JP2010023573A - Cargo liquid transport ship - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To loosen a stress of a mounting portion of an upper deck and a tank cover accompanied with a vertical bending load. <P>SOLUTION: A part of a cargo liquid tank projects via an opening 9 of an upper deck 8, and a tank cover is supported at an opening edge 12 of the upper deck 8 to cover a projecting portion of the cargo liquid tank. A ship width direction end of the opening edge 12 is constituted into a soft structure 8a having flexibility in a perpendicular direction. By such a constitution, a stress generated at the ship width direction end in a bottom part of the cover tank is absorbed by flexion of the opening edge 12, and the opening edge 12 takes charge of part of the stress. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cargo transportation ship equipped with a cargo fluid tank.

  A ship that transports cargo such as LNG is provided with a plurality of holds that are partitioned by vertical and horizontal bulkheads (vertical bulkheads and horizontal bulkheads) that form a hull, and a cargo liquid tank is mounted therein. When an independent spherical tank is mounted, a part of the tank is disposed so as to protrude upward from the upper deck through a substantially circular opening formed in the upper deck. The lower edge of a substantially hemispherical tank cover that covers the protruding portion of the tank is welded to the opening edge of the upper deck. Many brackets for supporting the weight of the tank cover (about 500 tons) are arranged on the lower surface side of the upper deck, and these brackets are connected to the vertical and horizontal bulkheads.

A large vertical stress is generated at the joint between the tank cover and the upper deck when vertical bending due to sagging or hogging acts on the hull. In particular, the stress tends to be concentrated at the end in the ship width direction or the end in the length direction of the joint portion, and the fatigue strength tends to be severe. Conventionally, methods such as increasing the number of brackets or locally increasing the thickness of the lower portion of the tank cover (see, for example, Patent Document 1) have been proposed in order to ensure fatigue strength around the joint portion.
JP 2005-96551 A

  However, if the number of brackets is increased as in the past, the hull weight and cost may increase, and the placement density of the brackets below the upper deck may increase and workability around the tank may deteriorate. is there. Further, when the tank cover is locally thickened, only the thickened portion becomes rigid, and conversely, the shared load acting on this portion increases. That is, there is a limit to the stress relaxation effect by stiffening the tank cover structure including an increase in plate thickness, and the stress cannot be relaxed beyond the limit. In addition, when such a thickened portion is locally formed, the manufacturing process of the tank cover becomes very complicated, and the hull weight increases.

  In view of this, an object of the present invention is to alleviate the stress at the joint portion between the upper deck and the tank cover accompanying the vertical bending of the hull, thereby improving the fatigue strength.

  In order to achieve the above object, a cargo carrier according to the present invention includes a tank cover in which a part of a cargo tank is protruded through an opening of an upper deck, and an opening edge of the upper deck covers the protruding portion of the cargo tank. And the upper deck at the end in the width direction of the opening edge is configured to have a flexible structure having flexibility in the vertical direction.

  According to such a configuration, the stress generated at the end in the ship width direction in the lower portion of the tank cover is absorbed by the deflection of the opening edge, and the opening edge shares the stress. As a result, the stress concentration generated at the end in the ship width direction in the joint between the upper deck and the tank cover is alleviated, and the fatigue strength is improved.

  The liquid tank may be disposed between vertical and horizontal bulkheads joined to the upper deck, and the upper deck at the end in the width direction of the opening edge may be cantilevered with respect to the bulkhead. . According to this configuration, it is possible to easily realize the flexible structure on the upper deck.

  A plurality of brackets are provided between the partition wall and the opening edge, and the arrangement density of the brackets in the vicinity of the ship width direction end of the opening edge is determined by the bracket at the ship edge direction end of the opening edge. It may be sparse with respect to the arrangement density. According to this configuration, the number of brackets is reduced, the hull weight and cost can be reduced, and workability around the tank is improved.

  It is preferable that the bracket is provided from a position where the maximum stress value generated at the opening edge portion of the upper deck and the maximum stress value generated at the tank cover are substantially the same to an end portion in the ship length direction. According to such a configuration, the load generated in the hull is shared between the upper deck and the tank cover in a balanced manner, and as a result, the fatigue strength of the entire upper deck and the tank cover is improved.

  As described above, according to the present invention, the stress concentration generated in the joint portion between the upper deck and the tank cover can be relaxed, so that the fatigue strength of the joint portion is improved. As a result, the service life of the cargo transportation ship can be improved, and the operation period in a navigating environment severe in fatigue such as in a cold region or a sea area where waves are large can be extended.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 (a) is a side view of a cargo liquid carrier 1 according to the present invention, and FIG. 1 (b) is a plan view thereof. As shown in FIGS. 1 (a) and 1 (b), the hull 2 of the cargo liquid carrier 1 is equipped with a plurality of cargo liquid tanks 3 arranged in the direction of the captain, and the cargo liquid tank 3 is represented by LNG and LPG. The cargo liquid such as liquefied gas is stored. Each cargo tank 3 is formed in an independent spherical shape and is accommodated in a hold 4 of the hull 2. The hold 4 is partitioned by a pair of longitudinal bulkheads 6 extending in the ship length direction inside the ship side skin 5 and a horizontal bulkhead (including a bulkhead for convenience) 7 extending between the longitudinal bulkheads 6 in the ship width direction. Is formed. A part of the liquid tank 3 accommodated in the hold 4 protrudes upward through a circular opening 9 (see FIG. 2) formed in the upper deck 8. The upper deck 8 is provided with a substantially hemispherical tank cover 10 that covers the protruding portion of the cargo tank 3.

  FIG. 2 is a cross-sectional view taken along line II-II in FIGS. 1 (a) and 1 (b). The liquid tank 3 is supported on the hull 2 side by a cylindrical skirt 11. The upper deck 8 extends inward in the left-right direction with respect to the longitudinal partition wall 6, and the opening 9 is formed in the extending portion. The tank cover 10 is formed by connecting a cylindrical body plate 14 to the lower end edge of a hemispherical spherical shell 13. The tank cover 10 is made of steel, and its weight is about 500 tons. The lower end portion of the body plate 14 is fixed to the opening edge portion 12 of the upper deck 8 by welding. A weld line 15 (see FIG. 4) between the tank cover 10 and the upper deck 8 extends in a circular shape on the upper deck 8 along the inner and outer peripheral surfaces of the trunk plate 14.

  FIG. 3 is a schematic view showing the hull structure in plan view. In the following drawings, illustration of the tank is omitted for convenience of explanation. As shown in FIG. 3, a hold forming wall 81 is arranged between the longitudinal partition walls 6 so as to sandwich the transverse partition wall 7 in the ship length direction. The hold forming wall 81 is connected to the longitudinal partition wall 6 and extends inward in the width direction of the ship so as to be along the arc of the opening 9 between the pair of base end portions 82 and 83. And a curved portion 84 that extends. The curved portion 84 is composed of a plurality of flat plates, and the planar shape of the curved portion 84 approximates to the arc of the opening 9 by connecting these flat plates. In this way, the hull 2 is provided with the hold forming wall 81 together with the horizontal bulkhead 7 as one of the bulkheads extending in the lateral direction between the pair of longitudinal bulkheads 6.

  The hold 4 that accommodates the tank 3 is not partitioned from the adjacent hold 4 via one horizontal partition. This hold 4 is partitioned from the adjacent hold 4 via two hold forming walls 81. That is, the hold forming wall 81 disposed immediately below the opening 9 for projecting the tank 3 accommodated therein, and the opening 9 for projecting the tank 3 accommodated in the adjacent hold 4 upward. It is partitioned from the adjacent hold 4 through the arranged hold forming wall 81.

  Between the longitudinal partition wall 6 and the opening edge portion 12 of the upper deck 8 and between the horizontal partition wall 7 and the opening edge portion 12, a bracket having a T-shape in a plan view including a proximal end bracket 21 and a distal end bracket 22. A plurality of members 20 are provided.

  In FIG. 4, the bracket member provided in the vicinity of the position P2 in FIG. 3 among these bracket members 20 is illustrated. Referring to FIGS. 3 and 4, focusing on the bracket member provided between the longitudinal partition wall 6 and the opening edge portion 12, the proximal bracket 21 includes the left and right inner surfaces of the longitudinal partition wall 6 and the opening of the upper deck 8. It is joined to the lower surface of the edge 12 and is formed in a substantially trapezoidal shape with the longitudinal partition wall 6 side having a long side. The proximal end bracket 21 extends in parallel with the horizontal partition wall 7, and the distal end forming a trapezoidal short side reaches just below the opening 9. The distal end bracket 22 is joined to the distal end of the proximal end bracket 21 and the lower surface of the opening edge portion 12, and extends in the tangential direction or the circumferential direction of the opening 9. Returning to FIG. 3, paying attention to the bracket member 20 provided between the horizontal partition wall 7 and the opening edge portion 12, the proximal bracket 21 is similar to the above in that the left and right inner surfaces of the horizontal partition wall 7 and the opening edge of the upper deck 8. It is joined to the lower surface of the part 12 and extends parallel to the longitudinal partition wall 6. The distal end bracket 22 is joined to the distal end of the proximal end bracket 21 in the same manner as described above. By providing the plurality of bracket members 20, the weight of the tank cover 10 (see FIG. 1 and the like) is supported on the upper deck 8.

  Conventionally, the bracket member 20 is provided so that the front end bracket 22 is evenly stretched in the circumferential direction of the opening 9, thereby ensuring the rigidity of the opening edge 12 of the upper deck 8. On the other hand, in the present embodiment, as shown in the drawing, no bracket member is provided at the end portion in the ship width direction, and the arrangement density of the bracket members at the end portion in the ship width direction is made sparser than the end portion in the ship length direction.

  FIG. 5 is a cross-sectional view of the hull taken along line VV shown in FIG. 6 is a cross-sectional view of the hull taken along line VI-VI shown in FIG. As shown in FIGS. 4 and 5, the front end bracket 22 of the bracket member 20 is intermittently arranged directly below the opening 9 along the circumferential direction from the ship length direction end P3 to the ship width direction end P1. Yes. Since the bracket member is not provided between the predetermined circumferential positions P2, the opening edge 12 of the upper deck 8 is not restrained in the vertical direction. That is, the end in the ship width direction of the opening edge 12 is a cantilever in which the end on the ship side outer plate 5 side is a fixed end supported by the longitudinal partition wall 6 and the end on the opening 9 side is a free end. It has a beam-like structure (see FIG. 6). Thus, the ship width direction end part of the opening edge part 12 comprises the flexible structure 8a (refer cross hatch area | region in FIG. 3, FIG. 5) which can be elastically deformed largely in the perpendicular direction compared with the circumference | surroundings.

  In this way, by configuring the flexible structure 8a without providing the bracket member 20 at the end in the width direction of the ship, when a longitudinal bending load is applied to the hull, the portion constituting the flexible structure 8a of the upper deck 8 is The load that bends in the vertical direction and acts on the tank cover 10 side is shared by the upper deck 8 side.

  Here, the stress generated in the upper deck 8 and the tank cover 10 when a vertical bending is applied to the model hull will be described with reference to FIGS. 7 to 9 with reference to FIGS.

  FIG. 7 is a graph for explaining the amount of vertical deflection of the upper deck 8 of the load carrier 1 according to the present invention, and FIG. 8 shows the stress generated on the trunk plate 14 of the tank cover 10 of the load carrier 1 according to the present invention. FIG. 9 is a graph for explaining the stress generated at the junction between the upper deck 8 of the load carrier 1 according to the present invention and the longitudinal bulkhead 6. The horizontal axis in FIGS. 7 to 9 indicates the circumferential position [deg] of the edge of the opening 9 in which the ship width direction end P1 (see FIG. 3) is 0 deg and the ship length direction end P3 (see FIG. 3) is 90 deg. Yes. The position P2 (see FIGS. 3, 8, and 9) is a predetermined circumferential position (θdeg) between P1 and P3, but is a circumferential position where the bracket member 20 starts to be provided, and the flexible structure 8a It is the limit position of the range to configure. In addition, P4 (refer FIG. 3, FIG. 7) is the circumferential direction position which becomes 45deg.

  Further, the vertical axis in FIG. 7 represents the amount of deflection [m] in the vertical direction of the upper deck 8, and the vertical axis in FIG. 8 represents the stress value generated at the ship width direction end P 1 of the tank cover 10 in the conventional structure as 1. The stress ratio and the vertical axis of FIG. 9 indicate the stress ratios representing the stress value generated at the ship width direction end P1 of the upper deck 8 as 1 in this embodiment. In addition, the stress value represented as the stress ratio 1 in FIG. 8 (that is, the stress value generated at the ship width direction end P1 of the tank cover 10 in the conventional structure) is the stress represented as the stress ratio 1 in FIG. It is about twice the value (that is, the stress value generated at the ship width direction end P1 of the upper deck 8 in this embodiment).

  In the conventional structure represented by the two-dot chain line Z1-Z3 in FIGS. 7 to 9, since the bracket member is evenly stretched in the circumferential direction as described above, the deflection amount of the upper deck 8 is related to the circumferential position. It is small (see Z1 in FIG. 7). Therefore, although the stress generated on the upper deck 8 side is small regardless of the circumferential position (see Z3 in FIG. 9), a large stress is generated at the ship width direction end P1 on the tank cover 10 side. It can be seen that the stress greatly decreases toward P3 (see Z2 in FIG. 8). As described above, in the conventional structure, the stress is concentrated at the ship width direction end P1 on the tank cover 10 side, so that the fatigue strength around the ship width direction end P1 is particularly severe.

  On the other hand, in the embodiment of the present invention represented by the solid line A1-A3 in FIGS. 7 to 9, the ship width direction end portion of the upper deck 8 forms the flexible structure 8a as described above. The amount of vertical deflection increases between P1 and the position P2 where the bracket member 20 is provided (see A1 in FIG. 7). Note that the amount of deflection changes so as to gradually decrease from the ship width direction end P1 toward the ship length direction end P2.

  Due to this increase in the amount of deflection, the stress (compression) generated at the ship width direction end P1 of the upper deck 8 is larger (about twice) than the conventional structure (see A3 in FIG. 9). However, since the upper deck 8 side shares the stress in this way, the stress (compression) generated at the ship width direction end P1 of the tank cover 10 is greatly reduced (about 0.15 times) (A2 in FIG. 8). reference).

  Since the flexible structure 8a is lost at the position P2 at which the bracket member 20 starts to be provided, the stress value is higher than that at the ship width direction end P1. The stress generated at the position P2 is higher than the stress value generated at the same position in the conventional structure, but the amount of increase is small. That is, the stress generated at the position P2 is smaller than the maximum stress value in the conventional structure (about 0.5 times).

  The shape of the tank cover 10 is hemispherical and has the property of maintaining the shape. Due to the nature of the tank cover 10, the stress concentrated on the ship width direction end P1 does not flow to the ship length direction end P2 as it is, and the tank cover 10 works to share the stress in a balanced manner over the entire circumference.

  As a result, the stress generated in the tank cover 10 is substantially constant regardless of the circumferential position as compared with the conventional structure. In addition, the stress value generated in the tank cover 10 and the upper deck 8 of the present embodiment is lower than the maximum stress value generated at the ship width direction end P1 of the tank cover 10 in the conventional structure at any circumferential position. Become.

  As described above, in the present embodiment, the end portion in the ship width direction of the opening edge 12 of the upper deck 8 has the flexible structure 8a, so that the fatigue strength of the tank cover 10 and the upper deck 8 as a whole is compared with the conventional case. Can be improved. In addition, since the flexible structure 8a is realized by omitting the bracket member, the tank cover 10 and other structures are not complicated. In addition, the weight of the tank cover 10 and the like is not increased to relieve stress, and an increase in hull weight and cost can be reduced.

  The position P2 (θ [deg]) at which the bracket member 20 starts to be provided can be changed as appropriate. By setting the position P2 on the ship length direction side (that is, by increasing θ), the region forming the flexible structure 8a is set. It is also possible to increase the amount of deflection of the upper deck 8 and share a larger stress on the upper deck 8 side. The stress generated on the upper deck 8 side can be set by the amount of deflection in this way, but this amount of deflection is not limited to the position P2, but the opening edge portion 12 having a cantilever shape shown in FIG. This also varies depending on the distance L from the longitudinal partition wall 6 to the opening 9. Therefore, this position P2 can be appropriately set according to the amount of load to be shared by the upper deck 8 and the distance L.

  At this time, it is preferable that the stress on the upper deck 8 side is not excessively increased so that the fatigue strength of the upper deck 8 does not become severe. For example, the position P2 may be set at a position where the maximum stress value generated on the upper deck 8 side and the maximum stress value generated on the tank cover 10 side are substantially the same. 8 and 9, the maximum stress value generated on the tank cover 10 side (see position P2 in FIG. 8) is the maximum stress value generated on the upper deck 8 side (see position P1 in FIG. 9). The values are almost equal. As a result, the load generated in the hull 2 is shared between the upper deck 8 and the tank cover 10 in a balanced manner, and as a result, the fatigue strength of the upper deck 8 and the tank cover 10 as a whole can be improved. .

  The present invention is widely applicable to a cargo liquid carrier ship provided with a tank cover, and can be suitably applied to a cargo liquid carrier ship provided with an independent spherical liquid tank.

(A) is a side view of the cargo transportation ship concerning the present invention, and (b) is the top view. It is sectional drawing shown along the II-II line | wire shown to Fig.1 (a) and (b). 1 is a plan view schematically showing a part of a hull structure of a cargo liquid carrier according to the present invention. It is a perspective view which shows the opening periphery of the upper deck of the cargo liquid carrier which concerns on this invention. It is sectional drawing shown along the VV line shown in FIG. It is sectional drawing shown along the VI-VI line shown in FIG. It is a graph explaining the amount of deflection of the vertical direction of the upper deck of the cargo transportation ship concerning the present invention. It is a graph explaining the stress which generate | occur | produces at the tank cover side of the cargo / liquid carrier ship which concerns on this invention. It is a graph explaining the stress which generate | occur | produces on the upper deck side of the cargo liquid carrier which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Load liquid carrier 2 Hull 3 Tank 5 Ship side outer plate 6 Longitudinal bulkhead 7 Horizontal bulkhead 8 Upper deck 9 Opening 10 Tank cover 12 Opening edge 20 Bracket member 81 Hold formation wall

Claims (4)

  A part of the cargo tank protrudes through the opening of the upper deck, and a tank cover that covers the protruding part of the cargo tank is joined to the opening edge of the upper deck. A cargo carrier carrying an upper deck having a flexible structure having flexibility in a vertical direction.   The cargo tank is disposed between vertical and horizontal bulkheads joined to the upper deck, and the upper deck at the edge of the opening edge in the ship width direction has a cantilever shape with respect to the bulkhead. The cargo transportation ship according to claim 1.   A plurality of brackets are provided between the partition wall and the opening edge, and the arrangement density of the brackets in the vicinity of the ship width direction end of the opening edge is determined by the bracket at the ship edge direction end of the opening edge. The cargo transportation ship according to claim 2, wherein the ship is sparse with respect to the arrangement density. The bracket is provided from a position where the maximum stress value generated in the opening edge portion of the upper deck and the maximum stress value generated in the tank cover are substantially the same to an end portion in the ship length direction. Item 4. The cargo transportation ship according to any one of Items 1 to 3.

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