An improved concrete multi-axial tension and compression stress combination test device and method

Abstract

An improved concrete multi-axial tension and compression stress combination test method belongs to the field of civil engineering test and inspection technology. It is characterized in that in the concrete multi-axial tension and compression stress combination test, the bases on both sides of the double-plate plastic brush are connected to the tensile surface of the concrete specimen and the pasting steel plate respectively by using adhesive, and the pasting steel plate is connected to the force transmission steel plate by bolts, and the force transmission steel plate is connected to the loading end by a ball joint. The loading end tension is transmitted to the brush teeth of the double-plate plastic brush through the steel plate, and then to the concrete specimen. The effects and benefits of the double-plate plastic brush pasting method adopted in the present invention are: the specimen axis is tensile, and the stress distribution is more uniform; because the brush teeth have very small stiffness, the loading end is prevented from generating a lateral constraint on the pasting surface of the specimen, so that the specimen is tested under a preset stress state, reducing the test error; the double-plate plastic brush is very light, simple to install, and low in cost, convenient for disposable use, easy to disassemble, and high in test efficiency, which greatly increases its ease of use and practicality.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering testing and inspection, and relates to a testing technology of a full axial tensile curve of concrete and a testing device and method for the strength of concrete under a multi-axial tensile and compressive stress combination state. Background Art

[0002] According to the different connection methods between the testing machine and the concrete specimen, the existing concrete axial tensile test methods can be divided into three basic types: embedded type, external clamping type and adhesive type (including single steel plate adhesive type, double steel plate adhesive type, steel brush adhesive type and single plate plastic brush adhesive type). The problems and disadvantages of these technologies are as follows:

[0003] (1)Built-in

[0004] Embedded [1,2] The test method has the following problems: ① It is difficult to ensure that the specimen is axially tensile, and the stress distribution in the specimen is relatively complex; ② There is stress concentration at the end of the steel bar, which is easy to be damaged; ③ It is not suitable for testing the strength of concrete under multi-axial tension and compression stress combination state. [1] Liang Zhengping, Lu Hairong, Huang Shuqin, etc. A simple concrete axial tensile test device [J]. Journal of Hydraulic Engineering, 1992, (8): 73-75. [2] Huo Hongyuan, Liang Zhengping, etc. A full-curve test and device for concrete axial tensile [J]. Journal of Hohai University, 1995, 23 (5): 26-31.

[0005] (2) External clamp type

[0006] External clamp [3] The test method has the following problems: ① The end of the specimen is clamped, which easily causes stress concentration and leads to local damage at the clamping part; ② The insufficient clamping friction easily leads to slippage of the clamping contact surface, and the test results are unstable; ③ It is not suitable for testing the strength of concrete under multi-axial tension and compression stress combination state. [3] Gopalaratnam VS, Surendra P S. Softening response of plain concrete in direct tension [J]. Journal of the American Concrete Institute, 1985, 82 (3): 310-323.

[0007] (3) Single steel plate adhesive

[0008] Single steel plate adhesive [4,5]The test method has the following problems: ① Although it is easy to ensure axial tension, there is still a phenomenon of uneven stress distribution; ② The steel plate attached to the surface of the specimen will hinder the lateral deformation of the concrete, increasing the error of the test results; ③ The steel plate attached to the specimen is thick and heavy, making the test operation difficult; ④ It is not suitable for testing the strength of concrete under multi-axial tension and compression stress combination state. [4] Shang Renjie, Zhao Guofan, Huang Chengkui. Experimental study on the full curve of axial tensile test of concrete under low-cycle cyclic load [J]. Journal of Hydraulic Engineering, 1996, (7): 82-87. [5] Guo Zhenhai. Strength and deformation of concrete (experimental basis and constitutive relationship) [M]. Beijing: Tsinghua University Press, 1997.

[0009] (4) Double steel plate adhesive

[0010] Double steel plate adhesive [6-9] The test method has the following problems: Although the double steel plate bonding method makes the stress transfer in the specimen more uniform and the specimen preparation is simpler than the single steel plate bonding method, the bonding steel plate still has the problem of constraining the lateral deformation of the specimen under multiaxial tension and compression stress conditions. [6] Peng Bo, Zheng Wei. Research on the test method of uniaxial direct tensile strength of concrete [J]. Journal of Hunan University, 2004, 31(2): 79-83. [7] Gu Huilin, Peng Bo. Test method of uniaxial direct tensile stress-strain full curve of concrete [J]. Journal of Building Materials, 2003, 6(1): 66-71. [8] Zhang Xue. Bond performance of steel bars and concrete under lateral tension / tension-compression combined stress state [D]. Dalian: Dalian University of Technology, 2014. [9] Zhang X, Dong W, Zheng JJ, et al. Bond behavior of plain round bars embedded inconcrete subjected to lateral tension [J]. Construction and Building Materials, 2014, 54: 17-26.

[0011] (5) Steel brush adhesive type

[0012] Steel brush adhesive [10,11]The test method has the following problems: Although the stress distribution at the end of the concrete specimen is uniform and the constraint effect of the loading end on the lateral deformation of the specimen under multiaxial tension and compression stress is avoided, the specimen installation is difficult due to the large mass of the steel brush, and it is very difficult to conduct large-scale concrete and multiaxial tension and compression stress combination tests.

[10] Song Yupu, Shen Jina, Jin Guoli. Multifunctional triaxial concrete test system [J]. Journal of Dalian University of Technology, 1992, 32(4): 460-464.

[11] Hampel T, Speck K, Scheerer S, et al. High-performance concrete under biaxial and triaxial loads [J]. Journal of Engineering Mechanics, ASCE, 2009, 135(11): 1274-1280.

[0013] (6) Single board plastic brush adhesive

[0014] Single board plastic brush adhesive [12-14] The test method has the following problems: Although the single-plate plastic brush is light and easier to install than the steel brush, the contact area between the brush tooth surface and the specimen is too small, so the brush teeth are prone to debonding, resulting in test failure.

[12] Li Guangwei, Wang Zhe, Wu Zhimin, et al. Combined test method for multiaxial tension and compression stress of concrete [P]. Chinese patent: ZL201110222277.5, 2011-7-17.

[13] Jiang Tao. Test and numerical simulation of the bonding performance of steel bars and self-compacting lightweight aggregate concrete under lateral tensile stress [D]. Dalian: Dalian University of Technology, 2020.

[14] Jiang T, Wu ZM, Ye HL, et al. Bond behavior of deformed bars in self-compacting lightweight aggregate concrete subjected to lateral tensions [J]. Journal of Materials in Civil Engineering, ASCE, 2019, 31(9): 04019176.

[0015] Based on this, the present invention provides an improved concrete multi-axial tension and compression stress combination test device and method. Summary of the invention

[0016] The purpose of the present invention is to provide an improved test device and test method for a multi-axial tensile and compressive stress combination test of concrete. The present invention adopts a double-plate plastic brush pasting test method to solve many problems existing in the prior art: ① It solves the problem of eccentric tension and uneven stress distribution of concrete specimens in axial tensile tests; ② It avoids the restraining effect of the loading end on the lateral deformation of concrete specimens under uniaxial tension and multi-axial tension and compression combined stress states; ③ It solves the problem of large mass and difficult installation in the steel brush pasting method; ④ It solves the problem of easy peeling and test failure caused by the small contact surface between the brush tooth surface and the specimen pasting in the single-plate plastic brush pasting method.

[0017] In order to achieve the above object, the technical solution adopted by the present invention is:

[0018] An improved concrete multi-axial tension and compression stress combination test device is used to load a concrete specimen 7. The combination test device comprises two tension spherical hinges 5, two pressure spherical hinges 6 and two loading devices with the same structure, wherein the loading device is composed of a double-plate plastic brush 1, a bonding steel plate 2, and a force transmission steel plate 3 combined by bolts 4.

[0019] The double-plate plastic brush 1 includes two upper and lower thin plate structures and a brush structure in the middle, and the two thin plate structures serve as a base. The shape and size of the base are the same as the tensile bonding surface of the concrete specimen 7; the brush tooth density and size of the brush structure are designed according to the axial tensile strength of the concrete specimen.

[0020] The adhesive steel plate 2 is a plate-like structure, and blind holes for installing bolts 4 are provided at its four corners.

[0021] The force transmission steel plate 3 is a plate-like structure with a through hole in the center, and through holes for installing bolts 4 and corresponding to the blind holes of the bonding steel plate 2 are provided at its four corners, and the two are fixed by bolts 4. The central through hole cooperates with the tensile spherical hinge 5.

[0022] The bases of the two double-plate plastic brushes 1 are respectively connected to the two tensile bonding surfaces of the concrete specimen 7 by gluing, and the other base of each double-plate plastic brush 1 is connected to the bonding steel plate 2 by gluing. Pressure spherical hinges 6 are installed on the other two opposite compressive sides of the concrete specimen 7.

[0023] An improved concrete multi-axial tension and compression stress combination test method is implemented based on the above device, that is, the concrete specimen 7 and the loading device are connected by double-plate plastic brush pasting. Specifically, the following steps are included:

[0024] The first step is to grind the four sides of the block-shaped concrete specimen 7 to make it smooth and expose the aggregate, grind the two base surfaces of the double-plate plastic brush 1 to make them smooth with sandpaper, and wipe the surface of the concrete specimen 7 and the base surface of the double-plate plastic brush 1 with anhydrous ethanol;

[0025] The second step is to evenly apply adhesive on the two opposite tensile bonding surfaces of the concrete specimen 7, place the base surfaces of two double-plate plastic brushes 1 on the bonding surfaces of the concrete specimen 7 for compaction, and clean the adhesive squeezed out from the gaps; the size of the double-plate plastic brush base is the same as the size of the tensile bonding surface of the concrete specimen 7.

[0026] The third step is to place the concrete specimen 7 with the double-plate plastic brushes 1 pasted on both sides in an environment of 25°C to 60°C for curing, and during the curing period, a heavy object is placed on the specimen to make the glue interface in a pre-compression state, and the specimen is taken out after the glue interface is completely cured;

[0027] In the fourth step, after the other base of each double-plate plastic brush is wiped clean with anhydrous ethanol, it is bonded to the bonding steel plate 2 with adhesive and compacted, and after the adhesive squeezed out from the gap is cleaned, it is continued to be cured in an environment of 25°C to 60°C in a pre-pressed state until the adhesive interface is completely cured;

[0028] Step 5: Connect and tighten each bonding steel plate 2 and the force transmission steel plate 3 with four bolts 4;

[0029] In the sixth step, the other end of each force transmission steel plate 3 is connected to the loading end of the electro-hydraulic servo testing machine through the tension spherical hinge 5, that is, the vertical load is applied to the concrete specimen 7 through the electro-hydraulic servo testing machine; the compression surfaces on both sides of the concrete specimen 7 perpendicular to the tension bonding surface are connected to the loading end of the electro-hydraulic servo testing machine through the pressure spherical hinge 6, that is, the horizontal lateral compressive stress is applied through the pressure spherical hinge 6. The specific tension and compression combined load is applied to the specimen through the electro-hydraulic servo triaxial testing machine, so as to complete the concrete multi-axial tension and compression stress combination test according to the predetermined loading scheme.

[0030] In the process of applying load to the concrete specimen 7 by the device and method of the present invention, the double-plate plastic brush pasting method not only makes the concrete specimen 7 realize axial tension and uniform stress distribution, but also avoids the constraint effect of the lateral deformation of the specimen surface caused by the tension spherical hinge 5 and the pressure spherical hinge 6 applying stress to the concrete specimen 7, so that the concrete specimen 7 is tested under the preset multi-axial tension and compression stress combination state, and the test accuracy is improved from the mechanical principle. It should be pointed out that, compared with the single-plate plastic brush pasting method, the structure of the double-plate plastic brush 1 is mainly to add a plastic thin plate as a base between the single-plate plastic brush teeth and the concrete specimen 7, and the base and the brush teeth are made in one piece, which increases the overall bonding strength when the single-plate plastic brush teeth are pasted with the specimen. Therefore, the double-plate plastic brush pasting method solves the problem of easy peeling and test failure caused by the small contact surface between the brush tooth surface and the specimen pasting in the single-plate plastic brush pasting method, so that the above-mentioned concrete multi-axial tension and compression stress combination test can be successfully carried out.

[0031] The effects and benefits of the present invention are:

[0032] The present invention improves the existing concrete multi-axial tension and compression stress test method by adopting a double-plate plastic brush pasting method, namely: 1. the specimen is subjected to stress axially, and the stress distribution is more uniform; 2. since the brush tooth stiffness of the double-plate plastic brush is very small, the lateral constraint effect of the loading end on the pasting surface of the specimen is avoided, and the specimen can be tested under a preset stress state, thereby reducing the test error from the mechanical principle; 3. the double-plate plastic brush is very light, and the weight of a single brush with a pasting area of ​​100mm×100mm is less than 100g, which is convenient for specimen installation; 4. the double-plate plastic brush is low in cost and is convenient for disposable use. After the test is completed, the double-plate plastic brush pasted on the steel plate can be directly cut off, and the pasted steel plate can be quickly recovered, thereby improving the test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of a double-plate plastic brush, wherein: (a) is a cross-sectional view of the double-plate plastic brush; (b) is a side view.

[0034] Figure 2 It is a schematic diagram of pasting steel plates, in which: (a) is a plan view of the pasted steel plates; (b) is a cross-sectional view.

[0035] Figure 3 Schematic diagram of a force transmission steel plate, wherein: (a) is a plan view of the force transmission steel plate; (b) is a cross-sectional view.

[0036] Figure 4 It is a schematic diagram of a double-plate plastic brush combination.

[0037] Figure 5 It is a schematic diagram of the application of the present invention in a multi-axial tension and compression test of concrete.

[0038] In the figure: 1 double-plate plastic brush; 2 adhesive steel plate; 3 force transmission steel plate; 4 bolt; 5 tension spherical hinge; 6 pressure spherical hinge; 7 concrete specimen. DETAILED DESCRIPTION

[0039] The specific implementation of the improved concrete multi-axial tension and compression stress combination test method proposed by the present invention is described in detail below in conjunction with the technical scheme and the accompanying drawings.

[0040] Example 1 The concrete specimen of the present invention is connected to the loading device by a double-plate plastic brush bonding method.

[0041] An improved concrete multi-axial tensile and compressive stress combination test device is used to load a concrete specimen 7. The combination test device includes two tensile spherical hinges 5, two pressure spherical hinges 6 and two loading devices with the same structure, and the loading device is composed of a double-plate plastic brush 1, a bonding steel plate 2, a force transmission steel plate 3 and a bolt 4. That is, the test device includes two double-plate plastic brushes 1 with the same structure, two bonding steel plates 2 with the same structure, two force transmission steel plates 3 with the same structure, eight bolts 4, two tensile spherical hinges 5 with the same structure, and two pressure spherical hinges 6 with the same structure. The double-plate plastic brush 1 includes two upper and lower thin plate structures and a brush structure located in the middle, and the two thin plate structures serve as a base. The shape and size of the base are the same as the tensile bonding surface of the concrete specimen 7; the brush tooth density and size of the brush structure are designed according to the axial tensile strength of the concrete specimen. In this embodiment, according to the C30 strength concrete cube specimen with a size of 150mm×150mm×150mm, the specific design of the double-plate plastic brush 1 is as follows: the base is a 150mm×150mm×2mm cube; the brush teeth of the brush structure are cylinders with a diameter of 1mm and a length of 10mm, and 400 of them are evenly distributed vertically to the base; the brush and the base are made of plastic in one piece.

[0042] The bonding steel plate 2 is a plate-like structure, and its four corners are provided with blind holes for installing bolts 4. The force transmission steel plate 3 is a plate-like structure with a through hole in the center, and its four corners are provided with through holes for installing bolts 4 and corresponding to the positions of the blind holes of the bonding steel plate 2, and the two are fixed by four bolts 4. The central through hole cooperates with the tensile spherical hinge 5. The bases of the two double-plate plastic brushes 1 are respectively connected to the two tensile bonding surfaces of the concrete specimen 7 by gluing, and the other base of each double-plate plastic brush 1 is connected to the bonding steel plate 2 by gluing. Pressure spherical hinges 6 are installed on the other two opposite compressive sides of the concrete specimen 7.

[0043] An improved concrete multi-axial tension and compression stress combination test method is implemented based on the above device, that is, the concrete specimen 7 and the loading device are connected by double-plate plastic brush pasting. It includes the following steps:

[0044] ① Use an angle grinder to grind each side of the concrete specimen 7 to expose the aggregate, and wipe it clean with anhydrous ethanol. Grind the base surface on both sides of the double-plate plastic brush 1 with sandpaper and wipe it clean with anhydrous ethanol;

[0045] ② Apply the adhesive evenly on the tensile bonding surface of the concrete specimen 7, stick this surface to the base surface on one side of the double-plate plastic brush 1 and compact it, and clean the adhesive squeezed out of the gap;

[0046] ③ Place the specimen with the double-plate plastic brush pasted on it in an environment of 25℃ for 24 hours. During the curing period, place a 5kg weight on the specimen to pre-press the pasted surface. After the glue interface is completely cured, take out the specimen.

[0047] ④ Use adhesive to stick the steel plate 2 and the other side base of the double-plate plastic brush 1 together and compact them, and continue to cure them in a 25°C environment under the pre-pressed state for 24 hours. After the adhesive interface is completely cured, take out the test piece;

[0048] ⑤ The bonding steel plate 2 is connected to the force transmission steel plate 3 through bolts 4, and the force transmission steel plate 3 is connected to the loading end of the electro-hydraulic servo testing machine through a tensile spherical hinge 5, and the lateral compressive stress of the specimen is applied through a pressure spherical hinge 6;

[0049] ⑥ Apply specific tension and compression combined loads to the specimen through the electro-hydraulic servo triaxial testing machine, so as to complete the concrete multi-axial tension and compression stress combination test according to the predetermined loading scheme.

[0050] Through the test verification, the concrete specimen 7 can successfully complete the test under the preset multi-axial tensile and compressive stress combination state, the failure occurs in the middle of the concrete specimen 7, and the double-plate plastic brush 1 and the concrete specimen 7 are well bonded.

[0051] Comparative Example 1: The concrete specimen and the loading device are connected by a single-plate plastic brush bonding method.

[0052] The test device of this comparative example 1 is basically the same as that of the above-mentioned embodiment 1, and the main difference is that in the above-mentioned embodiment 1, the concrete specimen 7 and the bonding steel plate 2 are bonded and connected by a double-plate plastic brush 1, while in this comparative example 1, the concrete specimen 7 and the bonding steel plate 2 are bonded and connected by a single-plate plastic brush. This single-plate plastic brush includes a thin plate structure as a base and a brush structure. In this comparative example 1, the concrete specimen 7 also adopts a 150mm×150mm×150mm cubic specimen, the concrete strength is C30, the aggregate particle size is ≤20mm, and the base of the single-plate plastic brush is a 150mm×150mm×2mm cube; the brush teeth of the brush structure are prisms with a diameter of 1mm and a length of 10mm, and 400 teeth are evenly distributed perpendicular to the base. The specific steps of this comparative example 1 are as follows:

[0053] ① Use an angle grinder to grind each surface of the concrete specimen 7 to expose the aggregate, and wipe it clean with anhydrous ethanol; grind the teeth and base surface of the veneer plastic brush with sandpaper and wipe it clean with anhydrous ethanol;

[0054] ② Apply the adhesive evenly on the tensile bonding surface of the concrete specimen 7, stick this surface to the brush tooth surface of the single-plate plastic brush and compact it, and clean the adhesive squeezed out of the gap;

[0055] ③ Place the test piece with the veneer plastic brush pasted in an environment of 25℃ for 24 hours. During the curing period, place a 5kg weight on the test piece to pre-press the pasted surface. Take out the test piece after the glue interface is completely cured.

[0056] ④ Use adhesive to stick the steel plate 2 and the base of the single-plate plastic brush together and compact them, and continue to cure them in an environment of 25°C under the pre-pressed state for 24 hours. After the adhesive interface is completely cured, take out the test piece;

[0057] ⑤ The bonding steel plate 2 is connected to the force transmission steel plate 3 through four bolts 4, and the force transmission steel plate 3 is connected to the loading end of the electro-hydraulic servo testing machine through the tension spherical hinge 5, and the lateral compressive stress of the specimen is applied through the pressure spherical hinge 6;

[0058] ⑥ Apply specific tension and compression combined loads to the specimen through the electro-hydraulic servo triaxial testing machine, so as to complete the concrete multi-axial tension and compression stress combination test according to the predetermined loading scheme.

[0059] The test conducted according to the test process of this comparative example 1 ended in failure. The phenomenon of failure is that when the single-plate plastic brush is used to apply load to the concrete specimen 7, the brush teeth are peeled off from the concrete specimen 7, especially the brush teeth pasted on the mortar. This is because the brush teeth are directly pasted to the tensile surface of the concrete specimen 7, and the contact area is only 314mm 2 , accounting for about 1.4% of the specimen surface, which causes stress concentration between the brush tip and the specimen bonding surface, resulting in peeling. In addition, since the tensile strength of the mortar on the surface of the concrete specimen is generally lower than the tensile strength of the aggregate, the brush teeth attached to the mortar are more likely to peel off.

[0060] From the above, it can be seen that, compared with the single-plate plastic brush pasting method, the structure of the double-plate plastic brush 1 is mainly to add a plastic thin plate as a base between the single-plate plastic brush teeth and the concrete specimen 7, and the base and the brush teeth are made in one piece, which greatly increases the contact area between the single-plate plastic brush teeth and the specimen pasting surface, effectively improves the bonding force, and weakens the stress concentration phenomenon between the brush tooth tip and the specimen pasting surface. In short, the double-plate plastic brush pasting method solves the problem of easy peeling and test failure caused by the small contact surface between the brush tooth surface and the specimen pasting in the single-plate plastic brush pasting method, so that the above-mentioned concrete multi-axial tensile and compressive stress combination test can be carried out more effectively and successfully. Therefore, the double-plate plastic brush pasting method proposed in the present invention is very necessary.

[0061] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. An improved concrete multi-axial tension and compression stress combination test device, used for loading a concrete specimen (7); characterized in that: The combined test device comprises two tension spherical hinges (5), two pressure spherical hinges (6) and two loading devices with the same structure, wherein the loading devices are composed of a double-plate plastic brush (1), an adhesive steel plate (2), a force transmission steel plate (3) and a bolt (4); The double-plate plastic brush (1) comprises two upper and lower thin plate structures and a brush structure located in the middle; the two thin plate structures serve as a base, and the shape and size of the base are the same as the tensile bonding surface of the concrete specimen (7); the brush tooth density and size of the brush structure are designed according to the axial tensile strength of the concrete specimen (7); The adhesive steel plate (2) is a plate-like structure, and blind holes for installing bolts (4) are provided at its four corners; The force transmission steel plate (3) is a plate-like structure with a through hole at the center, and the central through hole is used to cooperate with the tensile spherical hinge (5); through holes for installing bolts (4) are provided at the four corners of the force transmission steel plate (3), and it is fixed to the bonding steel plate (2) by bolts (4); One base of the two double-plate plastic brushes (1) is respectively connected to the two tensile bonding surfaces of the concrete specimen (7) by gluing, and the other base of each double-plate plastic brush (1) is connected to the bonding steel plate (2) by gluing; and pressure spherical hinges (6) are installed on the other two compressive side surfaces of the concrete specimen (7).

2. An improved concrete multi-axial tension and compression stress combination test method, implemented based on the device of claim 1, characterized in that: The concrete specimen (7) and the loading device are connected by a double-plate plastic brush bonding method; The following steps are involved: The first step is to grind the four sides of the block-shaped concrete specimen (7) to make it smooth and expose the aggregate, and grind the two base surfaces of the double-plate plastic brush (1) to make them smooth with sandpaper and clean them; The second step is to evenly apply adhesive to two opposite tensile bonding surfaces of the concrete specimen (7), place the base surfaces of two double-plate plastic brushes (1) on the bonding surfaces of the concrete specimen (7) to compact them, and clean the adhesive squeezed out from the gap; The third step is to place the concrete test piece (7) with the double-plate plastic brush (1) pasted on both sides in an environment of 25°C to 60°C for curing, and during the curing period, a heavy object is placed on the test piece to put the glue interface in a pre-compression state, and the test piece is taken out after the glue interface is completely cured; In the fourth step, the other base of each double-plate plastic brush is respectively bonded to the bonding steel plate (2) by adhesive and compacted, and after cleaning the adhesive squeezed out from the gap, it is continued to be cured in an environment of 25°C to 60°C in a pre-pressed state until the adhesive interface is completely cured; Step 5: Connect and tighten each bonding steel plate (2) and the force transmission steel plate (3) via bolts (4); In the sixth step, the other end of each force transmission steel plate (3) is connected to the loading end of the electro-hydraulic servo testing machine through the tension spherical hinge (5), and a vertical load is applied to the concrete specimen (7) through the electro-hydraulic servo testing machine; the other two sides of the pressure-bearing surfaces of the concrete specimen (7) are connected to the loading end of the electro-hydraulic servo testing machine through the pressure spherical hinge (6), and horizontal lateral compressive stress is applied through the pressure spherical hinge (6); and the concrete multi-axial tension and compression stress combination test is completed according to the predetermined loading scheme.

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