A device and method for reinforcing FRP to inhibit brittle failure

Abstract

The application provides a FRP reinforcing device and method for inhibiting brittle failure, relates to the field of beam reinforcing and repairing, and aims at the problem that the FRP plate is easy to peel off from the concrete, leading to reinforcing failure. The buckle is used to apply active pressure to the FRP plate to increase the friction between the FRP plate and the concrete, and improve the utilization rate of the FRP. A release mechanism is installed at the end of the FRP plate. The clamp and the elastic piece of the release mechanism are used to elastically constrain the end of the FRP plate, release the displacement of the end of the FRP plate, slow down the brittle peeling failure of the FRP plate, and effectively improve the ductility of the FRP plate and the concrete beam.

Description

Technical Field

[0001] This invention relates to the field of beam reinforcement and repair, and specifically to an FRP reinforcement device and method for suppressing brittle fracture. Background Technology

[0002] Existing concrete bridges face complex environments and various load types, leading to increasingly inadequate service performance and consequently affecting their operational capabilities and service life. To address this issue, fiber-reinforced polymer (FRP), a lightweight, high-strength, and corrosion-resistant material, is widely used in bridge reinforcement and renovation. FRP can be externally bonded to bridges, significantly enhancing their service performance.

[0003] However, although externally bonded FRP enhances the load-bearing capacity of concrete beams, the bond between the FRP and concrete is prone to premature delamination during service, leading to brittle failure of the concrete beams. Studies show that the utilization rate of externally bonded FRP in reinforcing concrete beams is only about 20%. This means that although FRP is widely used in bridge reinforcement, its potential has not been fully realized.

[0004] To address the aforementioned issues, several methods and devices for suppressing premature FRP delamination have been proposed in the prior art. These methods include using special adhesives and strengthening the mechanical fixation between FRP and concrete. While these methods do improve the utilization rate of FRP to some extent, when FRP delamination occurs, the concrete beam still exhibits brittle failure, resulting in a sharp drop in load-bearing capacity and making it difficult to meet the reinforcement requirements of the concrete beam during its service life. Summary of the Invention

[0005] The purpose of this invention is to address the deficiencies of existing technologies by providing an FRP reinforcement device and method to suppress brittle fracture. This method applies active pressure to the FRP board using fasteners to increase friction between the FRP board and concrete, thereby improving FRP utilization. Furthermore, a release mechanism is installed at the end of the FRP board. The clamps and elastic elements of the release mechanism work together to elastically constrain the end of the FRP board, elastically releasing the displacement at the end of the FRP board, mitigating brittle peeling failure of the FRP board, and effectively improving the ductility of both the FRP board and the concrete beam.

[0006] The first objective of this invention is to provide an FRP reinforcement device for suppressing brittle fracture, which employs the following solution:

[0007] include:

[0008] FRP sheets are attached to the bottom surface of concrete beams;

[0009] Fasteners are pressed onto FRP sheets and extend beyond the FRP sheets at both ends; the fasteners are fixed to the bottom surface of concrete beams.

[0010] The release mechanism includes a base and a clamp. The base is provided with a limiting groove for accommodating the clamp. The clamp is connected to the end of the FRP plate. The moving direction of the clamp along the limiting groove is collinear with the displacement direction of the end of the FRP plate when it is bent. The clamp is connected to an elastic element whose axis is arranged along the moving direction of the clamp. Release mechanisms are installed at both ends of the FRP plate. The clamp elastically releases the end displacement of the FRP plate as it deforms.

[0011] Furthermore, the base is U-shaped, with the groove serving as a limiting groove, and the FRP plate extends beyond one side edge of the limiting groove to connect to the clamp.

[0012] Furthermore, the fixture is provided with a clamping part extending into the fixture, the clamping part is arranged along the extension direction of the FRP plate, and the end of the FRP plate extends into the clamping part and is fixed.

[0013] Furthermore, the base is provided with a guide rod that passes through the limiting groove and the clamp, and the axis of the guide rod is parallel to the moving direction of the clamp.

[0014] Furthermore, the elastic element is inserted outside the guide rod, with one end abutting against one side wall of the limiting slide groove and the other end abutting against the clamp.

[0015] Furthermore, the base is provided with two guide rods, which are arranged at intervals, and each guide rod is provided with an elastic element.

[0016] Furthermore, the base of the release mechanism is fixed to the bottom end of the concrete beam, and the opening of the limiting groove faces the bottom of the concrete beam.

[0017] Furthermore, the fasteners are orthogonal to the FRP board, and multiple fasteners are spaced apart along the length of the FRP board, which is then bonded to the concrete beam.

[0018] A second objective of this invention is to provide a method for strengthening an FRP strengthening device that suppresses brittle fracture as described in the first objective, comprising:

[0019] Roughen the bottom surface of the concrete beam at the FRP board installation location to determine the fixing positions of the positioning fasteners and release mechanisms;

[0020] Install the FRP board on the bottom surface of the concrete beam, install the fasteners and fix it;

[0021] Install clamps at both ends of the FRP board and install the clamps into the limiting grooves of the base respectively, and fix the base to the concrete beam;

[0022] The fasteners, release mechanism, and FRP board work together to resist the peeling of the FRP board from the concrete beam.

[0023] Furthermore, the FRP board is bonded to the bottom surface of the concrete beam, and multiple fasteners are spaced apart and connected to the concrete beam respectively.

[0024] Compared with the prior art, the advantages and positive effects of this invention are:

[0025] (1) To address the problem that FRP boards are prone to peeling off from concrete, leading to reinforcement failure, active pressure is applied to the FRP board through fasteners to increase the friction between the FRP board and the concrete, thereby improving the utilization rate of FRP. In addition, a release mechanism is installed at the end of the FRP board. The clamps and elastic elements of the release mechanism work together to elastically constrain the end of the FRP board, elastically releasing the displacement of the end of the FRP board, slowing down the brittle peeling failure of the FRP board, and effectively improving the ductility of the FRP board and the concrete beam.

[0026] (2) Unlike existing rubber bearings that are installed on external structures, the release mechanism in this application is installed on the reinforced concrete beam body, which can be arranged as a whole, reducing dependence on external structures, suppressing instantaneous peeling of FRP, further improving the ductility of the reinforced beam, and avoiding brittle failure. It is not only suitable for the reinforcement of slab beams in large bridges, but also for the reinforcement of medium and small beams.

[0027] (3) While improving the load-bearing capacity of the reinforced beam, avoid brittle failure of the FRP reinforced beam, that is, avoid a sudden drop in load-bearing capacity, maintain the synergistic force between the FRP plate and the concrete beam during the deformation process, and improve the ductility of the reinforced beam. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] Figure 1 This is a schematic diagram of the FRP reinforcement device for suppressing brittle fracture in Embodiments 1 and 2 of the present invention.

[0030] Figure 2 This is a bottom view of the FRP reinforcement device for suppressing brittle fracture in Embodiments 1 and 2 of the present invention.

[0031] Figure 3 This is a comparison diagram of the FRP reinforcement device for suppressing brittle fracture in Embodiments 1 and 2 of the present invention and existing reinforcement methods.

[0032] Among them, 1. anchor bolts, 2. fasteners, 3. FRP plates, 4. elastic elements, 5. clamps, 6. guide rods, 7. concrete beams, and 8. bases. Detailed Implementation

[0033] Example 1

[0034] In a typical embodiment of the present invention, such as Figures 1-3 As shown, an FRP reinforcement device for suppressing brittle fracture is presented.

[0035] like Figure 3 As shown, the load-deformation curves of concrete beam 7 under three different reinforcement methods are compared to illustrate the features of the present invention.

[0036] When the external FRP board 3 reinforces the concrete beam 7, the FRP board 3 peels off during the process of increasing load, and once peeling occurs, it will quickly develop to the end, and the beam will reach the ultimate load (OA segment), resulting in low efficiency of FRP.

[0037] To suppress premature delamination of FRP board 3, researchers proposed a hybrid bonding FRP board 3 reinforcement (HB-FRP) technology. The HB-FRP reinforced concrete beam 7 is constructed by attaching steel plates to the externally bonded FRP board 3. By actively applying preload, the friction between the FRP board 3 and the concrete is increased, thereby suppressing premature delamination of the FRP board 3 and improving the utilization rate of the FRP board 3. The load continues to increase until the FRP board 3 delaminates to the end, at which point the beam reaches its ultimate load, and then the load drops sharply (section AB).

[0038] Based on this, this embodiment provides an FRP reinforcement device and method to suppress brittle fracture. On the basis of HB-FRP reinforcement technology, a release mechanism is arranged at the end of the concrete beam 7. The clamp 5 of the release mechanism is used to clamp the unattached FRP plate 3 at the end, and the elastic member 4 abuts against the clamp 5 to elastically resist the movement of the clamp 5. When the peeling of the FRP plate 3 develops to the end, the tensile force of the FRP plate 3 is transmitted to the arranged elastic member 4 through the clamp 5. The displacement of the end of the FRP plate 3 is elastically released by the deformation of the elastic member 4, thereby suppressing the instantaneous peeling of the FRP plate 3 and avoiding brittle peeling failure of the FRP plate 3. The load no longer drops suddenly, and then changes to a slow decrease with the increase of deformation, that is, it changes to ductile failure (after point B).

[0039] The FRP reinforcement device and method for suppressing brittle fracture will be described in detail below with reference to the embodiments.

[0040] See Figure 1 The FRP reinforcement device for suppressing brittle fracture includes an FRP plate 3, a fastener 2, and a release mechanism. All three are connected to the concrete beam 7 to be reinforced. The FRP plate 3 is pasted to the concrete beam 7, and the fastener 2 and the release mechanism are installed on the concrete beam 7 by anchor bolts 1. At the same time, the fastener 2 is pressed into the FRP plate 3, and the release mechanism is connected to the end of the FRP plate 3.

[0041] The FRP board 3 is attached to the bottom surface of the concrete beam 7 and shares the load with the concrete beam 7 to reinforce the concrete beam 7 and improve its load-bearing performance.

[0042] In this embodiment, the FRP board 3 is pasted onto the bottom surface of the concrete beam 7. The area on the concrete beam 7 where the FRP board 3 is pasted is roughened, and the board is pasted with adhesives such as carbon fiber adhesive, and then cured until the strength meets the standard.

[0043] like Figure 2 As shown, the fastener 2 is pressed onto the FRP plate 3 and extends to the outside of the FRP plate 3 at both ends. The fastener 2 is fixed to the bottom surface of the concrete beam 7.

[0044] In this embodiment, the fastener 2 is a steel fastener plate. The fastener 2 is orthogonal to the FRP plate 3. Multiple fasteners 2 are arranged at intervals along the length of the FRP plate 3 to apply pressure to the FRP plate 3 from multiple points and improve its cooperative stress resistance.

[0045] In addition, the fastener 2 is fixed to the concrete beam 7 by the anchor bolt 1. During installation, the mounting holes corresponding to the anchor bolt 1 are pre-drilled. After the FRP board 3 is pasted and the fastener 2 is arranged, the anchor bolt 1 is installed and torque is applied to tighten it.

[0046] In other alternative embodiments, the anchor bolt 1 can also be a tapered bolt, expansion bolt or other fastener to ensure that the fastener 2 is tightly fixed to the concrete beam 7, and at the same time apply a stable and uniform pressure to the FRP plate 3.

[0047] Combination Figure 1 and Figure 2 The release mechanism includes a base 8 and a clamp 5. The base 8 is provided with a limiting groove for accommodating the clamp 5. The clamp 5 is connected to the end of the FRP plate 3. The moving direction of the clamp 5 along the limiting groove is collinear with the displacement direction of the end of the FRP plate 3 when it is bent. The clamp 5 is connected to an elastic member 4 whose axis is arranged along the moving direction of the clamp 5.

[0048] The base 8 is U-shaped, and the groove position serves as a limiting groove. The FRP plate 3 extends beyond one side edge of the limiting groove to connect to the clamp 5. The clamp 5 is provided with a clamping part extending into the clamp 5. The clamping part is arranged along the extension direction of the FRP plate 3, and the end of the FRP plate 3 is inserted into the clamping part and fixed.

[0049] It is understandable that when the FRP plate 3 is bent, the displacement of its end is not necessarily in a straight line, but may change direction. Therefore, the clamp 5 can follow the movement of the end of the FRP plate 3, and the elastic element 4 can apply elastic resistance to the clamp 5 to slow down the displacement process of the end of the FRP plate 3.

[0050] To prevent the clamp 5 from detaching when moving within the limiting groove, the base 8 is provided with a guide rod 6 that passes through the limiting groove and the clamp 5, and the axis of the guide rod 6 is parallel to the moving direction of the clamp 5.

[0051] The elastic element 4 passes through the guide rod 6, with one end abutting against the side wall of the limiting slide groove and the other end abutting against the clamp 5, thus constraining the deformation direction of the elastic element 4. The elastic element 4 can be a high-toughness spring.

[0052] The base 8 is provided with two guide rods 6, which are arranged at intervals. Each guide rod 6 is provided with an elastic element 4, so that the two sides of the clamp 5 can be evenly stressed.

[0053] Release mechanisms are installed at both ends of the FRP plate 3. The clamp 5 releases the end displacement of the FRP plate 3 as it deforms.

[0054] The base 8 of the release mechanism is fixed to the bottom end of the concrete beam 7, and the opening of the limiting groove faces the bottom of the concrete beam 7.

[0055] Unlike existing technologies that use anchor bolts to fix I-beams to the bottom of the beam to improve its load-bearing capacity, this method, due to the significant weight of the I-beams, also affects the improvement of the beam's load-bearing capacity, and is only suitable for large bridge structures. In this embodiment, the FRP plate 3 is lightweight and high-strength, eliminating the influence of its own weight on the load-bearing capacity. This not only improves the load-bearing capacity of the reinforced beam but also, through a device, suppresses instantaneous peeling of the FRP, further improving the ductility of the reinforced beam and preventing brittle failure. This method is suitable not only for plate beam reinforcement in large bridges but also for the reinforcement of medium and small-sized beams.

[0056] Furthermore, unlike existing technologies that involve tensioning and prestressing FRP, this embodiment does not tension the FRP plate 3. Tensioned FRP is often used for prestressed reinforcement of large slab beams to counteract vertical deformation and thus increase the beam's load-bearing capacity. In this embodiment, the main objective is to improve the load-bearing capacity of the reinforced beam while preventing brittle failure (i.e., a sudden drop in load-bearing capacity) and enhancing the ductility of the reinforced beam. It is also suitable for reinforcing beams in small and medium-sized structures, making it widely applicable.

[0057] Example 2

[0058] In another typical embodiment of the present invention, such as Figures 1-3 As shown, a reinforcement method for an FRP reinforcement device that suppresses brittle fracture is presented.

[0059] The FRP reinforcement device for suppressing brittle fracture, as described in Example 1, includes the following steps:

[0060] Roughen the bottom surface of the concrete beam 7 at the installation position of FRP board 3 to fix the positioning fastener 2 and the release mechanism.

[0061] Install the FRP board 3 onto the bottom surface of the concrete beam 7, and install and fix the fastener 2;

[0062] Install clamps 5 at both ends of the FRP board 3, and install the clamps 5 in the limiting grooves of the base 8 respectively, and fix the base 8 to the concrete beam 7;

[0063] Fastener 2, the release mechanism and the FRP plate 3 work together to resist the peeling of the FRP plate 3 from the concrete beam 7.

[0064] Furthermore, the FRP board 3 is adhered to the bottom surface of the concrete beam 7, and multiple fasteners 2 are spaced apart and connected to the concrete beam 7 respectively.

[0065] In this embodiment, combined with Figures 1-3 The reinforcement method of FRP reinforcement device for suppressing brittle fracture is described in detail.

[0066] Reinforcement methods include:

[0067] Step 1: First, roughen the bottom surface of the concrete beam 7 where the FRP board 3 will be bonded, locate the positions for the anchor bolts 1, and drill holes using an electric hammer. After completing the above process, clean the roughened surface and bolt holes to prevent dust from affecting the bonding strength.

[0068] Step 2: Remove the concrete at the end of the concrete beam 7 where the base 8 is to be placed, and grind it smooth. Place the base 8, the high-toughness spring, and the clamp 5 of the FRP plate 3, and fix the high-toughness spring, the base 8, and the clamp 5 of the FRP plate 3 as a whole by using the guide rod 6. Then, insert the anchor bolts 1 to fix the base 8 to the concrete beam 7.

[0069] Step 3: Place the chemical adhesive into the hole and insert the anchor bolt 1. Clean the surface of the FRP board 3 to be pasted, apply carbon fiber adhesive after cleaning, and then paste the FRP board 3. Cure until the required strength is achieved. After completing the above steps, install the fastener 2 through the anchor bolt 1 position and tighten the nut of the anchor bolt 1 to apply torque.

[0070] During the process of developing strength in the carbon fiber adhesive, weights need to be evenly distributed on the FRP board 3 to prevent the carbon fiber from rebounding and causing air bubbles in the adhesive layer. When applying torque, apply torque evenly at the anchor bolts 1 on both sides of the fastener 2 to avoid uneven stress on the FRP board 3.

[0071] Step 4: After completing the above steps, use the clamps 5 of the FRP board 3 to clamp the unattached part of the FRP end and install it on the base 8 for fixation, thus completing the reinforcement.

[0072] In this embodiment, the difference between suppressing the peeling of FRP plate 3 and HB-FRP reinforcement is that when the peeling of FRP plate 3 develops to the end of concrete beam 7, brittle failure will not occur, resulting in a sudden drop in load. At this time, FRP plate 3 is constrained by clamp 5, and the tension is transmitted to the position of elastic member 4 through clamp 5. Elastic member 4 is deformed by the tension of FRP plate 3, the peeling of FRP plate 3 is suppressed, the peeling speed is reduced, FRP plate 3 will not undergo brittle failure, and the beam load changes from a sudden drop to a slow decrease as the beam deformation increases.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An FRP reinforcement device for suppressing brittle fracture, characterized in that, include: FRP sheets are attached to the bottom surface of concrete beams; Fasteners are pressed onto FRP sheets and extend beyond the FRP sheets at both ends. The fasteners are fixed to the bottom surface of concrete beams. The fasteners are orthogonal to the FRP sheets. The fasteners are spaced apart along the length of the FRP sheets. The release mechanism includes a base and a clamp. The base is provided with a limiting groove to accommodate the clamp. The clamp is connected to the end of the FRP plate. The moving direction of the clamp along the limiting groove is collinear with the displacement direction of the end of the FRP plate when it is bent. The clamp is connected to an elastic element whose axis is arranged along the moving direction of the clamp. Release mechanisms are installed at both ends of the FRP plate. The clamp elastically releases the end displacement of the FRP plate as it deforms. The base is provided with a guide rod that passes through the limiting slide groove and the clamp, and the axis of the guide rod is parallel to the moving direction of the clamp; the elastic element passes through the guide rod, one end of the elastic element abuts against one side wall of the limiting slide groove, and the other end abuts against the clamp.

2. The FRP reinforcement device for suppressing brittle fracture as described in claim 1, characterized in that, The base is U-shaped, with the groove serving as a limiting slide. The FRP plate extends beyond one edge of the limiting groove to connect to the clamp.

3. The FRP reinforcement device for suppressing brittle fracture as described in claim 2, characterized in that, The fixture is provided with a clamping part extending into the fixture. The clamping part is arranged along the extension direction of the FRP plate, and the end of the FRP plate is inserted into the clamping part and fixed.

4. The FRP reinforcement device for suppressing brittle fracture as described in claim 3, characterized in that, The base is provided with two guide rods, which are arranged at intervals, and each guide rod is provided with an elastic element.

5. The FRP reinforcement device for suppressing brittle fracture as described in claim 1, characterized in that, The base of the release mechanism is fixed to the bottom end of the concrete beam, and the opening of the limiting groove faces the bottom of the concrete beam.

6. The FRP reinforcement device for suppressing brittle fracture as described in claim 1, characterized in that, FRP panels are bonded to concrete beams.

7. A method for reinforcing an FRP reinforcement device for suppressing brittle fracture as described in any one of claims 1-6, characterized in that, include: Roughen the bottom surface of the concrete beam at the FRP board installation location to determine the fixing positions of the positioning fasteners and release mechanisms; Install the FRP board on the bottom surface of the concrete beam, install the fasteners and fix it; Install clamps at both ends of the FRP board and install the clamps into the limiting grooves of the base respectively, and fix the base to the concrete beam; The fasteners, release mechanism, and FRP board work together to resist the peeling of the FRP board from the concrete beam.

8. The reinforcement method of the FRP reinforcement device for suppressing brittle fracture as described in claim 7, characterized in that, FRP sheets are bonded to the bottom of concrete beams, and multiple fasteners are spaced apart and connected to the concrete beams.

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