JPS5997342A - Pendulum-type dynamic vibration absorber - Google Patents

Abstract

PURPOSE:To greatly reduce the frictional force which acts to a weight and to simplify the mechanism of a pendulum-type dyamic vibration absorber, by hanging the weight with a plurality of hangers at or near the top of a structural body and providing a damper which acts in the direction of vibration to be controlled. CONSTITUTION:Hangers 3 are attached to a support frame 1 in such a manner that the upper attached points of the hangers are spread on a plane perpendicular to the direction of that vibration of a structural body, which is to be controlled. As a result, the motion of a weight 2 is provided with a directionality. The natural frequency of a pendulum-type dynamic vibration absorber is set by adjusting the length of the hangers 3. The damping coefficient of the absorber is set by adjusting that of an oil damper 5 or by adjusting the lever ratio of a connecting rod 4. Various properties are thus adjusted to achieve optimal vibratory characteristic values against the vibratory characteristic values of the structural body whose vibration is to be restrained, to provide the dynamic absorber with a desired damping force. Since the frictional force in the absorber and its scale are small, the absorber can be used as a vibration restrainer for a main tower being built.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pendulum hole dynamic vibration absorber for suppressing horizontal vibration caused by wind or the like in a tower-like structure.

Tower-shaped 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. (
The main tower of a long bridge will be explained below as an example. ) In order to suppress the above-mentioned vibrations, the main method used in the past was to extend a cable from the tower and attach a damper to the end of the cable. Examples of this method include (1) a sliding block method that adds damping properties to the vibration system using Coulomb friction between the block and the slide; and (2) a hydraulic damper that adds damping properties to the vibration system using oil vortex resistance. There are additional hydraulic damping 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), there are problems with the stroke of the hydraulic damper. However, even though construction is underway, stringing the 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 cables.

Possible methods that do not involve stringing cables include aerodynamic measures and vibration damping using dynamic vibration absorbers. Aerodynamic measures include (a) method using partition plates and nets (Reference: Bridges and Foundations 1974-
3. Wind resistance stability and vibration damping method of suspension bridge main tower during construction J)
, (b) Cowling method (Reference: Mitsubishi Heavy Industries Technical Report vol.
-14, a 31977-5, ``Wind resistance stability when constructing the main tower of a long suspension bridge''), but all of them are beyond the realm of experimentation, and there are no examples of them being actually used. Additionally, there are various problems with the installation of these devices.

Next, the vibration damping method using a dynamic vibration absorber is also a method that does not require ropes.
Since the present invention is also included in this system, the basic principle thereof will be explained first. (In addition, the dynamic vibration absorber is T,
M, D rTuned Mass Damper j
It is sometimes called. ) Once we know the structure's size, mass, rigidity, etc.) and the mode shape of the target vibration, we can determine the following three characteristic values that are sufficient to determine the nature of the vibration. This can be shown as a model as shown in Figure 1. In the figure, MT is the equivalent mass of the structure (ts2/m), and KT is the equivalent spring of the structure (
'/m), CT indicates the equivalent damping of the structure (ts/m). This structure has a mass Md.

If a dynamic vibration absorber having vibration characteristic values of spring Kd and damping Cd is attached, the state is shown in FIG. 2 as a model. However, if the change in the resonance curve of a structure equipped with this dynamic vibration absorber (when the damping coefficient Cd of the dynamic vibration absorber is taken as a parameter) is similarly shown in a model, it becomes as shown in FIG. In Figure 6, the vertical axis is the response magnification, and the horizontal axis is the external force frequency ω0/natural frequency ωT.The curve of Cd = 0 in the diagram shows the state where there is no damping of the dynamic vibration reducer, and the curve of Cd = oc shows the dynamic vibration. This is a case where the mass Md of the vibration absorber is fixed to the mass MT of the structure, and the response amplitude is large in both cases. The curve Cd = Cd-i shows the state when a dynamic vibration absorber is installed, and the response amplitude of the structure decreases, and the curve Cd: Cd・opt shows the state when a dynamic vibration absorber with the optimal value of the damping coefficient is installed. The response amplitude of the structure decreases considerably.

That is, if a dynamic vibration absorber having appropriate values of Md, Kd, and Cd is attached to a structure, the amplitude of vibration due to external force can be considerably controlled.

With respect to MT, KT, and CT of the structure, there is the following relationship between Md SKd and Cd of the dynamic vibration absorber and damping efficiency (expressed as a logarithmic damping coefficient).

Optimal natural frequency ωd・opt of the dynamic vibration absorber Optimal damping coefficient Cd−opt of the dynamic vibration absorber As shown in the above formula < Md , Kd
, Cd are set, the logarithmic damping coefficient δT of the main structure is as follows.

When trying to create a dynamic vibration reducer according to the theory described above, the following problems arise.

(a) A frictional part enters the device mechanism, and the theoretical effect cannot be obtained.

(b) The dynamic vibration absorber is set to a predetermined natural frequency ・(ωd・opt
) and the damping coefficient (Cd=opt) requires a large amount of adjustment device power.

Therefore, there are very few examples of application of dynamic vibration absorbers to building structures and bridge structures, and since the vibration targeted by the present invention is in the horizontal direction, from this point of view, only those that can be taken up as prior art based on reliable materials, The following C1ticorp
It is comparable to the equipment in the Center Building.

Structure: Rice 1i: ! ＋Yo RiC1tico
rp Center building, height 274m Isomedullary mass ratio: 1150 Vibration period: 6.5 sec Dynamic vibration absorber: The weight is made of 400t concrete mass and has an oil film sliding surface. Zero weight stroke using gas spring and hydraulically controlled damper ±1.37m.

In this device, a huge weight is installed on the top floor of a building.
It is connected to a fulcrum on the floor via a hydraulic damper, but care has been taken to reduce the frictional force in (a) above, so an oil film is created and the device becomes large-scale. There is.

The target structure for this device was a huge building, which is probably why it became such a large-scale device. It cannot be adopted due to scale. For example, if the weight is for vibration damping of a main tower of a suspension bridge, the weight of the weight will be several -.

The device requires some ingenuity in how to slide this weight without causing friction.

The present invention solves the problems of the conventional dynamic vibration reducer, significantly reduces the frictional force acting on the weight, simplifies the mechanism, and provides a dynamic vibration absorber that is extremely effective as a vibration allocation device for construction work. The purpose is to provide.

The pendulum hole dynamic vibration absorber of the present invention is of a pendulum type with a weight suspended, and includes a support frame fixed at or near the top of a structure to be damped, and a plurality of suspension members on the support frame. a damper connecting rod whose lower end is pivoted to the weight and whose upper end is pivoted to the support frame so as to be able to swing in the direction of vibration to be controlled of the structure; The attenuator mounting fixed to the frame is characterized in that the attenuator is attached to a metal fitting and connected to the attenuator connecting rod. The details will be explained below with reference to embodiment figures.

FIG. 4 shows the structure of an embodiment in which a hydraulic damper is used as the damper of the pendulum hole dynamic vibration absorber of the present invention. A dynamic vibration reducer is installed at a high place at or near the top of the structure to be damped. In the figure, 1 is a support frame fixed to a structure, but if the structural members of the structure itself can be used, they are included. 2 is a weight,
It is attached to and suspended from the support frame 1 by a plurality of suspension members 6 attached to its upper part. As the hanging weight member 3, a wire rope or a metal rod whose attachment part is swingably attached is used. The suspension member 3 is attached to the support frame 1 in such a way that the upper mounting points are spread out on a plane perpendicular to the direction of vibration of the structure to be controlled.
, so that the movement of the weight 2 has directionality.

4 is a damper connecting rod whose lower end is pivoted to the upper part of the weight 2 and its upper end is pivoted to the support frame 1 so as to be able to swing in the damping direction; It is. 5
is a hydraulic damper, and the damper mounting fixed to the support frame 1 is attached to the metal fitting B, and in this case, it is connected to the middle of the upper and lower swing shafts of the damper connecting rod. (Also, depending on the circumstances of the work, it may be connected to the upper part of the upper swing shaft.) The mounting metal fittings can be omitted if a part of the structure can be used. The installation of a dynamic vibration absorber on a structure depends on the structure of the structure, and if the desired damping force can be obtained, the attenuator may be installed directly on the weight without using the above-mentioned attenuator connecting rod. However, it is preferable to attach the dynamic vibration absorber to the connecting rod from the viewpoint of workmanship and damping force adjustment.

5 and 6 show the structure of an embodiment using a viscoelastic (or viscous material) damper as the damper of the dynamic vibration absorber of the present invention. In the figures, the same symbols as in FIG. 4
The same member as in the figure is shown, and Te is a viscoelastic damper, and the damper mounting fixed to the support frame 1 is interposed between the metal fitting 6 and the damper connecting rod 4 and is connected to both. Figure 5 shows the case where the viscoelastic damper is directly connected to the damper connecting rod 4, and Figure 6 shows the case where the viscoelastic damper is attached to the arm 7.
This shows the case where they are connected via .

When using a hydraulic damper or a viscoelastic damper, the specifications are adjusted to obtain the optimum vibration characteristic value depending on the vibration characteristic value of the structure to be damped.
Provide the desired damping force to the dynamic vibration reducer. The natural frequency of the device can be adjusted by adjusting the length of the suspension member, and the damping coefficient can be adjusted by adjusting the damping coefficient of the oil damper or the lever ratio of the damper connecting rod (ratio of 41 and 12 in Figures 4 and 5). by. (If a viscoelastic damper is used, the dimensions of the viscoelastic material or less in Table 1 are adjusted.) According to the structure of the dynamic vibration absorber of the present invention as described above, the following effects can be obtained.

(1) The frictional force is the rotational frictional force at the fixed point of the suspension member and the frictional force of the oil damper reduced by the lever ratio (
(when using an oil damper), both of which are small, and are estimated to be at least smaller than when Teflon (static friction coefficient of about 0.06) is used for the sliding surface of the weight.

(2) The scale of the device is not so large that it can be used as a vibration damping device for the main tower under construction.

Next, the general specifications of the device when the dynamic vibration absorber of the present invention is applied to an actual structure will be described.

1) Structure: Suspension bridge main tower (height 133m, total type 6400m), vibration characteristic value of primary flexural vibration MT = 209.3 ts2/ 77LKT =
994.5 t/m 0T=1・452ts/m (logarithmic attenuation rate 0.01 phase 2)
Dynamic vibration absorber: Vibration characteristic values are shown in Table-1.

This calculates the specifications of the dynamic vibration reducer.

,', Md-βMT = 2.09 t s”/
m, °9 weight weight Wd = MdXg = 20.5
t = −−0,99 1+β, °, damping coefficient for oil damper frying...lt
When Jb=2:1, the general specifications of the device calculated from the vibration characteristic values of the dynamic vibration absorber are summarized as follows.

Weight type ff1Wd: 20.5 t = 2.6 as iron material
6m3 (1,77 Expressed as follows: Since the structural damping of the tower is about δ=0.01, it increases by #J20 times. Regarding the response [[--in other words, it has decreased to about 2 degrees.

[Brief explanation of drawings]

Figure 1 is a vibration model of the structure, Figure 2 is a model of the system with a dynamic vibration absorber installed, Figure 6 is a resonance study of the structure with the dynamic vibration absorber installed, Figure 4, FIGS. 5 and 6 are views (perspective views) of an embodiment of the pendulum-type movable gjik 4 of the present invention. MT: equivalent texture of the structure, I (T: equivalent number of springs of the structure,
CT: equivalent damping of the structure, Md: mass of dynamic vibration absorber, Kd
: Spring of dynamic vibration absorber, Cd : Capital reduction of dynamic vibration absorber, 1: Support frame, 2: Weight, 3: Percentage member, 4: Attenuator connecting rod, ps*pz: Swing shaft, 5: Hydraulic pressure Damper, Ri...
Viscoelastic body (viscous body) damper, 6: Attenuator is attached to metal fittings, 7: Viscoelastic body damper is attached to arm. Agent: Mr. Kimura Feeding Box 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1) A support frame fixed at or near the top of a structure to be damped, an electric picture suspended from the support frame via a plurality of suspension members, and control of the structure. a damper connecting rod whose lower end is pivoted to the weight and whose upper end is pivoted to the support frame so as to be able to swing in the desired vibration direction; A pendulum hole dynamic vibration absorber comprising a damper connected to the damper connecting rod. 2) The pendulum hole dynamic vibration absorber according to claim 1, wherein a hydraulic damper is used as the damper. 6) The pendulum hole dynamic vibration absorber according to claim 1, wherein a viscoelastic material or a viscous material damper is used as the damper.