A strength verification calculation method for steel tube concrete combined tower

Abstract

The present invention discloses a strength verification calculation method for a steel tube concrete combined tower, comprising the following steps: S1, according to the cross-sectional shape of the steel tube concrete combined tower, respectively calculating the cross-sectional properties of the steel part and the concrete part of the tower; S2, according to the parallel section assumption, calculating the cross-sectional strength according to the static equilibrium principle, and according to different load conditions, respectively verifying and calculating the bending strength, compressive strength, shear strength and torsional strength. The strength verification calculation method for the steel tube concrete combined tower provided by the present invention can significantly improve the calculation efficiency, save a lot of calculation time, and is easy to operate and has reliable calculation results.

Description

Technical Field

[0001] The invention relates to the technical field of wind turbine towers, and in particular to a strength verification calculation method for a steel tube concrete combined tower. Background Art

[0002] With the development trend of large-scale wind turbines, higher requirements are placed on the structural bearing capacity of the tower. In order to develop and utilize wind resources in low wind speed and high shear areas, the hub height of wind turbines needs to be increased. High towers have become the current trend of tower development; steel tube concrete combined towers can achieve cost reduction and efficiency improvement.

[0003] Strength verification is crucial for the dimensional design of tower structures. It is a question of balancing economy and safety. There is currently no relevant calculation method for strength verification of steel tube concrete composite towers. The existing finite element calculation can calculate the strength of geometric structures well, but the modeling calculation for the model is time-consuming. Summary of the invention

[0004] In order to solve the problems raised in the above background technology, the purpose of the present invention is to provide a strength verification calculation method for a steel tube concrete combined tower.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A strength verification calculation method for a steel tube concrete combined tower comprises the following steps:

[0007] S1, according to the cross-sectional shape of the steel tube concrete composite tower, the cross-sectional properties of the steel part and the concrete part of the tower are calculated respectively;

[0008] S2, based on the parallel section assumption, the section strength is calculated according to the principle of static equilibrium, and the bending strength, compressive strength, shear strength and torsional strength are checked and calculated according to different load conditions.

[0009] Furthermore, in step S1, the steel part of the tower includes n steel pipes and n tower pieces, the n steel pipes are evenly distributed in a circular range, the tower pieces are arc-shaped, and two adjacent steel pipes are connected by a tower piece;

[0010] The concrete part of the tower includes n concrete columns, which are cast in n steel pipes.

[0011] Furthermore, in step S1, the specific steps of calculating the cross-sectional properties of the steel part of the tower are as follows:

[0012] In the tower section, take the tower center O as the pole, arbitrarily select the x-axis as the polar axis, establish polar coordinates, use R to represent the tower segment radius, r to represent the steel tube radius, δR Indicates the wall thickness of the tower tube, δ r represents the wall thickness of the steel pipe, α represents the central angle of a tower segment arc, β represents the angle between the area where a steel pipe is located and the center of the tower, and k represents the rotation angle of the center of the first steel pipe relative to the x-axis;

[0013] Can get:

[0014]

[0015] According to the cosine formula:

[0016]

[0017] The formulas for the moment of inertia and static moment of the sector arc section are as follows:

[0018]

[0019]

[0020] Among them, I x,s represents the moment of inertia of the steel part relative to the x-axis, S x,s It represents the static moment of the steel part with respect to the x-axis;

[0021] When n ≥ 3, we have:

[0022]

[0023] And because r>>δ r , R>>δ R ,but:

[0024]

[0025] Among them, I r，s It represents the moment of inertia of the steel part relative to the center O of the circle.

[0026] Furthermore, in step S1, the concrete section properties are calculated using the moment of inertia and static moment formulas of the circular section:

[0027]

[0028]

[0029] S x，c =0

[0030] Among them, I x，c represents the moment of inertia of the concrete part with respect to the x-axis, S x，c represents the static moment of the concrete part relative to the x-axis, I r，c It represents the polar moment of inertia of the steel part with respect to the center O of the circle.

[0031] Furthermore, in step S2, according to the parallel section assumption, it is considered that each plane section perpendicular to the tower axis is still a plane after the tower is deformed by stretching, compression, torsion or bending, and is perpendicular to the deformed axis;

[0032] The static balance principle is that the internal force and external force of the tower section are equal, and the internal moment and external moment are equal.

[0033] Furthermore, when checking the bending strength, the bending moment is M, then according to the static equilibrium:

[0034] ∫ A σ.ydA=M

[0035] From the geometric equations and physical equations, we get:

[0036]

[0037] Where ρ is the radius of curvature of the neutral axis, A c and A s Represent the concrete area and steel area respectively, E c and E s They represent the elastic modulus of concrete and steel respectively, and are:

[0038] E c .I x，c +E s .I x，s =M.ρ

[0039]

[0040]

[0041] y max =max(R, Rsin(k+2πri / n)+r)

[0042] y max represents the maximum value from the center O, σ s，max Indicates the maximum value of normal stress of steel, σ c，max represents the maximum value of the positive stress of concrete, then:

[0043] Steel strength check: σ s，max <f y

[0044] Concrete strength check: σ c，max <f c

[0045] Where [σ] represents the allowable stress, and its value varies under different working conditions. yIndicates the design value of steel yield strength, f c Indicates the design value of concrete compressive strength.

[0046] Furthermore, when checking the compressive strength:

[0047] The pressure is N, then according to the static equilibrium: ∫ A σdA=N

[0048] E c εA c +E s εA s =N

[0049] Where ε is the positive strain;

[0050]

[0051]

[0052] Steel strength check: σ s，max <f y

[0053] Concrete strength check: σ c，max <f c

[0054] Furthermore, when checking the shear strength:

[0055] When the cross section is sheared, there is only shear stress, which is a two-dimensional stress state expressed as:

[0056] σ 1 =τ,σ 3 = -τ, σ 2 =0

[0057] According to the fourth strength theory, the equivalent stress is:

[0058] Equivalent stress, or Mises stress expression:

[0059]

[0060] The shear force is F, then according to static equilibrium: ∫ A τdA=F

[0061] G c γA c +G s γA s =F

[0062]

[0063]

[0064] Where γ represents the shear strain, G c represents the shear modulus of concrete, G s represents the shear modulus of steel, τ s，max represents the maximum shear stress of steel, τ c，max It represents the maximum shear stress of concrete;

[0065] Steel strength check:

[0066] Concrete strength check: τ c，max <f s

[0067] where σ r，s Indicates the maximum equivalent stress of steel, f s Indicates the design value of concrete shear strength.

[0068] Furthermore, when checking the torsional strength:

[0069] When the cross section is subjected to torsion, there is only shear stress, which is a two-dimensional stress state expressed as:

[0070] σ 1 =τ,σ 3 = -τ, σ 2 =0

[0071] According to the fourth strength theory, the equivalent stress is:

[0072] The torque is T, then according to the static equilibrium: ∫ A ρτdA=T

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] in represents the relative torsion angle per unit length, represents the torsion angle between the two sections, and x represents the distance between the two sections;

[0079] Steel strength check:

[0080] Concrete strength check: τ c，max <f s .

[0081] Compared with the prior art, the present invention has the following beneficial effects:

[0082] The strength verification calculation method of the steel tube concrete combined tower provided by the present invention can significantly improve the calculation efficiency, save a lot of calculation time, and is easy to operate and has reliable calculation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1 It is a cross-sectional schematic diagram of the steel tube concrete composite tower.

[0084] Figure 2 Calculation process diagram DETAILED DESCRIPTION

[0085] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following further describes how the present invention is implemented in conjunction with the accompanying drawings and specific implementation methods.

[0086] The present invention provides a strength verification calculation method for a steel tube concrete combined tower, comprising the following steps:

[0087] First, in step S1, the cross-sectional properties of the steel part and the concrete part of the tower are calculated respectively according to the cross-sectional shape of the steel tube concrete combined tower.

[0088] In this embodiment, the steel part of the tower includes n steel pipes and n tower segments. The n steel pipes are evenly distributed in a circular range. The tower segments are arc-shaped. Two adjacent steel pipes are connected by a tower segment. The concrete part of the tower includes n concrete columns, which are cast in the n steel pipes.

[0089] The specific steps to calculate the cross-sectional properties of the steel part of the tower are as follows:

[0090] Reference Figure 1 As shown in the figure, in the tower section, the tower center O is taken as the pole, the x-axis is arbitrarily selected as the polar axis, and the polar coordinates are established. R represents the radius of the tower segment, r represents the radius of the steel tube, and δ R Indicates the wall thickness of the tower tube, δ r represents the wall thickness of the steel pipe, α represents the central angle of a tower segment arc, β represents the angle between the area where a steel pipe is located and the center of the tower, and k represents the rotation angle of the center of the first steel pipe relative to the x-axis;

[0091] Can get:

[0092]

[0093] According to the cosine formula:

[0094]

[0095] The formulas for the moment of inertia and static moment of the sector arc section are as follows:

[0096]

[0097]

[0098] Among them, I x，s represents the moment of inertia of the steel part relative to the x-axis, S x，s It represents the static moment of the steel part with respect to the x-axis;

[0099] When n ≥ 3, we have:

[0100]

[0101] And because r>>δ r , R>>δ R ,but:

[0102]

[0103] Among them, I r，s It represents the moment of inertia of the steel part relative to the center O of the circle.

[0104] Similarly, the concrete section properties are calculated from the moment of inertia and static moment formulas of the circular section:

[0105]

[0106]

[0107] S x，c =0

[0108] Among them, I x，c represents the moment of inertia of the concrete part with respect to the x-axis, S x，c represents the static moment of the concrete part relative to the x-axis, I r，c It represents the polar moment of inertia of the steel part with respect to the center O of the circle.

[0109] Next, in step S2, based on the parallel section assumption and the principle of static equilibrium, the section strength is calculated, and according to different load conditions, the bending strength, compressive strength, shear strength and torsional strength are checked and calculated respectively.

[0110] According to the parallel section hypothesis, it is believed that the plane sections perpendicular to the tower axis remain planes after the tower is deformed by tension, compression, torsion or bending, and are perpendicular to the deformed axis; the principle of static equilibrium is that the internal force of the tower section is equal to the external force, and the internal moment is equal to the external moment.

[0111] In this embodiment, when checking the bending strength, the bending moment is M, then according to the static equilibrium:

[0112] ∫ A σ.ydA=M

[0113] From the geometric equations and physical equations, we get:

[0114]

[0115] Where ρ is the radius of curvature of the neutral axis, A c and A s Represent the concrete area and steel area respectively, E c and E s They represent the elastic modulus of concrete and steel respectively, and are:

[0116] E c .I x，c +E s .I x，s =M.ρ

[0117]

[0118]

[0119] y max =max(R, Rsin(k+2πri / n)+r)

[0120] y max represents the maximum value from the center O, σ s，max Indicates the maximum value of normal stress of steel, σ c，max represents the maximum value of the positive stress of concrete, then:

[0121] Steel strength check: σ s，ma x<f y

[0122] Concrete strength check: σ c，max <f c

[0123] Where [σ] represents the allowable stress, and its value varies under different working conditions. y Indicates the design value of steel yield strength, f c Indicates the design value of concrete compressive strength.

[0124] When checking the compressive strength:

[0125] The pressure is N, then according to the static equilibrium: ∫ A σdA=N

[0126] E c εAc +E s εA s =N

[0127] Here, ε is the positive strain.

[0128]

[0129]

[0130] Steel strength check: σ s，max <f y

[0131] Concrete strength check: σ c，max <f c .

[0132] When checking the shear strength:

[0133] When the cross section is sheared, there is only shear stress, which is a two-dimensional stress state expressed as:

[0134] σ 1 =τ,σ 3 = -τ, σ 2 =0

[0135] According to the fourth strength theory, the equivalent stress is:

[0136] Equivalent stress, or Mises stress expression:

[0137]

[0138] The shear force is F, then according to static equilibrium: ∫ A τdA=F

[0139] G c γA c +G s γA s =F

[0140]

[0141]

[0142] Where γ represents the shear strain, G c represents the shear modulus of concrete, G s represents the shear modulus of steel, τ s，max represents the maximum shear stress of steel, τ c，max It represents the maximum shear stress of concrete.

[0143] Steel strength check:

[0144] Concrete strength check: τ c，max <f s

[0145] where σ r，s Indicates the maximum equivalent stress of steel, f s Indicates the design value of concrete shear strength.

[0146] When checking the torsional strength:

[0147] When the cross section is subjected to torsion, there is only shear stress, which is a two-dimensional stress state expressed as:

[0148] σ 1 =τ,σ 3 = -τ, σ 2 =0

[0149] According to the fourth strength theory, the equivalent stress is:

[0150] The torque is T, then according to the static equilibrium: ∫ A ρτdA=T

[0151]

[0152]

[0153]

[0154]

[0155]

[0156] in represents the relative torsion angle per unit length, represents the torsion angle between the two sections, and x represents the distance between the two sections;

[0157] Steel strength check:

[0158] Concrete strength check: τ c，max <f s .

[0159] It is understandable that the load conditions are not limited to the above four cases. For the case of multiple load superposition, the maximum stress of the cross section can be determined according to the stress state analysis, so as to calculate the cross section strength.

[0160] In summary, the strength verification calculation method of the steel tube concrete combined tower provided by the present invention is based on the parallel section assumption of material mechanics and the section strength calculation formula under different load conditions is derived from the principle of static equilibrium. Only according to the formula, the section strength can be quickly evaluated, which has the characteristics of high calculation efficiency. In addition, the method provided by the present invention is easy to operate and can be written as a program, which greatly improves the calculation efficiency and can quickly adapt to the calculation of various sections.

[0161] In a specific embodiment, the material parameters of the tower are as follows:

[0162] 1) Steel

[0163] Elastic modulus: E s =210GPa; Poisson's ratio: μ s =0.3

[0164] 2) Concrete

[0165] Elastic modulus: E s =35GPa; Poisson's ratio: μ s =0.2

[0166] The cross-sectional geometric parameters of the tower are as follows:

[0167] R=3.0m;r=0.5m;δ R =δ r =0.03m

[0168] The load data is as follows:

[0169] M = 3 × 10 8 Nm; T = 3 × 10 8 Nm; N = 3 × 10 7 N; F = 3 × 10 7 N

[0170] Different load types are applied to the cross section, namely bending, compression, shear and torsion. The maximum equivalent stress of the cross section is calculated according to the above formula. The calculation results are shown in Table 1:

[0171] Table 1: Stress calculation results

[0172]

[0173] It can be seen from the table that the maximum equivalent stress theoretical value obtained by the method of the present invention is close to the maximum stress obtained by finite element calculation, which can be used to evaluate the cross-sectional strength and help optimize the cross-sectional size design, proving that the method provided by the present invention has good reliability.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A strength verification calculation method for a steel tube concrete combined tower, characterized in that: The steps include: S1, according to the cross-sectional shape of the steel tube concrete composite tower, the cross-sectional properties of the steel part and the concrete part of the tower are calculated respectively; S2, based on the parallel section assumption, the section strength is calculated according to the principle of static equilibrium, and the bending strength, compressive strength, shear strength and torsional strength are checked and calculated according to different load conditions; In step S1, the steel part of the tower includes n steel pipes and n tower pieces, the n steel pipes are evenly distributed in a circular range, the tower pieces are arc-shaped, and two adjacent steel pipes are connected by a tower piece; The concrete part of the tower consists of n concrete columns, which are cast in n steel pipes; In step S1, the specific steps of calculating the cross-sectional properties of the steel part of the tower are as follows: In the tower section, take the tower center O as the pole, arbitrarily select the x-axis as the polar axis, establish polar coordinates, use R to represent the tower segment radius, r to represent the steel tube radius, δ R Indicates the wall thickness of the tower tube, δ r represents the wall thickness of the steel pipe, α represents the central angle of a tower segment arc, β represents the angle between the area where a steel pipe is located and the center of the tower, and k represents the rotation angle of the center of the first steel pipe relative to the x-axis; You can get: According to the cosine formula: The formulas for the moment of inertia and static moment of the sector arc section are as follows: Among them, I x,s represents the moment of inertia of the steel part relative to the x-axis, S x,s It represents the static moment of the steel part with respect to the x-axis; When n ≥ 3, we have: And because r>>δ r , R>>δ R ,but: Among them, I r,s It represents the moment of inertia of the steel part relative to the center O; The concrete section properties are calculated using the moment of inertia and static moment formulas for circular sections: Among them, I x,c represents the moment of inertia of the concrete part with respect to the x-axis, S x,c represents the static moment of the concrete part relative to the x-axis, I r,c It represents the polar moment of inertia of the steel part with respect to the center O of the circle.

2. The strength verification calculation method of the steel tube concrete combined tower according to claim 1 is characterized in that: In step S2, according to the parallel section assumption, it is considered that each plane section perpendicular to the tower axis is still a plane after the tower is deformed by stretching, compression, torsion or bending, and is perpendicular to the deformed axis; The static balance principle is that the internal force and external force of the tower section are equal, and the internal moment and external moment are equal.

3. The strength verification calculation method of the steel tube concrete combined tower according to claim 2 is characterized in that: When checking the bending strength, the bending moment is M, then according to the static equilibrium: ∫ A σ.ydA=M From the geometric equations and physical equations, we get: Where ρ is the radius of curvature of the neutral axis, Ac and As are the concrete area and steel area, respectively, and E c and E s They represent the elastic modulus of concrete and steel respectively, and are: E c ·I x，c +E s .I x，s =M·ρ y max =max(R, Rsin(k+2πri / n)+r) y max represents the maximum value from the center O, σ s,max Indicates the maximum value of normal stress of steel, σ c,max represents the maximum value of the positive stress of concrete, then: Steel strength check: σ s，max <f y Concrete strength check: σ c，max <f c Among them, f y Indicates the design value of steel yield strength, f c Indicates the design value of concrete compressive strength.

4. The strength verification calculation method of the steel tube concrete combined tower according to claim 3 is characterized in that: When checking the compressive strength: The pressure is N, then according to the static equilibrium: ∫ A σdA=N AND c εA c +E s εA s =N Where ε is the positive strain; Steel strength check: σ s，max <f y Concrete strength check: σ c，max <f c .

5. The strength verification calculation method of the steel tube concrete combined tower according to claim 4 is characterized in that: When checking the shear strength: When the cross section is sheared, there is only shear stress, which is a two-dimensional stress state. The principal stresses are: σ1=τ,σ3=-τ,σ2=0 According to the fourth strength theory, the equivalent stress is: Equivalent stress, or Mises stress expression: The shear force is F, then according to static equilibrium: ∫ A τdA=F G c cA c +G s cA s =F Where γ represents the shear strain, G c represents the shear modulus of concrete, G s represents the shear modulus of steel, τ s,max represents the maximum shear stress of steel, τ c,max It represents the maximum shear stress of concrete; Steel strength check: Concrete strength check: τ c，max <f s where σ r,s Indicates the maximum equivalent stress of steel, f s Indicates the design value of concrete shear strength.

6. The strength verification calculation method of the steel tube concrete combined tower according to claim 5 is characterized in that: When checking the torsional strength: When the cross section is subjected to torsion, there is only shear stress, which is a biaxial stress state. The principal stresses are: σ1=τ,σ3=-τ,σ2=0 According to the fourth strength theory, the equivalent stress is: The torque is T, then according to the static equilibrium: ∫ A ρτdA=T in / dx represents the relative torsion angle per unit length, represents the torsion angle between the two sections, and x represents the distance between the two sections; Steel strength check: Concrete strength check: τ c，max <f s .

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