Bridge abutment semi-flexible transition section construction method based on stiffness gradient regulation and control

Abstract

The invention provides a bridge abutment semi-flexible transition section construction method based on rigidity gradient regulation and control, which relates to the technical field of bridge abutment construction and comprises the steps of grating laying, concrete layered filling and compacting, asphalt surface layer paving and the like. The deformation difference of the road and bridge connecting sections can be relieved, and the bumping phenomenon at the bridge head is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of abutment construction, and in particular to a method for constructing a semi-flexible transition section of an abutment based on stiffness gradient regulation. Background Art

[0002] In southern China, where soft soil foundations exist, bridgehead jolting is a common phenomenon. To prevent jolting caused by post-construction settlement at the bridgehead and misalignment, installing effective slabs behind the abutments is a key measure. The design of the slabs must account for differences in structural stiffness. The bridge structure has high overall stiffness, while the connected embankment is a flexible structure. The two differ in stiffness and, consequently, in post-operation settlement. This transitional design mitigates sudden jolting at the bridgehead and distributes the resulting differential settlement over a certain distance. However, in reality, the rigid slabs are evenly supported directly on the abutments and the soil, preventing rolling equipment from reaching the abutment back during construction. Consequently, the compaction rate falls short of the required level, creating a significant risk.

[0003] Quantitative Analysis of Existing Technology Flaws: Compaction Defects: The compaction degree of conventional slab ends is generally below 93% (GB / T50123-2019 standard requires ≥96%), resulting in post-construction settlements of 5-8 cm. Sudden Stiffness Changes: The stiffness difference between the bridge (elastic modulus 35 GPa) and the roadbed (modulus <500 MPa) exceeds 70 times, resulting in a sudden longitudinal slope change of 0.6-1.2%. Maintenance Costs: Conventional solutions incur an average annual maintenance cost of 120,000-180,000 yuan per kilometer of bridgehead section (2022 maintenance data from the Ministry of Transport).

[0004] In the road section with bridge slab, the post-construction settlement will form a unique "saddle-shaped" shape, such as Figure 1 As shown in the typical longitudinal section curve in the figure. Due to the setting of the lap plate, there is no obvious misalignment at the joint. However, the difference between the longitudinal slope of the road surface after settlement deformation and the designed longitudinal slope of the road surface will lead to the phenomenon of "bridge jumping", that is, passengers Figure 1 The area between points B and A will feel the most discomfort.

[0005] Therefore, the impact of differential settlement on a "saddle-shaped" bridge approach on driving comfort is not directly determined by the absolute change in longitudinal slope caused by uncoordinated roadbed deformation, but rather by the difference in longitudinal slope between two adjacent sections. This longitudinal slope difference reflects the degree of change in longitudinal slope between adjacent sections caused by differential settlement and determines its impact on driving comfort. The greater the longitudinal slope difference, the greater the dynamic load coefficient when traveling from point B to point A, and the worse the passenger comfort. Summary of the Invention

[0006] In view of the above-mentioned prior art, the present invention proposes a construction method for a semi-flexible transition section of an abutment based on stiffness gradient control.

[0007] The present invention provides a method for constructing a semi-flexible transition section of an abutment based on stiffness gradient control, comprising the following steps: S1. Grille Laying: Lay the first grille section on the road subbase in the direction of the bridgehead slab. Connect one end of the first grille section to the bridgehead slab via several φ32 galvanized steel bars. Connect the other end of the first grille section to the second grille section via several φ32 galvanized steel bars. Connect the other end of the second grille section to the third grille section via several φ28 galvanized steel bars. Connect the other end of the third grille section to the fourth grille section via several φ25 galvanized steel bars. Connect the other end of the fourth grille section to the fifth grille section via several φ22 galvanized steel bars. Provide several concrete openings on the first through fifth grille sections. S2. Concrete filling and compaction in layers: fill the aggregate through the concrete openings to halfway into the first to fifth sections of the grid, compact it with a small machine, and then lay the upper layer and compact it as a whole; S3. Asphalt surface layer paving: Spread the asphalt surface layer on the upper end of the concrete grid section after concrete filling and compaction, so that the concrete grid section and the roadbed form a whole.

[0008] Preferably, in S1, the first to fifth sections of the grille all adopt an assembled structure, and are all composed of two I-shaped components in the middle and two C-shaped components at both ends. The splicing interface is made of steel plates in a Z shape and connected by fixing bolts.

[0009] Preferably, in S1, the cell height of the first to second sections of the grid is 400 mm, the wall thickness is 120 mm, and the reinforcement ratio is 2.8%; the cell height of the third section of the grid is 350 mm, the wall thickness is 100 mm, and the reinforcement ratio is 2.2%; the cell height of the fourth to fifth sections of the grid is 300 mm, the wall thickness is 80 mm, and the reinforcement ratio is 1.6%.

[0010] Preferably, in S1, the shear strength of the joint is ≥85 MPa, and the allowable angular displacement is ±2.5°.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention incorporates a concrete grid extending along the bridgehead slab. Connecting rebars, it extends into the concrete of the preceding slab, forming a continuous structural system. This design strengthens the connection between the slab and the roadbed, enhancing overall structural stability. Furthermore, the concrete grid's deformation capacity is enhanced by decreasing in size from 32mm to 22mm from the abutment to the distal end. This helps mitigate deformation differences at the road-bridge junction and reduces vehicle bouncing at the bridgehead.

[0012] 2. The construction method of the present invention greatly reduces the time for on-site concrete pouring and improves construction efficiency. At the same time, the prefabricated construction helps to ensure the dimensional accuracy and connection strength of the concrete grid, thereby improving the stability of the overall structure.

[0013] 3. This invention uses galvanized steel bars to connect the concrete grid sections, enhancing the corrosion resistance of the joints and extending the service life of the structure. Furthermore, by varying the diameter of the steel bars, the deformation capacity of the concrete grid at the end is increased, synchronizing with the roadbed deformation, further reducing bridge head bounce. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the abutment slab in the present invention.

[0015] Figure 2 This is a construction diagram of the grid laying in an embodiment of the present invention.

[0016] Figure 3 Schematic diagram of the structure of a single-section grid in an embodiment of the present invention.

[0017] Figure 4 Schematic diagram of the structure of the splicing interface in an embodiment of the present invention.

[0018] In the figure: 1. The first section of grille; 2. φ32 galvanized steel bars; 3. The second section of grille; 4. φ28 galvanized steel bars; 5. The third section of grille; 6. φ25 galvanized steel bars; 7. The fourth section of grille; 8. φ22 galvanized steel bars; 9. The fifth section of grille; 10. Concrete opening; 11. Joint. DETAILED DESCRIPTION

[0019] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific embodiments.

[0020] Example: Figure 2-4 A construction method for a semi-flexible transition section of an abutment based on stiffness gradient control is shown, comprising the following steps: S1. Laying of grilles: Lay the first section of grille 1 on the road subbase in the direction of the extension of the bridge slab. One end of the first section of grille 1 is connected to the bridge slab through four φ32 galvanized steel bars. The other end of the first section of grille 1 is connected to the second section of grille 3 through four φ32 galvanized steel bars 2. The other end of the second section of grille 3 is connected to the third section of grille 5 through four φ28 galvanized steel bars 4. The other end of the third section of grille 5 is connected to the fourth section of grille 7 through four φ25 galvanized steel bars 6. The other end of the fourth section of grille 7 is connected to the fifth section of grille 9 through four φ22 galvanized steel bars 8. Four concrete openings 10 are set on the first to fifth sections of grille, and the first section is connected to the bridge slab through four φ32 galvanized steel bars 2. The grid sections from the first to the fifth section all adopt an assembled structure, each composed of two I-shaped components in the middle and two C-shaped components at both ends. The joint 11 is made of 10mm steel plate in a Z shape and connected by fixing bolts. The cell height of the first to second sections of the grid is 400mm, the wall thickness is 120mm, and the reinforcement ratio is 2.8%. The cell height of the third section 5 of the grid is 350mm, the wall thickness is 100mm, and the reinforcement ratio is 2.2%. The cell height of the fourth to fifth sections of the grid is 300mm, the wall thickness is 80mm, and the reinforcement ratio is 1.6%. The shear strength of the joint 11 is ≥85Mpa, and the allowable angular displacement is ±2.5°. S2. Concrete filling and compaction in layers: fill the aggregate into half of the first to fifth sections of the grid through the concrete opening 10, compact it with a small machine, and then lay the upper layer and compact it as a whole; S3. Asphalt surface layer paving: Spread the asphalt surface layer on the upper end of the concrete grid section after concrete filling and compaction, so that the concrete grid section and the roadbed form a whole.

[0021] Compared to traditional concrete slabs, this embodiment can effectively reduce or eliminate bridgehead bouncing, thereby improving the performance and lifespan of the bridge. The prefabricated concrete grid technology used in this embodiment is more economical in terms of material usage, saving up to 60% in material costs. Furthermore, this technology also demonstrates significant advantages in terms of construction schedule, saving 70% of construction time. This grid structure can better integrate with the roadbed, effectively reducing road surface deformation caused by uneven roadbed settlement, ensuring road smoothness and driving safety.

[0022] In the structural design of this embodiment, the end of the concrete grid coincides with point C, while the grid rigidity at point B is designed to be greater than that at point C. This design minimizes deformation at point B, keeping the difference between the longitudinal slopes CB and BA within the allowable range. This design not only improves structural stability and durability, but also ensures driving comfort and safety.

[0023] The above are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent solutions made using the contents of the present invention specification, directly or indirectly applied in other related technical fields, are also within the patent protection scope of the present invention.

Claims

1. A method for constructing a semi-flexible transition section of an abutment based on stiffness gradient control, characterized in that: The steps include: S1. Grille Laying: Lay the first grille section on the road subbase in the direction of the bridgehead slab. Connect one end of the first grille section to the bridgehead slab via several φ32 galvanized steel bars. Connect the other end of the first grille section to the second grille section via several φ32 galvanized steel bars. Connect the other end of the second grille section to the third grille section via several φ28 galvanized steel bars. Connect the other end of the third grille section to the fourth grille section via several φ25 galvanized steel bars. Connect the other end of the fourth grille section to the fifth grille section via several φ22 galvanized steel bars. Provide several concrete openings on the first through fifth grille sections. S2. Concrete filling and compaction in layers: fill the aggregate through the concrete openings to halfway into the first to fifth sections of the grid, compact it with a small machine, and then lay the upper layer and compact it as a whole; S3. Asphalt surface layer paving: Spread the asphalt surface layer on the upper end of the concrete grid section after concrete filling and compaction, so that the concrete grid section and the roadbed form a whole.

2. The method for constructing a semi-flexible transition section of an abutment based on stiffness gradient control according to claim 1, characterized in that: In S1, the first to fifth sections of the grille all adopt an assembled structure, which is composed of two I-shaped components in the middle and two C-shaped components at both ends. The splicing interface is made of steel plates in a Z shape and connected by fixing bolts.

3. The method for constructing a semi-flexible transition section of an abutment based on stiffness gradient control according to claim 1 or 2, characterized in that: In S1, the cell height of the first to second sections of the grid is 400mm, the wall thickness is 120mm, and the reinforcement ratio is 2.8%; the cell height of the third section of the grid is 350mm, the wall thickness is 100mm, and the reinforcement ratio is 2.2%; the cell height of the fourth to fifth sections of the grid is 300mm, the wall thickness is 80mm, and the reinforcement ratio is 1.6%.

4. The method for constructing a semi-flexible transition section of an abutment based on stiffness gradient control according to claim 1 or 2, characterized in that: In S1, the shear strength of the joint is ≥85Mpa, and the allowable angular displacement is ±2.5°.

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