A large-span flexible support bulkhead structure and design method

Abstract

The present invention relates to a large-span flexible support bulkhead structure and design method, belonging to the field of ship design and manufacturing technology. It includes adopting a uniform vertical skeleton structure without vertical girders; setting discontinuous horizontal stiffeners in areas where the compressive stress caused by the bending of high web beams is large; avoiding the installation of doors and windows in areas where the shear stress at the ends of the support bulkhead is large, and increasing the thickness of the end bulkhead plate; increasing the plate thickness in areas with large openings such as doors and windows; effectively connecting the upper and lower ends of the vertical stiffeners of the support bulkhead to the deck structure, and providing transition connection structures at the supporting ends on both sides of the bulkhead. The present invention meets the requirements of bending resistance, shear strength, rigidity and stability by setting uniform vertical stiffeners and adopting thin plates and small ribs to support the bulkhead structure. It can greatly reduce the size of the cabin wall components, shorten the span of the top deck and bottom deck, reduce the size of the double deck and bulkhead structure, increase the effective floor height and effective cabin area, and greatly reduce the weight of the structure.

Description

Technical Field

[0001] The invention relates to a large-span flexible support bulkhead structure and a design method thereof, belonging to the technical field of ship design and manufacturing. Background Art

[0002] There are one or more large loading compartments inside a dock ship or a ro-ro ship. The width of the large loading compartment can be more than 20 meters and the length can be more than 100 meters. No pillars can be installed inside the large loading compartment. Some ship types require a functional cabin deck between two large loading compartments or between the large loading compartment and the main deck (the height between the double decks is generally 2.5-3 meters). Figure 1 and Figure 2 As shown, there is no effective support above or below the two decks in a large span, and the top deck in the double deck is often the loading deck or flight deck, which needs to withstand the loads of heavy equipment such as roll-on / roll-off, take-off and landing, or open-air water pressure (the equivalent load can reach 2t / m 2 or larger), the bottom deck of the double deck needs to bear the uniformly distributed water pressure load of the cabin (the equivalent load can reach 1t / m 2 or larger). Due to the large span of the double deck, if both the top and bottom decks are designed as unsupported, large-span single decks, the deck crossbeam webs will need to be high and thick to meet strength and stiffness requirements, resulting in high weight and space costs. To shorten the effective span of the deck structure, the conventional method is to install pillars. However, since there is no effective support above the top deck and below the bottom deck, pillars are not suitable for large-span double decks. Therefore, the cabin wall structure between the large-span double decks needs to be used to support the top and bottom decks. If a transverse bulkhead is installed between the longitudinal walls of the loading hold, this transverse bulkhead can be designed as an effective supporting bulkhead for the large-span double deck. This transverse supporting bulkhead has a large span and no effective support below, so it is a large-span supporting bulkhead. The longitudinal bulkhead between the above-mentioned transverse supporting bulkheads can be designed as an effective supporting bulkhead. If the distance between the transverse supporting bulkheads is large (for example, greater than 20 meters), this longitudinal bulkhead is a large-span supporting bulkhead.

[0003] Large-span support bulkheads, as high-web beams, are subject to significant bending and shear stresses. Conventional designs employ a vertical girder and horizontal skeletal structure. However, this skeletal structure results in tall, large, and heavy vertical girder webs, and is also relatively complex to construct. Therefore, there is an urgent need to develop a structural design and method for large-span support bulkheads that, without strong support above or below, maintains sufficient bending and shear resistance to support the upper and lower deck structures. Furthermore, these structures possess advantages such as compact footprint, low weight, simplified construction, and ease of cabin layout. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problem of how to obtain a structural type and design method for a large-span supporting bulkhead so that the supporting bulkhead has sufficient bending and shear resistance to support the upper and lower deck structures without strong support above or below, while having the advantages of small space occupation, light weight, simple construction, and convenient cabin layout.

[0005] To achieve the purpose of solving the above-mentioned problems, the technical solution adopted by the present invention is to provide a large-span flexible support bulkhead structure, including adopting a uniform vertical skeleton structure without vertical girders; providing discontinuous horizontal stiffeners in areas where the compressive stress caused by the bending of the high web beam is large, that is, in the area above the neutral axis and close to the top deck; avoiding the installation of doors and windows in areas where the shear stress is large at the ends of the support bulkhead, and increasing the thickness of the end bulkhead plate; increasing the plate thickness in areas with large openings such as doors and windows; effectively connecting the upper and lower ends of the vertical stiffeners of the support bulkhead to the deck structure, and providing transition connection structures at the supporting ends on both sides of the bulkhead.

[0006] The present invention provides a design method for a large-span flexible support bulkhead structure, comprising preliminary design of component dimensions according to high web beams; establishing a finite element model of the top deck and bottom deck structures for strength and stability verification; and performing local optimization adjustments to obtain optimal structural dimensions. The design process and method include the following steps:

[0007] Step 1: Determine the supporting bulkhead system and load conditions; determine the effective supporting bulkhead system for the double deck; determine the span and spacing of the effective supporting bulkheads, with the span being the distance between the bulkhead end supports and the spacing being half the distance between the forward and aft supporting bulkheads; determine the loads and hazardous conditions for the top and bottom decks;

[0008] Step 2: Preliminary determination of the plate thickness and component dimensions of the supporting bulkhead;

[0009] Step 2.1: Consider the supporting bulkhead as a high web beam and the supporting bulkhead system as a cross beam system. Calculate the bending moment and shear force of the supporting bulkhead structure under hazardous conditions. The span of the supporting bulkhead is the same as in Step 1. Apply the sum of the top and bottom deck loads. The load-bearing width is the spacing between the supporting bulkheads. Calculate the modulus and shear area requirements of the supporting bulkhead as a high web beam based on the allowable bending and shear stresses specified in the specifications.

[0010] Step 2.2: Preliminarily determine the bulkhead plate thickness at the mid-span based on the modulus requirements of the high web beam, and the bulkhead plate thickness at the ends based on the shear area requirements. The thickness of the upper and lower flanges of the high web beam is the same as the thickness of the top and bottom decks. Determine the width of the upper and lower flanges of the high web beam supporting the bulkhead using the formula.

[0011] Step 2.3: Based on the width and thickness of the upper and lower wing plates and the height and thickness of the bulkhead plates determined in Step 2.2, determine the neutral axis height, mid-span bending stress, and end shear stress distribution of the high web beam; determine the horizontal reinforcement spacing and number based on stability requirements;

[0012] Step 2.4: The dimensions of the vertical stiffeners for the supporting bulkheads can be designed in accordance with the general supporting enclosure, i.e. calculated based on the stability requirements of the pillars under top deck loads. The bearing length can be taken as the spacing between the vertical stiffeners, and the bearing width can be taken as the spacing between the supporting bulkheads.

[0013] Step 2.5: For large-span supported bulkheads, vertical stiffeners may be of the minimum size according to the rules or the unified requirements of the ship, provided that stability requirements are met. Horizontal reinforcements above the neutral axis of the bulkhead near the upper wing plate may be discontinuous flat steel or profiles of the same thickness and height as the vertical stiffeners. Bulkhead plating may also be of the minimum thickness, provided that bending strength requirements are met.

[0014] Step 2.6: Design the connection structure and node type between the bulkhead and the top and bottom deck structures according to the deck structures above and below the bulkhead at different locations;

[0015] Step 3: Design verification and optimization adjustment;

[0016] Step 3.1: Select the appropriate range and establish the finite element model;

[0017] Step 3.2: Set appropriate boundary conditions and apply loads to perform hazardous conditions calculations; calculate structural stresses and displacements;

[0018] Step 3.3: Check the calculation results and optimize and adjust the component dimensions as needed. If the verification results do not meet the design requirements, adjust the supporting bulkhead plating thickness and stiffener dimensions, and further adjust the top and bottom deck structural dimensions until they meet the design requirements.

[0019] Step 3.4: Compare and analyze the similarities and differences between the results calculated in Step 3.3 and Step 2.3 to verify the elements of the simplified design method in Step 2. Adjust the above parameters based on the finite element analysis results. Further analyze whether the stress distribution of the supporting bulkhead satisfies the requirement of simply supported at both ends or rigidly fixed at both ends. Adjust the flexibility coefficients at both ends of the bulkhead based on the finite element analysis results. Further summarize the rules to improve the design accuracy of Step 2.

[0020] Preferably, the widths of the upper and lower wing plates supporting the bulkhead high web beam in step 2.2 are determined as follows:

[0021]

[0022] Where b eis the width of the high web beam strip of the supporting bulkhead; S is the spacing between the supporting bulkheads, in m; l is the span of the supporting bulkheads, in m.

[0023] Preferably, in the above step 2.3, the spacing and number of horizontal ribs are determined according to stability requirements within a certain range above the neutral axis at the mid-span and close to the upper wing plate.

[0024] Preferably, the vertical stiffener in step 2.5 is not less than HP80x6; and the bulkhead plate thickness is not less than 5 mm.

[0025] Preferably, in the connection structure and node type in step 2.6 above, the upper and lower ends of the vertical stiffeners are not beveled; the upper end is connected to the longitudinal with or without a bracket, or the upper end is directly connected to the adjacent member with a bracket; the lower end is connected to the deck by aligning the lower end with the longitudinal or by adding a stiffener.

[0026] Preferably, the appropriate range selected in step 3.1 above is a double-deck structure including a large-span support bulkhead, top deck, and bottom deck; the transverse boundary should at least extend to the strong support structure or continue outward to the side; the longitudinal boundary should at least include the area of interest and appropriately extend to a certain range, at least to the next transverse support bulkhead; for a refined analysis of the support bulkhead structure, the finite element mesh can be 50x50, the stiffener web can use 3 meshes, and a finer mesh can be used at the stiffener end nodes.

[0027] Preferably, setting appropriate boundary conditions in the above step 3.2 includes using simply supported boundary conditions at the bottom where there is strong support; simply supported boundary conditions can be used at the front and rear ends where there is strong support below; if there is no strong support at the front and rear ends, a freely deformable flat section or symmetrical boundary conditions can be used; the dangerous working conditions include the top deck and the bottom deck both bearing the maximum load; the top deck bearing the maximum load and the bottom deck bearing no load, or the top deck bearing no load and the bottom deck bearing the maximum load.

[0028] Preferably, the verification contents in the above step 3.3 include whether the maximum vertical deformation of the double deck meets the design requirements; whether the maximum stress of the double deck meets the allowable stress requirements; whether the stability of the plates and stiffeners of the supporting bulkheads meets the design requirements, in particular, whether the areas above the neutral axis of the supporting bulkheads with high compressive stress, the areas at both ends of the supporting bulkheads with high shear stress, and the average compressive stress of the cross section of the vertical stiffeners; and whether the stress concentration areas near the bulkhead door openings meet the design requirements.

[0029] Preferably, the elements of the simplified design method in step 2 of the verification analysis in step 3.4 above include the widths of the upper and lower wing panels and the load-bearing width of the supporting bulkhead.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] Compared with the conventional vertical girder plus horizontal reinforcement structure, the present invention has the following advantages:

[0032] (1) There are no large vertical beams, so it takes up less space in the cabin.

[0033] (2) All stiffeners are vertical, and the horizontal reinforcement near the top deck is a discontinuous structure. They do not need to pass through the girders, and there are no cuts or patching plates, making construction simple.

[0034] (3) Compared with the conventional horizontal frame strength structure, the supporting bulkhead itself is lighter in weight and can effectively support the top and bottom deck structures, shorten the span of the top and bottom deck structures, and significantly reduce the size of the top and bottom deck girders.

[0035] (4) Except that doors and windows should not be arranged within a certain range at the ends, there is no need to consider the arrangement of vertical girders and the position relationship between vertical girders and strength components of top deck and bottom deck, and the cabin layout is flexible.

[0036] (5) As the bulkhead structure adopts a uniform small stiffener structure without large vertical girders, the load is more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the layout of a large-span double-deck in the existing technology. Figure 1 .

[0038] Figure 2 This is a schematic diagram of the layout of a large-span double-deck in the existing technology. Figure 2 .

[0039] Figure 3 Schematic diagram of a conventional horizontal frame bulkhead structure.

[0040] Figure 4 This is a schematic diagram of the flexible support bulkhead structure of the present invention.

[0041] Figure 5 Schematic diagram of the layout of embodiment 1 of the large-span flexible support bulkhead.

[0042] Figure 6 This is a layout diagram of the restaurant area between a large-span double-deck structure in Example 2. DETAILED DESCRIPTION

[0043] In order to make the present invention more clearly understood, the preferred embodiments are described below in conjunction with the accompanying drawings. Figure 1-6 The detailed description is as follows:

[0044] Large-span supported bulkheads without support above or below are different from conventional supported bulkheads. Conventional supported bulkhead structures generally have smaller spans and are supported by rigid bulkheads, pillars or strong beam structures above or below. Therefore, conventional supported bulkheads can play the role of supporting bulkheads as long as vertical stiffeners are set according to the specifications and the vertical stiffeners meet the pillar design requirements. However, in some cases, such as large-span supported bulkheads between double decks, which have no support above or below and a large span, will generate large bending stress and shear stress under the action of deck loads. Therefore, in addition to meeting the vertical support requirements, large-span supported bulkheads also need to have sufficient bending and shear resistance. For this reason, the existing technology usually adopts a horizontal skeleton structure with vertical girders and horizontal reinforcements; Figure 3 As shown in Figure 1, the use of horizontal framing improves bending stiffness and structural stability under compressive stress, thereby enhancing bending and shear resistance. On the other hand, horizontal framing structures have weak vertical stiffness, requiring vertical girders to be installed at regular intervals to support the horizontal framing and provide vertical support. Horizontal framing bulkheads are typically used for strong structures such as shell plating, decks, and main longitudinal bulkheads that contribute to overall longitudinal strength. However, when used as supporting bulkheads between long-span double decks, they have the following disadvantages: First, the vertical girders are large, significantly reducing the utilization of the cabin area between the double decks. Second, the vertical girders are heavy, making the bulkhead structure heavier overall. Third, the horizontal framing passes through the vertical girders, requiring numerous through-holes or additional plates, making the construction process relatively complex. Fourth, the vertical girders need to align with the strong members of the top and bottom decks, making it difficult to install doors in these locations. This places significant restrictions on the placement of doors and windows on the supporting bulkheads, hindering cabin layout.

[0045] In order to solve the above technical problems, the technical solution of the present invention is as follows: Figure 4 As shown. Includes:

[0046] (1) A uniform vertical skeleton structure without vertical girders is adopted.

[0047] (2) Discontinuous horizontal stiffeners (flat steel or profiles) are installed in the area where the compressive stress caused by the bending of the high web beam is large, that is, above the neutral axis and within a certain range close to the top deck to meet the structural stability requirements.

[0048] (3) Avoid installing large doors and windows in areas with high shear stress at the ends of supporting bulkheads, and appropriately increase the thickness of the end bulkhead plating to improve its shear stability.

[0049] (4) For large opening areas such as doors and windows, the plate thickness can be appropriately increased as needed to improve structural continuity and alleviate stress concentration.

[0050] (5) The upper and lower ends of the vertical stiffeners supporting the bulkhead are effectively connected to the deck structure, and necessary transition connection structures are designed at the supporting ends on both sides of the bulkhead to improve the structural continuity and supporting effect.

[0051] Using the above-mentioned flexible support bulkhead structural design scheme, the component dimensions can be preliminarily designed according to the high web beam. Then, a finite element model including the top deck and bottom deck is established to check the strength and stability, and local optimization and adjustment are performed to obtain the optimal structural dimensions.

[0052] The basic design process and methods are as follows:

[0053] Step 1: Determine the support bulkhead system and load cases:

[0054] (1) Determine the effective support bulkhead system of the double deck. Any bulkhead with strong support below (such as the longitudinal wall aligned with the longitudinal wall of the loading hold below) can serve as the end support for other bulkheads. Any bulkhead with support at the end can serve as an effective support bulkhead and can also serve as the end support for other bulkheads. Similarly, the effective support bulkhead system of the double deck can be determined.

[0055] (2) Determine the span and spacing of the above-mentioned effective supported bulkheads. The span is taken as the distance between the bulkhead end supports, and the spacing is taken as half of the distance between the front and rear supporting bulkheads. Determine the loads and hazardous conditions of the top and bottom decks.

[0056] Step 2: Preliminary determination of the plate thickness and component size of the supporting bulkhead:

[0057] Step 2.1: Treat the supporting bulkhead as a high-web beam and the supporting bulkhead system as a cross-beam system. Calculate the bending moment and shear force of the supporting bulkhead structure under hazardous conditions. The supporting bulkhead span is the same as in Step 1. Apply the sum of the top and bottom deck loads. The bearing width is the spacing between the supporting bulkheads. Calculate the modulus and shear area requirements for the supporting bulkhead as a high-web beam based on the allowable bending and shear stresses specified in the code.

[0058] Step 2.2: Support the bulkhead using Figure 4 In the technical solution shown, the mid-span bulkhead plate thickness is preliminarily determined based on the module requirements of the high web beam, and the end bulkhead plate thickness is preliminarily determined based on the shear area requirements. The thickness of the upper and lower wing plates of the high web beam is the thickness of the top and bottom decks, and the width is preliminarily determined according to the following formula:

[0059] Where b e is the width of the high web beam strip of the supporting bulkhead; S is the spacing between the supporting bulkheads, in m; l is the span of the supporting bulkheads, in m.

[0060] Step 2.3: Based on the width and thickness of the upper and lower wing panels and the height and thickness of the bulkhead panels determined in Step 2.2, determine the neutral axis height, mid-span bending stress, and end shear stress distribution of the high web beam. High compressive stress due to bending exists within a certain range above the neutral axis at mid-span and near the upper wing panel. Determine the spacing and number of horizontal ribs based on stability requirements.

[0061] Step 2.4: The dimensions of the vertical stiffeners for the supporting bulkheads can be designed according to the general design of the supporting walls, that is, calculated based on the stability requirements of the pillars under top deck loads. The load-bearing length can be taken as the spacing between the vertical stiffeners, and the load-bearing width can be taken as the spacing between the supporting bulkheads.

[0062] Step 2.5: For long-span supported bulkheads, vertical stiffener stability is generally easier to achieve. Therefore, while meeting stability requirements, vertical stiffeners can be constructed using the minimum dimensions specified in the specifications or the ship's unified requirements, generally no less than HP80x6. Horizontal reinforcement above the bulkhead's neutral axis and near the upper wing plating can be constructed using discontinuous flat steel or profiles of equal thickness and height to the vertical stiffeners. While meeting bending strength requirements, the bulkhead plating can also be constructed using the minimum thickness, generally no less than 5mm.

[0063] Step 2.6: Design the connection structure and node type between the bulkhead and the top and bottom deck structures based on the deck structures above and below the bulkhead at different locations. Generally, the upper and lower ends of vertical stiffeners are not beveled. The upper end is connected to the longitudinals (with or without brackets) or directly connected to adjacent members with brackets, and the lower end is connected to the deck (with the lower end aligned with the longitudinals or with additional stiffeners).

[0064] Step 3: Design verification and optimization:

[0065] Step 3.1: Select an appropriate range and establish a finite element model. A double-deck structure with a long-span braced bulkhead, top deck, and bottom deck should be selected. The transverse boundary should extend at least to the strong supporting structure (e.g., the loading hold longitudinal wall) or outward to the side. The longitudinal boundary should at least include the area of interest and extend appropriately to at least the next transverse braced bulkhead. To provide a more refined analysis of the braced bulkhead structure, a 50x50 finite element mesh can be used. Three meshes can be used for the web of the stiffeners, and finer meshes can be used at nodes such as the stiffener ends.

[0066] Step 3.2: Set appropriate boundary conditions and apply loads to perform hazardous condition calculations. Use simply supported boundary conditions where there is strong support below (such as the longitudinal wall of the loading hold or the side shell). Use simply supported boundary conditions where there is strong support below the front and rear ends (such as the front end wall of the loading hold). If there is no strong support at the front and rear ends, use a freely deformable flat section or symmetrical boundary conditions. Three hazardous conditions are generally selected: one in which both the top and bottom decks bear the maximum load; two in which the top deck bears the maximum load and the bottom deck bears no load; and three in which the top deck bears no load and the bottom deck bears the maximum load. Calculate structural stresses and displacements.

[0067] Step 3.3: Verify based on the calculation results and optimize and adjust component dimensions as appropriate. The main verifications are: First, the maximum vertical deformation of the double deck meets the design requirements; second, the maximum stress of the double deck meets the allowable stress requirements; third, the stability of the supporting bulkhead plating and stiffeners meets the design requirements, especially the areas with high compressive stress above the neutral axis of the supporting bulkhead, the areas with high shear stress at both ends of the supporting bulkhead, and the average compressive stress in the vertical stiffener cross-section; fourth, the stress concentration areas near the bulkhead door opening. Based on the above verification results, if the design requirements are not met, the supporting bulkhead plating thickness and stiffener dimensions can be adjusted, and the top and bottom deck structural dimensions can be further adjusted until the design requirements are met.

[0068] Step 3.4 compares and analyzes the results from Step 3.3 and Step 2.3 to verify the simplified design method used in Step 2, such as the widths of the upper and lower wing panels and the load-bearing width of the supporting bulkhead. These parameters are adjusted based on the finite element analysis results. Next, the stress distribution of the supporting bulkhead can be further analyzed to determine whether it satisfies the requirement for simply supported or rigidly fixed ends. The flexibility coefficients at both ends of the bulkhead can be adjusted based on the finite element analysis results. This allows for further analysis of the design principles and improves the accuracy of Step 2.

[0069] In the above design process, step 1 is the preparation process, step 2 is the core process, and step 3 is the verification and follow-up step of step 2. Step 1 is to analyze the stress characteristics of the supporting bulkhead system based on the double-deck layout, thereby determining the supporting bulkhead system and hazardous working conditions. Step 2 is to conduct a preliminary design of the supporting bulkhead as a single-span beam according to the cross beam system, and determine the dimensions of the bulkhead plate and stiffeners. Step 3 is to conduct the final verification, optimization, and verification of the scheme, and at the same time, the simplified method of step 2 can be improved and perfected. Because the supporting bulkhead adopts a flexible structural design scheme with small stiffeners, the supporting bulkhead's support for the deck cannot be regarded as an absolutely rigid support. Therefore, the actual stress state and stress distribution of the supporting bulkhead and the top and bottom decks may differ from the previous assumptions. Therefore, it is necessary to combine the finite element calculation in step 3 for verification and optimization to ultimately meet the design requirements and optimize the structure. Secondly, as a large-span, high-web beam, the supporting bulkhead's parameters, such as the widths of its upper and lower wing panels, the load-bearing width, and the end flexibility coefficient, are complexly correlated with the cabin layout, the structural stiffness of the top and bottom decks, and the structural transition type of the supporting bulkhead end. Generally speaking, when the span and spacing of the supporting bulkhead are small, it can be considered that the supporting bulkhead provides full support for the deck. When the span and spacing of the supporting bulkhead are large, the supporting bulkhead only provides flexible support for the deck, and its upper and lower wing panel widths and load-bearing width will be smaller than the spacing between the supporting bulkheads. Therefore, finite element calculations can be performed to determine these parameters, improve step 2, and enhance its accuracy.

[0070] Example 1:

[0071] like Figure 5 For the arrangement of a living cabin between a large-span double-deck, the longitudinal walls (01-08) on both sides of the cabin are aligned with the main longitudinal bulkhead below. Above and below the double-deck between the main longitudinal bulkheads are large cabins with no effective support. The technical solution of the present invention can be used to design the transverse bulkheads (10-19) and longitudinal bulkheads (20-23) within the main longitudinal bulkheads as flexible support bulkheads to support the upper and lower deck strong transverse beams and longitudinal girders, shortening their span. The transverse bulkheads are designed as high-web beams supported between the main longitudinal bulkheads; the longitudinal bulkheads are designed as high-web beams supported between the transverse bulkheads. The longitudinal and transverse bulkheads can be made of 5mm thin plates and uniform vertical stiffeners HP100x6. The plate thickness near the support points at both ends of the bulkhead should be thickened to meet the stability requirements under shear stress. Horizontal ribs are added above the bulkhead to ensure that the bulkhead plate meets the stability requirements under bending and compressive stress. The area around openings such as doors is appropriately thickened.

[0072] For the structural types of flexible supported transverse bulkheads (10-19) and longitudinal bulkheads (20-23), refer to Figure 4 ,The above scheme and dimensions can be further optimized through finite element calculation, and finally a reasonable scheme is obtained.

[0073] Example 2

[0074] like Figure 6 This is a layout diagram of a restaurant area between a large-span double-deck. Due to the large number of diners, the restaurant area is large. The longitudinal walls (601-602) on both sides are aligned with the main longitudinal bulkhead below. The double-deck between the main longitudinal bulkheads is a large cabin above and below, without effective support. The technical solution of the present invention can be used to design the transverse bulkheads (610-613) and the internal long longitudinal wall (620) between the main longitudinal walls as flexible support bulkheads to support the upper and lower deck strong transverse beams and longitudinal girders, shortening their span. The transverse bulkheads are designed based on the high web beams supported between the main longitudinal bulkheads; the long longitudinal bulkheads are designed based on the high web beams supported between the transverse bulkheads. The longitudinal and transverse bulkheads can be made of 6mm thin plates and uniform vertical stiffeners HP120x6. The plate thickness near the support points at both ends of the bulkhead should be thickened to meet the stability requirements under shear stress. Horizontal ribs are added above the longitudinal and transverse bulkheads to ensure that the bulkhead plate meets the stability requirements under bending and compressive stress. The area around openings such as doors is appropriately thickened.

[0075] For the structural types of flexible supported transverse bulkheads (610-613) and longitudinal bulkheads (620), refer to Figure 4 ,The above scheme and dimensions can be further optimized through finite element calculation, and finally a reasonable scheme is obtained.

[0076] The technical solution of the present invention does not adopt the conventional vertical girder plus horizontal rib structure, but instead sets up uniform vertical stiffeners. Its core idea is to use thin plates and small ribs to lightweight support the bulkhead structure to meet the requirements of bending and shear strength, stiffness and stability. Since the web of the supporting bulkhead is relatively high, the bending stiffness is mainly provided by the upper wing plate (top deck) and the lower wing plate (bottom deck), so the bulkhead plate is relatively thin. In view of the low longitudinal compressive stability of the thin plate and vertical stiffener structure, horizontal ribs are added to the area with large compressive stress caused by bending near the upper wing plate to improve its longitudinal compressive stability. For the area with large shear stress at the end of the supporting bulkhead, the plate thickness is appropriately increased to improve its shear stability, so that the flexible bulkhead structure composed of thin plates and small ribs can effectively support the top deck and bottom deck structures. Doors should be avoided at the ends of supporting bulkheads. This also applies to conventional bulkheads. Because the cabin walls have a certain length, it is usually rarely required to open doors near the intersection of the two cabin walls, that is, at the cabin end support point. This is easy to do, but conventional bulkheads also need to avoid the vertical girder position when opening doors. Therefore, the flexible supporting bulkhead used in the present invention is more conducive to cabin layout.

[0077] After verification by actual ship application, the adoption of the above-mentioned flexible support bulkhead structure type can significantly reduce the component size of the cabin wall, while shortening the span of the top deck and bottom deck, so that the size of the double deck and bulkhead structure are greatly reduced, the effective floor height and effective cabin area are increased, and the structural weight is greatly reduced.

[0078] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A design method for a large-span flexible support bulkhead structure. The designed large-span flexible support bulkhead structure adopts a uniform vertical skeleton structure without vertical girders; discontinuous horizontal stiffeners are provided in areas where the compressive stress caused by the bending of the support bulkhead is large, that is, in areas above the neutral axis and close to the top deck; doors and windows are avoided in areas where the shear stress is large at the ends of the support bulkhead, and the thickness of the end bulkhead plate is increased; the plate thickness is increased in areas with large openings such as doors and windows; the upper and lower ends of the vertical stiffeners of the support bulkhead are effectively connected to the deck structure, and transition connection structures are provided at the support ends on both sides of the bulkhead. The method is characterized in that: The design method includes preliminary design of component dimensions based on the supporting bulkhead; establishing a finite element model of the top and bottom deck structures to verify strength and stability; and performing local optimization adjustments to obtain the optimal structural dimensions. The specific steps are as follows: Step 1: Determine the supporting bulkhead system and load conditions; determine the effective supporting bulkhead system for the double deck; determine the span and spacing of the effective supporting bulkheads, with the span being the distance between the bulkhead end supports and the spacing being half the distance between the forward and aft supporting bulkheads; determine the loads and hazardous conditions for the top and bottom decks; Step 2: Preliminary determination of the plate thickness and component dimensions of the supporting bulkhead; Step 2.1: Consider the supporting bulkhead as a high web beam and the supporting bulkhead system as a cross beam system. Calculate the bending moment and shear force of the supporting bulkhead structure under hazardous conditions. The span of the supporting bulkhead is the same as in Step 1. Apply the sum of the top and bottom deck loads. The load-bearing width is the spacing between the supporting bulkheads. Calculate the modulus and shear area requirements of the supporting bulkhead as a high web beam based on the allowable bending and shear stresses specified in the specifications. Step 2.2: Preliminarily determine the bulkhead plate thickness at the mid-span based on the modulus requirements of the high web beam, and the bulkhead plate thickness at the end based on the shear area requirements. The thickness of the upper and lower flange plates of the high web beam is the same as the thickness of the top and bottom decks. The width of the upper and lower flanges supporting the bulkhead high web beam is determined by the following formula: Where b e is the width of the flange plate of the high web beam supporting the bulkhead; S is the spacing between the supporting bulkheads, in m; l is the span of the supporting bulkheads, in m; Step 2.3: Determine the neutral axis height, mid-span bending stress, and end shear stress distribution of the high web beam based on the width and thickness of the upper and lower wing plates and the height and thickness of the bulkhead plates determined in Step 2.2; Determine the spacing and quantity of horizontal stiffeners based on stability requirements; Step 2.4: The dimensions of the vertical stiffeners for the supporting bulkhead can be designed in accordance with the general design of the supporting bulkhead, i.e. calculated according to the stability requirements of the pillars under the load of the top deck; The load-bearing length can be taken as the spacing between vertical stiffeners, and the load-bearing width can be taken as the spacing between supporting bulkheads; Step 2.5: For large-span supported bulkheads, vertical stiffeners shall be of the minimum size according to the rules or ship's unified requirements, provided that stability requirements are met. Horizontal stiffeners above the neutral axis of the bulkhead and near the upper wing plate may be discontinuous flat steel or profiles of the same thickness and height as the vertical stiffeners. Bulkhead plating may also be of the minimum thickness, provided that bending strength requirements are met. Step 2.6: Design the connection structure and node type between the bulkhead and the top and bottom deck structures according to the deck structures above and below the bulkhead at different locations; Step 3: Design verification and optimization adjustment; Step 3.1: Select the appropriate range and establish the finite element model; Step 3.2: Set appropriate boundary conditions and apply loads to perform hazardous conditions calculations; calculate structural stresses and displacements; Step 3.3: Check the calculation results and optimize and adjust the component dimensions as needed. If the verification results do not meet the design requirements, adjust the supporting bulkhead plating thickness and stiffener dimensions, and further adjust the top and bottom deck structural dimensions until they meet the design requirements. Step 3.4: Compare and analyze the similarities and differences between the results calculated in Step 3.3 and Step 2.3 to verify the elements of the simplified design method in Step 2. Adjust the above parameters based on the finite element analysis results. Further analyze whether the stress distribution of the supporting bulkhead satisfies the requirement of simply supported at both ends or rigidly fixed at both ends. Adjust the flexibility coefficients at both ends of the bulkhead based on the finite element analysis results. Further summarize the rules to improve the design accuracy of Step 2.

2. The design method of a large-span flexible support bulkhead structure according to claim 1, characterized in that: In step 2.3, the spacing and number of horizontal stiffeners are determined based on stability requirements within a certain range above the neutral axis at the mid-span and close to the upper wing plate.

3. The design method of a large-span flexible support bulkhead structure according to claim 1, characterized in that: In step 2.5, the vertical stiffener shall be no less than HP80x6; the bulkhead plate thickness shall be no less than 5mm.

4. The design method of a large-span flexible support bulkhead structure according to claim 1, characterized in that: In the connection structure and node type in step 2.6, the upper and lower ends of the vertical stiffeners are not beveled; the upper end is connected to the longitudinal with or without brackets, or the upper end is directly connected to the adjacent member with brackets; the lower end is connected to the deck by aligning the lower end with the longitudinal or by adding stiffeners.

5. The design method of a large-span flexible support bulkhead structure according to claim 1, characterized in that: The appropriate range selected in step 3.1 is a double-deck structure including a large-span supporting bulkhead, top deck, and bottom deck; the transverse boundary should at least extend to the strong supporting structure or continue outward to the side, and the longitudinal boundary should at least include the area of concern and appropriately extend to at least the next transverse supporting bulkhead; For a more refined analysis of the supporting bulkhead structure, the finite element mesh can be 50x50, the web of the stiffener can be 3 meshes, and a finer mesh can be used at the end nodes of the stiffener.

6. The design method of a large-span flexible support bulkhead structure according to claim 1, characterized in that: Setting appropriate boundary conditions in step 3.2 includes using simply supported boundary conditions where there is strong support below; using simply supported boundary conditions where there is strong support below the front and rear ends; if there is no strong support at the front and rear ends, a free-deformation flat section or symmetrical boundary conditions can be used; the dangerous working conditions include the top deck and the bottom deck both bearing the maximum load; the top deck bearing the maximum load and the bottom deck bearing no load, or the top deck bearing no load and the bottom deck bearing the maximum load.

7. The design method of a large-span flexible support bulkhead structure according to claim 1, characterized in that: The verification contents in step 3.3 include whether the maximum vertical deformation of the double deck meets the design requirements; whether the maximum stress of the double deck meets the allowable stress requirements; whether the stability of the plates and stiffeners supporting the bulkhead meets the design requirements; whether the areas with high compressive stress above the neutral axis of the supporting bulkhead and the areas with high shear stress at both ends of the supporting bulkhead meet the design requirements; whether the average compressive stress of the cross section of the vertical stiffener meets the design requirements; and whether the stress concentration areas near the bulkhead door opening meet the design requirements.

8. The design method of a large-span flexible support bulkhead structure according to claim 1, characterized in that: The elements of the simplified design method in step 2 of the verification analysis in step 3.4 include the width of the upper and lower wing panels and the load-bearing width of the supporting bulkhead.

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