High-rigidity UHPC (Ultra High Performance Concrete) tensile test clamp

Abstract

The utility model relates to a high-rigidity UHPC (Ultra High Performance Concrete) tensile test fixture. The high-rigidity UHPC tensile test fixture comprises a fixture chuck and a variable cross-section connecting rod, wherein the fixture chuck is used for clamping the end part of a test piece; the clamp chuck comprises a top plate, a side plate and a fixing structure with an arc. Side plates are respectively arranged on two sides of the same surface of the top plate; each side plate is a variable cross-section plate with the length gradually shortened from the side close to the top plate to the side away from the top plate, the opposite faces of the variable cross-section plates on the two sides are linear sides, and the opposite faces of the variable cross-section plates away from each other are inclined sides; arc fixing structures are arranged at the ends, away from the top plate, of the linear sides of the side plates correspondingly. The top plate is connected with the variable cross-section connecting rod through a variable cross-section connecting rod fixing hole formed in the face, opposite to the side plate, of the top plate. Compared with the prior art, the clamp provided by the utility model has the characteristic of high rigidity, and when the concrete reaches a peak load, a concrete test block can be prevented from being broken too fast, and a whole-process stress-strain curve of the concrete can be accurately measured.

Description

Technical Field

[0001] This utility model relates to the field of engineering testing equipment technology, and in particular to a high-rigidity UHPC concrete tensile testing fixture. Background Technology

[0002] Ultra-high performance concrete (UHPC) has become the preferred material for infrastructure upgrades and green building due to its superior compressive strength and durability, and is widely used in bridge reinforcement, prefabricated buildings, landmark projects, and tunnel repair. Therefore, obtaining the full stress-strain curve of UHPC concrete is crucial for studying and verifying its performance.

[0003] During tensile testing of concrete, the internal forces of the concrete specimen and the clamps decrease rapidly after the concrete reaches its peak load. The elastic potential energy of the clamps is converted into the plastic deformation energy of the concrete specimen. For example, the tensile testing clamps disclosed in Chinese patent applications CN108918256A and CN207095976U generally have low stiffness and large elastic energy storage, leading to excessively rapid plastic deformation of the concrete and premature fracture of the concrete specimen. Therefore, it is difficult to accurately measure the entire stress-strain curve of the concrete. Utility Model Content

[0004] The purpose of this invention is to solve the problem that the current fixture has a large elastic energy storage, which leads to the rapid plastic deformation of concrete and makes it difficult to accurately measure the entire process of concrete stress-strain. Therefore, this invention provides a high-rigidity UHPC concrete tensile test fixture.

[0005] The objective of this utility model can be achieved through the following technical solutions:

[0006] A high-rigidity UHPC concrete tensile test fixture includes a clamping head for holding the end of a concrete specimen and a variable cross-section connecting rod connecting the clamping head and the tensile test facility.

[0007] The clamp chuck includes a top plate, side plates, and an arc-shaped fixing structure;

[0008] The side plates are respectively set on both sides of the same surface of the top plate; the two side plates are variable cross-section plates with the length gradually shortening from the side closer to the top plate to the side farther away from the top plate. The side of the variable cross-section plates on both sides of the top plate that faces each other is the straight side, and the side that is farther away from each other is the inclined side.

[0009] The two side panels on the top plate are respectively provided with arc-shaped fixing structures at the ends of the straight side away from the top plate;

[0010] The top plate has a variable cross-section connecting rod fixing hole on the side opposite to the side plate; the variable cross-section connecting rod is installed and connected to the clamp chuck through the variable cross-section connecting rod fixing hole.

[0011] As a preferred technical solution, the clamp variable cross-section connecting rod includes a threaded segment and a smooth rod. The clamp variable cross-section connecting rod is fixedly connected to the clamp chuck through the threaded segment and connected to the tensile testing facility through the smooth rod.

[0012] As a preferred technical solution, the diameter of the smooth rod is larger than the diameter of the threaded segment, and the threaded segment and the smooth rod are connected by a variable diameter cross section.

[0013] As a preferred technical solution, the surface of the threaded segment is provided with external threads; the fixing hole of the variable cross-section connecting rod is a bolt hole, and the hole is provided with internal threads that mate with the threaded segment.

[0014] As a preferred technical solution, the threaded segment uses an M16 bolt, and the bolt hole is set as an M16 bolt hole.

[0015] As a preferred technical solution, the top plate is a steel plate, and the side plates are connected to the top plate by welding.

[0016] As a preferred technical solution, the arc shape of the arc-shaped fixing structure provided on both sides matches the shape of the variable cross-section segment of the concrete specimen.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1) A high-rigidity UHPC concrete tensile performance testing fixture. The fixture features a clamping head with equal strength and a variable cross-section connecting rod, which reduces fixture stress, increases fixture rigidity, reduces elastic energy storage, and prevents premature fracture of the concrete specimen. Therefore, it allows for relatively accurate measurement of the entire stress-strain curve of concrete.

[0019] 2) The clamp chuck designed in this utility model can effectively reduce the stress of the clamp chuck, improve the stiffness of the clamp chuck, and reduce the elastic energy storage of the clamp chuck by about 70%. While ensuring the increase in stiffness, it can save on the use of clamp chuck material.

[0020] 3) The lower part of the variable cross-section connecting rod is designed with M16 bolts; the small diameter reduces the additional bending moment. The upper part of the variable cross-section connecting rod is designed with a 33mm diameter smooth rod to connect the test equipment and increase the structural stiffness. By combining large and small diameters, the stiffness of the connecting rod is increased while avoiding excessive additional bending moment. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a high-rigidity UHPC concrete tensile test fixture according to this utility model.

[0022] Figure 2This is a front view schematic diagram of the clamp head structure in this utility model.

[0023] Figure 3 This is a side view of the clamp head structure in this utility model.

[0024] Figure 4 This is a top view schematic diagram of the clamp head structure in this utility model.

[0025] Figure 5 This is a schematic diagram of the variable cross-section connecting rod of the clamp head in this utility model.

[0026] The following are labeled in the diagram: 1. Clamp head; 2. Top plate; 3. Side plate; 4. Arc-shaped fixing structure; 5. Bolt hole; 6. Variable cross-section connecting rod; 7. Tensile testing equipment; 8. Concrete specimen. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. This embodiment is based on the technical solution of the present invention and provides detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0028] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0029] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0030] Example 1

[0031] The purpose of this invention is to provide a high-rigidity concrete tensile performance testing fixture capable of measuring the stress-strain curve of concrete throughout the entire process, such as... Figure 1 As shown, it includes clamps 1 with equal strength structure for holding both ends of concrete specimen 8, and variable cross-section connecting rods 6 connecting clamps 1 and tensile testing facility 7.

[0032] like Figure 2As shown, the clamp 1 with equal strength structure consists of a top plate 2, side plates 3, and an arc-shaped fixing structure 4. Side plates 3 are respectively provided on both sides of the same surface of the top plate 2. The two side plates 3 are variable cross-section plates whose length gradually decreases from the side closer to the top plate 2 to the side farther away from the top plate 2. The faces of the variable cross-section plates on both sides of the top plate 2 are straight sides, and the sides farther away from each other are inclined sides. An arc-shaped fixing structure 4 is provided at the end of the opposite straight side of the two side plates 3 away from the top plate 2. The arc shape of the arc-shaped fixing structure 4 matches the shape of the variable cross-section segment of the concrete specimen 8. A variable cross-section connecting rod fixing hole is provided on the side of the top plate 2 opposite to where the side plates 3 are located; the variable cross-section connecting rod 6 is installed and connected to the clamp 1 through the variable cross-section connecting rod fixing hole. Figure 2-3 As shown, in this embodiment, the top plate 2 is a Q345 steel plate with a length of 262mm, a width of 50mm, and a height of 100mm. A bolt hole 5 is drilled in the center of the top plate 2. The bolt hole 5 is an M16 bolt hole. The side plate 3 is divided into left and right sections. In this embodiment, the side plates 3 located on both sides of the top plate 2 are variable cross-section plates with an upper length of 80mm, a lower length of 60mm, a width of 50mm, and a height of 191mm. The distance between the two side plates is 102mm. The side plates 3 are welded to the top plate 2. An arc-shaped fixing structure 4 is connected to the straight side of the lower end of the side plate 3; the arc-shaped fixing structure 4 is an arc with a diameter of 70mm.

[0033] The lower 1 / 3 of the arc of the fixed arc structure is taken as the point of force application between the concrete specimen 8 and the clamp. The internal tensile force under the peak load of the concrete specimen is the vertical force at the point of application, and the transverse force can be obtained through vector calculation of the force. The top plate is a pure bending member, and the side plate is a tension-bending member. The stress of the top plate and the side plate can be obtained. The performance parameters of the clamp head proposed in this utility model are calculated. It can be found that the strength safety factor of the clamp head 1 under the dimensional parameters provided in this embodiment is 4, which greatly improves the stiffness of the clamp head compared with the existing clamps. At the same time, the elastic energy storage of the clamp head is reduced by about 70%. The calculation results show that this utility model effectively reduces the stress of the clamp head by designing the clamp head 1 with an equal strength structure, and saves the use of clamp head material while ensuring the improvement of stiffness.

[0034] like Figure 4 As shown, the variable cross-section connecting rod 6 of the fixture includes a threaded segment and a smooth rod. The variable cross-section connecting rod 6 is fixedly connected to the fixture chuck 1 through the threaded segment and connected to the tensile testing facility through the smooth rod. The diameter of the smooth rod is larger than the diameter of the threaded segment, and the threaded segment and the smooth rod are connected by a variable diameter cross-section. The surface of the threaded segment is provided with external threads, and the fixing hole of the variable cross-section connecting rod is a bolt hole 5, with internal threads that mate with the threaded segment. In this embodiment, the variable cross-section connecting rod 6 consists of a 200mm long M16 threaded segment and a 180mm long, 33mm diameter smooth rod, with the threaded segment and the smooth rod connected by a 20mm long variable diameter cross-section.

[0035] The internal tensile force under peak load on the concrete specimen is the internal force of the variable cross-section connecting rod. In this invention, the lower part of the variable cross-section connecting rod 6 is designed with an M16 bolt; the small diameter reduces the additional bending moment. The upper part of the variable cross-section connecting rod 6 is designed as a smooth rod with a diameter of 33mm, used to connect the test facility and increase the structural stiffness. By combining large and small diameters, the stiffness of the connecting rod is increased while avoiding excessive additional bending moment. Based on the dimensional parameters provided in this embodiment, the stress safety factor of the variable cross-section rod is 4, and the elastic energy storage of the connecting rod is reduced by approximately 68%. The calculation results show that the variable cross-section connecting rod 6 designed in this invention can effectively reduce the stress of the connecting rod and improve its stiffness.

[0036] like Figure 5 As shown, under normal conditions, the concrete specimen 8 is placed in the clamp 1 provided in this invention. The testing facility is connected to the large-diameter end of the variable cross-section connecting rod 6, and the clamp 1 is connected to the small-diameter end of the variable cross-section connecting rod 6. The testing facility applies a tensile force to the variable cross-section connecting rod 6, and the tensile force is transmitted to the specimen 8 through the clamp 1 at the arc-shaped fixing structure 4. The arc-shaped fixing structure 4 and the side plate 3 serve to fix the specimen 8, ensuring that the tensile force acts perpendicularly on the specimen 8.

[0037] Based on the structural design of the clamp chuck 1 with equal strength and the variable cross-section connecting rod 6, the concrete tensile test fixture device proposed in this invention can ensure that the concrete specimen does not break too quickly after the concrete reaches its peak load. Therefore, it is possible to obtain a relatively accurate stress-strain curve of the entire process of concrete.

[0038] The preferred embodiments of this utility model have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of this utility model without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of this utility model through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A high-stiffness UHPC concrete tensile testing fixture, characterized in that, Includes a clamping head (1) for holding the end of the concrete specimen (8) and a variable cross-section connecting rod (6) connecting the clamping head (1) and the tensile testing facility (7); The clamp chuck (1) includes a top plate (2), a side plate (3), and an arc-shaped fixing structure (4); The side plates (3) are respectively set on both sides of the same surface of the top plate (2); the two side plates (3) are variable cross-section plates whose length gradually shortens from the side closer to the top plate (2) to the side farther away from the top plate (2). The side of the variable cross-section plates on both sides of the top plate (2) facing each other is the straight side, and the side away from each other is the inclined side. The two side plates (3) on the top plate (2) are respectively provided with arc-shaped fixing structures (4) at the ends of the straight side away from the top plate (2); The top plate (2) has a variable cross-section connecting rod fixing hole on the side opposite to the side plate (3); the variable cross-section connecting rod (6) is installed and connected to the clamp chuck (1) through the variable cross-section connecting rod fixing hole.

2. The high-stiffness UHPC concrete tensile test fixture according to claim 1, characterized in that, The clamp variable cross-section connecting rod (6) includes a threaded segment and a smooth rod. The clamp variable cross-section connecting rod (6) is fixedly connected to the clamp chuck (1) through the threaded segment and connected to the tensile testing facility through the smooth rod.

3. The high-stiffness UHPC concrete tensile test fixture according to claim 2, characterized in that, The diameter of the smooth rod is larger than the diameter of the threaded segment, and the threaded segment and the smooth rod are connected by a variable diameter cross section.

4. A high-stiffness UHPC concrete tensile test fixture according to claim 2, characterized in that, The surface of the threaded segment is provided with external threads; the fixing hole of the variable cross-section connecting rod is a bolt hole (5), and the hole is provided with internal threads that mate with the threaded segment.

5. A high-stiffness UHPC concrete tensile test fixture according to claim 4, characterized in that, The threaded segment uses an M16 bolt, and the bolt hole (5) is set as an M16 bolt hole.

6. A high-stiffness UHPC concrete tensile test fixture according to claim 1, characterized in that, The top plate (2) is a steel plate, and the side plate (3) is connected to the top plate (2) by welding.

7. A high-stiffness UHPC concrete tensile test fixture according to claim 1, characterized in that, The arc shape of the arc-shaped fixing structure (4) provided on the side plates (3) on both sides matches the shape of the variable cross section of the concrete specimen (8).

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