Self-stressed FRP tendon anchoring system and anchoring method

Abstract

The present invention discloses a self-stressed FRP tendon anchoring system and anchoring method. The system includes an inner conical anchor cup with an enlarged front end, a positioning ring, a restraining ring, a wedge and an anchoring material. The anchor cup includes an inner conical rear end and a partially enlarged inner conical front end. The tail of the FRP tendon is mechanically anchored by the wedge and the restraining ring and fixed to the inner conical rear end through the positioning ring. The front end of the FRP tendon passes through the inner conical front end to apply pre-tensioning force. The anchoring material is segmented to cast the FRP tendon at the inner conical rear end and the inner conical front end. The present invention forms prestress inside the anchoring system by completing the casting and curing of the anchoring material in segments. When the FRP tendon (cable) is subjected to external tensile stress, the prestress at the front of the anchoring system is preferentially offset, and the middle and rear parts take priority, thereby solving the problem of limited effective anchoring length of FRP tendon (cable) bonded anchors and improving the anchoring efficiency of high-strength, large-tonnage FRP tendons (cables).

Description

Technical Field

[0001] The present invention relates to the field of civil engineering, and in particular to a self-stressed FRP tendon anchoring system and anchoring method, which are used for anchoring fiber reinforced composite tendons or cables in bridge structures and large-span space structures. Background Art

[0002] Fiber-reinforced composites (FRP), represented by carbon fiber composites (CFRP), are a new type of high-performance structural material, offering excellent properties such as light weight, high strength, corrosion resistance, and fatigue resistance. FRP materials often possess ultra-high tensile strength, and fabricating them into tension-only cables can fully exploit this tensile strength, making them suitable as primary tension members in large-span spatial structures (such as cable-net structures, beam-string structures) and cable-supported bridges. However, efficient anchoring of FRP tendons (cables) has always been a challenge, especially for large-tonnage FRP cables. Traditional bonded anchors have the following problems: The interfacial bond strength and deformation capacity between the FRP material and the anchoring colloid are limited, limiting the effective anchorage length. Once the anchorage length exceeds the effective anchorage length, further increases in length will not further improve the anchoring force (i.e., the contribution of the anchor tail to the anchoring action is significantly reduced at longer anchorage lengths). Furthermore, the notch effect at the front of the anchor causes stress concentration at the end of the FRP tendon, reducing anchoring efficiency. Existing anchors mainly improve the anchoring effect through two aspects: one is to optimize the performance of the anchor material, such as the variable stiffness scheme, reduce the elastic modulus of the front anchor material, and improve its deformation capacity, thereby reducing the stress concentration at the front end and increasing the contribution of the middle and rear anchor material. However, this method is limited by material properties and has limitations; the second is to change the anchor cup structure, limit the slippage of the anchor cone, and reduce the notch effect. This method cannot solve the problem of limited effective anchoring length. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a self-stressed FRP tendon anchoring system and anchoring method, which forms prestress inside the anchoring system by completing the pouring and curing of the anchoring material in sections.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A self-stressed FRP tendon anchoring system, comprising an inner tapered anchor cup with an enlarged front end, a positioning ring, a restraining ring, a wedge, and an anchoring material. The anchor cup comprises an inner tapered rear end and a partially enlarged inner tapered front end. The tail of the FRP tendon is mechanically anchored by the wedge and the restraining ring and fixed to the inner tapered rear end via the positioning ring. The front end of the FRP tendon passes through the inner tapered front end to apply pre-tension. The anchoring material is used to cast the FRP tendon in sections at the inner tapered rear end and the inner tapered front end.

[0006] The inner conical rear end includes a wedge-shaped segment with a wedge angle of α1 and a straight segment, the narrow end of the wedge-shaped segment is connected to one end of the straight segment, and the other end of the straight segment is connected to the inner conical front end;

[0007] The front end of the inner cone is wedge-shaped as a whole, with a wedge angle of α2, and the contraction direction is consistent with the direction of the wedge section of the rear end of the inner cone, and is partially enlarged on the side connected to the straight section, with an enlargement angle of β1, β1>α2;

[0008] The anchor cup further comprises an overall enlarged linear port, the connection side of the port and the inner conical front end is partially enlarged, and the enlargement angle is β2.

[0009] As a further solution of the present invention, the wedge block is installed in the splitting opening at the tail of the FRP bar, and the restraint ring is made of soft metal or FRP cloth wrapped around the FRP bar at the splitting opening.

[0010] As a further solution of the present invention, there are at least two positioning rings, one is sleeved on the tail of the FRP rib and its outer annular surface is engaged with the inner conical rear end, and the other is sleeved on the front end of the FRP rib and its outer annular surface is engaged with the port.

[0011] As a further solution of the present invention, when the FRP bar is replaced by an FRP bar bundle composed of multiple FRP bars, the positioning ring is correspondingly replaced by a wire dividing plate, and the wire dividing plate is provided with a positioning hole corresponding to each FRP bar.

[0012] An anchoring method for the self-stressed FRP tendon anchoring system as described above comprises the following steps:

[0013] The tail of the FRP bar is mechanically anchored by the wedge and the restraint ring and fixed to the tapered rear end of the anchor cup through the positioning ring. The front end of the FRP bar passes through the tapered front end of the anchor cup.

[0014] Pour anchoring material into the inner conical rear end of the anchor cup and anchor the tail of the FRP bar to the inner conical rear end;

[0015] After the anchor material is cured, a forward pre-tension is applied to the front end of the FRP reinforcement;

[0016] pouring the anchoring material at the conical front end of the anchor cup under tension;

[0017] After the anchor material reaches the required strength, unload the pre-tension and complete the anchoring.

[0018] As a further solution of the present invention, the step of mechanically anchoring the tail of the FRP bar by cooperating with a wedge and a restraining ring includes:

[0019] A restraining ring is set at a certain distance from the end face of the FRP reinforcement tail;

[0020] A split is formed at the tail of the FRP reinforcement symmetrically from the end surface to the restraint ring;

[0021] Insert a wedge into the split.

[0022] As a further solution of the present invention, the step of fixing the tail of the FRP bar to the tapered rear end of the anchor cup via a positioning ring comprises:

[0023] A positioning ring is installed in the inner conical rear end of the anchor cup, and the outer ring surface of the positioning ring is engaged in the inner conical rear end;

[0024] The FRP reinforcement passes through the inner annular surface of the positioning ring and is installed in the anchor cup.

[0025] The present invention adopts the above technical solution, which has the following beneficial effects: The present invention proposes a self-stressed FRP tendon (cable) anchoring system, which forms prestress inside the anchoring system by completing the pouring and curing of the anchoring material in sections. When the FRP tendon (cable) is subjected to external tensile stress, the prestress at the front of the anchoring system is offset first, and the middle and rear parts play a role first, thereby solving the problem of limited effective anchoring length of the FRP tendon (cable) bonded anchor, and at the same time greatly reducing the incision effect at the front end of the anchor, and the stress and deformation of the end anchoring material and the bonding interface will also be greatly reduced, thereby improving the anchoring efficiency of high-strength, large-tonnage FRP tendons (cables). The stress state of the rear section and the degree of stress and deformation reduction at the front end in the anchoring system depend on the size of the pre-tension force P during anchoring, and can be flexibly adjusted through design according to the actual stress roots of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 This is a cross-sectional view of the self-stressed FRP tendon anchoring system after anchoring is completed according to an embodiment of the present invention.

[0028] Figure 2 Schematic diagram of the anchor material segmentation of the self-stressed FRP tendon anchoring system according to an embodiment of the present invention.

[0029] Figure 3 Schematic diagram of the anchor cup segment of the self-stressed FRP tendon anchoring system according to an embodiment of the present invention.

[0030] Figures 4 to 8 Schematic diagram of the anchoring process of the self-stressed FRP tendon anchoring system according to an embodiment of the present invention.

[0031] Figures 9-13 Schematic diagram of the anchoring process of the self-stressed FRP tendon (cable) anchoring system according to an embodiment of the present invention.

[0032] The corresponding relationship of the marks in the accompanying drawings is as follows:

[0033] 1-anchor cup; 11-rear end of anchor cup; 111-wedge section; 112-straight section; 12-front end of anchor cup; 13-anchor cup port; 2-positioning ring; 3-restraint ring; 4-wedge block; 5-anchor material; 6-FRP tendon; 7-FRP tendon bundle; 8-wire separator; M1-first anchor section; M2-second anchor section; P-pretension. DETAILED DESCRIPTION

[0034] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0035] The present invention proposes a self-stressed FRP tendon (cable) anchoring system and anchoring method. By pouring and curing the anchoring material in sections, prestress is generated within the anchoring system. When the FRP tendon (cable) is subjected to external tensile stress, the prestress in the front of the anchoring system is preferentially offset, while the middle and rear sections take precedence. This solves the problem of limited effective anchoring length in FRP tendon (cable) bonded anchors. It also significantly reduces the notch effect at the anchor port, significantly reducing stress and deformation in the end anchor material and the bonding interface, thereby improving the anchoring efficiency of high-strength, large-tonnage FRP tendons (cables).

[0036] Example 1:

[0037] See Figures 1 to 3 As shown, the self-stressed FRP tendon anchoring system is used for anchoring a single FRP tendon 6, and includes an inner conical anchor cup 1 with an enlarged front end of the anchoring system, two positioning rings 2, a restraining ring 3, a wedge 4 and an anchor material 5.

[0038] The anchor cup 1 includes an inner tapered rear end (hereinafter referred to as the anchor cup rear end 11) and a partially enlarged inner tapered front end (hereinafter referred to as the anchor cup front end 12). The tail of the FRP bar 6 is mechanically anchored by the wedge block 4 and the constraint ring 3 and fixed to the anchor cup rear end 11 through the positioning ring 2. The front end of the FRP bar 6 passes through the anchor cup front end 12 to apply a pre-tension force F. The anchor material 5 is segmented to cast the FRP bar 6 at the anchor cup rear end 11 and the anchor cup front end 12. The anchor material 5 in the anchor cup rear end 11 is cast first, which is the first anchor section M1; the anchor material 5 in the anchor cup front end 12 is cast later, which is the rear anchor section M2.

[0039] Preferably, the anchor cup 1 in this embodiment is divided into three sections. Figure 3From left to right in the figure, there are: an anchor cup rear end 11, an anchor cup front end 12, and an anchor cup port 13. It should be understood that one anchor cup rear end 11 and one anchor cup front end 12 are necessary; in some embodiments, there may be multiple anchor cup front ends 12; in some embodiments, the anchor cup port 13 may not be included.

[0040] The rear end 11 of the anchor cup forms an inner tapered wedge section, so it can also be called an inner tapered rear end. Specifically, Figure 3 and Figure 4 As shown, the rear end 11 of the anchor cup is composed of a wedge-shaped section 111 and a straight section 112. The wedge angle of the wedge section 111 is α1. The wide end of the wedge section 111 faces outward, and the narrow end is connected to one end of the straight section 112. The other end of the straight section 112 is connected to the front end 12 of the anchor cup. The tapered structure of the rear end 11 of the anchor cup is similar to that of traditional anchors. This tapered structure achieves a "tightening with tension" effect. After the anchor material 5 of the first anchor section M1 has cured, it can provide a certain anchoring force for the FRP bar 6, thereby achieving pre-tensioning of the FRP bar 6.

[0041] The front end 12 of the anchor cup is wedge-shaped as a whole, with a wedge angle of α2. The wide end is connected to the straight section 112 of the rear end 11 of the anchor cup, and the narrow end is connected to the anchor cup port 13. In addition, the front end 12 of the anchor cup is partially enlarged at the connection side with the straight section of the "rear end of the anchor cup", and the enlargement angle is β1 (β1>α2). Figure 3 and Figure 4 The local amplification structure can reduce the shrinkage of the anchor material in the rear anchor section after the prestress is released during anchoring, thereby forming a self-stress balance system.

[0042] The anchor cup port 13 is an enlarged straight line, with the connection between the port and the front end 12 of the anchor cup partially enlarged by an angle β2. This enlarged port structure significantly reduces the notch effect of the inner cone bonded anchor, thereby improving anchoring efficiency. It also performs the same function as the enlarged angle β1 at the front end of the anchor cup: it reduces the retraction of the anchor material in the rear anchor section after the prestress is released during anchoring, thereby forming a self-stress balance system.

[0043] Furthermore, before pouring the anchor material of the anchor section at the tail of the FRP bar 6, a constraint ring 3 (soft metal or FRP cloth wrapped) is used to split a certain range of the tail of the FRP bar and install a wedge block 4. The wedge block 4 is embedded in the splitting opening at the tail of the FRP bar, and the constraint ring 3 is correspondingly arranged outside the FRP bar 6 at the splitting opening to provide a certain mechanical anchoring force, thereby improving the anchoring effect of the single FRP bar 6.

[0044] During the anchoring construction (i.e., anchoring), the anchoring system first mechanically anchors the outside of the FRP tendon 6 through the wedge block 4, then completes the casting and curing of the anchor material 5 of the tail anchoring section, and then completes the casting and curing of the front anchor material 5 under the pre-tensioned state under the action of the specified tension force P. Finally, the pre-tension force P is removed to complete the anchoring construction. After the anchoring is completed, a self-stress equilibrium state of tensioned FRP tendons is established inside the anchoring system. In this way, the tail anchoring section of the FRP tendon anchoring system will always remain in a stressed state, provide anchoring force, and will not be affected by the front anchoring length; when the FRP tendon is stressed, the notch effect at the front end of the anchor will be greatly reduced. The degree of reduction of the tail stress state and the front notch effect depends on the size of the pre-tension force P during anchoring, and can be flexibly adjusted according to the design.

[0045] Preferably, the FRP reinforcement is preferably carbon fiber reinforcement (CFRP reinforcement), Figures 4 to 8 , which are the specific steps of the anchoring method of the present invention for the CFRP bar, are as follows:

[0046] Step 1: Roughen the outer surface of the middle and rear part of the CFRP tendon anchorage section (e.g., sanding);

[0047] Step 2: Install the positioning ring 2 in the anchor cup 1, and install the CFRP bar through the positioning ring into the anchor cup 1. One positioning ring 2 is installed in the wedge section 111 of the rear end 11 of the anchor cup, and one positioning ring 2 is installed in the anchor cup port 13. The centers of the two positioning rings 2 are aligned to open positioning holes for the CFRP bar to pass through. Figure 4 As shown;

[0048] Step 3: Set a constraint ring 3 at a certain distance from the end face of the CFRP rib, such as Figure 4 As shown;

[0049] Step 4: Split the CFRP rib symmetrically from the end face to the position of the restraint ring 3 to form a split opening, and insert the wedge 4 into the split opening, as shown in the following figure: Figure 4 As shown;

[0050] Step 5: pour the anchor material 5 at the rear end of the anchor cup (anchor section first) and maintain it under specified conditions, such as Figure 5 As shown;

[0051] Step 6: After the anchoring material is cured, Figure 6 As shown in the figure, a pre-tension force P is applied to the CFRP tendons (cables), as shown in the figure. Figure 7 As shown;

[0052] Step 7: Cast the anchor material at the front end of the anchor cup and the end of the anchor cup (rear anchor section) under tension and maintain under specified conditions, such as Figure 8 As shown;

[0053] Step 8: After the anchor material has been cured and reached the required strength, unload the pre-tension and complete the anchoring.

[0054] Example 2:

[0055] See Figures 9-13 , is a schematic diagram of the anchoring process of the self-stressed FRP tendon (cable) anchoring system according to an embodiment of the present invention. In this embodiment, the FRP tendon can be an FRP tendon bundle 7 composed of multiple FRP tendons. The positioning ring in the rear end 11 of the anchor cup is replaced with a wire dividing plate 8, and a positioning hole is opened on the wire dividing plate 8 corresponding to each FRP tendon. The positioning ring in the anchor cup port 13 can still adopt a single-hole form, but the size of the central hole will be increased to accommodate the passage of the FRP tendon bundle 7. As the specifications of the FRP tendons increase, the anchoring system can be divided into three or more sections; the tail anchoring section can adopt a mechanical anchoring solution, thereby saving the time of pouring and curing the anchoring material in this section.

[0056] Cooperate Figures 9-13 The anchoring process of the self-stressed FRP tendon (cable) anchoring system of this embodiment includes the following steps:

[0057] Step 1: Roughen the outer surface of the middle and rear part of the FRP tendon anchorage section (e.g., sanding);

[0058] Step 2: Set a restraint ring 3 at a certain distance from the end face of each FRP tendon at the end of the tendon, such as Figure 9 As shown;

[0059] Step 3: Split each FRP tendon symmetrically from the end face to the position of the restraint ring 3 to form a split, and insert a wedge 4 into the split, as shown in the following figure: Figure 9 As shown;

[0060] Step 4: Install the wire splitter plate 8 and the positioning ring 2 in the anchor cup 1. Each FRP tendon passes through the wire splitter plate 8 and then passes through the positioning ring 2 and is installed in the anchor cup 1. The wire splitter plate 8 is installed in the wedge section 111 at the rear end 11 of the anchor cup, and the positioning ring 2 is installed in the anchor cup port 13. Figure 9 As shown;

[0061] Step 5: pour the anchor material 5 at the rear end of the anchor cup (anchor section first) and maintain it under specified conditions, such as Figure 10 As shown;

[0062] Step 6: After the anchoring material is cured, Figure 11 As shown in the figure, a pre-tension force P is applied to the FRP tendons, as shown in the figure. Figure 12 As shown;

[0063] Step 7: Cast the anchor material at the front end of the anchor cup and the end of the anchor cup (rear anchor section) under tension and maintain under specified conditions, such as Figure 13As shown;

[0064] Step 8: After the anchor material has been cured and reached the required strength, unload the pre-tension and complete the anchoring.

[0065] The present invention proposes a self-stressed FRP tendon (cable) anchoring system, which adopts segmented anchoring and forms a self-stress balance system in which the carbon fiber tendons inside the anchor cup are tensile through pre-tensioning. The middle and rear sections of the FRP tendon (cable) anchoring system will always remain in a stressed state, provide anchoring force, and will not be affected by the front anchoring length; when there is no external load, the FRP tendons (cables) at the front end of the anchoring system are subjected to reverse stress. When the FRP tendons (cables) are subjected to external tensile stress, the prestress at the front of the anchoring system is preferentially offset, and the middle and rear sections play a role first, thereby solving the problem of limited effective anchoring length of FRP tendon (cable) bonded anchors and improving the anchoring efficiency of high-strength, large-tonnage FRP tendons (cables). In addition, the notch effect at the front end of the anchor will be greatly reduced. Compared with ordinary anchors, when the FRP tendons (cables) are subjected to ultimate tensile force, the stress concentration at the port will be greatly reduced, and the stress and deformation of the end anchoring material and the bonding interface will also be greatly reduced. The stress state of the rear section and the degree of stress and deformation reduction at the front end in the anchoring system depend on the size of the pre-tension force P during anchoring and can be flexibly adjusted according to the design.

[0066] Although an embodiment of the present invention has been shown and described, this specific embodiment is merely an explanation of the present invention and is not a limitation of the invention. The specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples. After reading this specification, those skilled in the art may make modifications, substitutions and variations to the embodiment without creative contribution as needed without departing from the principles and purpose of the present invention. However, as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A self-stressed FRP tendon anchoring system, characterized by: It includes an inner conical anchor cup with an enlarged front end, a positioning ring, a restraining ring, a wedge and an anchoring material. The anchor cup includes an inner conical rear end and a partially enlarged inner conical front end. The tail of the FRP bar is mechanically anchored by the wedge and the restraining ring and fixed to the inner conical rear end through the positioning ring. The front end of the FRP bar passes through the inner conical front end to apply pre-tension. The anchoring material casts the FRP bar in sections on the inner conical rear end and the inner conical front end. The inner conical rear end includes a wedge-shaped segment with a wedge angle of α1 and a straight segment, the narrow end of the wedge-shaped segment is connected to one end of the straight segment, and the other end of the straight segment is connected to the inner conical front end; The front end of the inner cone is wedge-shaped as a whole, with a wedge angle of α2, and the contraction direction is consistent with the direction of the wedge section of the rear end of the inner cone, and is partially enlarged on the side connected to the straight section, with an enlargement angle of β1, β1>α2; The anchor cup further comprises an overall enlarged linear port, the connection side of the port and the inner conical front end is partially enlarged, and the enlargement angle is β2.

2. The self-stressed FRP tendon anchoring system according to claim 1, characterized in that: The wedge block is installed in the splitting opening at the tail of the FRP reinforcement, and the restraint ring is made of soft metal or FRP cloth wrapped around the FRP reinforcement at the splitting opening.

3. The self-stressed FRP tendon anchoring system according to claim 1, wherein: There are at least two positioning rings, one is sleeved on the tail of the FRP rib and its outer annular surface is engaged with the inner conical rear end, and the other is sleeved on the front end of the FRP rib and its outer annular surface is engaged with the port.

4. The self-stressed FRP tendon anchoring system according to claim 1, wherein: When the FRP bar is replaced by an FRP bar bundle composed of multiple FRP bars, the positioning ring is correspondingly replaced by a wire dividing plate, and a positioning hole is opened on the wire dividing plate corresponding to each FRP bar.

5. An anchoring method for the self-stressed FRP tendon anchoring system according to any one of claims 1 to 4, characterized in that: Including steps: The tail of the FRP bar is mechanically anchored by the wedge and the restraint ring and fixed to the tapered rear end of the anchor cup through the positioning ring. The front end of the FRP bar passes through the tapered front end of the anchor cup. Pour anchoring material into the inner conical rear end of the anchor cup and anchor the tail of the FRP bar to the inner conical rear end; After the anchor material is cured, a forward pre-tension is applied to the front end of the FRP reinforcement; pouring the anchoring material at the conical front end of the anchor cup under tension; After the anchor material reaches the required strength, unload the pre-tension and complete the anchoring.

6. The anchoring method according to claim 5, characterized in that: The steps for mechanically anchoring the tail of the FRP bar by using a wedge and a restraining ring include: A restraining ring is set at a certain distance from the end face of the FRP reinforcement tail; A split is formed at the tail of the FRP reinforcement symmetrically from the end surface to the restraint ring; Insert a wedge into the split.

7. The anchoring method according to claim 5, characterized in that: The step of fixing the tail of the FRP reinforcement to the tapered rear end of the anchor cup through a positioning ring comprises: A positioning ring is installed in the inner conical rear end of the anchor cup, and the outer ring surface of the positioning ring is engaged in the inner conical rear end; The FRP reinforcement passes through the inner annular surface of the positioning ring and is installed in the anchor cup.

Images