JPH11269818A - Aerodynamic damping device for box girder bridge with floor-slab overhang - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aerodynamic damping device for a box girder bridge, in which aerodynamic unstable vibrations generated in the box girder bridge with a floor-slab overhang, particularly a galloping as a kind of divergent vibrations dangerous to the bridge is used as an object to be inhibited, and maintenance inspection such as maintenance is not required and the weight of a metal is lowered by the reduction of wind load and which has the improved type shape of a box girder section considered to the landscape of the whole bridge and is formed in a design and can be utilized for a structural member. SOLUTION: An aerodynamic damping device 11 for the box girder bridge 10 with the floor-slab overhang has a box girder section 12 extended in the bridge axial direction and a floor slab section 3 overhung onto the top face of the box girder section 12 and the left and right of the top face of the box girder section 12, aiming at the installation of a corner-section forming section (a corner cut member 13 or a corner-notched member or the like) having a specified sectional shape to a box girder section 12 body. The corner-section forming section 13, in which a relative angle θ extends over 25-45 deg., is formed to the underside 12A of the box girder section 12 at that time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aerodynamic damping device for a box girder bridge with a slab overhang, and more particularly to an aerodynamic damping device for a box girder bridge with a slab overhang capable of reducing wind load. It is.

[0002]

2. Description of the Related Art Conventional vibration damping techniques for box girder bridges with overhanging floor slabs include, for example, a method of adding structural damping by a vibration damper (damper). This method has an effect on divergent vibration (galloping). Is small. As another damping method, there is an aerodynamic damping method in which a geometrically shaped aerodynamic damping member is installed.

For example, FIG. 6 is a cross-sectional view in a direction perpendicular to the bridge axis of a box girder bridge 1 with an overhang on a floor slab, showing a first example of a conventional aerodynamic damping structure in which a conventional aerodynamic damping member is installed. ing. The box girder bridge 1 with a floor slab overhang has a box girder part 2, a floor slab part 3, and a pair of deflectors 4 (aerodynamic damping members).

The box girder part 2 generates an exciting force due to the flow of air at the lower surface 2A thereof. Therefore, when the wind speed increases, the box girder bridge 1 with overhanging floor slabs may induce divergent vibration. Since the floor slab portion 3 projects left and right at a predetermined length on the upper surface of the box girder portion 2, especially when there is a cross wind from the left and right direction of the box girder bridge 1 with the floor slab overhang, The guiding action of the wind on both sides cannot be ruled out.

[0005] The deflector 4 is provided with a slight gap at the lower end corner 2B of the lower surface 2A of the box girder portion 2 and at the lower end corner 2B.
A pair is provided so as to surround B, and the air flow to the lower end of the box girder portion 2 is guided inside the deflector 4, and the separation flow can approach or reattach to the box girder portion 2 main body. . Therefore, by causing the reattachment phenomenon of the separated flow, it becomes possible to change a part of the exciting force into a damping force (change the phase characteristic), thereby reducing the total of the entire exciting force. In addition, it is possible to shift the wind speed at which the divergent vibration occurs to the high wind speed side.

FIG. 7 shows a second example of a conventional aerodynamic damping structure. In this box girder bridge 5 with overhanging floor slabs, a pair of skirt plates 6 are provided at lower end corners 2 B of the box girder 2. By providing the (aerodynamic damping member), the air current flows along the outside of the skirt plate 6, so that the box girder part 2 main body is similar to the case of the box girder bridge 1 with overhanging floor slab (FIG. 6). The separation flow can be approached or reattached.

FIG. 8 shows a third example of a conventional aerodynamic damping structure. In the box girder bridge 7 with overhanging floor slabs, the left and right of the box girder 2 and the lower part of the floor slab 3 are shown. By providing a pair of spoilers 8 (aerodynamic damping members) at a predetermined distance from the box girder portion 2, the airflow is forcibly separated at the end of the spoiler 8, and a box girder bridge with a slab overhang is provided. 1
As in the case of the box girder bridge 5 with overhang (FIG. 6) and the floor slab (FIG. 7), the separation flow can approach or reattach to the box girder 2 main body.

However, in the box girder bridges 1, 5, and 7 with the overhanging floor slabs of the respective configurations, the respective deflectors 4, the skirt plate 6 and the spoiler 8 are attached to the box girder portion 2 by a plate-like member. It is inevitable to take the appearance of a so-called "paste patch", and there is a problem that the overall design of the box girder bridges 1, 5, and 7 with overhanging floor slabs is significantly deteriorated. Furthermore, it is necessary to provide feedback to the design of the entire bridge again from the examination of the wind resistance including the damping structure, which leads to an increase in design cost and an increase in steel weight of the entire bridge. In addition, since the deflector 4, the skirt plate 6, the spoiler 8, and the like need to be mounted and held in a predetermined posture or form with respect to the box girder portion 2, there is a problem that maintenance and inspection such as maintenance is required.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is a kind of unstable aerodynamic vibration generated in a box girder bridge with a slab overhang, particularly a divergent vibration that is dangerous for a bridge. An object of the present invention is to provide an aerodynamic vibration damping device for a box girder bridge with a slab overhang, which suppresses certain galloping.

Another object of the present invention is to provide an aerodynamic vibration damping device for a box girder bridge with a slab overhang that does not require maintenance and inspection such as maintenance.

Another object of the present invention is to provide an aerodynamic vibration damping device for a box girder bridge with a slab overhang that can reduce the steel weight by reducing the wind load.

Further, the present invention has an improved shape of a box girder part in consideration of the whole bridge's scenery as well as its vibration damping measures, and is aerodynamically designed for a box girder bridge with a slab overhang which can be used for structural members. It is an object to provide a vibration damping device.

[0013]

That is, the present invention focuses on attaching a corner forming portion having a predetermined cross-sectional shape such as a corner cutout or a corner notch to a box girder main body. An aerodynamic vibration damping device for a box girder bridge with a slab overhang having an extended box girder portion, and an upper surface of the box girder portion and a floor slab projecting to the left and right of the upper surface of the box girder portion,
An aerodynamic vibration damping device for a box girder bridge with a slab overhang, characterized in that a corner forming portion having a relative angle of 25 to 45 degrees is provided on a lower surface of the box girder portion.

The corner forming section is for controlling the air flow by being attached to the lower surface of the box girder section, and can be formed by providing a corner cutout or a corner notch.

The relative angle is an angle formed by a straight line from the lower end corner of the lower surface of the box girder to the lower end corner of the corner forming portion and the lower surface of the box girder.

In the aerodynamic vibration damping device for a box girder bridge with a slab overhang according to the present invention, the box girder body is located near the center from both lower end corners of the box girder portion and has a corner cutout or a corner notch. Since the corner forming part having the cross-sectional shape of the box slab is formed, the air current caused by the wind flowing from the box girder with the slab overhang, especially from the direction perpendicular to the bridge axis, and further from the lower surface of the slab to the box girder part is formed. The air flow is guided to the corner forming portion on the lower surface of the box girder, thereby reducing the degree of the air flow separating from the surface portion of the box girder, and causing the separated flow to approach (reattach) to the main body side of the box girder. Can be. Therefore, the weight of steel can be reduced by reducing the wind load, and the cost of the product can be reduced. That is, by changing the lower shape of the box girder using a corner forming portion having a relative angle of 25 to 45 degrees, stabilization of wind resistance against divergent vibration is achieved, and its appearance is also changed to that of a conventional one. It can be better. In addition, it is possible to design the wind-stabilized cross section in advance, and it is possible to reduce the cost without requiring redesign. Furthermore, a lightweight member can be used for the corner forming portion, and it can be used as a post measure.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a box girder bridge 1 with a slab overhang provided with an aerodynamic damping device according to a first embodiment of the present invention.
0 will be described with reference to FIG. However, FIGS. 6 to 8
The same reference numerals are given to the same parts as those described above, and the detailed description thereof is omitted. FIG. 1 is a cross-sectional view of a box girder bridge 10 with a slab overhang, which is perpendicular to the bridge axis direction.
The zero aerodynamic damping device 11 is provided with a corner cutout 13 (corner forming portion) on the lower surface 12A of the box girder portion 12 corresponding to the box girder portion 2.

The corner cutout 13 is formed in a rectangular cross section, preferably at the center of the lower surface 12A, and having a relative angle θ in the range of 25 to 45 degrees. The relative angle θ is an angle formed by a straight line from the lower end corner 12B of the lower surface 12A to the lower end corner 13A of the corner cut portion 13 and the lower surface 12A. Further, as shown in the figure, the horizontal distance from the lower end corner 12B to the lower end corner 13A is, for example, 0.3
W1. This W1 is the width of the box girder portion 12.

The box girder 12 may be continuous or intermittent in the direction of the bridge axis. Further, the box girder portion 12 may be one box girder or two or more box girder in the width direction thereof, and the corner forming portion may be located in a space region therebetween.

FIG. 2 shows a conventional box girder bridge 1 with overhanging floor slabs.
4 is a cross-sectional view of the box girder bridge 10 with a slab overhang, which is different from the aerodynamic damping device 11 of the box girder 10 and has no corner cut portion 13 for comparison. That is, in the box girder bridge 14 with overhang on the floor slab, no corner cut portion 13 is provided on the lower surface 2A of the box girder portion 2, and the cross-sectional shape of the lower surface 2A is planar. The height H of the box girder part 2 is determined by the box girder part 12 in the aerodynamic vibration damping device 11 (FIG. 1) of the box girder bridge 10 with overhang on the floor slab.
And the total height of the corner cut portions 13.
Of course, in the aerodynamic damping device 11 (FIG. 1), the height of the box girder portion 12 itself can be arbitrary.

FIG. 3 is a cross-sectional view of a box girder bridge 20 with a slab overhang provided with an aerodynamic damping device according to a second embodiment of the present invention, which is perpendicular to the bridge axis direction. In the aerodynamic vibration damping device 21 of the girder bridge 20, the corner notch 2 having the relative angle θ of the corner notch 13 on the lower surface 12 </ b> A of the box girder 12.
2 (corner forming portion).

The corner notch 22 has a trapezoidal cross section, covers the lower surface 12A, and has a relative angle θ of 25 to 4.
It is desirable to be in the range of 5 degrees. The relative angle θ is an angle formed by a straight line (a slope of the corner notch 22) from the lower end corner 12B of the lower surface 12A to the lower end corner 22A of the corner notch 22 and the lower surface 12A, as in the case of FIG. is there. As shown in the figure, the horizontal distance from the lower end corner 12B to the lower end corner 22A is, for example, 0.3W1.

The aerodynamic vibration damping device 11 (FIG. 1) for the box girder bridge 10 with the slab overhang and the box girder bridge 2 with the slab overhang are provided.
Each of the changed portions (corner cut portion 13 and corner notch portion 22) of the aerodynamic vibration damping device 21 (FIG. 3) is made part of the structural member of the box girder portion 2 or separately formed of a lightweight material. In addition to being a member, it is also possible to adopt other shapes.

FIG. 4 is a box girder bridge 1 with an overhang of the floor slab of FIG.
4. Galloping occurrence with respect to the relative angle θ in each case of the box girder bridge 10 with a slab overhang (aerodynamic damping device 11) in FIG. 1 and the box girder bridge 20 with a slab overhang (aerodynamic damping device 21) in FIG. FIG. 4 is a graph showing the relationship between wind speeds. In FIG. 4, the uppermost graph is the case where the angle of attack α is −3 degrees, the middle graph is the case where the angle of attack α is 0 degrees, and the lowermost graph is The case where the angle of attack α is +3 degrees is shown. The angle of attack α is the box girder bridge 10, 1
4 and 20 are angles with respect to the horizontal direction of the wind entering from the left and right side directions (see FIG. 1). Galloping generation wind speed is a dimensionless one-sided amplitude (Amp / W
2) The wind speed at the time. Amp is one-sided amplitude in only one direction (plus direction or minus direction) of vibration generated in the bridge, and W2 is the width of the floor slab portion 3.

As shown in the graph of FIG. 4, the box girder bridge 10 with the slab overhang (the aerodynamic vibration damping device 11) and the box with the slab overhang are compared with the case of the conventional box girder bridge 14 with the overhang. In any case of the girder bridge 20 (the aerodynamic damping device 21), when the relative angle θ is in the range of 25 to 45 degrees, the galloping generated wind speed is large, that is, galloping (divergent vibration) is caused by the airflow flowing on the bridge surface. )
It can be seen that the occurrence of vibration is less likely to occur, and there is a damping effect on galloping.

FIG. 5 is a three-component curve showing the values of drag coefficient (CD), lift coefficient (CL) and aerodynamic moment (CM) with respect to the angle of attack α. However, CD = PD / (1/2 · ρ · V 2 · L · An) CL = PL / (1/2 · ρ · V 2 · L · W2) CM = M / (1/2 · ρ · V ² · L · W2 ² ), where the drag coefficient (CD) reflects the effect of wind load and has a greater effect on bridge design than other coefficients. The lift coefficient (CL) relates to the force applied from the vertical direction of the bridge, and the aerodynamic moment (CM) relates to the rotational or torsional force on the box girder 2. Where P
D is the drag, PL is the lift, M is the aerodynamic moment, ρ is the air density, V is the wind speed, L is the length of the bridge, and An is the area of the projection on the side of the bridge with respect to a length of 1 meter.

As can be seen from FIG. 5, the angle of attack α is −14.
In the range of up to +14 degrees, the drag coefficient (CD), the lift coefficient (CL) and the aerodynamic moment (CM) are all smaller than those of the conventional box girder bridge 10 with overhang. The aerodynamic damping device 11 is higher, and particularly the drag coefficient (CD) is 0.85 to 0.8.
It can be seen that there is a reduction effect of 51 and 40%, and it is possible to reduce the wind load.

[0028]

As described above, according to the present invention, since a corner forming portion such as a corner cut portion or a corner notch portion is provided on the lower surface of the box girder portion, cost can be reduced without redesign.
In addition, the steel weight can be reduced by reducing the wind load, and the cost of the product can be reduced. Furthermore, it is possible to design a bridge that is good in design, and it is possible to design in consideration of the landscape.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a box girder bridge 10 with a slab overhang provided with an aerodynamic damping device 11 according to a first embodiment of the present invention, which is perpendicular to the bridge axis direction.

FIG. 2 is a cross-sectional view of a conventional box girder bridge 14 with a slab overhang, and an aerodynamic vibration damping device 11 for a box girder bridge 10 with a slab overhang.
A structure in which no corner cut portion 13 is provided unlike the above is shown for comparison.

FIG. 3 is a cross-sectional view of a box girder bridge 20 with a slab overhang provided with an aerodynamic damping device 21 according to a second embodiment of the present invention, which is perpendicular to the bridge axis direction.

4 is a box girder bridge 14 with a slab overhang of FIG. 2, a box girder bridge 10 with a slab overhang of FIG. 1 (aerodynamic damping device 11), and a box girder bridge 20 with a slab overhang of FIG. Device 2
It is a graph which shows the relationship of the galloping generation wind speed with respect to the relative angle (theta) about each case of 1).

FIG. 5 is a three-component curve plotting values of a drag coefficient (CD), a lift coefficient (CL), and an aerodynamic moment (CM) with respect to an angle of attack α.

FIG. 6 is a cross-sectional view in a direction perpendicular to the bridge axis of the conventional box girder bridge 1 with overhanging floor slabs, showing a first example of an aerodynamic damping structure in which a conventional aerodynamic damping member is installed. .

FIG. 7 is a cross-sectional view perpendicular to the bridge axis of a box girder bridge 5 with a conventional floor slab overhang, showing a second example of the conventional aerodynamic damping structure.

FIG. 8 is a cross-sectional view in a direction perpendicular to the bridge axis of a conventional box girder bridge 7 with overhanging floor slabs, showing a third example of the conventional aerodynamic vibration control structure.

[Explanation of symbols]

1 Box girder bridge with overhang on floor slab (Fig. 6) 2 Box girder 2A Lower surface of box girder 2B Lower corner of box girder 2 3 Floor slab 4 Pair of deflectors (aerodynamic damping member) 5 Floor slab Box girder bridge with overhang (Fig. 7) 6 A pair of skirt plates (Aerodynamic damping member) 7 A box girder bridge with floor overhang (Fig. 8) 8 A pair of spoilers (Aerodynamic damping member) 10 Box with floor overhang Girder bridge (FIG. 1) 11 Aerodynamic damping device for box girder bridge 10 with overhang on slab (first embodiment, FIG. 1) 12 Box girder part 12A Lower surface of box girder part 12B Lower corner of lower surface 12A 13 Corner cut part (corner formation part) 13A Lower end corner of corner cut part 13 Box girder bridge with floor slab overhang (FIG. 2) 20 Box girder bridge with floor slab overhang (FIG. 3) 21 Box girder bridge with floor slab overhang 20 aerodynamic damping device (second embodiment, FIG. 3) 22 corner notch (corner formation) ) Lower corners θ relative angle 22A corner cutting section 22 (a lower end corner portion 12B of the lower surface 12A of the box girder 12
From the lower surface 12A of the corner cut portion 13 to the lower end corner 13A (the lower end corner 22A of the corner notch 22) and the lower surface 12A. Α Attack angle (box girder bridges 10, 14, 20 with overhanging floor slabs)
W1 Width of box girder 12 W2 Width of floor slab 3 H Height of box girder 2 CD Drag coefficient CL Lift coefficient CM Aerodynamic moment

Claims (3)

[Claims] 1. An aerodynamic control system for a box girder bridge with a slab extension, comprising: a box girder extending in the bridge axis direction; and an upper surface of the box girder and floor slabs projecting to the left and right of the upper surface of the box girder. An aerodynamic vibration damping device for a box girder bridge with a slab overhang, wherein a corner portion forming a relative angle of 25 to 45 degrees is provided on a lower surface of the box girder portion. 2. The aerodynamic vibration damping device for a box girder bridge with a slab overhang according to claim 1, wherein the corner forming portion is formed by providing a corner cut portion. 3. The aerodynamic vibration damping device for a box girder bridge with a slab overhang according to claim 1, wherein the corner forming portion is formed by providing a corner notch.