A tensile creep test device and method for high-strength concrete

Abstract

The invention relates to a tensile creep test device and method for high-strength concrete, comprising a double-spring tensile creep device and a concrete specimen creep strain collection method; the double-layer spring tensile creep device uses double springs to ensure the stability of the loading process and the later load holding; a linear differential displacement sensor is arranged on one side of the concrete test specimen, and a micrometer detector is arranged on the other side; under the premise of ensuring that the difference between the two collection methods is within the error range, the data points of the sensor are used in the early stage, and the reading points of the micrometer are used in the later stage, and the logarithmic plotting method is used to draw a graph, which can not only show the instantaneous deformation including elastic deformation in the initial stage of loading, but also prevent the deformation of several years from being close to the horizontal level, thereby overcoming the limitation of the traditional strain collection method that the values ​​in a shorter time cannot be distinguished and the values ​​in a longer time are located outside the graph; the test device and method have the characteristics of simple operation, low cost, applicability to long-term tensile creep testing, reliable data, etc.

Description

Technical Field

[0001] The invention relates to a tensile creep test device and method for high-strength concrete, belonging to the field of concrete structures and materials. Background Art

[0002] Creep is an important characteristic in studying the properties of concrete. Traditional research on the creep of mature concrete under compression is relatively mature, but research on the creep of concrete under tension, especially early concrete under tension, is rare. A large number of experiments have shown that whether concrete cracks or not not only depends on shrinkage, but is also greatly affected by tensile creep. Therefore, the study of tensile creep is of great significance. The tensile creep test mainly includes three parts, namely loading method, strain collection and specimen form.

[0003] There are many loading methods used in tensile creep devices, but they all have certain shortcomings. Lever loading is simple to make and low in cost, but it occupies a large area. Pulley loading is relatively stable, but the instrument is complex and has certain friction losses. These two loading methods also have shortcomings in terms of stable loads. For example, the steel block method has the problem of difficulty in loading and unloading steel blocks and load adjustment, and the water tank method has the disadvantage that water is easy to evaporate and cause load changes. Hydraulic loading can apply a high enough load, but the cost of hydraulic testing machines is extremely high. At present, the most widely used is spring loading, which has a simple device, low cost, and can apply a high enough load, but most of them are used as compressive creep devices, and the applied load is unstable. Therefore, it is of great significance to convert traditional compressive creep devices into tensile creep devices.

[0004] In terms of strain collection, traditional creep strain collection methods are mostly single displacement sensor collection and micrometer collection. However, the displacement sensor collection method is not suitable for creep collection cycles of many years. On the other hand, the displacement sensor needs to be powered on during operation, and there is a certain uncertainty in the collection process of several years. In addition, the cost of equipment such as sensors and collectors is too high, which is not conducive to the smooth development of the test. The micrometer collection method has the advantages of no need for power supply, stable readings, and no restrictions on measurement time and measurement position. However, the micrometer requires manual reading, and the collection frequency is limited. Therefore, only some discrete data can be collected, which has a certain one-sidedness in data collection. The traditional creep data plotting method is to perform linear plotting at fixed time intervals. Therefore, it is impossible to clearly distinguish the change of strain over time in the short period of time before loading. In addition, general tests stipulate that the measurement should start before the load is applied, and the elastic deformation during the loading process (i.e., the creep flexibility curve) must be included. The linear scale obviously cannot meet the relevant requirements. If you want to show the short-term strain situation, the linear plotting rule for the values ​​of longer time will be portrayed outside the chart, resulting in a lack of data integrity. In summary, it is recommended to collect and plot in the form of time logarithm.

[0005] In terms of fixing the specimens to the equipment, the common installation forms of the specimens are as follows: 1) Prefabricated anchors are placed at both ends of the specimens, which destroys the integrity of the specimens; 2) Gluing steel plates at both ends of the specimens with glue, which is limited by the tensile strength of the glue. Especially when the specimens tested are ultra-high performance concrete, they usually break at the glue bonding point, affecting the authenticity of the test data; 3) Using clamps to fix the two ends of the specimens, there is a situation where the clamping is not tight; 4) Using dog bone specimens, the clamps are clamped at the contraction points at both ends of the dog bones. This clamping form has stress concentration, and the ports are concentrated at the contact points, which increases the test error. For the tensile creep specimens of high-strength concrete, its high-strength properties have higher requirements for the installation form. Therefore, it is particularly critical and necessary to propose an effective tensile creep test method for high-strength concrete to carry out tensile creep tests on high-strength concrete. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a tensile creep test device and method for high-strength concrete to solve the problems in the prior art.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A tensile creep test device for high-strength concrete comprises a loading test device and a concrete test piece, wherein the concrete test piece is connected to the loading test device, a linear differential displacement sensor is arranged on one side of the concrete test piece, and a micrometer detector is arranged on the other side of the concrete test piece.

[0009] Preferably, the loading test device comprises a top plate, a bottom plate and three threaded rods, the upper ends of the three threaded rods are fixedly connected to the top plate, the lower ends of the three threaded rods are fixedly connected to the bottom plate, a sleeve, a force spring and a stabilizing spring are sequentially sleeved on the middle part of each threaded rod from top to bottom, a force plate is provided between the force spring and the stabilizing spring, a through hole is provided on the force plate, and the threaded rod is penetrated and arranged in the through hole; a force nut is provided on the threaded rod, and the force nut is arranged above the sleeve; the concrete test piece is arranged between the three threaded rods, the upper end of the concrete test piece is connected to the top plate through a connecting rod, and the lower end of the concrete test piece is connected to the force plate through a connecting rod.

[0010] Preferably, the sleeve, the force spring, the force plate and the stabilizing spring are all arranged between the top plate and the bottom plate.

[0011] Preferably, the concrete test piece comprises a concrete test piece, wherein steel plates are provided at both upper and lower ends of the concrete test piece, and pull rings are provided on the two steel plates, and the two pull rings are respectively connected to the connecting rod through ball joints.

[0012] Preferably, the pull ring is anchored inside the thick steel plate to provide support for the stretching of the device.

[0013] Preferably, the steel plate is fixedly connected to the concrete specimen by an adhesive.

[0014] Preferably, the concrete specimen is of dog-bone type.

[0015] The steel plates are attached to both ends of the high-strength concrete dog-bone specimen. The unique structure of the dog-bone specimen is used to increase the contact area at both ends and improve the bonding strength. The middle part of the specimen is thinner, which is conducive to the fracture of the specimen and convenient for obtaining the tensile creep displacement characteristics of the specimen as a whole. The steel plates are attached to the high-strength concrete dog-bone specimen, which is convenient for achieving the expected effect when the specimen is tensile creep.

[0016] Preferably, a spoke-type load sensor is provided between the connecting rod at the lower end of the concrete specimen and the force application plate.

[0017] Preferably, the linear differential displacement sensor comprises a displacement sensor and a displacement collector, the displacement sensor is connected to the concrete specimen via a fixed bracket, and the displacement sensor is connected to the displacement collector.

[0018] The linear differential displacement sensor is used to convert the physical quantity of the specimen creep displacement into an electrical signal, and collect the displacement change of the specimen during creep at a higher acquisition frequency;

[0019] The displacement sensor is placed on one side of the high-strength concrete dog-bone specimen to detect the displacement of the thin end of the middle part of the high-strength concrete dog-bone specimen;

[0020] The linear differential displacement sensor is used to collect the displacement data of the specimen and depict the curve change of the tensile creep displacement of the specimen;

[0021] Preferably, the micrometer tester comprises a micrometer, and the micrometer is connected to the concrete specimen via a fixed bracket.

[0022] The micrometer converts the general linear displacement into the rotational motion of the pointer through gears or levers, and is convenient for long-term and stable reading of the creep displacement characteristics of the test piece without power supply;

[0023] The fixed bracket is used to fix the micrometer, and the contact surface is kept as flat and stable as possible to facilitate accurate measurement of the micrometer.

[0024] The micrometer is placed on the other side of the dog-bone concrete specimen. By comparing the specimen displacement data collected by the displacement sensor on one side, the fitting effect of the micrometer discrete points on the specimen tensile creep displacement data is obtained.

[0025] The double-layer spring loading test device includes a spring portion, an upper thicker force application spring and a lower thinner stabilizing spring;

[0026] A spherical joint is installed on the upper and lower sides of the concrete specimen, mainly to prevent eccentric loading and stress concentration;

[0027] The spoke load sensor is installed on the force plate to record the change of load;

[0028] The sleeve mainly plays the role of transmitting force, which is convenient for the force nut to squeeze the force spring to generate tensile stress; the stiffness coefficient of the force spring is much larger than that of the stabilizing spring. When the two springs are deformed to the same position, the force generated by the former is much larger than that of the latter. The force spring can provide a larger load and is conducive to the supplement of the load after creep relaxation. The stabilizing spring can adjust the uniformity of the load and maintain the stability of the load;

[0029] The double-layer spring loading method can be used to apply a large load to high-strength concrete and keep the load constant.

[0030] Preferably, the steps of the test method are as follows:

[0031] Step 1: Cut off the top of both ends of the formed and aged dog-bone concrete specimen, grind the cut surface flat and clean it, wipe it with paper until the surface is dry, and use adhesive to stick steel plates with screw holes on both ends of the specimen;

[0032] Step 2: After the adhesive is dry, screw the pull ring into the screw hole of the steel plate, install the spoke load sensor, ball joint and the specimen with the pull ring installed on the loading test device, and install the linear differential displacement sensor and micrometer detector on both sides of the specimen respectively, adjust them to the appropriate position and fix them;

[0033] Step 3: Adjust the force nut to squeeze the force spring to generate tensile stress. In order to prevent inconsistent readings on both sides of the eccentric loading, the test piece should be aligned and preloaded before the test officially starts until the deformation difference on both sides of the test piece is less than 10% of its average value.

[0034] Step 4: At the beginning of the formal test, the linear differential displacement sensor and the micrometer are used simultaneously, and the value of the micrometer is recorded every 100,000 seconds. After 1 million seconds from the start of the creep test, the linear differential displacement sensor and the displacement collector are turned off, and the micrometer is used to record the deformation data. Thereafter, the data of the micrometer is recorded every 10 million seconds until the end of the test. The linear differential displacement sensor is turned on for three days at intervals of one cycle, and the recorded curve trend is fitted and compared with the scattered points of the micrometer reading; if it is within a reasonable range, the micrometer reading of the next cycle is taken;

[0035] Step 5: Use the logarithm of time to the base 10 as the horizontal axis to draw a creep flexibility curve. Use the data points of the linear differential displacement sensor for the first 1 million and the reading points of the micrometer for the later period.

[0036] The linear differential displacement sensor measures the intensive change trend of the creep change of the specimen by using the displacement sensor;

[0037] The micrometer is used to measure the discrete point samples of the creep change of the test piece;

[0038] The present invention adopts a displacement acquisition method combining a linear differential displacement sensor and a micrometer; using a logarithmic plotting method, the linear differential displacement sensor and the micrometer are used simultaneously before the creep test starts to several days after the test starts, that is, in the early stage of the creep test, and the value of the micrometer is recorded every several hours.

[0039] In the early stage of creep of concrete specimens, the deformation value of the micrometer is collected every few hours, and then the micrometer data is collected every few days, and finally every few weeks until the end of the creep test.

[0040] Combined creep collection method In the early stage of creep test, in order to prevent inconsistent data on both sides of eccentric loading, pre-loading is carried out before the test officially starts. It should be ensured that the deformation recorded by different instruments on both sides of the specimen should be less than 10% of their average value, and the test should be repeated after adjustment.

[0041] The traditional linear plotting method cannot depict the short-term values ​​of early creep, so the short-term deformation during the early loading process cannot be depicted; and the later longer time values ​​are depicted outside the graph, resulting in a loss of data integrity. Therefore, the logarithmic plotting method readings should be roughly evenly spaced in the logarithmic scale of the test duration, and the relationship between creep strain and time is plotted, where a scatter plot is drawn with the logarithmic value of time; the early time should be recorded in seconds, minutes and hours.

[0042] The present invention, when using the logarithmic plotting method, cleverly depicts and records the process that the concrete specimen creeps rapidly in the early stage, and as the creep process proceeds, the concrete specimen creeps more and more slowly. In the early stage, the linear differential displacement sensor is turned off a few days after the creep test begins, that is, after the early stage of the creep test. In the middle and late stages of the creep test, the micrometer readings are taken, and the discrete point reaction is used to depict the slow creep process of the concrete specimen.

[0043] During the middle and later stages of the test, keep the linear differential displacement sensor closed and use the micrometer to take frequency readings once or twice a day. For tests lasting many years, record the readings in days. For tests lasting several decades, record the readings in months until the creep test is completed.

[0044] The micrometer does not need to be powered on during the middle and later stages of creep data collection and is not restricted by collection time and location. The micrometer is lightweight and easy to use and read.

[0045] The innovation of the dog-bone specimen pasting method is to glue steel plates at both ends of the concrete specimen with glue, and each steel plate is anchored with a pull ring. Since the middle section of the dog-bone-shaped high-strength concrete specimen is thinner, it is easy to break under stress, which reduces the difficulty of the test and improves the test efficiency.

[0046] Dog-bone-shaped high-strength concrete. Since the bonded steel is not strong enough for high-strength concrete, a variable cross-section is required to provide an easy-to-break section. Therefore, the dog-bone-shaped high-strength concrete provides the relevant conditions. By gluing steel plates at both ends, the expected test results can be achieved.

[0047] This method provides a combined creep acquisition method based on a linear differential displacement sensor LVDT and a micrometer, which makes new improvements in the pasting form and loading method. Compared with the prior art, this method has the following significant advantages:

[0048] (1) It overcomes the limitation of the traditional long-term creep strain acquisition method that the linear scale of shorter time values ​​cannot be distinguished and the longer time values ​​are outside the graph;

[0049] (2) Compared with the use of a micrometer alone, creep measurement can be started before the load is applied, and can accurately measure the elastic deformation process, loading rate and short-term creep during loading;

[0050] (3) Compared with the single-use linear differential displacement sensor LVDT, it overcomes the problems of long-term unstable measurement results and power-on safety of the linear differential displacement sensor LVDT;

[0051] (4) The use of adhesive bonding ensures the integrity of the tensile specimen, so that the tensile force can be evenly distributed on the specimen, which significantly improves the stress concentration phenomenon. The variable cross-section structure of the dog-bone specimen is used to reduce the tensile stress shared by the adhesive layer, solving the problem that the tensile strength of high-strength concrete is higher than the bonding strength of the adhesive.

[0052] (5) The use of a double-layer spring loading test device overcomes the problems of difficulty in applying large loads and uneven load application, supplements the load for creep relaxation, and ensures the stability of the load. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a structural schematic diagram of a concrete test piece;

[0054] Figure 2 It is a side view of the concrete test piece;

[0055] Figure 3It is a structural schematic diagram of a long-term tensile creep test device for high-strength concrete;

[0056] Figure 4 is a schematic diagram of the structure of the top plate;

[0057] In the figure: 1. displacement sensor; 2. displacement collector; 3. micrometer; 4. fixing bracket; 5. pull ring; 6. steel plate; 7. concrete specimen; 8. fixing nut; 9. top plate; 10. force nut; 11. sleeve; 12. threaded rod; 13. ball joint; 14. force spring; 15. spoke load sensor; 16. stabilizing spring; 17. connecting rod; 18. force plate; 19. bottom plate; 20. through hole. DETAILED DESCRIPTION

[0058] The present invention is further explained below in conjunction with the accompanying drawings and specific implementation methods.

[0059] As can be seen from the accompanying drawings, a tensile creep test device for high-strength concrete includes a loading test device and a concrete test piece. The concrete test piece is connected to the loading test device, a linear differential displacement sensor is provided on one side of the concrete test piece, and a micrometer detector is provided on the other side of the concrete test piece.

[0060] The loading test device includes a top plate 9, a bottom plate 19 and three threaded rods 12, the upper ends of the three threaded rods 12 are fixedly connected to the top plate 9, the lower ends of the three threaded rods 12 are fixedly connected to the bottom plate 19, and a sleeve 11, a force spring 14 and a stabilizing spring 16 are sleeved in sequence in the middle of each threaded rod 12 from top to bottom, a force plate 18 is provided between the force spring 14 and the stabilizing spring 16, a through hole 20 is provided on the force plate 18, and the threaded rod 12 is penetrated and arranged in the through hole 20; a force nut 10 is provided on the threaded rod 12, and the force nut 10 is arranged above the sleeve 11; the sleeve 11, the force spring 14, the force plate 18 and the stabilizing spring 16 are all arranged between the top plate 9 and the bottom plate 19; the concrete test piece is arranged between the three threaded rods 12, the upper end of the concrete test piece is connected to the top plate 9 by a connecting rod 17, and the lower end of the concrete test piece is connected to the force plate 18 by a connecting rod 17.

[0061] The concrete test specimen comprises a concrete specimen 7 , wherein steel plates 6 are provided at both upper and lower ends of the concrete specimen 7 , and pull rings 5 ​​are provided on the two steel plates 6 , and the two pull rings 5 ​​are respectively connected to the connecting rod 17 through a ball joint 13 .

[0062] The steel plate 6 is fixedly connected to the concrete specimen 7 by an adhesive.

[0063] The concrete specimen 7 is of dog-bone type.

[0064] A spoke-type load sensor 15 is provided between the connecting rod 17 at the lower end of the concrete specimen 7 and the force application plate 18 .

[0065] The upper end of the threaded rod 12 is connected to the top plate 9 through a fixing nut 8 ; the sleeve 11 , the force spring 14 , the stabilizing spring 16 , and the force plate 18 are all movably connected to the threaded rod 12 .

[0066] The linear differential displacement sensor comprises a displacement sensor 1 and a displacement collector 2 . The displacement sensor 1 is connected to a concrete specimen 7 via a fixing bracket 4 . The displacement sensor 1 is connected to the displacement collector 2 .

[0067] The micrometer tester comprises a micrometer 3 , and the micrometer 3 is connected to a concrete test piece 7 via a fixing bracket 4 .

[0068] The linear differential displacement sensor is used to load to half of the target load at a loading rate of 100N / s before the combined acquisition method begins. At this time, the deformations recorded by the displacement sensors 1 and the micrometers 3 on both sides of the specimen are calculated to observe whether the deformation difference on both sides is less than 10% of the average value. If the difference is large, remove the load and reinstall the ball joint 13 until the deformation difference between the two ends of the specimen is less than 10% of the average value. After the calibration is accurate, the test begins; usually from the start of the test to one to two weeks after the start of the test, the creep displacement of the specimen is measured through the collection of displacement sensor 1 and displacement collector 2, and the trend of the change of the continuous curve of the relevant displacement change is obtained;

[0069] The micrometer 3 is also used at the same time as the displacement sensor 1 and the micrometer 3 at the beginning of the combined acquisition method (one to two weeks after the start of the test). The value of the micrometer 3 is recorded every 27.78 hours (100,000 seconds); and the distribution diagram of the discrete points of the displacement change is obtained; the distribution diagram of the discrete points of the displacement change should be plotted according to the logarithmic plotting method to make the relationship between the creep strain and time, where the time is the logarithmic value with a base of 10, and a scatter plot is drawn.

[0070] After confirming the accurate counting of micrometer 3 in the early stage, in the middle and late stages of tensile creep, turn off the displacement sensor 1 on one side of the specimen and directly use micrometer 3 to read. When reading micrometer 3, in the middle and late stages of tensile creep of the creep test, that is, one to two weeks after the start (1 million seconds), turn off the displacement sensor 1 and displacement collector 2, use micrometer 3 to record the deformation data, and then record the data of micrometer 3 once every 11.574 days until the creep test is completed. The recorded curve trend is fitted and compared with the scattered points of the micrometer 3 readings; the relationship between creep strain and time is also made, where time is the logarithmic value with a base of 10, and a scatter plot is drawn.

[0071] Furthermore, in order to prevent inconsistent data on both sides of the eccentric loading, the deformation difference on both sides of the specimen should be less than 10‰ of its average value when comparing the creep change curve trend of the linear differential displacement sensor and the discrete points collected by the micrometer 3 before the test officially starts.

[0072] The load of the double-layer spring loading test device needs to be adjusted regularly. If the tensile creep deformation is large one week before the test, the load sensor should be calibrated every three days; if the subsequent creep deformation is small, the load sensor should be calibrated every one month.

[0073] The high-strength concrete dog-bone concrete specimen 7 has steel plates 6 glued to its two ends, and a pull ring 5 is anchored on each steel plate 6 for fixing on the tensioning device.

[0074] In this embodiment, the displacement sensor 1 and the micrometer 3 are respectively placed on both sides of the dog-bone concrete specimen 7 to form a comparison.

[0075] The following is combined with the diagram to further illustrate the specific operation steps of the tensile creep test for high-strength concrete collected with base 10. The following examples are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0076] Step 1: Pour the concrete into the dog-bone test mold, remove the mold after 1 day and place it in a standard curing room for curing. After reaching the target age, take it out and cut off the top of about 1 cm at both ends, polish and clean the surface, and wipe it with paper until the surface is dry. Finally, use adhesive to stick the steel plate 6 with screw holes on both ends of the concrete specimen 7.

[0077] Step 2: After the adhesive is dry, screw the pull ring 5 into the screw hole of the steel plate 6, install the spoke load sensor 15, the ball joint 13 and the test piece with the pull ring 5 installed on the loading test device, and glue the fixed bracket 4 to both sides of the concrete test piece 7 with AB glue, then install the displacement sensor 1 and the displacement collector 2 on one side of the test piece, and then install the micrometer 3 on the other side of the test piece, adjust it to the appropriate position and fix it.

[0078] Step three: Adjust the force nut 10 so that it squeezes the force spring 14 to generate tensile stress. In order to prevent inconsistent readings on both sides of the eccentric loading, the test is aligned and preloaded before the test officially begins to ensure that the deformation difference on both sides of the specimen is less than 10% of its average value. Turn on the displacement sensor 1 to start collecting, set the sampling frequency to once per second, and load it to one-third of the target load at a loading rate of 100N / s. At this time, calculate the deformation recorded by different instruments on both sides of the specimen, and observe whether the deformation difference on both sides is less than 10% of its average value. If the difference is large, remove the load and readjust the position of the specimen until the deformation difference at both ends of the specimen is less than 10% of its average value.

[0079] Step 4: At the beginning of the formal test (11.574 days after the start of the test, i.e. 1 million seconds), displacement sensor 1 and micrometer 3 are used simultaneously. The value of micrometer 3 is recorded every 27.78 hours (100,000 seconds). 11.574 days (1 million seconds) after the start of the creep test, the displacement sensor 1 and displacement collector 2 are turned off, and micrometer 3 is used to record the deformation data. The data of micrometer 3 is recorded every 11.574 days thereafter until the end of the test. At intervals of one cycle (one month to half a year, depending on the creep test time), the displacement sensor 1 is turned on for three days of testing, and the recorded curve trend is fitted and compared with the scattered points of the micrometer 3 readings; if it is within a reasonable range, the micrometer 3 readings of the next cycle are taken. This is used to ensure the reliability of deformation data recorded by a single micrometer 3.

[0080] Step 5: Use the logarithm of time to the base 10 as the horizontal axis to draw a creep flexibility curve. Use the data points of the linear differential displacement sensor for the first 11.574 days and the reading points of the micrometer 3 for the later period.

[0081] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The protection scope of the present invention should be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims, that is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A tensile creep test device for high-strength concrete, characterized in that: It comprises a loading test device and a concrete test piece, the concrete test piece is connected to the loading test device, a linear differential displacement sensor is provided on one side of the concrete test piece, and a micrometer detector is provided on the other side of the concrete test piece; the loading test device comprises a top plate, a bottom plate and three threaded rods, the upper ends of the three threaded rods are fixedly connected to the top plate, the lower ends of the three threaded rods are fixedly connected to the bottom plate, a sleeve, a force spring and a stabilizing spring are sequentially sleeved on the middle part of each threaded rod from top to bottom, a force plate is provided between the force spring and the stabilizing spring, a through hole is provided on the force plate, and the threaded rod is penetrated and arranged in the through hole; a force nut is provided on the threaded rod, and the force nut is arranged above the sleeve; the concrete test piece is arranged between the three threaded rods, the upper end of the concrete test piece is connected to the top plate through a connecting rod, and the lower end of the concrete test piece is connected to the top plate through a connecting rod The connecting rod is connected to the force plate; the sleeve, the force spring, the force plate, and the stabilizing spring are all arranged between the top plate and the bottom plate; the concrete test specimen includes a concrete specimen, and the upper and lower ends of the concrete specimen are provided with steel plates, and the two steel plates are provided with pull rings, and the two pull rings are respectively connected to the connecting rod through a ball joint; the steel plate is fixedly connected to the concrete specimen through an adhesive; the concrete specimen is a dog bone type; a spoke load sensor is provided between the connecting rod at the lower end of the concrete specimen and the force plate; the linear differential displacement sensor includes a displacement sensor and a displacement collector, and the displacement sensor is connected to the concrete specimen through a fixed bracket, and the displacement sensor is connected to the displacement collector; the micrometer detector includes a micrometer, and the micrometer is connected to the concrete specimen through a fixed bracket; the test method for the tensile creep test device for high-strength concrete, the steps are as follows: Step 1: Cut off the top of both ends of the formed and aged dog-bone concrete specimen, grind the cut surface flat and clean it, wipe it with paper until the surface is dry, and use adhesive to stick steel plates with screw holes on both ends of the specimen; Step 2: After the adhesive is dry, screw the pull ring into the screw hole of the steel plate, install the spoke load sensor, ball joint and the specimen with the pull ring installed on the loading test device, and install the linear differential displacement sensor and micrometer detector on both sides of the specimen respectively, adjust them to the appropriate position and fix them; Step 3: Adjust the force nut to squeeze the force spring to generate tensile stress. In order to prevent inconsistent readings on both sides of the eccentric loading, the test piece should be aligned and preloaded before the test officially starts until the deformation difference on both sides of the test piece is less than 10% of its average value. Step 4: At the beginning of the formal test, the linear differential displacement sensor and the micrometer are used simultaneously, and the value of the micrometer is recorded every 100,000 seconds. After 1 million seconds from the start of the creep test, the linear differential displacement sensor and the displacement collector are turned off, and the micrometer is used to record the deformation data. Thereafter, the data of the micrometer is recorded every 10 million seconds until the end of the test. The linear differential displacement sensor is turned on for three days at intervals of one cycle, and the recorded curve trend is fitted and compared with the scattered points of the micrometer reading; if it is within a reasonable range, the micrometer reading of the next cycle is taken; Step 5: Use the logarithm of time to the base 10 as the horizontal axis to draw a creep flexibility curve. Use the data points of the linear differential displacement sensor for the first 1 million and the reading points of the micrometer for the later period.

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