Method for manufacturing a ship hull structure, method for designing a ship hull structure, and design program for a ship hull structure

Abstract

[Problem] To provide an index-based hull structure manufacturing method, design method and design program with which it is possible to prevent a breach of a cargo oil tank and oil outflow, or to reduce the amount of outflow, in the event of running aground. [Solution] The present invention includes: a step for selecting a steel plate to be applied to a hull structure 10 of a ship; a step for quantifying a stress-strain relationship of the steel plate; a step for using the stress-strain relationship to execute a grounding analysis of the hull structure 10 to which the steel plate is applied, to obtain a calculated value of a critical grounding speed; a step for determining a required value of the critical grounding speed; and a step for evaluating a grounding resistance of the hull structure 10 on the basis of the calculated and required values of the critical grounding speed. The hull structure 10 for which it has been determined, from the evaluation result of the grounding resistance, that the required value is satisfied, is manufactured.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a ship hull structure, a method for designing a ship hull structure, and a design program for a ship hull structure. [Background technology]

[0002] In recent years, marine pollution caused by maritime accidents such as ship collisions and groundings has become a social problem. For example, if a ship collides with a reef or other obstacle and its cargo oil tanks rupture, oil spills can occur, polluting the ocean and causing environmental damage. Therefore, it is important to design the ship's hull structure and select materials that can suppress the rupture of cargo oil tanks even if the ship collides with other ships or reefs.

[0003] Conventionally, in the event of a collision between ships, it has been disclosed in the following patent documents, etc., that damage to a ship can be reduced by applying highly ductile steel for ship hulls, which has superior ductility compared to conventional steel, to the sides of the ship.

[0004] For example, Patent Document 1 discloses a hull structure using highly ductile steel plates, in which one or more of the opposing outer or inner plates on the sides of the ship are required to have a total elongation of 1.4 times or more the total elongation value specified in the Unified Requirement W11 Rev.8 2014 of the International Association of Classification Societies (IACS), and which have been confirmed to satisfy the said specification.

[0005] Non-patent document 1 discloses a hull structure in which at least the outer plating of the bottom of the ship uses highly ductile steel plates whose total elongation is 1.4 times or more the total elongation value specified in the IACS Unified Requirement W11 Rev.8 2014.

[0006] In addition, Patent Document 2 discloses a double-hull tanker in which an outer hull and an inner hull are rigidly connected to each other via elements extending vertically and horizontally, and it is proposed to use steel having a high elongation at break for the inner hull.

[0007] Furthermore, Patent Document 3 discloses that for any one or two or more of the ship side outer plate, the anti-flexure member with the ship side outer plate, the inner hull, and the anti-flexure member with the inner hull, a steel material in which the product (σy×εu) of the yield stress σy and the uniform elongation εu is increased by 20% or more compared to the conventional IACS unified standard material (Unified Requirement W11), or a steel material in which the energy absorption amount up to the uniform elongation εu in the tensile test is increased by 20% or more, or a steel material in which the yield stress σy is equal to or higher and the uniform elongation εu is increased by 20% or more is applied.

[0008] In addition, steel plates for ship hulls that improve strength and ductility and increase the energy absorption against impact during a collision are disclosed in, for example, Patent Documents 4 to 8 and the like.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Non-Patent Documents

[0010] [Non-Patent Document 1] Written by Kazutoshi Ichikawa et al., published by the Japan Institute of Invention and Innovation, Public Technical Reference Number 2020-500973. [Non-Patent Document 2] Yamada et al., International Journal of Offshore and Polar Engineering, Vol. 18, No. 2, 2008, p. 1-9 [Non-Patent Document 3] Nguyen et al.,Ships and Offshore Structures,Vol.7,No.2,2012,p.197-213 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] The technologies disclosed in the above-mentioned Patent Documents 1 to 3 are designed to withstand collisions between ships and utilize high-ductility steel in the hull structure. However, there are elements that differ from collisions with other ships, such as the fact that reefs do not move upon impact with a collision with a reef, and that the deformation of the bottom of the hull moves until the ship that has collided with the reef comes to a stop. Non-Patent Document 1 discloses a hull structure that uses high-ductility steel plates for at least the outer plating of the bottom of the hull. However, since high-ductility steel is more expensive than conventional steel, it is desirable to limit its application to an extent that is effective in improving grounding resistance from the viewpoint of reducing shipbuilding costs.

[0012] Furthermore, while the aforementioned Patent Documents 4-8 disclose hull steel plates with improved strength and ductility, and increased energy absorption against impact during collisions, they only describe the impact absorption performance of the hull steel plates themselves. In other words, they do not specify the relationship with the actual hull structure, for example, the effect on grounding resistance when applied as hull steel plates. Moreover, when designing ships using these high-ductility steels, there has been no conventional indicator of grounding resistance that focuses on preventing rupture of cargo oil tanks.

[0013] This invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a ship hull structure, a design method, and a design program based on indicators that can prevent or reduce the amount of oil spills and rupture of cargo oil tanks in the event of grounding. [Means for solving the problem]

[0014] To solve the above problems, the present invention provides a method for manufacturing a ship hull structure, comprising the steps of: selecting a steel plate to be applied to the hull structure of a ship; quantifying the stress-strain relationship of the steel plate; performing a grounding analysis of the hull structure to which the steel plate is applied using the stress-strain relationship to obtain a calculated value of the critical grounding speed; determining a required value of the critical grounding speed; and evaluating the grounding resistance of the hull structure based on the calculated and required values ​​of the critical grounding speed, thereby manufacturing the hull structure that is determined to satisfy the required value based on the evaluation results of the grounding resistance.

[0015] In the method for manufacturing the hull structure, in the step of determining the calculated value of the critical grounding speed, a grounding analysis is performed under the condition of being fixed to a reef, and the critical grounding speed V cr This can also be calculated using the following formula (1).

[0016]

number

[0017] However, in the above formula (1), E S,cr : Energy absorbed by means other than hull motion up to the point of rupture of the cargo oil tank of the aforementioned vessel, E W,cr External work up to the rupture of the cargo oil tank of the aforementioned vessel, M: Displacement of the aforementioned vessel, including added water mass. That is the case.

[0018] In the method for manufacturing the hull structure, the required value for the critical grounding speed may be set to 5 knots under the condition that the vessel collides head-on with a reef.

[0019] In the method for manufacturing the hull structure described above, the vessel may be a crude oil tanker with a deadweight tonnage of 200,000 tons or more.

[0020] Furthermore, the present invention provides a method for designing a ship hull structure, comprising the steps of: selecting a steel plate to be applied to the hull structure of a ship; quantifying the stress-strain relationship of the steel plate; performing a grounding analysis of the hull structure to which the steel plate is applied using the stress-strain relationship to determine a calculated value of the critical grounding speed; determining a required value of the critical grounding speed; and evaluating the grounding resistance of the hull structure based on the calculated and required values ​​of the critical grounding speed, wherein the hull structure determined to satisfy the required value is determined from the evaluation results of the grounding resistance.

[0021] In the aforementioned hull structure design method, in the step of determining the calculated value of the critical grounding speed, a grounding analysis is performed under the condition of reef fixation, and the critical grounding speed V cr This can also be calculated using the following formula (1).

[0022]

number

[0023] However, in the above formula (1), E S,cr : Energy absorbed by means other than hull motion up to the point of rupture of the cargo oil tank of the aforementioned vessel, E W,cr External work up to the rupture of the cargo oil tank of the aforementioned vessel, M: Displacement of the aforementioned vessel, including added water mass. That is the case.

[0024] Further, the present invention causes a computer or a server as an information processing apparatus to perform steps of acquiring a hull structure of a ship, a selected steel plate, and application conditions of the steel plate to the hull structure, acquiring a quantified stress-strain relationship of the steel plate; acquiring ship conditions of the ship including a ship speed; acquiring reef conditions; performing a grounding analysis based on the hull structure, the application conditions, the stress-strain relationship, the ship conditions, and the reef conditions; obtaining a calculated value of a limit grounding speed based on the grounding analysis; obtaining a required value of a set limit grounding speed; and comparing the calculated value of the limit grounding speed with the required value to determine the grounding resistance, and provides a hull structure design program for deriving a hull structure determined to satisfy the required value.

[0025] In the step of determining the grounding resistance, when it is determined that the required value is not satisfied, at least one of the changed steel plate and the stress-strain relationship, the changed application conditions to the hull structure, and the changed ship conditions may be acquired, and the limit grounding speed may be obtained.

[0026] In the step of obtaining the calculated value of the limit grounding speed, a grounding analysis may be performed under the condition of reef fixation, and the limit grounding speed V cr may be calculated using the following formula (1).

[0027]

Equation

[0028] However, in the above formula (1), E S,cr : Energy absorbed other than hull movement up to the oil tank break of the ship E W,cr : External work up to the oil tank break of the ship M: Displacement including the added mass of the ship is as follows.

Advantages of the Invention

[0030] [Figure 1] This diagram illustrates the components of the double hull structure at the bow of the ship. [Figure 2] This graph shows the relationship between ship speed and the energy (Es, cr) consumed during grounding, excluding kinetic energy. [Figure 3] This flowchart shows the design procedure for a ship hull structure according to an embodiment of the present invention. [Figure 4] This is an explanatory diagram illustrating the schematic of a system for implementing a ship hull structure design program according to an embodiment of the present invention. [Figure 5] This is a side view showing the positional relationship between the hull model and the reef model. [Figure 6] This is a diagram showing a rocky reef model, where (a) shows the dimensions of the rocky reef model and (b) shows the overall shape of the rocky reef model. [Figure 7] This figure shows the results of an analysis of the damage to a ship's hull 20 seconds after a collision with a reef, when the ship's speed is varied. (a) shows the case when the ship's speed is 3 knots, (b) shows the case when the ship's speed is 4 knots, and (c) shows the case when the ship's speed is 5 knots. [Modes for carrying out the invention]

[0031] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. In this specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted.

[0032] <Hull structure> First, as an example of a hull structure (ship hull structure) 10, a double hull structure at the bow will be described. As shown in Figure 1, the bow side of the hull structure 10 has a bow section 11 forward of the collision bulkhead 20 (described later) and a tank section 12 adjacent to the bow section 11 aft of the collision bulkhead 20.

[0033] The double hull structure at the bow includes, as its main components, a collision bulkhead 20, outer plating 21, bow trans 22, bow longitudinal 23, tank longitudinal 24, inner plating 25, inner plating longitudinal 26, and floor 27.

[0034] The collision bulkhead 20 is provided at an appropriate length aft from the bow, dividing the bow section 11 and the tank section 12 on the bow side of the hull structure 10. A cargo oil tank (not shown) is located in the tank section 12 aft of the collision bulkhead 20.

[0035] The outer plating 21 is provided at the bottom of the hull, extending from the bow section 11 to the tank section 12. Hereinafter, the outer plating 21 at the bow section 11 will be referred to as the bow-side outer plating 21a, and the outer plating 21 at the tank section 12 will be referred to as the tank-side outer plating 21b. The bow transformer 22 is a transformer attached to the bow-side outer plating 21a. The bow longitudinal 23 is a longitudinal (flexibility-preventing material) attached to the bow-side outer plating 21a. The tank longitudinal 24 is a longitudinal (flexibility-preventing material) attached to the tank-side outer plating 21b.

[0036] The inner plate 25 is provided at the bottom of the tank section 12, facing the tank-side outer plate 21b. The inner plate longitudinal 26 is a longitudinal (flexing-resistant material) attached to the inner plate 25.

[0037] The floor 27 is provided in the tank section 12 at appropriate intervals between the tank-side outer plate 21b and the inner plate 25.

[0038] <Maximum grounding speed> The bow components described above are made of steel plates that meet the standards of the IACS Unified Requirement W11 Rev.9 2017, or, if necessary, high-ductility steel plates that have performance exceeding the strength and total elongation specified in the said Unified Requirement. However, until now, there has been no target indicator of grounding resistance that can be achieved by applying high-ductility steel plates.

[0039] Therefore, in this invention, the maximum speed at which a ship's cargo oil tank ruptures upon grounding is defined as the "maximum grounding speed," and this maximum grounding speed is used as an indicator of grounding resistance. The higher the maximum grounding speed, the more grounding-resistant the ship is considered to be. Furthermore, the maximum grounding speed is an easily understandable indicator for operators such as the captain and navigators. By designing the hull structure and selecting materials so that the maximum grounding speed is equal to or greater than the target value, it becomes possible to manufacture a ship with superior grounding resistance.

[0040] (First method for calculating critical grounding velocity) In the present invention, the first calculation method for determining the critical grounding velocity is a method that uses a collision analysis between a ship and a reef using the finite element method (FEM) (hereinafter referred to as grounding analysis).

[0041] For grounding analysis, a whole-ship model that models the entire vessel is used. In the whole-ship model, it is preferable to model as accurately as possible the shapes and arrangements of various members used in the hull structure, specifically the outer plating of the bottom of the hull forward and aft of the collision bulkhead, the transformers and stiffeners attached to that outer plating, the collision bulkhead, the inner plating of the bottom of the hull, the stiffeners attached to that inner plating, the floor, etc. It is preferable to quantify the stress-strain relationship of the steel plates used in each member using an appropriate method and incorporate it as the material constitutive law of the elastoplastic body of each member. The stress-strain relationship of the steel plates used in each member can be determined, for example, by a tensile test using a full-thickness test specimen with a gauge length of 200 mm and a width of 25 mm (more specifically, a tensile test specified in IACS Unified Requirement W2 Rev.3 2021). The conditions under which an element fractures are not particularly limited, but the fracture strain calculated according to the element size using Barba's law of equation (2) below may be used, referring to Non-Patent Literature 2.

[0042]

number

[0043] However, in equation (2) above, εt: Total strain (fracture strain) εu: Uniform distortion, c: material constant, W: width of the test specimen, t: thickness of the test specimen, L: Gauge length of the test specimen That is the case.

[0044] While the entire ship may be modeled using elastoplastic elements, it is also possible to use elastoplastic elements only for the bow area, which is likely to come into contact with reefs, and a rigid body model for the stern area, which is less likely to come into contact with reefs.

[0045] The reef model can be created according to the assumed shape and properties of the reef. For example, a reef model with a conical shape can be used. The sharper the tip of the reef, the more severe the conditions become, and the limiting grounding velocity tends to decrease. The reef model may be treated as a rigid body with its bottom displacement constrained, as a severe condition.

[0046] Several scenarios are possible for a ship to collide with a reef. For example, the ship may be traveling straight and colliding with the reef bow-first, assuming the collision occurs on the ship's centerline, or it may be offset from the centerline. Alternatively, the ship may be traveling diagonally or laterally relative to its length and colliding with the reef from the side. The penetration depth is defined as the vertical height from the bottom of the ship to the top of the reef at the time of collision. For the cargo oil tank to rupture, the penetration depth must be at least equal to the height from the bottom of the ship to the inner bottom plate. However, making the penetration depth too large results in unrealistic conditions and tends to increase the critical grounding speed. For example, for a ship with a height of 2.7m from the bottom of the ship to the inner bottom plate, a penetration depth of around 5.0m is preferable.

[0047] In grounding analysis, it is preferable to model the gravitational and buoyant forces acting on the ship under conditions as close to reality as possible. Unless the ship's weight, including its cargo, is accurately modeled and its balance cannot be maintained, an effective grounding analysis cannot be performed.

[0048] By performing this type of grounding analysis multiple times while varying the ship's speed, it is possible to derive the limit condition (upper limit) of the cruising speed at which the cargo oil tank will not rupture (no leakage will occur from the tank). The cruising speed can be selected from, for example, 1 knot to the maximum speed of the target ship. The maximum cruising speed at which the cargo oil tank will not rupture even if grounding occurs is the limit grounding speed. Below the limit grounding speed, the probability of leakage from the tank occurring even if grounding occurs becomes significantly lower. Therefore, cruising below the limit grounding speed can be considered a guideline for a safe cruising speed.

[0049] However, such grounding analyses are large-scale, moment-by-moment dynamic nonlinear analyses, and performing multiple analyses for each design condition requires significant computational cost and time. Therefore, a calculation method that can easily estimate the critical grounding velocity is preferable.

[0050] (Second method for calculating critical grounding speed) In this invention, the second calculation method for determining the critical grounding velocity is a method using a simplified estimation formula. The derivation of this simplified estimation formula will be explained below.

[0051] Assume a scenario in which a ship collides with a stationary reef. Let V be the ship's velocity before grounding, V' be the ship's velocity after grounding, M be the ship's displacement including added water mass, and E be the energy absorbed by the ship other than hull motion. S Therefore, according to the law of conservation of energy before and after grounding, equation (3) below holds true.

[0052]

number

[0053] The total energy generated by a ship running aground is mainly the sum of internal (strain) energy, kinetic energy, frictional energy, and other energies. Internal energy is the energy generated by the deformation of the ship. Kinetic energy is the energy generated by the movement of the hull. Frictional energy is the energy generated by friction between the ship and the reef or friction between the components of the ship. And the energy absorbed by the ship other than the hull movement as described above E S This is the sum of the energies obtained by subtracting the hull kinetic energy from the total energy.

[0054] The limiting grounding speed is V cr The energy E at the time the oil tank ruptured S to E S,cr Assuming that the cargo oil tank ruptures, the ship stops, and the ship's speed V' becomes 0 after the grounding. Then, equation (4) is derived from equation (3).

[0055]

number

[0056] Furthermore, by rearranging equation (4) above, equation (5) below is derived.

[0057]

number

[0058] Here, as shown in Figure 2, in the same collision scenario using the same ship and reef, even if the ship's speed V is changed, the energy E at the time the cargo oil tank ruptures remains the same. S,cr Simulation results have confirmed that it remains at a nearly constant value. Therefore, the ship's speed V is the critical grounding speed V cr The above conditions (for example, the ship's speed V, the critical grounding speed V) cr The grounding analysis was performed under the condition that the speed was sufficiently faster than the estimated speed, and the energy E S By determining this, the critical grounding velocity V can be determined without performing multiple grounding analyses. cr This makes it possible to estimate efficiently.

[0059] However, after diligent investigation by the inventors, it was confirmed that the actual grounding phenomenon does not match equation (5) above. This is thought to be because, when grounding analysis is performed under conditions where the reef is fixed, the system composed of the colliding side and the collided side is not closed, and an external force acts on such a system, so the law of conservation of energy does not hold. Therefore, the inventors have found that energy E S External work E W We devised a method to subtract E. The external work done at the time the leak in the oil tank occurred is E. W,cr Therefore, in equation (5) above, E S,cr (E S,cr -E W,cr By substituting with ), the following equation (1) is derived.

[0060]

number

[0061] External work E W,cr This is presumed to be the work performed by the reef. When the inventors determined the change in energy balance through grounding analysis, they found that the total energy, which is the sum of the internal energy, kinetic energy, and frictional energy mentioned above, increases with time. This increase is the external work E W,cr It is thought that the ship's speed V is the critical grounding speed V cr Under the above conditions, a grounding analysis was performed, and the energy E S and external work E W By determining the critical grounding speed V, cr It is possible to estimate this.

[0062] As described above, the critical grounding velocity can be calculated by performing grounding analyses using multiple FEMs, as in the first calculation method, or by using the simplified estimation formula (1), as in the second calculation method.

[0063] <Manufacturing and design procedures for hull structures> The manufacturing and design procedures for the hull structure 10 will be explained below, based on Figure 3.

[0064] First, the steel plates to be applied to the hull structure 10 are selected, and the application conditions for the hull structure are obtained (Step S1). The steel plates are those that meet the standards of at least the IACS Unified Requirement W11 Rev.9 2017, and in order to improve grounding resistance, high-ductility steel with increased energy absorption is used. Examples of high-ductility steel include those with a tensile strength (N / mm²). 2 The product of ) and total elongation is 120 N / mm 2The above-mentioned steel plates are used. Furthermore, for high-ductility steel, steel plates having a total elongation of 1.5 times or more the total elongation value specified in the IACS unified standard are preferable. In addition, as steel plates applied to the hull structure 10, mild steel that meets the standards compliant with the IACS unified standard can also be used, provided that it enhances the absorbed energy.

[0065] In the hull structure 10, the parts to which high-ductility steel is applied can be determined arbitrarily.

[0066] For example, high-ductility steel may be applied to a portion or all of the bow plating 21a at the bottom of the hull forward of the collision bulkhead 20. Furthermore, high-ductility steel may be used in part or all of the bow transformer 22 attached to the bow plating 21a made of high-ductility steel, and furthermore, high-ductility steel may be used in part or all of the bow longitudinal 23 attached to the bow plating 21a made of high-ductility steel. In addition, high-ductility steel may be used in part or all of the bow transformer 22 attached to the bow plating 21a made of high-ductility steel, and in part or all of the bow longitudinal 23 attached to the bow plating 21a made of high-ductility steel.

[0067] In this way, by applying a highly ductile steel plate to the bow section 11, the ship can be stopped before a reef reaches the cargo oil tank, preventing rupture of the cargo oil tank and leakage of oil.

[0068] Furthermore, high-ductility steel plates may be used for part or all of the collision bulkhead 20.

[0069] Furthermore, high-ductility steel plates may be used for part or all of the inner plate 25 of the bottom of the ship. In that case, high-ductility steel plates may also be used for part or all of the inner plate longitudinals 26 attached to the inner plate 25 in which the high-ductility steel plates are used.

[0070] Furthermore, high-ductility steel plates may be used for part or all of the tank-side outer plating 21b at the bottom of the ship aft of the collision bulkhead 20. In that case, high-ductility steel plates may also be used for part or all of the tank longitudinals 24 attached to the tank-side outer plating 21b on which the high-ductility steel plates are used.

[0071] Furthermore, high-ductility steel plates may be used for part or all of the floor 27.

[0072] In this way, by applying highly ductile steel plates to the tank section 12, even if the cargo oil tank ruptures, the vessel can be stopped early before the rupture area expands, thereby suppressing the extent of the rupture and the amount of oil spilled from the cargo oil tank.

[0073] Next, the stress-strain relationship of the selected steel plate is quantified (Step S2). This stress-strain relationship is quantified by, for example, a tensile test using a full-thickness base material specimen with a gauge length of 200 mm and a width of 25 mm (more specifically, a tensile test as specified in IACS Unified Requirement W2 Rev.3 2021). The stress-strain relationship changes depending on the steel plate applied to the hull structure 10, and the critical grounding speed also changes. For example, by using a highly ductile steel plate in a specific part of the hull structure 10, it is possible to suppress rupture of the cargo oil tank and increase the critical grounding speed compared to conventional steel plates.

[0074] The quantification of this stress-strain relationship does not necessarily have to be performed by tensile tests on the steel plates actually used. For example, the results of tensile tests conducted using test specimens taken from steel plates of equivalent IACS grade and similar thickness to those used in the hull structure may be used. Note that steel plates with thicknesses of 6 to 50 mm may be used in the hull structure.

[0075] Next, ship conditions including ship speed and reef conditions are obtained (steps S3 and S4), and a grounding analysis is performed based on the hull structure and application conditions obtained in step S1, the stress-strain relationship quantified in step S2, the ship conditions obtained in step S3, and the reef conditions obtained in step S4 (step S5). Then, the calculated value of the critical grounding speed for the hull structure 10 to which the steel plate selected in step S1 is applied is determined (step S6). The calculated value of the critical grounding speed is obtained by either the first calculation method or the second calculation method described above. In this case, a formulated stress-strain relationship may be used, or the value itself may be used.

[0076] On the other hand, the required value for the critical grounding speed is obtained (step S7). This required value can be determined, for example, according to the specifications desired by the ship owner. Alternatively, the required value may be the critical grounding speed when high-ductility steel having the predetermined tensile strength and total elongation performance described above is applied to a specific part of the hull. For example, 5 knots may be the required value under the condition that the ship collides head-on with a reef.

[0077] Then, the calculated value of the critical grounding speed in step S6 is compared with the required value of the critical grounding speed in step S7 (step S8). This comparison evaluates the grounding resistance of the hull structure 10. If the calculated value is higher than the required value, it is determined that the required value is satisfied, and the hull structure is derived (step S9), and the hull structure 10 is manufactured using the selected steel plates. If the calculated value is less than or equal to the required value, the process returns to step S1, step S2, or step S3 to review the type of steel plates, hull structure, ship conditions, etc., or to obtain the stress-strain relationship using a different method.

[0078] As described above, according to the present invention, the critical grounding speed can be used as a clear indicator of grounding resistance, and a hull structure that meets the required values ​​and has excellent grounding resistance can be designed and manufactured. Furthermore, the critical grounding speed can be easily determined by using equation (1) as in the second calculation method.

[0079] While the present invention is particularly effective when applied to very large crude oil carriers (VLCCs) with a carrying capacity of 200,000 tons or more, the types of vessels to which the present invention can be applied are not limited to those mentioned above.

[0080] <System Functional Configuration> Figure 4 is an explanatory diagram illustrating the schematic of the system for implementing the hull structure design program shown in Figure 3.

[0081] The hull structure design system 100 comprises a system body 101 consisting of an information processing device such as a computer or server, a condition input means 102, and a result output means 103. The system body 101 also includes a control unit 111, a first storage unit 112, a second storage unit 113, a program execution unit 114, and a communication unit 115. The program execution unit 114 executes steps S1 to S9 in Figure 3, and includes an application condition acquisition unit 121, a stress-strain relationship acquisition unit 122, a ship condition acquisition unit 123, a reef condition acquisition unit 124, a grounding analysis unit 125, a limit grounding speed calculation unit 126, a limit grounding speed requirement value acquisition unit 127, a grounding resistance determination unit 128, and a hull structure derivation unit 129.

[0082] The control unit 111 is a central processing unit, such as a circuit (hardware) or a CPU (Central Processing Unit). The control unit 111 executes instructions contained in the program (software) stored in the first storage unit 112 and the second storage unit 113. Specifically, the control unit 111 performs the functions of each unit 121 to 129 by operating according to the program. The functions of each unit 121 to 129 will be described later.

[0083] The first memory unit 112 and the second memory unit 113 are implemented using RAM (Random Access Memory), ROM (Read Only Memory), flash memory, HDD (Hard Disk Drive), SSD (Solid State Drive), etc., and each stores various programs and data related to the hull model, reef model, etc. For example, the first memory unit 112 can store pre-installed programs, pre-constructed hull models and reef models, etc., while the second memory unit 113 can store data such as the application conditions for acquired steel plates and hull structures, stress-strain relationships, ship conditions, reef conditions, and required values ​​for the limit grounding speed. It can also store the results of the grounding analysis, data from the analysis stages, and calculated values ​​of the limit grounding speed. Note that the memory units are not limited to this configuration, and any form can be adopted.

[0084] The communication unit 115 is a communication interface composed of, for example, a communication device for connecting to a communication network such as the Internet. The communication unit 115 is, for example, a wired or wireless LAN (Local Area Network), Bluetooth, or other communication interface. The communication unit 115 may also be a router for optical communication, a router for ADSL (Asymmetric Digital Subscriber Line), or a modem for various types of communication. This communication unit 115 can, for example, send and receive signals to and from the Internet or other communication devices in accordance with a predetermined protocol such as TCP / IP. The communication network connected to the communication unit 115 is composed of a network connected by wire or wireless, and may be, for example, the Internet, a home LAN, infrared communication, radio wave communication, or satellite communication.

[0085] The application condition acquisition unit 121 acquires the hull structure of the ship, the steel plate selected as a constituent material of the hull structure, and the application conditions of the steel plate to the hull structure (step S1 above). The stress-strain relationship acquisition unit 122 acquires the stress-strain relationship of the selected steel plate (step S2 above). The ship condition acquisition unit 123 and the reef condition acquisition unit 124 acquire the ship conditions and reef conditions of the ship, respectively (steps S3 and S4 above). The grounding analysis unit 125 performs a grounding analysis based on the ship conditions and reef conditions (step S5 above). The limit grounding speed calculation unit 126 calculates the limit grounding speed of the hull structure to which the selected steel plate is applied (step S6 above). The limit grounding speed requirement value acquisition unit 127 acquires the requirement value for the limit grounding speed (step S7 above). The grounding resistance determination unit 128 compares the calculated value from the limit grounding speed calculation unit 126 with the required value from the limit grounding speed requirement acquisition unit 127 and determines whether the calculated value is higher than the required value (step S8 above). Then, the hull structure derivation unit 129 derives the hull structure if the required value is satisfied (step S9 above).

[0086] The condition input means 102 is an input means for inputting initial conditions and conditions that have been changed if the calculated values ​​do not meet the requirements for the hull structure, steel plates, application conditions for steel plates, and the limit grounding speed requirement into the system main unit 101. The condition input means 102 consists of, for example, hardware keys such as a keyboard, a pointing device such as a mouse, a touch panel, a touchpad, etc.

[0087] The result output means 103 is an output means for presenting the input conditions, the determination results based on those conditions, and the hull structure. The result output means 103 is composed of a display device such as a display. Alternatively, the communication unit 115 may function as the result output means 103 and present the input conditions, the determination results based on those conditions, and the hull structure to an information processing device different from the information processing device having the system body 101.

[0088] The condition input means 102 and the result output means 103 may be partially or entirely integrated. In such cases, a touch panel display in which the touch panel and display are integrated may be used.

[0089] Furthermore, it is also possible to install the condition input means 102 and the result output means 103 in a remote location, and have the system main body 101, consisting of an information processing device such as a computer or server, function as a server, and connect the condition input means 102 and the result output means 103 to the system main body 101 via an information communication network to operate the design system 100. In this case, the design program is stored in a storage medium on the server, which acts as an information processing device, and the design is performed using the design program stored in the storage medium each time a ship hull structure is designed.

[0090] In this embodiment, the components of the system body 101 are not limited to the examples described above. For example, each component may be made up of general-purpose materials, or it may be made up of hardware specialized for the function of each component. Depending on the technological level at the time of implementing this embodiment, it is possible to change the hardware configuration used as appropriate.

[0091] Furthermore, the design program of this embodiment may be provided stored on a computer-readable storage medium. Examples of storage media include HDDs, SSDs, and various types of memory. In addition, the design program may not be continuously used from the one stored on the computer's storage medium, but rather updated with a new design program distributed, for example, via a network. [Examples]

[0092] We assumed a scenario in which a VLCC collides with a reef bow-first along its centerline, and performed a grounding analysis using FEM.

[0093] In the FEM analysis, the positional relationship between the hull model M1 and the reef model M2 is as shown in Figure 5. The condition was assumed that when the ship collides with the reef, the reef penetrates to a height of 5m from the bottom of the ship. The shape of the reef model M2 is approximately conical, as shown in Figure 6. For the specific shape of the reef model M2, the following equation (6) was applied, referencing the model in Non-Patent Document 3.

[0094]

number

[0095] Here, in equation (6) above, x r , y r and z r These are the longitudinal, horizontal, and vertical coordinates of the reef surface, respectively, L ref L is the reference length, and α and β are the shape parameters of the reef model M2. ref The floor-to-floor length will be applied as follows, and the floor-to-floor length L of the VLCC ref The length was set to 5000 mm. The shape parameters α and β of the reef model M2 were set to α=β=2, assuming severe grounding conditions. The reef model M2 was treated as a rigid body with its bottom displacement constrained.

[0096] Regarding the ship's speed, grounding analyses were conducted for five cases: V=3kt, 4kt, 5kt, 6kt, and 12kt, and the presence or absence of rupture in the cargo oil tank was evaluated. Note that 1 kt is a speed of 1 nautical mile (1852 m) per hour. Figure 7 shows the hull damage status (Mises stress distribution) 20 seconds after the ship collided with the reef, as an example of the grounding analysis results described above, for V=3kt, 4kt, and 5kt. In all cases of V=3kt, 4kt, and 5kt, the ship was stopped. At V=3kt, the ship stopped before the reef reached the collision bulkhead 20, so the cargo oil tank did not rupture (Figure 7(a)). On the other hand, at V=4kt, 5kt, 6kt, and 12kt, the reef reached the collision bulkhead 20, and the cargo oil tank ruptured (Figure 7(b), (c)). Note that the hull damage (Mises stress distribution) at V=6kt and 12kt is the same as that shown in Figures 7(b) and (c) for V=4kt and 5kt, so it is omitted from the illustration. From this, it was confirmed that under the current analysis conditions, the critical grounding speed is between 3kt and 4kt.

[0097] Table 1 shows the results of estimating the critical grounding velocity using equations (1) and (5) based on the analysis results for V=4kt, 5kt, 6kt, and 12kt. The estimated values ​​using equation (5) were all greater than 4kt, while the estimated values ​​using equation (1) were between 3kt and 4kt, which is consistent with the results of the grounding analysis described above. In other words, it was confirmed that under the conditions of this study, where the reef was fixed, the critical grounding velocity can be estimated with high accuracy using equation (1).

[0098] [Table 1]

[0099] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art to which the present invention belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these are also understood to fall within the technical scope of the present invention.

[0100] The embodiments disclosed herein are illustrative and not restrictive in all respects. The embodiments described above may be omitted, replaced, or modified in various ways without departing from the appended claims, the technical scope of the invention as described later, and the spirit thereof. For example, the constituent elements of the embodiments described above can be combined in any way without impairing their effects. Furthermore, such any combination will naturally yield the effects and benefits of each constituent element in the combination, as well as other effects and benefits that will be obvious to those skilled in the art from the description herein.

[0101] Furthermore, the effects described herein are merely descriptive or illustrative, and not limiting. In other words, the technology according to the present invention may produce other effects that will be apparent to those skilled in the art from the description herein, in addition to or instead of the effects described above.

[0102] Furthermore, the following configurations also fall within the technical scope of the present invention. [1] The process of selecting steel plates to be applied to the hull structure of a ship, A step of quantifying the stress-strain relationship of the steel plate, The process involves performing a grounding analysis of the hull structure to which the steel plate is applied using the stress-strain relationship described above, and determining the calculated value of the critical grounding speed. A step of determining the required value for the limit grounding speed, A step of evaluating the grounding resistance of the hull structure based on the calculated and required values ​​of the limit grounding speed, Equipped with, A method for manufacturing a ship hull structure, comprising manufacturing the ship hull structure that is determined to satisfy the required value based on the evaluation results of the grounding resistance. [2] In the process of determining the calculated value of the critical grounding speed, A grounding analysis was conducted under the condition of reef anchorage, and the critical grounding velocity V was determined. cr A method for manufacturing a ship hull structure as described in [1], wherein the following formula (1) is used to calculate the following. However, in the following equation (1), ES,cr : Energy absorbed by means other than hull motion up to the point of rupture of the cargo oil tank of the aforementioned vessel, E W,cr External work up to the rupture of the cargo oil tank of the aforementioned vessel, M: Displacement of the aforementioned vessel, including added water mass. That is the case. [3] A method for manufacturing a hull structure according to [1] or [2], wherein the required value for the critical grounding speed is 5 knots under the condition that the vessel collides head-on with a reef. [4] The aforementioned vessel is a crude oil tanker with a deadweight tonnage of 200,000 tons or more, and the method for manufacturing a hull structure according to any one of [1] to [3]. [5] The process of selecting steel plates to be applied to the hull structure of a ship, A step of quantifying the stress-strain relationship of the steel plate, The process involves performing a grounding analysis of the hull structure to which the steel plate is applied using the stress-strain relationship described above, and determining the calculated value of the critical grounding speed. A step of determining the required value for the limit grounding speed, A step of evaluating the grounding resistance of the hull structure based on the calculated and required values ​​of the limit grounding speed, Equipped with, A method for designing a hull structure, which determines the hull structure that satisfies the required value based on the evaluation results of the grounding resistance. [6] In the process of determining the calculated value of the critical grounding speed, A grounding analysis was conducted under the condition of reef anchorage, and the critical grounding velocity V was determined. cr The hull structure design method described in [5] is calculated using the following formula (1). However, in the following equation (1), E S,cr : Energy absorbed by means other than hull motion up to the point of rupture of the cargo oil tank of the aforementioned vessel, E W,cr External work up to the rupture of the cargo oil tank of the aforementioned vessel, M: Displacement of the aforementioned vessel, including added water mass. That is the case. [7] A computer or server as an information processing device, A step of obtaining the hull structure of a ship, a selected steel plate, and the conditions for applying the steel plate to the hull structure, The steps include obtaining a quantified stress-strain relationship of the steel plate, A step of obtaining the ship conditions of the ship, including the ship speed, Steps to obtain reef conditions, A step of performing a grounding analysis based on the hull structure, the application conditions, the stress-strain relationship, the ship conditions, and the reef conditions, The steps include: determining the critical grounding velocity based on the grounding analysis described above; The steps include obtaining the required value for the set limit grounding speed, A step of determining grounding resistance by comparing the calculated value of the limit grounding speed with the required value, Make it run, A hull structure design program that derives a hull structure determined to satisfy the aforementioned requirements. [8] A hull structure design program according to [7], which, in the step of determining the grounding resistance, determines if the required value is not satisfied, obtains at least one of the modified steel plate and stress-strain relationship, modified application conditions to the hull structure, and modified ship conditions, and determines the limit grounding speed. [9] In the step of determining the calculated value of the critical grounding speed, A grounding analysis was conducted under the condition of reef anchorage, and the critical grounding velocity V was determined. cr The hull structure design program described in [7] calculates this using the following formula (1). However, in the following equation (1), E S,cr : Energy absorbed by means other than hull motion up to the point of rupture of the cargo oil tank of the aforementioned vessel, E W,cr External work up to the rupture of the cargo oil tank of the aforementioned vessel, M: Displacement of the aforementioned vessel, including added water mass. That is the case.

[0103]

number

[0104] This invention can be applied to the manufacture and design of ship hull structures with excellent impact resistance in the event of grounding. [Explanation of symbols]

[0105] 10 Hull structure 11 Fore part 12 Tank section 20 Collision Bulkhead 21 Exterior Panel 21a Forward side skin 21b Tank side outer plate 22 Bow transformer 23 Bow Longitudinal 24 Tank Long 25 Inner plate 26 Inner panel long 27th floor

Claims

1. The process of selecting steel plates to be applied to the hull structure of a ship, A step of quantifying the stress-strain relationship of the steel plate, The process involves performing a grounding analysis of the hull structure to which the steel plate is applied using the stress-strain relationship described above, and calculating the critical grounding speed, A step of determining the required value for the limit grounding speed, A step of evaluating the grounding resistance of the hull structure based on the calculated and required values ​​of the limit grounding speed, Equipped with, A method for manufacturing a ship hull structure, comprising manufacturing the ship hull structure that is determined to satisfy the required value based on the evaluation results of the grounding resistance.

2. In the process of determining the critical grounding velocity, a grounding analysis is performed under the condition of reef fixation, and the critical grounding velocity V is determined. ｃｒ A method for manufacturing a ship hull structure according to claim 1, wherein the following formula (1) is used to calculate the following. However, in the following formula (1), E Ｓ，ｃｒ : Energy absorbed by means other than hull motion up to the point of rupture of the cargo oil tank of the aforementioned vessel, E Ｗ，ｃｒ External work up to the rupture of the cargo oil tank of the aforementioned vessel, M: Displacement of the aforementioned vessel, including added water mass. That is the case. [Math 1]

3. The method for manufacturing a hull structure according to claim 1 or 2, wherein the required value for the critical grounding speed is 5 knots under the condition that the vessel collides head-on with a reef.

4. The method for manufacturing a ship hull structure according to claim 1 or 2, wherein the ship is a crude oil tanker with a deadweight tonnage of 200,000 tons or more.

5. The process of selecting steel plates to be applied to the hull structure of a ship, A step of quantifying the stress-strain relationship of the steel plate, The process involves performing a grounding analysis of the hull structure to which the steel plate is applied using the stress-strain relationship described above, and calculating the critical grounding speed, A step of determining the required value for the limit grounding speed, A step of evaluating the grounding resistance of the hull structure based on the calculated and required values ​​of the limit grounding speed, Equipped with, A method for designing a hull structure, which determines the hull structure that satisfies the required value based on the evaluation results of the grounding resistance.

6. In the process of determining the calculated value of the critical grounding speed, A grounding analysis was conducted under the condition of reef anchorage, and the critical grounding speed V was determined. ｃｒ A method for designing a ship hull structure according to claim 5, wherein the following formula (1) is used to calculate the following. However, in the following formula (1), E Ｓ，ｃｒ : Energy absorbed by means other than hull motion up to the point of rupture of the cargo oil tank of the aforementioned vessel, E Ｗ，ｃｒ External work up to the rupture of the cargo oil tank of the aforementioned vessel, M: Displacement of the aforementioned vessel, including added water mass. That is the case. [Math 2]

7. A computer or server as an information processing device, A step of obtaining the hull structure of a ship, a selected steel plate, and the conditions for applying the steel plate to the hull structure, The steps include obtaining a quantified stress-strain relationship of the steel plate, A step of obtaining the ship conditions of the ship, including the ship speed, Steps to obtain reef conditions, A step of performing a grounding analysis based on the hull structure, the application conditions, the stress-strain relationship, the ship conditions, and the reef conditions, The steps include: determining the critical grounding velocity based on the grounding analysis described above; The steps include obtaining the required value for the set limit grounding speed, A step of determining grounding resistance by comparing the calculated value of the limit grounding speed with the required value, Make it run, A hull structure design program that derives a hull structure determined to satisfy the aforementioned requirements.

8. A hull structure design program according to claim 7, wherein, in the step of determining the grounding resistance, if it is determined that the required value is not satisfied, at least one of the modified steel plate and the stress-strain relationship, the modified application conditions to the hull structure, and the modified ship conditions is obtained, and the limit grounding speed is determined.

9. In the step of determining the calculated value of the critical grounding speed, A grounding analysis was conducted under the condition of reef anchorage, and the critical grounding speed V was determined. ｃｒ A ship hull structure design program according to claim 7, which calculates the following using formula (1). However, in the following formula (1), E Ｓ，ｃｒ : Energy absorbed by means other than hull motion up to the point of rupture of the cargo oil tank of the aforementioned vessel, E Ｗ，ｃｒ : External work up to the oil tank breach of the said ship, M: This is the displacement of the aforementioned vessel, including the added water mass. [Math 3]

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