Large-span closed torsion-resistant lattice system for offshore converter station

Abstract

The invention relates to the technical field of ocean engineering, in particular to a large-span closed torsion-resistant lattice system for an offshore converter station, which comprises a horizontal rigid layer, a top horizontal rigid layer and a top horizontal rigid layer, the horizontal rigid layer is divided into a bottom horizontal rigid layer and a top horizontal rigid layer which are vertically arranged in parallel at an interval, and the horizontal rigid layer comprises an in-plane support truss and an annular truss; the annular truss is of a space closed structure surrounding the periphery of the in-plane supporting truss. The transverse torsion-resistant partition vertically extends and is connected between the bottom horizontal rigid layer and the top horizontal rigid layer; the upper end and the lower end of the primary and secondary truss system are connected with the annular trusses of the bottom horizontal rigid layer and the top horizontal rigid layer respectively, and the primary truss and the secondary truss are perpendicular to each other and form a ring. According to the system, horizontal rigid layers at the bottom and the top of the integrated valve hall, transverse torsion-resistant partitions serving as internal cores and primary and secondary truss systems working cooperatively form a core stress framework, and internal equipment is protected to a higher degree in the marine environment.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, and in particular to a large-span closed anti-torsion lattice system for offshore converter stations. Background Technology

[0002] Offshore converter stations are key facilities in offshore DC transmission systems. Their superstructure, as an integrated platform, needs to support numerous loads, including valve halls, control equipment, and auxiliary systems. This platform is constantly subjected to complex marine environmental loads such as wind, waves, and currents, and will also undergo the unique challenge of floating transport at sea after construction. Therefore, its structural design must ensure sufficient overall rigidity, stability, and fatigue life while providing ample space for equipment layout and operation and maintenance. The valve hall, as the location for installing precision heavy equipment such as converter valves, typically requires a large span and high clearance, posing a significant challenge to the structural design of the superstructure.

[0003] Currently, the superstructure of such offshore converter stations generally adopts a traditional steel frame structure as its main load-bearing structure. This system typically consists of steel columns arranged regularly in the longitudinal and transverse directions, and beams connecting these columns, forming a basic spatial frame. On this basis, steel floor slabs are laid on each level to form deck levels capable of supporting equipment and personnel.

[0004] The above-mentioned structure exhibited the following technical problems during use: First, the overall torsional stiffness of the structure was significantly insufficient. Traditional frame systems are essentially open-section designs, with weak resistance to torque, making it difficult to effectively constrain torsional deformation inevitably generated under complex sea conditions and eccentric loads, posing a potential threat to the normal operation of internal precision electrical equipment. Second, the horizontal load transmission path was inefficient and inefficient. The frame structure relied on the bending of beam-column joints to transmit horizontal forces, resulting in a circuitous force transmission path, large structural deformation, and a tendency for stress concentration in the joint areas. Third, the overall stability of the structure, especially its deformation control capability under non-in-situ conditions such as floating transport, was weak. The flexural stiffness of large-span frames is limited, potentially leading to significant deflection during transport, affecting structural safety and positioning accuracy. Finally, there was a disconnect between the structural system and its intended function. To meet the load-bearing requirements of heavy equipment within large-span valve halls, additional local reinforcement is often required below the equipment. This patchwork design not only increases steel consumption and engineering complexity but also fails to achieve optimal utilization of material properties. Summary of the Invention

[0005] To address the problem mentioned in the background art that traditional frame-support systems lack sufficient torsional stiffness and are unable to effectively resist complex environmental loads, this invention establishes a complete spatial closed lattice system. This system integrates horizontal rigid layers at the bottom and top of the valve hall, transverse torsional partitions as the internal core, and a cooperating primary and secondary truss system to form the core load-bearing skeleton. The aim is to transform the large-span valve hall of a large offshore converter station into a steel structure capable of transmitting and distributing complex loads.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] A large-span closed torsional lattice system for offshore converter stations includes: a horizontal rigid layer, divided into a bottom horizontal rigid layer and a top horizontal rigid layer arranged in parallel at intervals, the horizontal rigid layer including an in-plane support truss and a circumferential truss, the circumferential truss being a spatially closed structure surrounding the periphery of the in-plane support truss; a transverse torsional partition, extending vertically and connecting between the bottom horizontal rigid layer and the top horizontal rigid layer; and a primary and secondary truss system, with its upper and lower ends respectively connected to the circumferential trusses of the bottom horizontal rigid layer and the top horizontal rigid layer, including a primary truss and a secondary truss, the primary truss and the secondary truss being perpendicular to each other and forming a ring.

[0008] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages: 1. By using closed circumferential trusses around the upper and lower horizontal rigid layers, the structure is transformed into a closed lattice, converting torque into circumferential axial force flow. Combined with lateral torsional partitions to limit local deformation, this directly improves the overall torsional stiffness. The in-plane support trusses in the horizontal rigid layers act as rigid partitions, directly transmitting shear force. The welding of the primary and secondary trusses with the circumferential trusses forms a spatial grid force transmission path, achieving efficient multi-path distribution of horizontal loads and avoiding stress concentration. The upper and lower horizontal rigid layers, together with the main truss, improve longitudinal bending stiffness, and the resulting highly statically indeterminate closed lattice structure ensures overall stability and deformation control during transportation. The horizontal rigid layers function as both structural torsional resistance and equipment load-bearing platforms, achieving integration of structural performance and usage requirements without the need for additional local reinforcement. By establishing a complete spatial closed lattice system, a higher level of protection is provided for internal equipment in marine environments.

[0009] 2. Improved torsional performance: Addressing the problem of insufficient torsional stiffness and ineffective resistance to complex environmental loads in traditional frame-brace systems, this invention achieves a fundamental shift in the force transmission mechanism by establishing a complete spatial closed lattice system. Specifically, by forming a continuous closed boundary around the horizontal rigid layer through a circumferential truss system, the torque borne by discrete nodes in traditional structures is transformed into a continuously distributed axial force flow along the circumferential direction. This torsional mechanism based on the theory of closed thin-walled members improves the torsional moment of inertia of the cross-section. Simultaneously, the transverse torsional partition, acting as an internal stiffening member, effectively limits the relative torsional deformation between the two valve chambers, forming a synergistic torsional resistance system of "outer ring, inner partition." This structural system fundamentally solves the problem of low torsional stiffness in traditional open thin-walled members, providing reliable torsional protection for internal precision electrical equipment.

[0010] 3. A rational spatial load transfer system was established: Addressing the issues of inefficient horizontal load transfer paths and poor spatial coordination, this invention provides strong in-plane stiffness through a horizontal rigid layer system. This layer, composed of steel trusses with in-plane supports and circumferential trusses, forms an effective rigid partition capable of directly and rationally transferring horizontal loads to the lateral force resisting system. The orthogonal grid formed by the primary and secondary truss systems, working in conjunction with the circumferential trusses, establishes a clear three-dimensional spatial force transfer path, solving the problem of circuitous load transfer paths in traditional structures. This multi-path load distribution mechanism not only improves force transfer efficiency but also enhances the stress distribution of the structure, preventing stress concentration.

[0011] 4. Enhanced overall structural stability: Addressing the weakness of traditional structures in deformation control during transportation, this invention utilizes a collaborative bending-resistance mechanism between the main truss and the horizontal rigid layer to create a load-bearing system with a larger cross-sectional height. This structural arrangement improves longitudinal bending stiffness and effectively controls deflection deformation during towed transportation. The welded connections between subsystems form a highly statically indeterminate spatial structure, providing multiple load transfer paths and significantly improving system redundancy and overall stability. The closed lattice structure maintains its structural integrity during transportation and in-situ operation, providing better protection for internal equipment.

[0012] 5. Achieving a balance between structural performance and functionality: The horizontal rigid layer system of this invention provides structural stiffness while directly meeting the load-bearing requirements of heavy electrical equipment inside the valve hall. This integrated design concept avoids the localized reinforcement required in traditional structures to meet equipment requirements, thus achieving the rational utilization of materials.

[0013] Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In addition, the dimensions or spacing between the components are exaggerated to show the position of each component, and the schematic diagrams are for illustrative purposes only.

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a layout diagram of the valve hall equipment of the present invention; Figure 3 , Figure 4 This is a schematic diagram of the bottom horizontal rigid layer structure of the present invention; Figure 5 , Figure 6 This is a schematic diagram of the top horizontal rigid layer structure of the present invention; Figure 7 This is a top view of the top horizontal rigid layer structure of the present invention; Figure 8 This is a schematic diagram of the transverse anti-torsional partition structure of the present invention; Figure 9 This is a schematic diagram of the main truss structure of the present invention; Figure 10 This is a schematic diagram of the secondary truss structure of the present invention.

[0016] In the diagram: 1. Bottom horizontal rigid layer; 2. Top horizontal rigid layer; 3. Lateral torsional partition; 4. Primary and secondary truss system; 11. Bottom circumferential truss; 111. Diagonal brace; 112. Chord; 12, 13, 14. Bottom in-plane support truss; 121. Top chord; 122. Bottom chord; 123. Web member; 21. Top in-plane support truss; 211. Top chord; 212. Bottom chord; 213. Web member; 22. Top circumferential truss; 221. Spatial closed lattice unit; 2211. Chord; 2212. Diagonal web member; 32. Lower M-shaped diagonal brace; 33. Upper M-shaped diagonal brace; 34, 35, 36. Bottom diaphragm web members; 41. Main truss; 411. Main truss deck beam; 412, 413, 414. Main truss columns; 415. First diagonal brace of the main truss; 416. Second diagonal brace of the main truss; 42. Secondary truss; 421. Secondary truss deck beam; 422. First diagonal brace of the secondary truss; 427. Support section; 423. Second diagonal brace of the secondary truss; 424, 425, 426. Secondary truss columns; 51, 52, 53, 54, 55, 56. Deck. Detailed Implementation

[0017] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0018] Terminology Explanation: 1. Lattice system: A structural form that transforms solid web members into a sparse skeleton by forming triangular units with chords and web members, in order to achieve large span and high stiffness.

[0019] 2. Valve Hall: A special factory building in the converter station that houses core electrical equipment such as valve groups. Its structure usually has requirements for large span, high clearance and electromagnetic shielding.

[0020] 3. Truss: A lattice-like load-bearing member consisting of straight bars connected at both ends by hinges. All loads are converted into axial forces in the bars, thus enabling transmission over long distances.

[0021] 4. Open thin-walled box-shaped member: A member with a box-shaped cross-section but not closed at the top or bottom. Its torsional stiffness is much lower than that of a closed box-shaped member. It is commonly found in composite beam bridges and other structures.

[0022] 5. Rigid diaphragm effect: refers to the effect of floor slabs or bridge decks having extremely high stiffness within their own plane, which can be regarded as a rigid plane that does not deform, thereby forcing all vertical components on the plane to deform and bear force in a coordinated manner.

[0023] 6. A transverse truss: In a spatial structure, a planar truss unit arranged transversely to connect the longitudinal main structure and transfer transverse loads.

[0024] To address the shortcomings of existing offshore converter station superstructures in terms of overall torsional stiffness, horizontal load transfer efficiency, and deformation control during transportation, this invention proposes an innovative all-steel three-dimensional spatial force-bearing system. This system systematically integrates bottom and top horizontal rigid layers, transverse torsional partitions, and primary and secondary truss systems to construct a rigid structural system with clearly defined force distribution, a rational force transmission path, and both high bending and torsional resistance.

[0025] like Figure 1 As shown, a large-span closed torsional lattice system for offshore converter stations includes: Horizontal rigid layer, such as Figure 3 , Figure 4 , Figure 5 , Figure 6As shown, it is divided into a bottom horizontal rigid layer 1 and a top horizontal rigid layer 2 arranged in parallel at intervals. The horizontal rigid layer includes an in-plane support truss and a circumferential truss. The circumferential truss is a spatial closed structure surrounding the periphery of the in-plane support truss. A transverse torsional partition 3 extends vertically and connects between the bottom horizontal rigid layer 1 and the top horizontal rigid layer 2; The primary and secondary truss system 4 is connected at its upper and lower ends to the circumferential trusses of the bottom horizontal rigid layer 1 and the top horizontal rigid layer 2, respectively. It includes a primary truss 41 and a secondary truss 42, which are perpendicular to each other and form a ring.

[0026] In the lattice system of this invention, the bottom and top horizontal rigid layers are arranged parallel to each other, providing the structure with two force boundaries, one above the other. The in-plane supporting truss itself provides strong in-plane shear stiffness and load-bearing capacity, effectively distributing floor loads and acting as a rigid partition. The outer circumferential truss is a spatially closed structure, forming a mechanically complete closed boundary. This allows the torque acting on the structure to be effectively converted into an axial force flow continuously distributed along the circumferential truss, fundamentally changing the mechanism of traditional open frames that rely on discrete nodes for torsional resistance, thus providing the main torsional stiffness. The vertically extending transverse torsional partition rigidly connects the bottom and top horizontal rigid layers, directly limiting the relative torsional deformation between the two large-span valve halls, and more effectively guiding the internal loads into the outer circumferential torsional path, forming a synergistic torsional resistance system with the circumferential truss and the outer ring. The primary and secondary truss system distributes the vertical loads through the grid via multiple paths and transfers the horizontal loads to the horizontal rigid layers and circumferential trusses with extremely high in-plane stiffness through the nodes. The aforementioned structure forms a highly statically indeterminate three-dimensional closed lattice. This closed lattice not only possesses high bending and torsional stiffness but also establishes clear, direct, and multiple load transfer paths, thereby solving the problems of weak torsional performance, low force transmission efficiency, and poor overall stability mentioned in the background technology, and providing a higher level of protection for internal equipment in marine environments.

[0027] like Figure 6 As shown, the circumferential truss is formed by connecting multiple spatial closed lattice units 221 end-to-end in the horizontal direction to form a ring. This modular construction method facilitates processing and assembly, while ensuring the continuous and uninterrupted transmission of circumferential forces. Each unit is connected end-to-end, jointly ensuring the mechanical integrity and continuity of the entire ring boundary, and enhancing the overall torsional resistance of the structure.

[0028] The spatial closed lattice unit 221 is a cuboid skeleton composed of chords. Each rectangular surface of the cuboid skeleton is provided with diagonally arranged diagonal braces 111, which ensures that the circumferential truss can not only withstand circumferential axial force, but also effectively resist in-plane shear force, thus working as a solid overall boundary.

[0029] like Figure 6 , Figure 7 As shown, the in-plane support truss includes an upper chord, a lower chord, and web members connecting them. The web members include diagonally arranged diagonal web members. The upper and lower chords mainly bear the axial force generated by the bending moment, while the diagonally arranged diagonally arranged web members efficiently bear and transmit in-plane shear force. This truss structure achieves extremely high in-plane stiffness with less material, enabling the floor load to be evenly transferred to the surrounding circumferential truss, and ensuring that the horizontal rigid layer performs a rigid diaphragm effect, coordinating the deformation of each vertical member.

[0030] like Figure 8 As shown, the transverse torsional partition 3 is provided with an M-shaped bracing system on both sides. The M-shaped bracing system includes a lower M-shaped brace 32 connecting the bottom horizontal rigid layer 1 and the intermediate deck layer, and an upper M-shaped brace 33 connecting the intermediate deck layer and the top horizontal rigid layer 2. These M-shaped braces provide additional lateral support and force transmission paths on the left and right sides of the transverse torsional partition 3. Connecting the partition to deck layers of different heights increases the stability of the structure in the vertical plane, effectively suppresses the lateral displacement of the partition and main truss 41 under transverse loads, and disperses and transmits some of the horizontal forces, thereby improving the overall lateral stiffness and spatial coordination performance of the structure.

[0031] Both the lower M-shaped diagonal brace 32 and the upper M-shaped diagonal brace 33 include two downward-sloping diagonal braces and two upward-sloping diagonal braces, which converge in the middle to form an "M"-shaped truss. The "M"-shaped arrangement allows the diagonal braces to withstand axial forces and provide good bending and shear resistance. Combined with the transverse anti-torsional partition 3, it forms a robust support frame in a localized area, further constraining the torsional and transverse deformation of the structure.

[0032] like Figure 9 As shown, the main truss 41 includes multiple decks arranged vertically at intervals, columns connecting adjacent decks, and first and second diagonal braces inclinedly connecting the columns to decks of different heights. This three-dimensional truss structure gives the main truss 41 high longitudinal bending and shear stiffness. The columns mainly bear vertical loads, while the inclined first and second diagonal braces effectively connect the decks of different heights to the columns, forming a stable triangular force transmission system that jointly bears longitudinal shear and bending moments, and is the main component resisting longitudinal lateral forces of the structure.

[0033] The first diagonal brace and the second diagonal brace are arranged symmetrically with respect to the middle deck. The first diagonal brace, the second diagonal brace, the columns and the deck together form a double "mi" - shaped structure. The double "mi" - shaped structure is a highly statically indeterminate and stable structural form. This arrangement enables the load to be transmitted through multiple paths and directions, greatly enhancing the stiffness and integrity of the node area of the main truss 41, avoiding stress concentration, and improving the bearing efficiency and stability of the main truss 41 under complex loads.

[0034] As Figure 10 shown, the secondary truss 42 includes multiple decks arranged at intervals in the vertical direction, columns connected between adjacent decks, and the first diagonal brace and the second diagonal brace arranged in parallel at intervals. The first diagonal brace and the second diagonal brace are obliquely connected between the columns and decks at different heights. The secondary truss 42, as a transverse distribution member, transmits the load to the main truss 41. Its double diagonal brace design improves its own stiffness and redundancy, ensures that there is a backup force - transmission path when one diagonal brace may fail, and enhances local stability.

[0035] The first diagonal brace of the secondary truss 42 has a support section 427 in the area of the bottom deck. The support section 427, the second diagonal brace and the bottom - horizontal rigid layer 1 cooperate to jointly form an "M" - shaped truss structure. The diagonal brace system of the secondary truss 42 is deeply integrated with the in - plane members of the bottom - horizontal rigid layer 1. This integration directly anchors the force of the secondary truss 42 on the rigid layer, expands the force - bearing range, enables the bottom - horizontal rigid layer 1 to also participate in the lateral anti - lateral system of the frame, and thus forms an extremely strong lateral support system at the lower part of the valve hall, effectively enhancing the overall stiffness and anti - deformation ability of the structure bottom.

[0036] Specifically: The embodiments of the lattice system include a bottom - horizontal rigid layer 1, a top - horizontal rigid layer 2, a transverse torsion - resistant partition 3, and a primary and secondary truss system 4. The bottom - horizontal rigid layer 1 is arranged in parallel below the top - horizontal rigid layer 2. The transverse torsion - resistant partition 3 is arranged at intervals in the transverse direction and perpendicular to the bottom - horizontal rigid layer 1 and the top - horizontal rigid layer 2. The primary and secondary truss system 4 is connected to each other and cooperatively between the horizontal rigid layer and the transverse torsion - resistant partition 3 to jointly form a core force - bearing framework.

[0037] The valve hall is located between the second - layer deck 52 and the fourth - layer deck 54. Two valve halls are arranged longitudinally. Each valve hall arranges 9 converter valves (as Figure 2 shown), and a GIS room is arranged in the valve hall.

[0038] The bottom - horizontal rigid layer 1 is a load - bearing member composed of a bottom - circumferential truss 11 and bottom - in - plane support trusses 12, 13, 14 that surround the outer periphery in a circle.

[0039] The outer bottom circumferential truss 11 is composed of a spatial closed lattice unit that continuously encircles the perimeter horizontally. This spatial closed lattice unit is a cuboid skeleton made of rods, and within each rectangular surface of this cuboid, diagonal braces 111 are arranged in a crisscross pattern. These diagonal braces divide each rectangular face into four stable triangular grids, thus making the entire cuboid a geometrically immutable stable body in three-dimensional space. This cuboid is connected end-to-end by sharing a chord 112, forming a closed force-bearing ring at the edge of the bottom horizontal rigid layer that can effectively transmit circumferential axial forces.

[0040] Within the area enclosed by the bottom circumferential truss 11, parallel in-plane support trusses 12, 13, and 14 are arranged. Each in-plane support steel truss consists of an upper chord 121, a lower chord 122, and web members 123 connecting them. The upper chord 121, lower chord 122, and web members 123 together form a load-bearing member with extremely high in-plane stiffness. The two ends of this internal truss are welded to the circumferential truss.

[0041] The bottom circumferential truss 11, composed of spatially closed lattice units, acts as a strong boundary, converting the torque acting on the structure into an axial force flow distributed along its circumference, providing the main torsional stiffness for the entire upper module. The in-plane support truss bears and distributes the vertical equipment loads and in-plane loads acting on the mezzanine, and rationally transfers them to the outer circumferential truss. The bottom circumferential truss 11 and the bottom in-plane support trusses 12, 13, and 14 are welded together to form a complete load-bearing unit, jointly ensuring that the bottom horizontal rigid layer acts as a rigid partition, effectively coordinating the overall deformation of the structure.

[0042] The top horizontal rigid layer 2 includes a top in-plane support truss 21 and a top circumferential truss 22 disposed around its periphery.

[0043] The top-plane in-plane supporting truss 21 consists of an upper chord 211, a lower chord 212, and web members 213 connecting them. These web members 213 connect adjacent upper and lower chords, forming a continuous and stable triangular grid inside the space frame. This structure allows loads to be rationally transferred in multiple directions through this grid system.

[0044] The top circumferential truss 22 is formed by the continuous arrangement of spatial closed lattice units 221 along the perimeter of the top horizontal rigid layer, forming a ring structure that is physically and mechanically completely closed.

[0045] The spatial closed lattice unit 221 consists of twelve chord members 2211 connected by nodes, forming a cubic spatial skeleton and creating the twelve edges of the structure. On each rectangular surface of the cuboid, two intersecting diagonal web members 2212 are connected. All chord members and diagonal web members together form a spatial truss structure. The chord members primarily bear the overall bending moment and axial force of the structure, while the intersecting diagonal web members on each face, through their collaborative work with the chord members, effectively bear and transmit the in-plane shear force acting on that surface, thereby greatly improving the spatial stiffness and overall stability of the structural unit.

[0046] The spatial closed lattice unit 221 serves as the basic force-bearing unit of the bidirectional orthogonal square grid. Its spatial shape can reasonably transform the vertical load from the upper chord node into the axial force of the diagonal web member, thus realizing the three-dimensional spatial transmission and distribution of the load.

[0047] The transverse torsional partition 3 extends through the height of the upper block and is arranged parallel to the transverse direction. Its lower chord is rigidly connected to the bottom horizontal rigid layer 1, and its upper chord is rigidly connected to the top horizontal rigid layer 2. This creates a stable in-plane shear force transfer interface at both the upper and lower heights of the structure, providing the transverse truss partition with bidirectional constraint in the vertical direction and a continuous torsional force path. The transverse truss partition 3 is positioned between two main trusses 41 and arranged parallel to the secondary truss system 42. Its web members and chord nodes are rigidly connected to the main and secondary truss systems, thus making the partition both a transverse stabilizing member between the main trusses and a vertical torsional connection member between the upper and lower rigid partitions, effectively improving the overall torsional performance of the structure.

[0048] To further enhance the spatial stability and vertical force transmission capacity of the area where the transverse truss partition 3 is located, two sets of M-shaped diagonal bracing systems are arranged on both sides, numbered 32 and 33 respectively. The upper M-shaped diagonal bracing 33 consists of two diagonal bracings inclined downward from the bottom deck beam 55 of the top horizontal rigid layer 2 and two diagonal bracings inclined upward from the top deck beam 52 of the bottom horizontal rigid layer 1, which converge in the middle to form an "M"-shaped truss geometry. The lower M-shaped diagonal bracing 32 consists of two diagonal bracings inclined downward from the third deck beam 53 and two diagonal bracings inclined upward from the top deck beam 52 of the bottom horizontal rigid layer 1, plus the bottom partition web members 34, 35, 36, etc. in the bottom horizontal rigid layer 1, which converge in the middle to form an "M"-shaped truss geometry. This arrangement creates a continuous oblique force path in the vertical direction, which can effectively limit the lateral displacement of the main truss under wind load, equipment eccentric load or transportation disturbance. At the same time, it provides additional lateral constraints for the lateral torsional partition, so that when the partition is subjected to torque and horizontal load, the deformation of its web members can be shared by the M-shaped diagonal bracing, thereby reducing the lateral deformation of the middle span and the stress concentration at the nodes.

[0049] The existence of the upper and lower M-shaped diagonal bracing systems enables the lateral torsion-resistant partition 3 to form a more compact spatial mechanical synergy with the main truss and the secondary truss. The arrangement of the M-shaped diagonal braces at different heights above and below forms diagonal force-transfer nodes with the bottom rigid isolation layer 1 and the top rigid isolation layer 2 respectively, enabling multi-path transfer of torque and horizontal forces between the upper and lower isolation layers. When the structure is subjected to lateral loads or overall torsional effects, the M-shaped diagonal braces form a stable bending and shear-resistant unit through their "three-bar-in-one" geometric system, providing effective lateral support for the partition web members. This enables the lateral truss partition 3 not only to bear the main force of torsional transfer but also to form an overall spatial truss effect with the assistance of the M-shaped truss, further enhancing the overall torsional stiffness, lateral stiffness, and spatial stability of the structure.

[0050] The primary and secondary truss system 4 adopts a hierarchical spatial force-transfer mechanism. Through the coordinated operation of the longitudinally load-bearing main truss 41 and the laterally distributing secondary truss 42, a stable orthogonal grid system is formed to jointly bear various loads acting on the valve hall structure.

[0051] As the longitudinally main load-bearing member, the main truss 41 adopts a three-dimensional space truss structure and is symmetrically arranged on both sides of the structure along the length direction of the valve hall. This truss system includes decks, the first main-truss diagonal brace 415, the second main-truss diagonal brace 416, the main-truss deck beam 411, and the main-truss columns 412 to 414.

[0052] The decks 51 to 56 are arranged in parallel from bottom to top to form the basic force-bearing layer. The main-truss deck beam 411 is arranged in parallel between the decks 52 and 53, playing a role in enhancing local stiffness. The main-truss columns 412 to 414 are arranged vertically at intervals from left to right and are perpendicular to the plane of each deck. The two diagonal braces are arranged symmetrically with respect to the deck 53.

[0053] The first main-truss diagonal brace 415 and the second main-truss diagonal brace 416 are located between the main-truss columns 412 and 414 and are symmetrically arranged with respect to the column 413 as the center. Specifically, the top end of the first main-truss diagonal brace 415 is connected to the intersection point of the main-truss column 412 and the fifth deck 55, the middle position is fixed to the intersection point of the column 413 and the fourth deck 54, and the bottom end is anchored to the intersection point of the column 414 and the third deck 53.

[0054] The first main-truss diagonal brace 415, the second main-truss diagonal brace 416, the column 413, and the deck 54 together form a complete "cross" structure, which enhances the overall stability of the structure. The two diagonal braces are symmetrically arranged with respect to the third deck 53, jointly forming a double "cross" structure, further enhancing the overall stiffness and stability of the primary and secondary truss system.

[0055] Secondary truss 42, as a transverse load-bearing member, is arranged perpendicular to the main truss 41, forming an orthogonal grid system together with the main truss 41. This system includes the deck, secondary truss columns 424, 425, and 426, secondary truss first diagonal brace 422, secondary truss second diagonal brace 423, and secondary truss deck beam 421.

[0056] Deck 51 to 56 are arranged in parallel from bottom to top, and secondary truss deck beam 421 is arranged in parallel between deck 52 and deck 53. Secondary truss columns 424, 425, and 426 are arranged vertically from left to right and are perpendicular to each deck. The first diagonal brace 422 of the secondary truss is inclinedly connected between two columns 426, and the first diagonal braces 422 of two adjacent secondary trusses are arranged symmetrically about the secondary truss column 424 between them.

[0057] The first diagonal brace 422 of the secondary truss has a support section 427 located between the first deck 51 and the second deck 52, which forms a diagonal member of the bottom horizontal rigid layer 1. A second diagonal brace 423 of the secondary truss is also connected between two adjacent columns 426. The second diagonal brace 423 of the secondary truss is arranged parallel to the first diagonal brace 422 of the secondary truss and is located on the upper side of the first diagonal brace 422 of the secondary truss.

[0058] The parallel-spaced secondary truss second diagonal brace 423, together with the secondary truss first diagonal brace 422 and the bottom horizontal rigid layer 1, form a large "M" shaped truss. Specifically, the top of the secondary truss first diagonal brace 422 is arranged on the column 425 between the secondary truss deck beam 421 and the third deck 53, and the bottom is arranged on the secondary truss columns 424 and 426 between the first deck 51 and the second deck 52; the top of the secondary truss second diagonal brace 423 is arranged on the column 425 between the fourth deck 54 and the fifth deck 55, and the bottom is arranged on the secondary truss columns 424 and 426 between the secondary truss deck beam 421 and the third deck 53.

[0059] The upper and lower chords of the main truss 41 are connected to the circumferential truss of the horizontal rigid layer at corresponding nodes by welding to ensure effective load transfer. The system also includes longitudinally arranged secondary trusses 42, which are arranged in three sets at intervals along the vertical direction, located on both sides and in the middle of the valve hall.

[0060] The diagonal bracing system works in conjunction with the bottom horizontal rigid layer 1 to form a traditional large "M" shaped truss under various working conditions, ensuring good overall stress distribution on the platform. By arranging the second diagonal bracing 423 of the secondary truss parallel and spaced on the upper side of the first diagonal bracing 422 of the secondary truss, a dual protection mechanism is formed, ensuring that the valve hall can form two sets of traditional large "M" shaped trusses in both sea transport and in-situ conditions, thereby improving the safety and reliability of the structure.

[0061] In this embodiment, a multiple load transfer path is constructed through the double "rice" - shaped structure of the main truss 41 and the double "M" - shaped truss structure of the secondary truss 42, forming a reasonable spatial stress system. This design not only improves the overall stiffness and stability of the structure but also ensures the safety performance under various working conditions, and is particularly suitable for the special use environment of the valve hall of an offshore converter station.

[0062] In summary, the horizontal rigid layer is a bearing member composed of a composite of an in - plane support truss system and a circumferential truss system.

[0063] The in - plane support truss system is entirely composed of steel structures, and its structural form is a truss - type floor slab composed of diagonal web members, vertical web members, and upper and lower chord members; among them, the diagonal web members are arranged cross - wise to form a stable triangular grid, and the vertical web members provide necessary vertical support. These supports and chord members in each direction achieve effective force transfer through welding, thus jointly forming a horizontal partition layer with extremely high in - plane stiffness. This structure remains transparent in physical form but forms a closed space lattice body that can transfer shear force in mechanical properties.

[0064] The circumferential truss system is continuously arranged along the perimeter of the horizontal rigid layer. This system strictly follows the plane contour of the upper module, forming a complete annular closed structure at the edge of the horizontal rigid layer. Its structural form adopts a spatial closed lattice unit, which is composed of upper chord members, lower chord members, diagonal web members, and vertical members to jointly form a stable triangular grid system. The chord members are made of large - sized H - shaped steel and are continuously arranged along the edge of the horizontal partition layer to ensure effective transfer of circumferential forces; the diagonal web members are arranged in a cross - brace or K - shape to form a stable shear - resistant grid with the chord members; the vertical members are set at the nodes to ensure cross - sectional geometric stability. In terms of connection structure, the chord members and the edge chord members of the horizontal rigid layer are welded to ensure continuous transfer of torque. Through its spatial closed characteristics, this system converts the torque into an axial force flow distributed along the circumference, providing the main torsional stiffness for the structure and acting as the boundary constraint of the horizontal partition layer to ensure its full play of the role of a rigid diaphragm.

[0065] The horizontal rigid layer system is composed of two subsystems, namely a steel truss with in - plane support and a circumferential truss, which are compounded by welding. The steel truss with in - plane support provides basic shear stiffness and three - dimensional support, bears equipment loads and realizes in - plane load distribution; the circumferential truss forms a closed boundary and converts the torque into a circumferential axial force. The in - plane stiffness of this system can coordinate the overall deformation of the structure, its torsional resistance performance is achieved through a closed force - transfer path, and it simultaneously meets the equipment bearing requirements and the structural stress requirements.

[0066] The aforementioned transverse torsional partition refers to a simple arrangement in the central structural design: a transverse truss partition is placed at the longitudinal center between the two valve halls. This transverse truss partition is arranged longitudinally along the block, extending from the bottom foundation to the top roof system. This truss employs a robust three-dimensional truss structure, forming a reliable connection with the horizontal rigid layers at the top and bottom. The chords of the transverse truss partition and the circumferential truss of the horizontal rigid layer are welded together at the connection points to ensure effective transfer of horizontal loads. Its synergistic mechanism lies in the following: the circumferential torsional system, as a basic closed profile, is the main path for torque transfer and balance; the transverse truss partition acts as a strong internal stiffener, effectively limiting the relative torsional deformation between the two valve halls and better guiding the internal loads into the main torsional path. This "outer ring, inner partition" configuration together constructs a spatially closed lattice structure.

[0067] The primary and secondary truss system forms the core enclosure structure and spatial load distribution system of the building blocks. This system achieves effective transfer of bending moment, shear force, and axial force through welded connections: loads are transferred to the secondary trusses via floor slabs, distributed by the secondary trusses, and then transmitted to the primary trusses, finally spreading to the overall structure through the connection nodes between the primary and circumferential trusses. Under horizontal loads, this system works in conjunction with the horizontal rigid layers to provide lateral stiffness, and its spatial grid arrangement effectively improves the overall stability and load distribution efficiency of the structure.

[0068] In terms of mechanical principles, this system forms a three-dimensional closed lattice structure through the welding of horizontal rigid layers, transverse torsional partitions, and primary and secondary truss systems. The system's bending resistance is provided collaboratively by the main trusses on both sides and the upper and lower horizontal rigid layers. The main trusses bear shear force and local bending moment, while the horizontal rigid layers bear axial force, forming a couple to resist the overall bending moment. Torsional resistance is based on the closed boundary formed by the circumferential trusses, converting torque into an axial force flow distributed circumferentially along the cross-section. The transverse torsional partitions enhance overall torsional efficiency by limiting local deformation and distributing internal forces. Load transfer achieves multi-path distribution through the orthogonal grid formed by the primary and secondary trusses and the in-plane stiffness of the horizontal rigid layers. Vertical loads are distributed through the grid system, while horizontal loads are transferred through the rigid partition effect. In terms of mechanical performance, this structural system exhibits high overall stiffness. Torsional stiffness is ensured by the circumferential truss system and lateral torsional partitions, while bending stiffness is achieved through the coordinated work of the main truss and horizontal rigid layers. In-plane stiffness is provided by the horizontal rigid layers. The structural synergy is demonstrated by the welded integration of subsystems into a cohesive working system, the horizontal partitions coordinating the deformation of vertical components, and the spatial grid achieving uniform load distribution. The system's force transmission path is clear and stable, establishing a distinct three-dimensional force transmission path, and the closed lattice form ensures overall stability. The mechanical performance of this structural system stems from its spatial closed lattice form and clear force transmission path, meeting structural performance requirements through the coordinated work of its subsystems. Furthermore, the numerous rigid connections between subsystems form a highly statically indeterminate spatial closed lattice, endowing the structure with higher safety redundancy and internal force redistribution capabilities.

[0069] This invention, through innovative structural system design, systematically solves the technical problems of traditional offshore converter station superstructure in terms of torsional performance, force transmission efficiency and deformation control, and provides a safe and reliable structural solution for large offshore converter stations.

[0070] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A large-span closed torsional lattice system for offshore converter stations, characterized in that, Comprising: A horizontal rigid layer, which is divided into a bottom horizontal rigid layer and a top horizontal rigid layer arranged in parallel at intervals up and down. The horizontal rigid layer includes an in-plane support truss and a circumferential truss. The circumferential truss is a space-closed structure surrounding the periphery of the in-plane support truss; A transverse torsion-resistant partition, vertically extending and connected between the bottom horizontal rigid layer and the top horizontal rigid layer; A primary and secondary truss system, with its upper and lower ends respectively connected to the circumferential trusses of the bottom horizontal rigid layer and the top horizontal rigid layer, including a primary truss and a secondary truss. The primary truss and the secondary truss are perpendicular to each other and enclose a ring shape.

2. The large-span closed torsional lattice system as described in claim 1, characterized in that, The circumferential truss is formed by connecting multiple space-closed lattice units end to end in the horizontal direction to form a ring shape.

3. The large-span closed torsional lattice system as described in claim 2, characterized in that, The space-closed lattice unit is a cuboid skeleton composed of chord members, and diagonal braces arranged in a cross pattern are provided in each rectangular surface of the cuboid skeleton.

4. The large-span closed torsional lattice system as described in claim 1, characterized in that, The in-plane support truss includes an upper chord member, a lower chord member, and web members connected between the two. The web members include obliquely arranged web members arranged in a cross pattern.

5. The large-span closed torsional lattice system as described in claim 1, characterized in that, M-shaped brace systems are provided on both sides of the transverse torsion-resistant partition. The M-shaped brace systems include a lower M-shaped brace group connected between the bottom horizontal rigid layer and the intermediate deck layer, and an upper M-shaped brace group connected between the intermediate deck layer and the top horizontal rigid layer.

6. The large-span closed torsional lattice system as described in claim 5, characterized in that, Both the lower M-shaped brace group and the upper M-shaped brace group include two obliquely downward braces and two obliquely upward braces, and the braces meet in the middle to form an "M"-shaped truss.

7. The large-span closed torsional lattice system as described in claim 1, characterized in that, The primary truss includes multiple decks arranged at intervals in the vertical direction, columns connected between adjacent decks, and first braces and second braces obliquely connected between the columns and decks at different heights.

8. The large-span closed torsional lattice system as described in claim 7, characterized in that, The first brace and the second brace are arranged symmetrically with respect to an intermediate deck. The first brace, the second brace, the columns, and the decks together form a double "rice"-shaped structure.

9. The large-span closed torsional lattice system as described in claim 1, characterized in that, The secondary truss includes multiple decks arranged at intervals in the vertical direction, columns connected between adjacent decks, and first braces and second braces arranged in parallel at intervals. The first brace and the second brace are obliquely connected between the columns and decks at different heights.

10. The large-span closed torsional lattice system as described in claim 9, characterized in that, The first brace of the secondary truss has a support section located in the area of the bottom deck. The support section, the second brace, and the bottom horizontal rigid layer cooperate to jointly form an "M"-shaped truss structure.

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