A new type of straight shear type concrete fracture performance test specimen and test method

Abstract

The application discloses a novel straight-shear type concrete fracture performance test specimen and a test method. The test specimen is in the shape of an ectopic notch. During the test, the test specimen is placed between two loading plates, and the length direction of the concrete part is perpendicular to the two loading plates. The two loading plates are loaded towards each other. Relative to the concrete part, the compression deformation of the steel block is almost zero, thus causing the relative deformation difference between the concrete part and the steel block. The two loading plates are continuously loaded towards each other, and the concrete part is fractured along the predetermined position. The method forms the deformation difference in the stress redistribution process through the different material stiffness on both sides of the crack, realizes the opposite displacement within the range of the test specimen, and causes the dislocation cracking. Since the crack is caused by the deformation difference inside the concrete part, there is no bending tensile stress influence. The application is used for solving the index test of the II type fracture performance of brittle materials such as ordinary concrete and rockfill concrete, improving the existing test method, and eliminating the influence of the bending tensile stress in the II type fracture test.

Description

TECHNICAL FIELD

[0001] The present application relates to a new type of straight shear concrete fracture performance test specimen and test method. BACKGROUND

[0002] The test of the mode II fracture performance of concrete materials is a major issue that is very concerned by the engineering field. So far, the mode II fracture performance test experimental method of ordinary concrete materials and rockfill concrete materials cannot avoid the influence of bending stress, and the test method itself and accuracy have certain problems, which has been a hot issue for scholars in various countries to study. The existing test methods have the following defects: the four-point bending test results are affected by bending stress in the later stage, the straight shear test specimen loading process also produces bending stress, and the Z-shaped test specimen also has a certain bending stress after cracking, which makes it difficult to obtain the true value of the true mode II fracture index through the test. SUMMARY

[0003] The present application is to solve the problems existing in the prior art and provides a new type of straight shear concrete fracture performance test specimen and test method. The test method is to form a deformation difference in the stress redistribution process by the large difference in material stiffness on both sides of the crack, realize the opposite displacement in the range of the test specimen, and cause the dislocation cracking. Since the crack is caused by the deformation difference inside the concrete specimen, there is no bending tensile stress. The present application is used to solve the index test of the mode II fracture performance of brittle materials such as ordinary concrete and rockfill concrete, improve the existing test method, and eliminate the influence of bending tensile stress in the mode II fracture test.

[0004] The technical scheme adopted by the present application is as follows:

[0005] A new type of straight shear concrete fracture performance test specimen, comprising a concrete piece and a steel block, the concrete piece is a block structure, two notched portions in rotational symmetry are arranged on the concrete piece, each notched portion is filled with a steel block, and the concrete piece is formed into an integral body with the steel block after being poured with concrete, the outer end surface of the steel block is higher than the outer end surface of the concrete piece, or the outer end surface of the steel block is flush with the outer end surface of the concrete piece.

[0006] Further, when the outer end surface of the steel block is higher than the outer end surface of the concrete piece, the height difference is within 1mm.

[0007] Further, the length of the concrete piece is 3 times the width, and the notched portion is arranged on the wide side of the concrete piece.

[0008] Further, the cross-sectional size of the steel block is 1 / 2 of the corresponding wide side cross-sectional width of the concrete piece.

[0009] The present application also provides a testing method of the novel straight-shear type concrete fracture performance testing specimen, the specimen is arranged between two loading plates, and the length direction of the concrete specimen is perpendicular to the two loading plates; the two loading plates are loaded towards each other, and the compression deformation of the steel block is almost zero relative to the concrete specimen, thus causing the relative deformation difference between the concrete specimen and the steel block, the two loading plates are continuously loaded towards each other and the vertical fracture of the concrete specimen occurs (a micro guide crack can also be arranged when the specimen is manufactured), the deformation difference is realized in the stress redistribution process through the change of the material stiffness on both sides of the crack, and the cracking is caused, and since the crack is caused by the deformation difference inside the concrete specimen, the bending tensile stress does not exist.

[0010] The present application has the following beneficial effects:

[0011] The present application is used for solving the testing of the two-type fracture mechanics performance indexes of the ordinary concrete material and the rockfill concrete material, improving the existing testing method, and eliminating the influence of the bending tensile stress in the two-type fracture testing.

[0012] The specimen adopts a concrete special-shaped specimen, and a steel block pad is arranged at the gap of the anti-symmetrical position of the specimen, the deformation difference formed in the loading process causes the cracking of the concrete specimen.

[0013] The outer end surface of the steel block is higher than the outer end surface of the concrete specimen, or the outer end surface of the steel block is flush with the outer end surface of the concrete specimen, when the structure that the outer end surface of the steel block is higher than the outer end surface of the concrete specimen is adopted, the loading plate first contacts the steel block, and then there is a small gap between the loading plate and the concrete specimen, with the loading of the loading plate, the small gap is compacted in the elastic deformation process, and then the loading is continued, the concrete specimen becomes full-section loading (i.e. the concrete specimen and the steel block are completely in contact with the loading plate) in the subsequent loading process, the deformation difference is realized in the stress redistribution process through the difference of the material stiffness of the superposed materials on both sides of the crack, and the cracking is caused. The crack is caused by the deformation difference inside the specimen, and the bending tensile stress does not exist. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a structure diagram of the outer end surface of the steel block being higher than the outer end surface of the concrete specimen.

[0015] Figure 2 It is a structure diagram of the outer end surface of the steel block being flush with the outer end surface of the concrete specimen.

[0016] Figure 3 It is a structure diagram of the concrete specimen.

[0017] Figure 4 It is a schematic diagram of the testing of the specimen of the present application through the loading plate.

[0018] Figure 5 It is a schematic diagram of the manufacturing of the specimen of the present application. EMBODIMENT

[0019] The application will be further described below with reference to the accompanying drawings.

[0020] As Figures 1 to 3 The application is a new type of straight shear concrete fracture performance test specimen, which comprises a concrete piece 1 and a steel block 2. The concrete piece 1 is in a block structure, and two notched portions 11 are arranged on the concrete piece 1 in a rotational symmetry. In this embodiment, the notched portions 11 are rectangular (i.e., the cracking section is a square section), and the cracking portion (i.e., the notched portion) is not limited to a square in actual use.

[0021] Each notched portion 11 is filled with the steel block 2, and the concrete piece 1 is integrated with the steel block 2 after being poured with concrete. The length of the concrete piece 1 is 3 times the width, the notched portion 11 is arranged on the wide side of the concrete piece 1, and the cross-sectional size of the steel block 2 is 1 / 2 of the corresponding wide side cross-sectional width of the concrete piece 1.

[0022] The outer end surface of the steel block 2 is higher than the outer end surface of the concrete piece 1 (such as Figure 1 ). When the outer end surface of the steel block 2 is higher than the outer end surface of the concrete piece 1, the height difference is within 1 mm. Alternatively, the outer end surface of the steel block 2 is flush with the outer end surface of the concrete piece 1 (such as Figure 2 ).

[0023] When the specimen is made, the two steel blocks 2 are arranged in a rotational symmetry in the steel film, and then the concrete is poured. When the specimen to be poured is a structure with a height difference, a thin steel plate 4 is placed in the steel film (such as Figure 5 ), and after molding, the thin steel plate 4 can be removed.

[0024] As Figure 4 When the specimen is tested, the loading plate 3 is subjected to an axial load on the testing machine, and after the elastic deformation is completed, the loading plate is completely attached to the loading surface specimen. In the subsequent loading process, with the development of plastic deformation, fracture failure occurs, which is as follows:

[0025] When the specimen with a height difference is tested, the small gap reserved by the specimen (i.e., the gap between the concrete piece 1 and the loading plate 3 after the steel block 2 is attached to the loading plate 3) is used to coordinate the initial elastic deformation of the loading. When the initial elastic deformation of the loading is completed, the loading plate is completely attached to the loading surface (i.e., completely attached to the concrete piece 1 and the steel block 2), and the subsequent loading starts to accumulate plastic deformation. The specimen is longitudinally divided into two equal-volume and equal-size parts, and the boundary is the position of the simulated cracking (the position of the simulated cracking is that a small guide crack is set during the manufacture of the specimen). The elastic modulus of the steel block is one order of magnitude larger than that of the concrete, and it can be considered that the loading process does not produce compression deformation. Due to the ex-situ arrangement of the steel block, the relative deformation difference of the two equal-volume parts of the specimen is formed, and with the development of plastic deformation, the specimen occurs two-type fracture.

[0026] The longitudinal direction of the test piece is the loading direction. When initially loading, the upper and lower loading plates are misaligned to load and suspend the half section. Because the gap is very small, when the test piece completes the elastic compression deformation, the loading plate and the test piece loading interface are completely attached. When continuing to load, the compression deformation of the steel block is almost equal to zero relative to the concrete test piece body, thus causing the relative deformation difference. When continuing to load, the fracture occurs along the predetermined position. Because the full section is directly loaded, the deformation difference is realized in the stress redistribution process through the difference in the stiffness of the superimposed materials on both sides of the crack, causing the cracking. The crack is caused by the internal deformation difference of the test piece and is not affected by the bending tensile stress.

[0027] When testing the test piece without the height difference, the process is consistent with the test process and structure of the test piece with the height difference, except that the loading plate is completely attached to the loading surface at the beginning.

[0028] The above only describes the preferred embodiments of the present application. It should be noted that those skilled in the art can make several improvements without departing from the principles of the present application, and these improvements should also be considered within the protection scope of the present application.

Claims

1. A novel direct shear concrete fracture performance test specimen, characterized in that: It includes a concrete component (1) and a steel block (2). The concrete component (1) is a block structure. Two notches (11) are provided on the concrete component (1) in a rotationally symmetrical manner. Each notch (11) is filled by the steel block (2). The concrete component (1) is formed integrally with the steel block (2) after being poured with concrete. The outer end face of the steel block (2) is higher than the outer end face of the concrete component (1), or the outer end face of the steel block (2) is flush with the outer end face of the concrete component (1).

2. The novel direct shear concrete fracture performance test specimen as described in claim 1, characterized in that: When the outer end face of the steel block (2) is higher than the outer end face of the concrete part (1), the height difference is within 1 mm.

3. The novel direct shear concrete fracture performance test specimen as described in claim 1, characterized in that: The length of the concrete component (1) is three times its width, and the notch (11) is provided on the wide side of the concrete component (1).

4. The novel direct shear concrete fracture performance test specimen as described in claim 3, characterized in that: The cross-sectional dimension of the steel block (2) is 1 / 2 of the width of the corresponding wide side cross-section of the concrete component (1).

5. A testing method for a novel direct shear concrete fracture performance test specimen as described in claim 1, characterized in that: The specimen is placed between two loading plates (3), and the length direction of the concrete part (1) is perpendicular to the two loading plates (3). The two loading plates (3) are loaded towards each other. The compression deformation of the steel block (2) is almost zero relative to the concrete part (1), thus causing a relative deformation difference between the concrete part (1) and the steel block (2). The two loading plates (3) are loaded towards each other and the concrete part (1) is vertically fractured. The deformation difference is achieved during the stress redistribution process by the change of material stiffness on both sides of the crack, causing cracking. Since the crack is caused by the internal deformation difference of the concrete part (1), there is no influence of bending tensile stress.

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