Reinforcement method of concrete beam by FRP grid lattice

Abstract

The application discloses a FRP grid lattice embedded reinforcing method for a concrete beam, which comprises the following steps: treating a surface layer of a bottom plate of the concrete beam, longitudinally and transversely slotting the bottom plate of the concrete beam to form lattice slots, layering and positioning FRP grids in the lattice slots, pouring a bonding medium, and curing the FRP grids. Compared with the traditional reinforcing method, the application restricts the deformation of the bonding medium and the FRP grid, effectively increases the bonding performance among the FRP grid, the bottom plate of the concrete beam and the bonding medium. In addition, by arranging special designed anchoring devices at the end area nodes of the FRP grid, the bonding between the FRP grid and the concrete beam is further enhanced, the early debonding and the layered damage mode of the bonding medium in the traditional FRP embedded reinforcing and the FRP grid surface pasting reinforcing methods can be effectively inhibited, and the high strength performance of the FRP material can be fully utilized in the reinforcing practice. The reinforcing method provided by the application can effectively improve the stiffness and the bearing capacity of the old concrete beam and prolong the service life of the old concrete beam.

Description

Technical Field

[0001] This invention belongs to the field of flexural reinforcement technology for concrete bridges, specifically relating to a method for reinforcing concrete beams by embedding FRP grids. Background Technology

[0002] With increasing service life and rising traffic loads, more and more aging bridges are facing structural damage and load-bearing capacity degradation. Repairing and reinforcing aging concrete beam bridges has become a crucial issue in civil engineering. Fiber-reinforced polymer (FRP) composites possess excellent properties such as lightweight, high strength, corrosion resistance, and fatigue resistance. In particular, FRP grids, composed of interwoven longitudinal and transverse FRP fibers, exhibit good strength in both directions, making them an ideal material for reinforcing concrete beam bridges.

[0003] Currently, there are two forms of FRP reinforcement for concrete beams: embedded reinforcement and surface bonding reinforcement. Existing embedded FRP reinforcement methods involve embedding FRP reinforcement bars or sheets in longitudinal grooves cut into the bottom of the concrete beam. However, this method is prone to debonding failure at the reinforcement interface, or, to prevent debonding failure, requires large or complex anchoring devices at the ends of the FRP reinforcement bars or sheets, necessitating extensive grooving in the concrete anchoring zone, causing additional damage to the concrete beam. For existing surface bonding FRP reinforcement methods, especially FRP grid surface bonding reinforcement, since both the bonding medium and the FRP grid are outside the concrete beam, they are unrestrained in the longitudinal and transverse directions under external loads, resulting in significant relative slippage at the contact surfaces between the concrete beam and the bonding medium, and between the FRP grid and the bonding medium. This easily leads to debonding failure between the bonding medium and the concrete beam. When the number of FRP grid reinforcement layers is too large, delamination failure is also prone to occur in the thickness direction of the bonding medium. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for FRP grid-structured embedding reinforcement of concrete beams.

[0005] The technical solution adopted to solve the above-mentioned technical problems is: a method for embedding and reinforcing concrete beams with FRP grid, comprising the following steps: Step 1. Surface treatment of concrete beam bottom slab Use a high-pressure water gun or air gun to remove the calcified and loose concrete material eroded by flowing water from the surface of the concrete beam bottom plate. For concrete beams with coatings, grind off the coating beforehand and wash away the dust with a high-pressure water gun to reveal a clear and clean concrete beam bottom plate. Step 2. Longitudinal and transverse slots are cut into the bottom slab of the concrete beam to form a lattice groove. Based on the horizontal laying position of the FRP grid on the bottom concrete beam slab, the groove outline and anchor hole markings are pre-drawn on the bottom concrete beam slab. Along the outline and according to the preset groove depth, longitudinal and transverse interwoven grid grooves are cut on the bottom concrete beam slab. The grid grooves are longitudinal along the length of the concrete beam, and anchor holes are opened according to the anchor hole markings. At the same time, grooves connected to the transverse grooves of the grid grooves are opened on the outer surface of the webs on both sides of the concrete beam. After the grooving is completed, a blower is used to clean up the remaining concrete debris. Step 3. Fix the FRP grid layers in layers and place them in the grid groove. First, at least one layer of FRP grid is fixed layer by layer through anchor fixing components to form an FRP grid assembly. There is a certain distance between two or more FRP grid layers. Then, a layer of adhesive medium is applied to the grid groove, the web groove and the anchor hole. The thickness of the adhesive medium layer is greater than the thickness of the FRP grid layer. The FRP grid assembly is placed in the grid groove so that the anchor bolts of the anchor fixing components are located in the anchor hole. The innermost FRP grid layer is in full contact with the adhesive medium layer. The two ends of the transverse fibers of each FRP grid layer are bent at a certain angle and embedded in the groove of the web. Step 4. Pour in the bonding medium and cure. The bonding medium is poured into the lattice groove and cured until it reaches the design strength, so that the FRP lattice layer, concrete beam, bonding medium and anchoring components form a whole under stress. Finally, the bottom surface of the concrete beam is smoothed to ensure that the bottom of the concrete beam is clean and flat.

[0006] As a preferred technical solution, the anchoring positioning component includes at least one set of pads, four anchor bolts, an upper adjusting nut, a lower adjusting nut, and a positioning nut. The pad set consists of an upper pad and a lower pad with identical structures. The four corners of the upper and lower pads are set on the four anchor bolts. The anchor bolts are threaded with positioning nuts that control the length of the anchor bolts extending into the anchor holes. The upper and lower pads are clamped on the FRP grid layer. The upper adjusting nut and the lower adjusting nut are set on the anchor bolts on both sides of the upper and lower pads.

[0007] As a preferred technical solution, in step 3, the spacing between two or more FRP grid layers is 1mm to 1 / 2 of the grid groove depth.

[0008] As a preferred technical solution, the bonding medium is epoxy resin or cement-based material.

[0009] The beneficial effects of this invention are as follows: (1) The method of grooving and injecting bonding medium used in this invention can minimize secondary damage to the beam. The bonding medium can be a high-strength and high-toughness bonding material, which can significantly enhance the structural strength and stiffness.

[0010] (2) The FRP grid bending reinforcement method proposed in this invention can further improve the bonding performance between the bonding medium and the concrete beam and between the FRP grid and the bonding medium, and effectively suppress the occurrence of debonding and delamination failure.

[0011] (3) The FRP grid node anchoring measures proposed in this invention can not only suppress the debonding and damage between the FRP grid and the concrete surface, but also adjust the embedment depth of the FRP grid in the groove, thus increasing the convenience of construction.

[0012] (4) The FRP grid node anchoring measures proposed in this invention can meet the requirements for multi-layer FRP grid reinforcement of concrete beams.

[0013] (5) The anchoring measure proposed in this invention, in which the FRP grid extends to the web and works together with the concrete beam through the bonding medium, can further suppress the delamination and debonding between the FRP grid and the concrete interface.

[0014] (6) This invention can effectively meet the needs of simply supported concrete beam bridges, continuous beam bridges and continuous rigid frame bridges to restore their bearing capacity through reinforcement. This reinforcement method is also applicable to the reinforcement of concrete beams in building structures. Moreover, this reinforcement method will not affect the usable floor area of ​​the building or the appearance of the structure. Attached Figure Description

[0015] Figure 1 This is a schematic flowchart of the FRP grid-structured embedded reinforcement method for concrete beams according to the present invention.

[0016] Figure 2 This is a schematic diagram of an inverted concrete beam structure reinforced using the method of the present invention in the embodiment.

[0017] Figure 3 yes Figure 2 The main view.

[0018] Figure 4 This is a three-dimensional structural diagram of the FRP grille assembly in the embodiment.

[0019] Figure 5 This is a front view of the FRP grille assembly in the embodiment.

[0020] Figure 6This is a schematic diagram of the FRP grid layer in the embodiment.

[0021] Figure 7 This is a structural schematic diagram of the anchor fixing component in the embodiment.

[0022] Among them: 1. Concrete beam; 2. FRP grid layer; 3. Grid groove; 4. Groove; 5. Anchor fixing component; 51. Upper pad; 52. Lower pad; 53. Anchor bolt; 54. Positioning nut; 55. Upper adjusting nut; 56. Lower adjusting nut. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments. Example

[0024] exist Figure 1 , 2 In section 3, a method for reinforcing concrete beams using an FRP (fiberglass reinforced plastic) grid embedded structure includes the following steps: Step 1. Surface treatment of the bottom slab of concrete beam 1 Use a high-pressure water gun or air gun to remove the calcified and loose concrete material that has been eroded by water from the surface of the concrete beam 1 base plate. For concrete beam 1 with a coating, grind off the coating of the concrete beam 1 base plate beforehand, and use a high-pressure water gun to wash away the dust on the concrete beam 1 base plate to reveal a clear and clean concrete beam 1 base plate. Step 2. Longitudinal and transverse slots are cut into the bottom slab of concrete beam 1 to form lattice slot 3. According to the horizontal laying position of the FRP grid on the bottom concrete beam 1, the groove outline and anchor hole markings are pre-drawn on the bottom plate of the concrete beam 1. Along the outline, longitudinal and transverse interwoven grid grooves 3 are cut on the bottom plate of the concrete beam 1 at a preset groove depth of 20-25 mm. The grid grooves 3 are longitudinal in the length direction of the concrete beam 1, and anchor holes are opened according to the anchor hole markings. At the same time, grooves 4 connected to the transverse grooves of the grid grooves 3 are opened on the outer surface of the webs on both sides of the concrete beam 1. After the grooving is completed, the remaining concrete debris is cleaned with a blower. Step 3. Fix the FRP grid in layers and place it in the grid groove 3. First, the three layers of FRP grid 2 are fixed layer by layer using anchor fixing components 5 to form an FRP grid assembly. The spacing between two adjacent FRP grid layers 2 is 1mm to 1 / 2 of the grid groove depth; in this embodiment, it is 8mm. Figure 4 , 5Then, a layer of adhesive medium is applied to the lattice groove 3, the web groove 4 and the anchoring hole. The thickness of the adhesive medium layer is greater than the thickness of the FRP lattice layer 2. The FRP lattice assembly is placed in the lattice groove 3 so that the anchor bolts 53 of the anchoring positioner 5 are located in the anchoring hole. The innermost FRP lattice layer 2 is in full contact with the adhesive medium layer. The two ends of the transverse fibers of each FRP lattice layer 2 are bent at a certain angle and embedded in the groove 4 of the web to further enhance the adhesion between the FRP lattice layer 2 and the concrete beam 1. Among them, such as Figure 6 , 7 The anchoring component 5 includes three sets of pads, four anchor bolts 53, an upper adjusting nut 55, a lower adjusting nut 56, and a positioning nut 54. The pads consist of an upper pad 51 and a lower pad 52 with identical structures. The four corners of the upper pad 51 and the lower pad 52 are fitted onto the four anchor bolts 53. By adjusting the distance between two adjacent sets of pads, the distance between two adjacent FRP grid layers 2 can be adjusted. The anchor bolts 53 are threaded with positioning nuts 54. The positioning nuts 54 are used to control the length of the anchor bolts 53 extending into the anchor holes, thereby eliminating errors in the opening depth of the anchor holes. Before inserting the anchor bolts 53 into the anchor holes, adjust the positioning nuts 54 of the four anchor bolts 53 to a suitable height. Starting from the FRP grid layer 2 closest to the positioning nuts 54, fix the FRP grid layer 2 layer by layer. The fixing method for each FRP grid layer 2 is as follows: first, fix the lower adjusting nut 56 at a suitable height for the anchor bolt 53, then sequentially fit the lower pad 52, FRP grid layer 2, upper pad 51, and upper adjusting nut 55 onto the anchor bolt 53. Tighten the upper adjusting nut 55 to clamp and fix the FRP grid layer 2 between the lower pad 52 and the upper pad 51. The fixing method of the FRP grid layer 2 in this embodiment avoids delamination and delamination damage to the greatest extent, and can also eliminate the error in the groove depth of the grid groove 3, improving the convenience of construction.

[0025] Step 4. Injecting the bonding medium A bonding medium is poured into the lattice groove 3 and cured until it reaches the design strength. This forms a unified load-bearing structure consisting of the FRP grid layer 2, concrete beam 1, bonding medium, and anchoring components 5. The bottom surface of the concrete beam 1 is then smoothed to ensure it is clean and flat. The concrete structure formed by the lattice groove 3 provides mechanical interlocking and anchoring to the transverse fibers in the FRP grid layer 2, limiting the slippage between the longitudinal fibers and the bonding medium, thus preventing debonding and damage between the FRP grid and the bonding medium.

[0026] In this embodiment, the bonding medium is a cement-based material, but it can also be an epoxy resin.

Claims

1. A method for reinforcing concrete beams using an FRP (fiberglass reinforced plastic) grid embedded structure, characterized in that, Includes the following steps: Step 1. Surface treatment of concrete beam bottom slab Use a high-pressure water gun or air gun to remove the calcified and loose concrete material eroded by flowing water from the surface of the concrete beam bottom plate. For concrete beams with coatings, grind off the coating beforehand and wash away the dust with a high-pressure water gun to reveal a clear and clean concrete beam bottom plate. Step 2. Longitudinal and transverse slots are cut into the bottom slab of the concrete beam to form a lattice groove. Based on the horizontal laying position of the FRP grid on the bottom plate of the concrete beam, the groove outline and anchor hole markings are pre-drawn on the bottom plate of the concrete beam. Along the outline, longitudinal and transverse interwoven grid grooves are cut on the bottom plate of the concrete beam according to the preset groove depth. The grid grooves are longitudinal along the length of the concrete beam, and anchor holes are opened according to the anchor hole markings. At the same time, grooves connected to the transverse grooves of the grid grooves are opened on the outer surface of the web on both sides of the concrete beam. After the grooving is completed, a blower is used to clean up the remaining concrete debris. Step 3. Fix the FRP grid layers in layers and place them in the grid groove. First, at least two layers of FRP grid are fixed layer by layer with anchor fixing components to form an FRP grid assembly. The spacing between two or more FRP grid layers is 1mm to 1 / 2 of the grid groove depth. Then, a layer of adhesive medium is applied to the grid groove, the web groove and the anchor hole. The thickness of the adhesive medium layer is greater than the thickness of the FRP grid layer. The FRP grid assembly is placed in the grid groove so that the anchor bolts of the anchor fixing components are located in the anchor hole. The innermost FRP grid layer is in full contact with the adhesive medium layer. The two ends of the transverse fibers of each FRP grid layer are bent at a certain angle and embedded in the groove of the web. Step 4. Pour in the bonding medium and cure. The bonding medium is poured into the lattice groove and cured until it reaches the design strength, so that the FRP lattice layer, concrete beam, bonding medium and anchoring components form a whole under stress. Finally, the bottom surface of the concrete beam is smoothed to ensure that the bottom of the concrete beam is clean and flat.

2. The FRP grid-structured embedding reinforcement method for concrete beams according to claim 1, characterized in that, The anchoring and positioning components include at least two sets of pad groups, four anchor bolts, an upper adjusting nut, a lower adjusting nut, and a positioning nut. Each pad group consists of an upper pad and a lower pad with identical structures. The four corners of the upper and lower pads are positioned on the four anchor bolts. The anchor bolts are threaded with positioning nuts that control the length of the anchor bolts extending into the anchor holes. The upper and lower pads are clamped on the FRP grid layer. Upper and lower adjusting nuts are provided on the anchor bolts located on both sides of the upper and lower pads.

3. The FRP grid-structured embedding reinforcement method for concrete beams according to claim 1, characterized in that, The bonding medium is epoxy resin or cement-based material.

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