JPH09273113A - Large span suspension bridge by cable system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the wind-resistant property, by arranging three or more cables symmetrically in the right and left sides with level differences from each other viewed from the bridgeaxial section and providing a plurality of frames retaining the arrangement reration in the bridge-axial direction. SOLUTION: A pair of upper stage cables 3 provided at the tower tops 2a of tower columns 2 and a pair of lower stage cables 4 provided at the outside steps 2b in the lower side face of the tower columns than the tower tops 2a, are arranged symmetrically in the right and left sides viewed from the bridge- axial section so as to have a level difference H and a breadthwise distance D. Hangers 5, 6 are suspended from the cables 3, 4 and the lower ends thereof are connected to a reinforcing girder 1 and a plurality or shape-retaining frames 7 to unchangeably keep the arrangement relation of respective cables 7 are fitted between the cables 3, 4 to increase the restrictive conditions. In this way, the tortional rigidity can be remarkably improved and the wind-resistant stability can be economically improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long suspension bridge, and more particularly to a structure of a long suspension bridge using a cable system for improving wind resistance stability in a windstorm of a long suspension bridge having a main span of 2000 m or more. .

[0002]

2. Description of the Related Art In a long suspension bridge having a main span of 2000 m or more, the wind resistance stability in a storm is a problem. As a means for securing this wind resistance stability,
There are many expectations for the cross-sectional rigidity of stiffening girders, especially the torsion constant. Therefore, for stiffening girders, the truss type has a large drag coefficient and a large force received from the wind, so the steel weight also increases to resist this. On the other hand, the flat box girder type has the advantage that the drag coefficient is small and the steel weight can be reduced accordingly, and the box girder type is said to be effective.

On the other hand, in the case of a long suspension bridge, it is difficult to provide sufficient stability against twisting and flutter by simply supporting a flat box girder with a normal hanger.
A means to secure wind resistance stability by increasing the girder height and plate thickness in the box girder form, and a means to temporarily add mass to a part of the box girder during a windstorm as a means to cope with this twist flutter. , Means for providing a cross hanger between the cable and the bridge girder, or means for reducing the self-excited aerodynamic force are already known.

[0004]

The various means proposed in the prior art as described above, even if some improvement in twist flutter is recognized, increase the weight of the stiffening girder, reduce the weight of the cable, and lower the girder. As for the structure, there is a problem such as an increase in weight, and there is room for consideration from the economical viewpoint, so it can be said that there is a problem in practicality. Further, the proposal to improve the wind resistance stability by improving the cable system has not been a significant improvement measure with the conventional one.

[0005]

SUMMARY OF THE INVENTION In view of the structural problems of the conventional long suspension bridge as described above, the present invention has an improved cable system to significantly improve the torsional rigidity and economically windproof. The purpose is to provide a long suspension bridge structure that can improve stability.

The invention of a long suspension bridge using a cable system according to claim 1 is, as a specific means therefor, that the cables are symmetrically arranged at least three or more in a height difference when viewed in a cross-sectional direction orthogonal to the bridge axis. It is characterized in that a plurality of shape retaining frames for maintaining the arrangement relationship of the cables constant are provided between the respective cables in the bridge axis direction.

According to the invention of the long suspension bridge by the cable system of claim 2, a plurality of cables are arranged with a height difference on each side viewed from the cross-sectional direction orthogonal to the bridge axis, and a plurality of cables with the same arrangement on the other side. It is characterized in that a shape holding frame for holding the arrangement relationship of these cables is provided between the cables on both sides including.

According to the invention of the long suspension bridge by the cable system of claim 3, the cable has three cables by two cables on both sides when viewed from the cross-sectional direction orthogonal to the bridge axis and one cable at the center having a height difference with these. And a shape holding frame for holding the triangular arrangement relation of these cables is provided between the three cables.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of a long suspension bridge using a cable system according to the present invention will be described with reference to an embodiment shown in the drawings. FIG. 1 is a cross-sectional view of the suspension bridge as a first embodiment as seen from a direction orthogonal to the bridge axis. 1 is a stiffening girder, 2 is a tower pillar, and this tower pillar 2 is provided with four cables 3, 4, 3, 4 on each of the left and right sides of the tower top 2a. ing.

These cables consist of an upper stage cable 3 on the tower top 2a on one side when viewed from the cross-sectional direction orthogonal to the bridge axis.
And a lower cable 4 on the outer step portion 2b on the side surface of the tower below the tower top portion 2a are arranged so as to have a height difference H and a lateral width interval D, and a plurality of cables 3 of the same arrangement on the other side. , 4 including the cables 3, 4, 3, 4 at the left and right symmetrical positions on both sides, the four cables form a square (trapezoidal) cross-section arrangement relationship.

Hangers 5 and 6 are hung from the four cables 3, 4, 3 and 4, respectively, and their lower ends are connected to both side portions of the stiffening girder 1 below. , 4, 3, 4 are provided with a plurality of shape holding frames 7 for keeping the arrangement relationship of these cables constant in the bridge axis direction.

The shape-retaining frame 7 has a trapezoidal cross-section arrangement relationship between the four cables 3, 4, 3, 4;
Any structure that can be integrally connected and held by one structural surface made of a material such as a beam, a girder, a metal plate, and a PC steel wire may be used.

In this embodiment, as shown in FIGS. 3 and 4, the shape-retaining frame 7 is formed in the shape of a box girder having a predetermined thickness W along the length direction of the cables 3 and 4, and the four corners are provided at the four corners. The cable through-holes 8 are opened respectively, but the cable through-holes 8 are different diameter holes having a small inner diameter R1 at the central portion and a large inner diameter R2 at both end portions, so that the cables 3 and 4 have the through-holes 8 respectively. It is relatively free to move inside, and at the upper and lower ends of the through hole 8 there are provided locking projections 9 for connecting the shape holding frame 7 to predetermined positions for the cables 3 and 4. ing.

The shape-retaining frame 7 includes cables 3,
It is not necessary to provide it over the entire length of 4, 3, 4 and, as shown in FIG. 2, a plurality of, for example, about 6 places may be provided in the portions adjacent to the column 2 in the main span and the side span. . Further, the position where the shape retaining frame 7 is attached to the cables 3, 4, 3 and 4 is preferably a portion where the hangers 5 and 6 are suspended, but four cables as in the trapezoidal arrangement relationship described above. Among them, when the upper cable 3 is located inside the cross section, the hanger 5 suspended from the upper cable 3 comes into contact with the shape-holding frame 7, so that the shape-holding frame 7 as shown in FIG. 7 is attached to a front or rear position separated from the suspended parts of the hangers 5 and 6.

5 and 6 show the cables 3, 4,
It is an embodiment showing another mounting structure of the shape retaining frame 7 for the cables 3, 4, and in this case, the respective cables 3, 4,
By attaching the hanging metal fitting 11 to the cables 3 and 4 via the cable band 10 and connecting the tip of the hanging metal fitting 11 to the shape holding frame 7 via the pin 12, the shape holding frame 7 is attached to each cable. To be In this case,
In the relationship between the upper cables 3 and 3 and the hanging fitting 11, the hanging fitting 11 is attached downward, but the lower cables 4 and
4 and the hanging metal fitting 11, the hanging metal fitting 11 is attached upward and the shape holding frame 7 is attached between the respective cables 3, 4, 3, 4.

FIG. 7 shows another embodiment showing the relationship between the cable and the shape-retaining frame. In this case, the cable has two cables 3 on both sides when viewed from the cross-sectional direction orthogonal to the bridge axis.
3 and one of the cables 4 at the center having a height difference from these cables, and the three cables are arranged in a triangular arrangement.
The same shape holding frame 7 for holding the triangular arrangement relationship of these cables between the three cables 3, 3, 4
Is provided.

Further, even in the case of using four cables as shown in FIG. 8, unlike the case of FIG. 1, the arrangement relationship of the inverted trapezoid is such that the upper cable 3 is outside the cross section and the lower cable 4 is inside the cross section. The present invention can be applied to such a structure, or a structure in which three cables are provided on each side and six cables in total as shown in FIG. Note that reference numeral 13 in the drawing is a lightweight opening hole.

[0018]

In the long suspension bridge using the cable system of the present invention, at least three or more cables are arranged with a height difference H when viewed from the cross-sectional direction, and the arrangement shape and spacing between these cables are fixed and held by the shape holding frame. Therefore, the twisting constant can be significantly improved by increasing the restraint of each cable.

The example of FIG. 1 was examined 5
Vibration characteristics were analyzed by an analytical model of a long span suspension bridge.
The outline is as follows: 3 spans of main span length 3000m, side span length 1500m, cable is 2 double cables on each side, the center distance of the cable is 38m in the upper stage, 48m in the lower stage, therefore the distance between the double cables on one side is 5m, Height difference is 15
m. The upper and lower cables have a sag ratio of 1/10 so that the initial tensions of all four cables are the same. For the analytical model, eigenvalue analysis was performed using a three-dimensional frame model.

For comparison, Case 0 as a basic system having no shape-holding frame, and the shape-holding frame between the main diameters were provided at eight locations at intervals of 236 m and 118 m from the L / 4 point to the tower side. Case 4 was compared with case 1, case 2 provided with 14 similar shape retaining frames, and case 3 provided with 18 similar shape retaining frames. The stiffening girder is a flat hexagonal box girder with a girder height of 7 m. Table 1 shows the structural specifications of its main structure, Table 2 shows the relationship between weight and polar moment of inertia, and Table 3 compares the vibration characteristics of each case. Show.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

Focusing on the cable system and the shape-retaining frame, the flexural and torsional frequencies and the flutter limit wind velocity by the Selberg formula were determined for the above-mentioned 5-span long suspension bridge.

From the analysis results shown in Table 3, there is no great difference in flexural frequency between the four cases. However, the torsion frequency is significantly affected by the installation of the shape-retaining frame, and it can be seen that the torsion frequency is improved. When this shape-maintaining frame is installed in 8 places between the main diameters, the flutter limit wind speed is 31.7% and 35.7 at 14 places.
%, It was improved by 40.5% at 18 places, and it was found that the system of the present invention has a large effect of improving wind resistance stability as compared with the cable system which has been studied recently.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a long suspension bridge formed by a cable system according to the present invention as seen from a direction orthogonal to a bridge axis.

FIG. 2 is a side view of a main span portion of the suspension bridge.

FIG. 3 is a partial front view showing a relationship between a cable and a shape holding frame.

4 is a cross-sectional view taken along the line AA of FIG.

FIG. 5 is the same partial front view as FIG. 3 in another embodiment.

6 is a cross-sectional view taken along the line BB in FIG.

FIG. 7 is a front view showing another embodiment of the shape retaining frame.

FIG. 8 is a front view showing another embodiment of the shape retaining frame.

FIG. 9 is a front view showing still another embodiment of the shape retaining frame.

[Explanation of symbols]

 1: Stiffening girder 2: Tower pillar 2a: Tower top 2b: Step portion 3,4: Cable 5,6: Hanger 7: Shape holding frame 8: Through hole 9: Locking protrusion 10: Cable band 11: Hanging metal fitting 12 :pin

Claims (3)

[Claims] 1. A cable is composed of at least three or more symmetrical arrays having a height difference when viewed in a cross-sectional direction orthogonal to a bridge axis, and maintains a constant array relationship between the cables. A long suspension bridge with a cable system, characterized in that a plurality of shape retaining frames are provided in the bridge axial direction. 2. A plurality of cables are arranged on each side with a height difference on one side when viewed in a cross-sectional direction orthogonal to the bridge axis, and between these cables on both sides including a plurality of cables of the same arrangement on the other side. The long suspension bridge by the cable system according to claim 1, further comprising a shape-retaining frame for maintaining the arrangement relationship of the cables. 3. The cable has a triangular arrangement relationship of three by two on both sides when viewed in a cross-sectional direction orthogonal to the bridge axis and one in the center having a height difference with these, and between the three cables. The long suspension bridge according to the cable system according to claim 1, further comprising a shape holding frame for holding the triangular arrangement relationship of these cables.