A modular gradient prestressing device and a fiber-reinforced composite material reinforcement method

Abstract

The present invention discloses a modular gradient prestressed device and a fiber reinforced composite material reinforcement method, the device comprising: a multi-stage gradient prestressed component, a heating component and a tensioning component. The tensioning component is connected to the reinforcement material to tension the reinforcement material; the tensioned reinforcement material is connected to the reinforced structure, and an adhesive is filled between the two; the multi-stage gradient prestressed component is connected to the reinforcement material, and after the tensioning component is removed, the multi-stage gradient prestressed component releases the prestress in a gradient manner to achieve gradient tensioning of the reinforcement material. The device also provides a heating component between the multi-stage gradient prestressed component and the reinforcement material, which is used to heat the reinforcement material to accelerate the curing process of the adhesive. The present invention designs device parameters based on the bonding interface performance between the reinforcement material and the structure to be reinforced, has the advantages of compact structure, convenient operation and high stability, and effectively solves the problems of complex device, lengthy tensioning and curing process, and low efficiency in the existing reinforcement technology.

Description

Technical Field

[0001] The invention relates to the field of civil engineering and traffic engineering, and in particular to a modular gradient prestressing device and a fiber reinforced composite material reinforcement method. Background Art

[0002] Fiber reinforced plastic (FRP) is an emerging structural repair and reinforcement material that has been widely used in various structural fields such as bridge engineering. In recent years, researchers have solved the problems of low strength utilization and material strain lag in traditional FRP reinforcement projects by applying prestress to FRP reinforced reinforced concrete beams. This method applies a certain amount of prestress to FRP in advance to make it bear part of the load in advance, and then adheres FRP to the surface of the structure with adhesives such as resin.

[0003] In the prior art, anchoring devices are used to apply prestress, and the gradient prestressed FRP reinforcement process needs to be operated step by step. Taking the setting of three-level gradient prestress as an example, the existing operation process needs to wait for the curing of the previous level of prestressing to be completed before the next level of prestressing can be set. The reinforcement process is too long and the construction efficiency is low. Summary of the invention

[0004] The present invention aims to solve the deficiencies in the prior art and provide a modular gradient prestressing device and a fiber reinforced composite material reinforcement method which have a compact structure, convenient operation and high stability.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A modular gradient prestressing device comprises: a multi-stage gradient prestressing component, a heating component and a tensioning component; the tensioning component is connected to the tensioning end of a reinforcement material for tensioning the reinforcement material; the tensioned reinforcement material is connected to a reinforced structure, and an adhesive is filled between the reinforcement material and the reinforced structure; the multi-stage gradient prestressing component is connected to the reinforcement material, and after the tensioning component is removed, the multi-stage gradient prestressing component releases prestress in a gradient manner to achieve gradient tensioning of the reinforcement material; a heating component is arranged between the multi-stage gradient prestressing component and the reinforcement material, and the heating component is used to heat the reinforcement material to accelerate the curing process of the adhesive.

[0007] As a further improvement of the present invention, the multi-stage gradient prestressed component includes: a gradient partition, a long screw rod, a connecting anchor plate and a plurality of springs with different stiffnesses; the bottom of the gradient partition is connected to the connecting anchor plate, and the connecting anchor plate is connected to the reinforcement material; the spring is arranged between two adjacent gradient partitions, the long screw rod is used to connect multiple gradient partitions in series, and a limit bolt is provided on one side of the connection between the long screw rod and the gradient partition.

[0008] As a further improvement of the present invention, the spring includes a first spring, a second spring and a third spring to form a three-level gradient prestressed component.

[0009] As a further improvement of the present invention, the shear stress borne by the end of the reinforcement material is calculated by (Formula 1):

[0010]

[0011] In the formula, τ g3 is the shear stress at the end of the third-level gradient, σ pre3 and σ pre4 is the prestress before and after the third level gradient, A is the cross-sectional area of ​​the reinforcement material, l g4 and l g3 is the coordinate before and after the third level gradient, d a is the cross-sectional bonding length of the reinforcement material.

[0012] As a further improvement of the present invention, the shear stress level caused by the prestress at the end of the reinforcement material is calculated by (Formula 2):

[0013] τ g =α pre ×(α1τ g1 +α2τ g2 +α3τ g3 ) (Formula 2)

[0014] In the formula, α pre is the prestress loss reduction coefficient, and α is the partial coefficient of shear stress transfer between each gradient segment.

[0015] As a further improvement of the present invention, according to the prestress difference between each level of gradient in the multi-level gradient prestressed component and the gradient segment length, the corresponding spring stiffness parameter in the multi-level gradient prestressed component is determined by (Formula 3):

[0016]

[0017] In the formula, k c is the spring stiffness, d F is the load difference between each level of gradient, d λ It is the compression deformation of the spring, and its value is the same as the elongation of the reinforcement material in the corresponding section.

[0018] As a further improvement of the present invention, the gradient partition includes a vertical plate and a horizontal plate arranged perpendicular to each other. The horizontal plate is provided with a plurality of threaded holes to connect the gradient partition with the connecting anchor plate. Threaded holes are symmetrically provided on both sides of the vertical plate for passing long screws. An installation hole is provided in the middle of the vertical plate for installing a spring.

[0019] As a further improvement of the present invention, the heating assembly includes a heating plate and a heating wire, the heating wire is nested in the heating plate and connected to an external heating power source, and the heating plate is laid on the surface of the reinforcement material to accelerate the curing process.

[0020] As a further improvement of the present invention, the reinforcing material is a fiber-reinforced composite material, and prestress can be applied.

[0021] As a general technical concept, the present invention also provides a fiber reinforced composite material reinforcement method based on the above modular gradient prestressing device, comprising the following steps:

[0022] Step S1, connecting the tensioning component to the tensioning end of the reinforcement material, and tensioning the reinforcement material;

[0023] Step S2, placing the tensioned reinforcement material on the surface of the reinforced structure or embedding it inside the reinforced structure, and filling it with a binder;

[0024] Step S3, laying the heating component on the surface of the reinforcement material;

[0025] Step S4, pasting the connection anchor plate of the multi-level gradient prestressed component on the surface of the reinforcement material to achieve the connection between the multi-level gradient prestressed component and the reinforcement material, and the multi-level gradient prestressed component covers the heating component;

[0026] Step S5, removing the tensioning assembly to drive the multi-stage gradient prestressing assembly to release the prestress in a gradient manner, thereby achieving the gradient prestressing setting of the reinforcement material;

[0027] Step S6: Connect the heating component to an external heating power source and heat the reinforcement material to accelerate the curing process of the adhesive.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] 1. The modular gradient prestressed device and fiber reinforced composite material reinforcement method of the present invention can realize accurate gradient prestressed design according to the reinforcement requirements. Anchor plates are pasted and connected at the designated positions of the reinforcement materials, gradient partitions, springs and other components are installed, and a gradient prestressed system is formed by screw combination to release the prestressed tensioning device. Due to the different stiffness of the springs, after the prestress is released, each section of the reinforcement material presents a gradient prestressed level. In addition, the curing environment temperature of the adhesive is increased by a rapid curing device, which significantly improves the curing efficiency and shortens the time required for reinforcement.

[0030] 2. The modular gradient prestressed device and fiber-reinforced composite reinforcement method of the present invention are suitable for reinforcement projects such as bending resistance, shear resistance, and renovation and expansion of existing structures. They are not limited by the material type of the reinforced structure and are suitable for a variety of materials such as concrete and steel. There are no special restrictions on the cross-sectional form and it is suitable for various cross-sectional forms such as rectangular, box-shaped, and T-shaped. In addition, the modular gradient prestressed device of the present invention itself is small in size and light in weight, causes little damage to existing structures, supports modular and systematic production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the overall structural principle of a modular gradient prestressing device in a specific embodiment of the present invention;

[0032] Figure 2 It is a schematic diagram of the structural principle of a multi-stage gradient prestressed component in a specific embodiment of the present invention;

[0033] Figure 3 It is a schematic diagram of the structural principle of the gradient partition in a specific embodiment of the present invention;

[0034] Figure 4 It is a schematic diagram of the structural principle of connecting anchor plates in a specific embodiment of the present invention;

[0035] Figure 5 It is a schematic diagram of the structural principle of a heating component in a specific embodiment of the present invention;

[0036] Figure 6 It is a schematic diagram of the gradient prestress distribution in a specific embodiment of the present invention;

[0037] Figure 7 It is a schematic diagram comparing direct anchoring and graded gradient anchoring loading in a specific embodiment of the present invention;

[0038] Figure 8 It is a comparative schematic diagram of direct anchoring and graded gradient anchoring during unloading in a specific embodiment of the present invention;

[0039] Fig. 9 It is a schematic diagram of the partitioning of the gradient prestressed section when performing finite element analysis in a specific embodiment of the present invention;

[0040] Fig.10 It is a schematic diagram of the constitutive relationship of the gradient spring during the finite element analysis in a specific embodiment of the present invention;

[0041] Fig.11 A schematic diagram of a single spring unit during finite element analysis in a specific embodiment of the present invention;

[0042] Fig.12 It is a schematic diagram of a segment spring unit during finite element analysis in a specific embodiment of the present invention;

[0043] Fig.13 It is a schematic diagram comparing the FRP strain distribution after the gradient prestressing is set in the finite element analysis in a specific embodiment of the present invention with the data collected in the actual test;

[0044] Fig.14 Schematic diagram of the effect of curing temperature on curing time and tensile strength in a specific embodiment of the present invention;

[0045] Fig.15 This is a schematic diagram of the relationship between curing temperature and curing time in a specific embodiment of the present invention;

[0046] Legend: 100, multi-stage gradient prestressed component; 200, heating component; 300, tensioning component; 400, reinforcement material; 500, reinforced structure; 101, gradient partition; 102, first spring; 103, second spring; 104, third spring; 105, long screw; 106, limit bolt; 107, connecting anchor plate; 1011, vertical plate; 1012, horizontal plate; 1013, mounting hole; 1014, threaded hole; 1015, reinforcing rib; 1071, bottom plate; 1072, bolt; 201, heating plate; 202, heating wire. DETAILED DESCRIPTION

[0047] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0048] In the description of the present invention, it should be understood that terms such as "side", "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or position relationship shown in the drawings, and are only used to facilitate description and simplify illustration, rather than indicating or implying that the referred device or element must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be regarded as limiting the present invention.

[0049] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0050] Example

[0051] like Figure 1 , Figure 2 and Figure 3 As shown, the modular gradient prestressing device of the present invention comprises a multi-stage gradient prestressing component 100, a heating component 200 and a tensioning component 300. The tensioning component 300 is connected to the tensioning end of the reinforcing material 400 to tension the reinforcing material 400; the tensioned reinforcing material 400 is connected to the reinforced structure 500, and an adhesive is filled between the reinforcing material 400 and the reinforced structure 500. The multi-stage gradient prestressing component 100 is connected to the reinforcing material 400. After the tensioning component 300 is removed, the multi-stage gradient prestressing component 100 releases the prestress in a gradient manner to achieve the gradient tensioning of the reinforcing material 400; a heating component 200 is arranged between the multi-stage gradient prestressing component 100 and the reinforcing material 400, and the heating component 200 is used to heat the reinforcing material 400 to accelerate the curing process of the adhesive. In this embodiment, the reinforcing material 400 is a fiber-reinforced composite material to which prestress can be applied; the tensioning component 300 adopts a conventional setting, and the specific form is not limited, and will not be repeated here.

[0052] In other embodiments, during the reinforcement process, the tensioning assembly 300 is first used to apply prestress to the reinforcement material 400, and then the multi-stage gradient prestressed assembly 100 is fixedly connected to the reinforcement material 400, and the tensioning assembly 300 can be removed.

[0053] like Figure 2 , Figure 3 and Figure 4 As shown, the multi-stage gradient prestressed component 100 includes: a gradient partition 101, a long screw 105, a connecting anchor plate 107 and a plurality of springs with different stiffnesses. The bottom of the gradient partition 101 is connected to the connecting anchor plate 107, and the connecting anchor plate 107 is connected to the reinforcing material 400; the spring is arranged between two adjacent gradient partitions 101, the long screw 105 is used to connect multiple gradient partitions 101 in series, and a limit bolt 106 is provided on one side of the connection between the long screw 105 and the gradient partition 101.

[0054] In this embodiment, the spring includes a first spring 102, a second spring 103 and a third spring 104 to form a three-level gradient prestressed component. Figure 1 and Figure 2 As shown, the third spring 104 is closest to the tensioning assembly 300, the first spring 102 is farthest from the tensioning assembly 300, and the stiffness of the first spring 102, the second spring 103 and the third spring 104 decreases in sequence. In a specific application, the number of springs is not limited to three groups, and can be increased or decreased according to the actual reinforcement project requirements.

[0055] In this embodiment, the limit bolt 106 is used to ensure the degree of prestress release of each section in the multi-stage gradient prestressed assembly 100, and a certain amount of sliding is allowed. The prestress begins to be released from the end of the multi-stage gradient prestressed assembly 100. If there is no limit bolt 106, the prestress will cause the spring with the smallest stiffness to be over-compressed. After adding the limit bolt 106, the spring maintains normal stiffness before the limit length; once the compression reaches the limit length, due to the limitation of the limit bolt 106, the connection becomes rigid and can no longer be compressed, and the stress will be transferred to the next section of the spring.

[0056] like Figure 3 and Figure 4 As shown, the gradient partition 101 includes a vertical plate 1011 and a horizontal plate 1012 which are arranged perpendicular to each other, and the connecting anchor plate 107 includes a bottom plate 1071, on which bolts 1072 are arranged. The horizontal plate 1012 is provided with a plurality of threaded holes 1014, and the bolts 1072 match the threaded holes 1014 to achieve the connection between the gradient partition 101 and the connecting anchor plate 107. The vertical plate 1011 is symmetrically provided with threaded holes 1014 on both sides for passing the long screw 105, and the middle part of the vertical plate 1011 is provided with a mounting hole 1013 for installing a spring. The spring is arranged between the two gradient partitions 101, and the corresponding spring stiffness can be calculated according to the prestress level and segment length of different sections of the reinforcement material 400 in the reinforcement design, and the gradient prestress is achieved at one time by setting a series of springs with different stiffnesses. Furthermore, a plurality of reinforcing ribs 1015 are provided between the vertical plate 1011 and the horizontal plate 1012 to improve the structural strength of the gradient partition 101 .

[0057] like Figure 5 As shown, the heating assembly 200 includes a heating plate 201 and a heating wire 202. The heating wire 202 is nested in the heating plate 201 and connected to an external heating power source. The heating plate 201 is laid on the surface of the reinforcement material 400. The heating assembly 200 can be designed according to the shape of the reinforcement material 400 and the glass transition temperature of the binder, such as the type and power of the heating material.

[0058] In this embodiment, according to the reinforcement requirements, the tension load required to be provided by the reinforcement material 400 is calculated, and according to the material properties of the reinforcement material 400 and the recommended prestress design value (i.e., the ratio to the ultimate strength of the material), it is calculated by (Formula 4):

[0059] F = σ × A × n (Formula 4)

[0060] Where F is the load provided by the reinforcement material, σ is the design value of the reinforcement material, A is the cross-sectional area of ​​a single piece / root of reinforcement material, and n is the number of reinforcement materials used.

[0061] In gradient prestressing reinforcement, by setting up gradient prestressing sections, the permanent anchors at the ends of the reinforcement materials can be omitted. Therefore, when performing gradient design, it is necessary to ensure that the ends of the reinforcement materials are reliably bonded. Figure 6 Taking the three-level gradient prestressing as an example, the shear stress borne by the end of the reinforcement material 400 is calculated by (Formula 1):

[0062]

[0063] In the formula, τ g3 is the shear stress at the end of the third-level gradient, σ pre3 and σ pre4 is the prestress before and after the third level gradient, A is the cross-sectional area of ​​the reinforcement material 400, l g4 and l g3 is the coordinate before and after the third level gradient, d a is the cross-sectional bonding length of the reinforcement material 400. That is, the shear stress on the reinforcement material in different sections is equal to the product of the difference in prestress level between the gradient sections and the cross-sectional area of ​​the reinforcement material, divided by the product of the gradient section length and the bonding length of the reinforcement material.

[0064] Considering that the shear stress between the gradient segments can be transferred, the shear stress level caused by the prestress at the end of the reinforcement material 400 is calculated by (Formula 2):

[0065] τ g =α pre ×(α1τ g1 +α2τ g2 +α3τ g3 ) (Formula 2)

[0066] In the formula, α pre is the prestress loss reduction coefficient, α is the partial coefficient of shear stress transfer between each gradient segment, and the specific value is determined according to the type of reinforcement material, adhesive type and bonding method.

[0067] Considering that the stress of the reinforcement material 400 will continue to increase during the stress process of the structure after reinforcement,

[0068] τ g ≤β×τ max (Formula 5)

[0069] In the formula, τ max is the maximum shear stress that can be sustained between the reinforcing material 400 and the reinforced structure 500, and β is the safety reduction factor, which is determined based on the structural stress conditions and operating conditions.

[0070] According to the above calculation process, the gradient prestressing level of each level and the corresponding gradient prestressing section length can be calculated. The gradients of each level can change uniformly or unevenly as needed. In addition, considering the construction convenience and the ability of each gradient section to withstand shear stress, the minimum length limit of the gradient section should be limited according to the specific reinforcement details.

[0071] Further, according to the prestress difference between each level of gradient in the multi-level gradient prestressed component 100 and the gradient segment length, the corresponding spring stiffness parameter in the multi-level gradient prestressed component 100 is determined by (Formula 3):

[0072]

[0073] In the formula, k c is the spring stiffness, d F is the load difference between each level of gradient, d λ is the compression deformation of the spring, and its value is the same as the elongation of the reinforcement material 400 in the corresponding section.

[0074] In this embodiment, the prestressed anchoring effect of the modular gradient prestressed device was experimentally investigated. Figure 7 and Figure 8 It can be seen that the modular gradient prestressing device successfully realizes gradient prestressing anchoring, and because the spring is used as a way to achieve gradient prestressing, each level of prestressing is relatively stable, and the fluctuation between the strain values ​​within the gradient segment is small.

[0075] Compared with the existing direct anchoring technology, the modular gradient prestressing device of the present invention can complete the setting of gradient prestressing at one time, greatly shortening the process time. Taking the setting of three-level gradient prestressing as an example, the existing technology needs to wait for the maintenance of each level of prestressing to be completed before setting the next level of prestressing. In addition, the existing prestressing device lacks a rapid curing system, and the curing time of the adhesive in each level of prestressing section is about 3 days. It takes at least 9 days to set up three levels of gradient prestressing. The modular gradient prestressing device of the present invention can complete the gradient prestressing setting at one time, and accelerate the curing efficiency of the adhesive through the heating component 200. The total setting time of the gradient prestress is greatly shortened to about 1 day, which significantly improves the process efficiency.

[0076] like Fig. 9 As shown, in this embodiment, a finite element analysis is also performed on the implementation effect of the modular gradient prestressing device. In order to accurately simulate the setting process of the gradient prestressing in the finite element analysis model, it is necessary to pre-divide the gradient prestressing sections, and then define the spring unit parameters and assign them to the corresponding sections, so as to realize the simulation of the setting process of the gradient prestressing. Fig. 9 , Fig.10 , Fig.11 , Fig.12 and Fig.13 As shown, the finite element results also verify the reliability and stability of the modular gradient prestressing device of the present invention.

[0077] In this embodiment, the adhesive and the bonding interface cured by the heating assembly 200 were tested. Fig.14 and Fig.15 As shown, the test results show that increasing the curing temperature of the adhesive can significantly reduce the time required for curing without reducing the performance of the adhesive and the bonding interface, verifying the effectiveness of the rapid curing device.

[0078] In this embodiment, for the prestressing process of the reinforcement material, a gradient prestress can be designed according to the specific reinforcement requirements. First, the connecting anchor plate is pasted at the designed position of the reinforcement material, and the gradient partition, spring and other components are installed, and then a complete set of gradient prestressing devices are assembled through screws, and then the prestressing tensioning device can be released. Due to the different stiffnesses of multiple springs, after the prestress is released, the prestress level of each section at the end of the reinforcement material will show a gradient change. The curing temperature of the adhesive is increased by a rapid curing device to achieve the effect of improving the curing efficiency and shortening the time required for reinforcement.

[0079] This embodiment also provides a fiber reinforced composite material reinforcement method based on the above modular gradient prestressing device, comprising the following steps:

[0080] Step S1 : Connect the tensioning assembly 300 to the tensioning end of the reinforcement material 400 , and tension the reinforcement material 400 .

[0081] Step S2: placing the tensioned reinforcement material 400 on the surface of the reinforced structure 500 or embedding it inside the reinforced structure 500, and filling it with adhesive.

[0082] Step S3: laying the heating component 200 on the surface of the reinforcement material 400 .

[0083] Step S4, sticking the connecting anchor plate 107 of the multi-stage gradient prestressed component 100 on the surface of the reinforcing material 400 to connect the multi-stage gradient prestressed component 100 with the reinforcing material 400, and the multi-stage gradient prestressed component 100 covers the heating component 200.

[0084] Step S5, dismantling the tensioning assembly 300 to drive the multi-stage gradient prestressing assembly 100 to release the prestress in a gradient manner, thereby achieving the gradient prestressing setting of the reinforcement material 400.

[0085] Step S6: Connect the heating component 200 to an external heating power source and heat the reinforcing material 400 to accelerate the curing process of the adhesive.

[0086] The modular gradient prestressed device of this embodiment can be applied to the reinforcement projects such as bending resistance, shear resistance and renovation and expansion of existing structures; the material type of the reinforced structure 500 is not limited, and can be concrete or steel materials; the cross-sectional form is also not limited, and can be rectangular, box-shaped, T-shaped, etc. The modular gradient prestressed device of the present invention has a small volume and weight, causes less damage to the existing structure, can be produced in a modular and systematic manner, and has broad application prospects.

[0087] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A modular gradient prestressing device, characterized in that: include: A multi-stage gradient prestressed component (100), a heating component (200) and a tensioning component (300); the tensioning component (300) is connected to the tensioning end of the reinforcement material (400) to tension the reinforcement material (400); the tensioned reinforcement material (400) is connected to the reinforced structure (500), and an adhesive is filled between the reinforcement material (400) and the reinforced structure (500); the multi-stage gradient prestressed component (100) is connected to the reinforcement material (400), and after the tensioning component (300) is removed, the multi-stage gradient prestressed component (100) releases the prestress in a gradient manner to achieve gradient tensioning of the reinforcement material (400); a heating component (200) is arranged between the multi-stage gradient prestressed component (100) and the reinforcement material (400), and the heating component (200) is used to heat the reinforcement material (400) to accelerate the curing process of the adhesive.

2. The modular gradient prestressing device according to claim 1, characterized in that: The multi-stage gradient prestressed component (100) comprises: a gradient baffle (101), a long screw (105), a connecting anchor plate (107) and a plurality of springs with different stiffnesses; the bottom of the gradient baffle (101) is connected to the connecting anchor plate (107), and the connecting anchor plate (107) is further connected to a reinforcing material (400); the spring is arranged between two adjacent gradient baffles (101), the long screw (105) is used to connect a plurality of gradient baffles (101) in series, and a limiting bolt (106) is arranged on one side of the connection between the long screw (105) and the gradient baffle (101).

3. The modular gradient prestressing device according to claim 2, characterized in that: The spring comprises a first spring (102), a second spring (103) and a third spring (104) to form a three-level gradient prestressed component.

4. The modular gradient prestressing device according to claim 3, characterized in that: The shear stress borne by the end of the reinforcement material (400) is calculated by (Formula 1): In the formula, τ g3 is the shear stress at the end of the third-level gradient, σ pre3 and σ pre4 is the prestress before and after the third level gradient, A is the cross-sectional area of ​​the reinforcement material (400), l g4 and l g3 is the coordinate before and after the third level gradient, d a is the cross-sectional bonding length of the reinforcement material (400).

5. The modular gradient prestressing device according to claim 4, characterized in that: The shear stress level at the end of the reinforcement material (400) due to the prestressing force is calculated by (Equation 2): τ g = α pre ×(α1τ g1 + α2τ g2 + α3τ g3 )(Equation 2) In the formula, α pre is the prestress loss reduction coefficient, and α is the partial coefficient of shear stress transfer between each gradient segment.

6. The modular gradient prestressed device according to claim 5, characterized in that: According to the prestress difference between each level of gradient in the multi-level gradient prestressed component (100) and the gradient segment length, the corresponding spring stiffness parameter in the multi-level gradient prestressed component (100) is determined by (Formula 3): In the formula, k c is the spring stiffness, d F is the load difference between each level of gradient, d λ is the compression deformation of the spring, and its value is the same as the elongation of the corresponding section reinforcement material (400).

7. The modular gradient prestressing device according to any one of claims 2 to 6, characterized in that: The gradient baffle (101) comprises a vertical plate (1011) and a horizontal plate (1012) which are arranged perpendicular to each other. The horizontal plate (1012) is provided with a plurality of threaded holes (1014) for connecting the gradient baffle (101) with a connecting anchor plate (107). The vertical plate (1011) is symmetrically provided with threaded holes (1014) on both sides for passing a long screw rod (105). The vertical plate (1011) is provided with a mounting hole (1013) in the middle for mounting a spring.

8. The modular gradient prestressing device according to any one of claims 1 to 6, characterized in that: The heating assembly (200) comprises a heating plate (201) and a heating wire (202); the heating wire (202) is nested in the heating plate (201) and connected to an external heating power source; the heating plate (201) is laid on the surface of the reinforcement material (400) to accelerate the curing process of the adhesive.

9. The modular gradient prestressing device according to any one of claims 1 to 6, characterized in that: The reinforcement material (400) is a fiber-reinforced composite material and can be prestressed.

10. A fiber reinforced composite material reinforcement method based on the modular gradient prestressing device according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step S1, connecting the tensioning assembly (300) to the tensioning end of the reinforcement material (400), and tensioning the reinforcement material (400); Step S2, placing the tensioned reinforcement material (400) on the surface of the reinforced structure (500) or embedded in the interior of the reinforced structure (500), and filling with adhesive; Step S3, laying the heating component (200) on the surface of the reinforcement material (400); Step S4, pasting the connection anchor plate (107) of the multi-stage gradient prestressed component (100) on the surface of the reinforcing material (400) to achieve the connection between the multi-stage gradient prestressed component (100) and the reinforcing material (400), and the multi-stage gradient prestressed component (100) covers the heating component (200); Step S5, dismantling the tensioning assembly (300) to drive the multi-stage gradient prestressing assembly (100) to release the prestress in a gradient manner, thereby achieving the gradient prestressing setting of the reinforcement material (400); Step S6: Connect the heating component (200) to an external heating power source and heat the reinforcing material (400) to accelerate the curing process of the adhesive.

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