An intermittent cross-brace structure for a high sea state high speed semi-submersible platform

Abstract

The application relates to an intermittent cross brace structure for a high-sea-condition high-speed semi-submersible platform, which comprises a cross brace and a high-strength cable, the cross brace is divided into two sections and is disconnected at a middle position of the semi-submersible platform, a collision-preventing and misalignment matching structure is arranged at the disconnected position, the two sections of the cross brace are connected by the high-strength cable to bear axial tensile load, and a cross brace end elbow is arranged at a connecting position of the cross brace and a column of the semi-submersible platform to provide transition. The intermittent cross brace structure for the high-sea-condition high-speed semi-submersible platform can effectively reduce stress concentration on the cross brace, and compared with a current continuous cross brace structure, can greatly reduce stress concentration of the cross brace caused by overall large deformation of the platform in the case of high-sea-condition large deformation, and provides a possibility for design of the semi-submersible platform under large-size high-sea conditions.

Description

Technical Field

[0001] This invention relates to a cross bracing structure for a semi-submersible platform, belonging to the field of semi-submersible platforms in marine engineering. Background Technology

[0002] With the increasing demand for deep-sea oil and gas mining and the growing desire for exploration of the deep-sea environment, the design of various marine structures suitable for harsh deep-sea environments has become increasingly important. As the size of marine engineering structures continues to increase and the severity of extreme marine environmental conditions required for design further improves, the challenges to the strength of marine structures themselves are also increasing exponentially.

[0003] A semi-submersible platform is a device that extracts crude oil or natural gas from the seabed in a semi-submerged state. It has the advantage of good resistance to wind and waves and is currently one of the most widely used oil drilling platforms in offshore drilling. Semi-submersible platforms are mostly integrated processing platforms, with a working deck on top and a floating structure below, connected by support columns.

[0004] Typically, the cross bracing structure of a semi-submersible platform serves to connect the platform's submersible body and the vertical supports, primarily resisting lateral separation forces generated during movement in waves. The cross bracing structure of a semi-submersible platform is usually a cylindrical hull (e.g., Haiyang Shiyou 982) or an oval cylindrical hull (e.g., Haiyang Shiyou 981). Its cross-section generally remains constant throughout its length. There are usually one or two cross braces between every two vertical supports, selected according to specific requirements.

[0005] This type of cross bracing structure is generally sufficient for conventional platform use. However, with the increasing size of offshore platforms and the harsher environments they face, the overall wave load level and deformation of the structure have significantly increased. This leads to large deformations in the cross bracing. The uniform cross-section of the cross bracing structure cannot distribute the deformation evenly. When the overall torsional deformation of the platform is large, stress concentration occurs at the ends of the cross bracing, which should not bear large torsional and shear stresses, causing damage to the entire structure. (See below.) Figure 1 The figure shows the stress distribution of a conventional cross-bracing structure under large deformation. It can be clearly seen that the stress is concentrated at both ends, while the stress level in the middle of the cross-bracing is lower.

[0006] The key issue is that this stress concentration is caused by overall deformation, and whether the cross braces are thickened or not does not affect the total deformation of the entire platform. Therefore, thickening the cross braces cannot effectively reduce the excessive stress on them. The stiffness provided by the cross braces relative to the platform's deck box is very small and cannot reduce overall deformation. Therefore, the amount of deformation within the entire cross brace range remains essentially unchanged regardless of the cross brace's thickness and size. This means that neither thickening nor increasing the girth of the cross braces can solve the problem.

[0007] Existing cross bracing designs are typically continuous structural members, with the cross-sectional shape remaining largely unchanged along the entire length. This type of cross bracing is sufficient for small platforms or platforms operating in relatively conservative sea states. However, for large offshore platforms operating in high sea states, the overall structural deformation is very large, and the stiffness settings of this type of cross bracing often cannot effectively eliminate stress concentration under large deformation. Therefore, this invention proposes a novel discontinuous cross bracing structure that can be used in the structure of large semi-submersible platforms operating in high sea states.

[0008] This invention proposes a novel type of cross brace. The cross brace is divided into two sections and connected at the middle by a high-strength cable. When the lower float is subjected to stress and tends to separate, the cable and the two cross brace sections provide support. When the lower float is subjected to stress and tends to move closer together, the cable is not stressed, and the two cross brace sections are directly connected to provide support. When the platform deforms due to torsion and shear, the connection points at the middle of the two cross brace sections are offset, reducing the overall structural deformation of the cross brace and ensuring that the stress level of the cross brace meets the relevant structural strength requirements. Summary of the Invention

[0009] The purpose of this invention is to provide an intermittent cross bracing structure for large-scale semi-submersible offshore platforms operating at high speeds and in high sea states, thereby solving the problem that the current cross bracing structures for semi-submersible platforms do not meet structural strength requirements under large deformations.

[0010] To solve the above problems, the present invention will adopt the following technical solution:

[0011] An intermittent cross brace structure for a high-sea-state, high-speed semi-submersible platform includes a cross brace and a high-strength cable. The cross brace is divided into two sections and is broken in the middle of the semi-submersible platform. The break point is equipped with an anti-collision and misalignment matching structure. The two cross brace sections are connected by a high-strength cable to withstand axial tensile stress. The cross brace end elbow plate is provided at the connection point between the cross brace and the column of the semi-submersible platform to provide a transition.

[0012] Furthermore, the cross brace has a cross-shaped partition inside, and circumferential reinforcing ribs are arranged on the outer plate of the cross brace.

[0013] Furthermore, the anti-collision and misalignment matching structure consists of a contact plate, a buffer pad, and a connecting plate disposed at the ends of the two cross braces.

[0014] Furthermore, the contact plate is divided into a concave plate and a convex plate. The concave plate and the convex plate are fixedly connected to the ends of the two cross braces by buffer pads and connecting plates, respectively, to limit the movement and prevent the two cross braces from separating and becoming misaligned. The concave plate and the convex plate have a relatively sufficient sliding distance to eliminate the influence of deformation on the entire cross brace.

[0015] Furthermore, the contact plate is made of polymer material or high-strength steel plate with lubricating oil; the contact plate and the buffer pad have appropriate chamfers on the inner side of the cross brace to prevent the high-strength cable from wearing out during use.

[0016] Furthermore, the connecting plate is a steel plate that is directly connected to the outer plate of the cross brace, providing support rigidity for the entire anti-collision and misalignment matching structure.

[0017] Furthermore, the connecting plate is connected to the outer cross brace plate, the high-strength cable support elbow plate, and the outer elbow plate of the cylinder by welding. The outer elbow plate of the cylinder and the high-strength cable support elbow plate provide sufficient support for the entire anti-collision and misalignment structure, ensuring that its strength and stiffness meet the requirements.

[0018] Furthermore, the high-strength cable is fixed in the cross brace by welding the high-strength cable fixing base to the cross brace; the size of the high-strength cable is determined according to the load of the semi-submersible platform, and one or more high-strength cables work simultaneously, and the stress is evenly distributed to the entire cross brace connection range through the fixing base pad, high-strength cable support elbow plate and cross-shaped partition connected to the high-strength cable fixing base.

[0019] Furthermore, a fixing base pad is provided behind the high-strength cable fixing base, and is connected to the anti-collision and misalignment matching structure through the high-strength cable support elbow plate; the high-strength cable fixing base is welded to the fixing base pad to play a sealing role, separating the entire connection part from the interior of the cross brace in a watertight manner, thus playing a role in separation and protection.

[0020] Furthermore, a waterproof diaphragm is provided outside the entire cross brace connection structure. This waterproof diaphragm is made of a highly resilient elastic material, which can serve both to separate and waterproof the structure and to enhance its aesthetic appeal.

[0021] The beneficial effects of this invention are:

[0022] The discontinuous cross brace structure of the present invention for high-sea-state, high-speed semi-submersible platforms can effectively reduce stress concentration on the cross brace. Under conditions of large deformation in high sea states, compared with the current continuous cross brace structure, it can significantly reduce the stress concentration phenomenon on the cross brace caused by large deformation of the entire platform, thus providing a possibility for the design of large-size semi-submersible platforms under high sea states. Attached Figure Description

[0023] Figure 1 This is a diagram showing the stress distribution of a conventional cross-section bracing structure under large deformation.

[0024] Figure 2 This is a schematic diagram of the overall structure of a semi-submersible platform;

[0025] Figure 3 This is a longitudinal cross-sectional view of the cross brace structure of the present invention;

[0026] Figure 4 yes Figure 3 AA cross-section diagram;

[0027] Figure 5 yes Figure 3 BB cross-section diagram;

[0028] Figure 6 yes Figure 3 CC cross-section diagram in the image. Detailed Implementation

[0029] Typical embodiments embodying the features and advantages of the present invention are described below:

[0030] It should be understood that the present invention can have various variations in different implementations, and the descriptions and illustrations therein are for illustrative purposes only and not intended to limit the invention.

[0031] like Figures 2 to 6 As shown, an offshore platform typically consists of a cross brace 1, a lower floating body 2, a column 3, an upper hull 4, and a living quarters and equipment area 5. The cross brace 1 structure provides the entire platform structure with resistance to forces that separate and converge along the cross brace axis.

[0032] The cross brace 1 is further divided into the following parts: cross brace end elbow plate 11, cylinder circumferential reinforcing rib 12, cross-shaped partition 13, cylinder outer elbow plate 14, contact plate 15, buffer pad 16, connecting plate 17, waterproof diaphragm 18, high-strength cable fixing base 19, high-strength cable 20, high-strength cable support elbow plate 21, fixing base pad 22, and cross brace outer plate 23.

[0033] This invention provides a transverse bracing structure for semi-submersible platforms suitable for navigation, operation, and self-sustaining in extreme sea conditions in deep-sea operations. This semi-submersible platform can be any semi-submersible platform with high-speed navigation capabilities, including scientific research platforms and mining platforms. Such platforms can operate in unlimited navigation areas, are not limited by operating water depth, and can survive in sea conditions that occur only once every thousand years. The variable load is determined by the hull dimensions, typically around 5000 tons.

[0034] Reference Figure 2 The semi-submersible platform in this embodiment mainly consists of two lower floating bodies 2, four vertical columns 3 set on the lower floating bodies 2, an upper hull 4 supported on the columns 3, and a living quarters and equipment area 5 on the upper hull 4. Two horizontal support structures 1 are set between every two horizontal columns 3, for a total of four horizontal supports 1.

[0035] The cross braces 1 are symmetrically arranged on both sides of the mid-section inside the columns 3, and the cross brace 1 structures between the first and last columns 3 are also symmetrically arranged. The cross brace 1 structures are symmetrically arranged about the mid-longitudinal section of the entire platform. Furthermore, the cross brace 1 structures are also symmetrical about their own cross-section in both the vertical and horizontal directions.

[0036] like Figure 3 As shown, the cross brace 1 is mainly composed of a cylindrical body 23, with an elbow plate 11 at the end of the cross brace providing a transition at the connection point with the column 3. The cross brace 1 has a cross-shaped partition 13 inside, and circumferential reinforcing ribs 12 are arranged on the outer plate 23 of the cross brace. The cross brace 1 is broken at the middle of the platform. In order to ensure that the cross brace structure can withstand axial tension and compression, the two sections of the cross brace are connected by a high-strength cable 20 to withstand axial tensile load. At the same time, there is an anti-collision connection structure at the ends of both sections of the cross brace, consisting of a contact plate 15, a buffer pad 16, and a connecting plate 17.

[0037] When the forces acting on the floating body 2 and the support column 3 in the waves cause the two cross braces to compress each other, the high-strength cable 20 is in a relaxed state and does not bear the load generated by the compression. The anti-collision connection structures at both ends of the cross brace 1 are in direct contact, directly connected by contact plates 15. A preferred choice for the contact plates 15 is a new type of polymer material. The two contact plates 15 should have a low coefficient of friction to allow sliding between them, while also having sufficient strength to ensure that the contact plates will not be damaged during repeated deformation and collisions. As an alternative, high-strength steel plates with lubricant can also be used, but the lubricant level needs to be checked regularly. The contact plates 15 are divided into concave and convex plates, which serve as limiting plates to prevent the two cross braces 1 from separating and becoming misaligned. The design of the concave and convex plates should ensure that the relative sliding distance between the two contact plates 15 is large enough to eliminate the effects of deformation on the entire cross brace.

[0038] The contact plate 15 and the buffer pad 16 should have appropriate chamfers on the inner side of the cylinder to prevent the high-strength cable 20 from wearing during use. The size of the chamfer is related to the relative offset of the two cross braces and needs to be determined based on the maximum deformation that the cross braces may undergo under the most dangerous working conditions of the designed platform. This ensures that they will not rub against the high-strength cable 20, and at the same time, it is necessary to ensure that there is still sufficient contact area to transfer compressive stress after the connecting plate 15 slides relative to each other.

[0039] The connecting plate 17 is made of conventional steel plate and is directly connected to the cylinder 23, providing the supporting rigidity of the entire anti-collision structure. The connecting plate 17 is connected to the outer cross brace plate 23, the high-strength cable support elbow plate 21, and the outer elbow plate 14 of the cylinder by welding. Among them, the outer elbow plate 14 of the cylinder and the high-strength cable support elbow plate 21 should provide sufficient support for the entire anti-collision structure to ensure that its strength and rigidity meet the requirements. In the designed structure, one elbow plate is arranged every 45° along the cylinder, for a total of 8 elbow plates in one circle. Figure 6 As shown.

[0040] The high-strength cable 20 is fixed to the high-strength cable fixing base 19. When the cross braces separate, the tension is transmitted to the high-strength cable fixing base 19 through the high-strength cable 20. The high-strength cable fixing base 19, through the fixing base pad 22 connected to it and the surrounding high-strength cable support elbow plates 21 and cross-shaped partitions 13, forms a whole. When the lower float and the column are subjected to lateral separation force, the load transmitted by the high-strength cable 20 is transferred layer by layer to the entire cross brace cylinder, ensuring that the entire support structure has sufficient strength and avoiding damage caused by local stress concentration. In addition, the fixing base pad 22 is welded to the high-strength cable fixing base 19, which plays a sealing role, separating the entire connection part from the interior of the cross brace in a watertight manner, thus playing a role in separation and protection. A waterproof diaphragm 18 is installed outside the entire connection structure. The waterproof diaphragm 18 is made of a high-toughness elastic material, which ensures that the connection structure can deform with the overall deformation of the platform and will not break when subjected to wave impact, thereby ensuring the water tightness of the entire connection and playing a certain role in waterproofing and corrosion prevention.

[0041] The size of the anti-collision connection structure determines the magnitude of the deformation relative to the center of the cylinder. Finite element simulation calculations are needed at the initial design stage to determine the maximum relative deformation between the two cylinder sections, thus determining the dimensions of the anti-collision structure. The anti-collision connection structure is typically designed to be larger than the cylinder diameter. This ensures that even if the centers of the two cylinder sections shift, the joint of the anti-collision connection structure can still provide sufficient support strength and eliminate the stress misalignment caused by the relative positional shift of the two cross brace outer plates due to platform deformation. This ensures that the cross brace structure can effectively support the entire platform.

[0042] The anti-collision connection structure typically consists of three parts: a steel plate, a buffer structure, and a surface sliding plate. The steel plate is for welding to the cylinder body; the buffer structure is usually made of polymer materials or rubber pads, and through reasonable calculations, the deformation under the design load is ensured to be within a certain range, so that excessive deformation of the buffer structure will not affect the overall support effect of the cross brace; the surface sliding plate is the part where the two cross braces directly contact each other. This part will directly contact each other, generating collisions and relative friction. Therefore, appropriate polymer materials need to be selected to ensure strength and lubrication. As a simple alternative, high-strength steel can be used and lubricated with a lubricant to achieve the same effect.

[0043] A watertight diaphragm, made of high-toughness fiber material, is installed outside the connecting structure in the middle of the entire cylinder. It serves to separate the structure for waterproofing and for aesthetic purposes.

Claims

1. A discontinuous cross bracing structure for a high-sea-state, high-speed semi-submersible platform, characterized in that: The system includes cross braces and high-strength cables. The cross braces are divided into two sections and broken at the middle of the semi-submersible platform. A collision prevention and misalignment matching structure is provided at the break point. The two cross brace sections are connected by a high-strength cable to withstand axial tensile loads. A cross brace end elbow plate is provided at the connection point between the cross brace and the column of the semi-submersible platform to provide a transition. The collision prevention and misalignment matching structure consists of contact plates, buffer pads, and connecting plates set at the ends of the two cross brace sections. The contact plates are divided into concave plates and convex plates. The concave plates and convex plates are fixedly connected to the ends of the two cross brace sections by buffer pads and connecting plates, respectively, to limit the movement and prevent the two cross braces from separating and becoming misaligned. The concave plates and convex plates have a relatively sufficient sliding distance to eliminate the influence of deformation on the entire cross brace.

2. The discontinuous cross-deck structure for high sea state, high speed semi-submersible platform of claim 1, wherein: The cross brace has a cross-shaped partition inside, and circumferential reinforcing ribs are arranged on the outer plate of the cross brace.

3. The intermittent cross-deck structure for high sea state and high speed semi-submersible platform of claim 1, wherein: The contact plate is made of polymer material or high-strength steel plate with lubricant; the contact plate and the buffer pad have appropriate chamfers on the inner side of the cross brace to prevent the high-strength cable from wearing out during use.

4. The intermittent cross-deck structure for high sea state and high speed semi-submersible platform of claim 1, wherein: The connecting plate is a steel plate that is directly connected to the outer plate of the cross brace, providing support rigidity for the entire anti-collision and misalignment matching structure.

5. The intermittent cross-deck structure for high sea state and high speed semi-submersible platform of claim 1, wherein: The connecting plate is connected to the outer cross brace plate, the high-strength cable support elbow plate, and the outer elbow plate of the cylinder by welding. The outer elbow plate of the cylinder and the high-strength cable support elbow plate provide sufficient support for the entire anti-collision and misalignment matching structure, ensuring that its strength and stiffness meet the requirements.

6. The intermittent cross-deck structure for high sea state and high speed semi-submersible platform of claim 1, wherein: The high-strength cable is fixed in the cross brace by welding the high-strength cable fixing base to the cross brace. The size of the high-strength cable is determined according to the load of the semi-submersible platform. One or more high-strength cables work simultaneously, and the stress is evenly distributed to the entire cross brace connection range through the fixing base pad, high-strength cable support elbow plate, and cross-shaped partition connected to the high-strength cable fixing base.

7. The intermittent cross bracing structure for a high-sea-state, high-speed semi-submersible platform according to claim 6, characterized in that: A fixing base pad is provided behind the high-strength cable fixing base, and is connected to the anti-collision and misalignment matching structure through the high-strength cable support elbow plate; the high-strength cable fixing base is welded to the fixing base pad to play a sealing role, separating the entire connection part from the interior of the cross brace in a watertight manner, thus playing a role in separation and protection.

8. The intermittent cross-deck structure for high sea state and high speed semi-submersible platform of claim 1, wherein: In addition to the entire cross bracing connection structure, a waterproof diaphragm is also provided. This waterproof diaphragm is made of a highly tough elastic material and can serve both to separate and waterproof the structure and to enhance its aesthetic appeal.

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