JP4078367B2 - Cable-stayed cable fixing structure - Google Patents

Description

  The present invention relates to a structure for fixing a cable staying cable, which is formed on the upper part of a main tower of a cable-stayed bridge, which is one type of bridge, and is used to support a bridge girder.

  A cable-stayed bridge is one in which a plurality of cable-stayed cables are stretched from the upper part of the main tower erected on the pier to the lower part of the bridge girder in the axial direction (the direction of the bridge axis). It has become. And in most large cable-stayed bridges, the cable girders that extend from both sides of the bridge pier are supported by extending cable-stayed cables from the main tower both in the longitudinal direction of the bridge. In such a cable-stayed bridge, cables from both sides are fixed on the upper part of the main tower, and a plurality of cable-stayed cables are arranged and fixed vertically. In particular, in the cable-stayed bridge, generally called the extradosed type, the height of the main tower is small and the distance between the cables in the vertical direction is small, so many cable-stayed cables are small in the upper part of the main tower. Fixed at intervals. For this reason, a large tensile force is transmitted to the upper part of the main tower from a plurality of cable stays in a small range. In addition, between the two cables stretched on both sides, it is fixed so that the tensile force is transmitted between each other, and the horizontal component of the tensile force transmitted from both cables is offset, so that the entire main tower is The structure has no large horizontal force.

  As mentioned above, the upper part of the main tower where a large tensile force is applied from multiple cable stays must be constructed so that the cable fixing position is set accurately and excessive stress concentration does not occur. It is necessary to have a structure in which a large horizontal force is smoothly transmitted between the cable stays stretched on both sides of the cable. For this reason, Patent Document 1 discloses a structure in which a steel member is used for the upper part of the main tower and the cable is fixed to the steel member, and concrete is wound around the steel member and supported on the pier. .

  This fixing structure has a box-shaped steel shell 100 made of steel at the upper part of the main tower as shown in a side view in FIG. A plurality of cable stays 110 are fixed. The steel shell portion 100 has side plates 101 supported on both sides of the cable 110 in a direction parallel to the cable 110 and perpendicular to the cable, and ends of the side plate 101 in the bridge axis direction. It is formed in a box shape with an end face plate 102 provided so as to be continuous with the portion at a right angle. A support member 103 is provided in the vicinity of both ends in the bridge axis direction of the two parallel side plates 101 so as to connect them, and the end of the cable cable 110 is locked to the support member 103. The support member 103 is a beam-like member having a plate-like member 103a in a direction perpendicular to the axis of the cable cable and a plate-like member 103b joined at a right angle to give sufficient rigidity, The reaction force of the cable cable 110 is transmitted to the side plates 101 on both sides via the support member 103. And since the reaction force from the cable tension cable 110 is transmitted to the vicinity of both ends in the bridge axis direction of the steel shell portion 100 through the support member 103, the horizontal component of the reaction force acting from the cable tension cable 110 is It acts in the opposite direction near both ends, and cancels out as a horizontal tensile force of the side plate 101. Also, the vertical component is composed of the reaction force of the cables on both sides, and the concrete member 104 formed so as to surround the steel shell 100 is connected to the concrete member 104 via the stud gibber 105 or from the bottom 106 of the steel shell. It is transmitted to the concrete of the tower and is supported by the bridge pier as the vertical axial force of the main tower.

In such a fixing structure, the steel shell 100 is accurately manufactured in a factory or the like, and is accurately installed in the field, whereby the fixing position of the cable-cable 110 is accurately determined, and high-precision construction is possible. Further, the cable-cable 110 can be fixed to the support member 103 made of steel so that the reaction force can be reliably transmitted.
JP 2002-348813 A

However, the conventional fixing structure as described above has a problem that the weight of the steel shell portion 100 to which the cable-cable 110 is fixed becomes excessive. In particular, the support member 103 to which the cable cable 110 is fixed is joined to the side plate 101 at both ends, and transmits a reaction force to the side plate 101 as a structure that resists bending moment like a beam between the side plates. As a result, the member size increases and the steel weight of this portion increases. Further, the side plate 101 also resists a large horizontal force, which increases the plate thickness and the steel weight.
When the weight of the steel shell portion 100 is increased in this way, it becomes difficult to lift the steel shell portion 100 with a crane or the like for installation on the upper part of the main tower, and it becomes necessary to divide it into a plurality of portions, so that the construction efficiency is remarkably deteriorated. Moreover, the steel plate thickness of each part becomes large, the work amount for joining by welding becomes remarkably large, and the cost becomes excessive.

  The present invention has been made in view of the circumstances as described above. The cable-stayed cable fixing portion in the upper part of the main tower is constructed with as little steel material as possible to improve work efficiency and reduce the cost for construction. The purpose is to reduce.

In order to solve the above-mentioned problem, the invention according to claim 1 is provided at the upper part of the main tower of the cable-stayed bridge, and obliquely below both the front and rear in the axial direction (bridge axis direction) of the cable-stayed bridge from the main tower. a fixing structure of a plurality of cable-stayed cables is stretched hanging bridge girder supporting, on both sides of the fixing portion in which the end portion of the cable-stayed cable is fixed so as to face from both bridge axis direction, the swash Two steel side plates are arranged in parallel with the tension surface of the tension cable, and concrete members are formed at both ends in the bridge axis direction of the steel side plates so as to connect the two steel side plates to each other, The cable staying cable is fixed so as to transmit reaction force to the concrete member between the steel side plates arranged in parallel through the concrete member, and the concrete member and the steel side plate are The reaction force acting from the cable Provided is a cable-stretched cable fixing structure which is connected to a steel side plate so as to be transmitted.

  In this fixing structure, the reaction force of the cable staying cable is once transmitted to the concrete member, and then transmitted from the concrete member to the steel side plates arranged on both sides of the end portion of the cable staying cable. And the horizontal component of the reaction force of the cable staying stretched from the main tower to both the front and back in the bridge axis direction acts as opposite tensile forces on both ends of the steel side plate in the bridge axis direction, canceling each other. Is done. Therefore, a large steel member is not required in the portion that transmits the reaction force of the cable stay to the steel side plate, and the amount of steel material can be greatly reduced. Further, the concrete member can be continuous with the concrete constituting the lower part of the main tower, and the vertical component of the reaction force of the cable stayed cable is also transmitted to the pier as the axial force of the main tower.

  The invention according to claim 2 is the fixing structure according to claim 1, wherein both the steel side plates arranged so as to be parallel to each other are connected to both ends of the steel side plate in the bridge axis direction. A cable positioning plate made of steel is provided, and the concrete member is placed so as to be in close contact with the outer surfaces of the two cable positioning plates facing in the bridge axis direction, and is attached to the end of the cable stayed cable The fixed fixing tool is fixed in contact with the cable positioning plate.

  In this fixing structure, the cable positioning plate made of steel can be accurately attached to the steel side plate in a factory or the like. Therefore, by fixing the fixing tool attached to the end of the cable according to the cable positioning plate, the cable can be easily placed at an accurate position. Further, by forming the concrete member so as to be in close contact with the cable positioning plate, the reaction force of the cable can be applied to the concrete member reliably and smoothly.

According to a third aspect of the present invention, in the fixing structure according to the second aspect, the cable positioning plate is provided for each of the cable stays arranged in a plurality of stages above and below, and these are continuous vertically. And the reinforcing bars which reinforce the concrete member shall be continuously arranged so that the outside of the cable positioning board and the steel side board may be surrounded horizontally.

  In this fixing structure, a cable positioning plate is provided for each of the cable cables arranged in a plurality of stages, and these are continuous vertically, so that they are in close contact with the outside of the cable positioning plate and the steel side plate. The concrete member can be easily formed so as to surround them. Therefore, the concrete member placed in this manner is firmly integrated with the steel side plate and the cable positioning plate. And the reinforcing bar arrange | positioned in a concrete member bears a part of horizontal component of the tensile force of a cable-stayed cable, and can make the main tower upper part a firm structure.

  As described above, in the cable-stretched cable fixing structure according to the present invention, the cable can be fixed using the concrete member effectively, and the reaction force can be smoothly transmitted. Therefore, it is possible to reduce the weight of the steel material and reduce the cost for constructing the upper part of the main tower by reducing the welding work amount.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic side view showing an extradosed type cable-stayed bridge in which the fixing structure of the present invention can be suitably employed.
This cable-stayed bridge is composed of a bridge girder 3 laid over the abutment 1 and the pier 2, a main tower 4 raised in the shape of a pier, and an oblique line on both sides in the axial direction of the bridge girder 3 from the upper part of the main tower 4. It has a plurality of cable stays 5 that are stretched downward and support the bridge girder in an oblique direction.
The extradosed type cable-stayed bridge has a relatively large bending rigidity of the bridge girder 3 and a small height of the main tower 4. As shown in FIG. 1, the cable stayed at is fixed in a small range in the upper part A of the main tower.

FIG. 2 is an enlarged side view of the upper part of the main tower. 3 is a plan sectional view of the same main tower, and FIG. 4 is a vertical sectional view.
In the range where the cable stay cable 5 at the upper part of the main tower is fixed, the steel side plate 11 is arranged so as to be parallel to and perpendicular to the axial direction of the bridge girder 3 (bridge axial direction). Two steel side plates 11 are provided in parallel on both sides of the fixed end portion of the cable-cable 5, and these steel side plates 11 are connected to each other in the vicinity of both ends in the bridge axis direction of the steel side plates 11. A cable positioning plate 12 is provided so as to be connected. The cable positioning plate 12 and the steel side plate 11 form a box shape. A continuous concrete member 13 is formed on the outside of the steel side plate 11 and the cable positioning plate 12 so as to be in close contact with and surround the outer surfaces. And it is firmly united by the stud dowel 14 planted by the steel side board 11. FIG.

  As shown in FIG. 5, the cable positioning plate 12 is provided with a through hole at a position where the cable is fixed, and a duct 15 is provided outside the cable positioning plate 12 so as to be continuous with the through hole. The end of 5 can be inserted into these ducts and through-holes so as to be inserted between the two steel side plates 11 formed into a box shape. Then, the fixing position is accurately set by fixing the cable cable 5 at a position inserted through the duct 15 and the through hole.

  In addition, the cable positioning plate 12 is provided at a portion where the cable staying cable 5 is fixed, and is inclined so as to be perpendicular to the axis of the cable staying cable 5 in accordance with the inclination of the cable staying cable 5. Between the positions where the cable stays 5 arranged in a plurality of stages are fixed, the cable is bent and continuous in the vertical direction.

Since the concrete member 13 is in close contact with the outer surfaces of the cable positioning plate 12 and the steel side plate 11, the reaction force acts on the concrete member 13 when the cable is placed and a tensile force is introduced. . The concrete member 13 functions as a beam supported at both ends by the steel side plate 11, and the horizontal component of the reaction force acting from the cable cable 5 is transmitted to the steel side plate 11. In addition, a reinforcing bar 16 is disposed on the concrete member 13 so as to be wound along the outer surfaces of the cable positioning plate 12 and the steel side plate 11, and is formed by the steel side plate 11 and the cable positioning plate 12 that are box-shaped. It is reinforced to surround the entire circumference of the box-shaped member.
The lower part of the concrete member 13 is continuous with the concrete 17 forming the main tower, and the concrete member 13 is firmly supported by the upper part of the main tower.

  The steel side plate 11 is connected to the concrete member 13 at both ends in the bridge axis direction, and the reaction force from the cable 5 is transmitted to the horizontal component in the opposite direction via the concrete member 13. It has become. Therefore, the tensile force acts by the horizontal force from both of the steel side plates 11, and the thickness is determined so as to resist this tensile force.

Next, a method for constructing the cable-stretched cable fixing structure in the upper part of the main tower as described above will be briefly described.
The lower part of the main tower has a reinforced concrete structure, and concrete is placed in order starting from the pier. And if it raises to predetermined height, the box-shaped steel member with which the steel side board and the cable positioning board 12 were joined will be lifted in a factory, and it will support on the upper part of the main tower which stood up. At this time, if the steel weight becomes large and it is difficult to install it on the upper part of the main tower, the steel members are divided and manufactured, and these are stacked up and down so that a cable with a predetermined number of stages can be fixed. You may install in.

  When the steel member is installed, the necessary reinforcing bars 16 are arranged around the steel member to assemble the formwork. Then, the concrete member 13 is formed so as to be in close contact with the steel side plate 11 and the cable positioning plate 12 while being placed on the outside of the box-shaped steel member while continuing on the already placed concrete 17.

  After the concrete is hardened, the end of the cable staying cable 5 is inserted into the duct 15 and the through hole, and the end of the cable staying cable 5 inside the box-shaped steel member, that is, between the two parallel steel side plates 11. The fixing tool 6 is mounted on the concrete member 13 and pressed against the concrete member 13 through the cable positioning plate 12. Then, a tensile force is introduced into the cable cable 5 by a jack (not shown). When a jack can be mounted between two parallel steel side plates 11, a tensile force can be introduced into the cable cable 5 at the upper part of the main tower. When the jack cannot be mounted on the upper part of the main tower, the jack can be mounted at a position where the cable staying cable 5 is fixed to the bridge girder 3 to introduce a tensile force.

  As shown in FIG. 6, the concrete portion 13 is left without placing the concrete at the center portion 13 in the bridge axis direction of the steel side plate 11 when the concrete member is first formed. It is desirable to form it in two parts surrounding each end. Then, a tensile force is introduced into the cable cable 5, and after a large horizontal tensile force is introduced into the steel side plate 11, the concrete is placed and continued. Thereby, it is possible to effectively prevent a vertical crack from occurring in the concrete member 13 outside the central portion of the steel side plate 11.

  In such a cable-stretched cable fixing structure, a reaction force of the cable-cable 5 to which a tensile force is introduced acts on the concrete member 13 and is transmitted from the concrete member 13 to the steel side plate 11. And the horizontal component of a reverse direction from the cable stayed cable 5 arrange | positioned at the both sides of the main tower 4 acts on the both ends vicinity in the bridge-axis direction of the steel side board 11, and it is the state which almost balanced as the tensile force of the steel side board 11 It becomes. Thus, since the cable cable 5 is fixed to the concrete member 13, it is not necessary to provide a beam-like member made of steel at this portion, and the steel weight can be reduced and the welding amount can be reduced. In particular, if the fixing portion of the cable cable 5 is made of a steel member, the thickness of the fixing member increases, and a lot of work is required for welding. However, the amount of welding work is greatly reduced by the above configuration. In addition, the cost can be reduced.

  Further, the vertical component of the reaction force acting from the cable stayed cable 5 is transmitted directly from the concrete member 13 to the concrete 17 at the lower part of the main tower or to the steel side plate 11 and then the concrete at the lower part of the main tower through the steel side plate 11. Is transmitted smoothly.

FIG. 7 is a cross-sectional plan view showing a cable-cable fixing structure according to another embodiment of the present invention.
As in the structure shown in FIGS. 2 to 5, this fixing structure has two steel side plates 51 parallel to the vertical direction, and is connected by two cable positioning plates 52 near both ends in the bridge axis direction. It is box-shaped. In addition, a concrete member 53 is formed so as to be in close contact with the outside of the steel side plate 51 and the cable positioning plate 52, and the cable staying cable 55 penetrates the concrete member 53 inside the cable positioning plate 52, and the fixing tool 56. Has been fixed by. The reaction force of the cable cable 55 is transmitted to the concrete member 53 and further transmitted to the steel side plate 51.

  In this fixing structure, the joint portion between the concrete member 53 and the steel side plate 51 is integrated by a reinforcing bar 58 inserted through a through hole 57 provided in the steel side plate 51 in place of the stud gibber of the fixing structure shown in FIG. It has become. From the position where the cable positioning plate 52 is joined to the steel side plate 51, a plurality of the through holes 57 are arranged in the vertical direction and the horizontal direction on the end side, and the rebar 58 is inserted through each of these. These reinforcing bars 58 penetrate through both of the two parallel steel side plates 51 and have a function of reinforcing the concrete member 53.

  Further, a protruding plate 59 protruding horizontally is provided from the outer side surface of the steel side plate 51, and a through hole 60 is also provided in this protruding plate. A plurality of the projecting plates 59 are provided at intervals in the vertical direction, and the vertical reinforcing bars 61 are inserted into the through holes 60 provided in these projecting plates so that the concrete member 53 and the steel side plate 51 are connected to each other. It is a solid unity.

  On the other hand, at both ends of the concrete member 53 in the bridge axis direction, the PC steel material 62 is disposed through the concrete member 53 in the horizontal direction, and prestress is introduced into the concrete member 53 by introducing tension. Thereby, the concrete member 53 is reinforced, and the reaction force of the cable stayed cable 55 is reliably transmitted to the steel side plate 51.

It is a schematic side view showing an extradosed type cable-stayed bridge in which the fixing structure of the present invention can be suitably employed. It is a side view of the upper part of the main tower of a cable-stayed bridge shown in FIG. FIG. 3 is a plan sectional view of the upper part of the main tower shown in FIG. 2. FIG. 3 is a vertical sectional view of the upper part of the main tower shown in FIG. 2. It is sectional drawing which shows the cable-stayed cable fixing | fixed part of the main tower shown in FIG. It is a plane sectional view which shows the placement method of the concrete member of the main tower upper part shown in FIG. It is a plane sectional view which shows the fixing structure of the cable-stayed cable which is other embodiment of this invention. It is a schematic side view which shows the structure of the main tower upper part in the conventional cable-stayed bridge. It is a plane sectional view of the structure of the main tower upper part shown in FIG.

Explanation of symbols

1: abutment, 2: pier, 3: bridge girder, 4: main tower, 5: cable-stayed cable, 6: fixing tool,
11: Steel side plate, 12: Cable positioning plate, 13: Concrete member, 14: Stud gibber, 15: Duct, 16: Rebar, 17: Concrete under the main tower,
51: Steel side plate, 52: Cable positioning plate, 53: Concrete member, 55: Oblique cable, 56: Fixing tool, 57: Through hole, 58: Reinforcing bar, 59: Overhang plate, 60: Through hole, 61: Reinforcing bar, 62: PC steel

Claims (3)

Fixing structure of a plurality of cable-stayed cables provided at the upper part of the main tower of the cable-stayed bridge and suspended from the main tower obliquely below both the front and rear in the axial direction of the cable-stayed bridge (bridge axial direction) Because
Two steel side plates are arranged on both sides of the fixing portion fixed so that the end portion of the cable stays opposite each other in the direction of the bridge axis , parallel to the stretched surface of the cable stay ,
Concrete members are formed at both ends in the bridge axis direction of the steel side plate so as to connect both of the two steel side plates to each other,
The cable stayed cable is fixed so as to transmit a reaction force to the concrete member between the steel side plates arranged in parallel through the concrete member,
The fixing structure of the cable stayed cable, wherein the concrete member and the steel side plate are connected so that a reaction force acting from the cable stayed cable is transmitted to the steel side plate. A cable positioning plate made of steel is provided at both ends in the bridge axis direction of the steel side plate so as to connect both of the two steel side plates arranged so as to be parallel to each other,
The concrete member is placed so as to be in close contact with the outer surfaces of the two cable positioning plates facing in the bridge axis direction,
2. The fixing structure for a cable-stretched cable according to claim 1, wherein the fixing tool attached to the end of the cable-cable is fixed in contact with the cable positioning plate. The cable positioning plate is provided for each of the cable stays arranged in a plurality of stages above and below, and these are continuous up and down,
3. The cable-stretched cable fixing structure according to claim 2, wherein the reinforcing bars that reinforce the concrete member are continuously arranged so as to horizontally surround the outside of the cable positioning plate and the steel side plate. .

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