A prefabricated box girder end sealing template rapid installation and dismounting device

Abstract

The utility model provides a prefabricated box girder end seal template quick installation and dismounting device belongs to the field of construction engineering technology. The device solves the problem of traditional end seal template dismounting needing to cut screw rod, being easy to rust and wasting material. It includes: end seal template, is equipped with the reserved hole, counter pull screw rod, is installed in the box girder anchoring position and detachable connecting piece. The detachable connecting piece is conical dismounting sleeve, is connected with counter pull screw rod through the reserved hole, the conical outer wall cooperates with the reserved hole to fix end seal template. It also includes the L type anchor bar welded on counter pull screw rod, is used for strengthening anchoring. The utility model only needs to spin out the sleeve when dismounting, need not to cut screw rod, and the front end of counter pull screw rod is away from the beam end face and has the protective layer distance. Dismounting is efficient, can guarantee durability, and the sleeve can be used in rotation, saves the cost.

Description

Technical Field

[0001] This utility model relates to the field of building engineering technology, specifically to a device for rapid installation and disassembly of precast box girder end formwork. Background Technology

[0002] As a crucial component in bridge engineering, the quality of the end sealing construction of prestressed concrete box girders directly affects the durability and service life of the structure. During the construction of precast box girders, the installation and dismantling of the end sealing formwork is an essential procedure, and the quality and efficiency of this procedure significantly impact the overall construction progress and project quality of the box girder.

[0003] In traditional precast box girder end-capping formwork construction, a continuous tie rod is typically used to pass through the formwork and connect to the internal anchoring system of the box girder to fix the end-capping formwork. While this method can ensure the stability of the formwork during concrete pouring, it has revealed many problems in practical applications.

[0004] Firstly, when using continuous tie rods to anchor the formwork, the rods need to penetrate the entire end formwork and extend to the outside of the box girder for tightening. After the concrete reaches the required demolding strength, the protruding rods must be cut before the formwork can be removed. This cutting process not only increases the number of construction steps and labor intensity but also prolongs the construction period and affects overall construction efficiency.

[0005] Secondly, after the tie rods are cut, their metal sections are directly exposed to the concrete surface, lacking a protective concrete layer. During long-term use, the exposed metal surface is highly susceptible to corrosion from moisture, chloride ions, and other corrosive media in the environment, forming rust channels. This corrosion not only affects the appearance quality of the box girder ends, but more seriously, it can extend along the tie rods into the box girder, corroding the prestressed tendon anchorage system and jeopardizing the structure's safety and durability.

[0006] Furthermore, the portion of the tie rod remaining inside the concrete after cutting cannot be removed and must remain permanently with the concrete. The exposed portion, due to insufficient length and irregular ends, is difficult to reuse in subsequent projects, resulting in material waste. In large-scale bridge construction, this accumulated material waste is considerable, increasing project costs and contradicting the principles of green construction and resource conservation.

[0007] To address the aforementioned issues, while some improvements have emerged in existing technologies, such as replacing continuous threaded rods with fixing bolts or using simple sleeves to assist disassembly, these solutions still have significant shortcomings. The use of fixing bolts often results in bolts that cannot be recycled and reused, still leading to material waste. The simple sleeve solution, due to its unreasonable sleeve structure design, results in large holes or inadequate sealing after disassembly, failing to guarantee sufficient concrete cover thickness and still posing durability risks. Furthermore, the existing solutions also have shortcomings in the connection method between the tie rod and the internal reinforcement of the box girder, easily leading to quality problems such as weak connections or exposed reinforcement. Utility Model Content

[0008] The purpose of this utility model is to provide a device for the rapid installation and dismantling of precast box girder end formwork, which can not only realize the rapid installation and dismantling of end formwork, but also ensure the quality of concrete protective layer, while realizing the reuse of materials and reducing construction costs.

[0009] To achieve the above objectives, this utility model employs the following technical solution: A device for quick installation and disassembly of precast box girder end-sealing template includes: an end-sealing template with pre-drilled holes; tie rods for installation at anchoring positions of the box girder; and a detachable connector that passes through the pre-drilled holes and is detachably connected to the tie rods for fixing the end-sealing template to the end of the box girder.

[0010] Furthermore: the detachable connector is a tapered detachable sleeve, which includes a tapered outer wall and an internal threaded hole. The diameter of the tapered outer wall gradually increases from the front end to the rear end, and the internal threaded hole is threadedly engaged with the pull rod.

[0011] Furthermore, it also includes L-shaped anchor bars, which are welded and fixed to the body of the tie rod, with the bent end of the L-shaped anchor bar extending away from the end cap template.

[0012] Furthermore: the welding position of the L-shaped anchor bar is close to the anchoring end of the tie rod, and the weld length between the L-shaped anchor bar and the tie rod is not less than 5d, where d is the diameter of the L-shaped anchor bar.

[0013] Furthermore: the end cap template is made of high-strength steel plate or fiberglass composite material, and the reserved holes are set at the positions of the box girder anchor plates.

[0014] Furthermore, the upper part of the end-sealing template is provided with a feeding hole for concrete pouring.

[0015] Furthermore, the taper of the tapered disassembly sleeve is 1:8 to 1:12, and the diameter of the large end of the tapered disassembly sleeve is 3-5 mm larger than the diameter of the reserved hole.

[0016] Furthermore, the rear end of the conical disassembly sleeve is provided with a polygonal operating head for use with a screwing tool.

[0017] Furthermore: the length of the tie rod is set so that its front end is threaded to the detachable connector, and the distance from the front end face of the tie rod to the end face of the box girder is 30-40mm.

[0018] Furthermore, it also includes an anchor plate, which is fixed inside the box girder. The anchor plate is provided with bolt holes, and the rear end of the tie rod is fixed in the bolt holes by a threaded connection.

[0019] Compared with the prior art, the present invention has the following advantages: I. This utility model achieves rapid installation and disassembly of the end-sealing template by employing a detachable connection method that uses a conical disassembly sleeve and a threaded engagement with the tie rod. During demolding, the template can be removed simply by unscrewing the conical disassembly sleeve in the reverse direction, eliminating the need to cut the tie rod. This eliminates the problems of cumbersome construction procedures, high labor intensity, and long construction periods associated with traditional cutting methods, significantly improving construction efficiency.

[0020] 2. After the conical dismantling sleeve is removed, the conical hole is resealed using mortar with the same mix ratio as the sealing concrete, which effectively seals the dismantling hole. Because the length of the tie rod is precisely designed, maintaining a distance of 30-40mm between its front end and the box girder end face, a sufficiently thick concrete protective layer is formed after the secondary sealing. This avoids the problem of direct exposure of the metal section caused by traditional cutting methods, effectively blocking the formation of corrosion channels and ensuring the durability and structural safety of the box girder end.

[0021] Third, the tapered dismantling sleeve, as a reusable component, can be reused in the construction of multiple box girders after dismantling. The tie rods do not need to be cut and can be completely retained inside the concrete to play an anchoring role, avoiding material waste, reducing construction costs, and meeting the requirements of green construction and resource conservation.

[0022] Fourth, by welding and fixing the L-shaped anchor bars to the tie rods, a reliable connection between the tie rods and the internal steel reinforcement system of the box girder is ensured, eliminating potential quality problems such as missing reinforcement bars or weak connections that may occur in traditional methods, and ensuring the integrity and reliability of the anchoring system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the device of this utility model; Figure 2 This is a cross-sectional view of the tapered sleeve and lead screw of this utility model; Figure 3 This is a schematic diagram of the connection between the L-shaped reinforcing bar and the tie rod of this utility model.

[0024] In the diagram: 1. Box girder; 2. Anchorage; 3. Conical disassembly sleeve; 4. Anchor plate; 5. End capping template; 6. L-shaped anchor bar; 7. Tie rod; 8. Welded connection. Detailed Implementation

[0025] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0026] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model 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, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] Reference Figures 1 to 3 As shown, the quick installation and disassembly device for the end formwork 5 of the precast box girder 1 provided by this utility model mainly includes the end formwork 5, tie rods 7, tapered disassembly sleeves 3, L-shaped anchor bars 6, and anchor plates 4.

[0028] The end-sealing formwork 5 is made of high-strength steel plate or fiberglass composite material, possessing sufficient rigidity and strength to withstand the lateral pressure during concrete pouring. Multiple pre-drilled holes are provided on the surface of the end-sealing formwork 5. The positions of these holes correspond to the bolt holes of the anchor plates 4 inside the box girder 1, ensuring that the tie rods 7 can accurately pass through and connect to the anchoring system. To facilitate concrete pouring, a feeding hole is also provided at the top of the end-sealing formwork 5. The size and location of the feeding hole are designed according to the specifications of the concrete delivery pipe and the pouring process requirements.

[0029] The tie rod 7 is made of high-strength threaded steel bar, and its diameter and strength grade are determined based on the specifications of the box girder 1 and the lateral pressure of the end-sealing concrete. The length design of the tie rod 7 is one of the key parameters of this device, requiring comprehensive consideration of factors such as the end structural dimensions of the box girder 1, the required anchorage depth, and the thickness of the concrete protective layer. Specifically, the length of the tie rod 7 should be set to ensure that after it is fixed through the bolt holes of the anchor plate 4 and connected to the tapered disassembly sleeve 3, the distance from the front end face of the tie rod 7 to the end face of the box girder 1 is controlled within the range of 30-40mm, preferably 35mm. This distance ensures that the tie rod 7 is not exposed on the concrete surface and also provides sufficient space for the protective layer thickness during subsequent sealing treatment.

[0030] The tapered disassembly sleeve 3 is the core component for achieving rapid disassembly and assembly. Its outer wall has a tapered structure, with the diameter gradually increasing from the front to the rear. The tapered disassembly sleeve 3 has a taper design of 1:8 to 1:12, a range verified through extensive engineering practice, ensuring both ease of disassembly and reliable fastening during concrete pouring. The tapered disassembly sleeve 3 has internally machined threaded holes, with the thread specification matching the external thread of the tie rod 7, ensuring a reliable threaded connection. The large end diameter of the tapered disassembly sleeve 3 is 3-5mm larger than the diameter of the pre-drilled hole on the end-sealing template 5. This dimensional fit allows the tapered disassembly sleeve 3 to firmly press the end-sealing template 5 onto the end face of the box girder 1 when screwed in. For ease of operation, the rear end of the tapered disassembly sleeve 3 is designed with a hexagonal or octagonal operating head for easy tightening with a wrench or special tools.

[0031] The L-shaped anchor bar 6 is installed to enhance the anchoring effect of the tie rod 7 within the concrete, while ensuring a reliable connection with the internal steel reinforcement system of the box girder 1. The L-shaped anchor bar 6 is made of steel bars of the same specifications as the ordinary steel bars in the box girder 1, bent into shape. One end is fixed to the tie rod 7 via a welded connection 8. The welding position is chosen near the anchoring end of the tie rod 7, i.e., near the anchor plate 4. The bent end of the L-shaped anchor bar 6 extends away from the end cap template 5, penetrating into the steel mesh inside the box girder 1. The welding quality directly affects the reliability of the connection; therefore, the weld length must meet the specification requirements, generally not less than 5d, where d is the diameter of the L-shaped anchor bar 6. For example, when using a 12mm diameter L-shaped anchor bar 6, the weld length should be not less than 60mm. Welding is performed using double-sided welding or full welding to ensure a full weld, free of slag inclusions, porosity, and other defects.

[0032] Anchor plate 4 is a component of the prestressed system of box girder 1, and is usually pre-embedded and fixed at the designed position at the end of box girder 1 during prefabrication. Anchor plate 4 has multiple bolt holes, originally used for installing prestressed anchors 2, but used for installing tie rods 7 during end sealing construction. The bolt holes are machined with internal threads, which mate with the external threads of the tie rods 7 to reliably fix the tie rods 7.

[0033] In practical construction applications, the usage process of this device is as follows: First, based on the specific dimensions of the box girder 1 and the position of the anchor plate 4, a tie rod 7 of appropriate length is customized. The length calculation of the tie rod 7 needs to consider factors such as the thickness of the anchor plate 4, the distance from the end of the box girder 1 to the anchor plate 4, the thickness of the end capping template 5, and the thickness of the reserved protective layer. For example, for a typical 30-meter precast box girder 1, the anchor plate 4 is 50mm thick, the distance from the anchor plate 4 to the beam end is 200mm, the end capping template 5 is 15mm thick, and the required protective layer thickness is 35mm. Then, the effective length of the tie rod 7 should be 200mm - 35mm = 165mm, plus the length required for the threaded connection at both ends.

[0034] Next, the welding of the L-shaped anchor bars 6 will be carried out. The L-shaped anchor bars 6 will be welded to the tie rods 7 according to the designed positions. One to two L-shaped anchor bars 6 can be welded to each tie rod 7 as needed. After welding, a quality inspection must be performed to ensure that the weld quality meets the requirements. Welding operations should preferably be carried out on the ground to ensure welding quality and construction safety.

[0035] After roughening the anchor holes at the ends of box girder 1, the tie rods 7 are installed. Each tie rod 7, with the welded L-shaped anchor bars 6, is screwed into the bolt holes of the anchor plate 4. A torque wrench is used to tighten the tie rods to the designed torque value, ensuring a secure connection between the tie rods 7 and the anchor plate 4. During installation, attention should be paid to the direction of the L-shaped anchor bars 6, ensuring that the bent ends face inwards towards the box girder 1 and effectively overlap with the reinforcing mesh inside the box girder 1.

[0036] After all tie rods 7 are installed, the end-sealing template 5 is positioned and installed. The end-sealing template 5 is hoisted to the end of the box girder 1, and adjustments are made to align the pre-drilled holes on the template with the installed tie rods 7. Once the template is in place, the tapered disassembly sleeves 3 are inserted one by one through the pre-drilled holes from the outside of the template and screwed onto the external threads of the tie rods 7. During the screwing process, the tapered outer wall of the tapered disassembly sleeve 3 gradually contacts the pre-drilled holes and generates a squeezing effect, firmly pressing the end-sealing template 5 onto the end face of the box girder 1. After all tapered disassembly sleeves 3 are installed, the flatness and verticality of the template are checked, and fine adjustments are made if necessary.

[0037] After the formwork is installed and fixed, the end-sealing concrete can be poured. The concrete is poured through the feeding hole at the top of the end-sealing formwork 5. The pouring process should be carried out in layers, with each layer not exceeding 300mm in thickness, and each layer should be thoroughly vibrated to ensure compaction. During vibration, direct contact between the vibrator and the tie rod 7 and the conical disassembly sleeve 3 should be avoided to prevent loosening of the connection.

[0038] After the concrete is poured, it undergoes curing. When the concrete strength reaches the design demolding strength (generally above 70% of the design strength), demolding can begin. During demolding, use a wrench or special tool to rotate the conical dismantling sleeve 3 in the opposite direction, completely unscrewing it from the tie rod 7 and removing it. Due to the conical structure, the conical dismantling sleeve 3 can easily detach from the concrete. After all conical dismantling sleeves 3 are removed, the end-capping formwork 5 can be completely removed.

[0039] After removing the conical disassembly sleeve 3, conical holes will be left on the concrete surface. These holes need to be sealed promptly. The sealing material is cement mortar with the same mix proportion as the sealing concrete. To ensure a tight seal, dry-hard mortar should be used, i.e., mortar with a low water-cement ratio and a slump close to zero. The dry-hard mortar is filled into the conical holes in stages, and after each stage, it is hammered inward with a rubber mallet to ensure thorough compaction. The conical shape, wider at the outside and narrower at the inside, facilitates the filling and compaction of the sealing material. After sealing, the surface of the hole should be flush with the concrete surface; smoothing may be necessary.

[0040] After the sealing treatment is completed, apply a moisturizing protective film or a curing agent to the sealed area and allow it to moisturize for no less than 7 days to ensure that the sealing mortar is fully hydrated and hardened to reach the design strength. Regular inspections should be conducted during the curing period to prevent the protective film from peeling off or the curing agent from becoming ineffective.

[0041] Through the above construction process, this device successfully solved many problems existing in the construction of traditional end-sealing formwork 5. The conical dismantling sleeve 3 can be reused in the construction of different box girders 1. According to engineering practice statistics, each conical dismantling sleeve 3 can be reused more than 50 times, greatly reducing material costs. The tie rod 7 does not need to be cut and is completely retained inside the concrete, which saves materials and avoids the risk of corrosion caused by exposed metal. Through reasonable protective layer thickness design and reliable sealing treatment, the durability of the end of the box girder 1 is ensured. The setting of L-shaped anchor bars 6 strengthens the anchoring effect and improves the integrity and safety of the structure.

[0042] The above embodiments are only for illustrating the technical concept and features of this utility model, and are intended to enable those skilled in the art to understand the content of this utility model and implement it accordingly. They should not be construed as limiting the scope of protection of this utility model. All equivalent transformations or modifications made in accordance with the spirit and essence of this utility model should be included within the scope of protection of this utility model.

Claims

1. A device for rapid installation and disassembly of precast box girder end-sealing formwork, characterized in that, include: End sealing template, wherein the end sealing template is provided with reserved holes; Tie rods are used for installation at the anchorage positions of box girders; A detachable connector passes through the pre-drilled hole and is detachably connected to the tie rod, used to fix the end cap template to the end of the box girder.

2. The rapid installation and disassembly device for precast box girder end-capping formwork according to claim 1, characterized in that, The detachable connector is a tapered detachable sleeve, which includes a tapered outer wall and an internal threaded hole. The diameter of the tapered outer wall gradually increases from the front end to the rear end, and the internal threaded hole is threaded into the pull rod.

3. The rapid installation and disassembly device for precast box girder end formwork according to claim 2, characterized in that, It also includes L-shaped anchor bars, which are welded and fixed to the body of the tie rod, with the bent end of the L-shaped anchor bar extending away from the end cap template.

4. The rapid installation and disassembly device for precast box girder end formwork according to claim 3, characterized in that, The welding position of the L-shaped anchor bar is close to the anchoring end of the tie rod, and the weld length between the L-shaped anchor bar and the tie rod is not less than 5d, where d is the diameter of the L-shaped anchor bar.

5. The rapid installation and disassembly device for precast box girder end-capping formwork according to claim 1, characterized in that, The end cap template is made of high-strength steel plate or fiberglass composite material, and the reserved holes are set at the positions of the box girder anchor plates.

6. The device for rapid installation and disassembly of precast box girder end-cap template according to claim 1, characterized in that, The upper part of the end-sealing template is provided with a feeding hole for concrete pouring.

7. The rapid installation and disassembly device for precast box girder end formwork according to claim 2, characterized in that, The taper of the tapered disassembly sleeve is 1:8 to 1:12, and the diameter of the large end of the tapered disassembly sleeve is 3-5 mm larger than the diameter of the reserved hole.

8. The device for rapid installation and disassembly of precast box girder end formwork according to claim 2, characterized in that, The tapered disassembly sleeve has a polygonal operating head at its rear end for use with a screwing tool.

9. The device for rapid installation and disassembly of precast box girder end formwork according to claim 1, characterized in that, The length of the tie rod is set so that after its front end is threaded to the detachable connector, the distance from the front end face of the tie rod to the end face of the box girder is 30-40mm.

10. The device for rapid installation and disassembly of precast box girder end-cap template according to claim 1, characterized in that, It also includes an anchor plate, which is fixed inside the box girder. The anchor plate has bolt holes, and the rear end of the tie rod is fixed in the bolt holes by a threaded connection.

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