JP2002089081A - Karman's vortex vibration suppressing device for tower- like structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration control device suppressing the vibration caused by the Karman's vortex generated around a tower-like structure by wind without restricting the external appearance design of the tower-like structure. SOLUTION: This vibration control device is provided with a rigidity changing means 5 capable of changing the natural frequency of the tower-like structure 1, a wind velocity detecting means 7 detecting the wind velocity blown to the tower-like structure 1, and an operation control means 9 operating the rigidity changing mechanism of the rigidity changing means 5 to change the natural frequency of the tower-like structure 1 when the wind velocity detected by the wind velocity detecting means 7 is the wind velocity generating the Karman's vortex having the generated frequency coinciding with the natural frequency of the tower-like structure 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping device for suppressing vibration of a tower-like structure caused by Karman vortices generated around the tower-like structure by wind.

[0002]

2. Description of the Related Art Generally, as shown in FIG.
When the pillars 2 are present in the wind flow 4, the pillars 2
Downstream, a Karman vortex 4a is generated. Since the Karman vortex 4a is alternately generated on both the left and right sides of the column 2 as shown in FIGS. 3A and 3B, the column 2 is periodically lifted by the pressure difference generated by the Karman vortex 4a. In response to this, it vibrates in a direction perpendicular to the direction of the flow of the wind (the direction of the dashed arrow in the figure), that is, to the left and right. This vibration occurs at the generation frequency f (Hz) of the Karman vortex 4a, and the generation frequency is represented by the following equation. f = St · V / D (1) Here, St is the number of Strahl, and is 0.
2. In the case of a prism, it is about 0.1. V (m / se
c) is a wind speed, D (m) is a representative dimension of the columnar object 2, and in the case of a cylinder, it is a diameter.

As can be seen from equation (1), since the generated frequency f changes in accordance with the wind speed V, when the wind speed V changes and the generated frequency f matches the natural frequency of the columnar object 2, the columnar shape is changed. The object 2 resonates and shakes violently.

Usually, in order to prevent this, the corner shape of the tower-like structure 1 is devised as shown in plan view in FIG. 7 (a). To prevent periodic generation of vortices, or to provide a wind hole 8 penetrating the structure 1 as shown in FIG. And so on.

[0005]

However, in the above-mentioned conventional method, since the projections and air holes must be provided on the outer surface of the structure, the appearance design of the structure is greatly restricted.

The present invention has been made in view of such circumstances, and has as its object to provide a tower-like structure that suppresses vibration caused by Karman vortices caused by wind without restricting the appearance design of the structure. An object of the present invention is to provide a vibration damping device for an object.

[0007]

Means for Solving the Problems In order to achieve the above object, an invention according to claim 1 is a vibration damper for suppressing vibration of a tower-like structure caused by a Karman vortex generated around the tower-like structure by wind. A device, a rigidity variable means capable of changing the natural frequency of the tower-like structure, a wind speed detection means for detecting a wind speed blown to the tower-like structure, and a wind speed detected by the wind speed detection means, Actuation control for changing the natural frequency of the tower-like structure by operating the variable-rigidity mechanism of the rigidity-variable means when the wind speed is such that a Karman vortex having a generation frequency corresponding to the natural frequency of the tower-like structure is generated. Means.

According to the above invention, the wind speed of the wind blown to the tower-like structure, detected by the wind speed detecting means, is a wind speed that generates a Karman vortex having a generation frequency corresponding to the natural frequency of the tower-like structure. In some cases, the variable stiffness mechanism is operated by the operation control means. Then, the rigidity changing means is operated by the operation to change the rigidity of the tower-like structure and change the natural frequency of the tower-like structure. Accordingly, it is possible to prevent the Karman vortex and the structure from resonating. In addition, since the stiffness varying means, the stiffness varying mechanism, and the operation control means do not need to be provided on the outer surface of the tower-like structure, the external design of the structure is not restricted.

According to a second aspect of the present invention, in the apparatus for suppressing Karman vortex vibration of a tower-like structure according to the first aspect, the rigidity varying means is a damping force variable damper incorporated in the tower-like structure. The control means operates the damping force variable mechanism of the damping force variable damper to change the natural frequency of the tower-like structure.

According to the above invention, the wind speed of the wind blown to the tower-like structure, detected by the wind speed detecting means, is a wind speed that generates a Karman vortex having a generation frequency corresponding to the natural frequency of the tower-like structure. In one case, the damping force variable mechanism of the damping force variable damper is operated by the operation control means to change the rigidity of the tower-like structure by the damping force variable damper, thereby changing the natural frequency of the tower-like structure. . Accordingly, it is possible to prevent the Karman vortex and the structure from resonating. Further, since the damping force variable damper is incorporated in the tower-like structure, it does not appear on the outer surface of the structure and does not limit the external design of the structure.

According to a third aspect of the present invention, in the Karman vortex vibration suppression device for a tower-like structure according to the second aspect, the variable damping force damper is an oil damper, and the variable damping force mechanism is an orifice diameter of the oil damper. Characterized in that it is an orifice diameter switching mechanism.

According to the above invention, the wind speed of the wind blown to the tower-like structure, detected by the wind speed detecting means, is a wind speed that generates a Karman vortex having a generation frequency corresponding to the natural frequency of the tower-like structure. In some cases, the orifice diameter switching mechanism of the oil damper is operated by the operation control means to change the orifice diameter of the oil damper. Then, since the damping force of the oil damper changes, the rigidity of the tower-like structure changes, and its natural frequency can be changed. Accordingly, it is possible to prevent the Karman vortex and the structure from resonating. In addition, since the orifice diameter of the oil damper is simply changed, the operation reliability is high and the oil damper can be installed at low cost.

According to a fourth aspect of the present invention, in the apparatus for suppressing Karman vortex vibration of the tower-like structure according to the second aspect, the variable damping force damper is a friction damper, and the variable damping force mechanism is a friction force of the friction damper. Is a frictional force switching mechanism that changes

According to the above invention, the wind speed of the wind blown to the tower-like structure, detected by the wind speed detecting means, is a wind speed that generates Karman vortices having a generation frequency corresponding to the natural frequency of the tower-like structure. In some cases, the friction control mechanism of the friction damper is operated by the operation control means. Then, since the frictional force of the friction damper changes, the rigidity of the tower-like structure changes, and its natural frequency can be changed. Accordingly, it is possible to prevent the Karman vortex from resonating with the structure. In addition, the simple operation of switching the frictional force of the friction damper makes the operation highly reliable and can be installed at low cost.

According to a fifth aspect of the present invention, there is provided the Karman vortex vibration suppressing device for a tower-like structure according to the first aspect, wherein the rigidity varying means is incorporated in the tower-like structure.
The operation control means operates a tension applying mechanism to the cable to change a natural frequency of the tower-like structure.

According to the above invention, the wind speed of the wind blown to the tower-like structure, detected by the wind speed detecting means, is a wind speed that generates a Karman vortex having a generation frequency corresponding to the natural frequency of the tower-like structure. In some cases, the tension control mechanism of the cable is operated by the operation control means. Then, tension is applied to the cable and the cable functions as a spring member, so that the rigidity of the tower-like structure changes and its natural frequency can be changed. Accordingly, it is possible to prevent the Karman vortex and the structure from resonating. In addition, because of the simple structure of applying tension, the operation is highly reliable and can be installed at low cost.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram showing an entire configuration of a Karman vortex vibration suppression device for a tower-like structure according to an embodiment of the present invention. FIG. 1A is a side view, and FIG. Is shown.

As shown in FIG. 1A, a tower-like structure 1 provided with a Karman vortex vibration suppression device according to this embodiment is provided.
Is a multi-layered structure 1 in which column and beam frames 3 are stacked and constructed in the height direction, and has a rectangular cross section. In the following,
As shown in FIG. 1 (b), the short-axis direction of the rectangular flat cross section is X
The direction and the long axis direction are defined as the Y direction.

Basically, the Karman vortex vibration suppressor is provided with a horizontal rigidity Kx of the tower-like structure 1 in the X and Y directions.
A stiffness changing means 5 capable of changing Ky (N / m), and wind speeds V in the X and Y directions of the wind blown to the tower-like structure 1
It comprises a wind speed detecting means 7 for detecting x and Vy, and an operation control means 9 for giving a command to a variable rigidity mechanism (not shown) for operating the variable rigidity means 5. Then, any one of the wind speeds Vx and Vy detected by the wind speed detecting means 7 generates a Karman vortex having a generated frequency corresponding to the natural frequency of the tower-like structure 1 in the Y direction or the X direction (hereinafter, referred to as “the wind speed”). When it reaches the vicinity of the resonance wind speeds Vrx and Vry.), The stiffness varying mechanism of the stiffness varying means 5 is operated to move the tower-like structure 1 in the Y direction or X direction.
By changing the natural frequencies fy and fx in the direction, the natural frequencies fy and fx are prevented from being coincident with the generation frequency of the Karman vortex, and resonance occurring between them is prevented.

The rigidity varying means 5 is provided on the column structure 3 for each level of the tower-like structure 1, and can change the rigidity in the X direction and the Y direction for each level. Then, in the present embodiment, the rigidity in the X direction of each level,
Alternatively, the rigidity in the Y direction is simultaneously increased or decreased by the rigidity variable mechanism, and the horizontal rigidity Kx, Ky in the X direction or the Y direction of the entire tower-like structure 1 is reduced to low rigidity Kxl, Kyl and high rigidity Kxh, The value is changed in two values with Kyh. In normal times, low rigidity Kxl, Ky
l, and the resonance wind speeds Vrx, Vry are the natural frequencies fy of the tower-like structure at the time of the low rigidity Kxl, Kyl.
It is a wind speed that generates Karman vortices having the same generation frequency as l and fxl, and is expressed by the following equation. Vrx = D · fxl / St (2) Vry = D · fxl / St (3)

The wind speed detecting means 7 is a wind direction anemometer provided for each layer, and measures the wind speed Vx and Vy of the wind blown to each layer in the X and Y directions in real time. The measurement data is transmitted to the operation control means 9.

When one of the wind speeds Vx and Vy as the measured data approaches the corresponding resonance wind speeds Vrx and Vry, the operation control means 9 changes the rigidity from the low rigidity Kxl and Kyl as the rigidity in the normal state to the high rigidity. Kxh, Kyh
A stiffness change command is transmitted to the stiffness changing mechanism of the stiffness changing means 5 so as to change to. When the wind speeds Vx and Vy in the corresponding directions depart from the resonance wind speeds Vrx and Vry, a rigidity return command is transmitted so as to return to the low rigidity Kxl and Kyl.

The operation control means 9 is a computer 9 comprising a storage section, a calculation section, an input terminal section, a display section, and the like, and is arranged in the tower-like structure 1. And it is connected to the anemometer 9 and the rigidity variable mechanism of the rigidity variable means 5 via a line, and transmits and receives the command and the measurement data.

The storage unit stores the resonance wind velocities Vrx and Vry calculated in advance based on the outer shape of the tower-like structure 1 and its natural frequency, and ± α% of the resonance wind velocities Vrx and Vry. The set rigidity change target range (see FIG. 2) is stored. The calculation unit compares the wind speeds Vx, Vy, which are the measurement data, with the rigidity change target range, and outputs the rigidity change command when it is determined that the wind speeds Vx, Vy are within the range. If it is determined that the value is out of the range, the rigidity return command is output.

In this determination, various control modes are registered in the storage unit. For example, when one or more wind speeds among the wind speeds of each layer enter the rigidity change target range, a rigidity change command is output. A control mode, a control mode for outputting a rigidity change command when the average wind speed of all layers falls within the range, and the like are registered. The selection of the control mode can be made by using a keyboard as an input terminal while watching the display.

Next, the operation of the Karman vortex vibration suppression device will be described with reference to FIGS. The operation is the same whether the wind direction is the X direction or the Y direction.
Hereinafter, only the case where the wind in the X direction is blown will be described.

In normal times, the rigidity varying means 5 for each layer is set to low rigidity by the rigidity varying mechanism, and the rigidity Ky in the Y direction of the entire tower-like structure 1 is low rigidity Kyl. The natural frequency of the tower-like structure 1 at this time is f
yl, and the resonance wind speed Vry at which the Karman vortex is generated at the fyl generation frequency is the wind speed given by the above equation (2).

The wind speed Vx in the X direction of the wind blown to the tower-like structure 1 is constantly measured by the wind direction anemometer 7 and transmitted to the computer 9 one by one. The measurement data Vx is compared in real time by an arithmetic unit in the computer 9 to determine whether it falls within the rigidity change target range, that is, Vrx ± α%. If it is determined that the wind speed Vx is within the range, the computer 9 transmits a stiffness change command to the stiffness changing mechanism,
Is switched to high rigidity, and the tower-like structure 1 has high rigidity K
yh (> Kyl), and the natural frequency changes from fyl to fyh (> fyl). Therefore, the natural frequency greatly deviates from the Karman vortex generation frequency fyl generated at the resonance wind speed Vry, so that the vibration of the tower-like structure 1 in the Y direction resonates with the generation of the Karman vortex, and the tower-like structure 1
Is prevented from vibrating significantly. Then, the wind speed Vx further increases, or conversely, the wind speed Vx decreases.
When x deviates from the rigidity change target range Vrx ± α%,
A rigidity return command is transmitted from the computer to the rigidity variable mechanism, and the tower-like structure 1 is switched to the normal low rigidity Kyl.

In this embodiment, the tower-like structure 1
In order to change the overall stiffness Kx, Ky, all the stiffness changing means 5 provided for each layer are switched simultaneously in the same direction. However, if the overall stiffness of the tower-like structure 1 can be changed, this is done. The present invention is not limited to this, and some of the rigidity varying means 5 may be selectively switched to change the rigidity of the entire tower-like structure 1.

In the present embodiment, the resonance wind velocities Vrx and Vry of the tower-like structure 1 are calculated in advance and stored in the storage unit in the computer 9.
The calculation unit may calculate each of x and Vy.

Here, a specific example of the rigidity varying means will be described. FIG. 3 to FIG. 5 are side views showing a state in which the rigidity varying means is incorporated in the columnar frame 3 of the tower-like structure, and show an oil damper, a friction damper, and a cable in order. In FIG. 3, the oil damper in FIG. 3 (a) is shown in a cutaway manner, and the views in the direction of arrows B and C in FIG. 3 (b) and FIG. This is shown in FIG.

The oil damper 11 shown in FIG. 3 is interposed between braces 3c and 3d provided on the column and beam frames 3 of each level, and attenuates horizontal relative displacement generated between layers of the tower-like structure. This is a vibration suppression device that suppresses horizontal vibration of the lever. The oil damper 11 includes a cylinder 13 and a piston 15 that defines the inside of the cylinder 13 as two hydraulic chambers 13a and 13b. The cylinder 13 is provided on one brace 3c, and the rod 15a of the piston 15 is provided on the other. Brace 3
d. The piston 15 has a pair of orifices 21 formed symmetrically with respect to the piston axis.
The two hydraulic chambers 13a and 13b communicate with each other. When the interlayer is displaced, the displacement is transmitted to the oil damper 11, and the piston 15 slides in the cylinder 13 in the axial direction. At this time, the oil in the hydraulic chambers 13a and 13b passes through the orifice 21. A flow resistance is generated, which acts as a damping force to dampen horizontal vibration.

However, since the oil damper 11 according to the present invention is also used as a rigidity varying means, the damper 11 is a damping force variable damper capable of changing the damping force.
That is, the damper 11 is capable of switching the damping force caused by the flow resistance between large and small by the orifice diameter switching mechanism for changing the orifice diameter, so that the horizontal rigidity of each layer can be changed by changing the damping force. It has become.

This orifice diameter switching mechanism is realized by dividing the piston 15 in the axial direction and comprising two members 17, 19, which are relatively rotatable about the axis. Are engaged so that they cannot be displaced relative to each other. One of these is the driving mechanism 25.
As a result, a rotating piston 17 driven and rotated about the axis is formed, and the other is a non-rotating piston 19 that cannot rotate. The non-rotating piston 19 has only the pair of orifices 21 described above as shown in FIG. 3C, while the rotating piston 17 has the pair of orifices 21 as shown in FIG. In addition to the orifice 21, an orifice 23 having a smaller diameter than the orifice 21 is formed on the same circumference at 90 degrees therefrom. And this rotating piston 1
When the orifice 7 is driven and rotated about the axis, and the orifice 21 or the small-diameter orifice 23 is matched with the orifice 21 of the non-rotating piston 19 to form an oil flow path, the orifice diameter is switched. Has become.

The friction damper 26 shown in FIG. 4 is interposed between the upper and lower beams 3a and 3b of the column-and-frame structure 3 of each story, and detects the relative displacement in the horizontal direction generated between the layers of the tower-like structure. This is a vibration damping device that is attenuated by the frictional force caused by the vibration.
The friction damper 26 includes a friction plate 29a fixed to the upper beam 3a via a column-shaped bracket 27a, and a lower beam 3b.
The sliding plate 29b is also fixed via a column-shaped bracket 27b, and the friction plate 29a and the sliding plate 29b are slidably abutted in the horizontal direction. Then, when the interlayer is displaced, the friction plate 29a and the slide plate 29b slide, and the vibration is attenuated by the frictional force generated at that time.

However, since the friction damper 26 according to the present invention is also used as a rigidity varying means, the damper 26 is a damping force variable damper capable of changing the frictional force as a damping force. That is, the damper 26 is provided with a gripping mechanism 31 as a frictional force switching mechanism that sandwiches the friction plate 29a and the sliding plate 29b together in a state where the friction plate 29a and the sliding plate 29b are overlapped, and the narrow pressure at this time can be changed to a large or small. Have been. And
By changing the narrow pressure to a large or small value, the contact force between the friction plate 29a and the sliding plate 29b can be changed to change the friction force during sliding to a large or small value. The horizontal rigidity can be changed.

The steel cable 33 shown in FIG. 5 is interposed between the upper and lower beams 3a and 3b of the column / column frame 3 of each level.
This is a stiffness varying means that functions as a spring member when a tension is applied to itself and imparts horizontal rigidity to the column-beam frame 3.
One end 33b of the cable 33 is fixed to the lower beam 3b of the beam-column frame 3, while the other end is wound around a winch 35 fixed to the upper beam 3a as a tension applying mechanism. The winch 35 applies tension to the cable 33.

Since the cable 33 acts as a spring member when tension is applied, the horizontal rigidity of the beam-to-column frame 3 increases when tension is applied. On the other hand, when no tension is applied, the cable 33 does not function as a spring member, so that the horizontal rigidity of the beam-column frame 3 does not change. Accordingly, by changing the tension of the cable 33 at the winch 35, the horizontal rigidity of the column structure 3 can be changed.

In the present embodiment, an oil damper, a friction damper, and a cable incorporated in a beam-column structure are shown as preferred examples of the means for varying the rigidity of the tower-like structure. What you can do is not limited to this.

[0040]

As described above, claims 1 and 2
According to the invention described in (1), since the Karman vortex and the structure can be prevented from resonating without restricting the external design of the tower-like structure, the tower-like structure having excellent durability, habitability, and aesthetic appearance You can build things.

According to the third to fifth aspects of the present invention, the apparatus can be installed at a low cost, has high operation reliability, does not require a load on maintenance, and can reduce the total cost of the tower structure.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an entire configuration of a Karman vortex vibration suppression device for a tower-like structure as an embodiment according to the present invention, wherein (a) is a side view, and (b) is a plan view.

FIG. 2 is a graph for explaining a rigidity change target range set around a resonance wind speed in which a rigidity varying unit according to the present invention operates, wherein a horizontal axis represents a wind speed, and a vertical axis represents a horizontal amplitude of a structure. is there.

FIG. 3 is a diagram showing a state in which an oil damper as a rigidity varying means is incorporated in a column-frame structure of a tower-like structure;
(A) shows a side view thereof, and (b) and (c) show a view taken along line B and a view taken along line C in (a), respectively.

FIG. 4 is a side view showing a state in which a friction damper as a stiffness varying unit is incorporated in a column structure of a tower-like structure.

FIG. 5 is a side view showing a state in which a cable as a rigidity varying means is incorporated in a column-beam frame of a tower-like structure.

FIG. 6 is a plan view showing Karman vortices generated downstream of a pillar in a flow of wind.

7A and 7B are plan views showing a conventional method for preventing the resonance between the Karman vortex and the tower-like structure, wherein FIG. 7A shows a method of providing protrusions at corners of the tower-like structure, and FIG. The method of providing an air hole in a tower-like structure will be described below.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tower-like structure, multilayer structure 3 Column-beam structure 5 Stiffness variable means 7 Wind speed detecting means 9 Operation control means, computer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masaru Emura 2-15-2 Konan, Minato-ku, Tokyo Obayashi Corporation Tokyo head office F-term (reference) 2D059 AA03 AA27 GG06 GG13 2E001 DG01 DG02 FA01 FA02 FA71 GA01 GA10 GA12 GA77 HB01 LA18 3J048 AA03 AB01 AC01 BE03 BE11 CB22 EA38

Claims (5)

[Claims] 1. A vibration damping device for suppressing vibration of a tower-like structure caused by a Karman vortex generated around the tower-like structure due to wind, wherein a rigidity capable of changing a natural frequency of the tower-like structure is provided. A variable means, a wind speed detecting means for detecting a wind speed blown to the tower-like structure, and a wind speed detected by the wind speed detecting means to generate a Karman vortex having a generation frequency corresponding to a natural frequency of the tower-like structure. Operation control means for operating the rigidity varying mechanism of the rigidity varying means to change the natural frequency of the tower-like structure when the wind speed is at a wind speed, and Kalman vortex vibration of the tower-like structure. Suppression device. 2. The stiffness varying means is a damping force variable damper incorporated in a tower-like structure, and the operation control means activates a damping force varying mechanism of the damping force-variable damper to change the damping force of the tower-like structure. The Karman vortex vibration suppression device for a tower-like structure according to claim 1, wherein the natural frequency is changed. 3. The tower-like structure according to claim 2, wherein the damping force variable damper is an oil damper, and the damping force variable mechanism is an orifice diameter switching mechanism for changing an orifice diameter of the oil damper. Karman vortex vibration suppression device. 4. The tower-like structure according to claim 2, wherein the variable damping force damper is a friction damper, and the variable damping force mechanism is a frictional force switching mechanism for changing a frictional force of the friction damper. Karman vortex vibration suppression device. 5. The tower according to claim 1, wherein the stiffness varying means is a cable incorporated in the tower-like structure, and the operation control means changes a natural frequency of the tower-like structure by operating a tension applying mechanism to the cable. The apparatus for suppressing Karman vortex vibration of a tower-like structure according to claim 1, wherein: