Multilayer FRP plate anchoring device and anchoring method

Abstract

The present invention discloses a multi-layer FRP plate anchoring device and anchoring method, wherein the anchoring method includes: an anchor plate, having an anchoring channel with an isosceles trapezoidal cross-sectional shape; a pad, a metal plate filled between the two layers of FRP plates in the anchoring area; a clip, filled between the surface of the upper and lower FRP plates and the anchoring channel; the clip is a wedge-shaped block with a small front end and a large rear end; a top plate, a square metal plate with square holes; connecting the pad and the clip to transmit shear force; a pin, a device for fixing the multi-layer pad and transmitting force from the pad to the top plate; the pin is a semi-cylinder. The multi-layer FRP plate anchoring method disclosed by the present invention can effectively anchor multi-layer composite material thin plates, and the anchoring length is shortened compared to FRP thick plates with the same cross-sectional area. The FRP plate undergoes ideal explosive destruction, which can give full play to the tensile strength of the material.

Description

Technical Field

[0001] The invention discloses a multi-layer FRP plate anchoring method, which belongs to the field of composite material anchoring and is a specially designed multi-layer anchoring method. Background Art

[0002] With the development of my country's economy, the application of fiber-reinforced composite materials in the construction sector is becoming increasingly widespread. Prestressed FRP slats are often used in building reinforcement and bridge cables, leveraging the material's advantages of lightweight, high strength, corrosion resistance, and fatigue resistance. These advantages enable buildings to meet updated requirements, extending building lifespans and increasing bridge spans. However, because FRP's lateral compressive and shear resistance is significantly lower than its tensile strength, anchoring FRP slats remains a challenge.

[0003] Narrow-section FRP sheets cannot meet the current requirements for large-tonnage cables and large-tonnage reinforcement. When using thick FRP sheets for anchoring, the anchor length is long and the shear lag effect can easily cause the FRP sheet to crush at the anchor outlet. Furthermore, thick FRP sheets are difficult to coil and transport when they are long. Therefore, it is more reasonable to use multiple narrow-section FRP sheets for simultaneous anchoring. For multi-layer FRP sheets, the required anchoring force is high, and given a certain anchoring length, the anchorage can easily fail due to asynchronous force. Therefore, it is necessary to develop an anchor that can effectively and simultaneously anchor multiple layers of FRP sheets. Summary of the Invention

[0004] This invention addresses the problems of existing prestressed FRP plate clip-type anchors, which are unable to effectively anchor large-tonnage FRP strips and require long anchoring lengths. By doing so, a multi-layer FRP plate anchoring method is proposed. This anchoring method can simultaneously anchor multiple prestressed FRP sheets, allowing each FRP sheet to be subjected to coordinated force, alleviating stress concentration, significantly shortening the anchoring length, and increasing the overall anchoring capacity of the anchor.

[0005] The specific scheme of the present invention is:

[0006] A multi-layer FRP plate anchoring device, comprising:

[0007] An anchor plate having an anchor channel with an isosceles trapezoidal cross-sectional area;

[0008] Clips, filling between the upper and lower surfaces of the outermost FRP plate and the anchor channel;

[0009] Pads, laid between every two layers of FRP panels in the anchoring area;

[0010] A top plate having two action portions and a connecting portion; the action portions are in contact with the rear end of the clip; and the connecting portion is used to connect to the pad;

[0011] A connecting piece is provided at the connecting portion of the top plate and is used to connect the top plate and the backing plate into a whole.

[0012] The connecting portion includes a hole, and the pad passes through the hole.

[0013] The connecting part also includes a semicircular groove; a semicircular pin hole adapted to the shape of the semicircular groove is provided on the pad; the connecting piece is a semicircular pin, which is provided in the semicircular groove of the connecting part and passes through the semicircular pin hole on the pad.

[0014] The contact portions of both sides of the backing plate with the FRP plate are provided with tooth patterns to increase the friction between the backing plate and the FRP plate.

[0015] The front half of the pad is inlaid with a rubber pad on the contact surface with the FRP plate, and the middle half is inlaid with an aluminum alloy plate on the contact surface with the FRP plate.

[0016] A multi-layer FRP plate anchoring method, using a multi-layer FRP plate anchoring device for anchoring, comprising:

[0017] A pad is sandwiched between every two layers of FRP plates, with the end of the pad extending 50-80 mm beyond the FRP plates;

[0018] Place the clip on the outer surface of the outermost FRP plate, with the front end of the clip flush with the front end of the backing plate, and apply lubricant on the outer surface of the clip;

[0019] Push the multilayer FRP plate with the clip and backing plate into the anchor plate from the large opening end, so that the front end of the clip extends 10-20 mm beyond the small opening end of the anchor plate;

[0020] Place the top plate at the rear end of the clamp, pass the end of the pad through the hole in the top plate, and insert the pin through the vertical hole in the top plate until it fits the top plate completely;

[0021] Push the top plate so that the multilayer FRP plate with the clip and the pad reaches the predetermined position where the end of the clip is 10-20 mm away from the anchor plate, completing the anchoring; the thrust of the top plate is 95% f u , f u is the ultimate tensile strength of the FRP plate.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) This invention anchors the multi-layer FRP panels by placing a backing plate between two layers of FRP panels and integrating the backing plate with the top plate via connectors. This increases the overall anchoring capacity of the anchor while improving the coordinated force-bearing performance of the multi-layer FRP panels. This prevents the problem of a single FRP panel slipping out of the anchor plate, causing anchor failure, a problem not found in traditional anchors. Because the friction coefficient between the backing plate and the FRP panel is greater than the friction coefficient between the FRP panels themselves, the backing plate avoids direct contact between the FRP panels, improving the integrity of the multi-layer FRP panels and the wedge-shaped clips within the anchor. The contact area of ​​the multi-layer (n) FRP panel anchoring method is n times that of the large-cross-section single-layer FRP panel anchoring method, thus theoretically shortening the anchoring length by n times.

[0024] 2) Different from the 100% in conventional steel clip anchor test f u The thrust value of the present invention is 95% of the thrust value. f u , which can ensure the clamping effect of the clips on the multi-layer FRP plates and pads, reduce the requirements on the tonnage of the jacking jack, and increase the safety of construction.

[0025] 3) By setting teeth on both sides of the pad, the integrity between the clip and the FRP plate is increased, and the self-locking characteristics of the clip anchor are better utilized.

[0026] 4) By inlaying rubber and aluminum alloy at the front end of the pad, the stiffness of the pad is changed, alleviating the stress concentration problem caused by the sudden change in stiffness at the loading end of the anchor.

[0027] 5) The construction process is simple and the anchoring performance is reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a longitudinal cross-sectional view of a multi-layer FRP plate anchoring method according to the present invention.

[0029] Figure 2 This is an assembly diagram of a multi-layer FRP plate anchoring method of the present invention.

[0030] Figure 3 This is a diagram of the internal assembly of an anchor plate for a multi-layer FRP plate anchoring method according to the present invention.

[0031] Figure 4 The present invention discloses a top plate of a multi-layer FRP plate anchoring method.

[0032] Figure 5 This is a longitudinal cross-sectional view of a base plate in a multi-layer FRP plate anchoring method according to the present invention.

[0033] Figure 6 This is the failure diagram of the existing thick FRP plate anchoring test.

[0034] Figure 7 This is the relationship diagram between the jacking load and the anchoring efficiency.

[0035] The figure includes: 1. Multi-layer FRP plate; 2. Steel anchor plate; 3. Clip; 4. Pad; 4-1. Pad body; 4-2. Pad rubber pad; 4-3. Pad aluminum alloy; 4-4. Pad hole; 5. Top plate; 6. Pin. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are further explained in detail below in conjunction with the accompanying drawings. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0037] The technical problem to be solved by the present invention is to overcome the problem that the existing FRP plate clip-type anchor cannot effectively clamp large-tonnage FRP plates, resulting in slippage of the FRP plates or local crushing of the FRP plates at the loading end. An anchoring method that can simultaneously anchor multiple layers of FRP plates is proposed, which greatly shortens the length of the anchor, improves the overall anchoring performance of the anchor, and can fully exert the tensile strength of the FRP plates, causing them to undergo ideal explosive-type destruction.

[0038] The invention will be further described below with reference to the accompanying drawings.

[0039] like Figure 1 As shown, the present invention provides an FRP plate anchoring method, comprising:

[0040] An anchor plate having an anchoring channel with an isosceles trapezoidal cross-section;

[0041] Clips, filling between the upper and lower surfaces of the FRP plate and the anchor channel;

[0042] The top plate is a metal plate with holes and grooves fixed to the rear end of the clip, which is used to transmit the force on the middle FRP plate to the clip.

[0043] In one embodiment, the FRP plate anchoring method further comprises:

[0044] The backing plate is a metal plate with holes; the number of holes at the rear end is the same as the number of pins used in the anchoring method, and the shape is the same as the cross-section of the pins and the groove of the top plate.

[0045] In one embodiment, the front of the pad is inlaid with rubber, the middle is inlaid with aluminum alloy, and the rear end is steel. The lengths of the three are 57.5 mm, 57.5 mm, and 115 mm, respectively. By changing the stiffness of the pad in a gradient, the radial stress of the FRP plate at the loading end of the anchor is reduced.

[0046] In one embodiment, the thickness of the top plate is 30 mm, and the thinnest thickness must not be less than 20 mm to ensure that the top plate has sufficient bending stiffness to transfer loads.

[0047] The backing plate achieves variable stiffness by inlaying different materials along the length of the FRP plate. Different gradient stiffness-to-length ratios include, but are not limited to, the following: 1:2:2, 1:1:3, 3:3:4, 2:3:5, 3:3:4, and 1:1:1:2. The thinnest point of the backing plate base must be no less than 2 mm, and the minimum thickness of the inlaid material must be no less than 2 mm. The materials inlaid in the front and middle of the backing plate include, but are not limited to, rubber and aluminum alloy, ensuring that stiffness gradually increases from front to back.

[0048] The free end of the clip extends 10-20 mm beyond the anchor plate to ensure good contact with the inner surface of the top plate. The loading end is flush with the backing plate and extends 10-20 mm beyond the steel anchor plate. The clip end is chamfered, the inner surface is serrated, and the outer surface is lubricated to reduce friction between the clip and the anchor plate. The clip can be made of materials including, but not limited to, steel, aluminum alloy, and composite materials.

[0049] The length of the pad extending from the free end of the anchor plate shall be at least 50 mm to ensure the length requirements of the clip, top plate and pin along the length direction of the FRP plate.

[0050] The cross-section of the pin includes but is not limited to a semicircle, a circle, a quadrilateral, etc., and can be adjusted according to the calculation results, and the shapes of the top plate groove and the pad hole can be adjusted accordingly.

[0051] The steps of the FRP plate anchoring method are as follows:

[0052] Step 1: Select several intact FRP plates 1 with a thickness of 2 mm or less, which are intact and have no surface damage.

[0053] Step 2: Determine the size of the FRP plate according to the project requirements, and use an angle grinder to cut the FRP plate 1 to the corresponding length;

[0054] Step 3: Place the cut FRP sheets 1 into the steel anchor plate 2. Insert a backing plate between each two FRP sheets extending from the free end (large opening) of the steel anchor plate 1. Ensure that the end of the backing plate extends 50-80 mm beyond the end of the FRP sheet. Place a clip 3 on the outer surface of the outer FRP sheet, ensuring that the front end of the clip 3 is flush with the backing plate.

[0055] Step 4: Push the top plate 5 from the end of the pad 4 toward the clip, and the pad 4 passes through the hole of the top plate 5. The inner surface of the top plate 5 contacts the back side of the clip 3, and the groove of the top plate 5 remains flush with the hole of the pad 4; insert the pin 6 into the groove of the top plate 5 from the upper side until the pin 6 is completely embedded in the top plate 5.

[0056] Step 5: Push the top plate 5 from the outside, so that the multi-layer FRP plate 1, the clip 3 and the backing plate 4 follow at the same time, until the front end of the clip 3 and the backing plate 4 exceeds the anchor plate 2 by about 10~20 mm. The pushing force is 95% f u ( f u is the ultimate tensile strength of the FRP plate), and the anchoring is completed.

[0057] The thrust force in the present invention is calculated by finite element method, and the thrust force is between 95% and 100%. f u It has no effect on the anchoring efficiency of the anchor, but is less than 95% f u When the anchoring efficiency begins to decrease gradually, see Figure 7 .

[0058] Repeat steps 1 to 5 to complete the anchoring of the other end. Example

[0059] like Figure 1 、 Figure 2 、 Figure 3 shown.

[0060] The steps of the FRP plate anchoring method are as follows:

[0061] Insert three BFRP plates with a size of 50 (width) x 2 (thickness) into the anchor plate, with the ends extending from the large opening of the anchor plate;

[0062] Two pads were placed between every two layers of BFRP plates at the large opening of the anchor plate, with the ends of the pads extending 60 mm beyond the FRP plates. The pads were made of three materials: rubber, aluminum alloy, and steel, with lengths of 58 mm, 58 mm, and 114 mm, respectively.

[0063] Place two clips on the upper and lower BFRP plates, with the front ends of the clips flush with the front ends of the backing plates;

[0064] Gently push the FRP plate with the clip and backing plate into the anchor plate, push the top plate from the end of the backing plate toward the clip, and let the backing plate pass through the square hole of the top plate. The front end of the top plate contacts the clip, and after fine-tuning the distance, ensure that the semicircular groove of the top plate and the semicircular hole of the backing plate are on the same projection plane;

[0065] The pin was inserted through the groove in the top plate and passed through the semicircular hole in the backing plate. After the top plate was integrated, a jack was used to push the top plate with a force equal to 95% of the ultimate strength of the BFRP plate, until the front ends of the clip and backing plate extended 20 mm beyond the anchor plate. Finite element simulation results showed that all three BFRP plates were simultaneously broken, with a tensile force of 374.4 kN. The maximum positive compressive stress of the FRP plate within the anchor was 94.58 MPa, and the anchoring efficiency coefficient reached 96%. (Note: The ultimate tensile stress of the BFRP plate is 1300 MPa).

[0066] The ultimate tensile force of the anchor using an all-steel pad is 366.6 kN, the anchoring efficiency coefficient is only 94%, and the maximum positive extrusion stress in the anchor plate is 93.43 MPa, which does not meet the anchoring efficiency coefficient of more than 95% required by the specification.

[0067] The anchoring efficiency coefficient and failure mode of the anchorage are obtained by combining clips with different lengths relative to the anchor plate with the all-steel pad, as shown in Table 1. When both the clip and the pad are extended out of the anchorage, the forward extrusion stress on the BFRP plate is the smallest and the anchoring efficiency coefficient is the highest.

[0068] Table 1 Effect of different relative lengths of clips and pads on anchoring efficiency coefficient

[0069] (Note: Due to the large dispersion of the ultimate compressive strength of BFRP plates, 100~150MPa is taken as the ultimate strength)

[0070] Tensile tests were conducted on the anchoring system of large-section BFRP plates, and the experimental results are shown in Table 2. For 100 × 5 mm BFRP plates, increasing the anchorage length and changing the clip material failed to increase the anchorage efficiency above 65%, with some even achieving less than 50%. For 80 × 4 mm BFRP plates, the anchorage efficiency was only approximately 70%, failing to effectively utilize the high strength of BFRP and resulting in low material utilization. Although reducing the cross-sectional size can improve anchorage efficiency, more anchors are required for the same reinforcement ratio, increasing reinforcement costs.

[0071] Table 2 Experimental test of anchorage of large-section BFRP plates

[0072] Therefore, the present invention has the advantages of being able to efficiently and reliably realize the anchoring of large-tonnage multi-layer FRP plates, shortening the length of the anchor by increasing the contact surface between layers, giving full play to the tensile strength of the FRP plates, and causing them to undergo ideal complete explosive destruction.

Claims

1. A method for anchoring a multi-layer FRP plate, comprising: anchoring the plate using a multi-layer FRP plate anchoring device; the multi-layer FRP plate anchoring device comprising: An anchor plate having an anchor channel with an isosceles trapezoidal cross-sectional area; Clips, filling between the upper and lower surfaces of the outermost FRP plate and the anchor channel; Pads, laid between every two layers of FRP panels in the anchoring area; A top plate having two action portions and a connecting portion; the action portions are in contact with the rear end of the clip; and the connecting portion is used to connect to the pad; A connecting piece, provided at the connecting portion of the top plate, for connecting the top plate and the backing plate into a whole; The anchoring method comprises: A pad is sandwiched between every two layers of FRP plates, with the end of the pad extending 50-80 mm beyond the FRP plates; Place the clip on the outer surface of the outermost FRP plate, with the front end of the clip flush with the front end of the backing plate, and apply lubricant on the outer surface of the clip; Push the multilayer FRP plate with the clip and backing plate into the anchor plate from the large opening end, so that the front end of the clip extends 10-20 mm beyond the small opening end of the anchor plate; Place the top plate at the rear end of the clamp, pass the end of the pad through the hole in the top plate, and insert the pin through the vertical hole in the top plate until it fits the top plate completely; Push the top plate so that the multilayer FRP plate with the clip and the pad reaches the predetermined position where the end of the clip is 10-20 mm away from the anchor plate, completing the anchoring; the thrust of the top plate is 95% f u , f u is the ultimate tensile strength of the FRP plate.

2. The method for anchoring a multi-layer FRP plate according to claim 1, wherein: The connecting portion includes a hole, and the pad passes through the hole.

3. The method for anchoring a multi-layer FRP plate according to claim 2, wherein: The connecting part also includes a semicircular groove; a semicircular pin hole adapted to the shape of the semicircular groove is provided on the pad; the connecting piece is a semicircular pin, which is provided in the semicircular groove of the connecting part and passes through the semicircular pin hole on the pad.

4. The method for anchoring a multi-layer FRP plate according to claim 3, wherein: The contact portions of both sides of the backing plate with the FRP plate are provided with tooth patterns to increase the friction between the backing plate and the FRP plate.

5. The method for anchoring a multi-layer FRP plate according to claim 3, wherein: The front half of the pad is inlaid with a rubber pad on the contact surface with the FRP plate, and the middle half is inlaid with an aluminum alloy plate on the contact surface with the FRP plate.

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