JPH0337058B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pendulum-type dynamic vibration absorber for suppressing horizontal vibrations caused by wind or the like in a tower-like structure. More specifically, tower-like structures, such as the main tower of a long bridge that becomes independent during construction, generate Karman vibrations due to relatively low wind speeds, which is harmful to the tower construction work and to the strength of the tower structure. Therefore, the present invention relates to a device for suppressing such vibrations.

[Conventional technology]

In order to suppress the above-mentioned vibrations, the conventional method was to extend a cable from the tower and attach a damper to the end of the cable. This method includes, for example,
(1) Sliding block method that adds damping properties to the vibration system using Coulomb friction between the block and slide; (2) Hydraulic damping that uses a hydraulic damper to add damping properties to the vibration system using the vortex resistance of oil. There are methods etc. However, in the case of (1), these methods lack quantitative reliability of the damping effect and have problems with block operability, and in the case of (2), although the problems of (1) are solved, However, even though construction is underway, the installation of cables poses a major problem in that it poses a considerable problem in securing the sea area and the location for installing the attenuator. Therefore, there is a need for a vibration damping method that does not require ropes. Dynamic vibration absorbers are examples of methods that do not require cables.

Patent application filed in 1984 as a vibration damping device using a dynamic vibration absorber.
There is a pendulum type described in the specification of No. 210553. In this method, if the structure has a long period, the length of the arm of the pendulum becomes so large that it may not be possible to attach it to the structure.

[Problem that the invention seeks to solve]

As is clear from the above explanation, conventional vibration damping devices have the following problems.

(a) Because the cable is stretched from the tower, it depends on the installation location.

(b) The damping force is unstable because it is damped by Coulomb friction.

(c) In conventional pendulum type dynamic vibration absorbers, the length of the arm increases as the natural frequency decreases.

(d) It is not possible to easily respond to changes in the weight of the structure to be damped.

(e) The cost will be high.

[Means for solving problems]

The spring-equipped pendulum type dynamic vibration absorber of the present invention includes a pendulum with a weight attached to an arm suspended from a fulcrum, and a damper that damps the pendulum vibration of the pendulum. This is a pendulum type dynamic vibration absorber that dampens pendulum vibration using a damper.A fulcrum is provided on a frame that is supported by a structure and movable within a substantially horizontal plane, and the frame is moved relative to the structure within this plane. A spring member is provided to vibrate, and the mass of the frame and the spring constant of the spring member are determined so that the frame vibrates following the vibration of the pendulum.

[Effect]

When vibration occurs in a structure to which the spring-equipped pendulum type dynamic vibration absorber of the present invention is installed, the pendulum is excited and starts pendulum vibration, as in the case of a conventional pendulum type dynamic vibration absorber. The kinetic energy is converted into thermal energy by the damper, the vibration energy of the structure is consumed, and the vibration of the structure is damped as much as possible. However, in the spring-equipped pendulum type dynamic vibration absorber of the present invention, the fulcrum is not fixed to the structure as in the past, but the fulcrum vibrates following the pendulum vibration of the pendulum. The period is longer than the period of a pendulum (the period of a conventional pendulum type dynamic vibration absorber) having an arm of the same length whose fulcrum is fixed to a structure.

〔Example〕

FIGS. 1a and 1b are schematic diagrams showing one embodiment of the present invention, in which a is a front view and b is a sectional view thereof.
In the figure, 1 and 1a are attached to the structure to be damped and support this dynamic vibration absorber;
a, 2b, 2c and 2d to 2i are frames 3, 3
rollers 4, 4a support the frame 3, 3a and the base 1,
Spring interposed between 1a, 7, 7a, 7
b and 7c are bearings fixed on the frames 3 and 3a, and 6 and 6a are bearings 7, 7b and 7, respectively.
pins provided between a and 7c, 8 and 8a are arms slidably fitted to the pins 6 and 6a, 9 and 9a are weights fixed to arms 8 and 8a by screws 10 and 10a, and 11 is 2 Pin 1 between book arms 8 and 8a
The viscoelastic dampers 13, 13a supported by the arms 8, 8a are the bearings 7, 7b, 7a, 7c and the arms 8, 8a.

Next, its operation will be explained. Now, in the spring-equipped pendulum type dynamic vibration absorber configured as described above, the damper 11 is removed, and the arms 8, 8a and the bearings 7, 7a are removed.
If the vibration direction of the structure to be damped and the direction of the base of the device are fixed so that they match, and the amount of the weight is adjusted, resonance can be achieved.

Therefore, if you release the above-mentioned fixation and attach the viscoelastic damper 11 to make it resonate again as described above, the damper 11 will be deformed into a parallelogram shape, and the kinetic energy will be converted into heat. It is converted into energy and scattered, and the structure to be damped is damped as much as possible.

The structure to be damped is, for example, the main tower of a long bridge, and if the main tower is equipped with the above-mentioned spring-loaded pendulum type dynamic vibration absorber to prevent forced vibration due to the Karman vortex force, its mechanical model diagram is as follows. The result will be as shown in Figure 2. In the figure, m ₁ is the mass of the structure to be damped, m ₂ is the mass of the bogie parts, X ₁ and X ₂ are the displacements caused by the vibration, and the motion when a periodic external force F = F ₀ sinpt is applied to m _1. It is known that the solution to the equation is expressed by equation [1].

(X ₁ /X _st ) ² [4μ ² γ ² + (γ ² − δ ² ) ² ] / {4μ ² γ ²・(γ ² −1 + βγ ² ) ² + [βδ ² γ ² − (γ ² −1 )(γ ² −δ ² )] ² }…[
1] However, X _st = F ₀ /k ₁ is the static deflection of the main vibration system due to force F ₀ ω ₂ = √ _{2 2} is the natural angular frequency of the dynamic vibration reducer β = m ₂ /m ₁ is the dynamic vibration absorber Mass ratio of the main mass δ＝ω ₂ /ω _o is the ratio of the natural angular frequency of the dynamic vibration reducer and the main vibration system γ＝ρ／ω _o is the frequency of the external force and the natural angular vibration of the main vibration system Number ratio Main system amplitude X ₁ =√ ₁ ² +
C ₂ ² damping is μ=c/2m ₂ ω ₂ FIG. 3 is a resonance curve diagram of the above equation [1]. The figure shows β = 1/20, but in actual vibration control of the main tower of a long bridge, β = approximately 1/200. In the figure,
When μ=0 (excluding the attenuator), the displacement due to resonance becomes infinite at two locations. Also, when μ=∞ (attenuator fixed), it can be seen that ρ/ω _o =1.0, which indicates a dangerous state. It is shown that the safest state is achieved by going from μ=0.32 to μ=0.10.

In the spring-equipped pendulum type dynamic vibration absorber, the stiffness of the spring, the weight and position of the weight, the damping coefficient of the viscoelastic body, etc. are mainly selected and used in order to create the above-mentioned safe condition.

FIG. 4 is an explanatory diagram of the operation of the dynamic vibration reducer shown in FIG. 1. The figure shows that the springs 13 and 13b are interposed between the arms 8 and 8a and the frame 3.

FIG. 5 is an explanation of another embodiment of the present invention, in which a spring 4a is provided but the spring 4 of FIG. 4 is not provided,
It also shows that it can operate even without the weight 9 and springs 13, 13b shown in FIG. 4. arrow 14
indicates the direction of vibration.

FIG. 6 is an explanatory view showing still another embodiment of the present invention, in which a piston-shaped viscous damper 11 is provided at an angle between arms 8 and 8a. It should be noted that this shows that the device can operate without the springs 13, 13b shown in FIG.

By the way, the mounting position of the attenuator is not limited to between the two arms 8 and 8a, but may be mounted at a place where there is relative movement due to vibration, for example, between the base 1 and the frame 3, or between the base 1 and the arm 8. , between the arm 8 and the frame 3.

In the embodiments shown in FIGS. 4 to 6 above, 2
Although the case where the attenuator is provided between the arms 8 and 8a of the book is shown, the number of arms may be one.

7a and 7b show a spring-equipped pendulum type dynamic vibration absorber according to another embodiment of the present invention, in which a is a front view and b is a cross-sectional view. In the figure, 1 is a base, 3 is a frame, and the same or corresponding parts as in FIG. 1 are given the same reference numerals. In this embodiment, there is only one arm 8, and the attenuator 11 is provided between the frame 3 and the base 1 via pins 12, 12b.

By attaching this device to a structure to be damped and aligning the direction of vibration with the direction of arrow 14, it is possible to cause resonance.The mechanical model diagram and resonance curve diagram of this spring-equipped pendulum type dynamic vibration absorber are shown below. are also the same as those shown in FIGS. 2 and 3 above.

In FIG. 8, an attenuator 11 is provided between the arm 8 and the base 1.

FIG. 9 shows an attenuator 11 provided between the frame 3 and the arm 8, and the dynamic model diagram and resonance curve diagram are as shown in FIGS. 2 and 3 as well as FIGS. 8 and 7. become.

〔Effect of the invention〕

As described in detail above, this invention has a frame that can move relative to the base, a spring between this frame and the base, and an arm equipped with a weight on the frame. A long-period dynamic vibration reducer can be obtained. Furthermore, since the period can be easily adjusted by moving the weight, it is possible to resonate with the natural frequency of the structure to be damped and damp the vibration by effectively utilizing the effect of the damper. In addition, the influence of Coulomb friction is extremely small, and there is no need to stretch cables. In addition, the base has a linear structure, and the effects of the present invention are extremely significant, such as lower manufacturing costs and easier maintenance.

[Brief explanation of the drawing]

1A and 1B show an embodiment of the present invention, in which a is a front view, b is a sectional view, FIG. 2 is a mechanical model diagram, FIG. 3 is a resonance curve diagram, and FIG. The figures are an explanatory diagram of the embodiment shown in Fig. 1, Fig. 5 is an explanatory diagram of another embodiment of the present invention, Fig. 6 is an explanatory diagram of another embodiment of the invention, and Figs. , which shows still another embodiment of the present invention, in which a is a front view, b is a sectional view,
FIG. 8 is a front view of another embodiment of the invention, and FIG. 9 is a front view of another embodiment of the invention. In the figure, 1 is the base, 2 is the roller, 3 is the frame, 4 is the spring, 8 is the arm, 9 is the weight, 1
1 is an attenuator. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A pendulum with a weight attached to an arm suspended from a fulcrum, and a damper for attenuating the pendulum vibration of the pendulum, the pendulum vibration of which is excited by the vibration of a structure. A pendulum type dynamic vibration absorber damped by the attenuator, wherein the fulcrum is provided on a frame supported by the structure and movable in a substantially horizontal plane, and the frame is moved against the structure within the plane. A spring member is provided to vibrate the frame, and the mass of the frame and the spring constant of the spring member are determined so that the frame vibrates following the vibration of the pendulum. Pendulum type dynamic vibration absorber.