Formwork system for cast-in-place construction of concrete box girder and installation method

Abstract

The invention belongs to the field of concrete box girder construction, and particularly relates to a formwork system for concrete box girder cast-in-place construction and an installation method. Comprising a bottom die, side dies, an inner die, a top plate, sealing ends and embedded parts. A support distribution beam is arranged below the bottom die, the square timber is arranged in the longitudinal direction of the box girder, and the square timber in the corresponding area of the web and the square timber in the corresponding area of the box chamber are fixedly connected with the bottom die bamboo plywood. The side formworks, the inner formwork and the top plate formwork are all of a bamboo plywood and square timber combined structure, and supporting and positioning assemblies are arranged in a matched mode. The bottom formwork, the side formworks, the inner formwork and the top plate formwork are all of bamboo plywood and square timber combined structures and are matched with the double-spliced steel pipe straps, the disc buckle type supports and the longitudinal and transverse diagonal bracings, a high-rigidity supporting system can be rapidly built, the square timber in the top plate formwork is connected with the longitudinal bridge direction double-spliced steel pipes through buckles, bolt fixing is not needed, and the assembling time of the top plate formwork is shortened.

Description

Technical Field

[0001] This invention belongs to the field of concrete box girder construction technology, specifically referring to a formwork system and installation method for cast-in-place concrete box girder construction. Background Technology

[0002] In the cast-in-place construction of concrete box girders, the formwork system is the core equipment that determines the geometric accuracy, structural strength, and appearance quality of the girder. As bridge engineering develops towards larger spans, wider widths, and thinner walls, existing systems struggle to meet the high standards required for modern bridge construction in terms of ensuring construction stability and improving operational efficiency.

[0003] Traditional formwork systems generally suffer from poor versatility and weak support: the bottom formwork often uses integral steel formwork, which needs to be reprocessed for box girders with different cross-sections, resulting in low equipment reuse rate and heavy weight. Installation and dismantling require the cooperation of large machinery, and the construction cycle is long. The side formwork and inner formwork support mostly rely on simple steel pipe scaffolding, which lacks rigid connection and anti-lateral displacement measures. Under the lateral pressure of concrete pouring, it is prone to outward expansion or inward contraction, resulting in deviation of web thickness and even the risk of formwork collapse.

[0004] In addition, traditional formwork joint treatment is rough, often using sponge strips for filling, which is prone to grout leakage due to concrete vibration and compression. After demolding, honeycomb and pitted surfaces are formed on the beam surface, resulting in high repair costs and affecting structural durability.

[0005] Traditional processes also have significant drawbacks in controlling the positions of embedded parts and functional holes: embedded pipes such as vent holes and grouting holes are mostly positioned manually, lacking a precise matching structure with the formwork, and are prone to displacement due to pouring vibration, resulting in poor prestressed grouting in the later stage; the inner formwork does not have pre-set mortar holes and vibration holes, resulting in uneven material distribution in the inner cavity of the box girder, which can easily form vibration blind spots, insufficient concrete density, excessive assembly time, and affect the progress. Summary of the Invention

[0006] In response to the above situation and to overcome the shortcomings of the existing technology, this invention provides a formwork system and installation method for cast-in-place concrete box girder construction. It effectively solves the problems of poor formwork versatility and insufficient support stability leading to box girder casting deformation, as well as cumbersome installation procedures, large positioning deviations of embedded parts, poor concrete surface quality after demolding, and low construction efficiency.

[0007] The technical solution adopted in this invention is as follows: This invention proposes a formwork system and installation method for cast-in-place concrete box girder construction, including: bottom formwork, side formwork, inner formwork, top plate, as well as end caps and embedded parts;

[0008] A support distribution beam is arranged below the bottom formwork, and the square timber is set along the longitudinal direction of the box girder. The square timber in the corresponding area of ​​the web plate and the square timber in the corresponding area of ​​the box chamber are respectively connected and fixed to the bamboo plywood of the bottom formwork.

[0009] The side mold, inner mold, and top plate template are all made of bamboo plywood and square timber combined structure, and are equipped with support and positioning components.

[0010] The end cap and embedded parts are installed at the ends of the box girder.

[0011] Furthermore, the side mold includes:

[0012] Outer mold, inner web mold;

[0013] The square timber of the inner side mold of the web plate is connected to the bamboo plywood panel of the side mold, and a double steel pipe back strap is provided on one side of the outer mold. The double steel pipe back strap is connected to the bamboo plywood of the mold on the outer side, and a disc buckle bracket is connected to the outer side of the double steel pipe back strap.

[0014] The bottom of the bracket is fixed to the distribution beam provided in the bottom mold, and the top of the bracket is provided with a top support, which is connected to the side mold;

[0015] The side formwork also includes a flange template connected to the bamboo plywood of the side formwork and extending away from the direction of the box girder, as well as longitudinal and transverse scissor braces set on the side formwork support and fixed to the support steel pipe.

[0016] The joint between the side mold and the bottom mold is coated with paraffin wax.

[0017] Furthermore, the transverse square timbers on the inner mold are fixedly connected to the bamboo plywood of the inner mold, and the back of the inner mold is provided with double-jointed steel pipe longitudinal beams, which are fixedly connected to the transverse square timbers.

[0018] The inner mold is equipped with an inner mold support, and the support is provided with scissor bracing connected by support steel pipes. The top support above the support is connected to the double-section steel pipe longitudinal beam.

[0019] The inner mold also includes positioning ribs, one end of which is connected to the web reinforcement or the bottom plate reinforcement, and the other end of which is connected to the bamboo plywood.

[0020] The joints of the inner mold are sealed with transparent tape, and the bamboo plywood of the upper and lower plates of the inner mold and the inner square wood have through holes for mortar and vibration.

[0021] Furthermore, the square timber inside the top plate template is fixedly connected to the bamboo plywood of the top plate, and the square timber is connected to the longitudinal double-splitting steel pipe by a snap fastener.

[0022] The longitudinal double-splitting steel pipe is connected to the top support of the bracket, and the top support of the bracket is nested with the steel pipe provided below the bracket;

[0023] The top slab template also includes diagonal bracing steel pipes. One end of the diagonal bracing steel pipe is connected to the longitudinal double-section steel pipe, and the other end of the diagonal bracing steel pipe is fixedly connected to a steel pipe on the support.

[0024] Furthermore, the top plate support is provided with scissor bracing that connects to the longitudinal double-section steel pipes;

[0025] A precision-rolled threaded steel tie rod connects the side mold and the inner mold. One end of the precision-rolled threaded steel tie rod is fixed to the double-section steel pipe of the side mold, and the other end of the precision-rolled threaded steel tie rod is fixed to the longitudinal beam of the double-section steel pipe of the inner mold.

[0026] Furthermore, the top of the sealing end has through-holes for reinforcing bars and through-holes for corrugated pipes, and the edge of the sealing end is connected to the reinforcing bars provided at the end of the box girder;

[0027] The template at the anchor head position of the beam end and the template at the support are connected to the end sealing template.

[0028] Furthermore, the embedded components include: vent hole embedded pipe, grouting hole embedded pipe, drainage hole embedded pipe and bridge deck drainage pipe;

[0029] One end of the pre-embedded pipe for venting holes and the pre-embedded pipe for grouting holes are connected to the reserved holes in the top slab template, and the other end of the pre-embedded pipe for venting holes and the pre-embedded pipe for grouting holes extends into the box girder.

[0030] Furthermore, the installation method for cast-in-place concrete box girder construction includes:

[0031] Step 1: Pre-stress the support frame. After pre-stressing, level the frame using a level instrument and adjust the height of the bottom formwork using loose steel plates to set the pre-camber of the box girder.

[0032] Step 2: Prepare and install the side mold: Check the geometric dimensions and flatness of the template, apply release agent evenly after pre-pressing and unloading, install the side mold according to the measured layout line, seal the joint between the side mold and the bottom mold, install the bracket on the outside of the side mold and adjust the elevation of the side mold;

[0033] Step 3: Install the inner mold: Install the precast inner mold on the inner mold support, position the inner mold with positioning ribs, seal the inner mold joints, and open the mortar holes and vibration holes on the upper and lower plates of the inner mold;

[0034] Step 4: Install the top slab formwork: Erect the lower steel pipes of the top slab support, measure the elevation and adjust the support top, and after acceptance, erect the longitudinal bridge steel pipes and diagonal braces, set the longitudinal bridge double steel pipes, and then install the bottom formwork of the top slab.

[0035] Step 5: Install end cap formwork and embedded parts and remove formwork: Install formwork and embedded parts at both ends of the box girder, and remove the formwork when the concrete meets the specified conditions.

[0036] Furthermore, in step two, the square timber and the side mold panel are fixedly arranged, and double steel pipes are provided on the outer mold. The side mold and the inner mold are connected by a precision-rolled threaded steel tie rod to fix the position of the side mold and the inner mold.

[0037] In step three, the inner mold is fixedly connected to the interior of the transverse square timber, and the inner mold is positioned by positioning ribs to fix the position of the inner mold;

[0038] The inner mold has upper and lower plates with mortar holes and vibration holes for instructing concrete and compacting it.

[0039] Furthermore, in step four, when the top plate bottom formwork is installed, the fixed top plate template is connected to the square timber and longitudinal double-splitting steel pipes to form a top plate support system. The longitudinal double-splitting steel pipes are spliced ​​using sleeve-type connectors.

[0040] In step five, the end-sealing template is made of rigid plate, and the end-sealing template is provided with openings to accommodate the end reinforcement and corrugated pipe of the box girder;

[0041] During installation, the embedded pipe connects to the pre-reserved hole in the top slab template for venting and grouting, and the bridge deck drainage pipe aligns with the drainage hole and connects to the box girder frame for drainage.

[0042] The beneficial effects achieved by the present invention using the above structure are as follows:

[0043] 1. The bottom formwork, side formwork, inner formwork, and top slab formwork all adopt a combination structure of bamboo plywood and square timber, combined with double-splitting steel pipe back straps, disc-lock brackets, and longitudinal and transverse scissor bracing, which can quickly form a high-rigidity support system. The square timber and longitudinal double-splitting steel pipes in the top slab formwork are connected by snap-fit, eliminating the need for bolt fixing and shortening the assembly time of the top slab formwork. The side formwork and inner formwork are fixed by tensioning with precision-rolled threaded steel rods to prevent the formwork from expanding outward or shrinking inward during pouring, ensuring uniform thickness of the box girder web. The sealing of the inner formwork joints and the setting of mortar holes and vibration holes solve the problems of grout leakage and insufficient concrete density.

[0044] 2. Installation Method: Pre-stressing and pre-cambering of the supports reduce the impact of support deformation. Construction is carried out in stages according to the sequence of "bottom formwork - side formwork - inner formwork - top slab - end caps and embedded parts." Precise operations, such as leveling with a level instrument and fine-tuning with top supports, ensure accurate formwork elevation and positioning. During the installation of the top slab formwork, the longitudinal double-span steel pipes are spliced ​​using sleeve-type connectors to quickly complete the steel pipe assembly. The embedded parts are precisely aligned with the reserved holes in the top slab. The end caps formwork has holes adapted to the reinforcing bars and corrugated pipes, meeting the functional requirements of prestressed construction and drainage, avoiding rework later, and further accelerating the construction progress. Attached Figure Description

[0045] Figure 1 This is an overall flowchart of the formwork system and installation method for cast-in-place concrete box girder construction proposed in this invention;

[0046] Figure 2 This is a detailed flowchart of the first step of the formwork system and installation method for cast-in-place concrete box girder construction proposed in this invention.

[0047] Figure 3 This is a detailed flowchart of step two of the formwork system and installation method for cast-in-place concrete box girder construction proposed in this invention.

[0048] Figure 4 This is a detailed flowchart of step three of the formwork system and installation method for cast-in-place concrete box girder construction proposed in this invention.

[0049] Figure 5 This is a detailed flowchart of step four of the formwork system and installation method for cast-in-place concrete box girder construction proposed in this invention.

[0050] Figure 6 This is a detailed flowchart of step five of the formwork system and installation method for cast-in-place concrete box girder construction proposed in this invention.

[0051] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0052] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0053] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "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.

[0054] like Figures 1-6 As shown, this invention proposes a formwork system for cast-in-place construction of concrete box girders, including: a bottom formwork, side formwork, inner formwork, top plate, and end caps and embedded parts; a support distribution beam is arranged below the bottom formwork, and the square timber is arranged along the longitudinal direction of the box girder. The square timber in the corresponding area of ​​the web and the square timber in the corresponding area of ​​the box chamber are respectively connected and fixed to the bamboo plywood of the bottom formwork; the side formwork, inner formwork, and top plate formwork all adopt a combination structure of bamboo plywood and square timber, and are equipped with supporting and positioning components; the end caps and embedded parts are set at the ends of the box girder.

[0055] In practical use, the formwork system consists of a bottom formwork, side formwork, inner formwork, top plate, end caps, and embedded parts. A support distribution beam is set under the bottom formwork, and the square timber in the corresponding areas of the web and box girder is set along the longitudinal direction of the box girder and fixed to the bamboo plywood of the bottom formwork to form the bottom formwork support skeleton. The side formwork, inner formwork, and top plate formwork all adopt a combination structure of bamboo plywood and square timber, with matching support and positioning components. The square timber of the bottom formwork is arranged in zones to adapt to the different stress requirements of the web and box girder. The pre-set end caps and embedded parts ensure no omissions in construction and lay the foundation for subsequent precise pouring.

[0056] The side formwork includes an outer side formwork and an inner side formwork for the web. The square timber of the inner side formwork is connected to the bamboo plywood panel of the side formwork. One side of the outer side formwork is provided with a double-splittered steel pipe back strap, which is connected to the bamboo plywood panel of the outer side formwork. A disc-buckle bracket is connected to the outer side of the double-splittered steel pipe back strap. The bottom of the bracket is fixed to the distribution beam of the bottom formwork, and the top of the bracket is provided with a top support, which is connected to the side formwork. The side formwork also includes a flange template connected to the bamboo plywood panel of the side formwork and extending away from the direction of the box girder, as well as longitudinal and transverse scissor braces set on the side formwork bracket and fixed to the steel pipe of the bracket. The joint between the side formwork and the bottom formwork is coated with paraffin wax.

[0057] In practical use, the side formwork consists of an outer side formwork and an inner side formwork for the web. The inner side formwork is made of square timber connected to bamboo plywood, while the outer side formwork has a double-span steel pipe support strap on one side, which connects to the bamboo plywood and is attached to a disc-buckle scaffold on the outside. The bottom of the scaffold is connected to the bottom formwork distribution beam, and the top support is connected to the side formwork. The side formwork includes extended flange templates and longitudinal and transverse scissor braces. The joint between the side formwork and the bottom formwork is coated with paraffin wax. The double-span steel pipe support strap and disc-buckle scaffold enhance the load-bearing capacity of the side formwork, while the scissor braces improve the overall stability of the scaffold and prevent deformation and displacement of the side formwork during pouring.

[0058] The inner mold is provided with transverse square timbers that are fixedly connected to the bamboo plywood of the inner mold. A double-splitting steel pipe longitudinal beam is provided on the back of the inner mold, and the double-splitting steel pipe longitudinal beam is fixedly connected to the transverse square timbers. The inner mold is equipped with an inner mold support, which is provided with scissor braces connected to the support steel pipes. A top support is provided above the support and connected to the double-splitting steel pipe longitudinal beams. The inner mold also includes positioning ribs, one end of which is connected to the web reinforcement or bottom reinforcement, and the other end of which is connected to the bamboo plywood. The joints of the inner mold are sealed with transparent tape, and the bamboo plywood of the upper and lower plates of the inner mold and the inner square timber have through holes for mortar and vibration.

[0059] In practical use, the inner formwork is fixed with transverse square timber and bamboo plywood, and a double-splitting steel pipe longitudinal beam is set at the back and connected to the transverse square timber; the inner formwork support is equipped with scissor bracing, and the top support of the support is connected to the double-splitting steel pipe longitudinal beam; one end of the positioning reinforcement is connected to the web / bottom plate reinforcement, and the other end is connected to the bamboo plywood; the joints of the inner formwork are sealed with transparent tape, and the bamboo plywood and square timber of the upper and lower plates pass through the mortar holes and vibration holes. The positioning reinforcement ensures the accurate position of the inner formwork, and the double-splitting steel pipe longitudinal beam and scissor bracing ensure the rigidity of the inner formwork; the transparent tape seals the joints to prevent grout leakage, and the mortar holes and vibration holes solve the problems of uneven material distribution and vibration blind spots in the inner cavity of the box girder, ensuring the density of the concrete.

[0060] The square timber inside the top slab template is fixedly connected to the bamboo plywood of the top slab, and the square timber is connected to the longitudinal double-splitting steel pipe by a snap fastener; the longitudinal double-splitting steel pipe is connected to the top support of the bracket, and the top support of the bracket is nested with the steel pipe provided below the bracket; the top slab template also includes diagonal bracing steel pipes, one end of which is connected to the longitudinal double-splitting steel pipe, and the other end of which is fixedly connected to the steel pipe provided on the bracket.

[0061] In practical application, the snap-fit ​​connection between the square timber and the longitudinal double-section steel pipe enhances the fit between the timber and the steel pipe, and also buffers the vibration load during concrete pouring, preventing the snap-fit ​​from loosening due to high-frequency vibration. The longitudinal double-section steel pipe is connected to the support bracket, and the support bracket is nested with the steel pipe below the support bracket. One end of the diagonal brace steel pipe is connected to the longitudinal double-section steel pipe, and the other end is connected to the support bracket steel pipe. The longitudinal double-section steel pipe and the diagonal brace form a stable support system. The nested support structure facilitates precise adjustment of the top slab elevation, solving the problems of difficult elevation control and unstable support of the top slab formwork, and ensuring the flatness of the poured top slab.

[0062] The top plate support is equipped with scissor bracing connected to the longitudinal double-section steel pipes; a fine-rolled threaded steel tie rod is connected between the side mold and the inner mold, one end of the fine-rolled threaded steel tie rod is fixed to the double-section steel pipe of the side mold, and the other end of the fine-rolled threaded steel tie rod is fixed to the longitudinal beam of the double-section steel pipe of the inner mold.

[0063] In practical application, the top slab support is equipped with scissor bracing connecting the longitudinal double-section steel pipes; the side formwork and inner formwork are connected by precision-rolled threaded steel tie rods, one end of which is connected to the double-section steel pipe of the side formwork, and the other end is connected to the longitudinal beam of the double-section steel pipe of the inner formwork. The scissor bracing enhances the lateral displacement resistance of the top slab support, while the precision-rolled threaded steel tie rods achieve the mutual tension and fixation of the side formwork and inner formwork, preventing the side formwork from expanding outward and the inner formwork from shrinking inward during pouring, ensuring the uniform thickness of the box girder web, and solving the problem of beam dimensional deviation caused by formwork displacement.

[0064] The sealing end has through-holes for reinforcing bars and corrugated pipes, and the edge of the sealing end is connected to the reinforcing bars at the end of the box girder; the formwork at the anchor head of the beam end and the formwork at the support are connected to the sealing end formwork.

[0065] In practical use, the end-sealing formwork passes through the holes of the reinforcing bars and corrugated pipes, with its edges connected to the end reinforcing bars of the box girder; the formwork at the anchor head position of the beam end and the formwork at the support are connected to the end-sealing formwork. Precise hole opening ensures smooth installation of the reinforcing bars and corrugated pipes, and the formwork at the anchor head and support is appropriately set to ensure the accuracy of prestressed construction and the fit of the support installation, solving the problems of hole position deviation of the end-sealing formwork and poor connection with the surrounding structure.

[0066] The embedded components include: vent hole embedded pipe, grouting hole embedded pipe, drainage hole embedded pipe and bridge deck drainage pipe; one end of the vent hole embedded pipe and the grouting hole embedded pipe are connected to the reserved hole of the top slab template, and the other end of the vent hole embedded pipe and the grouting hole embedded pipe extends into the box girder.

[0067] In practical use, the embedded parts include vent holes, grouting holes, drainage holes, and bridge deck drainage pipes. One end of the vent holes and grouting holes is connected to the reserved holes in the top slab formwork, and the other end extends into the box girder. The bridge deck drainage pipes are aligned with the drainage holes and connected to the box girder frame. The embedded pipes are precisely connected to the reserved holes in the top slab to ensure smooth venting and grouting operations. The bridge deck drainage pipes are connected to the box girder frame to ensure drainage function and solve the problem of functional failure caused by omissions or positional deviations of the embedded parts.

[0068] The installation methods used for cast-in-place concrete box girder construction include:

[0069] Step 1: Pre-stress the support frame. After pre-stressing, level the frame using a level instrument and adjust the height of the bottom formwork using loose steel plates to set the pre-camber of the box girder.

[0070] Step 2: Prepare and install the side mold: Check the geometric dimensions and flatness of the template, apply release agent evenly after pre-pressing and unloading, install the side mold according to the measured layout line, seal the joint between the side mold and the bottom mold, install the bracket on the outside of the side mold and adjust the elevation of the side mold;

[0071] Step 3: Install the inner mold: Install the precast inner mold on the inner mold support, position the inner mold with positioning ribs, seal the inner mold joints, and open the mortar holes and vibration holes on the upper and lower plates of the inner mold;

[0072] Step 4: Install the top slab formwork: Erect the lower steel pipes of the top slab support, measure the elevation and adjust the support top, and after acceptance, erect the longitudinal bridge steel pipes and diagonal braces, set the longitudinal bridge double steel pipes, and then install the bottom formwork of the top slab.

[0073] Step 5: Install end cap formwork and embedded parts and remove formwork: Install formwork and embedded parts at both ends of the box girder, and remove the formwork when the concrete meets the specified conditions.

[0074] In practical use, the steps are as follows: Step 1: After preloading the support frame, level the formwork with a level instrument and set the pre-camber for the bottom formwork using loose steel plates; Step 2: Check the flatness of the side formwork dimensions, apply release agent after unloading the preload, install the side formwork according to the ink line, seal the joints, install the outer support frame and adjust the elevation; Step 3: Install the precast inner formwork with the inner formwork support frame, position the positioning ribs, seal the joints, and open the mortar holes and vibration holes; Step 4: Erect the top slab support steel pipes, measure the elevation and adjust the top support, erect the longitudinal bridge steel pipes and diagonal braces, set double-splitting steel pipes, and install the top slab bottom formwork; Step 5: Install the end formwork and embedded parts, and remove the formwork after the concrete reaches the standard. Preloading and pre-camber settings reduce the impact of support deformation, release agent and joint sealing ensure the appearance of the beam, precise positioning and functional hole opening ensure construction quality, and controlled demolding conditions prevent damage to the beam.

[0075] In step two, the square timber and the side formwork panel are fixedly arranged, and double-splitting steel pipes are set on the outer formwork. The side formwork and the inner formwork are connected by precision-rolled threaded steel tie rods to fix the position of the side formwork and the inner formwork. In step three, the inner formwork is fixedly connected to the interior of the transverse square timber and the inner formwork. The inner formwork is positioned by positioning ribs to fix the position of the inner formwork. The upper and lower plates on the inner formwork are provided with mortar holes and vibration holes for instructing concrete and vibrating it to compact.

[0076] In practical use, step two: connect the square timber to the side formwork panels, with double-splitting steel pipes on the outer formwork. The side formwork and inner formwork are connected by precision-rolled threaded steel tie rods. Step three: connect the inner formwork to the transverse square timber, and use positioning ribs to position the inner formwork. The upper and lower plates of the inner formwork are equipped with mortar holes and vibration holes. The square timber and double-splitting steel pipes enhance the structural strength of the side formwork, while the precision-rolled threaded steel tie rods fix the relative positions of the side formwork and inner formwork. The positioning ribs ensure the accuracy of the inner formwork, and the mortar holes and vibration holes ensure the quality of pouring, solving the problems of loose formwork fixing and blind spots in pouring during installation.

[0077] In step four, during the installation of the top slab bottom formwork, the fixed top slab template is connected to the square timber and longitudinal double-splitter steel pipes to form a top slab support system. The longitudinal double-splitter steel pipes are spliced ​​using sleeve-type connectors. In step five, the end-sealing template is made of rigid plate material and has openings for fitting the end reinforcement and corrugated pipes of the box girder. During the installation of the embedded parts, the embedded pipes are connected to the holes reserved in the top slab template for venting and grouting, and the bridge deck drainage pipes are aligned with the drainage holes and connected to the box girder frame for drainage.

[0078] In practical application, step four: When splicing the longitudinal double-splitter steel pipes using sleeve-type connectors, the load-bearing capacity at the splice point should be consistent with that of the double-splitter steel pipe body to avoid the splice point becoming a weak link in the support system; step five: Use rigid plates for the end-sealing formwork, with holes to accommodate reinforcing bars and corrugated pipes; when installing the embedded parts, connect the embedded pipes to the reserved holes in the top slab, and align the bridge deck drainage pipes with the drainage holes to connect to the box girder skeleton. The stability of the top slab support system ensures the flatness of the pouring, and the rigid end-sealing formwork and precise hole positions ensure the structural connection accuracy; the precise connection of the embedded parts achieves the functional requirements, solving the problems of unstable top slab support, deformation of the end-sealing formwork, and installation deviation of the embedded parts.

[0079] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0080] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0081] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A formwork system for cast-in-place construction of concrete box girders, characterized in that: include: Bottom mold, side mold, inner mold, top plate, as well as end caps and embedded parts; A support distribution beam is arranged below the bottom formwork, and the square timber is arranged longitudinally along the box girder. The square timber in the corresponding area of ​​the web plate and the square timber in the corresponding area of ​​the box chamber are respectively connected and fixed to the bamboo plywood of the bottom formwork. The side mold, inner mold, and top plate template are all made of bamboo plywood and square timber combined structure, and are equipped with support and positioning components. The end cap and embedded parts are installed at the ends of the box girder.

2. The formwork system for cast-in-place construction of concrete box girders according to claim 1, characterized in that: The side mold includes: Outer mold, inner web mold; The square timber of the inner side mold of the web plate is connected to the bamboo plywood panel of the side mold, and a double steel pipe back strap is provided on one side of the outer mold. The double steel pipe back strap is connected to the bamboo plywood of the mold on the outer side, and a disc buckle bracket is connected to the outer side of the double steel pipe back strap. The bottom of the bracket is fixed to the distribution beam provided in the bottom mold, and the top of the bracket is provided with a top support, which is connected to the side mold; The side formwork also includes a flange template connected to the bamboo plywood of the side formwork and extending away from the direction of the box girder, as well as longitudinal and transverse scissor braces set on the side formwork support and fixed to the support steel pipe. The joint between the side mold and the bottom mold is coated with paraffin wax.

3. The formwork system for cast-in-place construction of concrete box girders according to claim 1, characterized in that: The transverse square timber on the inner mold is fixedly connected to the bamboo plywood of the inner mold, and a double-jointed steel pipe longitudinal beam is provided on the back of the inner mold, and the double-jointed steel pipe longitudinal beam is fixedly connected to the transverse square timber. The inner mold is equipped with an inner mold support, and the support is provided with scissor bracing connected by support steel pipes. The top support above the support is connected to the double-section steel pipe longitudinal beam. The inner mold also includes positioning ribs, one end of which is connected to the web reinforcement or the bottom plate reinforcement, and the other end of which is connected to the bamboo plywood. The joints of the inner mold are sealed with transparent tape, and the bamboo plywood of the upper and lower plates of the inner mold and the inner square wood have through holes for mortar and vibration.

4. The formwork system for cast-in-place construction of concrete box girders according to claim 1, characterized in that: The square timber inside the top slab template is fixedly connected to the bamboo plywood of the top slab, and the square timber is connected to the longitudinal double-splitting steel pipe by a snap fastener. The longitudinal double-splitting steel pipe is connected to the top support of the bracket, and the top support of the bracket is nested with the steel pipe provided below the bracket; The top slab template also includes diagonal bracing steel pipes. One end of the diagonal bracing steel pipe is connected to the longitudinal double-section steel pipe, and the other end of the diagonal bracing steel pipe is fixedly connected to a steel pipe on the support.

5. The formwork system for cast-in-place construction of concrete box girders according to claim 1, characterized in that: The top plate support is equipped with scissor bracing that connects to the longitudinal double-section steel pipes. A precision-rolled threaded steel tie rod connects the side mold and the inner mold. One end of the precision-rolled threaded steel tie rod is fixed to the double-section steel pipe of the side mold, and the other end of the precision-rolled threaded steel tie rod is fixed to the longitudinal beam of the double-section steel pipe of the inner mold.

6. The formwork system for cast-in-place construction of concrete box girders according to claim 1, characterized in that: The top of the sealing end has a steel bar hole and a corrugated pipe hole, and the edge of the sealing end is connected to the steel bar at the end of the box girder; The template at the anchor head position of the beam end and the template at the support are connected to the end sealing template.

7. The formwork system for cast-in-place construction of concrete box girders according to claim 1, characterized in that: The embedded components include: vent hole embedded pipe, grouting hole embedded pipe, drainage hole embedded pipe and bridge deck drainage pipe; One end of the pre-embedded pipe for venting holes and the pre-embedded pipe for grouting holes are connected to the reserved holes in the top slab template, and the other end of the pre-embedded pipe for venting holes and the pre-embedded pipe for grouting holes extends into the box girder.

8. The installation method for cast-in-place concrete box girder construction according to any one of claims 1-7, characterized in that: include: Step 1: Pre-stress the support frame. After pre-stressing, level the frame using a level instrument and adjust the height of the bottom formwork using loose steel plates to set the pre-camber of the box girder. Step 2: Prepare and install the side mold: Check the geometric dimensions and flatness of the template, apply release agent evenly after pre-pressing and unloading, install the side mold according to the measured layout line, seal the joint between the side mold and the bottom mold, install the bracket on the outside of the side mold and adjust the elevation of the side mold; Step 3: Install the inner mold: Install the precast inner mold on the inner mold support, position the inner mold with positioning ribs, seal the inner mold joints, and open the mortar holes and vibration holes on the upper and lower plates of the inner mold; Step 4: Install the top slab formwork: Erect the lower steel pipes of the top slab support, measure the elevation and adjust the support top, and after acceptance, erect the longitudinal bridge steel pipes and diagonal braces, set the longitudinal bridge double steel pipes, and then install the bottom formwork of the top slab. Step 5: Install end cap formwork and embedded parts and remove formwork: Install formwork and embedded parts at both ends of the box girder, and remove the formwork when the concrete meets the specified conditions.

9. The installation method for cast-in-place concrete box girder construction according to claim 8, characterized in that: In step two, the square timber and the side mold panel are fixedly arranged, and double steel pipes are provided on the outer mold. The side mold and the inner mold are connected by a precision-rolled threaded steel tie rod to fix the position of the side mold and the inner mold. In step three, the inner mold is fixedly connected to the interior of the transverse square timber, and the inner mold is positioned by positioning ribs to fix the position of the inner mold; The inner mold has upper and lower plates with mortar holes and vibration holes for instructing concrete and compacting it.

10. The installation method for cast-in-place concrete box girder construction according to claim 8, characterized in that: In step four, when the top plate bottom formwork is installed, the fixed top plate template is connected to the square timber and longitudinal double-splitting steel pipes to form a top plate support system. The longitudinal double-splitting steel pipes are spliced ​​using sleeve-type connectors. In step five, the end-sealing template is made of rigid plate, and the end-sealing template is provided with openings to accommodate the end reinforcement and corrugated pipe of the box girder; During installation, the embedded pipe connects to the pre-reserved hole in the top slab template for venting and grouting, and the bridge deck drainage pipe aligns with the drainage hole and connects to the box girder frame for drainage.

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