Construction method for tower-hung multi-buckle-cable cooperative incremental launching of steel box girder

Abstract

The invention discloses a construction method for cooperatively pushing a steel box girder through multiple tower-hung buckle cables, and relates to the technical field of bridge construction. The method comprises the steps that a pushing supporting system is arranged between a first abutment pier and a main tower; assembling the steel box girder to the position of a main tower; continuously pushing the steel box girder to penetrate through the main tower to form a first cantilever; a first buckle cable is installed on the main tower, and the two ends of the first buckle cable are connected with the steel box girders on the two sides of the main tower correspondingly; continuously pushing and synchronously assembling the subsequent sections; after the conditions are met, a second buckle cable is installed on the main tower; and the steps of pushing, assembling and buckle cable adding are repeated till the front end of the steel box girder moves to the second abutment pier. The multiple buckle cables connected with the beam body are sequentially and additionally arranged on the main tower, multi-point elastic supporting is provided for the long cantilever steel box beam in the pushing process, beam end downwarping is actively controlled, the structural stress is improved, guide beams can be greatly reduced or even eliminated, and the construction difficulty and cost are reduced.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, specifically to a method for constructing steel box girders using a tower-mounted multi-cable jacking system. Background Technology

[0002] Steel box girder bridges are a type of bridge structure mainly made of steel. They are widely used in modern bridge engineering due to their advantages such as high tensile strength, light weight, convenient construction, structural safety and reliability, and short erection period.

[0003] The incremental launching method, which uses a longitudinal launching system to slide precast steel box girders segment by segment forward to their designed positions, is a commonly used construction technique for steel box girder erection. Its advantages include eliminating the need for large-span scaffolding and heavy machinery under the bridge. Construction does not interfere with the terrain, water flow, or navigation under the bridge. It boasts a short construction period, low cost, and significant economic benefits. The launching speed can reach 12-15 meters per day, shortening the construction period by 30%-50% compared to traditional hoisting methods. Tools and equipment (such as jacks and sliding tracks) can be reused, reducing the cost per construction run. This method has become the preferred method for steel box girder erection.

[0004] For example, the Chinese invention patent with patent number "CN110904860A" entitled "A Method for Launching a Large-Span Flexible Steel Beam Based on Cable-Stayed Gauges" describes a launching construction method including the following steps: setting up an assembly platform and multiple temporary supports in the bridge construction area, and installing a walking-type launching device on each temporary support; assembling the guide beam, steel beam, and tower in segments on the assembly platform; installing and tensioning the cable stays on the front and rear sides of the steel beam, adjusting the front and rear cable stays to different initial tensions to pre-deflect the top of the tower backward by a certain angle; and starting the walking-type launching device to launch the guide beam, steel beam, tower, and cable stays. The cable-stayed system is advanced forward, spanning multiple large spans. A walking-type jacking device is activated to advance the system a certain distance each time, after which the steel beams are assembled segmentally. When the guide beam crosses a large span and is supported on the first temporary pier after crossing that span, the stay cables are tensioned. Similarly, when the tower crosses a large span and is supported on the first temporary pier after crossing that span, the stay cables are tensioned. After the tower crosses the last large span, the stay cables and tower are removed at a predetermined position. The walking-type jacking device continues to advance the system forward. Once the system reaches the designed position, the guide beam is dismantled segmentally, and the beam is lowered into place. This method utilizes the tower and stay cables as auxiliary measures, improving the stress and deflection of the steel beams and guide beams, thereby increasing the jacking span of the steel beams and solving the problem of difficult jacking of large-span bridges due to the inability to install temporary piers.

[0005] However, this method also has some problems. The tower and stay cables in this construction method are temporary structures, and the connection between the tower and the steel beam is a fixed structure. The tower is immovable relative to the steel beam. Therefore, during the jacking process of the steel beam, the length of the steel beam corresponding to the tower and stay cables is fixed. It can only serve as an auxiliary structure for the steel beam at the front end of the part connected to the guide beam. The structural strength of the steel beams assembled later cannot be increased by the tower and stay cables. The problem of jacking large spans of the steel beams still exists. In addition, the tower and stay cables actually increase the construction cost of the entire jacking process and also significantly increase the construction difficulty. Both the installation and dismantling of the tower will reduce construction efficiency, which does not meet the current requirements for efficiency and cost control in bridge construction. Summary of the Invention

[0006] The purpose of this application is to address the shortcomings of the aforementioned background technology and provide a method for constructing steel box girders using a tower-mounted multi-cable coordinated jacking system.

[0007] The technical solution of this application is: a construction method for tower-mounted multi-cable coordinated jacking of steel box girders, including the following steps: An assembly support system is installed between the first side pier and the main tower; The steel box girder is assembled based on the assembly support system until the front end of the assembled steel box girder extends to the position of the main tower. Continue to push the steel box girder so that it passes through the main tower along the longitudinal direction of the bridge and extends to the first preset length to form the first cantilever state; Install the first cable on the main tower and connect the two ends of the first cable to the steel box girder on both sides of the main tower. Continue to push the steel box girder along the longitudinal direction of the bridge, and simultaneously assemble the subsequent segments at the tail end of the steel box girder on the assembly support system; When the conditions for installing the second tie cable are met, the second tie cable is installed on the main tower, and the two ends of the second tie cable are connected to the steel box girders on both sides of the main tower. Repeat the above steps of jacking, assembling, and adding fastening cables until the front end of the steel box girder moves to the second side pier.

[0008] According to the construction method of a tower-mounted multi-cable coordinated jacking steel box girder provided in this application, the method of setting up an assembly support system between the first side pier and the main tower includes: setting up an assembly bracket and multiple temporary piers in the construction area between the first side pier and the main tower; the assembly bracket and multiple temporary piers are arranged sequentially at intervals along the bridge direction, and the assembly bracket is set close to the first side pier for the assembly operation of steel box girder segments; and installing a walking jacking device on the assembly bracket and each temporary pier.

[0009] According to the construction method of a tower-mounted multi-cable coordinated jacking steel box girder provided in this application, the method of assembling the steel box girder based on the assembly support system includes: assembling the steel box girder section by section on the assembly support; jacking the assembled steel box girder section forward with the walking jacking equipment on the assembly support so that its front end is supported on the adjacent temporary pier; repeating the above assembly and jacking steps until the front end of the steel box girder moves to the position of the main tower.

[0010] According to the construction method of tower-mounted multi-cable coordinated jacking of steel box girder provided in this application, a bracket is pre-built on the main tower; the front end of the steel box girder moves along the longitudinal direction of the bridge onto the bracket under the action of the walking jacking equipment.

[0011] According to the tower-mounted multi-cable coordinated jacking steel box girder construction method provided in this application, the method of continuing to jack the steel box girder so that it passes through the main tower along the bridge direction and extends to a first preset length includes: jacking the steel box girder along the bridge direction until the length of the front end of the steel box girder extending out of the bracket reaches the preset cantilever length allowed by the design under the current working conditions.

[0012] According to the construction method of a tower-mounted multi-cable coordinated jacking steel box girder provided in this application, the method of installing the first cable on the main tower includes: installing a support frame and guide wheel on the top of the main tower; installing lugs on the steel box girder corresponding to the designed position of the first cable; placing the middle part of the first cable on the guide wheel; connecting the two ends of the first cable to the corresponding lugs on the steel box girder on both sides of the main tower; and using a winch set on the steel box girder to tension and adjust the first cable.

[0013] According to the construction method of tower-mounted multi-cable coordinated jacking of steel box girder provided in this application, the first cable includes two steel cables symmetrically arranged with the center line of the steel box girder along the bridge direction as the center.

[0014] According to the construction method of tower-mounted multi-cable coordinated jacking of steel box girder provided in this application, the method of installing support frame and guide wheels on the top of the main tower includes: installing support frame on the top of the main tower, and installing multiple sets of guide wheel sets arranged at intervals along the transverse direction of the bridge on the upper end of the support frame, each set of guide wheel sets including multiple guide wheels arranged at intervals along the longitudinal direction of the bridge.

[0015] According to the construction method of a tower-mounted multi-cable coordinated jacking steel box girder provided in this application, the method of moving the front end of the steel box girder to the second pier includes: when the front end of the steel box girder is jacked to near the second pier, the first clasp is tensioned by a tensioning system connected to the first clasp, and the front end of the steel box girder is adjusted to make it slightly upturned; the steel box girder is continued to be jacked until the front end of the steel box girder moves above the predetermined beam placement position of the second pier; the tension of the tensioning system is gradually released, and the walking-type jacking equipment is simultaneously fine-tuned so that the front end of the steel box girder falls smoothly and is supported on the second pier.

[0016] The advantages of this application are as follows: 1. This application relates to a construction method for a steel box girder with a multi-cable-stayed tower and coordinated jacking. By introducing the innovative structure of multi-cable-stayed tower, a temporary cable suspension system is established between the main tower (a rigid support point) and the beams on both sides. The successive installation of the first, second, and even more cables is equivalent to providing additional elastic support points for the forward-extending cantilever beam. These cables are pulled diagonally from the top of the tower to the beam, generating an upward vertical component force, which actively balances the downward deflection moment generated by the beam's self-weight. Its direct effect is to greatly suppress the downward deflection at the front end of the steel box girder. This allows the originally required ultra-long and ultra-heavy guide beam to be significantly shortened, and even under specific working conditions... The guide beam can be completely eliminated, which not only reduces material costs and manufacturing difficulty, but more importantly, significantly reduces the difficulty of mounting the beam on the pier at the front end, making the jacking process smoother and safer. The cable system in this method is not passively stressed, but can be actively intervened through later adjustments. During the jacking process, the internal force distribution of the beam can be artificially changed by adjusting the tension of the cable. This application provides a highly streamlined and collaborative work process. The three key processes of jacking, assembly, and cable installation and tensioning are carried out in parallel, avoiding waiting time between processes. This high degree of collaboration maximizes construction efficiency and effectively shortens the total construction period. 2. This application clarifies that it is composed of an assembly support and multiple temporary piers, and adopts a walking-type jacking device. The temporary piers provide multi-point elastic support for long-distance, high-tonnage jacking, effectively reducing the span of the steel box girder and lowering the bending moment of the girder itself during the jacking process. Together with the cable system, they further optimize the stress on the girder. Compared with the traditional drag-type jacking, the walking-type jacking device has advantages such as high synchronous control accuracy, separate control of horizontal jacking force and vertical lifting force, and the ability to achieve lateral correction. This provides the equipment foundation for subsequent fine-tuning of the jacking device, ensuring that the steel box girder can be accurately and stably positioned under complex conditions of multiple jackings and multiple tensioning of the cable. The assembly operation is concentrated on the assembly support near the first side pier, forming a fixed working surface, which is conducive to organizing continuous construction. The jacking equipment on the temporary piers focuses on the jacking function, with clear division of labor and high system efficiency. 3. This application clarifies the standardized work units for assembly, jacking, and support, making the construction process highly regular and predictable, which facilitates construction management and quality control. This step-by-step approach ensures that the steel box girder can stably and according to plan reach the main tower position (the first pause point) and the installation position of each subsequent cable tie, which is the basis for the implementation of all subsequent coordinated steps. 4. The main tower of this application is usually a concrete structure, which may cause local damage if it directly bears the concentrated load of the steel box girder; the steel bracket can evenly and stably transfer the weight of the steel box girder to the appropriate part of the main tower, thus providing protection for the main tower; during the process of the steel box girder passing through the main tower, the bracket serves as a key temporary support point, ensuring the stability and alignment of the beam when passing through the main tower, and providing a precise positioning reference for the subsequent installation of the cable tie. 5. This application introduces the concepts of working condition design and preset cantilever length, reflecting the idea of ​​dynamic design and construction control. Before each jacking operation, a safe cantilever length, i.e., the preset cantilever length, should be calculated and determined based on factors such as the beam length, weight, number and tension of installed ties, and environmental loads. This ensures that the construction process is always within the elastic range of the structure, strictly avoiding the risk of structural instability or damage caused by excessively long cantilevers due to blind jacking, and embodies the essence of collaborative control in this method. 6. The winch in this application allows for adjustment of the cable length during the jacking process to accommodate changes in cable length. The support frame at the top of the tower and the pulleys on the support frame ensure continuous cable connection on both sides, eliminating the need for separate cables connected to the top of the tower on the front and rear sides. This reduces the number of times cable tension needs to be adjusted, facilitating operation for construction personnel and reducing construction costs. This application innovatively sets up a support frame and guide wheels at the top of the tower, treating one cable as a single unit, with its mid-span resting on the guide wheels and both ends pulling towards the beams on either side. This continuous cable design cleverly utilizes pulleys to connect the cable forces on both sides. When one side of the beam (such as the front end) deflects due to jacking, the pulleys can link the cable on the other side, allowing the cable forces on both sides to automatically seek a balance. This greatly simplifies the complexity of cable tension adjustment. Because it's a continuous cable system connected via pulleys at the top of the tower, the entire cable system only requires one tensioning device (such as a winch) to adjust the tension on both sides, eliminating the need for separate anchoring and tensioning systems for each cable. This significantly reduces the number of times and operation points for adjusting cable tension, simplifying the construction process, reducing equipment investment and labor costs, and also lowering the risks of working at height. Using a winch for tension adjustment is ideal for dynamic processes like jacking construction. As the beam moves forward, the angle and length between the cable and the beam change continuously. The winch can easily wind up and unwind the wire rope, adapting to these changes in real time and maintaining the cable tension within the design range, achieving true coordinated jacking. 7. The tie cable of this application includes two steel cables symmetrically arranged around the centerline of the steel box girder along the bridge direction. This arrangement allows the tension points of the tie cable to be symmetrically placed on both sides of the centerline of the beam along the bridge direction, ensuring that the vertical support force and horizontal component force provided by the tie cable pass through the shear center of the beam, avoiding additional torsional deformation and torque stress caused by eccentric tension. This is crucial for ensuring the stability of the beam's posture and structural safety during the jacking process. 8. This application clarifies that multiple sets of guide wheels can be installed on the tower top support frame, reserving space and structure for the subsequent installation of the second and third cable ties; each set of guide wheels contains multiple guide wheels arranged in the longitudinal direction of the bridge, which can distribute the concentrated load of the cable ties to multiple wheels, reducing the pressure and wear of individual wheels and improving the safety and durability of the device; the transverse spacing arrangement allows multiple cable ties to be arranged in an orderly manner at the tower top without interfering with each other; the multiple guide wheels in the longitudinal direction of the bridge ensure that the cable ties remain smooth when rolling with the beam, reducing frictional resistance and making cable force adjustment more sensitive and precise; 9. This application utilizes the active tensioning of the first tie cable to cause the previously sloping front end of the steel box girder to actively tilt upwards, artificially creating a space higher than the pier top elevation. This allows the jacking equipment to easily move the girder to its designed position without scraping against the pier. Once in place, instead of forceful jacking, the weight of the girder is smoothly transferred from the tie cable and jacking equipment to the permanent pier by gradually releasing the tie cable tension and simultaneously fine-tuning the walking-type jacking equipment (e.g., using the vertical jacks of the walking-type jacking equipment). This controlled, slow, and shock-free process significantly improves the safety and positioning accuracy of the pier placement. This perfectly illustrates the crucial role of tie cable coordination in solving construction challenges. Attached Figure Description

[0017] Figure 1 : A schematic diagram of the assembly support system layout in this application; Figure 2 This application provides a schematic diagram of the assembly of the steel box girder on the assembly support system. Figure 3 This application includes a schematic diagram of the steel box girder being pushed onto the bracket. Figure 4 This application includes a schematic diagram of the installation of the first fastening cable for the steel box girder; Figure 5 This application provides a schematic diagram of the steel box girder being pushed forward after the first set of ties is installed. Figure 6 This application includes a schematic diagram of the installation of the second tie cable on the steel box girder. Figure 7 : A schematic diagram of the steel box girder being pushed to the second side pier in this application; Figure 8 This application Figure 7 Enlarged diagram of part A in the diagram; Figure 9 This application Figure 7 Enlarged schematic diagram of part B (side view); Figure 10 This application Figure 7 Enlarged view of part B (front view); Wherein: 1—First side pier; 2—Second side pier; 3—Main tower; 4—Assembly support; 5—Temporary pier; 6—Walking jacking equipment; 7—Bracket; 8—Steel box girder; 9—Guide wheel; 10—Support frame; 11—First fastening cable; 12—Wind; 13—Pull lug; 14—Anchoring structure; 15—Second fastening cable. Detailed Implementation

[0018] The embodiments of this application are described in detail below, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0019] In the description of this application, it should be understood that the terms "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0021] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0022] This application relates to a tower-mounted multi-cable coordinated jacking construction method for steel box girders, aiming to solve the technical bottlenecks of traditional jacking processes, such as large front-end deflection, the need for long guide beams, and difficulties in pier mounting. The construction method of this application uses a tower-mounted multi-cable coordinated jacking system with the main tower as the high-point support and multiple cables as elastic lifting points. This fundamentally changes the stress pattern during the jacking process, significantly reducing or even eliminating the need for guide beams, thus lowering project costs. It transforms passive deformation bearing into active control, allowing adjustment of cable tension based on monitoring data throughout the jacking process and active lifting of the beam end during pier mounting. This achieves controllability of the construction process and high positioning precision, significantly improving construction safety and adaptability.

[0023] Specifically, such as Figures 1-10 As shown, the present application discloses a method for constructing a tower-mounted multi-cable coordinated jacking steel box girder, which includes the following steps: S1, such as Figure 1 As shown, an assembly support system is set between the first side pier 1 and the main tower 3 to provide a foundation for the subsequent assembly and jacking of the steel box girder 8; S2, such as Figure 2 As shown, based on the established assembly support system, the assembly of steel box girder 8 begins and continues until the front end of the assembled steel box girder 8 extends to the position of the main tower 3. S3, such as Figure 3 As shown, continue operating the jacking system to move the steel box girder 8 forward along the longitudinal direction of the bridge, passing through the main tower 3 and extending to the first preset length. At this time, the front end of the steel box girder 8 is in an unsupported state, forming the first cantilever state. S4, such as Figure 4 As shown, the first fastening cable 11 is installed on the main tower 3. During installation, the two ends of the first fastening cable 11 are reliably connected to the steel box girder 8 located on both sides of the main tower 3. S5, such as Figure 5 As shown, the steel box girder 8 continues to be pushed along the bridge direction. At the same time as the pushing is being carried out, the subsequent segments of the steel box girder 8 are simultaneously assembled in the assembly area, which is usually the rear of the assembly support system, so as to realize the continuous operation of pushing and assembly. S6, such as Figure 6 As shown, when the jacking reaches the preset second cable installation conditions, for example, when the front cantilever length reaches a certain critical value, the second cable 15 is installed on the main tower 3, and its two ends are connected to the steel box beams 8 on both sides of the main tower 3 respectively. S7, such as Figure 7 As shown, repeat the above steps of jacking, assembling, and adding fastening cables until the front end of the steel box girder 8 moves to the second pier 2 on the opposite bank, completing the jacking of the entire bridge.

[0024] This scheme utilizes the main tower as a high-point support, and through the gradual addition of ties, transforms the long cantilever steel box girder during the jacking process into a continuous structure with multi-point elastic support. Each additional ties is equivalent to adding an upward elastic fulcrum to the front beam, sharing the bending moment and deflection generated by the beam's self-weight, thus changing the structural stress system.

[0025] This construction method, through the synergistic effect of multiple anchor cables, fundamentally solves the problems of excessive front-end deflection and high stress in the jacking construction of large-span steel box girders. It transforms the jacking process from passively bearing deformation to actively controlling stress, eliminating the need for or significantly reducing the size of the front guide beam, thus lowering construction difficulty and cost. Simultaneously, the successive intervention of multiple anchor cables ensures that the girder remains in a safe stress state throughout the entire long jacking stroke, ultimately achieving high-precision, low-impact pier placement, significantly improving the adaptability and safety of the construction.

[0026] In some embodiments of this application, the method of setting up an assembly support system between the first side pier 1 and the main tower 3 is specifically defined.

[0027] An assembly support frame 4 and multiple temporary supports 5 are set up in the construction area between the first side pier 1 and the main tower 3 (e.g., Figure 1 The image shows two temporary piers 5. These assembly supports 4 and multiple temporary piers 5 are arranged sequentially and at intervals along the bridge direction. The assembly support 4 is located closest to the first side pier 1 and is specifically used for the assembly of the 8 segments of the steel box girder. In addition, a walking-type jacking device 6 is installed on the top of the assembly support 4 and each temporary pier 5.

[0028] This embodiment decomposes the assembly support system into two functionally distinct parts: the assembly support frame in the assembly area and the temporary piers in the support area. The assembly support frame provides a stable and centralized working platform for the assembly and welding of steel box girder segments. The temporary piers serve as intermediate support points, effectively reducing the span of the steel box girder during the jacking process. The walking-type jacking equipment integrates vertical jacking, longitudinal jacking, and lateral adjustment functions, distributed at each support point, enabling multi-point synchronous coordinated action.

[0029] The advantages of this structural layout are as follows: First, the functional zoning is clear, and the assembly and launching operations can partially overlap, improving construction efficiency. Second, the setting of multiple temporary piers greatly shortens the span of the steel box girder throughout the launching process, resulting in better internal forces within the girder and avoiding excessive deformation caused by an excessively large span. Third, the use of walking-type launching equipment enables precise and stable control of the movement of the steel box girder, providing strong support for the subsequent precise adjustment of the cable tensioning and overall alignment control, reflecting the mechanized and intelligent construction concept.

[0030] In other embodiments of this application, this embodiment specifically defines the assembly of the steel box girder 8 based on the assembly support system and the method by which the steel box girder reaches the main tower.

[0031] The specific assembly methods include: such as Figure 2 As shown, firstly, the steel box girder segments 8 are assembled one by one on the assembly support 4. After one or several segments are assembled, the walking-type jacking device 6 on the assembly support 4 is activated to push the assembled steel box girder segment 8 forward, so that its front end can be stably supported on the adjacent first temporary pier 5. Subsequently, the next segment is assembled on the empty assembly support 4, and jacking is performed again, so that the front end of the beam is successively supported on the subsequent temporary piers. This assembly-jacking process is repeated until the front end of the steel box girder 8 moves to the position of the main tower 3.

[0032] Meanwhile, a bracket 7 is pre-installed on the main tower 3, such as Figure 3As shown, the front end of the steel box girder 8 moves along the bridge direction under the continuous action of the walking-type jacking device 6, and finally moves smoothly to be supported on the bracket 7.

[0033] This embodiment describes a typical cyclical construction process of segmental assembly and sequential jacking. This process makes full use of the limited assembly space and achieves synchronous growth and advancement of the beam. The bracket on the main tower is a key temporary support structure, providing a precise and stable support point for the beam at the main tower location, allowing the beam to safely cross the main tower position.

[0034] The advantage of this cyclical operation method lies in maximizing the use of assembly supports and jacking equipment, enabling their reuse and reducing the investment cost of temporary facilities. Each step reliably delivers the front end of the beam to the next temporary pier or bracket, ensuring the beam is always supported and avoiding the risks of long-distance unsupported jacking. The introduction of brackets enables a smooth transition between the steel box girder and the main tower, protecting the main tower structure from accidental collisions and providing a stable working surface and accurate elevation benchmark for subsequent cable installation on the main tower. It is a crucial node connecting the jacking and cable-stayed systems.

[0035] In a further embodiment of this application, this embodiment limits the continuous jacking of the steel box girder 8 so that it passes through the main tower 3 along the longitudinal direction of the bridge and extends to a first preset length.

[0036] The specific operation is as follows: With the front end of the steel box girder 8 already supported on the main tower bracket 7, the jacking equipment is continued to move the steel box girder 8 along the bridge direction, and its front end gradually extends beyond the bracket 7. This extension process will continue until the length of the front end of the steel box girder 8 extending beyond the bracket 7 precisely reaches the maximum preset cantilever length allowed by the structural stress analysis calculation under the current construction conditions, as shown in Figure 3. In other words, the part of the front end of the steel box girder 8 extending beyond the bracket 7 will not affect the structural stability of the entire steel box girder 8, and will not cause the steel box girder 8 between the first side pier 1 and the main tower 3 to become unstable and tilt.

[0037] The first preset length here is not an arbitrary or fixed value, but a dynamic calculated value based on the real-time structural stress state. It represents the ultimate safe length that the front cantilever of the steel box girder can reach without the first tie cable installed. The determination of this length takes into account factors such as the stiffness, strength, and self-weight of the currently assembled beam segments.

[0038] This embodiment quantifies the abstract timing of cable installation into specific, operable cantilever length indicators, providing clear and scientific instructions for on-site construction. This ensures that the construction process remains within the designed safe range, avoiding structural instability or damage that may be caused by excessive cantilever, and serves as the first line of defense for the overall safety of the construction method. It requires strict adherence to the design conditions, reflecting a balance between safety and efficiency.

[0039] In a preferred embodiment of this application, the specific method for installing the first fastening cable 11 on the main tower 3 is described in detail.

[0040] The method specifically includes: such as Figures 8-10 As shown, firstly, a specially designed support frame 10 is installed at the top of the main tower 3, and guide wheels 9 are installed on the support frame 10. Simultaneously, secure lugs 13 are pre-installed or welded onto the steel box girder 8 at the design anchor points corresponding to the first tie cable 11. Then, the tie cable is installed by placing the middle section of a complete first tie cable 11 into the groove of the guide wheel 9 on the tower top support. The two ends of the tie cable are then lowered and connected to the corresponding lugs 13 on the front and rear sides of the steel box girder 8 of the main tower 3. Finally, using a winch 12 pre-installed on the steel box girder 8 in conjunction with pulley blocks, the connected first tie cable 11 is tensioned, adjusting its tension to the initial design value. An anchoring structure 14 connects the winch 12 to the first tie cable 11.

[0041] In this embodiment, the first cable is not anchored to the top of the tower, but rather extends like a rope across the guide wheel, with its two ends connected to the front and rear beams respectively. The guide wheel at the top of the tower serves as both a steering and support mechanism. The winch system is responsible for providing tension; since the cable is continuous, tensioning at one end allows for simultaneous adjustment of the cable tension on both sides.

[0042] This installation and connection method offers significant advantages: First, it simplifies the tower top structure, avoiding the need for complex and bulky permanent anchoring devices, simplifying construction and minimizing impact on the main tower itself. Second, it enables synchronized adjustment of cable tension. Since the cable is continuous, there's no need for separate anchoring of two cables at the tower top; tensioning via a winch allows simultaneous adjustment of the cable tension on both sides, automatically balancing the tension and significantly reducing the number of adjustments and workload. Finally, it adapts to dynamic changes. The winch system allows for real-time cable retraction and release during the jacking process, dynamically adjusting cable length and tension to accommodate changing geometric relationships and stress requirements, demonstrating excellent construction adaptability.

[0043] In some embodiments of this application, the connection position between the tie cable and the steel box girder is further optimized and defined. When the tie lug 13 is installed on the steel box girder 8 and connected to the first tie cable 11, the installation position of the tie lug 13 should be ensured. The first tie cable 11 includes two steel cables, which are arranged symmetrically with respect to the longitudinal centerline of the steel box girder 8. That is, the connection point between the two steel cables and the steel box girder 8 (i.e., the position of the tie lug 13) is arranged symmetrically with respect to the longitudinal centerline of the steel box girder 8.

[0044] Since steel box girders are typically thin-walled structures, their torsional stiffness is relatively weak. The tension of the cable is a concentrated force. If the points of application of the two cable forces are not symmetrical along the centerline of the beam (i.e., the shear center or the center of torsion), a moment couple will be generated, causing torsional deformation of the beam.

[0045] This embodiment, by symmetrically arranging the two steel cables of the tie cable, aims to ensure pure force distribution and avoid harmful torsional effects. This guarantees that the tension of the tie cable is entirely used to resist vertical bending without generating additional torque on the steel box girder. This is crucial for maintaining the stability of the steel box girder's cross-sectional shape, preventing local instability, and ensuring the safety of the structure during construction; it is an important detail reflecting meticulous design.

[0046] In other embodiments of this application, the support and guide wheel structure at the top of the tower are further defined to accommodate the needs of multiple ties. For example... Figure 9 and 10 As shown, the support frame 10 installed at the top of the main tower 3 does not only have one guide wheel, but multiple sets of guide wheel groups are installed at intervals along the transverse direction of the bridge, that is, the horizontal direction perpendicular to the longitudinal direction of the bridge. Each set of guide wheels itself can include multiple guide wheels 9 arranged at intervals along the longitudinal direction of the bridge, so as to better guide and support the cable ties.

[0047] The construction method in this embodiment involves multiple cables working in tandem, which inevitably requires multiple independent cable systems. Within the limited space at the top of the tower, the guide wheels of the steering mechanisms of these cable systems are staggered upwards on the transverse bridge to avoid mutual interference and to provide a clear and independent force transmission path for each cable.

[0048] This tower top structure has several advantages: First, it provides physical space for multiple cable ties, allowing the first, second, and even more cable ties to work efficiently and orderly at the tower top simultaneously without interference. Second, it improves the lateral stability of the entire cable tying system; the multi-point, multi-group arrangement increases the system's ability to resist wind loads or other lateral disturbances. Finally, the multiple longitudinal guide wheels in each group can better distribute the concentrated pressure of the cable ties at the tower top and accommodate the minute displacements caused by changes in the cable ties' angle.

[0049] In a preferred embodiment of this application, the final beam lowering step, in which the front end of the steel box girder 8 is moved to the second pier 2, is precisely defined.

[0050] When the front end of the steel box girder 8 is pushed very close to the second pier 2, the pushing is first paused. Then, through the tensioning system such as the winch connected to the first tie cable 11, the tie cable is actively tensioned, applying additional tension to adjust the front end of the steel box girder 8 upwards, making it slightly upturned and higher than the top surface elevation of the second pier 2. Next, while maintaining this upturned state, the steel box girder 8 is pushed slowly and precisely until its front end moves directly above the predetermined placement position of the girder on the second pier 2. Finally, the girder placement operation begins: the tension of the tensioning system is released gradually and in stages, and the vertical support force of the walking-type pushing equipment is simultaneously fine-tuned during this process, so that the front end of the steel box girder 8 falls smoothly and slowly, ultimately accurately supporting and landing on the support or pad of the second pier 2.

[0051] In this embodiment, the tension of the cable is used to artificially create an upward-pointing posture, allowing for easy crossing of the pier top. The subsequent beam lowering process is a precisely controlled reverse process, achieving impact-free positioning through the coordinated release of cable force and the supporting force of the jacking equipment.

[0052] This construction method has several advantages: First, it significantly reduces the difficulty of placing the steel box girder on the pier. Instead of bending down to find the pier, the girder steps over it, avoiding potential edge chipping or misalignment due to front-end deflection. Second, it achieves impact-free, high-precision girder placement. By gradually releasing cable tension and coordinating adjustments, the girder falls smoothly, eliminating impact loads on the piers and girder, thus protecting the structure. Third, it ensures the final alignment. This controlled girder placement method guarantees that the steel box girder accurately achieves the designed bridge alignment, laying a solid foundation for subsequent permanent connections and system conversion.

[0053] The present application discloses a construction method for a tower-mounted multi-cable coordinated jacking steel box girder, specifically as follows: Step 1: Construction preparation and support system construction like Figure 1 As shown, between the first side pier 1 and the main tower 3, a prefabricated support frame 4 and multiple temporary piers 5 are arranged sequentially along the bridge direction. The prefabricated support frame 4 is close to the first side pier 1 and is used for the assembly of subsequent steel box girder segments. A walking-type jacking device 6 is installed on the top of the prefabricated support frame 4 and each temporary pier 5. Simultaneously, a specially designed support frame is installed on the top of the main tower 3, with multiple sets of guide wheels spaced along the transverse direction. Each set of guide wheels contains multiple guide wheels 9 arranged along the bridge direction. Furthermore, temporary brackets 7 for supporting the steel box girder are pre-installed on the lower crossbeam or tower body of the main tower 3.

[0054] Step 2: First round of assembly and jacking up to the main tower like Figure 2 As shown, the steel box girder segments 8 are assembled one by one on the assembly support 4. After assembly, the walking-type jacking device 6 on it is used to push the girder segments forward, so that the front end is supported on the first temporary pier 5. The assembly-jacking steps are repeated so that the girder passes through each temporary pier in sequence, and finally the front end of the steel box girder 8 is moved smoothly to be supported on the bracket 7 of the main tower.

[0055] Step 3: Form the first cantilever and install the first fastening cable. like Figure 3 As shown, continue jacking until the front end of the steel box girder 8 extends beyond the bracket 7, forming a cantilever. Stop jacking when the cantilever length reaches the maximum preset length allowed by the current working condition design. At this point, install lugs 13 at the corresponding design positions on the steel box girder 8, ensuring that the lug positions are such that the two future tie cables are symmetrically arranged around the longitudinal centerline of the steel box girder 8. Figure 4 As shown, the middle of the first cable 11 is placed on a set of guide wheels 9 corresponding to the tower top support, and its two ends are lowered and connected to the lugs 13 of the steel box girder 8 on the front and rear sides of the main tower 3. The winch 12 on the steel box girder is started to tension the first cable 11 and adjust it to the initial design tension.

[0056] Step 4: Cyclic jacking, assembly, and installation of fasteners like Figure 5 As shown, the steel box girder 8 continues to be pushed forward, and subsequent segments are assembled at its tail end simultaneously. During the pushing process, the tension of the first tie cable 11 is adjusted in a timely manner by the winch 12 according to the monitoring data to adapt to changes in position.

[0057] like Figure 6 As shown, when the jacking reaches the preset condition again at the front cantilever, the jacking is paused. Following the same method as the first jacking cable, the second jacking cable 15 is installed on another set of guide wheels of the main tower, and its two ends are connected to the steel box girders 8 on both sides of the main tower and tensioned.

[0058] Repeat the above steps of jacking, assembling, and cable tension adjustment, and add more ties as needed until the front end of the steel box girder 8 is about to reach the second pier 2.

[0059] Step 5: Precise placement of piers and lowering of beams like Figure 7 As shown, when the front end of the steel box girder 8 is very close to the second pier 2, the jacking is paused. The tensioning system connected to the cable, such as the winch 12, is started to actively tension the cable, so that the front end of the steel box girder 8 is slightly tilted upwards, higher than the pier top elevation.

[0060] Maintaining this upward tilt, slowly and precisely push the steel box girder 8 until its front end reaches directly above the predetermined drop position of the second pier 2.

[0061] Begin the beam lowering procedure: gradually and in stages release the tension of the ties, and simultaneously fine-tune the vertical support force of each support point, especially the walking-type jacking equipment 6 on the temporary pier near the front end, so that the front end of the steel box girder 8 can be lowered smoothly and slowly until it is fully supported on the second side pier 2, completing the jacking of the entire bridge; finally, remove the ties, tower top supports and brackets and other temporary facilities.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the appended claims and their equivalents.

Claims

1. A method for constructing a steel box girder using a tower-mounted multi-cable jacking system, characterized in that: Includes the following steps: An assembly support system is installed between the first side pier (1) and the main tower (3); The steel box girder (8) is assembled based on the assembly support system until the front end of the assembled steel box girder (8) extends to the position of the main tower (3); Continue to push the steel box girder (8) so that it passes through the main tower (3) along the longitudinal direction of the bridge and extends to the first preset length to form the first cantilever state; Install the first cable (11) on the main tower (3) and connect the two ends of the first cable (11) to the steel box girder (8) located on both sides of the main tower (3); Continue to push the steel box girder (8) along the longitudinal direction of the bridge, and simultaneously assemble the subsequent segments at the tail end of the steel box girder (8) on the assembly support system; When the conditions for installing the second cable are met, the second cable (15) is installed on the main tower (3), and the two ends of the second cable (15) are connected to the steel box beams (8) on both sides of the main tower (3); Repeat the above steps of jacking, assembling and adding fastening cables until the front end of the steel box girder (8) moves to the second side pier (2).

2. The construction method for a tower-mounted multi-cable coordinated jacking of a steel box girder according to claim 1, characterized in that: The method of setting up an assembly support system between the first side pier (1) and the main tower (3) includes: setting up an assembly bracket (4) and multiple temporary piers (5) in the construction area between the first side pier (1) and the main tower (3); the assembly bracket (4) and multiple temporary piers (5) are arranged sequentially at intervals along the bridge direction, and the assembly bracket (4) is set close to the first side pier (1) for the assembly operation of the steel box girder (8) segment; and installing a walking jacking device (6) on the assembly bracket (4) and each temporary pier (5).

3. The construction method for a tower-mounted multi-cable coordinated jacking of a steel box girder according to claim 2, characterized in that: The method for assembling the steel box girder (8) based on the assembly support system includes: assembling the steel box girder (8) section by section on the assembly support (4); pushing the assembled steel box girder (8) section forward using the walking jacking device (6) on the assembly support (4) so ​​that its front end is supported on the adjacent temporary pier (5); repeating the above assembly and jacking steps until the front end of the steel box girder (8) moves to the position of the main tower (3).

4. The construction method for a tower-mounted multi-cable coordinated jacking of a steel box girder according to claim 3, characterized in that: A bracket (7) is pre-built on the main tower (3); the front end of the steel box girder (8) moves along the bridge direction to the bracket (7) under the action of the walking jacking device (6).

5. The construction method for a tower-mounted multi-cable coordinated jacking of a steel box girder according to claim 4, characterized in that: The method of continuing to push the steel box girder (8) so that it passes through the main tower (3) along the bridge direction and extends to the first preset length includes: pushing the steel box girder (8) along the bridge direction until the length of the front end of the steel box girder (8) extending out of the bracket (7) reaches the preset cantilever length allowed by the design under the current working conditions.

6. The construction method for a tower-mounted multi-cable coordinated jacking of a steel box girder according to claim 1, characterized in that: The method of installing the first fastening cable (11) on the main tower (3) includes: installing a support frame (10) and a guide wheel (9) on the top of the main tower (3); installing lugs (13) on the steel box girder (8) at the design position corresponding to the first fastening cable (11); placing the middle part of the first fastening cable (11) on the guide wheel (9); connecting the two ends of the first fastening cable (11) to the corresponding lugs (13) on the steel box girder (8) on both sides of the main tower (3); and using a winch (12) set on the steel box girder (8) to tension and adjust the first fastening cable (11).

7. The construction method for a tower-mounted multi-cable coordinated jacking of a steel box girder according to claim 6, characterized in that: The first tie cable (11) includes two steel cables arranged symmetrically around the centerline of the steel box girder (8) along the bridge direction.

8. The construction method for a tower-mounted multi-cable coordinated jacking of a steel box girder according to claim 6, characterized in that: The method of installing a support frame (10) and guide wheels (9) on the top of the main tower (3) includes: installing a support frame (10) on the top of the main tower (3), and installing multiple sets of guide wheels arranged at intervals along the transverse bridge direction on the upper end of the support frame (10), each set of guide wheels including multiple guide wheels (9) arranged at intervals along the longitudinal bridge direction.

9. A method for constructing a steel box girder using a multi-cable-stayed tower-mounted jacking system according to claim 6, characterized in that: The method for moving the front end of the steel box girder (8) to the second side pier (2) includes: when the front end of the steel box girder (8) is pushed to near the second side pier (2), the first tie cable (11) is tensioned by the tensioning system connected to the first tie cable (11), and the front end of the steel box girder (8) is adjusted to make it slightly upturned; the steel box girder (8) is pushed until the front end of the steel box girder (8) moves above the predetermined beam drop position of the second side pier (2); the tension of the tensioning system is gradually released, and the walking-type jacking device is simultaneously fine-tuned so that the front end of the steel box girder (8) falls smoothly and is supported on the second side pier (2).

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