A hollow cross-section GFRP crossarm with joints

Abstract

This invention discloses a hollow cross-section GFRP crossarm with joints, comprising a hollow circular tube, joints, and connecting structures. Multiple joints are provided, each a thick annular structure, arranged sequentially inside the hollow circular tube along its axial direction. The two outermost joints extend beyond the ends of the hollow circular tube. Two sets of connecting structures are provided, located at both ends of the hollow circular tube. Each connecting structure includes a blind flange, with a sleeve attached to the hollow circular tube on the end face of the blind flange near the tube. The inner ring of the sleeve has a connecting rod that connects to the outermost joint. This invention solves the problems of poor load-bearing performance and easy failure at the root of existing composite crossarms.

Description

Technical Field

[0001] This invention belongs to the field of power transmission equipment technology, specifically relating to a hollow cross-section GFRP crossarm with joints. Background Technology

[0002] Power transmission lines in a power grid system consist of transmission lines and poles, and the erection of these lines is inseparable from poles and crossarms. Transmission towers are crucial supporting structures in transmission lines, and their structure and materials directly affect the construction speed, economy, reliability, installation, maintenance, and repair of the transmission lines. Currently, the most widely used tower types in overhead transmission lines both domestically and internationally include wooden poles, concrete poles, and iron towers. Iron towers are the most commonly used type of tower for high-voltage and ultra-high-voltage transmission lines worldwide. Crossarms are angle irons horizontally fixed at the top of the pole and are an important component of the tower. Their function is to install insulators and fittings, support conductors and lightning protection wires, and maintain them at a safe distance as required.

[0003] In actual manufacturing and use, the commonly used crossarms are channel-type and box-type crossarms, which are welded together from a top plate, side plates, bottom plate, and a number of stiffening plates. The number of blanks is large, the blanking of side plates is wasteful, and various plate thicknesses are mixed together, resulting in a large amount of welding, which wastes welding materials and time. The existing crossarms have low instability load-bearing capacity, and users often experience twisting and deformation of the crossarm and crossarm seat during installation. At the same time, under excessive load, the pressure side of the composite crossarm root will fail. This is due to the difference in rigidity between the composite material and the 45# steel material. The stiffness changes abruptly at the connection between the core and the flange. After the load is applied, stress concentration will be generated at this part. Therefore, it is necessary to develop a composite crossarm with good load-bearing capacity and effective prevention of root failure. Summary of the Invention

[0004] The purpose of this invention is to provide a hollow cross-section GFRP crossarm with joints, which solves the problems of poor load-bearing performance and easy failure at the root of existing composite crossarms.

[0005] The technical solution adopted in this invention is a hollow cross-section GFRP crossarm with joints, comprising:

[0006] Hollow round tube;

[0007] The tube has multiple segments, each segment being a thick circular ring structure. These segments are arranged inside the hollow tube and sequentially along the axial direction of the hollow tube, with the two segments at the very ends extending beyond the ends of the hollow tube.

[0008] The connection structure is provided in two sets, located at both ends of the hollow circular tube. The connection structure includes a blind flange. A sleeve that connects to the hollow circular tube is provided on the end face of the blind flange near the hollow circular tube. The inner ring of the sleeve is provided with a connecting rod that connects to the outermost joint.

[0009] The outer ring of the hollow round tube is provided with a first external thread, and the inner ring of the sleeve is provided with a first internal thread corresponding to the first external thread. The first external thread and the first internal thread form a first connection part.

[0010] The connecting rod has a second external thread on its side wall, and the outermost joint inner ring has a second internal thread corresponding to the second external thread. The second external thread and the second internal thread form a second connection part.

[0011] The outer end face of the blind flange is provided with adhesive injection holes corresponding to the first connection part and the second connection part, respectively.

[0012] The adhesive used is an epoxy resin adhesive.

[0013] The outer ring of the sleeve is provided with a stress concentration ring, the inner ring of the sleeve is provided with a buffer groove, and the hollow tube is also provided with a channel connecting the buffer groove and the inside of the hollow tube. The channel is located between two adjacent joints at the end. The buffer groove, the channel and the inside of the hollow tube are all provided with stress absorption layers.

[0014] A set screw is also provided on the outside of the stress concentration ring. The other end of the set screw passes through the stress concentration ring and the hollow circular tube buffer groove in sequence and then abuts against the outer wall of the hollow circular tube.

[0015] Multiple vertebrae are arranged at equal intervals inside the hollow circular tube.

[0016] Both the hollow round tube and the joints are made of GFRP material.

[0017] All connecting structures are made of No. 45 steel.

[0018] The beneficial effects of this invention are:

[0019] The present invention discloses a hollow cross-section GFRP crossarm with joints. The crossarms with a certain thickness are set inside the hollow GFRP tube. The joints are set according to the principle of bionics and refer to the internal structure of some plants. The joints can prevent local instability and failure of the fibers of the hollow GFRP tube, and enhance the overall performance of the member. Therefore, the stability and load-bearing capacity of the crossarm are improved.

[0020] This invention discloses a hollow cross-section GFRP crossarm with joints. The outer ring of the hollow circular tube is provided with a first external thread, and the inner ring of the sleeve is provided with a first internal thread corresponding to the first external thread. A first connection part is formed between the first external thread and the first internal thread. A second external thread is provided on the side wall of the connecting rod. The inner ring of the outermost joint is provided with a second internal thread corresponding to the second external thread. A second connection part is formed between the second external thread and the second internal thread. The hollow circular tube of composite material and the sleeve of steel material are connected by threads to form the first connection part. The joint of composite material and the connecting rod of steel material are connected by threads to form the second connection part. At the same time, the first connection part and the second connection part are nested with each other to form a connection method in which the inner and outer parts work together, which makes the overall stability of the crossarm better and the load-bearing capacity stronger.

[0021] This invention discloses a hollow cross-section GFRP crossarm with joints. When a load is applied to the connection between the hollow circular tube and the flange, most of the stress is absorbed by the buffer groove, channel, and stress absorption layer inside the hollow circular tube after passing through the stress concentration ring and set screw. This reduces the stress applied to the composite material and the No. 45 steel plate at the end. Even if stress concentration is easily caused at the joint between the composite material and the steel plate due to changes in stiffness, most of the stress has been transferred to the stress absorption layer through the set screw. Therefore, the stress concentration at the joint between the composite material and the steel plate is effectively reduced, thereby effectively avoiding the problem of failure at the end of the composite crossarm. As a result, the overall load-bearing capacity and stability of the crossarm are improved. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the hollow cross-section GFRP crossbar of the present invention;

[0023] Figure 2 This is a schematic diagram of the assembly structure of the GFRP hollow circular tube and steel flange of the present invention;

[0024] Figure 3 This is a schematic diagram of the steel flange used in this invention;

[0025] Figure 4 This is a graph showing the relationship between load-bearing capacity and joint wall thickness obtained from the verification experiment of this invention.

[0026] In the diagram, 1. Hollow round tube, 2. Blind flange, 3. Joint, 4. Connecting sleeve, 5. Connecting rod, 6. Adhesive injection hole, 7. Buffer groove, 8. Channel, 9. Set screw, 10. Stress concentration ring. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0028] Example 1

[0029] This invention discloses a hollow cross-section GFRP crossarm with joints, such as... Figure 1-3 As shown, it includes: a hollow circular tube 1, joints 3, and connecting structures; multiple joints 3 are provided, each joint 3 is a thick ring structure, multiple joints 3 are arranged inside the hollow circular tube 1 and arranged sequentially along the axial direction of the hollow circular tube 1, the two outermost joints 3 both extend beyond the ends of the hollow circular tube 1; two sets of connecting structures are provided, located at the two ends of the hollow circular tube 1 respectively, the connecting structures include blind flanges 2, the blind flanges 2 are provided with sleeves 4 connected to the hollow circular tube 1 on the end face near the hollow circular tube, and the inner ring of the sleeves 4 is provided with connecting rods 5 connected to the outermost joint 3.

[0030] Furthermore, multiple joints 3 are arranged at equal intervals inside the hollow tube 1. The joints 3 are set according to the principle of bionics and refer to the internal structure of some plants. Joints 3 with a certain thickness are set inside the GFRP hollow tube 1 to prevent local instability and damage of the fibers of the GFRP hollow tube 1 and to enhance the overall performance of the rod.

[0031] Hollow circular tube 1 and rib section 3 are both made of GFRP. Research shows that GFRP transmission towers meet design requirements and can serve as a substitute for traditional transmission tower materials. Compared to steel trusses, GFRP transmission trusses not only solve the maintenance problems of steel, improve structural durability, and reduce costs, but also possess excellent overall load-bearing capacity and seismic performance. GFRP, as a lightweight, high-strength, corrosion-resistant, and electrically insulating material, effectively addresses the shortcomings and deficiencies of traditional transmission materials. GFRP can replace traditional steel crossarms to support transmission lines and can also be used as a load-bearing structure for the tower body. GFRP structures can withstand extreme environmental conditions without causing a decrease in the mechanical strength of the transmission tower; therefore, GFRP materials are widely used in transmission tower systems.

[0032] Example 2

[0033] Furthermore, based on Embodiment 1, the outer ring of the hollow tube 1 is provided with a first external thread, and the inner ring of the sleeve 4 is provided with a first internal thread corresponding to the first external thread, forming a first connecting part between the first external thread and the first internal thread. The side wall of the connecting rod 5 is provided with a second external thread, and the inner ring of the outermost joint 3 is provided with a second internal thread corresponding to the second external thread, forming a second connecting part between the second external thread and the second internal thread. The hollow tube 1 of the composite material and the sleeve of the steel material are connected by threads to form the first connecting part, and the joint 3 of the composite material and the connecting rod 5 of the steel material are connected by threads to form the second connecting part. At the same time, the first connecting part and the second connecting part are nested with each other, forming a connection method in which the inner and outer parts work together, making the overall stability of the crossarm better and the load-bearing capacity stronger.

[0034] Example 3

[0035] Furthermore, based on Embodiment 2, the outer end face of the blind flange 2 is provided with adhesive injection holes 6 corresponding to the first connecting part and the second connecting part, respectively. The adhesive used is epoxy resin adhesive. Therefore, after connecting the hollow round tube 1 and the connecting structures at both ends through the inner and outer threads, adhesive needs to be injected between the first connecting part and the second connecting part at both ends through the adhesive injection holes 6 on both sides.

[0036] This method ensures that the shaft is subjected to more uniform stress under pressure. The steel flange can protect the critical end of the GFRP from damage during the pressure process and prevent the specimen from rotating and moving during the test. The connection structure at both ends is used for connection at one end and for bearing pressure at the other end.

[0037] Example 4

[0038] Furthermore, based on embodiment 3, the outer ring of the sleeve 4 is provided with a stress concentration ring 10, the inner ring of the sleeve 4 is provided with a buffer groove 7, and the hollow tube 1 is also provided with a channel 8 that connects the buffer groove 7 and the interior of the hollow tube 1. The channel 8 is located between two adjacent joints 3 at the end. The buffer groove 7, the channel 8 and the interior of the hollow tube 1 are all provided with a stress adsorption layer, which is composed of an impact-resistant material.

[0039] Furthermore, a set screw 9 is provided on the outer side of the stress concentration ring 10. The other end of the set screw 9 passes through the stress concentration ring 10, the hollow tube 1, and the buffer groove 7 in sequence, and then abuts against the outer wall of the hollow tube 1. There are two set screws 9, which are symmetrically arranged along the central axis of the hollow tube 1. There are also two channels 8, which correspond one-to-one with the two set screws 9. The channels 8 and set screws on each side are all on a straight line parallel to the center line of the hollow tube 1. Therefore, when a load is applied to the connection between the hollow tube 1 and the flange, most of the stress is absorbed by the buffer groove 7, the channels 8, and the stress absorption layer inside the hollow tube 1 after passing through the stress concentration ring 10 and the set screws 9. This reduces the stress applied to the composite material and the No. 45 steel plate at the end. Thus, even if the joint between the composite material and the steel plate is prone to stress concentration due to changes in stiffness, most of the stress has been transferred to the stress absorption layer by the set screws 9, thereby effectively reducing the stress concentration at the joint between the composite material and the steel plate.

[0040] The stress-absorbing layer is made of HDPE resin, matrix asphalt and modified fiber. The mixture is cast on the hollow round pipe 1, channel 8 and the outside of channel 8, and forms a cylindrical absorption layer on the outside of channel 8. Finally, the sleeve and connecting rod are connected to the hollow round pipe 1 and the joint 3 in sequence.

[0041] Experimental verification

[0042] The structure of the present invention will be further explained in detail below with reference to finite element simulation calculations.

[0043] The finite element simulation takes a hollow circular tube with a height of 3378mm (the GFRP hollow circular tube 1 is placed vertically) as an example. By setting solid joints 3 with thicknesses of 50mm, 100mm, 150mm, 200mm and 300mm at each equally divided node inside the GFRP hollow circular tube 1, and changing the number of joints 3, 1, 2, 3 and 4 joints 3 are set at L / 2, L / 3, L / 4 and L / 5 of the GFRP hollow circular tube 1 respectively for simulation test research. The specific experimental parameters are shown in Table 1.

[0044] Table 1. Finite Element Component Setting Parameter Table

[0045]

[0046] Table 2. Finite element simulation results

[0047]

[0048] The finite element calculation results are shown in Table 2. Table 2 shows that the ultimate bearing capacity of the GFRP hollow tube 1 is improved after adding joints 3 inside the tube. When one joint 3 is placed at the mid-span of the GFRP hollow tube 1, the increase in bearing capacity of the member is 4.7%, 5.9%, 7.4%, 8.7%, and 11.1% for joints 3 with thicknesses of 50mm, 100mm, 150mm, 200mm, and 300mm, respectively. When one to four 50mm thick joints 3 are placed in the GFRP hollow tube 1, the peak load increases by 4.7%, 5.5%, 5.9%, and 6.8%, respectively. This indicates that the increase in the ultimate bearing capacity of the member becomes more and more significant with the increase in the thickness and number of joints 3.

[0049] This invention reduces the maximum mid-span stress and increases the mid-span deflection of the component by adding a spur joint 3 to the GFRP hollow tube 1, thereby enhancing the stability and deformation capacity of the structure. Finite element analysis was performed, and the simulation results with the spur joint 3 in the GFRP hollow tube 1 were compared with the experimental results of the GFRP hollow tube 1 without the spur joint 3. The comparison shows that the load-bearing capacity of the member is significantly improved after adding the spur joint 3.

[0050] Furthermore, the analysis of the influence of different thicknesses and numbers of joints 3 on the bearing capacity showed that as the thickness and number of joints 3 increased, the bearing capacity and deformation capacity of the member both increased.

[0051] Compared with the GFRP hollow tube without joint 3, the GFRP hollow tube 1 with joint 3 has a smaller slenderness ratio and significantly improved economic benefits under the same load-bearing capacity.

[0052] To further consider economic benefits and achieve optimal results, a study was conducted on the influence of the amount of "joints" on the load-bearing capacity of the members. A joint thickness of 50 mm was selected, and simulations were performed by varying the joint wall thickness. Similarly, taking a member with a length of 3378 mm and a cross-sectional dimension of Ф147×8.5 mm as an example, the parameters of each specimen are shown in Table 3, with joint wall thicknesses of 5 mm, 15 mm, 25 mm, 35 mm, 45 mm, and 55 mm, respectively.

[0053] Table 3 Component Parameter Table

[0054]

[0055] The ultimate bearing capacities of each specimen are shown in Table 4, where G8 represents a member without joints and Z-5 represents a member with solid joints. The table shows that the ultimate bearing capacity generally increases with increasing joint wall thickness, although the increase is relatively small. When the wall thickness increase is small, the bearing capacity improvement is significant; from 0mm to 5mm, the bearing capacity increases by 3.7%, while from 5mm to 60mm, the increase is only 1%. In conclusion, considering both economic benefits and the improvement in bearing capacity, it is recommended to select members with smaller joint wall thicknesses for processing and production.

[0056] Table 4. Finite element calculation results

[0057]

[0058] To further consider economic benefits and reduce material usage, a simulation analysis was conducted on changing the joint wall thickness. The results show that the load-bearing capacity increases with the increase of the joint wall thickness. When the wall thickness is small, the load-bearing capacity increases significantly with the increase of the wall thickness, but when the wall thickness is large, the increase in load-bearing capacity is small. Therefore, it is recommended to select members with smaller joint wall thickness for processing and production.

[0059] The embodiments described above are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any simple changes or equivalent substitutions of the technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention shall fall within the scope of protection of the present invention.

Claims

1. A hollow section GFRP cross arm with knuckles, characterized in that, The utility model relates to a kind of hollow circular tube (1);Bone joint (3) is provided with multiple, multiple the bone joint (3) is arranged inside the hollow circular tube (1) and sequentially arranged along the axial direction of hollow circular tube (1), and the two bone joint (3) of most two ends both exceed the end of hollow circular tube (1);Connecting structure is provided with two groups, and is located at the two ends of the hollow circular tube (1) respectively, and the connecting structure includes blind plate flange (2), the sleeve (4) of blind plate flange (2) is close to the end surface of hollow circular tube (1) and is provided with the connection of hollow circular tube (1) with the sleeve (4), the inner ring of sleeve (4) is provided with the connecting rod (5) connected with the outermost one bone joint (3), the outer thread of the outer ring of hollow circular tube (1) is provided with the first inner thread corresponding to the first outer thread, and the first outer thread and first inner thread form first connecting part between the first outer thread and first inner thread, the second outer thread is provided on the side wall of connecting rod (5), and the second inner thread corresponding to the second outer thread is provided in the inner ring of the outermost one bone joint (3), and the second outer thread and second inner thread form second connecting part between the second outer thread and second inner thread;The outer ring of sleeve (4) is provided with stress concentration ring (10), the inner ring of sleeve (4) is provided with buffer groove (7), and the upper hollow circular tube (1) is further provided with the passage (8) that is connected with the buffer groove (7) and the inside of hollow circular tube (1), and the passage (8) is located between the two bone joint (3) adjacent to end, and the buffer groove (7), passage (8) and the inside of hollow circular tube (1) are all provided with stress absorption layer. The outer end surface of the blind plate flange (2) is provided with adhesive injection hole (6) corresponding to the first connecting part and the second connecting part respectively. The adhesive uses epoxy resin adhesive. The outer side of the stress concentration ring (10) is further provided with a tight screw (9), and the other end of the tight screw (9) abuts on the outer side wall of the hollow circular tube (1) after passing through the stress concentration ring (10), the hollow circular tube (1) and the buffer groove (7) in sequence. Multiple bone joints (3) are arranged at equal intervals inside the hollow circular tube (1).

2. A hollow section GFRP cross arm with knuckles according to claim 1, characterized in that, The hollow circular tube (1) and the bone joint (3) are both made of GFRP material.

3. A hollow section GFRP cross arm with knuckles according to claim 2, characterized in that, The connecting structure is made of 45 steel.

4. The hollow-section GFRP cross arm with knots according to claim 1, characterized in that, ​ 5. The hollow-section GFRP cross arm with knots according to claim 1, characterized in that, ​ 6. The hollow-section GFRP cross arm with knots according to claim 1, characterized in that, ​ 7. The hollow-section GFRP cross arm with knots according to claim 1, characterized in that, ​

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