Repair structure and method for steel bridge main beam end based on ultra-high performance concrete

Abstract

The repair structure and method for the end of a steel bridge main beam based on ultra-high performance concrete belongs to the field of bridge repair structural technology and includes a UHPC-coated segment connected to the steel bridge main beam via a shear connector. The UHPC-coated segment is coated outside the rusted area at the end of the steel bridge main beam, and its length is greater than the rusted length of the steel bridge main beam. This application uses UHPC to repair the deteriorated cross-section of the end of a corroded steel bridge main beam. On the one hand, due to the dense structure and strong impermeability of UHPC, it can effectively prevent further corrosion of the end of the steel bridge main beam, thereby improving the durability of the steel bridge main beam. On the other hand, due to the light weight and high strength of UHPC, the load-bearing capacity of the repaired steel main beam is increased by more than 20% and the vertical stiffness is increased by more than 60% compared to its pre-damage state, significantly improving the structural stiffness and load-bearing capacity of the steel bridge main beam.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge repair structures, and more specifically, relates to a repair structure and method for the end of a steel bridge main beam based on ultra-high performance concrete. Background Art

[0002] Compared with traditional concrete bridges, steel beam bridges have a smaller deadweight, greater load-bearing capacity, stronger spanning capacity, greater underbridge clearance and lower bridge deck elevation, a slender structure, and good landscape effects. Most of the components are manufactured directly in the factory and assembled on site, with fast installation speed, short construction period, and easy repair and replacement. They are gradually being promoted and used in my country.

[0003] Although steel girder bridges are easy to construct and aesthetically pleasing, they also present some challenges in practical engineering applications. The steel plates at the ends of steel girder bridges are subject to long-term erosion and corrosion from water leaking through the bridge deck joints. This can cause structural defects and loss of mechanical properties, thereby reducing the bridge's strength and load-bearing capacity.

[0004] The commonly used method for repairing the ends of rusted steel bridge main beams is to replace the original rusted steel with new steel. Before construction, the ground stress around the piles is first checked. If the terrain and land bearing capacity meet the construction conditions, supports and jacks are erected. The superstructure of the damaged bridge is lifted up using the jacks, the damaged part is cut away, the surface paint of the part to be repaired is removed, lead treatment is performed, new steel is welded, and finally the surface is painted.

[0005] This traditional repair method has many defects. First, jacking and erecting supports have certain requirements for the bearing capacity of the land, and ground stress verification is required. This process is costly and time-consuming. Second, the traditional method requires a large amount of manual welding between steel and steel. The on-site manual welding process is complicated, a lot of surface treatment work must be done before welding, and the speed is slow. The structural ductility after welding is poor and there is a large amount of residual stress. Thirdly, the paint coating of the traditional repair method cannot effectively prevent the corrosion of the steel bridge main beam and has poor durability. The above problems are problems that need to be urgently solved in the repair of steel bridge main beams.

[0006] For example, the document entitled "Analysis of Defects of Existing Steel Structure Bridges and Research on Their Protection Technology" published in "Northern Transportation" in September 2021 mentioned that "corrosion diseases of steel structure bridges will cause extremely great harm to the safe and stable production and application of bridge construction projects"; for example, the review document entitled "Review of Academic Research on China Bridge Engineering 2021" published in the journal "China Journal of Highway and Transport" in February 2021 mentioned on page 12 that "welding is the main connection method for steel structure bridges at present. Initial welding defects and welding residual stresses cause geometric discontinuities, stress concentration and local plasticization on a microscopic scale, which significantly reduce the fatigue extension life of welding nodes." Summary of the Invention

[0007] In response to the above-mentioned technical problems, the present invention proposes a repair structure and method for the end of a steel bridge main beam based on ultra-high performance concrete, which can effectively prevent the continued rusting of the end of the steel bridge main beam, thereby improving the durability, bearing capacity and vertical stiffness of the steel bridge main beam. The construction and repair method has the advantages of less welding, no jacking, strong durability, fewer steps and easy operation during the construction process.

[0008] The present invention adopts the following specific technical solutions:

[0009] The repair structure for the end of a steel bridge main beam based on ultra-high performance concrete includes a UHPC-clad segment, which is connected to the steel bridge main beam through a shear connector. The UHPC-clad segment is wrapped around the outside of the rusted area at the end of the steel bridge main beam, and its length is greater than the rusted length of the steel bridge main beam.

[0010] Preferably, the UHPC cladding segment is composed of a UHPC web plate and a UHPC flange plate.

[0011] Preferably, the height of the UHPC web exceeds the height of the corroded portion of the steel bridge main beam by 0.2 m and is not less than 1 / 3 of the total height of the steel bridge main beam, and the thickness of the UHPC web is 2-5 cm.

[0012] Preferably, the UHPC flange plate is horseshoe-shaped, and the upper portion of the horseshoe-shaped UHPC flange plate is a variable thickness transition zone.

[0013] Preferably, the thickness of the UHPC flange plate is 5-7 cm, and the height of the variable thickness transition zone is 5-10 cm.

[0014] Preferably, the material of the UHPC sheathing segment is ultra-high performance fiber reinforced concrete or reactive powder concrete.

[0015] Preferably, the steel bridge main beam is composed of a steel top plate, a steel web and a steel bottom plate from top to bottom.

[0016] Preferably, the shear connectors are divided into lateral shear connectors and bottom shear connectors. The lateral shear connectors are arranged on the steel web at the end of the steel bridge main beam and embedded in the UHPC web. The bottom shear connectors are arranged on the uncorroded area of ​​the steel bottom plate at the end of the steel bridge main beam and embedded in the UHPC flange plate.

[0017] Preferably, the shear connectors are cylindrical head shear nails and / or welded steel bars.

[0018] A construction method based on the above-mentioned repair structure comprises the following steps:

[0019] S1: Remove the rust from the end of the steel bridge main beam and perform local sandblasting to remove the rust;

[0020] S2: Welding shear connectors on the steel web and bottom plate of the steel bridge main beam;

[0021] S3: Making UHPC cladding segment templates:

[0022] S3.1: Embed the shear connectors and steel bridge girder end cladding in the locations of the UHPC cladding segments;

[0023] S3.2: Pour UHPC materials to integrate the UHPC-clad repair structure with the steel bridge girder;

[0024] S3.3: After the UHPC-coated segment is cured, the formwork is removed and the construction is completed.

[0025] The beneficial effects of the present invention are:

[0026] Using dense, lightweight, and high-strength UHPC to wrap the deteriorated sections at the ends of the steel bridge main beams, fully utilizing UHPC's excellent impermeability, crack resistance, ultra-high mechanical properties, and ductility, can significantly enhance the durability, structural rigidity, and bearing capacity of the steel bridge main beams.

[0027] The UHPC flange plate is designed with a horseshoe-shaped variable thickness transition zone to prevent water flow accumulation and stress concentration, while helping the bottom plate to bear local pressure and improve structural stability.

[0028] The use of shear connectors to connect the steel bridge main beam and the UHPC-clad segments can enhance the structural shear resistance and structural integrity, making the stress distribution of each part more reasonable. At the same time, it can avoid a lot of manual welding work, significantly reduce residual stress, and improve structural safety.

[0029] The construction method of the present application does not require complicated surface treatment, ground stress verification and jacking, manual welding, or individual design for specific projects, and can significantly shorten construction period and reduce project costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the repair structure of the end of the steel bridge main beam based on ultra-high performance concrete according to the present invention;

[0031] Figure 2 for Figure 1 AA direction cross-section diagram.

[0032] 1. Steel bridge girder; 11. Steel top plate; 12. Steel web; 13. Steel bottom plate; 2. UHPC cladding segment; 21. UHPC web; 22. UHPC flange plate; 3. Shear connector; 31. Lateral shear connector; 32. Bottom shear connector; 4. Abutment; 5. Pier. DETAILED DESCRIPTION

[0033] The present invention is further illustrated below with reference to specific examples. Unless otherwise specified, the raw materials and methods used in the examples are commercially available and commonly used in the art. UHPC in this application stands for Ultra-High Performance Concrete.

[0034] Example 1

[0035] like Figure 1 、 2 As shown, abutment 4 on pier 5 connects to the end of a steel bridge girder 1. This embodiment of the ultra-high performance concrete (UHPC) steel bridge girder end repair structure consists of a steel bridge girder 1 and a UHPC-clad segment 2 connected by shear connectors 3. The UHPC-clad segment 2 is composed of a UHPC web 21 and a UHPC flange 22. From top to bottom, the steel bridge girder 1 comprises a steel top plate 11, a steel web 12, and a steel bottom plate 13. The shear connectors 3 are divided into lateral shear connectors 31 and bottom shear connectors 32. The UHPC-clad segment 2 is wrapped around the exterior of the corroded area at the end of the steel bridge girder 1 to compensate for the cross-sectional area lost due to corrosion. The UHPC-clad segment 2 is made of ultra-high performance fiber-reinforced concrete and / or reactive powder concrete, formulated according to the principle of maximum packing density. It has a low water-binder ratio and a dense structure. The addition of short, fine fibers (often primarily steel fibers) improves the material's strength and deformation properties. Compared with ordinary concrete and high-strength concrete, ultra-high performance concrete has ultra-high mechanical properties, ultra-high durability, excellent waterproofness, and adjustable and designable properties based on performance requirements.

[0036] The length of the UHPC-clad segment 2 is greater than the corroded length of the steel bridge girder 1. The height of the UHPC web 21 exceeds the corroded portion of the steel bridge girder by 0.2m and is no less than one-third of the total height of the steel bridge girder 1. The thickness of the UHPC web 21 is 2-5cm. The thickness of the UHPC flange 22 is 5-7cm, with a horseshoe-shaped cross-section. The upper portion of the horseshoe-shaped UHPC flange is a variable thickness transition zone with a height of 5-10cm. This variable thickness transition zone prevents water accumulation and stress concentration, while also helping to locally support the bottom plate.

[0037] Lateral shear connectors 31 are installed on the steel web 12 at the end of the steel bridge main beam 1 and embedded in the UHPC web 21. Bottom shear connectors 32 are installed on the uncorroded area of ​​the steel bottom plate 13 at the end of the steel bridge main beam 1 and embedded in the UHPC flange 22. Shear connectors 3 use cylindrical head shear nails and / or welded steel bars. The length of the lateral shear connector 31 is less than the thickness of the UHPC web 21, and the length of the vertical shear connector is less than the height of the UHPC flange 22. Installing shear connectors 3 can enhance the shear resistance and structural integrity of the structure, making the stress distribution of each component more reasonable.

[0038] The UHPC-coated segment 2 exhibits excellent crack and permeability resistance, protecting the ends of the steel bridge girder 1 from corrosive attack and enhancing the durability of the bridge. This excellent crack resistance is manifested in tensile strain hardening: when the tensile strain level exceeds 0.2%, the crack width of the UHPC-coated segment 2 does not exceed 0.05 mm. Its excellent permeability resistance is demonstrated by a permeability rating of no less than P35, a chloride ion permeability coefficient of less than 2.0 × 10⁻¹⁴ m² / s, and a carbonization depth of no more than 0.5 mm / year under natural conditions. The UHPC-coated segment 2 also exhibits excellent mechanical properties, enhancing the structural stiffness and load-bearing capacity of the repaired steel girder. These mechanical properties include a compressive strength of no less than 130 MPa and a tensile strength of no less than 7.0 MPa. The repaired steel bridge's load-bearing capacity is increased by more than 20%, its overall stiffness by more than 5%, and its vertical stiffness by more than 60% compared to its pre-damage state.

[0039] The UHPC cladding repair structure design in this embodiment adopts the same set of standard designs for typical bridge types, avoiding individual design and customized design shapes for specific projects.

[0040] Example 2

[0041] The ultra-high performance concrete (UHPC) steel bridge girder end repair structure in this embodiment consists of a steel girder 1 connected to a UHPC-clad segment 2 via a shear connector 3. The UHPC-clad segment 2 is composed of a UHPC web 21 and a UHPC flange 22. From top to bottom, the steel girder 1 comprises a steel top plate 11, a steel web 12, and a steel bottom plate 13. The shear connector 3 is divided into a lateral shear connector 31 and a bottom shear connector 32. The UHPC-clad segment 2 is wrapped around the exterior of the corroded area at the end of the steel girder 1 to compensate for the cross-sectional area lost due to corrosion. The UHPC-clad segment 2 is made of ultra-high performance fiber-reinforced concrete and / or reactive powder concrete, formulated according to the principle of maximum packing density. It has a low water-binder ratio and a dense structure. The addition of short, fine fibers (often primarily steel fibers) improves the material's strength and deformation properties. Compared with ordinary concrete and high-strength concrete, ultra-high performance concrete has ultra-high mechanical properties, ultra-high durability, excellent waterproofness, and adjustable and designable properties based on performance requirements.

[0042] The length of the UHPC-clad segment 2 is greater than the corroded length of the steel bridge girder 1. The height of the UHPC web 21 exceeds the corroded portion of the steel bridge girder by 0.2m and is no less than one-third of the total height of the steel bridge girder 1. The thickness of the UHPC web 21 is 2-5cm. The thickness of the UHPC flange 22 is 5-7cm, with a horseshoe-shaped cross-section. The upper portion of the horseshoe-shaped UHPC flange is a variable thickness transition zone with a height of 5-10cm. This variable thickness transition zone prevents water accumulation and stress concentration, while also helping to locally support the bottom plate.

[0043] Lateral shear connectors 31 are installed on the steel web 12 at the end of the steel bridge main beam 1 and embedded in the UHPC web 21. Bottom shear connectors 32 are installed on the uncorroded area of ​​the steel bottom plate 13 at the end of the steel bridge main beam 1 and embedded in the UHPC flange 22. Shear connectors 3 use cylindrical head shear nails and / or welded steel bars. The length of the lateral shear connector 31 is less than the thickness of the UHPC web 21, and the length of the vertical shear connector is less than the height of the UHPC flange 22. Installing shear connectors 3 can enhance the shear resistance and structural integrity of the structure, making the stress distribution of each component more reasonable.

[0044] The UHPC-coated segment 2 exhibits excellent crack and permeability resistance, protecting the ends of the steel bridge girder 1 from corrosive attack and enhancing the durability of the bridge. This excellent crack resistance is manifested in tensile strain hardening: when the tensile strain level exceeds 0.2%, the crack width of the UHPC-coated segment 2 does not exceed 0.05 mm. Its excellent permeability resistance is demonstrated by a permeability rating of no less than P35, a chloride ion permeability coefficient of less than 2.0 × 10⁻¹⁴ m² / s, and a carbonization depth of no more than 0.5 mm / year under natural conditions. The UHPC-coated segment 2 also exhibits excellent mechanical properties, enhancing the structural stiffness and load-bearing capacity of the repaired steel girder. These mechanical properties include a compressive strength of no less than 130 MPa and a tensile strength of no less than 7.0 MPa. The repaired steel bridge's load-bearing capacity is increased by more than 20%, its overall stiffness by more than 5%, and its vertical stiffness by more than 60% compared to its pre-damage state.

[0045] In this embodiment of the ultra-high performance concrete (UHPC) steel bridge girder end repair structure, the I-beam girder 1 is 528 mm tall and 14 mm thick. The UHPC sheathing segment 2 is 660 mm long and 230 mm tall. The UHPC web 21 is 45 mm thick, and the UHPC flange 22 is 73 mm thick and 50 mm tall. The variable thickness transition zone between the UHPC web 21 and the UHPC flange 22 is 50 mm wide. The shear connector 3 has a diameter of 10 mm and a length of 30 mm. The UHPC sheathing segment 2 provides a 15 mm thick protective layer for the shear connector 3.

[0046] The UHPC sheathed segment 2 is cast using ultra-high performance fiber reinforced concrete, and the shear connector 3 uses ultra-short cylindrical head shear studs.

[0047] Example 3

[0048] The ultra-high performance concrete (UHPC) steel bridge girder end repair structure in this embodiment consists of a steel girder 1 connected to a UHPC-clad segment 2 via a shear connector 3. The UHPC-clad segment 2 is composed of a UHPC web 21 and a UHPC flange 22. From top to bottom, the steel girder 1 comprises a steel top plate 11, a steel web 12, and a steel bottom plate 13. The shear connector 3 is divided into a lateral shear connector 31 and a bottom shear connector 32. The UHPC-clad segment 2 is wrapped around the exterior of the corroded area at the end of the steel girder 1 to compensate for the cross-sectional area lost due to corrosion. The UHPC-clad segment 2 is made of ultra-high performance fiber-reinforced concrete and / or reactive powder concrete, formulated according to the principle of maximum packing density. It has a low water-binder ratio and a dense structure. The addition of short, fine fibers (often primarily steel fibers) improves the material's strength and deformation properties. Compared with ordinary concrete and high-strength concrete, ultra-high performance concrete has ultra-high mechanical properties, ultra-high durability, excellent waterproofness, and adjustable and designable properties based on performance requirements.

[0049] The length of the UHPC-clad segment 2 is greater than the corroded length of the steel bridge girder 1. The height of the UHPC web 21 exceeds the corroded portion of the steel bridge girder by 0.2m and is no less than one-third of the total height of the steel bridge girder 1. The thickness of the UHPC web 21 is 2-5cm. The thickness of the UHPC flange 22 is 5-7cm, with a horseshoe-shaped cross-section. The upper portion of the horseshoe-shaped UHPC flange is a variable thickness transition zone with a height of 5-10cm. This variable thickness transition zone prevents water accumulation and stress concentration, while also helping to locally support the bottom plate.

[0050] Lateral shear connectors 31 are installed on the steel web 12 at the end of the steel bridge main beam 1 and embedded in the UHPC web 21. Bottom shear connectors 32 are installed on the uncorroded area of ​​the steel bottom plate 13 at the end of the steel bridge main beam 1 and embedded in the UHPC flange 22. Shear connectors 3 use cylindrical head shear nails and / or welded steel bars. The length of the lateral shear connector 31 is less than the thickness of the UHPC web 21, and the length of the vertical shear connector is less than the height of the UHPC flange 22. Installing shear connectors 3 can enhance the shear resistance and structural integrity of the structure, making the stress distribution of each component more reasonable.

[0051] The UHPC-coated segment 2 exhibits excellent crack and permeability resistance, protecting the ends of the steel bridge girder 1 from corrosive attack and enhancing the durability of the bridge. This excellent crack resistance is manifested in tensile strain hardening: when the tensile strain level exceeds 0.2%, the crack width of the UHPC-coated segment 2 does not exceed 0.05 mm. Its excellent permeability resistance is demonstrated by a permeability rating of no less than P35, a chloride ion permeability coefficient of less than 2.0 × 10⁻¹⁴ m² / s, and a carbonization depth of no more than 0.5 mm / year under natural conditions. The UHPC-coated segment 2 also exhibits excellent mechanical properties, enhancing the structural stiffness and load-bearing capacity of the repaired steel girder. These mechanical properties include a compressive strength of no less than 130 MPa and a tensile strength of no less than 7.0 MPa. The repaired steel bridge's load-bearing capacity is increased by more than 20%, its overall stiffness by more than 5%, and its vertical stiffness by more than 60% compared to its pre-damage state.

[0052] In this embodiment of the ultra-high performance concrete (UHPC) steel bridge girder end repair structure, the I-beam girder 1 is 528 mm tall and 14 mm thick. The UHPC sheathing segment 2 is 660 mm long and 230 mm tall. The UHPC web 21 is 45 mm thick, and the UHPC flange 22 is 73 mm thick and 50 mm tall. The variable thickness transition zone between the UHPC web 21 and the UHPC flange 22 is 50 mm wide. The shear connector 3 has a diameter of 10 mm and a length of 30 mm. The UHPC sheathing segment 2 provides a 15 mm thick protective layer for the shear connector 3.

[0053] The UHPC sheathed segment 2 is cast using ultra-high performance fiber reinforced concrete, and the shear connector 3 of this embodiment uses ultra-short cylindrical head shear nails and welded steel bars.

[0054] Example 4

[0055] A construction method for repairing the structure according to Example 1 and Example 2:

[0056] S1. Remove rust from the ends of the corroded steel bridge beams and perform local sandblasting. Compared to traditional repair methods, this method reduces the amount of complex surface treatment work during the construction process, avoids complex lead removal work, and prevents lead-containing waste from polluting the environment.

[0057] S2. Weld shear nails or construct other shear connectors on the steel web 12 and steel bottom plate 13 of the steel bridge main beam;

[0058] S3. Prepare UHPC coated segment templates, cover and bury the shear connector 3 and the end of the steel bridge main beam 1 in the UHPC coated segment 2, pour UHPC material to form a whole with the UHPC coated repair structure and the steel bridge main beam 1, and remove the template after the UHPC coated segment 2 is cured to complete the construction.

[0059] This construction process can avoid jacking and ground stress review, has lower requirements for the terrain and foundation bearing capacity around the bridge to be repaired, and has a wider range of applicability. It can also significantly shorten the construction period and reduce project costs.

[0060] In summary, the repair structure and method for the end of a steel bridge main beam based on ultra-high performance concrete of the present invention have the advantages of less welding, no jacking, strong durability, fewer steps, easy operation during the construction process, high strength after repair, and low residual stress. It is practical, beautiful, and has high economic benefits. It has broad application prospects in the field of steel bridge main beam repair.

[0061] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. Repair structure of the end of steel bridge girder based on ultra-high performance concrete, characterized by: The invention comprises a UHPC clad segment, wherein the UHPC clad segment is connected to the steel bridge main beam through a shear connector, and the UHPC clad segment is clad outside the rusted area at the end of the steel bridge main beam, and its length is greater than the rusted length of the steel bridge main beam; the UHPC clad segment is composed of a UHPC web plate and a UHPC flange plate; the UHPC flange plate is horseshoe-shaped, and the upper part of the horseshoe-shaped UHPC flange plate is a variable thickness transition zone; the thickness of the UHPC flange plate is 5-7 cm, and the height of the variable thickness transition zone is 1.5-2.5 cm. The UHPC web is 5-10 cm; the height of the UHPC web exceeds the height of the corroded part of the steel bridge main beam by 0.2 m and is not less than 1 / 3 of the total height of the steel bridge main beam, and the thickness of the UHPC web is 2-5 cm; the shear connector is divided into a lateral shear connector and a bottom shear connector. The lateral shear connector is arranged on the steel web at the end of the steel bridge main beam and embedded in the UHPC web. The bottom shear connector is arranged on the non-corroded area of ​​the steel bottom plate at the end of the steel bridge main beam and embedded in the UHPC flange plate.

2. The repair structure for the end of a steel bridge main beam based on ultra-high performance concrete according to claim 1, characterized in that: The UHPC sheathing segment is made of ultra-high performance fiber reinforced concrete or reactive powder concrete.

3. The repair structure for the end of a steel bridge main beam based on ultra-high performance concrete according to claim 1, characterized in that: The steel bridge main beam is composed of a steel top plate, a steel web plate and a steel bottom plate from top to bottom.

4. The repair structure for the end of a steel bridge main beam based on ultra-high performance concrete according to claim 1, characterized in that: The shear connectors are cylindrical head shear nails and / or welded steel bars.

5. A construction method for a repair structure according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: Remove the rust from the end of the steel bridge main beam and perform local sandblasting to remove the rust; S2: Welding shear connectors on the steel web and bottom plate of the steel bridge main beam; S3: Making UHPC cladding segment templates: S3.1: Embed the shear connectors and steel bridge girder end covers in the locations of the UHPC covered segments; S3.2: Pour UHPC materials to integrate the UHPC-clad repair structure with the steel bridge girder; S3.3: After the curing of the UHPC coated segments is completed, the formwork is removed and the construction is completed.

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