Finite element calculation method for displacement of liquid tank of ultra-large liquefied gas carrier

Abstract

The invention relates to a finite element calculation method for displacement of a liquid tank of an ultra-large liquefied gas carrier, which comprises the following steps of: carrying out grid division on a three-dimensional model of the liquid tank, setting material attributes of unit grids, adjusting material density, carrying out model diagnosis on the adjusted three-dimensional model of the finite element, and placing a rotary placing pier at a strong structure at the bottom of the liquid tank, modeling is carried out on the rotary laying pier through a Gap unit; node coupling is carried out on the liquid tank and the module vehicle set through the Rigid rigid unit bodies; performing liquid tank overturning analysis on the arrangement position of the module vehicle group, judging whether the liquid tank has an overturning risk or not, and if so, adjusting the arrangement of the module vehicle group; and carrying out stress analysis on the rotary placing pier, and if the rotary placing pier is broken due to overlarge bearing capacity or the stress strain of the liquid tank is overlarge, adjusting the placing pier. According to the method, displacement overturning property analysis and pier laying stress analysis are carried out by means of finite element calculation, overturning in the actual displacement process is avoided, damage to the liquid tank and the module vehicle set is avoided, and the safety of overall displacement of the liquid tank is improved.

Description

Technical Field

[0001] The invention relates to the field of liquefied gas ship construction, and in particular to a finite element calculation method for liquid tank displacement of a super-large liquefied gas ship. Background Art

[0002] In the process of building a liquefied gas ship, in order to achieve efficient construction of the independent liquid tank section of a very large liquefied gas ship, a self-propelled modular transporter (SPMT) is used to move the entire liquid tank, so that the construction reserved for the insulation of the liquid tank can be placed in a non-core plant area, reducing the use of crane resources to improve the construction efficiency of the liquid tank. Very large liquefied gas ships are fully refrigerated ships, also known as cryogenic tank pressure ships, with a tank capacity generally exceeding 50,000 cubic meters.

[0003] When the entire liquid tank is shifted, due to the high center of gravity of the liquid tank of the very large liquefied gas carrier and the fact that most of the liquid tanks are thin plate structures, the module car set is subject to the liquid tank's own gravity, and the liquid tank is subject to the support reaction force of the car set. During the movement, the center of gravity of the liquid tank shifts left and right, resulting in a greater risk of capsizing during transportation. In order to protect the car plate of the module car set, a certain number of rotating piers are also required to be placed between the module car set and the strong frame structure at the bottom of the liquid tank. The different placement positions of the rotating piers will also affect the structural safety of the liquid tank. During the displacement process, the rotating piers may be too small to support the weight of the entire liquid tank due to their small force projection area, resulting in damage to the structure of the rotating piers themselves, which may in turn cause the bottom structure of the liquid tank and the car plate of the module car set to break, resulting in serious safety accidents. Summary of the invention

[0004] In order to avoid safety accidents of liquid tanks during the displacement of liquid tanks, the present invention provides a finite element calculation method for the displacement of liquid tanks of very large liquefied gas ships, a finite element model of the liquid tank is established by SFRT (Ship-Right Fast track, SRFT) software, finite element calculation is performed on the displacement of the liquid tank, the structural strength of the liquid tank and the bearing stress of the rotating pier during displacement are analyzed, and adjustments are made according to the finite element calculation results to avoid safety accidents during the actual displacement process.

[0005] The technical objectives of the present invention are achieved through the following technical solutions:

[0006] A finite element calculation method for liquid tank displacement of a very large liquefied gas carrier, the method comprising:

[0007] Step 1: Create a three-dimensional model of the liquid tank;

[0008] Step 2: meshing the three-dimensional model of the liquid tank using finite element analysis software to form a finite element three-dimensional model;

[0009] Step 3: Set the material properties of the corresponding unit grid according to the actual material properties of the liquid tank, eliminate the overlapping points, and simplify the internal outfitting parts of the liquid tank;

[0010] Step 4: Adjust the material density of the models with different mesh unit sizes so that the weight and center of gravity of the finite element three-dimensional model are close to the actual weight and center of gravity of the liquid tank, and the deviation is controlled within 5%;

[0011] Step 5: Perform model diagnosis on the adjusted finite element three-dimensional model and modify abnormal points;

[0012] Step 6: Place a rotating pier at the bottom strong structure of the liquid tank in the finite element three-dimensional model. The rotating pier is modeled by the Gap unit. The stiffness coefficient of the Gap unit is Where E is the elastic modulus of the rotating pier, A is the projected force area of ​​the rotating pier, and H is the height of the rotating pier;

[0013] Step 7: The rotating pier Gap unit is used to couple the nodes of the liquid tank of the finite element three-dimensional model and the finite element model of the module train set through the Rigid rigid unit body;

[0014] Step 8: The module vehicles communicate with each other through bus signals to achieve coordination and synchronization between the module vehicles, and the whole vehicle can be raised or lowered through the height sensor;

[0015] Step 9: Perform a liquid tank overturning analysis on the layout position of the module train set to determine whether the liquid tank has a risk of overturning;

[0016] Step 10, performing a stress analysis on the rotating pier to calculate the maximum shear force and negative bending moment of the rotating pier;

[0017] Step 11: If the liquid tank does not have the risk of overturning, and the maximum shear force and negative bending moment of the rotating pier are less than the allowable shear force and allowable negative bending moment of the vehicle plate of the module set, then the degrees of freedom of the upper and lower nodes of the Gap unit in the vertical direction and all the degrees of freedom of the bottom of the module set are constrained, and the gravity acceleration is set to a proportional factor of 1.2. A reaction force is applied in the form of a surface load in the jacking area of ​​the rotating pier of the module vehicle plate;

[0018] If the bearing capacity of the rotating pier exceeds its own safety range and breaks, or the stress and strain of the liquid tank exceed the set safety threshold, execute step 6 to readjust the size, number and projected stress area of ​​the rotating pier until the bearing capacity of the rotating pier meets its own safety range.

[0019] Furthermore, in step 2, when meshing is performed, the mesh unit size is divided according to the rib spacing×longitudinal bone spacing.

[0020] Furthermore, in step 9, when the overturning analysis of the liquid tank is performed on the layout position of the modular vehicle group, the wind load force, braking force, dynamic load force, ramp force and centrifugal force of the liquid tank when it is shifted on the modular vehicle group are calculated respectively, and the combined external force of the wind load force, braking force, dynamic load force, ramp force and centrifugal force is calculated. The overturning moment and anti-overturning moment of the entire displacement are calculated based on the combined external force and the weight of the liquid tank itself. If the overturning moment is greater than the anti-overturning moment, there is a risk of overturning.

[0021] Furthermore, when calculating wind load, braking force, dynamic load, and ramp force, the liquid tank is calculated in two horizontal directions, the X direction and the Y direction, which are perpendicular to each other. One of the directions is designated as the forward direction of the module vehicle group, and the centrifugal force is calculated in the other direction.

[0022] Furthermore, the length, width and height of the liquid tank are L, W and H respectively, the X direction is perpendicular to the height and width directions, the Y direction is perpendicular to the length and height directions, and the X direction is designated as the forward direction of the modular vehicle group;

[0023] Wind load force F in the X direction 1x =C×Kh×q×(W×H)×μ;

[0024] Wind load force F in the Y direction 1Y =C×Kh×q×(L×H)×μ;

[0025] Among them, C is the wind load body coefficient, Kh is the wind pressure height variation coefficient, q is the basic wind pressure, and μ is the wind vibration coefficient.

[0026] Furthermore, the braking force F in the X direction 2x =G0×i 2x , braking force F in the Y direction 2Y =G0×i 2y , where i 2x and i 2y are the braking acceleration of the module train in the X direction and the Y direction, respectively, and G0 is the weight of the tank;

[0027] Dynamic load force F in X direction 3x =G0×i 3x , dynamic load force F in the Y direction 3Y =G0×i 3y , where i 3x and i 3y are the moving acceleration of the module vehicle group in the X direction and the moving acceleration in the Y direction respectively;

[0028] The ramp force F in the X direction 4x =G0×i 4x , the ramp force F in the Y direction 4Y =G0×i4y , where i 4x and i 4y They are the ramp angle in the X direction and the ramp angle in the Y direction respectively.

[0029] Furthermore, centrifugal force Where G0 is the weight of the liquid tank, V is the turning speed of the modular vehicle set, and R is the turning radius of the modular vehicle set.

[0030] Furthermore, when calculating the resultant external force, the resultant external force F in the X direction is calculated separately. 0x The resultant external force F in the Y direction 0Y ,

[0031] F 0x =F 1x +F 2x +F 3x +F 4x ,

[0032] F 0Y =F 1Y +F 2Y +F 2Y +F 4Y +F 5Y .

[0033] Compared with the prior art, the beneficial effect of the present invention lies in that, with the help of finite element calculation, the present invention arranges the module train at the bottom of the liquid tank to conduct displacement overturning analysis and pier force analysis. If there is a risk of overturning, the arrangement position of the module train is adjusted to avoid overturning of the liquid tank during the actual displacement process; through the force analysis of the pier, the size, number and projected force area of ​​the pier are adjusted to avoid damage to the rotating pier's own structure, damage to the liquid tank and the module train, and improve the safety of the overall displacement of the liquid tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the arrangement of the liquid tank bottom module vehicle set and the rotating pier in the present invention.

[0035] Figure 2 It is a schematic diagram of the axis numbering of the train set in the present invention.

[0036] In the figure:

[0037] 1. Liquid tank; 2. Modular vehicle group; 3. Rotating pier; 4. Anti-overturning lever arm. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below in conjunction with specific embodiments:

[0039] A finite element calculation method for liquid tank displacement of a very large liquefied gas carrier, the method comprising:

[0040] Step 1: Create a three-dimensional model of the liquid tank using CATIA software (Computer Aided Three-dimensional Interactive Application, CATIA);

[0041] Step 2: Use finite element analysis software to mesh the three-dimensional model of the liquid tank to form a finite element three-dimensional model. When meshing, the outer plate uses plate and shell units, and the components such as the strong frame use beam units. The mesh unit size of the finite element three-dimensional model of the liquid tank is divided according to the rib spacing × longitudinal bone spacing. The mesh is locally refined at some special structural locations such as openings.

[0042] Step 3: Set the material properties of the corresponding unit grid according to the actual material properties of the liquid tank, eliminate the coincidence points, and avoid affecting the finite element calculation results. As a preferred method, the outfitting parts inside the liquid tank can be simplified to improve the calculation efficiency without affecting the calculation.

[0043] Step 4: The simplification of the internal outfitting parts leads to deviations between the weight and center of gravity of the finite element three-dimensional model and the actual weight and center of gravity. Therefore, the material density of the models with different mesh unit sizes is adjusted to make the weight and center of gravity of the finite element three-dimensional model close to the actual weight and center of gravity of the liquid tank, and the deviation is controlled within 5%;

[0044] Step 5: Perform model diagnosis on the adjusted finite element three-dimensional model through DIAG (Model Diagnosis, DIAG), and modify the abnormal points until the finite element three-dimensional model meets the requirements;

[0045] Step 6: Place a rotating pier at the bottom strong structure of the liquid tank in the finite element three-dimensional model. The rotating pier is modeled by the Gap unit. The stiffness coefficient of the Gap unit is Where E is the elastic modulus of the rotating pier, A is the projected force area of ​​the rotating pier, and H is the height of the rotating pier;

[0046] Step 7: The rotating pier Gap unit is used to couple the nodes of the liquid tank of the finite element three-dimensional model and the finite element model of the module train set through the Rigid rigid unit body, so that the force transmission is continuous and uninterrupted to form a closed loop;

[0047] Step 8: The modular vehicles communicate with each other through bus signals to achieve coordination and synchronization between the modular vehicles, and the whole vehicle is raised and lowered through the height sensor, so as to achieve hard and soft merging, longitudinal or transverse merging. The modular vehicles are preferably symmetrical on the left and right sides to minimize the deformation of the liquid tank.

[0048] Step 9: Perform a liquid tank overturning analysis on the layout position of the module train set to determine whether the liquid tank has a risk of overturning;

[0049] When performing overturning analysis on the layout position of the module train, the wind load force, braking force, dynamic load force, ramp force and centrifugal force of the liquid tank when it is displaced on the module train are calculated respectively, and the combined external force of the wind load force, braking force, dynamic load force, ramp force and centrifugal force is calculated. The overturning moment and anti-overturning moment of the entire displacement are calculated based on the combined external force and the weight of the liquid tank itself. If the overturning moment is greater than the anti-overturning moment, there is a risk of overturning, and the layout position of the module train is adjusted, and step 9 is re-executed;

[0050] When calculating wind load, braking force, dynamic load and ramp force, the liquid tank is calculated in two horizontal directions, X and Y, which are perpendicular to each other. One of the directions is designated as the forward direction of the module vehicle group, and the centrifugal force is calculated in the other direction.

[0051] The length, width and height of the liquid tank are L, W and H respectively. The X direction is perpendicular to the height and width directions, and the Y direction is perpendicular to the length and height directions. The X direction is designated as the forward direction of the module train set (the Y direction can also be designated as the forward direction of the module train set, and the centrifugal force is calculated in the X direction accordingly).

[0052] Wind load force F in the X direction 1x =C×Kh×q×(W×H)×μ;

[0053] Wind load force F in the Y direction 1Y =C×Kh×q×(L×H)×μ;

[0054] Among them, C is the wind load body coefficient, Kh is the wind pressure height variation coefficient, q is the basic wind pressure, W×H is the windward area in the X direction, L×H is the windward area in the Y direction, and μ is the wind vibration coefficient.

[0055] Basic wind pressure q = 0.5×ρ×V, ρ is air density, V is wind speed.

[0056] Braking force F in X direction 2x =G0×i 2x , braking force F in the Y direction 2Y =G0×i 2y , where i 2x and i 2y are the braking acceleration of the module train in the X direction and the Y direction, respectively, and G0 is the weight of the tank;

[0057] Dynamic load force F in X direction 3x =G0×i 3x , dynamic load force F in the Y direction 3Y=G0×i 3y , where i 3x and i 3y are the moving acceleration of the module vehicle group in the X direction and the moving acceleration in the Y direction respectively;

[0058] The ramp force F in the X direction 4x =G0×i 4x , the ramp force F in the Y direction 4Y =G0×i 4y , where i 4x and i 4y They are the slope in the X direction and the slope in the Y direction respectively.

[0059] Centrifugal force Where G0 is the weight of the liquid tank, V is the turning speed of the modular vehicle set, and R is the turning radius of the modular vehicle set.

[0060] When calculating the resultant external force, calculate the resultant external force F in the X direction separately. 0x The resultant external force F in the Y direction 0Y ,

[0061] F 0x =F 1x +F 2x +F 3x +F 4x ,

[0062] F 0Y =F 1Y +F 2Y +F 3Y +F 4Y +F 5Y .

[0063] Preferably, the static friction force f between the liquid tank and the modular vehicle set is calculated, where f=G0×u0, and u0 is the static friction coefficient. If f is greater than the resultant external force and the braking force, the liquid tank will not slip during the movement of the modular vehicle set.

[0064] The overturning moment and anti-overturning moment of the entire tank during displacement are calculated based on the total external force received by the tank and the weight of the tank itself. Overturning moment = total external force × height of the center of gravity of the entire displacement, anti-overturning moment = tank weight × anti-overturning lever arm; since the size of the tank in the X-axis direction is larger than that in the Y-axis direction, it is easier to tip over in the Y-axis direction. The distance from the center of gravity of the tank in the Y-axis direction to the edge of the module train is selected as the length of the anti-overturning lever arm, such as Figure 1 shown.

[0065] If the overturning moment is greater than or equal to the anti-overturning moment, there is a risk of overturning; if the overturning moment is less than the anti-overturning moment, there is no risk of overturning.

[0066] Step 10, performing a stress analysis on the rotating pier to calculate the maximum shear force and negative bending moment of the rotating pier;

[0067] Specifically, Figure 1 and Figure 2 As shown, in this embodiment, four modular car sets are taken as an example, and the four modular car sets 2 are symmetrically distributed on the left and right sides, and are supported in a triangular shape as a whole. The axis lines and rotating piers are numbered in sequence along the modular car set 2 at the bow toward the modular car set at the tail. The number of car set axes is N, and the axis lines are numbered N1, N2, N3, ..., Ni-1, Ni in sequence; the rotating dock piers and axis lines are numbered continuously from the modular car set at the bow to the modular car set at the tail, and the rotating dock piers and axis lines symmetrical on the left and right sides have the same numbering; it should be noted that the numbering of the rotating piers is not one-to-one corresponding to the numbering of the axis lines, and one rotating pier may span several axis lines; the numbering of the rotating piers corresponding to the load above the rotating piers is F in sequence. N1″ 、F N2″ 、F N3″ , ..., F Ni-1″ 、F Ni″ ;

[0068] Then F Ni″ +F N2″ +F N3″ +...+F Ni-1″ +F Ni″ =G0.

[0069] In this embodiment, the front of the first two module trains and the front of the rear two module trains are in opposite directions. The distance between the front of the first module train and the front of the rear module train is LN", the distance between the front of the head module train and the center between N1" pier and N2" is LN1", the distance between the center between N1" pier and N2" pier and the center between N2" pier and N3" is LN2", ..., the distance between the center between Ni-2" pier and Ni-1" pier and the center between Ni-1" pier and Ni" pier is LNi-1", and the distance between the center between Ni-1" pier and Ni" pier and the front of the rear module train is LNi".

[0070] Then LN″=LN1″+LN2″+...+LNi-1″+LNi″;

[0071] The axle pressure of the front module train set is P1, and the axle pressure of the rear module train set is P2.

[0072] The load F of the rotating pier is Ni″ It can be expressed as:

[0073] When the rotating pier is located at the front module train set, P=P1; when the rotating pier is located at the rear module train set, P=P2.

[0074] Therefore, the load at the first rotating pier N1″

[0075] Load at the second rotating pier N2″

[0076] …

[0077] Load at the i-1th rotating pier Ni-1″

[0078] The load at the i-th rotating pier Ni″

[0079] Combined with F N1″ +F N2″ +F N3″ +...+F Ni-1″ +F Ni″ =G0 to obtain:

[0080]

[0081] Since there is no concentrated force, the shear force F at the rotating pier N1″ is SN1 It is equal to the number of axes n in front of the rotating pier N1″, which is a sudden change of n modules, and the axle pressure P1 of the vehicle group plus the load F at the rotating pier N1″. N1″ , it is stipulated that the downward mutation is negative, that is, F SN1 =-n×P1+F N1″ ,

[0082] Starting from the second rotating pier, the shear force F at the rotating pier Ni″ is SNi It is equal to the number of axes m between the rotating pier Ni″ and the rotating pier Ni-1″, which is the axle pressure of m modular trains plus the load F at the rotating pier Ni-1″. Ni-1″ , if the rotating pier Ni″ is located at the head module train, the module train axle pressure is P1, if the rotating pier Ni″ is located at the tail module train, the module train axle pressure is P2; it can be expressed as F SNi =-m×P1+F Ni-1″ or F SNi =-m×P2+F Ni-1″ , i≥2.

[0083] At the pier position where the shear force is the largest, the bending moment M is the largest. Since the integral dx of the shear force is the bending moment, the bending moment dM at the corresponding pier is calculated according to the calculation formula for the bending moment; the calculation formula for the bending moment is:

[0084] When calculating the bending moment, the front of the front module train set is taken as the origin O and the x-axis is established in the direction from the front module train set to the rear module train set. The y-axis is established perpendicular to the x-axis direction and intersecting the origin. The z-axis is established perpendicular to the x-axis and the y-axis. The x-axis and the y-axis are located in the horizontal direction, and the z-axis is located in the height direction of the liquid tank.

[0085] Step 11: If the liquid tank does not have the risk of overturning, and the maximum shear force and negative bending moment of the rotating pier are less than the allowable shear force and allowable negative bending moment of the vehicle plate of the module set, then the degrees of freedom of the upper and lower nodes of the Gap unit in the vertical direction and all the degrees of freedom of the bottom of the module set are constrained, and the gravity acceleration is set to a proportional factor of 1.2. A reaction force is applied in the form of a surface load in the jacking area of ​​the rotating pier of the module vehicle plate;

[0086] If the bearing capacity of the rotating pier exceeds its own safety range and breaks, or the stress and strain of the liquid tank exceed the set safety threshold, execute step 6 to readjust the size, quantity and projected stress area of ​​the rotating pier until the bearing capacity of the rotating pier meets its own safety range. For example, if the maximum bearing capacity of the rotating pier is 200t, the actual bearing capacity exceeds the maximum safe bearing capacity, the liquid tank stress exceeds the Q235 yield strength of 235MPa, and the liquid tank strain exceeds 10mm, it is necessary to readjust the size, quantity and projected stress area of ​​the pier until the bearing capacity of the rotating pier meets its own safety range.

[0087] This embodiment is only a further explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art can make non-creative modifications to this embodiment as needed, but as long as it is within the scope of the claims of the present invention, it will be protected by the patent law.

Claims

1. A finite element calculation method for liquid tank displacement of a very large liquefied gas carrier, characterized in that: The method includes: Step 1: Create a three-dimensional model of the liquid tank; Step 2: meshing the three-dimensional model of the liquid tank using finite element analysis software to form a finite element three-dimensional model; Step 3: Set the material properties of the corresponding unit grid according to the actual material properties of the liquid tank, eliminate the overlapping points, and simplify the internal outfitting parts of the liquid tank; Step 4: Adjust the material density of the models with different mesh unit sizes so that the weight and center of gravity of the finite element three-dimensional model are close to the actual weight and center of gravity of the liquid tank, and the deviation is controlled within 5%; Step 5: Perform model diagnosis on the adjusted finite element three-dimensional model and modify abnormal points; Step 6: Place a rotating pier at the bottom strong structure of the liquid tank in the finite element three-dimensional model. The rotating pier is modeled by the Gap unit. The stiffness coefficient of the Gap unit is Where E is the elastic modulus of the rotating pier, A is the projected force area of ​​the rotating pier, and H is the height of the rotating pier; Step 7: The rotating pier Gap unit is used to couple the nodes of the liquid tank of the finite element three-dimensional model and the finite element model of the module train set through the Rigid rigid unit body; Step 8: The module vehicles communicate with each other through bus signals to achieve coordination and synchronization between the module vehicles, and the whole vehicle can be raised or lowered through the height sensor; Step 9: Perform a liquid tank overturning analysis on the layout position of the module train set to determine whether the liquid tank has a risk of overturning; Step 10, performing a stress analysis on the rotating pier to calculate the maximum shear force and negative bending moment of the rotating pier; Step 11: If the liquid tank does not have the risk of overturning, and the maximum shear force and negative bending moment of the rotating pier are less than the allowable shear force and allowable negative bending moment of the vehicle plate of the module set, then the degrees of freedom of the upper and lower nodes of the Gap unit in the vertical direction and all the degrees of freedom of the bottom of the module set are constrained, and the gravity acceleration is set to a proportional factor of 1.

2. A reaction force is applied in the form of a surface load in the jacking area of ​​the rotating pier of the module vehicle plate; If the bearing capacity of the rotating pier exceeds its own safety range and breaks, or the stress and strain of the liquid tank exceed the set safety threshold, execute step 6 to readjust the size, number and projected stress area of ​​the rotating pier until the bearing capacity of the rotating pier meets its own safety range.

2. The finite element calculation method for liquid tank displacement of a very large liquefied gas carrier according to claim 1 is characterized in that: In step 2, when meshing is performed, the mesh unit size is divided according to the rib spacing×longitudinal bone spacing.

3. The finite element calculation method for liquid tank displacement of a very large liquefied gas carrier according to claim 1 is characterized in that: In step 9, when the overturning analysis of the liquid tank is performed on the layout position of the modular vehicle group, the wind load force, braking force, dynamic load force, ramp force and centrifugal force of the liquid tank when it is shifted on the modular vehicle group are calculated respectively, and the combined external force of the wind load force, braking force, dynamic load force, ramp force and centrifugal force is calculated. The overturning moment and anti-overturning moment of the entire displacement are calculated based on the combined external force and the weight of the liquid tank itself. If the overturning moment is greater than the anti-overturning moment, there is a risk of overturning.

4. The finite element calculation method for liquid tank displacement of a very large liquefied gas carrier according to claim 3 is characterized in that: When calculating wind load, braking force, dynamic load and ramp force, the liquid tank is calculated in two horizontal directions, X and Y, which are perpendicular to each other. One of the directions is designated as the forward direction of the module vehicle group, and the centrifugal force is calculated in the other direction.

5. The finite element calculation method for liquid tank displacement of a very large liquefied gas carrier according to claim 4 is characterized in that: The length, width and height of the liquid tank are L, W and H respectively, the X direction is perpendicular to the height and width directions, the Y direction is perpendicular to the length and height directions, and the X direction is designated as the forward direction of the module vehicle group; Wind load force F in the X direction 1x =C×Kh×q×(W×H)×μ; Wind load force F in the Y direction 1Y =C×Kh×q×(L×H)×μ; Among them, C is the wind load body coefficient, Kh is the wind pressure height variation coefficient, q is the basic wind pressure, and μ is the wind vibration coefficient.

6. The finite element calculation method for liquid tank displacement of a very large liquefied gas carrier according to claim 5 is characterized in that: Braking force F in X direction 2x =G0×i 2x , braking force F in Y direction 2Y =G0×i 2y , where i 2x and i 2y are the braking acceleration of the module train in the X direction and the Y direction, respectively, and G0 is the weight of the liquid tank; Dynamic load force F in X direction 3x =G0×i 3x , dynamic load force F in the Y direction 3Y =G0×i 3y , where i 3x and i 3y are the moving acceleration of the module vehicle group in the X direction and the moving acceleration in the Y direction respectively; The ramp force F in the X direction 4x =G0×i 4x , the ramp force F in the Y direction 4Y =G0×i 4y , where i 4x and i 4y They are the ramp angle in the X direction and the ramp angle in the Y direction respectively.

7. The finite element calculation method for liquid tank displacement of a very large liquefied gas carrier according to claim 6 is characterized in that: Centrifugal force Where G0 is the weight of the liquid tank, V is the turning speed of the modular vehicle set, and R is the turning radius of the modular vehicle set.

8. The finite element calculation method for liquid tank displacement of a very large liquefied gas carrier according to claim 7 is characterized in that: When calculating the resultant external force, calculate the resultant external force F in the X direction separately. 0x The resultant external force F in the Y direction 0Y , F 0x =F 1x +F 2x +F 3x +F 4x , F 0Y =F 1Y +F 2Y +F 3Y +F 4Y +F 5Y 。

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