Prefabricated box girder bottom pre-embedded steel plate assembly and installation and construction method

Abstract

The invention relates to the technical field of prefabricated box girder installation, and particularly discloses a prefabricated box girder bottom pre-embedded steel plate assembly and an installation construction method. The steel plate assembly comprises a steel plate assembly body, the steel plate assembly body comprises a bottom plate used for being anchored in concrete at the bottom of the prefabricated box girder, and an adjusting mechanism is arranged on the side wall of the bottom plate and used for adjusting the inclination of the bottom plate at the bottom of the prefabricated box girder before the prefabricated box girder is poured. The method comprises the steps that S1, the steel plate assembly is installed; s2, pouring the prefabricated box girder; s3, mounting a support; s4, mounting the prefabricated box girder; through combination of the steel plate assembly and the construction method, special formworks do not need to be customized for different gradients, and the production cost is saved; and all high-precision operations are completed on the ground, and factory prefabrication and rapid assembly of the box girder and the support are achieved.

Description

Technical Field

[0001] This invention relates to the field of precast box girder installation technology, specifically to a precast box girder bottom embedded steel plate assembly and its installation method. Background Technology

[0002] Precast box girders are widely used in highway and railway bridge construction due to their controllable quality and high construction efficiency. When a bridge has a longitudinal slope, a wedge-shaped structure needs to be installed at the bottom of the girder to ensure that the supports are horizontally stressed. Currently, the following two methods are mainly used: Precast concrete wedge blocks: Concrete wedge blocks are cast at the bottom of the box girder during precasting. This method has significant drawbacks: First, when adjacent cap beams are not parallel, or when there are many curves and variations in bridge deck width, the box girder has a variable cross-section. The position and slope of the wedge blocks need to be adjusted for each beam, requiring custom-made special-shaped beam supports or templates for each beam, resulting in high costs and poor versatility. Second, the positioning accuracy of the anchor sleeves for the bearings embedded in the sloping concrete is extremely difficult to control, and construction deviations can easily lead to difficulties in on-site bearing installation.

[0003] Post-construction welding of steel wedge blocks: After the box girder is erected, steel wedge blocks are welded on-site at the top of the high-altitude cap beam to adjust the slope. This method carries high operational risks, including falls from heights and welding fires, posing a threat to railway and highway lines operating below the bridge. Furthermore, the welding quality is highly dependent on the skill of the personnel, and the supports cannot be replaced later, resulting in poor maintainability. Summary of the Invention

[0004] This invention provides a precast box girder bottom embedded steel plate assembly and installation method, which can overcome some or all defects of the prior art.

[0005] According to the present invention, a precast box girder bottom embedded steel plate assembly includes: a steel plate assembly body, the steel plate assembly body including a bottom plate for anchoring in the concrete at the bottom of the precast box girder, and an adjustment mechanism provided at the side wall of the bottom plate for adjusting the inclination of the bottom plate at the bottom of the precast box girder before the precast box girder is poured.

[0006] Through this invention, when constructing precast box girders, construction workers first place the base plate from the embedded steel plate assembly onto the bottom surface inside the precast box girder casting mold, ensuring it is initially level. Then, using an adjustment mechanism—specifically, by rotating screws located on the sidewall of the base plate—the screws move up and down along the nuts, lifting one end of the base plate and adjusting its inclination. During this process, a high-precision level, total station, or 3D laser scanner is used for real-time monitoring to ensure that the longitudinal and transverse slopes of the plane formed on the upper surface of the base plate precisely meet the values ​​specified in the bridge design drawings. After slope adjustment, to prevent cement slurry from seeping under the base plate during subsequent concrete pouring, affecting its final slope and causing corrosion, sealant is injected along the gap between the outer edge of the base plate and the mold to form an effective seal. This prevents concrete from filling the gap between the base plate and the mold during pouring, which could cause the entire base plate to be embedded inside the precast box girder, affecting subsequent installation. After the steel plate components are installed and secured, the reinforcing steel skeleton of the box girder is tied within the mold. During this process, the uprights at the four corners of the base plate are tied to the reinforcing steel skeleton with steel wire ropes, ensuring that the base plate becomes an integral part of the entire reinforcing steel skeleton. After the reinforcement spacing, protective layer thickness, and other indicators are inspected and found to be qualified, concrete of the design grade is poured. During concrete pouring, attention must be paid to the vibration process to avoid disturbing the already finely adjusted base plate. After the concrete solidifies and undergoes the specified curing period, the base plate and the box girder form a high-strength, permanent solidified body, and its preset precise slope is completely preserved, forming a precast box girder with a customized bottom slope.

[0007] The precast box girders, having been cured and reached their design strength, are transported to the installation preparation area. On the ground, construction workers hoist the bridge bearings, which are wedge-shaped bearings that match the slope of the bottom of the girder, to the bottom of the box girder. The anchor bolt holes on the bottom plate of the bearing are aligned with the sleeves on the bottom plate. Then, high-strength bolts are passed through the anchor bolt holes on the bottom plate of the bearing and screwed into the sleeves to secure the bearing to the bottom plate. A torque wrench is used to ensure that the preload of all connecting bolts reaches the design value.

[0008] Using a bridge erecting machine or large lifting equipment, the precast box girder with the pre-assembled supports is hoisted; after being smoothly hoisted to the top of the pier cap beam of the target bridge span, it is slowly lowered; through measurement guidance and fine adjustment of the lifting equipment, the support base plate is precisely aligned with the preset anchor bolt position on the top of the cap beam, and it is ensured that the lower surface of the support base plate is clean, dry and completely in contact with the top surface of the cap beam; after being in place, the connecting anchor bolts between the support base plate and the cap beam are immediately installed and tightened to complete the final anchoring operation; at this point, the precast box girder installation is completed, its bottom slope has been precisely achieved through the pre-embedded steel plate components, and the support is in the designed horizontal stress state.

[0009] In summary, compared with existing technologies, this device, through the cooperation of screws and nuts, freely adjusts the inclination of the base plate instead of customized templates, enabling the production of box girders with different slopes on standard pedestals, thus significantly reducing the manufacturing cost of precast box girders. This device transforms the challenges of controlling slope and hole position accuracy at high altitudes and on-site into a precisely adjustable and easily inspectable mechanical operation in a ground factory, achieving millimeter-level installation accuracy. It also enables pre-connection of box girders and supports on the ground for overall hoisting, completely eliminating high-risk operations such as high-altitude welding, doubling construction efficiency and ensuring inherent safety.

[0010] Preferably, the base plate is rectangular in shape, and each of the four corners of the base plate is provided with a vertical pole.

[0011] With this invention, the uprights extend into the steel reinforcement cage of the precast bridge, and construction workers tie the uprights to the steel reinforcement cage with steel wire ropes, thereby facilitating the connection of the steel plate assembly to the steel reinforcement cage.

[0012] Preferably, the adjustment mechanism includes a nut connected to the side wall of the base plate, and a screw that is threaded into the nut is provided at the nut.

[0013] With this invention, construction workers can rotate the screw to move it towards the bottom of the box girder mold, thereby lifting one end of the base plate and making it easier for construction workers to adjust the tilt angle of the base plate at the bottom of the steel reinforcement cage.

[0014] Preferably, the upright includes a sub-connecting rod, and the lower end of the sub-connecting rod is provided with a sleeve; the inner side wall of the sleeve is provided with internal threads.

[0015] With this invention, when connecting the box girder support to the bottom plate, the construction personnel can connect the support and the sleeve by passing a bolt through the bottom plate of the support and engaging with the internal thread on the inner side wall of the sleeve; thus, it is convenient for the construction personnel to connect the support to the steel plate assembly.

[0016] Preferably, the base plate has connection holes at all four corners for the sleeve to extend into.

[0017] With this invention, when installing the base plate and the upright, the installer inserts the sleeve at the lower end of the upright into the connecting hole on the base plate, and then connects the sleeve to the base plate by welding, thus making it convenient for the installer to connect the base plate and the upright.

[0018] Preferably, the side wall of the sub-connecting rod is provided with a plurality of flanges spaced apart along the length of the sub-connecting rod.

[0019] With this invention, when construction workers are tying the uprights and steel reinforcement cages, they can tie the wire rope to the upper and lower ends of the flange. The flange blocks the wire rope, thus better preventing the wire rope from slipping on the sub-connecting rod and avoiding unreliable tying.

[0020] This invention provides a method for installing precast box girders, which is achieved by pre-embedded steel plate components at the bottom of the precast box girder as described above. The steps are as follows. S1, Steel Plate Assembly Installation Construction workers first place the base plate flat on the bottom surface inside the precast box girder casting mold. Then, they use measuring instruments to monitor and adjust the slope of the upper surface of the base plate to the design value through the adjustment mechanism. After the base plate is adjusted, they pour sealant along the bottom of the base plate to fill the gap between the base plate and the mold. S2, Precast Box Girder Casting After the steel plate components are installed, the steel reinforcement cage is tied inside the mold, and the bottom plate is tied to the bottom of the steel reinforcement cage. After the steel reinforcement cage is tied, concrete is poured to fix the bottom plate to the beam and then cured to finally form a precast box girder. S3, Support Installation At the bottom of the precast box girder after curing, the supports are connected to the base plate on the ground. S4. Precast box girder installation The precast box girder with supports is hoisted as a whole to the designed position of the pier cap beam, and the anchoring is completed after the bottom plate of the support is in contact with the top surface of the cap beam.

[0021] Through this invention, the combination of steel plate components and construction methods eliminates the need for customized templates for different slopes, saving production costs; and all high-precision operations are completed on the ground, realizing the factory prefabrication and rapid assembly of box girders and supports; at the same time, high-risk operations such as high-altitude welding and on-site slope adjustment are eliminated, significantly reducing construction risks; the bolt connection method facilitates the later inspection and replacement of supports, realizing safe, precise, and maintainable integrated construction.

[0022] As a preferred option, in step S3, the precast box girder is lifted up by a forklift to expose the bottom surface, and the construction workers use bolts to connect the support to the base plate.

[0023] With this invention, a forklift can lift the precast box girder to expose its bottom surface, making it easier for construction workers to install supports at the bottom of the precast box girder.

[0024] Preferably, in step S1, when pouring the sealant, the sealant is poured along the annular gap between the outer edge of the base plate and the mold.

[0025] With this invention, construction workers inject sealant along the annular gap between the outer edge of the base plate and the mold, thus sealing the outer edge of the base plate and preventing concrete from entering below the base plate during concrete pouring. After the concrete pouring is completed, when the forklift lifts the precast box girder to expose the bottom surface, the construction workers can simply remove the sealant from the outer edge of the base plate. By injecting sealant only at the outer edge of the base plate, it is prevented from filling the area below the base plate, which would make it difficult to remove later.

[0026] Preferably, in step S4, the bottom surface of the support and the top surface of the cap beam are cleaned before the bottom surface of the support contacts the top surface of the cap beam.

[0027] By cleaning the support base plate before it contacts the top surface of the cap beam, this invention ensures that the contact surfaces are clean and dry, thereby guaranteeing a tight fit across the entire area and the friction coefficient required by the design. This ensures uniform and reliable load transfer, avoids stress concentration, and fundamentally guarantees the long-term safety and stability of the support installation. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the main body of the steel plate assembly in Example 1.

[0029] Figure 2 This is an exploded view of the main body of the steel plate assembly in Example 1.

[0030] Figure 3 This is a schematic diagram of the upright pole in Example 1.

[0031] Figure 4 This is a schematic diagram of the internal thread in Example 1.

[0032] Figure 5 This is a schematic diagram of the installation of the main body and support of the steel plate assembly in Example 1. Detailed Implementation

[0033] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0034] Example 1 like Figure 1-5 As shown, this embodiment provides a precast box girder bottom embedded steel plate assembly, including a steel plate assembly body 100. The steel plate assembly body 100 includes a bottom plate 120 for anchoring in the bottom concrete of the precast box girder. An adjustment mechanism is provided at the side wall of the bottom plate 120. The adjustment mechanism is used to adjust the inclination of the bottom plate 120 at the bottom of the precast box girder before the precast box girder is poured.

[0035] In this embodiment, when constructing precast box girders, the construction workers first place the base plate 120 of the embedded steel plate assembly on the bottom surface inside the precast box girder casting mold, ensuring it is initially horizontal. Then, through an adjustment mechanism, specifically by rotating the screw 140 located on the side wall of the base plate 120, the screw 140 moves up and down along the nut 130, thereby lifting one end of the base plate 120 and adjusting its inclination. During this process, a high-precision level, total station, or 3D laser scanner is used for real-time monitoring to ensure that the longitudinal and transverse slopes of the plane formed by the upper surface of the base plate 120 precisely meet the values ​​specified in the bridge design drawings. After the slope adjustment is completed, in order to prevent cement slurry from seeping into the bottom plate 120 during subsequent concrete pouring and affecting its final slope and causing corrosion, sealant needs to be injected along the gap between the outer edge of the bottom plate 120 and the mold to form an effective seal. This will prevent the concrete from filling the gap between the bottom plate 120 and the mold during concrete pouring, which would cause the bottom plate 120 to be completely embedded in the precast box girder and affect subsequent installation. After the steel plate components are installed and fixed, the reinforcing steel skeleton of the box girder is tied inside the mold. During this process, the uprights 110 at the four corners of the base plate 120 are tied to the reinforcing steel skeleton with steel wire ropes to ensure that the base plate 120 becomes an inseparable bottom component of the entire reinforcing steel skeleton. After the steel bar spacing, protective layer thickness and other indicators are inspected and found to be qualified, concrete of the design grade is poured. During concrete pouring, attention should be paid to the vibration process to avoid disturbing the already finely adjusted base plate 120. After the concrete solidifies and has undergone the specified curing period, the base plate 120 forms a high-strength, permanent solidified body with the box girder, and its preset precise slope is completely preserved, forming a precast box girder with a customized bottom slope.

[0036] The precast box girder, having been cured and reached its design strength, is transported to the installation preparation area. On the ground, the construction workers hoist the bridge bearings, which are wedge-shaped bearings that match the slope of the bottom of the girder, to the bottom of the box girder. The anchor bolt holes on the bottom plate of the bearing are aligned with the sleeves 330 on the bottom plate 120. Then, high-strength bolts are passed through the anchor bolt holes on the bottom plate of the bearing and screwed into the sleeves 330 to secure the bearing to the bottom plate 120. A torque wrench is used to ensure that the preload of all connecting bolts reaches the design value.

[0037] Using a bridge erecting machine or large lifting equipment, the precast box girder with the pre-assembled supports is hoisted; after being smoothly hoisted to the top of the pier cap beam of the target bridge span, it is slowly lowered; through measurement guidance and fine adjustment of the lifting equipment, the support base plate is precisely aligned with the preset anchor bolt position on the top of the cap beam, and it is ensured that the lower surface of the support base plate is clean, dry and completely in contact with the top surface of the cap beam; after being in place, the connecting anchor bolts between the support base plate and the cap beam are immediately installed and tightened to complete the final anchoring operation; at this point, the precast box girder installation is completed, its bottom slope has been precisely achieved through the pre-embedded steel plate components, and the support is in the designed horizontal stress state.

[0038] In summary, compared with existing technologies, this device, through the cooperation of screws 140 and nuts 130, freely adjusts the inclination of the base plate 120, replacing customized templates, enabling the production of box girders with different slopes on standard pedestals, thus significantly reducing the manufacturing cost of precast box girders. This device transforms the challenges of controlling slope and hole position accuracy at high altitudes and on-site into a precisely adjustable and easily inspectable mechanical operation in a ground factory, achieving millimeter-level installation accuracy. It enables pre-connection of box girders and supports on the ground and overall hoisting, completely eliminating high-risk operations such as high-altitude welding, doubling construction efficiency and ensuring inherent safety.

[0039] In this embodiment, the base plate 120 is rectangular in shape, and each of the four corners of the base plate 120 is provided with a vertical pole 110.

[0040] In this embodiment, the upright 110 extends into the steel reinforcement cage of the precast bridge, and the construction workers tie the upright 110 to the steel reinforcement cage with steel wire ropes, thereby facilitating the construction workers to connect the steel plate assembly to the steel reinforcement cage.

[0041] In this embodiment, the adjustment mechanism includes a nut 130 connected to the side wall of the base plate 120, and a screw 140 that is threadedly engaged with the nut 130 is provided at the nut 130.

[0042] In this embodiment, the construction workers can rotate the screw 140 to move the screw 140 toward the bottom of the box girder mold, thereby lifting one end of the base plate 120, which makes it easier for the construction workers to adjust the tilt angle of the base plate 120 at the bottom of the steel reinforcement cage.

[0043] In this embodiment, the upright 110 includes a sub-connecting rod 310, and a sleeve 330 is provided at the lower end of the sub-connecting rod 310; the inner side wall of the sleeve 330 is provided with an internal thread 410.

[0044] In this embodiment, when connecting the box girder support and the base plate 120, the construction personnel can use bolts to pass through the base plate of the support and engage with the internal thread 410 on the inner side wall of the sleeve 330 to extend into the sleeve 330, thereby connecting the support and the sleeve 330; thus facilitating the construction personnel to connect the support to the steel plate assembly.

[0045] In this embodiment, the base plate 120 is provided with connection holes 210 at all four corners for the sleeve 330 to extend into.

[0046] In this embodiment, when the installer connects the base plate 120 and the upright 110, the sleeve 330 at the lower end of the upright 110 is inserted into the connecting hole 210 on the base plate 120, and then the sleeve 330 is connected to the base plate 120 by welding, which makes it convenient for the installer to connect the base plate 120 and the upright 110.

[0047] In this embodiment, the side wall of the sub-connecting rod 310 is provided with a plurality of flanges 320 spaced apart along the length direction of the sub-connecting rod 310.

[0048] In this embodiment, when the construction workers are tying the uprights 110 and the reinforcing steel cage, they tie the wire rope to the upper and lower ends of the flange 320. The flange 320 blocks the wire rope, thus effectively preventing the wire rope from slipping on the sub-connecting rod 310 and avoiding insecure tying.

[0049] This embodiment provides a method for installing precast box girders, which is achieved by the aforementioned precast box girder bottom embedded steel plate assembly. The steps are as follows. S1, Steel Plate Assembly Installation The construction workers first placed the base plate 120 flat on the bottom surface inside the precast box girder casting mold. Then, they used measuring instruments to monitor and adjusted the slope of the upper surface of the base plate 120 to the design value. After the base plate 120 was adjusted, they poured sealant along the bottom of the base plate 120 to fill the gap between the base plate 120 and the mold. S2, Precast Box Girder Casting After the steel plate components are installed, the steel reinforcement cage is tied inside the mold, and the bottom plate 120 is tied to the bottom of the steel reinforcement cage. After the steel reinforcement cage is tied, concrete is poured to fix the bottom plate 120 to the beam body and then cured to finally form a precast box girder. S3, Support Installation At the bottom of the precast box girder after curing, the support is connected to the base plate 120 on the ground. S4. Precast box girder installation The precast box girder with supports is hoisted as a whole to the designed position of the pier cap beam, and the anchoring is completed after the bottom plate of the support is in contact with the top surface of the cap beam.

[0050] Through this embodiment, the combination of steel plate components and construction methods eliminates the need for customized templates for different slopes, saving production costs; and all high-precision operations are completed on the ground, realizing the factory prefabrication and rapid assembly of box girders and supports; at the same time, high-risk operations such as high-altitude welding and on-site slope adjustment are eliminated, significantly reducing construction risks; the bolt connection method facilitates the later inspection and replacement of supports, realizing safe, precise, and maintainable integrated construction.

[0051] In this embodiment, in step S3, the precast box girder is lifted up by a forklift to expose the bottom surface, and the construction workers use bolts to connect the support to the base plate 120.

[0052] In this embodiment, a forklift lifts the precast box girder to expose its bottom surface, making it easier for construction workers to install supports at the bottom of the precast box girder.

[0053] In this embodiment, during step S1, when pouring the sealant, the sealant is poured along the annular gap between the outer edge of the base plate 120 and the mold.

[0054] In this embodiment, the construction workers inject sealant along the annular gap between the outer edge of the base plate 120 and the mold, thereby sealing the outer edge of the base plate 120 and preventing concrete from entering below the base plate 120 during concrete pouring. After the concrete pouring is completed, when the forklift lifts the precast box girder to expose the bottom surface, the construction workers can simply remove the sealant from the outer edge of the base plate 120. The sealant is only injected on the outer edge of the base plate 120 to prevent it from filling the area below the base plate 120, which would make it difficult to remove later.

[0055] In this embodiment, in step S4, before the bottom surface of the support contacts the top surface of the cap beam, the bottom surface of the support and the top surface of the cap beam are cleaned.

[0056] By cleaning the support base plate before it contacts the top surface of the cap beam in this embodiment, it is possible to ensure that the contact surface is clean and dry, thereby ensuring that the two can achieve a full-area tight fit and the friction coefficient required by the design. This makes the load transfer uniform and reliable, avoids stress concentration, and fundamentally ensures the long-term safety and stability of the support installation.

[0057] It is readily understood that those skilled in the art can combine, split, or reorganize the embodiments provided in this application to obtain other embodiments, all of which do not exceed the protection scope of this application.

[0058] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the embodiments shown are only part of the embodiments of the present invention. The actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A precast box girder bottom embedded steel plate assembly, characterized in that: The utility model relates to a prefabricated box girder bottom embedded steel plate assembly, which comprises a steel plate assembly body (100) including a bottom plate (120) for anchoring in the bottom concrete of a prefabricated box girder, wherein a side wall of the bottom plate (120) is provided with an adjusting mechanism for adjusting the inclination of the bottom plate (120) on the bottom of the prefabricated box girder before pouring the prefabricated box girder.

2. The precast box girder bottom embedded steel plate assembly according to claim 1, wherein: The bottom plate (120) is rectangular in shape, and vertical rods (110) are arranged at four corners of the bottom plate (120).

3. The precast box girder bottom embedded steel plate assembly according to claim 2, wherein: The adjusting mechanism comprises a nut (130) connected to the side wall of the bottom plate (120), and a screw (140) arranged at the nut (130) and threadedly matched with the nut (130).

4. The precast box girder bottom embedded steel plate assembly according to claim 3, wherein: The vertical rod (110) comprises a sub-connecting rod (310) provided with a sleeve (330) at a lower end thereof, and an internal thread (410) is arranged at an inner side wall of the sleeve (330).

5. The precast box girder bottom embedded steel plate assembly according to claim 4, wherein: The four corners of the bottom plate (120) are provided with connecting holes (210) for the sleeves (330) to extend into.

6. The precast box girder bottom embedded steel plate assembly according to claim 4, wherein: The side wall of the sub-connecting rod (310) is provided with a plurality of flanges (320) arranged at intervals along the length direction of the sub-connecting rod (310).

7. A prefabricated box girder installation construction method realized by the prefabricated box girder bottom embedded steel plate assembly according to any one of claims 1-6, comprising the following steps: S1, steel plate assembly installation Firstly, the bottom plate (120) is placed horizontally on the inner bottom surface of the pouring mold of the prefabricated box girder, and then a measuring instrument is used to monitor and adjust the inclination of the upper surface of the bottom plate (120) to the design value through the adjusting mechanism. After the adjustment of the bottom plate (120) is completed, sealant is poured under the bottom plate (120) to fill the gap between the bottom plate (120) and the mold; S2, prefabricated box girder pouring After the installation of the steel plate assembly is completed, the steel reinforcement cage is tied inside the mold, and the bottom plate (120) is tied to the bottom end of the steel reinforcement cage. After the steel reinforcement cage is tied, the bottom plate (120) is poured with concrete to be fixed with the girder body, and then cured to form a prefabricated box girder; S3, support installation The support is connected to the bottom plate (120) on the ground at the bottom of the cured prefabricated box girder; S4, prefabricated box girder installation The prefabricated box girder with the support is hoisted to the designed position of the pier cap beam, and the bottom plate of the support is attached to the top surface of the cap beam to complete the anchoring.

8. The method of claim 7, wherein: In step S3, the prefabricated box girder is lifted by a forklift to expose the bottom surface, and the support is connected to the bottom plate (120) by a bolt.

9. The method of claim 8, wherein: In step S1, when pouring the sealant, the sealant is poured along the annular gap between the outer edge of the bottom plate (120) and the mold.

10. The method of claim 9, wherein: In step S4, the bottom surface of the support and the top surface of the cap beam are cleaned before they are in contact.

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