Water distribution ring pipe rigidity and strength analysis method considering non-uniform pipe-soil gaps

Abstract

The invention belongs to the technical field of hydraulic generators, and particularly relates to a water distribution ring pipe rigidity and strength analysis method considering non-uniform pipe-soil gaps. According to the technical scheme, the water distribution ring pipe rigidity and strength analysis method considering the non-uniform pipe-soil gaps comprises the following steps that S1, a finite element model in the pressure maintaining pouring stage is established, and initial statics calculation is conducted; s2, constructing an operation condition finite element model containing a non-uniform pipe-soil gap; s3, analyzing the rigidity and strength of the water distribution ring pipe under the operation condition; and S4, post-processing and result analysis. The invention provides a water distribution ring pipe rigidity and strength analysis method considering a non-uniform pipe-soil gap. The defect that the non-uniform pipe-soil gap cannot be accurately considered in water distribution ring pipe rigidity and strength analysis in the prior art is overcome.

Description

Technical Field

[0001] This invention belongs to the field of hydro-generator technology, and specifically relates to a method for analyzing the rigidity of water distribution ring pipes considering non-uniform pipe-soil gaps. Background Technology

[0002] In hydropower projects, water conservancy hubs, and other fields requiring large-flow water transmission and distribution, water distribution ring pipes are critical structural components, and their structural safety and operational reliability are of paramount importance. Stiffness and strength analysis of water distribution ring pipes is a core component of engineering design and safety assessment.

[0003] In existing technologies, the main methods for analyzing the rigidity and strength of water distribution ring pipes include: First, the simplified analytical method: This method simplifies the water distribution ring pipe into basic structural units such as beams and shells, and performs calculations based on the theories of mechanics of materials and structural mechanics. However, this method typically ignores the complex interaction between the ring pipe and the surrounding concrete, especially the actual shape of the gap around the pipe, often resulting in calculations that deviate significantly from reality.

[0004] Second, the finite element method based on ideal contact: Finite element software is used to establish an overall model of the water distribution ring pipe and the surrounding concrete. When simulating the interaction between the pipe and the surrounding medium, it is usually assumed that there is complete contact (no gap) between them, or an idealized gap is set that is uniformly distributed along the circumference and axial direction of the ring pipe. Although this method considers the complexity of the structure and materials, it ignores the non-uniform gaps formed between the pipe and the surrounding medium due to factors such as construction (e.g., concrete pouring, pressure holding), temperature changes, and material shrinkage and creep in actual engineering. Therefore, it cannot accurately reflect the real impact of the existence and uneven distribution of gaps on the stress, deformation, and structural stiffness of the ring pipe.

[0005] Third, the finite element method considering uniform gaps: Some existing technologies attempt to introduce the gap between the pipe and the surrounding medium into the finite element model, but it is usually set as a constant gap value uniformly distributed along the pipe circumference. Although this simplification is closer to reality than complete contact, it still does not consider the non-uniformity of the gap caused by the construction process (especially the initial deformation caused by pressure-holding pouring) and changes in operating conditions. For example, the uneven deformation of concrete under pressure and the differential expansion / contraction under the influence of temperature gradients will lead to a complex non-uniform distribution of the actual gap along the pipe circumference.

[0006] The shortcomings of existing technologies: The aforementioned existing technologies fail to fully consider the non-uniform contact state and non-uniform gaps between the water distribution ring pipe and the surrounding medium (especially concrete) formed during construction, curing, and operation due to factors such as initial stress, deformation, and temperature effects. This non-uniformity significantly affects the stress state, stress concentration, deformation mode, and overall structural stiffness and strength assessment of the ring pipe. Ignoring or simplifying the treatment of this non-uniform gap may lead to distorted analysis results, making it impossible to accurately predict weak points in the structure, thereby affecting the safety and economy of engineering design. Summary of the Invention

[0007] In order to solve the above-mentioned problems in the prior art, the purpose of this invention is to provide a method for analyzing the rigidity of water distribution ring pipes that considers non-uniform pipe-soil gaps, thereby overcoming the defect in the prior art that fails to accurately consider non-uniform pipe-soil gaps in the rigidity analysis of water distribution ring pipes.

[0008] The technical solution adopted in this invention is as follows: A method for analyzing the rigidity and strength of a water distribution ring pipe considering non-uniform pipe-soil gaps includes the following steps: S1: Establish the finite element model for the pressure-holding pouring stage and perform initial static calculations; S2: Construct a finite element model of the operating conditions that includes non-uniform pipe-soil gaps; S3: Stiffness and strength analysis of water distribution ring pipe under operating conditions; S4: Post-processing and result analysis.

[0009] As a preferred embodiment of the present invention, step S1 specifically includes: S11: Based on the design drawings, establish a three-dimensional geometric model including the water distribution ring pipe, the end cap, the support, and the concrete poured around the ring pipe. S12: Perform finite element mesh generation on the established three-dimensional geometric model to generate a refined finite element mesh model; S13: Material property definition: Assign corresponding material properties to the water distribution ring pipe, the support pier, and the surrounding poured concrete; S14: Contact Relationship Settings: Define the contact relationship between the outer surface of the water distribution ring pipe and the inner surface of the surrounding concrete; S15: Load and boundary condition application: Apply load conditions to simulate pressure holding casting; S16: Initial Static Calculation: Perform finite element static analysis to calculate the stress, strain, and deformation of the water distribution ring pipe and surrounding concrete under the load during this pressure-holding pouring stage.

[0010] As a preferred embodiment of the present invention, in step S13, the material properties include elastic modulus, Poisson's ratio, density, and coefficient of thermal expansion.

[0011] As a preferred embodiment of the present invention, in step S15, the load conditions for applying simulated pressure-holding casting include: Hydrostatic pressure: The hydrostatic pressure applied inside the water distribution ring pipe during a pressure holding test or construction. Temperature load: Considering the heat of hydration of concrete, the temperature field caused by the difference between ambient temperature and the temperature of the medium inside the pipe, and the corresponding thermal stress; Boundary conditions: Apply reasonable displacement constraints to the model based on the actual support conditions.

[0012] As a preferred embodiment of the present invention, step S2 specifically includes: S21: Extract the deformed concrete model: Extract the finite element node coordinates or geometric shape of the deformed concrete part from the calculation results of step S1. S22: Obtain the undeformed water distribution ring pipe model: retain the finite element model or geometry of the water distribution ring pipe in the initial design state; S23: Reconstruct the analysis model: Combine the deformed concrete model or inner surface morphology extracted in step S21 with the undeformed water distribution ring pipe model in step S22 to construct a new finite element analysis model.

[0013] As a preferred embodiment of the present invention, in step S23, a new finite element analysis model is constructed: a non-uniform gap is naturally formed between the outer surface of the water distribution ring pipe and the inner surface of the deformed concrete, and the size and distribution of the gap reflect the result of the non-uniform deformation of the concrete under the initial load in step S1.

[0014] As a preferred embodiment of the present invention, step S3 specifically includes: S31: Redefining Material Properties: Redefine the material properties of concrete under operating conditions as needed; S32: Redefining the contact relationship: In the model reconstructed in step S23, the contact relationship between the outer surface of the water distribution ring pipe and the inner surface of the surrounding medium is redefined; S33: Apply operating loads and boundary conditions: Apply loads during normal operation of the water distribution loop on a model containing non-uniform gaps; S34: Static Calculation under Operating Conditions: Perform finite element static analysis to calculate the stress distribution, deformation, nodal displacement, and contact state of the water distribution ring pipe under operating loads, taking into account the influence of initial non-uniform gaps.

[0015] As a preferred embodiment of the present invention, in step S32, the contact relationship includes the initial non-uniform gap formed in step S2, and a contact algorithm is set that allows the gap to close and transmits pressure and friction after contact.

[0016] As a preferred embodiment of the present invention, in step S33, applying the load during normal operation of the water distribution ring pipe includes: Steady fluid load: Normal operating pressure inside the loop; Temperature load: Temperature stress caused by the temperature difference between the inside and outside of the pipe during operation; External loads include soil pressure, groundwater pressure, and the structure's self-weight. Boundary conditions: Apply structural constraints under operating conditions.

[0017] As a preferred embodiment of the present invention, step S4 specifically includes: S41: Result Extraction and Evaluation: Post-process the calculation results of step S3 to extract data on key parts of the water distribution ring pipe, including stress, strain, and displacement. S42: Stiffness and strength verification: The strength, stiffness and stability of the water distribution ring pipe are verified and evaluated according to relevant specifications and design requirements.

[0018] The beneficial effects of this invention are as follows: This invention presents an innovative method for constructing non-uniform gaps based on physical process simulation, and a two-stage analysis framework that incorporates this non-uniform gap as a key initial condition into the analysis of operating conditions. This significantly improves the realism and accuracy of the rigidity analysis of the water distribution ring pipe and overcomes the limitations of existing technologies in this regard. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method of the present invention; Figure 2 It is a three-dimensional model of the water distribution ring pipe, end cap, support pier, and concrete. Figure 3 It is a cloud map showing the contact state between the water distribution ring pipe and the concrete; Figure 4 It is an equivalent stress cloud diagram of the water distribution loop. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the invention can be combined with each other.

[0022] like Figure 1 As shown in the figure, the method for analyzing the rigidity of a water distribution ring considering non-uniform pipe-soil gaps in this embodiment includes the following steps: S1: Establish the finite element model for the pressure-holding and pouring stage and perform initial static calculations: S11: Based on the design drawings, establish a three-dimensional geometric model including the water distribution ring pipe, the end cap, the support, and the concrete poured around the ring pipe.

[0023] S12: Perform finite element mesh generation on the established three-dimensional geometric model to generate a refined finite element mesh model; ensure that the mesh quality meets the calculation accuracy requirements.

[0024] S13: Material Property Definition: Assign corresponding material properties to the water distribution ring pipe, supports, and surrounding concrete, including elastic modulus, Poisson's ratio, density, coefficient of thermal expansion, etc. The concrete properties defined here should reflect their characteristics during the pouring and initial setting stages.

[0025] S14: Contact Relationship Setting: Defines the contact relationship between the outer surface of the water distribution ring pipe and the inner surface of the surrounding concrete. This stage can be considered as an initial tight contact or a contact model that allows for minor normal separation and tangential friction, simulating the state during pouring.

[0026] S15: Load and Boundary Condition Application: Apply load conditions to simulate pressure-holding pouring, mainly including: ① Hydrostatic pressure: Apply hydrostatic pressure inside the water distribution ring pipe during the pressure-holding test or construction. ② Temperature load: Consider the temperature field and corresponding thermal stress caused by the heat of concrete hydration, the difference between ambient temperature and the temperature of the medium inside the pipe. ③ Boundary conditions: Apply reasonable displacement constraints to the model according to the actual support conditions, such as fixing the bottom of the support or the outer boundary of the concrete pouring area.

[0027] S16: Initial Static Calculation: Perform finite element static analysis to calculate the stress, strain, and deformation of the water distribution ring pipe and surrounding concrete under load during this pressure-holding pouring stage. Pay special attention to the deformation of the concrete around the ring pipe, such as... Figure 2 As shown.

[0028] S2: Construct a finite element model of the operating conditions including non-uniform pipe-soil gaps: S21: Extract the deformed concrete model: From the calculation results in step one, extract the finite element node coordinates or geometry of the deformed concrete portion. This deformation state reflects the influence of initial working conditions such as pressure holding and pouring on the shape of the concrete inner wall.

[0029] S22: Obtain the undeformed water distribution ring pipe model: retain the finite element model or geometry of the water distribution ring pipe in its initial design state (i.e., before deformation occurs).

[0030] S23: Reconstruct the Analysis Model: Combine the deformed concrete model (or its inner surface morphology) extracted in step S21 with the undeformed water distribution ring pipe model from step S22 to construct a new finite element analysis model. In this model, a non-uniform gap naturally forms between the outer surface of the water distribution ring pipe and the inner surface of the deformed concrete. The size and distribution of this gap reflect the result of the non-uniform deformation of the concrete under the initial load in step one. This model represents the structural state after considering the construction effects and before entering the operational phase. Here, "soil" refers to the medium around the ring pipe (mainly the deformed concrete in this process). If it is a buried pipe, a soil cover layer can be added to this model later.

[0031] S3: Stiffness and strength analysis under operating conditions: S31: Redefining Material Properties: As needed, the material properties of concrete under operating conditions can be redefined, such as considering the long-term elastic modulus and creep characteristics of concrete after it reaches its design strength. If there is external soil cover, the material properties of the soil cover should be defined.

[0032] S32: Redefining the Contact Relationship: In the model reconstructed in step S23, the contact relationship between the outer surface of the water distribution ring pipe and the inner surface of the surrounding medium (deformed concrete or backfill) is redefined. This contact should explicitly include the initial non-uniform gap formed in step two, and set contact algorithms (such as penalty function method, Lagrange multiplier method, etc.) that allow gap closure (contact) and the transmission of pressure and friction after contact.

[0033] S33: Applying Operating Loads and Boundary Conditions: On this model containing non-uniform gaps, apply loads during normal operation of the water distribution loop, mainly including: ① Steady fluid loads: Normal operating pressure inside the loop (dynamic water pressure can be simplified to equivalent static pressure or applied directly). ② Temperature loads: Temperature stress caused by the temperature difference between the inside and outside of the pipe during operation. ③ External loads: Such as overburden pressure, groundwater pressure, structural self-weight, etc. ④ Boundary conditions: Applying structural constraints under operating conditions.

[0034] S34: Static Calculation under Operating Conditions: Perform finite element static analysis to calculate the stress distribution, deformation, nodal displacements, and contact states (whether the gap is closed and the magnitude of the contact pressure) of the water distribution ring pipe under operating loads, considering the influence of the initial non-uniform gap. Figure 3 As shown.

[0035] S4: Post-processing and result analysis: S41: Result Extraction and Evaluation: Post-process the calculation results from step three to extract data such as stress, strain, and displacement of key parts of the water distribution ring pipe (such as welds, stress concentration areas, and areas with large deformation).

[0036] S42: Stiffness and Strength Verification: Based on relevant specifications and design requirements, verify and evaluate the strength (whether stress exceeds limits), stiffness (whether deformation meets requirements), and stability of the water distribution ring pipe. Analyze the specific impact of non-uniform gaps on the structural response, such as... Figure 4 As shown.

[0037] In summary, this invention employs a two-stage analysis approach. The analysis process of the water distribution ring pipe is divided into two independent but interconnected calculation stages: the "pressure-holding pouring (or similar construction) stage" and the "operational condition stage."

[0038] A quantitative construction method for non-uniform gaps. The core of this method is to combine the deformed shape of the surrounding medium (concrete) obtained from the simulation in the first stage (pressure holding and pouring) with the initial undeformed shape of the water distribution ring pipe, so as to explicitly and quantitatively construct the non-uniform pipe-soil (pipe-concrete) gap in the analysis model in the second stage (operating conditions).

[0039] The influence of the initial state is considered. Using the above method, the initial deformation (manifested as non-uniform gaps) generated during the construction stage is taken as the initial condition and substituted into the operational condition analysis, thereby more realistically reflecting the actual stress and deformation state of the structure under operational loads.

[0040] Refined contact simulation. In operational condition analysis, a contact algorithm capable of handling initial gaps and subsequent changes in contact state is employed to accurately simulate the complex interaction between the pipe and the surrounding medium when non-uniform gaps exist.

[0041] The closest existing technology may be the finite element method, but this assumes complete contact or a uniform gap between the pipe and the soil. Compared with these closest existing technologies, the technical solution of the present invention has the following significant technical advantages: More realistic reflection of physical reality: By simulating the effects of key construction stages (such as pressure holding pouring), this method can quantitatively capture and construct the non-uniform pipe-soil (pipe-concrete) gaps that exist in actual engineering due to initial stress deformation and temperature effects. Compared with the assumption of complete contact or uniform gaps, this greatly improves the model's approximation of physical reality.

[0042] Significantly improves analysis accuracy: By considering the existence and distribution of non-uniform gaps, it can more accurately predict the stress distribution (especially stress concentration), deformation mode, and pipe circumferential contact state of the water distribution ring pipe under operating loads. It avoids stress calculation deviations (which may be too high or too low, depending on the specific situation) and deformation prediction distortions caused by simplification assumptions (complete contact or uniform gaps).

[0043] More accurate structural safety assessment: Due to more accurate stress and deformation prediction, this method can provide a more reliable assessment basis for the strength, stiffness and stability of the water distribution ring pipe, which helps to discover potential weak points, improve the safety margin of structural design, or achieve optimized design under the premise of ensuring safety, and avoid unnecessary conservatism.

[0044] Revealing the impact of the construction process on structural performance: This method explicitly incorporates the impact of the construction process (pressure-holding pouring) into the analysis system, which can reveal the transmission effect of the initial deformation (manifested as non-uniform gaps) generated in this stage on the structural performance in the subsequent operation stage, providing an effective tool for understanding and controlling the impact of construction factors on the long-term performance of the structure.

[0045] Wider applicability: For large, complex, and demanding water distribution ring systems, especially ring systems in complex geological conditions or concrete-encased environments, the impact of non-uniform gaps is more prominent, making the advantages of this method more obvious and its applicability stronger.

[0046] In summary, the core advantage of this invention lies in its innovative non-uniform gap construction method based on physical process simulation, and the two-stage analysis framework that incorporates this non-uniform gap as a key initial condition into the operational condition analysis, thereby significantly improving the realism and accuracy of the rigidity analysis of the water distribution ring pipe and overcoming the limitations of existing technologies in this regard.

[0047] This invention is not limited to the above-described optional embodiments. Anyone can derive other various forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that falls within the scope of the claims of this invention shall be protected by this invention.

Claims

1. A method for analyzing the rigidity and strength of a water distribution ring pipe considering non-uniform pipe-soil gaps, characterized in that: Includes the following steps: S1: Establish the finite element model for the pressure-holding pouring stage and perform initial static calculations; S2: Construct a finite element model of the operating conditions that includes non-uniform pipe-soil gaps; S3: Stiffness and strength analysis of water distribution ring pipe under operating conditions; S4: Post-processing and result analysis.

2. The method for analyzing the rigidity of a water distribution ring considering non-uniform pipe-soil gaps according to claim 1, characterized in that: Step S1 specifically includes: S11: Based on the design drawings, establish a three-dimensional geometric model including the water distribution ring pipe, the end cap, the support, and the concrete poured around the ring pipe. S12: Perform finite element mesh generation on the established three-dimensional geometric model to generate a refined finite element mesh model; S13: Material property definition: Assign corresponding material properties to the water distribution ring pipe, the support pier, and the surrounding poured concrete; S14: Contact Relationship Settings: Define the contact relationship between the outer surface of the water distribution ring pipe and the inner surface of the surrounding concrete; S15: Load and boundary condition application: Apply load conditions to simulate pressure holding casting; S16: Initial Static Calculation: Perform finite element static analysis to calculate the stress, strain, and deformation of the water distribution ring pipe and surrounding concrete under the load during this pressure-holding pouring stage.

3. The method for analyzing the rigidity of a water distribution ring pipe considering non-uniform pipe-soil gaps according to claim 2, characterized in that: In step S13, the material properties include elastic modulus, Poisson's ratio, density, and coefficient of thermal expansion.

4. The method for analyzing the rigidity of a water distribution ring considering non-uniform pipe-soil gaps according to claim 2, characterized in that: In step S15, the load conditions for applying the simulated pressure-holding casting include: Hydrostatic pressure: The hydrostatic pressure applied inside the water distribution ring pipe during a pressure holding test or construction. Temperature load: Considering the heat of hydration of concrete, the temperature field caused by the difference between ambient temperature and the temperature of the medium inside the pipe, and the corresponding thermal stress; Boundary conditions: Apply reasonable displacement constraints to the model based on the actual support conditions.

5. The method for analyzing the rigidity of a water distribution ring pipe considering non-uniform pipe-soil gaps according to claim 1, characterized in that: Step S2 specifically includes: S21: Extract the deformed concrete model: Extract the finite element node coordinates or geometric shape of the deformed concrete part from the calculation results of step S1. S22: Obtain the undeformed water distribution ring pipe model: retain the finite element model or geometry of the water distribution ring pipe in the initial design state; S23: Reconstruct the analysis model: Combine the deformed concrete model or inner surface morphology extracted in step S21 with the undeformed water distribution ring pipe model in step S22 to construct a new finite element analysis model.

6. The method for analyzing the rigidity of a water distribution ring considering non-uniform pipe-soil gaps according to claim 5, characterized in that: In step S23, a new finite element analysis model is constructed: a non-uniform gap is naturally formed between the outer surface of the water distribution ring pipe and the inner surface of the deformed concrete. The size and distribution of the gap reflect the result of the non-uniform deformation of the concrete under the initial load in step S1.

7. The method for analyzing the rigidity of a water distribution ring pipe considering non-uniform pipe-soil gaps according to claim 6, characterized in that: Step S3 specifically includes: S31: Redefining Material Properties: Redefine the material properties of concrete under operating conditions as needed; S32: Redefining the contact relationship: In the model reconstructed in step S23, the contact relationship between the outer surface of the water distribution ring pipe and the inner surface of the surrounding medium is redefined; S33: Apply operating loads and boundary conditions: Apply loads during normal operation of the water distribution loop on a model containing non-uniform gaps; S34: Static Calculation under Operating Conditions: Perform finite element static analysis to calculate the stress distribution, deformation, nodal displacement, and contact state of the water distribution ring pipe under operating loads, taking into account the influence of initial non-uniform gaps.

8. The method for analyzing the rigidity of a water distribution ring pipe considering non-uniform pipe-soil gaps according to claim 7, characterized in that: In step S32, the contact relationship includes the initial non-uniform gap formed in step S2, and a contact algorithm is set to allow the gap to close and to transmit pressure and friction after contact.

9. The method for analyzing the rigidity of a water distribution ring pipe considering non-uniform pipe-soil gaps according to claim 7, characterized in that: In step S33, the loads applied during normal operation of the water distribution loop include: Steady fluid load: Normal operating pressure inside the loop; Temperature load: Temperature stress caused by the temperature difference between the inside and outside of the pipe during operation; External loads include soil pressure, groundwater pressure, and the structure's self-weight. Boundary conditions: Apply structural constraints under operating conditions.

10. A method for analyzing the rigidity of a water distribution ring pipe considering non-uniform pipe-soil gaps according to any one of claims 1 to 9, characterized in that: Step S4 specifically includes: S41: Result Extraction and Evaluation: Post-process the calculation results of step S3 to extract data on key parts of the water distribution ring pipe, including stress, strain, and displacement. S42: Stiffness and strength verification: The strength, stiffness and stability of the water distribution ring pipe are verified and evaluated according to relevant specifications and design requirements.

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