JP2021011736A - Girder reinforcement structure - Google Patents

Abstract

To provide a girder reinforcement structure capable of efficiently suppressing the dynamic response of a girder without interfering with the use of an existing girder.SOLUTION: A girder reinforcement structure to suppress the dynamic response of a girder 2 over a bridge pier 3, comprises a frame structure 4 in which a mooring part 41 arranged so as to surround a leg head 31 of the bridge pier, a bearing part 42 that comes into contact with a lower face 21 of the girder at a position protruding from the mooring part toward the center of the girder, and an inclined part 43 extending diagonally from the bearing part toward a bridge axial face 32 of the bridge pier are integrally formed from a frame material. Here, the load acting on the bearing part is transmitted to the leg head via the mooring part and to the bridge axial face 32 via the inclined part.SELECTED DRAWING: Figure 1

Description

The present invention relates to a girder reinforcement structure for suppressing the dynamic response of a girder spanned over a pier.

In recent years, the development of PRC (Prestressed Reinforced Concrete) technology has made it possible to reduce the rigidity of girders, and the number of bridges with large dynamic responses is increasing. In addition, as the traveling speed of trains and automobiles increases and the traffic volume increases, the dynamic response of the girder tends to increase, and the number of cases requiring reinforcement is increasing.

For example, in Patent Documents 1 and 2, by reinforcing the existing girder to increase the rigidity, it is possible to suppress the occurrence of resonance phenomenon in the girder due to train running and the occurrence of large shaking and bending. Is disclosed.

JP-A-2017-214669 JP-A-2017-218824

However, the work to reinforce the overall length of the girder in service must be carried out within various restrictions such as the train operation schedule, and the construction period and construction cost tend to increase. In some cases, direct reinforcement work for the girder cannot be performed.
Therefore, an object of the present invention is to provide a girder reinforcing structure capable of efficiently suppressing the dynamic response of the girder without hindering the use of the existing girder.

In order to achieve the above object, the girder reinforcing structure of the present invention is a girder reinforcing structure for suppressing the dynamic response of the girder bridged over the pier, and is arranged so as to surround the upper part of the pier. A mooring portion, a support portion that comes into contact with the lower surface of the girder at a position protruding from the mooring portion toward the center of the girder, and an inclined portion that extends obliquely from the support portion toward the side surface of the pier. The frame structure is integrally formed of a frame member, and the load acting on the bearing portion is transmitted to the upper part of the pier via the mooring portion and the side surface of the pier via the inclined portion. It is characterized by being transmitted to.

Here, a tensile force is generated in the mooring portion toward the bearing portion side, and a compressive force is generated in the inclined portion. In other words, a horizontal force acting toward the support portion side acts on the upper part of the pier, and a force in a direction intersecting the vertical plane acts on the side surface of the pier.

Further, the side surface of the pier may be provided with a pedestal portion having a surface orthogonal to the extending direction of the inclined portion. Further, the weight of the frame structure is preferably within 5% of the weight of the girder.

In the girder reinforcement structure of the present invention configured in this way, a frame structure in which a mooring portion, a support portion, and an inclined portion are integrally formed is attached to a bridge pier, and the support portion is brought into contact with the lower surface of the girder. The load acting on the bridge is transmitted to the upper part of the pier via the mooring portion and to the side surface of the pier via the inclined portion.

With such a configuration, it can be constructed only by the work below the girder, so that the use of the existing girder is not hindered. In addition, by using a pier with a relatively large yield strength, it becomes possible to efficiently suppress the dynamic response of the girder.

Further, in such a frame structure, since a tensile force is generated in the mooring portion toward the bearing portion and a compressive force is only generated in the inclined portion, it can be easily manufactured by the frame material.

Furthermore, from the frame structure, a horizontal force toward the bearing side acts on the upper part of the pier, and a force in the direction intersecting the vertical plane acts only on the side surface of the pier. In many cases, it is possible to suppress the dynamic response of the girder only by the original strength of the existing pier.

Here, by providing a pedestal portion having a surface orthogonal to the extending direction of the inclined portion on the side surface of the pier, the inclined portion can be easily arranged. Further, if the weight of the frame structure is kept within 5% of the weight of the girder, it is not necessary to reinforce the pier or the foundation, and the construction cost and the construction period can be reduced in many cases.

It is a perspective view explaining the structure of the reinforcement structure of the girder of this embodiment. It is a perspective view which looked at the frame structure from diagonally above. It is a perspective view which looked at the frame structure in the direction of a bridge axis. It is explanatory drawing which showed typically the force acting on the reinforcing structure of the girder of this embodiment. It is a perspective view explaining the structure of the reinforcement structure of the girder of Example 1. FIG. It is a perspective view which looked at the frame structure from above. It is a perspective view which looked up at the frame structure. It is explanatory drawing which illustrates the dimension of the frame structure. It is explanatory drawing which showed typically the force acting on the reinforcing structure of the girder of Example 1. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining the configuration of the girder reinforcing structure of the present embodiment, and FIGS. 2 and 3 are perspective views for explaining the configuration of the frame structure 4.

First, the bridge 1 provided with the girder reinforcement structure of the present embodiment will be described with reference to FIG. The bridge 1 is a structure in which a girder 2 is bridged between the piers 3 and 3 and between the pier 3 and the abutment (not shown). When the bridge 1 is a railway bridge, the train T runs on the track laid on the upper surface of the girder 2.

The girder 2 on which the end portion is placed on the upper end surface of the pier 3 is manufactured of PRC (Prestressed Reinforced Concrete), prestressed concrete (PC), reinforced concrete (RC), steel material, or the like. In short, it is applied to a girder 2 called a PC girder or a steel girder.

On the other hand, the pier 3 is constructed of reinforced concrete in a columnar or wall shape on a foundation portion composed of a footing 34, a foundation pile 35, or the like. The upper part of the pier 3 basically has a margin in bending strength and shearing strength unless the main reinforcing bars are reduced by means of paragraphs or the like.

The bridge pier 3 illustrated in the present embodiment has a shape in which the leg head 31 provided at the upper portion bulges in the direction orthogonal to the bridge axis. Here, the side surface of the columnar portion below the leg head 31 that appears in the bridge axis direction is referred to as the bridge axis direction surface 32, and the side surface in the direction orthogonal to the bridge axis is referred to as the width direction surface 33.

Then, the frame structure 4 constituting the girder reinforcing structure of the present embodiment is attached to the pier 3 having such a configuration, and the girder 2 is supported from the lower surface 21. That is, the frame structure 4 has a mooring portion 41 arranged so as to surround the leg head 31 of the bridge pier 3, and a bearing portion 42 that comes into contact with the lower surface 21 of the girder 2 at a position protruding from the mooring portion 41. An inclined portion 43 extending obliquely from the portion 42 toward the bridge axial surface 32 is integrally formed by the frame material.

Steel materials such as H-shaped steel, channel steel, and I-shaped steel can be used as the frame material constituting the frame structure 4. Further, the type of steel material and the size of the cross section can be suitable for each part. Hereinafter, the details of the frame structure 4 will be described with reference to FIGS. 2 and 3.

The mooring portion 41 is formed by a beam-shaped working portion 411 that comes into contact with the side surface of the leg head 31, and a beam-shaped protruding portion 421, 412 that projects from both ends of the working portion 411 toward the center of the girder 2, respectively. It is formed in a U-shape in a plan view.

The working portion 411 is brought into contact with the bridge axial plane on the side opposite to the bearing portion 42. Further, the inner surface of the overhanging portion 412 in the vicinity of the acting portion 411 is brought into contact with the width direction surface of the leg head 31. Here, the end portion of the working portion 411 and the end portion of the overhanging portion 412 are joined by a bolt or the like.

Then, a beam-shaped bearing portion 42 is bridged between the central ends of the girders 2 of the overhanging portions 421 and 412. That is, the working portion 411, the overhanging portions 421, 412, and the bearing portion 42 form a frame body having a substantially rectangular shape in a plan view.

A force in the direction of pushing down the support portion 42 supported by the inclined portion 43 acts on the frame body formed in this way, and the rise of the support portion 42 is restricted by the lower surface 21 of the girder 2, so that the leg head is specially formed. It can be fixed in the attached position without being fixed to 31. If necessary, a pedestal (not shown) for receiving the lower surfaces of the acting portion 411 and the overhanging portion 412 may be provided on the side surface of the leg head 31.

Rubber bearings 421, ... Are attached to the upper surface of the bearing portion 42 at intervals in the direction orthogonal to the bridge axis. The upper surface of the rubber bearing 421 comes into contact with the lower surface 21 of the girder 2. That is, the load from the girder 2 is input in the vertical direction with respect to the rubber bearing 421. Further, the rubber bearing 421 and the lower surface 21 of the girder 2 are only brought into contact with each other, but are not joined.

Then, the inclined portion 43 is obliquely extended from the support portion 42 toward the intermediate portion or the lower portion of the bridge axial surface 32 of the pier 3. As shown in FIG. 3, the inclined portion 43 is formed on an inclined surface which becomes a truss-like structure surface by the bundle member 431 and the inclined member 432.

The inclined portion 43 of the present embodiment is formed by three bundle members 431, ... That are substantially parallel to the bridge axis direction in a plan view, bundle members 431, 431, a support portion 42, and a lower frame portion 44. It is provided with diagonal members 432 and 432 that are diagonally bridged in the rectangular space to be formed.

The beam-shaped lower frame portion 44 forming the lower edge of the inclined portion 43 is a member that exerts a force from the frame structure 4 on the bridge axial surface 32 of the pier 3. That is, the vertical load input to the bearing portion 42 is transmitted horizontally to the mooring portion 41 and is also transmitted obliquely downward to the inclined portion 43.

Looking at the flow of such force from the pier 3 side, a horizontal force is input to the pier head 31 of the pier 3 from the acting portion 411, and the pier 3 is input from the lower frame portion 44 of the lower edge of the inclined portion 43. The force in the direction intersecting the bridge axial direction surface 32 of the bridge is input.

It is preferable to provide a pedestal portion 5 as shown in FIG. 4 between the lower frame portion 44 and the bridge axial direction surface 32 so that the force can be smoothly transmitted. The pedestal portion 5 has a mounting surface 51 that is a surface orthogonal to the extending direction of the inclined portion 43.

The lower frame portion 44 is fixed to the mounting surface 51 of the pedestal portion 5 with a post-construction anchor or the like. Here, the force acting from the lower frame portion 44 is mainly a pressing force in the direction orthogonal to the mounting surface 51, and no tensile force is generated on the post-construction anchor.

Then, the lower frame portion 44 and the working portion 411 of the mooring portion 41 are connected by a connecting portion 45. That is, the mooring portion 41, the inclined portion 43, and the connecting portion 45 form a triangle in a side view.

Next, the operation of the reinforcing structure of the girder of the present embodiment will be described.
FIG. 4 is a diagram schematically illustrating a force acting on the reinforcing structure of the girder of the present embodiment. This bridge 1 is a railway bridge, and train T runs at high speed.

The dynamic load generated by the running of the train T acts on the girder 2 via the wheels T2 of the bogie T1. Further, when the girder 2 vibrates due to the running of the train T, an inertial force due to the dead load of the girder 2 itself is also generated. That is, the acting load P acting on the support portion 42 of the frame structure 4 has a magnitude obtained by adding an inertial force to the train load.

On the other hand, from past studies, it has been found that the effect of reducing the dynamic response by adding a fulcrum cannot be obtained unless the fulcrum has a vertical rigidity of about 2000 kN / mm -4000 kN / mm for the double track. .. Therefore, assuming complete double-track loading, the design is performed assuming that the frame structure 4 is responsible for the acting load P, which is the total load generated by the train running.

That is, assuming that the design train load is 130 × 4 = 520 kN and the design dead load (inertial force) is about 300 kN, the working load P is about 1000 kN for the double track. Further, each member of the frame structure 4 uses a member having a frequency of 5 Hz or higher in order to avoid a frequency of about 3 Hz, which is a predominant frequency when a high-speed railway passes a train.

Further, since the weight increase works negatively in the event of an earthquake, the frame structure 4 should not be too heavy. For example, if the weight of the girder 2 is about 600 tons, the frame structure 4 has a weight of 5% or less, that is, 30 tons or less. For example, for safety reasons, it is preferable to manufacture the frame structure 4 having a weight of about 10 tons.

The frame structure 4 contacts the pier 3 at the intermediate portion or the lower portion of the pier head 31 and the bridge axial surface 32. The leg head 31 is brought into contact with the acting portion 411 so that only the horizontal force is transmitted. That is, the leg head 31 is embraced by the mooring portion 41 having a U-shape in a plan view so that the tensile force is not repeatedly loaded when the train T passes, and the horizontal force is resisted by the bearing pressure of concrete.

On the other hand, with respect to the bridge axial surface 32, the pedestal portion 5 is joined to the lower frame portion 44 by a post-construction anchor. After that, the shearing force that resists the vertical load and the compressive force that resists the horizontal force repeatedly act on the construction anchor when the train T passes. Considering this degree of influence, the number of post-construction anchors and the placement interval are determined.

In the girder reinforcement structure of the present embodiment configured as described above, the frame structure 4 in which the mooring portion 41, the bearing portion 42, and the inclined portion 43 are integrally formed is attached to the bridge pier 3, and the girder 2 is attached. The acting load P acting on the bearing portion 42 in contact with the lower surface 21 of the bridge is transmitted to the pier head 31 of the pier 3 via the mooring portion 41, and the bridge axial surface 32 of the pier 3 is transmitted via the inclined portion 43. To convey to.

With such a configuration, since it can be constructed only by the work below the girder 2, it does not interfere with the use of the existing girder 2. For example, if each member manufactured in a factory or the like is carried around the pier 3 and the frame structure 4 is assembled at a predetermined position by bolt joining, the frame structure 4 can be attached in a short time. In addition, such work does not hinder the running of the train T on the track laid on the upper surface of the girder 2.

Further, since the leg head 31 which is not provided as a paragraph of the main reinforcing bar has a relatively large bending strength and shear strength, the existing pier 3 can be used as it is without any special reinforcement. It is possible to efficiently suppress the dynamic response of the digit 2. That is, when the support portion 42 of the frame structure 4 adds a fulcrum to the center side of the girder 2 with respect to the pier 3, the dynamic response of the girder 2 can be reduced by the span shortening effect.

Then, in such a frame structure 4, a tensile force Q1 toward the support portion 42 side is generated in the mooring portion 41, but by using a frame material having a high tensile strength such as a steel material, the frame material has a high tensile strength. It can be manufactured easily and lightweight. Further, a compressive force Q2 is generated in the inclined portion 43, which can be easily dealt with by making the cross section and length so that buckling does not occur.

Further, from the frame structure 4, a horizontal force R1 toward the support portion 42 side acts on the pier head 31 of the pier 3, and the bridge axial surface 32 of the pier 3 intersects the vertical plane. Since the pressing force R2 in the direction only acts, it is possible to suppress the dynamic response of the girder 2 only by the proof stress originally possessed by the existing pier 3.

Specifically, the pier 31 of the pier 3 is surrounded by the mooring portion 41 and only a bearing load for the compressive strength predominant for the concrete structure is applied, and no tensile force is directly applied. It will not damage the existing pier 3. Further, since tensile fatigue does not occur in the post-construction anchor provided for fixing the lower frame portion 44 to the pier 3, damage to the existing pier 3 can be prevented.

Further, by providing the pedestal portion 5 having the mounting surface 51 orthogonal to the extending direction of the inclined portion 43 on the bridge axial direction surface 32 of the pier 3, the lower frame portion 44 of the lower edge of the inclined portion 43 is installed. Will be easy to do.

Further, by providing such a pedestal portion 5, it becomes possible to suppress the action of the tensile force on the post-construction anchor as much as possible, and it is possible to reduce the arrangement quantity of the post-construction anchor. That is, the force acting on the post-construction anchor can be easily made into a compressive force or a shearing force.

If the weight of the frame structure 4 is kept within 5% of the weight of the girder 2, it often falls within the allowable range of the design of the pier 3 and the foundation (34, 35), and the pier 3 and the like are reinforced. It will be possible to reduce the construction cost and construction period without doing so.

Hereinafter, an embodiment different from the girder reinforcing structure described in the above embodiment will be described with reference to FIGS. 5 to 9. The same or equivalent parts as those described in the above-described embodiment will be described with the same terms or the same reference numerals.

In the first embodiment, a frame structure 6 having a shape different from that of the frame structure 4 described in the above embodiment is used. The frame structure 6 of the first embodiment is also manufactured by using a steel material such as H-shaped steel, channel steel, or I-shaped steel as a frame material.

As shown in FIGS. 5 to 7, the frame structure 6 has a mooring portion 61 arranged so as to surround the leg head 31 of the bridge pier 3 and a lower surface 21 of the girder 2 at a position protruding from the mooring portion 61. The support portion 62 that comes into contact with the bridge and the inclined portion 63 that extends obliquely from the support portion 62 toward the bridge axial surface 32 are integrally formed by the frame material.

As shown in FIG. 6, the mooring portion 61 includes an action portion 611 arranged so as to surround the leg head 31 having a substantially rectangular plan view, and an overhang extending from the action portion 611 toward the center of the girder 2. Formed by part 612.

The inner surface of the action portion 611 having a rectangular shape in a plan view is brought into contact with the side surface of the leg head 31. The beam-shaped frame members on each side of the working portion 611 are joined by bolts or the like. Since a large force does not act on each member of the working portion 611, it is possible to reduce the weight by using a steel material having a relatively small cross section.

On the other hand, since a large tensile force is generated in the overhanging portion 612, the overhanging portion 612 is manufactured of a steel material having a relatively large cross section, and is reinforced with a diagonal material or the like as necessary. Then, a beam-shaped bearing portion 62 is provided at the central edge of the girder 2 of the overhanging portion 612.

Rubber bearings 621, ... Are attached to the upper surface of the bearing portion 62 at intervals in the direction orthogonal to the bridge axis. The upper surface of the rubber bearing 621 is brought into contact with the lower surface 21 of the girder 2 without being joined.

Then, the inclined portion 63 is obliquely extended from the support portion 62 toward the intermediate portion or the lower portion of the bridge axial surface 32 of the pier 3. As shown in FIG. 7, the inclined portion 63 is formed on an inclined surface by the main material 631 and the reinforcing member 632. In FIG. 7, the support portion 62 is not shown.

The inclined portion 63 of the first embodiment includes three main members 631, ... That are substantially parallel to the bridge axis direction in a plan view, and a reinforcing member 632 that is obliquely arranged at a corner portion. .. Here, a steel material having a large cross section is used for the main material 631, and a steel material having a small cross section is used for the reinforcing material 632.

The beam-shaped lower frame portion 64 forming the lower edge of the inclined portion 63 is a member that exerts a force from the frame structure 6 on the bridge axial surface 32 of the pier 3. That is, the vertical load input to the bearing portion 62 is transmitted horizontally to the mooring portion 61 and diagonally downward to the inclined portion 63.

A pedestal portion 5 can be provided between the lower frame portion 64 and the bridge axial direction surface 32 so that force can be smoothly transmitted. Further, the lower end side of the lower frame portion 64 can be molded into the same shape as the pedestal portion.

Then, as shown in FIG. 5, the action portion 611 of the mooring portion 61, the vicinity of the boundary of the overhanging portion 612, and the lower frame portion 64 are connected by a connecting portion 65. FIG. 8 shows an example of the dimensions of the frame structure 6.

Here, H-shaped steel having a cross-sectional height of 200 mm was used for the working portion 611, the lower frame portion 64, and the reinforcing material 632, and H-shaped steel having a cross-sectional height of 500 mm was used for the other members. In addition, in order to make the member 5Hz or higher avoiding the predominant frequency when passing a high-speed railway train, if it is an H-section steel with a cross-sectional shape of H-200 × 200 × 8 × 12, the length should be 1500 mm or less. -For H-beams with a cross-sectional shape of 500 x 500 x 25 x 25, the length should be 2400 mm or less.

Next, the operation of the reinforcing structure of the girder of the first embodiment will be described.
FIG. 9 is a diagram schematically illustrating a force acting on the reinforcing structure of the girder of the first embodiment. Here, the frame structure 6 is attached to the pier 3 so that the angle formed by the bridge axial surface 32 and the inclined portion 63 is θ.

This bridge 1 is also a railway bridge, and as the train T travels, a working load P of about 1000 kN in total of the train load and the inertial force of the girder 2 acts on the bearing portion 62. When the acting load P is loaded on the bearing portion 62 in the vertical direction, the force of Ptan θ is transmitted to the mooring portion 61 in the horizontal direction. This force acts as a horizontal force from the acting portion 611 to the leg head 31 of the pier 3. Further, as the reaction force, a tensile force of + Ptan θ is generated in the mooring portion 61.

On the other hand, a compressive force of −P / cos θ is generated in the inclined portion 63. Then, a force having a magnitude of P acts in the vertical direction and a force of Ptan θ acts in the horizontal direction on the bridge axial surface 32 of the pier 3 via the lower frame portion 64.

In the girder reinforcement structure of the first embodiment configured in this way, the additional load applied to the pier 3 by attaching the frame structure 6 is Ptan θ at the pier head 31 and Ptan θ at the bridge axial plane 32. , Only the resultant force of P in the vertical direction and Ptan θ in the horizontal direction.

In short, the frame structure 6 can reduce the dynamic response to the extent that these additional loads are acceptable, without adding any reinforcement to the piers 3. Further, the frame structure 6 which is effective in reducing the dynamic response can be installed only by reinforcing a part of the pier 3 as needed.

Further, the frame structure 6 of the first embodiment can shorten the extension of the inclined portion 63 as compared with the frame structure 4 described in the above embodiment. Here, the rigidity that can suppress the deflection of the girder 2 (equivalent vertical rigidity) is determined only by the length of the main material 631 of the inclined portion 63 and the axial rigidity. Therefore, for example, the inclined portion that can make the equivalent vertical rigidity 300 kN / mm or more. By determining the length to 63, the dynamic response of the digit 2 can be effectively suppressed.
Since other configurations and actions and effects are substantially the same as those of the above-described embodiment, description thereof will be omitted.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment or the first embodiment, and the design is such that the gist of the present invention is not deviated. Modifications are included in the present invention.

For example, in the above-described embodiment, the railway bridge on which the train T travels as the bridge 1 has been described, but the present invention is not limited to this, and the present invention is applied to a road bridge in which the girder vibrates due to the traveling of an automobile. Can be done.

Further, in the above-described embodiment, the pier 3 having a bulging leg head 31 has been described as an example, but the present invention is not limited to this, and the shape of the horizontal cross section is substantially uniform in the height direction. The present invention can be applied to various piers.

1: Bridge 2: Girder 21: Bottom surface 3: Pier 31: Leg head (upper part)
32: Bridge axial plane (side surface)
4: Frame structure 41: Mooring part 42: Support part 43: Inclined part 5: Pedestal part 51: Mounting surface 6: Frame structure 61: Mooring part 62: Supporting part 63: Inclined part P: Acting load Q1: Pull Force Q2: Compressive force R1: Horizontal force R2: Pushing pressure

Claims (5)

It is a reinforcement structure of the girder to suppress the dynamic response of the girder over the pier.
A mooring portion arranged so as to surround the upper portion of the pier, a bearing portion that contacts the lower surface of the girder at a position protruding from the mooring portion toward the center of the girder, and a side surface of the pier from the support portion. It is provided with a frame structure in which an inclined portion extending obliquely toward is formed integrally with a frame material.
A girder reinforcing structure, characterized in that the load acting on the bearing portion is transmitted to the upper part of the pier via the mooring portion and is transmitted to the side surface of the pier via the inclined portion. The girder reinforcing structure according to claim 1, wherein a tensile force is generated in the mooring portion toward the support portion side, and a compressive force is generated in the inclined portion. The first aspect of the present invention, wherein a horizontal force acting toward the support portion side acts on the upper part of the pier, and a force acting in a direction intersecting the vertical plane acts on the side surface of the pier. Reinforced structure of the girder. The girder reinforcing structure according to any one of claims 1 to 3, wherein a pedestal portion having a surface orthogonal to the extending direction of the inclined portion is provided on the side surface of the pier. The reinforcing structure for a girder according to any one of claims 1 to 4, wherein the weight of the frame structure is within 5% of the weight of the girder.