JP2002371516A - Main girder of cable stayed bridge having main girder constituted of sheet metal girder and installation method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a main girder of a cable stayed bridge whose main girder for realizing the cable stayed bridge having excellent stability and resistance against wind is constituted of a sheet metal girder and an installation method therefor. SOLUTION: A web 10c constituting the main girder 1 of the cable stayed bridge constitutes the main girder 1 in such a way that it is inclined for the vertical direction. When the cable stayed bridge is formed using this main girder 1, the webs 10c are installed in both side parts of the cable stayed bridge in such a way that lower parts of the webs 10c have such inclination that they are gradually separated onto an outer side or they approach an inner side gradually. Moreover, a hole 10d is formed in the web 10c to provide a wind passage partitioned by a horizontal girder 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a main girder structure used for a bridge or the like, and more particularly, to a main girder of a cable-stayed bridge in which the main girder is a plate girder and a method of installing the main girder.

[0002]

2. Description of the Related Art Conventionally, a box girder type has been mainly used for a main girder of a cable-stayed bridge. The box girder type is structurally rigid,
While having the advantage of excellent wind resistance stability, it has the disadvantage of being inferior in cost. As a result, construction of a cable-stayed bridge using an I-shaped plate girder as a main girder has recently been observed. This main girder type bridge has an excellent cost advantage.

FIG. 3 is a vertical sectional view orthogonal to a bridge axis S (perpendicular to the paper) of a conventional cable stayed bridge. On both sides along the longitudinal direction of the cable-stayed bridge, two main girders 1 connected to the overall length of the cable-stayed bridge are provided in parallel with each other. Cross beams 2 are arranged at regular intervals so as to connect spaces. On the upper surface formed by the two main girders 1 and 1 and each horizontal girder 2, a floor slab 3 serving as a road portion is installed. Also,
A flap 4 for rectifying the wind and stabilizing the cable stayed bridge is provided on a side surface of the cable stayed bridge. Near the middle of the cable-stayed bridge in the longitudinal direction, there is a main tower 6 that stands vertically from the ground.
Are provided, and a plurality of cables 5 are provided near the upper end.
Are connected above the main girder 1 and 1 with a space therebetween. As described above, the main part of the cable-stayed bridge formed by the two main girders 1 and 1, the cross girders 2 and the floor slab 3 of the cable-stayed bridge is supported by the cable 5 and the main tower 6.

[0004]

Since the cable-stayed bridge has a long length with a certain distance between fulcrums, it is necessary to secure sufficient strength and to have sufficient rigidity against torsion caused by wind. However, the main girder structure of the sheet girder type is inferior in rigidity to the box girder structure described above, which causes a problem in the wind resistance stability of the cable stayed bridge. Further, in order to suppress the influence of the wind, for example, a wind rectifying device such as the flap 4 is provided in each part of the cable-stayed bridge, which causes an increase in equipment cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a cable stayed bridge in which a main girder is made of sheet girder to realize a cable stayed bridge having excellent wind resistance. The purpose of the present invention is to provide a main girder and a method of installing the main girder.

[0006]

The present invention employs the following means in order to solve the above-mentioned problems. The main girder of a cable-stayed bridge in which a main girder supported via a cable from a main tower installed in the middle is a plate girder, wherein a cross section of the main girder is spaced apart from the main girder. It has a substantially I-shape having an upper flange, a lower flange, and a web connecting these flanges, wherein the web is inclined with respect to the vertical direction.

[0007] With such a configuration, a web inclined with respect to the vertical direction is formed on the main girder. The sheet girder thus formed is used as a girder of a cable-stayed bridge, so that a cross section in a vertical direction orthogonal to a bridge axis of the cable-stayed bridge has a substantially trapezoidal shape. The wind that strikes the side of the cable stayed bridge does not strike the web surface of the main girder at right angles, but is straightened by the inclination of the web. This allows the wind pressure to be applied to the cable stayed bridge,
And the generation of wind vortices that promote vibration will be reduced.

According to a second aspect of the present invention, the main girder of the first aspect is a main girder of a cable-stayed bridge comprising a plate girder, wherein the web is inclined with respect to the upper flange or the lower flange. It is characterized by having.

[0009] With this configuration, the main girder is formed with a web inclined with respect to the upper flange or the lower flange. The sheet girder thus formed is used as a girder of a cable-stayed bridge, so that a cross section in a vertical direction orthogonal to a bridge axis of the cable-stayed bridge has a substantially trapezoidal shape. In addition, it is preferable that the surfaces of the upper flange and the lower flange are horizontal, and the web is inclined with respect to this surface, thereby facilitating attachment to the cable-stayed bridge. The wind colliding with the side of the cable-stayed bridge
There is no right-angle impact on the web surface of the main girder, which is straightened by the inclination of the web. As a result, the wind pressure applied to the cable-stayed bridge and the occurrence of wind vortices that promote vibration are reduced.

The invention according to claim 3 is characterized in that a hole is formed in the web of the main girder.

[0011] With this configuration, holes are formed in the web, which is the inclined surface of the main girder. When this main girder is used in a cable-stayed bridge, a part of the wind rectified by the inclined web flows into the hole and passes between the main girders arranged on both sides of the cable-stayed bridge. In particular, if holes are formed symmetrically with respect to the vertical section including the bridge axis, the projected area of the side of the cable-stayed bridge will be reduced,
A reduction in air resistance is obtained.

According to a fourth aspect of the present invention, there is provided a method of installing a main girder of a cable-stayed bridge in which a main girder supported via a cable from a main tower erected in the middle is a plate girder. The cross section has a substantially I-shape having an upper flange and a lower flange spaced apart and a web connecting these flanges, and the main girder is installed such that the web has an inclination angle with respect to a vertical direction. It is characterized by being done.

[0013] By adopting such an installation method, the web of at least one main girder disposed on both sides of the cable stayed bridge is installed on the cable stayed bridge so as to have an inclination angle with respect to the vertical direction. . Therefore, the cross section in the vertical direction orthogonal to the bridge axis of the cable-stayed bridge has a substantially trapezoidal shape. In this substantially trapezoidal shape, there are a case where the lower side is a long side and a case where the lower side is a short side depending on the inclination direction of the web. As a result, the flow of wind that collides with the side surface of the cable stayed bridge is guided to the upper side or the lower side of the cable stayed bridge.

According to a fifth aspect of the present invention, there is provided a method for installing a main girder of a cable-stayed bridge in which the main girder is a sheet girder, wherein the main girder extends along both sides of the cable-stayed bridge. The main girder is disposed such that the lower portions of the webs on the both sides are gradually separated from each other.

By adopting such an installation method, the cross section of the web in the vertical direction perpendicular to the bridge axis has a substantially C shape. Due to such a shape, the wind colliding with the side surface of the cable stayed bridge is straightened by the inclination of the web, and flows largely over the main girder, that is, the upper side of the cable stayed bridge. Therefore, the wind pressure exerted on the cable stayed bridge is reduced. Alternatively, since the lower end of the web projects outward beyond the floor slab, the apparent girder width on which the fluid acts increases, and the wind resistance improves. The cable connected from the main tower to the upper part of the main girder is inclined with respect to the vertical direction. Therefore, according to the inclination angle of the cable and the main girder with respect to the vertical direction,
It is preferred to select the inclination angle of the web. This results in a balance of forces on the main girder from the cable.

According to a sixth aspect of the present invention, there is provided a method of installing a main girder of a cable-stayed bridge in which the main girder is a sheet girder, wherein the main girder extends along both sides of the cable-stayed bridge. The main girder is disposed so that the lower part of the web on the both sides is gradually approached.

With such an installation method, the cross section of the web in the vertical direction perpendicular to the bridge axis of the cable-stayed bridge has a substantially inverted C shape. With such a shape, the wind colliding with the side surface of the cable-stayed bridge is straightened by the inclination of the web, and flows largely under the main girder, that is, under the cable-stayed bridge. Therefore,
The wind pressure on the cable stayed bridge will be reduced. In addition, the fact that a large amount of wind flows under the cable-stayed bridge results in a reduction in wind flowing on the floor slab.

[0018]

Next, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIG. 1A shows a cable-stayed bridge according to a first embodiment of the present invention, in which a bridge axis S (perpendicular to the paper) is shown.
FIG. 3 is a vertical sectional view orthogonal to FIG. In FIG. 1, reference numeral 1 indicates a main girder 1 having the entire length of a cable-stayed bridge. The main girder 1 is provided on both sides along the longitudinal direction of the cable-stayed bridge. Reference numeral 2 denotes a horizontal girder 2 arranged at regular intervals in the longitudinal direction of the main girder 1 so as to extend between the two main girders 1 and 1 provided on both sides of the cable-stayed bridge.
Both ends of the cross beam 2 have a shape inclined in accordance with the inclination angle of both main beams 1, 1 described later. A floor slab 3 is laid on the upper surface of the framework formed by the cross beam 2 and the main beams 1 and 1.

FIG. 1B is a perspective view of a main girder member 10 constituting the main girder 1 used in the cable stayed bridge according to the present embodiment.
The main girder member 10 includes a web 10c having an inclination angle with respect to a vertical direction, and an upper flange 10 provided on the web 10c.
a and a lower flange 10 provided below the web 10c.
b. Upper flange 10a and lower flange 10
b is formed so as to have a plane substantially parallel to the horizontal plane, and the web 10c is viewed from the
It is inclined with respect to 0a and 10b.

FIG. 1 (c) is a partial side view of the main girder member 10 of FIG. 1 (b). Web 10 of main girder member 10
A hole 10d is formed in c. This hole 10d is
The cross beam 2 is formed so as not to interfere with the fixed position where the cross beam 2 is fixed. The shape of the hole 10d is a circular shape that can be easily processed. Of course, it is also possible to process it into a shape such as an ellipse or a square.

A plurality of main girder members 10 shown in FIG. 1B are formed, and their ends are abutted in the longitudinal direction, and are sequentially connected by welding or bolts and a plate-like fixing member (not shown). Two main girders 1 having the entire length of the cable-stayed bridge are formed. The main girder member 10
Has a symmetrical shape in a vertical section including the bridge axis S of the section shown in FIG. Therefore, the main girder member 1
0 is the same shape as the main girder member 10 on the symmetric side when rotated by 180 degrees in a direction that does not change the vertical direction, and is used as the same main girder member 10.

2 formed by a plurality of main beam members 10
As shown in FIG. 1A, the two main girders 1, 1 are installed in parallel at an interval corresponding to the width of the floor slab 3 to be laid. When these two main girders 1 and 1 are installed, they are installed so that the lower part of the inclined web 10c gradually approaches the center of the cable stayed bridge. Therefore, the installed webs 1 on both sides
The cross section of 0c has a substantially inverted C shape. Next, the horizontal girder 2 formed in accordance with the interval length between the two main girders 1 and the inclination angle of the web 10c is inserted into the two main girders 1 and 1 so as to be orthogonal to the longitudinal direction of the main girder 1. 1 to the inside side. A plurality of cross beams 2 are provided in consideration of the torsional rigidity of the cable stayed bridge, the strength of the floor slab 3, and the like. The space partitioned by the cross beam 2 is a hole 10d provided in the web 10c.
It functions as a passage for guiding the wind flowing from the bridge, and prevents the generation of vortices of the wind passing inside the cable-stayed bridge.
The main body of the cable-stayed bridge formed by the two main girders 1, 1 and the horizontal girders 2 and the floor slab 3 as described above, connects the main tower 6 (see FIG. 3) and the upper part of the two main girders 1, 1. It will be supported by the connecting cable 5 (see FIG. 3).

As described above, the wind stability of a cable-stayed bridge having a cross-sectional shape as shown in FIG. 1A is effective in the experimental results of a reduced model of a cable-stayed bridge. This measures the flutter limit wind speed of a cable-stayed bridge. According to this, when the web 10c of the main girder 1 is formed in the vertical direction (see FIG. 3), the critical wind speed is 42 m /
s. However, in a reduced model of a cable-stayed bridge in which the web 10c which is hydrodynamically similar to the present embodiment is a main girder 1 in which the vertical cross section has an inverted C shape, and in which the holes 10d are not formed in the web 10c, The flutter limit wind speed is 87m /
s or more was obtained. For reference, when the main girder 1 and the web 10c were installed vertically and the hole 10d was formed on the side surface of the web 10c, the flutter limit wind speed was 82 m / s. The measured values of the deflection amplitude and the torsional amplitude at this time are almost half as compared with the measured values of the reduced model in which the hole 10d is not formed in the web 10c in the conventional main girder 1 arranged in the vertical direction. was gotten. From the above experimental results, the configuration of the main girder combining the inclination of the web 10c and the holes 10d can be expected to further improve the critical wind speed.

The cable stayed bridge according to the present embodiment having the above-described structure has the following effects. As for the wind pressure received on the side of the cable stayed bridge, the generation of the vortex force that causes aerodynamic vibration is weakened by the inclination of the web 10c of the main girder 1, and the wind resistance stability is dramatically improved as compared with the conventional cable stayed bridge. . Therefore, it is not necessary to install a wind rectification device and the like, and the equipment cost can be reduced.

[Second Embodiment] The second embodiment of the present invention will be described below.
An embodiment will be described. FIG. 2 is a cross-sectional view of the cable-stayed bridge according to the present embodiment in a vertical direction orthogonal to the bridge axis S. In the present embodiment, the configuration of the main girder 1 is different from that of the first embodiment. Therefore, only the difference will be described.

In FIG. 2, both main girders 1 and 1 are installed in parallel at an interval corresponding to the width of the floor slab 3 to be laid. When the two main girders 1 and 1 are installed, the lower part of the slanted main girder 1 web 10c (see FIG. 1 (b)) extends over the outside of the cable-stayed bridge, for example, on both sides of the web 10c. The section is installed so as to have a substantially C-shape. The inclination angle of the web 10c with respect to the vertical direction is set to be substantially the same as the inclination angle with respect to the vertical direction of the cable 5 disposed on the upper surface of the main girder 1 from the main tower 6 (see FIG. 3).
Thereby, the directions of the forces applied to the main girder 1 and the cable 5 overlap on a straight line, and the balance of the forces is obtained. Between the two main girders 1, 1 formed in this way, a horizontal girder 2 is fixed so as to extend between these main girders 1, 1. Both ends of the cross beam 2 are each formed in a shape corresponding to the inclination angle of the web 10c. The cross beams 2 are provided at regular intervals in consideration of the torsional rigidity of the cable-stayed bridge, securing the strength of the floor slab 3, and the like.
It is fixed to the inner side surface of the main girders 1, 1 so as to be orthogonal to both main girders 1, 1. Further, holes 10d (see FIG. 1C) are provided in the webs 10c on both sides in the same manner as in the first embodiment. The wind flowing from the hole 10d passes through a passage partitioned by the ribs 2, and flows out from the opposite hole 10d. By such a wind flow,
The generation of wind vortices is suppressed.

The wind resistance of a cable-stayed bridge having a sectional shape as shown in FIG.
Effective experimental results are obtained as in the case of the embodiment. According to this, the cross-sectional shape of the web 10c that is hydrodynamically similar to the present embodiment has a C-shape, and the web 10c
In the reduced model of the cable-stayed bridge in which the hole 10d is not formed, the result that the flutter limit wind speed was 46 m / s or more was obtained. As described above, a favorable result was obtained as compared with the flutter limit wind speed of 42 m / s when the main girder 1 and the web 10c constituting the main girder 1 were installed in the vertical direction.

The cable stayed bridge of the present embodiment having the above-described structure has the following effects. The wind pressure received on the side of the cable stayed bridge is reduced by the inclination of the web 10c constituting the main girder 1, and the wind resistance stability is improved. Therefore, it is not necessary to install a wind rectification device and the like, and the equipment cost can be reduced.

As a modification of the above embodiments, the following configuration may be adopted. FIG. 1B shows the upper and lower flanges 10a and 10b formed as horizontal planes.
Main girder 1 using I-shaped steel material conventionally used
It is also possible to adopt a method in which the web 10c of the main girder 1 is installed so as to be inclined with respect to the vertical direction. With this configuration, the same effect as that of the above-described embodiment can be obtained, and the manufacturing cost of the main girder 1 can be reduced. In the first and second embodiments, the main girder 1
Has been described as being symmetrical in the vertical section including the bridge axis S, but the web 10c of one main girder 1 has been described.
It is also possible to configure only the inclination. Thereby, when constructing a cable-stayed bridge in a place where the wind direction is limited, the construction cost can be reduced.

[0030]

As described above, the present invention has the following effects. According to the first aspect of the present invention, since the web of the main girder used for the cable stayed bridge is inclined with respect to the vertical direction, when installed on the cable stayed bridge, the wind colliding with the side of the cable stayed bridge The flow can be guided smoothly, and the wind stability of the cable stayed bridge can be improved.

According to the second aspect of the invention, since the web of the main girder used for the cable-stayed bridge is inclined with respect to the upper flange or the lower flange, the upper flange or the lower flange is substantially horizontal. When installed on a cable-stayed bridge, the flow of wind that collides with the side of the cable-stayed bridge can be smoothly guided, and the wind stability of the cable-stayed bridge can be improved. Further, since the upper flange and the lower flange are substantially horizontal, when the main girders are connected, the work can be facilitated.

According to the third aspect of the present invention, since holes are formed in the web of the main girder used for the cable stayed bridge, the projected area of the side of the cable stayed bridge is reduced, and furthermore, the impinging wind reduces the holes. Since it passes, the air resistance is reduced and the wind resistance of the cable-stayed bridge is improved. In addition, since the weight of the main girder is reduced by the formation of the holes, the cost can be reduced.

According to the fourth aspect of the present invention, since the web of the main girder is installed on the cable-stayed bridge so as to have an inclination angle with respect to the vertical direction, the wind pressure of the wind colliding with the side of the cable-stayed bridge is reduced. At the same time, the wind before and after colliding with the cable stayed bridge is rectified, so that the wind resistance stability of the cable stayed bridge is improved.

According to the fifth aspect of the present invention, the main girder is disposed along both sides of the cable-stayed bridge, and is installed so that the lower portions of the webs on both sides are gradually separated from each other. It is possible to reduce the wind pressure on the cable-stayed bridge by guiding the flow of the wind colliding with the upper side, and to improve the wind resistance stability of the cable-stayed bridge. When the inclination angle of the web and the cable with respect to the vertical direction is substantially the same, the direction of the force applied to the cable,
The direction of the force applied to the main girder substantially overlaps on a straight line, and a force balance is obtained.

According to the sixth aspect of the present invention, the main girder is disposed along both sides of the cable-stayed bridge, and is installed so that the lower portions of the webs on both sides are gradually approached. It is possible to reduce the wind pressure on the cable-stayed bridge by guiding the flow of the wind that collides with the cable to the lower side, and to improve the wind resistance of the cable-stayed bridge.

[Brief description of the drawings]

FIG. 1 shows a cable-stayed bridge for explaining a first embodiment of the present invention. FIG. 1 (a) is a vertical sectional view orthogonal to a bridge axis of the cable-stayed bridge, and FIG. 1 (b) is a main girder. 1C is a perspective view of a main girder member, and FIG. 1C is a side view of a web forming a part of the main girder.

FIG. 2 is a vertical sectional view orthogonal to a bridge axis of a cable-stayed bridge for explaining a second embodiment of the present invention.

FIG. 3 is a vertical sectional view orthogonal to a bridge axis of a cable stayed bridge for explaining a conventional cable stayed bridge.

[Explanation of symbols]

 Reference Signs List 1 main girder 2 cross girder 3 floor slab 10a upper flange 10b lower flange 10c web 10d hole S bridge shaft

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yo Kameda 4--22 Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries, Ltd. Hiroshima Works (72) Inventor Hiroshi Morinaga 4-chome Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima No. 6-22 Mitsubishi Heavy Industries, Ltd. Hiroshima Works (72) Inventor Shinsuke 5-717-1, Fukahori-cho, Nagasaki-shi, Nagasaki F-term in Nagasaki Laboratory, Mitsubishi Heavy Industries, Ltd. F-term (reference) 2D059 AA07 AA27 AA41 BB08 CC25 GG06

Claims (6)

[Claims] 1. A main girder of a cable-stayed bridge in which a main girder supported via a cable from a main tower erected in the middle is a plate girder, wherein the cross section of the main girder is spaced apart from the main girder. The main girder has a flange, a lower flange, and a web connecting these flanges, and the web is inclined with respect to a vertical direction. The main girder of the bridge. 2. The main girder of the cable-stayed bridge according to claim 1, wherein the web is inclined with respect to the upper flange or the lower flange. 3. The main girder of a cable-stayed bridge according to claim 1, wherein a hole is formed in the web of the main girder. 4. A method of installing a main girder of a cable-stayed bridge in which a main girder supported via a cable from a main tower erected in the middle is a plate girder, wherein a cross section of the main girder is spaced apart. The main girder has an upper flange, a lower flange, and a web connecting these flanges, and the main girder is installed such that the web has an inclination angle with respect to a vertical direction. Installation method of the main girder of the cable stayed bridge where the main girder is made of sheet girder. 5. The main girder according to claim 4, wherein the main girder is disposed along both sides of the cable stayed bridge, and the main girder is installed so that the lower portions of the webs on the both sides are gradually separated. Installation method of main girder of cable stayed bridge where main girder is made of sheet girder. 6. The main girder according to claim 4, wherein the main girder is disposed along both sides of the cable-stayed bridge, and the main girder is installed so that the lower portions of the webs on the both sides gradually approach. Installation method of main girder of cable stayed bridge where main girder is made of sheet girder.