JPH02300405A - Bridge - Google Patents

Abstract

PURPOSE:To effectively suppress the torsional vibration of a bridge girder by providing a vibration controlling mass body for suppressing torsional vibrations and another vibration controlling mass body for suppressing vertical vibrations in parallel with each other at the central part in the length direction of the girder. CONSTITUTION:The girder 1 of an overpath, etc., is formed to the form of a parallel girder half-through bridge composed of a pair of girders 1A respectively having H cross sections and a roadbed installed between the intermediate height sections of the girders 1A. At each of the central parts of the two girders 1A in the length direction, the first vibration controlling dynamic damper 6 for suppressing torsional vibrations of the girder 1 and the second vibration controlling dynamic damper 6'' for suppressing vertical vibrations are arranged in parallel with each other in the length direction inside the webs of the girders 1A. Therefore, the torsional vibration can be suppressed economically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to bridges such as pedestrian bridges, and more particularly to bridges that are provided with vibration damping measures.

[Conventional technology]

For example, in a pedestrian bridge, if the walking period of a pedestrian matches the natural period of the vertical vibration of the bridge girder, the bridge girder will vibrate up and down as the pedestrian walks, causing discomfort to the pedestrian. Pedestrian bridges generally tend to have large spans, and although there is variation in the walking cycle of pedestrians, this variation shows a normal distribution, and the vertical vibration of the bridge girder is related to the cycle of pedestrian walking.
It is easy to match the period of motion.

In view of the above, a damping mass body that can freely vibrate vertically, a spring that matches the period of the vertical vibration of the mass body with the optimum natural period that reduces the resonance amplitude of the vertical vibration of the bridge girder, and a damping performance In order to improve the performance, it has been proposed to install a dynamic damper consisting of a damper that provides an optimal damping constant and to suppress the vertical vibration of the bridge girder of a pedestrian bridge using the mass effect (for example, Japan Society of Civil Engineers Proceedings No. 205).・September 1972, ``Study on dynamic design of pedestrian bridges considering pedestrian characteristics J).

[Problems to be Solved by the Invention] By the way, when vibrations of bridges, especially pedestrian bridges, are taken into account, bridge girders not only vibrate vertically due to walking etc., but also torsionally vibrate when the sides are exposed to wind. This is especially noticeable in those with roofs. When torsional vibration occurs, it is more difficult than when vertical vibration occurs.
Because it vibrates at a high frequency, pedestrians are known to experience strong discomfort even with the same displacement.

An object of the present invention is to effectively suppress torsional vibration of a bridge girder.

[Means for Solving the Problems] The characteristic structure of the bridge according to the present invention is that a vibration damping mass body is attached to a part of the bridge girder that is displaced due to torsional vibration so as to be able to vibrate freely in the direction of displacement of that part or in a direction close to the displacement direction. There are certain points.

Preferably, the mass body constitutes a dynamic damper including a spring for adjusting the vibration period of the mass body and a damper for damping the vibration of the mass body.

[Function] By adjusting the vibration period of the mass body to the natural period of the torsional vibration of the bridge girder with a spring and damping the vibration of the mass body with a damper, when torsional vibration occurs in the bridge girder, the vibration of the bridge girder is A dynamink damper in which the mass body vibrates in an opposite phase in response to torsional vibration, or a sensor that detects torsional vibration of a bridge girder and an actuator that vibrates the mass body in an opposite phase based on the detection of the sensor. By providing such a structure, it is possible to suppress I return vibration of the bridge girder. In the control technology that suppresses vibrations by vibrating mass bodies in opposite phases as described above, it is sufficient to add a mass body whose mass is extremely small compared to the mass of the bridge girder, for example, by vibrating the bridge girder itself. It has been found that the amount of mass, or material, required to be added to the bridge girder due to vibration is extremely small compared to the case where the bridge girder is made of concrete.

〔Effect of the invention〕

As a result, the present invention makes it possible to economically suppress the torsional vibration of the bridge girder, which causes strong discomfort to pedestrians, by minimizing the increase in weight of the bridge girder.

〔Example] Next, examples of the present invention will be shown.

This embodiment targets a large-span pedestrian bridge.

As shown in Figures 1 and 2, the pedestrian bridge consists of bridge girders (1
) is fixedly supported by a bridge pier (2), and the other longitudinal end of the bridge girder (1) is supported by a fixed part (3) via a bridge bearing plate so as to be freely movable in the longitudinal direction.

The bridge girder (1) is a pair of left and right girders (1A) with an H-shaped cross section.
This is a parallel girder bridge consisting of a subgrade (IB) and a subgrade (IB) constructed over the middle part of the bridge in the vertical direction.

This bridge girder (1) has columns (4
) is attached to the roof (5) over its entire longitudinal length.

In the central part of the two girders (1A) in the longitudinal direction, there is a first dynamic damper (6) for distribution for suppressing torsional vibration of the bridge girder (1), and a first dynamic damper (6) for damping the vertical vibration of the bridge girder (1). 2nd dynamic damper (6') for vibration damping
are arranged in a row in the longitudinal direction so as to be located inside the wafer of the girder (18).

As shown in FIGS. 3 and 4, the first Kinamitsu damper (5) is arranged in a vertical direction, which is an example of a direction close to the displacement direction of the girder (1A) that is displaced due to torsional vibration of the bridge girder (1). A steel mass body (7) (hereinafter referred to as an inertia block) is attached to the girder (1A) so as to be able to freely vibrate in the direction, and the inertia block (7) is attached between the inertia block (7) and the girder (1A). ) to match the natural period of torsional vibration of the bridge girder (1), and a spring (8) for adjusting the vibration period of the inertia block (7) to match the natural period of torsional vibration of the bridge girder (1). It is constructed by interposing an oil damper (9) for damping vibrations. (10) is a guide rail that guides the vertical swing of the inertia block (7) in cooperation with a guide roller (11) attached to the inertia block (7); (12) is a guide rail that guides the vertical swing of the inertia block (7); ) is a stopper using a rubber plate to restrict vibrations with an amplitude exceeding the setting, (IB) is a 'Jt metering adjustment valve copper, (14)
is a cover panel.

The second dynamic damper (6°) is the same as the first dynamic damper (6).

Therefore, the explanation thereof will be omitted.

In other words, the mounting parts of the first dynamic damper (6) and the second dynamic damper (6'') are displaced almost vertically during torsional vibration of the bridge girder (1); It is a girder (l^) that displaces in the vertical direction during any vibration, such as displacing in the vertical direction, and the first dynamic damper (6) and the second dynamic damper (
6''), the installation of the inertia block (7) is based on the principle of damping vibration by vibrating the parts in opposite phases in the direction of displacement, so both the first dynamic damper (6) and This made it possible to make the second dynamic damper (6″) the same.

The mass of each of the inertia blocks (7) is
It is adjusted to be approximately 0.5% of the mass of the bridge girder (1), and the vibration period of the inertia block (7) in the first dynamic damper (6) is equal to the natural period of torsional vibration of the bridge girder (1). The vibration period of the second dynamic damper (6゛) is adjusted so that the vibration period of the second dynamic damper (6゛) approximately corresponds to the natural period of the vertical vibration of the bridge girder (1).
It is adjusted by determining the spring constant of 8) and the damping constant of the oil damper (9). In addition, the spring (
The spring constant of 8) and the damping constant of the oil damper (9) are determined by the optimum natural frequency ratio (δ) and the optimum damping constant (
ζ).

δ= (Kg/mz)/(K,/m1)-1/(1+
β)ζ=J￥i7tō(1+77)' However, 1 for m1+: Mass of main vibration system (bridge girder), rigidity m, ,
: mass of additional mass (inertia block), rigidity β: mass ratio (m=/m,).

(15) is a handrail, and (16) is a lighting.

Next, we will show an experiment conducted by the present inventors to confirm the damping effect.

The weight of the bridge girder (1) is 220t, the natural frequency of the bridge girder (1) is 1.9011z for vertical vibration, and 2.25) for torsional vibration.
Targeting bridge z, the first and second dynamic dampers (6) and (6') were installed as described above. The mass of each inertia block (7) of the 11th second dynamic damper (6) and (6') is 550±20 kg, and the total * amount of the inertia block (7) of the second dynamic damper (6゛) is approximately 1% of the modal mass. In addition, the first and second dynamic dampers (6)
, (6″) natural frequencies and damping constants are shown in Table 1.

In each of the states in which the dynamic dampers (6) and (6') are activated and in the state in which they are not activated,
The bridge girder (1) was manually vibrated, and free vibration waveforms of vertical vibration and torsional vibration in each state were obtained by measurement, and based on these, the current constants of the bridge girder (1) were determined. The free vibration waveforms of vertical vibration when not operating and when activated are shown in Figures 5 and 6, and the free vibration waveforms of torsional vibration when not activated and activated are shown in Figures 7 and 8, respectively. Table 2 shows the attenuation constant of 1).

Table 1 Table 2 [Another example] Another embodiment of the present invention will be shown below.

[1] In the above embodiment, a second dynamic damper (6゛) was provided to suppress the vertical vibration of the bridge girder (1), but it is not necessary to provide it, and a damper is provided at the bottom of the subgrade (IB). One may be provided.

[2] In the above embodiment, the setting position of the mass body (7) in the longitudinal direction is free, but if the bridge girder (1) vibrates in the first order, as in the above embodiment, the amplitude is the highest. It is desirable to provide it in the center in the longitudinal direction. In other words, bridge girder (1)
Even if the vibration is secondary or tertiary vibration, it is preferable to provide the vibration at a location where the amplitude is the highest.

[31 In the above embodiment, the invention was applied to a pedestrian bridge, but the present invention can be applied to various types of bridges.

[41 Note that although reference numerals are written in the claims section for convenience of comparison with the drawings, the present invention is not limited to the structure of the attached drawings by the entry.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal side view, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, FIG. 3 is a side view of the main part, and FIG. The vertical front view and FIGS. 5 to 8 are vibration waveform diagrams. (1)... Bridge girder, (1A)... Part,
(6)...Dynamic damper, (7)...
... 1ft 1 body, (8) ... Spring,
(9)・・・Damper.

Claims (1)

[Claims] 1. Part (1A) that is displaced due to torsional vibration of the bridge girder (1)
) is provided with a damping mass body (7) that can freely vibrate in the displacement direction of the part (1A) or in a direction close to it. 2. The mass body (7) is connected to a dynamic damper (6) from a spring (8) for adjusting its vibration period and a damper (9) for damping vibrations of the mass body (7).
).The bridge according to claim 1.