US20050268565A1

US20050268565A1 - Vibration control apparatus and method, and high-rise building

Info

Publication number: US20050268565A1
Application number: US11/100,967
Authority: US
Inventors: Hideo Takabatake
Original assignee: Kanazawa Institute of Technology (KIT)
Current assignee: Kanazawa Institute of Technology (KIT)
Priority date: 2004-06-07
Filing date: 2005-04-07
Publication date: 2005-12-08
Also published as: JP4070213B2; JP2005344452A

Abstract

A vibration control apparatus is installed in a high-rise building. The vibration control apparatus 10 comprises an added mass member 20 having a predetermined mass, a column 22 for placing the added mass member 20 separated from the high-rise building, a vibration damping member 24 in contact with the column 22 and installation member 26. The natural frequency of the vibration control apparatus 10 is adapted to be substantially equal to the natural frequency of the high-rise building. At the time of earthquake, the vibration control apparatus and the high-rise building produce resonance, and the vibration energy of the column 22 is absorbed in the vibration damping member 24.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a vibration control apparatus and method for a high-rise building including slender and tall structure such as a chimney, a power pole, or a power pylon.
2. Description of the Related Art
Damage or collapse of structures such as power poles and power pylons caused by an earthquake can lead to long term lost of infrastructure. Thus, a lot of technologies to deal with earthquakes have been developed in order to prevent damage or collapse of buildings. For example, vibration control technology refers to technologies that acceleration energy caused by vibration of the ground is converted into energy such as physical energy, heat or plastic deformation of material and then absorbed.
As one of the vibration control technology, added mass mechanism is well known (for example, Japanese Unexamined Patent Application Publication No. 2003-278827). The added mass mechanism is also called as a “TMD (Tuned Mass Damper)” or a dynamic vibration absorber. According to the mechanism, a resonance mass is installed on the top of the building, and the vibration of the whole building is reduced by the vibration of the resonance mass at the time of earthquake. The resonance mass is supported with rails, springs or laminating rubbers on the top of the building. In most cases, damping mechanism such as an oil damper is added to the resonance mass. The added mass mechanism is effective for controlling the remarkable vibration of the top of the building due to bending distortion when the shape of the building is a long rectangular.
However, it is not practical in terms of installation work or cost to install large-scale and complicated mechanism like the TMD in the building such as a power pole and a power pylon. It is also difficult to install such a large-scale mechanism in existing buildings. Other conventional vibration control technology absorbs energy of vibration as physical shock or sound energy. However, such technology is not preferable due to noise emission.

SUMMARY OF THE INVENTION

The present invention is directed to provide vibration control technology for high-rise buildings using simple structure.
One aspect of the invention is a vibration control apparatus. The apparatus comprises a column, wherein one end thereof is installed to a target building and other end thereof is a free end, said free end having a mass; and a damping member for damping the cantilever vibration of said column.
According to the aspect, installing the apparatus with a simple column and a damping member in the part of the high-rise building may reduce the vibration of the building. Further, the apparatus of the aspect occupies less installation space than conventional vibration control apparatus.
Another aspect of the invention is also a vibration control apparatus on the top of a high-rise building. The apparatus comprises an added mass member having a predetermined mass; a column for placing said added mass member separated from said high-rise building; and a vibration damping member in contact with said column; wherein natural frequency of said vibration control apparatus is adapted to be substantially equal to natural frequency of said high-rise building.
Herein “a high-rise building” refers to a slender and tall structure which can be approximated to one degree analytical model. The high-rise building includes, but not limited to, a chimney, a power pole, a utility pole, an illumination pole, an advertising tower, a crane, a signal light, a railroad power pole, a power pylon, a road sign pillar and so on.
According to the aspect, natural frequency of the vibration control apparatus is adapted to be equal to natural frequency of a target high-rise building to produce resonance. The vibration energy of the column with the added mass member is absorbed by the vibration damping member. Therefore, the vibration of the building can be reduced using simpler structure than added mass mechanism employed by conventional vibration control technology.
The natural frequency of said vibration control apparatus may be configured to be variable at the time of installation or after installation in accordance with vibration nature of said high-rise building. Herein “in accordance with vibration nature” means that natural frequency may be varied to match with the vibration nature of the high-rise building under the variety of conditions. The condition includes, but not limited to, length, cross-sectional area, or weight of the high-rise building, presence/absence of attachment like a power transformer, or the number of overhead wires between power poles. Thus, it is possible to make an adjustment to the natural frequency of the vibration control apparatus at worksite in accordance with the vibration nature of target high-rise building, and therefore installation work efficiency may be improved.
Some approach may be taken to make natural frequency of the apparatus variable; to make installation position of the added mass member adjustable, to make bending stiffness of the column variable, or to make mass of the added mass member variable. When the natural frequency of the vibration control apparatus needs not to be variable, the added mass member and the column may be molded in one piece.
It is also possible that the column has multiple point mass by forming the column with attachment mechanism for two or more added mass member. Thus, the apparatus may produce vibration reduction effect corresponding to plural vibration modes of the high-rise building.
Another aspect of the invention is a vibration control method for a high-rise building. The method comprises installing a longitudinal member having natural frequency substantially equal to that of said high-rise building, one end of said member being fixed to the high-rise building and other end of said member being free; and installing damping member for damping the vibration of said longitudinal member.
According to the aspect, it is possible to reduce the vibration of the building only by making simple installation work in the existing building.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general view of a vibration control apparatus according to one embodiment of the invention;
FIG. 2 shows the vibration control apparatus installed on the top of a high-rise building;
FIG. 3A shows a calculation model for use in vibration simulation;
FIG. 3B shows a calculation model for use in vibration simulation;
FIG. 4 shows a calculation model for use in vibration simulation;
FIG. 5A is a graph of simulation result of model M0 showing maximum displacement in height;
FIG. 5B is a graph of simulation result of model M0 showing shearing force;
FIG. 5C is a graph of simulation result of model M0 showing bending moment;
FIG. 6A is a graph of simulation result of model M1 showing maximum displacement in height;
FIG. 6B is a graph of simulation result of model M1 showing shearing force;
FIG. 6C is a graph of simulation result of model M1 showing bending moment;
FIG. 7A is a graph of simulation result of model M2 showing maximum displacement in height;
FIG. 7B is a graph of simulation result of model M2 showing shearing force;
FIG. 7C is a graph of simulation result of model M2 showing bending moment;
FIG. 8 shows a calculation model of a power pole having a vibration control apparatus with two point masses;
FIG. 9 shows one variation of a vibration damping member;
FIG. 10 shows other variation of a vibration damping member;
FIG. 11A shows still other variation of a vibration damping member;
FIG. 11B shows still other variation of a vibration damping member;
FIG. 12 shows still other variation of a vibration damping member;
FIG. 13A shows still other variation of a vibration damping member;
FIG. 13B shows still other variation of a vibration damping member;
FIG. 14A shows still other variation of a vibration damping member;
FIG. 14B shows still other variation of a vibration damping member;
FIG. 15 shows still other variation of a vibration damping member.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described based on the preferred embodiments, which do not intend to limit the scope of the present invention, but exemplify the invention. All of the features and the combinations thereof described in the embodiment are not necessarily essential to the invention.
The present invention provides technology to reduce the vibration of a high-rise building including slender and tall structure such as a chimney, a power pole, or a power pylon. A vibration control apparatus is installed in a newly established or existing building. Natural frequency of the apparatus is adapted to be substantially equal to that of the building. Then, resonance between the apparatus and the building occurs at the time of earthquake.
Conventionally, a vibration control apparatus using an added mass mechanism is known to produce resonance between a target building and the added mass mechanism. The conventional apparatus works as follows; at the top of the building, the added mass mechanism having the weight of few percent of that of the building is installed such that the added mass mechanism can move horizontally. The natural frequency of the added mass mechanism is tuned equal to that of the building to produce resonance between them. Some damper is added to the added mass mechanism to absorb the vibration energy.
Instead of the vibration control apparatus with the horizontally-moved added mass mechanism stated above, the present invention provides an apparatus having a cantilever-type column and an added mass mechanism being supported by the column.
FIG. 1 is a general view of a vibration control apparatus 10 according to one embodiment of the invention. The vibration control apparatus 10 comprises an added mass member 20, a column 22, a vibration damping member 24 and an installation member 26. In FIG. 1, the added mass member 20 is a globe, but the added mass member 20 may be shaped like a box. It is preferable in terms of vibration reduction that the added mass member 20 is shaped such that it can be approximated to a point mass. The added mass member 20 may be made of, for example, metal or resin materials such as rubber or plastic. The added mass member 20 may be a case having a hollow body. By pouring fluid such as water, oil, or sand into the hollow body, the added mass member 20 may take desired weight.
The column 22 places the added mass member 20 separated from the installation member 26. One end of the column 22 is fixed to the installation member 26 and other end of the column 22 is a free end. In the free end of the column 22, the added mass member 20 is attached. The column 22 has a square cross section in FIG. 1, but the column 22 may have any shape of cross-section. The natural frequency of the vibration control apparatus 10 is determined mainly by the column 22 and the added mass member 20. The natural frequency will be described below referring to some equations. The natural frequency of the vibration control apparatus 10 is adapted to be substantially equal to that of a target high-rise building in beforehand.
It is preferable that an installation position of the added mass member 20 to the column 22 is variable. For example, the added mass member 20 may be formed as having a through hole 28 passing the center of itself. The through hole 28 may loosely engage with the column 22. Some internal threads are tapped at regular intervals on the surface of the column 22. After passing the column 22 into the through hole 28, a bolt is screwed into a internal thread to place the added mass member 20 above the bolt.
Alternatively, some holes are bored at regular intervals on the surface of the column 22. On the inner wall of the through hole 28 of the added mass member 20, a projection (not shown) is provided which can be moved inside the wall. When pushing the added mass member 20 toward the column 22, the projection is engaged with one of the holes on the surface of the column 22. Thus, the added mass member 20 may be fixed to the column 22.
Alternatively, the column 22 comprises an upper part and a lower part and upper part is fixed to the added mass member 20. The upper part is configured to slide outward form the lower part. By changing the length of the slide part, the position of the added mass member 20 may be variable. The present invention is not limited to these structure stated above and employ any structure such that the added mass member 20 can be moved upward/downward along the column 22. In another embodiment, the added mass member 20 and the column 22 may be molded in one piece.
The vibration damping member 24 damps the vibration of the column 22. The vibration damping member 24 is installed contact with the column 22. For enabling the vibration damping member 24 to produce the damping effect whichever direction the column 22 vibrates, the vibration damping member 24 is preferably installed to surround the column 22. However, the vibration damping member 24 may be installed to contact with only one part of the column 22.
In FIG. 1, the column 22 passes a hole bored in a cylindrical vibration damping member 24. The size and material of the vibration damping member 24 may determines a damping factor of the vibration control apparatus 10. Various kinds of materials can be used as material of the vibration damping member 24. The material includes, but not limited to, steel, viscosity fluid such as butane macromolecule, viscosity such as silicon, acrylic and viscoelasticity such as high damping rubber.
The length [1] shown in FIG. 1, which is overlapping length between the vibration damping member 24 and the column 22, may be determined based on the natural frequency in consideration of first mode damping of the vibration control apparatus 10 such that the natural frequency of the vibration control apparatus 10 is substantially equal to the frequency corresponding to first or other selected mode of the target high-rise building. For example, the damping constant of the vibration damping member 24 may be set to 0.05-0.5.
The installation member 26 has two functions; one is to install the vibration control apparatus 10 on the high-rise building and the other is to convey the vibration of the high-rise building to the column 22. In FIG. 1, the installation member 26 is shown as a rectangular board. However, the shape of the installation member 26 is not limited. The installation member 26 and the column 22 may be fixed by any methods such as welding, a screw, or fitting. It is preferable that the installation member 26 and the column 22 are fixed without a gap for effective transmission of the vibration to the column 22 and the added mass member 20.
As shown in FIG. 2, the vibration control apparatus 10 is installed on the top of the high-rise building 30 so that the column 22 stands vertically. The vibration control apparatus 10 may be installed, for example, by fastening the board of the installation member 26 to the floor of the building 30 using screws or burying the installation member 26 under the floor using concrete. The column 22 may be installed directly to the high-rise building without the installation member 26. Thus, the installation member 26 is not essential for the vibration control apparatus 10. The installation member 26 may be used in consideration of the installation situation of the apparatus 10. For example, considering the easiness of the installation, it is preferable to use the installation member 26. When the vibration control apparatus 10 does not comprise installation member 26, the column 22 may be fixed to the building 30 by hammering the column 22 into a hole bored on the floor of the building or welding the column 22 to steel structure of the building.
Next, how the vibration control apparatus 10 works will be described. When the high-rise building 30 is vibrated by the earthquake, the column 22 installed on the top of the building starts vibrating. Because the natural frequency of the vibration control apparatus 10 is adapted to be substantially equal to a selected natural frequency of the high-rise building 30, the column 22 of the apparatus 10 occurs resonance and vibrates widely. The vibration damping member 24 installed in the fixed end of the column 22 distorts. Then, the vibration energy of the whole high-rise building 30 is consumed in the vibration damping member 24. Therefore, the vibration of the whole high-rise building 30 may be damped faster than the building without the apparatus 10. Thereby, displacement, bending moment and shearing force are lowered larger than the building without the apparatus 10, and therefore the possibility of the damage or collapse of the high-rise building may be decreased.
The natural frequency ω₁may be calculated by following equation 1. $\begin{matrix} ω_{1} = {(\frac{k}{L})}^{2} \sqrt{\frac{EI}{m}} & [EQUATION 1] \end{matrix}$
where “k” is a coefficient for natural frequency in cantilever. When the vibration control apparatus 10 has uniform bending stiffness, k=1.8751041. “L” is length from a fixed end of the column 22 to the center of gravity of the added mass member 20. “EI” is bending stiffness of the column 22. “E” is a Young's modulus of the column 22, and “I” is the second moment of area of the column 22. “m” is mass of the added mass member 20. When the damping constant of the vibration damping member 24 is h, natural frequency ω_1Dof the vibration control apparatus 10 in consideration of damping is expressed as follows.
ω_1D=ω₁ {square root}{square root over (1−h ² )} [EQUATION 2]
A user of the vibration control apparatus 10 in advance calculates natural frequency ω₀of the high-rise building where the vibration control apparatus 10 is installed. Then, natural frequency ω_1Dof the vibration control apparatus 10 is adapted to be substantially equal to the natural frequency ω₀of the high-rise building. From ω_1D=ω₀, following equation may be derived. $\begin{matrix} \begin{matrix} ω_{0}^{2} = ω_{1}^{2} (1 - h^{2}) \\ = {(\frac{k}{L})}^{4} \frac{EI}{m} (1 - h^{2}) \end{matrix} & [EQUATION 3] \end{matrix}$
Mass m of the added mass member 20, second moment of area I of the column 22 and length L of the column 22 may be determined so as to satisfy the Equation 3.
In general the natural frequency ω₀of the high-rise building used in Equation 3 is the first natural frequency. However, when the period of the first natural frequency of the high-rise building is very long, the second moment of area I of the column 22 become very small and it occurs buckling due to the self-weight of the apparatus. In such a case, the natural frequency w may be changed to the second natural frequency of the high-rise building. Thus, the merit of the apparatus proposed here is to be easily adapted to any natural frequency selected from among the natural frequencies of the target high-rise building.
To make the natural frequency of the apparatus 10 variable, it is easy and preferable to adopt the above-mentioned mechanism for moving the installation position L of the added mass member 20. However, instead of the mechanism or along with the mechanism, another type of frequency variable mechanism may be used.
First, mass m of the added mass member 20 may be changed. For example, when the added mass member 20 is formed with hollow body, it is possible to make mass of the added mass member 20 variable by changing the amount of fluid poured into the hollow body. Alternatively, when many added mass members 20 having different mass are prepared, it is possible to make mass of the added mass member 20 variable by selecting one from them appropriately.
Second, bending stiffness EI of the column 22 may be changed. For example, when many columns 22 made of different materials are prepared or many columns 22 having different diameter are prepared, it is possible to make bending stiffness of the column 22 variable by selecting one column from them appropriately. When the added mass member and the column are molded in one piece, many molded parts with different installation position to the column and different mass of the added mass member are prepared in advance. By selecting one molded part, the natural frequency of the vibration control apparatus 10 may be variable.
User may change the natural frequency of the vibration control apparatus 10 by changing the installation position L of the added mass member 20 to match with the natural frequency of the high-rise building where the vibration control apparatus 10 is installed. Therefore, manufacturer of the apparatus 10 need not to produce the wide variety of the apparatus 10 for being matched with various natural frequencies. Further, because of the easiness of changing the natural frequency, user can finely adjust the natural frequency of the apparatus 10 in accordance with the real situation of the installation. For example, assume the high-rise building is a power pole. Even if the types of power poles are same, the natural frequency of each power pole is different according to the presence of a transformer, the number of a suspended electric wire, or a diameter or height of the power pole itself. Therefore, the natural frequency of the apparatus 10 should be changed on the worksite by moving the installation position of the added mass member 20 upward/downward or by adjusting the amount of fluid poured into the hollow body of the added mass member 20.
TMD mentioned above needs some structural unit such as rails or pulleys for moving the resonance mass horizontally and therefore the total volume of facilities become large. In addition, it is difficult to install the resonance mass on the narrow top of the building such as a power pole or a power pylon because some extent of installation area is needed for moving the resonance mass horizontally. In other words, the building suitable for TMD is limited.
In contrast, the vibration control apparatus according to the embodiment is easy to be installed on the narrow top of the building because the installation area is small for at least the base square of the installation member since the free end of the cantilever column is vibrated relative to the fixed end. In addition, the apparatus has simple structure and its weight is relatively light. As discussed below, assume the high-rise building is a power pole, the vibration control apparatus can exert sufficient damping performance only with about a 500-gram added mass member. This is less than 1% of the weight of the power pole, which is a one-several hundredth order.
Next, the simulation results for damping effectiveness when the vibration control apparatus according to the embodiment is installed on the top of the high-rise building.
FIG. 3A and FIG. 3B show a calculation model 40 for use in vibration simulation of a power pole due to an earthquake. The model is a power pole 42 of standard size having 12-meter full length. A vibration control apparatus 50 is installed on the top of the power pole 42. The power pole 42 is made by pre-stressed concrete. The power pole 42 has a hollow body as shown in FIG. 3B, thickness of the wall being 0.04 meter. Section diameters of the power pole 42 increases uniformly from its top to base. A diameter of the top of the power pole 42 is 0.19 meter, and a diameter of a base part of the power pole is 0.35 meter. The length of upper part exposing on the ground is 10 meters, and two-meter lower part is buried under the ground. In the calculation model, this lower part is assumed to be fixed. In FIG. 3A, the calculation model is shown having a transformer 44 in one side of the power pole 42 at eight meters upward from ground. It should be noted that FIG. 3A is depicted with emphasis of horizontal direction. Material characteristic of the power pole 42 used in the simulation is listed in Table 1.

TABLE 1

CROSS SECTIONAL AREA BASE 3.55 × 10⁻²

(m²) TOP 1.89 × 10⁻²

CONCRETE STRENGTH (N/mm²) 65

YOUNG'S MODULUS (N/m²) 2.535 × 10¹⁰

MASS DENSITY (kg/m³) 2.11 × 10³

WEIGHT OF A TRANSFORMER (kg) 142.0

DAMPING RATIO 0.02
For simulation, one model without the vibration control apparatus (referred to as “non-control power pole”) and three models M0-M2 with the vibration control apparatus (referred to as “control power pole”) are prepared. Model M0 is the power pole with no transformer, model M1 has a transformer in one side of the power pole (such as a model shown in FIG. 3A), and model M2 has transformers in both sides of the power pole.
FIG. 4 is an enlarged view of the vibration control apparatus 50 of the calculation model 40. Height of the vibration control apparatus 50 is one meter. In this calculation model 40, only an added mass member 52 and a column 54 are considered. An installation member and the shape of a vibration damping member are not considered. The weight of the added mass member 52 is m=0.5 (kg). The distance from a fixed end of the column 54 to the center of gravity of the added mass member 52 is fixed to L=1 (m). Under this condition, the natural frequency of the vibration control apparatus 50 keeps constant by changing the second moment of area I of the column 54. The section of the column 54 is a square and its material is iron. Damping ratio 10% and 20% are considered as damping constant of the apparatus 50. Bending stiffness EI of the column 54 for calculation models M0, M1 and M2 are listed in following table 2.

TABLE 2

EI (N · m²)

CONTROL POWER POLE CONTROL POWER POLE

(10% DAMPING RATIO) (20% DAMPING RATIO)

MODEL M0 2.387 2.424

MODEL M1 1.483 1.506

MODEL M2 1.075 1.092
As input earthquake waves, an original wave (90.90 kine (cm/s)) of Kobe marine meteorological observatory NS wave of an inland earthquake was employed. The bending system ignoring shearing distortion was analyzed by the Bernoulli-Euler beam theory, and the bending system considering shearing distortion was analyzed by the Timoshenko beam theory. Under the condition stated above, simulation results on displacement, shearing force and bending moment for control power pole models M0-M2 will be described below.
Model M0 (with no Transformer)
FIGS. 5A, 5B and 5C are graphs of simulation result of model M0. FIG. 5A shows maximum displacement in height of the power pole. The Horizontal axis of the graph represents displacement (m) and the vertical axis of the graph represents height (m) of the power pole from the ground. As can be seen from the graph, maximum displacement of the top of the power pole is decreased 30% when damping ratio is 10%, and is decreased 50% when damping ratio is 20%. Hereby, the effect of vibration control caused by installation of the vibration control apparatus is remarkable.
FIG. 5B shows shearing force of the power pole. The horizontal axis of the graph represents shearing force (N) and the vertical axis of the graph represents height (m) of the power pole from the ground. The shearing force takes maximum at the base part of the power pole. In either case of damping ratio 10% or 20%, the shearing force is decrease 17% at the base part.
FIG. 5C shows bending moment of the power pole. The horizontal axis of the graph represents a moment value (N m) and the vertical axis of the graph represents height (m) of the power pole from the ground. Bending moment also takes maximum at the base part of the power pole. The bending moment is decreased 30% when damping ratio is 10%, and is decreased 40% when damping ratio is 20%.
The above-mentioned simulation results are shown in Table 3. Table 3 shows the maximum bending moment and the maximum shearing force for a non-control power pole, control power pole of 10% or 20% damping ratio. A value in a parenthesis within Table 3 represents the ratio of values relative to short-term allowable bending moment or short-term allowable shearing force. If this ratio is equal to or less than 1, the power pole will not damaged.

TABLE 3

KOBE MARINE METEOROLOGICAL OBSERVATORY NS WAVE, MODEL M0

CONTROL CONTROL SHORT-TERM

POWER POLE POWER POLE ALLOWABLE

NON-CONTROL (10% DAMPING (20% DAMPING BENDING MOMENT/

POWER POLE RATIO) RATIO) SHEARING FORCE

MAXIMUM 61511 (1.43) 43770 (1.02) 37067 (0.86) 42990

BENDING MOMENT

M_max(N · m)

MAXIMUM 10960 (0.23) 9050 (0.19) 8987 (0.19) 47732

SHEARING FORCE

Q_max(N)
As can be seen from Table 3, for non-control power pole, since the maximum bending moment exceeds short-term allowable bending moment, it is possible for the power pole to be damaged or collapsed. In contrast, for control power pole, it is less possible for the power pole to be damaged or collapsed with 10% damping ratio, and it is very little possible for the power pole to be damaged with 20% damping ratio.
Model M1 (with a Transformer in one Side)
FIGS. 6A, 6B and 6C are graphs of simulation result of model M1. The horizontal axis and the vertical axis of each graph represent same with FIGS. 5A, 5B and 5C, respectively. Comparing FIG. 5A with FIG. 6A, the power pole with a transformer has larger maximum displacement in height than the power pole without a transformer. The first one has more damping effect. For example, the maximum displacement is decreased 50% when damping ratio is 10%. Referring to FIG. 6B and FIG. 6C, shearing force and bending moment are decreased 50% when damping ratio is 10%. Thus, the power pole with a transformer has greater vibration reduction due to the installation of the vibration control apparatus. The above-mentioned simulation results are shown in Table 4.

TABLE 4

KOBE MARINE METEOROLOGICAL OBSERVATORY NS WAVE, MODEL M1

CONTROL CONTROL SHORT-TERM

POWER POLE POWER POLE ALLOWABLE

NON-CONTROL (10% DAMPING (20% DAMPING BENDING MOMENT/

POWER POLE RATIO) RATIO) SHEARING FORCE

MAXIMUM 98514 (2.29) 47182 (1.10) 40752 (0.95) 42990

BENDING MOMENT

M_max(N · m)

MAXIMUM 18144 (0.38) 9599 (0.20) 9462 (0.20) 47732

SHEARING FORCE

Q_max(N)
As can be seen from Table 4, it is possible for the control power pole to be damaged with 10% damping ratio, and it is very little possible for the control power pole to be damaged with 20% damping ratio.
Model M2 (with Transformers on Both Sides)
FIGS. 7A, 7B and 7C are graphs of simulation result of model M2. The horizontal axis and the vertical axis of each graph represent same with FIGS. 5A, 5B and 5C. Comparing FIG. 6A with FIG. 7A, the power pole with transformers on both sides has larger maximum displacement in height than the power pole with a transformer on one side. The first one has more damping effect. For example, the maximum displacement is decreased 62% when damping ratio is 10%. Referring to FIG. 7B and FIG. 7C, shearing force is decreased 50% and bending force is decreased 60% relative to each maximum value by installing the vibration control apparatus. Thus, the vibration control apparatus according to the embodiment has remarkable effect on the power pole with transformers on both sides. The above-mentioned simulation results are shown in Table 5.

TABLE 5

KOBE MARINE METEOROLOGICAL OBSERVATORY NS WAVE, MODEL M2

CONTROL CONTROL SHORT-TERM

POWER POLE POWER POLE ALLOWABLE

NON-CONTROL (10% DAMPING (20% DAMPING BENDING MOMENT/

POWER POLE RATIO) RATIO) SHEARING FORCE

MAXIMUM 120340 (2.80) 48782 (1.13) 43195 (1.005) 42990

BENDING MOMENT

M_max(N · m)

MAXIMUM 20476 (0.43) 9985 (0.21) 9688 (0.20) 47732

SHEARING FORCE

Q_max(N)
As can be seen from Table 5, it is possible for the control power pole to be damaged with 10% damping ratio, and it is very little possible for the control power pole to be damaged with 20% damping ratio. It will be understood that the more the damping ratio of the vibration control apparatus, the more maximum bending moment and maximum shearing force are decreased.

Similar simulation was carried out about El-Centro NS 1940 wave, which was ocean type earthquake, and Taft EW wave including a long period, in which the maximum velocity of these waves are assumed to be 50 kine (cm/s). In either case, both maximum bending moment and maximum shearing force are decreased lower than the short-term allowable value, preventing the building from being damaged due to the earthquake using the vibration control apparatus. Simulation results of model M0-M2 for maximum bending moment are shown in following Table 6. A value in a parenthesis within Table 6 represents the ratio for short-term allowable bending moment (42990 Nm) of a power pole.

TABLE 6


MAXIMUM BENDING MOMENT M_max(N · m)

	EL CENTRO NS WAVE	TAFT EW WAVE

MODEL M0	NON-CONTROL POWER POLE	62548 (1.45)	38258 (0.89)
	CONTROL POWER POLE	29219 (0.68)	31029 (0.72)
	(10% DAMPING RATIO)
MODEL M1	NON-CONTROL POWER POLE	113580 (2.64)	65283 (1.52)
	CONTROL POWER POLE	32945 (0.77)	33242 (0.78)
	(10% DAMPING RATIO)
MODEL M2	NON-CONTROL POWER POLE	116200 (2.70)	55385 (1.29)
	CONTROL POWER POLE	32812 (0.76)	35751 (0.83)
	(10% DAMPING RATIO)

As can be seen from Table 6, the power pole becomes safe with 10% damping ratio for El Centro NS wave and Taft EW wave.
Generally, a high-rise building such as a power pole and a power pylon is not situated by itself but in most cases electric wires are suspended between neighboring buildings. When adjacent two power poles vibrates reversely each other or when displacement of one power pole is bigger than displacement of another power pole, both power poles are pulled by electric wires therebetween. Therefore, when arguing the vibration of high-rise buildings, the effect of electric wires should be concerned. Though the inventor also carried out simulation about this effect, detailed information is omitted herein because they hardly affect to simulation results.
As discussed above, vibration control apparatus according to the invention can reduce the vibration of high-rise buildings with simple structure. In addition, natural frequency of the vibration control apparatus may be tuned at worksite using variable added mass member or column in accordance with length, cross-section area, weight, presence of a transformer or the number of an overhead wire of a target high-rise building.
As indicated in the simulation result mentioned above, the weight of the vibration control apparatus is small as such only 500-gram weight is attached to the end of one meter length column. Therefore, the vibration control apparatus according to the invention has less restriction for installation. For example, the apparatus can be installed on the top of a thin building such as a power pole. Because of simple structure, the vibration control apparatus may be produced at low cost. Furthermore, the apparatus may be installed in both newly-constructed building and existing building. Because the size of the apparatus is much smaller than the size of high-rise buildings, the apparatus may be installed on the building with little loss of landscape. In addition, maintenance of the apparatus is very simple because the apparatus has no driving parts.
Some variations will be described below.
Similar simulation can be carried out on another building such as truss structure power pylon or high-rise buildings by approximating them to one dimension model. Therefore, the vibration control apparatus according to the invention may be installed on these buildings.
The vibration control apparatus may be installed in any place of the building instead of its top as long as the vibration of the building is transmitted to the apparatus. For example, the apparatus may be installed inside the building. The apparatus also may be installed on a hangover project into a horizontal direction from a wall of the building. However, the vibration of the building takes maximum value at its top, so the vibration reduction effect of the apparatus is higher when the apparatus is installed on the top of the building.
It is possible that the natural frequency of the apparatus is adapted to other vibration mode of the high-rise building except first vibration mode. For example, FIG. 8 shows a calculation model 140 where a vibration control apparatus 150 is installed on the top of a power pole 142, where two added mass members are attached to a column. The vibration control apparatus 150 comprises a column 154 and added mass members 152, 156. The added mass member 152 is positioned where first mode natural frequency of the power pole 142 is equal to the natural frequency of the vibration control apparatus 150. Similarly, the added mass member 156 is positioned where second mode natural frequency of the power pole 142 is equal to the natural frequency of the vibration control apparatus 150. Analyzing technique is same with one described above.
Same simulation was carried out to the power pole 142 with the vibration control apparatus 150 having two point masses shown in FIG. 8 with the simulation for the calculation model shown in FIG. 3. The simulation result shows that the vibration control apparatus having two point masses (referred to as “two-mass system”) make horizontal displacement of the top of the power pole less than the vibration control apparatus having one point mass (referred to as “one-mass system”). However, as for bending moment and shearing force at the base part of the power pole, which has large relationship with quake-proofness of the column, difference between the one-mass system and the two-mass system is not remarkable. This is because the first vibration mode is dominant in vibration of the building having relatively low height such as the power pole. In contrast, for example, in the high-rise building whose height exceeds 100 meters, frequency of the first vibration mode is in the order of dozens of seconds. Therefore, the second vibration mode becomes dominant than the first vibration mode. In such a case, the effect of the vibration control apparatus becomes higher in the two-mass system.
The vibration control apparatus with two masses has a merit that the natural frequencies of the apparatus can be easily equal to the natural frequencies corresponding to two target modes including the first natural frequency even if the period of the first natural frequency of the high-rise building is very long.
Even if the number of point masses of the vibration control apparatus is two, it is not essential that natural frequencies of the vibration control apparatus is equal to the first or second vibration mode of the natural frequency of the high-rise building. The target of point mass is to occur resonance with dominant vibration mode of dynamic response of the high-rise building. For example, if the first vibration mode is not dominant in the high-rise building, two point mass of the vibration control apparatus may be adapted to be equal to the second and third vibration modes of the natural frequency of the building.
Generally speaking, it is sufficient to take consideration of the first and second vibration modes for a high-rise building with its height as several ten meters order. However, since the number of the point masses is not limited in the vibration control apparatus according to the invention, the number of the point masses may be increased to be adapted to three or more vibration mode dominant to the dynamic response of the high-rise building. Of course, point mass may be adapted to fourth or more vibration mode.
Detailed structure is not limited to implement a vibration control apparatus of two-mass system. Other structure may be employed. For example, when some holes are bored at regular intervals on the surface of a column and, on the inner wall of a through hole of an added mass member 20, a projection is provided which can be moved inside the wall, a vibration control apparatus of two-mass system is easily produced by attaching two addition mass member to the column.
A vibration damping member may take other shape except cylindrical. And a vibration damping member may be made of other material except rubber. Now such variations will be described below.
Variation 1
FIG. 9 shows a variation that a vibration damping member is formed from layer type viscosity. The vibration damping member comprises three viscousity layers 80 a, 80 b, 80 c, each of them is made of different material. When lower layer 80 c is made of softer material than upper layer 80 a, the damping performance is increased because the upper layer 80a vibrates greater than the lower layer 80 c at the time that the building is vibrated.
As shown in FIG. 10, the vibration damping member comprises two roll type viscousity layers 90 a, 90 b. In this case, using higher hardness material for outer layer 90 b than for the inner layer 90 a, the damping performance is improved because the outer layer 90 b limits the vibration of the inner layer 90 a. For example, the inner layer 90 a may be made of rubber and the outer layer 90 b may be made of metal.
Variation 2
For changing the damping performance along with longitudinal column 22, structure shown in FIG. 11A and FIG. 11B may be employed. FIG. 11A is a front view of a vibration damping member and FIG. 11B is an A-A sectional view of FIG. 11A. Hollow outer shell 100 is made of metal. Cross sectional area of the outer shell 100 is changed at half of its height. The damping performance may be improved in its upper place by pouring viscosity 102 into the outer shell 100. Viscosity 102 may be fluid such as oil. Alternatively, work efficiency is improved by pouring rapid condensation rubber into the outer shell 100.
Variation 3
FIG. 12 shows another variation of the vibration damping member in consideration of efficiency at worksite. Hollow globes 112 filled with viscosity are prepared. After installing a column 22 and an outer shell 110, multiple globes 112 are filled in the hollow of the outer shell 110. To restrict the globe 112 out of the outer shell 110, a cover 114 is putted over the outer shell 110. By adjusting the number of globes 112 filled in the outer shell 110, damping ratio of the vibration apparatus may be changed. Alternatively, it is possible to improve the damping performance by pouring sand or oil into the globe 112. According to the variation 3, work efficiency may be improved at installation site.
Variation 4
FIG. 13A is a front view of still other variation of the vibration damping member. FIG. 13B is A-A cross sectional view of FIG. 13B. The vibration damping member comprises a column 22 and boards 120 attached thereto. The board has plural holes 122 and made of metal or rubber. The boards 120 are deformed largely due to the holes 122 at the time of earthquake and therefore the vibration is damped.
As shown in FIG. 14A, viscosity member 124 may be fitted into the holes 122. Because the viscosity member 124 transforms as shown in FIG. 14B when the temperature changes, temperature dependency of damping performance of the board 120 may be reduced. It should be noted that volume of deformation of viscosity member 124 are emphasized in FIG. 14A and FIG. 14B.
Variation 5
Damping performance of a vibration damping member may be kept constant relative to the change of temperature. FIG. 15 shows such variation. Viscosity 136 is put inside an outer shell 130. Then a lid 138 is placed over the viscosity 136. A cover 132 on the outer shell 130 and the lid 138 are coupled by expansion members 134. The expansion members 134 are made of shape-memory alloy and expand in response to the temperature. Thus, temperature dependency of damping performance of viscosity 136 can be reduced because the volume that viscosity 136 can deform is changed.
Although the present invention has been described by way of exemplary embodiments, it should be understood for those skilled in the art that many changes and substitutions may be made without departing from the spirit and the scope of the present invention which is defined by the appended claims.

Claims

1. A vibration control apparatus, comprising:

a column, wherein one end thereof is installed to a target building and other end thereof is a free end, said free end having a mass; and

a damping member for damping the cantilever vibration of said column.

2. A vibration control apparatus for a high-rise building, comprising:

an added mass member having a predetermined mass;

a column for placing said added mass member separated from said high-rise building; and

a vibration damping member in contact with said column;

wherein natural frequency of said vibration control apparatus is adapted to be substantially equal to natural frequency of said high-rise building.

3. The vibration control apparatus according to claim 2, wherein natural frequency of said vibration control apparatus is configured to be variable at the time of installation or after installation in accordance with vibration nature of said high-rise building.

4. The vibration control apparatus according to claim 3, wherein natural frequency of said vibration control apparatus is configured to be variable by enabling installation position of said added mass member to move upward or downward on said column.

5. The vibration control apparatus according to claim 4, wherein installation position of said added mass member can be adjustable in step.

6. The vibration control apparatus according to claim 3, wherein natural frequency of said vibration control apparatus is configured to be variable by making bending stiffness of said column variable.

7. The vibration control apparatus according to claim 3, wherein natural frequency of said vibration control apparatus is configured to be variable by making mass of said added mass member variable.

8. The vibration control apparatus according to claim 2, wherein said added mass member and said column are molded in one piece.

9. The vibration control apparatus according to claim 2, wherein damping ratio of said vibration damping member is variable.

10. The vibration control apparatus according to claim 9, further comprising a member for absorbing the temperature change of the damping ratio of said vibration damping member.

11. The vibration control apparatus according to claim 2, wherein said column has plural point mass for exerting the vibration reduction effect corresponding to plural vibration mode of said high-rise building.

12. The vibration control apparatus according to claim 11, wherein said column is configured to be attached with two or more added mass member.

13. The vibration control apparatus according to claim 2, wherein said high-rise building is a power pole.

14. The vibration control apparatus according to claim 2, wherein mass of said added mass member is a one-several hundredth order of the weight of said high-rise building.

15. A high-rise building having a vibration control apparatus at any part of the building, said vibration control apparatus comprising:

an added mass member having predetermined mass;

a vibration damping member in contact with said column;

16. A vibration control method for existing high-rise building, comprising:

installing a longitudinal member having natural frequency substantially equal to that of said high-rise building, one end of said member being fixed to said high-rise building and other end of said member being free; and

installing damping member for damping the vibration of said longitudinal member.