CN-115270299-B - Hierarchical redundancy optimization method for ship ice belt structure for improving ice load resistance

CN115270299BCN 115270299 BCN115270299 BCN 115270299BCN-115270299-B

Abstract

The invention relates to a hierarchical redundancy optimization method of a ship ice belt structure for improving ice load resistance, which comprises the following steps of determining the impact load of a ship ice belt ice on a ship side according to the ice level and design parameters of the ship, carrying out finite element modeling on a ship body structure, dividing each level of structure hierarchy of the ship side, respectively forming a plate grid structure, a plate frame structure or a component part of a transverse frame structure in the level of each structure hierarchy, firstly transmitting stress among inner components of each level when encountering the impact load of external ice on the ship ice, then expanding the stress to a higher level component, carrying out structural residual strength analysis based on a finite element technology, and evaluating the structural redundancy of the ship side through a key component hierarchical iteration damage method.

Inventors

YU JIANXING
JIN ZIHANG
YU YANG
WANG FUCHENG
Su Yefan
HUANG KAIHANG

Assignees

天津大学

Dates

Publication Date: 20260508
Application Date: 20220722

Claims (7)

1. A hierarchical redundancy optimization method for a ship ice belt structure for improving ice load resistance comprises the following steps: Firstly, determining the collision load of the side ice belt floating ice according to the ice level and design parameters of the ship; performing finite element modeling on a ship structure, and dividing each level of structure hierarchy of the broadside; thirdly, analyzing the residual strength of the structure based on a finite element technology, and evaluating the redundancy of the broadside structure through a key component grading iterative damage method; To ensure the safety of the vessel under extreme repeated collision loads, determining the ultimate strength measure σ accept represents the ultimate strength balance as: Wherein R eL is the yield strength of the material, R m is the tensile strength of the material, lambda is the load safety coefficient under the working condition of calculation, and C m is the nonlinear correction coefficient of the structural material; the structural redundancy is evaluated by adopting a key component grading iteration damage method, and the method comprises the following steps: 1) Carrying out finite element analysis on the floating ice collision of the structure according to the load working condition, taking a component with the largest stress in the current structure, and recording the stress value as sigma max , judging that the structure meets the requirement if sigma max is smaller than sigma accept , ending the analysis, taking the component as a key component of the current structure if sigma max is larger than sigma accept , and continuing the subsequent analysis; 2) Judging the structural level of the key component, carrying out damage simulation on the key component if the key component is in a first-stage structure, and then repeating the operation of the step 1), if the key component is in a second-stage structure, indicating that the damage risk is transferred from the first-stage component to the second-stage component, carrying out damage simulation on the key component, and then repeating the operation of the step 1), and if the key component is in a third-stage structure, indicating that the damage risk is transferred to the third-stage component, and ending the analysis; 3) After analysis is terminated, grading the structural redundancy, if the complete structure meets the requirement in finite element analysis, the structural redundancy is considered to be very high without optimization and reinforcement, if the complete structure is subjected to iterative damage analysis, only a first-stage component is damaged, the structural redundancy is evaluated to be R1 level, the structure is considered to have sufficient redundancy without optimization, if a second-stage component is damaged, the structural redundancy is evaluated to be R2 level, the structural redundancy is considered to be insufficient, the first-stage component is required to be optimized, and if a third-stage component is damaged, the structural redundancy is evaluated to be R3 level, and the structural redundancy is considered to be seriously insufficient and the first-stage component and the second-stage component are required to be optimized; The critical component damage simulation in the step 2) is carried out, wherein the damage mode is the most unfavorable condition, namely the end part of the component is broken; Step four, optimizing the structure of the side ice belt, namely, carrying out hierarchical optimization on corresponding components according to the structural redundancy analysis result in the step three, wherein the optimization goal is to ensure that structural damage is not transmitted from low-level components to high-level components under load working conditions; The fifth step of carrying out residual strength analysis and structural redundancy analysis on the optimized structure, if the optimization scheme meets the requirement, calculating and analyzing the structural quality change caused by the scheme, if the optimization scheme does not meet the requirement or the structural quality change is overlarge and exceeds 3%, continuing the fourth step until the structure meets the strength and structural redundancy requirement in the third step of analysis; And step six, determining a final ice belt structure hierarchical redundancy optimization scheme.
2. The hierarchical redundancy optimization method for ice bank structures of ships according to claim 1, wherein in the first step, the side ice bank floating ice collision equivalent load is: wherein, k value is related to ship displacement and ship engine output, and is expressed as: delta is the displacement of the ship under the working condition of the designed highest ice level; P is the actual continuous output power of the ship turbine, and the unit kW; a, b are related to the k value and ice load application area; c 1 is the probability that ice loading at different ice levels will occur in the leading region of the ice bank, the middle region of the ice bank, and the trailing region of the ice bank.
3. The hierarchical redundancy optimization method for the ice belt structure of the ship according to claim 1 is characterized in that in the first step, in order to simulate extreme load conditions of the ship when the ship sails in an ice area, three areas of an ice belt head area, an ice belt middle area and an ice belt tail area of the ice belt are respectively arranged to bear floating ice collision loads in a full-length range, the floating ice collision load conditions of the side ice belt are set to be p, the floating ice equivalent load is 1m in height, the floating ice equivalent load is uniformly distributed in the ice belt head area, the ice belt middle area and the ice belt tail area, and the load acting direction is perpendicular to an outer plate of the ship body.
4. The hierarchical redundancy optimization method for ice bank structures of ships according to claim 1, wherein in the second step, the levels of the structures of the division broadside stages are as follows: first stage: 1) Broadside longitudinal bones; 2) Rib structures including normal ribs, intermediate ribs, inter-deck ribs; Second stage: 1) Side stringers; 2) A strong rib; Third stage: 1) A deck sideboard; 2) A toggle plate structure comprising a bilge toggle plate and a beam toggle plate; 3) A bulkhead structure including a bulkhead horizontal truss, a bulkhead vertical truss, and a bulkhead plate; In a third step, the determined ultimate strength metric σ accept : Wherein R eL is the yield strength of the material, R m is the tensile strength of the material, lambda is the load safety coefficient under the working condition, and C m is the nonlinear correction coefficient of the structural material.
5. The hierarchical redundancy optimization method for the ice belt structure of the ship according to claim 1, wherein the second step method is that a finite element method is adopted to analyze the mechanical response of the ice belt structure at the floating ice collision, finite element modeling and meshing are carried out on the ship body structure according to ship design parameters and structural forms, hexahedron or tetrahedron units are adopted for the mesh meshing of the ice belt structure components at the side in order to simulate stress transmission and failure modes, each level of structure hierarchy of the side is divided for different ship structural forms so as to evaluate and optimize strength step by step, each structural hierarchy component respectively forms a plate grid, a plate frame structure or is used as a component part of a transverse frame structure in the present level, and when the external floating ice collision load is encountered, the stress is firstly transmitted among inner components of each level and then is expanded to higher-level components.
6. The hierarchical redundancy optimization method for the ice belt structure of the ship according to claim 1, wherein the third step comprises the steps of carrying out numerical simulation analysis by utilizing the finite element model of the ship body structure established in the second step, wherein boundary conditions are set to be that symmetrical constraint is applied to the transverse bulkhead end, namely x-direction displacement and y-direction and z-direction rotation angles are constrained, loading is carried out according to the side ice belt floating ice collision load determined in the first step, so that structural stress distribution conditions are obtained, and ultimate strength analysis and structural redundancy evaluation are carried out on the basis of the structural stress distribution conditions.
7. The method for optimizing hierarchical redundancy of ice bank structures of ships according to claim 1, wherein the optimizing method in the fourth step comprises the steps of increasing structural strength of key components, namely increasing component sizes or improving component steels, and increasing force transmission paths of the key components, namely adjusting structural forms of the components or increasing the number of the components in a structural level to be optimized.

Description

Hierarchical redundancy optimization method for ship ice belt structure for improving ice load resistance Technical Field The invention relates to the field of ship design and construction and reliability analysis, in particular to a method for optimizing a ship ice belt structure so as to improve the capability of resisting repeated collision of floating ice of a ship in an ice region under the condition of local damage. Background For ice area vessels, the harsh environment of the polar course ice floes place high demands on the vessel structure. In addition to wave load, vertical bending moment, corrosion effect and other factors, the ice area ship is very likely to suffer continuous collision of floating ice to the bow and side ice belt structures in the process of sailing in the polar sea area, and even causes local damage and failure of the ship body structure. In order to ensure the safety of the ice area ship under the condition of local failure of the structure, redundancy analysis and structural grading optimization should be performed on the ship side structure so that the ship still has sufficient safety margin under the collision damage condition. At present, the theory of structural redundancy is gradually introduced into the structural design of ships in face of the problem of residual strength under the local damage of the structure. In the SOLAS specifications issued in 2009, qualitative description and requirements are made of the structural strength and redundancy of bulk carriers. In addition, structural redundancy is demonstrated in the IMO MSC letter, requiring that the vessel should be designed and built with redundancy such that local damage to any of the reinforced structural members does not immediately result in the consequent collapse of the entire reinforced panel. Currently, domestic related researches mainly analyze the whole and partial structural redundancy of a conventional ship (such as bulk cargo ships, oil tankers and the like) under dangerous working conditions by redundancy balance calculation, failure path analysis and other methods. However, throughout the current related research, specific quantitative standard standards have not been formed at home and abroad for the structural redundancy of key areas of ice region ships under continuous collision of floating ice. Meanwhile, the redundancy evaluation system for different structural layers of the ship is less in research, and the corresponding structural evaluation and design method is not perfect. Therefore, in order to ensure the reliability of the ship in the ice area under the partial damage of the floating ice collision, the structural redundancy theory should be consulted, and the components with different structural layers are classified and analyzed to establish the hierarchical optimization method for the crashworthiness of the ship ice belt structure. Disclosure of Invention The invention aims to provide a hierarchical redundancy optimization method for a ship ice belt structure, which can improve ice load resistance. The method can effectively evaluate the structural redundancy of the ship ice belt structure under the continuous collision of the floating ice, and carry out iterative optimization on each level of structural members according to the stress conditions of different structural hierarchy members. And finally, analyzing the overall quality change of the structure after the optimization of different optimization schemes to obtain an optimal structure optimization scheme, and ensuring the safety and reliability of the ice belt structure under extreme sea conditions. The technical proposal is as follows: a hierarchical redundancy optimization method for a ship ice belt structure for improving ice load resistance comprises the following steps: Firstly, determining the collision load of the side ice belt floating ice according to the ice level and design parameters of the ship; In order to simulate extreme load working conditions of a ship when sailing in an ice area, three areas of an ice belt head area, an ice belt middle area and an ice belt tail area of an ice belt are respectively arranged to bear floating ice collision load in a full-length range, wherein the side ice belt floating ice collision load working conditions are set as that the floating ice equivalent load is p, the load height is 1m, the side ice belt floating ice collision load is uniformly distributed in the ice belt head area, the ice belt middle area and the ice belt tail area, and the load acting direction is perpendicular to an outer plate of a ship body; performing finite element modeling on a ship structure, and dividing each level of structure hierarchy of the broadside; The method comprises the steps of analyzing mechanical response of a side ice belt structure under the collision of floating ice by adopting a finite element method, carrying out finite element modeling and grid division on the hull structure according to s