Prestressed steel strand pulling method for steel-concrete combined section of novel inclined steel tower

Abstract

The invention relates to the field of steel strands, and discloses a prestressed steel strand pulling method for a steel-concrete combined section of a novel inclined steel tower, which comprises the following steps of: (a) blanking prestressed steel strands one by one according to a designed length, grouping the prestressed steel strands according to strands, and aligning the two ends of the prestressed steel strands; (b) removing 250mm-300mm of outer-layer steel wires at the two ends of each steel strand respectively, and reserving a central steel wire as a leading wire; (c) the steel strands sequentially penetrate through the corresponding holes in the bundle combing plate according to the preset number, and tension is applied to the whole bundle so that the whole bundle can be preliminarily straightened; (d) binding the middle section of the steel strand bundle at intervals of 1.0-1.5 m by using a soft iron wire with the diameter of 1-2 mm or a special nylon binding tape; according to the invention, effective control of the whole passing process of the prestressed steel strand bundle in an inclined, narrow and closed pipeline is realized through a bundle penetrating mechanism of integral bundle weaving, middle section constraint, two-end head guiding and cooperation of rear end self-weight lowering (thrust) and front end traction (pulling force).

Description

Technical Field

[0001] This invention relates to the field of steel strands, and more particularly to a method for threading prestressed steel strands in the steel-concrete composite section of a novel inclined steel tower. Background Technology

[0002] The structure of steel-concrete composite bridge towers is complex, especially in the junction area between the steel tower and the concrete column. Prestressed ducts often pass through the interface between the steel structure and concrete at an inclined angle. The duct space is limited, the line is tortuous, and the external structure is sealed, making construction extremely difficult. When threading prestressed steel strand bundles into such structures, the steel strands, being flexible cables, are prone to shifting, tangling, twisting, or localized jamming during the threading process. Once a steel strand becomes obstructed within the duct, the sealed structure prevents external intervention to clear the obstruction. Typically, the entire bundle of threaded steel strands must be extracted and re-threaded, which not only consumes significant manpower and time but also significantly impacts the main tower construction progress and may even pose a risk to the installation quality of the prestressed system.

[0003] Existing methods for threading steel strands mostly employ single-end traction, relying on winches or manual pulling to haul single strands or entire bundles of steel strands through the duct. While this method is applicable to horizontal or shallow-angle ducts, it lacks effective control over the overall shape and direction of travel of the steel strand bundle in prestressed ducts with large inclination angles, variable cross-sections, or confined spaces, making it difficult to guarantee the smoothness and reliability of the threading process. Furthermore, traditional methods do not effectively constrain the relative positions of the individual strands within the bundle, making relative slippage prone to occur during threading and further exacerbating the risk of entanglement.

[0004] Therefore, there is an urgent need for a method for threading prestressed steel strands in the steel-concrete composite section of a new type of inclined steel tower. This method should ensure that the entire bundle of steel strands maintains a stable shape and clear direction during the threading process without damaging the structure or relying on internal pipe intervention, and achieves efficient threading operations with a high success rate on the first attempt. Summary of the Invention

[0005] The purpose of this invention is to provide a method for threading prestressed steel strands in the steel-concrete composite section of a novel inclined steel tower to solve the above-mentioned problems. The specific technical solution is as follows: A method for threading prestressed steel strands in the steel-concrete composite section of a novel inclined steel tower includes the following steps: (a) Cut the prestressed steel strands one by one according to the design length, and group them by bundle and align the two ends; (b) Remove 250 mm-300 mm of the outer steel wire from both ends of each steel strand, leaving the central steel wire as the lead wire; (c) Pass the steel strands through the corresponding holes on the comb plate in sequence according to the preset number, and apply tension to the whole bundle to initially straighten it; (d) At intervals of 1.0 m to 1.5 m in the middle section of the steel strand bundle, use φ1–2 mm soft iron wire or special nylon binding tape to tie it; (e) Insert the lead wires at both ends of the steel strand bundle into the front end bundle guide device and the rear end bundle guide device according to their numbers and positions, so that the lead wires correspond one-to-one with the holes of the bundle guide device; (f) Pass the traction wire rope through the prestressed duct beforehand; (g) Connect the rear end guide device to the crane hook via a hoisting wire rope, and lift the steel strand bundle to directly above the inlet of the prestressed duct; (h) Fix one end of the traction wire rope to the front end guide device; (i) The crane is controlled to slowly lower the hook, and the steel wire rope is pulled by man or winch so that the steel strand bundle passes through the prestressed duct under its own weight and front-end traction. (j) After the threading is completed, install the fixed end anchor and the tensioning end temporary anchor at both ends of the pipe respectively.

[0006] As one of the improvements to the above technical solution, the bundle head guiding device is a metal component with multiple wire-threading holes, and the position of each wire-threading hole corresponds one-to-one with the bundling number of the steel strand bundle.

[0007] As one of the improvements to the above technical solution, after the traction wire rope passes through the outlet end of the prestressed pipe, it goes around the fixed pulley to change direction and then connects to the front end guide device.

[0008] As one of the improvements to the above technical solution, the prestressed duct is an angled duct installed in the steel-concrete composite section of the inclined steel tower, with its axis forming a non-zero angle with the vertical direction.

[0009] As one of the improvements to the above technical solution, the steel strand bundle maintains its overall shape during the threading process, and there is no relative slippage between the relative positions of each steel strand between the middle binding points.

[0010] As one of the improvements to the above technical solution, the wire-threading hole arrangement of the front-end bundle guide device and the rear-end bundle guide device is the same.

[0011] As one of the improvements to the above technical solution, before threading the prestressed duct, the traction wire rope is pre-threaded into the prestressed duct, and the outlet end of the traction wire rope is connected to the front end guide device after passing around the fixed pulley. The fixed pulley is fixed on the structural support on the outlet side of the prestressed duct to change the traction direction and keep the traction force acting along the duct axis.

[0012] The beneficial effects of the present invention are as follows: The present invention achieves effective control over the entire process of prestressed steel strand bundles passing through inclined, narrow, and closed pipes by means of overall bundling, mid-section constraint, end-point guidance, and a bundle-passing mechanism that coordinates the rear-end self-weight lowering (thrust) with the front-end traction (tension).

[0013] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the structure of the present invention.

[0016] In the diagram: 1. Hook; 2. Lifting wire rope; 3. Rear end guide device; 4. Lead wire; 5. Steel strand bundle; 7. Front end guide device; 8. Traction wire rope; 9. Prestressed duct; 10. Fixed pulley. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In existing technologies, for the prestressed construction of the steel-concrete composite section of a novel inclined steel tower, due to the enclosed structure, inclined ducts, and limited space, traditional strand threading methods often rely on single-end traction or manual pushing. As flexible cables, steel strands are prone to deflection, entanglement, kinking, and even jamming when threading into complex spatial ducts. Once threading is obstructed, because intervention inside the duct is impossible, it is usually necessary to pull out the entire bundle of steel strands and re-thread them, which is not only inefficient but also seriously affects the main tower construction progress and the installation quality of the prestressed system. Therefore, this invention provides a construction method that can ensure the overall stability of the steel strand bundle 5, clear guidance, and a high success rate of threading on the first attempt.

[0019] Please see Figure 1In this embodiment of the invention, a method for threading prestressed steel strands in a steel-concrete composite section of a novel inclined steel tower includes the following steps: First, determine the cutting length of each prestressed steel strand according to the design drawings, and make precise cuts taking into account tensioning, anchoring, and construction allowances. Then, gather the steel strands within the same bundle, straighten them, and align their ends to ensure consistency in subsequent bundling.

[0020] Subsequently, approximately 250 mm to 300 mm of the outer steel wire is stripped from both ends of each strand, leaving only the central single steel wire as the lead wire 4. The lead wire 4 is used for subsequent threading guidance; its stiffness is higher than that of the entire bundle of steel strands, facilitating threading into the guiding device and bearing traction force.

[0021] Next, the entire bundle of steel strands is sequentially threaded into a comb plate with a regular row of holes according to the preset number. After threading, a moderate tension is applied to the entire bundle to initially straighten it and eliminate slack. On this basis, along the middle section of the steel strand bundle 5, every 1.0 m to 1.5 m, φ1–2 mm soft iron wire or special nylon binding tape is used to circumferentially bind the individual steel strands, so that each individual steel strand remains relatively fixed during the threading process, preventing them from slipping, tangling or twisting.

[0022] Before threading the strands, first thread a traction steel wire rope 8 into the prestressed duct 9, running through the entire path to be threaded. Then, gather and fix the lead wires 4 at the rear end of the steel strand bundle 5, and connect them to the hook 1 of the crawler crane or tower crane through the hoisting steel wire rope 2; start the crane and slowly lift the entire bundle of steel strands to directly above the inlet of the prestressed duct 9, keeping it suspended in the air.

[0023] Simultaneously, the traction wire rope 8, which has already passed through the pipe outlet, is pulled back to the pipe inlet side, and its front end is securely connected to the convergence point of the lead wire 4 at the front end of the steel strand bundle 5. Then, the crane is controlled to slowly lower the hook 1, while simultaneously, the traction wire rope 8 is pulled manually or by a small winch. During this process, the steel strand bundle 5 generates a downward thrust due to its own weight, while the front-end traction force guides it forward along the pipe axis. The two work together to achieve a smooth, continuous, and unobstructed insertion of the entire bundle into the inclined pipe.

[0024] After the cable is threaded, fixed end anchors and temporary anchoring devices are installed at both ends of the pipe to prepare for subsequent tensioning operations.

[0025] This invention effectively solves the technical challenges of easy tangling, obstruction, and low efficiency in threading prestressed steel strands in inclined, narrow, and enclosed environments by employing a coordinated threading mechanism that combines overall bundling, mid-section constraint, and end-point guidance with rear-end self-weight lowering and front-end traction guidance. This method eliminates the need for internal duct operations, significantly improving the first-time success rate and construction efficiency, shortening the critical path construction period of the main tower, and simultaneously ensuring the installation accuracy and structural reliability of the prestressed system.

[0026] In the prestressed strand threading construction of the steel-concrete composite section of the inclined steel tower, the outlet end of the prestressed duct 9 is usually located at a high position or in a confined space. If a traction force is applied directly outward from the outlet end (such as manual pulling or direct connection with a winch), the traction direction often has a significant angle with the duct axis. This non-axial traction can easily cause the front end of the steel strand bundle 5 to shift laterally when entering the duct outlet, scrape against the edge of the duct opening, or even get stuck. This not only increases the threading resistance but may also damage the outer layer of the steel strands or cause the entire bundle to twist. Due to the enclosed structure, once stuck, it is usually necessary to pull out the entire bundle and re-thread it, which seriously affects the construction efficiency.

[0027] Therefore, in some embodiments, after the traction wire rope 8 passes through the outlet end of the prestressed duct 9, it changes direction by passing around the fixed pulley 10 and then connects to the front end guide device 7. Specifically, before threading the prestressed duct, the traction wire rope 8 is pre-threaded into the prestressed duct 9, and the outlet end of the traction wire rope 8 passes around the fixed pulley 10 and connects to the front end guide device 7. The fixed pulley 10 is fixed to the structural support on the outlet side of the prestressed duct 9 and is used to change the traction direction and keep the traction force acting along the duct axis.

[0028] In this embodiment, by setting a fixed pulley 10 at the outlet end of the prestressed pipe 9, the force direction of the traction wire rope 8 is adjusted from non-axial to along the pipe axis, which effectively eliminates the front end sway and pipe mouth friction resistance caused by the traction angle, improves the stability and controllability of the wire rope threading process, and reduces the risk of the steel strand bundle 5 getting stuck or damaged at the outlet section.

[0029] In the section where the inclined steel tower meets the concrete, the prestressed duct 9 is usually set at a non-vertical angle, with its axis forming a significant angle with the vertical direction. This type of inclined duct makes it difficult for the steel strand bundles 5 to fall naturally under their own weight during insertion. Furthermore, due to the enclosed structure and narrow space, traditional single-end traction or manual pushing methods easily cause the steel strand bundles 5 to shift, accumulate, bend locally, or even become entangled within the duct. Once insertion is obstructed, since the duct cannot be opened for clearing, the inserted portion must be completely removed and re-inserted, severely impacting construction efficiency and schedule. Therefore, the prestressed duct 9 of this invention is an angled duct set within the steel-concrete section of the inclined steel tower, with its axis forming a non-zero angle with the vertical direction. This invention, addressing the special structure of the non-vertical prestressed duct 9 in the steel-concrete section of the inclined steel tower, effectively overcomes the problems of high insertion resistance and poor guidance caused by the inconsistency between the gravity direction and the duct axis of the steel strand bundles 5 in the inclined duct.

[0030] Preferably, the steel strand bundle 5 maintains its whole bundle shape during the threading process, and there is no relative slippage between the middle binding points of each steel strand. The threading holes of the front end bundle guide device 7 and the rear end bundle guide device 3 are arranged in the same way.

[0031] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for threading prestressed steel strands in the steel-concrete composite section of a novel inclined steel tower, characterized in that, Includes the following steps: (a) Cut the prestressed steel strands one by one according to the design length, and group them by bundle and align the two ends; (b) Remove 250 mm-300 mm of the outer steel wire from both ends of each steel strand, leaving the central steel wire as the lead wire; (c) Pass the steel strands through the corresponding holes on the comb plate in sequence according to the preset number, and apply tension to the whole bundle to initially straighten it; (d) At intervals of 1.0 m to 1.5 m in the middle section of the steel strand bundle, use φ1–2 mm soft iron wire or special nylon binding tape to tie it; (e) Insert the lead wires at both ends of the steel strand bundle into the front end bundle guide device and the rear end bundle guide device according to their numbers and positions, so that the lead wires correspond one-to-one with the holes of the bundle guide device; (f) Pass the traction wire rope through the prestressed duct beforehand; (g) Connect the rear end guide device to the crane hook via a hoisting wire rope, and lift the steel strand bundle to directly above the inlet of the prestressed duct; (h) Fix one end of the traction wire rope to the front end guide device; (i) The crane is controlled to slowly lower the hook, and the steel wire rope is pulled by man or winch so that the steel strand bundle passes through the prestressed duct under its own weight and front-end traction. (j) After the threading is completed, install the fixed end anchor and the tensioning end temporary anchor at both ends of the pipe respectively.

2. The method for threading prestressed steel strands in the steel-concrete composite section of a novel inclined steel tower according to claim 1, characterized in that: The bundle head guide device is a metal component with multiple wire-threading holes, and the position of each wire-threading hole corresponds one-to-one with the bundling number of the steel strand bundle.

3. The method for threading prestressed steel strands in the steel-concrete composite section of a novel inclined steel tower according to claim 1, characterized in that: After the traction wire rope passes through the outlet end of the prestressed duct, it goes around the fixed pulley to change direction and then connects to the front end guide device.

4. The method for threading prestressed steel strands in the steel-concrete composite section of a novel inclined steel tower according to claim 1, characterized in that: The prestressed duct is an angled duct installed in the steel-concrete composite section of the inclined steel tower, with its axis forming a non-zero angle with the vertical direction.

5. The method for threading prestressed steel strands in the steel-concrete composite section of a novel inclined steel tower according to claim 1, characterized in that: The steel strand bundle maintains its overall shape during the threading process, and there is no relative slippage between the individual steel strands at the mid-section binding point.

6. The method for threading prestressed steel strands in the steel-concrete composite section of a novel inclined steel tower according to claim 1, characterized in that: The arrangement of the threading holes in the front and rear bundle guide devices is the same.

7. The method for threading prestressed steel strands in the steel-concrete composite section of a novel inclined steel tower according to claim 3, characterized in that: Before threading the prestressed duct, the traction wire rope is pre-threaded into the prestressed duct, and the outlet end of the traction wire rope is connected to the front end guide device after passing over the fixed pulley. The fixed pulley is fixed to the structural support on the outlet side of the prestressed duct and is used to change the traction direction and keep the traction force acting along the duct axis.

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