A 3D Design Method for Tie-up Bridges Based on CATIA V6

Abstract

The application relates to a kind of based on CATIA V6's binding bridge three-dimensional design method, and its steps are as follows: initially according to the decomposition of design information to construct different skeleton models;In the skeleton model, respectively through geometric shape, attribute field, interface feature and local coordinate system feature, skeleton design is carried out;Based on the skeleton model, different specific designs are carried out to generate different types of models;Based on the different types of models, special design activities are carried out respectively, and verification results are obtained, the information in the skeleton design is adjusted according to the feedback of verification to carry out design iteration;According to the change requirement, the skeleton design is adjusted, and the design information is adaptively changed;After the verification of each design activity is passed, and there is no new design change requirement, the design is completed;Based on the data after the design is completed, the variant design of new design object is carried out.The design method of the application realizes parallel design based on overall layout, and improves design efficiency.

Description

Technical Field

[0001] This invention relates to the field of three-dimensional design of large marine equipment, and more particularly to a three-dimensional design method in the field of top-down associative design using CATIA V6 as the implementation tool. Background Technology

[0002] I. Overview of lashed bridges

[0003] With the booming development of the shipping industry, container ships are increasingly favored by the international market. One of the core technologies of container ships is the design of lashing bridges. These bridges are used to secure containers above the main deck and transfer the load generated by container stacking to the hull structure. Furthermore, a major characteristic that distinguishes lashing bridges from other ship structures is their mass production design. Currently, container ships are showing a trend towards larger sizes and more standardized designs. Ultra-large container ships (over 20,000 TEU) have more than 10 types of lashing bridges, sometimes reaching nearly 30 units. This mass production and diversification places higher demands on the flexibility and adaptability of the structural design. The design of lashing bridges needs to maximize the ship's loading capacity to achieve economical transportation, while also ensuring that the arrangement of steel outfitting components meets the shipowner's personalized customization and the classification society's specifications. Therefore, achieving standardized and rapid creation of lashing bridges, improving design efficiency, and shortening the development cycle are particularly important.

[0004] II. Analysis of Traditional Design Methods

[0005] Currently, the design of lashed bridges in China still relies on two-dimensional drafting. Because the design of lashed bridges involves the needs of various stakeholders (component manufacturers, shipyards, and shipowners), requires consideration of the cross-coordination of design schemes from various disciplines across the entire ship, and must also meet the strength specifications of classification societies, the design activities, including professional collaboration, design changes, finite element calculations, lashed bridge prototype testing, and the generation of engineering drawings, pose significant challenges to the design methodology.

[0006] Due to the complex stress conditions of lashed bridges, and the lack of empirical design guidelines from classification societies, designers must perform finite element strength checks on each bridge. In traditional design methods, the finite element model, after being discretized into a mesh, cannot be parametrically deformed, necessitating manual modeling for each bridge. This results in a disconnect between the design drawings and the computational model, and also between individual lashed bridges. Consequently, traditional two-dimensional design methods lead to a significant amount of repetitive work and inevitably introduce human error.

[0007] The lashed bridge mainly consists of two types of components: structural parts and iron outfitting parts. It also includes crucial lashing components. Based on a two-dimensional design method, these three types of components can only be considered by a single designer, making it difficult to establish a collaborative relationship with other designers. Furthermore, all design verification activities rely on design drawings as input, requiring the creation of additional verification models, resulting in a clear separation of priorities in the design process.

[0008] II. Fundamentals of 3D Design Implementation

[0009] Based on the Feature-Based Design and Assembly Design mechanisms in CATIA V6 (Computer-graphics Aided Tree-dimensional Interactive Application), two different methods for propagating design changes are implemented: one is Engineering Chain (EC) based on feature construction, and the other is Feature link (FL) based on External Feature reuse. This provides a technical foundation for addressing design change issues to some extent. However, without a methodology, it is still impossible to directly achieve parallel collaborative design that meets the needs of design activities, nor can it accommodate flexible variant design changes. The main reason for this is that arbitrarily constructing relationships can lead to chaotic relationships, uncontrolled change propagation, and uncontrollable workload for model modification (e.g., ...). Figure 1 (as shown in (a)).

[0010] This invention introduces skeleton model design techniques (such as...) Figure 1 As shown in (b) in the figure, this provides a technical prerequisite for obtaining a more reasonable correlation.

[0011] IV. Overview of Related Technologies

[0012] The research by Fu Lei, Chu Dexin, Lü Guolin, and others provides a detailed introduction to the top-down design method based on a multi-level skeleton. However, these studies only demonstrate the effectiveness and superiority of the skeleton model in supporting associative design; they do not analyze design changes in design examples, nor do they cover different design activities such as drawing production and design verification, resulting in poor integration with actual product design.

[0013] Li Chuntong et al. conducted in-depth research on the structural optimization of ligature bridges using a combination of knowledge engineering, multi-objective optimization, and experimental simulation. Their main achievement was optimized design in terms of strength and vibration, providing support for the early-stage design of ligature bridges. However, these studies only considered structural issues and did not address the challenges of interdisciplinary collaboration and variant design. Furthermore, while some modeling practices were conducted using CAD systems, these studies did not cover the specific design content of the detailed design phase.

[0014] Xu Sihao et al. conducted in-depth research on the 3D design of tying bridges based on CATIA V6 and proposed a method that uses User Defined Features (UDFs) as the main means to solve the problem of two geometric differences when using the same 3D model for finite element calculation and when using it to generate design drawings. This provides a geometric technical foundation for the design methodology proposed in this invention.

[0015] V. Technical Issues

[0016] Based on the above background analysis, the specific problems faced in the design of lashed bridges are summarized as follows:

[0017] 1. The demand for mass production and diversified products;

[0018] 2. The design methodology for lashed bridges needs to be adaptable to changing requirements from various stakeholders and design activities;

[0019] 3. Ordinary two-dimensional design methods cannot meet the requirements for related changes to design information, nor can they support the collaborative requirements for multiple design tasks to be carried out in parallel;

[0020] 4. Existing 3D design tools lack methodological guidance and cannot establish an orderly change sequence to adapt to design changes;

[0021] 5. The multi-level skeleton design method is still in the theoretical research stage and has poor integration with actual product design.

[0022] Based on the above issues, the following key technical problems can be summarized:

[0023] 1. Establish an orderly connection between design information to respond to design changes;

[0024] 2. Decompose design information to meet design collaboration needs;

[0025] 3. Enable the reuse of design information to meet the design needs of mass production and diversification of products. Summary of the Invention

[0026] The present invention proposes a 3D design method for tying bridges based on CATIA V6. The decomposition and aggregation of design information in this design method are specifically reflected in the role of the skeleton model in the 3D design model in the overall product structure.

[0027] Function 1: Decompose global information into multiple levels, with each model edited by a single designer, thus creating a collaborative interface.

[0028] Function 2: It serves as a bridge between upstream and downstream, inheriting information from the upstream skeleton model and continuing to generate new designs, thus achieving the effect of related design and solving design change problems.

[0029] Function 3: Reuse of skeleton. Under the premise of interface standardization, a certain skeleton model and downstream related specific models can be reused in other layout models, thus serving variant design.

[0030] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0031] A 3D design method for ligature bridges based on CATIA V6 includes the following seven steps:

[0032] Step 1. Initially, construct different skeleton models based on the decomposition of design information;

[0033] Step 2. Design the skeleton in the skeleton model using geometric shape, attribute fields, interface features, and local coordinate system features respectively;

[0034] Step 3. Based on the skeleton model, carry out different specific designs to generate different types of models;

[0035] Step 4. Conduct specific design activities based on the different types of models mentioned above to obtain verification results, and readjust the information in the skeleton design based on the verification feedback to carry out design iteration;

[0036] Step 5. Adjust the skeleton design according to the change requirements and iterate the design information;

[0037] Step 6. The design is complete once all design activities have been verified and no new design change requests are required.

[0038] Step 7. Based on the data after the design is completed, develop variant designs for the new design object.

[0039] In step 1, the specific steps for skeleton decomposition are as follows:

[0040] (1) Establish a layout skeleton. Based on the number of container rows and the number of container layers at the BAY position where the lashing bridge is located, as well as the different characteristics of the bottom support, define a top-level skeleton containing all positioning information, which includes coordinate planes distributed in the ship length, ship width and vertical height.

[0041] (2) Based on the design characteristics of strength calculation, the structural skeleton model is decomposed for the next step of structural component design;

[0042] (3) Based on the operational requirements on the tying bridge, the iron outfitting skeleton model is decomposed for the next step of iron outfitting component design;

[0043] (4) Based on the binding characteristics of the binding rod, the eye plate skeleton model is decomposed for the next step of eye plate design.

[0044] In step 2, the specific steps for skeleton design are as follows:

[0045] (1) In the structural skeleton model, aggregate the geometric shape and attribute information of components such as structural panels and structural skeletons;

[0046] (2) In the outfitting skeleton model, the assembly coordinate system of components such as aisle attachments, aisle ladders, binding rod storage racks, cold box sockets, and aisle railings is aggregated. It also includes the geometric shape and attribute information of aisle railings and maintenance platforms. For aisle ladders, it is also necessary to aggregate the interface information of their corresponding platform openings and side plate openings.

[0047] (3) In the eye plate skeleton model, the assembly coordinate system of the eye plate is aggregated, as well as the geometric shape and attribute information of the reinforcement structure corresponding to the eye plate.

[0048] Step 3, the specific design includes:

[0049] (1) Construct structural sheet models and structural solid models based on the structural skeleton model;

[0050] (2) Construct the solid model of the iron outfitting based on the iron outfitting skeleton model;

[0051] (3) Based on the eyeplate skeleton model, construct the eyeplate solid model, load data and binding rod solid model respectively.

[0052] Step 4 includes the following design activities:

[0053] (1) Generate a finite element model for direct strength calculation based on the structural sheet model, define the load in the finite element model based on the load data, and perform finite element calculation to check the strength based on the finite element model and the load definition, and verify the rationality of the specifications of the structural components.

[0054] (2) Based on the partial iron outfitting entity model and structural entity model, combined with the binding rod entity model, a virtual prototype verification of binding is carried out to check the rationality of the iron outfitting component layout;

[0055] (3) The structural solid model, the iron outfitting solid model and the eye plate solid model constitute the final design result. Based on the structural solid model, the iron outfitting solid model and the eye plate solid model, the parts list and engineering drawings are obtained as the design deliverables.

[0056] Step 5 includes the following specific methods for design changes:

[0057] Feedback received at various stakeholder review stages generates different design change requests. Based on these requests, corresponding information is adjusted in the matching skeleton model. Based on the model's associative design characteristics, the specific model implements adaptive changes.

[0058] The relationship between the influencing factors, the impact results, and the corresponding skeleton model in design changes is as follows:

[0059] (1) Influencing factors: Adjustment of the attachment arrangement of the large hatch cover, resulting in: the setting of guide columns and the safety clearance for ensuring the vertical movement of the hatch cover, corresponding skeleton model: structural skeleton and iron outfitting skeleton.

[0060] (2) Influencing factors: The arrangement of the air duct in the transverse bulkhead below the lash bridge is adjusted, and the result is: the arrangement of the iron outfitting components of the lash bridge platform, and the corresponding skeleton model: iron outfitting skeleton.

[0061] (3) Influencing factors: The shipowner's personalized requirements for the passageway setting, the result of which is the arrangement of the iron outfitting components tied to the bridge, and the corresponding skeleton model: iron outfitting skeleton;

[0062] (4) Influencing factors: Component optimization design by component manufacturers, resulting in: adjustment of the eye ring placement position, corresponding skeleton model: eye plate skeleton;

[0063] (5) Influencing factors: Shipyard's restrictions on the specifications of structural components, resulting in: adjusting the specifications of structural components while meeting strength requirements, corresponding skeleton model: structural skeleton;

[0064] Step 6, the design completion includes: verifying the structural strength through structural strength calculations, checking and verifying the interference of the virtual prototype, generating a parts list, completing the engineering drawing output, and forming a model set containing all design process information. This model set can be used for overall reuse, i.e., variant design.

[0065] In step 7, the variant design includes:

[0066] (1) When the eye plate arrangement is the same between two types of tying bridges, the eye plate skeleton of bridge A is referenced to the layout model of bridge B. After relinking the upstream information of the eye plate skeleton model, the load data under the eye plate skeleton of bridge A and the solid model of the tying rod can be reused.

[0067] (2) When all components of two types of ligature bridges are similar but not identical, back up the completed model of bridge A, and fine-tune the original layout skeleton, structural skeleton, iron outfitting skeleton, and eyeplate skeleton models according to different schemes. Then perform a global update to obtain the specific model of bridge B. Redesign and verify based on these new specific models to obtain the completed model of bridge B.

[0068] The relationship between the variation factors in variant design and the reusable skeleton model is as follows:

[0069] (1) Variation factors: The narrowing of the ship's beam reduces the number of rows in the first two bays, affecting the result: the width of the lashing bridge on the first cargo hold needs to match the number of rows of the container, and the reusable skeleton model: arrange the skeleton;

[0070] (2) Variation Factor: Bay location without lashing requirements, resulting in: removal of all lashing-related accessories on one side, preservation of safe iron outfitting layout for passageway, and reusable frame model: iron outfitting frame.

[0071] (3) Variation factors: The supporting structure under the lashed bridge and the adjacent hull structure are different, which affects the result: The structural form of the lashed bridge support column is different. In order to ensure the construction space for the adjustment of the shear wall setting, the skeleton model can be reused: structural skeleton.

[0072] (4) Variation factors: Adjustment of the type of box ties adjacent to the BAY position affects the result: the 45' box causes a greater load on the tie bridge than the 40' box, requiring finite element calculation to redesign the structural specifications. Reusable skeleton models: structural skeleton and eye plate skeleton;

[0073] (5) Variation factors: number of container stacking layers, affecting the result: change in the setting height of the lashing bridge platform, reusable skeleton model: skeleton layout;

[0074] (6) Variation factors: Different BAY positions, but the same loading form, affecting the result: The position of the eye ring is the same, but the position in the middle of the ship is different, resulting in different channel layouts. Reusable skeleton model: eye plate skeleton.

[0075] The beneficial effects of this invention are:

[0076] 1. The design method of the present invention decomposes the design process of the tying bridge from a global to a professional perspective, which is conducive to collaboration among various disciplines, realizes parallel design based on overall layout, shortens the design cycle, and improves design efficiency.

[0077] 2. The design method of this invention can be adjusted and optimized according to the design requirements put forward by various disciplines, so as to achieve rapid iterative updates and meet personalized customization.

[0078] 3. Based on the relationship between the skeleton and its subordinate specific models, it can be reused as a whole in a new layout model, which reflects the reuse of design modules.

[0079] 4. Based on the complete data of the design, the overall adaptive update result can be obtained by simply adjusting the key information in the layout skeleton model. This is beneficial for obtaining different similar bridge design schemes from variant designs of typical bridges, reflecting the reusability of the design process. Attached Figure Description

[0080] Figure 1 A schematic diagram illustrating the model relationship before and after the introduction of the skeleton model;

[0081] Figure 2 Flowchart for the 3D design of a lashed bridge;

[0082] Figure 3 Schematic diagram of the components of a 3D design for a ballast bridge;

[0083] Figure 4 Design content diagrams for the layout framework;

[0084] Figure 5 Design the content diagram for the structural framework;

[0085] Figure 6 Design drawings for the iron outfitting frame;

[0086] Figure 7 Design content for the ocular skeletal framework;

[0087] Figure 8 The solid design results for the bridge tying are used to generate design drawings and BOM tables;

[0088] Figure 9 A schematic diagram for virtual prototype verification and finite element strength calculation of a ligature bridge;

[0089] Figure 10 A schematic diagram of a variant design of the lashing bridge on the same type of ship. Detailed Implementation

[0090] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0091] like Figures 2 to 10 As shown in the figure, the three-dimensional design method for ligature bridges based on CATIA V6 proposed in this embodiment of the invention includes the following seven steps:

[0092] Step 1. Initially, construct different skeleton models based on the decomposition of design information;

[0093] Step 2. Design the skeleton in the skeleton model using features such as geometric shape, attribute fields, interface features, and local coordinate system;

[0094] Step 3. Based on the skeleton model, carry out different specific designs to generate different types of models;

[0095] Step 4. Conduct specific design activities based on the different types of models mentioned above to obtain verification results. Based on the verification feedback, readjust the information in the skeleton design and iterate the design.

[0096] Step 5. Throughout the design process, there may be design change requests from different stakeholders. Adjust the skeleton design according to the change requirements and iterate the design information.

[0097] Step 6. The design is complete once all design activities have been verified and no new design change requests are required.

[0098] Step 7. Based on the data after the design is completed, variant designs of new design objects can be carried out.

[0099] To further illustrate the advantages of this invention in related and collaborative design, combined with Figure 3 The relationship between the various models in the above design process is explained in detail.

[0100] It's important to note that each model represents an independent process. This means that the structure, outfitting, and eyeplate frame can be handled simultaneously by three designers. This avoids the traditional approach of having one designer handle everything centrally or having three people work sequentially.

[0101] The specific implementation steps are as follows:

[0102] Step 1: Skeleton Decomposition

[0103] (1) Establish the layout framework, see Figure 4 Based on the number of container rows and layers at the bay where the lashing bridge is located, as well as the different characteristics of the bottom support, a top-level skeleton containing all positioning information can be defined, which includes coordinate planes distributed in the ship's length, width, and vertical height.

[0104] (2) Based on the design characteristics of strength calculation, decompose the structural skeleton model for the next step of structural component design.

[0105] (3) Based on the operational requirements of the bridge, the iron outfitting skeleton model is decomposed for the next step of iron outfitting design.

[0106] (4) Based on the binding characteristics of the binding rod, the eye plate skeleton model is decomposed for the next step of eye plate design.

[0107] Step 2: Skeleton Design

[0108] (1) In the structural skeleton model, the geometric shape and attribute information of components such as aggregated structural panels and structural skeletons are obtained, see... Figure 5 , 6, 7.

[0109] (2) In the outfitting skeleton model, the assembly coordinate system of components such as aisle attachments (self-closing rods and small chains), aisle ladders, binding rod storage racks, cold box sockets, and aisle railings is aggregated. This also includes the geometric shape and attribute information of the aisle railings and maintenance platforms. For aisle ladders, the interface information of their corresponding platform openings and side plate openings also needs to be aggregated.

[0110] (3) In the eye plate skeleton model, the assembly coordinate system of the eye plate is aggregated, as well as the geometric shape and attribute information of the reinforcement structure corresponding to the eye plate.

[0111] Step 3: Detailed design, see Figure 8

[0112] (1) Construct structural sheet model and structural entity model based on structural skeleton model respectively.

[0113] (2) Construct the solid model of iron outfitting based on the iron outfitting skeleton model.

[0114] (3) Based on the eyeplate skeleton model, construct the eyeplate solid model, load data and binding rod solid model respectively.

[0115] Step 4: Various design activities, see Figure 9

[0116] (1) A finite element model for direct strength calculation can be generated based on the structural sheet model, and load data can be used to define loads in the finite element model. Based on these conditions, finite element calculations can be carried out to check the strength and verify the rationality of the structural components' specifications.

[0117] (2) Based on the partial iron outfitting entity model and structural entity model, combined with the binding rod entity model, the binding virtual prototype verification can be carried out to check the rationality of the iron outfitting component layout.

[0118] (3) The structural solid model, the outfitting solid model, and the eyeplate solid model constitute the final design result. Based on these models, the parts list and engineering drawings are obtained as the design deliverables.

[0119] Step 5: Design Changes

[0120] Feedback received at each stakeholder review stage will generate different design change requests. Based on these requests, corresponding information can be adjusted within the matching skeleton model. Leveraging the associative design characteristics of the model, the specific model can adaptively adapt to changes. Table 1 below summarizes common design change scenarios.

[0121] Table 1. Design Changes, Impact Results, and Corresponding Skeleton Models

[0122]

[0123] Step 6: Design Completed

[0124] Design completion refers to the verification process, including structural strength calculations and checks, virtual prototype interference checks, generation of parts lists, and completion of engineering drawings. This results in a model set containing all design process information, which can be used for overall reuse, i.e., variant design.

[0125] Step 7: Variant design, see Figure 10

[0126] (1) When the eye plate arrangement is the same between two types of tying bridges, the eye plate skeleton of bridge A can be referenced to the layout model of bridge B. After relinking the upstream information of the eye plate skeleton model, the load data under the eye plate skeleton of bridge A and the solid model of the tying rod can be reused.

[0127] (2) When all components of two types of ligature bridges are similar but not identical, back up the completed model of bridge A, and fine-tune the original layout skeleton, structural skeleton, iron outfitting skeleton, and eyeplate skeleton models according to different schemes. Then perform a global update to obtain the specific model of bridge B. Redesign and verify based on these new specific models to obtain the completed model of bridge B.

[0128] Table 2. Variant Factors, Impact on Results, and Reusable Skeleton Model

[0129]

[0130] The above description is merely a preferred embodiment of the present invention and does not limit the implementation methods and scope of protection of the present invention. Those skilled in the art should recognize that all equivalent substitutions and obvious variations made based on the description and figures of this invention should be included within the scope of protection of this invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A three-dimensional design method for ligature bridges based on CATIA V6, characterized in that, It includes the following seven steps: Step 1. Initially, construct different skeleton models based on the decomposition of design information; the specific steps of skeleton decomposition are as follows: (1) Establish a layout skeleton. Based on the number of container rows and packing layers at the BAY position where the lashing bridge is located, as well as the different characteristics of the bottom support, define a top-level skeleton containing all positioning information, which includes coordinate planes distributed in the ship length, ship width and vertical height. (2) Based on the design characteristics of strength calculation, decompose the structural skeleton model for the next step of structural component design; (3) Based on the operational requirements on the tying bridge, the iron outfitting skeleton model is decomposed for the next step of iron outfitting component design; (4) Based on the binding characteristics of the binding rod, the eye plate skeleton model is decomposed for the next step of eye plate design; Step 2. Design the skeleton in the skeleton model using geometric shape, attribute fields, interface features, and local coordinate system features respectively; Step 3. Based on the skeleton model, conduct different specific designs to generate different types of models; Step 4. Conduct specific design activities based on the different types of models mentioned above to obtain verification results, and readjust the information in the skeleton design based on the verification feedback to carry out design iterations; Step 5. Adjust the skeleton design according to the change requirements and make adaptive changes to the design information; Step 6. Once all design activities have been verified and there are no new design change requests, the design is complete. Step 7. Based on the data after the design is completed, develop variant designs for the new design object.

2. The 3D design method for ligature bridges based on CATIA V6 according to claim 1, characterized in that, In step 2, the specific steps for skeleton design are as follows: (1) In the structural skeleton model, aggregate the geometric shape and attribute information of the structural plate frame and structural skeleton components; (2) In the outfitting skeleton model, the assembly coordinate system of the aisle attachments, aisle ladders, binding rod storage racks, cold box sockets, and aisle railing components is aggregated. This also includes the geometric shape and attribute information of the walkway railings and maintenance platform. For the aisle ladders, the interface information of their corresponding platform openings and side plate openings also needs to be aggregated. (3) In the eye plate skeleton model, the assembly coordinate system of the eye plate and the geometric shape and attribute information of the reinforcement structure corresponding to the eye plate.

3. The 3D design method for ligature bridges based on CATIA V6 according to claim 1, characterized in that, Step 3, the specific design includes: (1) Construct structural sheet models and structural solid models based on the structural skeleton model; (2) Construct the solid model of the iron outfitting based on the iron outfitting skeleton model; (3) Based on the eye plate skeleton model, construct the eye plate solid model, load data and binding rod solid model respectively.

4. The 3D design method for ligature bridges based on CATIA V6 according to claim 3, characterized in that, Step 4 includes the following design activities: (1) Generate a finite element model for direct strength calculation based on the structural sheet model, define the load in the finite element model based on the load data, and perform finite element calculation to check the strength based on the finite element model and the load definition, and verify the rationality of the specifications of the structural components. (2) Based on the partial iron outfitting entity model and structural entity model, combined with the binding rod entity model, a virtual prototype verification of binding is carried out to check the rationality of the iron outfitting component layout; (3) The structural solid model, the iron outfitting solid model and the eye plate solid model constitute the final design result. Based on the structural solid model, the iron outfitting solid model and the eye plate solid model, the parts list and engineering drawings are obtained as the design deliverables.

5. The 3D design method for ligature bridges based on CATIA V6 according to claim 1, characterized in that, Step 5 includes the following specific methods for design changes: Feedback received at various stakeholder review stages generates different design change requests. Based on these requests, corresponding information is adjusted in the matching skeleton model. Based on the model's associative design characteristics, the specific model implements adaptive changes.

6. The 3D design method for ligature bridges based on CATIA V6 according to claim 5, characterized in that, The relationship between the influencing factors, the impact results, and the corresponding skeleton model in design changes is as follows: (1) Influencing factors: Adjustment of the attachment arrangement of the large hatch cover, resulting in: the setting of guide columns and the safety clearance for ensuring the vertical movement of the hatch cover, corresponding skeleton model: structural skeleton and iron outfitting skeleton; (2) Influencing factors: The arrangement of the air duct in the transverse bulkhead below the lash bridge is adjusted, and the result is: the arrangement of the iron outfitting components of the lash bridge platform, corresponding to the skeleton model: iron outfitting skeleton. (3) Influencing factors: The shipowner's personalized requirements for the passageway setting, the result of which is the arrangement of iron outfitting components on the lashing bridge, and the corresponding skeleton model: iron outfitting skeleton; (4) Influencing factors: component optimization design by component manufacturers, resulting in: adjustment of the eye ring placement position, corresponding skeleton model: eye plate skeleton; (5) Influencing factors: Shipyard's restrictions on the specifications of structural components. The result is that the specifications of structural components are adjusted under the premise of meeting the strength requirements. The corresponding skeleton model is the structural skeleton.

7. The 3D design method for ligature bridges based on CATIA V6 according to claim 1, characterized in that, Step 6, the design completion includes: verifying the structural strength through structural strength calculations, checking and verifying the interference of the virtual prototype, generating a parts list, completing the engineering drawing output, and forming a model set containing all design process information. This model set can be used for overall reuse, i.e., variant design.

8. The 3D design method for ligature bridges based on CATIA V6 according to claim 1, characterized in that, In step 7, the variant design includes: (1) When the eye plate arrangement is the same between two types of tying bridges, the eye plate skeleton of bridge A is referenced to the layout model of bridge B. After relinking the upstream information of the eye plate skeleton model, the load data under the eye plate skeleton of bridge A and the solid model of the tying rod can be reused. (2) When all components of two types of ligature bridges are similar but not completely the same, back up the completed model of bridge A, fine-tune the original layout skeleton, structural skeleton, iron outfitting skeleton and eye plate skeleton model according to different schemes, and then perform a global update to obtain the specific model of bridge B. Based on these new specific models, redesign and verify to obtain the completed model of bridge B.

9. The 3D design method for ligature bridges based on CATIA V6 according to claim 8, characterized in that, The relationship between the variation factors in variant design and the reusable skeleton model is as follows: (1) Variation factors: The narrowing of the ship's beam reduces the number of rows in the first two bays, affecting the result: the width of the lashing bridge on the first cargo hold needs to match the number of rows of the container, and the reusable skeleton model: arrange the skeleton; (2) Variation factors: BAY position without tying requirements, impact result: all accessories related to tying are removed on one side, the iron outfitting arrangement for safe passage is preserved, and the reusable skeleton model: iron outfitting skeleton; (3) Variation factors: The supporting structure under the lashed bridge and the adjacent hull structure are different, which affects the result: The structural form of the lashed bridge support column is different. In order to ensure the construction space for the adjustment of the shear wall setting, the skeleton model can be reused: structural skeleton; (4) Variation factors: The type of box tied to the adjacent BAY position is adjusted, and the result is that the 45' box causes a greater load on the tied bridge than the 40' box. Finite element calculation is required to redesign the structural specifications. The skeleton model can be reused: structural skeleton and eye plate skeleton. (5) Variation factors: number of container stacking layers, affecting the result: change in the setting height of the lashing bridge platform, reusable skeleton model: skeleton layout; (6) Variation factors: Different BAY positions, but the same loading form, affecting the result: The position of the eye ring is the same, but the position in the middle of the ship is different, resulting in different channel layout. Reusable skeleton model: eye plate skeleton.

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