JP7093203B2 - Tower-shaped structure and its structural optimization method - Google Patents

Description

The present invention relates to a tower-shaped structure such as a facility for wind power generation and a method for optimizing the structure thereof.

In recent years, renewable energy has attracted attention as part of its energy policy, and wind power generation has been positioned as an important means of securing power sources.

In particular, the introduction of offshore wind power generation is being promoted mainly in the harbor area because the wind conditions are better than those on land and the environmental burden such as noise is small because it is far from the residential area.

Such a wind power generation facility is a tower equipped with a tower main body whose lower end is supported by a support structure and a wind power generation device including a wind turbine (nacelle rotor) supported by the upper end of the tower main body. It is a mold structure.

As the support structure, a landing type is generally used up to a water depth of about 60 m, and a floating type is used when the water depth is 60 m or deeper.

Further, as the landing type support structure, there are a caisson type, a monopile type, a pile jacket type, etc., and in recent years, a hybrid type that combines a reinforced concrete bottom slab and a jacket type has been adopted (for example, non-type). Patent Document 1).

In addition, some offshore wind power generation facilities of this type have a wind turbine center height of 60 m or more from the sea surface, and are expected to grow in size in the future.

On the other hand, the structural performance of such offshore wind power generation facilities is based on the Building Standards Law, and if the center height of the wind turbine exceeds 60 m from the sea surface, the structural performance evaluation is similar to that of buildings such as high-rise buildings. Is required.

That is, in Japan, where earthquakes occur frequently, in the case of structures with a height of more than 60 m, is the structural performance secured after evaluating the dynamic characteristics by time history response analysis using level 1 earthquake motion and level 2 earthquake motion? Is required to be examined.

In the time history response analysis, after modeling the structure with mass points, beams, springs, and damping, the ground surface is given a ground motion acceleration that changes with time, and changes in force and displacement at each position of the structure are measured. This is a structural calculation method that verifies the seismic safety of structures by simulating them from moment to moment with a computer.

On the other hand, the wind power generation facility is composed of a hollow tower-shaped tower body made of steel pipe from the top to the joint with the support structure, and the tower body is from about 2 m at the top to 5 m at the joint. It becomes a conical column whose outer diameter gradually increases to a certain extent, and can be regarded as a top heavy cantilever structure installed on the support structure.

Therefore, in the tower-shaped structure such as a wind power generation facility, the intrinsic mode swing width in the time history response analysis is shown in FIG. 5 due to such structural features.

That is, in a high-rise building such as a high-rise building, the swing width of the primary mode is generally predominant, and the swing width of the secondary and subsequent high-order modes is relatively small and the influence is small, whereas the tower type structure has a small influence. Since the swing width of the secondary and tertiary high-order modes is about the same as that of the primary mode, it is expected that the response acceleration tends to increase.

Unlike general high-rise buildings, such tower-shaped structures have a large response acceleration in the middle of the tower body, for example, near an altitude of 40 m or 60 m, which is a cause of overturning as a whole. In some cases, the layer shearing force becomes large, and the allowable value of the eccentricity is increased in order to ensure safety against overturning, that is, the support structure must be enlarged.

Further, when the size of the support structure is determined from the viewpoint of economic efficiency, there is a problem that the margin becomes small with respect to the allowable value of the eccentricity based on the size of the support structure.

Therefore, in such a tower-shaped structure, in view of the above-mentioned problems, it is sought to reduce the inherent mode swing width by applying a vibration damping device, as in a general high-rise building.

Foundation work vol. Pages 12, 11 to 15, December 15, 2013

However, regarding the application of the above-mentioned vibration control device, it may not be possible to secure a space for installing the vibration control device. Especially in the onshore / offshore wind power generation facility, there are restrictions on the location conditions, etc. It was sometimes difficult to secure.

In addition, this type of vibration damping device has a problem that the manufacturing cost is high and the construction cost is increased.

Therefore, in view of such conventional problems, the present invention has been made to provide a tower-shaped structure capable of reducing the response acceleration based on the natural mode swing width with a simple structure and a method for optimizing the structure thereof. It is a thing.

The feature of the invention according to claim 1 for solving the above-mentioned conventional problems is a hollow tower type tower main body whose lower end is supported by a landing type support structure, and the tower main body. In a tower structure with a heavy object supported at the top
The tower main body covers a predetermined range in the height direction corresponding to the height at which the maximum swing width of the higher-order vibration mode obtained by the eigenvalue analysis using the time history response analysis model of the tower structure is generated. It is provided with a rigidity strengthening portion, and the rigidity strengthening portion is to have a wall thickness portion having a certain thickness increased on the entire inner circumference .

A feature of the invention according to claim 2 is that, in addition to the configuration of claim 1, the heavy object is a device used for wind power generation.

The feature of the invention according to claim 3 is a hollow tower type tower main body whose lower end is supported by a landing type support structure, and a heavy object supported by the upper end of the tower main body. This is a structural optimization method for a tower-shaped structure in which the tower-shaped structure is the optimum structure for ensuring safety against overturning, and the tower body is provided with a tower for reducing response acceleration . A rigidity strengthening part is provided on the entire inner circumference of the main body with a thickened part having a certain thickness, and the position where the rigidity strengthening part is provided is a unique value using a time history response analysis model of the tower-shaped structure. The purpose is to set a predetermined range in the height direction corresponding to the height at which the maximum swing width of the higher-order vibration mode obtained by the analysis occurs.

By providing the structure according to claim 1, the tower-shaped structure according to the present invention can reduce the response acceleration based on the natural mode swing width with a simple structure, and can reduce the size of the support structure or reduce the size of the support structure. It is possible to increase the safety against a fall.

Further, in the present invention, by providing the configuration according to claim 2, it is possible to preferably reduce the response acceleration based on the natural mode swing width in the wind power generation facility.

Further, the method for optimizing the structure of the tower-type structure according to the present invention is provided with the configuration according to claim 3, so that the tower-type structure such as an offshore wind power generation facility can be safely overturned by a simple method. The optimum structure can be used to ensure the above. In addition, when optimizing the structure, the influence on the natural frequency can be suppressed.

It is a front view which shows an example of the tower type structure which concerns on this invention. It is the same side view. It is a partially enlarged sectional view which shows the rigidity strengthening part in FIG. It is a schematic diagram which shows the analysis model example of the tower type structure used for time history response analysis. It is a graph which shows the peculiar mode swing width with respect to the elevation of the conventional tower type structure. It is a graph comparing the peculiar mode swing width with respect to the altitude of the tower type structure which does not have a rigidity strengthening part and the tower type structure which concerns on this invention, and (a) is a tower type structure which does not have a rigidity reinforcement part. In the case, (b) shows the case of the tower-shaped structure according to the present invention. It is the graph which compared the response acceleration of the tower type structure which does not have a rigidity strengthening part and the tower type structure which concerns on this invention.

Next, an embodiment of the tower-shaped structure according to the present invention will be described with reference to the examples shown in FIGS. 1 to 7. In this embodiment, an offshore wind power generation facility will be described as an example of a tower-type structure. In the figure, reference numeral 1 is a water bottom portion, and reference numeral 2 is a tower-type structure such as an offshore wind power generation facility.

The tower-shaped structure 2 is supported by a support structure 3 installed on the bottom mound 6, a hollow tower-shaped tower main body 4 whose lower end is supported by the support structure 3, and an upper end of the tower main body 4. It is equipped with a device (hereinafter referred to as a wind power generation device) 5 used for wind power generation, which is a heavy object, and a tower main body 4 is erected on the support structure 3, and the support structure 3 and the tower main body 4 are provided. It forms a tower.

The support structure 3 is a landing type, and includes a caisson type, a monopile type, a pile jacket type, a hybrid type in which a reinforced concrete bottom slab and a jacket type are fused, and the like. In this embodiment, the hybrid type will be described as an example, but the method of the support structure 3 is not limited.

The support structure 3 includes a reinforced concrete bottom slab 7 placed on the water bottom mound 6 and a turret-shaped jacket 8 supported on the bottom slab 7, and the tower main body 4 is provided at the upper end of the jacket 8. The lower ends are joined.

The wind power generation device 5 includes a nacelle 5a supported at the upper end of the tower main body 4, a hub 5b rotatably supported by the nacelle 5a, and a blade 5c supported by the hub 5b, and receives wind power. The rotor including the 5b and the blade 5c rotates to generate electricity.

The tower main body 4 is configured by connecting a plurality of tower steel pipes 9, 9 ... In the vertical direction, and a hollow tower shape is formed from the top to the joint with the support structure 3, and the top (for example, for example). It has a conical columnar shape in which the outer diameter gradually increases from the outer diameter (outer diameter of about 2 m) to the joint (for example, the outer diameter of about 5 m).

Further, the tower main body 4 is located in the height direction at a position corresponding to the height at which the maximum swing width of the higher-order vibration mode obtained by the eigenvalue analysis using the time history response analysis model of the tower structure 2 is generated. The rigidity strengthening unit 10 is provided over a predetermined range (range of about 10 m), the response acceleration that causes the fall is reduced, and the structure is optimized to ensure the safety against the fall. There is.

As shown in FIG. 3, the rigidity strengthening portion 10 has a wall thickness portion 11 having an inner diameter increased by about 10% while keeping the outer diameter of the steel pipe 9 for a tower, and the rigidity of the portion is enhanced. It is designed to reduce the swing width of the belly in the higher vibration mode.

It is necessary to obtain the height at which the maximum swing width of the high-order vibration mode is generated in order to make the tower-shaped structure 2 the optimum structure for ensuring the safety against tipping. First, the tower-shaped structure 2 is formed according to the following steps. The natural mode swing width at each natural frequency with respect to the altitude of the structure 2 is obtained.

(Step 1)
As shown in FIG. 4, the tower-type structure 2 including the support structure 3, the tower main body 4, and the wind power generation device 5 and the ground are modeled by mass points, beams, springs, and damping, and the “response” of each node of the analysis model is modeled. The "acceleration time history" is extracted, and the inertial force time history _Wi (t) obtained by multiplying the "mass" of each node is obtained. In the modeling of the tower-shaped structure 2 including the support structure 3, the detailed structure of the support structure 3 may be subdivided and modeled, and the support structure 3 may be used in consideration of the structural characteristics. It may be modeled by replacing it with an equivalent "beam". Further, the ground refers to the ground that supports the tower-shaped structure 2 including the water bottom portion 1 and the water bottom mound 6.

(Step 2)
The layer shear force time history Qi (t) is obtained from the inertial force time history _Wi (t) of each node based on the following equation.
(Number 1)
Q ₁ (T) = W ₁ (t) · Q ₂ (t)
= W ₁ (t) + W ₂ (t) · Q ₃ (t)
= W ₁ (t) + W ₂ (t) + W ₃ (t) + · + Wi (t) · Q _{i + 1} (t)

(Step 3)
The maximum _{value Qimax is} extracted from the layer shear time history Qi (t) at each node.

(Step 4)
The overturning moment _MRI is calculated from the distance between each node.
(Number 2)
MRI = Q _imax x h _{i- (i + 1 )}

尚、転倒モーメントは、節点ｎ、即ち、支持構造物３の下端中央部に作用する転倒の原因となる力として求められる。 (Step 5)
The total vertical load V _total acting on the support structure 3 is obtained, the eccentricity e is calculated by the following equation, and it is confirmed that the eccentricity e is within the allowable value.

The overturning moment is obtained as a nodal point n, that is, a force acting on the central portion of the lower end of the support structure 3 to cause an overturn.

Since this tower-shaped structure 2 can be regarded as a top-heavy cantilever structure installed on the support structure 3, a time history response analysis model of the tower-shaped structure 2 is based on this structural feature. Perform the eigenvalue analysis used.

FIG. 5 is an example of the result of the eigenvalue analysis using the time history response analysis model of the tower type structure 2 having no rigidity strengthening portion 10.

Since the tower type structure 2 has the same swing width in the secondary and tertiary high-order modes as in the primary mode, the intermediate portion of the tower main body 4 in each high-order mode, in the present embodiment, is secondary. The response acceleration increases near an altitude of 40 m in the mode and around 60 m in the tertiary mode.

Further, as shown in FIG. 5B, in the 4th and 5th order modes, the natural frequency obtained by the eigenvalue analysis is about 10 Hz or higher, and the influence of the corresponding frequency included in the input seismic motion is affected. Often few.

Therefore, we pay attention to the antinode of the higher-order mode swing width of the second or higher order, and since the displacement of the structural member is generally inversely proportional to the rigidity of the member, the antinode of the higher-order mode swing width having the largest swing width than FIG. A position (in this embodiment, near an altitude of 60 m, which is the ventral position of the tertiary mode swing width having the largest swing width) is derived, and the abdominal position is over a predetermined range (a range of about 10 m) in the height direction. A rigidity strengthening portion 10 is provided.

In the tower-shaped structure 2 configured in this way, the rigidity of the portion of the tower-shaped structure 2 having a large response acceleration is strengthened by providing the rigidity strengthening portion 10, and the displacement can be suppressed. As shown in FIG. 7, the response acceleration of the entire tower structure is reduced, in particular, the response acceleration at the position where the rigidity strengthening portion 10 is provided is reduced, and as shown in FIG. 6, the swing width of the predetermined higher vibration mode is reduced. Is reduced.

On the other hand, in such a tower-shaped structure 2, if the natural frequency changes significantly, the dynamic response characteristics may be adversely affected. Therefore, when the natural frequencies obtained from the eigenvalue analysis using the time history response analysis model of the tower type structure 2 were compared, as shown in the table below, the natural frequencies were large depending on the presence or absence of the rigidity strengthening portion 10. There was no difference.

From the above, in this tower-shaped structure 2, the overturning moment is reduced, high safety against overturning can be ensured, and the size of the support structure 3 can be reduced accordingly.

In the above-mentioned embodiment, the example in which the rigidity strengthening portion 10 is provided at the maximum swing width position in the tertiary mode has been described, but the maximum of other higher-order modes such as the secondary mode, the quaternary mode, and the fifth-order mode. The rigidity strengthening portion 10 may be provided at a position corresponding to the height at which the swing width is generated.

Further, in the above-described embodiment, the offshore wind power generation facility has been described as an example, but the tower type structure 2 is not limited to this, and can be applied to onshore wind power generation facilities and other tower type structures. ..

1 Water bottom 2 Tower type structure 3 Support structure 4 Tower body 5 Wind power generation equipment 6 Water bottom mound 7 Bottom plate 8 Jacket 9 Steel pipe for tower 10 Rigidity strengthening part 11 Thick part

Claims (3)

In a tower-type structure having a hollow tower-type tower body whose lower end is supported by a landing-type support structure and a heavy object supported by the upper end of the tower body.
The tower main body covers a predetermined range in the height direction corresponding to the height at which the maximum swing width of the higher-order vibration mode obtained by the eigenvalue analysis using the time history response analysis model of the tower structure is generated. A tower-shaped structure including a rigidity-enhanced portion, wherein the rigidity-enhanced portion has a wall-thickened portion having a certain thickness increased on the entire inner circumference . The tower-shaped structure according to claim 1, wherein the heavy object is a device used for wind power generation. A tower-type structure having a hollow tower-type tower body whose lower end is supported by a landing-type support structure and a heavy object supported by the upper end of the tower body is safe against tipping over. It is a structural optimization method for tower-shaped structures that has the optimum structure to ensure the properties.
The tower main body is provided with a rigidity strengthening portion provided with a wall thickness portion having a certain thickness increased on the entire inner circumference of the tower main body for reducing response acceleration .
The position where the rigidity strengthening portion is provided is set to a predetermined range in the height direction corresponding to the height at which the maximum swing width of the higher-order vibration mode obtained by the eigenvalue analysis using the time history response analysis model of the tower structure is generated. A method for optimizing the structure of a tower-shaped structure, which is characterized by doing so.

Images