JPS6360254B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 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.

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 conventional method has been to extend a cable from the tower and attach a damper to the tip of the cable. For example, (1)
The sliding block method uses Coulomb friction between the block and the slide to add damping properties to the vibration system, and (2) the hydraulic damping method uses a hydraulic damper to add damping properties to the vibration system using the vortex resistance of oil. be. However, in case (1), these methods lack quantitative reliability of the damping effect and there is a problem with the operability of the block, and in case (2), although the problem of (1) is solved, However, stringing a cable 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.

As a method without stringing cables, aerodynamic measures,
Vibration damping using a dynamic vibration absorber can be considered. Aerodynamic measures include a partition plate, the method by Netsu (Reference: Bridges and Foundations 1974-3, "Wind stability and vibration damping method of suspension bridge towers during construction"), and (b) cowling method (Reference: Mitsubishi Heavy Industries Technical Report vol-14, No. 3 1977-5, ``Wind resistance stability when constructing a main tower of a long suspension bridge,'' etc., but all of them are beyond the realm of experimentation and there are no examples of actual use.
Additionally, there are various problems with how these devices are installed.

Next, since the vibration damping method using a dynamic vibration reducer is also a method that does not involve stringing ropes, and the present invention is also included in this method, we will first explain its basic principle.

(The dynamic vibration absorber is TMD “Tuned Mass
It is sometimes called "Damper." ) Once the size of the structure (mass, rigidity, etc.) and the mode shape of the target vibration are known, the following three characteristic values are determined that are sufficient to express the properties of this vibration. This can be shown as a model as shown in Figure 1. In the figure, M _T is the equivalent mass of the structure (ts ² /m), K _T
is the equivalent spring of the structure (t/m), and C _T is the equivalent damping of the structure (ts/m). This structure has a mass M _d ,
A model of a dynamic vibration reducer with vibration characteristic values of spring K _d and damping C _d is shown in FIG. 2. However, if the change in the resonance curve of a structure to which this dynamic vibration absorber is installed (when the damping coefficient C _d of the dynamic vibration absorber is taken as a parameter) is similarly shown in a model, it becomes as shown in Fig. 3. In FIG. 3, the vertical axis is the response magnification, and the horizontal axis is the external force frequency ω _p /natural frequency ω _T . In Figure 3, the curve C _d = O is for a state in which there is no damping of the dynamic vibration absorber, and the curve for C _d = ∞ is for a state in which the mass M _d of the dynamic vibration absorber is fixed to the mass M _T of the structure, both of which are The response amplitude is large. The curve C _d = C _d・i shows the state when a dynamic vibration absorber is installed, and the response amplitude of the structure decreases, and C _d = C _d

Claims (1)

[Scope of Claims] 1. A support frame fixed at or near the top of a structure to be damped, and the upper end of the structure fixed to the support frame on a plane perpendicular to the direction of vibration to be controlled by a line hinge. Two or more vertically elongated plates that are attached and swingably suspended and facing each other, and weights that are respectively attached to the lower part of the two or more opposing plates; A pendulum-type dynamic vibration absorber comprising a damper interposed between two or more adjacent plates and connected to the two or more plates. 2. The pendulum type dynamic vibration absorber according to claim 1, characterized in that a viscoelastic body or a viscous body damper is used as the damper. 3. The pendulum type dynamic vibration reducer according to claim 1, wherein a hydraulic damper is used as the damper.