Construction method of A-shaped main tower upper part gradually widening special-shaped lotus tower crown
By optimizing the support layout using BIM models and employing 3D laser CNC cutting, combined with the tight fit between the steel formwork ribs and the truss panels and the fixation of the inner triangular frame, the challenges of steel formwork adaptability, alignment control, construction safety, and high-strength concrete temperature control in the construction of the gradually widening irregular lotus-shaped tower crown of the A-shaped main tower were solved, achieving efficient and safe restoration of the tower crown shape.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- THE 5TH ENG MBEC
- Filing Date
- 2026-05-09
- Publication Date
- 2026-06-19
AI Technical Summary
Traditional construction techniques for the construction of the gradually widening, irregular lotus-shaped crown on the upper part of the A-shaped main tower present several challenges, including difficulties in positioning and reinforcing the steel formwork, insufficient precision in line control, poor overall rigidity and stability of the steel formwork, low construction efficiency, high risks associated with high-altitude operations, and insufficient space for manholes and other work. In particular, it is difficult to simultaneously address the issues of high-strength concrete temperature control and ultra-high-speed pumping.
The BIM model was used to optimize the support layout, combined with 3D laser CNC cutting and steel formwork assembly technology. Through the inner triangular frame + double channel steel + tie rod system, the inner triangular frame + double channel steel + tie rod were integrated for fixation. C60 high-strength concrete + viscosity reducer + layered pouring and ultra-high pumping were used. The steel formwork was pre-drilled and embedded parts were embedded with the steel formwork. C60 high-strength concrete + viscosity reducer + layered pouring + intelligent temperature control + ultra-high pumping were used. The steel anchor beam was kept at a constant temperature and finely adjusted at night. The positioning deviation was ≤3mm, which met the anchoring accuracy requirements of the cable stay and improved the construction accuracy, efficiency and safety.
It achieves precise matching between the steel formwork and the gradually widened line of the tower crown, and the large ribs of the steel formwork are tightly fitted with the truss pieces, solving the problems of poor compatibility and loose fit. The line deviation is ≤3mm and the fit gap is ≤2mm, which improves the construction accuracy, efficiency and safety, and meets the requirements of bridge construction design and specifications.
Smart Images
Figure CN122236035A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of building construction technology, specifically relating to a construction method for an A-shaped main tower with a gradually widening irregular lotus-shaped crown formed by truss supports and steel mold casting. Background Technology
[0002] In the design of long-span cable-stayed suspension bridges and urban landscape bridges, the A-shaped main tower is widely used due to its high structural rigidity, good overall stability, and simple and grand appearance. To further enhance the architectural aesthetics and landmark status, some A-shaped main towers adopt an irregularly shaped lotus-shaped crown design that gradually widens outward at the top, forming a unique shape with a conventional A-shaped double-inclined column lower body, an outwardly tilting crown upper part, and an overall petal-like gradually unfolding outline.
[0003] This type of A-shaped main tower structure has distinct characteristics: the lower part of the A-shaped main tower is a double-inclined A-shaped tower column with a relatively regular shape; after entering the upper crown area of the A-shaped main tower, the tower column gradually widens and extends outward, and the cross-sectional dimensions, outward tilt angle and curved surface shape change continuously with height. There is no standard fixed cross-section, and the difficulty of controlling the shape is significantly higher than that of conventional A-shaped main towers.
[0004] Currently, the construction of conventional A-shaped main towers mostly adopts standardized steel formwork, climbing formwork, or flip-formwork systems, which are suitable for straight sections of tower columns with relatively stable inclination angles. However, when applying traditional construction techniques to the construction of the upper, gradually widening, irregularly shaped lotus-shaped crown of an A-shaped main tower, the following prominent technical problems exist: 1. The positioning and reinforcement of steel formwork are difficult, and the accuracy of alignment control is insufficient. As the tower crown section gradually widens outward, the steel formwork is prone to outward displacement, torsion, and bulging under the lateral pressure of concrete. Traditional support systems are mostly rigid connections, which cannot be precisely adjusted according to the widening range. In addition, the steel formwork ribs and truss panels are not tightly fitted and have poor cooperative stress-bearing performance, which easily leads to the accumulation of alignment deviations, making it difficult to correct them later and affecting the structural stress and appearance quality. 2. The overall rigidity and stability of the steel formwork are difficult to guarantee. The tower body in the irregularly shaped widened section is subjected to complex forces, and the local stress concentration of the steel formwork is obvious. Since the main ribs of the steel formwork and the truss plates do not form a tightly integrated whole force-bearing system, the steel formwork is prone to shaking and deformation during the pouring and vibration process, which not only affects the molding quality of the concrete, but also poses a significant safety hazard for high-altitude construction. 3. High-altitude operations are cumbersome and inefficient: Due to the poor fit between the steel formwork ribs and the truss panels, repeated measurements, corrections, and reinforcements are required on-site, resulting in repetitive procedures and limited operating space. The poor fit between the steel formwork ribs and the truss panels necessitates numerous additional temporary reinforcement measures, leading to a large volume of high-altitude work, a long construction period, and a significant increase in labor intensity and safety risks. 4. The support system of the steel formwork is not compatible with the shape of the tower crown. There is no support in the area above the truss, resulting in problems such as insufficient space for manholes and insufficient working space: The lower part of the tower crown is a gradually widening curved surface, and the truss can only support up to the gradually widening side; the top 2m has been tapered into a standard straight section, and the truss cannot extend to support it, resulting in the top 2m of the steel formwork having no external support and having to be higher than the segmented pouring surface; In traditional construction, in order to fix the steel formwork higher than the segmented line, a continuous support or tie rod needs to be set on the outside of the tower crown. On the one hand, the tie rod is easy to intrude into the reserved manhole of the tower crown, affecting the subsequent construction and use of the manhole. On the other hand, the continuous support on the outside will occupy a lot of high-altitude working space, making it inconvenient for construction personnel to operate, and further increasing the risk and difficulty of high-altitude operations. 5. The tower crown is mostly a high-altitude, large-volume, high-strength concrete structure, which has a high risk of hydration heat cracking, great difficulty in ultra-high pumping, and extremely high positioning accuracy requirements for internal steel anchor beams and embedded parts. Traditional processes cannot meet the needs of temperature control, pumping and precise positioning.
[0005] For the unique structure of the gradually widening lotus-shaped crown at the top of the A-shaped main tower, existing construction techniques have significant shortcomings in terms of steel formwork compatibility, alignment control, fit between the steel formwork ribs and the truss panels, construction safety, temperature control of large-volume concrete, ultra-high pumping, and precise positioning. In particular, because the initial layering is fixed and subsequent section adjustments cannot be made in time, the problem of fixing the steel formwork sections that extend above the section lines is difficult to solve. Traditional external support and tie rod methods easily interfere with reserved manholes and encroach on the working space. There is an urgent need for a targeted construction method that is compatible with the gradually widening shape, can achieve a tight fit between the steel formwork ribs and the truss panels, can solve the problems of fixing the steel formwork sections, avoid interference from manholes and insufficient working space, and can also take into account the temperature control of high-strength concrete, ultra-high pumping, and precise positioning of steel anchor beams. This method can solve the above-mentioned technical problems and meet the requirements of engineering construction design and specifications. Summary of the Invention
[0006] The purpose of this invention is to provide a construction method for the gradually widening, irregularly shaped lotus crown of the A-shaped main tower, achieving precise matching between the steel formwork and the gradually widening line of the crown, and tight fit between the steel formwork ribs and the truss panels. This solves the problem of segmented fixing of the steel formwork, avoids interference from reserved manholes, and frees up working space. At the same time, it enables high-strength concrete hydration heat control, 280m-level ultra-high pumping, and high-precision positioning of steel anchor beams, improving construction accuracy, efficiency, and safety, accurately restoring the lotus crown design, and meeting the requirements of bridge construction design and specifications.
[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A construction method for an A-shaped main tower with a gradually widening, irregularly shaped lotus-shaped crown, characterized by the following specific steps: (1) Modeling: Complete the construction of the conventional tower columns at the bottom of the A-shaped main tower, clean up the construction area at the top of the tower, and set up a high-altitude operation platform; based on the tower crown design drawings, establish a three-dimensional BIM model of the gradually widening irregular lotus-shaped tower crown, clarify the outward expansion angle, cross-sectional dimensions, curved surface shape, and reserved manhole location of each height section of the tower crown, and determine the layout parameters of the truss, brackets, trusses, distribution beams, stiffening frame, steel anchor beams, embedded parts, inner triangular frame, and double-channel steel; combined with the structural characteristics of the gradually widening bottom of the tower crown and the inability of the truss to support the top 2-meter standard section, determine the position, parameters, and fixed points of the steel formwork above the segment line; at the same time, mark the contact points and contact accuracy requirements of the steel formwork ribs and trusses, and clarify the embedded positions of the inner triangular frame and double-channel steel; through BIM simulation of the entire construction process, carry out collision checks on the supports, embedded parts, catwalks, and main cable components, optimize the connection of each step and the layout of components, and avoid construction interference problems; (2) Installation of brackets, trusses, distribution beams, reserved triangular frames, double-channel steel stiffening frames, steel anchor beams and embedded parts: According to the positioning requirements of the BIM model, the bracket composed of "truss + distribution beam + bracket" is hoisted layer by layer at the preset position on the top of the A-shaped main tower to achieve force separation: the truss and distribution beam bear the horizontal lateral pressure, and the bracket only bears the vertical load; the stiffening frame, steel anchor beam and embedded parts of the tower crown are hoisted at the same time; the total station is used for real-time positioning and correction to ensure that the horizontality of the bracket installation, the verticality of the stiffening frame, the spacing and the outward tilt angle meet the design requirements; after the above components are installed, they are temporarily fixed to form the main force support system of the tower crown, providing a stable foundation for the subsequent steel formwork installation and truss installation; at the same time, the installation points of the triangular frames and double-channel steel are reserved on the inner side of the tower crown corresponding to the position of the steel formwork above the segment line to ensure that the subsequent fixed structure and the reserved manhole do not interfere with each other; (3) Steel mold processing and pre-assembly: Based on the parameters of each section of the tower crown obtained from the BIM model established in step (1), special irregular steel molds are processed. The steel mold panel is made of arc-shaped steel plate to accurately match the curved surface of the tower crown. Three-dimensional laser CNC cutting is used to ensure the processing accuracy is ≤0.1mm. The steel mold ribs are made of profile steel. The outline of the steel mold ribs is precisely matched with the inner side line of the corresponding tower crown truss to ensure that the subsequent steel mold ribs and truss are seamless. Three-dimensional holes are pre-drilled on the steel mold according to the BIM model for the pre-embedded parts to be accurately embedded with the steel mold. After the steel mold is processed, it is pre-assembled in sections on the ground to simulate the inner side line of the tower crown and the installation position of the truss. The steel mold line, splicing accuracy and simulated fitting effect of the steel mold ribs and truss are checked. The deviation parts are ground and adjusted to ensure that they meet the design requirements. Then, it is disassembled and transported to the construction area at the top of the tower. (4) Steel formwork installation: The pre-assembled qualified steel formwork is hoisted to the tower crown construction section by a tower crane. The position of the steel formwork is adjusted so that the steel formwork panel fits the designed curved surface of the tower crown. The pre-embedded parts such as climbing cones and bolts are installed along with the formwork through the pre-drilled holes of the steel formwork. For the steel formwork that is higher than the segment line, a fixed method of embedding a triangular frame on the inside is adopted. Specifically, a triangular frame is embedded at the reserved point on the inside of the tower crown, and the double-segmented channel steel is welded and fixed to the rigid frame of the tower crown. The double-segmented channel steel is welded to the rigid frame on both sides. The triangular frame is firmly connected to the double-segmented channel steel. Then, the tripod and the outer ring of steel formwork are connected as a whole by tie rods, so as to achieve a stable fixation of the steel formwork that is higher than the segment line, replacing the traditional outer support and tie rods, avoiding the tie rods from intruding into the reserved manhole of the tower crown, and freeing up the working space on the outside. After each section of steel formwork is installed, adjustable diagonal braces made of steel pipes are used for auxiliary reinforcement. One end of the adjustable diagonal brace is connected to the steel formwork, and the other end of the adjustable diagonal brace is fixed to the bracket or stiffening frame. The length and inclination angle of the diagonal brace are adjusted according to the outward tilt angle of the tower crown to ensure the stability of the steel formwork installation. (5) Truss installation: According to the positioning parameters and inner line requirements of the truss in the BIM model established in step (1), the truss is hoisted to the designated position in sections by a tower crane. The posture of the truss is adjusted so that the inner line of the truss is completely aligned with the design line of the BIM model. At the same time, the truss is pushed to fit tightly with the installed steel formwork ribs. High-strength bolts are used to fix the truss to the steel formwork ribs and stiffening frame to form a steel formwork and truss fitting as an integral force system, avoiding relative displacement between the steel formwork and the truss, and ensuring accurate fitting of the lotus-shaped outline of the tower crown. (6) High-precision positioning of steel anchor beams: steel anchor beams are set in the hollow section of the tower crown. The elevation is transferred by the zenith distance measurement method of the total station and the plane is positioned by the resection method. The cable guide and steel anchor beam are finely adjusted during the constant temperature period at night. The positioning deviation is controlled within ≤3mm. After completion, the limit is fixed to prevent deviation during the pouring process. (7) Adjustment: After the steel formwork, truss, and steel anchor beam are all installed, a total station and a 3D laser scanner are used to comprehensively monitor the overall shape of the tower crown, the fitting accuracy of the steel formwork and truss, the installation position of each component, and the positioning accuracy of the steel anchor beam. The monitoring data are compared and analyzed with the design parameters of the BIM model. If there is a deviation in the shape, an excessive fitting gap, or a component position deviation, the deviation is precisely corrected by adjusting the length of the adjustable diagonal brace, fine-tuning the tension of the tie rod, and correcting the connection position of the truss and the steel formwork. Ensure that the outward tilt angle, cross-sectional dimensions, and curved shape of the tower crown meet the design requirements, the fitting accuracy of the steel formwork and truss meets the standard, the cumulative shape deviation does not exceed 3mm, the positioning deviation of the steel anchor beam is ≤3mm, and the reserved manhole is free from any obstruction or interference. (8) Concrete pouring, temperature control and ultra-high pumping: After adjustment and acceptance, the tower crown concrete is poured; the tower crown is divided into a lower 11m hollow section constructed using climbing formwork and an upper 7m solid section constructed using brackets. The solid section of the tower crown is poured in layers of 5m + 2m; C60 high-strength concrete is used, with viscosity reducers added to optimize fluidity and crack resistance; cooling water pipes are laid, and intelligent temperature control and hydration heat monitoring are used to control the risk of cracking in large-volume concrete; a 48MPa ultra-high pressure ground pump and φ125 ultra-high pressure wear-resistant pump pipe are used to achieve a maximum pumping height of 280m. Continuous construction; the thickness of each concrete layer should not exceed 50cm. During vibration, avoid collisions between the vibrator and the steel formwork, truss, steel anchor beam and embedded parts to prevent deformation of the steel formwork, loosening of the bonding surface or displacement of components. Monitor the shape of the tower crown in real time during the pouring process. If any deviation occurs, stop the machine in time for adjustment. After the pouring is completed, cover with moisturizing material for curing. The curing time should not be less than 14 days. (9) Demolition work: After the concrete strength reaches more than 75% of the design strength, the demolition work shall be carried out. The demolition sequence shall follow the principle of "top first, bottom last". First, the adjustable diagonal braces, tie rods, triangular frames and double-channel steel temporary fixed components shall be removed, then the steel formwork shall be removed, and finally the brackets, trusses, distribution beams and temporary working platforms shall be removed. During the demolition process, the tower crane shall be used to slowly lift and lower the tower to avoid collision with the formed tower crown and the reserved manhole. After the demolition is completed, the tower crown shall be repaired, polished and cleaned to complete the overall construction of the tower crown.
[0008] Furthermore, in step (1), the foundation height of each segment after the tower crown is segmented is controlled at 2m, and the height above the steel mold segment of the segmentation line is not more than 0.5m; the fit gap between the steel mold rib and the truss plate is required to be no more than 2mm, and the cumulative linear deviation of the tower crown is no more than 3mm.
[0009] Furthermore, in step (4), the double-slotted channel steel is made of 16# channel steel and is welded to the stiffening frame on both sides with a welding length of not less than 100mm; the tie rod is made of Φ20 tie rod with a tension force of 15–20kN; the adjustable diagonal brace is made of Φ159 steel pipe.
[0010] Furthermore, in step (5), the gap between the steel mold rib and the truss plate is controlled within 2mm, and three high-strength bolts are set for each meter of the fitting length to form an overall force-bearing system.
[0011] Furthermore, in step (8), the strength and shape are monitored in real time during concrete curing to prevent shrinkage cracking and shape deviation.
[0012] This invention addresses the core construction techniques of an A-shaped main tower with a gradually widening, lotus-shaped crown structure. These techniques include: steel formwork ribs fitting snugly against the surrounding trusses; integrated fixing with an inner triangular frame, double-channel steel, and tie rods; a support structure composed of trusses, distribution beams, and brackets; 3D laser cutting; pre-drilling of steel formwork; embedding of pre-embedded parts along with the steel formwork; C60 high-strength concrete; viscosity reducer; layered pouring; intelligent temperature control; 280m ultra-high-speed pumping; nighttime constant-temperature fine-tuning of steel anchor beams; and segmented construction of the hollow and solid sections of the crown. Therefore, this invention offers the following advantages: 1. Adaptable to gradual widening shape, high precision of steel mold fitting: It achieves precise matching between the steel mold and the gradual widening line of the tower crown, and tight fitting between the steel mold ribs and the truss plates, solving the problems of poor adaptability and loose fitting. The line deviation is ≤3mm and the fitting gap is ≤2mm. 2. Achieve precise control over the tower crown's shape and high degree of shape reproduction: 3D laser cutting and BIM full-process control accurately reproduce the design shape of the lotus tower crown, perfectly reproducing the shape and meeting the requirements of bridge construction design and specifications, appearance and stress. 3. Solve the problem of fixing the high-rise steel formwork in sections and avoid interference with the reserved manhole: The inner triangular frame + double channel steel + tie rod system replaces the tie rod, does not intrude into the reserved manhole, and frees up working space; 4. Reasonable stress distribution of the support structure ensures efficient and safe construction: The "truss + distribution beam + bracket" structure separates the stress, improves the rigidity and stability of the steel formwork, reduces repeated high-altitude corrections, and increases efficiency while reducing risks. 5. Reliable temperature control and ultra-high pumping of high-strength concrete: C60 + viscosity reducer, layered pouring, and intelligent temperature control enable control of hydration heat in high-strength concrete and ultra-high pumping up to 280m, controlling hydration heat cracking. 6. High-precision positioning of steel anchor beams and embedded parts: pre-drilled holes in steel molds + embedded parts installed with the molds, and constant temperature fine-tuning at night, with a positioning deviation of ≤3mm, meeting the anchoring accuracy requirements of the stay cables, improving construction accuracy, efficiency and safety; 7. BIM full-process clash detection: Eliminates interference in advance, ensures smooth process transitions, reduces rework rates, and significantly improves construction safety and continuity; 8. The lotus-shaped design has a high degree of fidelity, and the concrete appearance quality is good, without defects such as grout leakage, pitting, or bulging. It successfully solves the problem of fixing steel molds that protrude above the segmentation line due to the segmentation of standard steel molds, effectively avoids the tie rods from intruding into the reserved manholes, releases the outer working space, makes it convenient for construction personnel to operate, and no safety hazards occurred during the construction process. It fully meets the design and construction specifications and verifies the feasibility and superiority of the construction method of this invention.
[0013] This invention solves the problems of poor steel formwork adaptation, loose fit, difficulty in fixing steel formwork, interference with manholes, small working space, easy cracking of large-volume concrete, difficulty in ultra-high pumping, and low positioning accuracy of steel anchor beams in the construction of traditional gradually widening lotus-shaped tower crowns. It is applicable to the construction of irregular lotus-shaped tower crowns for A-shaped main towers of long-span cross-sea bridges and has extremely high engineering application value. Attached Figure Description
[0014] Figure 1 is a schematic diagram of the overall elevation of the gradually widening irregular lotus-shaped crown at the top of the A-shaped main tower; Figure 2 is a schematic diagram of the standard elevation structure of the tower crown; Figure 3 is a schematic diagram of the standard side structure of the tower crown; Figure 4 shows a detailed diagram of the fit between the steel mold ribs and the truss panels; Figure 5 is a schematic diagram of the inner fixing system of the steel mold that extends above the segmentation line; Figure 6 is a schematic diagram of the arrangement of the support structure composed of truss, distribution beam and bracket; Figure 7 is a schematic diagram of the arrangement of the tower crown stiffening frame; In the diagram: 1—A-shaped main tower; 2—Gradually widening irregular lotus-shaped tower crown; 3—Hollow section of tower crown; 4—Solid section of tower crown; 5—Gradually expanding line of tower crown; 6—Segmented construction line; 7—Steel formwork section above the segmented line; 8—Concrete main body of tower crown; 9—Steel formwork panel; 10—Steel formwork rib; 11—Tension frame; 12—Reserved manhole; 13—Inner triangular frame; 14—Double-section channel steel; 15—Tie rod; 16—Tension frame; 17—Distribution beam; 18—Bracket; 19—Horizontal lateral pressure; 20—Vertical load; 21—Top surface of main tower; 22—Steel anchor beam; 23—Cable guide tube; 24—Embedded parts; 25—Limiting device; 26—Strengthened frame. Detailed Implementation
[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0016] A construction method for an A-shaped main tower with a gradually widening, irregularly shaped lotus crown, the specific steps of which are as follows: (1) Modeling: Complete the construction of the conventional tower columns at the bottom of the A-shaped main tower 1, clean up the construction area at the top of the tower, and set up a high-altitude work platform; based on the tower crown design drawings, establish a three-dimensional BIM model of the gradually widening irregular lotus-shaped tower crown 2, clarify the outward expansion angle, cross-sectional dimensions, curved surface shape, and reserved manhole 12 position of each height section of the tower crown, and determine the layout parameters of truss 11, bracket 18, truss 16, distribution beam 17, stiffening frame 26, steel anchor beam 22, embedded parts 24, inner triangular frame 13, and double-channel steel 14; combined with the structural characteristics of the gradually widening lower part of the tower crown and the inability of the truss to support the top 2-meter standard section, determine the position, parameters, and fixing points of the steel formwork above the segment line; at the same time, mark the contact points and contact accuracy requirements of the steel formwork large rib 10 and truss 11, and clarify the embedding positions of the inner triangular frame and double-channel steel; through BIM The entire construction process was simulated, and collision checks were carried out on the supports, embedded parts 24, catwalks, and main cable components. The connection between each step and the arrangement of components were optimized to avoid construction interference problems. After the tower crown was segmented, the foundation height of each segment was controlled at 2m, and the height above the segment line steel formwork segment 7 was not more than 0.5m. The fitting gap between the steel formwork rib 10 and the truss 11 was required to be no more than 2mm, and the cumulative linear deviation of the tower crown was not more than 3mm.
[0017] (2) Installation of bracket 18, truss 16, distribution beam 17, reserved triangular frame 13, double-channel steel 14 stiffening frame 26, steel anchor beam 22 and embedded parts 24: According to the positioning requirements of the BIM model, at the preset position on the top of the A-shaped main tower 1, hoist "truss 16 + distribution beam 17 + bracket 18" layer by layer. The assembled support structure achieves force separation: truss 16 and distribution beam 17 bear the horizontal lateral pressure, while bracket 18 only bears the vertical load; the stiffening frame 26, steel anchor beam 22, and embedded parts 24 of the tower crown are hoisted simultaneously; a total station is used for real-time positioning and correction to ensure that the horizontality of the bracket installation, the verticality of the stiffening frame 26, the spacing, and the outward tilt angle meet the design requirements; after the above components are installed, they are temporarily fixed to form the main load-bearing support system of the tower crown, providing a stable foundation for the subsequent installation of steel formwork and truss 11; at the same time, on the inner side of the tower crown, corresponding to the position of the steel formwork above the segment line, the installation points of the triangular frame 13 and double-channel steel 14 are reserved to ensure that the subsequent fixing structure does not interfere with the reserved manhole 12; (3) Steel mold processing and pre-assembly: Based on the parameters of each section of the tower crown obtained from the BIM model established in step 1, special irregular steel molds are processed. The steel mold panel 9 is made of arc-shaped steel plate to accurately match the curved surface of the tower crown. Three-dimensional laser CNC cutting is used to ensure that the processing accuracy is ≤0.1mm. The steel mold rib 10 is made of profile steel. The outline of the steel mold rib 10 is precisely matched with the inner side line of the corresponding position of the tower crown truss 11 to ensure that the subsequent contact surface between the steel mold rib 10 and the truss 11 is seamless. Three-dimensional holes are pre-drilled on the steel mold according to the BIM model for the pre-embedded parts 24 to be accurately embedded with the steel mold. After the steel mold is processed, it is pre-assembled in sections on the ground to simulate the inner side line of the tower crown and the installation position of the truss 11. The steel mold line, splicing accuracy and simulated contact effect between the steel mold rib 10 and the truss 11 are checked. The deviation parts are ground and adjusted to ensure that they meet the design requirements. Then, it is disassembled and transported to the construction area at the top of the tower. (4) Steel formwork installation: The pre-assembled qualified steel formwork is hoisted to the tower crown construction section by a tower crane. The position of the steel formwork is adjusted so that the steel formwork panel 9 fits the design curved surface of the tower crown. The pre-drilled holes in the steel formwork are used to complete the installation of pre-embedded parts such as climbing cones and bolts. For the steel formwork that is higher than the segment line, a fixing method of embedding a triangular frame 13 on the inner side is adopted. Specifically, the triangular frame 13 is embedded at the reserved point on the inner side of the tower crown. The double-slot steel 14 is welded to the rigid frame 26 of the tower crown on both sides. The welding length is not less than 100mm. The triangular frame 13 is firmly connected to the double-slot steel 14. Then, the three-way tie rod 15 is used to secure the triangular frame 13 to the tower crown. The corner frame 13 is integrated with the outer ring of steel formwork. The tension of the tie rod is 15-20kN, which realizes the stable fixation of the steel formwork section 7 above the segment line, replacing the traditional outer support and tie rod 15. This avoids the tie rod 15 from intruding into the reserved manhole 12 of the tower crown, while freeing up the working space on the outside. After each section of steel formwork is installed, an adjustable diagonal brace made of φ159 steel pipe is used for auxiliary reinforcement. One end of the adjustable diagonal brace is connected to the steel formwork, and the other end of the adjustable diagonal brace is fixed to the bracket 18 or the stiffening frame 26. The length and inclination angle of the diagonal brace are adjusted according to the outward tilt angle of the tower crown to ensure the stability of the steel formwork installation. (5) Installation of Truss 11: According to the positioning parameters and inner line requirements of the truss 11 in the BIM model established in step (1), the truss 11 is hoisted to the designated position in sections by a tower crane. The posture of the truss 11 is adjusted so that the inner line of the truss 11 is completely aligned with the design line of the BIM model. At the same time, the truss 11 is pushed to fit tightly with the installed steel formwork rib 10. The fitting gap is controlled within 2mm. Three high-strength bolts are set for each meter of fitting length to fix the truss 11 to the steel formwork rib 10 and the stiffening frame 26, forming a steel formwork and truss 11 fitting as an integral force system to avoid relative displacement between the steel formwork and the truss 11 and ensure the accurate fitting of the lotus-shaped outline of the tower crown. (6) High-precision positioning of steel anchor beam 22: Steel anchor beam 22 is set in the hollow section 3 of the tower crown. The elevation is transferred by the zenith distance measurement method of the total station and the plane is positioned by the resection method. The cable guide 23 and steel anchor beam 22 are finely adjusted during the constant temperature period at night. The positioning deviation is controlled within ≤3mm. After completion, the limit is fixed to prevent deviation during the pouring process. (7) Adjustment: After the steel formwork, truss 11, and steel anchor beam 22 are all installed, a total station and a 3D laser scanner are used to comprehensively monitor the overall shape of the tower crown, the fitting accuracy of the steel formwork and truss 11, the installation position of each component, and the positioning accuracy of the steel anchor beam 22. The monitoring data are compared and analyzed with the design parameters of the BIM model. If there is a deviation in the shape, an excessive fitting gap, or a component position deviation, the deviation is precisely corrected by adjusting the length of the adjustable diagonal brace, fine-tuning the tension of the tie rod 15, and correcting the connection position of the truss 11 and the steel formwork. Ensure that the outward tilt angle, cross-sectional dimensions, and curved shape of the tower crown meet the design requirements, the fitting accuracy of the steel formwork and truss 11 meets the standard, the cumulative deviation in shape does not exceed 3mm, the positioning deviation of the steel anchor beam 22 is ≤3mm, and the reserved manhole 12 is free from any obstruction or interference. (8) Concrete pouring, temperature control and ultra-high pumping: After adjustment and acceptance, the tower crown concrete is poured; the tower crown is divided into a lower 11m hollow section 3 constructed using climbing formwork and an upper 7m solid section 4 constructed using brackets 18. The solid section 4 is poured in layers of 5m + 2m; C60 high-strength concrete is used, with viscosity reducers added to optimize fluidity and crack resistance; cooling water pipes are laid, and intelligent temperature control and hydration heat monitoring are used to control the risk of cracking in large-volume concrete; a 48MPa ultra-high pressure ground pump and φ125 ultra-high pressure wear-resistant pump pipe are used to achieve a maximum pumping height of 280m. Continuous construction; the thickness of each concrete layer should not exceed 50cm. During vibration, avoid collisions between the vibrator and the steel formwork, truss 11, steel anchor beam 22, and embedded parts 24 to prevent deformation of the steel formwork, loosening of the bonding surface, or displacement of components. Monitor the shape of the tower crown in real time during the pouring process. If any deviation occurs, stop the machine in time for adjustment. After the pouring is completed, cover with moisturizing material for curing. The curing time should not be less than 14 days. During the curing period, monitor the strength and shape regularly to avoid shrinkage cracks and shape deviations. (9) Demolition work: After the concrete strength reaches more than 75% of the design strength, the demolition work shall be carried out. The demolition sequence shall follow the principle of "top first, bottom last". First, the temporary fixed components such as adjustable diagonal braces, tie rods 15, triangular frames 13 and double channel steel 14 shall be demolished. Then, the steel formwork shall be demolished. Finally, the brackets 18, trusses 16, distribution beams 17 and temporary working platforms shall be demolished. During the demolition process, tower cranes shall be used to slowly lift and lower the tower to avoid collision with the formed tower crown and the reserved manhole 12. After the demolition is completed, the tower crown shall be repaired, polished and cleaned to complete the overall construction of the tower crown.
[0018] This embodiment takes the construction of the gradually widening, irregularly shaped lotus crown 2 on the upper part of the 294m high A-shaped main tower as an example. The total height of the crown is 18m, consisting of an 11m hollow section 3 and a 7m solid section 4. It features an outwardly expanding, gradually changing lotus shape and includes a reserved manhole 12. Standard segmented steel molds are used, and the construction is carried out according to the following steps: (1). Modeling: Complete the construction of the lower tower column and set up the platform; build a BIM model in Revit, determine the segment construction line 6, component points and perform collision checks. After the tower crown is segmented, the foundation height of each segment is 2m, and the height of the steel formwork above the segment line is ≤0.5m. (2). Installation of supports and components: A support consisting of truss 16 + distribution beam 17 + bracket 18 is hoisted on the top surface 21 of the main tower to bear the horizontal lateral pressure 19 and vertical load 20; stiffening frame 26, steel anchor beam 22, and embedded parts 24 are installed. (3). Steel mold processing and pre-assembly: 3D laser cutting is used to make steel mold panel 9 and steel mold rib 10. Steel mold is pre-drilled and transported to the site after being pre-assembled on the ground and qualified. (4) Steel formwork installation: hoist the steel formwork and embed the pre-embedded parts 24 through the pre-drilled holes in the steel formwork; install the 16# inner triangular frame 13, double channel steel 14, and Φ20 tie rod 15 on the inner side of the tower crown, tension the tie rod 15–20kN, and fix the steel formwork section 7 that is higher than the segment line; use Φ159 adjustable diagonal bracing for auxiliary reinforcement; (5). Installation of truss 11: Install truss 11 according to the BIM line type, so that the gap between truss 11 and steel formwork large rib 10 is ≤2mm, and three high-strength bolts are set per meter to form an integral force system; (6) Fine adjustment of steel anchor beam: At night, the steel anchor beam 22 and cable guide 23 are finely adjusted under constant temperature, and the limiting device 25 is installed. The positioning deviation is ≤3mm; (7) Overall adjustment: Total station + 3D laser scanning correction, line deviation ≤3mm, fitting gap ≤2mm, to ensure no interference with the reserved manhole 12; (8). Concrete pouring and temperature-controlled pumping: the hollow section 3 of the tower crown is constructed by climbing formwork, and the solid section 4 of the tower crown is constructed in layers of 5m+2m; C60 + viscosity reducer, intelligent temperature control of cooling water pipes; 48MPa pump to achieve ultra-high pumping of 280m; curing for ≥14 days to form the main concrete body of the tower crown 8, and testing the strength and linearity during the curing period; (9) Demolition work: After the strength meets the standard, demolish in sequence to complete the construction.
[0019] In this embodiment, the construction method of the present invention was adopted and implemented strictly according to the established nine steps. The construction cycle of the tower crown was shortened by 15%, the fitting accuracy of the steel formwork and the truss was 100%, the deviation of the tower crown line was controlled within 3mm, the lotus shape was highly restored, the concrete appearance quality was good, and there were no defects such as leakage, pitting, or bulging. The problem of fixing the steel formwork that protrudes above the segment line due to the segmentation of the standard steel formwork was successfully solved, effectively preventing the tie rod from intruding into the reserved manhole, freeing up the outer working space, making it convenient for construction personnel to operate, and no safety hazards occurred during the construction process. It fully meets the design and construction specifications and verifies the feasibility and superiority of the construction method of the present invention.
[0020] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solutions and improved concepts of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A construction method for an A-shaped main tower with a gradually widening, irregularly shaped lotus-shaped crown, characterized in that: The specific steps are as follows: (1) Modeling: Complete the construction of the conventional tower columns at the bottom of the A-shaped main tower, clean up the construction area at the top of the tower, and set up a high-altitude operation platform; based on the tower crown design drawings, establish a three-dimensional BIM model of the gradually widening irregular lotus-shaped tower crown, clarify the outward expansion angle, cross-sectional dimensions, curved surface shape, and reserved manhole location of each height section of the tower crown, and determine the layout parameters of the truss, brackets, trusses, distribution beams, stiffening frame, steel anchor beams, embedded parts, inner triangular frame, and double-channel steel; combined with the structural characteristics of the gradually widening bottom of the tower crown and the inability of the truss to support the top 2-meter standard section, determine the position, parameters, and fixed points of the steel formwork above the segment line; at the same time, mark the contact points and contact accuracy requirements of the steel formwork ribs and trusses, and clarify the embedded positions of the inner triangular frame and double-channel steel; through BIM simulation of the entire construction process, conduct collision checks on the supports, embedded parts, catwalks, and main cable components, optimize the connection of each step and the layout of components, and avoid construction interference problems; (2) Installation of brackets, trusses, distribution beams, reserved triangular frames, double-channel steel stiffening frames, steel anchor beams and embedded parts: According to the positioning requirements of the BIM model, the bracket composed of "truss + distribution beam + bracket" is hoisted layer by layer at the preset position on the top of the A-shaped main tower to achieve force separation: the truss and distribution beam bear the horizontal lateral pressure, and the bracket only bears the vertical load; the stiffening frame, steel anchor beam and embedded parts of the tower crown are hoisted at the same time; the total station is used for real-time positioning and correction to ensure that the horizontality of the bracket installation, the verticality of the stiffening frame, the spacing and the outward tilt angle meet the design requirements; after the above components are installed, they are temporarily fixed to form the main force support system of the tower crown, providing a stable foundation for the subsequent installation of steel formwork and truss panels; at the same time, the installation points of the triangular frames and double-channel steel are reserved on the inner side of the tower crown corresponding to the position of the steel formwork above the segment line to ensure that the subsequent fixed structure and the reserved manhole do not interfere with each other; (3) Steel mold processing and pre-assembly: Based on the parameters of each section of the tower crown obtained from the BIM model established in step (1), special irregular steel molds are processed. The steel mold panel is made of arc-shaped steel plate to accurately match the curved surface of the tower crown. Three-dimensional laser CNC cutting is used to ensure the processing accuracy is ≤0.1mm. The steel mold ribs are made of profile steel. The outline of the steel mold ribs is precisely matched with the inner side line of the corresponding tower crown truss to ensure that the subsequent steel mold ribs and truss are seamless. Three-dimensional holes are pre-drilled on the steel mold according to the BIM model for the pre-embedded parts to be accurately embedded with the steel mold. After the steel mold is processed, it is pre-assembled in sections on the ground to simulate the inner side line of the tower crown and the installation position of the truss. The steel mold line, splicing accuracy and simulated fitting effect of the steel mold ribs and truss are checked. The deviation parts are ground and adjusted to ensure that they meet the design requirements. Then, it is disassembled and transported to the construction area at the top of the tower. (4) Steel formwork installation: The pre-assembled qualified steel formwork is hoisted to the tower crown construction section by a tower crane. The position of the steel formwork is adjusted so that the steel formwork panel fits the designed curved surface of the tower crown. The pre-embedded parts such as climbing cones and bolts are installed along with the formwork through the pre-drilled holes of the steel formwork. For the steel formwork that is higher than the segment line, a fixed method of embedding a triangular frame on the inside is adopted. Specifically, a triangular frame is embedded at the reserved point on the inside of the tower crown, and the double-segmented channel steel is welded and fixed to the rigid frame of the tower crown. The double-segmented channel steel is welded to the rigid frame on both sides. The triangular frame is firmly connected to the double-segmented channel steel. Then, the tripod and the outer ring of steel formwork are connected as a whole by tie rods, so as to achieve a stable fixation of the steel formwork that is higher than the segment line, replacing the traditional outer support and tie rods, avoiding the tie rods from intruding into the reserved manhole of the tower crown, and freeing up the working space on the outside. After each section of steel formwork is installed, adjustable diagonal braces made of steel pipes are used for auxiliary reinforcement. One end of the adjustable diagonal brace is connected to the steel formwork, and the other end of the adjustable diagonal brace is fixed to the bracket or stiffening frame. The length and inclination angle of the diagonal brace are adjusted according to the outward tilt angle of the tower crown to ensure the stability of the steel formwork installation. (5) Truss installation: According to the positioning parameters and inner line requirements of the truss in the BIM model established in step (1), the truss is hoisted to the designated position in sections by a tower crane. The posture of the truss is adjusted so that the inner line of the truss is completely aligned with the design line of the BIM model. At the same time, the truss is pushed to fit tightly with the installed steel formwork ribs. High-strength bolts are used to fix the truss to the steel formwork ribs and stiffening frame to form a steel formwork and truss fitting as an integral force system, avoiding relative displacement between the steel formwork and the truss, and ensuring accurate fitting of the lotus-shaped outline of the tower crown. (6) High-precision positioning of steel anchor beams: steel anchor beams are set in the hollow section of the tower crown. The elevation is transferred by the zenith distance measurement method of the total station and the plane is positioned by the resection method. The cable guide and steel anchor beam are finely adjusted during the constant temperature period at night. The positioning deviation is controlled within ≤3mm. After completion, the limit is fixed to prevent deviation during the pouring process. (7) Adjustment: After the steel formwork, truss, and steel anchor beam are all installed, a total station and a 3D laser scanner are used to comprehensively monitor the overall shape of the tower crown, the fitting accuracy of the steel formwork and truss, the installation position of each component, and the positioning accuracy of the steel anchor beam. The monitoring data are compared and analyzed with the design parameters of the BIM model. If there is a deviation in the shape, an excessive fitting gap, or a component position deviation, the deviation is precisely corrected by adjusting the length of the adjustable diagonal brace, fine-tuning the tension of the tie rod, and correcting the connection position of the truss and the steel formwork. Ensure that the outward tilt angle, cross-sectional dimensions, and curved shape of the tower crown meet the design requirements, the fitting accuracy of the steel formwork and truss meets the standard, the cumulative shape deviation does not exceed 3mm, the positioning deviation of the steel anchor beam is ≤3mm, and the reserved manhole is free from any obstruction or interference. (8) Concrete pouring, temperature control and ultra-high pumping: After adjustment and acceptance, the tower crown concrete is poured; the tower crown is divided into a lower 11m hollow section constructed using climbing formwork and an upper 7m solid section constructed using brackets. The solid section of the tower crown is poured in layers of 5m + 2m; C60 high-strength concrete is used, with viscosity reducers added to optimize fluidity and crack resistance; cooling water pipes are laid, and intelligent temperature control and hydration heat monitoring are used to control the risk of cracking in large-volume concrete; a 48MPa ultra-high pressure ground pump and φ125 ultra-high pressure wear-resistant pump pipe are used to achieve a maximum pumping height of 280m. Continuous construction; the thickness of each concrete layer should not exceed 50cm. During vibration, avoid collisions between the vibrator and the steel formwork, truss, steel anchor beam and embedded parts to prevent deformation of the steel formwork, loosening of the bonding surface or displacement of components. Monitor the shape of the tower crown in real time during the pouring process. If any deviation occurs, stop the machine in time for adjustment. After the pouring is completed, cover with moisturizing material for curing. The curing time should not be less than 14 days. (9) Demolition work: After the concrete strength reaches more than 75% of the design strength, the demolition work shall be carried out. The demolition sequence shall follow the principle of "top first, bottom last". First, the adjustable diagonal braces, tie rods, triangular frames and double channel steel and other temporary fixed components shall be removed. Then, the steel formwork shall be removed. Finally, the brackets, trusses, distribution beams and temporary working platforms shall be removed. During the demolition process, the tower crane shall be used to slowly lift and lower the tower to avoid collision with the formed tower crown and the reserved manhole. After the demolition is completed, the tower crown shall be repaired, polished and cleaned to complete the overall construction of the tower crown.
2. The construction method of the A-shaped main tower upper part widening special-shaped lotus tower crown according to claim 1, characterized in that: In step (1), after the tower crown is segmented, the foundation height of each segment is controlled at 2m, and the height of the steel mold above the segmentation line is not more than 0.5m; the fit gap between the steel mold rib and the truss plate is required to be no more than 2mm, and the cumulative linear deviation of the tower crown is no more than 3mm.
3. The construction method of the A-shaped main tower upper part widening special-shaped lotus tower crown of claim 1, characterized in that: In step (4), the double-channel steel is made of 16# channel steel and is welded to the stiffening frame on both sides with a welding length of not less than 100mm; the tie rod is made of Φ20 tie rod with a tension force of 15–20kN; the adjustable diagonal brace is made of Φ159 steel pipe.
4. The construction method of the A-shaped main tower upper part widening special-shaped lotus tower crown of claim 1, characterized in that: In step (5), the gap between the steel mold rib and the truss plate is controlled within 2mm, and three high-strength bolts are set for each meter of the fitting length to form an overall force system.
5. The construction method of the A-shaped main tower upper part widening special-shaped lotus tower crown of claim 1, characterized in that: In step (8), the strength and shape of the concrete are monitored in real time during the curing process to prevent shrinkage cracking and deviation in shape.