Continuous beam closure section box inner formwork support-frame-free system and construction method

Abstract

The invention discloses a continuous beam closure section box inner formwork supporting-frame-free system and a construction method, and belongs to the technical field of bridge engineering construction. In order to solve the problems that a full framing in a traditional closure section box is low in construction efficiency and large in space interference, the invention provides a combined type overall frame scheme. The system comprises a hanging basket structure and a combined template which are located on the outer side of a beam body, and an n-shaped support-frame-free frame arranged in a box. The beam bodies on the two sides form a temporary whole through rigid locking, the n-shaped frame is connected with the beam bodies and the outer side formworks through the opposite-pull fixing structures to form a space stress whole, a self-balancing formwork system is formed, and therefore independent stand column supports in a box are omitted. According to the method, rapid mounting and dismounting of the formwork are achieved, interference of supports, reinforcing steel bars and pipelines is thoroughly avoided, and the construction efficiency and quality of the closure section are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering construction technology, and in particular to a continuous beam closure section box girder formwork without support frame system and construction method. Background Technology

[0002] In the cantilever construction of continuous beam bridges, the closure segment is the key part connecting adjacent cantilever segments and realizing the structural system transition. Since the two beams have not yet formed a continuous load-bearing system during the closure construction, the construction loads such as the self-weight of the formwork and the self-weight of the concrete generated during the pouring of the closure segment must be borne by reliable temporary measures.

[0003] Currently, the commonly used technical solution is to erect full-span scaffolding or a densely arranged steel support system inside the closure section. However, this traditional support method has the following inherent drawbacks: Low construction efficiency: The small and complex shape of the internal cavity of the container leads to a large number of support rods, complicated installation procedures, and difficulties in spatial positioning and adjustment. Furthermore, the subsequent dismantling is also time-consuming and labor-intensive, which seriously restricts the overall construction progress.

[0004] Severe spatial interference: Dense support members and pre-arranged steel cages and prestressed ducts are prone to positional conflicts in a confined space. This not only affects the accuracy and efficiency of steel reinforcement binding and duct positioning, but also often forces on-site cutting and relocation adjustments of support members, further reducing construction controllability and structural quality.

[0005] Poor overall system integrity: Traditional supports are mostly point-type or decentralized, making it difficult to form a unified spatial force-bearing whole. The overall stiffness and stability of the formwork system are difficult to control, which is not conducive to deformation control during the concrete pouring process.

[0006] Therefore, there is an urgent need for a new type of formwork support system that can significantly reduce the number of support members inside the box girder, enable rapid installation and dismantling, and fundamentally avoid spatial interference with steel bars and prestressed pipes, so as to improve the industrialization, standardization and overall efficiency of the closure section construction. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies, such as low construction efficiency, significant spatial interference, and poor system integrity, in the construction of box girder closure sections. It provides a supportless formwork system and construction method for box girder closure sections of continuous beams. This system aims to replace scattered supports with a modular, integrated load-bearing frame, enabling rapid assembly and disassembly of the formwork and precise positioning, while completely eliminating interference with internal steel reinforcement pipes. This, in turn, improves construction efficiency and ensures project quality and safety.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A continuous beam closure segment box girder formwork system without support frame is proposed, the core of which lies in constructing a combined integral load-bearing frame. This system consists of an outer system and an inner system: External system: This includes the suspended platform structure using existing cantilever construction equipment (such as hanging baskets) and standardized modular formwork.

[0009] Internal system: A "∏"-shaped unsupported frame set inside the container. This frame is assembled from an inner top plate structure, an upper chamfered structure, a web structure, and a lower chamfered structure through a pre-set tie-and-fix structure, forming a spatial rigid frame that matches the outline of the container.

[0010] Connection and Locking: The aforementioned inner and outer systems are interconnected by a tie-locking structure and firmly anchored to the cast-in-place beam. Simultaneously, at both ends of the closure section, a rigid locking structure temporarily connects the two beams into a single unit.

[0011] A construction method for a continuous beam closure segment formwork system without support frames is disclosed. In this method, before closure construction, a rigid locking structure is used to temporarily integrate the beams on both sides of the closure segment. A combined formwork, inner top plate structure, upper chamfer structure, web structure, and lower chamfer structure are installed in the reinforcement cage section between the two beams. The formwork is multi-directionally constrained by tie-fixing structures one, two, three, and four, enabling the formwork system to form a self-balancing force structure during construction. Reinforcement binding and concrete pouring of the closure segment are completed within the space enclosed by the formwork, thus completing the closure segment construction without the need for temporary internal supports. Through the above design, the traditional "bottom-up, scattered support" force transmission mode is transformed into an overall coordinated force transmission mode of "formwork frame - tie system - two side beams", thereby eliminating all independent column-type temporary supports in the box girder.

[0012] (III) Beneficial Effects Compared with the prior art, the present invention has the following significant advantages: Construction efficiency is significantly improved: the use of a modular integral frame and standard tie-rod connection allows for clear on-site assembly units and quick connection, making installation and dismantling much faster than traditional full-span scaffolding, thus greatly shortening the construction cycle of the closure section.

[0013] Completely eliminate spatial interference: The "∏" shaped frame structure is clear, the members are simplified and their positions are preset, providing a wide and unobstructed working space for steel bar binding and prestressed pipe laying, which greatly improves construction accuracy and first-time pass rate.

[0014] The system has good integrity and stability: the frame and beams form a highly statically indeterminate spatial force-bearing whole through tension, with high overall stiffness, strong deformation control capability, and a safer and more controllable concrete pouring process.

[0015] High applicability: This system does not rely on the site and space under the bridge, and is particularly suitable for complex environments under bridges, such as crossing rivers, roads, and existing lines, where traditional supports are difficult to erect.

[0016] Compared with existing solutions that rely on the internal support system, this invention reconstructs the stress system of the closure section through the synergistic effect of the outer suspended basket support and the inner counter-tension self-balancing structure. Attached Figure Description

[0017] To illustrate the technical solutions in the embodiments of the present invention or the prior art more specifically and intuitively, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0018] Figure 1 This is a schematic diagram of the internal structure of the closure segment proposed in this invention; Figure 2 This is a schematic diagram of the hoisting structure and combined template proposed in this invention; Figure 3 This is a schematic diagram of the hoisting structure proposed in this invention; Figure 4 This is a schematic diagram of the tension-fixed structure proposed in this invention; Figure 5 This is a schematic diagram of the external structure of the closure segment proposed in this invention.

[0019] In the diagram: Inner top plate structure 1, Panel 1 11, Secondary beam 1 12, Main beam 1 13, Tie-fixing structure 1 14, Tie rod 141, Nut 142, Upper chamfer structure 2, Panel 2 21, Secondary beam 2 22, Auxiliary beam 23, Web structure 3, Panel 3 31, Secondary beam 3 32, Main beam 3 33, Tie-fixing structure 3 34, Lower chamfer structure 4, Rigid locking structure 5, Tie-fixing structure 4 6, Lifting structure 7, Hanging rod structure 8, Base plate 9, Combined formwork 10. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Reference Figure 1-5A continuous beam closure segment formwork system without a support frame and its construction method are disclosed. By employing an outer suspended platform structure, including a combined formwork 10 as the external system of the supportless frame system, and an inner "∏"-shaped supportless frame system as the internal system, comprising an inner top plate structure 1, an upper chamfer structure 2, a web structure 3, and a lower chamfer structure 4, the formwork and concrete pouring load of the closure segment no longer rely on the temporary support system inside the box girder. This allows for safe, stable, and controllable pouring of the closure segment concrete without the need for temporary internal supports, reducing construction difficulty and improving construction safety and quality stability.

[0022] Before the continuous beam closure construction, a rigid locking structure 5 is used to form a temporary integral structure on both sides of the closure section, enabling it to jointly bear the loads of the construction phase. Based on this, the present invention no longer uses an internal support system as the primary load-bearing means. Instead, it constructs an unsupported internal formwork system in the closure section that is compatible with the construction method. This system provides multi-directional constraints on the displacement and deformation of the formwork during the construction phase, allowing the formwork system to achieve a self-balancing stress state independent of the internal support system.

[0023] The construction load during the concrete pouring stage of the closure section is transformed from the traditional "inner box support bearing" to "formwork-fixed structure-existing beam collaborative bearing", thereby realizing the reconstruction of the force path during the construction stage of the closure section.

[0024] This invention, by setting up a combined template 10, an inner top plate structure 1, an upper chamfer structure 2, a web structure 3, a lower chamfer structure 4, and tie-fixing structures 14, 2, 34, and 4 6 in the closure section, limits the displacement and deformation of the template during the concrete pouring and early hardening stages, enabling the template system to form a stable stress-bearing closed state during the construction stage.

[0025] Under this stress state, the construction load generated by the concrete pouring of the closure section is directly transferred to the completed beams on both sides of the closure section through the formwork and fixed structure, and is no longer borne by the box girder support system. This allows the formwork to still meet the stability requirements of the construction stage without the temporary support inside the box girder, thus achieving safe pouring of the concrete in the closure section.

[0026] Based on the above technical concept and stress mechanism, the present invention provides a continuous beam closure segment box girder formwork without support frame system and construction method.

[0027] In the construction method described above, before the closure construction, a rigid locking structure 5 is used to form a temporary integral structure for the beams on both sides of the closure section. A combined formwork 10, an inner top plate structure 1, an upper chamfer structure 2, a web structure 3, and a lower chamfer structure 4 are set in the steel cage section located between the two beams. The formwork is multi-directionally limited by tie-fixing structures 14, 2, 34, and 4, so that the formwork system forms a self-balancing force structure during the construction stage. The steel reinforcement is tied and the concrete of the closure section is poured within the space enclosed by the formwork, thereby completing the closure section construction without setting up temporary supports inside the box girder.

[0028] Example 1: The present invention relates to a continuous beam closure segment box girder formwork without support frame system and construction method, applied to the construction of the mid-span closure segment of a continuous beam bridge. The bridge has a main span of 80m, a closure segment length of 2m, and the box girder is a single-box, single-cell variable-height structure. At closure, the beam height is approximately 4.5m, the top slab width is 12.5m, and the bottom slab width is 6.7m. The construction environment is complex, with an existing highway beneath the bridge, and the prestressed ducts inside the box girder are densely arranged, making traditional box girder support schemes difficult to implement.

[0029] Step 1): Remove one side of the hanging basket. Provided that structural stability is guaranteed, the forward-moving operating platform or non-load-bearing auxiliary components of the hanging basket on one side of the closure section are removed, creating a working space on one side of the closure section for installing the inner "∏"-shaped unsupported frame system. This step can be selectively performed or omitted depending on the actual site conditions, without affecting the implementation of the core system of this invention.

[0030] Step 2): Remove the inner guide beam and inner formwork of the hanging basket. After moving the cantilever construction formwork to the closure section construction position, release the rear anchor of the formwork, remove the inner guide beam and the original inner formwork, and retain only the outer web formwork, bottom slab formwork, and the main structure of the formwork, including the hoisting structure 7, the suspension rod structure 8, and the bottom slab 9. Adjust the elevation and position of the retained outer system to bring the combined formwork 10 into the design control state.

[0031] Step 3): Adjust the elevation according to the external hanging basket system, and tie the bottom slab and web reinforcement. The supervisor will inspect and accept the work. Using the outer web formwork and bottom slab formwork within the external hanging basket system, adjust and fix the elevation, alignment, and verticality of the closure section formwork. Install the bottom slab and web reinforcement within the adjusted formwork enclosure, and simultaneously position the prestressed ducts. After the reinforcement tying is completed, the supervising engineer will inspect and accept it on-site. Only after confirmation of compliance can the next step proceed. This step fully utilizes the load-bearing platform formed by the external hanging basket system, eliminating the need for any independent column-type temporary supports within the box girder.

[0032] Step 4): Install the "∏"-shaped unsupported formwork system for the continuous beam. In the closure section, the lower chamfer structure 4, web structure 3, upper chamfer structure 2, and inner top plate structure 1 are installed sequentially within the box girder compartment. These are then connected and fixed to the beams and the combined formwork 10 via tie-fixing structures 1-14, 2-15, 34-36, and 4-6, respectively. Pre-tensioning is applied to each tie-fixing structure to achieve multi-directional limiting of the formwork system in the horizontal, vertical, and spatial directions, enabling the inner and outer formwork systems and the beams on both sides to form a self-balancing force-bearing structure. This step requires no independent support within the box girder and is the core implementation step of this invention.

[0033] Step 5): Set up a rigid locking structure After the supportless system is installed, rigid locking structures 5 are installed at the embedded parts of the beams on both sides of the closure section to form a temporary rigid connection structure between the beams on both sides of the closure section. If necessary, temporary prestressed tendons are installed in conjunction with the rigid locking structure to enhance the overall stiffness of the locking structure and ensure that the cantilever beams on both sides have the ability to jointly bear the new load during construction.

[0034] Step 6): Pour concrete and complete the closure. After rigid locking is completed, the concrete for the closure section is poured in the following order within the enclosed space of the formwork: bottom slab, then web slab, and finally top slab. During the pouring process, the load of the newly poured concrete is transferred to the beams on both sides through the combined formwork 10, the tie-fixing structure, and the rigid locking structure 5. Once the concrete strength reaches the design requirements, the formwork system and the rigid locking structure are removed, allowing the closure section to transition from a construction stress state to a permanent stress state, thus completing the closure of the continuous beam.

[0035] The construction period of this embodiment is shorter than that of the traditional method, the closure section has a smooth alignment, and the crack width meets the standard control requirements.

[0036] Example 2: Application of modified side span closure section In the same bridge side span closure section (1.5m long), the beam height gradually changes to 2.5m, and the environment is a river crossing section. Optimization measures: Increase the density of tie rods to 141 (350mm spacing), using Q420 high-strength steel tie rods; pre-embed temperature sensors to dynamically adjust the locking timing (controlling the temperature difference to less than 10℃). The pouring sequence remains unchanged, but an additional insulation layer is added to the bottom slab to prevent early cracking. Results: Deformation meets control requirements, work efficiency is improved, and it is suitable for water-based operations.

[0037] Example 3: Monitoring and Emergency Response Strain gauges (tension rod 141) and displacement gauges (at key points of the formwork) were deployed throughout the entire process, and data was transmitted in real time. If the load exceeded the design value, emergency measures included: suspending pouring and tightening nuts 142; if the temperature changed suddenly, covering with insulation blankets. Quality inspection: ultrasonic testing showed that the concrete density met requirements, and the pull-out test confirmed the structural bearing capacity was qualified. This implementation verified the reliability and adaptability of the invention.

[0038] In addition, as a supplementary management tool, digital systems are applied during construction to improve quality management. These include the Shandong Railway Investment Construction Management Platform (BIM+GIS+IoT), an intelligent working system for engineering testing and inspection (mixing plant), intelligent monitoring equipment, a railway AI monitoring and early warning system, and a railway continuous beam alignment monitoring system. These systems enable real-time data collection, early warning, and quality control, ensuring construction safety and accuracy.

[0039] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A continuous beam closure section box girder formwork system without support frame, comprising a suspended basket structure set on the outside of the continuous beam and a combined formwork (10) located thereon, characterized in that, The continuous beam is also equipped with a "∏"-shaped unsupported frame system connected as a whole by a tie-fixing structure. The system includes an inner top plate structure (1), an upper chamfer structure (2), a web structure (3), and a lower chamfer structure (4). A rigid locking structure (5) is provided between the beams on both sides of the closure section. The suspended platform structure includes a hoisting structure (7) anchored to the top of the beam, and the hoisting structure (7) is connected to a base plate (9) horizontally set at the bottom of the beam through a suspension rod structure (8). Each structure in the "∏"-shaped unsupported frame system is connected to the beam, the base plate (9) or the combined template (10) through a tie-fixing structure and achieves multi-directional limiting, so that the "∏"-shaped unsupported frame system, the suspended basket structure and the combined template (10) together form a self-balancing template force-bearing structure with the beams on both sides as the force-bearing support.

2. The continuous beam closure segment box girder formwork without support frame system according to claim 1, characterized in that, The inner top plate structure (1) includes a panel (11), a secondary beam (12) and a main beam (13) arranged sequentially from the inside to the outside. The end of the main beam (13) is anchored to the beam body by a tie-fixing structure (14).

3. The continuous beam closure segment box girder formwork without support frame system according to claim 1, characterized in that, The upper chamfer structure (2) includes a panel two (21), a secondary beam two (22), an auxiliary beam (23) and a main beam two arranged sequentially from the inside to the outside. The end of the main beam two is anchored to the beam body through a tie-fixing structure two.

4. The continuous beam closure segment box girder formwork without support frame system according to claim 1, characterized in that, The web structure (3) includes a panel three (31), a secondary beam three (32) and a main beam three (33) arranged sequentially from the inside to the outside. The main beam three (33) is connected to the combined template (10) through a tie-fixing structure three (34).

5. The continuous beam closure segment box girder formwork without support frame system according to claim 1, characterized in that, The panel of the lower chamfer structure (4) is fixed to the beam by a tie-fix structure or a rigid support.

6. The continuous beam closure segment box girder formwork without support frame system according to claim 2, 3 or 4, characterized in that, The main beam one (13), main beam two and main beam three (33) are double-channel steel or double-steel pipe.

7. The continuous beam closure segment box girder formwork without support frame system according to claim 1, characterized in that, The tie-fixing structure includes a tie rod (141) and a nut (142) threaded to the end of the tie rod (141).

8. The continuous beam closure segment box girder formwork without support frame system according to claim 1, characterized in that, The rigid locking structure (5) includes steel sections arranged symmetrically along the beam axis, with both ends of the steel sections welded and fixed to embedded parts pre-embedded in the beam body.

9. A construction method for the closure segment of a continuous beam based on the system described in any one of claims 1-8, characterized in that, Includes the following steps: 1) Remove the inner guide beam and inner formwork of the hanging basket; after moving the cantilever construction hanging basket to the construction position of the closure section, release the rear anchor of the hanging basket, remove the inner guide beam and the original inner formwork of the hanging basket, and only retain the outer formwork of the web plate, the bottom plate formwork and the main structure of the hanging basket, including the hoisting structure (7), the rod structure (8) and the bottom plate (9); adjust the elevation and position of the retained outer system so that the combined formwork (10) is in the design control state; 2) Adjust the elevation according to the external hanging basket system, and tie the bottom slab and web reinforcement, and have it inspected and accepted by the supervisor; relying on the outer web formwork and bottom slab formwork in the external hanging basket system, adjust and fix the elevation, alignment and verticality of the closure section formwork; install the bottom slab and web reinforcement within the enclosed space of the adjusted formwork, and simultaneously complete the positioning of the prestressed ducts; after the reinforcement is tied, the supervising engineer shall inspect and accept it on site, and only after confirming that it is qualified can the next step be carried out; this step makes full use of the load-bearing platform formed by the external hanging basket system, and no independent column-type temporary support is required inside the box girder; 3) Install the "∏"-shaped unsupported frame system for the inner formwork of the continuous beam; install the lower chamfer structure (4), web structure (3), upper chamfer structure (2) and inner top plate structure (1) in sequence in the box girder of the closure section, and connect and fix them to the beam and the combined formwork (10) through tie fixing structure one (14), tie fixing structure two, tie fixing structure three (34) and tie fixing structure four (6); apply pre-tightening force to each tie fixing structure to realize the multi-directional limiting of the formwork system in the horizontal, vertical and spatial directions, so that the inner and outer formwork systems and the beams on both sides form a self-balancing force structure; this step does not require any independent support inside the box girder, and is the core implementation link of the technical solution of this invention; 4) Set up a rigid locking structure; After the installation of the supportless system is completed, install a rigid locking structure (5) at the embedded parts of the beams on both sides of the closure section so that the beams on both sides of the closure section form a temporary rigid connection structure; If necessary, set up temporary prestressed tendons in conjunction with the rigid locking structure to enhance the overall rigidity of the locking structure and ensure that the cantilever beams on both sides have the ability to jointly bear the new load during construction. 5) Pour concrete and complete the closure; After the rigid locking is completed, pour concrete for the closure section in the formwork enclosure space in the order of bottom plate, web plate and top plate; During the pouring process, the load of the newly poured concrete is transferred to the beams on both sides through the combined formwork (10), tie fixing structure and rigid locking structure (5); After the concrete strength reaches the design requirements, remove the formwork system and rigid locking structure, so that the closure section changes from the construction stress state to the permanent stress state, and complete the closure of the continuous beam.

10. The construction method according to claim 9, characterized in that, In step (4), the concrete pouring is carried out in the order of bottom slab, web slab, and top slab, and the entire construction process does not rely on any independent column-type temporary support system set up in the box to bear the concrete pouring load.

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