Positioning and assembling construction method for special-shaped variable-diameter circular tube inclined truss steel structure

Abstract

The invention discloses a positioning assembly construction method for a special-shaped variable-diameter circular tube inclined truss steel structure, and relates to the field of steel structures. The positioning assembly construction method of the special-shaped variable-diameter circular pipe inclined truss steel structure comprises the steps that the outer wall of a variable-diameter section of a circular pipe is equally cut in the circumferential direction to form a plurality of triangular openings, the variable-diameter section of the circular pipe is heated, then the openings are closed and sealed, and the variable-diameter circular pipe is obtained through welding; outputting a two-dimensional plane graph of the variable-diameter circular tube inclined truss, displaying the size and the positioning node of each variable-diameter circular tube in the spatial distortion direction and the bending inclination direction, positioning each variable-diameter circular tube and the part according to the two-dimensional plane graph, splicing and then welding to obtain the variable-diameter circular tube inclined truss; and the assembling jig frame is arranged, and the variable-diameter circular tube inclined trusses are sequentially positioned and fixed to the assembling jig frame to be subjected to pre-assembling welding. The positioning and assembling construction method of the special-shaped variable-diameter circular tube inclined truss steel structure can greatly reduce material waste and construction cost and shorten the construction period.

Description

Technical Field

[0001] The present application relates to the field of steel structures, and in particular to a positioning and assembly construction method for a special-shaped variable-diameter circular tube oblique truss steel structure. Background Art

[0002] Special-shaped steel truss structures are widely used in engineering construction due to their advantages of high structural strength, light weight and short construction period. Special-shaped steel truss structures require that round tubes be processed into variable diameter round tubes and then several round tube oblique trusses of different diameters be connected to form a truss structure. The existing variable diameter round tube processing method generally involves cutting the main body and pre-bending the two sides of the main body through a pressure device to process them into several tubes of different diameters and then butting them together. The mold cost is high and the construction period is long. In addition, the conventional steel structure trusses currently manufactured have corresponding symmetry and the material size is consistent, so the positioning is simple during the manufacturing process. However, when the steel truss structure used has a special-shaped structure with variable diameter, bending and spatial distortion, the variable diameter splicing, spatial distortion, intersecting line welds, more splicing welds, and three-dimensional spatial positioning and assembly between components, and the assembly, adjustment and positioning of the tire frame will cause great construction difficulties, further extending the construction period and increasing the construction cost. Summary of the invention

[0003] The purpose of the present application is to provide a positioning and assembly construction method for a special-shaped variable-diameter circular tube oblique truss steel structure, which can greatly reduce material waste and construction costs and shorten construction period.

[0004] This application is implemented as follows: The present application provides a positioning and assembly construction method for a special-shaped variable diameter circular tube oblique truss steel structure, comprising the following steps: The circumferences of the large-diameter end and the small-diameter end at both ends of the reduced diameter section of the circular tube are calculated, and the outer wall of the reduced diameter section of the circular tube is equally cut along the circumferential direction to form a plurality of triangular openings, the sum of the circumferential lengths of the ends of each opening is equal to the difference in circumference between the large-diameter end and the small-diameter end, and the reduced diameter section of the circular tube is heated, and each opening is closed and welded to obtain a reduced diameter circular tube; Output the two-dimensional plane diagram of the variable diameter circular tube oblique truss, display the size and positioning nodes of each variable diameter circular tube in the spatial twisting direction and bending slope direction, and locate, splice and weld each variable diameter circular tube and parts according to the two-dimensional plane diagram to obtain the variable diameter circular tube oblique truss; Arrange the assembly frame, position and fix each variable diameter circular tube oblique truss on the assembly frame in sequence for pre-assembly, and weld each variable diameter circular tube oblique truss to obtain a special-shaped variable diameter circular tube oblique truss steel structure.

[0005] In some optional implementation schemes, when the reducing section of the circular tube is heated and then closed to seal each opening, the reducing section is heated repeatedly, a transition positioning piece is set on the outer wall of the reducing section for positioning, and a manual hoist is used to push the reducing section to close and seal each opening.

[0006] In some optional implementation schemes, when welding to obtain a reduced diameter circular tube, a groove is formed at each opening and then the root is cleaned with a flux-cored wire before welding. After the welding is completed and the weld is inspected and qualified, the equal-strength weld is polished and smoothed to form a seamless joint.

[0007] In some optional implementation schemes, when various variable diameter circular tubes and parts are positioned according to a two-dimensional plane diagram to obtain a variable diameter circular tube oblique truss, the dimensions of various spatial distortions and bending parts of the variable diameter circular tube are located, and the outer sides of the spatial distortions and bending parts are heated, a manual hoist is used to apply compressive and tensile forces to the spatial distortions and bending parts, and baffles and arc-starting plates are set at the spatial distortions and bending parts for positioning, and then the spatial distortions and bending parts are spot welded to prevent rebound.

[0008] In some optional implementation schemes, when the various reduced diameter circular tubes and parts are positioned and spliced ​​according to the two-dimensional plan to obtain the reduced diameter circular tube oblique truss, the diagonal size of the reduced diameter circular tube oblique truss is checked, and the reduced diameter circular tube oblique truss is welded when the error is within the allowable range.

[0009] In some optional implementation schemes, when arranging the assembly tire frame, the elevation of each support point on the assembly tire frame and the axial distance of each support point are measured for positioning, and corbel positioning pieces are set on the assembly tire frame for positioning according to the different heights of the corbel positions of the variable diameter circular tube inclined truss, and then the positioning distance between each assembly tire frame is determined according to the corbel positions.

[0010] In some optional implementation schemes, when each variable diameter circular tube inclined truss is positioned and fixed on an assembly frame in sequence for pre-assembly, a two-dimensional plane figure is first calculated through a three-dimensional model of the special-shaped variable diameter circular tube inclined truss steel structure, the previous variable diameter circular tube inclined truss is hoisted on the assembly frame, the positions of each center of gravity line of the previous variable diameter circular tube inclined truss arranged at intervals along the length direction are measured and positioned with reference to the two-dimensional plane figure, the size deviation of the previous variable diameter circular tube inclined truss is verified, and then the next variable diameter circular tube inclined truss is hoisted, and positioned with reference to the two-dimensional plane figure according to the cross-sectional width distance between the previous variable diameter circular tube inclined truss and the next variable diameter circular tube inclined truss, and the previous variable diameter circular tube inclined truss and the next variable diameter circular tube inclined truss are welded.

[0011] In some optional implementation schemes, before welding a front variable diameter circular tube oblique truss and a rear variable diameter circular tube oblique truss, the distance between the diagonals of the front variable diameter circular tube oblique truss and the rear variable diameter circular tube oblique truss is measured and positioned with reference to a two-dimensional plane figure.

[0012] The beneficial effects of the present application are as follows: the positioning, assembly and construction method of the special-shaped variable diameter circular tube oblique truss steel structure provided by the present application comprises the following steps: calculating the circumference of the large diameter end and the small diameter end at both ends of the variable diameter section of the circular tube, cutting the outer wall of the variable diameter section of the circular tube in equal parts along the circumferential direction to form a plurality of triangular openings, the sum of the circumferential lengths of the ends of each opening being equal to the difference in circumference between the large diameter end and the small diameter end, heating the variable diameter section of the circular tube, closing and sealing each opening, and welding to obtain a variable diameter circular tube; outputting a two-dimensional plan view of the variable diameter circular tube oblique truss, displaying the dimensions and positioning nodes of each variable diameter circular tube in the spatial distortion direction and the bending slope direction, positioning each variable diameter circular tube and parts according to the two-dimensional plan view, splicing and welding them to obtain a variable diameter circular tube oblique truss; arranging an assembly frame, positioning and fixing each variable diameter circular tube oblique truss on the assembly frame in turn for pre-assembly, and welding each variable diameter circular tube oblique truss to obtain a special-shaped variable diameter circular tube oblique truss steel structure. The positioning, assembly and construction method of the special-shaped variable-diameter circular tube oblique truss steel structure provided in the present application adopts the method of cutting the circular tube into equal parts and then performing heating and shrinking welding to process the variable-diameter section of the circular tube, and uses two-dimensional plane positioning to carry out the construction of the spatial twisting direction and the bending slope direction of the variable-diameter circular tube, which can greatly reduce material waste, reduce construction costs, and shorten construction period. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 A schematic diagram of the process of positioning and assembling the construction method of the special-shaped variable diameter circular tube oblique truss steel structure provided in the embodiment of the present application; Figure 2 A schematic diagram of the structure unfolded along the circumferential direction when an opening is opened on a circular tube in the positioning and assembly construction method of the special-shaped variable-diameter circular tube oblique truss steel structure provided in an embodiment of the present application; Figure 3 A schematic diagram of the structure of the reduced diameter section obtained by heating and closing the openings and welding them together in the positioning and assembly construction method of the special-shaped reduced diameter circular tube oblique truss steel structure provided in the embodiment of the present application; Figure 4 A schematic diagram of the structure of the spatial distortion and bending slope of the variable diameter circular tube for processing the variable diameter circular tube oblique truss in the positioning and assembly construction method of the special-shaped variable diameter circular tube oblique truss steel structure provided in the embodiment of the present application; Figure 5A schematic diagram of the partial structure of the first section for positioning the spatial distortion and bending parts when processing the variable diameter circular tube of the variable diameter circular tube oblique truss in the positioning and assembly construction method of the special-shaped variable diameter circular tube oblique truss steel structure provided in the embodiment of the present application; Figure 6 A schematic diagram of the partial structure of the second section for positioning the spatial distortion and bending parts when processing the variable diameter circular tube of the variable diameter circular tube oblique truss in the positioning and assembly construction method of the special-shaped variable diameter circular tube oblique truss steel structure provided in the embodiment of the present application; Figure 7 A schematic diagram of the partial structure of the third section for positioning the spatial distortion and bending parts when processing the variable diameter circular tube of the variable diameter circular tube oblique truss in the positioning and assembly construction method of the special-shaped variable diameter circular tube oblique truss steel structure provided in the embodiment of the present application; Figure 8 A structural schematic diagram of checking the diagonal dimensions of the variable diameter circular tube oblique truss in the positioning and assembly construction method of the special-shaped variable diameter circular tube oblique truss steel structure provided in the embodiment of the present application; Fig. 9 A schematic structural diagram of a method for positioning and assembling a special-shaped variable diameter circular tube oblique truss steel structure provided in an embodiment of the present application, in which a laser level is used to measure the elevation of each support point on the assembly frame and the distance between the axes of each support point for positioning; Fig.10 A schematic structural diagram of a method for positioning and assembling a special-shaped variable diameter circular tube oblique truss steel structure provided in an embodiment of the present application, wherein a laser level is used to measure the positions of the center of gravity lines of the previous variable diameter circular tube oblique truss arranged at intervals along the length direction and reference is made to a two-dimensional plane figure for positioning; Fig.11 A schematic structural diagram of positioning according to a cross-sectional width distance between a preceding variable diameter circular tube oblique truss and a succeeding variable diameter circular tube oblique truss in a positioning and assembly construction method of a special-shaped variable diameter circular tube oblique truss steel structure provided in an embodiment of the present application with reference to a two-dimensional plane graphic; Fig.12 A schematic structural diagram of measuring the distance between the diagonal lines of a preceding variable diameter circular tube oblique truss and a succeeding variable diameter circular tube oblique truss by referring to a two-dimensional plane figure for positioning in a positioning and assembly construction method of a special-shaped variable diameter circular tube oblique truss steel structure provided in an embodiment of the present application; Fig.13 A structural schematic diagram of the positioning and assembly construction method of the special-shaped variable-diameter circular tube oblique truss steel structure provided in an embodiment of the present application, in which a laser level is used to observe the straightness to pre-splice and weld two variable-diameter circular tube oblique trusses.

[0015] In the figure: 100, round tube; 110, opening; 120, transition positioning piece; 130, manual hoist; 140, laser level positioning instrument; 150, center of gravity line; 160, corbel positioning piece. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0017] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0018] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0019] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the application is usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0020] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0021] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0022] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0023] The characteristics and performance of the positioning and assembly construction method of the special-shaped variable-diameter circular tube oblique truss steel structure of the present application are further described in detail below in conjunction with the embodiments.

[0024] The present application provides a method for positioning and assembling a special-shaped variable diameter circular tube oblique truss steel structure, comprising the following steps: Step 1: Place the sample on the jig, check the plane dimensions, and start the assembly process after checking that everything is correct. Figure 1 As shown, firstly, the circumference of the large-diameter end and the small-diameter end at both ends of the diameter-reducing section of the circular tube 100 is calculated by the circumference formula, and a computer-programmed CNC intersecting wire cutting machine is used to equally cut the outer wall of the diameter-reducing section of the circular tube 100 along the circumferential direction to form a plurality of triangular openings 110, and the sum of the lengths d of the ends of the openings 110 along the circumferential direction of the circular tube 100 is equal to the difference between the circumference of the large-diameter end and the circumference of the small-diameter end of the diameter-reducing section of the circular tube 100; like Figure 2 As shown, since the transition distance of the arc of the reducing section is not a smooth transition, it is necessary to repeatedly use flames to heat the reducing section of the round tube 100. After the reducing section of the round tube 100 is heated to 750-850°C, a transition positioning piece 120 is set on the outer wall of the reducing section for positioning, and a manual hoist 130 is used to push the reducing section to close and seal each opening 110 for welding. During welding, after a groove is opened in each opening 110, a flux-cored wire is used to clean the root and then weld. After welding is completed, the weld is inspected. After the weld is qualified, the equal-strength weld is polished and smoothed to form a seamless splicing to obtain a reducing round tube.

[0025] Step 2: Since the variable diameter circular tubes constituting the variable diameter circular tube oblique truss have spatial distortion and bending inclination, which is not conducive to positioning and assembly in three-dimensional space, a two-dimensional plane diagram of the variable diameter circular tube oblique truss is output by computer, and the dimensions and positioning nodes of the spatial distortion direction and bending inclination direction of each variable diameter circular tube are displayed on the two-dimensional plane diagram, and then the various variable diameter circular tubes and parts are positioned, spliced ​​and welded according to the two-dimensional plane diagram to obtain the variable diameter circular tube oblique truss; Specifically, Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown in the figure, according to the CAD two-dimensional plane drawing of the variable diameter circular tube oblique truss, the dimensions of each spatial distortion and bending part of the variable diameter circular tube are located as follows Figure 5 A1, A1', A2, A2', and the upstream and downstream multiple positions of the outer side surface of the space distortion and bending part of the variable diameter circular tube are heated to 750-850℃ respectively, and the manual hoist 130 is used to apply tension to the space distortion and bending part of the variable diameter circular tube, and baffles and arc-starting plates are set at the space distortion and bending part of the variable diameter circular tube for positioning. When the space distortion and bending part of the variable diameter circular tube reaches the preset degree, spot welding is performed to prevent rebound, so as to ensure the stability of the inclination and curvature of the space distortion and bending part of the variable diameter circular tube, and then the assembly process of other parts of the variable diameter circular tube oblique truss is carried out according to the lofting. After the assembly is completed, the size inspection before welding is carried out, such as Figure 8 As shown, the diagonal L of the variable diameter circular tube oblique truss is checked at the same time. d When the size and error are within the allowable range, a variable diameter circular tube oblique truss is obtained by welding.

[0026] Step 3: Arrange and assemble the tire frame, such as Fig. 9 As shown, a laser leveling device 140 is used to measure the elevation of each support point on the assembly frame and the distance between the axes of each support point for positioning, so as to ensure the flatness and external dimensions of the assembly of the variable diameter circular tube inclined truss, and a corbel positioning piece 160 is provided on the assembly frame for positioning according to the different heights of the corbel positions of the variable diameter circular tube inclined truss, and then the positioning distance between each assembly frame is determined according to the corbel positions of the variable diameter circular tube inclined truss, so that the elevation positioning of the assembly frame takes 1m from the ground as the reference zero point. Since the reference planes of the landing points of each assembly frame of the variable diameter circular tube inclined truss are different, it is necessary to lift the landing point of each assembly frame in turn by using a crane to a preset height and drop it to the position as shown in the figure. Figure 5 , Figure 6 and Figure 7 A1, A2, A3, A4 in; Each variable diameter circular tube oblique truss is positioned and fixed on the assembly frame in turn for pre-assembly. First, a three-dimensional model of the special-shaped variable diameter circular tube oblique truss steel structure is established by computer, and then a two-dimensional plane figure of the special-shaped variable diameter circular tube oblique truss steel structure is calculated according to the three-dimensional model. Then, the previous variable diameter circular tube oblique truss is hoisted on the assembly frame. Fig.10 As shown, the positions of the center of gravity lines 150 of the previous variable diameter circular tube oblique truss arranged at intervals along the length direction are measured by a laser leveling locator 140, and the positions are referenced to the two-dimensional plane figure, and the size deviation and horizontal position of the previous variable diameter circular tube oblique truss are checked to see if there is a deviation, and adjustments are made if there is a deviation; like Fig.11As shown, the next variable diameter circular tube inclined truss is then hoisted and positioned according to the cross-sectional widths a and b of the previous variable diameter circular tube inclined truss and the next variable diameter circular tube inclined truss from the reference plane two-dimensional figure, as shown in FIG. Fig.12 As shown, measure the diagonal L of the first variable diameter circular tube oblique truss and the second variable diameter circular tube oblique truss d The distance dimensions are positioned with reference to the two-dimensional plane figure. After the positioning is completed, the dimensions of each node of the previous variable diameter circular tube inclined truss and the next variable diameter circular tube inclined truss are matched again, such as Fig.13 As shown, a laser leveling device 140 is used to check whether the straightness and other aspects meet the requirements. After checking that everything is correct, the front and rear two variable diameter circular tube oblique trusses can be welded. Subsequently, the two variable diameter circular tube oblique trusses are spliced ​​and welded in sequence according to the above steps, and finally the special-shaped variable diameter circular tube oblique truss steel structure is assembled.

[0027] The positioning, assembling and construction method of the special-shaped variable diameter circular tube oblique truss steel structure provided in the embodiment of the present application adopts a computer-programmed CNC intersecting line cutting machine to cut the circular tube 100 into equal circles to obtain a plurality of triangular openings 110, and then uses flame heat processing to shrink and close the circular tube 100, and welds the openings 110 of the circular tube 100 to obtain a variable diameter circular tube, thereby realizing seamless splicing of the variable diameter sections of the circular tube 100, greatly reducing material waste during processing, reducing construction costs, shortening construction period, and improving the efficiency and stability of welding work. At the same time, a two-dimensional plan view of the variable diameter circular tube oblique truss is output through a computer, and flame heating is used in combination with a hand-cranked hoist to bend the variable diameter circular tube, and a baffle and a guide are combined to form a plurality of triangular openings 110, thereby forming a plurality of triangular openings 110, and a plurality of triangular openings 110 are formed. Arc plate assisted positioning solves the problem of difficult positioning and assembly of variable diameter circular tube oblique trusses caused by spatial distortion and bending inclination of variable diameter circular tubes, ensures stable positioning of inclination and spatial curvature, significantly reduces the construction period of variable diameter circular tube oblique trusses, and improves assembly quality. Finally, the position of each variable diameter circular tube oblique truss is located by converting three-dimensional space positioning to two-dimensional space positioning method. By finding assembly frame positioning points of several different reference planes and verifying the dimensions, the position accuracy of the variable diameter circular tube oblique trusses is improved, which simplifies the complexity of three-dimensional space positioning, improves the accuracy of single-piece assembly of variable diameter circular tube oblique trusses, ensures the quality of the overall structure, and reduces the assembly difficulty and time cost.

[0028] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

Claims

1. A positioning and assembly construction method for a special-shaped variable diameter circular tube oblique truss steel structure, characterized in that: The following steps are involved: The circumferences of the large-diameter end and the small-diameter end at both ends of the diameter-reducing section of the circular tube are calculated, and a plurality of triangular openings are formed by equally cutting the outer wall of the diameter-reducing section of the circular tube in the circumferential direction, wherein the sum of the circumferential lengths of the ends of the openings is equal to the circumference difference between the large-diameter end and the small-diameter end, and after heating the diameter-reducing section of the circular tube, the openings are closed and welded to obtain a diameter-reducing circular tube; Output a two-dimensional plane diagram of the variable diameter circular tube oblique truss, display the size and positioning nodes of each variable diameter circular tube in the spatial twisting direction and the bending slope direction, and position, splice and weld each variable diameter circular tube and parts according to the two-dimensional plane diagram to obtain the variable diameter circular tube oblique truss; Arrange an assembly frame, position and fix each variable diameter circular tube oblique truss on the assembly frame in sequence for pre-assembly, and weld each variable diameter circular tube oblique truss to obtain a special-shaped variable diameter circular tube oblique truss steel structure.

2. The positioning and assembly construction method of the special-shaped variable diameter circular tube oblique truss steel structure according to claim 1 is characterized in that: When the reducing section of the round tube is heated and each opening is closed, the reducing section is heated repeatedly, a transition positioning piece is set on the outer wall of the reducing section for positioning, and a manual hoist is used to push the reducing section to close each opening.

3. The positioning and assembly construction method of the special-shaped variable diameter circular tube oblique truss steel structure according to claim 1 is characterized in that: When welding to obtain a reduced diameter circular tube, after a groove is formed at each opening, the root is cleaned with a flux-cored wire and then welding is performed. After the welding is completed and the weld is tested and found to be qualified, the equal-strength weld is polished and smoothed to form a seamless splicing.

4. The positioning and assembly construction method of the special-shaped variable diameter circular tube oblique truss steel structure according to claim 1 is characterized in that: When positioning each of the variable diameter circular tubes and parts according to the two-dimensional plane diagram to obtain a variable diameter circular tube oblique truss, the dimensions of each spatial distortion and bending portion of the variable diameter circular tube are located, and the outer sides of the spatial distortion and bending portions are heated. A manual hoist is used to apply tension to the spatial distortion and bending portions, and baffles and arc-starting plates are set at the spatial distortion and bending portions for positioning, and then spot welding is performed on the spatial distortion and bending portions to prevent rebound.

5. The positioning and assembly construction method of the special-shaped variable diameter circular tube oblique truss steel structure according to claim 1 is characterized in that: When positioning and splicing the various reduced diameter circular tubes and parts according to the two-dimensional plan to obtain the reduced diameter circular tube oblique truss, the diagonal size of the reduced diameter circular tube oblique truss is checked, and when the error is within the allowable range, the reduced diameter circular tube oblique truss is welded to obtain the reduced diameter circular tube oblique truss.

6. The positioning and assembling construction method of the special-shaped variable diameter circular tube oblique truss steel structure according to claim 1 is characterized in that: When arranging the assembly tire frame, the elevation of each support point on the assembly tire frame and the axial distance of each support point are measured for positioning, and corbel positioning pieces are set on the assembly tire frame for positioning according to the different heights of the corbel positions of the variable diameter circular tube inclined truss, and then the positioning distance between each assembly tire frame is determined according to the corbel positions.

7. The positioning and assembly construction method of the special-shaped variable diameter circular tube oblique truss steel structure according to claim 1 is characterized in that: When each variable diameter circular tube inclined truss is positioned and fixed on the assembly frame in sequence for pre-assembly, firstly, a two-dimensional plane figure is calculated through the three-dimensional model of the special-shaped variable diameter circular tube inclined truss steel structure, the previous variable diameter circular tube inclined truss is hoisted on the assembly frame, the positions of each center of gravity line arranged at intervals along the length direction of the previous variable diameter circular tube inclined truss are measured and positioned with reference to the two-dimensional plane figure, the size deviation of the previous variable diameter circular tube inclined truss is verified, and then the next variable diameter circular tube inclined truss is hoisted, and positioned with reference to the two-dimensional plane figure according to the cross-sectional width distance between the previous variable diameter circular tube inclined truss and the next variable diameter circular tube inclined truss, and the previous variable diameter circular tube inclined truss and the next variable diameter circular tube inclined truss are welded.

8. The positioning and assembling construction method of the special-shaped variable diameter circular tube oblique truss steel structure according to claim 7 is characterized in that: Before welding the first variable diameter circular tube oblique truss and the second variable diameter circular tube oblique truss, the distance between the diagonal lines of the first variable diameter circular tube oblique truss and the second variable diameter circular tube oblique truss is measured and positioned with reference to a two-dimensional plane figure.

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