JPH1171712A - Cable stayed bridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To retain the weight of girders and increase the resistance against the torsional deformation and the stability against wind, by providing a pair of crossing cables diagonally connecting the side end of one face of a main tower and the side end of the other face of a main girder, in a two-face hanging type. SOLUTION: The main towers T1, T2 side and the main girder side vibrate in the reverse phase in the distance between T1a-Gb, and T1b-Ga at the torsional vibration of the main girder G and a relative deformation is brought. Hence, crossing cables are installed between both sides to restrict the the relative displacement and the displacement of the girders. When crossing cables are installed between the main towers T1, T2 and the main girder G, the girder vibrates around the main towers T1, T2 at the torsional deformation of the girder. Hence, a horizontal vibration is accompanied by the torsional deformation of the girder, in the structure. The resistance of the horizontal deflective rigidity of the girder against the torsional deformation and the resistance of the pneumatic force acting on the girder against the torsional vibration at the horizontal vibration increase respectively. In this way, the torsional vibration number and the wind speed bringing about fluttering can be increased. Hence, the stability against wind can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving the wind resistance of a cable stayed bridge.

[0002]

2. Description of the Related Art In cable-stayed bridges, wind stability is often a problem. The most important issue in the design of a cable-stayed bridge is flutter that causes divergent vibration at high wind speeds, and it must be designed so that this flutter does not occur within the design wind speed range. That is, it is particularly important to take measures to sufficiently increase the wind speed at which flutter occurs.

[0003] As a method for improving the wind speed exhibiting the flutter, a method of increasing the torsional rigidity of the girder, changing the shape of the fairing, installing a damper, and the like are conventionally known. It can be broadly classified into the following methods (Japan Road Association, “Road Bridge Wind Resistant Design Handbook” p.143, July 1991).・ Increase the rigidity of the bridge girder ・ Increase the weight of the bridge girder ・ Change the aerodynamic force generated by the wind (for example, change the cross-sectional shape of the girder) ・ Increase the damping (for example, by installing a damper) In order to increase the rigidity of the girder, the flutter generated on the cable-stayed bridge is mainly caused by the torsional vibration of the girder. Therefore, measures to increase the torsional rigidity of the girder are taken. Regarding the torsional rigidity of the girder, in addition to the torsional rigidity of the girder itself, the way in which the cable stayed bridge cable is tensioned also has an effect. In other words, the cable-stayed bridge cable suspension type is that the two-sided suspension type that supports the girder at both ends of the girder is more resistant to the torsional deformation of the girder than the single-sided suspension type that collects the cable at the center of the girder. Therefore, the rigidity of the spar against torsional deformation is increased. Therefore, when torsional rigidity is required, a two-sided suspension type is always adopted.

When increasing the torsional rigidity of a cable-stayed bridge, a method of increasing the torsional rigidity of a girder is usually employed. Regarding measures for cables, there is a measure to control the vibration of the main tower of the cable-stayed bridge by installing the cables so that they cross each other (Japanese Utility Model Laid-Open No. 7-10013).
No measures have been taken to reduce the vibration of the main girder of the cable stayed bridge.

[0005]

In the conventional method for increasing the torsional frequency, the method for increasing the torsional rigidity of the girder increases the girder weight, so that the diameter of the cable supporting the girder increases and the rigidity of the main tower increases. This increases the rigidity of the base of the main tower, causing a problem in economics.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems relating to economy, and increases resistance to torsion deformation of a girder without increasing weight of the girder, thereby improving wind resistance stability. The purpose is to:

[0007]

The cable-stayed bridge according to the present invention comprises:
A cable-stayed bridge of the two-sided suspension type is characterized by comprising at least one pair of crossover cables that diagonally connect one end of the main tower to the other end of the main girder. It also comprises a pair of horizontal cables that connect the main towers horizontally on the same side. Further, a horizontal cable and a cross cable are provided side by side.

In the cable-stayed bridge of the two-sided suspension type, the cable stayed cable expands and contracts to resist the deformation of the main girder due to the torsion deformation of the girder, but the main tower also deforms due to the expansion and contraction of the cable stayed cable.
Resists torsional deformation of girders. Now, the cable stayed bridge shown in FIG. 1 will be described as an example. In FIG. 1, two tower columns T1
a and T1b are represented by T1, two columns T2a and T
The main tower composed of 2b is T2, and the ends of the main girder G are Ga and Gb (subscripts a and b indicate both sides in the cross-sectional direction with respect to the center of the bridge). One end of the girder (eg, Ga
Cable) fixed on the same side of the tower (for example, on the T1a side).
When a girder generates torsional vibration, a pair of cable stays installed at both ends of the girder and a pair of tower columns connected to the cable stay cable alternately generate tension and compression. For example, a cable stayed cable connecting T1a-Ga and T2a-
When a tensile force acts on the cable staying cable connecting Ga, the cable staying cable connecting T1b-Gb and T2b-
A compression force acts on the cable staying cable connecting Gb. Accordingly, the cable stayed cable C generated by the torsional deformation of the spar
Due to the fluctuation of the tension, the main towers T1 and T2 also undergo torsional deformation.

FIG. 2 shows this state. The torsional deformation of the main girder and the main tower changes the distance between the top of the tower and the end of the main girder. For example, considering the distance between the tower top and the center of the center span of the main girder, when the Ga side is displaced downward, the Gb side is displaced upward due to torsional deformation. Therefore, accordingly, the T1a, T2a side is on the center span side, and the T1b,
The T2b side is deformed to the side span side.

In the present invention, a pair of cables C1a and C1b (T1a-
By adding Gb, T1b-Ga connecting cables crossing each other, the main tower is resistant to torsional deformation caused by torsional deformation of the main girder. That is, as shown in FIG. 2, during the torsional vibration of the spar, between T1a and Gb, between T1b and G1.
The distance between a and the main tower side and the main girder side vibrate in opposite phases, so that a relative displacement occurs. Therefore, by installing the cross cable between the two members where the relative displacement occurs, the relative displacement is restricted, which restricts the displacement of the girder.

Further, when a cross cable is installed between the main tower and the main girder, as shown in FIG. 3, the girder vibrates around the main tower when the girder is torsionally deformed. The structure is accompanied by vibration (see FIG. 3B). Therefore, it can be expected that the horizontal deflection rigidity of the spar resists torsional deformation, and that the aerodynamic force (which always becomes a damping force) acting on the spar during horizontal vibration resists torsional vibration. Therefore, the effect of resisting the torsional vibration of the girder is increased by merely crossing and installing a part of a normal cable stayed cable in addition to crossing the cables additionally.

Further, when one cable becomes thicker, the cable is divided into two cables (a so-called double cable), and even in such a case, the same cable can be obtained by crossing the inner cables. The effect is obtained.

The main towers T1a-T2a, T1b-T2
By connecting the cables b with a horizontal cable, it is possible to resist the torsional vibration of the spar. That is, as described with reference to FIG. 2, the distance between T1a and T2a and the distance between T1b and T2b fluctuate with the torsional vibration of the spar, and a relative displacement occurs. By connecting with a pair of horizontal cables so as to restrain the relative displacement, the deformation of the main tower and the torsional deformation of the girder can be restrained. According to the above-described method, it is possible to increase the rigidity of the main girder when the main girder is twisted, and as a result, it is possible to improve the torsional frequency and to increase the flutter developing wind speed. That is, wind resistance is improved.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 4 is a conceptual diagram of the cable stayed bridge according to Embodiment 1 of the present invention. The figure shows a cable-stayed bridge of three spans, a main tower T1 having two tower columns T1a and T1b,
A main tower T2 having two tower columns T2a and T2b;
And the cable-stayed cable C, the main tower T
A pair of main cables C1a and C1b, and a pair of main cables C2a and C2b are additionally installed between the main girder G and the main tower T2 and the main girder G, respectively.
A pair of auxiliary cables C1sa and C1sb, C2sa and C2
sb are crossed and additionally installed. That is, the main cable C1a diagonally connects the end of the left tower T1a of the main tower T1 and the right end Gb of the main girder G, and the main cable C1b is connected to the end of the right tower T1b and the left end of the main girder G. Part Ga
Are connected diagonally. The main cables C2a and C2b have the same connection relation, and the main columns T2a and T2b of the main tower T2 have the same connection relationship.
And the end of the main girder G are connected diagonally. As a result, the pair of main cables C1a, C1b and the pair of main cables C2a, C2b are installed crossing each other. The auxiliary cables C1sa, C1sb, C2sa, and C2sb are installed to prevent the balance between the horizontal tension on the central span and the horizontal tension on the lateral span acting on the main tower due to the additional installation of the main cable. Is done. The main cable and the auxiliary cable are preferably installed symmetrically with respect to the main tower.

The operation of this embodiment will be described by taking the main tower T1 as an example. By additionally installing the main cables C1a and C1b, it is possible to resist the torsional deformation of the main tower T1 due to the torsional deformation of the main girder G. That is, at the time of the torsional vibration of the girder, the distance between T1a-Gb and the distance between T1b-Ga vibrate in opposite phases on the main tower side and the main girder side, so that relative displacement occurs.
When the displacement between T1a and Gb increases, the main cable C1a resists. On the other hand, when the displacement between T1b and Ga increases, the main cable C1b resists and reduces the relative displacement. Therefore, according to the configuration of the present embodiment, the resistance to the torsional deformation of the bridge girder can be increased, and the fluttering wind speed can be increased.

In the present embodiment, the main cable has one stage, but it may be installed in two stages, upper and lower, or more stages as shown in FIG. In FIG. 5, a normal cable stayed cable is omitted.

Embodiment 2 FIG. FIG. 6 is a conceptual diagram of a cable stayed bridge according to Embodiment 2 of the present invention. Here, unlike the first embodiment, a crossover cable is formed by changing one of the connecting surfaces for the main tower and the main girder to the other surface side using a normal pair of cable-stayed cables C. Intermediate uppermost cable Cu1a, Cu1b (main tower T1 side), Cu2
a, Cu2b (main tower T2 side) is installed as a crossover cable. When crossing cables are installed between the main tower and the main girder,
At the time of the torsional vibration of the girder, the girder vibrates around the main tower, so that the structure is coupled to the horizontal deflection vibration of the girder. Therefore, the horizontal deflection rigidity of the girder contributes to the suppression of torsional deformation, thereby increasing the resistance of the girder to torsional vibration, and furthermore, the aerodynamic force acting on the girder during horizontal vibration (always a damping force) can be expected. By increasing the torsional rigidity and the aerodynamic force acting as the damping force, it is possible to increase the fluttering wind speed.

Embodiment 3 FIG. 7 is a conceptual diagram of a cable stayed bridge according to Embodiment 3 of the present invention. In FIG. 7, a normal cable stayed cable is omitted. Here, the first embodiment
Unlike this, a pair of horizontal cables C3a and C3b connecting the main towers on the same surface side is added. Also, the addition of the horizontal cables C3a and C3b breaks the balance between the horizontal tension on the central span and the horizontal tension on the lateral span acting on the main tower. Cables C3as1, C3bs1 (main tower T1 side), C3
as2 and C3bs2 (main tower T2 side) are installed.
At the time of the torsional vibration of the girder, the interval between the main towers T1a-T2a, T
The distance between 1b and T2b varies with the torsional vibration of the girder,
A relative displacement occurs. By connecting the main towers with horizontal cables C3a and C3b so as to restrain the relative displacement, the torsional vibration of the girder can be restrained. Also, cross cables C1a-C1b, C connecting the main tower and the main girder.
The functions and effects of 2a-C2b are the same as those of the first embodiment.
Therefore, according to the configuration of the present embodiment, the rigidity of the girder at the time of torsional vibration can be increased, so that the fluttering wind speed can be increased.

Note that the horizontal cable is installed in parallel with FIG.
This is also possible for the cable-stayed bridge shown in FIG.

[0020]

As described above, according to the present invention, the twisting of the girder can be achieved only by installing the cross cable that restrains the relative displacement between the main tower and the girder or the horizontal cable that restrains the relative displacement between the main tower and the girder. The resistance at the time of vibration is increased, and as a result, the torsional frequency is improved, so that the fluttering wind speed can be increased. Further, since the total weight of the bridge is not increased unlike the conventional method of increasing the torsional rigidity of the girder, the bridge is economically excellent.

[Brief description of the drawings]

FIG. 1 is a conceptual view of a cable stayed bridge according to the present invention.

FIG. 2 is a diagram showing the behavior of each member during torsional vibration.

FIG. 3 is a diagram illustrating an effect of a cross cable.

FIG. 4 is a conceptual diagram of the cable stayed bridge according to Embodiment 1 of the present invention.

FIG. 5 is a diagram showing a case where crossover cables are installed in two stages.

FIG. 6 is a conceptual diagram of a cable stayed bridge according to Embodiment 2 of the present invention.

FIG. 7 is a conceptual diagram of a cable stayed bridge according to Embodiment 3 of the present invention.

[Explanation of symbols]

T1, T2: Main tower T1a, T1b, T2a, T2b: Tower G: Main girder C: Cable stay cable C1a, C1b, C2a, C2b: Main cable C1sa, C1sb, C2sa, C2sb: Auxiliary cable Cu1a, Cu1b, Cu2a , Cu2b: uppermost cable C3a, C3b: horizontal cable C3as1, C3bs1, C3as2, C3bs2: auxiliary cable

Claims (3)

[Claims] 1. A cable-stayed bridge of a two-sided suspension type, comprising at least one pair of crossover cables diagonally connecting one end of a main tower and one end of a main girder diagonally. Cable-stayed bridge. 2. A cable-stayed bridge of a two-sided suspension type, comprising a pair of horizontal cables for connecting the main towers horizontally on the same side. 3. The cable-stayed bridge according to claim 1, further comprising the pair of horizontal cables.