Cracked concrete test specimen and method of crack propagation
By using non-tension reinforcement and locking devices to control crack width in concrete specimens, the problems of high cost and limited crack width in existing technologies are solved, achieving high-precision crack control and recyclability, and meeting the requirements for anchorage performance testing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CONSTR RES INST TESTING CENT CO LTD
- Filing Date
- 2023-09-01
- Publication Date
- 2026-07-21
AI Technical Summary
The use of high yield strength steel bars in existing concrete specimen anchorage performance tests results in high costs, difficulty in recycling, and limited maximum crack width, making it difficult to meet test requirements.
Non-tension steel bars are connected to the concrete substrate through pre-reserved through holes. A locking device is used to control the crack width and prevent the steel bars from bonding with the concrete. Threaded connections and bushings are used for fixation to achieve controllable crack expansion.
It reduces testing costs, improves the accuracy of crack width control, meets testing requirements, and the steel bars are recyclable, which is in line with the concept of energy conservation and environmental protection.
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Figure CN117232920B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of testing the physical properties of products, and more specifically, to a cracked concrete specimen and a method for crack propagation therefrom. Background Technology
[0002] Testing of mechanical anchors for concrete includes anchorage performance tests such as tensile and shear performance tests in cracked concrete, tensile performance tests for crack opening and closing, and seismic performance tests. These tests require cracked concrete specimens. When conducting tests on cracked concrete specimens, the anchors are installed with the cracks closed and then the cracks are expanded to the required width.
[0003] Existing methods for manufacturing concrete substrates require the placement of penetrating tensile reinforcement bars within the concrete. These bars are partially bonded to the concrete, and the opening and closing of cracks in the concrete are controlled by stretching the reinforcement bars. However, due to experimental requirements, the tensile reinforcement bars used must be of high yield strength. These bars have low production volumes, high costs, and are difficult to recycle after use. Furthermore, the mechanical properties of the reinforcement bars limit the maximum width of concrete cracks to a theoretical upper limit. Summary of the Invention
[0004] To address the aforementioned issues, this application provides a cracked concrete specimen and a method for crack propagation therefrom, which does not require the use of high-yield-strength steel reinforcement and offers high precision in controlling the crack width.
[0005] Specifically, the cracked concrete specimen includes:
[0006] A plurality of hexahedral concrete substrates, wherein a plurality of through holes are provided on the concrete substrates, and the through holes are provided in the same position on each concrete substrate. When the concrete substrates are arranged in a row, the through holes at the same position on each concrete substrate are connected and form elongated holes of equal diameter.
[0007] The reinforcing bar is provided in each of the elongated holes, and the reinforcing bar is fixedly connected only to the concrete substrate at both ends;
[0008] A locking device, installed on the concrete substrate, is used to lock or release two adjacent concrete substrates.
[0009] The number of through holes can be 4, 6, or 8, and they are distributed within the same cross-section of the concrete substrate, with all the through holes having parallel axes.
[0010] The steel bars mentioned are not "tension steel bars". In the general construction industry, "tension steel bars" refer to longitudinal steel bars cast in concrete. In existing cracked concrete specimens, the steel bars are cast in the concrete substrate and are considered tension steel bars. In the cracked concrete specimens provided in this application, the steel bars are inserted through reserved holes in the concrete substrate and are not considered tension steel bars in the traditional sense.
[0011] The reinforcing bars are fixedly connected only to the concrete substrates at both ends. The reinforcing bars are fixed to bushings via threads, and the bushings are fixed to the concrete substrates at both ends via pre-embedding. The concrete block in the middle is not fixed to the reinforcing bars; figuratively speaking, the concrete block in the middle passes through the reinforcing bars and can slide on them.
[0012] When the locking device locks two adjacent concrete substrates, the crack width between the two adjacent concrete substrates does not change without the external force damaging the cracked concrete specimen.
[0013] When the locking device releases two adjacent concrete substrates, the crack width between the two adjacent concrete substrates may change when a tensile force is applied to a concrete substrate at one end.
[0014] In one embodiment, the locking device includes:
[0015] At least one connection end, which is connected to the adjacent locking device and is connectable to one of the concrete substrates.
[0016] The locking device connecting the intermediate concrete substrate or the locking device connecting the two ends of the concrete substrate includes two connecting ends. In one embodiment, the locking device including the two connecting ends includes:
[0017] The main body of the hexahedron has a groove that runs through the thickness direction. A first through hole with the axis in the length direction is formed on the first groove wall. A first internal thread blind hole with the same inner diameter as the first through hole and a second through hole with the axis in the thickness direction are formed on the second groove wall. The two groove walls become the two connecting ends.
[0018] Bolts are used for connecting the main body to the concrete substrate and for connecting adjacent locking devices;
[0019] The first through hole and the first internal thread blind hole are used to connect to the connection end of the adjacent locking device by bolts, and the second through hole is used to connect to the concrete substrate by bolts.
[0020] Wherein, the length direction of the main body is the direction in which several concrete substrates are arranged side by side, and the thickness direction of the main body is the direction perpendicular to the length direction of the main body.
[0021] The locking devices for the two concrete substrates at the connecting ends can optionally include one of the connecting ends. In one embodiment, the locking device including one of the connecting ends comprises:
[0022] The main body of the connecting end is hexahedral, and a second threaded blind hole with the axis in the length direction and a third through hole with the axis in the thickness direction are formed on the main body;
[0023] Bolts are used for connecting the main body to the concrete substrate and for connecting adjacent locking devices;
[0024] The second internal thread blind hole is used to connect to the connection end of the adjacent locking device by bolts, and the third through hole is used to connect to the concrete substrate by bolts.
[0025] Wherein, the length direction of the main body is the direction in which several concrete substrates are arranged side by side, and the thickness direction of the main body is the direction perpendicular to the length direction of the main body.
[0026] In one embodiment, the locking device is installed above and below both sides of the concrete substrate.
[0027] In one embodiment, the cracked concrete specimen further comprises:
[0028] A bushing is disposed within the concrete substrate located at the end. The position and axis of the bushing are aligned with the through hole in the concrete substrate, and the inner wall of the bushing is threaded. When manufacturing the concrete substrate located at the end, the bushing is fixed within the concrete substrate by casting.
[0029] The reinforcing bar is threadedly connected to the bushing.
[0030] In one embodiment, the cracked concrete specimen further includes studs;
[0031] The first end of the bushing is connected to the reinforcing bar; the second end of the bushing is connected to the stud, which protrudes from the concrete substrate.
[0032] In one embodiment, the bushing includes two ends with a larger diameter and a middle section with a smaller diameter.
[0033] This application also provides a method for expanding the crack width of the cracked concrete specimen, wherein when expanding the crack, the locking device is used to ensure that there is only one crack that can be expanded among the rows of concrete substrates.
[0034] In one embodiment, the crack width expansion method further includes:
[0035] An outward tensile force is applied to the cracked concrete specimen, causing the width of the crack between the two concrete substrates that are prone to cracking to change.
[0036] Measure the width of the crack;
[0037] The tensile force is increased or decreased based on the measured width of the crack, thereby expanding the crack width to meet the test requirements.
[0038] Alternatively, an outward tensile force can be applied to the concrete substrate at one end of the cracked concrete specimen, or an outward tensile force can be applied to the concrete substrate at both ends of the cracked concrete specimen.
[0039] The cracked concrete specimen provided in this application comprises: a plurality of hexahedral concrete substrates, wherein when the concrete substrates are arranged side by side, the through holes at the same position on each concrete substrate are interconnected and form elongated holes of equal diameter; reinforcing bars, one of which is disposed in each elongated hole, and the reinforcing bars are fixedly connected only to the concrete blocks at both ends; and a locking device installed on the concrete substrates for locking or releasing two adjacent concrete substrates. This application utilizes the locking device to lock the concrete substrates on the cracked concrete specimen, leaving only one crack of variable width between them, locking the other two adjacent concrete substrates, and the reinforcing bars are fixed only to the concrete substrates at both ends. The external force that causes cracks in the cracked concrete specimen is transmitted through the locking device. When a tensile load is applied to the sleeves at both ends of the concrete, the sleeves drive the end concrete to move. The movement of the end concrete, through a locking device in a locked state, drives the adjacent concrete to move synchronously, keeping the crack width between them constant. Similarly, the locking device in a locked state can drive any part of the cracked concrete specimen to move synchronously with the end concrete. When the locking device is in an open state, the movement of the concrete on one side of the locking device cannot be transmitted to the concrete connected to it, thus changing the crack width between them.
[0040] In the technical solution provided in this application, the reinforcing bars are not "tension reinforcing bars". In the general construction industry, "tension reinforcing bars" refer to longitudinal reinforcing bars cast in concrete. In existing cracked concrete specimens, the reinforcing bars are cast in the concrete substrate and are tension reinforcing bars. In the cracked concrete specimens provided in this application, the reinforcing bars are inserted into the reserved through holes in the concrete substrate and are not tension reinforcing bars in the traditional sense.
[0041] Furthermore, in existing cracked concrete specimens, the length of the unbonded section between the concrete substrate and the reinforcing steel is limited, and the elongation of this unbonded section within the elastic range is also limited when the reinforcing steel is under tension. The elongation of the unbonded section determines the maximum width of the crack that can expand in concrete; therefore, the upper limit of the maximum crack width in existing cracked concrete specimens is relatively small. Compared to existing cracked concrete specimens, the reinforcing steel in this application is completely unbonded to the concrete substrate, so the elongation of the reinforcing steel is much greater than that of existing cracked concrete specimens, and also much greater than the test requirements.
[0042] Furthermore, the non-bonded connection between the reinforcing steel and the concrete substrate reduces the sensitivity of cracks to the movement of mechanisms applying tensile loads, thereby improving the accuracy of crack width control. Also, because it is non-bonded to the concrete substrate, the reinforcing steel can be easily recycled and reused, reducing testing costs and conforming to energy-saving and environmental protection principles.
[0043] This application also provides a method for expanding the crack width of the cracked concrete specimen, which is carried out using the cracked concrete specimen. The resulting technical effects include those described above, and will not be repeated here.
[0044] For further clarity, aspects and advantages of the embodiments disclosed in this application will become apparent in the following description or may be learned by practice of the embodiments disclosed in this application. Attached Figure Description
[0045] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation on the invention.
[0046] Figure 1 This is a schematic diagram of the structure of the cracked concrete specimen provided in Embodiment 1 of this application;
[0047] Figure 2 A schematic diagram of the locking device for the cracked concrete specimen provided in Embodiment 1 of this application;
[0048] Figure 3 This is a partially enlarged structural schematic diagram of the cracked concrete specimen provided in Embodiment 1 of this application. Detailed Implementation
[0049] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.
[0050] Example 1
[0051] Reference Figure 1 The diagram shows the structure of the cracked concrete specimen. This embodiment provides the cracked concrete specimen, which includes:
[0052] Five hexahedral concrete substrates 1, with four through holes 41 with parallel axes on the same cross section of each concrete substrate 1. The through holes 41 on each concrete substrate 1 are in the same position. When the concrete substrates 1 are arranged side by side, the through holes 41 at the same position on each concrete substrate 1 are connected and form elongated holes of equal diameter.
[0053] Reinforcing bar 2, one reinforcing bar 2 is provided in each of the elongated holes, and the reinforcing bar 2 is fixedly connected only to the concrete substrate 1 at both ends;
[0054] Locking devices (31 and 32), installed on concrete substrate 1, are used to lock or release two adjacent concrete substrates 1.
[0055] Among them, the steel bar 2 is only fixed to the concrete substrate 1 at both ends.
[0056] In this implementation, reinforcement bar 2 is a non-tension reinforcement bar.
[0057] In this embodiment, Figure 1 The concrete substrate 1 in the lower left corner and the concrete substrate in the upper right corner are fixed to the reinforcing bar 2 in the following ways:
[0058] When making these two concrete substrates 1, a bushing 21 is fixed inside the concrete substrate 1 by casting. The position of the bushing 21 is consistent with the axis and the through holes in the other concrete substrates 1. The inner wall of the bushing 21 is threaded, and the end of the reinforcing bar 2 is threaded. The reinforcing bar 2 is threaded to the bushing 21.
[0059] The spacing of the threads on the reinforcing bar 2 is determined based on the number of concrete substrates 1 contained in the cracked concrete specimen.
[0060] In this embodiment, the moving part of the machine that applies tension is connected to the steel bar 2 extending from the concrete substrate 1.
[0061] In another embodiment, the cracked concrete specimen further includes studs;
[0062] The first end of the bushing 21 is connected to the reinforcing bar 2; the second end of the bushing 21 is connected to the stud, which protrudes from the concrete substrate 1.
[0063] In this embodiment, the moving part of the machine that applies tension is connected to the stud extending from the concrete substrate 1.
[0064] Regardless of the implementation method chosen, the three concrete substrates in the middle are not fixed to the reinforcing bars 2, but are directly threaded onto the reinforcing bars 2 and can slide on the reinforcing bars 2.
[0065] In this example, such as Figure 1 The bushing 21 shown includes two ends with a larger diameter and a middle section with a smaller diameter, which facilitates a firm connection between the bushing 21 and the concrete substrate 1.
[0066] Combination Figure 2 In this embodiment, except for the rightmost locking device 32, all other locking devices 31 include two connecting ends 35. The locking device 31 includes:
[0067] The main body 33 of the hexahedron has a groove 34 that runs through the thickness direction. The first groove wall 341 of the groove 34 has a first through hole 36 with the axis in the length direction. The second groove wall 342 of the groove has a first internal thread blind hole 360 that is coaxial with the first through hole and has the same inner diameter, and a second through hole 37 with the axis in the thickness direction. The first groove wall 341 and the second groove wall 342 become the two connecting ends.
[0068] Bolts are used for connecting the main body 33 to the concrete substrate 1 and for connecting adjacent locking devices 31.
[0069] The first through hole 36 is used to connect with the first threaded blind hole 360 of the connecting end of the adjacent locking device 31 by bolts, and the second through hole 37 is used to connect with the concrete substrate 1 by bolts.
[0070] Among them, the length direction of the main body 33 is the direction in which the five concrete substrates 1 are arranged in a row ( Figure 1 The direction in the middle is from the lower left corner to the upper right corner of the figure. The thickness direction of the main body 33 is perpendicular to the length direction of the main body 33. The figure shows the direction of the locking device 31 relative to the concrete substrate 1.
[0071] The rightmost locking device 32 located at the end includes one of the connecting ends. The locking device 32 includes:
[0072] The main body 38, which serves as the connecting end, is hexahedral. The main body 38 has a second threaded blind hole 361 with its axis in the length direction and a third through hole 39 with its axis in the thickness direction.
[0073] Bolts are used for connecting the main body 38 to the concrete substrate 1 and for connecting the locking device 31 on the left side.
[0074] The second threaded blind hole 361 is used to connect to the connecting end 35 of the locking device 31 on the left side by bolts, and the third through hole 39 is used to connect to the concrete substrate 1 by bolts.
[0075] Similarly, the length direction of the main body 38 is the direction in which the five concrete substrates 1 are arranged side by side, and the thickness direction of the main body 38 is the direction perpendicular to the length direction of the main body 38. The figure shows the direction of the locking device 31 relative to the concrete substrate 1.
[0076] When the locking devices (31 and 32) lock two adjacent concrete substrates 1, the width of the crack between the two adjacent concrete substrates 1 will not change without the external force damaging the cracked concrete specimen. (Refer to...) Figure 1 and Figure 3 Point B in the text.
[0077] When the locking device 31 releases two adjacent concrete substrates 1, and tension is applied to one end of the concrete substrate 1, the crack width between the two adjacent concrete substrates 1 may change, as shown in the reference. Figure 1 and Figure 3 Point A in the diagram.
[0078] In this embodiment, locking devices (31 and 32) are installed on the upper and lower sides of both sides of the concrete substrate 1.
[0079] The cracked concrete specimen provided in this embodiment includes 5 concrete substrates 1, so there are 4 places where cracks can occur, thus allowing for 4 tests.
[0080] The cracked concrete specimens provided in this embodiment can be used for testing mechanical anchors for concrete in standard JG / T 160—2017.
[0081] Example 2
[0082] This embodiment provides a method for crack width propagation in cracked concrete specimens based on the method provided in Embodiment 1.
[0083] Before the cracks expand, locking devices (31 and 32) are used to allow the width of only one crack to vary between the rows of concrete substrates.
[0084] The crack width expansion method further includes:
[0085] An outward tensile force is applied to the cracked concrete specimen, causing the crack width between the two concrete substrates 1 (at point A) that are prone to cracking to change.
[0086] Measure the width of the crack;
[0087] The tensile force is increased or decreased based on the measured width of the crack, thereby expanding the crack width to meet the test requirements.
[0088] Alternatively, an outward tensile force can be applied to the concrete substrate at one end of the cracked concrete specimen, or an outward tensile force can be applied to the concrete substrate at both ends of the cracked concrete specimen.
[0089] The width of the crack is determined according to the test requirements for mechanical anchors for concrete in standard JG / T 160—2017.
[0090] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this technical solution 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. Therefore, they should not be construed as limitations on this technical solution.
[0091] In this technical solution, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this technical solution according to the specific circumstances.
[0092] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present technical solution. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0093] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.
Claims
1. A cracked concrete specimen, characterized in that, Include: A plurality of hexahedral concrete substrates, wherein a plurality of through holes are provided on the concrete substrates, and the through holes are provided in the same position on each concrete substrate. When the concrete substrates are arranged in a row, the through holes at the same position on each concrete substrate are connected and form elongated holes of equal diameter. The reinforcing bar is provided in each of the elongated holes, and the reinforcing bar is fixedly connected only to the concrete substrate at both ends; A locking device, installed on the concrete substrate, is used to lock or release two adjacent concrete substrates.
2. The cracked concrete specimen according to claim 1, characterized in that, The locking device includes: At least one connection end, which is connected to the adjacent locking device and is connectable to one of the concrete substrates.
3. The cracked concrete specimen according to claim 2, characterized in that, The locking device, comprising the two said connecting ends, includes: The main body of the hexahedron has a groove that runs through the thickness direction. A first through hole with the axis in the length direction is formed on the first groove wall. A first internal thread blind hole with the same inner diameter as the first through hole and a second through hole with the axis in the thickness direction are formed on the second groove wall. The two groove walls become the two connecting ends. Bolts are used for connecting the main body to the concrete substrate and for connecting adjacent locking devices; The first through hole and the first internal thread blind hole are used to connect to the connection end of the adjacent locking device by bolts, and the second through hole is used to connect to the concrete substrate by bolts.
4. The cracked concrete specimen according to claim 2, characterized in that, The locking device, which includes one of the connecting ends, comprises: The main body of the connecting end is hexahedral, and a second threaded through hole with the axis in the length direction and a third through hole with the axis in the thickness direction are formed on the main body. Bolts are used for connecting the main body to the concrete substrate and for connecting adjacent locking devices; The second threaded through hole is used to connect to the connection end of the adjacent locking device by bolts, and the third through hole is used to connect to the concrete substrate by bolts.
5. The cracked concrete specimen according to claim 1, characterized in that, The locking device is installed on the upper and lower sides of both sides of the concrete substrate.
6. The cracked concrete specimen according to claim 1, characterized in that, Also includes: A bushing is disposed within the concrete substrate located at the end. The position and axis of the bushing are aligned with the through hole in the concrete substrate, and the inner wall of the bushing is threaded. When manufacturing the concrete substrate located at the end, the bushing is fixed within the concrete substrate by casting. The reinforcing bar is threadedly connected to the bushing.
7. The cracked concrete specimen according to claim 6, characterized in that, It also includes studs; The first end of the bushing is connected to the reinforcing bar; the second end of the bushing is connected to the stud, which protrudes from the concrete substrate.
8. The cracked concrete specimen according to claim 6, characterized in that, The diameters at both ends of the bushing are larger than the diameter of the middle section of the bushing.
9. The method for crack width propagation in cracked concrete specimens according to claim 1, characterized in that, When the crack is extended, the locking device ensures that only one crack can be extended between the rows of concrete substrates.
10. The crack width propagation method according to claim 9, characterized in that, Also includes: An outward tensile force is applied to the cracked concrete specimen, causing the crack between the two concrete substrates that are prone to cracking to propagate. Measure the width of the crack; The tensile force is increased or decreased based on the measured width of the crack, thereby expanding the crack width to meet the test requirements.