A CFRP cable bonded anchoring system and related methods

Abstract

This invention relates to the field of CFRP cable anchoring technology, specifically to a CFRP cable adhesive anchoring system and related methods. The anchoring system pre-embeds the CFRP cable in a steel anchor cylinder via an adhesive medium, setting the number of symmetrical segments N at the end to 2 or 4 to prevent segmentation from causing CFRP cable failure. The segment angle between each segment and the corresponding CFRP cable axis is greater than 0° and less than or equal to 6° to prevent excessively large segment angles from causing shear damage to the CFRP cable due to bending, which could lead to CFRP cable failure. The overall failure of the CFRP cable is controlled by the tensile strength of the free segment. Under these constraints, through the wedge-shaped and constraining effects of each segment and the adhesive medium, the bonding performance and anchoring efficiency of the anchoring system are improved based on the same steel anchor cylinder, CFRP cable, and adhesive medium.

Description

Technical Field

[0001] This invention relates to the field of CFRP cable anchoring technology, and in particular to a CFRP cable adhesive anchoring system and related methods. Background Technology

[0002] Modern long-span cable-stayed bridges generally use traditional steel cables as their core load-bearing components. However, steel cables suffer from problems such as susceptibility to corrosion and high self-weight in practical engineering applications. The corrosion susceptibility of steel cables necessitates multiple cable replacements during the bridge's design life, resulting in significant economic costs. Furthermore, their substantial self-weight causes a significant sag effect, reducing structural load-bearing efficiency and limiting further increases in bridge span. Carbon fiber-reinforced polymer (CFRP), a high-performance material composed of high-performance carbon fibers and a resin matrix, shows promising application prospects in civil engineering structures, especially those operating in harsh environments.

[0003] Compared with steel cables, CFRP cables have the following advantages: (1) They are corrosion-free, avoiding the problem of cable replacement caused by steel cable corrosion, reducing later maintenance costs, and having better economic performance; (2) They are lightweight, with a density of about 1 / 5 that of steel cables, which can reduce the sag effect caused by the weight of long cables and improve the overall structural stiffness; (3) They have high strength, with a tensile strength of up to 3000 MPa, which is about twice that of high-strength steel bars; (4) They have excellent fatigue resistance, with the fatigue strength of CFRP cables reaching 70% of their static strength, making them particularly suitable for cable tail cables that need to withstand higher stress amplitudes and short hangers that are subject to strong constraints.

[0004] Because CFRP cables are anisotropic materials with low transverse shear strength (less than 10% of their tensile strength), efficient anchoring of CFRP cables remains a key challenge in practical applications. Traditional clamp-type anchoring systems are prone to shear damage to CFRP cables due to the clamps, making efficient anchoring difficult. In contrast, adhesive anchoring systems rely on the bonding effect between the sleeve and the adhesive medium (chemical adhesive force + friction + mechanical interlocking force) to form the anchoring force. Compared to clamp-type anchoring systems, adhesive anchoring systems offer superior fatigue resistance, simpler construction, and are more suitable for engineering applications. An adhesive CFRP cable anchoring system consists of a CFRP cable (reinforcement), a steel anchor tube, and an adhesive medium. The steel anchor tube is located at the end of the CFRP cable (reinforcement), through which the CFRP cable (reinforcement) passes. The adhesive medium is injected between the steel anchor tube and the CFRP cable (reinforcement), bonding them together to form a unified anchoring system.

[0005] In actual bridge engineering, the cables used are often large in tonnage, which leads to high requirements for the pull-out resistance of bonded anchorage systems, requiring long and large anchorage lengths. Currently, the anchorage efficiency of CFRP cable bonded anchorage systems for effectively anchoring large-tonnage cables still needs improvement. Therefore, it is necessary to address the problems of low anchorage efficiency and long anchorage lengths in CFRP cable anchorage systems. Furthermore, when designing CFRP cable bonded anchorage systems, the differences in the force mechanisms and failure mechanisms between steel cable bonded anchorage systems and CFRP cable bonded anchorage systems prevent the direct application of performance analysis and optimization design methods from steel cable bonded anchorage systems to CFRP cable bonded anchorage systems, resulting in low design efficiency for CFRP cable bonded anchorage systems. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low anchoring efficiency, long anchoring length and large size of existing CFRP cable anchoring systems, and to provide a CFRP cable bonded anchoring system and related methods.

[0007] In a first aspect, the present invention provides a CFRP cable bonding anchoring system, comprising a steel anchor cylinder, an adhesive medium, and a plurality of CFRP cables. The plurality of CFRP cables pass through the steel anchor cylinder and are fixed within the steel anchor cylinder by the adhesive medium. At least one CFRP cable, embedded in the steel anchor cylinder by the adhesive medium, is symmetrically divided into N segments at its end, where N is the number of segments, which is 2 or 4. The segmentation angle between each segment and the axial direction of the corresponding CFRP cable is greater than 0° and less than or equal to 6°. The longitudinal length of each CFRP cable segment is l. s The ratio of the segment length R to the length l of the CFRP cable in the bonding medium is greater than 0 and less than or equal to 1.

[0008] Preferably, the splitting angle between each lobe and the axial direction of the corresponding CFRP cable is greater than or equal to 4° and less than or equal to 5°;

[0009] Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 3° and less than 4°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 2° and less than or equal to 3°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 1° and less than or equal to 2°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 0° and less than or equal to 1°.

[0010] Preferably, the CFRP cable comprises a plurality of unidirectionally arranged fibers and a matrix material, wherein the matrix material bonds all the unidirectionally arranged fibers of the CFRP cable together to form a whole; And / or, all the CFRP cables in each of the steel anchor tubes are symmetrically divided into N segments at their ends by pre-embedding them in the steel anchor tubes through the bonding medium.

[0011] Preferably, the matrix material is resin; And / or, The bonding medium is ultra-high performance concrete, cement mortar, or resin.

[0012] In a second aspect, the present invention provides a method for analyzing the anchoring performance of a CFRP cable bonded anchoring system. First, the bond strength of each segmented CFRP cable in the anchoring system is calculated using a formula for calculating the bond strength of each segmented CFRP cable. The calculation formula is as follows:

[0013] In the formula: Let k be the segmentation coefficient of the CFRP cable. When the number of segments N=2, k=1.0; when the number of segments N=4, k=1.06. R is the segment length ratio, R=1. s / l;l s l represents the longitudinal length of the CFRP cable segment; l represents the length of the CFRP cable in the bonding medium. This is the distance between the two ends of the valve body; f is the diameter of the CFRP cable. cu The compressive strength of the bonding medium cube; Then through bonding strength The anchoring performance of the CFRP cable bonded anchoring system described above is analyzed.

[0014] In a third aspect, the present invention provides a design method for a CFRP cable bonded anchoring system, which is used to design such a CFRP cable bonded anchoring system, comprising the following steps: S1. Determine the tensile strength f of the CFRP cable based on the proposed CFRP cable. t And the diameter d, based on the tensile strength f t The design value of the breaking load of the CFRP cable is determined by the diameter d and the safety factor n. π is the mathematical constant pi. Determine the cubic compressive strength f of the bonding medium based on the proposed bonding medium. cu ; Based on the dimensional requirements of the anchoring system at the engineering site, determine the maximum allowable diameter D and maximum anchoring length l of the anchoring system. max ; Preliminary estimate of the length of the CFRP cable in the bonding medium ; The initial target number of CFRP cable segments is N=4; Preliminary calculation of the distance between the two opposite ends of the anchoring system for and The smaller value in; S2. The pull-out bearing capacity of the anchoring system shall not be less than the design value of the breaking load of the CFRP cable. The requirement is that the pull-out bearing capacity of the anchoring system equals the design value of the breaking load of the CFRP cable. Solve for the longitudinal length l of the CFRP cable segment within the length l of the anchoring system. s Solve the equation as follows:

[0015] In the formula, R is the ratio of the segment lengths, R = l s / l; S3. The longitudinal length l of the solved CFRP cable segment s Judge the rationality: If l s Greater than This indicates that l s Unreasonable, unfeasible, design halted; If l s Less than or equal to Then judge Is it valid? if If it is less than or equal to 0.14, it indicates that l s Reasonable, determined l s h, N, and l are now complete; if If it is greater than 0.14, it indicates that l s This is unreasonable. First, decrease h, and then use the new h to return to step S2 to calculate l. s Repeat step S3 until l s Reasonable, determined l s h, N, and l are now complete.

[0016] Preferably, in step S3, when l s After making it reasonable, it also includes optimization step S4; S4, l determined in step S3 s Based on h, N, and l, adjust N to 2, and then execute steps S2 and S3 sequentially until l.s Reasonable, determined l s h, N, and l are now complete.

[0017] Preferably, in step S4, when N is adjusted to 2, the length l of the CFRP cable in the bonding medium is shortened simultaneously, and then steps S2 and S3 are executed sequentially until l is reached. s Reasonable, determined l s h, N, and l are now complete.

[0018] In a fourth aspect, the present invention provides a method for processing a CFRP cable bonded anchoring system, comprising the following steps: S01, Split all CFRP cable ends into a specified number N and longitudinal length l. s N is 2 or 4; S02. Position all CFRP cables inside the steel anchor cylinder so that the split angle of the CFRP cables remains at the specified angle; S03. Insert an end cap into one end of the steel anchor cylinder. The end cap has a center hole corresponding to the unsplit end of the CFRP cable. Then, pass the unsplit end of the CFRP cable through the corresponding center hole. Next, inject the bonding medium into the steel anchor cylinder. After observing that the vent hole continuously discharges bubble-free medium, stop the grouting. S04. After grouting is completed, cover the other end of the steel anchor cylinder with a cap. The cap is perforated at the corresponding position of each split CFRP cable to ensure that each split CFRP cable passes through it and to ensure that the end of the steel anchor cylinder is sealed without leakage. Then, allow the sealed steel anchor cylinder to cure naturally. S05. After the curing is completed, remove the end caps at both ends of the steel anchor cylinder and check that there is no peeling between the bonding medium and the interface between the CFRP cable and the steel anchor cylinder, and that the split segments of the CFRP cable are not loose. Then proceed to the subsequent loading test or engineering application. The CFRP cable bonded anchoring system is now complete.

[0019] Preferably, in step S01, a clamp is used to lock the longitudinal length ls mark, and a marking line is drawn for the path of the CFRP cable to be split as required by the number of segments N to be split. A saw is used to cut along the marking line, and the cutting speed is controlled to avoid the fiber bundles of the CFRP cable from delaminating, so as to ensure that the segments are undamaged after splitting. In step S02, all CFRP cables are positioned inside the steel anchor cylinder, and a positioner is placed between the segments of the CFRP cables to keep the segment angle of the CFRP cables at a specified angle. In step S04, when using ultra-high performance concrete (UHPC) as the bonding medium, after natural curing, the steel anchor cylinder after being filled with the bonding medium needs to be placed in a water tank for water bath curing.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a CFRP cable bonding anchoring system. The CFRP cable is pre-embedded in a steel anchor cylinder via a bonding medium, with the number of symmetrical segments N being 2 or 4. Symmetrical segmentation ensures smooth segmentation, and due to the elastic-brittle nature of CFRP, it avoids chain reactions between segments caused by an excessive number of segments, thus preventing CFRP cable failure. The segmentation angle between each segment and the corresponding CFRP cable axis is greater than 0° and less than or equal to 6°, preventing excessively large segmentation angles from causing shear damage due to bending, which could lead to CFRP cable failure. The overall failure of the CFRP cable is controlled by the tensile strength of the free segment. Under these constraints, through the wedge-shaped and constraining effects of each segment and the bonding medium, the bonding performance and anchoring efficiency can be improved using the same steel anchor cylinder, CFRP cable, and bonding medium.

[0021] 2. This invention provides a method for analyzing the anchoring performance of a CFRP cable bonded anchoring system. Through a self-developed formula for calculating the bond strength of each segmented CFRP cable in the anchoring system, the bond strength of each segmented CFRP cable in the CFRP cable bonded anchoring system can be quickly and accurately estimated. This allows for a relatively quick and accurate assessment of bonding strength. The anchoring performance of the CFRP cable bonded anchoring system described above is analyzed.

[0022] 3. This invention provides a design method for a CFRP cable bonded anchoring system, initially determining the length of the CFRP cable in the bonding medium. The number of CFRP cable segments and the distance between the ends of two relative segments in the anchoring system. The maximum allowable values ​​for each parameter are used as a condition, and the tensile strength of the anchoring system is not less than the design value of the breaking load of the CFRP cable. The requirement is that the pull-out bearing capacity of the anchoring system equals the design value of the breaking load of the CFRP cable. Solve for the longitudinal length l of the CFRP cable segment within the length l of the anchoring system. s Then, the longitudinal length l of the CFRP cable segment is calculated. s To judge the reasonableness, if l s Greater than This indicates that l s Unreasonable, unfeasible, design halted; if l s Less than or equal to Then judge Whether it is true or false, if true, then it is determined.s The design is complete with h, N, and l. If the condition is not met, h needs to be reduced. The new h is then used to solve for the longitudinal length l of the CFRP cable segments within the length l of the anchoring system. s Then, determine the longitudinal length l of the CFRP cable segment within the solved anchoring system. s Reasonable, determined l s h, N, and l are now complete.

[0023] 4. This invention provides a processing method for a CFRP cable bonded anchoring system, which can process the CFRP cable bonded anchoring system with high quality, so that the bonding strength and anchoring efficiency can meet the design requirements. Attached Figure Description

[0024] Figure 1 An axial sectional view of a CFRP cable bonded anchoring system. Figure 1 The structure is symmetrical in the left and right directions. Figure 2 for Figure 1 Sectional view at point AA; Figure 3 for Figure 1 Sectional view at point BB; Figure 4 An axial sectional view (one end) of another CFRP cable bonded anchoring system. Figure 5 for Figure 4 A cross-sectional view at point A'-A'; Figure 6 for Figure 4 Another sectional view at point A'-A'; Figure 7 This is a dimensional schematic diagram of a CFRP cable bonding anchoring system; Figure 8 This is a flowchart illustrating a design method for a CFRP cable bonded anchoring system.

[0025] The markings in the diagram are: 1. Steel anchor cylinder; 2. Bonding medium; 3. CFRP cable; 4. Lobe; 5. Anchor plate; 6. Nut. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0027] Unless otherwise specified, the terms "upper," "lower," "left," "right," "center," "inner," and "outer," etc., used in the description of specific embodiments of the present invention to indicate orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is usually placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, and for enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0028] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," "parallel," and "coaxial" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, parallel, or coaxial. Slight tilt or deviation is permissible, as long as it does not affect the normal function of the relevant component. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," not that the structure must be perfectly horizontal; a slight tilt is acceptable. "Coaxial" means that two components are arranged as coaxially as possible, allowing them to move coaxially or approximately coaxially when their relative positions change. Alternatively, it can be simplified to mean that the corresponding device / component / element, when arranged in "horizontal," "vertical," "suspended," "parallel," or "coaxial" directions, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. For example, the deviation in the "coaxial" direction is controlled within 0.2-1mm, preferably within 0.2-0.5mm. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the solution of the present invention.

[0029] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0030] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as two, three, four, five, six, seven, eight, or nine, and can even exceed nine.

[0031] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to connection methods commonly used in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0032] Example 1 like Figures 1-3 As shown, this embodiment provides a CFRP cable bonding anchoring system, including a steel anchor cylinder 1, a bonding medium 2, and several CFRP cables 3. The number of CFRP cables 3 can be one. (Refer to...) Figures 4-6 It is set at the center of the steel anchor cylinder 1; the number of CFRP cables 3 can also be two or more, for example, multiple CFRP cables 3 can be referred to Figures 1-3 , Figure 1 In this structure, both ends of the CFRP cable 3 need to be anchored through steel anchor cylinders 1 and bonding medium 2. Several CFRP cables 3 pass through the steel anchor cylinders 1 and are fixed inside the steel anchor cylinders 1 through the bonding medium 2. Furthermore, the CFRP cables 3 are connected to the anchor plates 5 pre-set in the actual structure via nuts 6.

[0033] Conventional CFRP cables 3 are continuous at the ends without segmentation. In this embodiment, at least one CFRP cable 3 is symmetrically segmented into N segments 4 at its end via the bonding medium 2 embedded in the steel anchor cylinder 1, where N is the number of segments (2 or 4). The segmentation results in an even number of symmetrical segments 4, ensuring uniformity and enabling the segmentation operation. Furthermore, due to the brittle and elastic characteristics of CFRP, the number of segments does not exceed 4 to prevent cascading failure between segments and thus avoid CFRP cable 3 failure due to excessive segmentation. Figure 3 and Figure 5 As shown, the CFRP cable 3, embedded in the steel anchor cylinder 1 via the bonding medium 2, is symmetrically divided into two segments 4 at its end. However, not the entire length embedded in the steel anchor cylinder 1 necessarily requires segmentation. The longitudinal length l of the segmented CFRP cable 3 is... s Less than or equal to the length l of the CFRP cable 3 in the bonding medium 2; such as Figure 6 As shown, the CFRP cable 3 is pre-embedded in the steel anchor cylinder 1 through the bonding medium 2 and its end is symmetrically divided into 4 petals 4.

[0034] According to conventional theory, the larger the splitting angle between the petal 4 and the corresponding CFRP cable 3 along the axial direction, the stronger the constraint effect. However, research shows that the splitting angle between each petal 4 and the corresponding CFRP cable 3 along the axial direction is greater than 0° and less than or equal to 6°. This avoids excessively large splitting angles that could cause shear damage to the CFRP cable due to bending, leading to CFRP cable failure. The overall failure of the CFRP cable is controlled by the tensile strength of the free section of the CFRP cable, which refers to the portion between the anchoring systems at both ends of the CFRP cable. Under the above constraints, through the wedge-shaped action and constraint effect of each petal 4 and the bonding medium, the bonding strength and anchoring efficiency can be improved based on the same steel anchor cylinder 1, CFRP cable 3, and bonding medium 2. The longitudinal length l of the CFRP cable splitting... s The ratio of the segment length R to the length l of the CFRP cable in the bonding medium is greater than 0 and less than or equal to 1.

[0035] Wherein, the splitting angle between each lobe and the axial direction of the corresponding CFRP cable is greater than or equal to 4° and less than or equal to 5°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 3° and less than 4°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 2° and less than or equal to 3°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 1° and less than or equal to 2°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 0° and less than or equal to 1°.

[0036] In a preferred embodiment, the splitting angle between each lobe 4 and the axial direction of the corresponding CFRP cable 3 is greater than or equal to 4° and less than or equal to 5°, which best improves its bonding strength and anchoring performance.

[0037] In a preferred embodiment, all the CFRP cables 3 in each steel anchor cylinder 1 are pre-embedded in the steel anchor cylinder 1 through the bonding medium 2 and symmetrically divided into N petals 4 at their ends, resulting in the best anchoring effect.

[0038] In an optional embodiment, the CFRP cable 3 comprises a plurality of unidirectionally arranged fibers and a matrix material. The matrix material bonds all the unidirectionally arranged fibers of the CFRP cable 3 into a whole, which facilitates the segmentation operation along the fiber axis and avoids damage to the internal properties of the CFRP cable 3.

[0039] In an optional embodiment, the matrix material is a resin matrix.

[0040] In an optional embodiment, the bonding medium 2 is ultra-high performance concrete, cement mortar, or resin, etc.

[0041] This embodiment describes a CFRP cable bonded anchoring system. After the CFRP cable end is split, the contact area between the CFRP cable and the bonding medium increases, thereby increasing the total tensile strength between the CFRP cable and the bonding medium, and correspondingly, its nominal average bond strength increases. The split CFRP cable end forms separate lobes, each lobe forming a certain angle with the steel anchor cylinder. During pull-out, the bonding medium between the lobes creates a wedge-like effect, thus providing lateral restraint to the CFRP cable and improving the mechanical interlocking effect and pull-out bearing capacity of the anchoring system.

[0042] Based on the above-mentioned improvement mechanism, the performance improvement level of the CFRP cable anchoring system needs to be controlled by three parameters.

[0043] A. The number of segments N in a CFRP cable. The more segments (N) there are in the anchoring system, the larger the contact area between the CFRP cable and the bonding medium, resulting in a significant performance improvement. However, due to the brittle-elastic characteristics of CFRP cables, cascading failures may occur between the segments after splitting, meaning the failure of one segment can cause all the other segments to fail. Furthermore, the more segments there are, the larger the anchor cylinder becomes; therefore, in practical engineering, the design should be based on the dimensions of the anchoring zone. Thus, the number of segments (N) in the cable should ideally be controlled to within four segments.

[0044] B. The angle of the splitting lobes α The improvement in anchoring system performance initially increases and then decreases with increasing splitting angle α. When the splitting angle α is small, increasing the angle α promotes the wedge-shaped and constraining effect between each lobe and the bonding medium, thereby improving anchoring performance. However, once the splitting angle α increases to a certain level, shear damage caused by bending in the CFRP cable leads to CFRP cable failure. Thus, the overall failure of the CFRP cable is controlled by the tensile strength of the free segment of the CFRP cable, rather than by the performance of the anchoring system.

[0045] C. The longitudinal length of the CFRP cable split into 3 segments l s The performance improvement level of the anchoring system varies with the longitudinal length of the segment l s The improvement is significant, mainly due to the longitudinal length l of the segments. s The increased contact area between the CFRP cable and the bonding medium leads to a corresponding increase in pull-out bearing capacity. However, the longitudinal length l of the segment... s The lobing angle α should be determined in conjunction with the CFRP reinforcement to ensure that the radius of curvature of the CFRP reinforcement within the anchorage system is not too small, which could lead to breakage.

[0046] Example 2 like Figures 1-7 As shown, this embodiment provides a method for analyzing the anchoring performance of a CFRP cable bonded anchoring system. This method is based on a given CFRP cable bonded anchoring system to evaluate whether the anchoring system can effectively anchor the CFRP cable. First, the bond strength of each segmented CFRP cable 3 in the CFRP cable bonded anchoring system described in Embodiment 1 is calculated using the formula for calculating the bond strength of each segmented CFRP cable in the anchoring system. The unit is MPa, and the calculation formula is as follows:

[0047] In the formula: Let k be the segmentation coefficient of CFRP cable 3. When the number of segments N=2, k=1.0; when the number of segments N=4, k=1.06. R is the segment length ratio, R=1. s / l;l s l represents the longitudinal length of the CFRP cable 3 segment, in mm; l represents the length of the CFRP cable 3 in the bonding medium 2, in mm. h represents the distance between the two valve bodies 4, in mm. s The ratio is related to the splitting angle; f is the diameter of CFRP cable 3, in mm; cu The unit is the cubic compressive strength of the bonding medium 2, in MPa; Then through bonding strength The anchoring performance of the CFRP cable bonded anchoring system described above is analyzed, specifically: By bond strength Calculate the pull-out capacity of each segmented CFRP cable in the anchoring system: , The unit is N; π is the mathematical constant pi. Calculate the design breaking load of each segmented CFRP cable: , The unit is N; n is the safety factor; f t The tensile strength of CFRP cable 3 is expressed in MPa. The calculated tensile strength of each segmented CFRP cable is compared with that of the CFRP cable. Design value of breaking load of CFRP cable Comparison: like If so, the pull-out bearing capacity of the anchoring system meets the requirements; like If the anchoring system does not meet the pull-out bearing capacity requirements, then the anchoring system will not meet the requirements.

[0048] The anchoring performance analysis method for a CFRP cable bonded anchoring system described in this embodiment can quickly and accurately estimate the bond strength of each segmented CFRP cable in the anchoring system using a self-developed formula for calculating the bond strength of each segmented CFRP cable. This allows for a relatively quick and accurate assessment of bonding strength. The pull-out bearing capacity of each segmented CFRP cable in the CFRP cable bonded anchoring system described above was analyzed. Specific test data are shown in Table 1.

[0049] Table 1. Experimental Data

[0050] In Table 1, specimen number I represents a straight rib anchorage system; N and the following number represent a segmented anchorage system and the number of segments, respectively, such as N2 indicating 2 segments and N4 indicating 4 segments; 5d, 10d, and 15d all represent the length l of CFRP cable 3 in the bonding medium 2, which is also the anchorage length, such as 5d indicating an anchorage length of 5 times the CFRP cable diameter d; α and the following number represent the segment opening angle, such as α4 indicating a segment opening angle of 4°; R and the following number represent the reciprocal of the ratio of the anchorage length of the segmented part to the total anchorage length of the anchorage system, such as R3 indicating l s / l=1 / 3. C and the following numbers represent the thickness of the reinforcement protective layer, such as C2 indicating that the protective layer thickness is twice the CFRP cable diameter d. Table 1 shows that the protective layer thickness has little effect on the bond strength of the anchoring system; therefore, the bond strength... The calculation formula does not take into account the influence of the CFRP cable protective layer thickness, and the error between the predicted value and the measured value is small and within an acceptable range, which enables rapid prediction, improves the speed of anchoring performance analysis of the anchoring system, and thus saves construction time.

[0051] Example 3 For a CFRP cable, its tensile strength is Anchoring is performed with a diameter of d.

[0052] In direct anchoring (non-segmented anchoring), the formula for calculating the bond strength of the anchoring system is:

[0053] In the formula: l is the length of the CFRP cable in the bonding medium, i.e., the anchorage length; This refers to the cubic compressive strength of the bonding medium, expressed in MPa, such as the cubic compressive strength of concrete. The critical anchorage length is defined as the length at which the CFRP cable breaks and the anchorage system fails simultaneously (i.e., when the bond strength is reached). The unit is mm. Therefore, the following equilibrium conditions can be applied to... Perform the calculation:

[0054] Therefore, the tensile strength can be calculated. The compressive strength of a CFRP cable with diameter d in a bonding medium cube The minimum anchorage length required to ensure that the reinforcing bar breaks without slippage of the anchorage system. for:

[0055] Based on the above approach, the design process for a straight rib CFRP anchorage system is as follows: Determine its tensile strength based on the CFRP cable used and the bonding medium to be used. , Reinforcing bar diameter d, and compressive strength of the bonding medium cube Safety factor n.

[0056] Based on the above formula, calculate the critical anchorage length of the anchorage system. The unit is mm.

[0057] Taking safety factors into account, the required anchorage length of the anchorage system is finally determined. , The unit is mm.

[0058] The CFRP cable bonding anchoring system described in this invention is a segmented anchoring system. The bonding strength of the segmented anchoring system is based on the bonding strength of the straight bar anchoring system.

[0059] Specifically, based on the formula for calculating the bond strength of a straight rib anchorage system, and considering the influence of parameters such as the number of segments (N=2 or 4), the segment angle α (reflected by the segment distance, i.e., the distance h between the ends of two relative segments), and the segment length (i.e., the longitudinal length ls of the CFRP cable segment), a formula for calculating the bond strength of each segmented CFRP cable in a segmented anchorage system is proposed:

[0060]

[0061] In the formula: The longitudinal length of the CFRP cable segment is given by R, in mm; R is the segment length ratio, i.e., ls / l; h is the distance between the ends of two relative segments, in mm; k is the segmentation coefficient, which is 1.0 when N=2 and 1.06 when N=4. Furthermore, The segmentation angle should not be too large to prevent the reinforcing material from breaking.

[0062] Based on the above formula, the design process for a segmented anchoring system is proposed: like Figures 1-8 As shown, this invention provides a design method for a CFRP cable bonded anchoring system, used to design the CFRP cable bonded anchoring system described in Example 1, comprising the following steps: S1. Determine the tensile strength f of CFRP cable 3 based on the proposed CFRP cable 3. t And the diameter d, based on the tensile strength f t The design value of the breaking load of CFRP cable 3 is determined by the diameter d and the safety factor n. π is the mathematical constant pi. The cubic compressive strength f of the proposed bonding medium 2 is determined based on the bonding medium 2. cu ; Based on the dimensional requirements of the anchoring system at the engineering site, determine the maximum allowable diameter D and maximum anchoring length l of the anchoring system. max ; Preliminary calculation of the length of CFRP cable 3 in bonding medium 2 Its physical meaning is: the anchorage length of the initially proposed segmented anchorage system is the maximum allowable anchorage system size; The initial design number of CFRP cable segments is N=4; Preliminary calculation of the distance between the two relative petals 4 of the anchoring system for and The smaller value in the equation refers to the distance between the two relative petals 4 of the anchoring system. The following conditions must be met simultaneously: The physical meaning is: after the segments are split, the distance between the edge of the segment and the outer steel anchor cylinder is not less than one CFRP cable diameter d; The physical meaning is: to prevent the CFRP cable 3 from breaking.

[0063] S2. The pull-out bearing capacity of the anchoring system shall not be less than the design value of the breaking load of the CFRP cable 3. The requirement is that the pull-out bearing capacity of the anchoring system be equal to the design value of the tensile breaking load of CFRP cable 3. Solve for the longitudinal length l of the CFRP cable segment 3 within the length l of the anchoring system.s Solve the equation as follows:

[0064] In the formula, R is the ratio of the segment lengths, R = l s / l; the equation is l s A univariate function can be solved by finding l. s ; S3, the longitudinal length l of the 3-segment CFRP cable being solved. s Judge the rationality: First judge Is it true or false? If not, then l s Greater than This means that the length of the segments in the surface anchoring system needs to be greater than the length of the anchoring system itself. However, this is not feasible. Even if a segmented anchoring system is used, it cannot anchor a CFRP cable with a design load of F. This indicates that... s If the design is unreasonable and unfeasible, the design should be stopped. In actual engineering, it is necessary to improve the site conditions and increase the allowable dimensions of the anchoring system.

[0065] If l s Less than or equal to Then judge Is it valid? if If it is less than or equal to 0.14, it indicates that l s Reasonable, determined l s h, N, and l are now complete; if If it is greater than 0.14, it indicates that l s This is unreasonable. First, decrease h, and then use the new h to return to step S2 to calculate l. s Repeat step S3 until l s Reasonable, determined l s h, N, and l are now complete.

[0066] In a preferred embodiment, in step S3, when l s After making it reasonable, it also includes optimization step S4; S4, l determined in step S3 s Based on h, N, and l, we perform fine-tuning as follows: Considering the ease of engineering operation, we adjust N to 2, then k is set to 1.0. Then we execute steps S2 and S3 sequentially until l s Reasonable, determined l s h, N, and l are now complete.

[0067] Furthermore, in step S4, considering the ease of engineering operation, after adjusting N to 2, the length l of the CFRP cable 3 in the bonding medium 2 is shortened simultaneously. Then, steps S2 and S3 are executed sequentially until l is reached. s Reasonable, determined l s h, N, and l are now complete.

[0068] This embodiment describes a design method for a CFRP cable bonded anchoring system, initially determining the length of the CFRP cable 3 in the bonding medium 2. The number of segments in the CFRP cable and the distance between two relative segments in the anchoring system. The maximum values ​​allowed for each parameter are used as a condition, and the tensile strength of the anchoring system is not less than the design value of the breaking load of the CFRP cable 3. The requirement is that the pull-out bearing capacity of the anchoring system equals the design value of the breaking load of CFRP cable 3. Solve for the longitudinal length l of the CFRP cable segment 3 within the length l of the anchoring system. s Then, the longitudinal length l of the 3-segment CFRP cable is calculated. s To judge the reasonableness, if l s Greater than This indicates that l s Unreasonable, unfeasible, design halted; if l s Less than or equal to Then judge Whether it is true or false, if true, then it is determined. s If the design of h, N, and l is not valid, then h needs to be reduced. The new h is then used to solve for the longitudinal length l of the CFRP cable segment within length l of the anchoring system. s Then, determine the longitudinal length l of the CFRP cable 3 segments within the solved anchoring system. s Reasonable, determined l s The design of h, N, and l is completed. It can be adjusted step by step from large to small to ensure that the final design meets the requirements. It can be adjusted more quickly until the requirements are met, resulting in high design efficiency.

[0069] The research results show that, under the same anchorage length l, the segmented anchorage method for anchoring CFRP cables 3 can increase the bond strength by 31% to 44% compared with the straight bar anchorage method for CFRP cables. Therefore, the segmented anchorage system has higher anchorage efficiency; under the same conditions, the anchorage system length l can be reduced, thereby reducing construction difficulty and cost.

[0070] Example 4 This embodiment provides a processing method for a CFRP cable bonded anchoring system, used to process the CFRP cable bonded anchoring system described in Embodiment 1, including the following steps: S01. Split the CFRP cable 3 at one end into a specified number N and longitudinal length l. s N is 2 or 4; Before step S01, based on the performance improvement requirements, determine the number N and length l of the segments that need to be split at the end of the CFRP cable. s And angle α, which can be determined by the distance between the two valve ends. Control and select steel anchor cylinders of appropriate size.

[0071] For example: Based on the performance requirements of the anchoring system, with a nominal diameter of d for the CFRP cable, determine the key parameters: Anchoring method: Split anchoring; Number of lobes N: 2 or 4 lobes; Opening angle α: 2°, 4° or 6°, etc.; Split length ratio: ls / l = 1, 1 / 2 or 1 / 3, etc. (ls is the longitudinal length of the CFRP cable split, i.e., the split length; l is the length of the CFRP cable in the bonding medium, i.e., the anchorage length). Anchorage length: l = 10d, 15d or 20d, etc.

[0072] In an optional implementation, the anchorage length is determined according to the design. Calculate the corresponding s (e.g.) =120mm s / When = 1 / 2, (s=60mm); In step S01, a clamp such as a high-strength water pipe clamp (suitable for cable body with diameter d) is used to lock the longitudinal length ls mark. According to the required number of segments N to be split, a marking line is drawn for the path of the CFRP cable 3 to be split. A saw is used to slowly cut along the marking line, controlling the cutting speed to avoid the fiber bundles of the CFRP cable 3 from delamination, ensuring that the segments are undamaged after splitting, and achieving accurate length control. S02. Position all CFRP cables 3 inside the steel anchor cylinder 1 so that the split angle of the CFRP cables 3 is maintained at the specified angle. In an optional implementation, in step S02, all CFRP cables 3 are positioned inside the steel anchor cylinder 1, according to the opening angle (2° / 4° / 6°). Positioners are placed between the petals 4 of the CFRP cable 3 to keep the petal angle of the CFRP cable 3 at a specified angle; for example, when the number of petals N is 4, cross positioners are placed between the petals to achieve angle control. S03. Insert an end cap with a corresponding center hole at the unsplit end of the CFRP cable 3 into one end of the steel anchor cylinder 1. Then, pass the unsplit end of the CFRP cable 3 through the corresponding center hole. Next, inject the bonding medium 2 into the steel anchor cylinder 1. The bonding medium can be ultra-high performance concrete, cement mortar, or resin, etc. After observing that the vent hole continuously discharges bubble-free medium, stop the grouting. S04. After grouting is completed, cover the other end of the steel anchor cylinder 1 with a cap. The cap is perforated at the corresponding position of each of the split lobes 4 of the CFRP cable 3, ensuring that each of the split lobes 4 of the CFRP cable 3 passes through, and ensuring that the end of the steel anchor cylinder 1 is sealed without leakage. Then, place the sealed steel anchor cylinder 1 vertically in the positioning device and allow it to cure naturally. For example, allow it to cure naturally for 24 hours. If ultra-high performance concrete (UHPC) is used as the bonding medium, place the naturally cured anchoring system in a water tank at a temperature of 95°C for 48 hours of water bath curing until the strength reaches the design requirements.

[0073] S05. After the maintenance is completed, remove the end caps at both ends of the steel anchor cylinder 1, check that there is no peeling between the bonding medium 2 and the interface between the CFRP cable 3 and the steel anchor cylinder 1, and that the split segments 4 of the CFRP cable 3 are not loose. Then proceed to the subsequent loading test or engineering application. The CFRP cable bonded anchoring system is now complete.

[0074] The processing method of the CFRP cable bonded anchoring system described in this embodiment can process the CFRP cable bonded anchoring system with high quality, so that the anchoring performance can meet the design requirements.

[0075] This invention addresses the problems of long anchorage length and low efficiency in commonly used bonded anchorage systems for CFRP cables. It provides a bonded anchorage system and related methods for CFRP cables. The CFRP cable is split into two or four segments at the anchorage end. Each segment is opened at a certain angle, fixed, and pre-embedded in a steel anchor cylinder. Then, an adhesive medium is poured into the steel anchor cylinder, forming a segmented bonded anchorage system for CFRP cables. This invention increases the bonding area between the CFRP cable and the adhesive medium. Furthermore, the wedging effect generated by the adhesive medium sliding between the segments under load effectively enhances the mechanical interlocking and friction between the CFRP cable and the adhesive medium, thus significantly improving the bonding performance of the anchorage system. It solves the problems of large size, long anchorage length, and low bonding strength in CFRP cable anchorage systems, significantly improving the anchorage performance of bonded anchorage systems for CFRP cables while reducing construction costs and difficulty.

[0076] 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, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A CFRP cable bonding anchoring system, comprising a steel anchor cylinder, an adhesive medium, and a plurality of CFRP cables, wherein the plurality of CFRP cables pass through the steel anchor cylinder and are fixed within the steel anchor cylinder by the adhesive medium, characterized in that, At least one of the CFRP cables is pre-embedded in the steel anchor cylinder through the bonding medium, and its end is symmetrically divided into N segments, where N is the number of segments, which can be 2 or 4. The segmentation angle between each segment and the axial direction of the corresponding CFRP cable is greater than 0° and less than or equal to 6°. The longitudinal length l of the CFRP cable segment is... s The ratio of the segment length R to the length l of the CFRP cable in the bonding medium is greater than 0 and less than or equal to 1.

2. The CFRP cable bonding anchoring system according to claim 1, characterized in that, The splitting angle between each lobe and the corresponding CFRP cable axis is greater than or equal to 4° and less than or equal to 5°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 3° and less than 4°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 2° and less than or equal to 3°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 1° and less than or equal to 2°; Alternatively, the splitting angle between each lobe and the corresponding CFRP cable axis is greater than 0° and less than or equal to 1°.

3. A CFRP cable bonding anchoring system according to claim 1 or 2, characterized in that, The CFRP cable comprises a plurality of unidirectionally arranged fibers and a matrix material, wherein the matrix material bonds all the unidirectionally arranged fibers of the CFRP cable together to form a whole. And / or, all the CFRP cables in each of the steel anchor tubes are symmetrically divided into N segments at their ends by pre-embedding them in the steel anchor tubes through the bonding medium.

4. The CFRP cable bonding anchoring system according to claim 3, characterized in that, The matrix material is resin; And / or, The bonding medium is ultra-high performance concrete, cement mortar, or resin.

5. A method for analyzing the anchoring performance of a CFRP cable bonded anchoring system, characterized in that, First, calculate the bond strength of each segmented CFRP cable in the CFRP cable bonded anchoring system according to any one of claims 1-4 using the bond strength calculation formula for each segmented CFRP cable in the anchoring system. The calculation formula is as follows: In the formula: Let k be the segmentation coefficient of the CFRP cable. When the number of segments N=2, k=1.0; when the number of segments N=4, k=1.

06. R is the segment length ratio, R=1. s / l;l s l represents the longitudinal length of the CFRP cable segment; l represents the length of the CFRP cable in the bonding medium. This is the distance between the two ends of the valve body; f is the diameter of the CFRP cable. cu The compressive strength of the bonding medium cube; Then through bonding strength The anchoring performance of the CFRP cable bonded anchoring system described above is analyzed.

6. A design method for a CFRP cable bonded anchoring system, characterized in that, For designing a CFRP cable bonded anchoring system as described in any one of claims 1-4, the following steps are included: S1. Determine the tensile strength f of the CFRP cable based on the proposed CFRP cable. t And the diameter d, based on the tensile strength f t The design value of the breaking load of the CFRP cable is determined by the diameter d and the safety factor n. π is the mathematical constant pi. Determine the cubic compressive strength f of the bonding medium based on the proposed bonding medium. cu ; Based on the dimensional requirements of the anchoring system at the engineering site, determine the maximum allowable diameter D and maximum anchoring length l of the anchoring system. max ; Preliminary estimate of the length of the CFRP cable in the bonding medium ; The initial target number of CFRP cable segments is N=4; Preliminary calculation of the distance between the two opposite ends of the anchoring system for and The smaller value in; S2. The pull-out bearing capacity of the anchoring system shall not be less than the design value of the breaking load of the CFRP cable. The requirement is that the pull-out bearing capacity of the anchoring system equals the design value of the breaking load of the CFRP cable. Solve for the longitudinal length l of the CFRP cable segment within the length l of the anchoring system. s Solve the equation as follows: In the formula, R is the ratio of the segment lengths, R=l s / l; S3. The longitudinal length l of the solved CFRP cable segment s Judge the rationality: If l s Greater than This indicates that l s Unreasonable, unfeasible, design halted; If l s Less than or equal to Then judge Is it valid? if If it is less than or equal to 0.14, it indicates that l s Reasonable, determined l s h, N, and l are now complete; if If it is greater than 0.14, it indicates that l s This is unreasonable. First, decrease h, and then use the new h to return to step S2 to calculate l. s Repeat step S3 until l s Reasonable, determined l s h, N, and l are now complete.

7. The design method of a CFRP cable bonded anchoring system according to claim 6, characterized in that, In step S3, when l s After making it reasonable, it also includes optimization step S4; S4, l determined in step S3 s Based on h, N, and l, adjust N to 2, and then execute steps S2 and S3 sequentially until l. s Reasonable, determined l s h, N, and l are now complete.

8. The design method of a CFRP cable bonded anchoring system according to claim 7, characterized in that, In step S4, when N is adjusted to 2, the length l of the CFRP cable in the bonding medium is shortened simultaneously, and then steps S2 and S3 are executed sequentially until l is reached. s Reasonable, determined l s h, N, and l are now complete.

9. A processing method for a CFRP cable bonded anchoring system, characterized in that, For processing a CFRP cable bonded anchoring system as described in any one of claims 1-4, the following steps are included: S01, Split all CFRP cable ends into a specified number N and a longitudinal length l of the CFRP cable segments. s N is 2 or 4; S02. Position all CFRP cables inside the steel anchor cylinder so that the split angle of the CFRP cables remains at the specified angle; S03. Insert an end cap into one end of the steel anchor cylinder. The end cap has a center hole corresponding to the unsplit end of the CFRP cable. Then, pass the unsplit end of the CFRP cable through the corresponding center hole. Next, inject the bonding medium into the steel anchor cylinder. After observing that the vent hole continuously discharges bubble-free medium, stop the grouting. S04. After grouting is completed, cover the other end of the steel anchor cylinder with a cap. The cap is perforated at the corresponding position of each split CFRP cable to ensure that each split CFRP cable passes through it and to ensure that the end of the steel anchor cylinder is sealed without leakage. Allow the sealed steel anchor cylinder to cure naturally. S05. After the curing is completed, remove the end caps at both ends of the steel anchor cylinder and check that there is no peeling between the bonding medium and the interface between the CFRP cable and the steel anchor cylinder, and that the split segments of the CFRP cable are not loose. Then proceed to the subsequent loading test or engineering application. The CFRP cable bonded anchoring system is now complete.

10. A processing method for a CFRP cable bonded anchoring system according to claim 9, characterized in that, In step S01, a clamp is used to lock the longitudinal length ls mark. According to the required number of lobes N to be split, a mark line is drawn for the path of the CFRP cable to be split. A saw is used to cut along the mark line, and the cutting speed is controlled to avoid the fiber bundles of the CFRP cable from delaminating, ensuring that the lobes are undamaged after splitting. In step S02, all CFRP cables are positioned inside the steel anchor cylinder, and a positioner is placed between the segments of the CFRP cables to keep the segment angle of the CFRP cables at a specified angle. In step S04, when using ultra-high performance concrete (UHPC) as the bonding medium, after natural curing, the steel anchor cylinder after being filled with the bonding medium needs to be placed in a water tank for water bath curing.

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