Full-rotation crane ship stern crane working condition wave load forecasting method

Abstract

The invention relates to the technical field of ship hydrodynamic analysis, and discloses a full-rotation crane ship stern crane working condition wave load forecasting method, which comprises the following steps of: 1, establishing a wet surface model according to a main ship body molded line; 2, establishing an actual overhanging mass rod distribution model, and obtaining the weight gravity center and motion inertia parameters of the whole ship and the mass characteristics of each calculation section in the front range of the front end of the base supporting structure; 3, the mass of the overhanging part is disassembled into a plurality of parts; 4, respectively establishing corresponding triangular mass rod distribution models, and synthesizing the triangular mass rod distribution models with the mass distribution of the main ship body to obtain the mass characteristics of each calculation section in the range behind the front end of the base supporting structure; 5, synthesizing the profile quality characteristics obtained in the step 2 and the step 4 into the same quality characteristic file to obtain the quality characteristics of all the calculated profiles in the whole ship range; and 6, carrying out long-term or short-term forecasting on the wave load by adopting the obtained quality characteristic data of all the calculation profiles.

Description

Technical Field

[0001] The invention relates to the technical field of ship hydrodynamic analysis, and in particular to a method for predicting wave loads in a fully rotating crane ship stern crane working condition. Background Art

[0002] Large fully revolving crane vessels are specialized wind power construction vessels that integrate a series of processes such as port loading, marine transportation, hoisting, and piling. They have the ability to carry out operations such as offshore oil platforms, large cross-sea bridge construction, large structure hoisting, and salvage of extra-large sunken ships and objects, and have a very broad market application prospect. Wind power construction mainly includes single pile foundation piling, jacket foundation installation, negative pressure cylinder foundation installation, booster station installation, etc.

[0003] Fully revolving crane vessels tend to be larger, and the lifting weight, boom length and lifting height are constantly increasing. In order to maximize the main deck operating area and the horizontal lifting distance of the crane, the main crane is usually arranged at the stern of the hull and as close to the stern plate as possible. The weight of the suspended objects and booms outside the hull has an increasingly significant impact on the wave load of the crane vessel. As the key environmental load in the hull structure design, the reasonable prediction of wave load is crucial to the hull structure design.

[0004] The design conditions of crane vessels are mainly divided into navigation conditions and lifting operation conditions. For navigation conditions, the crane boom is placed on the shelf, and the direct calculation and prediction method of wave loads is similar to that of conventional ships. However, for lifting operation conditions, since the load and the boom extend out of the hull, and the lifting distance and height of the load are large, such as the stern crane operation condition, if the overhanging mass distribution model of the actual stern crane condition is used to predict the wave load based on the potential flow theory, the result will be that the wave bending moment does not "return to zero" at the tail. When a large full-revolving crane vessel is in the stern crane operation condition, the boom and the load are suspended behind the tail seal. If the wave load is predicted according to the actual mass distribution model, the result will be obviously ambiguous. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to accurately and reasonably predict the wave load.

[0006] In order to solve the above technical problems, the technical solution of the present invention is to provide a method for predicting wave loads of a fully rotating crane stern crane working condition, comprising the following steps:

[0007] Step 1: Establish a wet surface model based on the main hull lines;

[0008] Step 2: Establish the actual cantilever mass rod distribution model to obtain the center of gravity of the whole ship weight, motion inertia parameters and the mass characteristics of each calculated section in the range in front of the front end of the base support structure;

[0009] Step 3: Disassemble the overhanging mass into several parts according to the distribution pattern of the overhanging weight in the actual stern crane operation condition;

[0010] Step 4: According to the weight and center of gravity height of each disassembled overhanging part, the corresponding triangular mass rod distribution model is established, and the mass distribution of each disassembled cantilever part is synthesized with the mass distribution of the main hull to obtain the mass characteristics of each calculated section in the range behind the front end of the base support structure;

[0011] Step 5: Combine the section mass characteristics obtained in step 2 and step 4 into the same mass characteristic file to obtain the mass characteristics of all calculated sections within the entire ship;

[0012] Step 6: Use the wet surface model of step 1, the weight center of gravity and motion inertia parameters of the entire ship obtained in step 2, and the mass characteristic data of all calculated sections obtained in step 5 to make long-term or short-term predictions of wave loads.

[0013] Optionally, the overhanging part in step three is disassembled into two parts including a overhanging weight and a cantilever arm structure.

[0014] Optionally, the triangular mass rod distribution model established in step four includes the triangular mass distribution corresponding to the boom of the cantilever boom structure and the triangular mass distribution corresponding to the weight of the cantilevered weight, wherein the length of the base side of the triangle is the length of the base support structure, and the total mass of each triangular mass distribution is equal to the mass of each corresponding cantilever part.

[0015] Optionally, in step four, the mass of each cantilevered portion is placed at a corresponding center of gravity height within the longitudinal range of the base support structure and synthesized with the mass distribution of the main hull.

[0016] Optionally, the model building in steps 1 to 5 and the wave load prediction in step 6 are implemented by classification society hydrodynamic analysis software and finite element modeling software.

[0017] In summary, the wave load prediction method for the stern crane working condition provided by the method of the present invention is consistent with the actual situation in the whole ship motion, and the wave load distribution is consistent with the wave load distribution trend of each section obtained by the stress integration of the finite element calculation unit of the whole ship, with good fitting, approaching zero at the head and tail, ensuring the accuracy of the wave load prediction within the whole ship, and the wave load distribution is reasonable, which solves the unreasonable load distribution problem encountered in the wave load prediction of this type of ship. In the early stage of the project, accurate wave loads can be quickly obtained in a relatively short time, ensuring the rationality of the design, and can more realistically reflect the impact of large cantilevered heavy objects on wave loads. At the same time, it can also be applied to the wave load prediction of all similar offshore structures, which has great practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of load components of a target cross section for load calculation in the present invention;

[0019] Figure 2 This is a schematic diagram of the stern cantilevered weight model of the present invention;

[0020] Figure 3 This is a schematic diagram of the mass rod model established in step 4 of the present invention;

[0021] In the figure: 1. Overhanging weight; 2. Base support structure; 3. Main hull; 4. Cantilever arm structure; 5. Triangular mass distribution corresponding to the arm; 6. Triangular mass distribution corresponding to the weight; 7. Main hull mass distribution; 8. Front end of base; 9. Height of arm gravity center; 10. Height of suspended object gravity center 10. DETAILED DESCRIPTION

[0022] The following combination Figure 1-3 The present invention is described in further detail.

[0023] In the prior art, the wave load prediction principle and the wave load prediction results of the actual overhang mass distribution model using potential flow theory are analyzed as follows:

[0024] Wave loads are based on the six-degree-of-freedom steady-state motion equations of the rigid body of the hull in waves. After the ship motion response in regular waves is obtained, the D'Alembert principle is applied, which states that for all inertial forces or applied external forces of any physical system, the sum of the virtual work done after the virtual displacement of the load constraint conditions is equal to 0; or the sum of the external force acting on an object and the reaction of the dynamic force is equal to zero. It can be regarded as an application of Newton's second law, converting dynamic problems into static problems for processing. Some complex dynamic problems can be described by simple static principles, and the forces and moments in the cross section of the hull are calculated, that is, the vertical and horizontal shear forces and bending moments induced by waves, as well as the axial forces and torques.

[0025] The specific calculation method is as follows: Figure 1 As shown in the figure, for the partial length of the hull from the stern to any section x, the force and distance concentrated at point o in the cross section x of the hull are The six components are N, SF Y , SF Z ,TM,BM Y BM Z ;

[0026] According to the D'Alembert principle, the real fluid dynamic load acting on the hull of this length is balanced with the rigid body inertia force load, so there is a balance formula for the external force and the reaction force of the power for this section of the hull:

[0027]

[0028] Among them, the left-hand term is the various wave loads on the investigated section, and the right-hand term is the integral term of the wet surface dynamic pressure on this section of the hull and the hull inertia force load, etc.

[0029] For the full-revolving crane stern hoisting condition, as shown in the attached Figure 2 As shown in the figure, for the mass model, the boom and the weight are suspended behind the tail plate. Figure 2 When calculating the wave load of the section at X, all the masses after the section will be taken as a whole, together with the wet surface of the hull after the section, and the D'Alembert principle will be used to calculate the wave load at the target section X. However, in fact, the gravity of the cantilevered part does not directly act vertically on the hull in the corresponding wet surface range, but is transmitted to the main hull 3 through the entire crane barrel base, that is, the cantilevered mass after section X is separated from the wet surface. When calculating the wave load, the existing hydrodynamic software only identifies its mass distribution and center of gravity position for the mass model, and does not consider the mass redistribution caused by the cantilevered mass being transmitted to the hull through the base in practice. Therefore, when the hull is cut front and back with section X, the wet surface and mass after section X do not constitute a calculation model that conforms to the calculation theory. The wave loads of each section are obtained by integrating the fluctuating pressure of the wet surface and integrating the inertial force of the hull weight under the motion acceleration. Therefore, the wave load results of each section within the range from the tail seal to the front end of the crane base support structure 2 are inaccurate.

[0030] Therefore, the present invention discloses a method for predicting wave loads in a fully revolving crane stern crane working condition, comprising the following steps:

[0031] Step 1: Establish a wet surface model based on the main hull 3-line;

[0032] Step 2: Establishing the actual cantilever mass rod distribution model, obtaining the center of gravity of the whole ship weight, motion inertia parameters and the mass characteristics of each calculated section in the range before the front end 8 of the base support structure 2;

[0033] Step 3: according to the distribution pattern of the overhanging weight 1 in the actual stern crane operation condition, the mass of the overhanging part is disassembled into several parts;

[0034] Step 4: Reference Figure 3 , according to the weight and gravity center height of each disassembled overhanging part, the corresponding triangular mass rod distribution model is established, and the mass distribution of each disassembled overhanging part is synthesized with the mass distribution 7 of the main hull to obtain the mass characteristics of each calculated section in the range behind the base front end 8 of the base support structure 2;

[0035] Step 5: Combine the section mass characteristics obtained in step 2 and step 4 into the same mass characteristic file to obtain the mass characteristics of all calculated sections within the entire ship;

[0036] Step 6: Use the wet surface model of step 1, the weight center of gravity and motion inertia parameters of the entire ship obtained in step 2, and the mass characteristic data of all calculated sections obtained in step 5 to make long-term or short-term predictions of wave loads.

[0037] Example

[0038] In this embodiment, the model establishment and wave load prediction of each model are realized by the classification society hydrodynamic analysis software and finite element modeling software;

[0039] In this embodiment, the cantilevered part in step 3 is disassembled into two parts including a cantilevered weight 1 and a cantilevered boom structure 4, and a triangular mass distribution 5 corresponding to the boom of the cantilevered boom structure 4 and a triangular mass distribution 6 corresponding to the weight of the cantilevered weight 1 are respectively established, wherein the length of the base side of the triangle is the length of the base support structure 2, and the total mass of each triangular mass distribution is equal to the mass of each corresponding cantilevered part, and then the mass of each cantilevered part is placed at the corresponding center of gravity height within the longitudinal range of the base support structure 2 and synthesized with the mass distribution of the main hull 3, as shown in FIG. Figure 2 As shown, the triangular mass distribution 5 corresponding to the boom is placed at the corresponding boom gravity center height 9, and the triangular mass distribution 6 corresponding to the heavy object is placed at the corresponding hanging object gravity center height 10.

[0040] The present invention adopts the actual cantilever mass model, including the mass distribution of the cantilever part and the mass distribution of the rest of the hull, to determine the section mass characteristics of the wave load calculation section in the range in front of the front end of the base support structure 2; since the mass characteristics of the calculation section in the range in front of the front end of the base support structure 2 are not affected by the cantilever mass, that is, they are not affected by the mass redistribution caused by the cantilever mass being transferred to the main hull 3 through the base support structure 2 in practice. Therefore, the main hull 3 is cut front and back using the section in the range in front of the front end of the base support structure 2, and the wet surface and mass after the section form a calculation model that conforms to the calculation theory;

[0041] Then, the mass of the cantilevered parts, such as the cantilevered boom structure 4 and the cantilevered weight 1, is converted into a triangular mass distribution within the longitudinal range of the crane base support structure 2 and placed at the corresponding center of gravity height. The mass of the remaining hull is simulated by a set of mass rod models. After the two parts are synthesized, they are used to determine the section mass characteristics of each wave load calculation section within the range behind the front end of the base support structure 2;

[0042] The above two parts of the section mass characteristics are synthesized as the total section mass characteristic file for wave load calculation. During the calculation process, the weight center of gravity and motion inertia parameters of the main hull 3 still use the values ​​corresponding to the actual cantilever model to ensure the accuracy of the hull motion and wet surface wave pressure calculation. Finally, the D'Alembert principle is used to calculate the wave load of each section.

[0043] The method provided by the present invention provides a method for predicting wave loads for a stern crane working condition of a crane vessel, and the obtained whole ship motion is consistent with the actual situation, and the wave load distribution is consistent with the wave load distribution of each section obtained by integrating the stress of the finite element calculation unit of the whole ship, thereby ensuring the accuracy of the wave load prediction within the whole ship, and the wave load distribution is reasonable, thus solving the problem of unreasonable load distribution encountered in the wave load prediction for this type of ship.

[0044] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for predicting wave loads of a fully revolving crane stern crane working condition, characterized in that: The following steps are involved: Step 1: Establish a wet surface model based on the main hull (3) lines; Step 2: Establishing a mass rod distribution model of the actual cantilever, obtaining the center of gravity of the whole ship weight, motion inertia parameters and mass characteristics of each calculated section in the range in front of the front end (8) of the base support structure (2); Step 3: according to the distribution pattern of the overhanging weight (1) in the actual stern crane operation condition, the mass of the overhanging part is disassembled into several parts; Step 4: According to the weight and center of gravity height of each disassembled overhanging part, the corresponding triangular mass rod distribution model is established, and the mass distribution of each disassembled overhanging part is synthesized with the mass distribution of the main hull (7), so as to obtain the mass characteristics of each calculated section in the range behind the base front end (8) of the base support structure (2); Step 5: Combine the section mass characteristics obtained in step 2 and step 4 into the same mass characteristic file to obtain the mass characteristics of all calculated sections within the entire ship; Step 6: Use the wet surface model of step 1, the weight center of gravity and motion inertia parameters of the entire ship obtained in step 2, and the mass characteristic data of all calculated sections obtained in step 5 to make long-term or short-term predictions of wave loads.

2. The method for predicting wave loads of a fully revolving crane stern crane working condition according to claim 1 is characterized in that: In step 3, the cantilevered part is disassembled into two parts including a cantilevered weight (1) and a cantilevered arm structure (4).

3. The method for predicting wave loads of a fully revolving crane stern crane working condition according to claim 2 is characterized in that: The triangular mass rod distribution model established in step 4 includes the triangular mass distribution (5) corresponding to the boom of the cantilever boom structure (4) and the triangular mass distribution (6) corresponding to the weight of the cantilevered weight (1), wherein the length of the base side of the triangle is the length of the base support structure (2), and the total mass of each triangular mass distribution is equal to the mass of each corresponding cantilever part.

4. The method for predicting wave loads of a fully revolving crane stern crane working condition according to claim 3 is characterized in that: In step 4, the mass of each cantilevered part is placed at the corresponding center of gravity height within the longitudinal range of the base support structure (2) and synthesized with the mass distribution of the main hull (3).

5. The method for predicting wave loads of a fully revolving crane stern crane working condition according to claim 1 is characterized in that: The model building in steps 1 to 5 and the wave load prediction in step 6 are realized by classification society hydrodynamic analysis software and finite element modeling software.

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