Bridge and method for constructing a bridge

Abstract

To provide a bridge and a bridge construction method capable of lowering the height from a pier of a bridge to a floor slab.SOLUTION: A bridge 10 is provided with a plurality of main girders 15 supporting a floor slab 16, bridge piers 11 supporting the main girders 15, and seismic isolation bearings for connecting the bridge piers 11 and the main girders 15. The base isolation bearing is provided with support members 21 and tension members 26. The support member 21 has an overhanging part 21a protruding at a position higher than a lower part of the main girder 15, and is disposed around each main girder 15 on the bridge pier 11. The tension member 26 connects a lower part of the main girder 15 arranged between the plurality of support members 21 and the overhanging part 21a in a separated state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a bridge provided with a seismic isolation bearing and a method for constructing the bridge.

Background Art

[0002] Conventionally, a bridge supports a bridge girder (main girder) via a plurality of bearings on a plurality of bridge piers (abutments) arranged side by side in the bridge axis direction. Here, in order not to transmit seismic force to the bridge deck, a seismic isolation bearing may be used (see, for example, Patent Document 1). The bearing device described in this document includes a mechanism that generates a horizontal force in the opposite direction to the inertial force of the superstructure between the superstructure and the substructure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A rubber bearing may be used as the seismic isolation bearing. In this case, in order to reduce the horizontal rigidity, it is necessary to increase the layer thickness of the rubber, and it is necessary to increase the height of the rubber bearing to a certain extent. Therefore, conventionally, when changing a bridge using a steel bearing (metal bearing) of a fixed bearing or a movable bearing to a rubber bearing, the height of the bridge deck may increase.

Means for Solving the Problems

[0005] The bridge for solving the above problems is a bridge comprising a main girder supporting a floor slab, bridge piers supporting the main girder, and seismic isolation bearings connecting the bridge piers and the main girder, wherein the seismic isolation bearings have overhanging portions protruding at positions higher than the lower part of the main girder, and a plurality of support members arranged around the main girder on the bridge piers, and a tension member connecting the lower part of the main girder arranged between the plurality of support members and the overhanging portion in a separated state.

[0006] Also, a method for constructing a bridge for solving the above problems is a method for constructing a bridge comprising a main girder supporting a floor slab, bridge piers supporting the main girder, and seismic isolation bearings connecting the bridge piers and the main girder, wherein after constructing a plurality of support members having overhanging portions protruding at positions higher than the lower part of the main girder around the main girder on the bridge piers, the lower part of the main girder arranged between the plurality of support members and the overhanging portion are connected by a tension member in a separated state.

Effects of the Invention

[0007] According to the present invention, the height from the bridge piers of the bridge to the floor slab can be reduced.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0009] Hereinafter, with reference to FIGS. 1 to 5, an embodiment in which a bridge and a method for constructing the bridge are embodied will be described. Here, the bridge of the present embodiment will be described as a simple girder bridge in which a bridge girder (main girder) is hung on adjacent bridge piers (abutments). And in the method for constructing the bridge of the present embodiment, it is assumed that a seismic reinforcement repair work for replacing a conventional metal bearing with a seismic isolation bearing is carried out.

[0010] FIG. 1 is a front sectional view seen from the bridge axis direction of the bridge 10 after the repair work, FIG. 2 is a perspective view of the bridge 10, and FIGS. 3 to 5 are side sectional views seen from the bridge axis direction of the bridge 10. As shown in FIG. 2, the bridge 10 of the present embodiment includes a plurality of bridge piers (abutments) 11, a main girder 15, and a floor slab 16. The bridge piers 11 are arranged side by side at intervals in the bridge axis direction.

[0011] As shown in FIG. 1, on the bridge piers 11, seismic isolation bearings for supporting a plurality (here, three) of main girders 15 are provided respectively. This seismic isolation bearing is composed of a plurality of support members 21, a tension member 26, and a mounting member 25 provided on the main girder 15.

[0012] The plurality of support members 21 are fixed so as to surround the periphery of each main girder 15. Each support member 21 is arranged in both directions perpendicular to the bridge axis of the main girder 15. Each support member 21 is composed of, for example, reinforced concrete, and includes a projecting portion 21a and a main body portion 21b. The main body portion 21b supports the projecting portion 21a and is fixed on the bridge pier 11.

[0013] The projecting portion 21a is a portion that projects horizontally from the upper part of the main body portion 21b toward the main girder 15 side. The projecting portion 21a is provided so as to overlap with the end portion of the mounting member 25 when viewed from above.

[0014] A tension member 26 is provided to connect the end of each cantilever portion 21a and the attachment member 25 of the main girder 15. Each main girder 15 is suspended by two tension members 26 at the same pier 11. In this embodiment, each tension member 26 is arranged to extend in the vertical direction. The upper end of the tension member 26 is pin-joined to the cantilever portion 21a of the support member 21, and the lower end is pin-joined to the attachment member 25 of the main girder 15. Usually, the natural period of the bridge 10 is often set in the range of a little over 1 second to about 2 seconds. When setting these natural periods, the suspension length of the tension member 26 is set in the range of about 30 cm to 1 m.

[0015] The plurality of main girders 15 are arranged at intervals in the direction perpendicular to the bridge axis. And, a gap is provided between each main girder 15 and the upper surface of the pier 11. The main girder 15 is composed of an I-shaped cross-section and includes an upper flange portion 15a, a lower flange portion 15b, and a web portion 15w connecting these.

[0016] The attachment member 25 attached to the main girder 15 is provided above the lower flange portion 15b at the lower part of the main girder 15. Each attachment member 25 is fixed to the web portion 15w at a height corresponding to the suspension length of the tension member 26. Each attachment member 25 is a plate member protruding in both horizontal directions from the web portion 15w. The end of each attachment member 25 protrudes outside the end of the lower flange portion 15b. Also, a floor slab 16 is fixed to the upper surface of the upper flange portion 15a of each main girder 15.

[0017] (Construction method of the bridge) Next, with reference to FIGS. 1, 3 to 5, the construction method of the above-described bridge will be described. Here, the case where the conventional metal bearing is replaced with a seismic isolation bearing will be described.

[0018] Figure 3 shows a bridge 30 using a conventional metal bearing 31. This bridge 30 includes a plurality of piers 11 arranged side by side at intervals in the bridge axis direction. On each pier 11, a plurality of metal bearings 31 are arranged at intervals in a direction perpendicular to the bridge axis. On each metal bearing 31, a main girder 15 is fixed respectively. And the plurality of main girders 15 fix and support a floor slab 16 placed thereon.

[0019] First, as shown in Figure 4, a mounting member 25 is welded to the lower part of the main girder 15. In addition, holes for passing a tension member 26 are formed in advance at the ends of each mounting member 25. Then, a support member 21 is constructed on each pier 11 of the above-described conventional bridge 30. This support member 21 is constructed of cast-in-place reinforced concrete. In this case, holes for passing the tension member 26 are provided in the overhanging portion 21a of the support member 21. This hole is provided directly above the hole of the tension member 26. Note that the support member 21 made of a precast reinforced concrete member or a material other than concrete may be fixed to the pier 11 with an anchor or the like.

[0020] Next, as shown in Figure 5, the tension member 26 is passed through the holes of the support member 21 and the mounting member 25 of the main girder 15. Then, the lower end portion of the tension member 26 is pin-jointed in a state of protruding downward from the mounting member 25, and the upper end portion of the tension member 26 is pin-jointed in a state of protruding above the overhanging portion 21a of the support member 21.

[0021] After that, as shown in Figure 1, the metal bearing 31 disposed under the main girder 15 is removed. As a result, the main girder 15 is supported by being suspended from the pier 11 integrated with the support member 21 via the tension member 26.

[0022] (Function) In the bridge 10 of this embodiment, the main girder 15 that supports the floor slab 16 is suspended from the support member 21 of the pier 11 via the tension member 26. Therefore, it is isolated by a pendulum without arranging a bearing between the pier 11 and the main girder 15.

[0023] According to this embodiment, the following effects can be obtained. (1) In this embodiment, the main girder 15 is suspended via a tension member 26 from a support member 21 fixed on the pier 11. As a result, the bridge 10 floats within the height of the main girder 15 from the upper surface of the pier 11, so that the height from the upper surface of the pier 11 to the floor slab 16 can be reduced. In this case, regardless of the weight supported by the tension member 26, the natural period is determined by the suspension length. Therefore, by appropriately setting the suspension length, desired seismic isolation can be realized. Further, due to the characteristics of the pendulum, a restoring force acts so as to always return to the origin after an earthquake, so that no residual displacement remains.

[0024] (2) In this embodiment, the support member 21 and the tension member 26 constituting the seismic isolation structure are provided in the space above the pier 11. Thereby, a seismic isolation structure can be realized without a part of the seismic isolation structure protruding in the bridge axis direction of the pier 11.

[0025] (3) In this embodiment, since the main girder 15 only needs to be lifted from the upper surface of the pier 11, the support member 21 and the tension member 26 can be installed while the conventional metal bearing 31 is attached, and after the installation of these is completed, the metal bearing 31 can be removed and the main girder 15 can be suspended. Therefore, the height from the upper surface of the pier 11 of the bridge 10 to the floor slab 16 can be made the same as that of the conventional bridge 30 with the metal bearing 31. Further, in order to provide a new seismic isolation bearing instead of the conventional metal bearing 31, it is not necessary to jack up the main girder 15.

[0026] (4) In this embodiment, each tension member 26 extends in the vertical direction. Thereby, regardless of the direction of sway, the same length can be maintained in the plurality of tension members 26, so that the sway of the main girder 15 can be absorbed in a well-balanced manner.

[0027] (5) An attachment member 25 for pin-joining the tension member 26 is provided on the main girder 15 of this embodiment. Since the length of the tension member 26 can be changed by changing the attachment height of the attachment member 25, an appropriate natural period can be realized.

[0028] This embodiment can be implemented with the following modifications. This embodiment and the following modification examples can be implemented in combination with each other within a technically non - conflicting range. · In the above - described embodiment, an attachment member 25 for pin - joining the lower end of the tension member 26 was provided at the lower part of the main girder 15. The structure of providing the tension member 26 for suspending the main girder 15 at the lower part of the main girder 15 is not limited to this.

[0029] For example, as shown in FIG. 6, a bridge 41 may be formed by directly pin - joining the lower end of a tension member 36 to the lower flange portion 15b of the main girder 15. Thereby, the lower flange portion can be used as it is without providing the attachment member 25.

[0030] · In the above - described embodiment, in order to arrange the tension member 26 in the vertical direction, the hole of the overhanging portion 21a of the support member 21 is provided directly above the hole of the tension member 26. In this case, the lower flange portion 15b does not necessarily need to be directly below the overhanging portion 21a of the support member 21. For example, as shown in FIG. 6, the tension member 36 may be provided so as to be arranged obliquely.

[0031] · In the above - described embodiment, the overhanging portion 21a of the support member 21 is provided at a position lower than the upper flange portion 15a of the main girder 15. The overhanging portion 21a is not limited to a position lower than the upper flange portion 15a as long as it protrudes from a plurality of support members arranged on the bridge pier to connect the upper part of the tension member. For example, when making the tension member longer than the main girder according to the natural period, the overhanging portion may be arranged at a position higher than the floor slab, and the tension member may be suspended from this overhanging portion.

[0032] · In the above - described embodiment, the main girder 15 is supported by a seismic isolation bearing that can swing in the bridge - axis direction and the direction perpendicular to the bridge - axis by being suspended by the tension member 26. The main girder 15 may be configured to be swingable only in the bridge - axis direction without swinging in the direction perpendicular to the bridge - axis. For example, it may be a bridge 42 shown in FIG. 7. In this bridge 42, the attachment member 35 provided on the main girder 15 is arranged with a slight gap with respect to the surface on the main girder 15 side of the main body portion 21b of the support member 21. Thereby, when the main girder 15 tends to sway in the direction perpendicular to the bridge axis, since the attachment member 35 is in contact with the support member 21, displacement in the direction perpendicular to the bridge axis is suppressed. Further, a part of the support member 21 may be brought into contact with the lower flange portion 15b of the main girder 15, or another member fixed to the support member 21 may be brought into contact with a part of the main girder 15. Further, instead of abutting on the main body portion 21b, the attachment member 35 may have a length such that it is separated from the main body portion 21b by an allowable range amount for suppressing displacement. Also, not only in the direction perpendicular to the bridge axis, but also a structure for restricting the displacement amount in the bridge axis direction may be provided.

[0033] · The bridge 10 of the above-described embodiment includes a seismic isolation bearing by suspending the main girder 15 using the tension member 26 provided on the support member 21. Further, a vibration damping damper may be provided to attenuate the sway generated in the bridge.

[0034] For example, as in the case of the bridge 46 shown in FIG. 8, a fixing member M1 is provided below the main girder 15. Then, a vibration damping damper D1 is provided between the pier 11 and the fixing member M1. The attachment location of the vibration damping damper can be arbitrarily determined.

[0035] · The bridge 10 of the above-described embodiment has been described as a simple girder bridge provided with a simple girder straddling two adjacent piers (abutments) in the adjacent bridge axis direction. The configuration of the bridge is not limited to this, and for example, it may be a continuous bridge having a continuous girder (main girder) without joints straddling three or more piers (including abutments) arranged in the bridge axis direction.

[0036] As shown in FIG. 9, in the case of a multi-span continuous bridge 47, a vibration damping damper D2 is provided between the pier 12 supporting at the center of the continuous girder and the fixing member M2 provided below the main girder 15. Here, the vibration damping damper is not limited to one, and a plurality may be arranged side by side in the bridge axis direction.

[0037] · The bridge 10 of the above embodiment was constructed by seismic reinforcement renovation work that replaced the conventional metal bearing 31 with a seismic isolation bearing in the bridge 30. The configuration of the bridge 10 is not limited to seismic reinforcement renovation work, and it can also be used as the structure of a newly installed bridge 10.

[0038] Next, the technical ideas that can be grasped from the above embodiment and alternative examples are supplemented as follows. (a) A bridge according to any one of claims 1 to 3, characterized in that a vibration damping device for stopping the sway of the main girder is further provided. (b) A bridge according to any one of claims 1 to 3, or the bridge according to (a) above, characterized in that a displacement limiting member for limiting the displacement of the main girder is further provided.

Explanation of reference numerals

[0039] D1, D2... vibration damping dampers, M1, M2... fixing members, 10, 30, 41, 42, 46... bridges, 11, 12... bridge piers, 15... main girder, 15a... upper flange part, 15b... lower flange part, 15w... web part, 16... floor slab, 21... support member, 21a... overhanging part, 21b... main body part, 25, 35... mounting members, 26, 36... tension members, 31... metal bearing, 47... multi-span continuous bridge.

Claims

1. A bridge comprising a main girder supporting a floor slab, piers supporting the main girder, and a seismic isolation bearing connecting the piers and the main girder, wherein the main girder includes a lower flange portion and a mounting member provided on a web portion above the lower flange portion and protruding horizontally, the seismic isolation bearing has a cantilever portion protruding at a position higher than the lower part of the main girder, and a plurality of support members arranged around the main girder on the piers, and a tension member connecting the lower part of the main girder and the cantilever portion arranged between the plurality of support members in a separated state, and the cantilever portion and the mounting member are connected by the tension member. The bridge is characterized by this.

2. The bridge according to claim 1, wherein the mounting member protrudes horizontally more than the end of the lower flange portion.

3. A method for constructing a bridge comprising a main girder supporting a floor slab, piers supporting the main girder, and a seismic isolation bearing connecting the piers and the main girder, wherein the main girder includes a lower flange portion, an upper flange portion, and a web portion connecting the lower flange portion and the upper flange portion, a mounting member protruding horizontally is provided on the web portion above the lower flange portion of the main girder placed on an existing bearing, after constructing a plurality of support members having a cantilever portion protruding at a position higher than the lower part of the main girder around the main girder on the piers, the mounting member and the cantilever portion of the main girder arranged between the plurality of support members are connected by a tension member in a separated state, and then the existing bearing is removed. The method for constructing a bridge is characterized by this.

Images