A concrete crack opening and closing device

Abstract

This invention provides a concrete crack opening and closing device, belonging to the field of building material testing technology. It includes: an embedded component comprising at least one pair of parallel threaded rods, at least one steel plate clamp for isolating the concrete, and a small PVC pipe sleeved outside the threaded rods; and a load transmission component comprising a top rod passing through the embedded component, a two-hole pressure plate disposed on the outside of the concrete specimen and connected to the end of the threaded rods, and a nut threadedly engaged with the threaded rods. This invention achieves precise control of the crack width in the concrete specimen by setting up the threaded rods, nut, and steel plate clamp. Tightening the nut generates axial tension in the threaded rods, which is transmitted to the concrete specimen through the steel plate clamp, forming cracks at weak points. Precise control of the nut's rotation determines the elongation of the threaded rods, thereby achieving fine adjustment of the crack width.

Description

Technical Field

[0001] This utility model relates to the field of building material testing technology, and in particular to a concrete crack opening and closing device. Background Technology

[0002] In the field of building engineering technology, especially when conducting performance certification (such as European ETA certification or Chinese JGT-160 certification) for concrete anchoring products (such as self-tapping anchors), rigorous tensile and shear tests must be performed on concrete specimens with specific crack widths. These tests require the concrete specimens to have precise crack widths, such as 0.3mm, 0.5mm, 0.8mm, etc., and the cracks must remain stable during the test.

[0003] Currently, most methods for preparing cracked concrete specimens employ external loading, such as using jacks or similar equipment to forcibly split a cast, intact concrete specimen. These traditional methods have several drawbacks: firstly, the crack width is difficult to control precisely, resulting in poor repeatability; secondly, the loading process may cause irreversible damage to the specimen or generate invisible internal microcracks, affecting the accuracy and impartiality of the test results; and finally, a single device typically only generates cracks of one width, leading to low efficiency and the inability to repeatedly open and close cracks for reuse. Therefore, this application provides a concrete crack opening and closing device to meet this need. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a concrete crack opening and closing device to solve the existing problems.

[0005] To solve the above-mentioned technical problems, this utility model provides the following technical solution: A concrete crack opening and closing device includes: an embedded component comprising at least a pair of parallel threaded rods, at least one steel plate clamp for isolating concrete, and a small PVC pipe sleeved outside the threaded rods; a load conduction component comprising a top rod passing through the embedded component, a two-hole pressure plate disposed outside the concrete test block and connected to the end of the threaded rods, and a nut threadedly engaged with the threaded rods; wherein the steel plate clamp is sleeved outside the small PVC pipe, and a seepage-proof gap is reserved between the inner diameter of the small PVC pipe and the outer diameter of the threaded rods; by tightening the nut, an axial tensile force is applied to the threaded rods, which is converted into a splitting force on the concrete test block through the steel plate clamp, thereby causing cracks to form in the concrete test block at the steel plate clamp, and the width of the cracks is precisely controlled by controlling the rotation of the nut.

[0006] As a further improvement to the above technical solution: The pre-embedded component also includes a large PVC pipe, which is arranged in parallel between a pair of threaded rods, and the top rod passes through the large PVC pipe, with its two ends contacting the inner side of the two-hole pressure plate.

[0007] In a preferred embodiment of the present invention, the steel plate clamp is provided with a hole for passing through the large PVC pipe, and the gap between the hole diameter and the outer diameter of the large PVC pipe is less than 0.1 mm; the gap between the outer diameter of the small PVC pipe and the inner diameter of the large PVC pipe is less than 0.1 mm.

[0008] In a preferred embodiment of the present invention, the anti-seepage gap between the inner diameter of the small PVC pipe and the outer diameter of the threaded rod is less than 0.5 mm.

[0009] In a preferred embodiment of the present invention, the loading transmission assembly further includes a first washer, a second washer, and a planar thrust bearing, wherein the planar thrust bearing is disposed between the two-hole pressure plate and the nut via the first washer and the second washer.

[0010] In a preferred embodiment of the present invention, the pre-embedded components are provided in multiple sets, and the multiple sets of pre-embedded components are fixedly connected by a steel ring beam. The steel ring beam and the threaded rod in each set of pre-embedded components are tied and fixed by thin iron wire, so that the multiple sets of pre-embedded components are parallel to each other.

[0011] In a preferred embodiment of the present invention, the number of steel plate clips is determined according to the number of cracks to be generated, and each set of the pre-embedded components generates one crack.

[0012] In a preferred embodiment of the present invention, the threaded rod is a smooth rod or a section not bonded to the concrete in the section corresponding to the inside of the small PVC pipe, and its tension is transmitted to the concrete test block through the section where the steel plate clamp is bonded to the concrete.

[0013] Compared with the prior art, this utility model has at least the following beneficial effects: In the above scheme, by setting up a threaded rod, nut, and steel plate clamps, precise control of the crack width of the concrete specimen is achieved. Tightening the nut generates axial tension in the threaded rod, which is transmitted to the concrete specimen through the steel plate clamps, forming cracks at its weak points. The precise control of the nut's rotation determines the elongation of the threaded rod, thereby achieving fine adjustment of the crack width. This effectively solves the problems of difficult precise control of crack width and poor repeatability in existing technologies. The threaded rod operates within the elastic deformation range, and the crack can open and close with the rotation of the nut. In the experiment, the crack width can be adjusted multiple times to meet different testing requirements, improving the utilization rate of the specimen and solving the problem that existing technologies cannot achieve repeated opening and closing of cracks and multiple uses.

[0014] By setting up a planar thrust bearing, the sliding friction during nut rotation is converted into rolling friction, which allows the tensile force to be evenly transmitted to the concrete test block, avoiding damage to the test block caused by uneven loading and improving the accuracy of the test.

[0015] By setting up a steel ring beam and multiple sets of pre-embedded components, which are fixed into an overall frame by the steel ring beam, the parallelism between cracks is improved, and the number of cracks can be flexibly adjusted according to actual testing needs. In addition, the entire device is easy to install and operate, which effectively improves testing efficiency and reduces experimental costs. Attached Figure Description

[0016] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments of the present invention and, together with the specification, further serve to explain the principles of the present invention and enable those skilled in the art to implement and use the present invention.

[0017] Figure 1 A three-dimensional structural diagram of the embedded components in a concrete crack opening and closing device; Figure 2 A three-dimensional structural diagram of the load conduction component in a concrete crack opening and closing device; Figure 3 A three-dimensional structural diagram of a concrete test block in a concrete crack opening and closing device; Figure 4 This is a schematic diagram of the cross-sectional structure of a concrete test block in a concrete crack opening and closing device.

[0018] Figure label: 1. Steel plate clamps; 2. Small PVC pipe; 3. Threaded rod; 4. Large PVC pipe; 5. Top rod; 6. Reinforcing ring beam; 7. Two-hole pressure plate; 8. First washer; 9. Flat thrust bearing; 10. Second washer; 11. Nut; 12. Concrete test block.

[0019] As shown in the figure, specific structures and devices are marked in the figure to clearly illustrate the structure of the embodiment of this utility model. However, this is only for illustrative purposes and is not intended to limit this utility model to this specific structure, device and environment. Those skilled in the art can adjust or modify these devices and environments according to specific needs. Detailed Implementation

[0020] The present invention provides a concrete crack opening and closing device in conjunction with the accompanying drawings and specific embodiments. It should be noted that, to make the embodiments more detailed, the following embodiments are the best and preferred embodiments; for some known technologies, those skilled in the art can also use other alternative methods to implement the invention. Furthermore, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0021] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0022] Generally, terms can be understood at least partly from their use in context. For example, depending at least partly on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least partly on the context, to allow for the presence of other factors that are not necessarily explicitly described.

[0023] It is understood that the meanings of “on”, “above”, and “above” in this utility model should be interpreted in the broadest manner, such that “on” not only means “directly on” something, but also includes the meaning of being “on” something with an intervening feature or layer, and that “above” or “above” not only means “on” something, but also includes the meaning of being “on” something without an intervening feature or layer.

[0024] Furthermore, spatially related terms such as “below,” “under,” “lower,” “above,” and “upper” are used herein for convenience to describe the relationship of one element or feature to one or more other elements or features, as illustrated in the accompanying drawings. Spatially related terms are intended to cover different orientations in the use or operation of the device other than those depicted in the accompanying drawings. The device may be oriented in other ways, and the spatially related descriptive terms used herein can be interpreted similarly.

[0025] like Figures 1 to 4 As shown, an embodiment of this utility model provides a concrete crack opening and closing device, comprising: The embedded component includes at least one pair of parallel threaded rods 3, at least one steel plate clamp 1 for separating concrete, and a small PVC pipe 2 sleeved on the outside of the threaded rods 3. The loading and conduction assembly includes a top rod 5 inserted into the pre-embedded assembly, a two-hole pressure plate 7 set on the outside of the concrete test block 12 and connected to the end of the threaded rod 3, and a nut 11 threadedly engaged with the threaded rod 3. The steel plate clamp 1 is sleeved on the outside of the small PVC pipe 2. A seepage-proof gap is reserved between the inner diameter of the small PVC pipe 2 and the outer diameter of the threaded rod 3. An axial tensile force is applied to the threaded rod 3 by tightening the nut 11. This tensile force is converted into a splitting force on the concrete test block 12 through the steel plate clamp 1, thereby causing cracks in the concrete test block 12 at the steel plate clamp 1. The width of the crack is precisely controlled by controlling the rotation of the nut 11.

[0026] The specific principle is as follows: When in use, tightening the nut 11 on one side will simultaneously apply axial tensile force to the two threaded rods 3. This tensile force is transmitted to the surrounding concrete through the steel plate clamp 1 fixedly connected to it, thereby converting it into a splitting force on the concrete test block 12. This causes the test block to be precisely pulled apart at the weak surface where the steel plate clamp 1 is located, producing a crack. By precisely controlling the rotation angle (i.e., the amount of rotation) of the nut 11, the elongation of the threaded rod 3 can be controlled, thereby achieving precise control of the crack width. When unloading, loosening the nut 11 in the opposite direction will cause the threaded rod 3 to retract within the elastic deformation, and the crack will close.

[0027] The pre-embedded components also include a large PVC pipe 4, which is arranged in parallel between a pair of threaded rods 3, and the top rod 5 is inserted into the large PVC pipe 4, with its two ends contacting the inner side of the two-hole pressure plate 7.

[0028] The steel plate clamp 1 has a hole for passing through the large PVC pipe 4. The gap between the hole diameter and the outer diameter of the large PVC pipe 4 is less than 0.1 mm. The gap between the outer diameter of the small PVC pipe 2 and the inner diameter of the large PVC pipe 4 is less than 0.1 mm. By limiting the gap, cement, sand and gravel are prevented from flowing into the PVC pipe during pouring.

[0029] The seepage-proof gap between the inner diameter of the small PVC pipe 2 and the outer diameter of the threaded rod 3 is less than 0.5mm.

[0030] The load transmission assembly also includes a first washer 8, a second washer 10, and a planar thrust bearing 9. The planar thrust bearing 9 is set between the two-hole pressure plate 7 and the nut 11 through the first washer 8 and the second washer 10. It can convert the sliding friction when the nut rotates into rolling friction, reduce the tightening torque, and make the tension on both sides balanced, so as to prevent the pressure plate from tilting. There are multiple sets of pre-embedded components. The multiple sets of pre-embedded components are fixedly connected by a steel ring beam 6. The steel ring beam 6 and the threaded rod 3 in each set of pre-embedded components are tied and fixed by thin iron wire, so that the multiple sets of pre-embedded components are parallel to each other.

[0031] The number of steel plate clamps 1 is determined according to the number of cracks to be generated. Each set of pre-embedded components generates one crack. In specific implementation, multiple parallel cracks can be generated as needed. At this time, there are multiple sets of pre-embedded components. The multiple sets of pre-embedded components are fixedly connected into an integral frame by steel ring beams 6. The steel ring beams 6 and the threaded rods 3 in each set of pre-embedded components are tied and fixed at each intersection point by thin iron wire, so that the tensile structures of all sets are parallel to each other and the spacing is fixed. The number of steel plate clamps 1 is determined according to the number of cracks to be generated. Each set of pre-embedded components generates one crack. During operation, all nuts 11 located on the same side need to be tightened simultaneously so that each crack can open evenly and synchronously.

[0032] The threaded rod 3 is either a smooth rod or a section not bonded to the concrete in the section corresponding to the small PVC pipe 2. Its tension is transmitted to the concrete test block 12 through the section of the steel plate clamp 1 bonded to the concrete.

[0033] Working principle: When pouring concrete test block 12, steel plate clamps 1, small PVC pipes 2, threaded rods 3, large PVC pipes 4, and steel reinforcement ring beams 6 are pre-embedded inside the concrete test block 12. The small PVC pipe 2 must pass through the steel plate clamps and be centered, ensuring equal distances on both sides. The threaded rod 3 must pass through the small PVC pipe 2, with a clearance of less than 0.5mm between the inner diameter of the small PVC pipe 2 and the outer diameter of the threaded rod 3 to prevent cement, sand, and other materials from flowing into the small PVC pipe 2 during pouring. Similarly, the large PVC pipe 4 must pass through the steel plate clamps 1. The clearance between the pre-drilled hole in the steel plate clamps 1 and the outer diameter of the large PVC pipe 4, as well as the clearance between the outer diameter of the small PVC pipe 2 and the large PVC pipe 4, are considered. The gap should ideally be less than 0.1mm, and the large PVC pipe 4 and the threaded rod 3 should be kept as parallel as possible. In the height direction, two small PVC pipes 2, two threaded rods 3 and one large PVC pipe 4 form a tension structure, and the upper and lower threaded rods 3 are symmetrical about the large PVC pipe 4. A concrete specimen with cracks requires at least two tension structures depending on its width. The number of steel plate clips 1 required for a concrete specimen with cracks is determined according to the number of cracks required. When there are multiple tension structures, they need to be fixedly connected with a steel ring beam 6. The steel ring beam 6 is firmly tied to each threaded rod 3 with thin iron wire to ensure that each tension structure is parallel to each other.

[0034] After the concrete is poured, it must be cured for at least 21 days before it can be used for testing. During the test, the concrete test block needs to be opened to create cracks. A set of tensile structures is used, with a two-hole pressure plate 7 at each end. A first washer 8 is placed on the outside of one of the two-hole pressure plates 7. A planar thrust bearing 9 is placed between the first washer 8 and the second washer 10. A nut 11 is placed on the outside of the second washer 10. A top rod 5 is inserted into the large PVC pipe 4. The two ends of the top rod 5 contact the two-hole pressure plate 7. At the center of the two-hole pressure plate 7, all nuts 11 on one side are tightened by rotation, while maintaining the lever balance of the two-hole pressure plate 7. The nuts 11 of the other tensile structure groups are subjected to the same force. The tightening torque is applied evenly to all nuts, so that the threaded rod 3 is subjected to tensile force. Under the tensile force, the threaded rod 3 stretches and becomes longer. Before the threaded rod 3 is subjected to tensile force, the thread of the threaded rod 3 is... The threaded rod 3 inside the small PVC pipe 2 is firmly bonded to the concrete specimen 12. A small section of the threaded rod 3 is not bonded to the concrete specimen 12. Under the action of the steel plate clamp 1, the concrete specimen 12 is separated, with only a small portion of the concrete connected at the notch in the steel plate clamp 1. This small portion of connected concrete, under the force transmission action, has its tensile force transmitted to the concrete specimen 12, causing the concrete specimen 12 to receive an equal tensile force. The concrete specimen 12 can be easily pulled apart, creating a crack. A dial indicator is installed on both sides of the crack to measure its width. Since the threaded rod 3 is stretched in the elastic deformation zone, when the nut 11 on one side is loosened, the threaded rod 3 returns to its original state, and the crack in the concrete specimen 12 shrinks again. Ultimately, the opening and closing of the crack in the concrete specimen 12 can be controlled by adjusting the nut 11 on one side.

[0035] This utility model encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this utility model. To provide the public with a thorough understanding of this utility model, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand this utility model even without these detailed descriptions. Furthermore, to avoid unnecessary confusion regarding the essence of this utility model, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0036] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A concrete crack opening and closing device, characterized by, include: The embedded component includes at least one pair of parallel threaded rods (3), at least one steel plate clip (1) for separating concrete, and a small PVC pipe (2) sleeved on the outside of the threaded rods (3). The loading and conduction assembly includes a top rod (5) passing through the pre-embedded assembly, a two-hole pressure plate (7) set on the outside of the concrete test block (12) and connected to the end of the threaded rod (3), and a nut (11) threadedly engaged with the threaded rod (3). The steel plate clamp (1) is sleeved on the outside of the small PVC pipe (2), and a seepage-proof gap is reserved between the inner diameter of the small PVC pipe (2) and the outer diameter of the threaded rod (3); by screwing the nut (11), an axial tension is applied to the threaded rod (3), and the tension is converted into a splitting force on the concrete test block (12) through the steel plate clamp (1), so that the concrete test block (12) produces a crack at the steel plate clamp (1), and the width of the crack is precisely controlled by controlling the rotation of the nut (11).

2. The concrete crack opening and closing device according to claim 1, characterized in that, The pre-embedded component also includes a large PVC pipe (4), which is arranged in parallel between a pair of threaded screws (3), and the top rod (5) passes through the large PVC pipe (4), with its two ends contacting the inner side of the two-hole pressure plate (7).

3. The concrete crack opening and closing device according to claim 2, characterized in that, The steel plate clamp (1) has a hole for passing through the large PVC pipe (4), and the gap between the hole diameter and the outer diameter of the large PVC pipe (4) is less than 0.1 mm; the gap between the outer diameter of the small PVC pipe (2) and the inner diameter of the large PVC pipe (4) is less than 0.1 mm.

4. The concrete crack opening and closing device according to claim 3, characterized in that, The seepage-proof gap between the inner diameter of the small PVC pipe (2) and the outer diameter of the threaded rod (3) is less than 0.5 mm.

5. The concrete crack opening and closing device according to claim 2, wherein The loading transmission assembly also includes a first washer (8), a second washer (10) and a planar thrust bearing (9), the planar thrust bearing (9) being disposed between the two-hole pressure plate (7) and the nut (11) via the first washer (8) and the second washer (10).

6. A concrete crack opening and closing device according to any one of claims 1-5, characterized in that The pre-embedded components are provided in multiple sets, and the multiple sets of pre-embedded components are fixedly connected by a steel ring beam (6). The steel ring beam (6) and the threaded rod (3) in each set of pre-embedded components are tied and fixed by thin iron wire, so that the multiple sets of pre-embedded components are parallel to each other.

7. The concrete crack opening and closing device according to claim 6, characterized in that, The number of steel plate clips (1) is determined according to the number of cracks to be generated, and each set of the pre-embedded components generates one crack.

8. The concrete crack opening and closing device according to claim 1, wherein The threaded rod (3) is a smooth rod or a section that is not bonded to the concrete in the section corresponding to the small PVC pipe (2). Its tension is transmitted to the concrete test block (12) through the section where the steel plate clamp (1) is bonded to the concrete.

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