CN202389826U - Structure for preventing elephant-food buckling of large oil storage tanks - Google Patents

Abstract

The utility model relates to an oil storage device, and aims to provide a structure for preventing the elephant-food buckling of large oil storage tanks. The structure comprises a first ring wallboard arranged at the bottom-most part of a tank wall, and the outer side of the central position of the first ring wallboard is fixedly provided with a reinforcing ring; the reinforcing ring is arranged away from a connecting pipe, and the specific installation height of the reinforcing ring is determined according to the height of the first ring wallboard and the layout situations of the connecting pipe; the thickness of the reinforcing ring is an irrelevant variable, and the cross sectional area of the reinforcing ring is determined according to the installation height; and for different cross sectional areas of the reinforcing ring, different radial displacement curves of the tank wall of an oil tank can be obtained, and through taking a curve with the minimum curvature change, the cross sectional area corresponding to the curve is the optimal cross sectional area of the known corresponding installation height. Compared with a traditional method for improving the elephant-food buckling prevention capacity of large oil storage tanks through increasing the wall thickness, the structure disclosed by utility model can greatly save materials, and is easy to operate and high in feasibility.

Description

The prevention large-scale petroleum storing tank resembles the structure of sufficient flexing

Technical field

The utility model belongs to petrochemical complex oil storage apparatus field, relates to the structure that resembles sufficient flexing at the bottom of a kind of new prevention large-scale petroleum storing tank jar, is intended to improve the ability that the oil tank opposing resembles sufficient flexing.

Background technology

Large-scale petroleum storing tank is the key equipment in petroleum chemical industry, oil reserve base, and " resembling sufficient flexing " that high hydraulic pressure and axle pressure combined action cause is its typical failure forms.The direct harm that resembles sufficient flexing is to cause oil product to leak, contaminated environment, the harm ecologic balance, initiation fire and explosion accident.Because the imperfection of theoretical system,, be destroyed in the earthquake of being everlasting still the time by the large oil tank of current specifications production-release design until today.

The method that traditional raising large oil tank resembles sufficient flexing ultimate load comprises: the thickness that increases tank body wallboard and boundary plank; Be anchored at oil tank on the basis with anchor bolt; Change the ratio of height to diameter of oil tank, the diameter that promptly increases oil tank reduces the height of oil tank.But these methods all can significantly increase laid down cost, and economy is reduced, and feasibility is not high.

Therefore, petroleum chemical industry needs a kind of method of easy economy newly to prevent the sufficient flexing of resembling of petroleum storage tank.

The utility model content

The technical matters that the utility model will solve is, overcomes deficiency of the prior art, and a kind of structure of preventing large-scale petroleum storing tank to resemble sufficient flexing is provided.This structure mainly is that hazardous location is provided with the lightweight reinforcing pad in the large-scale petroleum storing tank bottom, to increase the ability that the storage tank opposing resembles sufficient flexing.The problem of most critical is: optimum assembly how to select reinforcing pad setting height(from bottom) and cross-sectional area.

Be the technical solution problem, the solution of the utility model is:

A kind of structure of preventing large-scale petroleum storing tank to resemble sufficient flexing is provided, is included in the first lap wallboard of tank skin bottommost, it is characterized in that, at reinforcing pad of the outside of first lap wallboard midway location fixed installation.

As improvement, the installation site of said reinforcing pad is avoided taking over concrete setting height(from bottom) h _sConfirm according to first lap wallboard height and adapter deployment scenarios.

As improvement, the thickness of said reinforcing pad is irrelevant variable; The cross-sectional area A of reinforcing pad _sBy setting height(from bottom) h _sConfirm, be specially: the setting height(from bottom) h of reinforcing pad _sAfter confirming, obtain the radial displacement curve of oil tank wall according to three groups of following formula:

$w_i=\frac{{2F}_i}{K_i}{e}^{-F_i{x}_i}[-Q_{i-1}\cos F_i{x}_i-F_i{M}_{i-1}(\cos F_i{x}_i-\sin F_i{x}_i)]+\frac{2F_i}{K_i}{e}^{-F_i(l_i-x_i)}$

$[Q_i\cos F_i(l_i-x_i)-F_i{M}_i(\cos F_i(l_i-x_i)-\sin F_i(l_i-x_i))]+\frac{\mathrm{\ρg}(H_{i-1}-x_i)}{K_i}+\frac{v{N}_{\mathrm{xi}}}{{\mathrm{RK}}_i}$

${\mathrm{<figure-callout\; id="1"\; label="w"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">w</figure-callout>}}_1=(C_{11}\cos F_1{x}_1+C_{21}\sin F_1{x}_1)e^{-F_1{x}_1}+(C_{31}\cos F_1{x}_1+C_{41}\sin F_1{x}_1)e^{F_1{x}_1}+\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">K</figure-callout>}}_1}\mathrm{\&rho;g}(H_0-h_s-x_1)+\frac{v{N}_{x1}}{K_{1}R}$

${\mathrm{<figure-callout\; id="0"\; label="w"\; filenames="HDA0000124613470000042.png,HDA0000124613470000051.png"\; state="\{\{state\}\}">w</figure-callout>}}_0=(C_{10}\cos F_1{x}_0+C_{20}\sin F_1{x}_0)e^{-F_1{x}_0}+(C_{30}\cos F_1{x}_0+C_{40}\sin F_1{x}_0)e^{F_1{x}_0}+\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">K</figure-callout>}}_1}\mathrm{\&rho;g}(H_0-x_0)+\frac{v{N}_{x1}}{K_{1}R}$

Can access different oil tank wall radial displacement curves for different reinforcing pad cross-sectional areas, get a wherein minimum curve of curvature change, the cooresponding cross-sectional area of this curve is corresponding known setting height(from bottom) h _sOptimum cross-sectional area A _s

The implementation method of the utility model is:

(1) selects a suitable setting height(from bottom) h according to first lap wallboard height and adapter deployment scenarios _s, the installation site of reinforcing pad should be avoided taking over;

(2) by setting height(from bottom) h _sConfirm the cross-sectional area A of reinforcing pad _s, and carry out the making of reinforcing pad according to known tank skin data;

(3) reinforcing pad is fixed in setting height(from bottom) h _sThe first lap wallboard outside at place.

Its theoretical foundation is following:

In the utility model, because large-scale petroleum storing tank foundation ring wallboard receives bigger hydraulic pressure, axial compression and base plate effect of contraction, interior force deformation is very complicated, resembles sufficient flexing and often occurs on this circle wallboard, and this zone also is the hazardous location of whole storage tank.Therefore reinforcing pad should be arranged on the bottom tank skin of oil tank.

Compared to the thickness of whole tank skin, reinforcing pad thickness can be ignored.And for the Theoretical Calculation in the utility model, reinforcing pad thickness is more little to be consistent with result of calculation more.But in practical application, often only limit reinforcing pad thickness, promptly satisfy the reinforcing pad bending stiffness and get final product less than the millesimal of first lap tank shell bending stiffness less than 1/10th of first lap tank shell thickness.

In the utility model, tank skin is designated as the first lap wallboard successively by the bottom to the top, the second circle wallboard, or the like.When calculating the tank skin radial displacement, oil tank wall is divided into three parts, first is the second circle wallboard and the above wallboard that respectively encloses thereof, and the radial displacement of i circle wallboard is designated as w _i(i=2,3 ..., together down); Second portion be first lap wallboard reinforcing pad with top, its radial displacement is designated as w ₁Third part be first lap wallboard reinforcing pad with the lower part, its radial displacement is designated as w ₀In addition, first lap wallboard and the discontinuous place of reinforcing pad contacting structure, radial displacement is designated as w _s

According to the elastic plate shell theory, receive hydraulic pressure P and axial compression N _xThe shell of effect, the BENDING DIFFERENTIAL EQUATION that its radial displacement w representes is:

$D\frac{d^{4}w}{{\mathrm{<figure-callout\; id="4"\; label="Dx"\; filenames="HDA0000124613470000012.png,HDA0000124613470000013.png"\; state="\{\{state\}\}">Dx</figure-callout>}}^4}+\frac{\mathrm{Et}}{R^2}w=p+\frac{v{N}_x}{R}$ (formula 1)

Wherein,

Be called the shell bending stiffness; E is the tank wall material modulus of elasticity; T is the tank skin wall thickness; P representes hydraulic pressure; V is a Poisson's ratio; N _xBe the suffered axial compression of wallboard; R is the storage tank radius.

The form of this differential equation general solution is:

$w=({\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_1\mathrm{Cos}\mathrm{Fx}+{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_2\mathrm{Sin}\mathrm{Fx})e^{-\mathrm{Fx}}+({\mathrm{<figure-callout\; id="3"\; label="C"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_3\mathrm{Cos}\mathrm{Fx}+{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HDA0000124613470000012.png,HDA0000124613470000013.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\mathrm{Sin}\mathrm{Fx})e^{\mathrm{Fx}}+\frac{1}{K}(p+\frac{v{N}_x}{R})$ (formula 2)

Wherein,

C ₁, C ₂, C ₃, C ₄Be the boundary condition coefficient, need confirm according to the boundary condition at wallboard two ends.Concerning than the cylinders shell, C ₃=C ₄=0.

According to principle of superposition, the radial displacement that the second circle wallboard and above i thereof enclose wallboard is:

$w_i=\frac{{2F}_i}{K_i}{e}^{-F_i{x}_i}[-Q_{i-1}\cos F_i{x}_i-F_i{M}_{i-1}(\cos F_i{x}_i-\sin F_i{x}_i)]+\frac{2F_i}{K_i}{e}^{-F_i(l_i-x_i)}$

$[Q_i\mathrm{Cos}{F}_i(l_i-x_i)-F_i{M}_i(\mathrm{Cos}{F}_i(l_i-x_i)-\mathrm{Sin}{F}_i(l_i-x_i))]+\frac{\mathrm{\&rho;\; g}(H_{i-1}-x_i)}{K_i}+\frac{v{N}_{\mathrm{Xi}}}{{\mathrm{RK}}_i}$ (formula 3)

The radial displacement of the above position of reinforcing pad, first lap tank shell place is:

${\mathrm{<figure-callout\; id="1"\; label="w"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">w</figure-callout>}}_1=(C_{11}\cos F_1{x}_1+C_{21}\sin F_1{x}_1)e^{-F_1{x}_1}+(C_{31}\cos F_1{x}_1$

${+C}_{41}\mathrm{Sin}{F}_1{x}_1)e^{F_1{x}_1}+\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">K</figure-callout>}}_1}\mathrm{\&rho;\; g}(H_0-h_s-x_1)+\frac{v{N}_{x1}}{K_{1}R}$ (formula 4)

Wherein, C ₁₁, C ₂₁, C ₃₁, C ₄₁Be the boundary condition coefficient, need confirm according to the boundary condition at wallboard two ends; First lap tank shell place reinforcing pad with the radial displacement of upper/lower positions is:

${\mathrm{<figure-callout\; id="0"\; label="w"\; filenames="HDA0000124613470000042.png,HDA0000124613470000051.png"\; state="\{\{state\}\}">w</figure-callout>}}_0=(C_{10}\cos F_1{x}_0+C_{20}\sin F_1{x}_0)e^{-F_1{x}_0}+(C_{30}\cos F_1{x}_0$

$+C_{40}\mathrm{Sin}{F}_1{x}_0)e^{F_1{x}_0}+\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">K</figure-callout>}}_1}\mathrm{\&rho;\; g}(H_0-x_0)+\frac{v{N}_{x1}}{K_{1}R}$ (formula 5)

Wherein, C ₁₀, C ₂₀, C ₃₀, C ₄₀Be the boundary condition coefficient, need confirm according to the boundary condition at wallboard two ends; Distinguishingly, at the radial displacement of oil tank wallboard and reinforcing pad contact position:

$w_s=\frac{(Q_{2s}-Q_{1s})R^2}{E_s{A}_s}$ (formula 6)

Wherein, w _sRadial displacement for tank skin and reinforcing pad contact position; Q _1s, Q _2sBe respectively the shearing of reinforcing pad upper and lower surface; R is the oil tank internal diameter; E _sModulus of elasticity for the reinforcing pad material; A _sCross-sectional area for reinforcing pad.

According to the compatibility of deformation relation of the discontinuous place of oil tank wall structure, oil tank wallboard and reinforcing pad contact position and the boundary condition of first lap tank skin bottom, the displacement equation that the associating base plate is found the solution above-mentioned tank skin three parts can be tried to achieve 8 known variables C in the equation respectively ₁₁, C ₂₁, C ₃₁, C ₄₁, C ₁₀, C ₂₀, C ₃₀, C ₄₀Thereby can obtain the radial displacement expression formula of whole tank body wallboard.

Based on European box hat design specification, resembling sufficient flexing critical load can be calculated as follows:

${{\stackrel{\&OverBar;}{\mathrm{\&lambda;}}}_{\mathrm{<figure-callout\; id="2"\; label="x"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">x</figure-callout>}}}^2=\frac{f_y}{{\mathrm{\&sigma;}}_{\mathrm{cl}}},$ $s=\frac{1}{400}\frac{r}{t},$ $\stackrel{\&OverBar;}{p}=\frac{\mathrm{pr}}{{\mathrm{t\&sigma;}}_{\mathrm{cl}}}$

${\mathrm{\&alpha;}}_{\mathrm{xpp}}=(1-\frac{{\stackrel{\&OverBar;}{p}}^2}{{{\stackrel{\&OverBar;}{\mathrm{\&lambda;}}}_x}^4})(1-\frac{1}{1.12+s^{1.5}})\left(\frac{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="HDA0000124613470000011.png,HDA0000124613470000012.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+1.21{{\stackrel{\&OverBar;}{\mathrm{\&lambda;}}}_x}^2}{s(s+1)}\right)$

σ _Cr=α _Xppσ _Cl(formula 7)

Wherein:

Be dimensionless slenderness ratio parameter; S is a radius-thickness ratio; σ _CrBe the flexing limit stress of box hat, σ _Ci=0.605Et/r is the classical flexing limit stress of elasticity;

Be the dimensionless circumference stress; σ _Cl=0.605Et/r is for considering the reduction coefficient of material plasticity influence; α _XppFor plasticity is cut down coefficient; E is a modulus of elasticity, and r, t are respectively the radius and the thickness of housing, f _yBe material yield intensity, P gets the maxim of the hydraulic pressure that possibly occur in the jar.

According to formula (7), the oil tank wallboard resembles sufficient flexing failure criteria and is:

N _x≤t σ _Cr(formula 8)

Can find out that the principal element that influences buckling load is tank skin hoop film internal force N _θ=pr/t, N _θIt is big more,

Also big more, the flexing ultimate load is more little.Therefore, the purpose that reinforcing pad is set will reduce oil tank foundation ring tank skin hoop film internal force exactly, improves the storage tank opposing and resembles sufficient deformation ability.

Known

By countries in the world oil tank earthquake resistant design code, N _XCalculate and be converted to constant often, therefore available w weighs N _θSize, the reinforcing pad action effect can be showed by w intuitively.Be that w is more little, it is big more that storage tank critical resembles sufficient buckling load, can resist preferably more and resemble sufficient flexing.

According to above equation and result of calculation thereof, can obtain the combination of optimum reinforcing pad setting height(from bottom) and cross-sectional area.At first, according to first lap wallboard height and adapter deployment scenarios, select a suitable setting height(from bottom) h at the midway location of first lap wallboard _s, make reinforcing pad avoid all adapters as far as possible.At this moment, can obtain corresponding different reinforcing pad cross-sectional area A _sThe tank skin deformation curve, these curves relatively, and choose a wherein minimum curve of curvature change, the cooresponding cross-sectional area of this curve is formed one group of optimum assembly with the setting height(from bottom) of having set.

The beneficial effect of the utility model is:

Pass through to increase wall thickness and improve the method that the large-scale storage tank opposing resembles sufficient flexion capabilities and compare with traditional, saving in material significantly, processing ease, feasibility is higher.

Description of drawings

Fig. 1 is the tank structure scheme drawing.

Fig. 2 is first lap wallboard and reinforcing pad structural representation figure;

Fig. 3 is first lap wallboard and reinforcing pad scheme drawing;

Fig. 4 is first lap wallboard and reinforcing pad transverse sectional view;

Fig. 5 is reinforcing pad and takes over the structural representation when intersecting.

Fig. 6 is reinforcing pad and takes over the scheme drawing when intersecting;

Fig. 7 is reinforcing pad and takes over the transverse sectional view when intersecting;

Label among the figure: 1 boundary plank, 2 center plates, 3 reinforcing pads, 4 first lap wallboards, 5 second circle wallboards, 6 are taken over.

Fig. 8 is an i circle wallboard mechanical relationship scheme drawing;

Fig. 9 is an i-1 circle wallboard mechanical relationship scheme drawing;

Among the figure, Q _I-1It is the shearing of i circle wallboard and i-1 circle wallboard junction; M _I-1It is the moment of flexure of i circle wallboard and i-1 circle wallboard junction; l _iIt is the height of i circle wallboard; x _iIt is the distance that any point encloses wallboard and i circle wallboard junction on the i circle wallboard apart from i-1; H _iIt is the distance between i circle wallboard and i+1 circle wallboard junction and liquid level;

Figure 10 is first lap wallboard and reinforcing pad mechanical relationship scheme drawing;

Among the figure, Q _1sAnd Q _2sBe respectively the shearing of reinforcing pad upper and lower surface; M _sMoment of flexure for the reinforcing pad place; x ₁Be the distance of the above position of first lap wallboard reinforcing pad any point apart from reinforcing pad; x ₀For first lap wallboard reinforcing pad with the distance of upper/lower positions any point apart from base plate; h _sBe the reinforcing pad setting height(from bottom); H ₀Be liquid surface total height;

Figure 11 is hour tank skin distortion situation of reinforcing pad circle area;

Figure 12 is reinforcing pad face loop product tank skin distortion situation when big.

The specific embodiment

With 15 * 10 ⁴m ³Large-scale petroleum storing tank is an example, and the utility model is further specified.Oil tank volume 15 * 10 ⁴m ³, diameter 100m, always up to 21.80m, water-filling height 20.18m, boundary plank stretches out the length C=120mm at tank skin center.Main technical details is seen shown in the table 1.

Table 1 15 * 10 ⁴m ³The large oil tank technical parameter

The reinforcing pad setting height(from bottom) is made as h _s=2.5m, the result is like Figure 11, shown in 12.

When reinforcing pad area big (Figure 12), like alp==100, radial displacement does not almost take place in the reinforcing pad place, and moment of flexure is very big, the indent very point that becomes, and local yielding possibly take place in this place material, has increased the possibility that storage tank resembles foot destruction on the contrary.Therefore, the reinforcing pad cross-sectional area should have optimal value.Near reinforcing pad cross-sectional area optimal value, bigger outside bulging deformation obtains good restraining on oil tank the 1st circle wallboard, does not add again near the reinforcing pad simultaneously to cause bigger local indent distortion.Can know that by Figure 11 near alp==1.0, such condition is satisfied in the tank shell distortion.

Promptly corresponding to setting height(from bottom) h _sThe reinforcing pad of=2.5m, cross-sectional area can farthest improve the ability that the storage tank opposing resembles sufficient flexing during for alp=1.0.

The reinforcing pad cross-sectional area A of this moment _s≈ 0.044 ², this area only is equivalent to the area that a diameter is the round thin steel of 0.237m, and is visible compared with increasing tank shell thickness, and reinforcing pad saving in material largely is set.

Claims (3)

1. structure of preventing large-scale petroleum storing tank to resemble sufficient flexing is included in the first lap wallboard of tank skin bottommost, it is characterized in that, at reinforcing pad of the outside of first lap wallboard midway location fixed installation.

2. structure according to claim 1 is characterized in that, the installation site of said reinforcing pad is avoided taking over concrete setting height(from bottom) h _sConfirm according to first lap wallboard height and adapter deployment scenarios.

3. structure according to claim 1 is characterized in that the thickness of said reinforcing pad is irrelevant variable, the cross-sectional area A of reinforcing pad _sBy setting height(from bottom) h _sConfirm, be specially:

The setting height(from bottom) h of reinforcing pad _sAfter confirming, obtain the radial displacement curve of oil tank wall according to three groups of following formula:

$w_i=\frac{{2F}_i}{K_i}{e}^{-F_i{x}_i}[-Q_{i-1}\cos F_i{x}_i-F_i{M}_{i-1}(\cos F_i{x}_i-\sin F_i{x}_i)]+\frac{2F_i}{K_i}{e}^{-F_i(l_i-x_i)}$

$[Q_i\cos F_i(l_i-x_i)-F_i{M}_i(\cos F_i(l_i-x_i)-\sin F_i(l_i-x_i))]+\frac{\mathrm{\&rho;g}(H_{i-1}-x_i)}{K_i}+\frac{v{N}_{\mathrm{xi}}}{{\mathrm{RK}}_i}$

$w_1=(C_{11}\cos F_1{x}_1+C_{21}\sin F_1{x}_1)e^{-F_1{x}_1}+(C_{31}\cos F_1{x}_1+C_{41}\sin F_1{x}_1)e^{F_1{x}_1}+\frac{1}{K_1}\mathrm{\&rho;g}(H_0-h_s-x_1)+\frac{v{N}_{x1}}{K_{1}R}$

$w_0=(C_{10}\cos F_1{x}_0+C_{20}\sin F_1{x}_0)e^{-F_1{x}_0}+(C_{30}\cos F_1{x}_0+C_{40}\sin F_1{x}_0)e^{F_1{x}_0}+\frac{1}{K_1}\mathrm{\&rho;g}(H_0-x_0)+\frac{v{N}_{x1}}{K_{1}R}$

In the above-mentioned formula, the implication of each code name and measure unit are: e is the end of Napier's logarithm;

F _iBe the inverse of the crooked half-wavelength of i circle tank shell, F _iIt is the inverse of the crooked half-wavelength of the 1st circle tank shell;

K _iBe the elasticity modulus of i circle wallboard, K _iElasticity modulus for the first lap wallboard; E is an elasticity modulus of materials; T is a tank shell thickness; R is the oil tank internal diameter;

Be the tank shell bending stiffness; V is a Poisson's ratio; ρ is a fluid density, and g is an acceleration due to gravity; w _iBe any point radial displacement on the i circle tank shell, w ₁Be that the 1st layer of tank shell reinforcing pad is with top any point radial displacement, w ₀Be that the 1st circle tank shell reinforcing pad is with lower part any point radial displacement; x _iBe the distance that any point encloses wallboard and i circle wallboard junction apart from i-1 on the i circle wallboard, x ₁Be that the 1st circle wallboard reinforcing pad is with the distance of top any point apart from reinforcing pad, x ₀Be that the 1st circle wallboard reinforcing pad is with the distance of lower part any point apart from base plate; Q _I-1Be the shearing of the-1i circle wallboard and i circle wallboard junction, Q _iIt is the shearing of i circle wallboard and i+1 circle wallboard junction; M _I-1Be the moment of flexure of i-1 circle wallboard and i circle wallboard junction, M _iIt is the moment of flexure of i circle wallboard and i+1 circle wallboard junction; l _iIt is the height of i circle wallboard; H _I-1Be the distance between i-1 circle wallboard and i circle wallboard junction and liquid level, H ₀It is the distance between the 1st circle wallboard and the 2nd circle wallboard junction and liquid level; N _XiIt is the suffered axial compression of i circle wallboard any point; N _X1It is the suffered axial compression of the 1st circle wallboard any point; C ₁₁, C ₂₁, C ₃₁, C ₄₁, C ₁₀, C ₂₀, C ₃₀, C ₄₀Be the boundary condition coefficient, need confirm according to the boundary condition at wallboard two ends;

Can access different oil tank wall radial displacement curves for different reinforcing pad cross-sectional areas, get a wherein minimum curve of curvature change, the cooresponding cross-sectional area of this curve is corresponding known setting height(from bottom) h _sOptimum cross-sectional area A _s

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