Anchoring system and anchoring method for thermoplastic resin-based composite parallel rod cable

Abstract

The present invention discloses an anchoring system and anchoring method for thermoplastic resin-based composite parallel rod cables, belonging to the technical field of fiber-reinforced resin composite anchoring. The present invention solves the problem of difficulty in anchoring thermoplastic composite cables for existing large-span space structures such as bridges and marine engineering, and avoids the problems of local shear failure, pull-out failure, large cable-anchor slippage, low anchoring efficiency, and large anchor size existing in traditional clamping anchors and bonding anchors. The present invention uses a pre-extrusion molding device to make each composite rod in the anchoring area into a corrugated rod body with different bending angles and end hooks, and injects a bonding material with a gradually increasing proportion of high-efficiency expansion agent mixed from the loading end to the free end of the anchor into the steel anchor barrel, and transmits the external load to the steel anchor barrel through the chemical bonding effect between the cable body and the bonding material, the mechanical bite effect, and the shearing and extrusion effect of the end hook of the cable and the centering plate.

Description

Technical Field

[0001] The invention relates to an anchoring system and an anchoring method for a thermoplastic resin-based composite parallel rod cable, belonging to the technical field of fiber-reinforced resin composite anchoring. Background Art

[0002] Steel cables used in large-span spatial structures such as bridges and marine engineering have serious corrosion, wear and fatigue damage problems during service, which not only poses a hidden danger to the safety performance of the structure and reduces the service life of the structure, but also costs a lot of money every year worldwide due to problems such as steel cable corrosion. In addition, when designing and constructing large-span spatial structures, the steel cables have a large mass and insufficient strength, which limits the span of the structure. Therefore, there is an urgent need for a corrosion-resistant, fatigue-resistant, lightweight and high-strength material to replace steel cables and solve the engineering problems of steel cables.

[0003] Fiber-reinforced resin composites have excellent mechanical, fatigue, corrosion and creep resistance properties, and can solve the corrosion and fatigue problems faced by steel cables. Fiber-reinforced resin composites are generally made of high-performance fibers and resin matrices through pultrusion. According to the different types of high-performance fibers, there are mainly carbon fiber composites, glass fiber composites, aramid fiber composites, and basalt fiber composites. At present, the resin matrix of composite materials is mainly thermosetting resin. After the resin is cured, a three-dimensional network structure is formed through chemical cross-linking. Thermosetting resin has the advantages of high mechanical properties, excellent bonding properties, small curing shrinkage, and good processability, but it has the problems of high brittleness, poor toughness, poor resistance to wet and hot corrosion, and poor bending and fatigue resistance. In contrast, thermoplastic resins have the advantages of good ductility, high toughness, bending resistance, wear resistance, fatigue resistance, and wet and hot corrosion resistance, and thermoplastic resins can be recycled and reshaped for recycling, so they are economical, highly plastic, and green and environmentally friendly. Therefore, from the perspective of mechanical properties, economic benefits, and environmental protection, composite rods made of thermoplastic resins instead of thermosetting resins have better development prospects.

[0004] Fiber composite materials are typical orthotropic materials. The strength and stiffness along the fiber direction are much greater than the strength and stiffness perpendicular to the fiber direction. Therefore, the shear and compressive strength of composite materials are low, which makes it difficult to anchor composite materials, especially composite cables composed of multiple tendons, which becomes extremely difficult and restricts the application of composite materials in civil engineering.

[0005] At present, the anchoring of thermosetting resin composite cables is mainly divided into clamping anchoring system and bonding anchoring system. The clamping anchoring system uses the mechanical bite force generated by the clip to balance the external load on the composite cable. It has the advantages of easy operation, high anchoring efficiency, and small cable-anchor slippage. However, the clip produces a cutting effect on the cable body, which is prone to local shear failure at the loading end of the anchor. Therefore, this type of anchor is rarely used in engineering. The bonding anchoring system uses the bonding force provided by the bonding material to balance the external load on the cable body. The local stress peak generated on the cable body is small, there is no initial damage, and it is widely used in engineering. However, the bonding anchoring system has problems such as insufficient bearing capacity of the bonding material and inconsistent deformation of the cable body and the bonding material. It is prone to pull-out failure and large cable-anchor slippage. However, these two types of anchoring systems are mainly suitable for the anchoring of thermosetting resin-based composite cables. Since thermoplastic resin-based composite cables have high toughness and large deformation when heated and stressed, the local shear deformation caused by the clips of traditional clamping anchors on thermoplastic resin-based composite cables is increased, making local shear fracture more likely to occur. Traditional bonding anchors are prone to slippage failure due to the large deformation of thermoplastic resin-based composite cables.

[0006] In summary, a single clamping anchor or bonding anchor cannot solve the problem of anchoring thermoplastic composite cables for large-span spatial structures such as bridges and marine engineering. Summary of the invention

[0007] In order to solve the problem of difficulty in anchoring thermoplastic composite cables used in existing large-span spatial structures such as bridges and marine engineering, and to avoid the problems of local shear failure, pull-out failure, large cable-anchor slippage, low anchoring efficiency and large anchor size existing in traditional clamping anchors and bonding anchors, the present invention provides an anchoring system and an anchoring method for thermoplastic resin-based composite parallel rod cables.

[0008] One of the purposes of the present invention is to provide an anchoring system for thermoplastic resin-based composite parallel rods, the system comprising a steel anchor cylinder 4, a first centering piece 2, a bonding filler 3 and a second centering piece 5 for anchoring the parallel rods 1, a conical through hole is coaxially provided in the steel anchor cylinder 4, the aperture of the conical through hole is distributed from small to large from the load end to the free end of the steel anchor cylinder 4, the first centering piece 2 is arranged at the small aperture end of the conical through hole, the second centering piece 5 is arranged at the large aperture end of the conical through hole, each parallel rod 1 passes through the first centering piece 2, the conical through hole and the second centering piece 5 in sequence, and the bonding filler 3 is poured into the remaining space of the conical through hole;

[0009] The parallel rod cable 1 is a thermoplastic resin-based composite material. The parallel rod cable anchored in the steel anchor tube 4 is a corrugated rod body with a hook at the end. The hook passes through the second pair of center pieces 5 and fits on the outer wall of the second pair of center pieces 5.

[0010] It is further defined that the parallel rod cable 1 has a 90° hook at 0.5 to 2 cm from the end thereof.

[0011] It is further defined that the corrugation of the parallel rod cable 1 adopts a two-dimensional waveform line round tooth surface, which conforms to the waveform of the sine curve function. When the diameter of the parallel rod cable is d, the amplitude is 0.2~1.0d, and the half wavelength is (π-1)d / 5n-(π-1)d / 10n, where n is the number of wavelengths.

[0012] It is further defined that the parallel rod cable 1 has a diameter of 5 mm.

[0013] It is further defined that the minimum thickness of the steel anchor cylinder 4 is ≥5 mm, and the thickness of the first centering piece 2 and the second centering piece 5 is ≥10 mm.

[0014] It is further defined that the bonding filler 3 is composed of epoxy resin, iron sand and a high-efficiency expansion agent.

[0015] It is further defined that the content of the high-efficiency expansion agent in the bonding filler 3 increases stepwise from the large-diameter end to the small-diameter end of the tapered through hole.

[0016] It is further defined that the through holes are evenly distributed at the center of the first pair of center sheets 2 and the through holes are evenly distributed around the circumference of the second pair of center sheets 5 .

[0017] The second object of the present invention is to provide a method for anchoring parallel rods, which uses the above-mentioned anchoring system, and the specific operating steps are as follows:

[0018] S1, using a pre-extrusion molding device to form a thermoplastic resin-based composite material rod into a corrugated parallel rod cable 1 with a hook at the end;

[0019] S2, install the parallel rod 1 in the anchoring system, ensure that the hook of the parallel rod 1 is tightly attached to the outer wall of the second pair of center pieces 5, and use sealant to seal the gap between the parallel rod 1, the second pair of center pieces 5 and the steel anchor tube 5, inject adhesive fillers 3 containing different contents of high-efficiency expansion agent in sequence, and finally use sealant to seal the gap between the parallel rod 1, the first pair of center pieces 2 and the steel anchor tube 5.

[0020] It is further defined that the center line of the parallel rod cable 1 coincides with the axis line of the steel anchor cylinder 4.

[0021] The present invention uses a pre-extrusion molding device to make each composite material rod in the anchoring area into a corrugated rod body with different bending angles and a hook at the end, and injects a bonding material with a gradually increasing proportion of high-efficiency expansion agent from the loading end to the free end of the anchor into the steel anchor barrel, and transmits the external load to the steel anchor barrel through the chemical bonding effect and mechanical bite between the cable body and the bonding material, and the shearing and squeezing effect of the hook at the end of the cable and the centering plate. Compared with the prior art, the present application also has the following beneficial effects:

[0022] (1) The present invention utilizes the heating, melting, cooling and molding characteristics of thermoplastic resin, and adopts a pre-extrusion molding device to make the composite material rod in the anchoring area into a corrugated rod body with different bending angles and end hooks. This not only increases the contact area with the bonding material and reduces the influence of the initial defects of the contact interface on the anchoring performance, but also generates a mechanical bite force between the cable body and the bonding material, thereby improving the anchoring efficiency.

[0023] (2) In the anchoring system of the present invention, the end hooks of the parallel rods and the centering plates, as well as the centering plates and the steel anchor barrel, are tightly fitted, so that when the cables are subjected to stress, part of the external load can be borne by the shearing and squeezing action of the end hooks of the composite rods and the centering plates, which can reduce the overall longitudinal slippage of the cables and make the longitudinal slippage of each composite rod tend to be evenly distributed, thereby reducing the influence of the clustering effect on the anchoring efficiency.

[0024] (3) The content of the high-efficiency expansion agent in the bonding filler of the present invention is stepped, and the variable stiffness bonding material is used to gradually increase the expansion extrusion force from the loading end to the free end of the anchor, thereby improving the anchor bearing capacity of the rear end of the anchor and avoiding local shear failure caused by the concentration of shear stress and compressive stress at the loading end of the anchor. In addition, the curing and expansion effect of the bonding material itself is used to apply annular prestress to the composite cable, eliminating the process of applying prestress before the tensile test of the traditional composite cable anchor system.

[0025] (4) The anchoring system provided by the present invention has a simple structure and is easy to use. It can be widely used in the anchoring technology of composite cables of different diameters. It solves the problem that the clips of traditional clamping anchors produce large local shear deformation on thermoplastic resin-based composite cables, which is more prone to local shear fracture, and the traditional bonding anchor has large deformation of thermoplastic resin-based composite rods or cables, which is prone to slippage failure. It effectively utilizes the advantages of thermoplastic resin-based composite cables, such as good ductility, high toughness, bending resistance, wear resistance, fatigue resistance, moisture and heat corrosion resistance, recyclability, and green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the main structure of the anchoring system for the thermoplastic resin-based composite material parallel rod cable provided by the present invention;

[0027] Figure 2 A schematic diagram of the main structure of an anchoring system for a thermoplastic resin-based composite parallel rod cable provided by the present invention;

[0028] Figure 3 A schematic diagram of a three-dimensional cross-sectional structure of an anchoring system for a thermoplastic resin-based composite parallel rod cable provided by the present invention;

[0029] Figure 4A schematic diagram of the free end of the anchoring system for the thermoplastic resin-based composite parallel rod cable provided by the present invention;

[0030] Figure 5 A schematic diagram of a loading end of an anchoring system for a thermoplastic resin-based composite parallel rod cable provided by the present invention;

[0031] In the figure, 1-parallel rods, 2-first pair of center pieces, 3-bonded filler, 4-steel anchor cylinder, 5-second pair of center pieces. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art. Specific implementation method one:

[0035] The anchoring system structure of the thermoplastic resin-based composite parallel rod cable in this embodiment is as follows: Figure 1-3 As shown, the anchoring system includes a steel anchor cylinder 4, a first centering piece 2, a bonding filler 3 and a second centering piece 5 for anchoring parallel rods 1. The first centering piece 2 is arranged at the small-diameter end of the tapered through hole, and the second centering piece 5 is arranged at the large-diameter end of the tapered through hole. Each parallel rod 1 passes through the first centering piece 2, the tapered through hole and the second centering piece 5 in sequence, and the bonding filler 3 is poured into the remaining space of the tapered through hole. The parallel rod 1 is a thermoplastic resin-based composite material. The parallel rod anchored in the steel anchor cylinder 4 is a corrugated rod body with a 90° hook at the end 0.5 to 2 cm. The hook passes through the second centering piece 5 and fits the outer wall of the second centering piece 5. In this way, the thermoplastic resin is heated, melted and cooled to form a 90° hook at the end of the parallel rod cable 1 within a length of 0.5 to 2 cm. When anchoring, the hook is close to the second pair of centering plates 5. When the cable is subjected to force, a part of the external load can be offset by the shearing and squeezing effect of the hook and the second pair of centering plates 5, which can not only reduce the overall longitudinal slip of the parallel rod cable 1, but also make the longitudinal slip of the parallel rod cable 1 tend to be evenly distributed, thereby reducing the influence of the clustering effect on the anchoring efficiency.

[0036] A conical through hole is coaxially provided in the steel anchor cylinder 4, and the aperture of the conical through hole is distributed from small to large from the load end to the free end of the steel anchor cylinder 4. The minimum thickness of the steel anchor cylinder 4 is ≥5mm, and the thickness of the first pair of center pieces 2 and the second pair of center pieces 5 is ≥10mm. The bonding filler 3 is composed of epoxy resin, iron sand and high-efficiency expansion agent. The content of the high-efficiency expansion agent in the bonding filler 3 increases stepwise from the large-aperture end to the small-aperture end of the conical through hole. In this way, the bonding filler 3 is injected into the steel anchor cylinder 4 by a pressure injector in the order of gradually increasing the proportion of the high-efficiency expansion agent from the loading end to the free end of the anchor. The greater the proportion of the expansion agent added, the greater the expansion and extrusion effect of the bonding filler 3, thereby making the bonding filler 3 with adjustable radial extrusion force on the parallel rod cable 1. After the bonding filler 3 is cured, the radial extrusion force on the parallel rod cable 1 gradually increases from the loading end to the free end of the anchor, thereby improving the anchoring force at the rear end of the anchoring system, reducing the shear stress and compressive stress peaks at the loading end of the anchoring system, and avoiding local shear failure due to stress concentration at the loading end. At the same time, the curing and expansion of the bonding filler 3 itself applies annular pressure to the parallel rod cable 1, eliminating the need to apply prestress before tensile testing of traditional composite material cable wedge-shaped bonding anchors.

[0037] The corrugation of the parallel rod cable 1 adopts a two-dimensional corrugated line round tooth surface, which conforms to the waveform of the sine curve function. When the diameter of the parallel rod cable is d, the amplitude is 0.2-1.0d, and the half wavelength is (π-1)d / 5n-(π-1)d / 10n, where n is the number of wavelengths. This arrangement avoids initial fiber damage or breakage of the corrugated parallel rod cable 1 in the anchoring area, and insufficient internal space of the steel anchor cylinder 4 during installation, and adopts a two-dimensional corrugated line to conform to the waveform round tooth surface of the sine curve function.

[0038] The minimum thickness of the steel anchor cylinder 4 is ≥5mm, and the thickness of the first centering piece 2 and the second centering piece 5 is ≥10mm. This arrangement is to prevent deformation when subjected to external loads, thereby affecting the anchoring performance.

[0039] Embodiment 1:

[0040] The anchoring system structure of the thermoplastic resin-based composite parallel rod cable in this embodiment is as follows: Figure 1-3As shown, the anchoring system includes a steel anchor cylinder 4, a first pair of centering pieces 2, a bonding filler 3 and a second pair of centering pieces 5 for anchoring parallel rods 1. A conical through hole is coaxially provided in the steel anchor cylinder 4. The aperture of the conical through hole is distributed from small to large from the load end to the free end of the steel anchor cylinder 4. The first pair of centering pieces 2 are arranged at the small aperture end of the conical through hole, and the second pair of centering pieces 5 are arranged at the large aperture end of the conical through hole. Each parallel rod 1 passes through the first pair of centering pieces 2, the conical through hole and the second pair of centering pieces 5 in sequence. The bonding filler 3 is poured into the remaining space of the conical through hole. The parallel rods anchored in the steel anchor cylinder 4 are corrugated rods with hooks at the ends. The hooks pass through the second pair of centering pieces 5 and fit the outer wall of the second pair of centering pieces 5. The ends of the parallel rods 1 are 1 cm apart and are hooked at 90 degrees. The corrugation of the parallel rod 1 adopts a two-dimensional wave line round tooth surface, which conforms to the waveform of the sine curve function. When the diameter of the parallel rod is d=5mm, the amplitude is 0.75, and the half wavelength is (π-1)4 / 15. The thickness of the steel anchor cylinder 4 is 4mm, the thickness of the first pair of center pieces 2 is 2mm, and the thickness of the second pair of center pieces 5 is 2mm. The center of the first pair of center pieces 2 is evenly distributed with through holes, and the circumference of the second pair of center pieces 5 is evenly distributed with through holes.

[0041] The anchoring method of the anchoring system of the thermoplastic resin-based composite parallel rod cable of this embodiment comprises the following steps:

[0042] Step 1: Take 16 carbon fiber composite rods with a diameter of 5 mm and nylon 6 as the resin matrix as the parallel rod cable 1, place one end of the parallel rod cable 1 in the pre-extrusion molding device and clamp it, and heat treat it in a high-temperature furnace at 225°C for 2 hours under a load of 25 kg. After heating and molding, repeat the above procedure for the other end of the carbon fiber composite rod until both ends have a 4° bending angle, a wavy thread shape, and a 1 cm long 90° hook at the end.

[0043] Step 2: Use acetone to clean the inner wall of the steel anchor cylinder 4, the parallel rods 1 in the anchoring area, the first pair of center pieces 2 and the second pair of center pieces 5. After the acetone is completely volatilized, insert the 16 parallel rods 1 into the first pair of center pieces 2 at the end of the anchor in sequence, and then insert the whole into the steel anchor cylinder, and then pass through the second pair of center pieces 5, so that the 90° bend at the end of each parallel rod 1 is close to the outer wall of the second pair of center pieces 5. Figure 4 As shown, the second pair of center pieces 5 are closely attached to the steel anchor cylinder 4, and a sealant is used to seal the gaps between the parallel rods 1, the second pair of center pieces 5 and the steel anchor cylinder 4 to prevent leakage when the adhesive material is injected.

[0044] Step 3: Prepare four kinds of adhesive fillers 3 with different contents of high-efficiency expansion agents to make adhesive materials with adjustable radial extrusion force on the parallel rod 1. Use a pressure injector to inject the four kinds of adhesive materials into the steel anchor tube 4 in the order of increasing proportion of high-efficiency expansion agents from the loading end to the free end of the anchor. After the injection is completed, fix the first centering piece 2 at the loading end. Figure 5 As shown, sealant is used to seal the gaps between the parallel rod cable 1, the first centering piece 2 and the steel anchor cylinder 4 to prevent leakage when the adhesive material is cured. Note that the first centering piece 2 and the second centering piece 5 need to be aligned so that the center line of the parallel rod cable 1 completely coincides with the center line of the anchoring system.

[0045] The four adhesive fillers 3 with different contents of high-efficiency expansion agents are as follows: the first one is composed of 60g epoxy resin, 100g iron sand and 30g high-efficiency expansion agent; the second one is composed of 60g epoxy resin, 100g iron sand and 40g high-efficiency expansion agent; the third one is composed of 60g epoxy resin, 100g iron sand and 50g high-efficiency expansion agent; the fourth one is composed of 60g epoxy resin, 100g iron sand and 60g high-efficiency expansion agent. The epoxy resin is TS epoxy resin provided by Shandong Dagong Composite Materials Co., Ltd., the diameter of the iron sand is 1mm, and the high-efficiency expansion agent is UEA expansion agent produced by Jianfeng Hongda Formula.

[0046] After the bonding material 3 is cured, a tensile test is performed, and the tensile strength of the carbon fiber composite cable is 1785 MPa and the elastic modulus is 142.51 GPa. The failure mode is an ideal burst of the free section of the sample, which shows that the anchoring system can effectively anchor the thermoplastic carbon fiber composite cable.

[0047] Embodiment 2:

[0048] The difference between this embodiment and embodiment 1 is: step one, take 36 glass fiber composite material rods with a diameter of 5 mm and polypropylene as the resin matrix as the parallel rod cable 1; step three, inject 6 kinds of bonding fillers 3 with different contents of high-efficiency expansion agent into the steel anchor tube 4 in sequence, and the specific 4 kinds of bonding fillers 3 with different contents of high-efficiency expansion agent are: the first kind is composed of 60g epoxy resin, 100g iron sand and 30g high-efficiency expansion agent; the second kind is composed of 60g epoxy resin, 100g iron sand and 40g high-efficiency expansion agent; the third kind is composed of 60g epoxy resin, 100g iron sand and 50g high-efficiency expansion agent; the fourth kind is composed of 60g epoxy resin, 100g iron sand and 60g high-efficiency expansion agent; the remaining operations and parameter settings are the same as those in embodiment 1.

[0049] After the bonding material 3 is cured, a tensile test is performed, and the tensile strength of the carbon fiber composite cable is 1945 MPa and the elastic modulus is 149.55 GPa. The failure mode is an ideal burst of the free section of the sample, which shows that the anchoring system can effectively anchor the thermoplastic carbon fiber composite cable.

[0050] Although the present invention has been disclosed as above in the preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A parallel rod anchoring system, characterized in that: It comprises a steel anchor cylinder, a first pair of center pieces, a bonding filler and a second pair of center pieces for anchoring parallel rods. A conical through hole is coaxially provided in the steel anchor cylinder. The aperture of the conical through hole is distributed from small to large from the load end to the free end of the steel anchor cylinder. The first pair of center pieces are arranged at the small aperture end of the conical through hole, and the second pair of center pieces are arranged at the large aperture end of the conical through hole. Each parallel rod passes through the first pair of center pieces, the conical through hole and the second pair of center pieces in sequence. The bonding filler is poured into the remaining space of the conical through hole. The parallel rod cable is a thermoplastic resin-based composite material. The parallel rod cable anchored in the steel anchor tube is a corrugated rod body with a hook at the end. The hook passes through the second pair of middle pieces and fits on the outer wall of the second pair of middle pieces. The bonding filler is composed of epoxy resin, iron sand and high-efficiency expansion agent; the content of the high-efficiency expansion agent in the bonding filler increases stepwise from the large-aperture end to the small-aperture end of the tapered through hole; The through holes are evenly distributed at the center of the first pair of sheets, and the through holes are evenly distributed around the circumference of the second pair of sheets.

2. The parallel rod anchoring system according to claim 1, characterized in that: The hook is located 0.5 to 2 cm from the end of the parallel rod.

3. The parallel rod anchoring system according to claim 1, characterized in that: The corrugation of the parallel rod cable adopts a two-dimensional waveform circular tooth surface, which conforms to the waveform of the sine curve function. When the diameter of the parallel rod cable is d, the amplitude is 0.2~1.0d, and the half wavelength is (π-1)d / 5n- (π-1)d / 10n, where n is the number of wavelengths.

4. The parallel rod anchoring system according to claim 3, characterized in that: The diameter of the parallel rod is 5mm.

5. The parallel rod anchoring system according to claim 1, characterized in that: The minimum thickness of the steel anchor cylinder is ≥5mm, and the thickness of the first pair of center plates and the second pair of center plates is ≥10mm.

6. A method for anchoring parallel rods, characterized in that: The anchoring system for the parallel rod cable according to any one of claims 1 to 5 comprises the following steps: S1, using a pre-extrusion molding device to form a thermoplastic resin-based composite material rod into a corrugated parallel rod cable with a hook at the end; S2, install the parallel rods in the anchoring system, ensure that the hooks of the parallel rods are tightly attached to the outer wall of the second pair of center pieces, and use sealant to seal the gaps between the parallel rods, the second pair of center pieces and the steel anchor cylinder, inject adhesive fillers containing different contents of high-efficiency expansion agents in sequence, and finally use sealant to seal the gaps between the parallel rods, the first pair of center pieces and the steel anchor cylinder.

7. The method for anchoring parallel rods according to claim 6, characterized in that: The center line of the parallel rod coincides with the axis of the steel anchor cylinder.

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