CN110926945A - Tensile creep test device and method for high-strength concrete - Google Patents

Abstract

The invention relates to a tensile creep test device and method for high-strength concrete, which comprises a double-spring tensile creep device and a concrete sample creep strain acquisition method; the double-layer spring tension creep device ensures the stability of the loading process and the later load holding by using double springs; a linear differential displacement sensor is arranged on one side of the concrete detection test piece, and a dial indicator detector is arranged on the other side of the concrete detection test piece; on the premise of ensuring that the difference between the two acquisition modes is within an error range, data points of the sensor are used in the early stage, reading points of the dial indicator are used in the later stage, and drawing is performed by a logarithm drawing method, so that the instantaneous deformation including elastic deformation in the initial loading stage can be displayed, the deformation for years can not be close to the level, and the limitation that the values in a short time cannot be distinguished and the values in a long time are outside the graph in the traditional strain acquisition method is overcome; the test device and the method have the characteristics of simple operation, low cost, suitability for carrying out the tension creep test for a long time, reliable data and the like.

Description

Tensile creep test device and method for high-strength concrete

Technical Field

The invention relates to a tensile creep test device and method for high-strength concrete, and belongs to the field of concrete structures and materials.

Background

Creep is an important characteristic for studying concrete properties, the traditional study is relatively mature on the creep of mature concrete in a compression state, the study on the creep of concrete in a tension state, particularly the study on the creep of concrete in an early stage in the tension state is rare, and a large number of tests show that whether the concrete cracks depends on shrinkage and is greatly influenced by tension creep, so that the research on tension creep is significant, and the tension creep test mainly comprises three parts, namely a loading mode, a strain acquisition and a test piece form.

The tension creep device uses many loading modes, but all have certain defects. The lever loading is simple to manufacture, the cost is lower, and the occupied area is large. The pulley loading is relatively stable, but the instrument is complex and has a certain friction loss. The two loading modes are also insufficient in the aspect of stabilizing the load, for example, the steel block method has the problems of difficult loading and unloading of the steel block and load adjustment, and the water tank method has the defects of load change caused by easy evaporation of water and the like. Hydraulic loading can apply a sufficiently high load, but the cost of the hydraulic tester is extremely high. At present, the most widely used is spring loading, the device is simple, the cost is low, and the enough high load can be applied, but most of the devices are used as creep devices, and the applied load has the problem of instability. Therefore, it is of great significance to modify a conventional creep device into a creep device.

In the aspect of strain acquisition, most of the traditional creep strain acquisition methods are single displacement sensor acquisition and dial indicator acquisition, however, the displacement sensor acquisition methods are not suitable for the acquisition period of creep for many years, and on the other hand, the displacement sensors need to be operated by alternating current during working, so that certain uncertainty exists in the acquisition process for years, and in addition, the cost of the sensors, the acquisition devices and the like is too high, so that the smooth development of tests is not facilitated. The dial indicator acquisition method has the advantages of no need of electrifying, stable reading, no limitation of measurement time and measurement position and the like, but the dial indicator needs manual reading, the acquisition frequency is limited, only some discrete data can be acquired, and the data acquisition has certain one-sidedness. The traditional creep data mapping method is to perform linear mapping at fixed time intervals. Therefore, the change in strain over time cannot be clearly distinguished in a short period of time prior to loading, and further general experiments stipulate that the measurement should be started before the load is applied, elastic deformation during loading (i.e. creep compliance curve) must be included, the linear scale clearly fails to meet the relevant requirements, while if one wants to show a short period of strain, the linear plotting rule will be plotted outside the graph for longer periods of time, resulting in a loss of data integrity. In summary, it is recommended that the collection and mapping be done logarithmically in time.

In the study of the fixture of the test piece to the apparatus, a general test piece mounting form has the following forms: 1) anchoring parts are prefabricated at two ends of the test piece, and the integrity of the test piece is damaged in the form; 2) the steel plates are adhered to two ends of the test piece by glue, the form is limited by the tensile strength of the glue, and particularly when the tested test piece is ultra-high-performance concrete, the test piece is usually broken at the glue adhesion part to influence the authenticity of test data; 3) the two ends of the test piece are fixed by the clamp, so that the situation of loose clamping exists; 4) utilize dog bone test piece, the clip centre gripping has stress concentration phenomenon in dog bone both ends shrink department, and this kind of centre gripping form exists the contact point for the experimental error grow. For the tensile creep test piece of the high-strength concrete, the high-strength property of the tensile creep test piece has higher requirements on the installation form, so that the effective tensile creep test method aiming at the high-strength concrete is particularly critical to the development of the tensile creep test of the high-strength concrete and is also necessary.

Disclosure of Invention

The invention provides a tensile creep test device and method for high-strength concrete, aiming at the defects in the prior art and solving the problems in the prior art.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the tensile creep test device for the high-strength concrete comprises a loading test device and a concrete detection test piece, wherein the concrete detection test piece is connected with the loading test device, a linear differential displacement sensor is arranged on one side of the concrete detection test piece, and a dial indicator detector is arranged on the other side of the concrete detection test piece.

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 application spring and a stabilizing spring are sequentially sleeved in the middle of each threaded rod from top to bottom, a force application plate is arranged between the force application spring and the stabilizing spring, a through hole is formed in the force application plate, and the threaded rods are arranged in the through hole in a penetrating manner; a force application nut is arranged on the threaded rod and is arranged above the sleeve; the concrete test piece sets up between three threaded rod, concrete test piece upper end passes through the connecting rod and links to each other with the roof, concrete test piece lower extreme passes through the connecting rod and links to each other with the application of force board.

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

Preferably, the concrete test piece comprises a concrete test piece, steel plates are arranged at the upper end and the lower end of the concrete test piece, pull rings are arranged on the two steel plates, and the two pull rings are connected with the connecting rod through spherical hinges respectively.

Preferably, the tension ring is anchored inside the thick steel plate, and provides support for the device to stretch.

Preferably, the steel plate is fixedly connected with the concrete sample through an adhesive.

Preferably, the concrete test piece is dog-bone type.

The steel plates are adhered to two ends of the high-strength concrete dog bone test piece, and by utilizing the unique structure of the dog bone test piece, the contact area is increased at the two ends, and the adhesion strength is improved; the middle part of the test piece is thin, so that the test piece is broken, and the overall tensile creep displacement characteristic of the test piece is conveniently obtained; the steel plate is adhered to the high-strength concrete dog bone test piece, so that the expected effect is achieved when the test piece is stretched and creeps conveniently;

preferably, a spoke type load sensor is arranged between the connecting rod at the lower end of the concrete sample and the force application plate.

Preferably, the linear differential displacement sensor comprises a displacement sensor and a displacement collector, the displacement sensor is connected with the concrete sample through a fixed support, and the displacement sensor is connected with the displacement collector.

The linear differential displacement sensor is used for converting the physical quantity of the creep displacement of the test piece into an electric signal and acquiring the displacement change of the test piece during creep at a higher acquisition frequency;

the displacement sensor is arranged on one side of the high-strength concrete dog bone test piece, and the displacement condition of the middle thin end of the high-strength concrete dog bone test piece is detected;

the linear differential displacement sensor is used for acquiring the displacement data of the test piece and drawing the curve change condition of the tensile creep displacement of the test piece;

preferably, the dial indicator detector comprises a dial indicator, and the dial indicator is connected with the concrete sample through a fixing support.

The dial indicator converts general linear displacement into rotary motion of a pointer through a gear or a lever, and is convenient for stably reading creep displacement characteristics of a test piece for a long time on the premise of no power supply;

the fixing support is used for fixing the dial indicator, the contact surface is kept smooth and stable as far as possible, and accurate measurement of the dial indicator is facilitated.

The dial indicator is arranged on the other side of the dog bone concrete test piece, and the fitting effect of discrete points of the dial indicator on the tensile creep displacement data of the test piece is obtained through comparison with the test piece displacement data collected by the displacement sensor on one side;

the loading test device of the double-layer spring comprises a spring part, a thicker force application spring at the upper layer and a thinner stable spring at the lower layer;

the upper and lower parts of the concrete sample are respectively provided with a spherical hinge which is mainly used for preventing eccentric loading and stress concentration;

the spoke type load sensor is arranged on the force application plate and used for recording the change of the load;

the sleeve mainly plays a role of transmission, so that the force application nut can conveniently extrude the force application spring to generate tensile stress; the stiffness coefficient of the force application spring is far greater than that of the stabilizing spring, when the two springs deform at the same position, the force generated by the force application spring is far greater than that of the stabilizing spring, the force application spring can provide larger load and is beneficial to supplement the load after creep relaxation, and the stabilizing spring can adjust the uniformity of the load and keep the stability of the load;

the double-layer spring loading mode can be used for applying large load to high-strength concrete and achieving constant load.

Preferably, the steps of the test method are as follows:

the method comprises the following steps: cutting off the tops of two ends of a formed dog-bone concrete sample at the age, polishing and flattening the cut surface, cleaning the cut surface, wiping the cut surface to be surface dry by using paper, and adhering steel plates with screw holes to two ends of the sample by using an adhesive;

step two: after the adhesive is dried, a pull ring is screwed into a steel plate screw hole, a spoke type load sensor, a spherical hinge and a test piece provided with the pull ring are installed on a loading test device together, a linear differential type displacement sensor and a dial indicator detector are installed on two sides of the test piece respectively, and the test piece is fixed after being debugged to a proper position;

step three: adjusting a force application nut to extrude a force application spring to generate tensile stress, and centering and preloading before formally starting a test in order to prevent the readings on the two sides of the eccentric loading from being inconsistent until the deformation difference of the two sides of the test piece is less than 10% of the average value;

step four: in the initial stage of a formal test, the linear differential displacement sensor and the dial indicator are used simultaneously, the numerical value of the dial indicator is recorded every 10 ten thousand seconds, the linear differential displacement sensor and the displacement collector are closed after the creep test starts for 100 ten thousand seconds, the dial indicator is used for recording deformation data, the data of the dial indicator is recorded every 1000 ten thousand minutes until the test is finished, the linear differential displacement sensor is opened every other period for testing for three days, and the recorded curve trend is matched and compared with scattered points of the reading of the dial indicator; if the current time is within the reasonable range, reading the dial indicator in the next period;

step five: the time is plotted on the horizontal axis with the logarithm of the base number of 10 bits as the creep compliance curve, the data point of the first 100 universal linear differential displacement sensors is plotted, and the reading point of the dial indicator is used in the later period.

The linear differential displacement sensor measures the dense change trend of the creep change of the test piece by using the displacement sensor;

the dial indicator is used for measuring discrete sample application of creep change of the test piece;

the invention adopts a displacement acquisition method combining a linear differential displacement sensor and a dial indicator; by using a logarithmic graph method, the linear differential displacement sensor and the dial indicator are simultaneously used before the creep test is started to after the test is started for a plurality of days, namely the early stage of the creep test. The values of the dial indicator are recorded every few hours.

In the creep early stage of the concrete specimen, the deformation value of the dial indicator is collected once in a plurality of hours, then the data collected by the dial indicator is collected once in a plurality of days, and finally the data is collected once in a plurality of weeks until the creep test is finished.

In the early stage of the creep test of the combined creep acquisition method, in order to prevent data on two sides of eccentric loading from being inconsistent, preloading is carried out before the test formally starts, deformation differences recorded by different instruments on two sides of a test piece are ensured to be less than 10% of the average value, and the combined creep acquisition method is responsible for retesting after adjustment.

The traditional linear mapping method cannot depict the value of the creep in the early stage in a short time, so that the deformation in the short time in the early stage loading process cannot be depicted; while later longer time values are characterized outside the graph, resulting in a loss of data integrity. Accordingly, log plot method readings should be approximately evenly spaced in a log scale of test duration, plotting creep strain versus time, where scatter plots are plotted against log values of time; where the early time should be recorded in seconds, minutes and hours.

In the logarithmic plotting method, the process that the creep of the concrete test piece is rapid in the early stage and gradually slows down along with the progress of the creep process is ingeniously depicted and recorded. The linear differential displacement sensor is used for closing a creep test in the early stage after days from the beginning of the creep test, namely after the early stage of the creep test. In the middle and later period of the creep test, dial gauge reading is adopted, and the slow creep process of the concrete sample is described by utilizing discrete point reaction.

Keeping the linear differential displacement sensor closed by the dial indicator in the middle and later stages of the test, and reading the frequency once to twice a day by using the dial indicator; for many years of testing, the number of days is recorded as a cycle; for decades of testing, several months are recorded; until the creep test was completed.

The dial gauge does not need to be electrified in the middle and later stages of creep data collection, is not limited by collection time and positions, is light in weight and is convenient to use and read data.

Paste dog bone test piece form innovation lies in pasting the steel sheet at concrete test piece both ends with glue, and each anchor of steel sheet connects a pull ring, because dog bone form high-strength concrete test piece middle part section is thinner, consequently easy atress fracture, reduced the experimental degree of difficulty, improved test efficiency.

The dog-bone-shaped high-strength concrete needs a variable cross section to provide an easy-to-break section due to the fact that the bond steel is not enough for the high-strength concrete, so that relevant conditions are provided for the dog-bone-shaped high-strength concrete, the steel plates are bonded with glue at two ends, and expected test effects can be achieved.

The combined creep acquisition method based on the linear differential displacement transducer LVDT and the dial indicator provided by the method is a novel improvement on the pasting form and the loading mode, and compared with the prior art, the method has the remarkable advantages that:

(1) the method overcomes the limitations that the values of the traditional long-term creep strain acquisition method in the short time of linear scale cannot be distinguished, and the values in the long time are outside the graph;

(2) compared with a single dial indicator, creep measurement can be started before a load is applied, and the elastic deformation process, the loading rate and short-time creep in the loading process can be accurately measured;

(3) compared with a single linear differential displacement transducer LVDT, the problems of unstable measurement result and safe power-on of the long-term linear differential displacement transducer LVDT are solved;

(4) the mode of selecting the adhesive to bond ensures the integrity of the tensile test piece, so that the tensile force can be uniformly distributed on the test piece, the stress concentration phenomenon is obviously improved, the tensile stress shared by the glue layer is reduced by utilizing the variable cross-section structure of the dog bone test piece, and the problem that the tensile strength of the high-strength concrete is higher than the adhesive bonding strength is solved.

(5) The loading test device with the double-layer spring is selected, so that the problems that large load is difficult to apply and the load is not uniform are solved, the load is supplemented for creep relaxation, and the stability of the load is ensured.

Drawings

FIG. 1 is a schematic structural diagram of a concrete test specimen;

FIG. 2 is a side view of a concrete test specimen;

FIG. 3 is a schematic diagram of a long-term tensile creep test apparatus for high strength concrete;

FIG. 4 is a schematic structural view of the top plate;

in the figure: 1. a displacement sensor; 2. a displacement collector; 3. a dial indicator; 4. fixing a bracket; 5. a pull ring; 6. a steel plate; 7. a concrete sample; 8. fixing a nut; 9. a top plate; 10. a force application nut; 11. a sleeve; 12. a threaded rod; 13. spherical hinge; 14. a force application spring; 15. a spoke type load sensor; 16. a stabilizing spring 17, a connecting rod 18, a force application plate 19 and a bottom plate; 20. and a through hole.

Detailed Description

The invention is further elucidated with reference to the drawings and the detailed description.

The tensile creep test device for the high-strength concrete comprises a loading test device and a concrete detection test piece, wherein the concrete detection test piece is connected with the loading test device, a linear differential displacement sensor is arranged on one side of the concrete detection test piece, and a dial indicator detector is arranged on the other side of the concrete detection test piece.

The loading test device comprises a top plate 9, a bottom plate 19 and three threaded rods 12, wherein 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, a sleeve 11, a force application spring 14 and a stabilizing spring 16 are sequentially sleeved in the middle of each threaded rod 12 from top to bottom, a force application plate 18 is arranged between the force application spring 14 and the stabilizing spring 16, a through hole 20 is formed in the force application plate 18, and the threaded rods 12 are arranged in the through hole 20 in a penetrating mode; a force application nut 10 is arranged on the threaded rod 12, and the force application nut 10 is arranged above the sleeve 11; the sleeve 11, the force application spring 14, the force application plate 18 and the stabilizing spring 16 are all arranged between the top plate 9 and the bottom plate 19; the concrete test piece sets up between three threaded rod 12, concrete test piece upper end passes through connecting rod 17 and links to each other with roof 9, concrete test piece lower extreme passes through connecting rod 17 and links to each other with application of force board 18.

The concrete test specimen comprises a concrete specimen 7, steel plates 6 are arranged at the upper end and the lower end of the concrete specimen 7, pull rings 5 are arranged on the two steel plates 6, and the two pull rings 5 are connected with a connecting rod 17 through spherical hinges 13 respectively.

The steel plate 6 is fixedly connected with a concrete test piece 7 through an adhesive.

The concrete test piece 7 is of a dog bone shape.

A spoke type load sensor 15 is arranged between a connecting rod 17 at the lower end of the concrete sample 7 and the force application plate 18.

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

The linear differential displacement sensor comprises a displacement sensor 1 and a displacement collector 2, wherein the displacement sensor 1 is connected with a concrete test piece 7 through a fixed support 4, and the displacement sensor 1 is connected with the displacement collector 2.

The dial indicator detector comprises a dial indicator 3, and the dial indicator 3 is connected with a concrete test piece 7 through a fixing support 4.

The linear differential displacement sensor is used for loading half of a target load at a loading rate of 100N/s before the start of a combined acquisition method. And at the moment, calculating the deformation recorded by different instruments of the displacement sensor 1 and the dial indicator 3 on two sides of the test piece, and observing whether the deformation difference on the two sides is less than 10 percent of the average value. And if the difference is larger, the load is unloaded, and the spherical hinge 13 is installed again until the deformation difference of the two ends of the test piece is less than 10 percent of the average value. After the check is accurate, starting the test; generally, the creep displacement condition of a test piece is measured from the beginning of a test to one week to two weeks after the beginning of the test by the collection of the displacement sensor 1 and the displacement collector 2, and the change condition trend of a related displacement change continuous curve is obtained;

the dial indicator 3 is also used together with the displacement sensor 1 at the beginning of the combined collection method (one to two weeks after the start of the test). The value of dial indicator 3 was recorded every 27.78 hours (10 ten thousand seconds); obtaining a distribution situation graph of the discrete points of the related displacement change; the graph of the distribution of displacement change discrete points should be drawn according to a logarithmic plotting method, wherein the creep strain is related to time, and the time is a logarithmic value with a base number of 10 digits, and the scatter diagram is drawn.

After the accurate counting of the dial indicator 3 is determined in the early stage, the displacement sensor 1 on one side of the test piece is closed in the middle and later stages of the tensile creep, and the dial indicator 3 is directly used for reading. When the dial indicator 3 reads, the displacement sensor 1 and the displacement collector 2 are closed at the middle and later stages of the creep test, namely one to two weeks (100 ten thousand seconds) after the start of the creep test, the deformation data is recorded by the dial indicator 3, and the data of the dial indicator 3 is recorded once in 11.574 days until the creep test is finished. Fitting and comparing the recorded curve trend with scattered points of the dial indicator 3 reading; a plot of creep strain versus time was also made, where time is a logarithmic value based on a 10-digit base, and a scatter plot was drawn.

Further, in order to prevent the data on the two sides of the eccentric loading from being inconsistent, the creep curve trend of the linear differential displacement sensor performed before the test formally starts should be compared with the discrete points collected by the dial indicator 3, so as to ensure that the deformation difference on the two sides of the test piece should be less than 10 per thousand of the average value.

The load of the loading test device of the double-layer spring needs to be adjusted regularly, the tensile creep deformation is large in 1 week before the test, and the load sensor is corrected once every 3 days; the subsequent creep deformation is small, and the load sensor is corrected once every 1 month.

The steel plate 6 is adhered to two ends of the high-strength concrete dog bone concrete test piece 7 by glue, and the steel plate 6 is anchored with a pull ring 5 for fixing on a stretching device.

In this embodiment, the displacement sensor 1 and the dial indicator 3 are respectively arranged on two sides of the dog bone concrete specimen 7 to form a contrast.

The following will further describe the specific operation steps of the tensile creep test on high strength concrete collected at the base of 10 with reference to the drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

The method comprises the following steps: pouring the concrete into the dog bone-shaped test mould, removing the mould after 1 day, and placing the mould in a standard curing room for curing. And taking out the glass to the target age, cutting off the tops of two ends by about 1cm, polishing the surface, cleaning, and wiping the glass with paper until the surface is dry. Finally, the steel plates 6 with screw holes are adhered to the two ends of the concrete sample 7 by using an adhesive.

Step two: after the adhesive is dried, the steel plate 6 screw hole is screwed in by the pull ring 5 after the adhesive is dried, the spoke type load sensor 15, the spherical hinge 13 and the test piece provided with the pull ring 5 are installed on a loading test device together, the fixed support 4 is installed on two sides of the concrete test piece 7 by AB glue respectively, then the displacement sensor 1 and the displacement collector 2 are installed on one side of the test piece, the dial indicator 3 is installed on the other side of the test piece, and the test piece is fixed after being debugged to a proper position.

Step three: the forcing nut 10 is adjusted to press the forcing spring 14 to generate a tensile stress. In order to prevent the readings on the two sides of the eccentric loading from being inconsistent, the centering and preloading are carried out before the formal test is started, and the deformation difference of the two sides of the test piece is ensured to be less than 10 percent of the average value. The displacement sensor 1 is turned on to start the acquisition, the sampling frequency is set to 1 second once, and the sampling frequency is loaded to one third of the target load at a loading rate of 100N/s. And calculating the deformation recorded by different instruments on two sides of the test piece, and observing whether the deformation difference on the two sides is less than 10 percent of the average value. And if the difference is larger, the load is unloaded, and the position of the test piece is readjusted until the deformation difference of the two ends of the test piece is less than 10 percent of the average value of the deformation difference.

Step four: at the initial stage of the actual test (11.574 days after the start of the test, i.e., 100 ten thousand seconds), the displacement sensor 1 and the dial gauge 3 are used together. The value of dial indicator 3 was recorded every 27.78 hours (10 ten thousand seconds). After 11.574 days (100 ten thousand seconds) from the start of the creep test, the displacement sensor 1 and the displacement pickup 2 were turned off, and the deformation data was recorded by the dial gauge 3, and thereafter, the data of the dial gauge 3 was recorded once in 11.574 days until the end of the test. Every other period (one month to half year, determined according to the creep test time), opening the displacement sensor 1 for testing for three days, and fitting and comparing the recorded curve trend with scattered points of the reading of the dial indicator 3; if the reading is within the reasonable range, the dial indicator 3 reading of the next period is carried out. This is used to ensure the reliability of the single dial indicator 3 recording the deformation data.

Step five: the creep compliance curve is plotted with time on the horizontal axis using the logarithm of the base number of 10 bits. Data points from the linear differential displacement transducer were used for the first 11.574 days and readings from the dial gauge 3 were used for the later days.

The above-mentioned embodiments are merely preferred embodiments of the present invention, and should not be construed as limiting the present invention, and the scope of the present invention should be defined by the claims, and equivalents including technical features of the claims, i.e., equivalent modifications within the scope of the present invention.

Claims (10)

1. The utility model provides a tensile creep test device to high-strength concrete which characterized in that: including load test device and concrete detection test piece, the concrete detection test piece links to each other with the load test device, concrete detection test piece one side is equipped with linear differential type displacement sensor, concrete detection test piece opposite side is equipped with the amesdial detector.

2. The tensile creep test apparatus for high-strength concrete according to claim 1, wherein: the loading test device comprises a top plate, a bottom plate and three threaded rods, wherein 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, the middle part of each threaded rod is sequentially sleeved with a sleeve, a force application spring and a stabilizing spring from top to bottom, a force application plate is arranged between the force application spring and the stabilizing spring, a through hole is formed in the force application plate, and the threaded rods are arranged in the through hole in a penetrating manner; a force application nut is arranged on the threaded rod and is arranged above the sleeve; the concrete test piece sets up between three threaded rod, concrete test piece upper end passes through the connecting rod and links to each other with the roof, concrete test piece lower extreme passes through the connecting rod and links to each other with the application of force board.

3. The tensile creep test apparatus for high-strength concrete according to claim 2, wherein: the sleeve, the force application spring, the force application plate and the stabilizing spring are all arranged between the top plate and the bottom plate.

4. The tensile creep test apparatus for high-strength concrete according to claim 2, wherein: the concrete test piece comprises a concrete test piece, steel plates are arranged at the upper end and the lower end of the concrete test piece, pull rings are arranged on the two steel plates, and the two pull rings are connected with the connecting rod through spherical hinges respectively.

5. The apparatus according to claim 4, wherein: the steel plate is fixedly connected with the concrete test piece through an adhesive.

6. The apparatus according to claim 5, wherein: the concrete test piece is dog bone type.

7. The apparatus according to claim 4, wherein: and a spoke type load sensor is arranged between the connecting rod at the lower end of the concrete test piece and the force application plate.

8. The tensile creep test apparatus for high-strength concrete according to claim 1, wherein: the linear differential displacement sensor comprises a displacement sensor and a displacement collector, the displacement sensor is connected with a concrete sample through a fixed support, and the displacement sensor is connected with the displacement collector.

9. The tensile creep test apparatus for high-strength concrete according to claim 1, wherein: the dial indicator detector comprises a dial indicator, and the dial indicator is connected with the concrete test piece through a fixing support.

10. A test method using the tensile creep test apparatus for high-strength concrete according to claims 1 to 9, characterized in that the test method comprises the steps of:

the method comprises the following steps: cutting off the tops of two ends of a formed dog-bone concrete sample at the age, polishing and flattening the cut surface, cleaning the cut surface, wiping the cut surface to be surface dry by using paper, and adhering steel plates with screw holes to two ends of the sample by using an adhesive;

step two: after the adhesive is dried, a pull ring is screwed into a steel plate screw hole, a spoke type load sensor, a spherical hinge and a test piece provided with the pull ring are installed on a loading test device together, a linear differential type displacement sensor and a dial indicator detector are installed on two sides of the test piece respectively, and the test piece is fixed after being debugged to a proper position;

step three: adjusting a force application nut to extrude a force application spring to generate tensile stress, and centering and preloading before formally starting a test in order to prevent the readings on the two sides of the eccentric loading from being inconsistent until the deformation difference of the two sides of the test piece is less than 10% of the average value;

step four: in the initial stage of a formal test, the linear differential displacement sensor and the dial indicator are used simultaneously, the numerical value of the dial indicator is recorded every 10 ten thousand seconds, the linear differential displacement sensor and the displacement collector are closed after the creep test starts for 100 ten thousand seconds, the dial indicator is used for recording deformation data, the data of the dial indicator is recorded every 1000 ten thousand minutes until the test is finished, the linear differential displacement sensor is opened every other period for testing for three days, and the recorded curve trend is matched and compared with scattered points of the reading of the dial indicator; if the current time is within the reasonable range, reading the dial indicator in the next period;

step five: the time is plotted on the horizontal axis with the logarithm of the base number of 10 bits as the creep compliance curve, the data point of the first 100 universal linear differential displacement sensors is plotted, and the reading point of the dial indicator is used in the later period.

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