Construction method for long-distance and large longitudinal slope steel trough beam bidirectional incremental launching closure

Abstract

The application discloses a long-distance large longitudinal slope steel trough beam bidirectional incremental launching closure construction method, and is used to solve the problems of high incremental launching support pier and large closure additional stress in the prior art. The incremental launching assembling platform is erected on the middle pier of the bridge, the first and second main beams are formed by bidirectional incremental launching to the two sides respectively, and the closure section space is reserved. When the closure is performed, the closure section steel beam is welded and fixed with one side main beam, and the temporary hinged bracket is installed on the other side to form a temporary hinged structure; then the temporary support is removed, the main beam is deformed freely under the action of the dead weight to release the residual stress; finally, the other side ring opening welding is completed, and the hinged bracket is removed. The application avoids the risk of high support pier through bidirectional incremental launching, effectively eliminates the additional stress after closure through the closure process of 'hinged + stress release', makes the stress state of the completed bridge consistent with the design, has high linear control precision, is safe and reliable in construction, and is especially suitable for the construction of large longitudinal slope long-distance steel trough beam bridges.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, specifically to a method for bidirectional jacking and closure of a long-distance, steeply sloping steel trough beam. Background Technology

[0002] In the construction of long-span steel trough beam bridges, the incremental launching method has become the mainstream construction technique for large-span, long-span steel structure bridges due to its advantages such as fast construction speed, easy control of the bridge alignment, and minimal impact on traffic and the environment below the bridge. Traditional incremental launching construction of long-span steel trough beams mostly adopts the conventional unidirectional launching process, that is, assembling the main beam segment by segment along the longitudinal axis of the bridge from one end to the other, and then continuously pushing it forward with jacks to gradually slide the main beam into place. This process is mature, reliable, and simple, and is widely used in bridges with flat slopes or slight longitudinal slopes.

[0003] However, for long-span, multi-span continuous steel channel beams with steep longitudinal slopes, the applicability of conventional unidirectional jacking technology is significantly reduced. During the jacking process, the main beam will generate a large longitudinal component force, and the reaction force distribution at the jacking support points will be extremely uneven. To meet the requirements for jacking force and alignment control, the temporary supports above the jacking jacks will reach a height of 2-3 meters. The excessively large height-to-width ratio of these supports results in poor overall stability, making them highly susceptible to instability, displacement, and even overturning during the jacking and sliding process. This introduces significant uncertainty regarding construction safety and structural controllability.

[0004] Meanwhile, traditional unidirectional jacking closure often adopts forced alignment and direct welding closure methods. During closure, the main beam is difficult to achieve free deformation and stress release, which easily generates large additional axial force, additional bending moment and constraint stress at the closure section. This results in a significant deviation between the actual stress state of the main beam after the bridge is completed and the design theoretical state, affecting the structural durability and linear smoothness.

[0005] Currently, the existing conventional unidirectional jacking process cannot solve the safety hazards caused by excessively high temporary supports under the large longitudinal slope conditions of this project, nor can it achieve the control target of no additional stress on the main beam and complete consistency with the design after closure. Therefore, developing a construction method suitable for long-span steel channel beams on large longitudinal slopes, avoiding the risks of high supports, and achieving closure without additional stress has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a method for bidirectional jacking and closure of long-distance, steeply sloping steel channel beams.

[0007] The technical solution of this invention is: a method for bidirectional jacking closure of a long-distance, steeply sloping steel trough beam, comprising the following steps: A jacking and assembly platform is erected in the middle pier area of ​​the bridge. Steel channel beams are jacked bidirectionally towards both ends of the bridge on the jacking and assembly platform to form the first main beam and the second main beam. Space is reserved in the jacking and assembly platform area for the installation of the closure section. Adjust the elevation of the first and second main beams that have been pushed into place, including adjusting the main beams to the design elevation and lowering the elevation of the steel beams at the pier top support points adjacent to the closure section by a predetermined displacement. Hoist the closure section steel beam to the reserved installation space for the closure section, and weld and fix the closure section steel beam to the ring of the main beam on one side; A hinged bracket is installed between the closure section steel beam and the main beam on the other side, so that the closure section steel beam and the main beam on the other side form a temporary hinged structure. Remove the temporary supports in the jacking assembly platform area to release the residual stress generated by the jacking construction and the constraints of the temporary supports; After the stress is released, weld the closure section of the steel beam to the ring joint of the main beam on the other side, and remove the hinged bracket; Adjust the elevation of the main beam to restore it to its designed stress state; The elevation of the entire steel channel beam was adjusted uniformly to ensure that the main beam alignment met the design requirements.

[0008] According to the bidirectional jacking and closure construction method for long-distance, steeply longitudinally slope steel trough beams provided by this invention, the method of bidirectionally jacking the steel trough beams towards both ends of the bridge includes: Assemble steel beam segments towards the greater mileage direction on the jacking assembly platform and install guide beams, then jack them into place in the greater mileage direction to form the first main beam segment; The guide beam is turned back to the jacking and assembly platform, and the steel beam segments in the direction of the smaller mileage are assembled. The segments are then jacked into place in the direction of the smaller mileage to form the second main beam.

[0009] According to the bidirectional jacking and closure construction method of long-distance, large longitudinal slope steel channel beam provided by the present invention, the method for adjusting the elevation of the first and second main beam sections that have been jacked into place includes: adjusting the first and second main beam sections that have been jacked into place to the design elevation, and lowering the elevation of the steel beam at the pier top support point on the side close to the closure section installation space by a preset displacement.

[0010] According to the bidirectional jacking closure construction method for long-distance, steeply longitudinal steel channel beams provided by this invention, the pier top support is the top support of the pier adjacent to the installation space of the closure section; the preset displacement is the displacement value determined according to the stress calculation of the bridge structure, which is used to provide displacement adjustment space for subsequent closure section docking, welding and stress release.

[0011] According to the bidirectional jacking closure construction method for long-distance, steeply longitudinal steel channel beams provided by this invention, the first welded ring is the ring between the closure section steel beam and the main beam on the lower mileage side, thus achieving a rigid connection on that side.

[0012] According to the bidirectional jacking closure construction method for long-distance steel channel beams with large longitudinal slopes provided by this invention, the hinged bracket is installed at the ring position between the steel beam of the closure section and the main beam in the large mileage direction. The temporary hinged structure allows the main beam to generate a small amount of rotation and displacement while ensuring vertical force transmission.

[0013] According to the bidirectional jacking and closure construction method for long-distance, steeply longitudinal steel channel beams provided by this invention, the method for releasing the residual stress generated by the jacking construction and temporary support constraints includes: removing the temporary supports in the jacking assembly platform area, allowing the main beam to sink freely under its own weight and adaptively adjust its alignment, thereby releasing the residual stress generated by the jacking construction and temporary support constraints, and making the main beam approach a stress-free state.

[0014] According to the bidirectional jacking closure construction method for long-distance, large longitudinal slope steel channel beams provided by this invention, the method of adjusting the elevation of the main beam to restore the main beam to the designed stress state includes: raising the steel beam that has fallen before closure by the preset displacement to offset the displacement difference reserved in the closure stage, so that the stress of the structure after the bridge is completed is consistent with the design.

[0015] According to the bidirectional jacking and closure construction method for long-distance steel channel beams with large longitudinal slopes provided by this invention, the method for uniformly adjusting the elevation of the entire steel channel beam includes: uniformly adjusting the elevation of the entire steel channel beam according to the construction monitoring instructions, and accurately adjusting the elevation, longitudinal slope and axis of the main beam to the design target position.

[0016] According to the bidirectional jacking and closure construction method for long-distance steel channel beams with large longitudinal slopes provided by this invention, before adjusting the first and second main beams that have been jacked into place to the design elevation, the axis, elevation and longitudinal slope of the first and second main beams are initially adjusted so that the overall alignment of the main beams initially meets the design longitudinal slope and elevation requirements.

[0017] The advantages of this invention are: 1. It solves the risk of unidirectional jacking of support piers on steep longitudinal slopes. The intermediate jacking platform is used for segmented bidirectional jacking, replacing the traditional full-length unidirectional jacking. This avoids the instability risk caused by temporary supports as high as 3m due to the large longitudinal slope, and significantly improves the safety and stability of the jacking construction.

[0018] 2. Truly achieve stress-free closure Through the pre-drop of the fulcrum, the hinged transition, the free fall beam unloading, and the fulcrum return to its original position, the main beam is in a natural stress state during the closure welding, without forced alignment. After the bridge is completed, there is no additional bending moment or additional axial force, and the stress state is completely consistent with the design.

[0019] 3. High linear control precision and strong adjustability By adopting step-by-step elevation adjustment and full-process monitoring and command control, the longitudinal slope, elevation, and axis deviation of the main beam are controllable, resulting in high closure accuracy and a smooth bridge alignment.

[0020] 4. Reasonable construction procedures and controllable construction risks The hinged structure preserves the adjustability of the system during the closure phase, avoiding irreversible stress deviations caused by one-time welding. The overall process is safe and controllable, with strong applicability, and can provide a reference for similar long-span steel channel beam projects with large longitudinal slopes. Attached Figure Description

[0021] Figure 1 Flowchart of the bidirectional jacking and closure construction method for long-distance, steeply longitudinal steel trough beams according to the present invention; Figure 2 : A schematic diagram of the first main beam assembly construction of this invention; Figure 3 : A schematic diagram of the assembly and construction of the second main beam of this invention; Figure 4 : A schematic diagram showing the completion of the jacking of the first and second main beams of this invention; Figure 5 : A schematic diagram of the construction of the steel beam segment above the platform of this invention; Figure 6 : Construction schematic diagram of the closure section steel beam and hinged bracket of the present invention; Wherein: 1—jacking assembly platform; 2—jacking jack; 3—guide beam; 4—first main beam section; 5—second main beam section; 6—steel beam segment above the platform; 7—closing section steel beam; 8—hinged bracket. Detailed Implementation

[0022] Embodiments of the present invention 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 the present invention, and should not be construed as limiting the present invention.

[0023] In the description of this invention, 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 invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] 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 invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] This invention provides a method for constructing a long-distance, steeply sloping steel channel beam with bidirectional jacking closure. A jacking assembly platform is erected in the middle pier area of ​​the bridge, and the first and second main beams are formed by bidirectional jacking in both directions (high and low mileage), reserving space for the closure section installation. After jacking into place, preliminary alignment adjustments are made, and the main beams are precisely adjusted to the design elevation. The steel beams at the adjacent pier top support points of the closure section are lowered by a predetermined displacement. After hoisting the closure section steel beam, it is first welded and fixed to the main beam ring on the low mileage side. Then, a hinged bracket is installed on the high mileage side to form a temporary hinged structure. Subsequently, the temporary support is removed, allowing the main beam to sink freely under its own weight, fully releasing the residual stress generated by the jacking and temporary support constraints. After stress release, the ring on the high mileage side is welded and the hinged bracket is removed. The lowered steel beam is then raised back to the predetermined displacement, restoring the main beam to its design stress state. Finally, according to construction monitoring instructions, the elevation of the entire steel channel beam is uniformly adjusted to ensure that the main beam elevation, longitudinal slope, and axis accurately meet the design requirements. This method achieves stress-free closure, ensures that the stress on the completed bridge is completely consistent with the design, has high precision in alignment control, avoids the risk of instability of high piers, and ensures controllable construction safety. It is suitable for long-distance steel channel beam projects with large longitudinal slopes.

[0027] Specifically, a method for bidirectional jacking closure of long-distance, steeply sloping steel trough beams, such as... Figure 1 As shown, the specific steps include: S1. Construct a jacking assembly platform 1 in the middle pier area of ​​the bridge (e.g., Figure 2 As shown, in this embodiment, a jacking assembly platform 1 is erected between piers #3 and #4, and jacking jacks 2 are installed on the jacking assembly platform 1. The steel channel beam is jacked bidirectionally towards both ends of the bridge (along the bridge direction) on the jacking assembly platform 1 to form the first main beam 4 and the second main beam 5. Space is reserved in the area of ​​the jacking assembly platform 1 for the installation of the closure section (e.g., ...). Figure 5 A is shown.

[0028] S2. Adjust the elevation of the first main beam 4 and the second main beam 5 that have been pushed into place to meet the requirements for subsequent closure.

[0029] S3. Hoist the closure section steel beam 7 to the reserved closure section installation space, and first weld and fix the closure section steel beam 7 to the ring of one of the main beams (e.g., the left main beam) to form a rigid connection.

[0030] S4. Install a hinged bracket 8 between the closure section steel beam 7 and the main beam on the other side (e.g., the right main beam) to form a temporary hinged structure between the closure section steel beam 7 and the main beam on the other side. This hinged structure can transmit vertical forces while allowing the main beam to undergo slight rotation and axial displacement in the horizontal direction.

[0031] S5. Remove the temporary supports in area 1 of the jacking assembly platform to allow the main beam to sink naturally under its own weight, releasing the residual stress generated in the beam body by the jacking construction and the constraints of the temporary supports.

[0032] S6. After the residual stress has been fully released, weld the closure section steel beam 7 firmly to the ring joint of the main beam on the other side, and then remove the hinged bracket 8.

[0033] S7. Readjust the main beam elevation to restore the main beam to its designed stress state.

[0034] S8. Adjust the elevation of the entire steel channel beam uniformly to ensure that the alignment of the main beam of the entire bridge (including longitudinal slope, elevation, and axis) meets the design requirements.

[0035] In practical applications, if the length of the jacking assembly platform 1 is too long, after the jacking operation of the first main beam 4 is completed, the first main beam 4 can be completely detached from the jacking assembly platform 1. Subsequently, the assembly and jacking operation of the second main beam 5 can be carried out on the jacking assembly platform 1. After the jacking operation of the second main beam 5 is completed, the second main beam 5 will be completely detached from the jacking assembly platform 1, and the area above the jacking assembly platform 1 will be empty. At this time, steel beam segments can continue to be assembled based on the jacking assembly platform 1 to form the steel beam segment 6 above the platform (e.g., Figure 5 As shown in the diagram, after the steel beam segment 6 above the platform is assembled, it can be connected with the first main beam 4 to form a new first main beam 4. At this time, the reserved installation space for the closure section is actually the space between the second main beam 5 and the steel beam segment 6 above the platform. This space can be located directly above the jacking assembly platform 1 or diagonally above the jacking assembly platform 1, depending on the actual construction requirements.

[0036] Under steep longitudinal slopes, traditional unidirectional jacking can lead to excessively high temporary supports, and the forced alignment during closure can generate additional stress. The construction method of this invention shortens the unilateral jacking length and reduces the support height by jacking the intermediate pier in both directions. Simultaneously, by employing a sequence of welding one side first, hinged to the other side, releasing stress, and then welding the other side, the closure segment is not rigidly constrained before stress release, allowing the beam to deform freely and thus eliminating residual stress. Finally, two elevation adjustments achieve stress recovery and alignment fine-tuning, respectively.

[0037] The construction method of this invention can significantly reduce the safety risks of jacking construction on a large longitudinal slope and avoid instability of high piers; achieve closure without additional stress, and ensure that the structural stress of the completed bridge is completely consistent with the design; achieve high precision in alignment control through step-by-step elevation adjustment, resulting in a smooth and aesthetically pleasing bridge alignment; and ensure that the overall process is reasonable and the construction risks are controllable.

[0038] In some embodiments of the present invention, this embodiment refines the bidirectional pushing method in step S1. Specifically, it includes: S11. On the top-pushing assembly platform 1, such as Figure 2 As shown, the steel beam segments are first assembled in the direction of the greater mileage (e.g., the end of the bridge), and a guide beam 3 is installed at the front end to reduce the cantilever bending moment. Then, the jacking equipment is started to push the steel beam segments together with the guide beam 3 in the direction of the greater mileage segment by segment until all steel beam segments on that side are pushed into place, forming the first main beam 4.

[0039] S12. Remove guide beam 3 from the high mileage end and reverse its direction, as follows: Figure 3 As shown, the steel beam segments are transported back to the jacking assembly platform 1. On the jacking assembly platform 1, the steel beam segments moving towards the smaller mileage direction (e.g., the direction of the bridge's starting point) are reassembled, and guide beams 3 are installed (at this time, guide beams 3 face the smaller mileage direction). Then, the segments are jacked one by one towards the smaller mileage direction until all steel beam segments on that side are in place, forming the second main beam 5, as shown. Figure 4 As shown.

[0040] S13. At this point, space is left in area 1 of the jacking assembly platform for the installation of the closure section. The closure is then completed following the steps described above.

[0041] Using the same jacking equipment and guide beams for directional and time-sharing operations avoids the need for two sets of guide beams for bidirectional jacking, reducing equipment costs. Resource sharing is achieved by turning the guide beams around. Jacking in the high-mileage and low-mileage directions separately allows for independent control of the alignment on each side, avoiding mutual interference caused by simultaneous bidirectional jacking.

[0042] This embodiment features flexible construction organization and high equipment utilization, making it particularly suitable for the construction of long-distance steel channel beams with steep longitudinal slopes. The guide beam turning operation is mature and reliable, effectively controlling the cantilever bending moment during the jacking process and ensuring structural safety.

[0043] In other embodiments of the present invention, this embodiment optimizes the method for adjusting the elevation of the first main beam 4 and the second main beam 5 that have been jacked into place in step S2 above, specifically: S21. Adjust the first main beam section 4 and the second main beam section 5, which have been jacked into place, to the design elevation. Jacks can be used to lift or lower the beams at the pier top support points, in conjunction with elevation monitoring equipment, to ensure that the elevations of each control point of the main beam match the design values.

[0044] S22. Determine the top support point of the pier adjacent to the installation space of the closure section (i.e., the pier top support point). Figures 2-5 (See the support point at the top of pier #3 shown). The elevation of the steel beam at this support point will be artificially lowered by a predetermined displacement. This predetermined displacement is determined based on the stress calculation of the bridge structure, and can be, for example, 10mm to 50mm. The specific value is obtained through finite element analysis and is used to provide displacement adjustment space for subsequent closure section connection, welding, and stress release. The elevation of the main beam at other supports remains unchanged.

[0045] Adjusting the main beam to the design elevation first ensures the accuracy of the overall alignment after closure. Then, lowering the adjacent pier top supports by a predetermined displacement artificially creates a lower point, allowing the closure section to be in a relaxed state during installation. When the temporary supports are subsequently removed, the main beam will sink under its own weight; this predetermined displacement provides space for this sinking, preventing damage to the beam due to forced descent. Simultaneously, the lowering amount can also be used to adjust the annular gap of the closure section, facilitating alignment and welding.

[0046] This embodiment employs a two-step method of leveling before lowering, ensuring both the initial accuracy of the main beam's alignment and providing controllable deformation space for stress release. The preset displacement is determined based on design calculations, which is scientific and reasonable, avoiding excessive structural deformation caused by blind lowering and ensuring construction safety.

[0047] In a further embodiment of the present invention, this embodiment defines the first welded ring as the ring between the closure section steel beam 7 and the main beam on the low mileage side. The specific method is as follows: After the closure section steel beam 7 is hoisted into place, the lower mileage end of the closure section steel beam 7 (i.e. the end closer to the starting point of the bridge) is first aligned with the ring of the main beam that has been pushed into place on the lower mileage side.

[0048] The ring position is fixed by using matching processes (such as temporary alignment plates, positioning pins, etc.), and then full-section welding is performed to form a rigid connection on this side.

[0049] After the welding on the low mileage side is completed, there is still a gap between the high mileage end of the closure section steel beam 7 and the high mileage side main beam, and the hinged bracket 8 will be installed subsequently.

[0050] The choice of the lower mileage side as the first welding side is based on construction habits or terrain conditions (e.g., the lower mileage side has an open site, facilitating welding operations). Welding one side first creates a rigid fixation, ensuring the basic spatial positioning of the closure segment steel beam 7 and preventing overall displacement. Retaining a hinge on the other side allows the beam to freely expand and contract during subsequent stress release.

[0051] This embodiment clarifies the selection criteria for the side to be welded first, providing a clear direction for the construction operation. Welding one side first can improve the installation stability of the closure segment, prevent unexpected displacement of the closure segment before stress release, and at the same time, it does not affect the function of the hinge on the other side.

[0052] In a preferred embodiment of the present invention, this embodiment describes in detail the installation position and structural function of the articulated bracket 8. Specifically, it includes: like Figure 6 Therefore, the articulated bracket 8 is installed at the annular position between the closure section steel beam 7 and the main beam in the high-mileage direction. The articulated bracket 8 consists of an upper bracket, a lower bracket, and a pin. The upper bracket is welded to the end of the closure section steel beam 7, and the lower bracket is welded to the end of the main beam in the high-mileage direction. The two are connected by a horizontal pin.

[0053] This temporary hinged structure forms a hinge in the vertical force transmission path, meaning it only transmits shear force (vertical force) and not bending moment. At the same time, due to the clearance and rotational freedom of the pin, the main beam is allowed to undergo slight rotation (i.e., angle of rotation) and axial displacement (expansion and contraction) in the longitudinal direction.

[0054] During the subsequent removal of temporary supports and release of residual stress, the main beam on the high mileage side can rotate freely and move slightly axially relative to the closure section steel beam 7, thereby avoiding the generation of additional bending moments.

[0055] Traditional rigid closure methods lock the residual stress accumulated during the jacking process within the beam. This embodiment uses a hinged bracket 8 to transform one side of the ring into a movable hinge, effectively giving the beam a chance to relax. After the temporary support is removed, the beam naturally adjusts its alignment under its own weight. Any residual stress will drive the beam to produce slight displacement or rotation until the internal stress tends to be uniform. The hinged structure does not resist rotation, therefore it does not generate new additional stress.

[0056] The articulated bracket 8 in this embodiment has a simple structure and clear force transmission, reliably achieving the goal of stress release. Vertical force transmission ensures that the closure segment will not fall under its own weight, while rotational and displacement degrees of freedom ensure that residual stress is fully released. Compared with traditional rigid closure, this embodiment significantly reduces the additional stress on the completed bridge and improves structural durability.

[0057] In some embodiments of the present invention, this embodiment details a specific method for releasing residual stress generated by the jacking construction and temporary support constraints. This includes: It has been confirmed that all temporary supports in area 1 of the jacking assembly platform (including temporary pads on the pier top, steel pipe support frames, etc.) are ready for removal.

[0058] The temporary supports were dismantled gradually, proceeding from the middle to both ends or from one side to the other. Synchronous unloading technology was used during the dismantling process to avoid impact.

[0059] After all temporary supports were removed, the main beam began to sink freely under its own weight. Due to the different settlement at each support point, the main beam's alignment would adjust adaptively, and the residual constraints such as the original jacking traction force and support reaction force within the beam would gradually disappear.

[0060] Once the main beam has settled and stabilized (usually requiring a period of time, such as 2-4 hours, and monitoring to ensure the deformation no longer changes), the internal stress of the main beam is close to a stress-free state (i.e., only subjected to bending stress caused by its own weight, without additional axial force or bending moment).

[0061] During the jacking construction process, residual stress will be generated in the beam due to factors such as traction, jacking, and uneven temporary support. This stress is locked in by the temporary support. After the support is removed, the beam, as a statically determinate or statically indeterminate structure, will redistribute its internal forces through its own deformation (sinking, rotation) until the equilibrium condition is met. At this point, the residual stress is released, and the beam is in a natural state of self-weight stress.

[0062] This embodiment achieves automatic release of residual stress through a simple support removal operation, requiring no additional equipment or complex processes. The free-sinking process adaptively adjusts the alignment to ensure that the beam's state before closure is as close as possible to the theoretical stress-free state, thereby guaranteeing that the stress on the completed bridge after welding is consistent with the design.

[0063] In other embodiments of the present invention, this embodiment optimizes the method of adjusting the main beam elevation to restore the main beam to its designed stress state, specifically, how to lift the steel beam that has fallen before closure back to the preset displacement. This includes: After the steel beam 7 of the closure section is welded to the ring of the main beam on the high mileage side and the hinged bracket 8 is removed, the steel beam at the pier top support point with the previously lowered preset displacement is lifted.

[0064] Using synchronous lifting jacks, the steel beam at the fulcrum is slowly and evenly raised, with the amount of raising exactly equal to the preset displacement during the previous fall.

[0065] During the lifting process, the changes in the internal forces of the main beam and the reaction forces at the supports are monitored to ensure that the stress state of the entire bridge after lifting is consistent with the design calculations.

[0066] After raising the object to its position, insert a permanent pad or pour a bearing pad stone at the fulcrum to lock the elevation.

[0067] Before the bridge closure, the pier top support was intentionally lowered by a predetermined displacement to provide deformation space for stress release. After stress release, the steel beam at this support point was actually in a low position. If it was not reset, the support point would not reach the design elevation after the bridge is completed, leading to an altered stress state (such as the generation of negative bending moment). By raising it by the same amount of displacement, the previously reserved displacement difference was precisely offset, restoring the main beam to the design stress state and ensuring that the structural stress after the bridge is completed is completely consistent with the design.

[0068] This embodiment realizes the complete process of lowering, releasing, and lifting, ensuring that the closure construction does not affect the final bridge's stress distribution. The lifting amount is equal to the lowering amount, the logic is clear, the operation is simple, and it can be precisely controlled by jacks, resulting in high reset accuracy. This method avoids the additional stress problems caused by forced alignment in traditional closure methods.

[0069] In a further embodiment of the present invention, this embodiment illustrates a specific method for uniformly adjusting the elevation of the entire steel channel beam. This includes: S81. After completing all closure welding, removing the articulated brackets 8, and repositioning, a full-bridge construction monitoring system is set up, including setting up elevation monitoring points, axis monitoring points, and strain gauges at each pier top and mid-span.

[0070] S82. According to the construction monitoring instructions, the monitoring center issues a unified target value for elevation adjustment. This target value is calculated based on the completed bridge alignment design documents and measured data, and usually needs to take into account factors such as longitudinal slope, vertical curve, and pre-camber.

[0071] S83. Install hydraulic jacks at each pier top support point and perform lifting or lowering operations in batches and stages according to monitoring instructions. For multi-support structures, use a synchronous control system to ensure coordinated lifting and lowering of each support point.

[0072] S84. During the adjustment process, the elevation, longitudinal slope, and axis deviation of each measuring point are fed back in real time. The monitoring system performs closed-loop control based on the deviation until all parameters reach the design target position.

[0073] S85. Lock the support and pour the pad stone to complete the final linear fixation.

[0074] Due to the unavoidable errors during the jacking, closure, and stress release processes (such as jacking positioning errors, welding deformation, and temperature effects), the final bridge alignment may deviate from the design. This embodiment uses construction monitoring commands for unified adjustments, essentially utilizing the adjustable margins at each support point to perform a final, precise adjustment of the entire bridge alignment, eliminating accumulated errors and ensuring that the alignment, longitudinal slope, and axis simultaneously meet the design requirements.

[0075] This embodiment achieves high-precision control of the bridge alignment, significantly improving the quality of the completed bridge. Closed-loop adjustment driven by monitoring commands can correct deviations in real time, avoiding human error. After unified elevation adjustment, the main girder has a smooth longitudinal slope, accurate elevation, and straight axis, resulting in an aesthetically pleasing bridge alignment and good driving comfort.

[0076] In other embodiments of the present invention, this embodiment describes a specific method for performing preliminary adjustments before adjusting the main beam to the design elevation. This includes: (1) After the first main beam 4 and the second main beam 5 are pushed into place, the axis, elevation and longitudinal slope of each main beam are checked immediately.

[0077] (2) Use the jacks or pads at the temporary support points on the pier top to make rough adjustments to the main beam: control the axial deviation of the main beam within ±10mm, the elevation deviation within ±20mm, and the longitudinal slope roughly conforms to the design slope (allowable deviation ±0.1%).

[0078] (3) This preliminary adjustment applies only to the segmented main beams themselves and does not involve the closure section. After the adjustment, the overall alignment of the main beams should initially meet the design longitudinal slope and elevation requirements, creating a good foundation for subsequent precise adjustments and closure.

[0079] After the main beam is jacked into place, there may be significant positional deviations (e.g., due to jacking slippage errors, temperature deformation, pier construction errors, etc.). Directly performing precise adjustments could lead to difficulties or exceed adjustment limits due to excessive initial deviations. By first making preliminary adjustments to bring the alignment of each main beam segment closer to the design alignment, the adjustment range is narrowed, making subsequent precise adjustments smoother and more efficient, and avoiding excessive impact on the closure section's ring gap.

[0080] This embodiment employs a tiered adjustment strategy of initial and fine-tuning, reducing the difficulty and risk of a single adjustment. Initial adjustments quickly eliminate large deviations, while subsequent precise adjustments require only minor tweaks, improving construction efficiency and adjustment accuracy. Simultaneously, the main beam alignment after the initial adjustment is closer to the final design, facilitating the hoisting and alignment of the closure section steel beam 7 and reducing misalignment at the circumference.

[0081] Specifically, such as Figure 1 As shown, the incremental launching and closure construction method for long-distance, steeply longitudinal slope steel trough beam bridges of the present invention can be carried out according to the following steps: Step 1: Construction preparation and jacking platform erection A jacking assembly platform 1 is erected in the middle pier area of ​​the bridge (usually near the approximate midpoint of the bridge's total length). This platform should have sufficient load-bearing capacity, flatness, and assembly space. Meanwhile, jacking slides, jacks, and alignment devices are installed on each permanent and temporary pier of the bridge.

[0082] Step 2: Bidirectional jacking to form two main beam sections. (1) Pushing forward in a high-mileage direction: such as Figure 2 As shown, steel beam segments are assembled on the jacking assembly platform 1 towards the greater mileage direction, with guide beam 3 installed at the front end. A multi-point synchronous jacking system is used to push the steel beam segments one by one towards the greater mileage direction until all segments on that side are in place, forming the first main beam 4.

[0083] (2) Guide beam turning around: such as Figure 3As shown, the guide beam 3 at the high mileage end is removed, its direction is reversed, and it is transported back to the jacking assembly platform 1.

[0084] (3) Pushing forward in the direction of small mileage: such as Figure 4 As shown, steel beam segments are assembled on the jacking assembly platform 1 in the direction of the smaller mileage, and guide beam 3 (facing the smaller mileage) is reinstalled. This process is repeated segment by segment until the second main beam 5 is formed.

[0085] (4) Assemble the steel beam segment 6 above the jacking assembly platform 1, such as Figure 5 As shown, the steel beam segment 6 above the platform is connected to the first main beam 4. At this time, a space is left between the steel beam segment 6 above the platform and the second main beam 5 (i.e., near the intermediate pier) for the installation of the closure section, the length of which is equal to the design length of the closure section steel beam 7.

[0086] Step 3: Preliminary Linear Adjustment Preliminary adjustments were made to the axis, elevation, and longitudinal slope of the first main beam segment 4 and the second main beam segment 5, which had already been jacked into place. Using jacks or wedge-shaped pads on the temporary supports on the pier top, the axis deviation of each main beam segment was controlled within ±10mm, the elevation deviation within ±20mm, and the longitudinal slope deviation within ±0.1%, so that the overall alignment of the main beam initially met the design requirements for longitudinal slope and elevation.

[0087] Step 4: Precisely adjust the elevation and pre-drop. (1) The first main beam 4 and the second main beam 5 were precisely adjusted to the design elevation. A precision level and a total station were used for monitoring. At each pier support point, the elevation of each control point of the main beam was finely adjusted by jacks to make it match the design value, with an allowable deviation of ±5mm.

[0088] (2) Determine the pier top support point adjacent to the installation space of the closure section (i.e., the first permanent or temporary pier top support point on both sides of the closure section). Based on the preset displacement calculated in the design (e.g., 30mm), lower the elevation of the steel beam at this support point by that displacement. The lowering is achieved by returning oil to the jack or removing the pad block, and the actual elevation after the lowering is recorded.

[0089] (3) The elevation of the main beam at other support points remains unchanged.

[0090] Step 5: Hoisting and single-sided welding of the closure section steel beam The prefabricated closure section steel beam 7 is hoisted into the reserved closure section installation space. The position of the closure section steel beam 7 is adjusted so that its small mileage end is aligned with the ring opening of the small mileage side main beam (i.e., the second main beam 5). It is temporarily fixed with matching connecting plates. After checking that the ring opening gap and misalignment meet the welding requirements, full-section welding is carried out to form a rigid connection on the small mileage side.

[0091] Step 6: Install hinge bracket 8 to form a temporary hinge. At the annular junction between the high-mileage end of the closure section steel beam 7 and the high-mileage side main beam (i.e., the main beam structure formed by the steel beam segment 6 above the platform and the first main beam 4), a hinged bracket 8 is installed, such as... Figure 6 As shown. The articulated bracket 8 consists of an upper bracket, a lower bracket, and a pin, which are welded to the ends of the closure section steel beam 7 and the main beam on the high mileage side, respectively. After installation, this connection can transmit vertical shear force, but allows the main beam to undergo slight rotation (not exceeding ±0.5°) and axial displacement (±10mm) in the longitudinal direction.

[0092] Step 7: Remove temporary supports and release residual stress. Dismantle all temporary supports (including temporary pads and steel pipe supports at the intermediate piers) in sequence in area 1 of the jacking assembly platform. The dismantling process should be carried out in stages and symmetrically to avoid impact. After all temporary supports are removed, the main beam will begin to sink freely under its own weight. After standing for 2-4 hours, once the deformation of the main beam has stabilized and the reactions at each support point have stabilized, the residual stress in the beam will have been basically released, and the main beam will be close to a stress-free state.

[0093] Step 8: Weld the other side of the ring and remove the hinged bracket 8 After the stress is released, weld the ring joint between the closure section steel beam 7 and the main beam on the high mileage side. Before welding, remove oil and rust from the vicinity of the hinged bracket 8. After welding, wait for the weld to cool to room temperature, then remove the hinged bracket 8 (it can be cut or the connecting bolts can be unscrewed).

[0094] Step 9: Reset and restore the designed stress. The steel beam at the pier top support point, which was lowered in step four, is slowly lifted using synchronous jacks. The lifting amount is equal to the preset displacement (e.g., 30mm) from the initial drop. During the lifting process, the reaction force at the support point and the internal force of the main beam are monitored to ensure that the design values ​​are reached. After lifting to the correct position, permanent supports are installed at the support point or high-strength bearing pads are poured to lock the elevation. At this point, the main beam returns to its designed stress state.

[0095] Step 10: Fine-tune the unified elevation to complete the bridge alignment (in conjunction with claim 9). Based on instructions from the construction monitoring system, a final unified elevation adjustment was performed on the entire steel channel beam. Lifting equipment was deployed at each pier top support point, and the elevation of each point was adjusted in batches according to monitoring instructions, while simultaneously adjusting the longitudinal slope and axis. Closed-loop control was employed until the three-dimensional coordinates of all measuring points met the design targets (elevation error ≤ ±5mm, axis error ≤ ±5mm, longitudinal slope deviation ≤ 0.05%). Finally, the supports were locked, completing the bridge.

[0096] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for bidirectional jacking and closure construction of a long-distance, steeply sloping steel trough beam, characterized in that, Includes the following steps: A jacking and assembly platform is erected in the middle pier area of ​​the bridge. The steel channel beam is jacked bidirectionally towards both ends of the bridge on the jacking and assembly platform to form the first main beam and the second main beam. Space is reserved in the jacking and assembly platform area for the installation of the closure section. Adjust the elevation of the first and second main beam sections that have been jacked into place; Hoist the closure section steel beam to the reserved installation space for the closure section, and weld and fix the closure section steel beam to the ring of the main beam on one side; A hinged bracket is installed between the closure section steel beam and the main beam on the other side, so that the closure section steel beam and the main beam on the other side form a temporary hinged structure. Remove the temporary supports in the jacking assembly platform area to release the residual stress generated by the jacking construction and the constraints of the temporary supports; After the stress is released, weld the closure section of the steel beam to the ring joint of the main beam on the other side, and remove the hinged bracket; Adjust the elevation of the main beam to restore it to its designed stress state; The elevation of the entire steel channel beam was adjusted uniformly to ensure that the main beam alignment met the design requirements.

2. The method for bidirectional jacking and closure of long-distance, steeply sloping steel trough beams according to claim 1, characterized in that, Methods for bidirectionally jacking steel channel beams towards both ends of a bridge include: Assemble steel beam segments towards the greater mileage direction on the jacking assembly platform and install guide beams, then jack them into place in the greater mileage direction to form the first main beam segment; The guide beam is turned back to the jacking and assembly platform, and the steel beam segments in the direction of the smaller mileage are assembled. The segments are then jacked into place in the direction of the smaller mileage to form the second main beam.

3. The method for bidirectional jacking and closure of long-distance, steeply sloping steel trough beams according to claim 1, characterized in that, The method for adjusting the elevation of the first and second main beams that have been jacked into place includes: adjusting the first and second main beams that have been jacked into place to the design elevation, and lowering the elevation of the steel beam at the pier top support point on the side near the installation space of the closure section by a preset displacement.

4. The method for bidirectional jacking and closure of long-distance, steeply sloping steel trough beams according to claim 3, characterized in that, The pier top support point is the top support point of the pier adjacent to the installation space of the closure section; the preset displacement is a displacement value determined according to the stress calculation of the bridge structure, which is used to provide displacement adjustment space for subsequent closure section docking, welding and stress release.

5. The method for bidirectional jacking and closure of long-distance, steeply sloping steel trough beams according to claim 2, characterized in that, The first welded ring is the ring between the closure section steel beam and the main beam on the lower mileage side, achieving a rigid connection on that side.

6. The method for bidirectional jacking and closure of long-distance, steeply sloping steel trough beams according to claim 2, characterized in that, The articulated bracket is installed at the ring position between the steel beam of the closure section and the main beam in the high-mileage direction. The temporary articulated structure allows the main beam to rotate and displace slightly while ensuring vertical force transmission.

7. The method for bidirectional jacking and closure of long-distance, steeply sloping steel trough beams according to claim 1, characterized in that, The method for releasing the residual stress generated by the jacking construction and temporary support constraints includes: removing the temporary supports in the jacking assembly platform area, allowing the main beam to sink freely under its own weight and adaptively adjust its alignment, thereby releasing the residual stress generated by the jacking construction and temporary support constraints, and bringing the main beam close to a stress-free state.

8. The method for bidirectional jacking and closure of long-distance, steeply sloping steel trough beams according to claim 4, characterized in that, The method for adjusting the elevation of the main beam to restore it to the designed stress state includes: raising the steel beam that was lowered before closure by the preset displacement to offset the displacement difference reserved during the closure stage, so that the stress of the structure after the bridge is completed is consistent with the design.

9. The method for bidirectional jacking and closure of long-distance, steeply sloping steel trough beams according to claim 1, characterized in that, The method for uniformly adjusting the elevation of the entire steel channel beam includes: uniformly adjusting the elevation of the entire steel channel beam according to the construction monitoring instructions, and accurately adjusting the elevation, longitudinal slope and axis of the main beam to the design target position.

10. The method for bidirectional jacking and closure of long-distance, steeply sloping steel trough beams according to claim 1, characterized in that, Before adjusting the first and second main beam sections, which have already been jacked into place, to the design elevation, preliminary adjustments are made to the axis, elevation, and longitudinal slope of the first and second main beam sections to ensure that the overall alignment of the main beams initially meets the design requirements for longitudinal slope and elevation.

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