A concrete ultimate tensile clamp

Abstract

This utility model discloses a concrete ultimate tensile strength fixture, including a fixture frame with an equilateral trapezoidal cross-section. A mounting plate is fixedly connected to the top of the fixture frame, and a rotatable movable joint is located at the center of the mounting plate. Movable clamping plates are located at both ends of the bottom of the frame body. Each movable clamping plate includes a hinge portion hinged to the fixture frame and an extension portion fixedly connected to the lower surface of the hinge portion. The two hinge portions have inclined clamping surfaces on opposite sides. The extension portions extend out of the fixture frame along the inclined direction of the clamping surfaces and maintain the same inclination angle as the hinge portions. This application solves the problems of specimens frequently breaking at the clamping end and data deviations caused by misalignment when using traditional ultimate tensile strength fixtures.

Description

Technical Field

[0001] This utility model relates to the field of building construction technology, specifically to a concrete ultimate tensile clamp. Background Technology

[0002] The ultimate tensile strength of concrete refers to the strain of concrete at failure load, and it is an important indicator for measuring the crack resistance of concrete. It has significant application value in concrete panel engineering, crack control, seismic design, and material performance research.

[0003] The ultimate tensile test specimen for concrete is typically a 600mm x 196mm x 100mm figure-eight shaped specimen. The specimen is a column with isosceles trapezoidal ends and a 100mm x 100mm square cross-section in the tensile region. During the test, the specimen is clamped at both ends using a slotted clamp, which is then mounted on a testing machine for tensile testing. Equal and opposite concentrated forces are applied to both ends, subjecting the tensile region in the middle of the specimen to tensile stress. The maximum strain at tensile failure is used to assess the concrete's resistance to tensile deformation until fracture.

[0004] However, during actual indoor testing using custom-made traditional tensile clamps, the specimen often breaks at locations not within the pre-defined 100*100 mm area, but rather at the clamping points, leading to inaccurate data such as lower values. Furthermore, in tensile testing, the ideal stress state is axial central tension. However, the connection between traditional clamps and the testing machine is typically rigid, with fixed relative angles and positions after installation. If there are even slight angular deviations or misalignments in the clamps themselves or during installation, these deviations are forcibly transmitted to the specimen, resulting in small eccentric tension, affecting the test results and failing to reflect the actual field ultimate tensile strength. Summary of the Invention

[0005] To solve the above-mentioned technical problems, this utility model provides a concrete ultimate tensile clamp, which solves the problem that specimens often break at the clamping end when using traditional ultimate tensile clamps, and the data results are deviated due to inaccurate alignment.

[0006] A concrete ultimate tensile clamp includes a clamp body and a clamp frame with an isosceles trapezoidal cross-section. A mounting plate is fixedly connected to the top of the clamp frame, and a rotatable movable joint is provided at the center of the mounting plate. Movable clamping plates are provided at both ends of the bottom of the frame body. Each movable clamping plate includes a hinge portion hinged to the clamp frame and an extension portion fixedly connected to the lower surface of the hinge portion. The two hinge portions have inclined clamping surfaces on opposite sides. The extension portions extend out of the clamp frame along the inclined direction of the clamping surfaces and maintain the same inclined angle plane as the hinge portions.

[0007] A further technical solution is to set the length of the extension to 40-50mm.

[0008] A further technical solution is: the clamp frame includes a first side frame and a second side frame arranged at intervals and in parallel. The cross-section of the first side frame and the second side frame is an isosceles trapezoid. The mounting plate is fixedly connected between the tops of the first side frame and the second side frame by hexagonal bolts. The movable clamping plate is connected between the bottoms of the first side frame and the second side frame by a rotating shaft. Fasteners are provided on the rotating shaft.

[0009] A further technical solution is as follows: the rotatable joint includes an outer sleeve, a connecting shaft, and a connecting post. The top of the connecting shaft is provided with a clamping rod, and the bottom of the connecting shaft is provided with a spherical rotating head. The inner sleeve has a spherical groove at its center that matches the rotating head. The top of the spherical groove has a through hole for accommodating the connecting shaft. The through hole extends through to the top surface of the outer sleeve. The connecting post is fixedly connected to the bottom center of the outer sleeve and is threadedly connected to the mounting plate.

[0010] A further technical solution is: a through mounting hole is provided at the center of the top of the mounting plate, and matching threads are provided on the inner wall of the mounting hole and the outer wall of the connecting column.

[0011] The beneficial effects of this utility model are:

[0012] Traditional clamping devices often result in uneven contact between the clamp and the specimen, potentially leading to stress concentration and premature fracture at the clamping end due to shear force. This application addresses this by adding an extension at the bottom of the hinge, closer to the central 100*100 tension area. This effectively extends the point of application of the clamping force, resulting in a larger contact area between the movable clamp and the specimen, and a more uniform distribution of the clamping force. This prevents premature failure at the clamping end due to shear force or stress concentration, ensuring the accuracy of test data and avoiding underestimation of strength values ​​caused by incorrect fracture location.

[0013] This application utilizes a rotatable joint, with a rotating head connected to a spherical groove inside the outer sleeve, providing a degree of freedom at the connection. This allows for minor rotational adjustments of the fixture at the connection to compensate for potential misalignment. During the tensile test, if there is a slight initial misalignment in the specimen or fixture, the rotatable joint automatically adjusts its angle, ensuring that the line of action of the tensile force automatically converges towards the central axis of the specimen. This ensures that the applied tensile force is transmitted along the central axis of the specimen as much as possible throughout the test, minimizing bending moment generation, resulting in more accurate and reliable performance data, and the specimen's failure mode is more consistent with expectations. Attached Figure Description

[0014] Figure 1 This is an elevation view of the ultimate tensile fixture.

[0015] Figure 2 This is the elevation view of the movable clamping plate.

[0016] Figure 3 This is a cross-sectional view of the rotatable movable joint.

[0017] Figure 4 It is an isometric drawing of the movable clamping plate of the fixture.

[0018] Figure 5 This is a schematic diagram of the ultimate tensile fixture holding the specimen.

[0019] In the picture:

[0020] 1. Fixture frame; 11. First side frame; 12. Second side frame; 13. Mounting plate; 14. Hex bolt; 2. Movable clamping plate; 21. Hinge part; 22. Extension part; 23. Fastener; 24. Through hole; 3. Rotatable movable joint; 31. Outer sleeve; 32. Connecting shaft; 33. Rotating head; 34. Clamping rod; 33. Connecting column; 4. Specimen. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the present invention, and therefore only show the components relevant to the present invention.

[0022] In the description of this utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the utility model.

[0023] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0024] A concrete ultimate tensile clamp, such as Figure 1-5As shown, the fixture frame 1 has an isosceles trapezoidal cross section. A mounting plate 13 is fixedly connected to the top of the fixture frame 1. A rotatable movable joint 3 is provided at the center of the mounting plate 13. Movable clamping plates 2 are provided at both ends of the bottom of the frame body. The movable clamping plate 2 includes a hinge part 21 that is hinged to the fixture frame 1 and an extension part 22 that is fixedly connected to the lower surface of the hinge part 21. The two hinge parts 21 have an inclined clamping surface on opposite sides. The extension part 22 extends to the outside of the fixture frame 1 along the inclined direction of the clamping surface and maintains the same inclined angle plane as the hinge part 21.

[0025] Preferably, the length of the extension 22 is set to 40-50 mm. The extension 22 and the hinge 21 are made of steel plate.

[0026] The clamp frame 1 includes a first side frame 11 and a second side frame 12 arranged at intervals and in parallel. The cross-sections of the first side frame 11 and the second side frame 12 are isosceles trapezoids with smooth transitions at the corners. The mounting plate 13 is fixedly connected between the tops of the first side frame 11 and the second side frame 12 by hexagonal bolts 14. The movable clamping plate 2 is connected between the bottoms of the first side frame 11 and the second side frame 12 by a rotating shaft. Fasteners 23 are provided on the rotating shaft. Specifically, the rotating shaft uses hexagonal bolts, and the fasteners 23 can be hexagonal nuts.

[0027] The rotatable joint 3 includes an outer sleeve 31, a connecting shaft 32, and a connecting post 33. The top of the connecting shaft 32 is provided with a clamping rod 34, and the bottom of the connecting shaft 32 is provided with a spherical rotating head 33. The center of the inner sleeve is provided with a spherical groove that matches the rotating head 33. The top of the spherical groove is provided with a through hole 24 for accommodating the connecting shaft 32. The through hole 24 extends through to the top surface of the outer sleeve 31. The connecting post 33 is fixedly connected to the center of the bottom of the outer sleeve 31 and is threadedly connected to the mounting plate 13.

[0028] The mounting plate 13 has a through mounting hole at the top center, and the inner wall of the mounting hole and the outer wall of the connecting column 33 are provided with matching threads.

[0029] The following is an illustration through a specific example.

[0030] The concrete ultimate tensile specimen was a 600mm*196mm*100mm figure-eight 4 specimen, which was a column with an isosceles trapezoidal shape at both clamping ends and a square cross section of 100mm*100mm in the middle tension part.

[0031] In Example 1, the concrete ultimate tensile clamp of this application was used for testing. The clamp frame of this ultimate tensile clamp has a first and second side frame with a height of 290mm, an upper base width of 90mm, and a lower base width of 260mm. The mounting plate has a width of 80mm and a length of 125mm. The hinge of the movable clamping plate has a height of 100mm, an upper base width of 13mm, and a lower base width of 48mm. A φ20 through hole is provided at the bottom of the hinge, and the extension length of the extension part is 50mm. The outer sleeve of the rotatable movable joint has a diameter of 50mm, the rotating head has a diameter of 25mm, the connecting shaft has a diameter of 16mm, the clamping column has a diameter of 40mm, and the connecting column has a diameter of 30mm and a length of 15mm.

[0032] In use, first remove the rotating shaft and unload the movable clamping plate 2. Insert the V-shaped end of the specimen 1 between the first side frame 11 and the second side frame 12 of the clamp frame 1. Then, fix the movable clamping plates 2 on both sides between the first side frame and the second side frame using the rotating shaft and fasteners 23, so that the clamping surfaces of the movable clamping plates are tightly against the two sides of the V-shaped end. After installing clamps on both sides of the V-shaped end of the specimen, clamp the jaws of the testing machine onto the clamping rods of the rotatable movable joints of the clamps at both ends of the specimen. After the specimen is connected to the testing machine, start the testing machine to begin the concrete ultimate tensile test.

[0033] In Comparative Example 1, a common fixture with essentially the same dimensions as that in Example 1 was used for testing. The difference between this common fixture and the fixture in Example 1 is that the mounting plate is fixedly connected to the clamping rod by bolts, and the movable clamping plate only has a hinged part and no extension part. The installation and use method of the fixture in Comparative Example 1 during testing is similar to that of the fixture in Example 1.

[0034] Example 1 and Comparative Example 1 were tested on concrete ultimate tensile tests on specimens with identical arrays. The test results are shown in Tables 1 and 2.

[0035] Table 1

[0036]

[0037] Table 2

[0038]

[0039] Note: Four specimens constitute one group. If fewer than two of the test values ​​are available, the test results for that group are invalid.

[0040] Therefore, this application can effectively solve the problems that specimens often break at the clamping end when using traditional ultimate tensile strength clamps, and that inaccurate alignment causes deviations in data results.

[0041] Based on the above-described preferred embodiments of this utility model, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A concrete ultimate tensile clamp, comprising a clamping body, characterized in that, The fixture frame includes an isosceles trapezoidal cross-section. A mounting plate is fixedly connected to the top of the fixture frame. A rotatable joint is provided at the center of the mounting plate. Movable clamping plates are provided at both ends of the bottom of the frame body. Each movable clamping plate includes a hinge portion that is hinged to the fixture frame and an extension portion that is fixedly connected to the lower surface of the hinge portion. The two hinge portions have an inclined clamping surface on opposite sides. The extension portion extends out of the fixture frame along the inclined direction of the clamping surface and maintains the same inclined angle plane as the hinge portion.

2. The concrete ultimate tensile clamp according to claim 1, characterized in that, The length of the extension is set to 40-50mm.

3. A concrete ultimate tensile clamp according to claim 1, characterized in that, The clamp frame includes a first side frame and a second side frame arranged at intervals and in parallel. The cross-section of the first side frame and the second side frame is an isosceles trapezoid. The mounting plate is fixedly connected between the top of the first side frame and the second side frame by hexagonal bolts. The movable clamping plate is connected between the bottom of the first side frame and the second side frame by a rotating shaft. Fasteners are provided on the rotating shaft.

4. A concrete ultimate tensile clamp according to claim 1, characterized in that, The rotatable joint includes an outer sleeve, a connecting shaft, and a connecting post. The top of the connecting shaft is provided with a clamping rod, and the bottom of the connecting shaft is provided with a spherical rotating head. The center of the inner sleeve is provided with a spherical groove that matches the rotating head. The top of the spherical groove is provided with a through hole for accommodating the connecting shaft. The through hole extends through to the top surface of the outer sleeve. The connecting post is fixedly connected to the center of the bottom of the outer sleeve and is threadedly connected to the mounting plate.

5. A concrete ultimate tensile clamp according to claim 4, characterized in that, The mounting plate has a through mounting hole at the top center, and the inner wall of the mounting hole and the outer wall of the connecting column are provided with matching threads.

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