Method for installing arched steel tower with long and thin structure

Abstract

The invention belongs to the technical field of sail-shaped cable-stayed bridge construction, and relates to a long and thin structure arched steel tower installation method which comprises the steps that a bridge lower structure and a main tower are constructed, and an auxiliary tower root embedded section, a top connecting piece and related construction components are embedded in the main tower; during main tower construction, an attached tower fixing section and a main beam are synchronously installed, and the attached tower fixing section is fixedly connected with the main tower through welding and a steel truss set; a support is erected on a girder bridge floor, tower-attached sections are assembled according to the inverted arch posture, the pre-bias value and the pre-camber are preset, and rotating hinges are installed; a vertical rotating cable, a back cable and a cable wind cable which are made of steel strands are arranged, and testing is completed; one-time vertical rotation welding of one section of the attached tower is achieved through synchronous traction of a continuous jack, and then secondary vertical rotation is conducted on the whole section of the attached tower; after vertically rotating in place, welding and fixing, and dismounting related equipment and a bracket; the invention aims to solve the problems of high overhead operation risk, difficulty in control of construction precision, large temporary support investment, low work efficiency and insufficient adaptability of a traditional mounting method.

Description

Technical Field

[0001] This invention belongs to the field of construction technology for sail-shaped cable-stayed bridges, and relates to a method for installing slender arched steel towers. Background Technology

[0002] As bridge engineering develops towards landscaping and landmark status, slender arched steel towers, such as those with sail-shaped structures, are increasingly widely used in modern cable-stayed bridge construction due to their unique architectural design and mechanical properties. These steel towers typically feature large spans, high heights, slender structures, and complex arch curves. They not only need to meet the core requirements of traffic flow but also serve the function of showcasing urban cultural landscapes. The level of their construction technology directly affects the overall quality, safety, and aesthetic appearance of the bridge.

[0003] In the actual installation of slender arched steel towers, traditional construction methods face numerous prominent problems. On the one hand, high-altitude operations are extremely risky. These steel towers are often nearly 100 meters high, and traditional scaffolding and high-altitude hoisting methods require a large amount of assembly and welding work to be completed at high altitudes. They are greatly affected by extreme weather conditions such as wind, rain, and snow, making it difficult to ensure the safety of construction personnel. Moreover, the harsh working environment at high altitudes makes it difficult to accurately control welding quality and assembly precision. On the other hand, temporary scaffolding is costly. Traditional scaffolding methods require the construction of large support structures extending from the ground to the top of the tower. Given the curved shape of the slender arched structure, the design and erection of scaffolding is difficult, resulting in high material consumption. Furthermore, the dismantling of scaffolding also poses safety hazards. At the same time, traditional methods are inefficient. The complexity and safety requirements of high-altitude operations lead to extended construction periods, making it difficult to meet the needs of efficient progress in large-scale bridge projects. Especially for the special shape of slender arched structures, existing technologies cannot achieve precise positioning and stable construction.

[0004] Based on a review of relevant materials, there are currently two main solutions for the installation of arched steel towers. One is the bidirectional traction vertical rotation construction method for cable-stayed bridge steel arch towers disclosed in CN104532756A. Its principle is to hinge the steel arch tower to the main pier structure using a vertical rotation hinge. After assembling the steel arch tower segments using a jig, the entire structure is vertically rotated using the coordinated traction of the tie cables, balance cables, and stabilizing cables. Once in position, it is welded and fixed. The advantage of this method is that it reduces some high-altitude work through vertical rotation technology and can ensure the stability of the rotation process through cable force control, making it suitable for the installation of large-size, heavy steel arch towers. However, its disadvantages are that it can only achieve a single vertical rotation, its adaptability to the complex curved shapes of slender arched steel towers is insufficient, the jig still requires a certain height, the amount of high-altitude work is not fundamentally reduced, the investment in temporary cables and jigs is still significant, and the construction accuracy is significantly affected by the coordinated control of cable force. Another type is the traditional scaffolding method, which uses ground-mounted or spanning scaffolds as a construction platform to assemble and weld steel tower segments. Its advantages include stable support for the steel tower segments during construction and intuitive assembly positioning. However, its disadvantages are significant: temporary scaffolding consumes a lot of materials, has a long setup and dismantling period, and is costly. Furthermore, for tall, slender structures, the overall rigidity and stability of the scaffolding are difficult to guarantee, making it susceptible to external environmental influences. At the same time, the risks and quality control challenges of high-altitude operations remain unresolved. In summary, existing methods fail to fully meet the construction requirements of slender arched steel towers, and cannot simultaneously balance safety, precision, cost, and efficiency. Therefore, there is an urgent need for an installation method that can significantly reduce the amount of high-altitude work, precisely control construction accuracy, reduce investment in temporary measures, and improve construction efficiency to address the pain points of existing technologies. Summary of the Invention

[0005] This invention provides a method for installing slender arched steel towers, which solves the problems of high risk of high-altitude operations, difficulty in controlling construction accuracy, large investment in temporary supports, low efficiency, and difficulty in adapting to the construction needs of slender arched structures such as sail-shaped structures in traditional installation methods for tall arched steel towers.

[0006] To solve the above problems, the technical solution adopted by the invention is as follows: The installation method for a slender arched steel tower includes the following steps: Step 1: Construct the bridge substructure; Step 2: Construct the main tower, pre-embed the auxiliary tower root section at the lower end of the main tower, pre-embed the auxiliary tower top connector at the top of the main tower, and pre-embed wall ties, vertical rotation construction platform, vertical rotation force point and related components of the vertical rotation docking operation platform at the corresponding height during the construction of the main tower. Step 3: During the construction of the main tower, the auxiliary tower fixing section and the main beam are installed simultaneously. The auxiliary tower fixing section is welded and fixed to the pre-embedded section at the base of the auxiliary tower and the main tower respectively. The main tower and the auxiliary tower fixing section are connected by welding through steel truss assembly. Step 4: Erect the auxiliary tower assembly support on the main beam bridge deck, and assemble the second and first auxiliary tower sections in sequence according to the inverted arch posture. During assembly, preset the pre-offset value and pre-camber, and then accurately position and install the secondary hinge and primary hinge. Step 5: Install the vertical turning cable, back cable, and guy cable. All three are made of steel strand and have anchor boxes at both ends to complete the test preparation before vertical turning. Step Six: Using continuous jacks to synchronously pull the vertical rotation cable, rotate the first section of the auxiliary tower once. After it is in place, weld it to the second section of the auxiliary tower to form the complete auxiliary tower section. Remove the rotating hinge once. Step 7: Continue to use continuous jacks to synchronously pull the vertical rotation cable and perform a second vertical rotation on the entire attached tower section; Step 8: After the second vertical rotation into place, weld and fix the end of the entire section of the attached tower to the top connecting piece of the attached tower, and weld and fix the bottom to the fixed section of the attached tower; Step 9: Remove the vertical rotation equipment and supports to complete the installation.

[0007] The principle and advantages of this solution are as follows: The principle of this scheme is to achieve safe and efficient installation of slender arched steel towers through the coordinated application of phased construction and secondary vertical rotation technology. In the initial stage of construction, the foundation construction of the bridge substructure, main tower and main beam is completed first. At the same time, pre-embedded components for connecting the auxiliary towers are pre-set on the main tower to provide a stable load-bearing foundation and connection benchmark for the subsequent installation of the auxiliary towers. The construction of the main tower is carried out simultaneously with the installation of the fixed sections of the auxiliary towers and the reinforcement and consolidation are strengthened by steel truss assemblies to ensure the initial stability of the auxiliary tower installation. In the core process, a low-height assembly support was erected on the main girder bridge deck. The auxiliary tower segments were assembled in an inverted arch posture with preset pre-offset values ​​and pre-camber, controlling the structural alignment accuracy from the source. Through the precise setting of primary and secondary hinges, and in conjunction with a stable traction system composed of vertical rotating cables, back cables, and guy cables, the synchronous traction of continuous jacks was used to achieve the primary vertical rotation and docking of one section of the auxiliary tower and the secondary vertical rotation and positioning of the entire auxiliary tower. During the rotation, the center of gravity of the structure was balanced by the coordinated force of the cables, ensuring a smooth and controllable rotation. Finally, the auxiliary tower was reliably connected to the main tower and the fixed section of the auxiliary tower by welding. The entire process revolved around the core logic of low-height operation on the bridge deck and phased rotation, avoiding the technical pain points of traditional high-altitude assembly and overall rotation.

[0008] Compared to existing technologies, which often employ single vertical rotation or high-altitude scaffold assembly, making it difficult to balance safety, accuracy, and cost, this solution utilizes a two-stage vertical rotation design to reduce the working height from nearly 100 meters to less than 6 meters. This significantly reduces the risks associated with high-altitude hoisting and operations, solving the problems of extreme weather conditions and personnel safety in traditional methods, thus substantially improving construction safety. Regarding construction accuracy, this solution employs pre-set pre-offset and pre-camber values ​​during bridge deck assembly, precise hinge positioning, and hydraulic synchronous traction control. This allows for more precise control of the linear deviation of slender arch structures. Compared to the limitations of traditional scaffold assembly methods, which are susceptible to high-altitude environmental interference and cannot adapt to complex curved shapes with a single vertical rotation, this solution better meets the installation accuracy requirements of slender arch structures such as sail-shaped structures. In terms of cost and efficiency, this solution eliminates the need for large temporary scaffolding, with the height of the assembled scaffolding controlled within 0.5-3 meters, significantly reducing investment in temporary measures. Furthermore, the centralized bridge deck operation mode simplifies the construction process, and the secondary vertical rotation eliminates the need to repeatedly build high-altitude platforms. Compared to the traditional scaffolding method's high material consumption, long construction period, and high equipment investment per vertical rotation, construction efficiency is significantly improved, enabling the rapid installation of towers nearly 100 meters high. In addition, this solution effectively balances the center of gravity shift problem during the vertical rotation of slender structures through a phased rotation and cable stabilization system, avoiding the drawbacks of traditional methods such as structural instability and high rotation difficulty. It achieves the effects of ensuring safety during low-altitude operations, improving accuracy through phased rotation, and increasing efficiency with low-cost investment, making it suitable for the construction needs of slender arched steel towers.

[0009] Furthermore, in step two, the pre-embedded section at the base of the auxiliary tower and the main tower are integrally cast using a steel-concrete composite section. The integrity of the concrete and the high strength of the steel form a synergistic force-bearing system, significantly improving the load-bearing capacity and deformation resistance of the anchoring structure. This effectively resists the vertical loads, horizontal thrust, and torque generated during the vertical rotation and operation of the auxiliary tower, preventing structural damage caused by stress concentration at the connection point. Simultaneously, the integral casting process eliminates the connection gap between the pre-embedded section and the main tower, reducing energy loss during force transmission and ensuring uniform force distribution, further guaranteeing structural stability. Combined with additional prestressing and tie rod measures, the reliability and durability of the anchoring are significantly enhanced, preventing loosening and cracking due to repeated loads during long-term use. This provides a solid foundation for the safe conduct of subsequent secondary vertical rotation construction of the auxiliary tower and the long-term stable operation of the overall steel tower structure.

[0010] Furthermore, in step three, the main beam is constructed using a scaffolding method. The scaffolding's load-bearing capacity meets the requirements for main beam construction, bridge deck pylon assembly, and pylon vertical rotation. The main beam can be a steel beam, a steel-concrete composite beam, or a cast-in-place concrete beam. The scaffolding method provides a stable and reliable working platform for the main beam's construction, ensuring the quality of the main beam construction. Its pre-designed high load-bearing capacity allows the main beam to be directly used as the load-bearing foundation for pylon assembly and vertical rotation, eliminating the need for additional independent load-bearing structures. This significantly reduces the investment in temporary measures and construction land occupation, shortening the construction cycle. The compatible design of multiple main beam types allows for flexible selection based on the overall structural stress requirements of the bridge, project cost budget, and construction environment conditions. This not only meets the personalized needs of different bridge projects but also avoids the problem of incompatible construction methods due to main beam type limitations. At the same time, it allows the scaffolding and the main beam to form a collaborative load-bearing system, effectively dispersing concentrated loads during pylon vertical rotation, ensuring structural stability and safety during construction, and providing solid support for the smooth implementation of the secondary vertical rotation process.

[0011] Furthermore, in step four, the auxiliary tower assembly support is supported on the diaphragm or web of the main beam. When the support position does not meet the requirements, a distribution beam is added to the main beam deck to bear the concentrated load. The diaphragm and web are the main load-bearing components of the main beam. Directly supporting the assembly support on these components can fully utilize the structural strength of the main beam itself and avoid the concentrated load of the support acting on the non-weak areas of the main beam, which could lead to local deformation or damage. When the support position is limited by the division of the auxiliary tower segments and cannot match the diaphragm or web, adding a distribution beam can effectively disperse the concentrated load, expand the contact area of ​​the load, and convert the local concentrated force into a uniformly distributed load to be transferred to the main beam. This ensures that the auxiliary tower assembly support has sufficient support stiffness, which not only avoids the main beam from exceeding the limit deformation due to concentrated load, but also provides a stable working platform for the precise assembly of the auxiliary tower segments, reduces displacement deviation during the assembly process, and lays a solid foundation for the precision control of subsequent secondary vertical rotation construction.

[0012] Furthermore, in step five, the upper ends of the vertical slewing cable and the rear back cable are connected to the anchor box assembly pre-embedded in the main tower, and the lower ends are respectively connected to the second section of the auxiliary tower and the main beam; there are two sets of guy cables arranged in a V-shape, with the upper ends connected to the second section of the auxiliary tower and the lower ends connected to the main beam. The anchor box assembly pre-embedded in the main tower, combined with the stress-bearing plate, can evenly transfer the cable tension to the main structure of the main tower, avoiding structural damage caused by local stress concentration and ensuring the stable transmission of traction and balance forces; the vertical slewing cable focuses on providing vertical traction force, and the rear back cable forms a connection with the main beam. The reverse constraint counteracts the horizontal thrust generated on the main tower during the vertical rotation, ensuring the main tower is in a balanced state. The two sets of outward-facing wind cables can form bidirectional limits in both the longitudinal and transverse directions, effectively resisting interference such as lateral wind force and structural eccentricity that may occur during the vertical rotation, suppressing the swaying and displacement of the auxiliary tower. At the same time, the outward-facing structure can form an inward constraint force through its own tension, further enhancing the overall rigidity and stability of the auxiliary tower during the vertical rotation. The synergistic effect of the three ensures the smooth and controllable vertical rotation process and provides strong support for construction accuracy.

[0013] Furthermore, in step five, two sets of vertical rotation cables and two sets of rear cables are set up and arranged in parallel. The spacing is calculated and determined based on the structural dimensions of the attached tower, the vertical rotation height, the hinge gap, and the accuracy indicators. If necessary, brackets are welded on both sides of the attached tower to increase the spacing. By optimizing the cable arrangement, the stability and accuracy control of the vertical rotation process are enhanced. The two sets of parallel cable arrangements can form a symmetrical force-bearing structure, ensuring that the traction force and the reverse constraint force are evenly applied to the attached tower, avoiding the offset or torsion of the attached tower caused by unilateral force, while improving the overall load-bearing capacity of the cable to cope with the changing load requirements during the vertical rotation. The reasonable spacing calculated based on key parameters can adapt to the construction requirements of attached towers of different specifications, ensure the optimal force angle of the cable, and reduce energy loss. The addition of brackets can further flexibly adjust the spacing, effectively enhance the lateral stiffness of the tall attached tower during vertical rotation, suppress lateral deformation, and thus improve the vertical rotation accuracy, ensuring that the attached tower segments can be accurately connected, providing a solid guarantee for the smooth and controllable secondary vertical rotation construction.

[0014] Furthermore, in step six, the first vertical rotation employs hydraulic synchronous control technology, with the back cable and the vertical rotation cable being loaded and unloaded synchronously and symmetrically, and the guy cable always maintaining a pre-tensioned state. After the first vertical rotation, when the first section of the attached tower is in a large cantilever state, additional guy cables are added for reinforcement. The hydraulic synchronous control technology can precisely control the loading and unloading rhythm of the cable body, ensuring that the horizontal component force of the back cable and the vertical rotation cable remains consistent, avoiding the main tower from shifting or being damaged due to force imbalance, while making the vertical rotation process of the first section of the attached tower smooth and controllable, reducing structural deformation caused by uneven force. The continuous pre-tensioning of the guy cable can constrain the four-way displacement of the attached tower in real time, resisting external interference such as wind, and further improving the stability of the vertical rotation process. The addition of guy cables for the large cantilever state of the first section of the attached tower after the first vertical rotation can effectively compensate for the weak points of the structure at this stage, prevent the risk of vibration or instability caused by excessive cantilever length, create stable conditions for the precise welding of the first and second sections of the attached tower, and also lay a solid safety foundation for the subsequent second vertical rotation construction.

[0015] Furthermore, in step seven, during the secondary vertical rotation, the tension of the guy cables is adjusted as the rotation angle increases to maintain the four-way balance and stability of the entire auxiliary tower section. As the secondary vertical rotation angle gradually increases, the center of gravity of the entire auxiliary tower section continuously rises, and the longitudinal center position gradually shifts and reverses, significantly increasing the challenges to the longitudinal and lateral stability of the structure. At this time, by dynamically adjusting the tension of the guy cables, the unbalanced moment caused by the shift in the center of gravity can be offset in real time, suppressing the swaying, torsion, or lateral deformation of the structure caused by changes in force. At the same time, maintaining four-way balance and stability can avoid additional stress on the mating surfaces of the auxiliary tower section with the main tower top connector and the auxiliary tower fixed section, preventing damage or mating deviation at the connection, ensuring that the entire auxiliary tower section is always on the preset vertical rotation trajectory, laying the foundation for subsequent precise welding and fixing, and effectively avoiding construction safety risks and quality hazards caused by structural instability.

[0016] Furthermore, in step eight, after the entire auxiliary tower section is vertically rotated into place, it is temporarily tied to the end of the main tower and hinged for fixation. The alignment is adjusted using jacks and pull hoists before welding and fixing. The temporary tying and hinged fixing can quickly lock the approximate position of the entire auxiliary tower section, preventing it from shifting or swaying due to external interference or its own force, and providing a stable foundation for subsequent alignment adjustments. The combined use of jacks and pull hoists can finely adjust the spatial posture of the entire auxiliary tower section, effectively compensating for possible alignment deviations during the vertical rotation, ensuring that the mating surfaces of the auxiliary tower end and the top connector, and the bottom and the fixed section are completely fitted, avoiding stress concentration or structural deformation caused by forced welding. Welding and fixing are carried out after the alignment is adjusted to the design requirements, which can ensure welding quality and connection strength, making the auxiliary tower and the main tower form a stable whole, providing a reliable guarantee for the long-term safe operation of the steel tower.

[0017] Furthermore, in step five, the connection points of the vertical rotation cable, back cable, guy cable, and main beam and auxiliary tower are all welded with load-bearing lugs. The lugs have pre-drilled load-bearing pin holes and are hinged to the anchor box via pins. The load-bearing lugs can concentrate the tension of the cable to the main structure of the main beam or auxiliary tower, avoiding damage to the connection points due to excessive local stress. The pre-drilled pin holes, together with the pins, achieve a hinged connection with the anchor box, ensuring the firmness of the connection without restricting the degree of freedom of rotation in the vertical rotation plane. This allows the auxiliary tower to rotate flexibly along a preset trajectory during the vertical rotation process, avoiding additional stress on the cable due to forced constraints. This connection method can also reduce the stress loss between the cable and the structure, ensure the accurate transmission of traction force, balance force, and stability force, and facilitate installation, debugging, and subsequent dismantling during construction, improving construction efficiency and providing a reliable connection guarantee for the smooth progress of the secondary vertical rotation process. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method steps of the present invention; Figure 2 Installation diagram of the slender arched steel tower of the invention; Figure 3 This is a schematic diagram of the installation structure of the slender arched steel tower of the present invention; Figure 4 This is a schematic diagram of the installation structure of the slender arched steel tower of the present invention; Figure 5 This is a schematic diagram of the installation structure of the slender arched steel tower of the present invention. Detailed Implementation

[0019] The reference numerals in the accompanying drawings include: 1. Bridge substructure; 2. Main tower; 3. Main beam; 41. Embedded section at the base of the auxiliary tower; 42. Fixed section of the auxiliary tower; 43. Second section of the auxiliary tower; 44. First section of the auxiliary tower; 45. Top connector of the auxiliary tower; 431. Entire section of the auxiliary tower; 51. Steel truss assembly; 52. Abutment for the auxiliary tower; 61. Secondary hinge; 62. Primary hinge; 71. Vertical cable; 72. Back cable; 73. Guy cable.

[0020] Example 1 As attached Figure 1-5 As shown, the installation method for a slender arched steel tower includes the following steps: Step 1: Construct the bridge substructure; Step 2: Construct the main tower, pre-embed the auxiliary tower root section at the lower end of the main tower, pre-embed the auxiliary tower top connector at the top of the main tower, and pre-embed wall ties, vertical rotation construction platform, vertical rotation force point and related components of the vertical rotation docking operation platform at the corresponding height during the construction of the main tower. Step 3: During the construction of the main tower, the auxiliary tower fixing section and the main beam are installed simultaneously. The auxiliary tower fixing section is welded and fixed to the pre-embedded section at the base of the auxiliary tower and the main tower respectively. The main tower and the auxiliary tower fixing section are connected by welding through steel truss assembly. Step 4: Erect the auxiliary tower assembly support on the main beam bridge deck, and assemble the second and first auxiliary tower sections in sequence according to the inverted arch posture. During assembly, preset the pre-offset value and pre-camber, and then accurately position and install the secondary hinge and primary hinge. Step 5: Install the vertical turning cable, back cable, and guy cable. All three are made of steel strand and have anchor boxes at both ends to complete the test preparation before vertical turning. Step Six: Using continuous jacks to synchronously pull the vertical rotation cable, rotate the first section of the auxiliary tower once. After it is in place, weld it to the second section of the auxiliary tower to form the complete auxiliary tower section. Remove the rotating hinge once. Step 7: Continue to use continuous jacks to synchronously pull the vertical rotation cable and perform a second vertical rotation on the entire attached tower section; Step 8: After the second vertical rotation into place, weld and fix the end of the entire section of the attached tower to the top connecting piece of the attached tower, and weld and fix the bottom to the fixed section of the attached tower; Step 9: Remove the vertical rotation equipment and supports to complete the installation.

[0021] The principle of this scheme is to achieve safe and efficient installation of slender arched steel towers through the coordinated application of phased construction and secondary vertical rotation technology. In the initial stage of construction, the foundation construction of the bridge substructure, main tower and main beam is completed first. At the same time, pre-embedded components for connecting the auxiliary towers are pre-set on the main tower to provide a stable load-bearing foundation and connection benchmark for the subsequent installation of the auxiliary towers. The construction of the main tower is carried out simultaneously with the installation of the fixed sections of the auxiliary towers and the reinforcement and consolidation are strengthened by steel truss assemblies to ensure the initial stability of the auxiliary tower installation. In the core process, a low-height assembly support was erected on the main girder bridge deck. The auxiliary tower segments were assembled in an inverted arch posture with preset pre-offset values ​​and pre-camber, controlling the structural alignment accuracy from the source. Through the precise setting of primary and secondary hinges, and in conjunction with a stable traction system composed of vertical rotating cables, back cables, and guy cables, the synchronous traction of continuous jacks was used to achieve the primary vertical rotation and docking of one section of the auxiliary tower and the secondary vertical rotation and positioning of the entire auxiliary tower. During the rotation, the center of gravity of the structure was balanced by the coordinated force of the cables, ensuring a smooth and controllable rotation. Finally, the auxiliary tower was reliably connected to the main tower and the fixed section of the auxiliary tower by welding. The entire process revolved around the core logic of low-height operation on the bridge deck and phased rotation, avoiding the technical pain points of traditional high-altitude assembly and overall rotation.

[0022] Compared to existing technologies, which often employ single vertical rotation or high-altitude scaffold assembly, making it difficult to balance safety, accuracy, and cost, this solution utilizes a two-stage vertical rotation design to reduce the working height from nearly 100 meters to less than 6 meters. This significantly reduces the risks associated with high-altitude hoisting and operations, solving the problems of extreme weather conditions and personnel safety in traditional methods, thus substantially improving construction safety. Regarding construction accuracy, this solution employs pre-set pre-offset and pre-camber values ​​during bridge deck assembly, precise hinge positioning, and hydraulic synchronous traction control. This allows for more precise control of the linear deviation of slender arch structures. Compared to the limitations of traditional scaffold assembly methods, which are susceptible to high-altitude environmental interference and cannot adapt to complex curved shapes with a single vertical rotation, this solution better meets the installation accuracy requirements of slender arch structures such as sail-shaped structures. In terms of cost and efficiency, this solution eliminates the need for large temporary scaffolding, with the height of the assembled scaffolding controlled within 0.5-3 meters, significantly reducing investment in temporary measures. Furthermore, the centralized bridge deck operation mode simplifies the construction process, and the secondary vertical rotation eliminates the need to repeatedly build high-altitude platforms. Compared to the traditional scaffolding method's high material consumption, long construction period, and high equipment investment per vertical rotation, construction efficiency is significantly improved, enabling the rapid installation of towers nearly 100 meters high. In addition, this solution effectively balances the center of gravity shift problem during the vertical rotation of slender structures through a phased rotation and cable stabilization system, avoiding the drawbacks of traditional methods such as structural instability and high rotation difficulty. It achieves the effects of ensuring safety during low-altitude operations, improving accuracy through phased rotation, and increasing efficiency with low-cost investment, making it suitable for the construction needs of slender arched steel towers.

[0023] In step two, the pre-embedded section at the base of the auxiliary tower and the main tower are integrally cast using a steel-concrete composite section. The integrity of the concrete and the high strength of the steel form a synergistic force-bearing system, significantly improving the load-bearing capacity and deformation resistance of the anchoring structure. This effectively resists the vertical loads, horizontal thrust, and torque generated during the vertical rotation and operation of the auxiliary tower, preventing structural damage caused by stress concentration at the connection point. Simultaneously, the integral casting process eliminates the connection gap between the pre-embedded section and the main tower, reducing energy loss during force transmission and ensuring uniform force distribution, further guaranteeing structural stability. Combined with additional prestressing and tie rod measures, the reliability and durability of the anchoring are significantly enhanced, preventing loosening and cracking due to repeated loads during long-term use. This provides a solid foundation for the safe conduct of subsequent secondary vertical rotation construction of the auxiliary tower and the long-term stable operation of the overall steel tower structure.

[0024] In step three, the main girder is constructed using the scaffolding method. The scaffolding's load-bearing capacity meets the requirements for main girder construction, bridge deck tower assembly, and tower rotation. The main girder can be a steel beam, a steel-concrete composite beam, or a cast-in-place concrete beam. The scaffolding method provides a stable and reliable working platform for the main girder's construction, ensuring its quality. Its pre-designed high load-bearing capacity allows the main girder to be directly used as the foundation for tower assembly and rotation, eliminating the need for additional independent load-bearing structures. This significantly reduces the investment in temporary measures and construction land occupation, shortening the construction cycle. The compatible design of multiple main girder types allows for flexible selection based on the overall structural stress requirements of the bridge, project cost budget, and construction environment conditions. This not only meets the personalized needs of different bridge projects but also avoids the problem of incompatible construction methods due to main girder type limitations. Simultaneously, the scaffolding and the main girder form a collaborative load-bearing system, effectively dispersing concentrated loads during tower rotation and ensuring structural stability and safety during construction, providing solid support for the smooth implementation of the secondary rotation process.

[0025] In step four, the gantry assembly support is supported on the diaphragm or web of the main beam. When the support position does not meet the requirements, a distribution beam is added to the main beam deck to bear the concentrated load. The diaphragm and web are the main load-bearing components of the main beam. Directly supporting the assembly support on these components can fully utilize the structural strength of the main beam itself and avoid the concentrated load of the support acting on non-weak areas of the main beam, which could lead to local deformation or damage. When the support position is limited by the division of the gantry segments and cannot match the diaphragm or web, adding a distribution beam can effectively disperse the concentrated load, expand the contact area of ​​the load, and convert the local concentrated force into a uniformly distributed load to the main beam. This ensures that the gantry assembly support has sufficient support stiffness, which not only avoids the main beam from exceeding the limit deformation due to concentrated load, but also provides a stable working platform for the precise assembly of the gantry segments, reduces displacement deviation during the assembly process, and lays a solid foundation for the precision control of subsequent secondary vertical rotation construction.

[0026] In step five, the upper ends of the vertical slewing cable and the rear back cable are connected to the anchor box assembly pre-embedded in the main tower, and the lower ends are respectively connected to the second section of the auxiliary tower and the main beam; there are two sets of guy cables arranged in a V-shape, with the upper ends connected to the second section of the auxiliary tower and the lower ends connected to the main beam. The anchor box assembly pre-embedded in the main tower, together with the stress-bearing stiffener, can evenly transfer the tension of the cable to the main structure of the main tower, avoiding structural damage caused by local stress concentration and ensuring the stable transmission of traction and balance forces; the vertical slewing cable focuses on providing vertical traction force, and the rear back cable forms a reverse force through its connection with the main beam. The constraints counteract the horizontal thrust generated on the main tower during the vertical rotation, ensuring the main tower's stress balance. The two sets of outward-facing wind cables can form bidirectional limits in both the longitudinal and transverse directions, effectively resisting interference such as lateral wind force and structural eccentricity that may occur during the vertical rotation, suppressing the swaying and displacement of the auxiliary tower. At the same time, the outward-facing structure can form an inward constraint force through its own tension, further enhancing the overall rigidity and stability of the auxiliary tower during the vertical rotation. The synergistic effect of the three ensures the smooth and controllable vertical rotation process and provides strong support for construction accuracy.

[0027] In step five, two sets of vertical rotation cables and two sets of rear cables are set up and arranged in parallel. The spacing is determined by calculation based on the structural dimensions of the attached tower, the vertical rotation height, the hinge clearance, and accuracy indicators. If necessary, brackets are welded to both sides of the attached tower to increase the spacing. By optimizing the cable arrangement, the stability and accuracy control of the vertical rotation process are enhanced. The two sets of parallel cable arrangements can form a symmetrical force-bearing structure, ensuring that the traction force and the reverse constraint force are evenly applied to the attached tower, avoiding the offset or torsion of the attached tower caused by unilateral force, and improving the overall load-bearing capacity of the cable to cope with the changing load requirements during the vertical rotation. The reasonable spacing calculated based on key parameters can adapt to the construction requirements of attached towers of different specifications, ensure the optimal force angle of the cable, and reduce energy loss. The addition of brackets can further flexibly adjust the spacing, effectively enhance the lateral stiffness of the tall attached tower during vertical rotation, suppress lateral deformation, and thus improve the vertical rotation accuracy, ensuring that the attached tower segments can be accurately connected, providing a solid guarantee for the smooth and controllable secondary vertical rotation construction.

[0028] In step six, the first vertical rotation employs hydraulic synchronous control technology, with the back cable and the vertical rotation cable being loaded and unloaded synchronously and symmetrically, and the guy cable always maintaining a pre-tensioned state. After the first vertical rotation, when the first section of the attached tower is in a large cantilever state, additional guy cables are added for reinforcement. The hydraulic synchronous control technology can precisely control the loading and unloading rhythm of the cable body, ensuring that the horizontal component force of the back cable and the vertical rotation cable remains consistent, avoiding displacement or damage to the main tower due to force imbalance, while making the vertical rotation process of the first section of the attached tower smooth and controllable, reducing structural deformation caused by uneven force. The continuous pre-tensioning of the guy cable can constrain the four-way displacement of the attached tower in real time, resist external interference such as wind, and further improve the stability of the vertical rotation process. The addition of guy cables for the large cantilever state of the first section of the attached tower after the first vertical rotation can effectively compensate for the weak points of the structure at this stage, prevent the risk of vibration or instability caused by excessive cantilever length, create stable conditions for the precise welding of the first and second sections of the attached tower, and lay a solid safety foundation for the subsequent second vertical rotation construction.

[0029] In step seven, during the secondary vertical rotation, the tension of the guy cables is adjusted as the rotation angle increases to maintain the four-way balance and stability of the entire auxiliary tower section. As the secondary vertical rotation angle gradually increases, the center of gravity of the entire auxiliary tower section continuously rises, and the longitudinal center position gradually shifts and reverses, significantly increasing the challenges to the longitudinal and lateral stability of the structure. At this time, by dynamically adjusting the tension of the guy cables, the unbalanced moment caused by the shift in the center of gravity can be offset in real time, suppressing the swaying, torsion, or lateral deformation of the structure caused by changes in force. At the same time, maintaining four-way balance and stability can avoid additional stress on the mating surfaces of the auxiliary tower section with the main tower top connector and the auxiliary tower fixed section, preventing damage or docking deviation at the connection, ensuring that the entire auxiliary tower section is always on the preset vertical rotation trajectory, laying the foundation for subsequent precise welding and fixing, and effectively avoiding construction safety risks and quality hazards caused by structural instability.

[0030] In step eight, after the entire auxiliary tower section is vertically rotated into place, it is temporarily tied to the end of the main tower and hinged for fixation. The alignment is adjusted using jacks and pull hoists before welding and fixing. The temporary tying and hinged fixing can quickly lock the approximate position of the entire auxiliary tower section, preventing it from shifting or swaying due to external interference or its own force, and providing a stable foundation for subsequent alignment adjustments. The combined use of jacks and pull hoists can finely adjust the spatial posture of the entire auxiliary tower section, effectively compensating for possible alignment deviations during the vertical rotation, ensuring that the mating surfaces of the auxiliary tower end and the top connector, and the bottom and the fixed section are completely fitted, avoiding stress concentration or structural deformation caused by forced welding. Welding and fixing are carried out after the alignment is adjusted to the design requirements, which can ensure welding quality and connection strength, making the auxiliary tower and the main tower form a stable whole, providing a reliable guarantee for the long-term safe operation of the steel tower.

[0031] In step five, load-bearing lugs are welded to the connection points of the vertical rotation cable, back cable, guy cable, main beam, and auxiliary tower. The lugs have pre-drilled load-bearing pin holes and are hinged to the anchor box via pins. These lugs concentrate the tension of the cable to the main structure of the main beam or auxiliary tower, preventing damage to the connection points due to excessive local stress. The pre-drilled pin holes, in conjunction with the pins, achieve a hinged connection with the anchor box, ensuring both the strength of the connection and not restricting the rotational freedom within the vertical rotation plane. This allows the auxiliary tower to rotate flexibly along a preset trajectory during vertical rotation, preventing additional stress on the cable due to forced constraints. This connection method also reduces stress loss between the cable and the structure, ensuring accurate transmission of traction, balance, and stability forces. Furthermore, it facilitates installation, debugging, and subsequent dismantling during construction, improving construction efficiency and providing a reliable connection guarantee for the smooth progress of the secondary vertical rotation process.

[0032] This implementation method is based on a special construction scenario for high-speed node bridges, targeting a sail-shaped slender arched steel tower with a height of 86 meters and a span of 62 meters.

[0033] I. Pre-construction preparations Technical preparation By combining the dimensions of the bridge substructure, the design parameters of the main tower, and the arch curve of the auxiliary tower, a 1:1 three-dimensional model was built using BIM technology to simulate the entire process of the secondary vertical rotation, and to optimize the segment division, hinge position, and cable arrangement scheme of the auxiliary tower.

[0034] Calculate the pre-deflection and pre-camber of the attached tower segments: the pre-deflection of the first attached tower segment is set to 30mm, the pre-deflection of the second attached tower segment is set to 25mm, and the pre-camber is set according to L / 5000 of the segment length to offset the inelastic deformation caused by the self-weight of the structure.

[0035] Prepare specialized construction plans, safety technical briefing documents, and emergency response plans. Conduct specialized training for construction personnel on BIM operation, hydraulic synchronous control, welding technology, and high-altitude operation safety. Only those who pass the assessment can be allowed to work.

[0036] Materials and equipment preparation The main material is Q355B grade high-strength steel. The tower section is prefabricated in the factory and undergoes dual non-destructive testing (UT) + MT (magnetic particle testing) before leaving the factory. The welding quality meets the first-class standard. The steel strand is Φs15.2mm high-strength low-relaxation type with a tensile strength standard value ≥1860MPa.

[0037] Core equipment configuration: continuous jack (rated traction force 500t, synchronization accuracy ±1mm), hydraulic synchronization control system (number of control points ≥8), total station (angle measurement accuracy ±0.5″, distance measurement accuracy ±(1mm+2ppm×D)), anemometer (measurement range 0-60m / s), tensioning jack (for use with cable pretensioning).

[0038] Processing of pre-embedded anchor box components, load-bearing lugs, hinges and other components: double-sided welding is used for anchor box welds, Φ50mm load-bearing pin holes are reserved in lugs, and the tolerance is ±0.2mm is ensured by boring process; the machining accuracy of hinge axis is controlled within ±0.1mm, and lithium-based grease is applied to ensure flexible rotation.

[0039] (III) On-site preparation The construction site is leveled and compacted to a bearing capacity of ≥250kPa, meeting the requirements for equipment stacking and transportation.

[0040] Mark the assembly area of ​​the auxiliary tower on the main girder bridge deck, mark the positions of the transverse diaphragms and webs, and pre-embed distribution beam connecting steel plates with a thickness of ≥20mm; erect a vertical rotation construction platform and a docking operation platform, with the platform guardrail height ≥1.2m and lay anti-slip steel plates.

[0041] Twelve BIM positioning and monitoring points were set up at the top of the main tower, the ends of each segment of the auxiliary tower, and the hinge position, respectively, and connected to the data acquisition system to realize real-time monitoring of the construction process.

[0042] Basic structure construction (I) Construction of the bridge substructure The piers, abutments, and foundations must be poured in accordance with standard bridge construction specifications. Construction can only continue after the foundation concrete strength reaches 85% or more of the design strength. The verticality deviation of the piers should be ≤1 / 3000, and the top surface elevation error should be ±5mm.

[0043] Main tower construction The main tower concrete is poured using a climbing formwork process, with each pour reaching a height of 4.5-6m. The curing time is no less than 7 days, and the formwork is removed after the concrete strength reaches 100% of the design strength.

[0044] The lower end of the main tower is pre-embedded at the root of the auxiliary tower. It is integrally cast in the form of a steel-concrete composite section. The steel of the pre-embedded section is welded and fixed to the steel bars of the main tower. Additional prestressing and tie rod measures are used to enhance the anchorage reliability. The top of the main tower is pre-embedded with the top connector of the auxiliary tower. The connector is firmly welded to the main reinforcement of the main tower. The flatness error of the top surface is ≤3mm.

[0045] When the main tower is constructed to the corresponding height, pre-embedded wall ties, vertical rotation force points and other components are used, and the exposed parts are coated with anti-rust paint. The deviation of the pre-embedded position is within ±10mm.

[0046] Construction of the fixed section of the auxiliary tower and the main beam When the main tower is constructed to the third section, the auxiliary tower fixing section is installed simultaneously. It is welded to the root pre-embedded section and the main tower by bevel welding, with a weld height of ≥12mm. Non-destructive testing is carried out after welding.

[0047] The main tower and the auxiliary tower are connected by welding steel truss assemblies. The angle between the web members and chord members of the steel truss is controlled between 45° and 60°, and the nodes are rigidly connected to ensure overall rigidity.

[0048] The main beam is constructed using a scaffolding method. The scaffolding is made of steel pipe columns with high rigidity. The spacing and material selection of the scaffolding structure meet the load-bearing requirements. After the scaffolding is erected, it is preloaded with 1.2 times the design load for ≥72 hours. The load is unloaded after the settlement is stable. The main beam is a steel-concrete composite beam (which can be replaced with steel beams or cast-in-place concrete beams according to design requirements). After the steel beams are installed and welded, the concrete bridge deck is poured. The main beam construction scaffolding is removed after the concrete strength reaches 90%.

[0049] Tower assembly and hinge installation Tower assembly support erection The assembly support is preferentially supported on the main beam diaphragm or web. A 200mm×200mm×10mm pad is installed at the bottom of the upright, and an adjustable top support is installed at the top to adjust the height.

[0050] If the support location does not match the segment division of the auxiliary tower, I45b I-beam distribution beams are added to the main beam bridge deck at a spacing of 0.8m, and welded and fixed to the pre-embedded steel plates of the main beam to distribute the concentrated load.

[0051] After the support structure is erected, the following tests are conducted: verticality deviation ≤ 1 / 1000, top horizontal displacement ≤ 5mm, to ensure that the requirements for the assembly and vertical rotation load of the attached tower are met.

[0052] Segmental assembly of the tower Assemble the second and first sections of the auxiliary tower in sequence according to the inverted arch posture. Use a 100t truck crane for hoisting. A dedicated person is in charge of directing the hoisting process to avoid collisions with the support frame.

[0053] The segment position is adjusted using a total station, with an axis deviation of ≤3mm and a joint gap between adjacent segments of ≤2mm. Once the requirements are met, a temporary connecting plate is used for fixation. The pre-deviation value and pre-camber are monitored in real time, and the segment posture is finely adjusted by the support bracket.

[0054] Hinged Mounting After the auxiliary tower segment is assembled, the secondary hinge and primary hinge are precisely positioned and installed. The deviation between the hinge axis and the design axis is ≤1mm, and the levelness error is ≤0.2mm / m.

[0055] After installing the hinge, apply lithium-based grease and install a protective cover to prevent foreign objects from entering, ensuring smooth and unobstructed rotation.

[0056] Cable installation and pre-vertical rotation testing Cable installation Two sets of parallel arrangements are set up for the vertical rotation cable and the back cable. The spacing is determined to be 5.7m based on the height of the attached tower section (3.2m), the vertical rotation height (86m) and the accuracy index. 25mm thick and 1.7m long brackets are welded on both sides of the attached tower to increase the spacing and enhance the lateral stiffness.

[0057] The upper ends of the vertical slewing cable and the back cable are connected to the pre-embedded anchor box assembly of the main tower (with a stress-bearing stiffening plate installed outside the anchor box), and the lower ends are connected to the second section of the auxiliary tower and the main beam, respectively; the two sets of wind cables are arranged in an outward V-shape (60° angle), with the upper end connected to the second section of the auxiliary tower and the lower end connected to the main beam.

[0058] The connection points between the cable body and the main beam and the auxiliary tower are welded with load-bearing lugs (30mm thick). The lugs are pre-drilled with load-bearing pin holes and are hinged to the anchor boxes via pins. After the pins are installed, they are fixed with cotter pins. Anchor boxes are set at both ends of the cable body. One end is fixed to the cable body, and the other end is hinged to the connection point via pins, which does not restrict vertical rotation.

[0059] Test before vertical rotation Pre-tension the vertical cable, back cable, and guy cable. The pre-tension stress is 10% of the design stress. Hold the load for 30 minutes. After checking that the cable anchorage is free from slippage or loosening, unload the cable.

[0060] Start the hydraulic synchronization control system for no-load test run to test the synchronization accuracy of the jacks and the sensitivity of the cable tension adjustment to ensure normal equipment operation.

[0061] Construction will be suspended if environmental parameters are monitored, wind force is ≥6, visibility is ≤200m, or there is rain or snow, and will resume only when environmental conditions meet the requirements.

[0062] Secondary vertical rotation construction One vertical rotation Hydraulic synchronous control technology is adopted to load and unload the back cable and the vertical cable synchronously and symmetrically, with a loading rate of ≤5MPa / min, maintaining consistent horizontal force and ensuring balanced force on the main tower.

[0063] The guy cable is always kept in a pre-tensioned state (pre-tension force is 20% of the design tension) to control the four-way stability of the attached tower, with a swing amplitude ≤5mm.

[0064] Pull the vertical rotation cable at a speed of 0.5° / min to rotate one section of the attached tower once, stop when it reaches 45°, and check the attitude of the attached tower and the stress on the cable.

[0065] After the first section of the auxiliary tower is in place, it is welded to the second section of the auxiliary tower to form the complete auxiliary tower section. CO2 gas shielded welding is used, with a welding current of 200-250A and a voltage of 24-28V. The weld is continuous and full, and non-destructive testing is performed after welding.

[0066] After one vertical rotation, one section of the attached tower is in a large cantilever state. Two sets of guy cables are added for reinforcement (with an angle of ≥45° with the horizontal direction) to ensure structural stability. The first rotating hinge is removed and the installation position is cleaned.

[0067] Repairs and improvements can be made to the exterior paint of the attached towers on the low-altitude bridge surface.

[0068] Second vertical rotation Continue to use continuous jacks to synchronously pull the vertical rotation cable, and perform a second vertical rotation of the entire attached tower section at a speed of 0.3° / min to avoid instability caused by excessive speed.

[0069] As the vertical rotation angle increases (for every 10° increase), the tension of the guy cable is adjusted. The tension is monitored in real time by a tension sensor to maintain the four-way balance and stability of the entire attached tower section, with the top horizontal displacement ≤8mm.

[0070] The BIM positioning and monitoring system is used to track the attitude of the attached tower. When the deviation in alignment exceeds the allowable value, the deviation is corrected by adjusting the jack traction force and the tension of the guy cable.

[0071] Stop traction when the vertical rotation reaches the designed angle (82°), keep the cable tension constant, and prepare for docking and fixing.

[0072] Connection fixing and finishing construction Temporary fixing and line type adjustment Temporary tying measures using steel tie rods and turnbuckles are adopted to hinge and fix the entire auxiliary tower section to the end of the main tower to prevent displacement and swaying.

[0073] Weld support points on both sides of the top connector of the auxiliary tower, and use jacks (rated jacking force 200t) and pull hoists (rated pulling force 50t) to adjust the alignment to ensure that the end of the auxiliary tower is completely fitted with the top connector and the bottom is completely fitted with the fixed section, with a gap of ≤1mm.

[0074] Welding Fixing After the alignment is adjusted to be satisfactory, welding is carried out to fix it. The symmetrical welding method is used, and the transverse weld is welded first and then the longitudinal weld is welded to avoid welding deformation.

[0075] During the welding process, the temperature and deformation of the attached tower are monitored in real time. A layered welding process is adopted, with each layer being 3-5mm thick. The interlayer temperature is controlled at 80-150℃, and the tower is allowed to cool naturally to room temperature after welding.

[0076] After the weld is completed, 100% non-destructive testing (UT+MT) is performed, and it meets the requirements of Class I weld in the "Standard for Acceptance of Construction Quality of Steel Structures" (GB50205-2020).

[0077] Equipment and support dismantling The equipment was dismantled in the order of "cable body first, then support". The cable body was unloaded in stages with an unloading rate of ≤3MPa / min to avoid structural impact caused by sudden unloading.

[0078] The vertical rotating cable, back cable, wind cable, rotating hinge and related equipment were dismantled in sequence, followed by the dismantling of the attached tower assembly support and steel truss assembly. The dismantling was carried out from top to bottom in sections, with a dedicated person in charge of monitoring.

[0079] Anti-corrosion coating and acceptance Rust removal treatment was carried out on the attached tower and connecting parts, with a rust removal grade of Sa2.5. Anti-corrosion coating was applied within 4 hours after rust removal.

[0080] The coating system consists of three layers: epoxy zinc-rich primer (dry film thickness 80μm) + epoxy micaceous iron oxide intermediate paint (dry film thickness 120μm) + fluorocarbon topcoat (dry film thickness 60μm). After coating, the adhesion is tested and the adhesion is ≥5MPa.

[0081] A comprehensive inspection of the steel tower installation quality was conducted, including alignment deviations, weld quality, and corrosion protection effectiveness. Once the measured items met the design and specification requirements, the acceptance documents were signed, and the installation was completed.

[0082] Example 2 Implementation steps: Step 1: Construction of the bridge substructure 1; Step 2: Construct the main tower 2. During the construction of the lower end of the main tower 2, pre-embed the sub-tower root pre-embedded section 41, and pre-embed the sub-tower top connector 45 at the top of the main tower 2. During the construction of the main tower 2, relevant components such as wall ties, vertical rotation construction platforms, vertical rotation force points, and vertical rotation docking operation platforms should be pre-embedded at the corresponding heights. The sub-tower root pre-embedded section 41 is integrally connected with the main tower 2 and can be cast as a whole in the form of a steel-concrete composite section, with additional prestressing, tie rods, and other measures to enhance the anchoring.

[0083] Step 3: Simultaneously with the construction of the main tower 2, the auxiliary tower fixing section 42 and the main beam 3 are installed. The auxiliary tower fixing section 42 is welded and fixed to the pre-embedded section 41 at the base of the auxiliary tower. The auxiliary tower fixing section 42 is welded and fixed to the main tower 2 using a steel truss assembly 51. The main beam 3 is constructed using a scaffolding method. The scaffolding must meet the load-bearing requirements for the main beam, the bridge deck auxiliary tower assembly, and the vertical rotation of the auxiliary tower. The main beam is typically used to reduce the weight of the bridge, but it can also be a steel-concrete composite beam or a cast-in-place concrete beam. The specific choice depends on the design requirements and structural stress, and is not the only possible method.

[0084] Step 4: Erect the auxiliary tower assembly support 52 on the main beam 3 bridge deck. Assemble the second auxiliary tower section 43 and the first auxiliary tower section 44 in sequence according to the structural alignment. Install the secondary hinge 61 and the primary hinge 62. The auxiliary tower assembly support 52 is first supported on the transverse diaphragm or web of the main beam 3 according to the auxiliary tower segment division. Otherwise, a distribution beam should be added on the main beam 3 bridge deck to bear the concentrated load force to ensure that the auxiliary tower assembly support 52 has sufficient support rigidity. The second auxiliary tower section 43 and the first auxiliary tower section 44 should take into account the non-elastic deformation of the structural self-weight of the auxiliary tower in the final completed condition. The pre-offset value and pre-camber should be set in advance. The second auxiliary tower section 43 and the first auxiliary tower section 44 are assembled in an inverted arch posture. The secondary hinge 61 and the primary hinge 62 should be accurately positioned and installed after the auxiliary tower segment is assembled to reduce the impact of welding deformation and ensure absolute position and level accuracy.

[0085] Step 5: Install vertical slewing cable 71, backstay cable 72, and guy cable 73. Complete all necessary tests and preparations for vertical rotation. Vertical slewing cable 71, backstay cable 72, and guy cable 73 are made of steel strand; the specific quantity is matched based on the stress analysis of the working conditions. The upper ends of vertical slewing cable 71 and backstay cable 72 are connected to the main tower 2, and the lower ends are connected to the auxiliary tower section 43 and the main beam 3, respectively. The upper end of guy cable 73 is connected to the auxiliary tower section 43, and the lower end is connected to the main beam 3. For the connection points between vertical slewing cable 71, backstay cable 72, and guy cable 73 and the main beam 3 and auxiliary tower section 44, respectively, load-bearing lugs need to be welded at the corresponding positions on the auxiliary tower and main beam. Load-bearing pin holes should be pre-drilled on the lugs. For the connection points between vertical slewing cable 71, backstay cable 72, and main tower 2, anchor boxes need to be pre-embedded during the construction of main tower 2, and load-bearing structures should be installed outside the anchor boxes. The stiffening plate has pre-drilled holes for load-bearing pins. Anchor boxes are installed at both ends of the vertical rotation cable 71, back cable 72, and guy cable 73. One end of the anchor box is fixed to the cable body. The hollow anchor box can be used to install tension jacks for tensioning and anchoring the cable body. The other end is equipped with ear plates of the corresponding specifications to the connection points. Load-bearing pins are inserted and hinged to their respective connection points, without restricting the rotation of the vertical rotation plane. Two sets of vertical rotation cables 71 and back cable 72 are arranged in parallel. The spacing is calculated based on the structural dimensions of the attached tower, the vertical rotation height, the hinge gap, and the accuracy index, and is taken as large as possible. If necessary, brackets can be welded to both sides of the attached tower to increase the spacing, thereby enhancing the lateral stiffness, stability, and vertical rotation accuracy of the tall attached tower. Two sets of guy cables 73 are arranged with a slight outward V-shape to assist in enhancing the longitudinal and lateral stability control of the attached tower structure during the vertical rotation process.

[0086] Step Six: Using continuous jacks to synchronously pull the vertical rotation cable 71, perform a first vertical rotation of the auxiliary tower section 44. After vertical rotation to the correct position according to the structural alignment, weld it to the auxiliary tower section 43 to form a whole. Remove the first rotation hinge 62. The vertical rotation requires an operating platform to be erected on the main tower 2. Emphasis should be placed on ensuring symmetrical force on the vertical rotation cable 71 and the backstay cable 72. Hydraulic synchronous control technology is used for the vertical rotation. During the process, the backstay cable 72 and the rotating cable 71 are synchronously and symmetrically loaded and unloaded to maintain consistent horizontal force components and ensure balanced force on the main tower 2. During the vertical rotation, the guy cable 73 is always in a pre-tensioned state to control the four-way stability of the auxiliary tower structure. After the first vertical rotation, weld it to the auxiliary tower section 43 to form the entire auxiliary tower section 431, which serves as the segment for the second vertical rotation. Before the second vertical rotation, the original auxiliary tower section 44 is in a large cantilever state. Guy cables can be added on both sides for reinforcement to ensure structural safety. After removing the first rotation hinge 62, repairs and improvements can be made to the exterior paint of the auxiliary tower on the low-altitude bridge surface. Step 7: Using continuous jacks to synchronously pull the vertical rotation cable 71, a second vertical rotation is carried out on the entire auxiliary tower section 431, which is formed by welding the second auxiliary tower section 43 and the first auxiliary tower section 44 after the first vertical rotation. As the angle of the second vertical rotation of the auxiliary tower gradually increases, the center height of the entire auxiliary tower section 431 gradually increases, the longitudinal position of the center gradually decreases and reverses. The stability of the longitudinal and transverse structure of the auxiliary tower is particularly important. It is necessary to keep the guy cable 73 taut and balanced at all times to control the four-way stability of the entire auxiliary tower section 431 structure.

[0087] Step 8: After the auxiliary tower is rotated into position for the second time, the end is welded and fixed to the top connecting piece 45 of the auxiliary tower, and the bottom is welded and fixed to the fixed section 42 of the auxiliary tower. After the auxiliary tower is rotated into position for the second time, temporary tie measures can be adopted to make the entire section 431 of the auxiliary tower hinged and fixed to the end of the main tower. Then, support points are welded on both sides of the top connecting piece 45 of the auxiliary tower. Jacks, pull hoists and other tools are used to adjust the alignment to ensure the accurate docking of the auxiliary tower.

[0088] Step 9: Remove the vertical rotating cable 71, back cable 72, guy cable 73, steel truss assembly 51, auxiliary tower assembly support 52, secondary rotating hinge 61 and other auxiliary tower vertical rotating related equipment and components, and complete the installation of auxiliary tower 2.

[0089] This embodiment is based on the construction scenario of the arched auxiliary tower of a sail-shaped cable-stayed bridge with a single tower structure, and focuses on the slender arched steel tower with a height of 95 meters and a span of 60 meters.

[0090] I. Pre-construction preparations Technical preparation: Based on the design parameters of the bridge substructure 1, main tower 2, and the arch curve of the auxiliary tower, a 1:1 three-dimensional model was built using BIM technology to simulate the entire process of the secondary vertical rotation, optimize the segment division, hinge position, and cable arrangement of the auxiliary tower; calculate the pre-offset value and pre-camber of auxiliary tower segment 43 and auxiliary tower segment 44 (the pre-offset value is set to 35mm and 30mm respectively, and the pre-camber is set according to the segment length L / 4500) to offset the inelastic deformation of the structure's self-weight; prepare a special construction plan and safety technical briefing documents, and conduct special training for construction personnel on BIM operation and hydraulic synchronous control.

[0091] Material and equipment preparation: The main material is Q355B grade high-strength steel. The tower sections are prefabricated in the factory and then subjected to UT+MT non-destructive testing. The steel strands are Φs15.2mm high-strength low-relaxation type, and the quantity is determined according to the stress analysis of the working conditions. The core equipment is configured with continuous jacks (rated traction force 600t), hydraulic synchronous control system, total station, anemometer and other core equipment. The pre-embedded anchor box components, load-bearing lugs, secondary hinge 61, primary hinge 62 and other components are processed to ensure that the accuracy meets the requirements.

[0092] Site preparation: Level and compact the construction site, with a bearing capacity ≥280kPa; erect the main tower 2 construction scaffolding and vertical rotation construction platform and vertical rotation docking operation platform, and fully hang safety protection nets on the outside; delineate the auxiliary tower assembly area on the main beam 3 bridge deck, mark the positions of the transverse diaphragm and web plate, and pre-embed the distribution beam connecting steel plate; set up BIM positioning monitoring points and connect the data acquisition system.

[0093] II. Foundation Structure Construction (I) Step 1: Construction of the bridge substructure 1 The piers, abutments, and foundations must be poured according to standard bridge construction specifications. Construction can only continue after the foundation concrete strength reaches at least 85% of the design strength. The verticality deviation of the piers should be ≤1 / 3000, and the top surface elevation error should be ±5mm, providing a stable foundation for subsequent structural construction.

[0094] (II) Step Two: Construction of Main Tower 2 The main tower 2 concrete was poured using a climbing formwork process, with each pour reaching a height of 4.8m. The curing time was no less than 7 days, and the formwork was removed after the concrete strength reached 100% of the design strength.

[0095] During the construction of the lower end of the main tower 2, the pre-embedded section 41 at the root of the auxiliary tower is pre-embedded. It is cast as a whole in the form of a steel-concrete composite section, with additional prestressing and tie rod measures to enhance the anchoring. The pre-embedded section 41 at the root of the auxiliary tower is fixed to the main tower 2 as a whole.

[0096] The top of the main tower 2 is pre-embedded with a connecting piece 45 for the top of the tower. The connecting piece is firmly welded to the main reinforcement of the main tower 2, and the flatness error of the top surface is ≤3mm.

[0097] When the main tower 2 is constructed to the corresponding height, pre-embedded wall ties, vertical rotation force points and other related components are used, and the exposed parts are coated with anti-rust paint. The deviation of the pre-embedded position is within ±10mm.

[0098] (III) Step 3: Simultaneously install the auxiliary tower fixing section 42 and the main beam 3 Simultaneously with the construction of the main tower 2, the auxiliary tower fixing section 42 and the main beam 3 are installed: the auxiliary tower fixing section 42 and the pre-embedded section 41 at the root of the auxiliary tower are welded together, with a weld height ≥12mm, and non-destructive testing is performed after welding; the auxiliary tower fixing section 42 and the main tower 2 are welded together with steel truss group 51, and the angle between the web members and chord members of the steel truss is controlled between 45° and 60°, and the nodes are rigidly connected.

[0099] The main girder 3 is constructed using the scaffolding method. The scaffolding must meet the load-bearing requirements for the construction of the main girder 3, the assembly of the bridge deck towers, and the vertical rotation of the towers. In this embodiment, the main girder 3 is a steel beam (which can be replaced with a steel-concrete composite beam or a cast-in-place concrete beam according to design requirements). The main girder is constructed using the scaffolding method, and the scaffolding is made of steel pipe columns with high rigidity. The spacing and material selection of the scaffolding structure meet the load-bearing requirements. After the scaffolding is erected, a preload of 1.2 times the design load is applied for ≥72 hours. The load is unloaded after the settlement stabilizes.

[0100] III. Attached Tower Assembly and Hinge Installation A scaffolding 52 for the auxiliary tower is erected on the main girder 3 bridge deck. Based on the segment division of the auxiliary tower, the scaffolding 52 is initially supported at the transverse diaphragms or webs of the main girder 3. If the support location is insufficient, a distribution beam is added to the main girder 3 bridge deck to bear the concentrated load, ensuring that the scaffolding 52 has sufficient support rigidity. A 200mm×200mm×10mm pad is installed at the bottom of the scaffolding uprights, and an adjustable top support is installed at the top to adjust the height. After erection, the verticality deviation is checked to be ≤1 / 1000, and the top horizontal displacement is ≤5mm.

[0101] Attached tower segment assembly: Attached tower section 2 (43) and section 1 (44) are assembled sequentially according to the structural alignment and inverted arch posture, using a 120t truck crane for hoisting. A dedicated person directs the hoisting process. The segment positions are adjusted using a total station, ensuring an axial deviation ≤3mm and a butt joint gap between adjacent segments ≤2mm. Once these requirements are met, temporary connecting plates are used for fixation. During assembly, the segment posture is strictly controlled according to the preset pre-deflection and pre-camber values ​​to counteract the inelastic deformation caused by the structure's own weight.

[0102] Hinge Installation: After the attached tower segment is assembled, accurately position and install the secondary hinge 61 and the primary hinge 62 to reduce the impact of welding deformation on the hinge accuracy. The deviation of the centerline of the secondary hinge 61 and the primary hinge 62 from the design axis is ≤1mm, and the levelness error is ≤0.2mm / m. After installation, apply lithium-based grease and install a protective cover to prevent foreign matter from entering.

[0103] IV. Cable Installation and Pre-Rotation Testing Install vertical rotating cable 71, back cable 72, and guy cable 73: all three are made of steel strand. Anchor boxes are set at both ends of the cable body. One end of the anchor box is fixed to the cable body, and the other end is set with ear plates of the corresponding specifications to the connection point. The force-bearing pin is inserted and hinged to the respective connection point, without restricting the rotation of the vertical rotating plane.

[0104] Connection requirements: The upper ends of the vertical slewing cable 71 and the backstay cable 72 are connected to the anchor box assembly pre-embedded in the main tower 2 (a stiffening plate is set outside the anchor box, and the stiffening plate has a pre-reserved stress pin hole), and the lower ends are connected to the second section of the auxiliary tower 43 and the main beam 3, respectively; the upper end of the guy cable 73 is connected to the second section of the auxiliary tower 43, and the lower end is connected to the main beam 3. The connection points of the vertical slewing cable 71, the backstay cable 72, and the guy cable 73 with the main beam 3 and the first section of the auxiliary tower 44 are all welded with stress-bearing lugs at the corresponding positions on the auxiliary tower and the main beam 3, and stress pin holes are pre-reserved on the lugs.

[0105] Cable arrangement requirements: Two sets of vertical rotating cables 71 and two sets of back cables 72 are arranged in parallel. The spacing is determined based on the structural dimensions of the attached tower, the vertical rotation height, the hinge gap, and the accuracy index (the spacing is set to 2.2m in this embodiment). If necessary, brackets are welded on both sides of the attached tower to increase the spacing and enhance the lateral stiffness, stability, and accuracy of the vertical rotation. Two sets of wind cables 73 are arranged with a slight outward V-shape to help enhance the longitudinal and lateral stability of the attached tower structure during the vertical rotation.

[0106] Pre-vertical rotation test: Pre-tension the vertical rotation cable 71, back cable 72, and guy cable 73 (pre-tension stress is 10% of the design stress, held for 30 minutes) and check that the anchorage is free from slippage and loosening; start the hydraulic synchronous control system for no-load test run and test the equipment operation status; monitor environmental parameters and suspend construction when the wind force is ≥6 or in rainy or snowy weather.

[0107] V. One-time vertical rotation construction An operating platform was erected on the main tower 2, and operators carried out vertical rotation construction on the platform, focusing on ensuring the symmetrical force on the vertical rotation cable 71 and the back cable 72.

[0108] A continuous jack is used to synchronously pull the vertical rotation cable 71 to carry out a vertical rotation operation on section 44 of the auxiliary tower. The vertical rotation adopts hydraulic synchronous control technology. During the process, the back cable 72 and the vertical rotation cable 71 are synchronously and symmetrically loaded and unloaded (loading rate ≤ 5MPa / min) to maintain the consistency of the horizontal component force and ensure that the main tower 2 is subjected to balanced force.

[0109] During the vertical rotation, the guy cable 73 is always in a pre-tensioned state to control the four-way stability of the attached tower structure, with a swing amplitude of ≤5mm; the BIM positioning and monitoring system is used to track the attitude of section 44 of the attached tower in real time, and the cable tension is adjusted in time to correct deviations when they are detected.

[0110] After vertically rotating the first section 44 of the auxiliary tower into place according to the structural line, it is welded to the second section 43 of the auxiliary tower to form the complete section 431 of the auxiliary tower. CO2 gas shielded welding is used, with a welding current of 200-250A and a voltage of 24-28V. The weld is continuous and full, and non-destructive testing is performed after welding.

[0111] After one vertical rotation, section 44 of the attached tower is in a large cantilever state. The reinforcement measures of the guy cables on both sides are added (the angle between the guy cables and the horizontal direction is ≥45°) to ensure the structural safety.

[0112] Remove hinge 62 and clean the installation location; the exterior paint of the attached tower on the low-altitude bridge surface can be repaired and improved.

[0113] VI. Secondary vertical rotation construction A continuous jack was used to synchronously pull the vertical rotation cable 71 for a secondary vertical rotation of the entire 431 section of the auxiliary tower. As the rotation angle gradually increased, the center of gravity of the entire 431 section of the auxiliary tower gradually increased, while the longitudinal position of the center gradually decreased and reversed. It was necessary to keep the guy cable 73 taut and under balanced stress at all times to control the four-directional stability of the 431 section of the auxiliary tower structure. Every 10° of vertical rotation, the attitude of the 431 section of the auxiliary tower was monitored using a total station. The tension of the guy cable 73 was adjusted to counteract the unbalanced torque caused by the shift in the center of gravity, ensuring that the 431 section of the auxiliary tower rotated along the preset trajectory with a horizontal displacement of ≤8mm at the top. Pulling was stopped when the vertical rotation reached the design angle (88°), and the cable tension was kept constant.

[0114] VII. Fixing and Connecting After the auxiliary tower is rotated into place for the second time, temporary tie measures (steel tie rods + turnbuckles) are used to hinge and fix the entire auxiliary tower section 431 to the end of the main tower 2 to avoid displacement and shaking.

[0115] Weld support points on both sides of the top connector 45 of the auxiliary tower, and use jacks (rated jacking force 200t) and pull hoists (rated pulling force 50t) to adjust the alignment, so as to ensure that the end of the entire section 431 of the auxiliary tower is completely fitted with the mating surface of the top connector 45 of the auxiliary tower and the bottom is completely fitted with the mating surface of the fixed section 42 of the auxiliary tower, with a mating gap ≤1mm.

[0116] After the alignment is adjusted to the design requirements, welding is carried out for fixation: first weld the transverse welds and then weld the longitudinal welds, using a symmetrical welding method to avoid welding deformation; during the welding process, the temperature and deformation of the attached tower are monitored in real time, and a layered welding process is adopted (each layer is 3-5mm thick, and the interlayer temperature is 80-150℃). After welding, the welds are allowed to cool naturally to room temperature; after the welds are completed, 100% non-destructive testing is carried out, and they meet the requirements of Class I welds.

[0117] 8. Equipment and Support Removal The relevant equipment and components will be dismantled in the order of "cable body first, then support structure": First, dismantle the vertical rotating cable 71, the rear back cable 72, and the guy cable 73 (the cable body will be unloaded in stages, with an unloading rate ≤3MPa / min). Then, dismantle the steel truss assembly 51, the attached tower assembly support 52, the secondary rotating hinge 61, and the related equipment and components for vertical rotation. The support structure will be dismantled from top to bottom, in sections, with dedicated personnel supervising the process. The dismantled materials and equipment will be sorted, stacked, and promptly removed.

[0118] IX. Anti-corrosion coating and acceptance Rust removal treatment was carried out on the attached tower and connecting parts, with a rust removal grade of Sa2.5. Anti-corrosion coating was applied within 4 hours after rust removal.

[0119] The coating system consists of three layers: epoxy zinc-rich primer (dry film thickness 80μm) + epoxy micaceous iron oxide intermediate paint (dry film thickness 120μm) + fluorocarbon topcoat (dry film thickness 60μm). After coating, the adhesion is tested and the adhesion is ≥5MPa.

[0120] A comprehensive inspection of the steel tower installation quality was conducted, including alignment deviations, weld quality, and corrosion protection effectiveness. Once the measured items met the design and specification requirements, the acceptance documents were signed, and the auxiliary tower installation was completed.

[0121] This is merely an embodiment of the present invention. Commonly known structures and characteristics of the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the filing date or priority date, are aware of all prior art in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the description of specific embodiments in the specification can be used to interpret the content of the claims.

Claims

1. A method of installing an arch-shaped steel tower of an elongated structure, characterized by, Includes the following steps: Step 1: Construct the bridge substructure; Step 2: Construct the main tower, pre-embed the auxiliary tower root section at the lower end of the main tower, pre-embed the auxiliary tower top connector at the top of the main tower, and pre-embed wall ties, vertical rotation construction platform, vertical rotation force point and related components of the vertical rotation docking operation platform at the corresponding height during the construction of the main tower. Step 3: During the construction of the main tower, the auxiliary tower fixing section and the main beam are installed simultaneously. The auxiliary tower fixing section is welded and fixed to the pre-embedded section at the base of the auxiliary tower and the main tower respectively. The main tower and the auxiliary tower fixing section are connected by welding through steel truss assembly. Step 4: Erect the auxiliary tower assembly support on the main beam bridge deck, and assemble the second and first auxiliary tower sections in sequence according to the inverted arch posture. During assembly, preset the pre-offset value and pre-camber, and then accurately position and install the secondary hinge and primary hinge. Step 5: Install the vertical turning cable, back cable, and guy cable. All three are made of steel strand and have anchor boxes at both ends to complete the test preparation before vertical turning. Step Six: Using continuous jacks to synchronously pull the vertical rotation cable, rotate the first section of the auxiliary tower once. After it is in place, weld it to the second section of the auxiliary tower to form the complete auxiliary tower section. Remove the rotating hinge once. Step 7: Continue to use continuous jacks to synchronously pull the vertical rotation cable and perform a second vertical rotation on the entire attached tower section; Step 8: After the second vertical rotation into place, weld and fix the end of the entire section of the attached tower to the top connecting piece of the attached tower, and weld and fix the bottom to the fixed section of the attached tower; Step 9: Remove the vertical rotation equipment and supports to complete the installation.

2. The method of installing an elongated structural arch steel tower of claim 1, wherein, In step two, the pre-embedded section at the base of the auxiliary tower and the main tower are integrally cast in the form of a steel-concrete composite section.

3. The method of installing an elongated structural arch steel tower of claim 1, wherein, In step three, the main beam is constructed using the scaffolding method. The bearing capacity of the scaffolding meets the requirements for the construction of the main beam, the assembly of the bridge deck towers, and the vertical rotation of the towers. The main beam is a steel beam, a steel-concrete composite beam, or a cast-in-place concrete beam.

4. The method of installing an elongated structural arch steel tower of claim 1, wherein, In step four, the auxiliary tower assembly support is supported on the transverse diaphragm or web of the main beam. When the support position does not meet the requirements, a distribution beam is added to the main beam bridge deck to bear the concentrated load.

5. The method of installing an elongated structural arch steel tower of claim 1, wherein, In step five, the upper ends of the vertical swivel cable and the back cable are connected to the anchor box assembly pre-embedded in the main tower, and the lower ends are connected to the second section of the auxiliary tower and the main beam, respectively; there are two sets of wind cables arranged in an outward V-shape, with the upper ends connected to the second section of the auxiliary tower and the lower ends connected to the main beam.

6. The method of installing an elongated structural arch steel tower of claim 1, wherein, In step five, two sets of vertical rotating cables and two sets of rear cables are set up and arranged in parallel. The spacing is determined by calculation based on the structural dimensions of the attached tower, the vertical rotating height, the hinge gap and the accuracy index. If necessary, brackets are welded on both sides of the attached tower to increase the spacing.

7. The method for installing a slender arched steel tower according to claim 1, characterized in that, In step six, hydraulic synchronous control technology is used for the first vertical rotation, and the back cable and the vertical rotation cable are loaded and unloaded synchronously and symmetrically, and the guy cable is always kept in a pre-tensioned state; when the section of the attached tower is in a large cantilever state after the first vertical rotation, additional guy cables are added for reinforcement.

8. The method for installing a slender arched steel tower according to claim 1, characterized in that, In step seven, during the second vertical rotation, the tension of the guy cable is adjusted as the vertical rotation angle increases to maintain the four-way balance and stability of the entire attached tower section.

9. The method for installing a slender arched steel tower according to claim 1, characterized in that, In step eight, after the entire auxiliary tower section is rotated into place for the second time, it is temporarily tied to the end of the main tower and fixed by hinge. The alignment is adjusted by jacks and pull hoists before welding and fixing.

10. The method for installing a slender arched steel tower according to claim 1, characterized in that, In step five, load-bearing lugs are welded to the connection points of the vertical slewing cable, back cable, wind cable, main beam, and auxiliary tower. The lugs are pre-drilled with load-bearing pin holes and are hinged to the anchor box via pins.

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