FRP sleeve reinforcement construction method for reinforced concrete column

Abstract

The invention relates to an FRP sleeve reinforcement construction method for a reinforced concrete column, and belongs to the technical field of construction of civil buildings, bridge engineering, ancient buildings, water supply and drainage engineering and the like. The method comprises the following steps: firstly, prefabricating a duct piece, placing the duct piece around a pier column, winding an FRP coiled material on the duct piece to manufacture an FRP sleeve, then putting a plurality of splitting rods into a gap between the duct piece and the pier column, pushing the duct piece by the splitting rods, applying circumferential prestress to the whole FRP sleeve, pouring concrete into the gap outside the splitting rods, withdrawing the splitting rods after the concrete reaches preset strength, and then pouring the concrete. The FRP sleeve is simple in appearance, durable and attractive after being reinforced, and the FRP sleeve is not provided with external connecting pieces such as a clamp and an anchorage device and is also not provided with butt joints, so that the durability of internal concrete is ensured. The construction does not need large tensioning equipment, and the operation is simple. The FRP sleeve manufactured in the scheme is integrated, the bearing capacity of the reinforced concrete column after reinforcement can be greatly improved, workers with special skills are not needed, and cost is saved.

Description

Technical Field

[0001] The invention relates to a reinforcement construction method for a reinforced concrete column, in particular to an FRP sleeve reinforcement construction method for a reinforced concrete column, and belongs to the technical field of maintenance and reinforcement construction of water supply and drainage projects in the fields of civil engineering, bridge engineering, ancient buildings, and hydraulic engineering. Background Art

[0002] The bearing capacity and durability of reinforced concrete columns such as frame columns in existing buildings, piers in bridges, and supporting columns of water aqueducts will be reduced during long-term service due to the influence of harsh external environment and human factors, so there is a large demand for reinforcement and repair. The traditional reinforcement methods mainly include increasing the cross-section reinforcement method and external bonding steel reinforcement method. The increasing cross-section method can effectively improve the bearing capacity of reinforced concrete columns, but at the same time it increases the deadweight and stiffness of the components, which will increase the seismic effects on the structure and is not conducive to earthquake resistance. The steel-cladding method effectively improves the bearing capacity of reinforced concrete columns by externally cladding steel plates, but in adverse environments, the external steel plates will rust, affecting the durability of the overall structure.

[0003] Fiber reinforced polymer (FRP) is a new generation of high-efficiency energy-saving materials, and is the focus of research and development in my country, including manufacturing and application. FRP has the excellent characteristics of light weight, high strength and corrosion resistance, and has been widely used in the field of seismic reinforcement and reinforcement of civil engineering. According to the different fiber reinforcements, FRP can be divided into glass fiber reinforced plastic (GFRP), carbon fiber reinforced plastic (CFRP), aramid fiber reinforced plastic (AFRP), basalt fiber reinforced plastic (BFRP), etc. The FRP reinforcement method of columns that has emerged in recent years is easy to construct. The internal concrete is in a three-dimensional stress state under the constraint of the external FRP. Especially in seismic reinforcement, it can greatly improve the displacement ductility of the column without basically increasing the bending strength of the column, and improve the energy consumption capacity, and has been promoted and applied.

[0004] Compared with the use of multiple FRP sleeve belts or FRP strips, the use of a whole FRP sleeve can provide more effective lateral support for the internal concrete and better durability protection for the concrete, and should be promoted and applied first.

[0005] The general FRP outsourcing reinforcement method will make the stress of the FRP material lag behind the original structure. Only through prestressing can the internal force distribution of the original structure be changed and the stress-strain lag phenomenon be eliminated. The prestress generated in the FRP material by pouring micro-expansion concrete is too small; the longitudinal tensioning method along the winding direction, considering the large friction resistance, requires a large tensioning force, and has high requirements for tensioning equipment and construction. In addition, the construction sequence of tensioning first and then anchoring is adopted, and the setting of the anchor end is cumbersome, which greatly increases the difficulty of construction; the method of tensioning the transverse prestress at the vertical joint, the anchor end and the anchor are exposed on the column surface without a protective layer, which not only increases the shape of the column and affects the appearance, but also the loose joints affect the durability protection of the internal concrete, which is easy to fail in the natural environment and has low durability.

[0006] Therefore, finding a new method to apply transverse prestress to the entire FRP sleeve has important engineering application value. Summary of the invention

[0007] In order to overcome the deficiencies in the prior art, the present invention develops a FRP sleeve reinforcement construction method for reinforced concrete columns, the purpose of which is to allow ordinary workers to reinforce reinforced concrete columns with FRP sleeves through less complicated operations, and the FRP sleeves have circumferential prestressing.

[0008] The FRP sleeve reinforcement construction method of the reinforced concrete column of the present invention comprises the following specific steps:

[0009] S1. Construction preparation: prepare splitting rods, FRP coils and corresponding adhesives; make pipe segments, and the bottom surface of the pipe segments extends out the connecting steel bars;

[0010] S2. Surface treatment of reinforced concrete columns: grinding the surface of the reinforced concrete columns to expose the internal concrete and make the surface rough; finely treating and grinding the position where the splitting rods are placed to make the surface flat or round;

[0011] S3. Install the pipe segments: drill holes around the reinforced concrete column on its supporting surface, inject glue into the holes, install the pipe segments, and extend the connecting steel bars of the pipe segments into the holes;

[0012] S4, making FRP sleeve: brushing adhesive on the outer surface of the pipe segment, wrapping FRP cloth, forming FRP layer; repeating the operation until the FRP layer reaches the specified number of layers, forming FRP sleeve;

[0013] S5. Apply prestress: Place multiple splitting rods with protective tubes vertically into the gap between the pipe segment and the reinforced concrete column; the splitting rods push the pipe segment to make the entire FRP sleeve have annular prestress, and the corresponding strain is,

[0014]

[0015] Where: R0 is the cross-sectional radius of the reinforced concrete column;

[0016] L0 is the distance between the outer surface of the reinforced concrete column and the inner surface of the segment;

[0017] D is the thickness of the segment;

[0018] Δ is the radial outward thrust of the splitting rod on the segment;

[0019] S6. Casting of cast-in-place layer: inject structural adhesive into the gap between the bottom surface of the segment and the supporting surface of the segment; pour concrete in the gap outside the protective tube of the splitting rod. After the concrete reaches the predetermined strength, withdraw the splitting rod, pull out the protective tube, and pour concrete in the remaining hole.

[0020] Preferably, the pipe segments are prefabricated using ultra-high performance concrete.

[0021] Preferably, the splitting rod is in the shape of an elongated strip, with a plurality of splitting heads extending from one side along the length direction; and the splitting heads are spaced at equal intervals.

[0022] Preferably, the inner side surface of the pipe segment and the side surfaces adjacent thereto are roughened, and steel bars extend from these side surfaces to enhance the bonding strength of the joint surfaces.

[0023] Preferably, in step S3, after the segments are placed, the gap sizes between adjacent segments are equal.

[0024] Preferably, the concrete poured on site is ultra-high performance concrete or self-compacting concrete with an expansion agent.

[0025] Preferably, the protective tube is a plastic tube; the bottom of the protective tube is closed.

[0026] Preferably, the pipe segments have the same size and specification.

[0027] Preferably, one side of the splitting head of the splitting rod faces the reinforced concrete column.

[0028] Preferably, the construction step is increased,

[0029] S7. FRP sleeve protection treatment: Adhesive and mortar are sprayed on the surface of the FRP sleeve, or paint is directly used with the same color as the original pier concrete, and sprayed in layers and multiple times to form a protective layer.

[0030] The FRP sleeve in the technical solution of the present invention is made of FRP cloth, the fibers of which are continuous fibers, and the material is any one of carbon fiber, glass fiber, aramid fiber or basalt fiber, or a combination thereof. The FRP cloth is unidirectional cloth or bidirectional cloth.

[0031] The beneficial effects of the present invention include the following aspects:

[0032] (1) The technical solution of the present invention adopts the FRP sleeve method to strengthen the reinforced concrete column. The high-strength FRP material has prestress, which can effectively constrain the internal concrete, so that the concrete is in a three-dimensional stress state, thereby improving the bearing capacity of the column;

[0033] (2) The FRP sleeve of the present invention has no external connectors such as clamps and anchors, and no butt joints, and has a simple and beautiful appearance after reinforcement;

[0034] (3) The present invention can complete all reinforcement construction through simple on-site operation by workers. It does not require workers with special skills, thus saving costs and reducing construction costs;

[0035] (4) The construction method of the present invention requires relatively small equipment and does not require large or bulky construction tools and machinery, which reduces labor intensity and facilitates operation in places with inconvenient construction environments. It has strong adaptability to construction sites and a wide range of applications.

[0036] (5) The present invention connects the prefabricated pipe segments with the support of the reinforced concrete column, so that the pipe segments and the support are integrated, thereby enhancing the bending and shear bearing capacity of the bottom of the reinforced concrete column;

[0037] (6) The prefabricated segments of the present invention are made of ultra-high performance concrete and combined with high-performance FRP materials, which can effectively improve the bearing internal force and seismic performance of the reinforced concrete columns after reinforcement;

[0038] (7) The self-compacting concrete used in the present invention can avoid quality problems such as voids, facilitate the pouring of concrete, and improve the reinforcement speed and quality;

[0039] (8) By adding expansion agent to cast-in-place concrete, the volume shrinkage of concrete during the hardening process can be avoided. After the concrete expands slightly, it can be more strongly bonded to the reinforced concrete column and the pipe segment, and the prestress value in the outer FRP sleeve can be increased, which can greatly improve the bending, shear and torsion resistance of the reinforced section, making it easier to achieve the optimal design of the reinforcement effect;

[0040] (9) The present invention closely combines prefabrication, cast-in-place and prestressing technologies to successfully achieve the technical goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the appearance of the reinforced pier column;

[0042] Figure 2 This is a schematic diagram of the pier column surface after roughening in the reinforcement section;

[0043] Figure 3 This is a schematic diagram after the pipe segment is supported;

[0044] Figure 4 for Figure 3 Schematic diagram of the top view of the middle BB section;

[0045] Figure 5 This is a schematic diagram of the FRP casing after fabrication;

[0046] Figure 6 Schematic diagram of the expansion of the FRP sleeve;

[0047] Figure 7 for Figure 6 Schematic diagram of the top view of the middle CC section;

[0048] Figure 8 This is a schematic diagram after the splitting rod is removed.

[0049] Reference numerals: cap top surface 1, pier 2, pouring layer 3, FRP sleeve 4, segment layer 5, segment 6, oil inlet pipe 7, oil outlet pipe 8, splitting rod 9, protective tube 10, cast-in-place concrete 11. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0051] The directional words in the embodiments are based on the customary terms in engineering and are not strictly defined. For example, "upper" means the upper surface of the built part of the structure, and also includes the upper surface of the auxiliary components located obliquely above its influence range; when indicating the direction, "upper" includes both directly above and obliquely above. Directional words such as "left" and "right", "upper" and "lower" are only used to facilitate the description in conjunction with the drawings. The directional words used are only for the convenience of describing this patent, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as a limitation on this patent.

[0052] The present invention has no limitation on the cross-sectional shape of the reinforced concrete column. The reinforcement method is applicable to reinforced concrete columns with cross-sectional shapes of various shapes. In the embodiment, only a circular cross-sectional shape is used for description.

[0053] Example 1

[0054] The schematic diagram of the appearance after the construction of this embodiment is shown in Figure 1 The reinforced concrete column to be reinforced is a bridge pier 2, with a diameter of 2.0m and a cap top surface 1. Figure 1As shown, the reinforcement design is for a section of 3.0 m at the bottom of the pier 2, and a FRP sleeve 4 made of carbon fiber material is prepared for reinforcement. The outside of the pier 2 is a pouring layer 3, and between the pouring layer 3 and the FRP sleeve 4 is a prefabricated segment layer 5 of ultra-high performance concrete.

[0055] The construction method of the technical solution in the present invention comprises the following steps:

[0056] S1. Construction preparation: prepare splitting rods, FRP coils and corresponding adhesives; make pipe segments 6, the bottom surface of pipe segments 6 extends out of the bottom connecting steel bars, see Figure 3 The pipe segment 6 is arc-shaped and is prefabricated with ultra-high performance concrete. The concave inner side of the pipe segment and the adjacent side are roughened. Steel bars extend from these sides to enhance the bonding strength of the bonding surface. The splitting rod 9 is long and has multiple splitting heads extending from one side along the length direction. The spacing between the splitting heads is equal. Figure 6 The splitting rod 9 can be customized, or a plurality of conventional hydraulic splitters can be connected in series.

[0057] S2. Surface treatment of reinforced concrete column: Because the surface concrete of pier 2 has carbonized about 15mm, and in order to enhance the bonding strength, the surface of the reinforced section of pier 2 is grinded with an angle grinder, and the depth is controlled at about 20mm, while the thickness of the protective layer of pier 2 is 40mm; if there are still cracks, if the depth does not exceed 20mm, a "V"-shaped groove is carved and filled with epoxy resin sealant; if the depth is deeper, the epoxy resin sealant is injected according to the "Bi Ke method", see Figure 2 The position where the splitting rod 9 is placed is finely processed and polished to make the surface flat or round.

[0058] S3. Install the pipe segments: drill holes around the reinforced concrete column on its supporting surface, inject glue into the holes, install the pipe segments 6, and extend the bottom connecting steel bars of the pipe segments 6 into the holes; after the pipe segments 6 are placed, the gaps between adjacent pipe segments 6 are equal in size, both about 100 mm, see Figure 4 .

[0059] S4, making FRP sleeve: brush adhesive on the outer surface of the pipe segment 6, wrap FRP cloth to form FRP layer; repeat the operation until the FRP layer reaches the specified number of layers to form FRP sleeve 4, see Figure 5 The FRP sleeve 4 is made of FRP cloth, the fibers of which are continuous fibers, and the material may be any one of carbon fiber, glass fiber, aramid fiber or basalt fiber, or a combination thereof. The FRP cloth is unidirectional cloth or bidirectional cloth.

[0060] S5. Apply prestress: A plastic tube with a thickness of 5 mm is sealed with a plastic sheet as a protective tube 10. Figure 7 , Figure 7The connecting steel bars on the side of the pipe segment 6 are not shown. A plurality of splitting rods 9 with protective tubes 10 are vertically placed in the gap between the pipe segment 6 and the reinforced concrete column; the splitting head of the splitting rod 9 faces the reinforced concrete column. The oil outlet pipe 8 of the splitting rod 9 is closed, the oil inlet pipe 7 is opened and oil is introduced, and the splitting rod 9 pushes the pipe segment 6 to move outward, so that the entire FRP sleeve 4 has an annular prestress. Figure 6 , the corresponding strain is,

[0061]

[0062] Where: R0 is the cross-sectional radius of the reinforced concrete column;

[0063] L0 is the distance between the outer surface of the reinforced concrete column and the inner surface of the segment;

[0064] D is the thickness of the segment;

[0065] Δ is the radial outward thrust of the splitting rod on the segment;

[0066] S6, pouring cast-in-place layer: inject structural glue into the gap between the bottom surface of the pipe segment 6 and the top surface 1 of the pedestal; pour self-compacting concrete with expansion agent into the gap outside the protective tube 10 of the splitting rod 9, remove the splitting rod 9 after the concrete reaches the predetermined strength, then pull out the protective tube 10, pour self-compacting concrete into the remaining hole, and cast-in-place concrete 11 Figure 8 .

[0067] S7. FRP sleeve protection treatment: Adhesive and mortar are sprayed on the surface of FRP sleeve 4, or paint is directly applied with the same color as the original pier concrete, and the coating is carried out in layers and multiple times to form a protective layer.

[0068] The preferred embodiments listed above further illustrate the objectives, technical solutions and advantages of the present invention in detail. It should be understood that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for reinforcing reinforced concrete columns with FRP sleeves, characterized in that: The construction includes the following specific steps: S1. Construction preparation: prepare splitting rods, FRP coils and corresponding adhesives; make pipe segments, and the bottom surface of the pipe segments extends out the connecting steel bars; S2. Surface treatment of reinforced concrete columns: grinding the surface of the reinforced concrete columns to expose the internal concrete and make the surface rough; finely treating and grinding the position where the splitting rods are placed to make the surface flat or round; S3. Install the pipe segments: drill holes around the reinforced concrete column on its supporting surface, inject glue into the holes, install the pipe segments, and extend the connecting steel bars of the pipe segments into the holes; S4. Making FRP sleeves: applying adhesive on the outer surface of the pipe segment, wrapping FRP cloth, and forming an FRP layer; repeating the operation until the FRP layer reaches the specified number of layers, forming an FRP sleeve; S5. Apply prestress: Place multiple splitting rods with protective tubes vertically into the gap between the pipe segment and the reinforced concrete column; the splitting rods push the pipe segment to make the entire FRP sleeve have annular prestress, and the corresponding strain is, Where: R0 is the cross-sectional radius of the reinforced concrete column; L0 is the distance between the outer surface of the reinforced concrete column and the inner surface of the segment; D is the thickness of the segment; Δ is the radial outward thrust of the splitting rod on the segment; S6. Casting of cast-in-place layer: inject structural adhesive into the gap between the bottom surface of the segment and the supporting surface of the segment; pour concrete in the gap outside the protective tube of the splitting rod. After the concrete reaches the predetermined strength, withdraw the splitting rod, pull out the protective tube, and pour concrete in the remaining hole.

2. The FRP sleeve reinforcement construction method for reinforced concrete columns according to claim 1, characterized in that: The pipe segments are prefabricated using ultra-high performance concrete.

3. The FRP sleeve reinforcement construction method for reinforced concrete columns according to claim 1, characterized in that: The splitting rod is in the shape of an elongated strip, and a plurality of splitting heads extend from one side along the length direction; and the spacings between the splitting heads are equal.

4. The FRP sleeve reinforcement construction method for reinforced concrete columns according to claim 1, characterized in that: The inner side surface of the pipe segment and the adjacent side surfaces are roughened, and steel bars extend out from these side surfaces to enhance the bonding strength of the joint surface.

5. The FRP sleeve reinforcement construction method for reinforced concrete columns according to claim 1, characterized in that: In step S3, after the segments are placed, the gap sizes between adjacent segments are equal.

6. The FRP sleeve reinforcement construction method for reinforced concrete columns according to claim 1, characterized in that: The concrete poured on site is ultra-high performance concrete or self-compacting concrete with expansion agent.

7. The FRP sleeve reinforcement construction method for reinforced concrete columns according to claim 1, characterized in that: The protective tube is a plastic tube; the bottom of the protective tube is closed.

8. The FRP sleeve reinforcement construction method for reinforced concrete columns according to claim 1, characterized in that: The pipe segments have the same size and are of the same specification.

9. The FRP sleeve reinforcement construction method for reinforced concrete columns according to claim 1, characterized in that: One side of the splitting head of the splitting rod faces the reinforced concrete column.

10. The FRP sleeve reinforcement construction method for reinforced concrete columns according to claim 1, characterized in that: Add construction steps, S7. FRP sleeve protection treatment: Adhesive and mortar are sprayed on the surface of the FRP sleeve, or paint is directly used with the same color as the original pier concrete, and sprayed in layers and multiple times to form a protective layer.

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