A method for designing a swivel pile cap based on finite element analysis
By using finite element analysis and grouped pile foundation methods, the reaction force at the top of the rotating pile cap was accurately solved, and a tension-compression bar model was constructed. This solved the conservatism problem of traditional design methods, realized an economical and reasonable reinforcement design, and improved the durability and safety of the bridge.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HANGZHOU LOCAL RAILWAY DEV
- Filing Date
- 2026-04-17
- Publication Date
- 2026-06-09
AI Technical Summary
In the design of rotating foundations, existing technologies rely on conservative calculation methods to meet actual stress characteristics and lack refined reinforcement design methods.
The finite element method is used to establish a finite element model of the rotating pile cap, group the pile foundations and solve the pile top reaction force, construct a tension and compression bar model, and accurately design the reinforcement.
This approach ensures that the stress distribution of the rotating pier is consistent with reality, the reinforcement is more economical and reasonable, the durability and safety of the bridge are improved, and a complete design process is formed.
Smart Images
Figure CN122174329A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of bridge engineering design, and in particular to a method for designing the reinforcement of rotating pier caps based on finite element analysis. Background Technology
[0002] Regarding the design method for the ultimate bearing capacity of pier caps, the "Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" mainly divides the calculation into two methods based on the relationship between the distance from the center of the outer row of piles under the pier cap to the edge of the pier cap and the height of the pier cap: one is to treat the pier cap as a cantilever beam and calculate its normal section bearing capacity; the other is the tension-compression rod model method to calculate the bearing capacity of the tension rods and the inclined compression rods. However, a large number of studies at home and abroad have shown that for pier caps constructed using rotation, their planar structural dimensions are larger than the pier cap thickness, which often cannot meet the calculation assumptions of the tension-compression rod pier cap design method in the code; the pile foundation dimensions of rotated pier caps are often large, and the vertical support stiffness is large. In this case, the pier cap is difficult to meet the assumption of a rigid pier cap, and the pile top reaction force exhibits the characteristic of "the middle piles are subjected to greater force, and the piles on both sides are subjected to less force." The traditional method for calculating the reinforcement of the pier cap is often conservative.
[0003] Previous studies have used the finite element method to perform local stress analysis on rotating foundations. However, these methods mostly focus on stress state analysis and lack a complete process and methodology to directly guide refined reinforcement design.
[0004] Therefore, there is an urgent need for a method that can accurately solve the reaction force at the top of the rotating pile cap and use this as a basis for accurate and efficient reinforcement design. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a finite element analysis-based reinforcement design method for rotating pile caps. This method can accurately solve the pile top reaction force of the rotating pile cap and construct a tension / compression bar model based on the pile top reaction force, thereby achieving refined reinforcement design for the rotating pile cap.
[0006] The objective of this invention is achieved through the following technical solutions: A method for designing reinforcement of a rotating pile cap based on finite element analysis, wherein a plurality of pile foundations are provided below the rotating pile cap for supporting it, and a ball joint is provided above the rotating pile cap, characterized in that the method includes the following steps: S1. Establish the finite element analysis model of the rotating bearing platform; S2. Group several pile foundations according to the straight-line distance between the pile center and the center of the rotating pile cap, and group pile foundations with the same straight-line distance from the pile center to the rotating center into the same group. S3. Apply the self-weight to the structure and apply a rotational load to the top surface of the ball joint. Solve for the pile top reaction force of each group of pile foundations. S4. Construct a spatial tension-compression bar model of the rotating pile cap based on the pile top reaction force, and solve the internal forces of the compression bars and tension bars in the spatial tension-compression bar model of each group of pile foundations. S5. Based on the internal forces of the tie rod, design the reinforcement and solve for the bearing capacity of the tie rod and compression rod.
[0007] In step S1, based on the design drawings, a geometric model of the ball joint, the rotating pile cap, and the pile foundation is established, and the ball joint is treated as being coplanar with the rotating pile cap, the pile foundation, and the rotating pile cap, wherein the ball joint and the rotating pile cap are connected at a common node.
[0008] In step S3, the normal stress of the pile top solid element of the pile foundation in the i-th group is first solved, and then the pile top reaction force of the single pile in the i-th group is obtained by integral calculation.
[0009] The internal force of the compression members in the i-th group of pile foundations is calculated using the following formula: ; In the formula, For the internal forces of the compression members in the pile foundation, For the pile top reaction force of the pile foundation, The angle between the compression member and the horizontal plane.
[0010] The internal forces in the tie rods of the i-th pile foundation include internal forces in the x-direction and internal forces in the y-direction, which are calculated using the following formula: ; ; In the formula, The internal force in the x-direction of the tie rod is... The internal force in the y-direction of the tie rod is... This refers to the reaction force at the top of the pile foundation. The effective height of the foundation, x and y are the first The longitudinal and transverse distances between the center of the pile root and the center of the pile cap. The angle between the diagonal compression member and the horizontal plane.
[0011] Configure ordinary steel reinforcement in the x-direction of the tie rod according to the internal force of the tie rod. ; Configure the tie rod with reinforcing bars in the y-direction ; The load-bearing capacity of the tie rod satisfies the calculation formula: ; The bearing capacity of the compression member satisfies the calculation formula: ; In the formula, This is the structural importance coefficient. Let the cross-sectional area of the compression member be _____. , This represents the design value of the equivalent compressive strength of the concrete compression member. Calculate the width of the compression member. Take the center distance of the piles, and The value should not exceed 3 times the pile side length or 3 times the pile diameter. This is the design value of the tensile strength of the steel reinforcement. The effective range of the reinforcing bar is the cross-sectional area of the steel bar within the effective width of the tie rod under stress. The effective range is taken as 0.75 times the pile diameter from the center of the pile top.
[0012] The advantages of this invention are: 1) Compared with traditional reinforcement methods, by accurately solving the pile foundation support reaction force, a tension and compression bar model of the rotating pile cap was constructed. The stress on the pile cap is consistent with the actual situation, and the reinforcement is more economical and reasonable.
[0013] 2) It can anticipate and control the tensile and compressive stress levels of the rotating pier during the design phase, thereby improving the durability and safety of the bridge.
[0014] 3) A complete closed-loop process from detailed analysis to precise design has been formed, which is easy to integrate into the existing bridge design system. Attached Figure Description
[0015] Figure 1 This is a flowchart of the steps of the present invention; Figure 2 This is a model diagram of the rotating support platform designed for this invention; Figure 3 This is a schematic diagram of the pile foundation grouping in this invention; Figure 4 This is a model diagram of the spatial tension / compression rod of the rotating body support in this invention. Detailed Implementation
[0016] The following examples further illustrate the features and other related characteristics of the present invention in detail, to facilitate understanding by those skilled in the art: Example: Figures 1 to 4 As shown, the reinforcement design method for the turntable foundation based on finite element analysis in this embodiment includes the following steps: 1) Establish a solid finite element analysis model: Using the preprocessing functions of AutoCAD or general finite element software, geometric models of the spherical hinge, rotating pile cap, and pile foundation are established based on the design drawings. The spherical hinge is treated as being coplanar with the rotating pile cap, and the pile foundation is treated as being coplanar with the rotating pile cap. Solid elements are used for the concrete pile cap; the pile foundation can use solid elements or a combination of solid elements and beam elements; the rotating spherical hinge uses solid elements. After assigning material properties to the elements, meshing is performed to complete the finite element model establishment, as follows: Figure 2 As shown. The mesh is mainly composed of regular hexahedral meshes, with dimensions meeting the analysis accuracy requirements; material properties are assigned to the rotating spherical hinge, the pile cap, and the pile foundation, all of which are linear elastic materials. The rotating spherical hinge and the concrete pile cap share a common node connection. The pile bottom is constrained.
[0017] 2) Grouping the pile foundations: like Figure 3 As shown, the piles are arranged according to the straight-line distance between the pile center and the pile cap center. Grouping, distance Identical piles belong to the same group.
[0018] 3) Load and post-process the calculation results: Apply the structure's own weight, and apply a rotational load to the top surface of the ball joint. Then, the normal stress of the solid element at the top of the pile in the i-th group is solved respectively. And the result is obtained by integration. Pile top reaction force of a single pile in the group .
[0019] 4) Construct a spatial tension / compression member model of the rotating foundation and solve for the internal forces in the tension and compression members: like Figure 4 As shown, a spatial tension-compression strut model of the rotating pier is constructed. Figure 4 In the middle, the angle between each group of inclined compression members and the horizontal plane is . The distance between the convergence point of the diagonal compression members at point O and the top surface of the foundation. R is the radius of the equivalent load region; The effective height of the pier cap; 'a' is the distance from the intersection of the outermost diagonal compression member axis and the top surface of the pier cap to the edge of the load application, which can be taken from the "Design Specifications for Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts". . It is the horizontal distance from the center of the outermost pile to the center of the pile cap.
[0020] In the i-th group of piles, the internal force of the single pile compression member for: ; The internal force of the tie rod in the x direction is: ; Pull rod The directional internal force is: ; In the formula: The effective height of the foundation, x and y are the longitudinal and transverse distances from the center of the i-th pile to the center of the pile cap, respectively.
[0021] 5) Design reinforcement based on the internal forces in the tie rod, and solve for the bearing capacity of the tie rod and compression rod: Ordinary steel bars are used in the x-direction of the tie rod. ; Configure the tie rod with reinforcing bars in the y-direction The load-bearing capacity of the tie rod should meet the following requirements. The formula for calculating the bearing capacity of a compression member is: In the formula: This is the structural importance coefficient, typically taken as 1.1; Let the cross-sectional area of the compression member be _____. ; The equivalent compressive strength design value of the concrete compression member is taken from Appendix B of the "Design Specification for Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" (JTG3362-2018); Calculate the width of the compression member. Take the center distance of the piles, and The value should not exceed 3 times the pile side length or 3 times the pile diameter. This is the design value of the tensile strength of the steel reinforcement. This refers to the cross-sectional area of the reinforcing steel bars within the effective width range of the tie rod under load. The effective range is defined as 0.75 times the pile diameter from the center of the pile top.
[0022] Although the above embodiments have described the concept and embodiments of the present invention in detail, those skilled in the art will recognize that various improvements and modifications can still be made to the present invention without departing from the scope of the claims, and therefore will not be elaborated here.
Claims
1. A method for designing reinforcement of a rotating pile cap based on finite element analysis, wherein a plurality of pile foundations are provided below the rotating pile cap for supporting it, and a ball joint is provided above the rotating pile cap, characterized in that: The method includes the following steps: S1. Establish the finite element analysis model of the rotating bearing platform; S2. Group several pile foundations according to the straight-line distance between the pile center and the center of the rotating pile cap, and group pile foundations with the same straight-line distance from the pile center to the rotating center into the same group. S3. Apply the self-weight to the structure and apply a rotational load to the top surface of the ball joint. Solve for the pile top reaction force of each group of pile foundations. S4. Construct a spatial tension-compression bar model of the rotating pile cap based on the pile top reaction force, and solve the internal forces of the compression bars and tension bars in the spatial tension-compression bar model of each group of pile foundations. S5. Based on the internal forces of the tie rod, design the reinforcement and solve for the bearing capacity of the tie rod and compression rod.
2. The method for designing reinforcement of a rotating foundation based on finite element analysis according to claim 1, characterized in that: In step S1, based on the design drawings, a geometric model of the ball joint, the rotating pile cap, and the pile foundation is established, and the ball joint is treated as being coplanar with the rotating pile cap, the pile foundation, and the rotating pile cap, wherein the ball joint and the rotating pile cap are connected at a common node.
3. The method for designing reinforcement of a rotating foundation based on finite element analysis according to claim 1, characterized in that: In step S3, the normal stress of the pile top solid element of the pile foundation in the i-th group is first solved, and then the pile top reaction force of the single pile in the i-th group is obtained by integral calculation.
4. The method for designing reinforcement of a rotating foundation based on finite element analysis according to claim 1, characterized in that: The internal force of the compression members in the i-th group of pile foundations is calculated using the following formula: ； In the formula, For the internal forces of the compression members in the pile foundation, For the pile top reaction force of the pile foundation, The angle between the compression member and the horizontal plane.
5. The method for designing reinforcement of a rotating foundation based on finite element analysis according to claim 1, characterized in that: The internal forces in the tie rods of the i-th pile foundation include internal forces in the x-direction and internal forces in the y-direction, which are calculated using the following formula: ； ； In the formula, The internal force in the x-direction of the tie rod is... The internal force in the y-direction of the tie rod is... This refers to the reaction force at the top of the pile foundation. The effective height of the foundation, , For the first The longitudinal and transverse distances between the center of the pile root and the center of the pile cap. The angle between the diagonal compression member and the horizontal plane.
6. The method for designing reinforcement of a rotating foundation based on finite element analysis according to claim 5, characterized in that: Configure the tie rod according to the internal force of the tie rod. Ordinary steel bars in the direction ; Configure pull rod directional reinforcing bars ; The load-bearing capacity of the tie rod satisfies the calculation formula: ; The bearing capacity of the compression member satisfies the calculation formula: ; In the formula, This is the structural importance coefficient. Let the cross-sectional area of the compression member be _____. , This represents the design value of the equivalent compressive strength of the concrete compression member. Calculate the width of the compression member. Take the center distance of the piles, and The value should not exceed 3 times the pile side length or 3 times the pile diameter. This is the design value of the tensile strength of the steel reinforcement. The effective range of the reinforcing bar is the cross-sectional area of the steel bar within the effective width of the tie rod under stress. The effective range is taken as 0.75 times the pile diameter from the center of the pile top.