Mechanical model and design method for long-distance and city gas pipeline design

Abstract

This invention relates to the field of gas pipeline design technology, specifically a mechanical model and design method for long-distance and urban gas pipelines. The former includes constructing a sub-model for the design wall thickness of straight pipe sections using design specifications and selected yield strength values; constructing a sub-model for the design wall thickness of bends by combining the comparison rules between pipeline design pressure and gas transmission pipeline pressure parameters; constructing a corresponding stability calculation and verification model based on the relationship between the load projected per unit length of the pipeline by external forces and the bearing capacity of the foundation; ignoring the variation in Poisson's ratio at the maximum internal pressure of the pipeline, constructing a sub-module for calculating and verifying the equivalent stress of straight pipe sections; and introducing the axial deformation stress caused by temperature changes on bends, constructing a sub-module for calculating and verifying the equivalent stress of bends. This invention avoids the problems existing in gas pipeline engineering design based solely on design specifications, and is more consistent with actual site conditions in stability calculation and verification, equivalent stress calculation and verification, etc., thus improving the rationality of long-distance and urban gas pipeline design.

Description

Technical Field

[0001] This invention relates to the field of gas pipeline design technology, specifically a mechanical model and design method for long-distance and urban gas pipelines. Background Technology

[0002] Currently, for stable gas supply, the design of gas pipeline projects relies on the "Code for Design of Gas Pipeline Engineering" GB50251-2015. The design process begins with obtaining local planning, feasibility studies, geological surveys, and safety design facility specifications. Next, the transport medium and design pressure are determined. Then, based on the "Code for Design of Gas Pipeline Engineering," different steel pipe material codes, minimum yield strengths, precision grades, pipe diameters, and wall thicknesses are calculated and selected. Finally, the equivalent stress caused by external loads, internal forces, and temperature, as well as seismic design calculations and verifications, are performed on the steel pipe to complete the gas pipeline design. However, existing design methods have the following problems: the wall thickness calculation for determining steel pipe strength does not take design pressure into account; pipeline stability verification cannot be tailored to different loads; the influence of equivalent stress on straight and curved sections in practical applications is not fully considered; and wall thickness settings for curved sections do not incorporate design redundancy. Therefore, the accumulation of these problems can lead to inaccurate pipeline design results and unreasonable situations, affecting the design and application of gas pipelines. Summary of the Invention

[0003] This invention provides a mechanical model and design method for long-distance and urban gas pipelines, which overcomes the shortcomings of the existing technology and can effectively solve the problems of unreasonable design in the existing design methods for long-distance and urban gas pipelines in terms of pipeline wall thickness calculation, pipeline stability calculation and verification.

[0004] One of the technical solutions of this invention is achieved through the following measures: a design mechanical model for long-distance and urban gas pipelines, comprising:

[0005] The pipeline wall thickness determination model includes a straight pipe section design wall thickness sub-model and a bend design wall thickness sub-model. Specifically, the yield strength value is selected based on the pipeline design pressure, and the straight pipe section design wall thickness sub-model is constructed using the design specifications and the selected yield strength value. The bend design wall thickness model is constructed by combining the comparison rules between the pipeline design pressure and the gas transmission pipeline pressure parameters.

[0006] Stability calculation and verification model: Based on the relationship between the load on the projected area of ​​the external force acting on the unit length of the pipeline and the bearing capacity of the base layer, a corresponding stability calculation and verification model is constructed.

[0007] The equivalent stress calculation and verification model includes a sub-module for equivalent stress calculation and verification of straight pipe sections and a sub-module for equivalent stress calculation and verification of bends. Specifically, the change of Poisson's ratio when the pipeline bears the maximum internal pressure is ignored, and a sub-module for equivalent stress calculation and verification of straight pipe sections is constructed. The axial deformation stress caused by temperature change on the bend is introduced, and a sub-module for equivalent stress calculation and verification of bends is constructed.

[0008] Seismic strength design and verification model: Construct a seismic strength design and verification model in conjunction with design specifications.

[0009] The following are further optimizations and / or improvements to the above-mentioned technical solution:

[0010] The above-mentioned pipe wall thickness determination model includes a design wall thickness sub-model for straight pipe sections and a design wall thickness sub-model for bends, specifically:

[0011] (1) Select the yield strength value based on the pipeline design pressure, and construct a sub-model of the straight pipe section design wall thickness using the design specifications and the selected yield strength value, as shown below:

[0012]

[0013] Where, δ α The proposed design wall thickness for the straight pipe section; P is the pipe design pressure; D is the pipe outer diameter; σ α This refers to the yield strength value with a set coefficient. Where is the weld coefficient; F is the strength design coefficient; t is the temperature reduction coefficient;

[0014] (2) Set the comparison rules between the pipeline design pressure and the gas transmission pipeline pressure parameters, and determine the sub-model of the bend design wall thickness, as shown below:

[0015] For gas transmission pipelines with a design pressure of 1.6MPa≦P≦2.5MPa, the radius of curvature of the design bend should be ≥3D, and the wall thickness of the design bend should be the positive deviation of the design wall thickness of the straight section ≥0.5mm.

[0016] For gas transmission pipelines with a design pressure ≥ 4.0 MPa, the radius of curvature of the designed bend should be ≥ 6D, and the wall thickness of the bend should be determined according to the specifications.

[0017] The aforementioned stability calculation and verification model includes a first stability calculation and verification sub-model, a second stability calculation and verification sub-model, and a third stability calculation and verification sub-model, specifically:

[0018] (1) For the case of buried pipelines subjected to concentrated load compaction, the first stability calculation and verification sub-model is determined as follows:

[0019] Pipeline stability calculation:

[0020] Pipeline stability check:

[0021] Where Z is the load factor; y c denoted as , where is the pipe bending deflection value; E is the pipe elastic modulus; I is the pipe moment of inertia; l is the integral length of the pipe deformation interface; G is the load of the projected area of ​​the external force acting on the unit length of the pipe, G = w1 + w2, where w1 is the weight of the projected area of ​​the deformation interface L to the soil above the pipe, and w2 is the vertical pressure of the external force acting on the ground above the pipe.

[0022] (2) For the case of buried pipelines subjected to uniformly distributed load compaction, the second stability calculation and verification sub-model is determined as follows:

[0023] Pipeline stability calculation:

[0024] Pipeline stability check:

[0025] Where Z is the load factor; y c denoted as , where is the pipe bending deflection value; E is the pipe elastic modulus; I is the pipe moment of inertia; l is the integral length of the pipe deformation interface; G is the load of the projected area of ​​the external force acting on the unit length of the pipe, G = w1 + w2, where w1 is the weight of the projected area of ​​the deformation interface L to the soil above the pipe, and w2 is the vertical uniformly distributed pressure of the external force acting on the ground above the pipe.

[0026] (3) Verify the stress change of the cross section of the pipeline under load, and determine the third stability calculation and verification sub-model, as shown below:

[0027] Pipe cross-sectional stability calculation:

[0028] Pipe cross-sectional stability check: σ f ≤[σ s ]Δ x =D1-D

[0029] Where M is the moment; W is the section modulus of bending; σ f The normal stress of the pipe cross section; [σ s ] is for checking allowable stress; Δ x D represents the geometric deformation of the cross section; D is the outer diameter of the pipe in the initial state; D1 is the maximum outer diameter of the pipe after deformation.

[0030] The above equivalent stress calculation and verification model includes a sub-module for equivalent stress calculation and verification of straight pipe sections and a sub-module for equivalent stress calculation and verification of bends;

[0031] (1) The equivalent stress calculation and verification submodule for straight pipe sections ignores the change in Poisson's ratio when the pipeline is under maximum internal pressure.

[0032] The equivalent stress of the straight pipe section is determined based on the axial and radial deformation stresses caused by temperature changes, as shown below:

[0033] Calculation of axial deformation stress in straight pipe section: σ L =Eα(t1-t2)

[0034] Calculation of radial deformation stress in straight pipe sections:

[0035] Equivalent stress check of straight pipe section: σ e =σ h +σ L <0.9σ s

[0036] Where, σ L σ represents the axial deformation stress caused by temperature change; E is the elastic modulus of the pipeline; α is the temperature change coefficient; t1 is the ambient temperature at the installation site; t2 is the pipeline's own temperature during operation; σ s σ is the minimum yield strength specified in the pipe standard. h The radial stress is for the straight pipe section.

[0037] (2) The equivalent stress calculation and verification submodule for the bend introduces the axial deformation stress caused by temperature change on the bend. Based on the radial deformation stress and the axial deformation stress caused by temperature change, the equivalent stress of the bend is determined as follows:

[0038] Calculation of axial deformation stress of bend: σ hmax =β q σ o

[0039] Calculation of radial deformation stress in the bend section:

[0040] Equivalent stress check for bend: σ e =σ h +σ hmax <σ b

[0041] Where, σ hmax β is the axial deformation stress caused by temperature change. q =1.8[1-(r / R)] 2 ](1 / λ) 2 / 3 , r is the nominal diameter, R is the radius of curvature of the bend, M is the moment generated by the pipe temperature stress on the radius of the pipe cross-section, and σ is the torque. b σ represents the tensile strength of the pipe. h This represents the radial stress of the bend.

[0042] The above-mentioned seismic strength design and verification model includes:

[0043] (I) Strength Design and Verification Model for Straight Pipe Sections under Seismic Action:

[0044] (1) The maximum circumferential stress during a seismic event in a straight pipe section is shown below:

[0045]

[0046]

[0047] Where α is the peak ground acceleration; υ is the peak ground velocity; T g The characteristic period of the seismic response spectrum; V SG ε represents the equivalent shear wave velocity of the soil layer at the site. max This represents the maximum axial tensile and compressive stress in the pipeline caused by ground motion.

[0048] (2) Seismic check of straight pipe sections, as shown below:

[0049] When ε max When +ε≤0|ε max +ε|≤[ε c V

[0050] When ε max When +ε>0|ε max +ε|≤[ε t V

[0051] Among them, [ε c [ε] represents the allowable axial compressive stress for vibration resistance of buried pipelines; t ε represents the allowable axial tensile stress for vibration resistance of buried pipelines; ε represents the equivalent strain of the pipeline under operating conditions. σ e Here, E represents the equivalent stress value of the straight pipe section, and E is the elastic modulus of the steel pipe.

[0052] (3) Allowable strain values ​​are as follows:

[0053] A. Allowable compressive strain

[0054]

[0055] Where δn is the pipe design wall thickness, and D is the pipe outer diameter;

[0056] B. Allowable tensile stress

[0057] [ε t V = 0.01

[0058] (II) Strength Design and Verification Model for Bends under Seismic Motion:

[0059] (1) The maximum circumferential stress during a bent-pipe earthquake is shown below:

[0060]

[0061]

[0062] Where α is the peak ground acceleration; υ is the peak ground velocity; T g The characteristic period of the seismic response spectrum; V SG ε represents the equivalent shear wave velocity of the soil layer at the site. max This represents the maximum axial tensile and compressive stress in the pipeline caused by ground motion.

[0063] (2) Seismic check of the bend, as shown below:

[0064] When ε max When +ε≤0|ε max +ε|≤[ε c V

[0065] When ε max When +ε>0|ε max +ε|≤[ε t V

[0066] Among them, [ε c [ε] represents the allowable axial compressive stress for vibration resistance of buried pipelines; t ε represents the allowable axial tensile stress for vibration resistance of buried pipelines; ε represents the equivalent strain of the pipeline under operating conditions. σ e Here, E represents the equivalent stress value of the straight pipe section, and E is the elastic modulus of the steel pipe.

[0067] (3) The allowable strain values ​​are as follows:

[0068] A. Allowable compressive strain

[0069]

[0070] Where δn is the pipe design wall thickness, and D is the pipe outer diameter;

[0071] B. Allowable tensile stress

[0072] [ε t V = 0.01

[0073] The second technical solution of the present invention is achieved through the following measures: a design method for long-distance and urban gas pipelines, comprising:

[0074] Define the design pressure and determine the design wall thickness of the straight pipe section using the straight pipe section design wall thickness sub-model;

[0075] Stability calculations and verifications are performed using a stability calculation and verification model, including:

[0076] (1) Determine whether the load on the projected area of ​​the external force acting on the unit length of the pipe is greater than or equal to the bearing capacity of the base layer;

[0077] (2) In response to the bearing capacity of the base layer, it is determined whether the buried pipeline is subjected to concentrated load or uniform load. If it is subjected to concentrated load, the first stability calculation and verification sub-model is used to calculate and verify the bending deflection of the steel pipe. If it is subjected to uniform load, the second stability calculation and verification sub-model is used to calculate and verify the bending deflection of the steel pipe.

[0078] (3) In response to the bearing capacity of the base layer, the normal stress of the pipe cross section is calculated and checked using the third stability calculation and verification sub-model;

[0079] The equivalent stress calculation and verification of straight pipe sections and bends are performed using the equivalent stress calculation and verification submodules for straight pipe sections and bends.

[0080] The wall thickness of the straight pipe section is determined by combining the design wall thickness of the straight pipe section and using the design wall thickness sub-model of the bend pipe.

[0081] Using the seismic strength design and verification model, the seismic motion design calculation and verification were completed.

[0082] This invention provides a mechanical model and design method for long-distance and urban gas pipelines, which avoids the problems existing in the design of gas pipelines based on the "Code for Design of Gas Pipeline Engineering". It makes the determination of wall thickness, stability calculation and verification, and equivalent stress calculation and verification more in line with the actual site conditions, thereby improving the rationality of the design of long-distance and urban gas pipelines and improving the accuracy of pipeline design wall thickness. Attached Figure Description

[0083] Appendix Figure 1 This is a schematic diagram of the model structure of the present invention.

[0084] Appendix Figure 2 This is a flowchart of the design method of the present invention. Detailed Implementation

[0085] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0086] The following examples refer to the "Code for Design of Gas Pipeline Engineering" GB 50251-2015, which came into effect on October 1, 2003. It was revised based on the 1994 edition of the original code, compiled by the Oil and Gas and Pipeline Construction Design Professional Standardization Committee, drawing on years of experience in gas pipeline engineering design and referencing existing domestic industry standards and relevant international standards. The main contents include general principles, terminology, gas transmission technology, routes, structural design of pipelines and pipeline accessories, gas transmission stations, underground gas storage facilities, monitoring and system scheduling, power supply and distribution, water supply and drainage and fire protection, auxiliary production facilities such as heating, ventilation and air conditioning, welding and inspection, pigging and pressure testing, drying, energy conservation, environmental protection, and occupational safety and health regulations.

[0087] The present invention will be further described below with reference to embodiments and accompanying drawings:

[0088] Example 1: This embodiment of the invention discloses a design mechanical model for long-distance and urban gas pipelines, including:

[0089] I. Pipeline wall thickness determination model, including a sub-model for designing the wall thickness of straight pipe sections and a sub-model for designing the wall thickness of bends, specifically:

[0090] The pipe wall thickness determination model includes a straight pipe section design wall thickness sub-model and a bend pipe design wall thickness model, specifically:

[0091] (1) Select the yield strength value based on the pipeline design pressure, and construct a sub-model of the straight pipe section design wall thickness using the design specifications and the selected yield strength value, as shown below:

[0092]

[0093] Where, δ α The proposed design wall thickness for the straight pipe section; P is the pipe design pressure; D is the pipe outer diameter; σ α This refers to the yield strength value with a set coefficient. t is the weld coefficient (taken as 1); F is the strength design coefficient; t is the temperature reduction coefficient (when the temperature is less than 120℃, the value of t is taken as 1.0).

[0094] The yield strength value is selected based on the pipeline design pressure. The yield strength value may include a preset coefficient. Therefore, the preset coefficient can be adjusted according to the pipeline design pressure to select and adjust the yield strength value.

[0095] Compared to the existing method of directly using the minimum yield strength specified in the steel pipe standard when calculating the design wall thickness of straight pipe sections according to the "Code for Design of Gas Pipeline Engineering" GB 50251-2015, as shown in the following formula, this embodiment makes the determination of the design wall thickness of straight pipe sections more accurate and more in line with design requirements.

[0096] In the formula: refer to the "Specification".

[0097] Where δ is the calculated wall thickness of the steel pipe; P is the design pressure; D is the outer diameter of the pipe; σ s φ is the minimum yield strength (MPa) specified in the steel pipe standard; φ is the weld coefficient, which is taken as 1; F is the strength design coefficient; t is the temperature reduction coefficient, which is taken as 1.0 when the temperature is less than 120℃.

[0098] (2) Set the comparison rules between the pipeline design pressure and the gas transmission pipeline pressure parameters, and determine the sub-model of the bend design wall thickness, as shown below:

[0099] For gas transmission pipelines with a design pressure of 1.6MPa≦P≦2.5MPa, the radius of curvature of the design bend should be ≥3D, and the wall thickness of the design bend should be the positive deviation of the design wall thickness of the straight section ≥0.5mm.

[0100] For gas transmission pipelines with a design pressure ≥ 4.0 MPa, the radius of curvature of the designed bend should be ≥ 6D, and the wall thickness of the bend should be determined according to the specifications.

[0101] For gas transmission pipelines with a design pressure ≥ 4.0 MPa, the bend wall thickness is determined according to specifications, specifically using the following formula:

[0102] δ b =δ·m

[0103] Where, δ b δ is the calculated wall thickness of the bend; R is the radius of curvature of the bend; m is the wall thickness magnification factor of the bend; and D is the outer diameter of the bend.

[0104] The aforementioned gas pipeline design scope includes: urban gas pipelines with a pressure of 1.6MPa ≤ P ≤ 4.0MPa and long-distance gas pipelines with a pressure of 4.0MPa and above. Specifically, this includes 1.6MPa urban sub-high-pressure pipelines, 2.5MPa and 4.0MPa urban high-pressure pipelines, and long-distance gas pipelines with a pressure of 4.0MPa and above. (Note: This design template can be used as a reference for the design of urban gas pipelines with a pressure of 0.4MPa ≤ P ≤ 0.8MPa.)

[0105] In contrast to the existing "Code for Design of Gas Transmission Pipeline Engineering" GB 50251-2015, which uniformly increases the wall thickness of bends regardless of the design pressure, this invention fully considers design redundancy and sets a comparison rule between the pipeline design pressure and the gas transmission pipeline pressure parameters. It sets different bend wall thicknesses for different design pressures, rather than uniformly increasing the wall thickness of bends for all pressures.

[0106] II. Stability Calculation and Verification Model: A stability calculation and verification model is constructed based on the relationship between the load projected per unit length of the pipe by external forces and the bearing capacity of the base layer. Specifically:

[0107] The stability calculation and verification model includes a first stability calculation and verification sub-model, a second stability calculation and verification sub-model, and a third stability calculation and verification sub-model, specifically:

[0108] (1) For the case of buried pipelines subjected to concentrated load compaction, the first stability calculation and verification sub-model is determined as follows:

[0109] Pipeline stability calculation:

[0110] Pipeline stability check:

[0111] Where Z is the load factor (which can be 1.30); y c denoted as ρ, where ρ is the pipe bending deflection value; E is the pipe elastic modulus; I is the pipe moment of inertia; l is the integral length of the pipe deformation interface; G is the load of the projected area of ​​the external force acting on the unit length of the pipe, G = w1 + w2, where w1 is the weight of the projected area of ​​the deformation interface L to the soil above the pipe, and w2 is the vertical pressure of the external force acting on the ground above the pipe.

[0112] The aforementioned gas pipeline route is subject to heavy vehicle traffic, which causes pipeline deflection and deformation, and the stress form is concentrated load. When buried pipelines are subjected to concentrated loads, the pipeline will bend downwards and generate deflection. Therefore, the first stability calculation and verification sub-model is the calculation and verification of pipeline bending deflection.

[0113] The methods for obtaining the integral length l of the pipe deformation interface mentioned above include: 1. Determining it based on field measurement data; 2. If no reference value is available, initially setting it as follows: for steel pipes, the integral length l of the steel pipe deformation interface = 10D (D is the outer diameter of the pipe), and for PE plastic pipes...

[0114] For PE plastic pipes, the integral length of the deformation interface is l = 5D (where D is the outer diameter of the pipe). The exact length may vary slightly depending on the geological conditions and soil layers on-site, and the integral length of the pipe deformation interface can be finely adjusted.

[0115] (2) For the case of buried pipelines subjected to uniformly distributed load compaction, the second stability calculation and verification sub-model is determined as follows:

[0116] Pipeline stability calculation:

[0117] Pipeline stability check:

[0118] Where Z is the load factor (which can be 1.30); yc denoted as , where is the bending deflection value of the steel pipe; E is the elastic modulus of the steel pipe; I is the moment of inertia of the steel pipe; l is the integral length of the deformation interface of the steel pipe; G is the load of the projected area of ​​the external force acting on the unit length of the pipe, G=w1+w2, where w1 is the weight of the projected area of ​​the deformation interface L to the soil above the pipe, and w2 is the vertical uniformly distributed pressure of the external force acting on the ground above the pipe.

[0119] The aforementioned gas pipelines pass through or are laid under roads, and are affected by the gravity and impact loads of heavy vehicles, causing the pipelines to deflect and deform. The stress form is generally a uniformly distributed load. When buried pipelines are subjected to uniformly distributed load compaction, the pipeline bends downward and produces a small deflection. Therefore, the second stability calculation and verification sub-model is the calculation and verification of the bending deflection of the steel pipe.

[0120] The methods for obtaining the integral length l of the pipeline deformation interface mentioned above include: 1. Determining it based on actual measurement data accumulated on site; 2. If no reference value is available, initially setting it as follows: for steel pipes, the integral length l of the deformation interface is 10D (D is the outer diameter of the pipe); for PE plastic pipes, the integral length l of the deformation interface is 5D (D is the outer diameter of the pipe). The integral length l of the pipeline deformation interface may vary slightly on site due to different geological soil layers, and can be finely adjusted.

[0121] (3) Verify the stress change of the cross section of the pipeline under load, and determine the third stability calculation and verification sub-model, as shown below:

[0122] Pipe cross-sectional stability calculation:

[0123] Pipe cross-sectional stability check: σ f ≤[σ s ]Δ x =D1-D

[0124] Where M is the moment; W is the section modulus of bending; σ f The normal stress of the pipe cross section; [σ s ] is for checking allowable stress; Δ x D represents the geometric deformation of the cross section; D is the outer diameter of the pipe in the initial state; D1 is the maximum outer diameter of the pipe after deformation.

[0125] When the aforementioned pipeline is subjected to external loads, the stress change of the pipeline's cross-section under load is checked, and the normal section is deformed. The geometric deformation of the normal section can be limited to... The range is defined. For example, if the pipeline is subjected to an external load and becomes elliptical (not a deformation caused by internal forces), it will not affect the pipeline's pressure-bearing nature, but a large diameter and a small diameter will appear. Then, strength calculations are used to check the design wall thickness δ of the large diameter. h1 Because in strength calculations δ h Proportional to D, if D1 increases by δ h1If the load is not increased, the bearing capacity of the steel pipe will theoretically decrease. The geometric deformation of the cross-section after deformation can be verified by equivalent check and seismic check to see if it meets the design calculation requirements. If it does, then the deformation of D1-D can be used as Δ. x Verification criteria. (Δ) x =D1-D.

[0126] The existing "Code for Design of Gas Pipeline Engineering" GB 50251-2015 stipulates that the radial stability check of gas pipelines should be calculated according to the following formula. When the pipeline is deeply buried or the external load is large, the stability should be checked under the condition of no internal pressure.

[0127] calculate: W = w1 + w2

[0128] Verification: Δ x =0.03D m

[0129] The formula in the aforementioned design specification adds a decomposition of the characteristic values ​​of the subgrade bearing capacity to the denominator: subgrade coefficient, subgrade wrap angle, soil deformation modulus, etc.; the moment of inertia of the steel pipe has also been adjusted accordingly. Because the formula originates from a double integral derivation, its calculated data will undergo substantial changes when combined with the foundation bearing capacity. This formula model is based on the derivation of the "elastic deformation formula," reflecting only the amount of deflection deformation; it cannot reflect the geometric deformation occurring in the radial direction of the steel pipe's cross-section. In contrast, the stability calculation and verification model in this invention fully considers both deflection deformation and the geometric deformation occurring in the radial direction of the pipe's cross-section, making the stability calculation and verification more accurate and the pipeline design more rational.

[0130] III. Equivalent stress calculation and verification model, including the equivalent stress calculation and verification submodule for straight pipe sections and the equivalent stress calculation and verification submodule for bends;

[0131] Specifically as follows:

[0132] (1) The equivalent stress calculation and verification submodule for straight pipe sections ignores the change in Poisson's ratio when the pipeline bears the maximum internal pressure. Based on the axial deformation stress and radial deformation stress caused by the temperature change of the straight pipe section, the equivalent stress of the straight pipe section is determined as follows:

[0133] Calculation of axial deformation stress in straight pipe section: σ L =Eα(t1-t2)

[0134] Calculation of radial deformation stress in straight pipe sections:

[0135] Equivalent stress check of straight pipe section: σ e =σ h +σ L <0.9σ s

[0136] Where, σ L σ represents the axial deformation stress caused by temperature change; E is the elastic modulus of the pipeline; α is the temperature change coefficient; t1 is the ambient temperature at the installation site; t2 is the pipeline's own temperature during operation; σ h The radial stress is for the straight pipe section.

[0137] In the existing "Code for Design of Gas Pipeline Engineering" GB 50251-2015, μ is Poisson's ratio, μσ n The Poisson ratio, which reflects the change in the maximum internal pressure of the pipeline, can be used as an identification property of pipeline deformation performance, but its application in calculating axial strain needs to be carefully considered.

[0138] Where μσ n The Poisson's ratio reflects the change in the maximum internal pressure of the pipeline. Where ε0 refers to the transverse strain and ε refers to the longitudinal strain, therefore ε0 = -με; similarly, μσ n Essentially, this reflects με, which ε = -με; therefore, the axial strain calculated in this way is negative (due to axial compression). Substituting this into the original equation, we get σ L =μσ n +Eα(t 1- The axial stress calculated in t2) is actually smaller.

[0139] in, When δ n When designing the wall thickness, the Poisson's ratio is constrained in this state and will not undergo lateral or longitudinal strain. Therefore, the axial stress of the pipeline during operation is only the change in axial stress caused by the temperature change during pipeline operation. Therefore, the equivalent stress calculation and verification submodule of the straight pipe section in this invention ignores the change in Poisson's ratio when the pipeline bears the maximum internal pressure, and directly uses the axial deformation stress caused by the temperature change of the pipeline during operation as the axial stress of the pipeline during operation.

[0140] Furthermore, in the existing "Code for Design of Gas Pipeline Engineering" GB 50251-2015, for constrained thermal expansion straight pipe sections, the equivalent stress, i.e., σ, should be calculated according to the maximum shear stress strength theory. e =σ h -σ L <0.9σ s The "maximum shear stress strength theory" reflects the stress relationship between a plane subjected to biaxial force, where one principal stress forms an arbitrary angle on a cross section and the other principal stress is parallel to the X-axis, and each has its own shear stress. The derivation yields σ1-σ2≤[σ], but in reality, σ... L With σ hBoth should be considered as two principal stresses acting on the pipe section, perpendicular to each other and located on the principal plane where the shear stress is zero. This is fundamentally different from the case where σ1-σ2≤[σ]. Therefore, the equivalent stress of the constrained thermally expanding straight pipe section should not be considered as the maximum stress minus the minimum stress. Thus, in this invention, the equivalent stress is checked based on the sum of the radial deformation stress of the pipe and the axial deformation stress caused by temperature change.

[0141] (2) The equivalent stress calculation and verification submodule for the bend introduces the axial deformation stress caused by temperature change on the bend. Based on the radial deformation stress and the axial deformation stress caused by temperature change, the equivalent stress of the bend is determined as follows:

[0142] Calculation of axial deformation stress of bend: σ hmax =β q σ o

[0143] Calculation of radial deformation stress in the bend section:

[0144] Equivalent stress check for bend: σ e =σ h +σ hmax <σ b

[0145] Where, σ hmax β is the axial deformation stress caused by temperature change. q =1.8[1-(r / R)] 2 ](1 / λ) 2 / 3 , r is the nominal diameter (maximum inner diameter of the pipe), R is the radius of curvature of the bend, M is the moment generated by the pipe temperature stress on the radius of the pipe cross-section, and σ is the torque. b σ represents the tensile strength of the pipe. h This represents the radial stress of the bend.

[0146] Compared with existing design specifications, the above calculation and verification of equivalent stress in bends introduces axial deformation stress caused by temperature changes, making the calculation and verification of equivalent stress in bends more accurate and the design results of gas pipelines more in line with actual conditions.

[0147] IV. Seismic Strength Design and Verification Model: A seismic strength design and verification model is constructed based on design codes, as detailed below:

[0148] (I) Strength Design and Verification Model for Straight Pipe Sections under Seismic Action:

[0149] (1) The maximum circumferential stress during a seismic event in a straight pipe section is shown below:

[0150]

[0151]

[0152] Where α is the peak ground acceleration; υ is the peak ground velocity; T g The characteristic period of the seismic response spectrum; V sG ε represents the equivalent shear wave velocity of the soil layer at the site. max This represents the maximum axial tensile and compressive stress in the pipeline caused by ground motion.

[0153] (2) Seismic check of straight pipe sections, as shown below:

[0154] When ε max When +ε≤0|ε max +ε|≤[ε c V

[0155] When ε max When +ε>0|ε max +ε|≤[ε t V

[0156] Among them, [ε c [ε] represents the allowable axial compressive stress for vibration resistance of buried pipelines; t ε represents the allowable axial tensile stress for vibration resistance of buried pipelines; ε represents the equivalent strain of the pipeline under operating conditions. σ e Here, E represents the equivalent stress value of the straight pipe section, and E is the elastic modulus of the steel pipe.

[0157] (3) Allowable strain values ​​are as follows:

[0158] A. Allowable compressive strain

[0159]

[0160] Where δn is the pipe design wall thickness, and D is the pipe outer diameter;

[0161] B. Allowable tensile stress

[0162] [ε t V = 0.01;

[0163] (II) Strength Design and Verification Model for Bends under Seismic Motion:

[0164] (1) The maximum circumferential stress during a bent-pipe earthquake is shown below:

[0165]

[0166]

[0167] Where α is the peak ground acceleration; υ is the peak ground velocity; Tg The characteristic period of the seismic response spectrum; V SG ε represents the equivalent shear wave velocity of the soil layer at the site. max This represents the maximum axial tensile and compressive stress in the pipeline caused by ground motion.

[0168] (2) Seismic check of the bend, as shown below:

[0169] When ε max When +ε≤0|ε max +ε|≤[ε c V

[0170] When ε max When +ε>0|ε max +ε|≤[ε t V

[0171] Among them, [ε c [ε] represents the allowable axial compressive stress for vibration resistance of buried pipelines; t ε represents the allowable axial tensile stress for vibration resistance of buried pipelines; ε represents the equivalent strain of the pipeline under operating conditions. σ e Here, E represents the equivalent stress value of the straight pipe section, and E is the elastic modulus of the steel pipe.

[0172] (3) The allowable strain values ​​are as follows:

[0173] A. Allowable compressive strain

[0174]

[0175] Where δn is the pipe design wall thickness, and D is the pipe outer diameter;

[0176] B. Allowable tensile stress

[0177] [ε t V = 0.01.

[0178] Example 2: As shown in the attached document Figure 2 As shown, this embodiment of the invention discloses a design method for long-distance and urban gas pipelines, including:

[0179] Step S101: Determine the design pressure and use the straight pipe section design wall thickness sub-model to determine the design wall thickness of the straight pipe section;

[0180] Step S102: Determine if the load G of the projected area of ​​the external force acting on the unit length of the pipe is greater than the bearing capacity f of the base layer. ak Or is it equal to the bearing capacity of the base layer f? ak Here f ak Provided by the surveying unit;

[0181] Step S103, in response to the load-bearing capacity of the base course (G>f)ak If the buried pipeline is subjected to concentrated load or uniform load, the first stability calculation and verification sub-model is used to calculate and verify the bending deflection of the steel pipe. If it is subjected to uniform load, the second stability calculation and verification sub-model is used to calculate and verify the bending deflection of the steel pipe. It should be noted that when using the first stability calculation and verification sub-model to verify the bending deflection of the steel pipe and the second stability calculation and verification sub-model to verify the bending deflection of the steel pipe, it is necessary to determine whether the verification is passed (i.e. whether the verification formula is met). If it is not met, it is necessary to return to step S101 to readjust the design wall thickness of the straight pipe section.

[0182] Step S104, in response to the base bearing capacity (G = f) ak If the third stability calculation and verification sub-model is used, the normal stress of the pipe cross section is calculated and verified. It should be noted that in this step, the normal stress of the pipe cross section is verified (i.e. whether the verification formula is met) using the third stability calculation and verification sub-model. If it is not met, it is necessary to return to step S101 to readjust the design wall thickness of the straight pipe section.

[0183] Step S105: Using the equivalent stress calculation and verification submodules for straight pipe sections and bends, complete the equivalent stress calculation and verification for straight pipe sections and bends. In this step, the equivalent stress of straight pipe sections and bends is verified (i.e., whether the verification formula is met). If it is not met, return to step S101 to readjust the design wall thickness of the straight pipe section.

[0184] Step S106: Combine the design wall thickness of the straight pipe section with the wall thickness of the bend pipe and use the bend pipe design wall thickness sub-model to determine the wall thickness of the bend pipe.

[0185] Step S107: Use the seismic strength design and verification model to complete the seismic motion design calculation and verification. Use the seismic strength design and verification model to complete the seismic motion design verification (i.e., whether it meets the verification formula). If it does not meet the formula, return to step S101 to readjust the design wall thickness of the straight pipe section.

[0186] Example 3: This embodiment of the invention discloses a storage medium storing a computer program that can be read by a computer. The computer program is configured to execute a long-distance and urban gas pipeline design method when running.

[0187] The aforementioned storage media may include, but are not limited to, USB flash drives, read-only memory, portable hard drives, magnetic disks, optical disks, and other media capable of storing computer programs.

[0188] Example 4: This embodiment of the invention discloses an electronic device, including a processor and a memory. The memory stores a computer program, which is loaded and executed by the processor to implement a design method for long-distance and urban gas pipelines.

[0189] The processor described above can be a central processing unit (CPU), a general-purpose processor, a digital signal processor (DSP), an ASIC, an FPGA, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. It can also be a combination that implements computational functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc. The memory can include, but is not limited to, various media capable of storing computer programs, such as USB flash drives, read-only memory, portable hard drives, magnetic disks, or optical disks.

[0190] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0191] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0192] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0193] The above technical features constitute the preferred embodiment of the present invention, which has strong adaptability and optimal implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the requirements of different situations.

Claims

1. A design method for long-distance and urban gas pipelines, characterized in that, The method is implemented based on the design mechanical model of long-distance and urban gas pipelines, which includes: The pipe wall thickness determination model includes a sub-model for designing the wall thickness of straight pipe sections and a sub-model for designing the wall thickness of bends. The sub-model for designing the wall thickness of bends is shown below: If 1.6MPa≦P≦2.5MPa, then the radius of curvature of the designed bend is ≥3D, the design wall thickness of the bend is the positive deviation of the design wall thickness of the straight section is ≥0.5mm, P is the design pressure of the pipeline, and D is the outer diameter of the pipeline. If P ≥ 4.0 MPa, then the radius of curvature of the designed bend should be ≥ 6D, and the design wall thickness of the bend should be determined according to the specifications. The stability calculation and verification model is constructed based on the relationship between the load on the projected area of ​​the external force acting on the unit length of the pipe and the bearing capacity of the base layer. The equivalent stress calculation and verification model includes sub-modules for calculating and verifying equivalent stress in straight pipe sections and equivalent stress calculation and verification in bends. The sub-module for calculating and verifying equivalent stress in straight pipe sections ignores the change in Poisson's ratio when the pipe bears maximum internal pressure. It determines the equivalent stress in the straight pipe section based on the axial and radial deformation stresses caused by temperature changes, as shown below: in, E represents the axial deformation stress of the straight pipe section; E is the elastic modulus of the pipe. It is the coefficient of temperature change; The ambient temperature at the installation site; This refers to the temperature of the pipeline itself during operation. This refers to the radial deformation stress of the straight pipe section; Design wall thickness for straight pipe sections; Equivalent stress in the straight pipe section; The minimum yield strength specified in the steel pipe standard; The seismic strength design and verification model was constructed in accordance with the design code, and the seismic strength design and verification were completed. The method includes: Determine the pipeline design pressure, use the straight pipe section design wall thickness sub-model to determine the straight pipe section design wall thickness, and adjust the straight pipe section design wall thickness through the following checks. If the checks fail, readjust the straight pipe section design wall thickness. Determine whether the load on the projected area per unit length of the pipe caused by the external force is greater than or equal to the bearing capacity of the base layer. If the load exceeds the bearing capacity of the base layer, it is determined whether the buried pipeline is subjected to concentrated load or uniform load. If it is subjected to concentrated load, the first stability calculation and verification sub-model is used to calculate and verify the bending deflection of the steel pipe. If it is subjected to uniform load, the second stability calculation and verification sub-model is used to calculate and verify the bending deflection of the steel pipe. In response to the load-bearing capacity of the base layer, the calculation and verification of the normal stress of the pipe cross section are completed using the third stability calculation and verification sub-model; The equivalent stress calculation and verification model was used to complete the equivalent stress calculation and verification of straight pipe sections and bends; The design wall thickness of the straight pipe section is combined with the design wall thickness of the bend pipe sub-model to determine the design wall thickness of the bend pipe; The seismic strength design and verification model was used to complete the seismic strength calculation and verification.

2. The design method for long-distance and urban gas pipelines according to claim 1, characterized in that, The sub-model for the design wall thickness of the straight pipe section is used to determine the pipeline design pressure. Based on the pipeline design pressure, the yield strength value is selected, and the design wall thickness of the straight pipe section is determined, as shown below: in, Design wall thickness for straight pipe sections; The yield strength value is selected based on the pipeline design pressure; t is the weld coefficient; F is the strength design coefficient; t is the temperature reduction coefficient.

3. The design method for long-distance and urban gas pipelines according to claim 1, characterized in that, The stability calculation and verification model includes a first stability calculation and verification sub-model, a second stability calculation and verification sub-model, and a third stability calculation and verification sub-model, specifically: For buried pipelines subjected to concentrated rolling loads, the first stability calculation and verification sub-model is determined as follows: Where Z is the load factor; Let represent the first stability of the pipeline; I represent the pipeline moment of inertia; l represent the integral length of the pipeline deformation interface; and G represent the load on the projected area of ​​the external force acting on a unit length of the pipeline. , Let L be the projected area of ​​the deformable interface and the weight of the soil above the pipe. The vertical pressure exerted by external forces on the ground above the pipe; For buried pipelines subjected to uniformly distributed compaction loads, a second stability calculation and verification sub-model is determined, as shown below: in, For the second stability of the pipeline; The stress change in the cross-section of the pipeline under load is checked, and the third stability calculation and check sub-model is determined, as shown below: Where M is the moment; W is the section modulus of bending. For the third stability of the pipeline; To check the allowable stress; This represents the geometric deformation of the cross section. This represents the maximum outer diameter of the pipe after deformation.

4. A storage medium, characterized in that, The storage medium stores a computer program that can be read by a computer, and the computer program is configured to execute the long-distance and urban gas pipeline design method as described in any one of claims 1 to 3 when it runs.

5. An electronic device, characterized in that, It includes a processor and a memory, wherein the memory stores a computer program, which is loaded and executed by the processor to implement the long-distance and urban gas pipeline design method as described in any one of claims 1 to 3.

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