A method for rapid assembly and reinforcement of a hollow slab beam of a transverse bridge UHPC prefabricated part

Abstract

The application discloses a kind of hollow slab beam quick assembly reinforcing methods of transverse bridge UHPC prefabricated piece, comprising: S1, prestressed tendon is first tensioned;S2, in the tensioned state of prestressed tendon, UHPC material is poured;S3, after curing, the connection of prestressed tendon and external tensioning equipment is cut off;S4, remove broken concrete in hinge joint, and water flow flush and gouging hinge joint in the outer surface of hollow beam slab;S5, temporary support is used to support hollow beam slab, and formwork is erected and is sequentially poured into micro-expansion fiber concrete, water-swelling polyurethane material layer in hinge joint;S6, anchor bolt is planted in the bottom surface of hollow slab beam and gouging treatment and anchor bolt is planted, and gouging surface is coated with structural adhesive;S7, UHPC prefabricated piece is bolted with structural adhesive and hollow slab beam;S8, remove temporary support.The application is combined with prestressed tendon using UHPC prefabricated piece, so that the carrying capacity is improved, and the crack resistance is improved, and the corrosion problem of traditional steel reinforcement is solved completely, and the service life is prolonged.

Description

Technical Field

[0001] This invention relates to the field of rapid assembly and reinforcement of hollow slab beams in transverse UHPC precast components. More specifically, this invention relates to a method for rapid assembly and reinforcement of hollow slab beams in transverse UHPC precast components. Background Technology

[0002] Precast concrete hollow slab girders are widely used in small and medium-span bridges due to their economical material use and well-defined stress distribution. The hinge joints play a crucial role in the transverse connections of hollow slab girders, but they are also their weakest point. Under vehicle loads, especially heavy traffic, the hinge joints of hollow slab girders are prone to damage (such as concrete spalling and water seepage and efflorescence), leading to individual slab stress, transverse cracking, and other defects, reducing the bridge's load-bearing capacity and durability.

[0003] To address the common problem of single-slab stress in existing prefabricated hollow slab girder bridges caused by the failure of hinge joints in the transverse connection structure of the main beams, researchers have proposed various reinforcement methods for the hinge joint structure, such as bonding steel plates and carbon fiber to the bottom plate, in order to improve the working performance of the hinge joint and avoid single-slab stress. However, the above-mentioned hinge joint reinforcement methods are limited to improving the local bearing capacity of the hinge joint between the main beams and cannot fundamentally solve the problem of single-slab stress in prefabricated hollow slab girder bridges, nor can they enhance the transverse load distribution and improve the overall stress state of the bridge. Summary of the Invention

[0004] To achieve these objectives and other advantages according to the present invention, a preferred embodiment of the present invention provides a method for rapid assembly and reinforcement of hollow slab beams of transverse UHPC precast components, comprising the following steps: S1, Tensioning of non-metallic prestressed tendons First, fix the non-metallic prestressing tendons on the tensioning equipment and apply the tension force required by the design to put the non-metallic prestressing tendons in a tensile state. S2, Casting UHPC-encased non-metallic prestressed tendons While the non-metallic prestressing tendons are kept under tension, UHPC material is poured to wrap around the non-metallic prestressing tendons. After the UHPC hardens, it forms a tight bond with the non-metallic prestressing tendons, forming an I-shaped UHPC precast component. S3. Disconnect the tensioning equipment after proper maintenance. After the UHPC is cured to its design strength, the connection between the non-metallic prestressing tendons and the external tensioning equipment is cut off to obtain the UHPC precast component. S4. Remove the broken concrete inside the hinge joint, and use high-pressure water jet to flush and roughen the outer surface of the hollow beam slab inside the hinge joint. S5. Temporary supports are used to support the hollow beams and slabs to reduce or eliminate the disturbance of the hollow beams and slabs under operating loads. The formwork is erected and micro-expansion fiber concrete is poured into the hinge joint. A layer of water-swellable polyurethane material is poured on top of the micro-expansion fiber concrete in the hinge joint. S6. Install anchor bolts on the bottom surface of the hollow slab beam and roughen the surface before installing anchor bolts. Apply structural adhesive to the roughened surface. S7. Securely fasten the UHPC precast components to the structural adhesive and hollow slab beams using anchor bolts. S8. Temporary supports are removed after the hinge joint concrete and structural adhesive meet the design requirements.

[0005] Preferably, in step S1, the non-metallic prestressing tendons adopt a variable cross-section design, wherein the cross-sectional area of ​​the mid-span section is larger than that of the end section, so as to optimize the prestress distribution and reduce the stress concentration of the end anchorage.

[0006] Preferably, when disconnecting the tensioning equipment in step S3, a phased release process is adopted: first release 50% of the tension, let it stand for 12 to 24 hours, and then completely cut off the non-metallic prestressing tendons to reduce the residual stress gradient of the UHPC precast component.

[0007] Preferably, in step S5, a gap of 2-5mm is reserved between the UHPC precast component and the hollow slab beam. After the structural adhesive cures, it forms a flexible buffer layer to absorb micro-vibrations under vehicle load.

[0008] Preferably, 0.8% to 1.5% carbon nanofibers are incorporated into the UHPC to form a conductive network with adjustable resistivity. The resistance change rate of the UHPC preform is linearly related to the crack width.

[0009] Preferably, in step S5, 1%~2% of piezoelectric ceramic particles with a particle size of 20~50μm are added to the joint grout. When the resistance change rate of the conductive UHPC is detected... When the content is ≥5%, cracks exist on the surface. The signal generator automatically applies local vibration with a frequency of 50~100Hz and an amplitude of 0.1~0.3MPa to the piezoelectric ceramic in the grouting area to promote the secondary flow of unhardened grout to fill the micro-cracks.

[0010] Preferably, the web of the UHPC precast component adopts a three-layer gradient structure, with the inner layer containing 1.5% steel fiber, the middle layer containing 0.8% carbon nanotubes, and the outer layer containing 2% basalt fiber. The tensile strength of the steel fiber is ≥2500MPa, the conductivity of the carbon nanotubes is ≥1000S / m, and the temperature resistance of the basalt fiber is ≥800℃. Each layer is gradually transitioned.

[0011] Preferably, the UHPC precast component adopts an I-shaped cross section and is provided with stiffening ribs at the position corresponding to the hinge joint of the hollow slab to improve the shear resistance of the UHPC precast component.

[0012] Preferably, the width of the upper flange of the I-shaped cross-section is greater than the width of the lower flange.

[0013] Preferably, strain sensors are longitudinally installed on the lower flange plate at the position corresponding to the hinge joint of the hollow slab of the UHPC precast component, and vertical strain sensors are installed on both sides of the stiffening rib along the transverse bridge direction to monitor the working status of the UHPC precast component.

[0014] This invention offers at least the following beneficial effects: It provides a rapid assembly and reinforcement method for hollow slab beams using transverse UHPC precast components. The method combines UHPC precast components with non-metallic prestressed tendons, enhancing the load-bearing capacity and crack resistance of the reinforced hollow slab beams. Simultaneously, it completely solves the corrosion problem associated with traditional steel reinforcement, extending the service life. The distributed prestressed structure ensures more uniform stress transmission. The factory prefabrication + on-site assembly process shortens the construction cycle, reduces traffic interruption time, and ensures that construction under the bridge does not affect existing traffic on the bridge. The perforated steel plate and grouting technology enable simultaneous hinge joint repair and transverse reinforcement, achieving a synergistic stress-bearing efficiency of over 95% between the new and old structures, systematically solving the stress problem of single-slab beams. Since UHPC has a density less than 1 / 3 that of steel, the increased bridge weight after reinforcement is less than 5%, avoiding adverse effects on the original bridge foundation.

[0015] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the rapid assembly of the hollow slab beam of the transverse UHPC prefabricated component in this invention.

[0017] Figure 2 This is another schematic diagram of the rapid assembly of the hollow slab beam of the transverse UHPC prefabricated component in this invention. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0019] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious modifications will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0020] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "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, the above terms should not be construed as limiting this invention.

[0021] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0022] like Figure 1-2 As shown, a preferred embodiment of the present invention provides a rapid assembly and reinforcement method for hollow slab beams of transverse UHPC precast components, comprising the following steps: S1, Tensioning of non-metallic prestressed tendons First, fix the non-metallic prestressing tendons on the tensioning equipment and apply the designed tension force to put the non-metallic prestressing tendons in a tensile state; during the tensioning process, the loading rate needs to be controlled to avoid sudden stress changes.

[0023] S2, Casting UHPC-encased non-metallic prestressed tendons While the non-metallic prestressing tendons are kept under tension, UHPC material is poured to wrap around the non-metallic prestressing tendons. After the UHPC hardens, it forms a tight bond with the non-metallic prestressing tendons, forming an I-shaped UHPC precast component. S3. Disconnect the tensioning equipment after proper maintenance. After the UHPC is cured to the design strength, the connection between the non-metallic prestressing tendons and the external tensioning equipment is cut off to obtain UHPC precast component 1; S4. Remove the broken concrete inside the hinge joint, and use high-pressure water jet to flush and roughen the outer surface of the hollow beam slab 2 inside the hinge joint; this can better bond the new and old concrete at the interface and improve performance.

[0024] S5. Temporary supports are used to support the hollow beam slab 2 to reduce or eliminate the disturbance of the hollow beam slab 2 under the operating load. The formwork is erected and micro-expansion fiber concrete is poured into the hinge joint 5 on the surface of the hollow beam slab 2. A layer of water-swellable polyurethane material is poured on top of the micro-expansion fiber concrete in the hinge joint. S6. Install anchor bolts on the bottom surface of hollow slab beam 2 and roughen the surface before installing anchor bolts. Apply structural adhesive 4 to the roughened surface. S7. Securely bolt the UHPC precast component 1 to the structural adhesive 4 and the hollow slab beam 2 using anchor bolts. After S8, the hinge joint concrete and structural adhesive 4 meet the design requirements, the temporary supports are removed.

[0025] First, the non-metallic prestressing tendons are tensioned. One end of the selected non-metallic prestressing tendon is fixed to the anchor end of the tensioning device, and the other end passes through the tensioning end of the device. Tension is gradually applied using the device until the tendon reaches the predetermined tensile state. Next, while the tendon remains under tension, UHPC material is evenly poured around it using a casting device, completely encasing the tendon. After compaction, an I-shaped UHPC precast slab is formed. Once the UHPC precast slab has cured to its design strength, the connection between the non-metallic prestressing tendon and the tensioning device is severed using a cutting tool, resulting in the UHPC precast component. Subsequently, holes are drilled at the designed spacing and positions on the bottom surface of the hollow slab beam, anchor bolts are inserted, and the surface is roughened to increase roughness before applying a layer of structural adhesive. Finally, the UHPC precast components are bolted to the structural adhesive and hollow slab beams with anchor bolts to ensure a firm connection. The hinge joint is covered with a perforated steel plate, and grout is injected into the hinge joint through the holes in the steel plate for reinforcement.

[0026] In this process, micro-expansion fiber concrete is injected into the hinge joint 5 on the surface of the hollow beam slab 2. A water-swellable polyurethane material layer is then injected on top of the micro-expansion fiber concrete in the hinge joint. The injection of micro-expansion fiber concrete is mainly to improve the crack resistance and durability of the hinge joint concrete. The injection of the water-swellable polyurethane material layer is mainly to prevent water from seeping into the hinge joint through road surface cracks and flowing through the hinge joint, thus affecting the durability of the hinge joint and the aesthetics of the bottom surface of the beam.

[0027] The above technical solution ensures a tight bond between the non-metallic prestressing tendons and the UHPC by first tensioning the non-metallic prestressing tendons and then casting the UHPC, thereby improving the overall performance of the precast slab. The I-shaped section design makes reasonable use of material properties to enhance the load-bearing capacity of the precast slab, enabling the reinforced hollow slab beam to better withstand loads and improve the stability and safety of the structure.

[0028] In another technical solution, the non-metallic prestressing tendons in step S1 adopt a variable cross-section design, wherein the cross-sectional area of ​​the mid-span section is larger than that of the end section, so as to optimize the prestress distribution and reduce the stress concentration of the end anchorage.

[0029] The above technical solution employs non-metallic prestressing tendons with variable cross-section design, which can optimize the prestress distribution according to the stress characteristics of different parts of the hollow slab beam. The larger cross-sectional area in the mid-span section provides sufficient prestress to withstand the mid-span bending moment, while the smaller cross-sectional area at the ends reduces anchorage stress concentration, effectively reducing the risk of failure caused by stress concentration at the ends and improving the durability and reliability of the reinforced structure.

[0030] In another technical solution, a phased release process is adopted when disconnecting the tensioning equipment in step S3: first release 50% of the tension, let it stand for 12 to 24 hours, and then completely cut off the non-metallic prestressing tendons to reduce the residual stress gradient of the UHPC precast component.

[0031] The above technical solution employs a phased release of tension, gradually reducing the tension in the non-metallic prestressing tendons. This allows for the uniform release of internal stress within the UHPC precast component, significantly reducing the residual stress gradient. This avoids cracks or internal damage to the precast component due to sudden stress changes, ensuring the structural integrity of the precast component, extending its service life, and improving the quality of the reinforcement project.

[0032] In another technical solution, a 2-5mm gap is reserved between the UHPC precast component and the hollow slab beam in step S7. After the structural adhesive is cured, a flexible buffer layer is formed to absorb the micro-vibrations under vehicle load.

[0033] The 2-5mm gap is a small space intentionally left between the UHPC precast component and the hollow slab beam when connecting them. The flexible buffer layer formed after the structural adhesive cures can absorb the micro-vibrations generated by the hollow slab beam under vehicle loads. In step S7, during the connection of the UHPC precast component and the hollow slab beam, after applying the structural adhesive, a 2-5mm gap is left between the UHPC precast component and the hollow slab beam by adjusting the tightness of the anchor bolts or using shims. After the structural adhesive cures, this gap is filled to form a flexible buffer layer. This is subsequently reinforced by grouting into the hinge joint using a perforated steel plate.

[0034] The 2-5mm gap, combined with the flexible buffer layer formed by the structural adhesive, effectively absorbs the micro-vibrations generated by vehicle loads. This reduces the impact of vibration on the connection points, prevents fatigue damage caused by vibration, enhances the stability and durability of the reinforced structure, and lowers later maintenance costs.

[0035] In another technical solution, 0.8% to 1.5% carbon nanofibers are incorporated into UHPC to form a conductive network with adjustable resistivity. The rate of change of resistance in the UHPC preform is linearly related to the crack width. =3.2 × crack width / mm.

[0036] The above technical solution incorporates carbon nanofibers into UHPC to form a conductive network, establishing a linear relationship between the resistance change rate of the precast component and the crack width, thus enabling real-time, quantitative detection of cracks in hollow slab beams. When cracks appear in the structure, they can be detected promptly, and corresponding measures can be taken to prevent further crack propagation, ensuring structural safety and improving structural maintainability.

[0037] In another technical solution, in step S7, 1%~2% of piezoelectric ceramic particles with a particle size of 20~50μm are added to the joint grout. When the resistance change rate of the conductive UHPC is detected... When the content is ≥5%, cracks exist on the surface. The signal generator automatically applies local vibration with a frequency of 50~100Hz and an amplitude of 0.1~0.3MPa to the piezoelectric ceramic in the grouting area to promote the secondary flow of unhardened grout to fill the micro-cracks.

[0038] Piezoelectric ceramic particles are added to the hinge joint grout and linked to a conductive UHPC detection system. When a crack is detected, the piezoelectric ceramics automatically apply local vibration, promoting secondary flow of the grout. This allows the grout to better fill micro-cracks, improving the grouting quality and density of the hinge joint, enhancing the integrity and waterproofing performance of the reinforced structure, and improving the structure's durability.

[0039] In another technical solution, the web of the UHPC precast component adopts a three-layer gradient structure. The inner layer contains 1.5% steel fiber, the middle layer contains 0.8% carbon nanotubes, and the outer layer contains 2% basalt fiber. The tensile strength of the steel fiber is ≥2500MPa, the conductivity of the carbon nanotubes is ≥1000S / m, and the temperature resistance of the basalt fiber is ≥800℃. Each layer is gradually transitioned.

[0040] The HPC precast slab web features a three-layer gradient structure: an inner layer of steel fibers to enhance tensile strength, a middle layer of carbon nanotubes to impart electrical conductivity, and an outer layer of basalt fibers to improve temperature resistance. The gradual transition between layers allows the precast slab to possess different performance advantages in different locations, meeting the comprehensive performance requirements for hollow core beam reinforcement and improving the overall performance and applicability of the precast slab.

[0041] In another technical solution, the UHPC precast component adopts an I-shaped cross section and is equipped with stiffening ribs at the position corresponding to the hinge joint of the hollow slab to improve the shear resistance of the UHPC precast component and avoid the occurrence of single-slab stress conditions.

[0042] In another technical solution, the width of the upper flange of the I-shaped section is greater than the width of the lower flange, and the width of the lower flange can be adjusted according to actual needs.

[0043] In another technical solution, strain sensors are longitudinally installed on the lower flange plate at the corresponding position of the hinge joint of the hollow slab of the UHPC precast component, and vertical strain sensors are installed on both sides of the stiffening rib along the transverse bridge direction to monitor the working status of the UHPC precast component.

[0044] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A rapid assembly and reinforcement method for hollow slab beams of transverse UHPC precast components, characterized in that, Includes the following steps: S1, Tensioning of non-metallic prestressed tendons First, fix the non-metallic prestressing tendons on the tensioning equipment and apply the tension force required by the design to put the non-metallic prestressing tendons in a tensile state. S2, Casting UHPC-encased non-metallic prestressed tendons While the non-metallic prestressing tendons are kept under tension, UHPC material is poured to wrap around the non-metallic prestressing tendons. After the UHPC hardens, it forms a tight bond with the non-metallic prestressing tendons, forming an I-shaped UHPC precast component. S3. Disconnect the tensioning equipment after proper maintenance. After the UHPC is cured to its design strength, the connection between the non-metallic prestressing tendons and the external tensioning equipment is cut off to obtain the UHPC precast component. S4. Remove the broken concrete inside the hinge joint, and use high-pressure water jet to flush and roughen the outer surface of the hollow slab beam inside the hinge joint. S5. Use temporary supports to support the hollow slab beam to reduce or eliminate the disturbance of the hollow slab beam under the operating load, erect the formwork and pour micro-expansion fiber concrete into the hinge joint, and pour a water-swellable polyurethane material layer on top of the micro-expansion fiber concrete in the hinge joint. S6. Anchor bolts are installed and the surface of the hollow slab beam is roughened. Structural adhesive is then applied to the roughened surface. S7. Securely fasten the UHPC precast components to the structural adhesive and hollow slab beams using anchor bolts. S8. Temporary supports are removed after the hinge joint concrete and structural adhesive meet the design requirements.

2. The rapid assembly and reinforcement method for hollow slab beams of transverse UHPC precast components according to claim 1, characterized in that, In step S1, the non-metallic prestressing tendons adopt a variable cross-section design, in which the cross-sectional area of ​​the mid-span section is larger than that of the end section, in order to optimize the prestress distribution and reduce the stress concentration of the end anchorage.

3. The rapid assembly and reinforcement method for hollow slab beams of transverse UHPC precast components according to claim 1, characterized in that, When disconnecting the tensioning equipment in step S3, a phased release process is adopted: first release 50% of the tension, let it stand for 12 to 24 hours, and then completely cut off the non-metallic prestressing tendons to reduce the residual stress gradient of the UHPC precast component.

4. The rapid assembly and reinforcement method for hollow slab beams of transverse UHPC precast components according to claim 1, characterized in that, In step S7, a 2-5mm gap is reserved between the UHPC precast component and the hollow slab beam. After the structural adhesive cures, it forms a flexible buffer layer to absorb the micro-vibrations under vehicle load.

5. The rapid assembly and reinforcement method for hollow slab beams of transverse UHPC precast components according to claim 1, characterized in that, The web of the UHPC precast component adopts a three-layer gradient structure. The inner layer contains 1.5% steel fiber, the middle layer contains 0.8% carbon nanotubes, and the outer layer contains 2% basalt fiber. The tensile strength of the steel fiber is ≥2500MPa, the conductivity of the carbon nanotubes is ≥1000S / m, and the temperature resistance of the basalt fiber is ≥800℃. Each layer is gradually transitioned.

6. The rapid assembly and reinforcement method for hollow slab beams of transverse UHPC precast components according to claim 1, characterized in that, The UHPC precast components adopt an I-shaped cross section and are equipped with stiffening ribs at the positions corresponding to the hinge joints of the hollow slabs to improve the shear resistance of the UHPC precast components.

7. The rapid assembly and reinforcement method for hollow slab beams of transverse UHPC precast components according to claim 6, characterized in that, The width of the upper flange of the I-shaped cross-section is greater than the width of the lower flange.

8. The rapid assembly and reinforcement method for hollow slab beams of transverse UHPC precast components according to claim 6, characterized in that, Strain sensors are installed longitudinally on the lower flange plate at the corresponding position of the hinge joint of the hollow slab of the UHPC precast component, and vertical strain sensors are installed on both sides of the stiffening rib along the transverse bridge direction to monitor the working status of the UHPC precast component.

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