JP3000190B2 - Cable-stayed bridge cable damping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable damping device for a cable-stayed bridge, and more particularly to a cable damper for damping wind and vibration of a cable installed on a cable-stayed bridge by a vehicle or the like and preventing the cable from being broken. The present invention relates to a damping device for a cable-stayed cable.

[0002]

2. Description of the Related Art Generally, a cable stayed bridge is a flexible structure having low rigidity, and the wind resistance of a plurality of cables installed on the cable stayed bridge is an important factor in its design. As a method for coping with the vibration of the cable due to the wind, there are aerodynamic measures for stabilizing the cross-sectional shape of the cable itself, but various other structural measures described below are also implemented.

[0003] As one of the structural measures, a vibration damping method of connecting cables with a stainless wire or a special jig has conventionally been adopted. However, in recent years, besides the method of connecting cables with a stainless wire or a special jig as described above, a damper method such as an oil damper or a viscous shear type damper has been adopted as an effective vibration damping method of the cable. is there.

For example, as shown in FIG. 8, an oil damper 1 has a structure attached between a base end of a cable 3 laid on a cable stayed bridge at a fixing portion 2 and a bridge girder 4 of the cable stayed bridge. . In this oil damper 1, two oil dampers 1 are generally provided for one cable 3 so as to cope with elliptical vibration of the cable 3 due to wind.

On the other hand, the viscous shear damper can cope with two-way vibration in a plane formed by a plurality of cables 3 and an out-of-plane that forms an angle with the plane, as shown in FIG. In this case, one viscous shear damper 5 may be provided for one cable 3, which is awarded as an effective means. The use of high-damping rubber for the cable 3 has already been reported at the 46th Annual Meeting of the Japan Society of Civil Engineers [September 1, 1991
9th], but there is no specific description.

[0006]

However, in the method of connecting the cable 3 with a stainless wire or the like, it is necessary to install the cable 3 at a high position. Met. In addition, it has an attenuating effect on vibrations in the plane formed by the plurality of cables 3, but cannot deal with vibrations outside the plane that forms an angle with the plane of the cables 3. there were. Furthermore, in the design stage, it is difficult to grasp in advance the attenuation effect of the stainless steel wire, and in order to control the vibration only by increasing the frequency, the stainless steel wire must be installed every 30 to 40 m pitch. There was a problem in that it required two stainless wires.

[0007] On the other hand, in the case of the oil damper 1, only a one-way damping effect is obtained, and as described above, one line is required to have freedom in directionality so as to cope with elliptical vibration caused by wind. In this case, two or more oil dampers 1 must be installed for the cable 3, which increases the number of installations. Further, the vibration damping characteristics of the oil damper 1 depend on the viscosity coefficient, and the viscosity coefficient changes depending on the temperature, so that the vibration damping effect becomes unstable. Further, the oil inside the oil damper 1 may increase in temperature during operation and its viscosity may be reduced, so that sufficient damping performance may not be exhibited. It has been found that the oil damper 1 has an insufficient damping effect in a minute amplitude range.

On the other hand, in the case of the viscous shear damper 5, unlike the oil damper 1, one cable 3 differs from the oil damper 1 because it can cope with in-plane and out-of-plane vibrations of the cable 3.
One viscous shear type damper 5 may be installed for this purpose, and since the viscous body has excellent weather resistance and durability, it is easy to maintain and manage. Since there is no vibration, there is an advantage that it can follow micro vibrations.

However, the above-described oil damper 1
And the viscous shear type damper 5, these damper systems have an external structure in which one end of the dampers 1, 5 is directly fixed to the cable 3 and the other end is directly fixed to the bridge girder 4 near the fixing portion 2 of the cable 3. Dampers 1, 5
In addition to the fact that the bridge itself becomes large and the appearance is impaired as a cable-stayed bridge, and that the oil and viscous material have a large temperature dependency, the temperature of the bridge It is easily affected and the performance becomes unstable within the temperature range of use conditions. Further, the metal members constituting the dampers 1 and 5 are often exposed to the outside air, and the portions are easily deteriorated. For this reason, the current situation is that sufficient consideration has not been given to the mounting structure.

In view of the above, the present invention has been proposed in view of the above-mentioned problems, and an object of the present invention is to construct a cable-stayed bridge without impairing the beauty of a cable-stayed bridge by using a material having a small temperature dependency. Another object of the present invention is to provide an excellent cable-stayed bridge cable damping device.

[0011]

As a technical means for achieving the above object, the present invention relates to a cable stayed bridge cable centered on a portion near a fixing portion to which a base end of the cable stayed bridge cable is connected. A high-attenuation rubber molded body is disposed at a symmetrical peripheral position and is interposed between a base end portion of a cable-stayed bridge cable and a fixing portion, and has the following features. The high damping rubber of the molded product has a loss coefficient ta at a shear strain of 10 to 30%.
nδ is 0.3 to 1.0, and the shear modulus is 6 to 40.
kgf / cm ² . The high-damping rubber comprises a compound of one or more rubbers selected from natural rubber, polyisoprene rubber, polybutadiene rubber and butadiene styrene rubber, and has a loss coefficient tan δ of 0.5 or more. The molded article of the high attenuation rubber is covered with rubber having excellent weather resistance. The molded article of the high attenuation rubber is covered with a rubber which is excellent not only in weather resistance but also in air permeability. A portion including a molded article of high-attenuation rubber interposed between a base end portion and a fixing portion of the cable stayed bridge cable is covered with a waterproof cover.

[0012]

In the vibration damping device for a cable-stayed bridge cable according to the present invention,
When a cable stayed bridge cable vibrates due to wind or rain due to the use of a molded article of high damping rubber, the molded article is deformed based on the spring constant of the high damping rubber, and the cable stays due to the energy damping action due to the deformation. Damping the input vibration of the bridge cable. Here, since the high damping rubber forming the molded body has a small temperature dependency, it is hardly affected by the bridge surface temperature, and the performance can be stabilized within the temperature range of the use condition. Furthermore,
The high damping rubber of the form has enough loss for vibration damping of the cable
Cable and cable with shear modulus
Expected damping performance required as a damper for
It has both performances of rigidity.

Further, as the above-mentioned high attenuation rubber, natural rubber is used.
Rubber, polyisoprene rubber, polybutadiene rubber and pig
One or more rubbers selected from diene styrene rubber
With a loss factor tanδ of 0.5 or more
If you select a certain one, you can achieve a more stable damping effect.
It is possible to realize a vibration damping device that can be effectively used.

[0014]

Further, the molded article of the high attenuation rubber is covered with a rubber having excellent weather resistance and air blocking property, or the portion including the molded article is covered with a waterproof cover, so that the molded article is oxidized and deteriorated. And protect the molded body from ozone destruction and improve durability.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vibration damping device for a cable-stayed bridge cable according to the present invention will be described with reference to FIGS.

The embodiment of the present invention shown in FIGS. 1 and 2 uses a plurality of (six in the figure) molded bodies 11 formed of a high-damping rubber such as natural rubber in a cylindrical shape. The rubber molded body 11 is symmetrically positioned around the cable 12 at a location near the fixing section 13 to which the base end of the cable-stayed bridge cable 12 (hereinafter simply referred to as a cable) is connected, for example, in a radial manner. It has a structure arranged at equal intervals and interposed between the base end of the cable 12 and the fixing unit 13. Therefore, when vibrations due to wind, traveling vehicles, and the like are input to the cable 12,
The molded article 1 is formed based on a spring constant of the high damping rubber, which will be described later.
1 is deformed, and the vibration of the cable 12 is suppressed by the energy damping action due to the deformation.

The high-damping rubber forming the molded body 11 has a loss coefficient tan δ of 0.3 to 1.0 and a shear modulus of 6 to 40 kgf / cm ² . The loss coefficient tan δ is 0.3 to 1.0 and the shear modulus is 6 to
By simultaneously satisfying both physical properties of 40 kgf / cm ^2, a vibration damping effect as a vibration damping device for a cable-stayed bridge cable is exhibited. Here, the loss coefficient tan of the high damping rubber
δ may be 0.3 or more, but more preferably 0.5 or more. If the loss coefficient tan δ is smaller than 0.3, the desired damping effect cannot be obtained. If the loss coefficient tan δ is larger than 1.0, the damping effect is large, but the temperature dependency and the amplitude dependency are large. The damping effect becomes unstable.
Here, the above-mentioned high attenuation is defined as 20 ° C. and shear strain 2
It means that the loss factor tan δ ≧ 0.05 under 5%.

Further, the shear modulus is 6 kgf / cm ^2.
If it is smaller than the above, the loss factor tan δ is remarkably small at 0.2 or less because the content of the filler is small. If the loss coefficient tan δ is small as described above, the logarithmic decay rate described below becomes low, so that it cannot be used as a vibration damping device for a cable-stayed bridge cable.

Conversely, the shear modulus is 40 kgf / cm.
^If it is larger than ² , for example, the shear modulus is 100 kgf
/ Cm ² , it is assumed that the cable is attached to a cable requiring a spring constant of 70 ton / m. Here, assuming that the height of the molded body 11 is 2 cm, the shear cross-sectional area is 14c.
m ² , and when three molded bodies 11 are used, the shear cross-sectional area per one becomes 4.6 cm ² . This is approximately equal to the height of the molded body 11 at a diameter of 2.4 cm, is easily affected by bending, and has poor fatigue characteristics. Although it is conceivable to reduce the number and increase the spring constant per molded body, it is preferable to attach three or more molded bodies in order to arrange the molded bodies in a well-balanced manner.

Further, when the shear modulus is greater than 40 kgf / cm ² , the loss coefficient tan δ is large. May not be stable.

On the other hand, specific examples of the high attenuation rubber include rubber such as SBR, NBR, BR, silicon rubber, EPDM, and butyl rubber, or fillers, oils, couplings, etc. There is a rubber compound or the like in which an agent is compounded, and particularly, natural rubber, polyisoprene rubber, polybutadiene rubber, and butadiene styrene rubber are preferable.

Further, as described above, it is preferable that the high damping rubber has a small temperature dependency. For example, the high elasticity rubber has a physical property value in which the temperature ratio of shear modulus [−10 ° C./20° C.] is 3.0 or less. For example, the temperature dependence of a viscous material is about 5 at room temperature.
While the physical property value changes by 10 to 40 times when the temperature decreases by 0 ° C., the physical property value of the high attenuation rubber changes by about 2 times when the temperature decreases by 50 ° C., and the high attenuation rubber has smaller temperature dependency. As a result, it is hardly affected by the bridge surface temperature, and the performance can be stabilized within the temperature range of the use condition.

The molded body 11 may be a laminate of a high-damping rubber and a hard plate such as a steel plate. Also, the cross-sectional shape is not limited to the above-described circular shape, and in addition, square, rhombic,
The shape is not limited, such as a sector shape, but a circular shape is preferable in terms of production, and a hollow shape may be used.

More specifically, the molded article 11 of high-attenuating rubber is integrally attached to the upper and lower metal fittings 14 and 15 by vulcanization or the like, and one upper metal fitting 14 is fixed to the holder 16 with bolts or the like. The holder 16 is fastened to the cable 12 laid on the cable-stayed bridge by the clamp ring 17, and the other lower metal fitting 15 is bolted through the flange 18 to the fixing ring 1.
9 and the fixing ring 19 is fastened to the fixing portion 13 fixed to the bridge girder 20 of the cable stayed bridge. Then, each component including the above-described molded body 11 is fixed to the fixing unit 13 and the cable 1.
2 is covered with a waterproof cover 21 stretched around the base end. As shown in FIG.
A plurality (six in the figure) of the cables 4, 15 and the holders 16 are also arranged radially around the cable 12.

It is practical that the mounting position of the high-attenuation rubber molded body 11 is within a range of 0.03 to 0.15 times the entire length of the cable 12 from the fixed end of the cable 12. That is, if the length is smaller than 0.03 times the total length of the cable 12 and too close to the fixed end of the cable 12, the required damping effect cannot be obtained. If it is installed at a high position from the fixed end of 12, the installation work and the exchange work become difficult.

As described above, the molded body 11 is connected to the cable 12
In the vicinity of the fixing unit 13 to which the base end of the cable 12 is connected, the fixing unit 13 is arranged at a symmetrical peripheral position around the cable 12 and is interposed between the base end of the cable 12 and the fixing unit 13 to provide an external appearance. Simplification can be achieved. In particular, since each constituent member including the molded body 11 is covered with the waterproof cover 21 stretched around the fixing portion 13 and the base end of the cable 12, the appearance is improved and the metal portion is improved. And the like are not exposed to the outside air, so that deterioration due to rust or the like hardly occurs.

Here, the optimum spring constant for vibration damping can be obtained from the design specifications of the cable, the mounting position of the molded body 11, and the loss coefficient tan δ. The spring constant K is determined by K = G * A / H, where G is the shear modulus of elasticity of the molded body 11, H is the height, and A is the shear cross-sectional area.

In general, the bending effect of the molded product 11 due to the shear strain is smaller when the height is smaller than the diameter thereof, and when the shear strain is smaller, the smaller the shear strain is, the more stable the long-term stability is. . On the other hand, the amplitude of the molded body 11 is about 1 to 5 mm with respect to the vibration of the cable 12,
It is about 0 mm. Here, the shear strain is set so as to be 50% or less, more preferably 10 to 30%. Therefore, the spring constant of one molded body 11 is 100 to 3
When the pressure is 50 kgf / cm, the height of the molded body 11 is about 10 to 50 mm, and the diameter of the columnar section is 40 to 8 mm.
About 0 mm is preferable.

For example, assuming that a spring constant required for damping the vibration of one cable 12 is 70 ton / m, an example of the size and the number of the molded bodies 11 is 50 to
Six cylindrical molded bodies 11 having a height of 60 mm and a height of 20 mm
[Natural rubber] is preferably arranged radially at equal intervals. In addition, when the same spring constant [70 ton / m] is used, four molded bodies 11 having an outer diameter of 30 mm and a height of 15 mm may be radially arranged. Note that the spring constant required for the entire apparatus is the sum of the spring constants of the individual compacts 11. In order to determine the spring constant required for damping the vibration of one cable 12 as described above, the radially arranged molding 11
The spring constant increases as the shear cross-sectional area of the molded body 11 increases, and conversely, the spring constant decreases as the shear cross-sectional area decreases. Therefore, the spring constant of the molded body 11 can be adjusted by increasing or decreasing its shear cross-sectional area. Also, the molded body 11
When the height of is higher, the spring constant is smaller, and conversely, when the height is lower, the spring constant is larger.

In the above embodiment, the case where a cylindrical and solid molded body 11 is used as shown in FIG. 3A has been described. However, as described above, the spring constant required for damping the vibration of the cable 12 is reduced. When the size is small, for example, the size of the molded body 11, that is, the one having a small shear cross-sectional area may be used, and therefore, the molded body 11 having a small outer diameter may be used.
For example, as shown in FIG. 3B, a cylindrical and hollow molded body 11 ′ can be used. In this way, it is easy to manufacture the molded bodies 11 and 11 'having the same outer diameter and different spring constants between a solid body and a hollow body. As a result, if the solid molded body 11 and the hollow molded body 11 'are combined and arranged radially as shown in FIG. 4, the spring constant of the entire device required for damping the vibration of the cable 12 is reduced. Can be easily realized.
The ratio of reducing the spring constant is determined by the number of combinations of the solid compact 11 and the hollow compact 11 '.

In addition, in order to increase or decrease the spring constant of the entire apparatus, it is possible to increase or decrease the number of the molded bodies 11 in addition to increasing or decreasing the shearing sectional area of the molded body 11 described above. When increasing or decreasing the number of the molded bodies 11, it is desirable that the above-mentioned molded bodies 11 are arranged in a well-balanced manner at point-symmetrical positions with respect to the cable 12, but as shown in FIG. 5, five molded bodies 11 or as shown in FIG. It is also possible to arrange one molded body 11 at a line symmetrical position around the cable 12. If the number of the molded bodies 11 is reduced in this way, the spring constant of the entire device is reduced,
Conversely, if the number of formed bodies 11 is increased, the spring constant is increased.

Therefore, when increasing or decreasing the spring constant of the whole apparatus, in addition to increasing or decreasing the shearing cross-sectional area of the above-mentioned molded body 11, if the number of the molded bodies 11 is increased or decreased, the combination is appropriately made. In addition, it is possible to finely adjust the rate at which the spring constant of the entire apparatus is increased or decreased.

The causes of vibration of the cable 12 include vortex excitation by wind, wake galloping, rain vibration by rainfall, and the like. For each vibration factor, if the damping effect is generally represented by a logarithmic damping rate Δ, the vortex excitation For logarithmic decay rate Δ> 0.01 to 0.015,
For wake galloping, logarithmic decay rate Δ>
With respect to 0.05 and rain vibration, if the logarithmic decay rate Δ> 0.02 to 0.03, generation of vibration can be substantially suppressed. On the other hand, the molded body 11 described above has a high loss coefficient tan δ at 20 ° C. and 25% of shear strain of 0.3 to 1.0 and a shear modulus of 6 to 40 kgf / cm ^2. Since the damping rubber is used, a logarithmic damping ratio Δ> 0.03 is obtained, and it is possible to substantially suppress the occurrence of vibration. If the loss coefficient tan δ is 0.5 or more, the logarithmic decay rate Δ> 0.
05 becomes possible, and the molded body 11 exhibiting a further damping effect can be realized.

For example, as shown in FIG.
Is held by the vibrating section 23, and the vibrating section 23 of the vibrator 22 is vibrated in the direction indicated by the arrow in the drawing, so that the cable 12 is given vibration at a predetermined test frequency and amplitude. Thereafter, the point at which the cable 12 oscillates at a predetermined amplitude is detected by the vibrometer 24, and at the time of the detection, the cable 12 is automatically released from the holding state by the vibrator 23 of the vibrator 22. I do. Then, the waveform until the cable 12 stops oscillating is monitored by a measuring instrument such as an oscilloscope, and the logarithmic decay rate is determined from the waveform.

The following data were obtained for three specimens (using three molded bodies) by an experiment conducted based on the method of measuring the logarithmic decrement.

[Specimen a] Shear cross-sectional area 54 cm ² [per piece] Height 2 cm Spring constant 106 ton / m Shear modulus 13 kgf / cm ² Loss coefficient tan δ 0.55 Logarithmic damping rate Δ 0.07

[Specimen b] Shear cross-sectional area 7 cm ² [per piece] Height 2 cm Spring constant 15 ton / m Shear modulus 15 kgf / cm ² Loss coefficient tan δ 0.1 Logarithmic damping rate Δ 0.01

[Specimen c] Shear cross-sectional area 7 cm ² [per piece] Height 2 cm Spring constant 3 ton / m Shear modulus 3 kgf / cm ² Loss coefficient tan δ 0.3 Logarithmic damping rate Δ 0.009

From the above results, the specimen a having a logarithmic decay rate of 0.07 is particularly preferred.

Incidentally, since the vibration damping device is often used outdoors, the outer periphery of the high damping rubber of the molded body 11 is
It is preferable to coat with rubber having excellent weather resistance such as ethylene-propylene rubber or chloroprene rubber, and the thickness of the coated rubber is preferably about 1 to 5 mm. When the thickness of the coating rubber is large, the weather resistance is improved, but since the attenuation characteristics of ethylene-propylene rubber and chloroprene rubber and the like are small, the overall loss coefficient tan δ including the coating rubber is small, When the thickness is small, the weather resistance is reduced. As a result, the thickness of the covering rubber is more preferably about 2 to 3 mm.

Further, the outer periphery of the high attenuation rubber of the molded body 11 is
Covering with a rubber such as butyl rubber which is excellent in ventilation blocking property in addition to weather resistance can realize a vibration damping device having good long-term durability. Here, the butyl rubber generally has a low gas permeability, and the air permeability value of the butyl rubber is about 5 if the air permeability value of the natural rubber is 100. Therefore, it is preferable to use halogenated butyl rubber, for example, chlorobutyl rubber or bromobutyl rubber, as the covering rubber in order to improve the ventilation blocking property. The thickness of the covering rubber is preferably about 1 to 5 mm as described above, and 2 to 3 mm in order to sufficiently exhibit both the damping property and the weather resistance.
mm is preferable.

The loss coefficient tan δ of the butyl rubber as the coating rubber is 0.2 to 0.3, whereas the loss coefficient tan δ of the ethylene-propylene rubber is 0.1 to 0.3.
Since it is 0.15, it is preferable to use butyl rubber having a large loss coefficient for the coated rubber in order to exhibit the damping performance of the molded body 11 including the coated rubber. Even if this butyl rubber is halogenated chlorobutyl rubber, bromobutyl rubber, or the like, the vulcanization time can be shortened and workability is better than that of butyl rubber. Further, a blend of these and ethylene propylene rubber may be used.

[0044]

According to the cable-stayed bridge cable vibration damping device of the present invention, the use of a high-damping rubber molded body allows
Since the high damping rubber that forms the molded body has a small temperature dependency, it is hardly affected by the bridge surface temperature, stabilizes the performance within the temperature range of use conditions, and dramatically improves reliability. . In addition, the high damping rubber of the molded body
Has sufficient loss coefficient and shear modulus for damping
Therefore, the vibration of the cable is effectively suppressed.

As the above-mentioned high attenuation rubber, natural rubber is used.
Rubber, polyisoprene rubber, polybutadiene rubber and pig
One or more rubbers selected from diene styrene rubber
With a loss factor tanδ of 0.5 or more
If you select a certain one, you can achieve a more stable damping effect.
It is possible to realize a vibration damping device that can be effectively used.

[0046]

Further, by covering the high attenuation rubber with a rubber having excellent weather resistance and ventilation blocking properties, or by covering with a waterproof cover, the high attenuation rubber is prevented from oxidative deterioration, ultraviolet rays and ozone destruction. Thus, it is possible to provide a high-quality vibration damping device having excellent long-term durability.

[Brief description of the drawings]

FIG. 1 is a front view including a partial cross section showing an embodiment of the present invention.

FIG. 2 is an enlarged view of arrow A in a state where a waterproof cover of FIG. 1 is removed.

3A is a cross-sectional view showing a solid high-damping rubber molded article, and FIG. 3B is a cross-sectional view showing a hollow high-damping rubber molded article.

FIG. 4 is a cross-sectional view showing an example of the arrangement of a molded product of a high-attenuating rubber having different solid and hollow shapes.

FIG. 5 is a cross-sectional view showing an example of a case where the number of molded articles of high-damping rubber is reduced.

FIG. 6 is a cross-sectional view showing another example when the number of molded products of high-damping rubber is reduced.

FIG. 7 is a cross-sectional view for explaining a method of measuring a logarithmic decay rate.

FIG. 8 is a perspective view showing a conventional example using an oil damper.

FIG. 9 is a front view showing another conventional example using a viscous shear damper.

[Explanation of symbols]

 11 molded article of high attenuation rubber 12 cable-stayed bridge cable 13 fixing part 21 waterproof cover

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) E01D 11/04 E01D 1/00

Claims (5)

(57) [Claims] 1. A loss coefficient t at a shear strain of 10 to 30% at a symmetrical peripheral position around a cable stayed bridge cable near a fixing portion to which a base end of the cable stayed bridge cable is connected.
an δ is 0.3 to 1.0 and the shear modulus is 6 to 4
A cable-stayed bridge cable vibration damping device, wherein a molded article of high-attenuation rubber having a weight of 0 kgf / cm ² is arranged and interposed between a base end of the cable-stayed bridge cable and a fixing portion. 2. The high-damping rubber comprises a compound of one or more rubbers selected from natural rubber, polyisoprene rubber, polybutadiene rubber and butadiene styrene rubber, and has a loss factor tan δ of 0.5 or more. The cable-stayed bridge cable vibration damping device according to claim 1, wherein: 3. The vibration damping device for a cable-stayed bridge cable according to claim 1, wherein the molded article of high attenuation rubber is covered with rubber having excellent weather resistance. 4. The cable-stayed bridge cable vibration damping device according to claim 3, wherein the molded article of the high attenuation rubber is covered with a rubber which is excellent not only in weather resistance but also in ventilation blocking property. 5. The cable-stayed bridge cable according to claim 1, wherein a portion including a molded article of high-attenuation rubber interposed between a base end portion and a fixing portion is covered with a waterproof cover. 4. The vibration damping device for a cable-stayed bridge cable according to 4.