JP7123870B2 - Girder reinforcement structure - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a girder reinforcement structure for suppressing the dynamic response of a girder spanned over a bridge 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 response is increasing. In addition, as the speed of trains and automobiles increases and the amount of traffic increases, the dynamic response of girders tends to increase, and the number of cases requiring reinforcement is increasing.

For example, in Patent Documents 1 and 2, by reinforcing the existing girders to increase their rigidity, a resonance phenomenon occurs in the girders due to train running, and a girder reinforcement structure that can suppress the occurrence of large shaking and deflection. is disclosed.

JP 2017-214699 A JP 2017-218824 A

However, the construction to reinforce the entire length of the girder in service must be carried out within various restrictions such as train operation schedules, and the construction period and construction costs tend to increase. In addition, there are cases where direct reinforcement work on girders cannot be performed.
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a girder reinforcement structure capable of efficiently suppressing the dynamic response of girder without interfering with the use of existing girder.

In order to achieve the above object, the girder reinforcement structure of the present invention is a girder reinforcement structure for suppressing the dynamic response of a girder spanned over a bridge pier, and is arranged to surround the upper part of the pier. a mooring portion; a bearing portion that contacts the lower surface of the girder at a position projecting from the mooring portion toward the center of the girder; and an inclined portion that extends obliquely from the bearing portion toward the side surface of the pier. is integrally formed by frame members, and the load acting on the bearing portion is transmitted to the upper portion of the pier through the mooring portion and to the side surface of the pier through the inclined portion. is transmitted to

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

Moreover, it is possible to adopt a configuration in which a pedestal portion having a surface perpendicular to the extending direction of the inclined portion is provided on the side surface of the pier. Furthermore, 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 constructed as described above, a frame structure integrally formed with a mooring portion, a bearing portion, and an inclined portion is attached to a bridge pier, and the bearing portion is in contact with the lower surface of the girder. The load acting on the pier is transmitted to the upper part of the pier via the mooring part and to the side of the pier via the inclined part.

With such a configuration, it can be constructed only by work below the girders, so that the use of the existing girders is not hindered. In addition, by using piers that have a relatively large margin of strength, it is possible to effectively suppress the dynamic response of the girders.

In addition, in such a frame structure, a tensile force directed toward the support portion is generated in the mooring portion and a compressive force is generated only in the inclined portion, so that the frame structure can be easily manufactured using a frame material.

Furthermore, from the frame structure, a horizontal force acts on the upper part of the pier toward the bearing part, and a force in a direction crossing the vertical plane acts on the side of the pier. In many cases, it is possible to suppress the dynamic response of the girder only with the bearing capacity originally possessed by the existing piers.

Here, by providing a pedestal portion having a surface orthogonal to the extending direction of the inclined portion on the side surface of the bridge pier, the inclined portion can be easily arranged. Also, if the weight of the frame structure is kept within 5% of the weight of the girder, there is no need to reinforce the bridge piers and foundations, and in many cases it is possible to reduce construction costs and construction periods.

FIG. 2 is a perspective view for explaining the configuration of a girder reinforcing structure according to the present embodiment; It is the perspective view which looked at the frame structure from diagonally upward. It is the perspective view which looked at the frame structure in the bridge axis direction. FIG. 4 is an explanatory diagram schematically showing a force acting on the girder reinforcement structure of the present embodiment; FIG. 2 is a perspective view illustrating the configuration of the reinforcement structure for the girder of the first embodiment; It is the perspective view which looked at the frame structure from upper direction. FIG. 4 is a perspective view looking up at the frame structure; FIG. 4 is an explanatory diagram illustrating dimensions of a frame structure; FIG. 4 is an explanatory diagram schematically showing a force acting on the reinforcement structure of the girder of Example 1;

BEST MODE FOR CARRYING OUT THE INVENTION 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 this embodiment, and FIGS. 2 and 3 are perspective views for explaining the configuration of the frame structure 4. As shown in FIG.

First, a bridge 1 provided with a girder reinforcement structure according to the present embodiment will be described with reference to FIG. This bridge 1 is a structure in which a girder 2 spans between piers 3 and 3 and between a pier 3 and an 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 girders 2 whose ends are placed on the upper end surfaces of the piers 3 are made of PRC (Prestressed Reinforced Concrete), prestressed concrete (PC), reinforced concrete (RC), steel, or the like. In short, it is applied to the girders 2 called PC girders or steel girders.

On the other hand, the bridge piers 3 are constructed of reinforced concrete in the form of columns or walls on a foundation composed of footings 34, foundation piles 35, and the like. The upper part of the pier 3 basically has a margin of bending strength and shear strength unless the number of main reinforcing bars is reduced due to steps or the like.

The bridge pier 3 exemplified in the present embodiment has a shape in which the leg head 31 provided on the upper part protrudes in the direction perpendicular to the bridge axis. Here, the side surface appearing in the bridge axis direction of the columnar portion below the leg head 31 is defined as the bridge axis direction surface 32 , and the side surface perpendicular to the bridge axis is defined as the width direction surface 33 .

The frame structure 4 that constitutes the girder reinforcement structure of the present embodiment is attached to the bridge pier 3 having such a configuration, and supports the girder 2 from the lower surface 21 . That is, the frame structure 4 includes a mooring portion 41 arranged to surround the leg head portion 31 of the pier 3, a bearing portion 42 projecting from the mooring portion 41 and brought into contact with the lower surface 21 of the girder 2, and a bearing An inclined portion 43 extending obliquely from the portion 42 toward the bridge axis direction surface 32 is integrally formed by the frame member.

Steel materials such as H-shaped steel, channel steel, and I-shaped steel can be used for the frame material that constitutes the frame structure 4 . Also, the type of steel material and the size of the cross section can be suitable for each part. Details of the frame structure 4 will be described below with reference to FIGS.

The mooring part 41 has a beam-shaped working part 411 that contacts the side surface of the leg head 31 and beam-shaped projecting parts 412 that project from both ends of the working part 411 toward the center of the girder 2. It is formed in a U shape in plan view.

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

A beam-shaped support portion 42 is bridged between the ends of the overhanging portions 412 , 412 on the center side of the girder 2 . That is, the action portion 411, the overhanging portions 412, 412, and the support portion 42 form a substantially rectangular frame in plan view.

A force in the direction of pushing down the bearing portion 42 supported by the inclined portion 43 acts on the frame thus formed, and the rise of the bearing portion 42 is restricted by the lower surface 21 of the girder 2. 31, it can remain in the installed position without fixing. Note that a support (not shown) for receiving the lower surfaces of the action portion 411 and the projecting portion 412 may be provided on the side surface of the leg head 31 as necessary.

Rubber bearings 421, . . . The upper surface of this rubber bearing 421 comes into contact with the lower surface 21 of the girder 2 . That is, the load from the girder 2 is vertically input 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 and are not joined together.

The inclined portion 43 extends obliquely from the support portion 42 toward the intermediate portion or lower portion of the axial direction surface 32 of the pier 3 . As shown in FIG. 3 , the inclined portion 43 is formed into an inclined surface that becomes a truss-like structure surface by bundle members 431 and diagonal members 432 .

The inclined portion 43 of the present embodiment is formed by three bundles 431, . diagonal members 432, 432 that are diagonally spanned across a rectangular space formed by

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

Looking at such a flow of force from the side of the pier 3, a horizontal force is input to the leg head portion 31 of the pier 3 from the action portion 411, and the lower frame portion 44 of the lower edge of the inclined portion 43 is applied to the pier 3. A force in a direction intersecting with the bridge axis direction surface 32 of is input.

Between the lower frame portion 44 and the bridge axis direction surface 32, it is preferable to provide a pedestal portion 5 as shown in FIG. 4 so that 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 post-installed anchors or the like. Here, the force acting from the lower frame portion 44 is mainly the pressing force in the direction orthogonal to the mounting surface 51, and no tensile force is generated in the post-installed anchor.

A connecting portion 45 connects the lower frame portion 44 and the action portion 411 of the mooring portion 41 . That is, the mooring portion 41, the inclined portion 43, and the connecting portion 45 form a triangle when viewed from the side.

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

A dynamic load generated by 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 the inertial force to the train load.

On the other hand, based on past studies, it has been found that adding a fulcrum does not reduce the dynamic response unless the fulcrum has a vertical stiffness of about 2000 kN/mm - 4000 kN/mm for a double track. . Therefore, a design is made on the assumption that the frame structure 4 bears the acting load P, which is the total load generated by the running of the train, assuming complete double-track loading.

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 applied load P for the double track is about 1000 kN. Each member of the frame structure 4 uses a frequency of 5 Hz or higher in order to avoid a frequency of about 3 Hz, which is the dominant frequency when a high-speed railroad train passes.

In addition, the frame structure 4 should not be too heavy because the increase in weight will have a negative effect in the event of an earthquake. For example, if the weight of the girder 2 is about 600 tons, the weight of the frame structure 4 should be within 5%, that is, within 30 tons. For example, it is preferable to manufacture the frame structure 4 with a weight of about 10 tons for safety.

The frame structure 4 contacts the bridge pier 3 at the leg head portion 31 and the middle or lower portion of the axial direction surface 32 . The leg head 31 is brought into contact so that only the horizontal force is transmitted from the acting portion 411 . That is, in order to prevent the tensile force from being repeatedly applied when the train T passes, the leg head portion 31 is held by the mooring portion 41 which is U-shaped in plan view, and the horizontal force is resisted by the bearing pressure of the concrete.

On the other hand, the surface 32 in the bridge axial direction is joined to the lower frame portion 44 at the position of the pedestal portion 5 by post-installed anchors. Thereafter, shear force resisting vertical load and compressive force resisting horizontal force are repeatedly applied to the construction anchor when the train T passes. Considering this degree of influence, the number of post-installed anchors and the arrangement 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 Acting load P acting on the bearing portion 42 that is in contact with the lower surface 21 is transmitted to the leg head portion 31 of the pier 3 via the mooring portion 41, and the axial direction surface 32 of the pier 3 via the inclined portion 43. be transmitted to

With such a configuration, it can be constructed only by work below the girder 2, so the use of the existing girder 2 is not hindered. For example, if each member manufactured in a factory or the like is carried around the bridge pier 3 and bolted to assemble the frame structure 4 at a predetermined position, the installation can be completed in a short time. Further, such work does not hinder the running of the train T on the track laid on the upper surface of the girder 2 .

Furthermore, since the leg head 31, in which the main reinforcing bars are not stepped, etc., has a relatively large margin in bending resistance and shear resistance, the existing pier 3 can be used as it is without special reinforcement. is possible and can effectively suppress the dynamic response of digit 2. That is, when the supporting point 42 of the frame structure 4 adds a fulcrum closer to the center of the girder 2 than the pier 3, the dynamic response of the girder 2 can be reduced due to the span shortening effect.

In such a frame structure 4, a tensile force Q1 is generated in the mooring portion 41 toward the bearing portion 42 side. It can be manufactured easily and lightly. In addition, although a compressive force Q2 is generated in the inclined portion 43, it can be easily dealt with by selecting a cross section and length that do not cause buckling.

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

Specifically, the leg head 31 of the bridge pier 3 is surrounded by the mooring portion 41 and is only subjected to a bearing load against the compressive strength that is outstanding for a concrete structure, and a tensile force is not directly applied. The existing bridge piers 3 are not damaged. In addition, since tensile fatigue does not occur in post-construction anchors provided for fixing the lower frame portion 44 to the pier 3, damage to the existing pier 3 can be prevented.

Furthermore, by providing the pedestal portion 5 having the mounting surface 51 orthogonal to the extending direction of the inclined portion 43 on the axial direction surface 32 of the bridge pier 3, the lower frame portion 44 at the lower edge of the inclined portion 43 is installed. can be done easily.

Further, by providing such a pedestal portion 5, it is possible to suppress the application of tensile force to the post-installed anchors as much as possible, and the number of post-installed anchors to be arranged can be reduced. That is, the force acting on the post-installed anchor can be easily converted to compressive force or shear force.

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

An embodiment different from the girder reinforcing structure described in the above embodiment will be described below with reference to FIGS. 5 to 9. FIG. It should be noted that the same terminology or the same reference numerals will be used to describe the same or equivalent portions as those described in the above embodiment.

In Example 1, 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 Example 1 is also manufactured using steel materials such as H-section steel, channel steel, and I-section steel as frame materials.

As shown in FIGS. 5 to 7, the frame structure 6 includes mooring portions 61 arranged so as to surround the leg heads 31 of the bridge piers 3, and the lower surface 21 of the girder 2 at a position projecting from the mooring portions 61. A support portion 62 that contacts the bridge and an inclined portion 63 that extends obliquely from the support portion 62 toward the bridge axis direction surface 32 are integrally formed of a frame member.

As shown in FIG. 6, the mooring portion 61 includes an action portion 611 arranged to surround the leg head portion 31, which is substantially rectangular in plan view, and an overhang projecting from the action portion 611 toward the center of the girder 2. 612.

The inner surface of the acting portion 611 having a square shape in plan view is brought into contact with the side surface of the leg head portion 31 . The beam-shaped frame members that form the sides of the action portion 611 are joined together by bolts or the like. Since a large force does not act on each member of the action 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 made of a steel material having a relatively large cross section, and is reinforced with diagonal members or the like as necessary. A beam-like support portion 62 is provided on the edge of the projecting portion 612 on the center side of the girder 2 .

Rubber bearings 621, . . . The upper surface of this rubber bearing 621 is brought into contact with the lower surface 21 of the girder 2 without joining.

The inclined portion 63 extends obliquely from the support portion 62 toward the intermediate portion or lower portion of the axial direction surface 32 of the pier 3 . The inclined portion 63 is formed on an inclined surface by a main member 631 and a reinforcing member 632, as shown in FIG. 7, illustration of the support portion 62 is omitted.

The inclined portion 63 of the first embodiment includes three main members 631, . . Here, a steel material with a large cross section is used for the main member 631 and a steel material with a small cross section is used for the reinforcing member 632 .

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

A pedestal portion 5 can be provided between the lower frame portion 64 and the bridge axis direction surface 32 so that force can be smoothly transmitted. Also, the lower end portion side of the lower frame portion 64 can be formed in the same shape as the pedestal portion.

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

Here, H-section steel with a section height of 200 mm was used for the working portion 611, the lower frame section 64, and the reinforcing member 632, and H-section steel with a section height of 500 mm was used for the other members. In addition, in order to avoid the dominant frequency of high-speed railroad trains passing by 5Hz or higher, the length of H-shaped steel with a cross-sectional shape of H-200 x 200 x 8 x 12 should be 1500 mm or less. -For H-shaped steel with a cross section of 500 x 500 x 25 x 25, the length shall be 2400 mm or less.

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

This bridge 1 is also a railway bridge, and as the train T runs, an acting load P of about 1000 kN, which is the sum of the train load and the inertial force of the girder 2, acts on the bearings 62 . When the supporting portion 62 is loaded with the acting load P in the vertical direction, a 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 portion 31 of the pier 3 . Moreover, 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 of P in the vertical direction and a force of P tan θ in the horizontal direction act on the axial direction surface 32 of the pier 3 via the lower frame portion 64 .

In the girder reinforcement structure of Example 1 configured in this way, the additional load applied to the pier 3 by attaching the frame structure 6 is Ptan θ at the pedestal head 31 and , the resultant force of P in the vertical direction and Ptan θ in the horizontal direction.

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

Further, in the frame structure 6 of Example 1, the extension of the inclined portion 63 can be shortened compared to the frame structure 4 described in the above embodiment. Here, the rigidity (equivalent vertical rigidity) that can suppress the deflection of the girder 2 is determined only by the length and axial rigidity of the main member 631 of the inclined portion 63. By determining the length of 63, the dynamic response of digit 2 can be effectively suppressed.
Other configurations and effects are substantially the same as those of the above-described embodiment, so description thereof will be omitted.

The embodiments of the present invention have been described in detail above with reference to the drawings. Modifications are included in the invention.

For example, in the above embodiment, a railway bridge on which a train T runs has been described as the bridge 1, but the invention is not limited to this, and the present invention can also be applied to a road bridge in which girders vibrate due to the running of automobiles. can be done.

Further, in the above-described embodiment, the pier 3 having a bulging leg head 31 was described as an example, but the pier 3 is not limited to this. The present invention can also be applied to bridge piers.

1 : Bridge 2 : Girder 21 : Underside 3 : Pier 31 : Leg head (upper part)
32: Bridge axis direction surface (side surface)
4: frame structure 41 : mooring portion 42 : bearing portion 43 : inclined portion 5 : pedestal portion 51 : mounting surface 6 : frame structure 61 : mooring portion 62 : bearing portion 63 : inclined portion P : acting load Q1 : tension Force Q2: Compressive force R1: Horizontal force R2: Pressing force

Claims (3)

A girder reinforcement structure for suppressing the dynamic response of a girder spanned over a bridge pier,
A mooring portion arranged to surround an upper portion of the pier; a bearing portion projecting from the mooring portion toward the center of the girder and in contact with the lower surface of the girder; and a side surface of the pier extending from the bearing portion. A frame structure in which an inclined portion extending obliquely downward toward is formed integrally with shaped steel ,
The mooring portion is formed by a working portion that contacts the side surface of the upper portion of the pier on the side opposite to the bearing portion, and an overhanging portion that projects horizontally from the working portion toward the center of the girder. , the beam-shaped support portion is provided at the end portion of the overhang portion on the center side of the girder,
The load acting from the girder in the direction of pushing down the bearing portion is transmitted as a horizontal force from the acting portion to the upper portion of the pier via the overhang portion, and is transmitted to the intermediate portion of the pier via the inclined portion. or the reinforcement structure of the girder, characterized in that it is transmitted to the side surface of the lower part . 2. The girder reinforcement structure according to claim 1 , wherein a pedestal portion having a surface orthogonal to the extending direction of the inclined portion is provided on a side surface of the pier. The girder reinforcement structure according to claim 1 or 2 , wherein the weight of said frame structure is within 5% of the weight of said girder.

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