CN114004125A - Method for calculating peak value of stress concentration coefficient of tube node under axial force load and application - Google Patents
Method for calculating peak value of stress concentration coefficient of tube node under axial force load and application Download PDFInfo
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- CN114004125A CN114004125A CN202111295504.7A CN202111295504A CN114004125A CN 114004125 A CN114004125 A CN 114004125A CN 202111295504 A CN202111295504 A CN 202111295504A CN 114004125 A CN114004125 A CN 114004125A
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- G06—COMPUTING; CALCULATING OR COUNTING
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- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
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- G06F2113/00—Details relating to the application field
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- G06F—ELECTRIC DIGITAL DATA PROCESSING
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- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Abstract
The invention discloses a method for calculating a stress concentration coefficient peak value of a three-plane Y-shaped tube node under the action of axial force load and application thereof, and belongs to the technical field of fatigue safety evaluation of steel tube structures in civil engineering and ocean engineering. In engineering, fatigue design is carried out by adopting an S-N curve method based on hot spot stress, so that the accurate prediction of the stress concentration coefficient of the pipe node is an important basis for carrying out the fatigue design. At present, a stress concentration coefficient calculation formula of a three-plane Y-tube node is lacked. In order to solve the problem, the invention establishes a three-plane Y-shaped tube node numerical model library with different geometric parameters, and provides a calculation formula of the stress concentration coefficient peak value of the loaded plane of the three-plane Y-shaped tube node through calculation and analysis. The formula perfects a space tube node stress concentration coefficient calculation system, and provides a convenient and reliable method for three-plane Y-shaped tube node fatigue safety evaluation.
Description
Technical Field
The invention relates to the technical field of fatigue safety evaluation of civil and ocean engineering steel pipe structures, in particular to a method for calculating a pipe node stress concentration coefficient peak value under axial force load and application.
Background
The high strength to weight ratio makes steel one of the best quality structural materials in civil engineering construction. The steel pipe member is widely applied to various engineering structures due to good material mechanical properties, and the joint of the steel pipe member is a pipe joint. The pipe nodes can be divided into two categories of plane pipe nodes and space pipe nodes, wherein the plane pipe nodes refer to pipe nodes with axes of all rod pieces in the same plane, and the pipe nodes with axes not all in the same plane are space pipe nodes. In recent decades, with the wide application of steel pipe structures in large-scale engineering, the original plane pipe joints cannot meet the engineering requirements, and many forms of space pipe joints are produced at the same time.
The three-plane Y-shaped pipe node is a typical space pipe node and is mostly found in a three-pile foundation structure of an offshore wind turbine in a intertidal zone area in the southeast coast of China. The offshore wind turbine foundation structure needs to resist complex cyclic loads such as wind load, wave load, ocean current load, water level change, growth of marine organisms, scouring and erosion and the like in a service period. Therefore, fatigue safety evaluation is an important link in designing the foundation structure of the offshore wind turbine.
At present, the most commonly adopted method for fatigue design of pipe nodes is an S-N curve method based on hot spot stress. The method comprises the steps of firstly calculating nominal stress on each supporting rod of a pipe node according to external loads borne by each rod piece of the pipe node, secondly calculating stress concentration coefficient values under different loads according to a formula, thirdly multiplying the nominal stress by the peak value of the stress concentration coefficient to obtain hot spot stress, and lastly obtaining the fatigue life of the pipe node according to the hot spot stress values and an S-N curve of a material.
In summary, how to accurately predict the stress concentration coefficient of the pipe node is an important basis for performing structural fatigue safety evaluation. At home and abroad, a plurality of recommended formulas for stress concentration coefficients of different types of tube nodes exist, but a stress concentration coefficient peak value calculation formula of a three-plane Y-shaped tube node under the action of axial force load is lacked.
Disclosure of Invention
In view of the above, the invention provides a method for calculating the peak value of the stress concentration coefficient of a tube node under an axial force load and an application thereof, and provides a convenient and reliable method for carrying out fatigue safety evaluation on a three-plane Y-shaped tube node by adopting an S-N curve method based on hot spot stress aiming at a calculation formula of the peak value of the stress concentration coefficient of the three-plane Y-shaped tube node under the action of the axial force load.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for calculating the stress concentration coefficient peak value of a three-plane Y-shaped tube node under an axial force load comprises the following steps:
acquiring a first geometric parameter, wherein the first geometric parameter comprises: the chord length-thin ratio alpha, the chord diameter-thickness ratio gamma, the chord wall-thickness ratio tau and the support-chord included angle theta;
calculating the stress concentration coefficient peak value of the chord member of the three-plane pipe node according to the first geometric parameter;
the three-plane pipe node chord stress concentration coefficient peak value calculation formula is as follows:
optionally, the chord length-to-thickness ratio is calculated by the following formula:
wherein D is the outer diameter of the chord member, LCCalculating the length of the representative chord;
the calculation formula of the chord diameter-thickness ratio is as follows:
wherein T is the chord wall thickness, and D is the chord outer diameter;
the calculation formula of the chord member wall thickness ratio is as follows:
wherein T is the strut wall thickness and T is the chord wall thickness.
Optionally, the chord slenderness ratio alpha belongs to [6,15], the chord diameter-thickness ratio gamma belongs to [25,40], the chord wall-thickness ratio tau belongs to [0.5,0.9], and the support-chord clip angle theta belongs to [30 degrees ], 60 degrees ].
A method for calculating the stress concentration coefficient peak value of a three-plane Y-shaped tube node under an axial force load comprises the following steps:
acquiring a second geometric parameter, wherein the second geometric parameter comprises: the length-slenderness ratio alpha of the chord, the diameter ratio beta of the brace to the chord, the diameter-thickness ratio gamma of the chord, the wall-thickness ratio tau of the chord and the brace-chord included angle theta;
calculating the stress concentration coefficient peak value of the three-plane pipe node supporting rod according to the second geometric parameters;
the stress concentration coefficient peak value calculation formula of the tri-plane pipe node stay bar is as follows:
optionally, the chord length-to-thickness ratio is calculated by the following formula:
wherein D is the outer diameter of the chord member, LCCalculating the length of the representative chord;
the calculation formula of the strut-chord diameter ratio is as follows:
wherein D is the outer diameter of the stay bar, and D is the outer diameter of the chord;
the calculation formula of the chord diameter-thickness ratio is as follows:
wherein T is the chord wall thickness, and D is the chord outer diameter;
the calculation formula of the chord member wall thickness ratio is as follows:
wherein T is the strut wall thickness and T is the chord wall thickness.
Optionally, the chord slenderness ratio alpha belongs to [6,15], the strut-chord diameter ratio beta belongs to [0.4,0.75], the chord diameter-thickness ratio gamma belongs to [25,40], the chord wall thickness ratio tau belongs to [0.5,0.9], and the strut-chord included angle theta belongs to [30 degrees ], 60 degrees ].
The application of the method for calculating the stress concentration coefficient peak value of the three-plane Y-shaped tube node under the axial force load comprises the following steps:
calculating the nominal stress of the plane according to a material mechanics formula;
calculating according to the first geometric parameter to obtain a stress concentration coefficient peak value of the chord member of the three-plane pipe joint;
calculating according to the second geometric parameters to obtain stress concentration coefficient peak values of the brace rods of the three-plane pipe nodes;
comparing the stress concentration coefficient peak value of the chord member of the three-plane pipe node with the stress concentration coefficient peak value of the brace rod of the three-plane pipe node, and taking the larger value as the stress concentration coefficient peak value of the Y-shaped pipe node of the three-plane pipe;
and multiplying the nominal stress by the stress concentration coefficient peak value to obtain a three-plane Y-shaped tube node hot spot stress value.
According to the technical scheme, compared with the prior art, the invention discloses a method for calculating the stress concentration coefficient peak value of the three-plane Y-shaped pipe node under the axial force load and application thereof, and provides a calculation formula of the stress concentration coefficient peak value of the loaded plane of the three-plane Y-shaped pipe node through calculation and analysis. The formula perfects a space tube node stress concentration coefficient calculation system, and provides a convenient and reliable method for three-plane Y-shaped tube node fatigue safety evaluation.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a front view of a tri-planar Y-tube node;
FIG. 2 is a top view of a tri-planar Y-tube node;
FIG. 3 is an axial force load condition diagram;
FIG. 4 is a chord side α sensitivity analysis;
FIG. 5 is a strut-side α sensitivity analysis;
FIG. 6 is a chord side sensitivity analysis chart;
FIG. 7 is a graph of a strut lateral sensitivity analysis;
FIG. 8 is a chord side sensitivity analysis chart;
FIG. 9 is a graph of a strut side sensitivity analysis;
FIG. 10 is a chord side τ sensitivity analysis chart;
FIG. 11 is a graph of strut-side τ sensitivity analysis;
FIG. 12 is a chord side θ sensitivity analysis chart;
fig. 13 is a strut-side θ sensitivity analysis chart.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a method for calculating the stress concentration coefficient peak value of a three-plane Y-shaped tube node under an axial load, which comprises the following steps:
a typical three-plane Y-tube node is shown in figures 1 and 2. In the figure, LCCalculating length, L, for chords1Length of upper chord, D outer diameter of chord, T wall thickness of chord, lBThe length is calculated for the strut, d is the strut outer diameter, t is the strut wall thickness, and theta is the strut-chord angle. The geometric parameters considered by the stress concentration coefficient peak value calculation formula are as follows: the chord length-thin ratio alpha is calculated according to the formula (1); the diameter ratio beta of the brace to the chord is calculated according to the formula (2); the chord diameter-thickness ratio gamma is calculated according to the formula (3); the chord wall thickness ratio tau is calculated by the method shown in formula (4); strut-chord clip angle θ.
First, considering that the three-plane Y-shaped tube node is subjected to the axial force load by the T1 plane stay only, as shown in fig. 3, the axial force load direction coincides with the axial direction of the T1 plane stay, and the maximum value of von Mises equivalent stress caused by the axial force load at each position of the three-plane Y-shaped tube node is smaller than the yield strength of the steel material of the tube node.
Second, 1920 three-plane Y-tube node numerical models with different geometric parameters are established, wherein a typical numerical model is shown in FIG. 4. The values of the geometric parameters of each numerical model are shown in table 1.
Table 1 numerical model geometric parameter values
And thirdly, applying the load conditions of the first step on the numerical model established in the second step, respectively calculating, totally performing 1920 calculations to obtain 1920 groups of calculation results, counting the calculation results of each model, and performing parameter sensitivity analysis. The sensitivity analysis for α is shown in fig. 4 and 5, for β in fig. 6 and 7, for γ in fig. 8 and 9, for τ in fig. 10 and 11, and for θ in fig. 12 and 13.
And fourthly, respectively carrying out multidimensional nonlinear fitting analysis on the SCF peak values on the chord side and the strut side according to the parameter sensitivity analysis results to obtain stress concentration coefficient peak value calculation formulas of the chord and the strut of the three-plane Y-shaped tube node T1, wherein the stress concentration coefficient peak value calculation formulas are respectively shown in a formula (5) and a formula (6).
In the formula, alpha is the length-slenderness ratio of the chord, beta is the ratio of the strut-chord diameter, gamma is the ratio of the chord diameter to the chord thickness, tau is the wall thickness ratio of the chord, and theta is the included angle of strut-chord. The value ranges of the parameters are shown in table 2.
TABLE 2 geometric parameters application Range
| Geometric parameters | α | β | γ | τ | θ |
| Value range | [6,15] | [0.4,0.75] | [25,40] | [0.5,0.9] | [30°,60°] |
Furthermore, the embodiment also provides an application of the method for calculating the stress concentration coefficient peak of the node of the three-plane Y-shaped tube under the axial force load.
Specifically, geometric parameters of a three-plane Y-shaped tube node in a three-pile foundation structure of an offshore wind turbine are shown in table 3, the tube node is shown in fig. 2, and a T1 plane stay bar bearing axial force F is 7852.65 kN. The hot spot stress calculation process of the pipe joint under the working condition is as follows.
TABLE 3 three-plane Y-tube nodal geometry parameters
| Parameter(s) | L(m) | D(m) | T(mm) | l(m) | d(m) | t(mm) | θ(°) | α | γ | β | τ |
| |
35 | 5 | 78.13 | 16 | 3.3 | 64.06 | 52 | 14 | 32 | 0.66 | 0.82 |
The first step is as follows: and calculating the nominal stress of the T1 plane according to a material mechanics formula.
The second step is that: substituting the geometric parameters in table 3 into equation (5), the peak value of the stress concentration coefficient on the chord member side of the pipe node is calculated to be 18.52.
The third step: substituting the geometric parameters in the table 3 into the formula (6), and calculating to obtain that the peak value of the stress concentration coefficient at one side of the pipe node stay bar is 11.34.
The fourth step: and comparing the stress middle coefficient peak values of the chord member and the brace rod, and taking a larger value (namely 18.52) as the stress concentration coefficient peak value of the three-plane Y-shaped pipe node.
The fifth step: and multiplying the nominal stress by the peak value of the stress concentration coefficient to obtain the hot spot stress value of the three-plane Y-shaped tube node under the working condition of 223.35 MPa.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. A method for calculating the stress concentration coefficient peak value of a three-plane Y-shaped tube node under an axial force load is characterized by comprising the following steps:
acquiring a first geometric parameter, wherein the first geometric parameter comprises: the chord length-thin ratio alpha, the chord diameter-thickness ratio gamma, the chord wall-thickness ratio tau and the support-chord included angle theta;
calculating the stress concentration coefficient peak value of the chord member of the three-plane pipe node according to the first geometric parameter;
the three-plane pipe node chord stress concentration coefficient peak value calculation formula is as follows:
2. the method for calculating the peak stress concentration coefficient of the node of the three-plane Y-shaped tube under the axial load according to claim 1,
the calculation formula of the chord length-thin ratio is as follows:
wherein D is the outer diameter of the chord member, LCCalculating the length of the representative chord;
the calculation formula of the chord diameter-thickness ratio is as follows:
wherein T is the chord wall thickness, and D is the chord outer diameter;
the calculation formula of the chord member wall thickness ratio is as follows:
wherein T is the strut wall thickness and T is the chord wall thickness.
3. The method for calculating the peak value of the stress concentration coefficient of the node of the three-plane Y-shaped pipe under the axial load is characterized in that the chord length-slenderness ratio alpha belongs to [6,15], the chord diameter-thickness ratio gamma belongs to [25,40], the chord wall-thickness ratio tau belongs to [0.5,0.9], and the strut-chord included angle theta belongs to [30 degrees ] and [ 60 degrees ].
4. A method for calculating the stress concentration coefficient peak value of a three-plane Y-shaped tube node under an axial force load is characterized by comprising the following steps:
acquiring a second geometric parameter, wherein the second geometric parameter comprises: the length-slenderness ratio alpha of the chord, the diameter ratio beta of the brace to the chord, the diameter-thickness ratio gamma of the chord, the wall-thickness ratio tau of the chord and the brace-chord included angle theta;
calculating the stress concentration coefficient peak value of the three-plane pipe node supporting rod according to the second geometric parameters;
the stress concentration coefficient peak value calculation formula of the tri-plane pipe node stay bar is as follows:
5. the method for calculating the peak stress concentration coefficient of the node of the three-plane Y-shaped tube under the axial load according to claim 4,
the calculation formula of the chord length-thin ratio is as follows:
wherein D is the outer diameter of the chord member, LCCalculating the length of the representative chord;
the calculation formula of the strut-chord diameter ratio is as follows:
wherein D is the outer diameter of the stay bar, and D is the outer diameter of the chord;
the calculation formula of the chord diameter-thickness ratio is as follows:
wherein T is the chord wall thickness, and D is the chord outer diameter;
the calculation formula of the chord member wall thickness ratio is as follows:
wherein T is the strut wall thickness and T is the chord wall thickness.
6. The method for calculating the peak value of the stress concentration coefficient of the node of the three-plane Y-shaped pipe under the axial force load is characterized in that the chord length-slenderness ratio alpha belongs to [6,15], the strut-chord diameter ratio beta belongs to [0.4,0.75], the chord diameter-thickness ratio gamma belongs to [25,40], the chord wall thickness ratio tau belongs to [0.5,0.9] and the strut-chord included angle theta belongs to [30 degrees ] and 60 degrees ].
7. The application of the method for calculating the stress concentration coefficient peak value of the three-plane Y-shaped tube node under the axial force load is characterized by comprising the following steps of:
calculating the nominal stress of the plane;
calculating according to the first geometric parameter to obtain a stress concentration coefficient peak value of the chord member of the three-plane pipe joint;
calculating according to the second geometric parameters to obtain stress concentration coefficient peak values of the brace rods of the three-plane pipe nodes;
comparing the stress concentration coefficient peak value of the chord member of the three-plane pipe node with the stress concentration coefficient peak value of the brace rod of the three-plane pipe node, and taking the larger value as the stress concentration coefficient peak value of the Y-shaped pipe node of the three-plane pipe;
and multiplying the nominal stress by the stress concentration coefficient peak value to obtain a three-plane Y-shaped tube node hot spot stress value.
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Application publication date: 20220201 |