JP5893231B1 - Hull structure with excellent collision resistance and design method of hull structure - Google Patents

Abstract

The hull structure is a part of one or more members of the outer side plate or the inner plate facing each other on the side of the ship, or all the parts thereof. It has a hull structure using a high ductility steel plate that is imposed as a specification and has been confirmed to satisfy the above specification, having a total elongation of 1.4 times or more of the total elongation value defined in 2014). Furthermore, it is preferable to use the highly ductile steel sheet as a stiffener associated with a portion (outer plate, inner plate) using the steel plate.

Description

  The present invention relates to a hull structure excellent in collision resistance that can suppress a hull breakage particularly in a large ship that has collided with a ship side, and a method for designing the hull structure.

  Single carrier hull structures (single hulls) are still used in bulk carriers such as ore carriers and coal carriers. The cargo from these ships does not pollute the ocean, but the ships are also loaded with fuel oil and the like, and the spill of fuel oil causes marine pollution. For this reason, it is necessary to suppress a hull breakage due to a collision accident or the like.

  In addition, oil spills from tankers have become an international issue because they cause more significant marine pollution. In recent years, switching to a double hull structure (double hull) is progressing in order to suppress oil spillage due to a collision accident or the like. It has also been pointed out that double hulls are less effective than single hulls, although the oil leakage rate is reduced.

  It is possible to improve the collision resistance of the hull structure by increasing the number of oil tanks, increasing the height of the double bottom, and increasing the distance between the double sides. However, these measures increase the construction cost and operation cost, and reduce the mounting efficiency. On the other hand, the value of the product of yield stress and uniform elongation or uniform elongation to any one or more of ship side skin, stiffener with ship side skin, inner plate, stiffener with inner plate There has been proposed a hull structure using a steel material in which the energy absorption amount or the yield stress is equal or greater and the uniform elongation itself is increased (for example, see Patent Document 1). Moreover, the steel plate for ship bodies which improved the intensity | strength and ductility and increased the absorbed energy with respect to the impact at the time of a collision is proposed (for example, refer patent documents 2-6).

JP 2002-87373 A Japanese Patent Laid-Open No. 11-193438 JP-A-11-193441 JP-A-11-193442 Japanese Patent Laid-Open No. 11-246934 JP-A-11-246935

It is not obvious whether the amount of energy absorbed until the inner plate breaks is governed by uniform elongation, and other members (upper deck, bilge, The contribution to hull breakage control that Trans, Stringer) has is not clear.
Therefore, the hull structure of Patent Document 1 has a problem that a rational hull design is impossible. Considering the suppression of the final breakage that occurs in the impacted ship by causing the impact ship to make a side collision with the impacted ship, it is not the uniform elongation as in Patent Document 1, but the total elongation up to the breakage. It is necessary to consider.
In Patent Document 1, the steel material quantitatively defined based on the uniform elongation, that is, the value of the product of the yield stress and the uniform elongation, the energy absorption amount until the uniform elongation, or the yield stress is equal to or greater than one. A steel material in which the elongation itself is increased by 20% or more has been proposed. However, even if the uniform elongation is increased by 20% in this way, it is considered that the local elongation is not substantially changed. Therefore, the total elongation, which is the sum of the uniform elongation and the local elongation, increases only by a little less than 20%. Therefore, it does not reach the regulation of the total elongation of the present invention described later, and the breakage cannot be suppressed.
Further, Patent Document 1 simply aims to greatly increase the amount of energy that can be absorbed before a breakage occurs in a hull of a double hull structure (double hull). There is no description, and there is no description about conditions that do not cause a break in the single hull structure (single hull).

Moreover, when using the steel sheet described in Patent Documents 2 to 6, although the energy absorbed at the time of collision can be increased, like the hull structure of Patent Document 1, the total elongation at which the steel sheet breaks is not considered, There is room for improvement in hull breakage control.
Patent Documents 2 to 6 describe that when a collision accident occurs between ships, the hull is prevented from breaking and a hole is prevented from opening or the fracture area can be reduced as compared with a conventional steel plate. Although there is only a description of the impact absorption performance of a single steel plate, there is no description regarding the relationship with the actual hull structure and conditions that do not cause breakage.

  In view of such circumstances, the present invention has a hull structure excellent in collision resistance, in which the energy that can be absorbed by the member is increased so as to suppress the breakage of the hull with the hull structure unchanged from the conventional one. The issue is to provide

The gist of the present invention is as follows.
(1) The value of the total elongation defined in the unified standard of the International Classification Society (IACS) (Unified Requirements W11 Rev. 8 2014) for some parts of the outer skin of the ship side or for all parts of the outer skin. A hull structure with excellent impact resistance, characterized by having a hull structure using a high-ductility steel plate that is confirmed to satisfy the above-mentioned specification, in which a total elongation of 1.4 times or more is imposed as a specification. The term “impact resistance” as used herein refers to a property that can suppress a hull breakage even when subjected to a side collision of another ship at a predetermined speed.
(2) Furthermore, having a hull structure using the high-ductility steel plate in a part of the inner plate facing the outer plate where the high-ductility steel plate is used or all of the inner plate. The hull structure according to (1) above, which is characterized.
(3) The value of the total elongation specified by the unified standard of the International Classification Society (IACS) (Unified Requirements W11 Rev. 8 2014) for a part of the inner plate of the ship side or all of the inner plate. A hull structure with excellent impact resistance, characterized by having a hull structure using a high-ductility steel plate that is confirmed to satisfy the above-mentioned specification, in which a total elongation of 1.4 times or more is imposed as a specification.
(4) Furthermore, having a hull structure using the high-ductility steel plate in a part of the outer plate facing the inner plate in which the high-ductility steel plate is used or all parts of the outer plate. The hull structure according to (3) above, which is characterized.
(5) Further, any of the above (1) to (4), wherein the high ductility steel plate is used for a part or all of a stiffener associated with the portion where the high ductility steel plate is used. Crab hull structure. The stiffener in the present invention is a general term for all members for suppressing the bending / deformation of the plate material constituting the hull including the outer plate and the inner plate. For example, in the case of a double hull, A member (Longi) for suppressing out-of-plane bending. For example, in the case of a single hull, in addition to a member for suppressing out-of-plane bending, a member for mainly suppressing out-of-plane bending of the outer plate. (Aggregate).
(6) The hull structure according to any one of (1) to (5), wherein the high-ductility steel plate is used for a part or all of the stringer.
(7) The hull structure according to any one of (1) to (6), wherein the high-ductility steel plate is used for a part or all of the upper deck.
(8) The hull structure according to any one of (1) to (7), wherein the high-ductility steel plate is used for a part or all of a bilge.
(9) The hull structure according to any one of (1) to (8) above, wherein the high ductility steel plate is used for a part or all of a transformer.
(10) The hull structure according to any one of (1) to (9) above, wherein a thickness of the highly ductile steel sheet is more than 12 mm and not more than 50 mm.
(11) In the outer side plate of the ship side, a part where the breakage needs to be suppressed is specified, and a steel sheet used for the part is specified as a unified standard (Unified Requirements W11 Rev. 8) of the International Classification Association (IACS). A design method for a hull structure using a high-ductility steel plate that has been confirmed to satisfy the above-mentioned specification, in which a total elongation of 1.4 times or more of the value of the total elongation specified in 2014) is imposed. .
(12) Further, in the inner plate facing the outer plate in which the high ductility steel plate is used, a portion where it is necessary to suppress the breakage is specified, and the high ductility steel plate is used for the steel plate used for the portion. The method for designing a hull structure as described in (11) above, wherein
(13) In the inner plate of the ship side part, the part which needs to suppress the breakage is specified, and the unified standard (Unified Requirements W11 Rev. 8) of the International Classification Association (IACS) is used for the steel plate used for the part. A design method for a hull structure using a high-ductility steel plate that has been confirmed to satisfy the above-mentioned specification, in which a total elongation of 1.4 times or more of the value of the total elongation specified in 2014) is imposed. .
(14) Further, in the outer plate facing the inner plate in which the high-ductility steel plate is used, a portion where it is necessary to suppress breakage is specified, and the high-ductility steel plate is used for the steel plate used in the portion. The method for designing a hull structure as described in (13) above, wherein
(15) Further, the high ductility steel plate is used for a steel plate used for a part or all of the stiffener associated with the portion where the high ductility steel plate is used. 14) The hull structure design method described in any one of 14).
(16) The hull structure design method according to any one of (11) to (15), wherein the high-ductility steel plate is used as a steel plate used for a part or all of the stringer.
(17) The hull structure design method according to any one of (11) to (16), wherein the high-ductility steel plate is used as a steel plate used for a part or all of the upper deck.
(18) The hull structure design method according to any one of (11) to (17), wherein the high-ductility steel plate is used for a steel plate used for a part or all of the bilge.
(19) The hull structure design method according to any one of (11) to (18), wherein the high-ductility steel plate is used as a steel plate used for a part or all of the transformer.

  According to the present invention, it is possible to provide a hull structure with excellent collision resistance that can suppress the occurrence of a hull breakage due to, for example, a collision of a large ship without a significant increase in cost. Is extremely prominent.

It is a figure for demonstrating the member of a double hull structure. It is the figure which expanded the ship side part bottom part in FIG. It is a figure for demonstrating the collision scenario of the analysis by a finite element method. It is a figure explaining an example of the absorption energy analysis result of each member by a finite element method, and is a figure which shows the ratio of the absorbed energy of each member in case all the members of a double hull structure are conventional steel. However, OS: Outer plate, IS: Inner plate, LongiWeb: Stiffener web portion, Longi Face: Stiffener flange surface portion, Trans: Transformer, STR: Stringer, UPDK: Upper deck (upper deck), BILGE: Bilge, T.BHD: Trans bulkhead, S.BHD: Swash bulkhead. Here, the stiffener web portion generally means a portion perpendicular to the outer plate or the inner plate accompanied by the stiffener in the portion constituting the stiffener, and the stiffener flange surface portion is generally a stiffener. The part which is parallel to the outer plate | board or inner plate | plate with which a stiffener accompanies in the part which comprises. It is a figure explaining an example of the absorption energy analysis result of each member by the finite element method, and the ratio of the absorbed energy of each member when the outer plate, inner plate and fender of the double hull structure are high ductility steel plates FIG. It is a figure explaining an example of the absorption energy analysis result of each member by a finite element method, and is a figure which shows the ratio of the absorbed energy of each member in case all the members of a hull are high ductility steel plates. It is a figure explaining the absorbed energy analysis result of the ship to be collided by the finite element method, and the amount of energy absorbed by the ship to be collided until the breakage occurs in the inner plate (loading of oil spill occurs) or until the end of the collision. It is a comparison figure of absolute value. It is a figure explaining an example of the analysis result of the damage of the inner board by a finite element method, and is a figure which shows the damage of an inner board in case it is 1.3 times the value of the total elongation of a unified standard. It is a figure explaining an example of the analysis result of the damage of the inner board by a finite element method, and is a figure which shows the damage of an inner board in case it is 1.4 times the value of the total elongation of a unified standard. It is a figure explaining an example of the analysis result of the damage of the inner board by a finite element method, and is a figure which shows the damage of an inner board in case it is 1.5 times the value of the total elongation of a unified standard. It is a figure explaining an example of an analysis result of damage of an inner board by a finite element method, and the outer board of a double hull structure, an inner board, and a fender are 1.5 times the value of the total elongation of a unified standard It is a figure which shows the analysis result of the damage of the inner board in a case. It is a schematic diagram for demonstrating the collision scenario of the analysis by the finite element method in a single hull structure. It is a figure explaining the absorption energy analysis result of the bulk carrier by a finite element method, and is a comparison figure of the absolute value of the energy amount absorbed by the bulk carrier until a fracture occurs in an outer plate. It is a figure explaining an example of the analysis result of the damage of the outer plate by a finite element method, and shows the damage of the outer plate in 1.4 seconds after the collision start when the outer plate and the aggregate of the bulk carrier are conventional steel FIG. It is a figure explaining an example of the analysis result of damage of the outer plate by a finite element method, and damage of the outer plate in 1.4 seconds after the start of collision when the outer plate of the bulk carrier and the aggregate are high ductility steel plates FIG. It is a figure explaining an example of the analysis result of the damage of the outer plate by a finite element method, and is a figure which shows the damage of the outer plate in 6 seconds after the collision when the outer plate and the aggregate of the bulk carrier are conventional steel. . It is a figure explaining an example of the analysis result of the damage of the outer plate by a finite element method, and is the figure which shows the damage of the outer plate in 6 seconds after the collision when the outer plate and the aggregate of the bulk carrier are high ductility steel plates. is there. It is a comparison figure of the critical collision speed of the VLCC which collides with the bulk carrier (the critical speed at which no breakage occurs in the bulk carrier). It is a figure explaining an example of the analysis result of the damage of the outer plate by a finite element method, and is a figure showing damage of the outer plate at the time of the end of collision when the outer plate and the aggregate of the bulk carrier are conventional steel. It is a figure explaining an example of an analysis result of damage of an outer board by a finite element method, and is a figure showing damage of an outer board at the end of a collision in case an outer board and an aggregate of a bulk carrier are high ductility steel plates.

As shown in FIGS. 1 and 2, main members constituting the double hull structure of the oil tank are the ship side outer plate 10 and the inner plate 11, the stiffener 12 associated with the outer plate 10 and the inner plate 11, respectively. 13, transformer 14, stringer 15, upper deck 16 and bilge 17. The present inventors have found that large crude carrier (V ery L arge C rude oil C arrier, that VLCC) assuming collisions, the finite element method the energy is absorbed by deformation and deformation of the members of the double hull structure (FEM).

In the analysis by FEM, as shown in FIG. 3, a scenario is assumed in which a collision ship collides from 90 degrees to 12 kt near the center of the hull of a stopped ship (V _A = 0 kt). The analysis was performed until the speed (kt) of the ship to be collided and the speed V _B (kt) of the collision ship became equal. Here, 1 kt is the speed of 1 nautical mile (1852 m) per hour.
This 12 kt is a speed limit on the Nakanose route, etc., established by the Japan Maritime Traffic Safety Law Enforcement Regulations (Ordinance No. 9 of the Ministry of Transport on March 27, 1973). Also, the collision ship was the same VLCC as the collision ship, and the loading state of the collision ship was a full load state in which the initial kinetic energy was the largest and the influence of inertial force was large. This is one of the most severe collision scenarios for a ship to be collided. And when all members of the hull of the ship to be collided are conventional steel (total elongation 17%) (case 1), the outer plate, inner plate and fenders of the hit ship (with stiffener and outer plate with outer plate) When the fender is the high ductility steel plate (total elongation 27%) (case 2), and the case where all the hulls of the collision ship are the high ductility steel plate (case 3), FEM analysis is performed. The ratio of absorbed energy of each member was determined. The total elongation of 17% in case 1 is determined as follows. That is, the steel plate often used for ships has a thickness of 15 mm to 20 mm, and has a strength classification of 36 according to the unified standard of the International Classification Association (IACS) (Unified Requirements W11 Rev. 8 2014) described later. Therefore, the total elongation of 17% defined by the unified standard is the representative value of the conventional steel. And in order to grasp | ascertain the absorbed energy etc. of the ship using a highly ductile steel plate, in case 2 and case 3, it is not 23.8% which is 1.4 times the total elongation of 17% of conventional steel, but a high ductility steel plate In consideration of the manufacturing variation, the analysis was performed on the assumption that the average total elongation of the high ductility steel sheet was 27%.

The ratios of energy absorbed by the deformation of the double hull structure member in the analysis of case 1, case 2 and case 3 are shown in FIGS. 4, 5 and 6, respectively. As shown in FIG. 5 and FIG. 6, when a high ductility steel plate is applied to at least the outer plate, the inner plate, and the fender, the total ratio of these absorbed energy (OS + IS + Longi Web + Longi Face) is 50. It can be seen that it exceeds%. On the other hand, as shown in FIG. 4, when all the members are conventional steels, the total ratio of the absorbed energy of the outer plate, the inner plate and the fender is 50% or less. Therefore, when energy is efficiently absorbed by the high ductility steel plate, it is considered preferable to apply the high ductility steel plate to at least the outer plate, the inner plate, and the fender. 4 to 6, among the outer plate, the inner plate, and the fender, the fenders represent Longi Web and Longi Face. The total 50% of the absorbed energy ratio of the outer plate, the inner plate, and the fender is the total energy absorbed by OS, IS, Longi Web, and Longi Face. By applying the high ductility steel plate, the occurrence of breakage of the outer plate and the inner plate is greatly delayed by the high ductility effect. When a rupture occurs in the inner plate, cargo oil flows into the ocean and becomes a large-scale ocean pollution. Therefore, it is important to absorb as much collision energy as possible before the occurrence of the rupture in the inner plate. FIG. 7 shows a comparison of absolute values of energy absorbed by the ship to be collided up to the time when the inner plate breakage occurs or until the time when the collision is finished in Case 1, Case 2 and Case 3. In case 3, since the inner plate has no breakage, the energy absorbed by the ship to be collided up to the time when the collision is completed is shown. From FIG. 7, it can be seen that the amount of energy absorption up to the outflow of cargo oil can be significantly improved with the expansion of the applicable members of the high ductility steel sheet.
Here, the difference in absorbed energy between case 3 and case 1 (1816 MJ) and the ratio of absorbed energy of the outer plate, inner plate and fender to which the high ductility steel plate of FIG. 4 is applied (50% = 0.50). When the absorbed energy (478 MJ) of case 1 is added to the product of (908 MJ) and the absorbed energy of case 2 is estimated, it is 1386 MJ. This value is almost the same value as the absorbed energy 1393MJ (absorbed energy of case 2 in FIG. 7) obtained by the analysis by the finite element method. From this, by the analysis by the finite element method, the absorbed energy of the high ductility steel plate application rate of 100% and 0% and the absorbed energy of each member having the high ductility steel plate application rate of 0% (conventional steel 100%) as shown in FIG. If the ratio is calculated in advance, it can be seen that the absorbed energy when the applied member of the high ductility steel sheet is changed can be predicted.
In many cases, the application ratio of the high ductility steel sheet is determined in advance from the construction cost of the ship. In such a case, if the ratio of the absorbed energy for each member in the case of using the conventional steel as shown in FIG. 4 is obtained in advance by analysis by the finite element method, the ratio of the absorbed energy for each member and the weight of the member. From the ratio of the ratio, the priority (economic efficiency) of the applied member of the high ductility steel sheet can be evaluated. That is, by applying a high ductility steel sheet from a member having a high ratio (= absorbed energy ratio / weight ratio), a member to which the high ductility steel sheet should be applied can be easily determined.

Next, in addition to the outer plate and inner plate, stiffeners, transformers, stringers, upper decks, and bilges that accompany each of them are in accordance with the unified standard of the International Association of Classification Societies (IACS) (Unified Requirements W11 Rev. 8 2014). The analysis results of the damage to the inner plate when using steel plates having total elongations 1.3 times, 1.4 times and 1.5 times the specified total elongation values are shown in FIGS. 10 shows. 8 to 10 are views after 6 seconds from the start of the collision. 8 to 10 are views of the inner plate viewed from the inside of the cargo tank inside the hull, and the starboard half of the ship to be collided is not displayed. As shown in FIG. 8, when the value of total elongation is 1.3 times, a fracture (a crack passing through the inner plate) occurs in the inner plate. On the other hand, as shown in FIGS. 9 and 10, when the value of the total elongation is 1.4 times or more, no breakage occurs in the inner plate. Further, in FIG. 8, there are a plurality of cracks / damages in the lower part of the tank, but in FIG. 9 and FIG. 10, it can be confirmed that the plurality of cracks / damages are not generated.
The total elongation values defined in the unified standard (Unified Requirements W11 Rev. 8 2014) are as shown in Table 1. Table 1 defines the minimum elongation value that the hull material to be used should satisfy, depending on the plate thickness and Grade. In the unified standard, alphabets (A, B, D, E, and F) in Grade indicate differences in test temperatures required in the Charpy impact test, and numerals (32, 36, and 40) indicate strength categories. The high ductility steel sheet has an elongation exceeding the standard value of the total elongation shown in Table 1 and therefore satisfies the unified standard.

  In consideration of the above analysis results, manufacturing cost, and productivity, an embodiment of the hull structure of the present invention is as follows.

According to the present invention, the total elongation of 1.4 times or more of the total elongation value defined in the IACS standard is imposed as a specification on a part of the outer plate of the ship side or all of the outer plate. And it is a hull structure using the high ductility steel plate confirmed to satisfy the above specifications. Furthermore, it is preferable to use the high ductility steel plate at a part of the inner plate facing the outer plate where the high ductility steel plate is used or at all sites of the inner plate.
In addition, the present invention imposes as a specification a total elongation of 1.4 times or more of the total elongation value defined in the IACS standard on all parts of the inner plate on the side of the ship or all the inner plate. It is a hull structure using a high ductility steel plate that has been confirmed to satisfy the above specifications. Furthermore, it is preferable to use the high ductility steel plate in a part of the outer plate facing the inner plate in which the high ductility steel plate is used or in all parts of the outer plate.
Furthermore, it is more preferable to use the high ductility steel plate for a part or all of the fender associated with the portion (outer plate, inner plate) where the high ductility steel plate is used.
Furthermore, it is still more preferable to use the said high ductility steel plate for a part or all of a stringer. Furthermore, it is still more preferable to use the said high ductility steel plate for a part or all of an upper deck. Furthermore, it is still more preferable to use the said high ductility steel plate for a part or all of a bilge. Furthermore, it is still more preferable to use the said high ductility steel plate for a part or all of a transformer.
FIG. 7 shows that the absolute value of the amount of energy absorption increases as the number of members to which the high ductility steel plate is applied increases. From the above, it is desirable to apply the high ductility steel sheet to as many members as possible. However, from the viewpoint of economic efficiency and efficient energy absorption, it is desirable to apply to the outer plate, the inner plate and the stiffener first. In this case, the application to the stiffener accompanying the inner plate is stopped, and the high ductility steel plate is applied to the outer plate, the inner plate and the variation applied to the stiffener accompanying the outer plate or the outer plate and the inner plate. There can be variations. When only one of the outer plate and the inner plate is the high ductility steel plate, the outer plate is made higher than the inner plate because the energy absorption amount of the outer plate is higher than the absorbed energy amount of the inner plate. It is more preferable. However, this does not prevent the use of the highly ductile steel plate only for the inner plate. Moreover, you may use a highly ductile steel plate for a ship bottom structure, a bow structure, and a stern structure. Further, a high ductility steel plate may be used for the upper structure (bridge or the like).

  In the stress-strain curve, energy absorption is large even after uniform elongation. Therefore, in the present invention, in order to suppress the final breakage, the total elongation of the steel material used for the member is considered. When the high ductility steel plate is applied to an outer plate, an inner plate, and a fender, a side surface collision at 12 knots which is a speed limit in a general harbor does not cause a breakage in the inner plate. Thus, it is economically reasonable to limit the applicable member of the high ductility steel sheet.

As described above, the present invention uses a high-ductility steel sheet that has a total elongation of 1.4 times or more of the total elongation value defined in the IACS unified standard as a specification and is confirmed to satisfy the specification. However, in terms of quality control of the high ductility steel plate, the realistic production target of the high ductility steel plate may be 1.5 times or 1.5 times or more. The average of the total elongation of the high ductility steel sheet can be regarded as about 1.5 times the value of the total elongation defined by the unified standard of IACS or 1.5 times or more. In the embodiment described later, an example using 1.5 times this is shown as the present invention. The specification of the total elongation of the high ductility steel sheet is not limited to 1.4 times or more of the total elongation value defined in the IACS standard, but may be a higher value, for example, 1.5 times or more or 27% or more. Absent.
It is known that the total elongation value depends on the test piece. The total elongation value defined in the IACS standard is based on a flat test piece having a GL (distance between gauge points) = 200 mm and w (width) = 25 mm. When using a specimen other than this test piece, for example, a known method such as 2.2.2 of Table 2 of Steel Ship Rules K of the Japan Maritime Association and Table K. From 2.2, the following conversion formula (1) may be used.

Here, n: total elongation when using an arbitrary test piece, E: total elongation when using a flat test piece with GL (distance between gauge points) = 200 mm, w (width) = 25 mm, A: arbitrary The cross-sectional area of the test piece, L: the distance between the marks of any test piece.

  The present invention can be applied to a small ship in addition to a large ship, but is particularly effective when applied to a large ship. The steel plate used for such a large vessel has a plate thickness greater than 12 mm and 50 mm or less. For example, steel plates having a size of more than 12 mm and not more than 50 mm are often used for the outer plate and the inner plate, and steel plates having a thickness of more than 12 mm and not more than 30 mm are used for the stiffener. Therefore, the plate thickness of the high ductility steel plate used in the present invention is preferably more than 12 mm and 50 mm or less. Furthermore, the thickness of steel plates (especially outer plates) used in these large ships is often more than 20 mm, and the high ductility steel plate used in the present invention has an application range of more than 20 mm. You may restrict | limit to this member. In addition, as a general rule, the yield strength of each classification society corresponding to Grade shown in Table 1 is 235 MPa or more (IACS Normal Strength Steel), 315 MPa or more (IACS strength category 32), 355 MPa or more ( IACS strength classification 36) A steel plate for ship structure having a class of 390 MPa or more (IACS strength classification 40). As a general rule, the tensile strength of the steel sheet is 400 MPa or more and 660 MPa or less.

  Although the effect of the present invention is specifically shown by the VLCC having a particularly large effect, for example, as shown in FIG. 5, it is possible to secure nearly 30% of the absorbed energy at the time of collision with only the outer plate, and Considering the absolute value of the amount of energy that can be absorbed by the plate, it has a single hull structure (single hull), such as a bulk carrier (ore carrier), where the time until the sinking is short after the break and the collision safety is also strictly questioned. Even if it is applied, the effect of suppressing breakage is exhibited. In the claims of the present invention, two members, an outer plate and an inner plate, are distinguished. In the case of a single hull structure, it can be considered that the outer plate is also an inner plate (conversely, the inner plate can also be considered as an outer plate). Therefore, even in the case of a single hull structure, it is within the technical scope of the present invention. It is. Needless to say, the fuel oil tank portion (such as a bulk hull basically having a single hull structure) in which the oil leakage is feared due to the breakage at the time of collision such as a bulk carrier. When applied to a (local) double hull structure surrounded by an outer plate and an inner plate), the tank portion suppresses breakage and has an effect of suppressing oil leakage. Even in the case of a ship having a single hull, when the high ductility steel sheet is used, there is a high possibility that a breakage will not occur at the time of collision, although it depends on the ship speed and the collision angle. In other words, it is possible to increase the collision speed that does not cause a break in the hull. Or even if a breakage occurs at the time of a collision, the breakage can be made extremely small. For this reason, collision safety can be improved.

The total elongation of 1.4 times or more of the total elongation value specified in the IACS unified standard is very high, and it is satisfactory unless a steel sheet is manufactured by a special manufacturing method that satisfies this high total elongation. It is a level that can not be. However, there is some variation in the total elongation value. For this reason, when a steel sheet is manufactured by a normal manufacturing method, a steel sheet having a total elongation characteristic that is 1.4 times or more of the total elongation value specified in the IACS unified standard is accidentally produced. There are cases where it is accidentally used for hull construction. However, such a case does not belong to the technical scope of the present invention. In order to implement this invention, it is necessary to specify the ship side steel plate member which needs to suppress a fracture, and to use the said high ductility steel plate for the steel plate used for the said member. In particular, in the outer plate or the inner plate, it is necessary to specify the portion where it is necessary to suppress the fracture, and to use the high ductility steel plate as the steel plate used for the portion. Specifically, a total elongation value of 1.4 times or more of the total elongation value specified in the IACS unified standard is required in the steel sheet specifications and the like (which is manufactured to meet the specifications, and then It is intended to use only steel sheets that have been confirmed to have a total elongation (measured in a tensile test of 1) of 1.4 times or more of the total elongation value specified in the IACS standard. In other words, the member that needs to suppress the breakage is specified, and the steel plate used for the ship side steel plate member has a total elongation of 1.4 times or more of the total elongation value defined in the unified standard of IACS. The design method of the hull structure which uses the high ductility steel plate imposed as a specification and confirmed to satisfy the specification is intended. As a result of such an intended hull structure design method, only steel sheets that have been confirmed to be 1.4 times or more of the total elongation value specified in the IACS standard are specified for hull structure. It is possible to obtain a hull structure characterized by having a hull structure used for a ship side steel plate member (a member that needs to suppress breakage).
In addition, the steel plate used for the hull structure needs to satisfy the standards of each classification society based on the unified standard of IACS. For this reason, tensile tests are performed at a frequency defined by the standards of each classification society. Usually, only steel sheets whose test results satisfy the steel material specifications and the like are determined to pass the inspection of each steel company, and the tensile test results and the like are described in the steel material inspection certificate and the like. Steel inspection certificates, etc. are handed over to shipbuilding companies that have been ordered from steel companies after receiving confirmation from the inspectors of each classification society.
In the present invention, “1.4 times the value of the total elongation specified in the IACS unified standard is imposed as a specification” means that the value of the total elongation prescribed in the IACS unified standard in the steel sheet specification etc. It is intended that a total elongation value of 1.4 times or more is required. Computerization of steel materials transactions between shipbuilders and steel companies is advancing, and in many cases, documents such as steel sheet specifications are not sent. In the present invention, the specification may be imposed by a method not based on a document such as data transmission. Also, “confirmed that the above specifications were satisfied” means that the tensile test was conducted at least as often as specified by the standards of each classification society, and the total elongation measured as a result of the inspection by each steel company. Is intended to be confirmed to be at least 1.4 times the total elongation value specified in the IACS unified standard. This confirmation is generally performed by a computer system in each steel company (for example, the computer system determines whether or not the test result satisfies a required value such as a steel sheet specification).

  The ship side steel plate member that needs to suppress the breakage (the part where the breakage needs to be suppressed on the outer or inner plate) depends on the hull structure designer's approach to collision safety. Depends heavily on For example, in a bulk carrier, a part where there is no ballast tank and the hold has one outer plate (that is, a part where there is no inner plate) is identified as an outer plate that needs to suppress breakage, The high ductility steel plate may be used. Or the site | part with the outer plate used as a part of fuel tank may be specified as the outer plate | board which needs to suppress a fracture, and the said highly ductile steel plate may be used for the outer plate | board of the said site | part.

  Further, for example, in a tanker, an outer plate that faces a portion (inner plate portion) where a tank in which product oil (crude oil in the case of a crude oil tank) is stored is required to suppress the breakage. You may identify with a board. In this case, the said site | part becomes a substantially whole site | part in the height direction and length direction of an outer plate, and uses the said high ductility steel plate for the outer plate | board of the site | part. Depending on the hull designer's approach to collision safety, the high ductility steel plate may be used for the inner plate facing the outer plate using the high ductility steel plate, and the outer plate and the You may use the said high ductility steel plate for a part or all of the stiffener accompanying the inner plate.

In addition, for example, in a spherical tank type LNG ship, a part of the ship side skin that is closest to the spherical tank in which LNG is stored may be specified as a skin that needs to suppress the breakage. In this case, since the tank has a spherical shape, the portion does not need to be a portion that covers the entire tank in a plan view and a side view, and may be only a portion where the tank is closest. And you may use the said highly ductile steel plate for the outer plate | board of the specified site | part. If necessary, the part around the ship side skin that the spherical tank is closest to may be identified as the skin that needs to suppress the breakage.
Regardless of the type of ship, in addition to the outer plate, the inner plate and the stiffener, part or all of the stringer, part or all of the upper deck, part or all of the bilge, part of the transformer Or you may use the said high ductility steel plate for all.
The above method is a method for identifying a member that needs to suppress a breakage from the design drawing of the hull. You may identify the member which needs to suppress the breakage by performing the absorption energy analysis of each member by the finite element method. For example, using FIG. 4 which shows the ratio of the absorbed energy for each member in the case of conventional steel, the outer plate with the highest absorbed energy is identified as the member that needs to suppress the fracture, and the high ductility steel plate is used as the outer plate. May be used. Also, from the comparison of the analysis results of FIGS. 4 to 7 and the respective construction costs, the outer plate and the inner plate are identified as members that need to suppress breakage, and the high ductility steel plate is used for the outer plate and the inner plate. May be. Similarly, after comparing the analysis results of FIGS. 8 to 10 and later-described FIG. 11 and the respective construction costs, the outer plate and the inner plate are identified as members that need to suppress breakage, and the outer plate and The inner plate may be specified as a member that particularly needs to suppress breakage, and the high ductility steel plate may be used for the outer plate, the inner plate, and the fenders associated with each.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood.

  First, the effect when the present invention is applied to a double hull structure (double hull) will be described. Among the members shown in FIG. 1, the outer plate, the inner plate, and the fenders associated with each of the members are 1.5% of the value of the total elongation defined in the unified classification of the International Classification Society (IACS) (Unified Requirements W11). Assuming the case where a steel plate having a total elongation of double is used, the damage of the inner plate was analyzed by FEM in the collision scenario shown in FIG. As a result, as shown in FIG. 11, it became clear that cracks in the inner plate and cracks did not reach.

  Next, effects when the present invention is applied to a single hull structure (single hull) will be described. Assuming an accident in which the VLCC collides with a single-hull bulk carrier, the present inventors have determined the energy absorbed by deformation and deformation of the bulk carrier member by FEM.

In the FEM analysis, as shown in FIG. 3, a severe scenario was assumed in which the VLCC collides from 90 degrees to 12 kt near the center of the hull of the stopped bulk carrier (V _A = 0 kt). Specifically, as shown in FIG. 12, the VLCC bow collided with the bulk carrier outer plate 20 having a single hull structure, and the analysis was performed up to 6 seconds after the collision. This collision location is assumed to be a severe collision position with respect to the outer plate breakage. In FIG. 12, the starboard half of the bulk carrier is not displayed.
When all members of the bulk carrier hull are conventional steel (total elongation 17%) (case 4), the bulk carrier outer plate 20 and the aggregate 21 associated with the outer plate 20 are made of high ductility steel plates (total elongation 27%). ) (Case 5) was analyzed by FEM. The aggregate 21 is a stiffener that is provided along with the outer plate 20 to suppress out-of-plane bending of the outer plate 20. Note that the total elongation of 17% in Case 4 is the lower limit value of the total elongation defined in the IACS unified standard. The total elongation 27% in case 5 corresponds to 1.5 times the total elongation 17% in case 4.

  FIG. 13 shows a comparison of absolute values of energy absorbed by the bulk carrier before the occurrence of the outer plate breakage in the analysis of Case 4 and Case 5. From FIG. 13, it became clear that the amount of energy absorbed until the occurrence of a fracture in the outer plate can be greatly improved by applying the high ductility steel plate to the outer plate and the aggregate (stiffener) of the bulk carrier.

  Moreover, the analysis result of the damage of the outer plate | plate in the analysis of case 4 and case 5 is shown in FIGS. 14-17 is the figure which looked at the outer plate | board from the outer side of the bulk carrier.

  14 and 15 are diagrams of Case 4 and Case 5 after 1.4 seconds from the start of the collision. As shown in FIG. 14, when conventional steel is used for the outer plate and the aggregate (stiffener), the outer plate has a fracture (a crack passing through the outer plate). On the other hand, as shown in FIG. 15, when a highly ductile steel plate is used for the outer plate and the aggregate (stiffener), no breakage occurs in the outer plate.

FIGS. 16 and 17 are diagrams when the velocity (kt) of the bulk carrier and the velocity V _B (kt) of the VLCC are equal to each other, and are diagrams after 6 seconds from the start of the collision in this analysis. As shown in FIG. 16, when conventional steel is used for the outer plate and the aggregate (stiffener), the outer plate is greatly damaged. On the other hand, as shown in FIG. 17, when a high ductility steel plate is used for the outer plate and the aggregate (stiffener), a breakage occurs in the outer plate, but the damage degree of the outer plate is a case where conventional steel is used. Smaller than From the above, it is clear that the application of high-ductility steel plates to the bulk carrier skin and aggregate (stiffeners) can greatly delay the occurrence of skin breaks and reduce the breakage. Became.

  Furthermore, the present inventors calculated the critical collision velocity of VLCC based on the energy absorbed by the bulk carrier shown in FIG. The critical collision speed is a speed at which a fracture occurs in the outer plate of the bulk carrier, in other words, a critical speed at which no fracture occurs in the outer plate.

  FIG. 18 shows the estimated value of the critical collision speed of VLCC in Case 4 and Case 5. In Case 4, when the VLCC speed exceeds 3 kt, a break occurs in the bulk carrier outer plate. However, in Case 5, no break occurs in the bulk carrier outer plate even if the VLCC speed increases to 5 kt. It was. As a result, it became clear that the critical collision speed is greatly improved by applying the high ductility steel plate to the outer plate and the aggregate (stiffener) of the bulk carrier.

In this regard, the present inventors also assumed a scenario in which VLCC collides from 90 degrees to 5 kt near the center of the hull of a stopped bulk carrier (V _A = 0 kt), and also performed analysis by FEM. . In this analysis, the speed of the VLCC is different from the analysis performed in FIGS. 12 to 17 described above, but the other conditions are the same.

FIG. 18 and FIG. 19 are diagrams when the bulk carrier velocity V _A (kt) and the VLCC velocity V _B (kt) are equal, and in this analysis, are diagrams after 6 seconds from the start of the collision. . As shown in FIG. 19, when the outer plate and the aggregate of the bulk carrier were conventional steel (total elongation 19%), a fracture occurred in the outer plate. On the other hand, as shown in FIG. 20, when the outer plate and the aggregate of the bulk carrier were high ductility steel plates (total elongation of 28.5%), no breakage occurred in the outer plate. The analyzed bulk carrier outer plate and the like had an IACS strength classification of 36 and a plate thickness of 25 to 30 mm. For this reason, the analysis was performed by setting the total elongation of the conventional steel as 19% according to Table 1 and the total elongation of the high ductility steel sheet as 1.5%, 28.5%.
When the application range of the high ductility steel plate is limited to members having a thickness of more than 20 mm, it is desirable that the total elongation of the high ductility steel plate exceeds 27% in consideration of manufacturing variations. This also applies to the double hull structure.

  Here, for example, the Japan Ship and Ocean Engineering Society Lecture Proceedings No. 17 Paper No. 2013A-GS10-4 “Construction and Classification of Ship Accident Databases on Coasts of Japan Based on the Decisions of the Japan Marine Accident Tribunal” According to the data, the frequency of collision accidents when the speed of the collision ship is 5 kt or less is about 20% of the entire collision accident. This data includes ship types other than bulk carriers, but generally, assuming the same frequency of occurrence for large bulk carriers, high-ductile steel plates are applied to the bulk carrier outer plate and aggregate (stiffener). By doing so, it has been found that the occurrence of a fracture in the outer plate can be suppressed in a collision accident of about 20% of the accident in which the bulk carrier is a collision ship. This is well suited to economic rationality, considering the prevention of human life and cargo damage due to collisions, and the protection of the marine environment.

Next, Yasuhira Yamada, Hisayoshi Endo and Preben
Terndrup Pedersen et al. “Effect of Buffer Bow Structure in
Ship-Ship Collision '' International Journal of Offshore
and Polar Engineering, Vol.18 No.2, 2008, p. 1-9, the calculation method of the above-mentioned limit collision speed will be described according to the following equations (2) to (4). As a calculation condition, as shown in FIG. 3, it is assumed that the collision ship (Vessel B) collides from 90 degrees right in the vicinity of the center of the hull of the stopped collision ship (Vessel A). The parameters for calculating the critical collision speed are as follows.
V _A : Collision ship speed (= 0)
V _B: Collision Ship speed _{M A:} the impacted ship wastewater (including additional water mass)
M _B: Collision Ship wastewater (including additional water mass)
E _s : Energy absorbed by the impacted ship before the end of the collision

  Then, the kinetic energy conservation law and the momentum conservation law are applied immediately before and after the collision. Here, it is assumed that when the vehicle collides at the limit collision speed, the speeds of the two ships after the collision are equal to V ′. Also, it is assumed that there is no rigid rotation of the hull. In such a case, the following formula (2) is derived from the kinetic energy conservation law, and the following formula (3) is derived from the momentum conservation law.

Clear the V 'above equation (2) from equation (3), the following equation (4) is obtained by solving for V _B. Then, E _s in the equation (4) is, in the case of a collision at the limit impact velocity energy E _s which the collision vessel has absorbed other than ship motion until the collision _terminates, when it is _cr, the E _s, the _cr Based on this, the critical collision speed V _{B, cr} is calculated.

In the present invention, in calculating the limit collision speed shown in FIG. 18, the ship to be collided is fixed (M _A = ∞), and the above equation (4) is simplified to the following equation (5) to limit collision. The speed V _{B, cr} is calculated.

  The present invention is useful for a ship in which excellent collision resistance is important in the hull structure.

DESCRIPTION OF SYMBOLS 10 Outer plate 11 Inner plate 12 Stiffener 13 associated with outer plate Stiffener 14 associated with inner plate Transformer 15 Stringer 16 Upper deck 17 Bilge 20 Outer plate 21 Aggregate (stiffener)
22 Upper deck 23 Stiffener 24 Bilge 25 Transformer

Claims (20)

A part of the outer side plate of the ship side part or all the parts of the outer plate satisfy the standard conforming to the unified classification of the International Classification Society (IACS) (Unified Requirements W11 Rev. 8 2014) , and the IACS Uses high-ductility steel sheets with a strength class of 32, 36, or 40 that have been confirmed that the total elongation of 1.4 times or more of the total elongation value stipulated by the unified standard is imposed as a specification and that the specification is satisfied. A hull structure characterized by having a hull structure. Furthermore, it has a hull structure using the high-ductility steel plate in a part of the inner plate facing the outer plate where the high-ductility steel plate is used or in all parts of the inner plate. The hull structure according to claim 1. A part of the inner plate of the ship side part or all the parts of the inner plate satisfy the standard conforming to the unified classification of the International Classification Society (IACS) (Unified Requirements W11 Rev. 8 2014) , and the IACS Uses high-ductility steel sheets with a strength class of 32, 36, or 40 that have been confirmed that the total elongation of 1.4 times or more of the total elongation value stipulated by the unified standard is imposed as a specification and that the specification is satisfied. A hull structure characterized by having a hull structure. Furthermore, it has a hull structure using the high ductility steel plate in a part of the outer plate facing the inner plate in which the high ductility steel plate is used or in all parts of the outer plate. The hull structure according to claim 3. Furthermore, the said high ductility steel plate was used for a part or all of the stiffener accompanying the said site | part in which the said high ductility steel plate was used, The Claim 1 characterized by the above-mentioned. Hull structure. Furthermore, the hull structure as described in any one of Claims 1-5 which used the said high ductility steel plate for a part or all of a stringer. The hull structure according to any one of claims 1 to 6, wherein the high-ductility steel plate is used for part or all of the upper deck. Furthermore, the hull structure as described in any one of Claims 1-7 using the said high ductility steel plate for a part or all of a bilge. Furthermore, the hull structure as described in any one of Claims 1-8 which used the said high ductility steel plate for a part or all of a transformer. The hull structure according to any one of claims 1 to 9, wherein a thickness of the highly ductile steel sheet is more than 12 mm and not more than 50 mm. The hull structure according to any one of claims 1 to 9, wherein a thickness of the highly ductile steel sheet is more than 25 mm and not more than 50 mm. In the outer plate of the ship side, the part that needs to suppress the breakage is specified, and the steel sheet used for the part is in accordance with the unified standard of the International Classification Society (IACS) (Unified Requirements W11 Rev. 8 2014) . A strength class 32 that satisfies a standard that is compliant, is imposed with a total elongation of 1.4 times or more of the total elongation value defined in the unified standard of the IACS , and is confirmed to satisfy the specification ; A hull structure design method using 36 or 40 high-ductility steel sheets. Furthermore, in the inner plate facing the outer plate in which the high ductility steel plate is used, the portion that needs to suppress the fracture is specified, and the high ductility steel plate is used for the steel plate used in the portion. The method for designing a hull structure according to claim 12 . In the inner plate of the ship side part, the site | part which needs to suppress a breakage is specified, and the unified classification (Unified Requirements W11 Rev.8 2014) of the international classification society association (IACS) is used for the steel plate used for the said site | part. A strength class 32 that satisfies a standard that is compliant, is imposed with a total elongation of 1.4 times or more of the total elongation value defined in the unified standard of the IACS , and is confirmed to satisfy the specification ; A hull structure design method using 36 or 40 high-ductility steel sheets. Furthermore, in the outer plate facing the inner plate in which the high ductility steel plate is used, a site where the breakage needs to be suppressed is identified, and the high ductility steel plate is used for the steel plate used for the site. The method for designing a hull structure according to claim 14 . Further, the steel sheet to be used for part or all of the stiffeners associated with the site where the high ductility steel sheet is used, any one of claims 12 to 15, wherein the use of the high-ductility steel sheet one The hull structure design method described in the item. Further, the steel sheet to be used for part or all of the stringer, the design method of the hull structure according to any one of claims 12 to 16, wherein the use of the high ductility steel sheet. The hull structure design method according to any one of claims 12 to 17 , wherein the highly ductile steel plate is used as a steel plate used for a part or all of the upper deck. The hull structure design method according to any one of claims 12 to 18 , wherein the high ductility steel plate is used for a steel plate used for a part or all of a bilge. The hull structure design method according to any one of claims 12 to 19 , wherein the high ductility steel plate is used as a steel plate used for a part or all of a transformer.