An end-non-cured FRP bar anchoring system and anchoring method

Abstract

This invention discloses an end-uncured FRP rebar anchoring system and method. The anchoring system includes FRP rebar, a sleeve, a steel rod, a cap, an end plate, a positioning plate, and grout. The FRP rebar is divided into an uncured fiber bundle segment and a cured portion. The sleeve is an inner conical cylinder with a constant outer diameter and a reduced inner diameter, with a groove at the large-diameter end. During anchoring, one end of the FRP rebar is sequentially passed through the central holes of the end plate and positioning plate, and then exits through the large-diameter port of the sleeve. The uncured fiber bundle of the FRP rebar is then wound around the steel rod, and the end is adhered to the surface of the cured FRP rebar. The steel rod is then placed in the groove at the large-diameter end of the sleeve. Finally, grout is injected into the sleeve, and the cap is closed. Anchoring is completed after high-temperature curing and cooling. This invention performs "soft" and "hard" segmentation treatment on the FRP rebar, bending and winding the FRP rebar around the steel rod and bonding it with the grout, thus reducing the anchor length while anchoring the FRP rebar.

Description

Technical Field

[0001] This invention relates to FRP bars in the field of civil engineering, and to an FRP bar anchoring system and anchoring method with non-cured ends. Background Technology

[0002] Fiber-reinforced polymer (FRP) bars are a new type of composite material made by using continuous fibers as reinforcement, resin as the matrix, and curing through a pultrusion process followed by specific surface treatment. They possess advantages such as lightweight, high strength, corrosion resistance, and good fatigue resistance. FRP bars and prestressed FRP bars can effectively replace steel bars and steel strands in civil engineering, fully utilizing their high strength and corrosion resistance. They have broad application prospects in structural reinforcement, prestressed concrete structures, and bridge cables. When applying FRP bars, especially prestressed FRP bars, effective anchoring is crucial to realizing their mechanical properties; however, efficient anchoring of FRP bars remains a significant technical challenge.

[0003] Currently, commonly used FRP (Fiberglass Reinforced Plastic) rebar anchors are wedge-type anchors and bonded anchors. Wedge-type anchors mainly anchor FRP rebars using wedge-shaped wedges and anchor cups. When using wedge-type anchors, severe stress concentration effects, i.e., the notch effect, often occur at the anchor ends. Since the transverse shear strength of FRP rebar is weak, only one-tenth of its tensile strength, the notch effect causes premature transverse shear failure of the FRP rebar, leading to premature anchoring failure and reduced anchoring effectiveness. Bonded anchors mainly rely on the bonding force between the adhesive inside the sleeve and the surface of the FRP rebar to anchor it. Compared to the wedges (mostly metal wedges) in wedge-type anchors, the grout in bonded anchors has lower stiffness, resulting in less transverse pressure on the FRP rebar and reducing damage. However, bonded anchors require a sufficiently long anchorage length to achieve adequate anchorage, resulting in large anchorage sizes that are inconvenient for engineering applications. Furthermore, as the anchorage length increases, the quality of the grout filling inside the anchorage decreases, potentially further reducing the anchorage effect. These limitations mean that bonded anchors are currently mainly used for anchoring smaller diameter FRP bars, and it is difficult to achieve reliable anchorage for large diameter FRP bars. Therefore, to overcome the notch effect of existing wedge-type anchors and the large length of bonded anchors, and to achieve efficient anchorage of FRP bars, it is necessary to propose an FRP bar anchorage system and method with non-cured ends. Summary of the Invention

[0004] Purpose of the invention: To address the shortcomings of existing technologies, the purpose of this invention is to provide a reliable and easy-to-operate end-non-cured FRP bar anchoring system and method. By segmenting a single FRP bar into "soft" and "hard" sections, the FRP bar is bent and wrapped around a steel bar in the anchoring system and bonded with grout, achieving efficient anchoring while significantly reducing the length of the anchor (sleeve).

[0005] Technical solution: The end-non-cured FRP bar anchoring system of the present invention includes FRP bars, caps and sleeves. The sleeve is an inner conical cylinder with a constant outer diameter and a reduced inner diameter. The large-diameter end of the sleeve is provided with two rectangular grooves along the radial direction. Grouting material is injected into the sleeve.

[0006] FRP reinforcement includes uncured fiber bundle segments and cured fiber bundle segments;

[0007] A steel rod is placed inside a rectangular groove. The middle part of the steel rod has a circular cross-section with uncured fiber bundles wrapped around it, and the two ends of the steel rod have an arc-shaped cross-section that fits into the rectangular groove.

[0008] One end of the sleeve is fitted with an end plate with a central hole; inside the sleeve is a positioning plate with a central hole, and the positioning plate has a hole for the grout to pass through. One end of the FRP reinforcement passes through the central hole of the end plate and the positioning plate.

[0009] FRP reinforcement uses continuous fibers as the reinforcing material and resin as the matrix.

[0010] The bow-shaped section includes a superior arc bow-shaped section and a inferior arc bow-shaped section.

[0011] The cap has two protrusions that match the rectangular groove in the radial direction, thereby sealing the large-diameter port of the sleeve.

[0012] The end plate is circular and is inserted into the small-diameter end of the sleeve.

[0013] The end plate and positioning plate are provided with an inclined angle to engage with the sleeve, so as to ensure that the end plate and positioning plate do not slide out of the sleeve.

[0014] The inclination angle of the end plate and the positioning plate is 1° to 4° so that they can be inserted into the inner conical sleeve.

[0015] The anchoring method of the end-non-cured FRP bar anchoring system of the present invention includes the following steps:

[0016] (1) Insert the end plate into one end of the sleeve, insert the positioning plate into the sleeve, and pass one end of the FRP bar through the center hole of the end plate and the positioning plate and out of the large diameter port of the sleeve, so that the cured fiber bundle segment of the FRP bar is fixed in the center of the sleeve.

[0017] (2) After impregnating the uncured fiber bundle segment with impregnating adhesive, wrap it around the steel rod n+0.5 turns (n≧1), and stick a section of the end of the uncured fiber bundle segment to the surface of the cured fiber bundle segment;

[0018] (3) Place the flat surfaces at both ends of the steel rod with the uncured fiber bundle segments wrapped around it on the flat surface of the rectangular groove of the sleeve;

[0019] (4) Inject grout from the large-diameter port of the sleeve. After the grout is flush with the large-diameter port of the sleeve, insert the protrusion of the cap into the rectangular groove of the sleeve until the cap is flush with the large-diameter port of the sleeve.

[0020] (5) Heat the grouting material and then anchor the FRP reinforcement after the grouting material has solidified and cooled.

[0021] In step (2), the end of the uncured fiber bundle segment extends to the positioning plate.

[0022] In step (5), the grouting material is heated by a high-temperature curing method.

[0023] Working principle: In the end-uncured FRP bar anchoring system of the present invention, the FRP bar uses continuous fiber as the reinforcing material and resin as the matrix. However, during the pultrusion curing of the continuous fiber to form the FRP bar, the ends of the FRP bar are not pultruded and cured, while the remaining part is pultruded and cured. This results in the FRP bar containing an uncured fiber bundle portion and a cured portion. By utilizing the "soft" and flexible winding characteristics of the uncured fiber bundle, the uncured fiber bundle is wound on the steel bar and combined with the bonding effect of the grout to achieve efficient anchoring.

[0024] The sleeve is a steel inner conical cylinder with a constant outer diameter and a reduced inner diameter. The internal conical angle is selected to be 1° to 4°. Two rectangular grooves are symmetrically arranged radially at the large-diameter end of the sleeve. A steel rod is placed in the groove at the large-diameter end of the sleeve to wind the uncured fiber bundles at the ends of the FRP reinforcement. The uncured fiber bundles are wound around the steel rod n+0.5 turns (n≧1). The steel rod is designed with a variable cross-section along its length. The middle part is designed with a circular cross-section to prevent damage to the fiber bundles during winding. The two ends are designed with an arc-shaped cross-section, with the flat surfaces of the two ends placed in the grooves at the large-diameter end of the sleeve to prevent the steel rod from rotating in the grooves. To allow the steel rod to fit into the groove at the large-diameter end of the sleeve, the length of the steel rod is less than the radial distance between the inner walls of the two grooves, and the diameter is less than the width of the grooves.

[0025] To ensure a tight bond between the uncured fiber bundles and the steel rod during winding, the uncured fiber bundles are impregnated with an impregnating adhesive before winding. After winding, a section of the uncured fiber bundle extends out and is adhered to the cured portion of the FRP reinforcement. The cap is circular with two symmetrical rectangular protrusions arranged radially. The diameter of the circle matches the inner diameter of the large-diameter end of the sleeve, and the length and width of the rectangular protrusions match the length and width of the rectangular grooves on the sleeve. This allows the circular cap to engage with the large-diameter port of the sleeve, and the two rectangular protrusions to engage with the two rectangular grooves, thus sealing the large-diameter port of the sleeve. To ensure sufficient space between the steel rod and the cap for the required number of turns of the uncured fiber bundles on the steel rod, the depth of the grooves is greater than the sum of the sag of the steel rod end, the thickness of the uncured fiber bundle winding portion, and the thickness of the cap.

[0026] The end plate is annular, with a central hole diameter larger than the cured portion of the FRP reinforcement (0.5mm-1mm). This allows the cured portion of the FRP reinforcement to pass through the central hole without compromising its positioning. The outer diameter of the annular ring matches the inner diameter of the sleeve's small-diameter port, and its outer surface angle matches the inner surface angle of the sleeve. The positioning plate is also annular, with a central hole diameter matching that of the end plate. Its outer diameter matches the inner diameter at one-third of the distance from the sleeve's small-diameter port, and its outer surface angle matches the inner surface angle of the sleeve. Holes for grout to pass through are provided on the annular surface. After the end plate and positioning plate are sequentially inserted into the sleeve, the cured section of the FRP reinforcement passes through the two central holes of both plates. The end plate and positioning plate, arranged along the length of the sleeve, position the cured portion of the FRP reinforcement at the center of the sleeve.

[0027] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0028] (1) Compared with existing bonded anchors, the present invention sets a groove at the large-diameter end of the anchor sleeve and puts a steel rod therein. By designing the FRP bar as a "soft" uncured section and a "hard" cured section, the uncured fiber bundle is wrapped around the steel rod and extends into the sleeve, while part of the cured section is also in the sleeve. On the one hand, the bonding force of the FRP bar is greatly improved due to the increase in the actual anchorage length of the FRP bar in the sleeve. On the other hand, the uncured fiber bundle is wrapped around the steel rod, and the wrapping effect provides additional anchorage force for the FRP bar. Therefore, the anchoring system of the present invention greatly improves the anchoring effect of the FRP bar, thereby realizing the anchoring of FRP bars with larger diameters.

[0029] (2) Compared with existing bonded anchors, the anchor length required by the anchoring system of the present invention is significantly reduced when anchoring FRP bars of the same diameter.

[0030] (3) Compared with existing wedge-type anchors, since the anchoring system of the present invention does not use wedge-shaped wedges, the anchoring system of the present invention avoids the end cutting effect caused by wedge-shaped wedges in the wedge-type anchors, and reduces the damage of end stress concentration to FRP bars. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the end-non-cured FRP bar anchoring system of the present invention;

[0032] Figure 2 This is a cross-sectional view (I-I) in the structural schematic diagram of the end-non-cured FRP bar anchoring system of the present invention;

[0033] Figure 3 This is a schematic diagram of the FRP bar in the end-non-cured FRP bar anchoring system of the present invention;

[0034] Figure 4 This is a schematic diagram of the sleeve and steel bar combination structure in the end-non-cured FRP bar anchoring system of the present invention;

[0035] Figure 5 This is a schematic diagram of the uncured fiber bundle winding in the end-uncured FRP bar anchoring system of the present invention.

[0036] Figure 6 This is a schematic diagram of the capping system in the end-non-cured FRP bar anchoring system of the present invention;

[0037] Figure 7 This is a schematic diagram of the end plate in the end-non-cured FRP bar anchoring system of the present invention;

[0038] Figure 8 This is a schematic diagram of the positioning plate in the end-non-cured FRP bar anchoring system of the present invention. Detailed Implementation

[0039] When using the present invention to anchor FRP, the anchoring methods at both ends of the FRP bar are the same. This embodiment takes anchoring one end of the FRP bar and wrapping the uncured fiber bundle around the steel rod 1.5 times as an example, and describes the implementation of the present invention with reference to the accompanying drawings.

[0040] like Figure 1 and Figure 2 As shown, the end-non-cured FRP bar anchoring system of the present invention includes an FRP bar 1, a sleeve 2, a steel bar 3, a cap 4, an end plate 5, a positioning plate 6, and grouting material 7.

[0041] like Figure 3 As shown, the FRP reinforcement 1 uses continuous fibers as the reinforcing material and resin as the matrix, including uncured fiber bundle segment 1-1 and cured fiber bundle segment 1-2.

[0042] like Figure 1 , Figure 2 and Figure 4 As shown, sleeve 2 is a steel inner conical cylinder with a constant outer diameter and a reduced inner diameter. The internal conical angle of sleeve 2 is selected to be 1° to 4°, with 3° being the recommended angle. Two rectangular grooves 2-1 are symmetrically opened radially at the large-diameter end of sleeve 2. The two ends of steel rod 3 are placed in the grooves 2-1 at the large-diameter end of sleeve 2 for winding the uncured fiber bundle segment 1-1 at the end of FRP reinforcement 1. The uncured fiber bundle segment 1-1 is wound around steel rod 3 1.5 times, and the winding method is as follows. Figure 5 As shown, in order to ensure the tight bond between the uncured fiber bundle segment 1-1 and the steel rod 3 during the winding process, the uncured fiber bundle segment 1-1 is first impregnated with impregnating adhesive before winding. After winding, a section of the end of the uncured fiber bundle segment 1-1 extends out and is pasted on the surface of the cured fiber bundle segment 1-2 of the FRP bar. The length of the end of the uncured fiber bundle segment 1-1 extending out is based on the fact that it is close to the positioning plate 6 after the anchoring is completed.

[0043] like Figure 5 As shown, the steel rod 3 has a variable cross-section along its length. The middle part 3-1 has a circular cross-section for winding the uncured fiber bundle segment 1-1 of the FRP reinforcement 1, preventing damage to the uncured fiber bundle segment 1-1 during the winding process. The two ends 3-2 of the steel rod have arc-shaped cross-sections. The planes of the two ends 3-2 are placed in the grooves 2-2 at the large-diameter end of the sleeve 2 to prevent the steel rod 3 from rotating in the rectangular grooves 2-1. In order for the steel rod 3 to be inserted into the rectangular grooves 2-1 at the large-diameter end of the sleeve, the length of the steel rod 3 is less than the radial distance between the inner walls of the two rectangular grooves 2-1, taking 1 mm as an example. The diameter of the steel rod 3 is less than the width of the grooves 2-1, taking 0.5 mm as an example.

[0044] like Figure 6 As shown, the cap 4 is circular, with two rectangular protrusions 4-1 symmetrically arranged radially. The circular diameter of the cap 4 is smaller than the inner diameter of the large-diameter port of the sleeve 2, and the length and width of the rectangular protrusions 4-1 are smaller than the length and width of the two rectangular grooves 2-1 on the sleeve 2. This allows the circular cap 4 to engage with the large-diameter port of the sleeve 2, and the two rectangular protrusions 4-1 to engage with the two rectangular grooves 2-1, thus achieving a seal on the large-diameter port of the sleeve 2. Figure 1 and Figure 2 As shown, the depth of the groove 2-1 at the large diameter end of the sleeve 2 is greater than the sum of the height of the arc-shaped section 3-2 of the steel rod 3, the thickness of the uncured fiber bundle 1-1 winding portion, and the thickness of the cap 4, so as to ensure that the space between the steel rod 3 and the cap 4 can meet the requirement that the uncured fiber bundle 1-1 can be wound around the steel rod 3 for the corresponding number of turns.

[0045] like Figure 7As shown, the end plate 5 is annular, and the diameter of the central hole 5-1 of the end plate is larger than the diameter of the cured part 1-2 of the FRP rib 1, such as 0.5mm to 1mm, so that the cured part 1-2 of the FRP rib 1 can pass through the central hole 5-1 of the annulus, without affecting the positioning of the cured part 1-2 of the FRP rib 1 by the end plate 5 due to the large hole diameter. The outer diameter of the annulus matches the inner diameter of the small diameter port of the sleeve 2, and the inclination angle of the outer surface of the end plate 5 is the same as the inclination angle of the inner surface of the sleeve 2, thereby ensuring that when the end plate 5 is put into the sleeve 2, the end plate 5 is stuck in the small diameter port of the sleeve 2 and is not slipped out.

[0046] like Figure 8 As shown, the positioning plate 6 is annular, and the diameter of the central hole 6-1 of the positioning plate is the same as the diameter of the central hole 5-1 of the end plate 5. In this embodiment, the outer diameter of the positioning plate 6 is matched with the inner diameter at 1 / 3 of the distance from the small diameter port of the sleeve 2, and the inclination angle of the outer surface of the positioning plate 6 is the same as the inclination angle of the inner surface of the sleeve 2, so as to ensure that when the positioning plate 6 is placed in the sleeve 2, the positioning plate 6 is stuck in the sleeve 2 and will not be slipped out. At the same time, holes for the grouting material 7 to pass through are provided on the annular surface of the positioning plate 6 to ensure that the entire internal space of the sleeve 2 is filled when the grouting material 7 is injected.

[0047] like Figure 1 and Figure 2 As shown, after the end plate 5 and the positioning plate 6 are inserted into the sleeve 2, the cured section 1-2 of the FRP rib 1 passes through the center hole 5-1 of the end plate 5 and the center hole 6-1 of the positioning plate 6. The end plate 5 and the positioning plate 6, which are arranged along the length of the sleeve 2, play a positioning role for the cured part 1-2 of the FRP rib 1, so that the FRP rib 1 is in the center position of the sleeve 2.

[0048] The anchoring method for the end-non-cured FRP reinforcement of the present invention is as follows:

[0049] (1) Place the end plate 5 and the positioning plate 6 into the sleeve 2 in sequence. Utilize the tilt angle of the surfaces of the end plate 5 and the positioning plate 6 to make the end plate 5 lock into the small diameter port of the sleeve 2 and the positioning plate 6 lock into the 1 / 3 distance from the small diameter port of the sleeve 2. Pass one end of the FRP rib 1 through the center hole of the end plate 5 and the positioning plate 6 in sequence and pass out through the large diameter port of the sleeve 2, so that the cured part 1-2 of the FRP rib 1 is fixed in the center of the sleeve 2.

[0050] (2) After impregnating the uncured fiber bundle segment 1-1 with impregnating adhesive, wrap it around the steel rod 3 for 1.5 turns. Extend a section of the end of the uncured fiber bundle segment 1-1 and attach it to the surface of the cured fiber bundle segment 1-2 of the FRP reinforcement 1. The extension length of the end of the uncured fiber bundle segment 1-1 should be close to the positioning plate 6 after anchoring. Figure 1 and 2 As shown;

[0051] (3) Place the flat end of the steel rod 3, which is wrapped with uncured fiber bundle 1-1, on the flat surface of the groove 2-1 of the sleeve 2;

[0052] (4) Inject grout 7 into the large-diameter port of sleeve 2. After the grout 7 is flush with the large-diameter port of sleeve 2, insert the protrusion 4-1 of the cap 4 into the groove 2-1 of sleeve 2 and press the cap 4 tightly so that the outer surface of the cap 4 is flush with the large-diameter port of sleeve 2.

[0053] (5) The grouting material 7 is heated by high temperature curing method. After the grouting material 7 is completely cured and cooled, the anchoring of FRP bar 1 is completed.

Claims

1. An end-non-cured FRP bar anchoring system, characterized in that: It includes FRP reinforcement (1), cap (4) and sleeve (2). The sleeve (2) is an inner conical cylinder with a constant outer diameter and a reduced inner diameter. The large-diameter end of the sleeve (2) is provided with two rectangular grooves (2-1) along the radial direction. Grouting material (7) is injected into the sleeve (2). The FRP reinforcement (1) includes an uncured fiber bundle segment (1-1) and a cured fiber bundle segment (1-2); A steel rod (3) is placed in the rectangular groove (2-1). The middle part (3-1) of the steel rod (3) is a circular cross-section of an uncured fiber bundle segment (1-1) wrapped around it. The two ends (3-2) of the steel rod (3) are arc-shaped cross-sections that fit into the rectangular groove (2-1). One end of the sleeve (2) is fitted with an end plate (5) with a central hole; a positioning plate (6) with a central hole is provided inside the sleeve (2), and the positioning plate (6) has a hole for the grout (7) to pass through. One end of the FRP reinforcement (1) passes through the central hole of the end plate (5) and the positioning plate (6).

2. The end-non-cured FRP bar anchoring system according to claim 1, characterized in that: The FRP reinforcement (1) uses continuous fiber as the reinforcing material and resin as the matrix.

3. The end-non-cured FRP bar anchoring system according to claim 1, characterized in that: The bow-shaped section includes a superior arc bow-shaped section and a inferior arc bow-shaped section.

4. The end-non-cured FRP bar anchoring system according to claim 1, characterized in that: The cover (4) is provided with two protrusions (4-1) in the radial direction that match the rectangular groove (2-1).

5. The end-non-cured FRP bar anchoring system according to claim 1, characterized in that: The end plate (5) is circular.

6. The end-non-cured FRP bar anchoring system according to claim 1, characterized in that: The end plate (5) and the positioning plate (6) are provided with an inclination angle that can be inserted into the sleeve (2).

7. The end-non-cured FRP bar anchoring system according to claim 6, characterized in that: The tilt angle is 1° to 4°.

8. An anchoring method for an end-non-cured FRP bar anchoring system as described in claim 1, characterized in that: Includes the following steps: (1) Insert the end plate (5) into one end of the sleeve (2), insert the positioning plate (6) into the sleeve (2), and pass one end of the FRP bar (1) through the center hole of the end plate (5) and the positioning plate (6) and out of the large diameter port of the sleeve (2) so that the cured fiber bundle segment (1-2) of the FRP bar (1) is fixed in the center of the sleeve (2). (2) After impregnating the uncured fiber bundle segment (1-1) with impregnating adhesive, wrap it around the steel rod (3) n+0.5 turns (n≧1), and stick a section of the end of the uncured fiber bundle segment (1-1) onto the surface of the cured fiber bundle segment (1-2); (3) Place the flat surfaces of the two ends (3-2) of the steel rod (3) wrapped with the uncured fiber bundle segment (1-1) on the flat surface of the rectangular groove (2-1) of the sleeve (2); (4) Inject grout (7) into the large-diameter port of the sleeve (2). After the grout (7) is flush with the large-diameter port of the sleeve (2), insert the protrusion (4-1) of the cap (4) into the rectangular groove (2-1) of the sleeve (2) until the cap (4) is flush with the large-diameter port of the sleeve (2). (5) Heat the grout (7) and after the grout (7) has solidified and cooled, the anchorage of the FRP bar (1) is completed.

9. The anchoring method for the end-non-cured FRP bar anchoring system according to claim 8, characterized in that: In step (2), the end of the uncured fiber bundle segment (1-1) extends to the positioning plate (6).

10. The anchoring method for the end-non-cured FRP bar anchoring system according to claim 8, characterized in that: In step (5), the grouting material (7) is heated by a high-temperature curing method.

Images