A design method for LNG ship patching

Abstract

This invention provides a method for designing LNG carrier patch plates. By calculating the corresponding static and dynamic pressures under static and dynamic pressure conditions, the normal and shear stresses at the locations of the through-ribs are calculated. Based on the normal and shear stresses and their allowable values, the method compares and determines whether the initial patch plate design needs optimization or modification. If the normal and shear stresses are greater than the corresponding allowable stresses, the connection area is increased by adjusting the stiffener and patch plate design; conversely, if the normal and shear stresses are less than the corresponding allowable stresses, the connection area is reduced, and a through-type design without stiffeners or patch plates is used. This invention establishes a relationship between the normal and shear stresses on the through-ribs at the LNG carrier's through-cut, along with pressure, the spacing of the through-ribs, the spacing between strong frames / support webs, the connection coefficient, and the connection area. This allows for a simple and efficient determination of whether the LNG carrier patch plate design meets design requirements, further improving design efficiency.

Description

Technical Field

[0001] This invention belongs to the field of ship design and manufacturing technology, and specifically relates to a design method for LNG ship patch plates. Background Technology

[0002] The cuts made to allow the steel reinforcement to pass through the web of the main supporting member, and the arrangement of related plates, should be designed to minimize stress concentration around the perimeter and on the web stiffeners of the main supporting member. According to relevant methods and regulations in ship structural mechanics and codes, there are fairly detailed design specifications and calculation verification methods for the arrangement of cuts and related plates, the normal stress (if any) of the web stiffeners of the main supporting member, and the shear stress of the shear connection of the web. However, for the plate design of special LNG carriers, there is currently no detailed and convenient design method.

[0003] Therefore, how to provide a design method for LNG ship patch plates that establishes the relationship between the normal and shear stresses on the through-ribs at the through-cut of the LNG ship and the compressive stress, the spacing of the through-ribs, the strong frame spacing / support web spacing, the connection coefficient and the connection area, and easily and efficiently determine whether the LNG ship patch plate design meets the design requirements and improve design efficiency has become an urgent technical problem to be solved. Summary of the Invention

[0004] This invention provides a method for designing LNG ship patch plates. By establishing relationships between the normal and shear stresses and pressures on the through-ribs at the LNG ship's through-cut, the spacing of the through-ribs, the strong frame spacing / support web spacing, the connection coefficient, and the connection area, it is possible to easily and efficiently determine whether the LNG ship patch plate design meets the design requirements, thereby further improving design efficiency.

[0005] In this embodiment of the invention, a method for designing LNG ship patch plates is provided, comprising:

[0006] S101. Based on the preliminary patch design scheme, calculate the connection area A1 between the web stiffener and / or elbow plate and the through-grain, the direct connection area A2 between the through cut and the through-grain, and the connection area A3 between the patch or collar plate and the through-grain. According to the location of the through-grain, divide it into static pressure condition and dynamic pressure condition, and calculate the corresponding static pressure and dynamic pressure under the two conditions.

[0007] S102. Based on the known actual arrangement of the spacing s of the through-ribs and the strong frame spacing / support web spacing l, determine the corresponding connection coefficient Cs of the through-ribs. According to the static pressure, dynamic pressure, connection area, through-rib spacing s, strong frame spacing / support web spacing l and connection coefficient Cs, calculate the normal stress and shear stress at the position of the through-ribs according to the correlation into static pressure condition and dynamic pressure condition.

[0008] S103. Based on the normal stress and shear stress and the allowable normal stress and allowable shear stress, compare and determine whether the design scheme of the preliminary patch plate needs to be optimized or modified.

[0009] S104. If the normal stress and shear stress are greater than the corresponding allowable stress, the connection area is increased by adjusting the design of the stiffeners and the reinforcement plate; conversely, if the normal stress and shear stress are less than the corresponding allowable stress, the connection area is reduced, and a through-type form without stiffeners or reinforcement plates is adopted.

[0010] Furthermore, based on the location of the through-grain material, the working conditions are divided into static pressure and dynamic pressure, and the corresponding static and dynamic pressures under the two working conditions are calculated, including:

[0011] The static pressure includes water pressure and internal compartment pressure. The water pressure is positively correlated with the water head, which depends on the maximum value of the following four calculated distances: the distance from the calculation point to 2 / 3 of the distance from the top of the compartment to the overflow pipe; the distance between the calculation point and the position points above the top of the compartment determined by the ship's length; the distance between the calculation point and the structural draft; and the distance between the calculation point and 2 / 3 of the distance from the endplate bulkhead or freeboard deck. In addition to considering the deep compartment pressure, the internal compartment pressure also needs to consider the effects of liquid cargo pressure and steam pressure at the inner shell bulkheads in the cargo hold area.

[0012] The dynamic pressure is the pressure exerted by the liquid on the hull by the ship's motion, including the combined force of liquid pressure and / or sloshing force; wherein, the bow and stern regions of the LNG ship also include impact pressure shear stress.

[0013] Further, the method includes:

[0014] Shear stress calculations were performed and verified under both static and dynamic pressure conditions to determine the shear stress calculation formula.

[0015]

[0016] In the formula, τ dc Shear force at the shear connection with the PSM web, N / mm 2 'p' represents the calculated pressure at the reinforcing rib, divided into static and dynamic pressure conditions, both of which must meet the requirements, in N / mm². 2 C s The connection coefficient is 1 when the through-rib is a symmetrical stiffener; 1.41 when the through-rib is an asymmetrical stiffener and only directly connected; and 1.12 when the through-rib is an asymmetrical stiffener and has a patch plate or collar plate.

[0017] Further, the method includes:

[0018] The normal stress calculations and verifications were performed under both static and dynamic pressure conditions to determine the formula for normal stress calculation.

[0019]

[0020] In the formula, σ fb The normal stress at the connection between the web stiffener and the elbow plate of the PSM is N / mm. 2 .

[0021] Furthermore, the method includes: patch design and stiffener design;

[0022] The patch design includes: the design of the cut type and the design of the patch type; the design of the cut type determines the direct connection area A2 between the cut and the through-grain material, and the design of the patch type determines the connection area A3 between the patch or collar plate and the through-grain material.

[0023] The design of the reinforcing ribs includes: whether to select or not to select the reinforcing ribs, the size of the reinforcing ribs, whether to include the rounded soft toe of the reinforcing ribs, and whether to include the elbow plate or back elbow plate of the reinforcing ribs. The design of the reinforcing ribs determines the connection area A1 of the web reinforcement ribs and the through-ribs.

[0024] Further, the method includes:

[0025] The size of the connection area A1 between the web reinforcement and / or elbow plate and the through-grain is positively correlated with the thickness of the web reinforcement and / or elbow plate and the length of the connection contact surface; the size of the direct connection area A2 between the through incision and the through-grain is positively correlated with the thickness of the web plate and the length of the direct connection contact surface between the incision and the through-grain; the size of the connection area A3 between the patch or collar plate and the through-grain is positively correlated with the thickness of the web plate and the length of the connection contact surface between the patch or collar plate and the through-grain.

[0026] Furthermore, the stiffener includes three forms: ordinary straight stiffener, stiffener with rounded arc, and stiffener combined with back elbow plate. Among them, the stiffener combined with back elbow plate is superior to the stiffener with rounded arc, and superior to the ordinary straight stiffener.

[0027] Furthermore, the patch includes at least one or more of the following: a ground patch, a non-ground patch, a watertight patch, an embedded patch, and a ball-end patch. The embedded patch has superior strength compared to the watertight patch, the ball-end patch, the ground patch, and the non-ground patch.

[0028] The beneficial effects of this invention are as follows:

[0029] As can be seen from the above scheme, the embodiments of the present invention provide a design method for LNG ship reinforcement plates. By calculating the corresponding static and dynamic pressures under static and dynamic pressure conditions, the normal stress and shear stress at the location of the penetrating ribs are calculated. Based on the normal stress and shear stress and the allowable normal stress and allowable shear stress, a comparison is made to determine whether the preliminary reinforcement plate design needs optimization or modification. If the normal stress and shear stress are greater than the corresponding allowable stress, the connection area is increased by adjusting the stiffener design and reinforcement plate design; conversely, if the normal stress and shear stress are less than the corresponding allowable stress, the corresponding connection area is reduced, and a penetrating form without stiffeners or reinforcement plates is used. The technical solution of the present invention establishes a relationship between the normal stress and shear stress on the penetrating ribs at the LNG ship penetration cut and the pressure, the spacing of the penetrating ribs, the strong frame spacing / support web spacing, the connection coefficient, and the connection area. This allows for a simple and efficient determination of whether the LNG ship reinforcement plate design meets the design requirements, further improving design efficiency. Attached Figure Description

[0030] Figure 1 A flowchart illustrating an embodiment of the present invention for designing a patch plate for an LNG ship;

[0031] Figure 2 A schematic diagram of the static pressure head illustrating an LNG ship patch plate design method according to an embodiment of the present invention;

[0032] Figure 3 A schematic diagram illustrating the definition of connection surface geometric parameters in an LNG ship patch plate design method according to an embodiment of the present invention;

[0033] In the diagram, h0 is the height of the calculated position of the through-grain from the baseline, h1 is the height of the tank top from the baseline, h2 is the height of the overflow pipe outlet from the tank top, h3 is the height of the (virtual) freeboard deck from the baseline, h4 is the height of the load line from the baseline, h5 is the height of the cargo tank inner shell deck from the baseline, A1 is the connection area between the web stiffener and / or elbow plate and the through-grain, A2 is the direct connection area between the cut and the through-grain, and A3 is the connection area between the patch plate or collar plate and the through-grain. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0035] In this embodiment of the invention, a method for designing LNG carrier patch plates is proposed. The method uses corresponding calculation formulas to link the normal stress of the stiffeners (if any) and the shear stress of the web and patch plates of the main supporting components through static / dynamic loads, the connection area between the stiffeners or elbow plates (if any) and the patch plates, as well as the yield strength of the materials. The method compares the calculated normal stress of the stiffeners (if any) and the shear stress of the web or patch plates with the allowable normal stress and allowable shear stress to determine whether the LNG carrier patch plate design meets the design requirements.

[0036] like Figure 1 As shown, Figure 1 This is a flowchart illustrating a method for designing a patch plate for an LNG ship, according to an embodiment of the present invention.

[0037] Figure 1 A method for designing plating for LNG carriers includes:

[0038] S101. Based on the preliminary patch design scheme, calculate the connection area A1 between the web stiffener and / or elbow plate and the through-grain, the direct connection area A2 between the through cut and the through-grain, and the connection area A3 between the patch or collar plate and the through-grain. According to the location of the through-grain, divide it into static pressure condition and dynamic pressure condition, and calculate the corresponding static pressure and dynamic pressure under the two conditions.

[0039] S102. Based on the known actual arrangement of the spacing s of the through-ribs and the strong frame spacing / support web spacing l, determine the corresponding connection coefficient Cs of the through-ribs. According to the static pressure, dynamic pressure, connection area, through-rib spacing s, strong frame spacing / support web spacing l and connection coefficient Cs, calculate the normal stress and shear stress at the position of the through-ribs according to the correlation into static pressure condition and dynamic pressure condition.

[0040] S103. Based on the normal stress and shear stress and the allowable normal stress and allowable shear stress, compare and determine whether the design scheme of the preliminary patch plate needs to be optimized or modified.

[0041] S104. If the normal stress and shear stress are greater than the corresponding allowable stress, the connection area is increased by adjusting the design of the stiffeners and the reinforcement plate; conversely, if the normal stress and shear stress are less than the corresponding allowable stress, the connection area is reduced, and a through-type form without stiffeners or reinforcement plates is adopted.

[0042] In another embodiment of the present invention, based on the location of the through-grain material, the working conditions are divided into static pressure conditions and dynamic pressure conditions, and the corresponding static pressure and dynamic pressure under the two working conditions are calculated, including:

[0043] The static pressure includes water pressure and internal compartment pressure. The water pressure is positively correlated with the water head, which depends on the maximum value of the following four calculated distances: the distance from the calculation point to 2 / 3 of the distance from the top of the compartment to the overflow pipe; the distance between the calculation point and the position points above the top of the compartment determined by the ship's length; the distance between the calculation point and the structural draft; and the distance between the calculation point and 2 / 3 of the distance from the endplate bulkhead or freeboard deck. In addition to considering the deep compartment pressure, the internal compartment pressure also needs to consider the effects of liquid cargo pressure and steam pressure at the inner shell bulkheads in the cargo hold area.

[0044] The dynamic pressure is the pressure exerted by the liquid on the hull by the ship's motion, including the combined force of liquid pressure and / or sloshing force; wherein, the bow and stern regions of the LNG ship also include impact pressure shear stress.

[0045] In another embodiment of the present invention, the method includes:

[0046] Shear stress calculations were performed and verified under both static and dynamic pressure conditions to determine the shear stress calculation formula.

[0047]

[0048] In the formula, τ dc Shear force at the shear connection with the PSM web, N / mm 2 'p' represents the calculated pressure at the reinforcing rib, divided into static and dynamic pressure conditions, both of which must meet the requirements, in N / mm². 2 C s The connection coefficient is 1 when the through-rib is a symmetrical stiffener; 1.41 when the through-rib is an asymmetrical stiffener and only directly connected; and 1.12 when the through-rib is an asymmetrical stiffener and has a patch plate or collar plate.

[0049] In another embodiment of the present invention, the method includes:

[0050] The normal stress calculations and verifications were performed under both static and dynamic pressure conditions to determine the formula for normal stress calculation.

[0051]

[0052] In the formula, σ fb The normal stress at the connection between the web stiffener and the elbow plate of the PSM is N / mm. 2 .

[0053] In another embodiment of the present invention, the method includes: patch design and stiffener design;

[0054] The patch design includes: the design of the cut type and the design of the patch type; the design of the cut type determines the direct connection area A2 between the cut and the through-grain material, and the design of the patch type determines the connection area A3 between the patch or collar plate and the through-grain material.

[0055] The design of the reinforcing ribs includes: whether to select or not to select the reinforcing ribs, the size of the reinforcing ribs, whether to include the rounded soft toe of the reinforcing ribs, and whether to include the elbow plate or back elbow plate of the reinforcing ribs. The design of the reinforcing ribs determines the connection area A1 of the web reinforcement ribs and the through-ribs.

[0056] In another embodiment of the present invention, the method includes:

[0057] The size of the connection area A1 between the web reinforcement and / or elbow plate and the through-grain is positively correlated with the thickness of the web reinforcement and / or elbow plate and the length of the connection contact surface; the size of the direct connection area A2 between the through incision and the through-grain is positively correlated with the thickness of the web plate and the length of the direct connection contact surface between the incision and the through-grain; the size of the connection area A3 between the patch or collar plate and the through-grain is positively correlated with the thickness of the web plate and the length of the connection contact surface between the patch or collar plate and the through-grain.

[0058] In another embodiment of the present invention, the stiffener includes three forms: ordinary straight stiffener, stiffener with arc, and stiffener combined with back elbow plate. The stiffener combined with back elbow plate is superior to the stiffener with arc and superior to the ordinary straight stiffener.

[0059] In another embodiment of the present invention, the patch plate includes at least one or more of the following: a ground patch plate, a non-ground patch plate, a watertight patch plate, an embedded patch plate, and a ball-end patch plate. The embedded patch plate has a strength superior to that of a watertight patch plate, a ball-end patch plate, a ground patch plate, and a non-ground patch plate.

[0060] In this embodiment of the invention, based on the structural characteristics of LNG carriers, a different plating design method than that described in conventional ship types such as bulk carriers and oil tankers is adopted. This method establishes new calculation formulas for normal stress and shear stress, and compares these formulas with allowable normal stress and allowable shear stress to verify whether the LNG carrier plating design meets mechanical design requirements. Relationships are established between the normal and shear stresses on the through-ribs at the LNG carrier's penetration points and the compressive stress, the spacing of the through-ribs, the strong frame spacing / support web spacing, the connection coefficient, and the connection area. By simply adjusting the connection area of ​​the through-ribs, it is easy and efficient to determine whether the LNG carrier plating design meets the design requirements, improving design efficiency and demonstrating strong practicality.

[0061] like Figure 2 and Figure 3 As shown, Figure 2 A schematic diagram of the static pressure head illustrating an LNG ship patch plate design method according to an embodiment of the present invention; Figure 3 This diagram illustrates the definition of the geometric parameters of the connection surface in an LNG ship patch plate design method according to an embodiment of the present invention.

[0062] Pressure calculations are divided into two conditions: static pressure and dynamic pressure. Static pressure calculations generally use head selection, such as... Figure 2 The calculation location 1 is located in the ship's hull area, and the four pressure heads corresponding to the water pressure heads are as follows: |(h1+1300)-h0|、|h4-h0|、 The water pressure head at location 1 is calculated by taking the largest of the four pressure heads mentioned above, and if... Figure 2 The calculation location 2 is located in the inner hull of the ship's cargo hold and will be affected by the LNG cargo pressure and steam pressure. The LNG cargo pressure head is |h5-h0|, and the steam pressure is the design value. Then, the larger of the water pressure and the LNG cargo static pressure is taken. The dynamic pressure calculation under the dynamic pressure condition has many factors to consider. It can be calculated according to the requirements of the classification society, or it can be obtained by adding a safety factor to the static pressure.

[0063] Shear stress calculation is divided into shear stress calculation and verification under static pressure conditions and shear stress calculation and verification under dynamic pressure conditions. The shear stress calculation formula is as follows:

[0064]

[0065] Normal stress calculation is divided into normal stress calculation and verification under static pressure conditions and normal stress calculation and verification under dynamic pressure conditions. The formula for normal stress calculation is as follows:

[0066]

[0067] In the formula, τ dc Shear force at the shear connection with the PSM web, N / mm 2 'p' represents the calculated pressure at the reinforcing rib, divided into static and dynamic pressure conditions, both of which must meet the requirements, in N / mm². 2 C s The connection coefficient is 1 when the through-rib is a symmetrical stiffener; 1.41 when the through-rib is an asymmetrical stiffener and only directly connected; and 1.12 when the through-rib is an asymmetrical stiffener and has a patch plate or collar plate.

[0068] Among them, the calculation of shear force and normal stress is divided into static pressure condition and dynamic pressure condition. Under the static pressure condition, A1 / A2 / A3 correspond to the construction dimensions, while under the dynamic pressure condition, A1 / A2 / A3 correspond to the net dimensions after deducting corrosion. The reinforcing ribs of flat steel and T-shaped steel are symmetrical reinforcing ribs, while the reinforcing ribs of bulb flat steel and angle steel are asymmetrical reinforcing ribs.

[0069] Figure 3 In China, patch design and rib design are usually considered together. Patch design includes the design of the cut type and the selection of the patch type, such as... Figure 3 The design of the incision type determines the direct connection area A2 between the incision and the through-grain material; the design of the patch type determines the connection area A3 between the patch or collar plate and the through-grain material; the design of the stiffener includes whether to select the stiffener, the size of the stiffener, whether the stiffener has a rounded soft toe, and whether the stiffener has an elbow plate or back elbow plate. The design of the stiffener determines the connection area A1 between the web reinforcement and the through-grain material.

[0070] The allowable stress for the connection between the through-grain and the PSM, based on experience, is as follows for LNG carriers:

[0071] Static pressure condition:

[0072] σ perm =0.6f y N / mm 2 f y The yield strength of the stiffener elbow plate material;

[0073] τ perm =0.3f y N / mm 2 f y The yield strength of the web / patch material;

[0074] Dynamic pressure condition:

[0075] σ perm =0.84S m f y N / mm 2 f y For the yield strength of the stiffener plate material, S m This is the strength reduction factor;

[0076] τ perm =0.42S m f y N / mm 2 f y S represents the yield strength of the web / patch material. m This is the strength reduction factor.

[0077] in:

[0078] f y The corresponding value for ordinary steel is 235 N / mm. 2 H32 high-strength steel is rated at 315 N / mm². 2 H36 high-strength steel is rated at 315 N / mm². 2 ;

[0079] S mThe value is 1.0 for ordinary steel, 0.95 for H32 high-strength steel, and 0.908 for H36 high-strength steel.

[0080] This invention provides a method for designing LNG ship plating, which involves comparing the σ values ​​under static and dynamic pressure conditions. fb ≤σ perm , τ dc ≤τ perm Whether all conditions are met simultaneously depends on the comparison and calculation results. This determines the cut type, the need for patching, and the type of patching in the patching design; the need for stiffeners, and the type and size of stiffeners; and the thickness and material of the web and stiffeners.

[0081] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for designing a patching plate for LNG ships, characterized in that, The method includes: S101. Based on the preliminary patch design scheme, calculate the connection area A1 between the web stiffener and / or elbow plate and the through-grain, the direct connection area A2 between the through cut and the through-grain, and the connection area A3 between the patch or collar plate and the through-grain. According to the location of the through-grain, divide it into static pressure condition and dynamic pressure condition, and calculate the corresponding static pressure and dynamic pressure under the two conditions. Based on the location of the through-grain, the working conditions are divided into static pressure and dynamic pressure. The corresponding static pressure and dynamic pressure under the two working conditions are calculated, including: The static pressure includes water pressure and internal compartment pressure. The water pressure is positively correlated with the water head, which depends on the maximum value of the following four calculated distances: the distance from the calculation point to 2 / 3 of the distance from the top of the compartment to the overflow pipe; the distance between the calculation point and the position points above the top of the compartment determined by the ship's length; the distance between the calculation point and the structural draft; and the distance between the calculation point and 2 / 3 of the distance from the endplate bulkhead or freeboard deck. In addition to considering the deep compartment pressure, the internal compartment pressure also needs to consider the effects of liquid cargo pressure and steam pressure at the inner shell bulkheads in the cargo hold area. S102, Based on the known actual arrangement of the spacing s of the through-beams, the strong frame spacing / support web spacing l Determine the connection coefficient Cs corresponding to the through members based on static pressure, dynamic pressure, connection area, through member spacing s, and strong frame spacing / support web spacing. l And the connection coefficient Cs, according to the correlation, the normal stress and shear stress at the location of the through-grain are calculated under static pressure and dynamic pressure conditions; S103. Based on the normal stress and shear stress and the allowable normal stress and allowable shear stress, compare and determine whether the design scheme of the preliminary patch plate needs to be optimized or modified. S104. If the normal stress and shear stress are greater than the corresponding allowable stress, the connection area is increased by adjusting the design of the stiffeners and the reinforcement plate; conversely, if the normal stress and shear stress are less than the corresponding allowable stress, the connection area is reduced, and a through-type form without stiffeners or reinforcement plates is adopted.

2. The LNG ship patch plate design method according to claim 1, characterized in that, The method includes: Shear stress calculations were performed and verified under both static and dynamic pressure conditions to determine the shear stress calculation formula. In the formula, Shear force at the shear connection with the PSM web, N / mm 2 , To calculate the pressure at the reinforcing ribs, two working conditions are considered: static pressure and dynamic pressure. Both conditions must meet the requirements in N / mm². 2 C s The connection coefficient is 1 when the through-rib is a symmetrical stiffener; 1.41 when the through-rib is an asymmetrical stiffener and only directly connected; and 1.12 when the through-rib is an asymmetrical stiffener and has a patch plate or collar plate.

3. The LNG ship patch plate design method according to claim 2, characterized in that, The method includes: The normal stress calculations and verifications were performed under both static and dynamic pressure conditions to determine the formula for normal stress calculation. In the formula, The normal stress at the connection between the web stiffener and the elbow plate of the PSM is N / mm. 2 .

4. The LNG ship patch plate design method according to claim 1, characterized in that, The method includes: patch design and stiffener design; The patch design includes: the design of the cut type and the design of the patch type; the design of the cut type determines the direct connection area A2 between the cut and the through-grain material, and the design of the patch type determines the connection area A3 between the patch or collar plate and the through-grain material. The design of the reinforcing ribs includes: whether to select or not to select the reinforcing ribs, the size of the reinforcing ribs, whether to include the rounded soft toe of the reinforcing ribs, and whether to include the elbow plate or back elbow plate of the reinforcing ribs. The design of the reinforcing ribs determines the connection area A1 of the web reinforcement ribs and the through-ribs.

5. The LNG ship patch plate design method according to claim 4, characterized in that, The method includes: The size of the connection area A1 between the web reinforcement and / or elbow plate and the through-grain is positively correlated with the thickness of the web reinforcement and / or elbow plate and the length of the connection contact surface; the size of the direct connection area A2 between the through incision and the through-grain is positively correlated with the thickness of the web plate and the length of the direct connection contact surface between the incision and the through-grain; the size of the connection area A3 between the patch or collar plate and the through-grain is positively correlated with the thickness of the web plate and the length of the connection contact surface between the patch or collar plate and the through-grain.

6. The LNG ship patch plate design method according to claim 4, characterized in that, The stiffener includes three forms: ordinary straight stiffener, stiffener with arc, and stiffener combined with back elbow plate. Among them, the stiffener combined with back elbow plate is superior to the stiffener with arc and superior to the ordinary straight stiffener.

7. A method for designing LNG ship patch plates according to any one of claims 1 to 6, characterized in that, The patch includes at least one or more of the following: ground patch, non-ground patch, watertight patch, embedded patch, and ball-head patch. The embedded patch has better strength than the watertight patch, the ball-head patch, the ground patch, and the non-ground patch.

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