A method for reliability evaluation and adjustment of a container ship deck stowage and lashing plan

Abstract

This invention relates to a method for reliability assessment and adjustment of deck stacking and lashing schemes for container ships. First, the expected deck stacking and lashing scheme is determined based on mainstream design, the shipowner's specific requirements, and the need for scheme balance. Then, calculation parameters are obtained based on the expected deck stacking and lashing scheme. These parameters are then input into lashing calculation software for calculation, and the reliability of the deck stacking and lashing scheme is assessed based on the calculation results to determine if adjustments are needed. Finally, schemes deemed unreliable are continuously subjected to "adjustment-calculation-evaluation-re-adjustment" until both deck stacking and lashing schemes are reliable. Through accurate reliability assessment and closed-loop adjustment of the deck stacking and lashing schemes, the final scheme is continuously optimized, resulting in a deck stacking and lashing scheme that is suitable for the ship type, safe, reliable, and meets expectations, thereby avoiding problems such as deck stacking weight reduction and lashing failure during actual operation.

Description

Technical Field

[0001] This invention relates to the technical field of shipbuilding, and in particular to a method for reliability assessment and adjustment of container ship deck stacking and lashing schemes. Background Technology

[0002] With the increasing complexity of container ship loading through high deck stacking and multi-layered lashing, coupled with the ongoing incidents of deck stack collapses and container falls during voyages, all parties are paying closer attention to deck stacking and lashing design. Operators seek solutions that achieve high stacking and lashing without excessive complexity, aiming for high returns on low investment. Therefore, given a specific deck stacking and lashing scheme, evaluating its reliability according to regulations and adjusting the design based on the results is particularly important.

[0003] Currently, most actual shipbuilding projects only consider the impact of deck overload on hatch cover design. For example, a large overload might lead to a reinforced hatch cover structure, potentially causing the lifting weight to exceed the limits of the dock crane. Additionally, some design firms can provide overload distribution data. However, overall, the relationship between overload and lashing is rarely considered in the design phase, and the research is not in-depth enough. The reasons for this are threefold: firstly, shipowners lack sufficient attention to this aspect, with unclear indicators at the project initiation stage; secondly, lashing component manufacturers are not sufficiently involved in the early stages, and by the time the ship is delivered, the project is already finalized, with only overload results provided; and finally, some design firms lack the necessary knowledge and selectively ignore this aspect to expedite the project. These factors combined result in insufficient or inappropriate reliability assessments of deck overload and lashing schemes, leading to problems such as decreased deck overload and lashing failures during actual operation. Summary of the Invention

[0004] To at least partially solve the aforementioned problems in the prior art, the present invention provides a method for reliability assessment and adjustment of container ship deck stacking and lashing schemes.

[0005] A method for reliability assessment and adjustment of container ship deck stacking and lashing schemes, the assessment and adjustment method comprising:

[0006] Step S1: Determine the expected deck weight stacking and lashing scheme, wherein the expected deck weight stacking and lashing scheme is determined based on the ship type, shipowner requirements, and scheme balance requirements.

[0007] Step S2: Select calculation parameters that are compatible with the expected deck stacking weight and lashing scheme, wherein the calculation parameters include ship parameters, navigation parameters, lashing component and container parameters, stacking parameters and lashing parameters;

[0008] Step S3: Input the calculation parameters into the lashing calculation software to obtain the stress state of the container structure and lashing system under the expected deck weight and lashing scheme;

[0009] Step S4: Confirm the reliability of the expected deck weight stacking and lashing scheme based on the stress state. If not, proceed to step S5; if yes, proceed to step S6.

[0010] Step S5: Adjust the expected deck weighting and lashing scheme, and then return to step S2 after adjustment until both the deck weighting and lashing schemes are reliable.

[0011] Step S6: Output the target deck weighting and lashing scheme.

[0012] Optionally, the intended tying scheme further includes:

[0013] Choose a lashing scheme corresponding to a ship type one level higher than the current ship type;

[0014] Similar ship types should use the same lashing method;

[0015] Choose a binding method, which includes external binding, internal binding, wind binding, and Mickey Mouse binding.

[0016] Optionally, determining the deck stacking scheme based on the ship type refers to the size classification of deck stacking and the stacking values ​​for different ship types under the size classification; determining the lashing scheme based on the ship type refers to the lashing scheme corresponding to different ship types; the shipowner's requirements refer to the deck stacking and lashing schemes proposed by the shipowner; the scheme balance requirements refer to the balance between the flexibility and economy of deck loading and the safety of the lashing scheme.

[0017] Optionally, the determination of the expected deck weighting and lashing scheme is based primarily on the shipowner's needs and the need for a balance between the schemes.

[0018] Optionally, the calculation parameters are all obtained from the tender documents, which include general layout drawings, preliminary loading manuals, and technical solutions for each specialty.

[0019] Optionally, confirming the reliability of the expected deck stacking and lashing scheme based on the stress state means evaluating the reliability of the deck stacking and lashing scheme by checking whether the container parameters and lashing component parameters exceed the limits.

[0020] Optionally, the container parameter exceeding the standard means that the container parameter values ​​at 3 or more points exceed 100% of the safe working load. The container parameters refer to the pressure of the corner support column, the force of the corner fastener, and the utilization rate of both.

[0021] The term "out of standard for binding component parameters" refers to the binding component parameters exceeding the safe working load.

[0022] Optionally, when adjusting the expected deck stacking weight, if the container parameters still have a large margin, the overall stacking weight distribution can be adjusted. If the container parameters have exceeded the standard, the weight of the upper stacked containers should be reduced first to reduce the load in the overloaded area, and then it should be determined whether it is necessary to reduce the number of heavy containers at the bottom.

[0023] Optionally, adjusting the expected binding scheme includes adjusting the binding bridge parameters and adjusting the binding method. The binding bridge parameter adjustment refers to adjusting the height of the bridge binding layer platform, and the binding method adjustment refers to adding binding points, changing single binding to double binding, and changing inner binding to outer binding.

[0024] In a method for reliability assessment and adjustment of container ship deck stacking and lashing schemes according to the present invention, the expected deck stacking and lashing schemes are first determined based on the ship type, shipowner requirements, and scheme balance requirements, providing a basis for subsequent calculations and adjustments. Then, calculation parameters are obtained based on the expected deck stacking and lashing schemes. These parameters are then input into lashing calculation software for calculation to obtain the stress state of the container structure and lashing system under the expected deck stacking and lashing schemes. The reliability of the expected deck stacking and lashing schemes is confirmed based on the stress state, thus determining whether adjustments are needed. Finally, schemes deemed unreliable are continuously subjected to "adjustment-calculation-evaluation-re-adjustment" until both deck stacking and lashing schemes are reliable. Through accurate assessment of the reliability of deck stacking and lashing schemes and closed-loop adjustments, the final scheme is continuously optimized, resulting in a deck stacking and lashing scheme that is suitable for the ship type, safe, reliable, and meets expectations, thereby avoiding problems such as deck stacking weight reduction and lashing failure during actual operation. Attached Figure Description

[0025] Figure 1 This is a flowchart of a method for reliability assessment and adjustment of container ship deck stacking and lashing scheme according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a binding scheme according to an embodiment of the present invention. Detailed Implementation

[0027] The following reference Figure 1 and Figure 2 This invention describes a method for reliability assessment and adjustment of container ship deck stacking and lashing schemes.

[0028] Deck stacking weight refers to the weight of containers stacked on the main deck or hatch covers of a container ship, especially medium-sized and larger container ships. It represents the total weight of each ROW container from top to bottom. Classified by size, deck stacking weight includes 20-foot container stacking weight, 40-foot container stacking weight, and counterweight for mixed 20-foot and 40-foot containers. Different stacking weights reflect the ship's adaptability and compatibility with various loading conditions during operation. Theoretically, a higher stacking weight indicates greater loading capacity. Lashing scheme refers to the method of lashing containers on the main deck or hatch covers of a container ship, especially medium-sized and larger container ships.

[0029] refer to Figure 1 This invention provides a method for reliability assessment and adjustment of container ship deck stacking and lashing schemes. The assessment and adjustment method includes:

[0030] Step S1: Determine the expected deck weighting and lashing scheme, that is, select the deck weighting and lashing scheme according to the ship type, and determine the expected deck weighting and lashing scheme in combination with the shipowner's clear requirements and the scheme balance requirements.

[0031] Furthermore, determining the deck stacking scheme based on ship type refers to the size classification of deck stacking and the stacking values ​​for different ship types within that size classification. Taking 40-foot container stacking as an example, the deck stacking weight for ultra-large container ships of 20,000-24,000 TEU is 220-240 tons; for post-Panamax container ships of 15,000-20,000 TEU, it is 200-220 tons; for large container ships of 90,000-15,000 TEU, it is 180-200 tons; for medium-sized container ships of 4,000-9,000 TEU, it is 160-180 tons; and for feeder container ships under 4,000 TEU, it is 140-160 tons. The stacking values ​​for different ship types under other size classifications will not be detailed here.

[0032] Furthermore, determining the lashing scheme based on the ship type refers to the lashing scheme corresponding to different ship types.

[0033] Specifically, for feeder container ships with a capacity of less than 4,000 TEU, the lashing scheme is a single-layer lashing bridge, single lashing, or double lashing.

[0034] For medium-sized container ships with a capacity of 4,000 TEU to 9,000 TEU, the lashing scheme is a double-layer lashing bridge with a single or double lashing layer on top.

[0035] For large container ships with a capacity of 90,000 TEU to 15,000 TEU, the lashing scheme consists of two or three layers of lashing bridges and two single lashing bridges on top.

[0036] For 15,000-20,000 TEU post-Panamax container ships, the lashing scheme consists of three layers of lashing bridges and two single lashing layers on top.

[0037] For ultra-large container ships with a capacity of 20,000 TEU to 24,000 TEU, the lashing scheme consists of four layers of lashing bridges, with the top two layers having one double lashing layer and the top layer having one single lashing layer.

[0038] Furthermore, the anticipated lashing schemes also include selecting a lashing scheme for a vessel type one level higher than the current vessel type based on the shipowner's adaptability needs; selecting the same lashing scheme for similar vessel types based on fleet operational uniformity requirements; and selecting lashing methods based on actual scenarios. For example, taking large container ships of 10,000-15,000 TEU as an example, selecting a lashing scheme for a vessel type one level higher than the current vessel type based on the shipowner's adaptability needs means that the shipowner will ultimately choose the lashing scheme corresponding to a 15,000-20,000 TEU post-Panamax container ship. Lashing methods include external lashing, internal lashing, wind lashing, and Mickey Mouse lashing, etc.

[0039] Furthermore, the shipowner's requirements refer to the deck stacking and lashing scheme clearly and without objection proposed by the shipowner. For example, the shipowner specifies that the deck stacking of a 15,000 TEU post-Panamax container ship is 200 tons for 40-foot containers, with refrigerated containers at the bottom of the stack, and specifies the lashing scheme as three layers of lashing bridges and two layers of single external lashing on top.

[0040] Furthermore, the requirement for balanced solutions refers to the balance between the flexibility and economy of deck loading and the safety of the lashing scheme.

[0041] It should be noted that the determination of the expected deck weight stacking and lashing scheme is primarily based on the shipowner's needs and the requirement for a balanced scheme. That is, when there is a conflict between the deck weight stacking and lashing scheme determined based on the ship type and the deck weight stacking and lashing scheme obtained from the shipowner's needs and the requirement for a balanced scheme, the latter shall prevail.

[0042] Step S2: Select calculation parameters that match the expected deck stacking weight and lashing scheme. The selection of calculation parameters should be based on factors such as the ship's own design, loading conditions, and navigation area, and a verification working condition should be selected to ensure the reliability of the calculation results. Calculation parameters include ship parameters, navigation parameters, lashing component and container parameters, stacking parameters, and lashing parameters.

[0043] Specifically, ship parameters are the inherent design and configuration of the target vessel, generally comprising two parts. One part is the ship's main dimensions, including length, length between perpendiculars, beam, and depth. The other part consists of parameters affecting the ship's attitude control and the external loads on containers, including block coefficient, side area coefficient, and the presence or absence of bilge keels or anti-roll tanks, as well as the presence or absence of a bow baffle. These parameters can all be found in the ship's design documents.

[0044] Navigation parameters include the ship's own state parameters, navigation area parameters, and sea state parameters during navigation. State parameters include draft, initial metacentric height, ship's center of gravity height, speed, and the ship's six degrees of freedom motion parameters under these conditions. Among these, initial metacentric height has a significant impact on deck load and requires special attention. The calculation of the six degrees of freedom motion parameters is complex and is usually derived from the specifications based on the hull lines, without the need for additional manual calculation. Navigation area parameters are determined by referring to the navigation area table based on the ship's route. Most ships with unlimited navigation areas have fixed values. However, for ships specifically operating on the North Atlantic route, special attention should be paid to the specifications due to the harsh sea conditions. Sea state parameters include deck waves and crosswinds. For medium and larger container ships, deck waves are generally located at the bow quarter of the ship's length. The wave load affects the number and orientation of container layers and can be determined according to specifications. Crosswinds have different values ​​for the top-tier containers and can also be selected with reference to specifications.

[0045] Lacing components include lashing rods, baskets, bottom locks, and intermediate locks. The main parameters for each component are safe working load, tensile stress, and shear force. Additionally, the bottom lock and intermediate locks require input of flange thickness and working separation height. It should be noted that connections between adjacent ROWs must also be entered. Container parameters include the dimensions and weight (maximum weight and tare weight) of each container type, bow and stern stiffness, and the pressure and lashing force that each corner and support column can withstand. Lacing component parameters can be obtained from certificates, while container parameters can be found in ISO standards. Preferably, a database based on historical data is established for reuse and easier searching.

[0046] Stacking parameters include location, container arrangement, and weight distribution. Location includes the distance between the bay and the stern perpendicular, the distance between the row and the centerline, and the height of the bottom container from the baseline. Container arrangement includes container type and the total number of layers in the bay. All of these values ​​can be found in the ship design data. Weight distribution needs to be entered row by row and layer by layer according to the deck weight, and the height of the lashing layers must be considered. Generally, the heaviest containers are at the bottom, and the weight gradually decreases from bottom to top, with the total weight not exceeding the deck weight and the weight of the upper layer not exceeding the weight of the lower layer. In actual evaluation, multiple trials and adjustments are required to find a reasonable weight distribution.

[0047] Lap-and-lash parameters include lashing bridge parameters and lashing schemes. Lap-and-lashing bridge parameters include the lashing bridge height and the stiffness of each lashing bridge level. The lashing bridge height refers to the distance from each platform level to the bottom container. The lashing bridge height can be measured from the lashing bridge drawings, while the stiffness of each lashing bridge level is generally specified by the standards. The lashing scheme includes the lashing arrangement and the components of the distance from the lashing points to the container corners in each direction of the coordinate system. The lashing arrangement can be obtained from the construction specifications or lashing bridge drawings that reflect the requirements of the construction specifications. The lashing distances need to be extracted through 3D model simulation or measured in various views of the plan. Measurements in the Y-direction (breadth) and Z-direction (height) should be as accurate as possible.

[0048] Step S3: Input the calculation parameters into the lashing calculation software to obtain the stress state of the container structure and lashing system under the expected deck weight and lashing scheme. After all calculation parameters are prepared and checked for accuracy, input them into the lashing calculation software one by one. Different software may have slight differences in the input steps or interface, and some parameters can be calculated automatically without manual input, but the overall approach is the same. The input process should be carefully recorded to avoid omissions. If the input does not match the actual situation, it will affect the judgment of the results. After inputting, you can click "Calculate".

[0049] Step S4: Confirm the reliability of the expected deck weight-bearing and lashing scheme based on the stress state. If not, proceed to step S5; if yes, proceed to step S6.

[0050] Confirming the reliability of the expected deck stacking and lashing scheme based on the stress state means assessing its reliability by checking whether the container parameters and lashing parameters exceed the limits. If the container parameters and lashing parameters exceed the limits, the deck stacking and lashing scheme is unreliable. Conversely, if they are within limits, the scheme is reliable. Typically, under significant deck stacking or lashing stress, one or more values ​​of the container or lashing parameters will exceed the limits. These exceedances will be directly highlighted by numerical values ​​or bright boxes. Furthermore, the utilization rate of the container and lashing parameters can be viewed, providing a clear understanding of the available usage margin.

[0051] Specifically, container parameters refer to the pressure of the corner bracing columns, the force of the corner fasteners, and the utilization rate of both. Typically, these values ​​should be controlled within 80% of the safe working load, and can reach 100% under the deck design load, with a few individual points reaching 101%. In practical application, if all three points exceed 100%, it is considered unsafe and adjustments should be made.

[0052] If the parameters of the lashing device exceed the safe working load, the lashing will fail by default and needs to be adjusted. The actual stress on the lashing device will be lower than the safe working load, and the utilization rate of most of them is below 80%.

[0053] Step S5: Adjust the expected deck weighting and lashing scheme, and then return to step S2 after the adjustment until both the deck weighting and lashing schemes are reliable.

[0054] Furthermore, regarding the expected deck stacking weight adjustment: If there is still a large margin in the container parameters, the overall stacking weight distribution can be adjusted. For example, increase the number of heavy containers at the bottom, and adjust the weight gradually from bottom to top. If the margin in each parameter is small, focus on adjusting the weight of containers in the middle and upper parts of the stack, selecting the 1-5 ton range and gradually adjusting containers in 1-5 layer heights. After adjustment, repeat steps S2-S5 to select, input, and calculate calculation parameters, evaluate results, and adjust the scheme until the deck stacking weight meets reliability requirements. The above adjustment method is called forward adjustment. Conversely, if the container parameters have exceeded the safe working load, the adjustment method is exactly the opposite of forward adjustment, called reverse adjustment. That is, prioritize reducing the weight of the upper stacked containers, reduce the load in the overloaded area, and then determine whether it is necessary to reduce the number of heavy containers at the bottom. Regardless of whether it is forward or reverse adjustment, the calculated results of the adjusted container parameters and lashing parameters should be checked again.

[0055] Furthermore, adjustments to the anticipated lashing scheme are necessary. These adjustments include changes to the lashing bridge parameters and the lashing method. Adjusting the lashing bridge parameters generally involves adjusting the height of the lashing platform. Increasing the platform height increases deck weight, reduces the utilization rate of lashing components, and improves the reliability of the scheme. However, raising the lashing bridge means increased material volume and higher costs, which is disadvantageous for the shipyard. Regarding adjustments to the lashing method, if the goal is to increase deck weight and lashing reliability, the number of lashing points should be increased, and double lashing is more stable than single lashing. Alternatively, internal lashing can be changed to external lashing, as external lashing is more effective for tensile force transfer. However, it should be noted that these adjustments will increase container parameter values, especially the support column pressure. If the original results are already close to the limits, this adjustment should not be selected.

[0056] Step S6: Output the target deck weighting and lashing scheme.

[0057] refer to Figure 2 The deck stacking and lashing scheme of deck stack 11 of a certain Panamax container ship BAY58 is described as an example, where 11 is the deck stack, 12 is the ROW position, and 13 is the lashing arrangement.

[0058] 1) Determine the expected deck stacking weight and lashing scheme. The deck stacking weight for a 40-foot container ship on a Panamax vessel is 200-220 tons. The lashing scheme is three layers of lashing bridges, with two single lashing bridges at the top. The shipowner's requirement is a deck stacking weight of 200 tons, with more heavy containers to be placed in the lower deck. The lashing scheme only specifies a three-layer lashing bridge design. The specific lashing scheme will be determined by the shipyard based on the need for a balanced approach.

[0059] Furthermore, the specific lashing scheme is determined as follows: There are many lashing options available under the three-layer lashing bridge, and the bridge height itself can be combined between 8 feet 6 inches and 9 feet 6 inches. Specific lashing methods can be combined between single and double lashing, and inner and outer lashing. The lashing arrangement 13 under ROW position 12 can also be freely combined. Considering balance, the lashing scheme is more suitable for the top two layers of the container. Considering structural weight, the lashing bridge height is selected as 8 feet 6 inches. Considering that outer lashing is beneficial to heavy containers, all intermediate ROWs use outer lashing. The Mickey Mouse position should use double inner lashing to protect against wind pressure. On the port side, the middle ROW has a single outer lashing, and the outermost ROW has a single inner lashing; on the starboard side, the middle ROW has double outer lashing on the upper layer and a single outer lashing on the lower layer, and the outermost ROW has a single inner lashing on the bottom layer and double inner lashing on the upper layer.

[0060] 2) Selection of calculation parameters. All calculation parameters were obtained from the tender documents, such as the general layout plan, preliminary loading manual, and various professional technical solutions, to ensure accuracy. Details are as follows:

[0061] The ship's parameters include its main dimensions, length, length between perpendiculars, beam, depth, design draft, structural draft, box coefficient, side area coefficient, presence of bilge keel, absence of anti-rolling tanks, and presence of a wave-breaking wall at the bow.

[0062] Navigation parameters include standard draft, initial stability, ship center of gravity height, and speed. The ship is navigating globally, with a default navigation area coefficient of 1. Six-degree-of-freedom motion parameters are automatically calculated based on this coefficient. Lateral wind pressure is selected with a wind speed of 40 m / s. Since BAY58 is not within the bow 1 / 4 length range, deck waves are not considered.

[0063] For the binding parameters, three sizes of binding rods are selected: short rod, standard rod, and extra-long rod, with lengths ranging from 2.4 meters to 3.2 meters. The binding rod diameter is 25 mm, Young's modulus is 140 kN / mm², and the safe working load under tension is 245 kN. The basket is connected to the binding rod, and the default safe working load is the same. The bottom locking flange thickness is 28 mm, the separation value is 18 mm, the safe working load under tension is 245 kN, and the safe working load under shear is 210 kN, allowing for vertical separation. The middle locking flange thickness is 15 mm, the separation value is 12 mm, the safe working load under tension is 245 kN, and the safe working load under shear is 210 kN, allowing for vertical separation. There is no connection between adjacent ROWs.

[0064] For container parameters, a 40-foot container has a length of 40 feet, a width of 8 feet, a height of 8.5 feet, a corner support area of ​​3800 mm², a stiffener area of ​​2000 mm², an elastic modulus of 206 kN / mm², a tare weight of 3.5 tons, a maximum weight of 30.5 tons, a door side stiffness of 3.5 kN / mm, a non-door side stiffness of 15.4 kN / mm, and a side stiffness of 5.7 kN / mm. The safe working loads under horizontal and vertical lashing are 225 kN and 250 kN respectively, the combined safe working load is 300 kN, the stern and side safe working loads are 150 kN, the safe working loads under corner support tension and compression are 375 kN and 848 kN respectively, and the safe working loads under base casting tension and compression are 250 kN and 982.55 kN respectively.

[0065] For stacking parameters, refer to Figure 2 According to design parameters, the distance from the stern perpendicular to BAY58 indicates a total of 20 ROWs (Rows 12 and 19). Specifically, the ROWs on the port side are 20, 18, 16, 14, 12, 10, 08, 06, 04, and 02, with the hull numbered 00. The ROWs on the starboard side are 01, 03, 05, 07, 09, 11, 13, 15, 17, and 19. The distances between each ROW on the port side and the hull are known from the design parameters. The distances on the starboard side are symmetrical to those on the port side but are negative. The height of the bottom stacked containers from the baseline is known from the design parameters. ROW 20 on the port side and ROW 19 on the starboard side are stacked in 10 layers, while the other ROWs are stacked in 12 layers. The bottom container uses a bottom lock, and the other containers use intermediate locks. The stacking weight of the intermediate ROWs is 200 tons. The bottom 5 layers of containers weigh 30.5 tons, the 6th and 7th layers weigh 25 tons and 5 tons respectively, and the layers above 8 weigh 3.5 tons each. For the outermost ROW20 and ROW19, based on experience, the stack weight will decrease significantly due to lateral wind pressure. In this case, a stack weight of 144 tons was selected, with the bottom three layers at 30.5 tons, the fourth layer at 20 tons, the fifth layer at 18 tons, and each layer above that at 3.5 tons.

[0066] For the lashing parameters, the height of each platform of the lashing bridge is converted into the height from the baseline, and the stiffness is automatically calculated from the input height. For lashing arrangement 13, the lashing distance is the distance from the eye plate to the corner of the container, which needs to be converted into components dx, dy, and dz in the ship's XYZ coordinate system. This can be measured using 2D drawings or a 3D model. Taking ROW10 as an example, the bottom of the 5th layer container is connected to the 3rd layer of the lashing bridge with a single external lashing. The dx is 0.65m, dy is 2.39m, and dz is 2.62m. These measurements are recorded sequentially.

[0067] 3) Input and Calculation. After the above calculation parameters are fully prepared and carefully checked, input them into the respective modules of the binding calculation software, click check, and if no data omission is indicated, start the calculation.

[0068] 4) Reliability Assessment. Regarding container parameters, the pressure on the port side corner posts ROW20-ROW00 and ROW19 of the bottom layer containers ranges from 858kN to 967kN, exceeding the permissible installation working load of 848kN, with a maximum utilization rate of 114%, totaling 12 points. Therefore, this is considered unsafe and adjustments should be made. The pressure on the starboard side ROW01-ROW17 of the first layer and the port side corner posts ROW20-ROW10 and ROW19 of the second layer containers exceeds 80% of the permissible installation working load, approaching 98%, totaling 16 points. Subsequent adjustments should consider eliminating the excessive working load phenomenon in the second layer containers. Regarding lashing parameters, the tension of the right-side lashing bar at the top of the fifth layer container on the port side ROW20 exceeds 80%, and this occurs symmetrically on the starboard side ROW19. This indicates significant wind pressure influence at this location; although only two points are affected, attention should be paid to whether parameter adjustments improve the situation. Analysis of the above results reveals two problems under the same 200-ton stacking weight. First, the lashing schemes for the port center ROW and the starboard ROW differ: the port ROW uses a single external lashing on the upper layer, while the starboard ROW uses double external lashing. In this case, the weight of the port center ROW could be reduced or changed to the same double external lashing as the starboard ROW. Considering the need to verify the limits under different lashing arrangements, this case chooses to reduce the weight. Second, both port ROW20 and starboard ROW19 exhibited stress exceeding the safe working load on the bottom first-layer container and stress exceeding 80% of the safe working load on the second-layer container. Considering that starboard ROW20 already uses double internal lashing, there are no other lashing arrangements available, and the impact is already known from the comparison between the port and starboard center ROWs. Therefore, this case chooses to reduce the weight. In other words, the solution to both problems is to reduce the weight.

[0069] 5) Adjust the deck stacking weight. Since 12 locations have exceeded the safe working load, concentrated in the bottom first layer, with the maximum exceeding the safe working load by 114% located at port ROW20 and starboard ROW19, and considering the owner's need to meet the requirements of the bottom heavy containers as much as possible, the stacking weight should be reduced. For the port center ROW, starting with the unsecured sixth layer of containers, the weight should be adjusted from 25 tons to 20 tons. The total stacking weight of port ROW20 and starboard ROW19 should be significantly reduced from 144 tons to 105 tons. The bottom three layers should have weights of 30.5 tons, 30.5 tons, and 20 tons respectively, and all layers above should have weights of 3.5 tons. Adjust the lashing scheme. According to the assessment results, the lashing parameters only show warnings, with no locations exceeding the maximum safe load. Moreover, the port and starboard center ROWs already serve as a control and do not require further adjustment; observation is sufficient.

[0070] 6) Re-enter and recalculate the adjusted parameters, and evaluate the results. At this point, the excessive working load has been eliminated, with only one lashing bar at the top of the bottom first layer container and the fifth layer containers on port ROW20 and starboard ROW19 showing a warning. The pressure on the container corner posts is slightly below the permissible installation working load of 848kN, with a utilization rate of approximately 98%. From a safe operational perspective, the stacking weight should not be increased further.

[0071] 7) Therefore, based on the adjusted assessment results, the final reliable plan for BAY58 is as follows: the deck stack weight is 200 tons for the middle ROW, 105 tons for the port ROW20 and starboard ROW19, and the lashing scheme is double external lashing on the upper layer, single external lashing on the lower layer, and single internal lashing on the bottom layer and double internal lashing on the upper layer for the outer ROW.

[0072] In summary, this invention first determines the expected deck weight and lashing scheme based on mainstream design, the shipowner's specific requirements, and the need for scheme balance, providing a foundation for subsequent calculations and adjustments. Then, based on the expected deck weight and lashing scheme, calculation parameters are obtained. These parameters are then input into lashing calculation software for computation, and the reliability of the deck weight and lashing scheme is assessed based on the calculation results to determine if adjustments are needed. Finally, schemes deemed unreliable are continuously subjected to "adjustment-computation-evaluation-re-adjustment" until both deck weight and lashing schemes are reliable. Through accurate reliability assessment and closed-loop adjustment of the deck weight and lashing scheme, the final scheme is continuously optimized, resulting in a deck weight and lashing scheme that is suitable for the ship type, safe, reliable, and meets expectations, thereby avoiding problems such as deck weight reduction and lashing failure during actual operation.

[0073] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for reliability assessment and adjustment of container ship deck stacking and lashing schemes, characterized in that, The assessment and adjustment methods include: Step S1: Determine the expected deck weight stacking and lashing scheme, wherein the expected deck weight stacking and lashing scheme is determined based on the ship type, shipowner requirements, and scheme balance requirements. Step S2: Select calculation parameters that are compatible with the expected deck stacking weight and lashing scheme, wherein the calculation parameters include ship parameters, navigation parameters, lashing component and container parameters, stacking parameters and lashing parameters; Step S3: Input the calculation parameters into the lashing calculation software to obtain the stress state of the container structure and lashing system under the expected deck weight and lashing scheme; Step S4: Confirm the reliability of the expected deck weight stacking and lashing scheme based on the stress state. If not, proceed to step S5; if yes, proceed to step S6. Step S5: Adjust the expected deck weighting and lashing scheme, and then return to step S2 after adjustment until both the deck weighting and lashing schemes are reliable. Step S6: Output the target deck weighting and lashing scheme.

2. The method for reliability assessment and adjustment of container ship deck stacking and lashing schemes according to claim 1, characterized in that, The proposed ligation plan also includes: Choose a lashing scheme corresponding to a ship type one level higher than the current ship type; Similar ship types should use the same lashing method; Choose a binding method, which includes external binding, internal binding, wind binding, and Mickey Mouse binding.

3. The method for reliability assessment and adjustment of container ship deck stacking and lashing schemes according to claim 1, characterized in that, Determining the deck stacking scheme based on ship type refers to the size classification of deck stacking and the stacking values ​​for different ship types under the size classification; determining the lashing scheme based on ship type refers to the lashing scheme corresponding to different ship types; the shipowner's requirements refer to the deck stacking and lashing schemes proposed by the shipowner; the scheme balance requirements refer to the balance between the flexibility and economy of deck loading and the safety of the lashing scheme.

4. The method for reliability assessment and adjustment of container ship deck stacking and lashing schemes according to claim 1 or 3, characterized in that, The determination of the expected deck weighting and lashing scheme is mainly based on the shipowner's needs and the need for a balanced scheme.

5. The method for reliability assessment and adjustment of container ship deck stacking and lashing schemes according to claim 1, characterized in that, The calculation parameters were all obtained from the tender documents, which included the general layout drawing, preliminary loading manual, and technical solutions for each specialty.

6. The method for reliability assessment and adjustment of container ship deck stacking and lashing schemes according to claim 1, characterized in that, The aforementioned confirmation of the reliability of the expected deck stacking and lashing scheme based on the stress state refers to assessing the reliability of the deck stacking and lashing scheme by checking whether the container parameters and lashing component parameters exceed the limits.

7. The method for reliability assessment and adjustment of container ship deck stacking and lashing schemes according to claim 6, characterized in that, The container parameters exceeding the standard refers to the container parameter values ​​at 3 or more points exceeding 100% of the safe working load. The container parameters refer to the pressure of the corner support column, the force of the corner fastener, and the utilization rate of both. The term "out of standard for binding component parameters" refers to the binding component parameters exceeding the safe working load.

8. The method for reliability assessment and adjustment of container ship deck stacking and lashing schemes according to claim 6, characterized in that, When adjusting the expected deck stacking weight, if the container parameters still have a large margin, the overall stacking weight distribution can be adjusted. If the container parameters have exceeded the standard, the weight of the upper stacked containers should be reduced first to reduce the load in the overloaded area, and then it should be determined whether it is necessary to reduce the number of heavy containers at the bottom.

9. The method for reliability assessment and adjustment of container ship deck stacking and lashing schemes according to claim 6, characterized in that, Adjusting the expected binding scheme includes adjusting the binding bridge parameters and the binding method. The adjustment of the binding bridge parameters refers to adjusting the height of the binding layer platform, and the adjustment of the binding method refers to adding binding points, changing single binding to double binding, and changing inner binding to outer binding.

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