Hollow steel pipe for transmission line tower - UHPC three-column tower

Abstract

The present invention relates to the technical field of transmission line towers, and is a hollow steel tube-UHPC three-column tower frame for transmission line towers, which includes a plurality of column segments with decreasing external dimensions from top to bottom. The present invention has a reasonable and compact structure and is easy to use. It is achieved by locally thickening the upper and lower inner sides of the hollow concrete prefabricated tube, simultaneously providing internal tie bars in the thickened portion, providing full-length external tie bars throughout the entire tube, and fitting a steel tube fixedly installed with a connecting flange on the outer side of the thickened portion, and pre-planting a plurality of bolts with their inner ends located in the concrete prefabricated tube in the steel tube. This effectively improves the overall stiffness, connection strength, bearing capacity, and stability of the column limbs, and also fully utilizes the strength of the material, effectively reducing the steel ratio of the column limbs, saving concrete usage, reducing the deadweight of the column limbs, and facilitating earthquake resistance. It also saves material usage, facilitates transportation and hoisting, reduces project costs, and has good economic benefits.

Description

Technical Field

[0001] The invention relates to the technical field of transmission line towers, in particular to a hollow steel pipe-UHPC three-column tower frame for transmission line towers. Background Art

[0002] Transmission line towers are pole-shaped and tower-shaped structures that support overhead transmission line conductors and ground wires, maintaining a certain distance between them and the earth. Their safety and reliability are directly related to the safe operation of the entire transmission line. In overhead transmission line projects, tower construction costs account for approximately 30% or more of the project's capital investment, directly determining the economic viability of the line. With the construction of my country's ultra-high voltage (UHV) power grid and the promotion and application of new transmission technologies such as multi-circuit lines on the same tower, compact lines, and large-section conductors, the trend toward heavier loads and larger-scale transmission line towers has become increasingly evident. The development of a resource-saving and environmentally friendly society, the safety and stability of large power grids, and the complex and unusual nature of climate change are placing higher demands on the safety, reliability, economic efficiency, and environmental performance of tower structures, necessitating the urgent need for new transmission line tower structures. Summary of the Invention

[0003] The present invention provides a hollow steel tube-UHPC three-column tower for transmission line towers, which overcomes the shortcomings of the above-mentioned existing technologies and can effectively solve the problems of relatively weak bending and shearing resistance, poor integrity and high cost of existing large-scale power line towers with high loads.

[0004] The technical solution of the present invention is achieved through the following measures: a hollow steel tube-UHPC three-column tower for a transmission line tower, comprising a plurality of column segments whose external dimensions decrease from top to bottom, and each column segment is in the shape of a cone with a small upper portion and a large lower portion. All column segments are fixedly installed together in sequence from small to large to form a conical tower, and the cross-section of the conical tower gradually increases from top to bottom; each column segment comprises a crossbeam, a connecting flange and three column limbs distributed in a triangular shape, each column limb is a hollow steel tube concrete column limb, a crossbeam is fixedly installed between two adjacent column limbs on the left and right, and a connecting flange for connecting the two adjacent column limb segments on the upper and lower ends of each column limb is fixedly installed.

[0005] The following are further optimizations and / or improvements to the above technical solutions:

[0006] Each of the above-mentioned hollow steel tube concrete column limbs can include an upper steel tube, a lower steel tube, longitudinal reinforcement and a hollow concrete precast pipe. The concrete precast pipe includes an upper expanded diameter pipe section, a cylindrical pipe section and a lower expanded diameter pipe section with equal outer diameters. The upper end and the lower end of the cylindrical pipe section are respectively integrally formed with an upper expanded diameter pipe section and a lower expanded diameter pipe section. The wall thickness of the upper expanded diameter pipe section gradually increases from bottom to top, and the wall thickness of the lower expanded diameter pipe section gradually increases from top to bottom. The wall thickness of the lower end of the upper expanded diameter pipe section and the wall thickness of the upper end of the lower expanded diameter pipe section are both equal to the wall thickness of the cylindrical pipe section; an upper steel tube is provided on the outside of the upper expanded diameter pipe section, and a lower steel tube is provided on the outside of the lower expanded diameter pipe section. Connecting flanges are fixedly installed on the upper end of the upper steel pipe and the lower end of the lower steel pipe. A number of longitudinal reinforcements are evenly distributed and fixedly installed along the circumference between the above-mentioned two connecting flanges, and all longitudinal reinforcements are pre-buried in the concrete precast pipe.

[0007] Each of the above-mentioned longitudinal reinforcements may include external reinforcements, upper internal reinforcements and lower internal reinforcements. External reinforcements parallel to the outer side walls of the precast concrete pipes are embedded in the concrete precast pipes near one side of the upper steel pipe and the lower steel pipe. The upper and lower ends of the external reinforcements are respectively fixedly installed with the corresponding connecting flanges. Upper internal reinforcements parallel to the inner wall of the upper expanded diameter pipe section are embedded in the upper expanded diameter pipe section corresponding to the inner position of each external reinforcement. The lower end of the upper internal reinforcement extends to the inner side of the upper part of the cylindrical pipe section and is parallel to the inner wall of the cylindrical pipe section. Lower internal reinforcements parallel to the inner wall of the lower expanded diameter pipe section are embedded in the lower expanded diameter pipe section corresponding to the inner position of each external reinforcement. The upper end of the lower internal reinforcement extends to the inner side of the lower part of the cylindrical pipe section and is parallel to the inner wall of the cylindrical pipe section. The upper end of the upper internal reinforcement and the lower end of the lower internal reinforcement are respectively fixedly installed with the corresponding connecting flanges.

[0008] The above-mentioned hollow steel tube concrete column limbs may also include reinforcing rib plates, stud assemblies and annular stirrups. Several reinforcing rib plates are evenly distributed along the circumference between the upper steel tube and the connecting flange and between the lower steel tube and the connecting flange; several stud assemblies with inner ends embedded in the prefabricated concrete tube are fixedly installed at upper and lower intervals in the upper and lower steel tubes, and each stud assembly includes several studs evenly distributed along the circumference; several annular stirrups are provided at upper and lower intervals in the cylindrical tube section corresponding to the outer side of the longitudinal reinforcement.

[0009] The wall thickness of the upper end of the above-mentioned upper expanded diameter pipe section can be 1.5 to 2.5 times the wall thickness of its lower end, and the wall thickness of the lower end of the lower expanded diameter pipe section can be 1.5 to 2.5 times the wall thickness of its upper end; the height of the upper steel pipe and the height of the lower steel pipe can both be 1 to 3 times their outer diameters; the outer diameters of the upper and lower steel pipes are equal, and the wall thickness of the cylindrical pipe section can be 1 / 10 to 1 / 5 of the outer diameter of the upper steel pipe.

[0010] The three column limbs can be distributed in an equilateral triangle.

[0011] The concrete of the hollow steel tube concrete column can be ultra-high performance concrete.

[0012] The crossbeam may include an upper connecting rod and a lower connecting rod, and the upper connecting rod and the lower connecting rod are fixedly installed with an upper and lower spacing between two adjacent left and right column members.

[0013] The present invention has a reasonable and compact structure and is easy to use. It partially thickens the inner side of the upper and lower parts of the hollow concrete prefabricated pipe, and at the same time sets internal tie bars in the thickened parts, sets full-length external tie bars on the entire pipe, and sets a steel pipe fixedly installed with a connecting flange on the outer side of the thickened part, and pre-plants a number of studs with the inner ends located in the concrete prefabricated pipe in the steel pipe, thereby effectively improving the overall rigidity, connection strength, bearing capacity and stability of the column limb, greatly enhancing the bending and shearing resistance of large-scale power line towers with large loads, and making full use of The strength of the material used can effectively reduce the steel ratio of the column limbs, save concrete consumption, reduce the deadweight of the column limbs, which is beneficial to earthquake resistance, save material consumption, facilitate transportation and lifting, reduce the project cost, and have good economic benefits; the concrete uses ultra-high performance concrete, which can effectively improve the durability and earthquake resistance of the column limbs, save concrete consumption, and reduce the deadweight of the column limbs; all column limb segments are standardized factory-produced components and are installed in sections on site, which is simple to construct and is more conducive to the rapid assembly of large-scale power line towers with heavy loads, significantly improving construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Attachment Figure 1 This is a schematic diagram of the main structure of the column limb segment in Examples 1-8 of the present invention.

[0015] Attachment Figure 2 For attachment Figure 1 Schematic diagram of the main cross-sectional structure of the hollow steel tube concrete column.

[0016] Attachment Figure 3 For attachment Figure 1 Schematic diagram of the cross-sectional structure enlarged at AA in the middle.

[0017] Attachment Figure 4 For attachment Figure 1 Schematic diagram of the cross-sectional structure with the BB in the middle enlarged.

[0018] Attachment Figure 5 For attachment Figure 1 Schematic diagram of the cross-sectional structure at CC in the middle.

[0019] The codes in the accompanying drawings are: 1 for connecting flange, 2 for upper steel pipe, 3 for lower steel pipe, 4 for upper expanded diameter pipe section, 5 for cylindrical pipe section, 6 for lower expanded diameter pipe section, 7 for external tie bar, 8 for upper internal tie bar, 9 for lower internal tie bar, 10 for reinforcing rib plate, 11 for annular stirrup, 12 for bolt, 13 for upper connecting rod, and 14 for lower connecting rod. DETAILED DESCRIPTION

[0020] The present invention is not limited to the following embodiments, and specific implementation methods can be determined based on the technical solutions of the present invention and actual conditions.

[0021] In the present invention, for the convenience of description, the relative position relationship of each component is described based on the Figure 1 For example, the positional relationships of front, back, up, down, left, and right are determined according to the layout directions of the drawings in the specification.

[0022] The present invention will be further described below in conjunction with the embodiments and accompanying drawings:

[0023] Example 1: As shown in the attached Figure 1-5 As shown, the hollow steel tube-UHPC three-column tower for the transmission line tower includes several column segments with decreasing external dimensions from top to bottom, and each column segment is in the shape of a cone with a small upper part and a large lower part. All the column segments are fixed together in order from small to large to form a conical tower, and the cross section of the conical tower gradually increases from top to bottom; each column segment includes a crossbeam, a connecting flange 1 and three column limbs distributed in a triangular shape, each column limb is a hollow steel tube concrete column limb, a crossbeam is fixedly installed between the two adjacent column limbs on the left and right, and a connecting flange 1 for connecting the two adjacent column limb segments is fixedly installed on the upper and lower ends of each column limb.

[0024] Through such an arrangement, the conical tower structure with a triangular cross-section has high stability, and the two adjacent column stages can be connected by flange 1 and threaded fasteners, which is quick to install, reliable in connection, and has better integrity; the column segments can be standardized in the factory according to the design requirements and connected in sections on site, which is more conducive to the rapid assembly of large-load and large-scale power line towers, simple in construction, and higher in work efficiency; each column adopts a hollow steel tube concrete structure, which gives the column the advantages of high bearing capacity, high overall stiffness, and good stability, effectively improving the overall bending and shearing resistance of the tower; when ultra-high performance concrete is used, the durability and seismic resistance of the column can be further improved, the amount of concrete used can be saved, the dead weight of the column can be reduced, and the cost of the tower can be greatly reduced.

[0025] According to the requirements, the above-mentioned fixed installation can be achieved through a detachable installation method or a non-detachable installation method in the prior art. The fixed installation in this embodiment is achieved by welding. In this embodiment, the connecting flange 1 is disc-shaped, and a number of through holes are evenly distributed along the circumference thereof. The upper and lower adjacent connecting flanges 1 (that is, the upper and lower connecting flanges 1 that are in contact with each other) can be connected and fastened by bolts, nuts and flat spring washers.

[0026] The above-mentioned hollow steel tube-UHPC three-column tower for transmission line towers can be further optimized and / or improved according to actual needs:

[0027] Example 2: As shown in the attached Figure 1-5 As shown, each hollow steel tube concrete column limb includes an upper steel tube 2, a lower steel tube 3, longitudinal reinforcement and a hollow concrete precast tube. The concrete precast tube includes an upper expanded diameter tube section 4, a cylindrical tube section 5 and a lower expanded diameter tube section 6 with equal outer diameters. The upper and lower ends of the cylindrical tube section 5 are respectively integrally formed with the upper expanded diameter tube section 4 and the lower expanded diameter tube section 6. The wall thickness of the upper expanded diameter tube section gradually increases from bottom to top, and the wall thickness of the lower expanded diameter tube section 6 gradually increases from top to bottom. The wall thickness of the lower end of the upper expanded diameter tube section 4 and the wall thickness of the upper end of the lower expanded diameter tube section 6 are both equal to the wall thickness of the cylindrical tube section 5; an upper steel tube 2 is provided on the outside of the upper expanded diameter tube section 4, and a lower steel tube 3 is provided on the outside of the lower expanded diameter tube section 6. A connecting flange 1 is fixedly installed on the upper end of the upper steel tube 2 and the lower end of the lower steel tube 3. A number of longitudinal reinforcements are evenly distributed and fixedly installed along the circumference between the above two connecting flanges 1, and all longitudinal reinforcements are pre-buried in the concrete precast tube.

[0028] By such an arrangement, the concrete precast tube with large wall thickness at both ends and small wall thickness in the middle, and the outer shape still maintaining a cylindrical and hollow shape, can make the column limbs have higher bending and shear resistance while greatly reducing the weight of the concrete precast tube. In combination with the longitudinal reinforcement embedded in the concrete precast tube, and the upper steel tube 2 and the lower steel tube 3 sleeved on the upper and lower outer sides of the concrete precast tube, the two ends of the longitudinal reinforcement, the upper end of the upper steel tube 2 and the lower end of the lower steel tube 3 are fixedly installed on the corresponding connecting flange 1 at the same time, which can further enhance the integrity of the hollow steel tube concrete column limb, improve the connection strength between the two ends of the concrete precast tube and the corresponding connecting flange 1, and make the column limbs have high bearing capacity, large overall rigidity and good stability, and make full use of the strength of the material. The steel pipes only partially arranged outside the concrete precast tube can greatly reduce the steel ratio of the column limb, save concrete consumption, reduce the dead weight of the column limb, which is beneficial to earthquake resistance, and also save material consumption, which is convenient for transportation and lifting, greatly reduces the project cost, and has good economic benefits.

[0029] According to the requirements, since the three column limbs are distributed in a triangle, each column limb is tilted toward the center of gravity of the tower, but the connecting flanges 1 fixedly installed at both ends of the column limb are both set horizontally.

[0030] Example 3: As shown in the attached Figure 1-5As shown, each longitudinal tie bar includes an outer tie bar 7, an upper inner tie bar 8 and a lower inner tie bar 9. The outer tie bar 7 parallel to the outer side wall of the concrete precast pipe is pre-embedded in the concrete precast pipe near the upper steel pipe 2 and the lower steel pipe 3. The upper and lower ends of the outer tie bar 7 are respectively fixed to the corresponding connecting flange 1. The upper inner tie bar 8 parallel to the inner wall of the upper enlarged diameter pipe section 4 is pre-embedded in the upper enlarged diameter pipe section 4 corresponding to the inner side of each outer tie bar 7. The lower end of the upper inner tie bar 8 extends to the inner side of the upper part of the cylindrical pipe section 5 and is parallel to the inner wall of the cylindrical pipe section 5. The lower inner tie bar 9 parallel to the inner wall of the lower enlarged diameter pipe section 6 is pre-embedded in the lower enlarged diameter pipe section 6 corresponding to the inner side of each outer tie bar 7. The upper end of the lower inner tie bar 9 extends to the inner side of the lower part of the cylindrical pipe section 5 and is parallel to the inner wall of the cylindrical pipe section 5. The upper end of the upper inner tie bar 8 and the lower end of the lower inner tie bar 9 are respectively fixed to the corresponding connecting flange 1.

[0031] Through such an arrangement, the double rows of tie bars arranged in parallel along the outer wall and inner wall of the precast concrete pipe can effectively enhance the connection strength between the precast concrete pipe and its corresponding connecting flange 1, further enhance the strength of the outer wall and inner wall of the precast concrete pipe, effectively improve the overall mechanical properties of the precast concrete pipe, and enhance its bending and shearing resistance; the internal tie bars adopt a segmented design, so as to ensure the strength of the precast concrete pipe while effectively saving the use of steel.

[0032] According to the requirements, in this embodiment, the distance that the upper inner tensioning bars 8 and the lower inner tensioning bars 9 extend into the circular tube column section 5 is 40 cm. The two ends of all the external tensioning bars 7, the upper ends of all the upper inner tensioning bars 8 and the lower ends of the lower inner tensioning bars 9 are fixed on the corresponding connecting flanges 1 by welding.

[0033] Example 4: As shown in the attached Figure 1-5 As shown, the hollow steel tube concrete column also includes a reinforcing rib plate 10, a stud assembly and annular stirrups 11. Several reinforcing rib plates 10 are evenly distributed along the circumference between the upper steel tube 2 and the connecting flange 1 and between the lower steel tube 3 and the connecting flange 1; several stud assemblies with inner ends embedded in the prefabricated concrete tube are fixedly installed at upper and lower intervals in the upper steel tube 2 and the lower steel tube 3, and each stud assembly includes several studs 12 evenly distributed along the circumference; several annular stirrups 11 are provided at upper and lower intervals in the cylindrical tube section 5 corresponding to the outer side of the longitudinal reinforcement.

[0034] By such arrangement, the reinforcing rib plate 10 can effectively enhance the connection strength between the upper steel pipe 2, the lower steel pipe 3 and their corresponding connecting flanges 1, thereby effectively improving the bending and shearing resistance of the tower frame; the outer end is fixedly installed together with the inner wall of the steel pipe, and the inner end is pre-embedded in the precast concrete pipe. Its function is equivalent to the rivet in the prior art, which can greatly enhance the connection strength between the steel pipe and the precast concrete pipe, and can effectively avoid the separation of the precast concrete pipe and the steel pipe during use, while also improving the overall bending and shearing resistance of the column limb; in the absence of steel pipe support, the annular stirrups 11 and the external tension bars 7 can be interwoven into a mesh, thereby further enhancing the strength of the concrete precast pipe without steel pipe (i.e., the cylindrical pipe section 5), effectively improving the bending and shearing resistance of the cylindrical pipe section 5, making it lightweight while having high mechanical properties.

[0035] According to the requirements, in this embodiment, the fixed installation between the reinforcing rib plate 10 and the corresponding steel pipe and the connecting flange 1, and between each stud 12 and the corresponding steel pipe inner wall are achieved by welding methods in the existing public technology; in this embodiment, the distance between the upper and lower adjacent studs 12 is 10 cm, and the spacing between the upper and lower adjacent annular stirrups 11 is 40 cm. The studs 12 are cylindrical head welding studs for arc stud welding in the existing public technology.

[0036] Example 5: As shown in the attached Figure 2 As shown, the wall thickness of the upper end of the upper expanded diameter pipe section 4 is 1.5 to 2.5 times the wall thickness of its lower end, and the wall thickness of the lower expanded diameter pipe section 6 is 1.5 to 2.5 times the wall thickness of its upper end; the height of the upper steel pipe 2 and the height of the lower steel pipe 3 are both 1 to 3 times their outer diameters; the outer diameters of the upper steel pipe 2 and the lower steel pipe 3 are equal, and the wall thickness of the cylindrical pipe section 5 is 1 / 10 to 1 / 5 of the outer diameter of the upper steel pipe 2.

[0037] By such an arrangement, in this embodiment, when the wall thickness of the upper end of the upper expanded diameter pipe section 4 is twice the wall thickness of its lower end, and the wall thickness of the lower end of the lower expanded diameter pipe section 6 is twice the wall thickness of its upper end, the overall strength and rigidity of the precast concrete pipe can be ensured, and the weight of the precast concrete pipe can be reduced to the maximum extent, concrete can be saved, and the cost performance of the precast concrete pipe can be improved; when the height of the upper steel pipe 2 and the height of the lower steel pipe 3 are both twice their outer diameters, the connection strength between the upper and lower ends of the precast concrete pipe and the connecting flange 1 can be ensured, and the steel pipe material can be saved to the maximum extent, effectively reducing the production cost; when the wall thickness of the cylindrical pipe section 5 is 1 / 10 to 1 / 5 of the outer diameter of the steel pipe, the strength of the precast concrete pipe can meet the design requirements and the weight of the precast concrete pipe can be avoided to be too large.

[0038] Example 6: As shown in the attached Figure 1 、 4 As shown in Figure 5, the three column limbs are distributed in an equilateral triangle.

[0039] Through such an arrangement, when the three column limbs in the column limb segment are distributed in an equilateral triangle, since the equilateral triangle has the greatest symmetry and uniformity, the stress of the three column limbs in the structure can be evenly distributed, thereby effectively improving the structural stability of the column limb segment.

[0040] Example 7: As shown in the attached Figure 1-5 As shown, the concrete of the hollow steel tube concrete column is ultra-high performance concrete.

[0041] Through this setting, ultra-high performance concrete (UHPC) has super-high durability and super-high mechanical properties compared to ordinary concrete. After proper reinforcement, its mechanical properties are close to those of steel structures. At the same time, it has excellent wear resistance and explosion resistance, is more suitable for thin-walled structures, and has better wind erosion resistance.

[0042] Example 8: As shown in the attached Figure 1-2 As shown in Figures 4-5, the crossbeam includes an upper connecting rod 13 and a lower connecting rod 14, and the upper connecting rod 13 and the lower connecting rod 14 are fixedly installed between two adjacent left and right column members at intervals.

[0043] This arrangement allows the double crossbeam composed of the upper connecting rod 13 and the lower connecting rod 14 to better enhance the tower's bending and shear resistance. As required, in this embodiment, the ends of the upper connecting rod 13 are welded to two adjacent upper steel tubes 2, and the ends of the lower connecting rod 14 are welded to two adjacent lower steel tubes 3. The width of each upper connecting rod 13 is smaller than that of the lower connecting rod 14. In this embodiment, the upper and lower connecting rods 13, 14 are fixed to the outer sides of the corresponding steel tubes by welding. Alternatively, they can be fixed using threaded fasteners, threaded connections, or other embedded components as known in the art.

[0044] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or removed according to actual needs to meet the requirements of different situations.

Claims

1. A hollow steel tube-UHPC three-column tower for transmission line towers, characterized in that It includes several column segments with decreasing dimensions from top to bottom, and each column segment is in the shape of a cone with a small top and a large bottom. All column segments are fixed together in order from small to large to form a tapered tower frame, and the cross section of the tapered tower frame gradually increases from top to bottom; each column segment includes a crossbeam, a connecting flange and three column limbs distributed in a triangle, each column limb is a hollow steel tube concrete column limb, a crossbeam is fixedly installed between the two adjacent column limbs on the left and right, and a connecting flange for connecting the upper and lower adjacent column segments is fixedly installed at the upper and lower ends of each column limb, and each hollow steel tube concrete column limb includes an upper steel pipe, a lower steel pipe, longitudinal reinforcement and a hollow concrete Prefabricated pipe, concrete prefabricated pipe includes an upper expanded diameter pipe section, a cylindrical pipe section and a lower expanded diameter pipe section with equal outer diameters. The upper and lower ends of the cylindrical pipe section are respectively integrally formed with the upper expanded diameter pipe section and the lower expanded diameter pipe section. The wall thickness of the upper expanded diameter pipe section gradually increases from bottom to top, and the wall thickness of the lower expanded diameter pipe section gradually increases from top to bottom. The wall thickness of the lower end of the upper expanded diameter pipe section and the wall thickness of the upper end of the lower expanded diameter pipe section are both equal to the wall thickness of the cylindrical pipe section; an upper steel pipe is provided on the outside of the upper expanded diameter pipe section, and a lower steel pipe is provided on the outside of the lower expanded diameter pipe section. Connecting flanges are fixedly installed on the upper end of the upper steel pipe and the lower end of the lower steel pipe. Several longitudinal reinforcements are evenly distributed and fixedly installed along the circumference between the above two connecting flanges, and all longitudinal reinforcements are pre-buried in the concrete prefabricated pipe.

2. The hollow steel tube-UHPC three-column tower for transmission line tower according to claim 1 is characterized in that Each longitudinal tie bar includes an outer tie bar, an upper inner tie bar and a lower inner tie bar. The outer tie bar parallel to the outer side wall of the precast concrete pipe is embedded in the precast concrete pipe near the upper steel pipe and the lower steel pipe. The upper and lower ends of the outer tie bar are respectively fixed to the corresponding connecting flanges. The upper inner tie bar parallel to the inner wall of the upper expanded diameter pipe section is embedded in the upper expanded diameter pipe section corresponding to the inner position of each outer tie bar. The lower end of the upper inner tie bar extends to the inner side of the upper part of the cylindrical pipe section and is parallel to the inner wall of the cylindrical pipe section. The lower inner tie bar parallel to the inner wall of the lower expanded diameter pipe section is embedded in the lower expanded diameter pipe section corresponding to the inner position of each outer tie bar. The upper end of the lower inner tie bar extends to the inner side of the lower part of the cylindrical pipe section and is parallel to the inner wall of the cylindrical pipe section. The upper end of the upper inner tie bar and the lower end of the lower inner tie bar are respectively fixed to the corresponding connecting flanges.

3. The hollow steel tube-UHPC three-column tower for transmission line towers according to claim 1 or 2, characterized in that The hollow steel tube concrete column also includes reinforcing rib plates, stud assemblies and annular stirrups. Several reinforcing rib plates are evenly distributed along the circumference between the upper steel tube and the connecting flange and between the lower steel tube and the connecting flange. Several stud assemblies with their inner ends embedded in the prefabricated concrete tube are fixedly installed at upper and lower intervals in the upper and lower steel tubes, and each stud assembly includes several studs evenly distributed along the circumference. Several annular stirrups are provided at upper and lower intervals in the cylindrical tube section corresponding to the outer side of the longitudinal reinforcement.

4. The hollow steel tube-UHPC three-column tower for transmission line towers according to claim 1 or 2, characterized in that The wall thickness of the upper end of the upper expanded diameter pipe section is 1.5 to 2.5 times the wall thickness of its lower end, and the wall thickness of the lower expanded diameter pipe section is 1.5 to 2.5 times the wall thickness of its upper end; the height of the upper steel pipe and the height of the lower steel pipe are both 1 to 3 times their outer diameters; the outer diameters of the upper and lower steel pipes are equal, and the wall thickness of the cylindrical pipe section is 1 / 10 to 1 / 5 of the outer diameter of the upper steel pipe.

5. The hollow steel tube-UHPC three-column tower for transmission line tower according to claim 3 is characterized in that The wall thickness of the upper end of the upper expanded diameter pipe section is 1.5 to 2.5 times the wall thickness of its lower end, and the wall thickness of the lower expanded diameter pipe section is 1.5 to 2.5 times the wall thickness of its upper end; the height of the upper steel pipe and the height of the lower steel pipe are both 1 to 3 times their outer diameters; the outer diameters of the upper and lower steel pipes are equal, and the wall thickness of the cylindrical pipe section is 1 / 10 to 1 / 5 of the outer diameter of the upper steel pipe.

6. The hollow steel tube-UHPC three-column tower for transmission line towers according to claim 1, 2 or 5, characterized in that The three column limbs are distributed in an equilateral triangle; or / and, the concrete of the hollow steel tube concrete column limbs is ultra-high performance concrete.

7. The hollow steel tube-UHPC three-column tower for transmission line towers according to claim 3 is characterized in that The three column limbs are distributed in an equilateral triangle; or / and, the concrete of the hollow steel tube concrete column limbs is ultra-high performance concrete.

8. The hollow steel tube-UHPC three-column tower for transmission line towers according to claim 4, characterized in that The three column limbs are distributed in an equilateral triangle; or / and, the concrete of the hollow steel tube concrete column limbs is ultra-high performance concrete.

9. The hollow steel tube-UHPC three-column tower for transmission line towers according to claim 1, 2, 5, 7, or 8, characterized in that The crossbeam includes an upper connecting rod and a lower connecting rod, and the upper connecting rod and the lower connecting rod are fixedly installed between two adjacent column members on the left and right with an upper and lower interval.

10. The hollow steel tube-UHPC three-column tower for transmission line towers according to claim 6, characterized in that The crossbeam includes an upper connecting rod and a lower connecting rod, and the upper connecting rod and the lower connecting rod are fixedly installed between two adjacent column members on the left and right with an upper and lower interval.

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