Half-ship floating total longitudinal strength evaluation method

Abstract

The invention provides a half-ship floating total longitudinal strength evaluation method, which comprises the following steps: firstly, selecting a section with the maximum ship body bending moment as an evaluation calculation section according to floating stowage, and obtaining the section bending moment and the section shearing force of the evaluation calculation section, the evaluation calculation section comprising a deck section and a ship bottom shell plate section; then profile characteristics of the evaluation calculation profile are obtained, total longitudinal bending stress and total longitudinal shearing stress are obtained, and the total longitudinal bending stress comprises the total longitudinal stress at the deck and the total longitudinal stress at the hull bottom outer plate; and calculating the total longitudinal bending stress balance and the total longitudinal shearing stress balance according to the total longitudinal strength evaluation balance of the whole ship design. And finally, evaluating the result, comparing the total longitudinal stress and total longitudinal bending stress at the deck, the total longitudinal stress and total longitudinal bending stress at the ship bottom outer plate, and the total longitudinal shearing stress and total longitudinal shearing stress, so as to judge the safety of the ship structure. The total longitudinal strength of half-ship floating is evaluated when the ship is in a state that the ship is not completely built.

Description

Technical Field

[0001] The present invention relates to the technical field of shipbuilding, and in particular to a method for evaluating the longitudinal strength of a half-ship float. Background Art

[0002] In the modern shipbuilding process, with the improvement of construction efficiency, shipyards often build multiple different types of ships in the same dock at the same time in order to improve production efficiency. However, since the design, materials, construction process and construction progress of each ship are different, the time required for each stage of the construction process will also be different. This results in that when a ship is at the important stage of being moved from the dock to the water, other ships in the same dock may not be fully ready to be launched, especially their floating status may not be ideal.

[0003] Ships that are not well floated may need to be floated before they are fully built. When floating in this state, due to the incompleteness of the ship structure, existing specifications or standards are often not directly applicable, because these specifications are usually based on the design of a complete ship. In addition, when the entire ship is subjected to the buoyancy of the dock water, in order to ensure the safety of the ship during the launching process, the rapid assessment of its longitudinal strength becomes an urgent problem to be solved. Summary of the invention

[0004] In view of the problems existing in the prior art mentioned above, the present application provides a method for evaluating the longitudinal strength of a half-floating ship, which is used to evaluate the longitudinal strength of a half-floating ship when the ship is in a state where the construction has not been completed.

[0005] To achieve the above and other related purposes, the present invention provides a method for evaluating the longitudinal strength of a half-ship buoyancy, comprising the following steps:

[0006] According to the floating load, the section with the largest hull bending moment is selected as the evaluation calculation section, and the section bending moment and section shear force of the evaluation calculation section are obtained. The evaluation calculation section includes the section at the deck and the section at the bottom outer plate;

[0007] Obtaining the section properties of the evaluation calculation section, the section properties include the section modulus at the deck, the section modulus at the bottom shell, the moment of inertia of the evaluation calculation section to the horizontal neutral axis of the evaluation calculation section, and the static moment of the effective longitudinal members above the horizontal neutral axis to the horizontal neutral axis;

[0008] Obtain the total longitudinal bending stress and total longitudinal shear stress. The total longitudinal bending stress includes the total longitudinal stress at the deck and the total longitudinal stress at the bottom shell plate.

[0009] The total longitudinal bending stress criterion and the total longitudinal shear stress criterion are obtained according to the total longitudinal strength evaluation criterion of the whole ship design;

[0010] The evaluation results are compared with the total longitudinal stress and total longitudinal bending stress criteria at the deck, the total longitudinal stress and total longitudinal bending stress criteria at the bottom shell, and the total longitudinal shear stress and total longitudinal shear stress criteria to determine the safety of the ship structure.

[0011] Alternatively, the total longitudinal stress at the deck σ Deck , total longitudinal stress at the bottom shell σ Bottom And the total longitudinal shear stress τ is obtained by the following formula:

[0012] σ Deck =M / SM Deck ;

[0013] σ Bottom =M / SM Bottom ;

[0014] τ=Q*S y *0.5 / (I y *t);

[0015] Where M is the section bending moment of the evaluated section, in Nm; Q is the section shear force of the evaluated section, in t; SM Deck is the section modulus at the deck, in m 3 ;SM Bottom is the section modulus of the bottom outer plate, in m 3 ;I y is the moment of inertia, in m 4 ; S y is the static moment, in m 3 ; σ Deck is the total longitudinal stress at the deck, in N / mm 2 ; σ Bottom is the total longitudinal stress at the bottom outer plate, in N / mm 2 ; τ is the total longitudinal shear stress, in N / mm 2 .

[0016] Alternatively, the total longitudinal stress at the deck σ Deck , total longitudinal stress at the bottom shell σ Bottom And the total longitudinal shear stress τ is obtained by the following formula:

[0017] σ Deck =(110%~125%)M / SM Deck ;

[0018] σ Bottom =(110%~125%)M / SM Bottom ;

[0019] τ=(120%~130%)Q*S y *0.5 / (I y*t).

[0020] Optionally, the floating stowage is obtained according to the longitudinal length and the cross-sectional height of the vessel in a semi-floating state.

[0021] Optionally, the total longitudinal bending stress criterion σ 许用 and the total longitudinal shear stress criterion is τ 许用 Obtained by the following formula:

[0022] σ 许用 =175 / K;

[0023] τ 许用 =110 / K;

[0024] Where K is the material coefficient, unit N / mm 2 ; σ 许用 is the total longitudinal bending stress criterion, in N / mm 2 ; τ 许用 is the total longitudinal shear stress criterion, in N / mm 2 .

[0025] Optionally, when the total longitudinal stress at the deck is less than the total longitudinal bending stress criterion, the total longitudinal stress at the bottom outer plate is less than the total longitudinal bending stress criterion, and the total longitudinal shear stress is less than the total longitudinal shear stress criterion, it is judged that the ship structure meets the safety requirements.

[0026] Optionally, when the total longitudinal stress at the deck is not less than the total longitudinal bending stress criterion, or the total longitudinal stress at the bottom outer plate is not less than the total longitudinal bending stress criterion, or the total longitudinal shear stress is not less than the total longitudinal shear stress criterion, it is judged that the ship structure does not meet the safety requirements.

[0027] Optionally, when the ship structure does not meet the safety requirements, the floating loading is recalculated to reduce the section bending moment and section shear force.

[0028] Optionally, the floating loading calculation is performed by filling the ballast tank with water or adding weights.

[0029] Optionally, when performing floating loading calculations, the ship's heel angle does not exceed 0.5 degrees.

[0030] As described above, the method for evaluating the longitudinal strength of a half-ship float provided by the present invention has at least the following beneficial technical effects:

[0031] In the method for evaluating the total longitudinal strength of a half-ship floating of the present invention, first, according to the floating loading, the section with the largest bending moment of the hull is selected as the evaluation calculation section, and the section bending moment and section shear force of the evaluation calculation section are obtained, and the evaluation calculation section includes the section at the deck and the section at the bottom outer plate. Then, the section characteristics of the evaluation calculation section are obtained, and the section characteristics include the section modulus at the deck, the section modulus at the bottom outer plate, the moment of inertia of the evaluation calculation section to the horizontal neutral axis of the evaluation calculation section, and the static moment of the effective longitudinal components above the horizontal neutral axis to the horizontal neutral axis. According to the evaluation calculation section, the total longitudinal bending stress and the total longitudinal shear stress are obtained, and the total longitudinal bending stress includes the total longitudinal stress at the deck and the total longitudinal stress at the bottom outer plate. The total longitudinal bending stress criterion and the total longitudinal shear stress criterion are calculated according to the total longitudinal strength evaluation criterion of the whole ship design. The final evaluation results are compared with the total longitudinal stress and total longitudinal bending stress criterion at the deck, the total longitudinal stress and total longitudinal bending stress criterion at the bottom outer plate, and the total longitudinal shear stress and total longitudinal shear stress criterion to judge the safety of the ship structure. The above-mentioned half-ship floating total longitudinal strength evaluation method can be used for the half-ship floating total longitudinal strength evaluation of incomplete gas carriers, bulk carriers, container ships, oil tankers and other ship types, so as to realize the half-ship floating total longitudinal strength evaluation when the ship is not yet fully built. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic flow chart of a method for evaluating the longitudinal strength of a half-ship float in an embodiment of the present invention.

[0033] Figure 2 Shown is a schematic diagram of a complete hull beam structure in an embodiment of the present invention.

[0034] Figure 3 Shown is a schematic diagram of the cross-sectional structure of a complete hull beam in an embodiment of the present invention.

[0035] Figure 4 Shown is a schematic diagram of the half-ship hull beam structure in an embodiment of the present invention.

[0036] Figure 5 Shown is a schematic diagram of the cross-sectional structure of a half-ship hull beam in an embodiment of the present invention.

[0037] Reference numerals

[0038] 11. Bottom outer plating; 12. Hull inner bottom plating; 13. Side outer plating; 14. Main deck; 15. Bottom tank sloping plating; 16. Top tank sloping plating; 17. Bottom longitudinal girder; 18. Longitudinal ribs; 2. Maximum section of half-ship bending moment; 3. Interrupted section of longitudinal members; 4. Horizontal neutral axis. DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0040] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Although the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation, the form, quantity, positional relationship and proportion of each component in actual implementation can be changed at will under the premise of realizing the technical solution of this party, and the component layout form may also be more complicated.

[0041] Embodiment 1

[0042] This embodiment provides a method for evaluating the longitudinal strength of a half-ship float. Figure 1 As shown, the method comprises the following steps:

[0043] S100: selecting a section with the largest hull bending moment as an evaluation calculation section according to the floating load, and obtaining a section bending moment and a section shear force of the evaluation calculation section, wherein the evaluation calculation section includes a section at the deck and a section at the bottom outer plate;

[0044] Before the overall longitudinal strength assessment of the half-ship floating is performed, the floating loading is calculated according to the longitudinal length range and cross-sectional height range of the ship in the half-ship floating state. Specifically, firstly, based on the progress and plan of production and construction, the specific status of the ship at the current stage is determined, including the longitudinal length range of the ship, the cross-sectional height range, whether the main equipment is on board, the integrity status of the cabin, etc. For the subsequent floating loading calculation, the weight and center of gravity of all onboard equipment such as the hull, equipment, and production tooling are collected according to the state of the ship. Then, after entering the half-ship model and weight data, the floating loading calculation is performed. The floating loading calculation mainly adopts the form of ballast tank water pumping or adding weight iron, requiring the ship to float smoothly, and the longitudinal and transverse inclinations must strictly control the safety angles. Under normal circumstances, the transverse inclination angle does not exceed 0.5 degrees. After the floating loading calculation is completed, the floating loading calculation report is finally output, which includes the section bending moment and section shear force of the floating ship.

[0045] When evaluating the longitudinal strength of a half-ship, refer to Figure 4 First, according to the floating loading calculation report, the half-ship bending moment maximum section 2 is selected as the evaluation calculation section. When calculating the half-ship bending moment maximum section 2, professional structural calculation software is used. In this embodiment, refer to Figure 2 and Figure 3, input the characteristics of the corresponding half-ship bending moment maximum section 2 in Mars, including the bottom outer plate 11, the inner bottom plate 12 of the hull, the side outer plate 13, the main deck 14, the bottom tank sloping plate 15, the top tank sloping plate 16, the bottom longitudinal girder 17 and all the longitudinal continuous plate frames and the longitudinal ribs 18 above. Ensure that the scope and size of the structural model strictly correspond to the actual structural design of the floating ship here. The ship design should adopt a bilaterally symmetrical structural form. In the case of bilaterally symmetrical structural design, only the half-side section model of the ship is input.

[0046] S200: Obtaining section characteristics of the evaluation calculation section, wherein the section characteristics include a section modulus at the deck, a section modulus at the bottom outer plate, a moment of inertia of the evaluation calculation section to a horizontal neutral axis of the evaluation calculation section, and a static moment of an effective longitudinal member above the horizontal neutral axis to the horizontal neutral axis;

[0047] The section modulus at the deck, the section modulus at the bottom shell and the static moment of the effective longitudinal members above the horizontal neutral axis to the horizontal neutral axis are in m. 3 The unit of inertia moment of the horizontal neutral axis of the section is m 4 . Specifically, refer to Figure 5 , Section modulus is a physical quantity that measures the ability of a section to resist bending deformation, and it reflects the efficiency of the section shape in resisting bending stress. SM Deck Refers to the section modulus at the deck. The larger this value is, the stronger the ability of the deck section to resist deformation when subjected to bending load. The bottom outer plate 11 is an important structural part of the bottom of the hull, directly bearing the pressure from the water flow and the impact of underwater objects. Therefore, the section modulus SM of the bottom outer plate is Bottom It is also an important indicator for evaluating the strength and safety of the hull structure. The moment of inertia is a physical quantity that describes the ability of a section to resist torsion and bending deformation. y Refers to the moment of inertia of the evaluated section about the horizontal neutral axis 4 of the evaluated section. The neutral axis is usually the axis to which the sum of the static moments of all area elements in the section is zero. The magnitude of the moment of inertia reflects the ability of the section to resist bending deformation when subjected to a bending moment perpendicular to the horizontal neutral axis 4. The static moment is a physical quantity that describes the rotational effect of the area distribution on a certain axis. S y It refers to the static moment of all effective longitudinal members above the horizontal neutral axis 4 to the horizontal neutral axis 4. This value reflects the contribution of these members to the overall rotation behavior of the section when subjected to forces perpendicular to the horizontal neutral axis 4. The size and distribution of the static moment are crucial to maintaining the stability of the hull structure and preventing torsional deformation.

[0048] S300: Obtaining total longitudinal bending stress and total longitudinal shear stress according to the evaluated calculated section, wherein the total longitudinal bending stress includes total longitudinal stress at the deck and total longitudinal stress at the bottom outer plate;

[0049] Calculating the total longitudinal stress at the deck and the total longitudinal stress at the bottom outer plate are two key steps in calculating the total longitudinal bending stress. The total longitudinal bending stress refers to the stress generated at each section when the hull structure is subjected to the bending moment distributed along the length of the ship. This stress is one of the important factors in evaluating the strength and stiffness of the hull structure. The unit of the section bending moment is tm. The section bending moment is multiplied by the acceleration 9.18 and converted into the section bending moment in Nm. The total longitudinal stress at the deck σ Deck , total longitudinal stress at the bottom shell σ Bottom And the total longitudinal shear stress τ is obtained by the following formula:

[0050] σ Deck =M / SM Deck ;

[0051] σ Bottom =M / SM Bottom ;

[0052] τ=Q*S y *0.5 / (I y *t);

[0053] Where M is the section bending moment of the evaluated section, in Nm; Q is the section shear force of the evaluated section, in t; SM Deck is the section modulus at the deck, in m 3 ;SM Bottom is the section modulus of the bottom outer plate, in m 3 ;I y is the moment of inertia, in m 4 ; S y is the static moment, in m 3 ; σ Deck is the total longitudinal stress at the deck, in N / mm 2 ; σ Bottom is the total longitudinal stress at the bottom outer plate, in N / mm 2 ; τ is the total longitudinal shear stress, in N / mm 2 .

[0054] Because there is no half-ship floating strength assessment specification, and there are certain unforeseen differences between the actual on-site conditions and the input of the overall floating load calculation. From the safety margin, add 10% to 25% of the margin to the assessed section bending moment (in tm), and add 20% to 35% of the margin to the assessed section shear force (in t). At this time, the total longitudinal stress σ Deck , total longitudinal stress at the bottom shell σ Bottom And the total longitudinal shear stress τ is obtained by the following formula:

[0055] σ Deck =(110%~125%)M / SMDeck ;

[0056] σ Bottom =(110%~125%)M / SM Bottom ;

[0057] τ=(120%~130%)Q*S y *0.5 / (I y *t).

[0058] S400: Obtain the total longitudinal bending stress criterion and total longitudinal shear stress criterion based on the total longitudinal strength evaluation criterion of the whole ship design;

[0059] Since there is no longitudinal strength assessment standard for half-ships, considering the floating state is a wave-free dock state, the longitudinal strength assessment standard of the classification society for the whole ship design, that is, the longitudinal bending stress standard σ 许用 175 divided by the material coefficient K, in N / mm 2 , total longitudinal shear stress criterion τ 许用 110 divided by the material coefficient K, in N / mm 2 , total longitudinal bending stress criterion σ 许用 and the total longitudinal shear stress criterion is τ 许用 Obtained by the following formula:

[0060] σ 许用 =175 / K;

[0061] τ 许用 =110 / K;

[0062] The material coefficient K is selected according to the actual material level of the longitudinal structure of the calculated section, corresponding to: 1 for 235-level strength steel, 0.78 for 315-level strength steel, and 0.72 for 355-level strength steel. From a safety perspective, when there are multiple levels of strength steel in the longitudinal components of the section, a low-level material coefficient should be selected with sufficient margin.

[0063] S500: Evaluate the result, compare the total longitudinal stress at the deck with the total longitudinal bending stress criterion, the total longitudinal stress at the bottom outer plate with the total longitudinal bending stress criterion, and the total longitudinal shear stress with the total longitudinal shear stress criterion, so as to judge the safety of the ship structure.

[0064] In order to ensure the safety of the hull structure under floating or similar working conditions and prevent structural damage caused by excessive stress, its total longitudinal stress and total longitudinal shear stress are evaluated. When the total longitudinal stress at the deck is less than the total longitudinal bending stress criterion, the total longitudinal stress at the bottom outer plate is less than the total longitudinal bending stress criterion, and the total longitudinal shear stress is less than the total longitudinal shear stress criterion, the ship structure is judged to meet the safety requirements. When the total longitudinal stress at the deck is not less than the total longitudinal bending stress criterion, or the total longitudinal stress at the bottom outer plate is not less than the total longitudinal bending stress criterion, or the total longitudinal shear stress is not less than the total longitudinal shear stress criterion, the ship structure is judged not to meet the safety requirements. When the ship structure does not meet the safety requirements, the floating load is recalculated to reduce the section bending moment and section shear force.

[0065] Reference Figure 4 , when evaluating the total longitudinal strength of a ship under floating or similar conditions, it is necessary not only to pay attention to the safety of the maximum bending moment section 2 of the half-ship, but also to fully consider other potential dangerous sections. By focusing on evaluating these areas, the overall safety of the ship structure can be evaluated more comprehensively and accurately. Specifically, after evaluating the total longitudinal strength at the maximum bending moment of the floating ship, if the ship structure meets the safety requirements, other dangerous sections are selected for evaluation. Among them, the more dangerous sections are the longitudinal member interruption sections 3, such as the section where the engine room and the cargo hold are connected or the section where the cargo hold and the bow are connected. Because the longitudinal member here is interrupted and cannot be included in the section characteristic calculation, and the change in the outer plate line shape, that is, the reduction in area, the section modulus of the deck section and the section modulus of the bottom outer plate section of the section are often much smaller, resulting in the calculated total longitudinal stress at the deck and the total longitudinal stress at the bottom outer plate will increase year-on-year. For this section, it is necessary to continue to focus on the evaluation according to the above steps. This method of evaluating the total longitudinal strength of the half-ship floating is crucial for ship design, operation and maintenance, and helps to timely discover and solve potential structural safety problems. It is possible to evaluate the longitudinal strength of a half-floating ship when the ship is not yet fully built.

[0066] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for evaluating the longitudinal strength of a half-ship floating, characterized in that: The following steps are involved: According to the floating load, a section with the largest hull bending moment is selected as an evaluation calculation section, and a section bending moment and a section shear force of the evaluation calculation section are obtained, wherein the evaluation calculation section includes a section at the deck and a section at the bottom outer plate; Obtaining section properties of the evaluation calculation section, the section properties including section modulus at the deck, section modulus at the bottom outer plate, moment of inertia of the evaluation calculation section to the horizontal neutral axis of the evaluation calculation section, and static moment of effective longitudinal members above the horizontal neutral axis to the horizontal neutral axis; Obtaining total longitudinal bending stress and total longitudinal shear stress, wherein the total longitudinal bending stress includes total longitudinal stress at the deck and total longitudinal stress at the bottom outer plate; The total longitudinal bending stress criterion and the total longitudinal shear stress criterion are obtained according to the total longitudinal strength evaluation criterion of the whole ship design; The evaluation results are compared with the total longitudinal stress at the deck and the total longitudinal bending stress criterion, the total longitudinal stress at the bottom outer plate and the total longitudinal bending stress criterion, and the total longitudinal shear stress and the total longitudinal shear stress criterion to determine the safety of the ship structure.

2. The method for evaluating the longitudinal strength of a half-ship floating according to claim 1, characterized in that: The total longitudinal stress σ at the deck Deck , the total longitudinal stress σ at the bottom outer plate Bottom And the total longitudinal shear stress τ is obtained by the following formula: σ Deck =M / SM Deck ; σ Bottom =M / SM Bottom ; τ=Q*S y *0.5 / (I y *t); Wherein, M is the section bending moment of the evaluation calculation section, in Nm; Q is the section shear force of the evaluation calculation section, in t; SM Deck is the section modulus of the deck, in m 3 ;SM Bottom is the section modulus of the bottom outer plate, in m 3 ;I y is the moment of inertia, in m 4 ; S y is the static moment, in m 3 ; σ Deck is the total longitudinal stress at the deck, in N / mm 2 ; σ Bottom is the total longitudinal stress at the bottom outer plate, in N / mm 2 ; τ is the total longitudinal shear stress, in N / mm 2 .

3. The method for evaluating the longitudinal strength of a half-ship floating according to claim 2, characterized in that: The total longitudinal stress σ at the deck Deck , the total longitudinal stress σ at the bottom outer plate Bottom And the total longitudinal shear stress τ is obtained by the following formula: σ Deck =(110%~125%)M / SM Deck ; σ Bottom =(110%~125%)M / SM Bottom ; τ=(120%~130%)Q*S y *0.5 / (I y *t)。 4. The method for evaluating the longitudinal strength of a half-ship floating according to claim 1, characterized in that: The floating load is obtained according to the longitudinal length and the cross-sectional height of the ship in the half-floating state.

5. The method for evaluating the longitudinal strength of a half-ship floating according to claim 1, characterized in that: The total longitudinal bending stress criterion σ 许用 and the total longitudinal shear stress criterion is τ 许用 Obtained by the following formula: s 许用 =175 / K; t 许用 =110 / K; Where K is the material coefficient, unit N / mm 2 ;σ allowable is the total longitudinal bending stress criterion, unit is N / mm 2 ; τ is the total longitudinal shear stress criterion, in N / mm 2 .

6. The method for evaluating the longitudinal strength of a half-ship floating according to claim 1, characterized in that: When the total longitudinal stress at the deck is less than the total longitudinal bending stress criterion, the total longitudinal stress at the bottom outer plate is less than the total longitudinal bending stress criterion, and the total longitudinal shear stress is less than the total longitudinal shear stress criterion, it is judged that the ship structure meets the safety requirements.

7. The method for evaluating the longitudinal strength of a half-ship floating according to claim 1, characterized in that: When the total longitudinal stress at the deck is not less than the total longitudinal bending stress criterion, or the total longitudinal stress at the bottom outer plate is not less than the total longitudinal bending stress criterion, or the total longitudinal shear stress is not less than the total longitudinal shear stress criterion, it is judged that the ship structure does not meet the safety requirements.

8. The method for evaluating the longitudinal strength of a half-ship floating according to claim 7, characterized in that: When the ship structure does not meet the safety requirements, the floating loading is recalculated to reduce the section bending moment and the section shear force.

9. The method for evaluating the longitudinal strength of a half-ship floating according to claim 1, characterized in that: The floating loading calculation is performed by filling the ballast tank with water or adding weights.

10. The method for evaluating the longitudinal strength of a half-ship floating according to claim 1, characterized in that: When performing floating loading calculations, the ship's heel angle shall not exceed 0.5 degrees.

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