A hull section checking method considering superstructure effectiveness

Abstract

The application relates to a hull section checking method considering the effective degree of superstructure, which adopts a calculation method of stress reduction factor k x based on a simplified finite element model x . By abandoning the difficult-to-calculate and difficult-to-verify parameter: area reduction factor η, a coefficient k h for the stress of the main hull is introduced on the basis of the stress reduction factor k x , the stress at each position of the whole section is calculated according to the stress reduction factor and the coefficient of the main hull, so that the calculation result is more accurate, and on the basis of the stress reduction factor k x considering the effective degree of superstructure, an estimation method based on a simplified finite element model is adopted. In the method, the stress reduction factor k x is not estimated by using various empirical formulas or theoretical formulas derived by ideal models, but a simplified finite element model is established according to the structural characteristics of specific ship types for calculation, so that the result can be more accurate for the structural characteristics of different ship types.

Description

Technical Field

[0001] This invention relates to the field of hull structure section verification technology, and in particular to a method for hull structure section verification of ships with long superstructures. Background Technology

[0002] The relationship between the superstructure and the main hull of a ship is as follows: Figure 1 As shown, the superstructure exists as an auxiliary structure on the main hull, and most ships have a superstructure. It is generally believed that short superstructures (or lightweight superstructures) do not contribute to the overall longitudinal strength and are not considered in hull section verification. However, for long superstructures (or heavy-duty superstructures), because they are relatively long compared to the main hull and have a larger and closer contact area with it, they are generally considered to contribute to the overall longitudinal strength like the main hull and should be considered in hull section verification.

[0003] Although the superstructure is generally considered to contribute to the overall strength, due to structural discontinuities between the superstructure and the main hull, as well as the lower stiffness of the superstructure relative to the main hull, a mismatch in deformation occurs when the two are subjected to longitudinal loads. The visual manifestation of this in cross-sectional verification is that while the superstructure does contribute to the longitudinal strength, it does not fully participate. This phenomenon of the superstructure not fully contributing to the longitudinal strength is generally described in the field of ship hull structures as superstructure effectiveness (or simply superstructure effectiveness).

[0004] Superstructure effectiveness is a term used in ship hull structure to describe the degree to which the superstructure contributes to overall longitudinal strength. The value ranges from 0 to 100%, where 0 indicates that the superstructure does not contribute to overall longitudinal strength at all, and 100% indicates that the superstructure fully contributes to overall longitudinal strength.

[0005] like Figure 2 The effect of superstructure effectiveness on stress during section verification shows that higher superstructure effectiveness means the superstructure itself needs to bear more overall longitudinal load, resulting in higher stress in the superstructure. For the main hull, higher superstructure effectiveness means the superstructure shares more load, leading to lower stress in the main hull (generally focusing on the upper deck). Conversely, lower superstructure effectiveness results in lower stress in the superstructure and higher stress in the main hull.

[0006] Currently, the conventional description of superstructure effectiveness generally uses two parameters: stress reduction factor k. x And the area reduction factor η.

[0007] The stress reduction factor is derived from the stress itself in the superstructure and is expressed as the ratio of the actual stress received by the superstructure to the stress assuming 100% participation of the superstructure in the total strength. This can be represented as shown in the diagram above:

[0008]

[0009] The area reduction factor, derived from the perspective of the superstructure's impact on the main hull, expresses the effectiveness of the superstructure as the ratio of the section area (i.e., plate thickness) of the superstructure that actually contributes to the overall strength to its actual plate thickness. In other words, since the superstructure does not fully participate in the overall strength calculation, the section properties cannot be calculated based on the actual plate thickness and should be reduced accordingly. The formula is as follows:

[0010]

[0011] Where A1 represents the cross-sectional area of ​​the superstructure calculated based on the degree to which the superstructure participates in the total strength, A act It represents the cross-sectional area applied to the superstructure.

[0012] In the initial design phase, the stress reduction factor k x Both the area reduction factor η and the stress reduction factor k can be estimated using simplified formulas. x Currently, whether it is the simplified finite element method or the Smanski method, the results obtained are quite close to the true values. However, the area reduction factor η itself is a parameter that describes the properties. In actual verification, even when precise stress results are available in the later stages of the design phase, it is still impossible to obtain the parameter accurately.

[0013] The application of superstructure effectiveness is to accurately calculate the true stress of each deck layer, namely σ1 and σ4, in the section verification. The two definitions mentioned above are also for these two parameters respectively.

[0014] The following is a method for using these two parameters in profile verification:

[0015] The basic principle of traditional calculation methods that consider the effectiveness of the superstructure is as follows: Figure 3 As shown, the basic steps are divided into the following steps:

[0016] (1) Estimate the area reduction factor η;

[0017] (2) Calculate the new ideal stress distribution curve (i.e., the traditional method line in the figure above, i.e., the straight line where σ6 and σ7 are located) based on the area reduction factor η.

[0018] (3) The stress value of the main hull is directly taken from the value of the corresponding deck on the curve. For example, the stress value of the upper deck of the main hull is σ6.

[0019] (4) The stress of the superstructure is the value of the corresponding deck on the curve, multiplied by a coefficient w. For example, the stress value σ5 in the superstructure is calculated as σ5 = wσ7.

[0020] Currently, the calculation process for different standards and patents is consistent, namely the above 4 steps. The difference lies in the calculation methods for parameters such as η and w. The following is a list of the current hull section verification process that focuses on the effectiveness of the superstructure.

[0021] The Lloyd's Register of Shipping (Lloyd's Register) standard outlines the following procedure for verifying hull sections that take into account the effectiveness of the superstructure (since the procedure is essentially the same, the above diagram will be used):

[0022] (1) The area reduction factor η is calculated using the following estimation formula:

[0023] η=7((ε-5)γ 4 +94(5-ε)γ 3 +2800(ε-5.8)γ 2 +27660(9-ε)γ)f(λ,N)×10 -7

[0024] (2) Calculate the new ideal stress distribution curve (i.e., the traditional method line in the figure above, i.e., the straight line where σ6 and σ7 are located) based on the area reduction factor η.

[0025] (3) The stress value of the main hull is directly taken from the value of the corresponding deck on the curve. For example, the stress value of the upper deck of the main hull is σ6.

[0026] (4) The stress of the superstructure is the value of the corresponding deck on the curve, multiplied by a coefficient w. In the Lloyd's classification society specification, w = η, that is, the coefficient is considered to be equal to the area reduction coefficient calculated in (1). Therefore, the stress value σ5 in the superstructure is calculated as σ5 = ησ7.

[0027] (1) Other parameters defined by Lloyd's Classification Society are as follows:

[0028]

[0029] N is the number of floors in the superstructure, which does not exceed 2;

[0030]

[0031] L is the length of the hull;

[0032]

[0033] l1 is the length of the first layer superstructure, and l2 is the length of the second layer superstructure.

[0034] The following is a method for verifying hull sections considering superstructure effectiveness, as outlined in the Practical Handbook of Ship Design:

[0035] (1) The stress reduction factor k is calculated using the following formula. x ;

[0036]

[0037] (2) The area reduction factor η is calculated using the following formula;

[0038]

[0039] (3) Calculate the new ideal stress distribution curve (i.e., the traditional method line in the figure above, i.e., the straight line where σ6 and σ7 are located) based on the area reduction factor η.

[0040] (4) The stress value of the main hull is directly taken from the value of the corresponding deck on the curve. For example, the stress value of the upper deck of the main hull is σ6.

[0041] (5) The superstructure stress is the value of the corresponding deck on the curve, multiplied by a coefficient w. In the ship design manual, w = k x That is, it is assumed that the coefficient is still equal to the stress reduction coefficient calculated in (1), so the stress value σ5 in the superstructure is calculated as σ5=k x σ7;

[0042] (6) Other parameters of the method in the Practical Manual of Ship Design are defined as follows:

[0043] x is the distance from the end of the superstructure;

[0044] l is the length of the superstructure;

[0045]

[0046]

[0047] B1 is the beam of the ship after deducting the opening of the superstructure deck;

[0048] f and F are the cross-sectional areas of the superstructure and the main hull in the calculation section, respectively;

[0049] e1 and e2 are the vertical coordinates of the neutral axis of the superstructure and the main hull in the calculation section, respectively;

[0050] i0 and I0 are the vertical moments of inertia of the superstructure and the main hull on the calculated cross-section, respectively.

[0051] The method described in patent number CN108595791B, which considers the effectiveness of the superstructure, is as follows:

[0052] (1) Calculate the stress reduction factor k x

[0053] Where k x The calculations are performed using empirical formulas from the aforementioned design manuals or the Smansky method.

[0054] (2) Calculate the area reduction factor η;

[0055]

[0056] (3) Calculate the new stress reduction factor k x1 The calculation formula is as follows:

[0057]

[0058] (4) Calculate the new ideal stress distribution curve (i.e., the traditional method line in the figure above, i.e., the straight line where σ6 and σ7 are located) based on the area reduction factor η.

[0059] (5) The stress value of the main hull is directly taken from the value of the corresponding deck on the curve. For example, the stress value of the upper deck of the main hull is σ6.

[0060] (6) The stress of the superstructure is the value of the corresponding deck on the curve, multiplied by a coefficient w. In this patent, w = k x1 That is, it is assumed that the coefficient is still equal to the stress reduction coefficient calculated in (1), so the stress value σ5 in the superstructure is calculated as σ5=k x1 σ7

[0061] As mentioned earlier, the basic process of the current methods involves obtaining a new stress distribution curve through an area reduction factor η, then directly taking the value from this curve for the main hull, and multiplying the value on the superstructure by a coefficient w. The differences between the methods lie in the values ​​and calculation methods of the area reduction factor η and the coefficient w.

[0062] However, as mentioned earlier, the area reduction factor η is a very difficult quantity to obtain. Various methods for calculating the area reduction factor either estimate it directly based on empirical formulas or use the stress reduction factor k. x While conversions can be performed, the conversion relationships lack a solid mechanical foundation. Furthermore, the area reduction factor is a parameter that is fundamentally difficult to verify, especially using numerical calculation methods such as the whole-ship finite element method. This compromises the accuracy of values ​​calculated using traditional methods.

[0063] Furthermore, regarding the stress reduction factor k xIts definition is clear and it has a relatively mature theoretical background. Although Smansky's estimation method is relatively complete, it is only derived through the ideal model of coupled deformation of the double beam theory. For the layout of superstructures with different structural forms, such as multi-story superstructures, multi-story superstructures with different lengths, and superstructures with different internal support forms, the accuracy of the estimation by this theory is also greatly limited. Summary of the Invention

[0064] To address the two problems mentioned above, this invention proposes the following solutions: First, it proposes a stress reduction factor k based on a simplified finite element model. x The calculation methods include a simplified modeling method and process for the finite element model, and a new method for verifying the hull section considering the effectiveness of the superstructure. This method discards the difficult-to-calculate and verify parameter—the area reduction factor η—and uses the stress reduction factor k, which has a more mature theoretical background. x Based on this, a coefficient k for the main hull stress is introduced. h This changes the entire profile verification process, resulting in more accurate calculation results. Furthermore, a simplified finite element model-based estimation method is proposed for the stress reduction factor of the superstructure's effectiveness.

[0065] To achieve the above objectives, the technical solution of the present invention is: a hull section verification method considering the effectiveness of the superstructure, employing a stress reduction factor k based on a simplified finite element model. x The calculation method discards parameters that are difficult to calculate and verify, such as the area reduction factor η, and the stress reduction factor k x Based on this, a coefficient k for the main hull stress is introduced. h The stress at various locations along the entire cross-section is calculated based on the stress reduction factor and the main ship system number, making the calculation results more accurate. Simultaneously, the stress reduction factor k, which considers the effectiveness of the superstructure, is also considered. x Based on this, an estimation method based on a simplified finite element model is adopted.

[0066] Furthermore, the stress reduction factor k based on the simplified finite element model x The calculation methods include a simplified finite element modeling method and a method for calculating the stress reduction factor based on the simplified model.

[0067] Furthermore, the simplified finite element modeling method comprises the following steps:

[0068] (1) Select the midship section of the ship including the superstructure, and create a finite element model of the midship section without considering the influence of the line shape;

[0069] (2) Copy and stretch the finite element model of the midship section along the ship direction until it is equal to the size of the actual ship. At the same time, adjust the length of the main hull and the superstructure to make them equal to the length of the main hull and the superstructure of the actual ship, and adjust the longitudinal distribution of the plate thickness of each longitudinal structure to make it basically consistent with the actual ship drawings.

[0070] (3) Apply MPC points, i.e., multi-point constraints, to the ends of the finite element model of the midship section.

[0071] Furthermore, in step (1), all major structures of the midship section must have the same major structural dimensions, including the ship's width, the height of each deck, the plate thickness of each structure, and the dimensions of the aggregate as shown in the midship section drawing.

[0072] Furthermore, in step (3), the MPC type is selected as REB2, the independent point of MPC is selected as the neutral axis of the end section, and the non-independent point is selected as all the nodes of the longitudinal member of the section. The nodes of the independent point and the non-independent point are associated with the X, Y, and Z three-degree-of-freedom linear displacement constraints.

[0073] Furthermore, the method for calculating the stress reduction factor based on the simplified model comprises the following steps:

[0074] (1) Apply end constraints at the MPC points at the ends of the finite element model of the midship section, where the linear displacements in the Y and Z directions are constrained at the independent points of the MPC at the tail end of the model; the linear displacements in the X, Y, and Z directions and the angular displacement Rx around the X axis are constrained at the independent points of the MPC at the head end of the model.

[0075] (2) Apply end moment at the MPC point at the end of the finite element model of the midsection, apply an arbitrary end moment M around the Y axis at the independent point of the MPC at the tail end of the model, and apply an end moment -M at the independent point of the MPC at the head end of the model that is equal in magnitude and opposite in direction to the tail moment.

[0076] (3) Perform finite element analysis on the above model to obtain the stress values ​​of the finite element elements of the model. Extract the average value of the normal stress in the X direction of all elements of the superstructure deck on the calculation section as the actual σ of the superstructure deck on this section. x-s ;

[0077] (4) Based on the simplified model, calculate the moment of inertia I and the Z coordinate z0 of the neutral axis of the cross section;

[0078] (5) Calculate the stress reduction factor for this profile.

[0079] Furthermore, in step (5), the stress reduction factor for this profile is calculated using the following formula:

[0080]

[0081] Among them, zs Let Z be the Z-coordinate of the superstructure deck on this cross-section.

[0082] Furthermore, the coefficient k of the main hull stress h Calculate using the following formula:

[0083]

[0084] In the formula: f and F are the cross-sectional areas of the superstructure and the main hull on the calculation section, respectively; e1 and e2 are the vertical coordinates of the neutral axis of the superstructure and the main hull on the calculation section, respectively; i0 and I0 are the vertical moments of inertia of the superstructure and the main hull on the calculation section, respectively.

[0085] Furthermore, the method for calculating the stress at various locations along the entire cross-section based on the stress reduction factor and the main ship system number comprises the following steps:

[0086] (1) Calculate the stress curve when the superstructure is assumed to contribute 100% to the total strength, i.e., the straight line containing σ2 and σ3, which is the curve.

[0087]

[0088] Where, σ zi The vertical coordinate is z i The stress value at time M act I represents the bending moment at that section of the actual ship. act This represents the moment of inertia that takes into account 100% of the superstructure's contribution to the overall strength.

[0089] (2) For the stress at each structural location of the main hull, the stress value is the value on the curve calculated in step (1), multiplied by the main hull system number k. h , i.e. σ hi =k h σ zi-hull , where σ hi For the stress of the required cross-section of the main hull section, σ zi-hull This represents the stress on the curve related to the main hull in step (1);

[0090] (3) For the stress of the superstructure, the stress value is the value on the curve calculated in step (1), multiplied by the stress reduction factor k. x , i.e. σ ti =k x σ zi-top , where σ ti For the stress of the superstructure section in the required cross-section, σ zi-top This represents the stress on the curve related to the superstructure in step (1).

[0091] Furthermore, the stress curve when the superstructure contributes 100% to the total strength is determined using the calculation formula in step (1), i.e., σ.zi With vertical structural height z i The variation curve is the basic formula for ship profile verification.

[0092] The beneficial effects of this invention are:

[0093] (1) Stress reduction factor k x Instead of using various empirical formulas or theoretical formulas derived from ideal models for estimation, we establish simplified finite element models for calculation based on the specific structural characteristics of ship types. The results are more accurate and better suited to the structural characteristics of different ship types.

[0094] (2) Discarding the area reduction factor, a value that lacks theoretical basis and cannot be accurately calculated and verified, we use the stress reduction factor and the main ship system number, which are more theoretical and have a clearer definition, to calculate the stress values ​​of the main ship hull and the superstructure, and the calculation results are more accurate.

[0095] (3) The actual calculation process is relatively simple. There is no need to consider changes in the neutral axis position and the moment of inertia caused by the effectiveness of the superstructure. Only one stress curve of the superstructure participating 100% in the total strength needs to be calculated. This is very easy to obtain in actual calculation. The superstructure can be regarded as part of the main hull.

[0096] (4) The calculation method of the main ship system number is also derived from the double beam theoretical model, which is relatively theoretical. Attached Figure Description

[0097] Figure 1 It refers to the relationship between the superstructure and the main hull of a ship;

[0098] Figure 2 The effect of the superstructure's effectiveness on stress during section verification;

[0099] Figure 3 This is the basic principle of traditional calculation methods that consider the effectiveness of the superstructure;

[0100] Figure 4 This invention describes the principle and calculation effect of the calculation method for considering the effectiveness of the superstructure.

[0101] Figure 5 This is a cross-sectional view of the midship section;

[0102] Figure 6 It is a simplified finite element model;

[0103] Figure 7 It is a simplified finite element model. Detailed Implementation

[0104] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0105] This invention provides a method for verifying ship hull sections considering superstructure effectiveness, such as... Figure 4 As shown, this includes the stress reduction factor k based on the simplified finite element model. x The calculation method discards the difficult-to-calculate and verify parameter—the area reduction factor η—and uses the stress reduction factor k, which has a more mature theoretical background. x Based on this, a coefficient k for the main hull stress is introduced. h The stress at various locations along the entire cross-section is calculated based on the stress reduction factor and the main ship system number, changing the entire cross-section verification process and making the calculation results more accurate. Simultaneously, the stress reduction factor k, which considers the effectiveness of the superstructure, is also considered. x Based on this, an estimation method based on a simplified finite element model is adopted.

[0106] Stress reduction factor k based on simplified finite element model x The calculation methods include a simplified finite element modeling method and a method for calculating the stress reduction factor based on the simplified model.

[0107] 1. The entire hull section verification method considering the effectiveness of the superstructure adopts the entire process steps of (1)-(12):

[0108] (1) Select a cross-section of the midship area including the superstructure, and without considering the influence of the ship's hull form, create a finite element model of the midship section. Requirements: All major structures in the midship section must be present, and the main structural dimensions (breadth, deck heights, plate thicknesses, and frame dimensions, etc.) must be consistent with the midship section drawings. Figure 5 As shown in Figure 6:

[0109] (2) Copy and stretch this model along the ship's direction until it matches the dimensions of the actual ship. Simultaneously, adjust the lengths of the main hull and superstructure to match the lengths of the actual ship's main hull and superstructure, respectively. Also, adjust the longitudinal distribution of the plate thicknesses of each longitudinal structure to ensure it is basically consistent with the actual ship's drawings. Figure 7 As shown.

[0110] (3) Apply MPC points (Multi-Point Constraint, a common element type in the finite element method for ship structures) to the end of the model. Select REB2 as the MPC type. Select the independent points of the MPC at the neutral axis of the end section, and select all nodes of the longitudinal members of the section as the non-independent points. Associate the nodes of the independent and non-independent points with X, Y, and Z three-degree-of-freedom linear displacement constraints. (The above terms are all common attributes of MPC property settings and are also commonly used attributes of MPC at the end of ship section analysis.)

[0111] (4) Apply end constraints to the MPC points set in (3), wherein the independent points of the MPC at the tail end of the model constrain the linear displacement in the Y and Z directions; the independent points of the MPC at the head end of the model constrain the linear displacement in the X, Y, and Z directions and the angular displacement Rx around the X axis.

[0112] (5) Apply end moment to the MPC point set in (3), apply an arbitrary end moment M around the Y axis to the independent point of MPC at the tail end of the model, and apply an end moment -M with the same magnitude and opposite direction to the tail moment to the independent point of MPC at the head end of the model.

[0113] (6) Perform finite element analysis on the above model to obtain the stress values ​​of the finite element elements of the model. Extract the average value of the normal stress in the X direction of all elements of the superstructure deck on the calculation section as the actual σ of the superstructure deck on this section. x-s ;

[0114] (7) Based on the simplified model, calculate the moment of inertia I and the Z coordinate z0 of the neutral axis of the cross section;

[0115] (8) Calculate the stress reduction factor of the profile according to the following formula.

[0116]

[0117] Among them, z s Here is the Z-coordinate of the superstructure deck on this cross-section; the other parameters are as described above.

[0118] (9) Calculate the main ship system number k h Calculate using the following formula:

[0119]

[0120] In the formula: f and F are the cross-sectional areas of the superstructure and the main hull on the calculation section, respectively; e1 and e2 are the vertical coordinates of the neutral axis of the superstructure and the main hull on the calculation section, respectively; i0 and I0 are the vertical moments of inertia of the superstructure and the main hull on the calculation section, respectively.

[0121] (10) Calculate the stress curve when the superstructure is assumed to contribute 100% to the total strength, i.e., the straight line containing σ2 and σ3, which is the curve.

[0122]

[0123] Where, σ zi The vertical coordinate is z i The stress value at time M act I represents the bending moment at that section of the actual ship. act This represents the moment of inertia that takes into account 100% of the superstructure's contribution to the overall strength.

[0124] The stress curve, i.e., σ, is determined by the above formula when the superstructure contributes 100% to the total strength. zi With vertical structural height z i The variation curve is the basic formula for ship profile verification.

[0125] (11) For the stress at each structural location of the main hull, the stress value is the value calculated on the curve in (10), multiplied by the main hull system number k. h , i.e. σ hi =k h σ zi-hull , where σ hi For the stress of the required cross-section of the main hull section, σ zi-hull This represents the stress on the curve with respect to the main hull section in (10);

[0126] (12) For the stress of the superstructure, the stress value is the value on the curve calculated in (10), multiplied by the stress reduction factor k. x , i.e. σ ti =k x σ zi-top , where σ ti For the stress of the superstructure section in the required cross-section, σ zi-top The stress on the curve in (10) is related to the superstructure.

[0127] 2. A simplified model creation method for calculating the stress reduction factor, namely, calculation steps (1)-(3);

[0128] 3. The method for calculating the stress reduction factor based on the simplified model, i.e., steps (4)-(8);

[0129] 4. The formula for calculating the main ship system number, namely the formula in (9), is proposed for the first time and contains a complete theoretical derivation process;

[0130] 5. The calculation method for calculating the stress at each position of the entire cross section based on the stress reduction factor and the main ship system number, i.e., the overall steps of (10)-(12), is different from other methods that consider the area reduction factor.

Claims

1. A method for verifying ship hull sections considering superstructure effectiveness, characterized in that: Stress reduction factor based on simplified finite element model is adopted. k x The calculation method discards parameters that are difficult to calculate and verify: area reduction factor. η In stress reduction factor k x Based on this, a coefficient for the stress of the main hull is introduced. k h The stress at various locations along the entire cross-section is calculated based on the stress reduction factor and the main ship system number, resulting in more accurate calculations. Furthermore, the stress reduction factor considering the effectiveness of the superstructure is also taken into account. k x Based on this, an estimation method based on a simplified finite element model is adopted, wherein: The steps for calculating the stress reduction factor based on the simplified model are as follows: (1) Apply end constraints at the MPC points at the ends of the finite element model of the midship section, wherein the linear displacements in the Y and Z directions are constrained at the independent points of the MPC at the tail end of the model; the linear displacements in the X, Y, and Z directions and the angular displacement Rx around the X axis are constrained at the independent points of the MPC at the head end of the model. (2) Apply end moment at the MPC point at the end of the finite element model of the midship section, apply an arbitrary end moment M around the Y axis at the independent point of the MPC at the tail end of the model, and apply an end moment -M with the same magnitude and opposite direction to the tail moment at the independent point of the MPC at the head end of the model. (3) Perform finite element calculations on the above model, obtain the stress values ​​of the finite element elements of the model, and extract the average value of the normal stress in the X direction of all elements of the superstructure deck on the calculation section as the actual stress of the superstructure deck on this section. σ x-s ; (4) Calculate the moment of inertia of the cross section based on the simplified model. I and the center axis Z coordinate z 0; (5) Calculate the stress reduction factor for this profile; The method for calculating the stress at various locations along the entire cross-section based on the stress reduction factor and the main ship system number involves the following steps: (1) Calculate the stress curve assuming the superstructure contributes 100% to the total strength, i.e. σ 2 and σ The straight line containing 3 is the curve. in, σ zi For vertical coordinates z i The stress value at time M act I represents the bending moment at that section of the actual ship. act This represents the moment of inertia that takes into account 100% of the superstructure's contribution to the overall strength. (2) For the stress at each structural location of the main hull, the stress value is the value on the curve calculated in step (1), multiplied by the main hull system number. k h ,Right now σ hi = k h σ zi-hull ,in σ hi For the stress of the main hull section of the required cross-section, σ zi-hull This represents the stress on the curve related to the main hull in step (1); (3) For the stress of the superstructure, the stress value is the value on the curve calculated in step (1), multiplied by the stress reduction factor. k x ,Right now σ ti = k x σ zi-top ,in σ ti For the stress of the superstructure section in the required cross-section, σ zi-top This represents the stress on the curve related to the superstructure in step (1).

2. The hull section verification method considering superstructure effectiveness according to claim 1, characterized in that: The stress reduction factor based on the simplified finite element model k x The calculation methods include a simplified finite element modeling method and a method for calculating the stress reduction factor based on the simplified model.

3. The hull section verification method considering superstructure effectiveness according to claim 2, characterized in that: The simplified finite element modeling method comprises the following steps: (1) Select the midship section of the ship including the superstructure, and create a finite element model of the midship section without considering the influence of the line shape; (2) Copy and stretch the finite element model of the midship section along the ship direction until it is equal to the size of the actual ship. At the same time, adjust the length of the main hull and the superstructure so that they are equal to the length of the main hull and the superstructure of the actual ship, and adjust the longitudinal distribution of the plate thickness of each longitudinal structure so that it is basically consistent with the actual ship drawings. (3) Apply MPC points, i.e., multi-point constraints, to the ends of the finite element model of the midship section.

4. The hull section verification method considering superstructure effectiveness according to claim 3, characterized in that: In step (1), all major structures in the midship section must have major structural dimensions, including the ship's width, the height of each deck, the plate thickness of each structure, and the dimensions of the aggregate, which must be consistent with the midship section drawings.

5. The hull section verification method considering superstructure effectiveness according to claim 3, characterized in that: In step (3), the MPC type is selected as REB2, the independent point of MPC is selected as the neutral axis of the end section, and the non-independent point is selected as all the nodes of the longitudinal member of the section. The nodes of independent and non-independent points are associated with X, Y and Z three-degree-of-freedom linear displacement constraints.

6. The hull section verification method considering superstructure effectiveness according to claim 1, characterized in that: In step (5), the stress reduction factor for this profile is calculated using the following formula: in, z s Let Z be the Z-coordinate of the superstructure deck on this cross-section.

7. The hull section verification method considering superstructure effectiveness according to claim 6, characterized in that: The coefficient of the main hull stress k h Calculate using the following formula: In the formula: f , F These are the cross-sectional areas of the superstructure and the main hull, respectively, calculated in section. e 1, e 2 represents the vertical coordinates of the neutral axis of the superstructure and the main hull in the calculation section; i 0, I 0 represents the vertical moment of inertia of the superstructure and the main hull on the calculated cross-section.

8. The hull section verification method considering superstructure effectiveness according to claim 1, characterized in that: The stress curve when the superstructure contributes 100% to the total strength is determined by the calculation formula in step (1), i.e. σ zi With vertical structural height z i The variation curve is the basic formula for ship profile verification.

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