CN115384721B - Calculation method for structural strength of three-column floating type fan foundation stay bar - Google Patents
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Abstract
The invention discloses a method for calculating structural strength of a three-column floating type fan foundation stay bar, which comprises the following steps: step one, selecting dangerous working conditions and corresponding waveforms of four fan foundations which are easy to fail or destroy; step two, determining the wavelength according to waveforms of four dangerous working conditions, and determining the wave period and wave height under the four dangerous working conditions according to a wave theory formula; step three, determining the wave load born by the fan foundation; step four, building a beam system structural model of the fan foundation; step five, six boundary conditions are applied to the beam system structural model; step six, carrying out finite element dispersion on the beam system structural model to form a finite element model of a one-dimensional grid; step seven, wave load is applied in the finite element model; step eight, statics analysis is carried out to obtain the maximum axial compressive stress and the maximum combined stress of the stay bar under four dangerous working conditions; and step nine, judging whether the structural strength of the stay bar is enough. The invention can remarkably improve the calculation efficiency.
Description
Technical Field
The invention relates to a method for calculating structural strength of a three-column floating type fan foundation stay bar.
Background
Floating wind power corresponds to stationary wind power, and is defined and differentiated depending on whether the foundation structure of the wind turbine is a stationary structure or a floating structure. From the experience of offshore oil, the investment costs of a fixed foundation generally increase exponentially with increasing water depth due to increased loading of the fixed foundation at the seabed, etc. When the water depth exceeds a certain depth, the investment gain of the fixed fan becomes worse. Based on offshore oil experience, a critical water depth will occur beyond which the investment gain of floating wind power will be higher than that of stationary wind power. The floating wind power research has the meaning of reducing the investment cost of the floating wind power so as to realize the utilization of the offshore wind energy in the deep sea.
The three currently prevailing types of floating wind turbine foundations are semi-submersible, TLP (tension leg), and SPAR (mono column). The semi-submersible floating type fan foundation with wide application and mature technology is a foundation form which is more suitable for the development of offshore wind power at the present stage. The semi-submersible floating fan foundation generally comprises a plurality of upright posts and a connecting structure thereof, wherein at present, the upright posts are mainly made of steel cylinders, the connecting structure is mainly made of reinforced plates, round tubes, square tubes and other structures, and the stay bars are the connecting structures among the upright posts. In order to ensure the wave resistance of the foundation, the distance between the upright posts is often larger, and the supporting rod is subjected to larger load, so that the floating type fan foundation has higher requirement on the strength of the supporting rod.
At present, a calculation method for the structural strength of the ocean platform in the ocean engineering industry is mature, and a design wave method is generally adopted to analyze the total strength of the ocean platform. According to the method, wave parameters are designed according to the main scale of the platform, wave load borne by the platform is calculated through potential flow theory, and the wave load is mapped into a finite element model to carry out total intensity analysis. The method can also be applied to the structural strength calculation of the three-column floating type fan foundation stay bar, but the method needs to calculate the wave load by using potential flow theory and map the load into a finite element model, has higher requirements on the integrity of the model, is not applicable to the conceptual design stage of fuzzy structure, and is complex, and the steps are complex and time-consuming.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for calculating the structural strength of a three-column floating type fan foundation stay bar, which can remarkably improve the calculation efficiency, thereby quickly and preliminarily determining the size of the stay bar structure.
The purpose of the invention is realized in the following way: a method for calculating structural strength of a three-column floating type fan foundation stay bar comprises the following steps:
step one, selecting dangerous working conditions, namely, selecting dangerous working conditions and corresponding waveforms, wherein the four fan foundations are easy to fail or destroy;
Step two, wave parameters are determined, the wavelengths under four dangerous working conditions are determined according to the waveforms of the four dangerous working conditions, and the wave period and wave height under the four dangerous working conditions are determined according to a wave theory formula;
Step three, load determination, namely determining wave loads born by three upright posts of the fan foundation;
Step four, building a structural model, namely building a beam system structural model of a fan foundation in a ANSYSDESIGN MODELER module;
Step five, boundary conditions are applied, wherein six boundary conditions are applied to the beam system structural model, namely three vertical upward spring constraints, two wave direction horizontal displacement constraints and one vertical wave direction horizontal displacement constraint;
Step six, finite element dispersion is carried out on the beam system Structural model in a ANSYS STATIC Structural module to form a finite element model of a one-dimensional grid;
step seven, load application, in which wave load is applied to the finite element model, the direction of the wave load is determined by waveforms of four dangerous working conditions, and the wave load is applied to the centroid of the draft part of the upright post in the form of point load;
step eight, carrying out statics analysis in a ANSYS STATIC Structural module to obtain the maximum axial compressive stress sigma dc of the stay bar and the maximum combined stress sigma mc of the stay bar under four dangerous working conditions;
And step nine, checking the strength, namely checking the yield strength of the stay bar material and the maximum combined stress sigma mc of the stay bar, checking the buckling strength of the stay bar material and the maximum axial compressive stress sigma dc of the stay bar, and judging whether the structural strength of the stay bar is enough.
According to the method for calculating the structural strength of the three-column floating type fan foundation stay bar, the first dangerous working condition is the working condition with the largest 0-degree incident angle separating force, the second dangerous working condition is the working condition with the largest 0-degree incident angle extruding force, the third dangerous working condition is the working condition with the largest 30-degree incident angle separating force, and the fourth dangerous working condition is the working condition with the largest 30-degree incident angle extruding force.
The method for calculating the structural strength of the three-upright floating type fan foundation stay bar comprises the following steps:
A. wavelength determination, namely determining the relation between the wavelength L and the spacing B of the upright post under four dangerous working conditions according to waveforms in the four dangerous working conditions in a one-to-one correspondence manner:
In the formula (1), L 1 is the wavelength under the first dangerous working condition; l 2 is the wavelength under the second dangerous condition; l 3 is the wavelength under the third dangerous working condition; l 4 is the wavelength under the fourth dangerous working condition; b is the spacing of the upright posts;
B. Wave period is determined, and a wave period T formula is obtained according to a linear wave theory:
in the formula (2), L is a wavelength; k is the wave number of the wave, D is the depth of water;
C. Wave height determination, calculating wave height H according to a linear wave height formula (3):
in the formula (3), T is a wave period; h 100 is the wave height of century.
The method for calculating the structural strength of the three-column floating type fan foundation stay bar comprises the following steps of:
In formula (4), F N is wave load; ρ is the sea water density; c A is an additional mass coefficient, C A＝1;CD is a drag coefficient when the column is cylindrical, C D =1 when the column is cylindrical; a is the area of the cross section of the upright post; d is the diameter of the upright post; the horizontal movement acceleration of the water particles; v is the horizontal movement speed of the water particles;
Obtaining the horizontal motion velocity v of water particles in waves according to a linear wave theory:
obtaining horizontal motion acceleration of water particles in waves according to linear wave theory
In the formulas (5) and (6), H is wave height; k is the wave number of the wave,L is the wavelength; d is the depth of water; z is the depth of the water particle; x is the propagation direction of the wave; omega is the circular frequency of the wave; t is time.
In the above calculation method for structural strength of the three-column floating fan foundation brace, when the step five is performed, the spring stiffness restrained by the set spring is equivalent to the water buoyancy load, and the calculation formula of the spring stiffness K s is as follows:
In the formula (7), ρ is the sea water density; d is the diameter of the upright post; g is the gravitational acceleration coefficient 9.8N/Kg.
The method for calculating the structural strength of the three-upright floating type fan foundation stay bar comprises the following steps:
A. Yield strength check, the allowable yield stress of the brace bar [ σ s ] is determined by:
[σs]＝σs/Ss
Wherein sigma s is the yield strength of the stay bar material and MPa; s s is the yield safety coefficient of the stay bar material;
B. Buckling strength check, allowable buckling stress [ σ cr ] of the stay bar is determined by:
[σcr]＝σcr/Scr
Wherein sigma cr is the buckling strength of the stay bar material and MPa; s cr is the buckling safety coefficient of the strut material.
The buckling strength σ cr of the pressed rod material is calculated as follows:
In formula (8): σ E is the stress in euler, MPa, L is the unsupported length of the rod piece; r is the radius of gyration inertia of the cross section corresponding to the unsupported length l of the rod; k is an equivalent length coefficient; e is the Young's modulus of the stay bar material;
The structural strength of the brace will only be sufficient when the maximum combined stress of the brace is less than the allowable yield stress of the brace [ sigma s ], i.e., sigma mc＜[σs ], while the maximum axial compressive stress of the brace is less than the allowable buckling stress of the brace [ sigma cr ], i.e., sigma dc＜[σcr ].
The method for calculating the structural strength of the three-column floating type fan foundation stay bar has the following characteristics:
the method has the advantages that the requirement on the integrity of the model is low, the calculation steps and the model are optimized and simplified to the greatest extent, the calculation efficiency can be remarkably improved, the size of the stay bar structure can be rapidly and preliminarily determined, and the method is very suitable for stay bar strength calculation in the structural fuzzy conceptual design stage.
Drawings
FIG. 1 is a schematic diagram of a three-column floating fan foundation in accordance with the present invention;
FIG. 2 is a flow chart of a method of calculating structural strength of a three-column floating fan foundation brace of the present invention;
FIG. 3a is a schematic view of the wave force applied to the fan foundation under the first dangerous condition selected in the first step of the present invention;
FIG. 3b is a schematic waveform diagram illustrating a first dangerous condition selected in the first step of the present invention;
FIG. 4a is a schematic view of the wave force applied to the fan foundation under the second dangerous condition selected in the first step of the present invention;
FIG. 4b is a schematic waveform diagram illustrating a second dangerous condition selected in the first step of the present invention;
FIG. 5a is a schematic view of wave forces applied to a fan foundation under a third dangerous condition selected in step one of the present invention;
FIG. 5b is a schematic waveform diagram illustrating a third dangerous condition selected in the first step of the present invention;
FIG. 6a is a schematic view of wave forces applied to a fan foundation under a fourth dangerous condition selected in step one of the present invention;
FIG. 6b is a schematic waveform diagram illustrating a fourth dangerous condition selected in the first step of the present invention;
FIG. 7 is a schematic view of a beam structure model of a fan foundation constructed in step four of the present invention;
FIG. 8 is a schematic diagram of boundary conditions imposed on the beam structure model in step five of the present invention;
Fig. 9 is a schematic diagram of a finite element model obtained after the step six of the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings.
The invention relates to a method for calculating structural strength of a stay bar of a three-column floating fan foundation, which is applicable to the three-column floating fan foundation, and comprises a first column 11, a second column 12 and a third column 13 which are arranged at three corners of an equilateral triangle, three groups of stay bars 2 (shown in figure 1) which are connected between the first column 11 and the second column 12, between the second column 12 and the third column 13 and between the first column 11 and the third column 13 in a one-to-one correspondence manner, the distance between the three columns is 160m, the diameter of the columns is 15m, the height of the columns is 30m, The ultimate strength of the stay bar material is 355MPa, the total weight of the fan foundation is 7570.45t, and the draft of the upright post is 14m.
Referring to fig. 2, the method for calculating the structural strength of the three-column floating fan foundation stay bar of the present invention includes the following steps:
Firstly, dangerous working conditions are selected, a floating fan foundation is subjected to waves with different directions and different wavelengths during service, but foundation failure or damage often occurs under dangerous working conditions, so that four dangerous working conditions of the selected three-column floating fan foundation exist, the first dangerous working condition is a working condition with the maximum separation force at an incidence angle of 0 DEG, at the moment, a first column 11 is positioned at a peak position, a second column 12 and a third column 13 are positioned between the peak and the trough, and a group of stay bars 2 connected between the second column 12 and the third column 13 are subjected to separation forces with opposite axial directions (see fig. 3a and 3 b); the second dangerous working condition is the working condition that the extrusion force of the incident angle of 0 degrees is maximum, at this moment, the first upright 11 is positioned at the trough position, the second upright 12 and the third upright 13 are positioned between the trough and the crest, so that a group of stay bars 2 connected between the second upright 12 and the third upright 13 are subjected to extrusion force which is opposite to each other in the axial direction (see fig. 4a and 4 b); the third dangerous condition is the maximum condition of 30 ° incidence angle separating force, at this time, the third upright 13 is located between a peak and a subsequent trough, the second upright 12 and the first upright 11 are located between the peak and the previous trough, so that a group of stay bars 2 connected between the third upright 13 and the second upright 12 and a group of stay bars connected between the third upright 13 and the first upright 11 are subjected to 30 ° incidence angle separating force (see fig. 5a and 5 b); the fourth dangerous working condition is the working condition that the extrusion force of the incident angle of 30 degrees is maximum, at this moment, the third upright 13 is positioned between one trough and the next crest, the second upright 12 and the first upright 11 are positioned between the trough and the next crest, so that a group of stay bars 2 connected between the third upright 13 and the second upright 12 and a group of stay bars 2 connected between the third upright 13 and the first upright 11 are subjected to extrusion force of 30 degrees (see fig. 6a and 6 b);
Step two, wave parameters are determined, the wavelengths under four dangerous working conditions are determined according to the waveforms of the four dangerous working conditions, and the wave period and wave height under the four dangerous working conditions are determined according to a wave theory formula;
A. Wavelength determination, namely determining the relation between the wavelength L and the spacing B of the upright post under four dangerous working conditions according to waveforms in the four dangerous working conditions in a one-to-one correspondence manner:
In the formula (1), B is the distance between the upright posts; l 1 is the wavelength under the first dangerous working condition; l 2 is the wavelength under the second dangerous condition; l 3 is the wavelength under the third dangerous working condition; l 4 is the wavelength under the fourth dangerous working condition;
B. Wave period determination, obtaining a wave period T formula (2) according to a linear wave theory:
in the formula (2), L is a wavelength; k is the wave number of the wave, D is the water depth, and 50m is taken;
C. wave height determination, namely calculating wave height H according to a linear wave height formula (3) recommended in the maritime industry:
In the formula (3), T is a wave period; h 100 is the wave height of century, and is 20m;
According to the above formulas (1), (2) and (3), the wave parameters under four dangerous working conditions are finally formed, see the following table 1:
TABLE 1
| Working conditions of | Wavelength L (m) | Wave period T(s) | Wave height H (m) |
| Working condition 1 | 320 | 16.50 | 18.32 |
| Working condition 2 | 320 | 16.50 | 18.32 |
| Working condition 3 | 277.13 | 14.79 | 18.01 |
| Working condition 4 | 277.13 | 14.79 | 18.01 |
Thirdly, determining the load, wherein the buoyancy and the wave load borne by the brace are far smaller than those of the upright post because the dimension of the brace is far smaller than that of the upright post, so that only the wave load acting on the upright post is considered; the load to which the column is subjected is divided into a gravitational load, a buoyancy load and a wave load. The total weight load is determined according to the actual weight of the structure, and the influence of gravity on the structural strength of the stay bar is small due to the scale, so that the total weight load of the fan foundation is equally divided and then is only applied to three upright posts, and the three upright posts can offset the gravity under the action of buoyancy due to the triangular characteristic of the three upright posts, so that the gravity load and the buoyancy load are not applied to the final upright posts, and only the wave load on the upright posts is required to be determined; the diameter of the upright post of the existing three-upright post floating type fan foundation is 15m, the wavelength of four dangerous working conditions is 270-320 m, the upright post belongs to a small component relative to waves, the use condition of Morisen Morison equation is met, and the wave load is calculated by adopting Morisen Morison equation which is widely applied in ocean engineering, wherein the wave load is as follows:
In formula (4), F N is wave load; ρ is the sea water density; c A is an additional mass coefficient, C A＝1;CD is a drag coefficient when the column is cylindrical, C D =1 when the column is cylindrical; a is the area of the cross section of the upright post; d is the diameter of the upright post; the horizontal movement acceleration of the water particles; v is the horizontal movement speed of the water particles;
Obtaining the horizontal motion velocity v of water particles in waves according to a linear wave theory:
obtaining horizontal motion acceleration of water particles in waves according to linear wave theory
In the formulas (5) and (6), H is wave height; k is the wave number of the wave,L is the wavelength; d is the depth of water; z is the depth of the water particle; x is the propagation direction of the wave; omega is the circular frequency of the wave; t is time;
The wave loads to which the first, second and third columns 11, 12 and 13 are subjected under four dangerous conditions are obtained according to the above formulas (4), (5) and (6), see the following table 2
TABLE 2
Step four, building a structural model, and building a beam system structural model of a fan foundation in a ANSYS DESIGN model module; the main structure of the fan foundation is the upright post and the stay bar, the strength of the upright post is not in the consideration range of the invention, so that the whole model is simplified into a beam system structural model, the stay bar in the beam system structural model is provided with an actual stay bar section, the upright post is not provided with the section, and finally, the actual quality of each part of the fan foundation is provided with the whole structural model (see figure 7);
Applying boundary conditions, namely applying three spring constraints in the vertical direction, two wave direction horizontal displacement constraints and one wave direction horizontal displacement constraint in the vertical direction on the beam system structural model; namely, a spring constraint 31 is applied vertically upwards to the bottoms of the first upright 11, the second upright 12 and the third upright 13, a wave-direction horizontal displacement constraint 32 is applied to the bottoms of the first upright 11 and the third upright 13, and a wave-direction horizontal displacement constraint 33 is applied to the bottoms of the first upright 11 (see fig. 8); the spring stiffness is equivalent to the water buoyancy load, and the calculation formula (7) of the spring stiffness K s is as follows:
In the formula (7), ρ is the sea water density; d is the diameter of the upright post; g is the gravity acceleration coefficient of 9.8N/Kg; the stiffness K s＝1.77×106 N/m of the spring is calculated.
Step six, performing finite element dispersion on the beam system model in ANSYS STATIC Structural modules to enable the beam system structure model to be dispersed into a finite element model of a one-dimensional grid, wherein the size of the grid is determined according to the precision required by calculation (see figure 9);
Step seven, load application, namely applying the wave load determined in the step three in a finite element model, wherein the direction of the wave load is determined by waveforms of four dangerous working conditions, and the wave load is applied to the centroid of the draft part of the upright column in the form of point load;
step eight, statics analysis is carried out on the finite element model after wave load and boundary conditions are applied in a ANSYS STATIC Structural module, so as to obtain maximum axial compressive stress sigma dc and maximum combined stress sigma mc of the stay bar under four dangerous working conditions, and the method is particularly shown in the following table 3,
TABLE 3 Table 3
Step nine, strength checking, namely checking the yield strength of the stay bar material and the maximum combined stress sigma mc of the stay bar, checking the buckling strength of the stay bar material and the maximum axial compressive stress sigma dc of the stay bar, and judging whether the structural strength of the stay bar is enough;
A. When checking the yield strength, the allowable yield stress [ sigma s ] of the brace is determined by the following formula:
[σs]＝σs/Ss
Wherein sigma s is the yield strength of the stay bar material and MPa; s s is the yield safety coefficient of the stay bar material, and 1.25 is taken;
Resulting in [ σ s ] =284
Checking the yield strength of the brace bar material with a maximum combined stress of brace bar σ mc, wherein the maximum combined stress of brace bar σ mc =48.26 is smaller than the allowable yield stress of brace bar [ σ s ] =284, i.e., σ mc＜[σs ];
B. when checking the buckling strength, the allowable buckling stress [ sigma cr ] of the stay bar is determined by the following steps:
[σcr]＝σcr/Scr
Wherein sigma cr is the buckling strength of the stay bar material and MPa; s cr is the buckling safety coefficient of the strut material.
The buckling strength σ cr of the pressed rod material is calculated as follows:
In formula (8): σ E is the stress in euler, MPa, L is the unsupported length of the rod piece; r is the radius of gyration inertia of the cross section corresponding to the unsupported length l of the rod; k is an equivalent length coefficient, and 0.65 is taken; e is the Young's modulus of the stay bar material;
resulting in [ σ cr ] = 83.04
Checking the buckling strength of the brace bar material and the maximum axial compressive stress sigma dc of the brace bar, wherein the maximum axial compressive stress sigma dc = 47.44 of the brace bar is smaller than the allowable buckling stress [ sigma cr ] = 83.04 of the brace bar, namely sigma dc＜[σcr ];
In summary, the maximum combined stress σ mc of the brace is less than the allowable yield stress of the brace [ σ s ], i.e., σ mc＜[σs ], while the maximum axial compressive stress of the brace, σ dc, is less than the allowable buckling stress of the brace [ σ cr ], i.e., σ dc＜[σcr ], the structural strength of the brace is sufficient.
The above embodiments are provided for illustrating the present invention and not for limiting the present invention, and various changes and modifications may be made by one skilled in the relevant art without departing from the spirit and scope of the present invention, and thus all equivalent technical solutions should be defined by the claims.
Claims (6)
1. The method for calculating the structural strength of the three-column floating type fan foundation stay bar is characterized by comprising the following steps of:
step one, selecting dangerous working conditions, namely, selecting dangerous working conditions and corresponding waveforms, wherein the four fan foundations are easy to fail or destroy;
Step two, wave parameters are determined, the wavelengths under four dangerous working conditions are determined according to the waveforms of the four dangerous working conditions, and the wave period and wave height under the four dangerous working conditions are determined according to a wave theory formula;
Step three, load determination, namely determining wave loads born by three upright posts of the fan foundation;
Step four, building a structural model, namely building a beam system structural model of a fan foundation in a ANSYSDES I GN model I module;
Step five, boundary conditions are applied, wherein six boundary conditions are applied to the beam system structural model, namely three vertical upward spring constraints, two wave direction horizontal displacement constraints and one vertical wave direction horizontal displacement constraint;
step six, finite element dispersion is carried out on the beam system structural model in ANSYS STAT I C Structura l modules to form a finite element model of a one-dimensional grid;
step seven, load application, in which wave load is applied to the finite element model, the direction of the wave load is determined by waveforms of four dangerous working conditions, and the wave load is applied to the centroid of the draft part of the upright post in the form of point load;
Step eight, carrying out statics analysis, namely carrying out statics analysis in a ANSYS STAT IC Structura l module to obtain maximum axial compressive stress sigma dc of the stay bar and maximum combined stress sigma mc of the stay bar under four dangerous working conditions;
And step nine, checking the strength, namely checking the yield strength of the stay bar material and the maximum combined stress sigma mc of the stay bar, checking the buckling strength of the stay bar material and the maximum axial compressive stress sigma dc of the stay bar, and judging whether the structural strength of the stay bar is enough.
2. The method of claim 1, wherein the step of selecting the first dangerous condition is a maximum 0 ° angle of incidence separation force condition, selecting the second dangerous condition is a maximum 0 ° angle of incidence extrusion force condition, selecting the third dangerous condition is a maximum 30 ° angle of incidence separation force condition, and selecting the fourth dangerous condition is a maximum 30 ° angle of incidence extrusion force condition.
3. The method for calculating the structural strength of the three-column floating fan foundation stay according to claim 1, wherein the step two is performed, comprising:
A. wavelength determination, namely determining the relation between the wavelength L and the spacing B of the upright post under four dangerous working conditions according to waveforms in the four dangerous working conditions in a one-to-one correspondence manner:
In the formula (1), L 1 is the wavelength under the first dangerous working condition; l 2 is the wavelength under the second dangerous condition; l 3 is the wavelength under the third dangerous working condition; l 4 is the wavelength under the fourth dangerous working condition; b is the spacing of the upright posts;
B. Wave period is determined, and a wave period T formula is obtained according to a linear wave theory:
in the formula (2), L is a wavelength; k is the wave number of the wave, D is the depth of water;
C. Wave height determination, calculating wave height H according to a linear wave height formula (3):
in the formula (3), T is a wave period; h 100 is the wave height of century.
4. The method for calculating structural strength of a three-column floating fan foundation brace of claim 1, wherein the step three is performed using the morrison equation to calculate the wave load as follows:
In formula (4), FN is wave load; ρ is the sea water density; c A is an additional mass coefficient, C A＝1;CD is a drag coefficient when the column is cylindrical, C D =1 when the column is cylindrical; a is the area of the cross section of the upright post; d is the diameter of the upright post; the horizontal movement acceleration of the water particles; v is the horizontal movement speed of the water particles;
Obtaining the horizontal motion velocity v of water particles in waves according to a linear wave theory:
Obtaining horizontal motion acceleration v of water particles in waves according to a linear wave theory:
in the formulas (5) and (6), H is wave height; k is the wave number of the wave, L is the wavelength; d is the depth of water; z is the depth of the water particle; x is the propagation direction of the wave; omega is the circular frequency of the wave; t is time.
5. The method for calculating structural strength of a three-column floating fan foundation brace according to claim 1, wherein in the fifth step, the spring rate of the set spring constraint is equivalent to the water buoyancy load, and the calculation formula of the spring rate K s is as follows:
In the formula (7), ρ is the sea water density; d is the diameter of the upright post; g is the gravitational acceleration coefficient 9.8N/Kg.
6. The method for calculating structural strength of a three-column floating fan foundation stay according to claim 1, wherein the step nine is performed, comprising:
A. Yield strength check, the allowable yield stress of the brace bar [ σ s ] is determined by:
[σs]＝σs/Ss
Wherein sigma s is the yield strength of the stay bar material and MPa; s s is the yield safety coefficient of the stay bar material;
B. Buckling strength check, allowable buckling stress [ σ cr ] of the stay bar is determined by:
[σcr]＝σcr/Scr
Wherein sigma cr is the buckling strength of the stay bar material and MPa; s cr is the buckling safety coefficient of the stay bar material;
The buckling strength σ cr of the pressed rod material is calculated as follows:
In formula (8): σ E is the stress in euler, MPa, L is the unsupported length of the rod piece; r is the radius of gyration inertia of the cross section corresponding to the unsupported length l of the rod; k is an equivalent length coefficient; e is the Young's modulus of the stay bar material;
The structural strength of the brace will only be sufficient when the maximum combined stress of the brace is less than the allowable yield stress of the brace [ sigma s ], i.e., sigma mc＜[σs ], while the maximum axial compressive stress of the brace is less than the allowable buckling stress of the brace [ sigma cr ], i.e., sigma dc＜[σcr ].
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