JPS5930006Y2 - Vibration damping devices in bridges - Google Patents

Description

[Detailed explanation of the invention] This invention is designed to prevent the movement of vehicles such as cars or trains, earthquakes, etc.
A control system for bridges with multiple stages of vibration absorbers installed in series, which can attenuate and reduce bridge girder vibrations caused by external force such as wind loads through dynamic absorption, ensuring mechanical stability and safety of the bridge. This relates to a shaking device.

In general, if a bridge is to be schematically illustrated from a vibration engineering perspective, as shown in FIG. A vibration system is formed.

In the bridge vibration system, when the weight body 1 is vibrated by an external force that vibrates periodically, the weight body 1 has a circular vibration frequency W
The transmissibility when the above-mentioned vibration resonates outward, that is, the response curve Hw, is the natural circular frequency W of the bridge vibration system, as shown in FIG. 5B.

- Moon (forms steep peaks of rising and falling slopes that peak at 7M).

Therefore, the circular frequency W. Under vibration conditions in which external forces vibrating periodically in the vicinity act on the heavy body 1, that is, the bridge girder, it is not possible to ensure the safety of the bridge, vehicles and people passing through the bridge, and There are various drawbacks such as causing discomfort to people.

Therefore, recently, the Proceedings of the Japan Society of Civil Engineers No. 205, September 1972,
As experimentally disclosed in the study on dynamic design of pedestrian bridges considering pedestrian characteristics published in June, vibration conditions where the bridge is vibrated by an external force that periodically vibrates at a circular frequency near Wo. Below, the natural circular frequency of the conventional bridge is 45 balls b<the above circular frequency W.

, a weight body 1 corresponding to a bridge girder, a weight 1a of mass m, and an elastic body 2a with an elastic constant of damping constant C.
By installing a vibration absorber 1'a consisting of a damper 3a as shown in FIG. 6A, the natural circular frequency of the two-way vibration system 1' can be reduced to the circular frequency W.

Therefore, the response curve Hw showing the transmissibility of the vibration system 1' to the external force has W as shown in FIG. 6B.

There is a double-headed natural resonance peak a1. which forms a valley at the point Wl and a peak with a steep rising slope at the pixels W1 and W2. Since a2 is formed, the circular frequency is W.

It is possible to achieve mechanical stability of the bridge against nearby external forces.

However, if the double-shape vibration system 1' is excited by an external force near the circular frequency W1 or W2, the transmissibility Hw will have a sharp natural resonance peak at W, , W, , as described above. a1. In order to take the apex value of a2, when an external forcing force having multi-frequency components such as a traveling vehicle, earthquake, wind load, etc. acts, the circular frequency W1. It resonates near W2, and the vibration becomes a problem.

In this case, in order to increase the damping effect of the bridge by the vibration absorber over all frequencies, it is necessary to make the damping constant C of the damper 3a that constitutes the vibration absorber 1'a sufficiently high. The dynamic damping effect of the device 1'a cannot be expected, and there is a serious weakness in improving the damping effect over the entire frequency range, and even if a sufficient damping constant C is set, the above-mentioned optimal In order to achieve a good damping effect, the mass ratio m/M of the heavy body 1 and the weight 1a must be set at about 1:20. Although this is possible for bridges, it becomes a practical problem for heavy bridges such as suspension bridges and cable-stayed bridges; for example, for a bridge girder weighing 1000 tons, the weight of the vibration absorber must be set to 50 tons. There are still various problems such as:

In addition, in order to absorb the impact load applied to the bridge girder, there is a structure in which the above-mentioned bridge girder is provided with a buffer section made by alternately laminating elastic bodies such as anti-vibration rubber and metal plates.
Although it can absorb impact loads applied in the stacking direction, for example, the longitudinal and horizontal directions of bridge girders,
Almost no absorption effect can be obtained against an impact load applied in a direction different from the lamination direction.

In addition, in the above structure, when an impact load is applied, each elastic body compresses and deforms simultaneously and uniformly, so that even if the external force applied to the bridge girder is applied in the lamination direction, If the bridge has periodic vibration near its natural frequency, it is impossible to prevent large vibrations from occurring in the bridge girder.

In view of these circumstances, this idea was developed by installing a vibration damping device consisting of multiple stages of vibration absorbers connected in series, each consisting of an elastic body, a damper, and a weight, at a predetermined position on the bridge girder, thereby creating a synergistic effect between the vibration absorbers. This allows the weight ratio of the allocating device to the bridge girder to be set extremely small, and also reduces the damping constant C of the attenuator.
By appropriately setting , the response curve showing the transmissibility of the coupled vibration system consisting of the bridge and damping device to the external force is flattened in the frequency domain of the external force, and the external forcing force of multiple wave components acts. Another object of the present invention is to provide a vibration damping device for a bridge that can easily improve the vibration damping effect and ensure the mechanical stability and safety of the bridge.

An embodiment of the vibration damping device for a bridge according to this invention will be described below with reference to the drawings.

Figure 1 shows an embodiment of the vibration damping device for a bridge according to this invention. In the figure, 6 is a vibration absorber, and this vibration absorber 6 has a mass m2
Weight 21. It consists of an elastic body 22 with an elastic constant of 2 and a damper 23 made of viscous fluid such as oil with a damping constant of C2.Furthermore, 5 is a vibration absorber, and this vibration absorber 5 overlays the entire vibration absorber 6. A weight 11. which is shaped like a weight and has a mass m1 and is made of the case 11 of the vibration absorber 6. It is composed of an elastic body 12 with an elastic constant of 1 and a damper 13 made of viscous fluid such as oil with a damping constant C1. In this way, the vibration absorber 5 forms a double structure with a built-in vibration absorber 6 to suppress vibration. Device 7 is configured.

FIG. 2A is a schematic diagram showing a vibration system in which the above-mentioned vibration damping device 7 is attached to a bridge girder, and 8 is composed of a bridge 4 and an allocating device 7 formed by connecting two stages of vibration absorbers 5 and 6 in series. The bridge 4 is a coupled vibration system consisting of a heavy body 1 with a mass M, which is a bridge girder, an elastic body 2 with an elastic constant, and a damper 3 with a damping constant C.
It is composed of

The case 11 and weight 21 in Figure 1 are the mass m19 in Figure 2 A.
Each corresponds to a weight of m2.

Next, the operation of the above configuration will be explained.

As shown in FIG. 2B, the response curve Hw showing the transmissibility of the coupled vibration system 8 to an arbitrary vibration external force corresponds to the circular vibration Number W
3. W4. There are unique resonance peaks b1. at three points of W5. b2. b
3, and the circular frequency W3. In order to blunt the response of the coupled vibration system 8 to external vibrational forces in the vicinity of W4°W5, the natural resonance peaks b, b2 . By setting the peak value of b3 low, the response curve Hw has a gentle slope with respect to the circular frequency W, and is flattened as much as possible. W4. The response of the coupled vibration system 8 can be blunted and flattened not only to the vibration external force near W5 but also to any vibration external force, and the vibration of the heavy body 1 caused by the vibration external force can be suppressed by the elastic body. Weight 1 by 12
1, the vibration of the weight 11 is absorbed by the damper 13, and the vibration of the weight 11 is transmitted and converted into the vibration of the weight 21 by the elastic body 22, and the vibration of the weight 21 is absorbed by the damper 13. By absorbing the vibrations by the damper 23, it is possible to ensure the mechanical stability and safety of the bridge against external forces including multiple wave components caused by vehicle travel, earthquakes, aerodynamic disturbances, and the like.

In other words, by installing a plurality of vibration absorbers 5 and 6 in series, these vibration absorbers 5 and 6 perform coupled vibration, that is, the vibration absorbers 5 and 6 absorb kinetic energy between each other, thereby reducing vibrations occurring in the bridge. can be kept to a minimum.

In addition, when the vibration damping device 7 is mounted on the bridge 4 to achieve an optimal damping effect against the vibration external force of the bridge 4, the mass ratio of the weight body 1 and the weights 11 and 21 is M: ml. : m2=1000 : 10 : 1
For example, for a bridge weighing 1000 tons, the weight of the vibration damping device may be 11 tons, and compared to the weight of conventional vibration damping devices not only for huge bridges but also for light weight bridges. The weight can be significantly reduced by doing so.

As clearly shown in FIG. 3, which is a schematic perspective view when the damping device 7 shown in FIG. 1 is mounted on the bridge girder 1, the mounting position of the damping device 7 in the X-X axis direction is vibration curve d,
As shown in e, the belly part is 1/4 of the total length l of the bridge girder 1.
．． Since we concentrate on 2/4.3/4 points, these l /4,
It is most effective to install it in the 2 l /4.31 /4 position, and the installation position in the Y-Y axis direction is X-
Installing them symmetrically with respect to the X-axis can achieve the optimum effect in insulating and damping the vibrations of the bridge 1.

FIG. 4A shows a modification of the vibration damping device 7 shown in FIG. 1. In contrast to the damper 13 in FIG. Oil dampers, air dampers, etc. are used, and in FIG. 4A, the same parts as in FIG. 1 are given the same numbers, and detailed explanation thereof will be omitted.

Further, FIG. 4B shows another modification in which the vibration absorber 6 is connected to the bridge via an elastic body 12', and the effect is the same as that of the embodiment. The same parts as in FIG. 1 are given the same numbers and detailed explanation thereof will be omitted.

As detailed below, this idea is based on the following:
By installing a vibration damping device consisting of multiple stages of vibration absorbers connected in series, each consisting of an elastic body, a damper, and a weight, the response of the multi-coupled vibration system consisting of the bridge girder and the damping device to external forces can be determined. The curve is flattened as much as possible in the entire frequency range of the external force that the bridge receives, expanding the vibration damping effect to the entire vibration range, and significantly reducing the weight ratio of the vibration damping device to the bridge. Since it can be set, it can sufficiently exhibit insulation vibration damping effects not only for small bridges but also for large bridges such as cable-stayed bridges and suspension bridges, and can ensure mechanical stability and safety of the bridge. A vibration damping device can be provided.

[Brief explanation of drawings]

Fig. 1 is an example of a vibration damping device for a bridge according to the invention, Fig. 2A is a schematic diagram of a vibration system in which the vibration damping device of Fig. 1 is attached to a bridge, and Fig. 2B is a characteristic diagram of the same. Figure 3 is a schematic perspective view of the vibration damping device installed on a bridge, Figures 4 A and B are variations of the vibration damping device in Figure 1, and Figure 5 A is a vibration model of a bridge without the vibration damping device installed. 5B is a characteristic diagram of the same, FIG. 6A is a schematic diagram of a vibration system in which a conventional vibration damping device is mounted on a bridge, and FIG. 6B is a characteristic diagram of the same. 1... Bridge girder, 5, 6... Vibration absorber, 7.
... Vibration damping device, 11゜21 ... Weight, 1
2.22...Elastic body, 13.23...
Attenuator.

Claims (1)

[Scope of utility model registration request] A vibration damping device for a bridge, characterized in that a plurality of vibration absorbers each consisting of an elastic body, a damper, and a weight are set in series at predetermined positions on a bridge girder.