A method for asynchronous construction of a tower cover beam of a single-column cable-stayed bridge

Abstract

The application discloses a kind of single-column cable-stayed bridge tower cover beam asynchronous construction methods, comprising: main tower construction is set to the position above cover beam, cover beam is supported by bracket system construction, while upper tower column continues synchronous construction using hydraulic climbing formwork, realize the asynchronous construction of main tower and cover beam.In the process of synchronous construction of main tower and cover beam, while cover beam construction is carried out by bracket system, pre-stressed construction is also installed between cover beam and main tower, and multiple pre-stressed steel strands are tensioned in batches.The application realizes efficient, accurate and reliable connection of tower column and cover beam reinforcement by tower cover beam asynchronous construction, continuous construction of upper tower column hydraulic climbing formwork, cover beam operation using triangular bracket system and synchronous installation of pre-stressed construction, thereby greatly shortening the construction period and ensuring the construction quality and safety of key connection parts.

Description

Technical Field

[0001] This invention relates to the field of civil engineering bridge construction technology. More specifically, this invention relates to an asynchronous construction method for the cap beam of a single-column cable-stayed bridge tower. Background Technology

[0002] In the construction of long-span cable-stayed bridges, various types of bridge towers (such as the widely used single-column towers) are key load-bearing structures. While single-column towers are relatively simple to construct and require less resource investment, the traditional construction method of supporting cantilevered cap beams on both sides relies on ground-based scaffolding, which has significant drawbacks: the tower columns must be completely halted during cap beam construction. This results in severe delays in tower column construction during the cap beam construction period, becoming a key bottleneck restricting overall project efficiency, and also presenting significant risks to connection quality and safety during simultaneous high-altitude operations. Therefore, there is an urgent need to develop targeted construction control technologies to address the aforementioned challenges in the construction progress and coordination of tower columns and cap beams. Summary of the Invention

[0003] One objective of this invention is to provide an asynchronous construction method for the tower and cap beam of a single-column cable-stayed bridge, addressing the problem of long construction periods caused by the need for simultaneous construction of the tower and cap beam, which relies on ground-based scaffolding. Through asynchronous tower and cap beam construction, while the upper tower is continuously constructed using hydraulic climbing formwork, a triangular bracket system is employed for cap beam construction and prestressing installation is carried out simultaneously. This achieves efficient, precise, and reliable connection between the tower and cap beam reinforcement, thereby significantly shortening the construction period and ensuring the construction quality and safety of critical connection points.

[0004] To address the aforementioned technical problems, this invention provides an asynchronous construction method for the cap beam of a single-column cable-stayed bridge tower, comprising: when the main tower is constructed to a predetermined position above the cap beam, the cap beam is supported by a bracket system during construction, while the upper tower column continues to be constructed synchronously upwards using hydraulic climbing formwork, thereby achieving asynchronous construction of the main tower and the cap beam.

[0005] Preferably, during the simultaneous construction of the main tower and the cap beam, while the cap beam is being constructed using a bracket system, prestressing is also being installed between the cap beam and the main tower, with multiple prestressed steel strands being tensioned in batches.

[0006] Preferably, the bracket system includes multiple triangular bracket structures symmetrically arranged below the cap beams on both sides of the main tower to support the cap beam construction; the bracket structure includes main horizontal beams and main longitudinal beams arranged in a crisscross pattern, which are welded together as a whole; a distribution beam is provided above the main horizontal beam as a bottom formwork support structure for the cap beam construction; a bracket support beam is provided below the main longitudinal beam, which forms a triangular structure with the bracket diagonal brace; the upper end of the bracket diagonal brace is fixed to the bracket support beam, and the lower end is fixed to the bracket bracket bracket; the bracket bracket is pre-embedded in the main tower; a load-bearing block is provided between the bracket support beam and the main longitudinal beam.

[0007] Preferably, the distribution beams and main longitudinal beams of multiple bracket structures on the same side are connected as an integral structure, and the bracket support beams and bracket diagonal braces of multiple bracket structures on the same side are connected as an integral support structure by bracket connecting braces and scissor braces. The bracket diagonal braces of the same bracket structure are also connected by bracket connecting braces to strengthen the support structure.

[0008] Preferably, steel strands are installed between two symmetrical bracket structures along the same transverse direction of the cap beam, passing through the interior of the main tower and anchored at both ends to the bracket support beams of the bracket structures on both sides.

[0009] Preferably, the main tower wall and the inner bracket diagonal brace are padded with pads above the bracket bracket legs. The main tower wall is also pre-embedded with a limiting bracket, which is located in the space above the main tower wall and the inner bracket diagonal brace. A support block is provided above the pre-embedded bracket, which is supported on the lower bottom surface of the inner end of the bracket support beam. A pad is also padded between the end of the bracket support beam and the main tower wall, and the steel strand passes through the pad.

[0010] Preferably, a tensioner is installed between the end of the bracket support beam and the main tower wall of the steel strand, which is used to tension the steel strand to adjust the tension force of the steel strand. The tensioner is installed in the space between the end of the bracket support beam and the main tower wall or inside a hollow pad. A pressure sensor is connected in series at the rear end of the anchor of the steel strand to monitor the actual tension value of the steel strand. An inclination sensor is installed at the cantilever end of the bracket support beam to monitor the angle change of the bracket support beam. The system also includes a control system, which includes a wireless acquisition module to acquire data from the pressure sensor and the inclination sensor. The control system controls the tensioner to tension the steel strand during the concrete pouring process based on the acquired data.

[0011] Preferably, the control system controls the tensioner to tension the steel strands during concrete pouring based on the acquired data, specifically including the following steps: First, calculate the current total load W2 using the formula: W2 = k(F2 - F1) + W1; where k is the load-tension conversion coefficient, calculated using the formula k = L / h, where L is the length of the bracket support beam, and h is half the height of the bracket system; F2 is the real-time tension value of the steel strand collected by the pressure sensor, F1 is the initial tension value of the steel strand, and W1 is the self-weight of the template system. Secondly, the finite element model of the bracket system built into the control system can be used to calculate the theoretical elastic deformation value Q1 at the front end of the bracket system under the current load by inputting the current total load W2 into the model. Next, the control system obtains the actual deformation value Q2 measured by the tilt sensor, calculates whether the absolute value of Q2-Q1 is less than the designed allowable error range, and if it is less, no intervention is performed; if it is greater, the next step is performed. Finally, the steel strands are tensioned using a tensioner, and the absolute values ​​of Q2-Q1 are monitored and calculated in real time until they are adjusted to within the allowable error range.

[0012] Preferably, the bracket system is pre-elevated to a higher top elevation during installation, with the pre-elevation height equal to... ,in For elastic deformation, It is an inelastic deformation. For long-term deformation; in, The following steps are taken: First, a finite element model including the main tower and the bracket system is established; second, the self-weight of the formwork and the weight of the concrete to be poured are applied to the model; finally, the maximum vertical displacement value at the cantilever end of the bracket system is calculated using the model, which is the theoretically required elastic deformation pre-camber value to be compensated. ; The following steps are taken to obtain the inelastic deformation value: First, a finite element model including the main tower and the bracket system is established. Second, the self-weight of the formwork and 1.2 times the weight of the concrete to be poured are applied to the model, and the full load is held for a set time. Finally, after complete unloading, the maximum vertical displacement change at the cantilever end of the bracket system before and after unloading is calculated, which is the inelastic deformation value. ; for 2-3 times.

[0013] The present invention has at least the following beneficial effects: The construction method of this invention is simple, safe, reliable, and convenient to operate, ensuring construction quality and reducing construction costs. It has good application prospects, demonstrating excellent technical characteristics and superior economic performance, and possesses great value for widespread application. The main features include the following: Safety: For the large cantilever cap beam, shear boxes are pre-embedded on the tower column as the lower support point of the triangular bracket system, which avoids the vertical force of the conventional corbel bracket relying on the weld seam for shear. The force is clear, safe and reliable. The tower column and cap beam are carried out in two independent units without interference. The tower column climbing formwork adopts full enclosure to avoid vertical work intersection and ensure the safety of the cap beam construction workers.

[0014] Economic advantages: It avoids the delays caused by the construction of the tower limbs due to the cap beam, allowing for two separate working faces in the vertical direction of the bridge tower. This also avoids conflicts between the climbing formwork for the tower limbs and the cap beam support. The asynchronous construction method eliminates the need for disassembling and assembling the climbing formwork for the tower limbs, saving on construction equipment costs. Furthermore, it shortens the overall construction period; at least six bridge tower segments can be completed during the cap beam construction phase, saving on project management costs. The corbel triangular support system significantly saves on steel compared to conventional ground-supported scaffolding and can be reused.

[0015] Wide range of applications: asynchronous construction of large cantilever prestressed cap beams for single-column concrete bridge towers, especially suitable for the construction of high-altitude large cantilever cap beams.

[0016] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the overall construction process of the present invention; Figure 2 This is an elevation view of the beam bracket of the present invention; Figure 3 This is a cross-sectional view of the beam bracket of the present invention; Figure 4 This is a schematic diagram of the temporary work platform structure of the present invention; Figure 5 This is a schematic diagram of the beam reinforcement binding construction platform structure of the present invention; Figure 6 This is a schematic diagram of the structure of the crossbeam presser foot mold of the present invention; Figure 7 This is a schematic diagram of the arrangement of the crossbeam inner cavity support of the present invention; Figure 8 This is a layout diagram of the beam tensioning construction platform of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Main tower, 2. Bracket corbel, 3. Bracket connecting brace, 4. Shear brace, 5. Bracket diagonal brace, 6. Bracket support beam, 7. Pad block, 8. Unloading block, 9. Limiting corbel, 10. Support block, 11. Steel strand, 12. Main crossbeam, 13. Main longitudinal beam, 14. Distribution beam. Detailed Implementation

[0019] To better understand the purpose, structure, and function of this invention, the invention will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0020] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] like Figures 1 to 8 As shown, this invention provides an asynchronous construction method for the cap beam of a single-column cable-stayed bridge tower, comprising: when the main tower is constructed to a predetermined position above the cap beam, the cap beam is supported by a bracket system during construction, while the upper tower column continues to be constructed synchronously upwards using hydraulic climbing formwork, thereby achieving asynchronous construction of the main tower and the cap beam. During the synchronous construction of the main tower and the cap beam, while the cap beam is being constructed through the bracket system, prestressing is also being installed simultaneously between the cap beam and the main tower.

[0022] In one specific implementation scheme, the bridge tower structure addressed in this application is as follows: symmetrical cap beam structures are installed on both sides of the junction of the middle and lower tower columns of the main tower. The cap beams are prestressed concrete components, with a transverse width of 26m, a longitudinal width of 10.52m, and a height of 5m, featuring a single-box, three-cell rectangular cross-section. The cantilever length of each cap beam is 8.5m, and the support is 11.8m from the centerline of the bridge tower. The main tower and cap beams are constructed using an asynchronous construction process: the main tower cap beams are supported by a triangular bracket system, while the upper tower columns are constructed upwards using hydraulic climbing formwork, and prestressing is completed simultaneously during this stage. The triangular bracket load-bearing system consists of an upper limiting bracket and a lower shear box bearing the vertical load, with continuous steel strands constraining the horizontal force, ensuring clear force distribution and reliable safety.

[0023] This invention provides an asynchronous construction method for the cap beam of a single-column cable-stayed bridge tower. The construction process is as follows: Figure 1 As shown.

[0024] 1. The main tower is constructed by climbing formwork to two segments above the cap beam, and construction continues to the next segment. The cap beam construction is carried out simultaneously during this process. For example, after the climbing formwork reaches the 14th segment, the installation of the crossbeam support and bottom formwork begins, followed by the binding of the bottom reinforcing steel and the laying of prestressed ducts. Then, the inner and outer formwork of the crossbeam are installed, concrete is poured, and finally, prestressing tensioning, grouting, and anchor sealing are carried out. The tower crossbeam is cast in one continuous pour.

[0025] II. Bracket system design and construction, such as Figure 2 and Figure 3 As shown.

[0026] The bracket system includes multiple triangular bracket structures, symmetrically arranged below the cap beams on both sides of the main tower 1 to support the cap beam construction; the bracket structure includes main horizontal beams 12 and main longitudinal beams 13 arranged in a crisscross pattern, welded together as a whole; a distribution beam 14 is provided above the main horizontal beams as a bottom formwork support structure for the cap beam construction; a bracket support beam 6 is provided below the main longitudinal beams, forming a triangular structure with the bracket diagonal brace 5; the upper end of the bracket diagonal brace is fixed to the upper part of the bracket support beam, and the lower end is fixed to the bracket bracket bracket 2, which is pre-embedded in the main tower; a load-bearing block 8 is provided between the bracket support beam and the main longitudinal beam. (On the same side) Figure 3 The distribution beams and main longitudinal beams of multiple bracket structures in the left-right direction (i.e., longitudinal direction) are connected as an integral structure. The bracket support beams 3 and bracket diagonal braces of multiple bracket structures on the same side are connected as an integral support structure by bracket connecting braces and scissor braces 4. The bracket diagonal braces of the same bracket structure are also connected by bracket connecting braces to strengthen the support structure. A bracket structure includes two bracket diagonal braces, one inner and one outer, both of which are connected to the bracket bracket at the lower end and fixedly connected to the two ends of the bracket support beam at the upper end.

[0027] The crossbeam flange side bracket system adopts a triangular bracket structure, which consists of a distribution beam, main longitudinal beam, main crossbeam, bracket support beam, bracket diagonal brace, bracket connecting brace, bracket corbel, limiting corbel, and unloading block. The bracket structure has four rows, connected by bracket connecting brace and scissor brace to form an integral support structure. Unloading blocks are installed above the bracket support beams, and above the unloading blocks is the main crossbeam structure (2HM588×300), with a spacing of 3000mm. Above the main crossbeams is the main longitudinal beam structure (HM588×300), which is welded to the main crossbeam, with a spacing of 1200mm / 1650mm. Above the main crossbeams is a distribution beam structure (2I20a, I20a) serving as the bottom formwork support structure.

[0028] Along the same transverse direction of the cap beam ( Figure 2 A steel strand 11 is installed between two symmetrical bracket structures (in the left-right direction) on the main tower. It passes through the main tower and its two ends are fixedly connected to the bracket support beams of the two side bracket structures. The steel strand is reserved during the construction of the main tower and is used to connect the two side bracket structures, stabilizing the entire bracket structure. Simultaneously, the steel strand can transmit shear force to the brackets on both sides, forming a self-balancing system for the two side brackets and achieving a certain degree of anti-overturning performance.

[0029] The main tower wall and the inner bracket diagonal brace are padded with pads 7 above the bracket corbels. A limiting corbel 9 is also pre-embedded in the main tower wall, located in the space above the main tower wall and the inner bracket diagonal brace. A support block 10 is provided above the pre-embedded corbel, supporting the lower surface of the inner end of the bracket support beam. Pads are also padded between the end of the bracket support beam and the main tower wall. The limiting corbel is a pre-embedded component, and the pads and support blocks are used to support the upper bracket. Because the main tower of this application is relatively high and the crossbeams of the cap beams on both sides are large, the stress on the bracket structure during construction is also large. The stress stability of the bracket structure is increased by setting steel strands and limiting corbels, thereby increasing the overall load-bearing capacity.

[0030] Installation of bracket brackets and bracket structure. After the climbing formwork is raised to two sections above the cap beam, the installation of bracket brackets and bracket structure begins.

[0031] 1. Installation of Embedded Parts: During the construction of the joint segment between the tower column and the cap beam, anchor plates, shear boxes, tie rod holes, and PVC pipes for the bracket limiting bracket are pre-embedded at the designated locations. A steel mesh is installed below the limiting bracket for reinforcement. If some main reinforcement bars need to be cut at the bracket, the cut bars are welded to the limiting bracket, and additional vertical reinforcement bars are added for reinforcement.

[0032] 2. Temporary Working Platform: When the tower column is constructed to a suitable position, pre-embedded triangular bracket brackets are installed. Construction workers hang a suspended basket at the bottom of the hydraulic climbing formwork platform, and install triangular bracket supports to form a temporary working platform. The platform is 1.5m wide and the guardrail is 1.2m high. Figure 4 As shown.

[0033] 3. Installation of Brackets and Bracket Structure: A tower crane is used for overall lifting and installation. Construction workers stand on a temporary work platform, adjust the position of the brackets to ensure the pre-embedded holes are aligned, and then weld the brackets to the anchor plates. Tie rods are then inserted and tensioned as required. The brackets are lifted using a tower crane, with lifting lugs welded to the top of the bracket. Steel wire ropes and shackles are used for lifting. After the bracket is installed and welded in place, the intermediate bracket connecting supports are lifted. Finally, the top steel strands of the bracket are installed and tensioned. A work platform is installed on the tower column before installing the bracket.

[0034] 4. Install the unloading blocks, main crossbeams, main longitudinal beams, and distribution beams in sequence: After the triangular brackets are installed, surveyors use a total station to accurately measure their top surface elevation. The elevation is adjusted according to the bottom elevation of the crossbeams and the actual unloading blocks. The main crossbeams and main longitudinal beams are made of structural steel. Before installation, surveyors use a total station to level the unloading blocks and mark the installation line positions. The main crossbeams are 9.5m long, and the main longitudinal beams are 13m long. Both are lifted from two points using a tower crane, with the distance between the lifting points and both ends being L / 5. Two 6m long 6×37S+IWR-A14mm steel wire ropes are used with GB / T25854-6-DW5 shackles for lifting. After hoisting into place, surveyors use a total station to re-measure the plane position and elevation of the load-bearing beams. The top surface elevation of each longitudinal and crossbeam must be strictly measured, with an elevation deviation ≤3mm. Considering the influence of elastic deformation, the top elevation of the support is pre-raised.

[0035] Once the bracket system is installed, subsequent construction processes such as formwork installation and concrete pouring will place significant stress on it. Therefore, it is necessary to pre-raise the top elevation during the installation of the bracket system. The pre-raise height = ,in For elastic deformation, It is an inelastic deformation. For long-term deformation; among them, To obtain the instantaneous elastic deformation under construction loads, the following steps are taken: First, a finite element model including the main tower and the bracket system is established; second, the self-weight of the formwork and the weight of the concrete to be poured are applied to the model; finally, the maximum vertical displacement value at the cantilever end of the bracket system is calculated using the model, which is the theoretically required elastic deformation pre-camber value to be compensated. ; To address the non-recoverable deformation caused by loosening between bracket nodes, tightness of gaps, and compression of timber formwork, the following method is used: First, a finite element model including the main tower and bracket system is established; second, the self-weight of the formwork and 1.2 times the weight of the concrete to be poured are applied to the model, and the full load is held for a set time, typically 24-48 hours; finally, after complete unloading, the maximum vertical displacement change at the cantilever end of the bracket system before and after loading is calculated, which represents the inelastic deformation value. ; This refers to the long-term deflection of concrete itself due to creep and shrinkage during the hardening process, which is generally obtained through experience. 2-3 times, the value used in this application is 2-3 times. 2 times.

[0036] The bracket system is pre-elevated to the top elevation before formwork and concrete construction. Deformation of the bracket system needs to be monitored during construction, and the support of the bracket system is controlled by adjusting the tension of the steel strands, ensuring safe construction. Tensioners are installed between the end of the bracket support beam and the main tower wall to tension the steel strands and adjust their tension. These tensioners are located either within the space between the end of the bracket support beam and the main tower wall or inside a hollow pad. A pressure sensor is connected in series at the rear end of the steel strand anchor to monitor the actual tension value of the steel strand. An inclination sensor is installed at the cantilever end of the bracket support beam to monitor changes in the beam's angle. A control system is also included, comprising a wireless acquisition module to obtain data from the pressure and inclination sensors. Based on the acquired data, the control system controls the tensioners to tension the steel strands during concrete pouring.

[0037] The control system, based on the acquired data, controls the tensioner to tension the steel strands during concrete pouring. Specifically, the steps include: First, calculating the current total load W2 using the formula: W2 = k(F2 - F1) + W1; where k is the load-tension conversion coefficient, obtained through the formula k = L / The calculation is as follows: L is the length of the support beam of the bracket, and h is half the height of the bracket system; F2 is the real-time tension value of the steel strand collected by the pressure sensor, F1 is the initial tension value of the steel strand, and W1 is the self-weight of the template system; secondly, the control system has a built-in finite element model of the bracket system. The current total load W2 calculated above is input into the model to calculate the theoretical elastic deformation value Q1 at the front end of the bracket system under the current load; thirdly, the control system obtains the actual deformation value Q2 measured by the tilt sensor and calculates whether the absolute value of Q2-Q1 is less than the design allowable error range. If it is less, no intervention is performed; if it is greater, the next step is performed; finally, the steel strand is tensioned by the tensioner, and the absolute value of Q2-Q1 is monitored and calculated in real time until it is adjusted to within the allowable error range.

[0038] 5. Install the bottom mold.

[0039] III. Installation of reinforcing steel bars and prestressed ducts.

[0040] 1. The cap beam and tower column are constructed asynchronously. When the tower column is constructed at the junction, the main reinforcement bars and chamfered reinforcement bars of the cap beam must be pre-embedded on the outside of the tower column. Half-threading is made at the interface between the pre-embedded main reinforcement bars and the formwork. The sleeve is installed and tightened in place. The pre-embedded first-level sleeve is fixed with a positioning frame. The end of the sleeve is sealed with tape and nailed to the formwork.

[0041] 2. Pre-embed anchor plates and some corrugated pipes. The corrugated pipes are wrapped with transparent tape at the ends of the cap beam to prevent grout from entering. After the tower column construction is completed and the formwork is removed, the location of the corrugated pipes is chiseled out with an electric hammer. The tape wrapped around the corrugated pipes and the stones and other debris inside the pipes are cleaned out, and the corrugated pipes are extended to connect with the upper cap beam.

[0042] 3. Before installing the reinforcing bars and prestressed ducts, erect scaffolding on the triangular brackets. The scaffolding should be arranged with a step distance of 1.5m, a horizontal spacing of 0.9m, and a longitudinal spacing of 1.5m, with a total erection height of 6m. A 1.2m high guardrail should be installed, and the bottom of the scaffolding should be securely welded to the cap beam support. The scaffolding layout diagram is shown below. Figure 5 As shown.

[0043] IV. Installation of formwork for cap beams.

[0044] 1. The tower column formwork uses climbing formwork for the central tower column, while the outer formwork for the horizontal beams uses standardized steel formwork. The bottom formwork and chamfered formwork for the horizontal beams also use standardized steel formwork. The end formwork at the post-cast strip is made of sealing mesh. The inner formwork for the horizontal beams and tower column box grate is made of 18mm bamboo plywood. The vertical ribs are made of 10cm×10cm square timber spaced 30cm apart, and the horizontal backing strips are made of 2[16a channel steel spaced 1m apart. The panels are fixed to the vertical ribs with nails, and the backing strips are fixed to the vertical ribs with long screws. The formwork tie rods are made of A20mm round steel.

[0045] 2. To prevent concrete from overflowing at the chamfered corner of the base slab due to pressure difference during concrete pouring, a pressure foot mold is installed at the chamfered corner. The pressure foot mold is connected and fixed to the inner mold vertical ribs by structural steel. The mold length is 50cm. Figure 6 As shown.

[0046] 3. Top Slab Formwork Installation: The inner cavity support for the crossbeams uses a socket-type disc-lock full-span steel pipe scaffold, with A48×3.2mm steel pipes for the scaffold uprights. The inner cavity support for the crossbeams is arranged at 1.5m intervals, with the uprights spaced 0.9m×0.9m apart. [10 channel steel is placed on the top support, spaced 0.9m apart. PVC pipes are pre-installed on the bottom plate of the crossbeams, and the disc-locks are installed inside the PVC pipes. After the scaffolding is erected and inspected, the bottom formwork is installed, using a tower crane in conjunction with manual labor in sections. M20×60 bolts are used to connect the formwork panels. Waterstop strips are applied at the joints between two formwork panels to prevent grout leakage; the two sections of formwork panels are tightly fitted, and the misalignment between adjacent steel formwork panels should not exceed 2mm. A schematic diagram of the scaffolding layout is shown below. Figure 7 As shown.

[0047] V. Concrete pouring for the cap beam.

[0048] During the pouring of the cap beam, a flexible hose and tremie pipe were used for concrete placement to ensure a free fall of less than 2 meters. Dragging or pushing the concrete with a vibrator was strictly prohibited. The pouring sequence was as follows: first pour the root of the web, then the bottom slab and the upper part of the web, and finally the top slab. Concrete was poured symmetrically, from the cantilever end towards the fixed side. Vertical placement proceeded from low to high. YDC4500-200 through-type jacks were used for prestressing the concrete beams, and the prestressing tensioning platform utilized the outer scaffolding platform.

[0049] Soil compaction should be performed using 30mm and 50mm immersion vibrators. During compaction, avoid collisions between the vibrator and the formwork, corrugated pipes, cooling water pipes, and other embedded parts. Curing with the formwork in place should be adopted. The formwork should be frequently watered to keep it moist, and the demolding time of the outer formwork should be appropriately extended. The curing time should be no less than 14 days.

[0050] VI. Prestressed construction.

[0051] The steel strands are threaded manually. Before threading, the inner liner of the corrugated pipe is removed, and compressed air is used to remove any accumulated water and debris from the pipe. Tensioning is performed using intelligent jacks, and grouting is done using an intelligent vacuum grouting process. Safety platforms are installed on both sides of the top of the bracket for prestressing tensioning and grouting. Figure 8 As shown. A prestressing system runs transversely between the main tower and the cap beam, increasing prestress and improving the overall structural stability of the main tower and cap beam. The cap beam is equipped with 46 prestressed steel strands of model 15-17. The steel strands are arranged in 7 rows on the flange side with a vertical spacing of 50cm; the steel strands are arranged in 4 rows on the span side with a vertical spacing of 20cm. Prestressing is achieved through tensioning at both ends. All prestressing anchor points are located on the outside of the tower column using a deep-buried hole process. YDC4500-200 through-hole jacks are used for prestressing tensioning of the crossbeams. The construction platform for prestressing tensioning of the crossbeams utilizes the external scaffolding platform. The prestressed steel strands are tensioned in batches. N1, N2, N3, and N4 steel strands are tensioned after the cap beam reaches more than 90% of its design strength, and N5, N6, and N7 steel strands are tensioned after the main beam is poured.

[0052] VII. Formwork and scaffolding removal Dismantling sequence: dismantle the inner cavity formwork → dismantle the inner cavity support → dismantle the outer and side formwork → dismantle the bottom formwork → dismantle the distribution beam → dismantle the longitudinal and cap beams → dismantle the triangular bracket.

[0053] Using a combination of hand-operated hoists and a tower crane, dismantle the distribution beams one by one. Disconnect the longitudinal beams from the top cap beam of the triangular brackets, use the hand-operated hoists to pull the longitudinal beams outside the cap beam's base plate area, and then use the tower crane to lift them to the ground. Disconnect the top cap beam of the triangular brackets from the triangular brackets, and dismantle the cap beams one by one. Lower the winch steel rope through the pre-drilled holes on the cap beam's base plate, setting two lifting points for each row of triangular brackets. Tighten the winch steel rope, disconnect the horizontal couplings between the triangular brackets, release the winch rope, and lower the triangular brackets to the ground one by one.

[0054] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention, and other modifications can be easily implemented by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A method for asynchronous construction of the cap beam of a single-column cable-stayed bridge tower, characterized in that, include: When the main tower is constructed to the position set above the cap beam, the cap beam is supported by a bracket system, while the upper tower column continues to be constructed synchronously using hydraulic climbing formwork, thus realizing asynchronous construction of the main tower and the cap beam. The bracket system includes multiple triangular bracket structures symmetrically arranged below the cap beams on both sides of the main tower to support the cap beam construction. Each bracket structure includes intersecting main horizontal and vertical beams, welded together as a whole. A distribution beam is provided above the main horizontal beam, serving as the bottom formwork support structure for the cap beam construction. A bracket support beam is provided below the main vertical beam, forming a triangular structure with the bracket diagonal brace. The upper end of the bracket diagonal brace is fixed to the bracket support beam, and the lower end is fixed to the bracket bracket bracket, which is embedded within the main tower. A load-bearing block is provided between the bracket support beam and the main vertical beam. A steel strand is installed between two symmetrical bracket structures along the same transverse direction of the cap beam. It passes through the interior of the main tower and is anchored at both ends to the bracket support beams of the bracket structures on both sides. The main tower wall and the inner side of the bracket diagonal brace are padded with pads above the bracket bracket legs. The main tower wall is also pre-embedded with a limiting bracket, which is located in the space above the main tower wall and the inner side of the bracket diagonal brace. A support block is set above the limiting bracket, which is supported on the lower bottom surface of the inner end of the bracket support beam. A pad is also padded between the end of the bracket support beam and the main tower wall, and the steel strand passes through the pad. A tensioner is installed between the end of the bracket support beam and the main tower wall of the steel strand to tension the steel strand and adjust its tension force. The tensioner is located in the space between the end of the bracket support beam and the main tower wall or inside a hollow pad. A pressure sensor is connected in series at the rear end of the anchor of the steel strand to monitor the actual tension value of the steel strand. An inclination sensor is installed at the cantilever end of the bracket support beam to monitor the angle change of the bracket support beam. The system also includes a control system, which includes a wireless acquisition module to acquire data from the pressure sensor and the inclination sensor. The control system controls the tensioner to tension the steel strand during the concrete pouring process based on the acquired data.

2. The asynchronous construction method for the cap beam of a single-column cable-stayed bridge tower as described in claim 1, characterized in that, During the simultaneous construction of the main tower and the cap beam, while the cap beam was being constructed using a bracket system, prestressing was also being installed between the cap beam and the main tower, with multiple prestressed steel strands being tensioned in batches.

3. The asynchronous construction method for the cap beam of a single-column cable-stayed bridge tower as described in claim 1, characterized in that, The distribution beams and main longitudinal beams of multiple bracket structures on the same side are connected as an integral structure. The bracket support beams and bracket diagonal braces of multiple bracket structures on the same side are connected as an integral support structure through bracket connecting braces and scissor braces. The bracket diagonal braces of the same bracket structure are also connected through bracket connecting braces to strengthen the support structure.

4. The asynchronous construction method for the cap beam of a single-column cable-stayed bridge tower as described in claim 1, characterized in that, The control system, based on the acquired data, controls the tensioner to tension the steel strands during concrete pouring, specifically including the following steps: First, calculate the current total load W2 using the formula: W2 = k(F2 - F1) + W1; where k is the load-tension conversion coefficient, calculated using the formula k = L / h, where L is the length of the bracket support beam, and h is half the height of the bracket system; F2 is the real-time tension value of the steel strand collected by the pressure sensor, F1 is the initial tension value of the steel strand, and W1 is the self-weight of the template system. Secondly, the finite element model of the bracket system built into the control system can be used to calculate the theoretical elastic deformation value Q1 at the front end of the bracket system under the current load by inputting the current total load W2 into the model. Next, the control system obtains the actual deformation value Q2 measured by the tilt sensor, calculates whether the absolute value of Q2 - Q1 is less than the designed allowable error range, if it is less than, no intervention is performed, if it is greater than, proceed to the next step; Finally, the steel strands are tensioned using a tensioner, and the absolute value of Q2 - Q1 is monitored and calculated in real time until it is adjusted to within the allowable error range.

5. The asynchronous construction method for the cap beam of a single-column cable-stayed bridge tower as described in claim 1, characterized in that, The bracket system is pre-elevated at the top elevation during installation. The pre-elevation height = f1 + f2 + f3, where f1 is elastic deformation, f2 is inelastic deformation, and f3 is long-term deformation. The value of f1 is obtained as follows: First, a finite element model including the main tower and the bracket system is established; second, the self-weight of the formwork and the weight of the concrete to be poured are applied to the model; finally, the maximum vertical displacement value of the cantilever end of the bracket system is calculated through the model, which is the elastic deformation f1 that needs to be compensated in theory. f2 is obtained as follows: First, a finite element model including the main tower and the bracket system is established; second, the self-weight of the template and 1.2 times the weight of the concrete to be poured are applied to the model and the full load is held for a set time; finally, after complete unloading, the maximum vertical displacement change value of the cantilever end of the bracket system before loading and after unloading is calculated, which is the inelastic deformation f2. f3 is 2-3 times f1.

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