X-braced structural load-bearing system and its design method

Abstract

This invention discloses an X-bracing structural support system and its design method for deep-water jacket structures. The jacket structure includes a launching truss and several main horizontal layers. An X-bracing structural support system is installed between two adjacent main horizontal layers, relying on the main facade of the jacket structure. The X-bracing structural support system includes X-shaped supports located within the main facade and out-of-plane struts located outside the main facade. The X-shaped supports are configured to be fixedly connected to and support the jacket structure at their outer ends, and have X-shaped support nodes in the middle. One end of the out-of-plane strut is fixedly connected to the X-shaped support node, and the other end is fixedly connected to the launching truss of the jacket structure on the same side. Compared to conventional X-bracing node forms, by setting out-of-plane supports and adopting a modified effective length coefficient for the X-shaped supports, the number of main horizontal layers of the jacket structure is reduced, and the overall weight of the jacket structure is lowered. This design method can provide effective guidance for engineering design, ensuring the safety and reliability of the large-span X-bracing structural support system for deep-water jacket structures.

Description

Technical Field

[0001] This invention relates to the field of marine oil and gas development equipment technology, and in particular to an X-bracing structure load-bearing system and its design method. Background Technology

[0002] Offshore oil and gas exploration and development typically involves conventional sea areas with depths of less than 200 meters. In recent years, as offshore oil and gas exploration and development has gradually moved into deeper waters, a number of oil and gas fields with depths of 200 to 400 meters have been discovered. Sea areas with depths exceeding 200 meters are generally referred to as deep-sea environments, and sea areas with depths exceeding 300 meters are referred to as ultra-deep-sea environments.

[0003] In waters shallower than 200 meters, jacket platforms are widely used due to their superior structural safety and economic efficiency. In deep or ultra-deep waters of 200–400 meters, jacket platforms remain a more competitive platform type compared to floating platforms. However, compared to conventional waters, jacket platforms face significant design challenges. Deep-water jacket design must withstand harsh environmental loads while simultaneously controlling weight to accommodate the limitations of existing domestic construction resources.

[0004] The X-bracing structure is a crucial component of the jacket structure, playing a vital role in maintaining its stability when positioned on the main facade. For deep-water, especially ultra-deep-water jackets, controlling the number of main horizontal layers and increasing the span of the X-bracing structure are key design considerations. However, current X-bracing structures for deep-water jackets cannot achieve the goal of reducing the overall weight of the jacket to meet the design requirements of deep-water jackets. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide an X-bracing structure load-bearing system and its design method, which aims to effectively control the number of main horizontal layers of the jacket structure and reduce the overall weight of the jacket structure while ensuring the structural rigidity and stability of the jacket.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of this invention provides an X-bracing structure support system for a deep-water jacket foundation. The jacket foundation includes a launching truss and several main horizontal layers. The X-bracing structure support system is installed between two adjacent main horizontal layers, relying on the main facade of the jacket foundation. The X-bracing structure support system includes an X-shaped support located within the main facade and an out-of-plane strut located outside the main facade. The X-shaped support is configured to connect to and support the jacket foundation through its outer end, and has an X-shaped support node in the middle. One end of the out-of-plane strut is connected to the X-shaped support node, and the other end is connected to the launching truss of the jacket foundation on the side in which it is located.

[0008] According to some embodiments of the present invention, the jacket has main legs forming the main facade and main horizontal members located in the main horizontal layer; the X-shaped support is composed of 4 in-plane struts, the outer ends of the 4 in-plane struts are fixedly connected to the intersection of the main horizontal members and the main legs of the jacket, and the other ends are connected to the X-shaped support node.

[0009] According to some embodiments of the present invention, the duct frame has four main legs, which are arranged in a stern pattern and form four main facades.

[0010] The design method for an X-bracing structure bearing system provided in the second aspect of the present invention includes: constructing a finite element model of an X-shaped support with out-of-plane struts and setting material parameters to simulate the behavior of the X-shaped support; setting boundary conditions for finite element analysis, including setting the support conditions, loading methods, and constraint conditions of the out-of-plane struts and the X-shaped support; applying a load to the loaded end of the X-shaped support, gradually changing the tension-compression ratio to find the critical buckling load factor of the X-shaped support; and correcting the effective length coefficient of the X-shaped support in the jacket design based on the critical buckling load factor.

[0011] According to some embodiments of the present invention, the effects of initial geometric defects and residual stresses of out-of-plane struts and X-shaped supports are ignored when simulating X-shaped supports, and the cross-section remains unchanged by default during loading.

[0012] According to some embodiments of the present invention, the boundary conditions for finite element analysis are set, including setting the support conditions, loading methods, and constraint conditions of the out-of-plane struts and X-shaped supports. This includes: considering the limiting effect of the flexibility of the drainage truss on the stability of the X-shaped supports with out-of-plane struts in the jacket structure; to realistically simulate the working conditions of the out-of-plane struts, the drainage truss at the actual connection point of the out-of-plane struts is transformed into an equivalent elastic support; a fixed constraint is set at the unloaded end of the X-shaped support, and the axial displacement is released at the loaded end, and an axial load is applied; considering the influence of the out-of-plane struts on the overall structural stability, an equivalent stiffness elastic support is used at the end of the out-of-plane struts in the simulation to characterize the limitation of the external drainage truss on the X-shaped supports with out-of-plane struts; by converting the deformation degree of the model at the connection point between the end of the out-of-plane struts and the drainage truss under static constant load, the equivalent axial stiffness and equivalent rotational stiffness are obtained.

[0013] According to some embodiments of the present invention, with the out-of-plane support point as the origin of the coordinate axis, the axial direction of the out-of-plane strut as the Z-axis, and the vertical direction as the Y-axis, axial static forces are applied at the origin of the relative coordinate system during simulation. The axial deformation of the out-of-plane support point due to the force is measured, and the equivalent axial stiffness in the relative coordinate system direction is calculated through a transformation formula. A relative Cartesian coordinate system and a cylindrical coordinate system are constructed for the out-of-plane support point. A constant torque is applied at the corresponding position, and the arc change of the element near the out-of-plane support point caused by the torque is measured. The equivalent rotational stiffness in each direction at the out-of-plane support point is calculated through a transformation formula.

[0014] According to some embodiments of the present invention, the X-shaped support is part of the main body of the jacket platform. The jacket platform has high rigidity, and in the simulation, it is assumed that the unloaded end of the X-shaped support is fixed to the jacket platform. In order to fully consider the impact of extreme working conditions on structural stability, the loaded end of the X-shaped support is considered to have two cases: sliding support and movable hinge support.

[0015] According to some embodiments of the present invention, a load is applied to the loaded end of an X-shaped brace, and the tension-compression ratio is gradually varied to find the critical buckling load factor of the X-shaped brace. This includes: applying a load to the loaded end of the X-shaped brace for two cases of the loaded end of the X-shaped brace, with the tension-compression ratio varying from -1.0 to 1.0, until the X-shaped brace buckles to obtain the critical buckling load of the X-shaped brace, and calculating the critical buckling load factor.

[0016] According to some embodiments of the present invention, a buckling analysis module is used to perform buckling stability analysis on an X-shaped brace. Tensile and compressive loads are applied to the two in-plane struts at the loaded end of the X-shaped brace, with the tension-to-compression ratio varying from -1.0 to 1.0. During the loading process, the tension-to-compression ratio is kept constant while ensuring axial loading, and the in-plane critical buckling load P is obtained. cr .

[0017] According to some embodiments of the present invention, based on the calculation formula: Calculate the critical buckling load factor, where P cr0 P is the critical buckling load of the out-of-plane strut. cr Let E0 be the critical buckling load of the X-shaped support, E0 be the elastic modulus of the out-of-plane strut, I0 be the moment of inertia of the out-of-plane strut section, and L0 be the length of the out-of-plane strut.

[0018] The present invention has the following advantages due to the adoption of the above technical solutions:

[0019] 1. The X-bracing structure bearing system provided in this embodiment of the invention relies on the horizontal layer of the underwater truss to provide out-of-plane support for the X-shaped support on the main facade of the jacket, ensuring the rigidity and stability of the X-bracing structure. This enables the design of large-span X-bracing structures. Increasing the span of the X-shaped support can significantly reduce the number of main horizontal layers of the jacket, effectively reducing the weight of the jacket. On the one hand, it can save steel investment, and on the other hand, it allows the weight of the deep-water jacket to adapt to the limitations of domestic construction resources. This is of great significance for promoting the economic and effective development of deep-water oil and gas fields.

[0020] 2. The design method of the X-braced structure bearing system provided in the embodiments of the present invention can be used for numerical analysis and design of the X-braced structure bearing system. The standard values ​​obtained by the design method can be used to fill the gaps in the current standards, provide a theoretical basis for design, and verify the reliability of the large-span X-braced structure bearing system. Attached Figure Description

[0021] Figure 1 This is a plan view of the X-shaped structure load-bearing system in some embodiments of the present invention;

[0022] Figure 2 This is a main elevation view of the X-shaped structure load-bearing system in some embodiments of the present invention;

[0023] Figure 3 This is a structural schematic diagram of the X-shaped structure load-bearing system in some embodiments of the present invention;

[0024] Figure 4 This is a schematic diagram of the design method of the X-bracing structure load-bearing system in some embodiments of the present invention.

[0025] Numbers in the attached drawings:

[0026] 10 is the main facade;

[0027] 20 is an X-shaped support;

[0028] 30 is an out-of-plane strut;

[0029] 40 is an in-plane strut;

[0030] 50 is the main leg;

[0031] 60 is the main horizontal member of the jacket structure;

[0032] 70 is an X-shaped support node;

[0033] 80 represents the horizontal layer of the drainage truss. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the system or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "assembly," "setup," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] In deep-water jacket systems, the X-bracing structure is a crucial component, playing a vital role in maintaining structural stability when placed on the main elevation. However, in related technologies, the small span of the X-bracing structure and the excessive number of main horizontal layers result in an excessively large overall weight of the jacket, making it unsuitable for the design requirements of deep-water jacket systems.

[0038] In view of this, the present invention provides an X-bracing structure load-bearing system and its design method. In this system, out-of-plane struts are installed outside the X-bracing structure on the main facade. One end of each out-of-plane strut connects to the X-shaped support node of the X-bracing structure, and the other end connects to the drainage truss of the jacket structure. This out-of-plane strut ensures the stiffness and stability of the X-shaped support, especially for large-span X-bracing structures. The increased span of the X-shaped support significantly reduces the number of main horizontal layers of the jacket structure, thereby reducing the overall weight of the jacket structure. Furthermore, the design method for the X-bracing structure load-bearing system can be used for numerical analysis and design of such systems. This method fills gaps in current standards, provides a theoretical basis for design, and can verify the reliability of large-span X-bracing structure load-bearing systems.

[0039] The following is a detailed description of an X-bracing structure load-bearing system and its design method provided by an embodiment of the present invention, with reference to the accompanying drawings.

[0040] Example 1:

[0041] Reference Figure 1 As shown, a large-span X-bracing structure bearing system is set between two adjacent main horizontal layers of the jacket structure, relying on each of the four main facades 10 of the jacket structure. The X-bracing structure bearing system includes X-shaped supports 20 located inside the main facade 10 of the jacket structure and out-of-plane struts 30 located outside the frame of the main facade 10 of the jacket structure.

[0042] Reference Figure 2 As shown, within the main facade 10 of the jacket structure, the X-shaped support 20 consists of four in-plane struts 40. One end of the in-plane strut 40 is connected to the intersection of the main horizontal member 60 and the main leg 50 of the jacket structure, and the other end intersects at a point, which is called the X-shaped support node 70.

[0043] Reference Figure 3 As shown, the jacket has four main legs 50, which are arranged in a stern pattern to form four main facades 10. The drainage truss is located inside the four main facades 10. One end of the out-of-plane strut 30 is connected to the horizontal layer 80 of the drainage truss, and the other end is connected to the X-shaped support node 70. The out-of-plane strut 30 provides out-of-plane support for the X-shaped support 20. The out-of-plane strut 30 supports and fixes the in-plane strut 40, effectively shortening the effective length of the in-plane strut 40, enabling the in-plane strut 40 to withstand greater buckling loads.

[0044] The X-shaped structural support system provided by this invention forms a support system between the main horizontal layers of the jacket framework, consisting of the horizontal layer 80 frame of the drainage truss, the out-of-plane struts 30, and the surrounding X-shaped supports 20, providing horizontal and lateral stiffness for the jacket framework. This significantly increases the span between the main horizontal layers of the jacket framework, thereby significantly reducing the number of main horizontal layers, effectively saving steel and reducing the installation weight of the jacket framework.

[0045] Example 2:

[0046] Reference Figure 4 The design method of the X-bracing structure bearing system provided in Example 1 includes: setting boundary conditions for finite element analysis, including setting the support conditions, loading methods and constraint conditions of out-of-plane struts and X-shaped supports; applying load to the loaded end of the X-shaped support, and gradually changing the tension-compression ratio to find the critical buckling load factor of the X-shaped support; and correcting the effective length coefficient of the X-shaped support in the jacket calculation model according to the critical buckling load factor.

[0047] The design method for the X-bracing structure load-bearing system specifically includes the following steps S1 to S4.

[0048] Step S1: Construct a finite element model of a large-span X-bracing structure with out-of-plane support, set material parameters, and optionally ignore the effects of initial geometric defects and residual stresses of the out-of-plane struts and X-shaped supports during simulation, and assume that the cross-section remains unchanged during loading.

[0049] Step S2: Set the boundary conditions for finite element analysis, including setting the support conditions, loading methods, and constraint conditions for out-of-plane struts and X-shaped supports. Specifically, considering the limiting effect of the flexibility of the drainage truss on the stability of the X-shaped support structure with out-of-plane support in the main structure, in order to realistically simulate the working conditions of the out-of-plane support, the drainage truss at the actual connection of the out-of-plane support is transformed into an equivalent elastic support; the unloaded end of the X-shaped support is set with a fixed constraint, the loaded end releases the axial displacement, and an axial load is applied, so as to simulate the behavior of the structure in the actual stress process.

[0050] Step S2.1: In this invention, the influence of out-of-plane support on the overall structural stability is emphasized. Therefore, in the simulation, an equivalent stiffness elastic support is used at the end of the out-of-plane support rod to characterize the restriction of the external truss on the structure with out-of-plane support X-bracing. The equivalent axial stiffness and equivalent rotational stiffness are obtained by converting the deformation degree of the model at the connection position between the end of the out-of-plane support and the truss under static constant load.

[0051] Step S2.1.1: Calculate the equivalent axial stiffness: With the out-of-plane support point as the origin of the coordinate system, the axial direction of the out-of-plane support as the Z-axis, and the vertical direction as the Y-axis, apply axial static force at the origin of the relative coordinate system during the simulation, measure the axial deformation of the out-of-plane support point due to the force, and calculate the equivalent axial stiffness in the direction of the relative coordinate system through the conversion formula.

[0052] Step S2.1.2: Calculate the equivalent rotational stiffness: Construct a relative Cartesian coordinate system and a cylindrical coordinate system for the out-of-plane support point, apply a constant torque at the corresponding position, measure the arc change of the element near the out-of-plane support point caused by the torque, and calculate the equivalent rotational stiffness in each direction at the out-of-plane support point through the conversion formula.

[0053] Step S2.2: The X-shaped support is part of the jacket structure. Since fixed marine structures, such as jacket platforms, have high rigidity, the unloaded end of the X-shaped support is assumed to be fixed to the jacket during the simulation. Furthermore, to fully consider the impact of extreme working conditions on structural stability, the loaded end is considered to have both a more conservative sliding support and a more dangerous movable hinge support.

[0054] Step S3: Buckling stability analysis: For different cases in step 2.2, apply load to the loaded end of the X-shaped support, with the tension-compression ratio varying from -1.0 to 1.0, until the X-shaped support buckles, and obtain the critical buckling load of the X-shaped support. The critical buckling load factor is then calculated using theoretical formulas.

[0055] Step S3.1: Perform buckling stability analysis on the X-shaped brace using the buckling analysis module. Apply tensile and compressive loads to the two in-plane struts at the loaded end of the X-shaped brace. The tensile-compression ratio varies from -1.0 to 1.0. During the loading process, keep the tensile-compression ratio constant and ensure axial loading to obtain the in-plane critical buckling load P. cr .

[0056] Step S3.2: Calculate the critical buckling load factor according to the theoretical formula. The calculation formula is as follows: Among them, P cr0 P is the critical buckling load of the out-of-plane strut. cr For the critical buckling load of the X-shaped support, E 0 Let P be the elastic modulus of the out-of-plane strut, I0 be the moment of inertia of the out-of-plane strut section, and L0 be the length of the out-of-plane strut. The P obtained in step S3.1... cr The out-of-plane strut parameters E0, I0, and L0 are then substituted into the calculation formula to obtain the critical buckling load factor.

[0057] Step S4: Jacket X-bracing structure design: In the jacket structure design process, the effective length coefficient is corrected in the jacket calculation model. The correction coefficient used is the critical buckling load factor calculated in step 3.2.

[0058] In this invention, by performing finite element analysis on the stability of an X-bracing structure with out-of-plane support, the results show that the degree of freedom at the loaded end, the force at the loaded end, the elastic support stiffness of the out-of-plane support, and the wall thickness of the out-of-plane support all affect the stability of the structure.

[0059] This invention reduces steel consumption and lowers the installation weight of the jacket structure by setting out-of-plane supports and applying a modified effective length coefficient to the X-bracing structure. At the same time, the design method of the X-bracing structure load-bearing system proposed in this invention, based on the modified coefficient value obtained by the design method, can fill the gap in the current specifications, thereby providing effective guidance for engineering design and ensuring the safety and reliability of the large-span X-bracing structure load-bearing system of deep-water jackets.

[0060] It should be noted that the "and / or" in the text includes three options. Taking "A and / or B" as an example, it includes technical option A, technical option B, and technical option that satisfies both A and B.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for an X-bracing structural support system for a deep-water jacket, the jacket comprising a launching truss and several main horizontal layers, wherein the X-bracing structural support system is installed between two adjacent main horizontal layers along the main facade of the jacket, the X-bracing structural support system comprising X-shaped supports located within the main facade and out-of-plane struts located outside the main facade; wherein... The X-shaped support is configured to connect to and support the jacket structure via its outer end, and has an X-shaped support node in the middle; one end of the out-of-plane strut is connected to the X-shaped support node, and the other end is connected to the run-out truss of the jacket structure on its side. The jacket structure has main legs forming the main facade and main horizontal members located on the main horizontal layer. The X-shaped support consists of four in-plane struts. The outer ends of the four in-plane struts are connected to the intersection of the main horizontal members and the main legs of the jacket structure, and the other ends are connected to the X-shaped support nodes. The jacket structure has four main legs, which are arranged in a rectangular shape and form four main facades. The design method is characterized by including: Step S1: Construct a finite element model of an X-shaped support with out-of-plane struts and set material parameters to simulate the behavior of the X-shaped support; Step S2: Set the boundary conditions for finite element analysis, including setting the support conditions, loading methods, and constraint conditions for out-of-plane struts and X-shaped supports, including: Considering the limiting effect of the flexibility of the truss on the stability of the X-shaped support with out-of-plane struts in the jacket structure, in order to realistically simulate the working conditions of the out-of-plane struts, the truss at the actual connection of the out-of-plane struts is transformed into an equivalent elastic support. The unloaded end of the X-shaped support is fixedly constrained, while the loaded end releases axial displacement and applies axial load. Considering the impact of out-of-plane struts on the overall structural stability, equivalent stiffness elastic supports are used at the ends of the out-of-plane struts in the simulation to characterize the constraint of the external truss on the X-shaped supports with out-of-plane struts. The equivalent axial stiffness and equivalent rotational stiffness are obtained by converting the deformation of the model at the connection position between the end of the external strut and the water truss under static constant load. Step S3: Apply a load to the loaded end of the X-shaped brace, and gradually change the tension-compression ratio to find the critical buckling load factor of the X-shaped brace; Step S4: Based on the critical buckling load factor, correct the effective length coefficient of the X-shaped support in the jacket design.

2. The design method of the X-bracing structure load-bearing system according to claim 1, characterized in that, In step S1, the effects of initial geometric defects and residual stress of the out-of-plane struts and X-shaped supports are ignored when simulating the X-shaped supports, and the cross-section remains unchanged by default during the loading process.

3. The design method of the X-bracing structure load-bearing system according to claim 2, characterized in that, Step S3 involves applying a load to the loaded end of the X-shaped support, with the tension-compression ratio varying within a certain range. The critical buckling load of the X-shaped brace is obtained by calculating the critical buckling load factor until the X-shaped brace buckles.

4. The design method of the X-bracing structure load-bearing system according to claim 3, characterized in that, Step S3 includes the following specific steps: Step S3.1: Perform buckling stability analysis on the X-shaped brace using the buckling analysis module. Apply tensile and compressive loads to the two in-plane struts at the loaded end of the X-shaped brace, with the tension-to-compression ratio varying within a certain range. During the loading process, the tension-compression ratio remains constant and axial loading is ensured to obtain the in-plane critical buckling load; Step S3.2: According to the calculation formula: Calculate the critical buckling load factor, where P cr0 P is the critical buckling load of the out-of-plane strut. cr Let E0 be the critical buckling load of the X-shaped support, E0 be the elastic modulus of the out-of-plane strut, I0 be the moment of inertia of the out-of-plane strut section, and L0 be the length of the out-of-plane strut.

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