperature concrete and the air, it is impossible to accurately measure the axial tensile strain of concrete at the target low temperature. Summary of the invention

[0003] The purpose of the present invention is to provide a low-temperature concrete axial tensile strain measurement device and a measurement method, which solves the problem that the axial tensile strain of a concrete specimen cannot be directly measured in situ at low temperature.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a concrete axial tensile strain measuring device under low temperature, comprising a low temperature box, a strain measuring structure and a temperature control structure, wherein a test section of a specimen is located in the low temperature box, the low temperature box is provided with an inlet, the inlet is used to communicate with an external low temperature medium source, the temperature control structure is used to control the temperature in the low temperature box, the strain measuring structure is provided on the specimen, and the strain measuring structure is used to measure the axial tensile strain of the specimen.

[0006] Preferably, the strain measurement structure includes a first clamp, a second clamp, a micrometer and a ejector pin, the first clamp and the second clamp are arranged opposite to each other, the first clamp is used to clamp the upper part of the specimen, the second clamp is used to clamp the lower part of the specimen, the micrometer is connected to the first clamp, the ejector pin is connected to the second clamp, and the testing end of the micrometer is used to contact the ejector pin.

[0007] Preferably, a cushion block is provided between the first clamp and the test piece, and between the second clamp and the test piece. The first clamp and the second clamp are provided with fastening bolts, and the fastening bolts are used to press the cushion block and the test piece together.

[0008] Preferably, the strain measurement structure further includes a limiting shaft, the limiting shaft is connected to the first clamp and the second clamp respectively, and the limiting shaft is used to ensure that the first clamp and the second clamp are level.

[0009] Preferably, there are two micrometers and two ejector pins, and the two micrometers are respectively located on two sides of the test piece.

[0010] Preferably, the temperature control structure includes a plurality of thermocouples and a plurality of temperature controllers, the thermocouples and the temperature controllers correspond one to one, the thermocouples are used to collect the temperature signal of the test section of the specimen in the low-temperature box, and transmit the temperature signal to the temperature controller, the temperature controller is electrically connected to the electric control box, and the electric control box controls the amount of low-temperature medium introduced.

[0011] Preferably, the plurality of thermocouples are arranged at equal intervals from top to bottom.

[0012] Preferably, the low-temperature medium is arranged in a storage tank, the storage tank is connected to the inlet, a liquid pump is arranged between the storage tank and the inlet, the storage tank is connected to an air pump, the air pump is connected to the liquid pump, and the liquid pump and the air pump are electrically connected to the electric control box respectively.

[0013] The present invention also provides a measurement method using the low temperature concrete axial tensile strain measurement device, comprising the following steps:

[0014] First, install the cryogenic box to the test section of the concrete specimen. After the cryogenic box is installed, install the first clamp and the second clamp on the upper and lower sides of the test section, use the limit shaft to fix the distance between the first clamp and the second clamp, and ensure that the first clamp and the second clamp are level, and tighten the fastening bolts on the first clamp and the second clamp so that the first clamp and the second clamp clamp the specimen;

[0015] After the first fixture and the second fixture are installed, the dial gauge and the ejector are installed, the first fixing bolt is tightened to fix the dial gauge to the first fixture, the ejector is used to compress the telescopic end needle of the dial gauge, and the ejector is fixed by the second fixing bolt;

[0016] After the micrometer is installed, remove the limit shaft and load the specimen;

[0017] During the test, the target temperature is input on the electric control box, the working switch is turned on, and the low-temperature medium is input into the low-temperature box to cool the concrete specimen. When the target temperature is reached in the low-temperature box, the electric control box controls the liquid pump and the air pump to stop working. When the temperature in the low-temperature box is lower than the target temperature during the test, the electric control box controls the liquid pump and the air pump to start working, and this process is repeated;

[0018] When the target temperature is reached in the low-temperature box, the testing machine is used to perform axial tensile loading on both ends of the concrete specimen;

[0019] When axial tensile loading is applied to both ends of the specimen, the dial gauge moves axially with the specimen, and the test end of the dial gauge compressed by the ejector pin begins to extend, thereby testing the axial tensile deformation of the test section of the concrete specimen. The ratio of the deformation of the dial gauge to the length of the test section is the axial tensile strain of the test section of the concrete specimen.

[0020] Compared with the prior art, the present invention has achieved the following technical effects:

[0021] The present invention can accurately control the temperature in the low-temperature box through the temperature control structure, so that the concrete specimen can be kept in the target low-temperature state during the measurement time, and the deformation of the measuring section under the low-temperature axial load can be accurately measured using the strain measurement structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a schematic diagram of a device for measuring axial tensile strain of concrete at low temperature according to the present invention;

[0024] Figure 2 The invention provides a low temperature box, a strain measurement structure and a test piece axonometric measurement Figure 1 ;

[0025] Figure 3 The invention provides a low temperature box, a strain measurement structure and a test piece axonometric measurement Figure 2 ;

[0026] Figure 4 A top view of the cryostat, strain measurement structure and test piece of the present invention;

[0027] Figure 5 It is a front view of the cryostat, strain measurement structure and test piece of the present invention;

[0028] Figure 6 It is a side view of the cryostat, strain measurement structure and test piece of the present invention (without infinite axis);

[0029] Figure 7 for Figure 6 AA section view;

[0030] Among them: 1- low temperature box, 2- test piece, 3- inlet, 4- first fixture, 5- second fixture, 6- micrometer, 7- ejector pin, 8- spacer, 9- fastening bolt, 10- limit shaft, 11- connecting bolt, 12- first fixing bolt, 13- second fixing bolt, 14- thermocouple, 15- temperature controller, 16- storage tank, 17- liquid pump, 18- air pump, 19- working switch, 20- first regulating valve, 21- second regulating valve, 22- electric control box. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The purpose of the present invention is to provide a low-temperature concrete axial tensile strain measuring device, which solves the problem that the axial tensile strain of a concrete specimen cannot be directly measured in situ at low temperature.

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] like Figures 1 to 7 As shown: This embodiment provides a concrete axial tensile strain measurement device under low temperature, including a low temperature box 1, a strain measurement structure and a temperature control structure. The test section of the specimen 2 is located in the low temperature box 1. The low temperature box 1 is provided with an inlet 3, and the inlet 3 is used to communicate with an external low temperature medium source. The external low temperature medium is preferably liquid nitrogen. The temperature control structure is used to control the temperature in the low temperature box 1. The strain measurement structure is arranged on the specimen 2, and the strain measurement structure is used to measure the axial tensile strain of the specimen 2.

[0035] Specifically, in this embodiment, the strain measurement structure includes a first clamp 4, a second clamp 5, a micrometer 6 and an ejector pin 7. The first clamp 4 and the second clamp 5 are arranged opposite to each other. The first clamp 4 is used to clamp the upper part of the specimen 2, and the second clamp 5 is used to clamp the lower part of the specimen 2. A cushion block 8 is arranged between the first clamp 4 and the specimen 2, and between the second clamp 5 and the specimen 2. The first clamp 4 and the second clamp 5 are provided with a fastening bolt 9, and the fastening bolt 9 is used to press the cushion block 8 and the specimen 2. The micrometer 6 is connected to the first clamp 4, and the ejector pin 7 is connected to the second clamp 5. The test end of the micrometer 6 is used to contact the ejector pin 7. There are two micrometers 6 and two ejector pins 7, and the two micrometers 6 and the two ejector pins 7 are respectively located on both sides of the specimen 2. In this embodiment, the micrometers 6 on both sides of the specimen 2 are used to measure the axial tensile deformation of the test section of the specimen 2. The micrometer 6 is divided into a test end and a display end. The micrometer 6 measures the deformation of the test section of the test piece 2 by the extension and retraction of the needle at the test end, and the display screen at the display end displays the extension and retraction amount of the needle of the micrometer 6.

[0036] In this embodiment, the strain measurement structure further includes a limit shaft 10 , which is respectively connected to the first clamp 4 and the second clamp 5 via connecting bolts 11 , and the limit shaft 10 is used to ensure that the first clamp 4 and the second clamp 5 are level.

[0037] In this embodiment, the temperature control structure includes a plurality of thermocouples 14 and a plurality of temperature controllers 15. The plurality of thermocouples 14 are arranged at equal intervals from top to bottom. Preferably, there are three thermocouples 14. The top thermocouple 14 is used to measure the temperature of the upper edge of the test section of the specimen 2. The middle thermocouple 14 is used to measure the temperature in the middle of the test section of the specimen 2. The bottom thermocouple 14 is used to measure the temperature of the lower edge of the test section of the specimen 2. The thermocouples 14 and the temperature controllers 15 correspond one to one. The thermocouples 14 are used to collect the temperature signal of the test section of the specimen 2 in the low-temperature box 1 and transmit the temperature signal to the temperature controller 15. The degree of each thermocouple 14 can be read by the corresponding temperature controller 15. The temperature controller 15 is electrically connected to the electric control box 22, and the electric control box 22 controls the amount of low-temperature medium introduced.

[0038] In this embodiment, considering that there may be a gap between the cryogenic box 1 and the surface of the test piece 2, which may cause the liquid nitrogen in the cryogenic box 1 to leak, during the test, the gap between the cryogenic box 1 and the test piece 2 is plugged with thermal insulation cotton to suppress the leakage of liquid nitrogen and ensure that the temperature measured by each thermocouple 14 in the cryogenic box 1 is as close as possible to the actual temperature value of the test piece 2.

[0039] In this embodiment, the cryogenic medium is arranged in the storage tank 16, the storage tank 16 is connected to the inlet 3, a liquid pump 17 is arranged between the storage tank 16 and the inlet 3, the storage tank 16 is connected to the air pump 18, the air pump 18 is connected to the liquid pump 17, and the liquid pump 17 and the air pump 18 are respectively electrically connected to the electric control box 22. The gas enters the storage tank 16 through the air pump 18 and the liquid pump 17, providing power for the extrusion of the liquid nitrogen, and the liquid nitrogen changes from liquid to gas through the liquid pump 17, and then enters the cryogenic box 1, so that the cryogenic box 1 forms a low temperature environment of 0°C to -70°C.

[0040] In this embodiment, after turning on the working switch 19, when the temperature in the low-temperature box 1 is higher than the target temperature, the electrical control box 22 controls the liquid pump 17 and the air pump 18 to start working; when the temperature in the low-temperature box 1 reaches the target temperature, the electrical control box 22 controls the liquid pump 17 and the air pump 18 to stop working.

[0041] Working method of the low temperature concrete axial tensile strain measuring device of this embodiment:

[0042] First, install the cryogenic box 1 to the test section of the concrete specimen 2, and connect the inlet 3 on the cryogenic box 1 to the metal hose. After the cryogenic box 1 is installed, install the first clamp 4 and the second clamp 5 on the upper and lower sides of the test section, use the limit shaft 10 to fix the distance between the first clamp 4 and the second clamp 5, and ensure that the first clamp 4 and the second clamp 5 are level, tighten the fastening bolts 9 on the first clamp 4 and the second clamp 5 so that the first clamp 4 and the second clamp 5 clamp the specimen 2, and ensure that the first clamp 4 and the second clamp 5 do not slide during the stretching process of the specimen 2;

[0043] After the first fixture 4 and the second fixture 5 are installed, the dial gauge 6 and the ejector pin 7 are installed, and the first fixing bolt 12 is tightened to fix the dial gauge 6 to the first fixture 4. The telescopic end needle of the dial gauge 6 is compressed by the ejector pin 7, and the ejector pin 7 is fixed by the second fixing bolt 13;

[0044] After the micrometer 6 is installed, the limit shaft 10 is removed and the specimen 2 is loaded;

[0045] During the test, the target temperature is inputted into the electric control box 22, the working switch 19 is turned on, and the liquid nitrogen starts to be inputted from the liquid storage tank into the cryogenic box 1 through the liquid pump 17 to cool the concrete specimen 2. The air pump 18 is connected to the storage tank 16 through a plastic hose, and the liquid pump 17 is connected to the cryogenic box 1 through a metal pipe. When the target temperature is reached in the cryogenic box 1, the electric control box 22 controls the liquid pump 17 and the air pump 18 to stop working. When the temperature in the cryogenic box 1 is lower than the target temperature during the test, the electric control box 22 controls the liquid pump 17 and the air pump 18 to start working, and this is repeated, wherein the first regulating valve 20 of the air pump 18 can adjust the gas, and the second regulating valve 21 of the liquid pump 17 can adjust the output rate of the liquid nitrogen;

[0046] When the target temperature is reached in the low temperature box 1, the testing machine is used to perform axial tensile loading on both ends of the concrete specimen 2;

[0047] When axial tensile loading is applied to both ends of the specimen 2, the micrometer 6 moves axially with the specimen 2, and the test end of the micrometer 6 compressed by the ejector pin 7 begins to extend, thereby testing the axial tensile deformation of the test section of the concrete specimen 2. The ratio of the deformation of the micrometer 6 to the length of the test section is the axial tensile strain of the test section of the concrete specimen 2.

[0048] In this embodiment, liquid nitrogen is input into the cryogenic box 1 by using an air pump 18 and a liquid pump 17 to cool the concrete specimen 2 so that the test section of the specimen 2 is in a low temperature environment. The temperature in the cryogenic box 1 is measured by a thermocouple 14, and the thermocouple 14 is connected to a temperature controller 15. The liquid nitrogen input rate is controlled by an electric control box 22 to control the temperature in the cryogenic box 1. The micrometer 6 and the ejector pin 7 are clamped by a first clamp 4 and a second clamp 5 fixed to the specimen 2 to test the deformation of the low temperature section of the concrete specimen 2.

[0049] Compared with the prior art, the present embodiment can control the liquid nitrogen input rate through the thermocouple 14 and the temperature controller 15, accurately control the temperature in the cryogenic box 1, and keep the concrete specimen 2 in the target low temperature state during the measurement time. The present embodiment uses the micrometer 6 to accurately measure the deformation of the measuring section under the low temperature axial load.

[0050] The present specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A device for measuring axial tensile strain of concrete at low temperature, characterized in that: It includes a low temperature box, a strain measurement structure and a temperature control structure. The test section of the specimen is located in the low temperature box. The low temperature box is provided with an inlet, which is used to communicate with an external low temperature medium source. The temperature control structure is used to control the temperature in the low temperature box. The strain measurement structure is arranged on the specimen, and the strain measurement structure is used to measure the axial tensile strain of the specimen.

2. The low temperature concrete axial tensile strain measuring device according to claim 1 is characterized in that: The strain measurement structure includes a first fixture, a second fixture, a micrometer and a thimble, the first fixture and the second fixture are arranged opposite to each other, the first fixture is used to clamp the upper part of the specimen, the second fixture is used to clamp the lower part of the specimen, the micrometer is connected to the first fixture, the thimble is connected to the second fixture, and the testing end of the micrometer is used to contact the thimble.

3. The low temperature concrete axial tensile strain measuring device according to claim 2 is characterized in that: A cushion block is provided between the first clamp and the test piece, and between the second clamp and the test piece. The first clamp and the second clamp are provided with fastening bolts, and the fastening bolts are used to press the cushion block and the test piece together.

4. The low temperature concrete axial tensile strain measuring device according to claim 2 is characterized in that: The strain measurement structure further includes a limiting shaft, which is connected to the first clamp and the second clamp respectively, and is used to ensure that the first clamp and the second clamp are level.

5. The low temperature concrete axial tensile strain measuring device according to claim 2 is characterized in that: There are two micrometers and two ejector pins, and the two micrometers are respectively located on two sides of the test piece.

6. The low temperature concrete axial tensile strain measuring device according to claim 1 is characterized in that: The temperature control structure includes a plurality of thermocouples and a plurality of temperature controllers, and the thermocouples and the temperature controllers correspond one to one. The thermocouples are used to collect the temperature signal of the test section of the specimen in the low-temperature box and transmit the temperature signal to the temperature controller. The temperature controller is electrically connected to the electric control box, and the electric control box controls the amount of low-temperature medium introduced.

7. The low temperature concrete axial tensile strain measuring device according to claim 6 is characterized in that: The plurality of thermocouples are arranged at equal intervals from top to bottom.

8. The low temperature concrete axial tensile strain measuring device according to claim 6, characterized in that: The low-temperature medium is arranged in a storage tank, the storage tank is connected to the inlet, a liquid pump is arranged between the storage tank and the inlet, the storage tank is connected to an air pump, the air pump is connected to the liquid pump, and the liquid pump and the air pump are electrically connected to the electric control box respectively.

9. A method for measuring the axial tensile strain of concrete at low temperature using the device for measuring the axial tensile strain of concrete at low temperature according to any one of claims 1 to 8, characterized in that: The following steps are involved: First, install the cryogenic box to the test section of the concrete specimen. After the cryogenic box is installed, install the first clamp and the second clamp on the upper and lower sides of the test section, use the limit shaft to fix the distance between the first clamp and the second clamp, and ensure that the first clamp and the second clamp are level, and tighten the fastening bolts on the first clamp and the second clamp so that the first clamp and the second clamp clamp the specimen; After the first fixture and the second fixture are installed, the dial gauge and the ejector are installed, the first fixing bolt is tightened to fix the dial gauge to the first fixture, the ejector is used to compress the telescopic end needle of the dial gauge, and the ejector is fixed by the second fixing bolt; After the micrometer is installed, remove the limit shaft and load the specimen; During the test, the target temperature is input on the electric control box, the working switch is turned on, and the low-temperature medium is input into the low-temperature box to cool the concrete specimen. When the target temperature is reached in the low-temperature box, the electric control box controls the liquid pump and the air pump to stop working. When the temperature in the low-temperature box is lower than the target temperature during the test, the electric control box controls the liquid pump and the air pump to start working, and this process is repeated; When the target temperature is reached in the low-temperature box, the testing machine is used to perform axial tensile loading on both ends of the concrete specimen; When axial tensile loading is applied to both ends of the specimen, the dial gauge moves axially with the specimen, and the test end of the dial gauge compressed by the ejector pin begins to extend, thereby testing the axial tensile deformation of the test section of the concrete specimen. The ratio of the deformation of the dial gauge to the length of the test section is the axial tensile strain of the test section of the concrete specimen.

Images