Method for improving fatigue in the dome deck area of an lng carrier

Abstract

The application relates to a method for improving fatigue of a LNG ship dome deck area, which comprises a dome deck, an inner deck, a rib plate, a middle longitudinal girder, a flat iron and a T-shaped section, the T-shaped section corresponding to the position of a transverse bulkhead side longitudinal girder and the flat iron above the T-shaped section are replaced by a local longitudinal girder, the upper and lower sides of the local longitudinal girder are connected with the lower end surface of the dome deck and the upper end surface of the inner deck respectively, and the length of each local longitudinal girder is greater than that of the transverse bulkhead side longitudinal girder; each local longitudinal girder and each flat iron are disconnected at the rib plate, and each T-shaped section penetrates through the rib plate at the rib plate. The local longitudinal girder is used to replace part of the T-shaped section and the flat iron, so that the fatigue nodes of the corner area of the connection part of the transverse bulkhead side longitudinal girder and the inner deck at the corresponding position can meet the design requirements.

Description

Technical Field

[0001] This invention relates to the field of ship design and manufacturing, and specifically to a method for improving fatigue in the dome deck area of ​​an LNG carrier. Background Technology

[0002] In LNG carriers, the corners of the bulkhead and deck longitudinal girder exhibit significant fatigue stress due to variations in the size, thickness, and structural strength of the plates and profiles used. This is particularly pronounced in large LNG carriers, such as those exceeding 200,000 cubic meters, where the fatigue stress is even more pronounced. Existing technologies, such as... Figure 1 and Figure 2 As shown, a center longitudinal girder is located between the dome deck and the inner deck, positioned along the ship's centerline. Several parallel flat steel bars are installed below the dome deck on either side of the center longitudinal girder. T-shaped profiles are installed above the inner deck on either side of the center longitudinal girder, corresponding to these flat steel bars. Transverse bulkheads are located below the inner deck. The intersection of the transverse bulkheads and the inner deck, i.e., the corner area, is where the transverse bulkhead's center longitudinal girder corresponds to the center longitudinal girder. Side longitudinal girder sections are installed on either side of the center longitudinal girder, corresponding to the T-shaped profiles above. Due to the different specifications and strengths of the side longitudinal girder sections and the T-shaped profiles—one being plate material and the other a profile—the welding points are prone to generating significant fatigue stress, which does not meet shipbuilding requirements. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for improving fatigue in the dome deck area of ​​an LNG ship. By modifying the structure, the problem of high fatigue stress in the corner areas is solved.

[0004] The technical objective of this invention is achieved through the following technical solution:

[0005] A method for improving fatigue in the dome deck area of ​​an LNG carrier includes a central longitudinal girder between the dome deck and the inner deck, with its upper and lower sides connecting the lower end face of the dome deck and the upper end face of the inner deck, respectively; several flat irons are installed parallel to the central longitudinal girder on the lower end face of the dome deck on both sides of the central longitudinal girder, and several T-shaped profiles are installed parallel to the central longitudinal girder on the upper end face of the inner deck on both sides of the central longitudinal girder, with the flat irons and T-shaped profiles corresponding one-to-one; several parallel ribs are installed along a direction perpendicular to the central longitudinal girder; and a transverse bulkhead is installed below the inner deck. The transverse bulkhead includes the central longitudinal girder and the side longitudinal girder. The central longitudinal girder corresponds to the central longitudinal girder, and the side longitudinal girder corresponds to the T-shaped profile. The T-shaped profile and the flat iron above the T-shaped profile at the corresponding position of the side longitudinal girder are replaced with partial longitudinal girder. The upper and lower sides of the partial longitudinal girder are connected to the lower end face of the dome deck and the upper end face of the inner deck, respectively. The length of each partial longitudinal girder is greater than the length of the side longitudinal girder. Each partial longitudinal girder and each flat iron is broken at the rib plate, and each T-shaped profile passes through the rib plate.

[0006] Furthermore, the thickness of the flat iron is a, 25mm≤a≤40mm; the thickness of the local longitudinal girder is b, 10mm≤b≤15mm.

[0007] Furthermore, each end of a partial longitudinal girder terminates at one side of a rib plate. On the other side of the rib plate at the end of the partial longitudinal girder, triangular elbow plates are installed between the angle between the flat iron and the rib plate and between the T-profile and the rib plate. The thickness of the triangular elbow plate is thinner than the thickness of the flat iron.

[0008] Furthermore, the thickness of the triangular elbow plate is half the thickness of the flat iron.

[0009] Furthermore, at the rib plate at the end of the local longitudinal girder, an insert plate is embedded and installed. The thickness of the insert plate is greater than the thickness of the local longitudinal girder, and the insert plate extends downward from the dome deck beyond the triangular elbow plate between the flat iron and the rib plate.

[0010] Furthermore, the thickness of the insertion plate is d, where 15mm < d ≤ 20mm.

[0011] Furthermore, the insert plate is rectangular. When installing the insert plate, the corners where the partial longitudinal girder connects the dome deck and the rib plate are cut off to form rectangular holes, and then the insert plate is embedded and welded into the rectangular holes.

[0012] Furthermore, a transition bevel is provided at the position where the insert plate connects with the local longitudinal girder, and the transition bevel is a Y-shaped bevel.

[0013] Furthermore, the bevel length of the transition bevel is 4*(db)mm.

[0014] Furthermore, the flat iron, partial longitudinal girder, triangular elbow plate, and insert plate are aligned on one side, and the thickness of the flat iron, insert plate, triangular elbow plate, and partial longitudinal girder decreases sequentially.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. This invention replaces part of the T-shaped steel and flat iron with partial longitudinal girder, so that the fatigue nodes in the corner area where the transverse bulkhead side longitudinal girder connects to the inner deck meet the design requirements.

[0017] 2. By using triangular elbow plates and insert plates, this invention avoids new node fatigue problems caused by the thickness difference between the flat iron and the local longitudinal girder due to the introduction of local longitudinal girder. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structural layout of the original LNG ship dome deck area.

[0019] Figure 2This is a schematic diagram of the original transverse bulkhead side longitudinal girder and inner deck connection.

[0020] Figure 3 This is a top view of the dome deck area of ​​the LNG ship in this invention.

[0021] Figure 4 yes Figure 3 AA view.

[0022] Figure 5 This is a schematic diagram showing the position of the ribs at the ends of the longitudinal girder in the dome deck area of ​​an LNG ship in this invention.

[0023] Figure 6 This is a three-dimensional schematic diagram of the dome deck area structure of the LNG ship in this invention.

[0024] Figure 7 This is a schematic diagram of the transition bevel setting of the insertion plate in this invention.

[0025] Figure 8 This is a schematic diagram showing the alignment of the flat iron, triangular elbow plate, insert plate, and partial longitudinal girder in this invention.

[0026] In the diagram, 1. Dome deck; 2. Flat steel; 3. Inner deck; 4. T-shaped profile; 5. Central longitudinal girder; 6. Partial longitudinal girder; 7. Triangular elbow plate; 8. Insert plate; 9. Transition bevel; 10. Central longitudinal girder of transverse bulkhead; 11. Side longitudinal girder of transverse bulkhead; 12. Rib plate. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments:

[0028] The original structural design of the dome deck area of ​​the LNG ship is as follows: Figure 1 and Figure 2 As shown,

[0029] A central longitudinal girder 5 is installed between the dome deck 1 and the inner deck 3. The central longitudinal girder 5 is located at the centerline of the hull and is a plate structure. Several parallel flat irons 2 are installed below the dome deck 1 on both sides of the central longitudinal girder 5. T-shaped profiles 4 are installed above the inner deck 3 on both sides of the central longitudinal girder 5, corresponding to the flat irons 2. A transverse bulkhead is installed below the inner deck 3. The intersection of the transverse bulkhead and the inner deck is also the corner area. On both sides of the central longitudinal girder 10 of the transverse bulkhead, corresponding to the T-shaped profiles 4 above, transverse bulkhead side longitudinal girders 11 are installed. The transverse bulkhead side longitudinal girders are plate structures, and the T-shaped profiles are profiles. Due to the differences in specifications and structural types of the transverse bulkhead side longitudinal girders and T-shaped profiles, the corner area between the transverse bulkhead and the inner deck has a large fatigue stress.

[0030] Based on this, the present invention provides a method for improving fatigue in the dome deck area of ​​an LNG carrier, such as... Figures 3-6As shown, a central longitudinal girder 5 is provided between the dome deck 1 and the inner deck 3. The upper and lower sides of the central longitudinal girder 5 are respectively connected to the lower end face of the dome deck 1 and the upper end face of the inner deck 3. Several flat irons 2 are provided parallel to the central longitudinal girder 5 on the lower end face of the dome deck on both sides of the central longitudinal girder 5. Several T-shaped profiles 4 are provided parallel to the central longitudinal girder 5 on the upper end face of the inner deck on both sides of the central longitudinal girder 5. The flat irons 2 and T-shaped profiles 4 correspond one-to-one. Several parallel ribs 12 are provided along the direction perpendicular to the central longitudinal girder 5. Along the length direction of the flat irons 2, each flat iron 2 includes several sections of flat iron. The flat irons 2 have a cut-off end at the position of the rib 12. The T-shaped profiles 4 are continuous structures, and each T-shaped profile 4 continuously passes through several ribs 12.

[0031] A transverse bulkhead is provided below the inner deck 3. The transverse bulkhead includes a central longitudinal girder 10 and side longitudinal girder 11. The central longitudinal girder 10 corresponds to the central longitudinal girder 5, and the side longitudinal girder 11 corresponds to the T-shaped profile 4. Considering that the strength of the T-shaped profile is lower than that of the side longitudinal girder 11, it is not necessary to provide the side longitudinal girder 11 for every T-shaped profile. Instead, the side longitudinal girder 11 can be provided every other T-shaped profile. The T-shaped profile 4 and the flat iron 2 above the T-shaped profile at the corresponding side longitudinal girder 11 position can be replaced with a partial longitudinal girder 6. The upper and lower sides of the partial longitudinal girder 6 are connected to the lower end face of the dome deck 1 and the upper end face of the inner deck 3, respectively. The length of each partial longitudinal girder 6 is greater than the length of the side longitudinal girder 11. The partial longitudinal girder 6 breaks at the position where it encounters the rib plate 12 to form a cut-off end.

[0032] In one embodiment, the thickness of the dome deck 1 is greater than 30mm to ensure overall strength, the thickness of the flat iron is a, 25mm≤a≤40mm; the thickness of the local longitudinal girder is b, 10mm≤b≤15mm.

[0033] In one embodiment, due to the difference in thickness between the local longitudinal girder and the flat iron, the addition of the local longitudinal girder leads to fatigue nodes at the intersections of the flat irons on both sides of the rib plate and the local longitudinal girder with the rib plate. Based on this, triangular elbow plates 7 are installed on the opposite side of the rib plate at the end of the local longitudinal girder, between the angle between the flat iron 2 and the rib plate 12, and between the T-profile 4 and the rib plate 12. The thickness of the triangular elbow plate 7 is thinner than the thickness of the flat iron 2, and the triangular elbow plate 7 is a right triangle. Through-weld holes are provided in the triangular elbow plate 7 at the angle between the rib plate 12 and the flat iron 2. The triangular elbow plate 7 allows for a better transition from the flat iron 2 to the local longitudinal girder 6, reducing misalignment and fatigue problems caused by the difference in plate thickness.

[0034] Preferably, the thickness of the triangular elbow plate is half the thickness of the flat iron.

[0035] Preferably, an insert plate 8 is embedded at the rib plate 12 at the end of the partial longitudinal girder 6. The thickness of the insert plate 8 is greater than the thickness of the partial longitudinal girder 6. The insert plate 8 extends downward from the dome deck 1 beyond the triangular elbow plate 7 between the flat iron 7 and the rib plate 12. In one embodiment, the thickness of the insert plate 8 is d, where 15mm < d ≤ 20mm.

[0036] The insert plate 8 is rectangular. When installing the insert plate 8, the corner where the partial longitudinal girder 6 connects the dome deck 1 and the rib plate 12 is cut off to form a rectangular hole. Then, the insert plate 8 is embedded and welded into the rectangular hole. A transition bevel 9 is provided at the junction of the insert plate 8 and the partial longitudinal girder 6. Figure 7 As shown, a welding bevel is provided at the welding position between the insert plate 8 and the partial longitudinal girder 6. A transition bevel 9 is used to transition to the welding position. The transition bevel 9 can also reduce the stress concentration problem caused by the difference in plate thickness. The transition bevel is a Y-shaped bevel. Preferably, the bevel length L of the transition bevel is 4*(db)mm.

[0037] Preferably, the insert plate 8 has a rounded corner at the opposite angle of the angle between the dome deck 1 and the rib plate 12, with a rounded corner radius R of 100mm.

[0038] In one embodiment, such as Figure 8 As shown, the flat iron 2, the partial longitudinal girder 6, the triangular elbow plate 7, and the insert plate 8 are aligned on one side, and the thickness of the flat iron 2, the insert plate 8, the triangular elbow plate 7, and the partial longitudinal girder 6 decreases sequentially.

[0039] This embodiment is merely a further explanation of the present invention and is not intended to limit the present invention. Those skilled in the art can make non-inventive modifications to this embodiment as needed after reading this specification, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for improving fatigue in the dome deck area of ​​an LNG carrier, characterized in that, A central longitudinal girder is installed between the dome deck and the inner deck, with its upper and lower sides connecting the lower end face of the dome deck and the upper end face of the inner deck, respectively. Several flat irons are installed parallel to the central longitudinal girder on the lower end face of the dome deck on both sides of the central longitudinal girder, and several T-shaped profiles are installed parallel to the central longitudinal girder on the upper end face of the inner deck on both sides of the central longitudinal girder, with the flat irons and T-shaped profiles corresponding one-to-one. Several parallel ribs are installed along a direction perpendicular to the central longitudinal girder. A transverse bulkhead is installed below the inner deck, and the transverse bulkhead includes a... Longitudinal girder and transverse bulkhead side longitudinal girder; transverse bulkhead middle longitudinal girder is set with corresponding middle longitudinal girder, and transverse bulkhead side longitudinal girder is set with corresponding T-shaped profiles; replace the T-shaped profiles and the flat iron above the T-shaped profiles at the corresponding transverse bulkhead side longitudinal girder positions with partial longitudinal girder, the upper and lower sides of the partial longitudinal girder are respectively connected to the lower end face of the dome deck and the upper end face of the inner deck, and the length of each partial longitudinal girder is greater than the length of the transverse bulkhead side longitudinal girder; each partial longitudinal girder and each flat iron is broken at the rib plate, and each T-shaped profile penetrates the rib plate at the rib plate.

2. The method for improving fatigue in the dome deck area of ​​an LNG carrier according to claim 1, characterized in that, The thickness of the flat iron is a, 25mm≤a≤40mm; the thickness of the partial longitudinal girder is b, 10mm≤b≤15mm.

3. The method for improving fatigue in the dome deck area of ​​an LNG ship according to claim 2, characterized in that, Each section of the local longitudinal girder terminates at one end of the rib plate. On the other side of the rib plate at the end of the local longitudinal girder, triangular elbow plates are installed between the angle between the flat iron and the rib plate and between the T-profile and the rib plate. The thickness of the triangular elbow plate is thinner than the thickness of the flat iron.

4. The method for improving fatigue in the dome deck area of ​​an LNG carrier according to claim 3, characterized in that, The thickness of the triangular elbow plate is half the thickness of the flat iron.

5. A method for improving fatigue in the dome deck area of ​​an LNG carrier according to claim 3, characterized in that, At the end of the partial longitudinal girder, an insert plate is embedded in the rib plate. The thickness of the insert plate is greater than the thickness of the partial longitudinal girder. The insert plate extends downward from the dome deck beyond the triangular elbow plate between the flat iron and the rib plate.

6. The method for improving fatigue in the dome deck area of ​​an LNG carrier according to claim 5, characterized in that, The thickness of the insertion plate is d, where 15mm < d ≤ 20mm.

7. A method for improving fatigue in the dome deck area of ​​an LNG carrier according to claim 6, characterized in that, The insert plate is rectangular. When installing the insert plate, the corners where the dome deck and rib plate are connected by the longitudinal girder are cut off to form a rectangular hole, and then the insert plate is embedded and welded into the rectangular hole.

8. A method for improving fatigue in the dome deck area of ​​an LNG carrier according to claim 7, characterized in that, A transition bevel is provided at the position where the insert plate connects to the local longitudinal girder. The transition bevel is a Y-shaped bevel.

9. A method for improving fatigue in the dome deck area of ​​an LNG carrier according to claim 8, characterized in that, The bevel length of the transition bevel is mm.

10. A method for improving fatigue in the dome deck area of ​​an LNG carrier according to claim 5, characterized in that, The flat iron, partial longitudinal girder, triangular elbow plate, and insert plate are aligned on one side, and the thickness of the flat iron, insert plate, triangular elbow plate, and partial longitudinal girder decreases in sequence.

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