JPH01312106A - Cable stayed bridge - Google Patents

Abstract

PURPOSE:To reduce a compressive force working on a main girder and reduce the number of diagonal members by a method wherein the upper end section of the main tower of a cable stayed bridge is projected in the longitudinal direction of the main girder, and wherein the diagonal members overhang from the upper end section, and wherein angles crossed between the diagonal members and the main girder are made small. CONSTITUTION:A cable stayed bridge is basically composed of a main tower 1, a main girder 2, diagonal members 4 overhung slantwise between the main tower 1 and the main girder 2, and a connecting member 3. The main tower 1 is formed with an upper section opened in the shape of V, and both the upper end sections are arranged in the overhanging direction and in the longitudinal direction of the main girder 2. Besides, both the end sections of the main tower 1 are connected to each other with the connecting member 3. For the connecting member 3, PC steel wires may be used, or a normal girder member may be used, or a member resisting tension should be used. As a result, a compressive force working on the main girder is reduced, and a suspending force can be made greater, and the number of the skew members can be decreased.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a cable-stayed bridge.

[Prior Art] A cable-stayed bridge is a bridge in which a main girder C is lifted by diagonal members extending diagonally from an erected main tower a.

As conventional cable-stayed bridges, those shown in FIGS. 4 and 5 have been developed.

That is, the main tower a stands vertically from the bottom to the top, and diagonal members are diagonally extended from the vertical top of the main tower a.

[Problems to be solved by this invention]

In a cable-stayed bridge as described above, the height h from the main girder C to the top of the main tower a is approximately twice (2h) the length l from the main tower a to the highest point of the stay beam. ing. Therefore, even if the tension T is introduced into the diagonal members, the lifting force for the main girder C can only be obtained by about 172 of this tension T.

Therefore, in order to lift the main girder C, many diagonal members are required, which increases the labor and cost of construction.

In addition, most of the tension T in the diagonal members becomes a force (horizontal force) that pulls the main girder C toward the main tower a, and a large compressive force acts on the portion of the main girder C near the main tower a from the left and right. Therefore, the portion of the main girder C near the main tower a must have a structure that can withstand this excessive compressive stress, and in order to make the main girder C high in strength, construction becomes extensive and costs increase.

This invention was made to solve the above-mentioned problems, and provides a cable-stayed bridge that is easy to construct and has a low construction cost by reducing the number of diagonal members and simplifying the structure of the main girder. The purpose is to

[Means to solve the problem]

In the cable-stayed bridge according to the present invention, at least the upper end of the main tower projects along the longitudinal direction of the main girder, and the main girder is lifted by diagonal members extending from the main tower.

[For production]

The length ρ of the diagonal member from the overhang of the main tower to the connecting portion to the main girder becomes shorter, and the crossing angle of the diagonal member with respect to the main girder becomes larger.

Therefore, the horizontal component of the tensile force of the diagonal member is small, and the lifting force is large.

Therefore, the number of diagonal members can be reduced, and the strength of the main girder does not need to be increased too much.

〔Example〕

Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.

In FIG. 1, 1 is a main tower, and the upper part above the main girder 2 is formed into a V shape.

The upper end of the main tower 1 extends in a direction in which the upper end extends along the longitudinal direction of the main girder 2.

A horizontal PC steel material 3 parallel to the longitudinal direction of the main girder 2 is stretched over the top of the character-shaped main tower 1, and receives the tensile force of the left and right diagonal members 4, 4.

As described above, diagonal members 4.4 are diagonally extended from the upper end of the main tower 1. In this way, the upper part of the main tower 1 has a V shape and overhangs in the longitudinal direction of the main girder 2, and the diagonal member 4 of the main girder 2
The length to the reaching part becomes shorter. Therefore, the main girder 2 of the diagonal member 4
The horizontal component of the tensile force generated in the diagonal member 4 becomes smaller. Moreover, the lifting force, which is the vertical component of this tensile force, increases.

If the lifting force increases in this way, the required lifting force can be obtained even if the number of diagonal members 4 is at least, and the compression horns acting on the main girder 2 near the main tower 1 become smaller, increasing the strength of the main girder 2. There is no need to make it larger.

In addition, this invention also provides a PC steel material 3 in the ■-shaped main tower 1.
Instead, a prestressed concrete beam 5 may be provided as shown in FIG.

As shown in Fig. 3, the upper part of the main tower 1 is divided into two parts, each of which is V-shaped, and the diagonal members 4 are extended from these two parallel ■-shaped parts 6, 6. 2 may be hung on two sides.

Further, in the above embodiment, only the upper end of the main tower 1 protrudes in the longitudinal direction of the main girder 2, but it may be formed with the same width from the bottom to the top.

〔Effect of the invention〕

This invention has the above configuration, and since at least the upper end of the main tower protrudes along the longitudinal direction of the main girder, the intersection angle between the diagonal members protruding from the upper end and the main girder is greater than that of the conventional one. The horizontal component of the tensile force of the diagonal member becomes small, the compressive stress acting on the main girder becomes small, and the lifting force becomes large. Therefore, the number of diagonals can be reduced, and there is no need to increase the strength of the main girder, making construction easier and reducing construction costs.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of a cable-stayed bridge according to the present invention;
2 and 3 are perspective views of the main tower portion of another embodiment, FIG. 4 is a perspective view of a conventional cable-stayed bridge, and FIG. 5 is a side view thereof. 1. Main tower, main girder, 3. PC steel, 4. Diagonal members.

Claims (1)

[Claims] (1) In a cable-stayed bridge where the main girder is suspended by diagonal members extending from the main tower, at least the upper end of the main tower protrudes along the longitudinal direction of the main girder, and the main girder is suspended by the diagonal members extending from the main tower. A cable-stayed bridge characterized by being suspended.