A cantilever type steel formwork structure and construction method

Abstract

The application provides a jacking formwork structure of an upper-pitched type steel and a construction method. The jacking formwork structure of the upper-pitched type steel comprises a support assembly, a cantilever bearing assembly, an anti-overturning anchoring assembly, a longitudinal beam assembly and a bottom formwork system. The support assembly comprises first and second vertical columns which are vertically arranged above a top plate of a steel main beam. The cantilever bearing assembly comprises a cantilever beam which is horizontally arranged at the top end of the first and second vertical columns. The anti-overturning anchoring assembly is arranged between the second vertical column and the steel main beam. The longitudinal beam assembly is arranged above the cantilever beam and extends along the longitudinal direction of the bridge. The bottom formwork system is supported and lapped below the cantilever end of the cantilever beam. The pull rod assembly is connected to the longitudinal beam assembly at the upper end and connected to the jacking formwork main beam at the lower end. The construction load is directly transmitted to the top plate of the steel main beam by using the jacking formwork structure of the upper-pitched type steel, and the road resources under the bridge are not occupied, thereby perfectly solving the contradiction between construction and traffic passing in the municipal viaduct reconstruction and eliminating the complex traffic diversion work.

Description

Technical Field

[0001] This invention belongs to the field of elevated composite beam construction technology, and specifically relates to an upward-cantilevered steel formwork structure and construction method. Background Technology

[0002] In traditional composite beam design, the flange areas on both sides of the bridge typically utilize downward-extending steel structures as the formwork for reinforced concrete pouring. However, with the optimization and refinement of bridge design theory, in order to reduce project costs and steel consumption, design units have gradually eliminated permanent steel structure supports at the bottom of the flanges, instead designing the flanges as pure reinforced concrete cantilever structures. Since there are no longer permanent steel structures available at the bottom of the flanges, construction units typically employ traditional ground-supported scaffolding construction techniques to support the flange formwork and the weight of the concrete. However, in practical engineering applications, traditional ground-supported scaffolding construction has the following drawbacks:

[0003] Ground-mounted scaffolding requires extremely limited space on the construction site. In urban centers or elevated road upgrade projects on existing roads, ground traffic is typically very busy. Erecting ground-mounted scaffolding inevitably occupies a large amount of road space, making traffic diversion extremely difficult and severely impacting the travel of surrounding residents and the operation of urban traffic. In addition, if there are underground pipelines on the ground, complex pipeline relocation or protection is required, further restricting the construction progress.

[0004] Ground-mounted scaffolding transfers enormous construction loads directly to the ground, thus placing strict requirements on the foundation's bearing capacity. In areas with weak foundations, large-scale foundation reinforcement is necessary, which not only adds extra procedures but also incurs high foundation treatment costs. Scaffolding at the wing plates typically features "high height, narrow width, and long length," resulting in poor overall stability. The risk of scaffolding instability and collapse is high during concrete pouring. Furthermore, the extensive work area at height presents significant safety hazards such as falls from height and falling objects, placing immense pressure on on-site safety management. Summary of the Invention

[0005] To address the problems of traditional ground-mounted scaffolding solutions being subject to significant environmental constraints, long construction periods, high costs, and significant safety risks, this invention provides an upward-cantilevered steel formwork structure and its construction method.

[0006] The technical solution of the present invention is as follows:

[0007] An upward-cantilevered steel formwork structure, comprising:

[0008] The support assembly includes a first column and a second column, which are respectively erected above the top plate of the steel main beam;

[0009] A cantilever load-bearing component includes a cantilever beam, which is laterally disposed at the top of the first column and the second column, and its cantilever end extends to the side of the first column away from the second column.

[0010] An anti-overturning anchoring assembly is installed between the second column and the steel main beam to lock the cantilever beam onto the second column.

[0011] The longitudinal beam assembly is disposed above the cantilever beam and extends longitudinally along the bridge.

[0012] The bottom formwork system, which is supported and overlapped below the cantilever end of the cantilever beam, includes a main formwork beam, a secondary formwork beam, and a bottom formwork panel; the main formwork beam is located below the secondary formwork beam, and the bottom formwork panel is laid on top of the secondary formwork beam;

[0013] The tie rod assembly is connected at the upper end to the longitudinal beam assembly and at the lower end to the main beam of the suspended formwork, so as to transfer the load of the bottom formwork system to the cantilever load-bearing assembly.

[0014] Furthermore, the steel main beam includes a first steel main beam and a second steel main beam;

[0015] The first column is located at the middle of the width direction of the top plate of the first steel main beam, and the second column is located at the middle of the width direction of the top plate of the second steel main beam.

[0016] Furthermore, the anti-overturning anchoring assembly includes an Ω-shaped threaded steel bar, one end of which is connected to the second column and the other end is welded to the top plate of the second steel main beam to resist the upward tensile force generated by the cantilever beam.

[0017] Furthermore, the bottom end of the first column and the top plate of the first steel main beam, the bottom end of the second column and the top plate of the second steel main beam, and the connection between the cantilever beam and the top of the first and second columns are all connected by double-sided full fillet welds with a weld leg size of not less than 5mm.

[0018] Furthermore, the longitudinal beam assembly adopts a double steel pipe arrangement, which is fixed to the cantilever beam by fasteners;

[0019] The tie rod assembly uses tie bolts. The upper end of the tie rod assembly is locked to the longitudinal beam assembly by a U-shaped clip, and the lower end passes through the main beam of the suspended formwork and is fixed by a nut.

[0020] Furthermore, the pull rod assembly includes a first pull rod and a second pull rod;

[0021] The upper ends of the first tie rod and the second tie rod are connected to the longitudinal beam assembly, and the lower ends pass through the PVC channels pre-embedded in the cantilever section of the bridge deck and are fixed to the main beam of the suspended formwork. The PVC channels are filled with mortar after the formwork is removed.

[0022] Furthermore, the cantilever end of the cantilever beam is 600mm long; the main beam of the suspended formwork is made of channel steel, and its width is greater than the width of the cantilever section of the bridge deck, so as to extend outward to form a working platform.

[0023] The secondary beams of the suspended formwork are made of square timber and are arranged at intervals along the length of the main beam of the suspended formwork, with a spacing of 300mm between adjacent secondary beams.

[0024] Furthermore, the bottom formwork system also includes a side formwork assembly, which is disposed at the edge of the bottom formwork panel and includes a side formwork panel, small wooden joists, and diagonal braces;

[0025] The side formwork panel has horizontally arranged small wooden ribs at the top, middle and bottom of the side facing away from the concrete pouring area. The diagonal brace is arranged between the side formwork assembly and the bottom formwork panel to support the side formwork assembly.

[0026] A construction method for an upward-cantilevered steel formwork structure, used to construct any of the above-mentioned upward-cantilevered steel formwork structures, comprising:

[0027] S1. Positioning and welding support components: Mark and install the first and second columns on the top plate of the steel main beam, and weld them together for fixation;

[0028] S2. Install the cantilever load-bearing component, hoist the cantilever beam to the top of the first column and the second column, adjust the position and weld it in place, and install the anti-overturning anchor component. Connect one end of the Ω-shaped threaded steel of the anti-overturning anchor component to the second column and weld the other end to the top plate of the second steel main beam.

[0029] S3. Install the longitudinal beam assembly, lay double steel pipe longitudinal beams above the cantilever beam, and use fasteners to overlap and fix them;

[0030] S4. Assemble the bottom formwork system and the side formwork system, install the main formwork beam and the secondary formwork beam below the cantilever end of the cantilever beam, lay the bottom formwork panel, and install the side formwork assembly;

[0031] S5. Install the tie rod assembly and pre-tighten it. Install the tie rod assembly, connect the longitudinal beam to the main beam of the formwork, and adjust the elevation and pre-tightening force.

[0032] Furthermore, it also includes:

[0033] S6. Acceptance and pouring: After inspection and acceptance, concrete bridge deck pouring construction shall be carried out.

[0034] S7. After the concrete reaches the demolding strength, remove the side formwork assembly, tie rod assembly, bottom formwork system and longitudinal beam assembly;

[0035] Cut and remove the portions of the first and second columns that extend above the concrete bridge deck; retain the steel profiles at the base of the first and second columns embedded in the concrete bridge deck, and clean up and reuse the remaining steel components.

[0036] The beneficial effects of this invention are as follows:

[0037] This invention employs an upward-cantilevered steel formwork structure, directly transferring construction loads to the top slab of the main steel beam without occupying road resources beneath the bridge. This perfectly resolves the conflict between construction and traffic flow in municipal elevated road reconstruction, eliminating the need for complex traffic diversion work. Simultaneously, this structure completely avoids requirements on foundation bearing capacity, eliminating the need for expensive foundation reinforcement and the need to consider the relocation and protection of underground pipelines. This significantly broadens the applicability of this technology, making it particularly suitable for complex construction environments with limited space.

[0038] In this invention, the load is transferred upwards from the bottom formwork system to the longitudinal beams and cantilever beams via tie rod assemblies, and finally stably supported on the steel main beams by the columns. This intuitive force transmission path makes force calculation simple and accurate, facilitating real-time monitoring during construction. Furthermore, by scientifically designing the anti-overturning anchoring components and tie rod assemblies, a stable triangular force system is formed, effectively resisting the overturning moment and shear force at the cantilever end, significantly reducing the risk of scaffold instability and collapse during high-altitude operations, and comprehensively ensuring construction safety.

[0039] The main structure of this invention uses common materials found on construction sites, such as structural steel, steel pipes, and tie bolts, eliminating the need for expensive non-standard components and making procurement extremely convenient. Except for the base steel sections of the first and second columns, which need to be retained, the rest of the formwork system can be disassembled and reused, significantly reducing investment costs. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of an upward-cantilevered steel formwork structure provided in an embodiment of this application;

[0041] Figure 2 This is a top view schematic diagram of an upward-cantilevered steel formwork structure provided in an embodiment of this application;

[0042] Figure 3 This is a schematic diagram of a reusable part of an upward-cantilevered steel formwork structure provided in an embodiment of this application;

[0043] Figure 4 This is a flowchart of a construction method for an upward-cantilevered steel formwork structure provided in an embodiment of this application.

[0044] In the diagram: 11. Top plate of the first main steel beam; 12. Top plate of the second main steel beam; 21. First column; 22. Second column; 3. Cantilever beam; 4. Longitudinal beam assembly; 51. First tie rod; 52. Second tie rod; 61. Main beam of the suspended formwork; 62. Secondary beam of the suspended formwork; 63. Bottom formwork panel; 71. Side formwork panel; 72. Timber joists; 73. Diagonal bracing; 8. Anti-overturning anchoring assembly. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0046] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected" and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0048] Example 1:

[0049] refer to Figures 1-3 The cantilevered steel formwork structure provided in this embodiment includes a support assembly, a cantilever load-bearing assembly, an anti-overturning anchoring assembly 8, a longitudinal beam assembly 4, a bottom formwork system, and a tie rod assembly.

[0050] The supporting components include a first column 21 and a second column 22. Both the first column 21 and the second column 22 are made of 12# channel steel, possessing high vertical compressive bearing capacity and structural rigidity. The first column 21 is vertically fixed to the middle position of the width direction of the top plate 11 of the first steel main beam, and the second column 22 is vertically fixed to the middle position of the width direction of the top plate 12 of the second steel main beam. The symmetrical arrangement of the structure can effectively balance the eccentric load generated by the subsequent upper structure, avoiding structural tilting and deformation problems caused by unilateral eccentric loading.

[0051] In this embodiment, the maximum installation height of the column is set to 400mm. During the actual installation process, the column height can be slightly adjusted according to the cross slope of the bridge design to ensure that the top elevation of the first column 21 and the second column 22 are consistent, providing a horizontal installation benchmark for the superstructure and eliminating the inclined stress condition.

[0052] To ensure the integrity of the connection and the reliability of the load, the bottom of the first column 21 and the top plate 11 of the first main steel beam, and the bottom of the second column 22 and the top plate 12 of the second main steel beam, are connected by double-sided full fillet welds. The weld leg size at all welding positions is not less than 5mm, which effectively ensures the node connection strength between the column and the main steel beam and avoids problems such as detachment and loosening under load.

[0053] The cantilever load-bearing component, located at the top of the support assembly, is the core cantilever load-bearing skeleton of the suspended formwork structure. The core component of the cantilever load-bearing component is the cantilever beam 3. In this embodiment, the cantilever beam 3 is made of 12# channel steel, with a total length of 4300mm for a single beam. Multiple cantilever beams 3 are evenly distributed along the longitudinal direction of the bridge at 2m intervals to ensure uniform stress distribution. Considering the column spacing and the total length of the bottom formwork system, the cantilever beam 3 can also be set to other lengths. The cantilever beam 3 is horizontally supported at the tops of the first column 21 and the second column 22, and is fixed to the pre-set welding positions at the tops of the two columns using double-sided full fillet welds with a weld leg size of not less than 5mm, forming a stable load-bearing structure. The side of the cantilever beam 3 facing away from the second column 22 and extending outwards forms a cantilever end, with a fixed length of 600mm. The cantilever end area corresponds to the construction area of ​​the bridge cantilever section.

[0054] The anti-overturning anchor component 8 is located between the support component and the cantilever load-bearing component, serving as a safety reinforcement for the cantilever structure and mitigating the inherent defects of eccentric stress in cantilever structures. After the cantilever beam 3 is formed, its eccentric stress characteristics will generate a continuous upward pulling force on the second column 22, which can easily lead to column warping, joint cracking, and overall structural overturning. The anti-overturning anchor component 8 anchors the second column 22 to the second steel main beam, forming a reliable force-complementary system with the support component and the cantilever load-bearing component. This effectively constrains the vertical displacement and horizontal offset of the second column 22, counteracts the overturning moment and upward pulling force generated at the cantilever end of the cantilever beam 3, and locks the connection node between the cantilever beam 3 and the second column 22, significantly improving the stability and safety reserve of the cantilevered steel formwork structure.

[0055] The longitudinal beam assembly 4 is laid along the longitudinal length of the bridge and is set on the top surface of the cantilever beam 3. The longitudinal beam assembly 4 uses the cantilever beam 3 as a stable load-bearing base and forms an overall grid structure with the transversely arranged cantilever beam 3. This can pre-distribute the concentrated load generated by subsequent construction longitudinally and avoid the problem of single-point stress concentration.

[0056] The bottom formwork system is suspended below the cantilever end of the cantilever beam 3. The bottom formwork system mainly includes the main suspended beam 61, the secondary suspended beam 62, the bottom formwork panel 63, and the side formwork components. Among them, the main suspended beam 61 is the main load-bearing component of the bottom formwork system. It is made of No. 8 channel steel and is located at the bottom of the overall bottom formwork structure. The overall cantilever width is greater than the design width of the cantilever section of the bridge deck. The outward extension can also serve as a construction operation platform, integrating load-bearing and construction functions.

[0057] The secondary beams 62 of the suspended formwork are made of 80mm×40mm square timber and are evenly distributed laterally along the length of the main beam 61 of the suspended formwork. Within the 600mm cantilever construction range, a total of 3 secondary beams 62 are arranged, with the spacing between adjacent secondary beams controlled at 300mm. By evenly distributing the upper load, the formwork is prevented from deforming under pressure.

[0058] The bottom formwork panel 63 is made of 15mm thick plywood, which is fully laid on top of all the suspended formwork secondary beams 62 to form the bottom forming base surface for concrete pouring. The panel surface has high flatness, which can effectively ensure the forming quality of the bottom surface of the bridge deck.

[0059] The side formwork assembly is located at the edge of the bottom formwork panel 63 to control the side forming dimensions of the cantilever section of the bridge deck and resist lateral pressure from the concrete. The side formwork assembly includes a side formwork panel 71, timber joists 72, and diagonal braces 73. The side formwork panel 71 is also made of 15mm thick plywood, and its height is 2cm higher than the design thickness of the bridge deck to meet the requirements of ultra-high concrete pouring. 80mm×40mm timber joists 72 are horizontally arranged at the top, middle, and bottom of the side formwork panel 71 facing away from the concrete pouring area. The bottom timber joists 72 are fixed to the bottom formwork panel 63, while the top and middle timber joists 72 are fixed to the side formwork panel 71, achieving self-reinforcement of the side formwork. Diagonal braces 73 are arranged at 600mm intervals between the side formwork panel 71 and the bottom formwork panel 63. The diagonal braces 73 are made of 80mm×40mm timber and effectively constrain the displacement of the side formwork through the triangular support structure, preventing bulging and displacement of the formwork during pouring. The bottom formwork system uses the cantilever load-bearing component as the core suspension bearing foundation. At the same time, it relies on the regular planar layout of the longitudinal beam component 4 to complete the precise alignment setting. It can effectively bear the self-weight of concrete and construction load, and initially collect the load to the bottom suspended formwork main beam 61. Relying on its own overall structural rigidity to ensure the concrete forming accuracy, it is an important load-bearing structure for the concrete forming construction of the cantilever section of the bridge.

[0060] The tie rod assembly is vertically positioned between the upper longitudinal beam assembly 4 and the lower bottom formwork system, serving as the core force transmission structure for achieving the suspended locking and force-sealed closure of the bottom formwork system. In this embodiment, the tie rod assembly includes a first tie rod 51 and a second tie rod 52, both of which use M16 tie bolts with a longitudinal spacing of 300mm. The upper end of the tie rod is locked and fixed to the double steel pipe longitudinal beam assembly 4 using a U-shaped clamp, achieving upper-end limiting and fixing; the lower end of the tie rod is pre-passed through the PVC channel embedded in the cantilever section of the bridge deck, then through the through hole in the web of the main beam 61 of the suspended formwork, and finally locked and fixed with a nut, forming a complete vertical tie structure.

[0061] After the concrete pouring is completed and reaches the design strength, and the suspended formwork structure is removed, the PVC ducts reserved inside the bridge deck are filled with special mortar to ensure the integrity and waterproof performance of the bridge deck structure and to avoid structural defects caused by the remaining ducts. The tie rod assembly suspends and locks the bottom formwork system in the air through vertical tie action, offsetting the downward force generated by the self-weight of the bottom formwork system and the concrete load, and orderly transferring all the loads collected by the bottom formwork upward to the longitudinal beam assembly 4, and then evenly distributed to the cantilever load-bearing assembly through the longitudinal beam assembly 4, and finally transmitted to the main steel beam through the support assembly, completing the closed loop of the entire cantilever steel suspended formwork structure, ensuring no settlement or displacement throughout the formwork construction process, and ensuring structural stability and reliability.

[0062] Compared to traditional construction structures, this embodiment employs an upward-cantilever support system, directly transferring all construction loads to the top slab of the steel main beam. It relies entirely on the main bridge structure for load-bearing capacity, eliminating the need for ground-mounted scaffolding and avoiding the occupation of road space beneath the bridge. This perfectly resolves the core conflict between bridge deck construction and traffic flow under the bridge in municipal elevated road reconstruction projects, effectively eliminating complex traffic diversion and fencing setup work. Furthermore, this structure completely eliminates reliance on the bearing capacity of the construction site's foundation, eliminating the need for expensive pretreatment procedures such as foundation leveling, compaction, and reinforcement. It also avoids complex construction challenges such as underground pipeline relocation and specialized protection, greatly expanding the applicable scenarios for this construction technology, especially suitable for complex construction environments with limited space, such as urban elevated roads, narrow sections, and areas with dense pipelines.

[0063] This embodiment features a clear and intuitive vertical force transmission logic. The concrete self-weight and construction live load are collected by the bottom formwork system and then transmitted upwards through the tie rod assembly to the longitudinal beam assembly 4 and the cantilever beam 3. Finally, the load is stably transferred to the main steel beam structure through the supporting columns. This force transmission path has a clear hierarchy and well-defined forces, significantly simplifying the structural stress calculation process. The stress calculation accuracy is high, facilitating stress monitoring and quality control throughout the construction process. Simultaneously, through the coordinated operation of the anti-overturning anchor assembly 8 and the vertical tie rod assembly, a stable composite force system is formed at the cantilever end. This effectively resists the overturning moment and shear load generated by the concrete pouring at the cantilever end, suppressing structural deformation, warping, and instability. It completely avoids the collapse risk of traditional high-altitude scaffolding and comprehensively improves the safety and reliability of bridge cantilever section construction.

[0064] Furthermore, the overall structural components in this embodiment all utilize standard building materials commonly found on construction sites, such as steel profiles, steel pipes, square timber, and tie bolts. There is no need to customize non-standard components, making material procurement convenient and highly versatile, effectively reducing material procurement costs and production cycles. Simultaneously, the entire cantilevered steel formwork structure possesses excellent disassembly and reusability. (Refer to...) Figure 3 The marked dotted lines indicate that, except for the steel sections at the base of the first column 21 and the second column 22 which need to be retained as permanent support bases, the rest of the bottom formwork system, tie rod assembly, longitudinal beam assembly 4, and cantilever load-bearing auxiliary structures can be disassembled and reused as a whole, greatly reducing the input of one-time materials and significantly reducing the overall construction cost of the project, thus possessing good economic benefits and engineering promotion value.

[0065] Example 2

[0066] refer to Figure 4 This application provides a construction method for an upward-cantilevered steel formwork structure, including:

[0067] S1. Positioning and welding support components: Mark and set the first column 21 and the second column 22 on the top plate of the steel main beam, and weld them together.

[0068] Before construction, the installation points for the columns were precisely marked at the midpoint of the width of the top plate 11 of the first main steel beam and the top plate 12 of the second main steel beam. The pre-fabricated No. 12 channel steel columns 21 and 22 were vertically erected at the corresponding marked points. The column heights were slightly adjusted according to the bridge's design slope to ensure that the top elevations of the two columns were uniform and horizontally aligned. After adjustment and positioning, the connection between the bottom of the columns and the top plate of the main steel beam was fixed with double-sided full fillet welds, with a weld leg size of not less than 5mm, ensuring that the support components and the main steel beam form a rigid, integrated support structure.

[0069] S2. Install the cantilever load-bearing component, hoist the cantilever beam 3 to the top of the first column 21 and the second column 22, adjust the position and weld it in place, and install the anti-overturning anchor component 8. Connect one end of the Ω-shaped threaded steel of the anti-overturning anchor component 8 to the second column 22, and weld the other end to the top plate 12 of the second steel main beam.

[0070] The prefabricated No. 12 channel steel cantilever beam 3 was hoisted as a whole to the top of the first column 21 and the second column 22. The installation position was precisely aligned and adjusted to ensure that the cantilever beam 3 was horizontally arranged and that the cantilever end extended outward by 600mm to match the construction width of the bridge cantilever. After the position was calibrated correctly, both ends of the cantilever beam 3 were fixed to the top of the columns by double-sided full welding with fillet welds. The weld leg size was not less than 5mm, forming a stable cantilever load-bearing frame. Subsequently, the anti-overturning anchoring component 8 was installed. One end of the Ω-shaped threaded steel was reliably connected to the stress-bearing side wall of the second column 22, and the other end was welded and fixed to the top plate 12 of the second steel main beam. The anchoring structure offset the upward pull force and overturning moment generated by the eccentric force at the cantilever end, completing the safety reinforcement of the cantilever structure.

[0071] S3. Install the longitudinal beam assembly 4, lay double steel pipe longitudinal beams above the cantilever beam 3, and use fasteners to overlap and fix them.

[0072] Longitudinal beam assemblies 4 are installed along the longitudinal length of the bridge on the top surface of all cantilever beams 3. These assemblies are arranged in a double-steel-pipe parallel configuration, with each pipe running the entire length of the bridge. Adjacent pipes are secured by overlapping fasteners with an overlap length of at least 300mm. The double steel pipes are then locked and fixed to the top surface of the cantilever beams 3 using fasteners. The longitudinal beam assemblies 4 and the transverse cantilever beams 3 form a crisscrossing grid load-bearing structure, ensuring even distribution of loads and providing a regular installation reference for the tie rod assemblies.

[0073] S4. Assemble the bottom formwork system and the side formwork system. Install the main formwork beam 61 and the secondary formwork beam 62 below the cantilever end of the cantilever beam 3, lay the bottom formwork panel 63, and install the side formwork assembly.

[0074] Assemble the overall bottom formwork system below the cantilever end of the cantilever beam 3. First, hoist and install the main formwork beam 61 made of No. 8 channel steel, ensuring that the width of the main formwork beam 61 covers and exceeds the width of the cantilever section of the bridge deck, and also serves as a construction operation platform. Then, lay the secondary formwork beams 62 made of 80mm×40mm square timber horizontally above the main formwork beam 61, with the spacing between the secondary beams strictly controlled at 300mm to evenly distribute the construction load. After the secondary beams are set up, lay 15mm thick plywood as the bottom formwork panel 63, ensuring that the panel surface is flat and the splices are tight. Finally, install the side formwork assembly. A 15mm thick side formwork panel 71 is erected on the edge of the bottom formwork panel 63, with the side formwork height exceeding the designed thickness of the bridge deck by 2cm. 80mm×40mm wooden joists 72 are horizontally fixed at the top, middle, and bottom of the back side of the side formwork panel 71, and wooden diagonal braces 73 are arranged at 600mm intervals between the side formwork and the bottom formwork panel 63 to form a triangular support system, which effectively resists the lateral pressure of the concrete and prevents the formwork from expanding or running.

[0075] S5. Install the tie rod assembly and pre-tighten it. Install the tie rod assembly, connect the longitudinal beam to the main beam 61 of the formwork, and adjust the elevation and pre-tightening force.

[0076] M16 tie bolts are inserted into the pre-set PVC channels in the cantilever section of the bridge deck to form the first tie rod 51 and the second tie rod 52, with the longitudinal spacing between the two tie rods controlled at 300mm. The upper end of the tie rod is locked and fixed to the double steel pipe longitudinal beam assembly 4 by a U-shaped clamp, and the lower end is temporarily fixed with a nut after passing through the PVC channel and the through hole in the web of the main beam 61 of the suspended formwork. The elevation is calibrated and the preload is adjusted by fine-tuning the tie rod nuts to ensure that the overall elevation and flatness of the bottom formwork system meet the design requirements, ensuring that the entire suspended formwork structure is subjected to uniform stress, without loosening or deformation, thus completing the structural stress closed loop.

[0077] This embodiment also includes S6. Acceptance and pouring: After the inspection and acceptance are qualified, the concrete bridge deck pouring construction is carried out.

[0078] After the entire cantilevered steel formwork structure is assembled, a comprehensive self-inspection and special acceptance are carried out on the component installation spacing, welding quality, tie pre-tightening force, formwork flatness and overall structural stability. Only after the acceptance is qualified can the concrete bridge deck pouring construction begin.

[0079] S7. Formwork Removal and Component Reuse: After the bridge deck concrete reaches the designed demolding strength, formwork removal will proceed sequentially: first, remove the side formwork components, then disassemble the tie rod components, bottom formwork system, and upper longitudinal beam components 4. The columns will be treated by cutting and removing the exposed steel sections of the first column 21 and the second column 22 that extend above the concrete bridge deck, retaining the steel sections embedded in the concrete at the column base as permanent foundations. The remaining removed steel sections, steel pipes, bolts, and square timber components can be cleaned and repaired for reuse in subsequent projects. After formwork removal, the exposed PVC ducts in the bridge deck will be filled with special mortar to ensure structural integrity and waterproofing performance.

[0080] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A cantilevered steel formwork structure, characterized in that, include: The support assembly includes a first column and a second column, which are respectively erected above the top plate of the steel main beam; A cantilever load-bearing component includes a cantilever beam, which is laterally disposed at the top of the first column and the second column, and its cantilever end extends to the side of the first column away from the second column. An anti-overturning anchoring assembly is installed between the second column and the steel main beam to lock the cantilever beam onto the second column. The longitudinal beam assembly is disposed above the cantilever beam and extends longitudinally along the bridge. The bottom formwork system, which is supported and overlapped below the cantilever end of the cantilever beam, includes a main formwork beam, a secondary formwork beam, and a bottom formwork panel; the main formwork beam is located below the secondary formwork beam, and the bottom formwork panel is laid on top of the secondary formwork beam; The tie rod assembly is connected at the upper end to the longitudinal beam assembly and at the lower end to the main beam of the suspended formwork, so as to transfer the load of the bottom formwork system to the cantilever load-bearing assembly.

2. The upward-cantilevered steel formwork structure as described in claim 1, characterized in that, The steel main beam includes a first steel main beam and a second steel main beam; The first column is located at the middle of the width direction of the top plate of the first steel main beam, and the second column is located at the middle of the width direction of the top plate of the second steel main beam.

3. The upward-cantilevered steel formwork structure as described in claim 2, characterized in that, The anti-overturning anchoring assembly includes an Ω-shaped threaded steel bar, one end of which is connected to the second column and the other end is welded to the top plate of the second steel main beam to resist the upward tensile force generated by the cantilever beam.

4. The upward-cantilevered steel formwork structure as described in claim 2, characterized in that, The bottom end of the first column and the top plate of the first steel main beam, the bottom end of the second column and the top plate of the second steel main beam, and the connection between the cantilever beam and the top of the first and second columns are all connected by double-sided full fillet welds with a weld leg size of not less than 5mm.

5. The upward-cantilevered steel formwork structure as described in claim 1, characterized in that, The longitudinal beam assembly adopts a double steel pipe arranged side by side and is fixed to the cantilever beam by fasteners; The tie rod assembly uses tie bolts. The upper end of the tie rod assembly is locked to the longitudinal beam assembly by a U-shaped clip, and the lower end passes through the main beam of the suspended formwork and is fixed by a nut.

6. The upward-cantilevered steel formwork structure as described in claim 1, characterized in that, The pull rod assembly includes a first pull rod and a second pull rod; The upper ends of the first tie rod and the second tie rod are connected to the longitudinal beam assembly, and the lower ends pass through the PVC channels pre-embedded in the cantilever section of the bridge deck and are fixed to the main beam of the suspended formwork. The PVC channels are filled with mortar after the formwork is removed.

7. The upward-cantilevered steel formwork structure as described in claim 1, characterized in that, The cantilever end of the cantilever beam is 600mm long; the main beam of the suspended formwork is made of channel steel, and its width is greater than the width of the cantilever section of the bridge deck, so as to extend outward to form a working platform. The secondary beams of the suspended formwork are made of square timber and are arranged at intervals along the length of the main beam of the suspended formwork, with a spacing of 300mm between adjacent secondary beams.

8. The upward-cantilevered steel formwork structure as described in claim 1, characterized in that, The bottom formwork system also includes a side formwork assembly, which is disposed at the edge of the bottom formwork panel and includes a side formwork panel, small wooden joists, and diagonal braces; The side formwork panel has horizontally arranged small wooden ribs at the top, middle and bottom of the side facing away from the concrete pouring area. The diagonal brace is arranged between the side formwork assembly and the bottom formwork panel to support the side formwork assembly.

9. A construction method for an upward-cantilevered steel formwork structure as described in any one of claims 1-8, characterized in that, include: S1. Positioning and welding support components: Mark and install the first and second columns on the top plate of the steel main beam, and weld them together for fixation; S2. Install the cantilever load-bearing component, hoist the cantilever beam to the top of the first column and the second column, adjust the position and weld it in place, and install the anti-overturning anchor component. Connect one end of the Ω-shaped threaded steel of the anti-overturning anchor component to the second column and weld the other end to the top plate of the second steel main beam. S3. Install the longitudinal beam assembly, lay double steel pipe longitudinal beams above the cantilever beam, and use fasteners to overlap and fix them; S4. Assemble the bottom formwork system and the side formwork system, install the main formwork beam and the secondary formwork beam below the cantilever end of the cantilever beam, lay the bottom formwork panel, and install the side formwork assembly; S5. Install the tie rod assembly and pre-tighten it. Install the tie rod assembly, connect the longitudinal beam to the main beam of the formwork, and adjust the elevation and pre-tightening force.

10. The construction method for the cantilevered steel formwork structure as described in claim 9, characterized in that, Also includes: S6. Acceptance and pouring: After inspection and acceptance, concrete bridge deck pouring construction shall be carried out. S7. After the concrete reaches the demolding strength, remove the side formwork assembly, tie rod assembly, bottom formwork system and longitudinal beam assembly; Cut and remove the portions of the first and second columns that extend above the concrete bridge deck; retain the steel profiles at the base of the first and second columns embedded in the concrete bridge deck, and clean up and reuse the remaining steel components.

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