A formwork with continuous steel fibers at concrete joints

Abstract

The utility model belongs to the technical field of civil engineering, and specifically discloses a template with continuous steel fibers at concrete joints, which solves the problems in the prior art that the steel fibers at the interface are discontinuous, the steel fibers cannot play an effective bridging role after the UHPC matrix is ​​cracked, and the crack width at the joint is difficult to control at a low level. The utility model comprises a hard thin plate and an elastic strip, wherein the elastic strip is covered on one side of the hard thin plate, the part of the elastic strip whose length after stretching exceeds the length of the hard thin plate is fixed on the other side of the hard thin plate, and the side of the elastic strip that is not in contact with the hard thin plate is provided with steel fibers. The use of this template will not damage the UHPC matrix and can realize the active design of the distribution form of the steel fibers at the interface, thereby greatly increasing the integrity of the joint and improving the utilization rate of the steel fibers.

Description

Technical Field

[0001] The utility model relates to the technical field of civil engineering, in particular to a template with continuous steel fibers at concrete joints. Background Art

[0002] Ultra-high performance concrete (UHPC) is a new type of cement-based composite material with the advantages of ultra-high strength / toughness / durability, energy saving / environmental protection, etc. It has broad application prospects in new construction and reinforcement projects in the fields of bridges, military industry, construction, etc. Joints need to be set in the step-by-step casting of UHPC materials or prefabricated assembled structures. Studies have shown that the interface bonding strength of UHPC at the joints is weak and the structural integrity is poor. In response to the above problems, current engineering practice and scientific research use methods such as applying interface agents, optimizing interface structural forms, setting reinforcements, roughening interfaces, shallowly burying wire mesh, and special foam templates to improve the bonding performance of UHPC joint interfaces.

[0003] Applying interface agent, optimizing interface structure and setting reinforcement can improve the interface bonding strength, but the steel fibers at the interface are still discontinuous. After the UHPC matrix cracks, the steel fibers cannot play an effective bridging role, and the crack width at the joint is difficult to control at a low level. In addition, the above three methods increase the complexity and cost of construction and have certain application limitations.

[0004] For example, CN212670274U discloses a cast-in-place joint structure of ultra-high performance concrete beams and slabs with embedded reinforcing steel plates. Embedded reinforcing steel plates are arranged at the bottom of prefabricated UHPC beams and slabs to form composite beams and slabs, which can give full play to the tensile properties of steel and solve the problem of discontinuous steel fibers and weak stress at the interface between new and old concrete in ultra-high performance concrete wet joints. The local stiffness of prefabricated UHPC beams and slabs is further improved, and the crack resistance and overload resistance are significantly improved. The construction is convenient and the safety performance is better. However, the length, orientation and distribution of the exposed steel fibers are uncontrollable, which makes the randomness of the interface bonding strength and crack width control ability greater. Utility Model Content

[0005] The purpose of the utility model is to solve the problems in the prior art that the steel fibers are discontinuous at the interface, the steel fibers cannot play an effective bridging role after the UHPC matrix cracks, and the crack width at the joint is difficult to control at a low level. To solve the above problems, the utility model provides the following technical solutions: a combined formwork that ensures the continuity of steel fibers at the joints of ultra-high performance concrete, including a hard thin plate and an elastic strip, the elastic strip covering one side of the hard thin plate, the portion of the elastic strip whose length after stretching exceeds the length of the hard thin plate is fixed to the other side of the hard thin plate, and the side of the elastic strip that is not in contact with the hard thin plate is provided with steel fibers.

[0006] The utility model firstly wraps a hard sheet with the same width with a pre-tensioned elastic strip and fixes the elastic strip through a connecting buckle, then punches a hole on the surface of the elastic strip and inserts a 1 / 2 length of steel fiber, relaxes the elastic strip and fixes it again through the connecting buckle, then uses the elastic strip-hard sheet assembly as a casting template for the UHPC joint interface, casts UHPC on the side where the steel fiber is exposed, and then maintains the cast UHPC. After reaching the target age, the connecting buckle of the casting template is unfastened, the hard sheet is first removed, and then the elastic strip is peeled off to expose the remaining 1 / 2 length of the steel fiber, and finally the UHPC is cast for the second time on the side where the steel fiber is exposed to form a UHPC cross-section joint.

[0007] The elastic strip of the utility model can apply three-dimensional confining pressure to the inserted steel fiber through pre-tensioning-relaxation operation to better fix the steel fiber and prevent the displacement or falling of the steel fiber during the pouring of UHPC; secondly, UHPC has excellent fluidity, and the elastic strip filling the template seam can prevent UHPC from leaking; in addition, the elastic strip is soft and easy to disassemble. The hard thin plate has sufficient strength and rigidity, and is mainly used to withstand various loads that may occur during the construction process to ensure the stability of the pouring template.

[0008] Preferably, the elastic strip is connected to the hard thin plate by wrapping the hard thin plate, and the width of the hard thin plate is the same as the width of the elastic strip.

[0009] Preferably, a connecting buckle component 1 is provided at both ends of the elastic strip, a connecting buckle component 2 is provided on the hard thin plate, and the elastic strip is connected to the hard thin plate through the connecting buckle component 1 and the connecting buckle component 2.

[0010] The connecting buckles of the utility model are various in form, and the main purpose is to fix the elastic strip to realize the pre-tensioning and relaxation of the elastic strip.

[0011] Preferably, a plurality of holes are opened on the surface of the elastic strip, and the steel fibers are inserted into the holes on the elastic strip.

[0012] Preferably, the hole on the elastic strip is a through hole, and the diameter of the through hole is 0.2 mm to 1 mm.

[0013] The holes in the elastic strip of the utility model are through holes, and the hole diameter is the diameter of the steel fiber used in UHPC (the common value is 0.2~1mm). The characteristic parameters such as the diameter, number, direction, and arrangement of the holes (embedded steel fibers) can be actively designed according to the stress on the joint.

[0014] Preferably, the thickness of the elastic strip is half the length of the steel fiber.

[0015] Preferably, the thickness of the hard thin plate is one third to one half of the thickness of the elastic strip.

[0016] The thickness of the elastic strip of the utility model is set according to the length of the steel fiber, which is 1 / 2 of the length of the steel fiber, that is, steel fibers of equal length are respectively embedded in the new and old UHPCs, ensuring uniform steel fiber-UHPC bonding performance on both sides of the joint; the thickness of the hard thin plate is 1 / 2 to 1 / 3 of the thickness of the elastic strip.

[0017] Preferably, the length of the elastic strip in a relaxed state is not greater than the length of the hard thin plate, and the material of the elastic strip is a material with elasticity and softness.

[0018] The elastic strip and the hard thin plate of the utility model can be customized and mass-produced in factories, and are preferably made of inexpensive materials, so the cost is very low, and the length of the elastic strip is not greater than that of the hard thin plate.

[0019] The beneficial effects of the utility model are as follows: 1. The elastic strip of the utility model can apply three-way confining pressure to the inserted steel fibers through a pre-tensioning-relaxation operation to better fix the steel fibers and prevent the steel fibers from shifting or falling off during the pouring of UHPC; secondly, UHPC has excellent fluidity, and the elastic strip fills the template seam to prevent UHPC leakage; in addition, the elastic strip is soft and easy to disassemble, while the hard thin plate has sufficient strength and rigidity, and is mainly used to withstand various loads that may occur during the construction process to ensure the stability of the pouring template.

[0020] 2. The utility model provides an interface construction technology for ensuring the continuity of steel fibers at UHPC joints, which will not damage the UHPC matrix and can realize the active design of the distribution morphology of steel fibers at the interface, thereby greatly increasing the integrity of the joints and improving the utilization rate of steel fibers. The joints constructed by this method have good bonding strength and crack control capabilities, thereby improving the bending bearing capacity and durability of the jointed structure.

[0021] 3. The new type of combined formwork proposed by the utility model can be mass-produced, reused and low-cost, the corresponding construction technology is simple, the construction process is standardized, the construction quality is reliable, and no noise and dust pollution are generated, which has good economic and social benefits.

[0022] 4. The utility model is applicable to various UHPC structural forms such as T-beams, I-beams, small box beams, composite beams, etc., and can be applied to UHPC horizontal joints of various sizes, with wide applicability and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the utility model;

[0024] Figure 2 This is a schematic diagram of the utility model combined formwork in place and pouring one side of UHPC;

[0025] Figure 3 This is a schematic diagram of pouring the other side of UHPC in the utility model;

[0026] Figure 4 This is a structural diagram of the elastic strip of Example 1 of the utility model;

[0027] Figure 5 This is a structural diagram of a hard thin plate according to Embodiment 1 of the present utility model;

[0028] Figure 6 This is a structural diagram of the elastic strip of Embodiment 2 of the utility model;

[0029] Figure 7 This is a structural diagram of a hard thin plate according to Embodiment 2 of the present utility model;

[0030] Figure 8 This is a structural diagram of the elastic strip of Embodiment 3 of the utility model;

[0031] Fig. 9 This is a structural diagram of a hard thin plate according to Embodiment 3 of the present utility model;

[0032] In the figure: 1-hard thin plate; 2-elastic strip; 3-steel fiber; 4-form body; 5-cast UHPC; 6-hardened UHPC; 7-connector assembly 2; 8-connector assembly 1. DETAILED DESCRIPTION

[0033] The specific implementation of the technical solution of the present invention is further described below through examples and in conjunction with the accompanying drawings.

[0034] Embodiment 1:

[0035] In the prior art, the roughening method increases the interface roughness and exposes part of the steel fibers 3 to improve the interface bonding strength. However, this method damages the UHPC matrix and the steel fibers 3, has limited effect on improving the interface bonding strength, and has low construction efficiency and strong subjectivity in controlling the degree of roughening. In order to improve the construction efficiency of the above method, some scholars have proposed a shallow buried wire mesh method, which can expose the fibers and obtain a certain interface roughness, thereby improving the interface bonding strength. However, the length, orientation and distribution of the exposed steel fibers 3 are uncontrollable, which makes the interface bonding strength and crack width control ability more random.

[0036] In order to optimize the distribution of steel fibers 3 at the interface, other scholars have proposed a special foam board method, which allows steel fibers 3 to partially penetrate into the foam board along the length direction, serving as a template for casting UHPC, and connecting steel fibers 3 to adjacent new and old UHPC. However, the foam board has low rigidity and is difficult to provide effective support for large-volume UHPC structures; secondly, the raw material porosity of the foam board itself is relatively large, and the fixing effect on the inserted steel fibers 3 is not ideal; in addition, if part of the steel fibers 3 penetrate obliquely into the foam board, the foam board will be damaged when the mold is removed, and its reuse cannot be achieved.

[0037] It can be seen that the existing methods for improving the interfacial bonding performance of UHPC have some shortcomings, and proposing relevant innovative technologies has great practical value.

[0038] The purpose of the utility model is to solve the problem that the steel fibers 3 at the interface are discontinuous in the prior art, the steel fibers 3 cannot play an effective bridging role after the ultra-high performance concrete matrix cracks, and the crack width at the joint is difficult to control at a low level. To solve the above problems, the utility model embodiment 1 provides the following technical solutions: Please refer to Figure 1 A combined formwork for ensuring the continuity of steel fibers 3 at the joints of ultra-high performance concrete comprises a hard sheet 1 and an elastic strip 2, wherein the elastic strip 2 covers one side of the hard sheet 1, and the portion of the elastic strip 2 whose length after stretching exceeds the length of the hard sheet 1 is fixed on the other side of the hard sheet 1, and the side of the elastic strip 2 that is not in contact with the hard sheet 1 is provided with steel fibers 3.

[0039] See also Figure 2 and Figure 3 The utility model firstly wraps the pre-tensioned elastic strip 2 around the hard sheet 1 of the same width and fixes the elastic strip 2 by a connecting buckle, then punches a hole on the surface of the elastic strip 2 and inserts a 1 / 2 length of steel fiber 3, relaxes the elastic strip 2 and fixes it again by the connecting buckle, then uses the elastic strip 2-hard sheet 1 combination as the casting formwork body 4 of the ultra-high performance concrete joint interface, casts the ultra-high performance concrete on the side where the steel fiber 3 is exposed, and then cures the cast UHPC 5. After reaching the target age, it will become hardened UHPC 6, then unfastens the connecting buckle of the casting formwork, first removes the hard sheet 1, then peels off the elastic strip 2, exposes the remaining 1 / 2 length of steel fiber 3, and finally casts the ultra-high performance concrete for the second time on the side where the steel fiber 3 is exposed to form an ultra-high performance concrete cross-section joint.

[0040] The elastic strip 2 of the utility model can apply three-dimensional confining pressure to the inserted steel fiber 3 through pre-tensioning-relaxing operation to better fix the steel fiber 3 and prevent the steel fiber 3 from shifting or falling off during the pouring of ultra-high performance concrete; secondly, ultra-high performance concrete has excellent fluidity, and the elastic strip 2 fills the template seam to prevent ultra-high performance concrete from leaking; in addition, the elastic strip 2 is soft and easy to disassemble. The hard thin plate 1 has sufficient strength and rigidity, and is mainly used to withstand various loads that may occur during the construction process to ensure the stability of the pouring template.

[0041] The elastic strip 2 is connected to the hard sheet 1 by wrapping the hard sheet 1 , and the width of the hard sheet 1 is the same as that of the elastic strip 2 .

[0042] A connecting buckle component 1 8 is provided at both ends of the elastic strip 2, and a connecting buckle component 2 7 is provided on the hard thin plate 1. The elastic strip 2 is connected to the hard thin plate 1 through the connecting buckle component 1 8 and the connecting buckle component 2 7.

[0043] The connecting buckles of the utility model are various in form, and the main purpose is to fix the elastic strip 2 to achieve pre-tensioning and relaxation of the elastic strip 2.

[0044] A plurality of holes are opened on the surface of the elastic strip 2 , and the steel fibers 3 are inserted into the holes on the elastic strip 2 .

[0045] The holes opened on the elastic strip 2 are through holes, and the diameter of the through holes is 0.2 mm to 1 mm.

[0046] The holes in the elastic strip 2 of the utility model are through holes, and the hole diameter is the diameter of the steel fiber 3 used in UHPC (the common value is 0.2-1 mm). The characteristic parameters such as the diameter, number, direction, and arrangement of the holes (embedded steel fibers 3) can be actively designed according to the stress on the joint.

[0047] The thickness of the elastic strip 2 is half of the length of the steel fiber 3 .

[0048] The thickness of the hard sheet 1 is one third to one half of the thickness of the elastic strip 2 .

[0049] The thickness of the elastic strip 2 of the utility model is set according to the length of the steel fiber 3, which is 1 / 2 of the length of the steel fiber 3, that is, the steel fibers 3 of equal length are respectively buried in the new and old ultra-high performance concrete, ensuring uniform steel fiber 3-ultra-high performance concrete bonding performance on both sides of the joint; the thickness of the hard thin plate 1 is 1 / 2~1 / 3 of the thickness of the elastic strip 2.

[0050] The length of the elastic strip 2 in a relaxed state is not greater than the length of the hard thin plate 1 , and the material of the elastic strip 2 is a material with elasticity and softness.

[0051] The elastic strip 2 and the hard sheet 1 of the utility model can be customized and mass-produced in factories, and are preferably made of inexpensive materials, with very low costs, and the length of the elastic strip 2 is not greater than that of the hard sheet 1.

[0052] In this embodiment 1, a steel fiber 3 with a diameter of 0.2 mm and a length of 18 mm is used, and the designed volume content of the steel fiber 3 is 2%; the elastic strip 2 is a rubber strip with a thickness of 9 mm, and the hard sheet 1 is an acrylic sheet with a thickness of 3 mm. Figure 4 and Figure 5 As shown, the connecting buckle component 1 8 is a hole with a fixing ring set at both ends of the rubber strip, and the connecting buckle component 2 7 is a plurality of rows of small protrusions set on the acrylic sheet. When in use, the connecting buckle components 1 8 at both ends of the rubber strip are put on the connecting buckle components 2 7 at the corresponding position of the acrylic sheet to fix the rubber strip. The plurality of rows of protrusions on the acrylic sheet can realize the pre-tensioning and relaxation of the rubber strip by adjusting the fixing position.

[0053] The specific implementation process of the interface construction technology for ensuring the continuity of the steel fibers 3 at the joints of ultra-high performance concrete using the combined formwork of this embodiment is as follows:

[0054] First, wrap the pre-stressed rubber strip around the acrylic sheet so that the first connector is fixed on the second connector away from the edge of the acrylic sheet. The number of steel fibers 3 at the joint is calculated based on the designed volumetric dosage of steel fibers 3. Random holes are punched on the rubber strip at the above number, and then the steel fibers 3 are inserted. After completion, the first connector is fixed on the second connector close to the edge of the hard sheet 1. The production of the combined formwork is now completed.

[0055] Then, after the combined formwork is in place, ultra-high performance concrete is poured on the side where the steel fiber 3 is exposed. After reaching the target age, the connection buckle is unfastened, and the acrylic sheet and the rubber strip are removed in turn, so that the other side of the steel fiber 3 is exposed;

[0056] Finally, a second pouring of ultra-high performance concrete is performed on one side of the exposed steel fiber 3 to form an ultra-high performance concrete cross-section joint.

[0057] Embodiment 2:

[0058] In Example 2 of the present invention, a composite template for ensuring the continuity of steel fibers 3 at the joints of ultra-high performance concrete adopts steel fibers 3 with a diameter of 0.2 mm and a length of 16 mm, and the designed volume content of the steel fibers 3 is 1.8%; the elastic strip 2 adopts a silicone strip with a thickness of 8 mm, and the hard thin plate 1 adopts an aluminum alloy thin plate with a thickness of 2.5 mm. The rest is the same as in Example 1, such as Figure 6 and Figure 7As shown, the connecting buckle is a Velcro pasted on both ends of the silicone strip, the connecting buckle component 1 8 is a hook surface pasted on one end of the silicone strip, and the connecting buckle component 2 7 is a multi-row wool surface pasted on the other end of the silicone strip. The pre-tensioning and relaxation of the silicone strip can be achieved by adjusting the pasting position.

[0059] The specific implementation process of the interface construction technology for ensuring the continuity of the steel fibers 3 at the joints of ultra-high performance concrete using the combined formwork of this embodiment is as follows:

[0060] First, wrap the pre-tensioned silicone strip around the aluminum alloy sheet so that the first connection buckle is fixed on the second connection buckle away from the edge of the silicone strip; the number of steel fibers 3 at the joint is calculated based on the designed volumetric dosage of the steel fibers 3, and holes are randomly punched at angles on the silicone strip according to the above number, and then the steel fibers 3 are inserted. After completion, the first connection buckle is fixed on the second connection buckle away from the edge of the silicone strip, and the production of the combined formwork is completed;

[0061] Then, after the combined formwork is in place, ultra-high performance concrete is poured on the side where the steel fiber 3 is exposed. After reaching the target age, the connection buckle is unfastened, and the aluminum alloy sheet and the silicone strip are removed in sequence, so that the other side of the steel fiber 3 is exposed;

[0062] Finally, a second pouring of ultra-high performance concrete is performed on one side of the exposed steel fiber 3 to form an ultra-high performance concrete cross-section joint.

[0063] Embodiment 3:

[0064] In Example 3 of the present utility model, a combined formwork for ensuring the continuity of steel fibers 3 at the joints of ultra-high performance concrete adopts steel fibers 3 with a diameter of 0.2 mm and a length of 14 mm, and the designed volume content of the steel fibers 3 is 2.2%; the elastic strip 2 adopts a TPE strip with a thickness of 7 mm, and the hard thin plate 1 adopts a resin thin plate with a thickness of 2 mm. The remaining structures are the same as those of Examples 1 and 2, such as Figure 8 and Fig. 9 As shown, the first connecting buckle component 8 is an elastic rope loop with a fixing belt arranged at one end of the TPE strip, and the second connecting buckle component 7 is a multi-row buckle arranged at the other end of the TPE strip. The TPE strip can be pre-tensioned and relaxed by adjusting the position of the first connecting buckle on the second connecting buckle.

[0065] The specific implementation process of the interface construction technology for ensuring the continuity of the steel fibers 3 at the joints of ultra-high performance concrete using the combined formwork of this embodiment is as follows:

[0066] First, wrap the pre-tensioned TPE strip with a resin sheet so that the first connection buckle is fixed on the second connection buckle far away from the edge of the TPE strip; the number of steel fibers 3 at the joint is calculated based on the designed volumetric dosage of the steel fibers 3, and holes are randomly punched at the rubber strip according to the above number, and then the steel fibers 3 are inserted. After completion, the first connection buckle is fixed on the second connection buckle close to the edge of the TPE strip, and the production of the combined template is completed;

[0067] Then, after the combined formwork is in place, ultra-high performance concrete is poured on the side where the steel fiber 3 is exposed. After the target age is reached, the connection buckle is unfastened, and the resin sheet and the TPE strip are removed in sequence, so that the other side of the steel fiber 3 is exposed;

[0068] Finally, a second pouring of ultra-high performance concrete is performed on one side of the exposed steel fiber 3 to form an ultra-high performance concrete cross-section joint.

[0069] Based on the above embodiments, the following conclusions can be drawn: the elastic strip 2 of the utility model can apply three-way confining pressure to the inserted steel fiber 3 through a pre-tensioning-relaxation operation to better fix the steel fiber 3 and prevent the steel fiber 3 from shifting or falling off during the pouring of ultra-high performance concrete; secondly, ultra-high performance concrete has excellent fluidity, and the elastic strip 2 fills the template seam to prevent leakage of ultra-high performance concrete; in addition, the elastic strip 2 is soft and easy to disassemble, while the hard thin plate 1 has sufficient strength and rigidity, and is mainly used to withstand various loads that may occur during the construction process to ensure the stability of the pouring template.

[0070] The utility model provides an interface construction technology for ensuring the continuity of the steel fibers 3 at the joints of ultra-high performance concrete, which will not damage the UHPC matrix and can realize the active design of the distribution morphology of the steel fibers 3 at the interface, thereby greatly increasing the integrity of the joints and improving the utilization rate of the steel fibers 3. The joints constructed by this method have good bonding strength and crack control capabilities, thereby improving the bending bearing capacity and durability of the jointed structure.

[0071] The novel combined formwork proposed by the utility model can be mass-produced and reused at low cost, the corresponding construction technology is simple, the construction process is standardized, the construction quality is reliable, and no noise and dust pollution are generated, thereby having good economic and social benefits.

[0072] The utility model is applicable to various UHPC structural forms such as T-beams, I-beams, small box beams, composite beams, etc., and can be applied to UHPC horizontal joints of various sizes, and has wide applicability and high reliability.

[0073] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present utility model.

Claims

1. A formwork with continuous steel fibers at concrete joints, characterized in that: The invention comprises a hard thin plate (1) and an elastic strip (2), wherein the elastic strip (2) covers one side of the hard thin plate (1), a portion of the elastic strip (2) whose length after stretching exceeds the length of the hard thin plate (1) is fixed to the other side of the hard thin plate (1), and a side of the elastic strip (2) not in contact with the hard thin plate (1) is provided with steel fibers (3).

2. A formwork for continuous steel fibers at concrete joints according to claim 1, characterized in that: The elastic strip (2) is connected to the hard thin plate (1) by wrapping the hard thin plate (1), and the width of the hard thin plate (1) is the same as the width of the elastic strip (2).

3. A formwork with continuous steel fibers at concrete joints according to claim 1, characterized in that: The two ends of the elastic strip (2) are provided with a first connecting buckle component (8), the hard thin plate (1) is provided with a second connecting buckle component (7), and the elastic strip (2) is connected to the hard thin plate (1) via the first connecting buckle component (8) and the second connecting buckle component (7).

4. A formwork for continuous steel fibers at concrete joints according to claim 1, characterized in that: A plurality of holes are formed on the surface of the elastic strip (2), and the steel fibers (3) are inserted into the holes on the elastic strip (2).

5. A formwork for continuous steel fibers at concrete joints according to claim 4, characterized in that: The hole opened on the elastic strip (2) is a through hole, and the diameter of the through hole is 0.2 mm to 1 mm.

6. A formwork for continuous steel fibers at concrete joints according to claim 1 or 4, characterized in that: The thickness of the elastic strip (2) is half the length of the steel fiber (3).

7. A formwork with continuous steel fibers at concrete joints according to claim 1, 2 or 3, characterized in that: The thickness of the hard thin plate (1) is one third to one half of the thickness of the elastic strip (2).

8. A formwork for continuous steel fibers at concrete joints according to claim 6, characterized in that: The length of the elastic strip (2) in a relaxed state is no greater than the length of the hard thin plate (1), and the material of the elastic strip (2) is a material having elasticity and softness.

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