Bridges – Suspension
Patent
1997-02-18
1998-12-22
Lisehora, James
Bridges
Suspension
14 21, 14 771, E01D 1100, E01D 1102
Patent
active
058506527
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of suspending a bridge-girder of a suspension bridge and more particularly to a bridge-girder suspension method capable of controlling the generation of flutters on the bridge-girder.
BACKGROUND TECHNOLOGY
The conventional suspension bridge has been constructed of main towers, cables suspended among the main towers themselves and between the outermost main towers and the lands (or shores) adjacent thereto, respectively, and a bridge-girder extending between the lands (or shores) through the main towers and suspended by the cables through hanger ropes.
That is, the bridge-girder is suspended by main cables through hanger ropes on both sides thereof.
Now, in the case of a huge suspension bridge, the main towers become extremely high so that vortex induced oscillation generates on the bridge and since both sides of the bridge-girder is suspended merely by the hanger ropes, there has arisen the problem that flutters generate on the bridge-girder.
Accordingly, an object of the present invention is to provide a bridge-girder suspension method capable of controlling the flutters and vortex induced oscillation generating on the bridge-girder and towers.
DISCLOSURE OF THE INVENTION
A first aspect of the bridge-girder suspension method according to the present invention resides in that where a bridge-girder is suspended by main cables supported by main towers through hanger ropes, a portion around the center of each of horizontal beams mounted in sequence at a plurality of positions on each of the main towers in the direction of the height thereof and both sides of the bridge-girder are connected by obliquely extending auxiliary cables.
Further, a second aspect of the bridge-girder suspension method according to the present invention resides in that where a bridge-girder is suspended by main cables supported by main towers through the hanger ropes, a portion around the center of each of horizontal beams mounted in sequence at a plurality of positions on each of the main towers in the direction of the height thereof and both sides of the bridge-girder are connected by a plurality of auxiliary cables extending obliquely down to the right side, and a plurality of auxiliary cables extending obliquely down to the left side, of the bridge-girder.
Still further, in the above-mentioned second aspect of the method according to the present invention, the pluralities of right and left auxiliary cables having their first ends connected to each of the horizontal beams are connected to both sides of the bridge-girder, respectively, in such a manner that outer the auxiliary cables are located with respect to the center of each of said horizontal beams, the closer the second ends thereof to the main tower to which the auxiliary cables are attached.
According to the above-described first and second aspects of the bridge-girder suspension method of the present invention, a plurality of auxiliary cables extending obliquely from the central portion of each of the horizontal beams down to the right side, and a plurality of auxiliary cables extending obliquely from the central portion of the horizontal beam down to the left side, of the bridge-girder to thereby suspend the bridge-girder, so that the torsional natural frequency increases and therefore, flutters and vortex induced oscillation harmful to the bridge-girder are controlled.
Further, the horizontal beams arranged vertically along the main tower at predetermined intervals are connected to the bridge-girder by means of the auxiliary cables so that the main tower is restrained and thereby the vortex induced oscillation generating on the main tower is controlled.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic perspective view of a suspension bridge in a first mode according to the present invention;
FIG. 2 is a perspective view of an essential part of the suspension bridge in the first mode, the view illustrating how auxiliary cables are arranged;
FIG. 3 is a graph showing the natural freq
REFERENCES:
patent: 509781 (1893-11-01), Weiss
patent: 595906 (1897-12-01), Dandridge
patent: 3745601 (1973-07-01), Appelt
patent: 4866803 (1989-09-01), Nedelcu
Tanaka Hiroshi
Yamamura Nobumichi
Hitachi Zosen Corporation
Hochberg D. Peter
Lisehora James
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