A stress calculation method for ring-stiffened cylindrical shell structures

Abstract

The present invention relates to a stress calculation method for a ring-stiffened cylindrical shell structure, comprising: S1, determining the dimensions of the ring-stiffened cylindrical shell structure: the dimensions of the shell plate include the inner surface radius R of the shell and the shell plate thickness t; the dimensional parameters of the ribs are determined according to their structural form; and further comprising the rib spacing l, calculating the pressure P c , elastic modulus E of the material, Poisson's ratio μ of the material; S2, calculate relevant parameters according to the structural dimensions of the ring-stiffened cylindrical shell, including rib parameters: rib area A, rib root radius R w , rib panel radius R f , rib core radius R c , Rib effective area A eff Shell parameters: u, β; Stress coefficient: #imgabs0#S3, calculate shell stress, including the circumferential stress of the mid-span of the intercostal shell plate #imgabs1# The total longitudinal stress σ1 on the inner surface of the shell plate at the root of the rib; S4, calculate rib stress, including the average rib stress σ f , rib root stress σ Fw and the rib panel stress σ Ff The present invention takes into account the influence of the eccentricity of the ring rib reinforcement and can accurately calculate the stress of the inner and outer rib panels and the stress of the rib root.

Description

Technical Field

[0001] The present invention belongs to the technical field of ship engineering structure design, and in particular relates to a structural stress calculation method considering the influence of eccentricity of ring rib reinforcement. Background Art

[0002] Currently, submersible structures typically utilize pressure-bearing, ring-stiffened cylindrical shells with annular stiffeners. This strength calculation method fails to consider the effects of eccentricity, resulting in identical results for both inner and outer rib structures. Furthermore, the stresses in the rib panels and at the rib roots cannot be calculated. This method relies on simplifying the ring-stiffened cylindrical shell into a complex curved elastic foundation beam rigidly fixed at both ends to elastic supports. When solving for the reaction forces exerted by the ring ribs on the shell, the stresses across the entire cross-section of the ring-stiffened ribs are assumed to be equal, and the entire cross-sectional area is assumed to be concentrated at a location coinciding with the shell plate centroid. This can lead to errors in actual results.

[0003] This method was improved in the design guidelines for a certain type of submersible structure. The submersible ring rib structure was decomposed into three parts: the rib web, the rib panel, and the cylindrical shell. The three parts were solved simultaneously to obtain the effect of the eccentricity of the ring-stiffened cylindrical shell rib on the stress of the cylindrical shell plate and rib. However, the equations of this method are complex to solve. In order to simplify the calculation in engineering applications, the stress coefficient determined by the parameters u and β was plotted. K1,K f The curve graph is calculated by looking up the graph. The graph is drawn based on the highest extreme value of the beam-column effect to consider the influence of the longitudinal force on the calculation results of the ring-stiffened cylindrical shell, that is, assuming that 2uγ=1. This assumption brings some errors; and human errors will occur when reading the curve values in the graph during the calculation process; in addition, the applicability to complex ring-stiffened structures is poor. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a stress calculation method for a ring-stiffened cylindrical shell structure in response to the deficiencies of the above-mentioned existing technologies. The method takes into account the influence of the eccentricity of the ring-stiffened reinforcement and can accurately calculate the stress of the inner and outer rib panels and the stress of the rib roots.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is:

[0006] A stress calculation method for a ring-stiffened cylindrical shell structure comprises the following steps:

[0007] S1. Determine the dimensions of the ring-stiffened cylindrical shell structure: The ring-stiffened cylindrical shell structure includes a pressure-resistant shell plate and annular ribs. The dimensions of the shell plate include the inner surface radius R of the shell and the shell plate thickness t. The dimensional parameters of the ribs are determined according to their structural form. The dimensions of the ring-stiffened cylindrical shell structure also include the rib spacing l and the calculated pressure P. c , elastic modulus E of the material, Poisson's ratio μ of the material;

[0008] S2. Calculate relevant parameters based on the structural dimensions of the ring-stiffened cylindrical shell, including rib parameters: rib area A, rib root radius R w , rib panel radius R f , rib core radius R c , Rib effective area A eff ; Shell parameters: u, β; Stress coefficient: K1,K f ;

[0009] S3. Calculate shell plate stress, including the circumferential stress on the mid-span of the intercostal shell plate The total longitudinal stress σ1 on the inner surface of the shell plate at the root of the rib;

[0010] S4. Calculate rib stress, including rib average stress σ f , rib root stress σ Fw and the rib panel stress σ Ff .

[0011] In the above solution, step S2 specifically includes the following steps:

[0012] (2.1) Calculate the rib area A;

[0013] (2.2) Calculate the rib root radius R w , rib panel radius R f , rib core radius R c ;

[0014] (2.3) Calculate the effective rib area A eff :

[0015]

[0016] (2.4) Calculate the shell parameters u, β:

[0017]

[0018] (2.5) Calculate the stress coefficient K1,K f :

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] In the above scheme, when the annular rib is a T-shaped material, the dimensional parameters of the rib include the web thickness s w , web height h w , panel thickness s f , panel width b f ;but

[0029] (2.1) Calculate the rib area A:

[0030] A=s w h w +s f b f

[0031] (2.2) Calculate the rib root radius R w , rib panel radius R f , rib core radius R c :

[0032] Inner ribs:

[0033] R w =R

[0034] R f =Rh w -s f

[0035] R c =R-(s w h w (h w / 2)+s f b f (h w +s f / 2)) / A

[0036] Outer ribs:

[0037] R w =R+t

[0038] R f =R+h w +s f +t

[0039] R c =R+t+(s w hw (h w / 2)+s f b f (h w +s f / 2)) / A.

[0040] In the above scheme, when the annular rib is of other structural forms including bulb flat steel, angle steel, etc., the dimensional parameters of the rib include height h, area A and center y0; then

[0041] (2.1) Calculate the rib area A:

[0042] Calculate the rib root radius R by consulting the Structural Mechanics Handbook or calculating (2.2) w , rib flange radius R f , rib core radius R c :Inner ribs:

[0043] R w =R

[0044] R f =Rh

[0045] R c =R-y0

[0046] Outer ribs:

[0047] R w =R+t

[0048] R f =R+h+t

[0049] R c =R+t+y0.

[0050] In the above solution, step S3 specifically includes the following steps:

[0051] (3.1) Calculation of the circumferential stress on the mid-span surface of the intercostal shell

[0052]

[0053] (3.2) Total longitudinal stress on the inner surface of the shell plate at the root of the rib

[0054]

[0055] In the above solution, step S4 specifically includes the following steps:

[0056] (4.1) Calculation of average rib stress

[0057]

[0058] (4.2) Calculation of rib root stress

[0059]

[0060] (4.3) Calculation of rib panel stress

[0061]

[0062] The beneficial effects of the present invention are:

[0063] 1. The present invention provides a stress calculation method for a ring-stiffened cylindrical shell structure. The principle of this method is to accurately solve the support reaction of the ring rib on the shell by performing an area integral on the stress over the entire ring rib cross section. The rib effective area formula is introduced through theoretical derivation for calculation, taking into account the effect of the eccentricity of the ring rib reinforcement. The relationship between the rib root stress and rib panel stress formulas and the original rib strength formula is derived using the principle of equal radial displacement at the rib.

[0064] 2. The stress coefficient is calculated directly using the formula K1,K f , eliminating the influence of the "beam-column effect" assumption.

[0065] 3. The method of the present invention can be used to calculate the stress of ring-stiffened cylindrical shells with complex rib forms.

[0066] In summary, the method of the present invention is applied to the stress calculation of pressure-bearing ring-stiffened cylindrical shell structures. It has the advantages of high calculation accuracy, fast calculation speed, clear calculation principle, convenience for designers to carry out optimization design during the structural design process, and convenience for engineering application. It can provide safe, reliable and solid support for the refined design and lightweight design of ring-stiffened cylindrical shell structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0068] Figure 1 This is a simplified diagram for calculating parameters of a ring-stiffened cylindrical shell with internal ribs in an embodiment of the present invention;

[0069] Figure 2 This is a simplified diagram for calculating the parameters of a ring-stiffened cylindrical shell with external ribs in an embodiment of the present invention. DETAILED DESCRIPTION

[0070] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0071] The present invention proposes a stress calculation method for a ring-stiffened cylindrical shell structure, comprising the following steps:

[0072] S1. Determine the dimensions of the ring-stiffened cylindrical shell structure:

[0073] The ring-stiffened cylindrical shell structure includes a pressure-resistant shell plate and annular ribs; the shell plate dimensions include the inner surface radius R = 1200 mm and the shell plate thickness t = 10 mm; the rib size parameters are determined according to the structural form. In this embodiment, T-shaped materials are used as an example, and their size parameters include the web thickness s w =7mm, web height h w =70mm, panel thickness s f =7mm, panel width b f =35mm, the structural dimensions of the ring-stiffened cylindrical shell also include the rib spacing l = 189mm, the calculated pressure P c =6.4MPa, the elastic modulus of the material E=1.96×10 5 MPa, Poisson's ratio of the material μ = 0.3.

[0074] S2. Calculate relevant parameters based on the structural dimensions of the ring-stiffened cylindrical shell, including rib parameters: rib area A, rib root radius R w , rib panel radius R f , rib core radius R c , Rib effective area A eff ; Shell (including shell plate and ribs) parameters: u, β; Stress coefficient: K1,K f The specific steps include:

[0075] (2.1) Calculate the rib area A:

[0076] A=s w h w +s f b f =735

[0077] (2.2) Calculate the rib root radius R w , rib panel radius R f , rib core radius R c :

[0078] Inner ribs (see Figure 1 ):

[0079] R w =R=1200

[0080] R f =Rh w -s f =1123

[0081] R c =R-(s w h w (hw / 2)+s f b f (h w +s f / 2)) / A=1152.2

[0082] External ribs (see Figure 2 ):

[0083] R w =R+t=1210

[0084] R f =R+h w +s f +t=1287

[0085] R c =R+t+(s w h w (h w / 2)+s f b f (h w +s f / 2)) / A=1257.8

[0086] (2.3) Calculate the effective rib area A eff

[0087]

[0088] (2.4) Calculate the shell parameters u, β:

[0089]

[0090]

[0091] (2.5) Calculate the stress coefficient K1,K f

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101] S3. Calculate shell plate stress, including the circumferential stress on the mid-span of the intercostal shell plate The total longitudinal stress σ1 on the inner surface of the shell plate at the root of the rib. Specifically, it includes the following steps:

[0102] (3.1) Calculation of the circumferential stress on the mid-span surface of the intercostal shell

[0103]

[0104] (3.2) Total longitudinal stress σ1 on the inner surface of the shell plate at the root of the rib

[0105]

[0106] S4. Calculate rib stress, including rib average stress σ f , rib root stress σ Fw and the rib panel stress σ Ff The specific steps include:

[0107] (4.1) Calculate the average rib stress σ f

[0108]

[0109] (4.2) Calculate the stress σ at the rib root Fw

[0110]

[0111] (4.3) Calculate the rib panel stress σ Ff

[0112]

[0113] Note: In the above embodiments, “inside” in brackets refers to the calculation results when the ribs are inside, and “outside” refers to the calculation results when the ribs are outside.

[0114] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A stress calculation method for a ring-stiffened cylindrical shell structure, characterized in that: The following steps are involved: S1. Determine the dimensions of the ring-stiffened cylindrical shell structure: The ring-stiffened cylindrical shell structure includes a pressure-resistant shell plate and annular ribs; the dimensions of the shell plate include the inner surface radius R of the shell and the shell plate thickness t; the dimensional parameters of the ribs are determined according to their structural form; the dimensions of the ring-stiffened cylindrical shell structure also include the rib spacing , calculate the pressure , elastic modulus E of the material, Poisson's ratio of the material ; S2. Calculate relevant parameters based on the structural dimensions of the ring-stiffened cylindrical shell, including rib parameters: rib area A, rib root radius , rib panel radius , rib core radius , rib effective area ; Shell parameters: ; Stress coefficient: ; Step S2 specifically includes the following steps: (2.1) Calculate the rib area A; (2.2) Calculate the rib root radius , rib panel radius , rib core radius ; (2.3) Calculate the effective area of ribs : (2.4) Calculate shell parameters : (2.5) Calculate the stress coefficient : ； S3. Calculate shell plate stress, including the circumferential stress on the mid-span of the intercostal shell plate , the total longitudinal stress on the inner surface of the shell plate at the root of the rib ; S4. Calculate rib stress, including rib average stress , rib root stress and rib panel stress .

2. The stress calculation method of the ring-stiffened cylindrical shell structure according to claim 1 is characterized in that: When the annular rib is a T-shaped material, the dimensional parameters of the rib include the web thickness. , web height , panel thickness , panel width ;but (2.1) Calculate the rib area A: (2.2) Calculate the rib root radius , rib panel radius , rib core radius : Inner ribs: Outer ribs: 。 3. The stress calculation method of a ring-stiffened cylindrical shell structure according to claim 1 is characterized in that: When the annular rib is of other structural forms including bulb flat steel, angle steel, etc., the dimensional parameters of the rib include height h, area A and center y0; then (2.1) Calculate the rib area A: Obtained by consulting a structural mechanics handbook or performing calculations (2.2) Calculate the rib root radius , rib flange radius , rib core radius : Inner ribs: Outer ribs: 。 4. The stress calculation method of a ring-stiffened cylindrical shell structure according to claim 1, characterized in that: The step S3 specifically includes the following steps: (3.1) Calculation of circumferential stress on the mid-surface of the intercostal shell at mid-span (3.2) Total longitudinal stress on the inner surface of the shell plate at the root of the rib 。 5. The stress calculation method of a ring-stiffened cylindrical shell structure according to claim 1 is characterized in that: The step S4 specifically includes the following steps: (4.1) Calculation of average rib stress (4.2) Calculation of rib root stress (4.3) Calculation of rib panel stress 。

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