JPH11264112A - Lower structure of railway viaduct and design method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely ensure safety of a train traveling on a viaduct even in the case it encouters a great earthquake. SOLUTION: The lower structure 4 of a railway viaduct 1 is so constituted that inverted V-steel frame brace members 3 are arranged to an in-plane space of frame structure 2 formed of reinforced concrete and, at the same time, the neighborhoods of the tops of them are connected to the lower surface of the central part of a beam for the frame structure 2 through energy absorption members 7. The lower structure 4 is so constituted that natural frequency at right angles to the bridge axis of the diaduct 1 exceeds 2Hz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lower structure of a railway viaduct on which a railroad track is laid and a method of designing the lower structure.

[0002]

2. Description of the Related Art As bridges on which railway vehicles travel, there are so-called viaducts which are continuously constructed in urban areas, in addition to narrow bridges which cross rivers and straits. From the viewpoint of efficient land use, such viaducts are continuously constructed in the space on roads, railways, or rivers. It also contributes to eliminating traffic jams.

[0003] By the way, the lower structure of such a railway viaduct is usually usually constructed as a reinforced concrete ramen structure. When designing and constructing the railway viaduct, of course, not only the soundness of the viaduct itself during an earthquake, The safety of traveling vehicles must also be fully considered.

[0004]

However, in the case of encountering an unexpectedly large earthquake, there is some concern in the conventional viaduct whether or not the safety of the traveling vehicle can be ensured.

The present invention has been made in view of the above-described circumstances, and has been developed in consideration of the above-mentioned circumstances, and is intended to provide a railway viaduct capable of reliably ensuring the safety of vehicles traveling on the viaduct even in the event of a huge earthquake. An object of the present invention is to provide a substructure and a design method thereof.

[0006]

In order to achieve the above object, a lower structure of a railway viaduct according to the present invention is, as described in claim 1, a ramen structure arranged in a direction orthogonal to a bridge axis, and the ramen structure. And a brace material arranged in an in-plane space of the structure, and the brace material is connected to the ramen structure via a predetermined energy absorbing member.

[0007] Further, the lower structure of the railway viaduct according to the present invention has a natural frequency of 2H in a direction orthogonal to the bridge axis of the railway viaduct.
It is configured to be z or more.

The method for designing a railway viaduct undercarriage according to the present invention adds the relationship between the vibration frequency at the track laying position of the viaduct and the lateral displacement amplitude of the track. A graph is created by superimposing a driving safety limit curve dividing a safety area and a derailment area relating to driving safety on a curve group obtained for each vibration acceleration, and using the graph, the driving corresponding to the designed excitation acceleration is performed. The vibration frequency of the safety limit curve is determined, and the ramen structure and the surface of the ramen structure arranged in the direction orthogonal to the bridge axis so that the natural frequency of the viaduct in the direction orthogonal to the bridge axis is equal to or higher than the vibration frequency. It is to design a lower structure of a railway viaduct composed of a brace material arranged in an inner space and connected to the ramen structure via a predetermined energy absorbing member.

In the substructure of the railway viaduct according to the first aspect of the present invention, the energy absorbing member interposed between the ramen structure and the brace material is provided in response to the vibration of the seismic motion along the direction orthogonal to the bridge axis. Absorb vibration energy,
Quickly converge the viaduct sway. On the other hand, the input seismic energy is the hysteresis of the energy absorbing member,
The ramen structure and the brace material, which are consumed in the form of viscous damping and the like, and are the main structures of the viaduct undercarriage, maintain soundness with almost no damage. Therefore, after the earthquake, by replacing the energy absorbing member with a new one, the use of the viaduct can be continued as before.

The energy absorbing member may be constructed in any manner, but may be, for example, a hysteretic damping member made of extremely mild steel or a thin steel sheet with slits.
What kind of material the ramen structure and the brace material are made of is optional. The brace material can be made of, for example, PC steel wire.
It is a general form that the brace material is made of a steel frame.

The position of the energy absorbing member may be determined as appropriate depending on the shape and arrangement of the brace material. For example, the brace material may be formed in an inverted V-shape, and the vertex and the ramen structure may be used. And the lower center of the beam.

As described above, how to construct the viaduct lower structure including the ramen structure, the brace material and the energy absorbing member is arbitrary, but the natural frequency of the railway viaduct in the direction orthogonal to the bridge axis is 2 Hz or more. With such a configuration, the rolling of the viaduct is effectively suppressed, and the traveling safety of the vehicle traveling on the railway viaduct is greatly improved. The size of the cross section of the ramen structure, the brace material, or the like may be determined by vibration analysis, a vibration experiment using a vibrator, or the like.

[0013] In the design method of the invention according to claim 3, first, the relationship between the vibration frequency at the laying position of the viaduct and the lateral displacement amplitude of the track is calculated in a curve group obtained for each vibration acceleration. A graph is created by superimposing a driving safety limit curve that separates a safety area and a derailment area related to safety.

Next, the vibration frequency of the driving safety limit curve corresponding to the designed vibration acceleration is calculated using the graph.

Next, a ramen structure arranged in the direction orthogonal to the bridge axis and a predetermined space disposed in the in-plane space of the ramen structure so that the natural frequency of the viaduct in the direction orthogonal to the bridge axis is equal to or higher than the excitation frequency. A lower structure of a railway viaduct composed of a brace material connected to the ramen structure via the energy absorbing member of (1) is designed.

In this way, the running safety of the vehicle running on the viaduct is reliably guaranteed within the range of the designed acceleration.

In order to design the lower structure of the viaduct so that the natural frequency of the viaduct in the direction orthogonal to the bridge axis is equal to or higher than the excitation frequency obtained from the above graph, the ramen structure, A method of determining the cross section of the brace material or the like by a vibration analysis, a vibration experiment using a vibrator, or the like is considered.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a railway viaduct according to the present invention; It is to be noted that the same reference numerals are given to components and the like that are substantially the same as those in the conventional technology, and description thereof will be omitted.

(First Embodiment) FIG. 1 is a cross-sectional view of a railway viaduct 1 including a lower structure 4 and an upper structure 5 including a bridge girder and the like bridged over the lower structure 4 as viewed from the bridge axis direction. As can be seen from the figure, the lower structure 4 of the railway viaduct 1 according to the present embodiment has an inverted V-shaped steel frame brace member 3 arranged in the in-plane space of a rigid frame structure 2 made of reinforced concrete and a top portion thereof. The vicinity is connected to the beam center lower surface of the rigid frame structure 2 via the energy absorbing member 7.

In the lower structure 4, the cross sections of the rigid frame structure 2, the brace material 3 and the energy absorbing member 7 are determined so that the natural frequency of the viaduct 1 in the direction orthogonal to the bridge axis is 2 Hz or more. In determining these cross sections, the cross section may be determined, for example, by analysis, or an exciter may be mounted on the viaduct 1 or an experimental model thereof to perform a vibration experiment, and the viaduct or the experimental model may be actually 2 Hz.
The cross section of each member described above may be determined so as to resonate as described above.

If the rigidity described above can be ensured by arranging the brace members 3, the foundation beams 6 connecting the legs of the ramen 2 may be omitted. By omitting such foundation beams, the construction cost of the lower structure 4 can be significantly reduced.

Here, in determining each cross section of the ramen structure 2, the brace material 3, and the energy absorbing member 7, as shown in the restoring force characteristic of FIG. Rather than assuming an earthquake that deforms within the range of ₁ ), the energy absorbing member 7 yields down (when point A in the same figure) when it encounters a large direct earthquake, and the form of hysteresis attenuation In order to be able to efficiently absorb the seismic energy, it is good to assume that the maximum value of each member falls between θ ₁ and θ _{2 in} FIG.

That is, on the premise that the lower structure 4 vibrates in a state where the rigidity is lower than the initial rigidity, the lower structure is configured such that the natural frequency of the viaduct 1 in the direction orthogonal to the bridge axis is 2 Hz or more. Preferably, the cross section of each member is determined. Incidentally, by setting the thus cross-section, with respect to the degree of earthquakes modified within the scope of the initial stiffness (0~θ ₁ in FIG. 2), greater rigidity can be maintained than 2 Hz.

The overall restoring force characteristic of the lower structure 4 is as follows.
As can be seen from FIG. 2, the curve is continuous from the origin O to B, C, and D, but may be regarded as a restoring force characteristic continuing from the origin O to C and D in design. In this case, the stiffness P ₂ / θ ₂ extending from the origin O to C can be considered as an equivalent stiffness in consideration of the actual hysteretic behavior on the assumption of a huge earthquake.

In the lower structure 4 of the railway viaduct 1 according to the present embodiment, the railroad viaduct 1 is designed such that the natural frequency in the direction orthogonal to the bridge axis is 2 Hz or more, thereby suppressing the lateral vibration of the viaduct. Thus, the driving safety of a vehicle traveling on the road is greatly improved.

FIGS. 3 and 4 are analysis results showing the operation and effect of the lower structure 4 of the railway viaduct 1 according to the present embodiment, and the contents thereof will be described below.

First, FIG. 3 shows the relationship between the vibration frequency at the track laying position of the railway viaduct 1 and the lateral displacement amplitude of the track for each vibration acceleration to obtain a curve group 11,
By examining how the running safety at each excitation frequency changes depending on the magnitude of the lateral displacement amplitude, plot ○ in the figure if safe and × in case of derailment,
Next, a curve is drawn at the boundary between the safety area where the circles are distributed and the derailment area where the crosses are distributed, and the curve is drawn as the driving safety limit curve 1
2 is a graph defined as 2 and superimposed on curve group 11.
In examining the traveling safety, the traveling speed was 10
0 km / h.

From this graph, it is difficult to secure running safety at an excitation frequency of 1 Hz or less even at an acceleration of about 500 gal. The upper limit of acceleration that can secure
It can be seen that the upper limit further increases to about 1400 gal at an excitation frequency of 2 Hz.

Therefore, the value on the ground surface is 300 gal.
If the target is a relatively large earthquake, the natural frequency of the viaduct is set to about 1.5 Hz, even if the amplification from the ground surface is taken into consideration. Sex is ensured.

Further, even in the case of a large-scale direct earthquake whose value on the ground surface exceeds 800 gal, if the natural frequency of the railway viaduct 1 is set to about 2 Hz or more, It is understood that the running stability of the vehicle can be sufficiently ensured.

Next, FIG. 4 shows an analysis in which the relationship between the natural frequency of the viaduct and the derailment coefficient (Q / P) was examined for three types of ground using two actual seismic waves (maximum acceleration; 300 gal). It is the graph which showed the result. here,
Q represents the horizontal force applied to the track from the chassis of the traveling vehicle, P represents the dynamic wheel load applied to the track from the chassis, and the larger the Q / P, the lower the running stability. The running speed is 260 km
/ H.

From this graph, it can be seen that the derailment coefficient is large around 1 Hz, whereas the derailment coefficient is relatively small above 2 Hz, and driving safety is improved.

As described above, according to the lower structure 4 of the railway viaduct 1 according to the present embodiment, the ramen structure 2 is disposed in the in-plane space of the ramen structure 2 and connected to the ramen structure via the energy absorbing member 7. With the brace material 3, the shaking of the seismic motion along the direction orthogonal to the bridge axis,
An energy absorbing member 7 interposed between the ramen structure 2 and the brace material 3 absorbs the vibration energy,
The shaking of the viaduct 1 is quickly converged.

On the other hand, the input energy of the seismic motion is consumed as the hysteresis damping of the energy absorbing member 7, and the ramen structure 2 and the brace material 3, which are the main structures of the lower structure 4 of the viaduct 1, are hardly damaged and sound. Maintain sex. Therefore, after the earthquake, by replacing the energy absorbing member 7 with a new one, the use of the railway viaduct 1 can be continued as before.

Further, according to the lower structure 4 of the railway viaduct 1 according to the present embodiment, a displacement design centering on the deformation performance of the energy absorbing member 7 becomes possible, and it depends on the complicated RC deformation performance as in the prior art. A more rational design is possible than the designed method.

Further, according to the lower structure 4 of the railway viaduct 1 according to the present embodiment, it is possible to recover the residual deformation of the ramen structure 2 due to the earthquake by taking a reaction force from the brace material 3. Damage control at the time can be easily performed.

Further, according to the lower structure 4 of the railway viaduct 1 according to the present embodiment, the natural frequency of the railway viaduct 1 in the direction orthogonal to the bridge axis is 2 Hz or more. Therefore, it is possible to suppress the lateral swing of the viaduct 1 and reliably secure the traveling safety of the vehicle traveling thereon.

In the present embodiment, the upper structure 5 of the railway viaduct 1 has not been described in detail, but the structure type is arbitrary, and the conventional (ramen-type) upper structure using a heavy concrete slab is of course. The thing that adopted a hollow bridge girder, the one that used lightweight materials for the railing, the one that supported the track with a predetermined elastic bearing without using heavy ballast, and the girder that supported only a single line of railway Naturally, a structure in which a desired number of wires are provided so as to form a double track or a double track (for example, an upper structure described in Japanese Patent Application No. 9-312039) is also an object. In addition, among these upper structures except for the conventional type, all can reduce the weight. Therefore, when the present invention is applied to the upper structure of this type, each member constituting the lower structure 4 is required. Can be reduced.

In this embodiment, the lower structure 4 has a two-layer structure, but it goes without saying that the lower structure 4 may have a single-layer structure.

In the present embodiment, the hysteresis damping type is used as the energy absorbing member. However, the energy absorbing member is not limited to this type, and it is also possible to use a viscous damping type or a friction damping type. It is.

(Second Embodiment) Next, a second embodiment will be described.

FIG. 5 is a flowchart showing a procedure of a method for designing a railway viaduct lower structure according to this embodiment. As can be seen from the figure, in the design method according to the present embodiment, first, a curve group in which the relationship between the excitation frequency at the viaduct track laying position and the lateral displacement amplitude of the track is obtained for each excitation acceleration Then, a graph is created as shown in FIG. 3 in which a driving safety limit curve that separates a safety region and a derailment region relating to driving safety is superimposed as shown in FIG. The driving safety limit curve is the same as the concept described in the first embodiment, and thus the description thereof is omitted here.

Next, the vibration frequency of the traveling safety limit curve corresponding to the designed vibration acceleration is determined using the graph (step 102). The graph of FIG. 6 shows a method for reading that the excitation frequency is about 1.6 Hz when the excitation acceleration in design is 1000 gal.

Next, the lower structure of the viaduct is designed so that the natural frequency of the viaduct in the direction orthogonal to the bridge axis is equal to or higher than the excitation frequency obtained in step 102, which is 1.6 Hz in the above example (step 103). .

Here, as in the case of the first embodiment, the lower structure of the viaduct has an inverted V-shaped steel bracing member 3 disposed in the in-plane space of the rigid frame structure 2 formed of reinforced concrete, and the vicinity of the top thereof has energy. A method is conceivable in which the section is connected to the lower surface of the center of the beam of the rigid frame structure 2 via the absorbing member 7, and the cross section of each member is determined by vibration analysis, a vibration experiment using a vibrator, or the like.

The concept of the magnitude of the earthquake and the rigidity in determining the cross section of each member are almost the same as those in the first embodiment, and the description thereof is omitted here.

In this way, if the lower structure of the viaduct is designed so that the natural frequency of the viaduct in the direction perpendicular to the bridge axis is 1.6 Hz or more in the above-described example, the vibrational acceleration within the designed range can be obtained. In the above example, at 1000 gal, as can be seen from FIG. 6, the vibration acceleration falls below the traveling safety limit curve, and the traveling safety of the vehicle traveling on the viaduct is ensured.

As described above, according to the method for designing a viaduct lower structure according to the present embodiment, the viaduct is set such that the natural frequency of the viaduct in the direction orthogonal to the bridge axis becomes a value corresponding to the designed acceleration. Since the lower structure is designed, in the case of an earthquake corresponding to the designed acceleration, it is possible to suppress the roll of the viaduct and secure the traveling safety of the vehicle traveling on the viaduct.

In the present embodiment, the case where the excitation acceleration on the raceway surface is 1000 gal is taken as an example. However, when the designed acceleration is more severe, for example, 1500 gal, as shown in FIG. The natural frequency of the viaduct may be set to about 2.2 Hz, and conversely 900 gal
In this case, the frequency may be set to about 1.5 Hz.

[0050]

As described above, according to the substructure of the railway viaduct according to the first aspect of the present invention, the ramen structure and the brace material are used for the vibration of the seismic motion along the direction perpendicular to the bridge axis. The energy absorbing member interposed therebetween absorbs the vibration energy and quickly converges the vibration of the viaduct. On the other hand, the input seismic motion energy is consumed as hysteresis damping and viscous damping of the energy absorbing member, so that the seismic resistance is remarkably improved, and the ramen structure and brace material, which are the main structures of the viaduct lower structure, are hardly damaged Maintain soundness without receiving it. Therefore, after the earthquake, by replacing the energy absorbing member with a new one, the use of the viaduct can be continued as before. In addition, the displacement design centering on the deformation performance of the energy absorbing member becomes possible, and a more rational design becomes possible than the conventional design method depending on the complicated RC deformation performance. Further, by taking a reaction force from the brace material, it becomes possible to restore the residual deformation of the ramen structure due to the earthquake, and damage control during the earthquake can be easily performed.

Further, according to the understructure of the railway viaduct of the present invention according to the second aspect, even in the case of a large direct earthquake, the running safety of the vehicle traveling on the viaduct while suppressing the lateral movement of the viaduct. Is also ensured.

According to the method of designing a viaduct undercarriage for a railway according to the third aspect of the present invention, when an earthquake corresponding to the designed acceleration occurs, the overpass of the viaduct is suppressed and the vehicle is driven on the viaduct. It is possible to ensure the traveling safety of the vehicle to be operated.

[0053]

[Brief description of the drawings]

FIG. 1 is a sectional view of a lower structure of a railway viaduct according to a first embodiment as viewed from a bridge axis direction.

FIG. 2 is a graph showing restoring force characteristics of a viaduct understructure.

FIG. 3 is a graph showing the operation and effect of the lower structure of the railway viaduct according to the first embodiment.

FIG. 4 is a graph showing the operation and effect of the lower structure of the railway viaduct according to the first embodiment.

FIG. 5 is a flowchart showing a procedure of a method of designing a railway viaduct lower structure according to the second embodiment.

FIG. 6 is a graph showing a method of obtaining an excitation frequency of a traveling safety limit curve corresponding to a design excitation acceleration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Railway viaduct 2 RC frame 3 Brace material 4 Viaduct lower structure 5 Viaduct upper structure 7 Energy absorption member

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[Procedure amendment]

[Submission date] March 19, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

The method for designing a railway viaduct undercarriage according to the present invention adds the relationship between the vibration frequency at the track laying position of the viaduct and the lateral displacement amplitude of the track. A graph is created by superimposing a driving safety limit curve dividing a safety area and a derailment area relating to driving safety on a curve group obtained for each vibration acceleration, and using the graph, the driving corresponding to the designed excitation acceleration is performed. The vibration frequency of the safety limit curve is determined, and the ramen structure and the surface of the ramen structure arranged in the direction orthogonal to the bridge axis so that the natural frequency of the viaduct in the direction orthogonal to the bridge axis is equal to or higher than the vibration frequency. It is to design a lower structure of a railway viaduct composed of a brace material arranged in an inner space and connected to the ramen structure via a predetermined energy absorbing member. Further, the lower structure of the railway viaduct according to the present invention is, as described in claim 4, a ramen structure disposed in a direction orthogonal to the bridge axis and a predetermined energy absorbing member disposed in an in-plane space of the ramen structure. And a brace material connected to the ramen structure, the lower structure of a railway viaduct, which excites a relationship between an excitation frequency at a track laying position of the railway viaduct and a lateral displacement amplitude of the track. A graph is created by superimposing a driving safety limit curve dividing a safety area and a derailment area relating to driving safety on a curve group obtained for each acceleration, and using the graph, the driving safety corresponding to a design excitation acceleration is used. The vibration frequency of the limit curve is determined, and the natural frequency of the railway viaduct in the direction orthogonal to the bridge axis is designed to be equal to or higher than the vibration frequency.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

In the method for designing a railway viaduct undercarriage according to claim 3 and the railway viaduct undercarriage according to claim 4, first, the excitation frequency and the lateral displacement of the track at the laying position of the track of the viaduct are laid out. A graph is created by superimposing a traveling safety limit curve dividing a safety region and a derailment region relating to traveling safety on a curve group for which the relationship with the amplitude is obtained for each excitation acceleration.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0041

[Correction method] Change

[Correction contents]

Second Embodiment Next, a lower structure of a railway viaduct according to a second embodiment and a method of designing the lower structure will be described.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction contents]

As in the first embodiment, the lower structure of the railway viaduct according to the present embodiment has an inverted V-shaped steel bracing member 3 disposed in the in-plane space of a rigid frame structure 2 made of reinforced concrete. The vicinity of the top is connected to the beam center lower surface of the ramen structure 2 via the energy absorbing member 7. In the present embodiment, the lower structure of the railway viaduct is the same as that of the railway viaduct lower structure shown in the flowchart of FIG. It is designed according to the procedure of the design method. That is, in designing the lower structure of the railway viaduct according to the present embodiment, first, the relationship between the excitation frequency at the track laying position of the viaduct and the lateral displacement amplitude of the track was determined for each excitation acceleration. A graph is created as shown in FIG. 3 in which a curve group is superimposed with a driving safety limit curve that separates a safety region and a derailment region relating to driving safety (step 101). The driving safety limit curve is the same as the concept described in the first embodiment, and thus the description thereof is omitted here.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0045

[Correction method] Change

[Correction contents]

Here, a method of determining the cross section of each member constituting the lower structure of the railway viaduct may be determined by vibration analysis, a vibration experiment using an exciter, or the like.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction contents]

As described above, according to the lower structure of the railway viaduct and the design method thereof according to the present embodiment, the natural frequency in the direction orthogonal to the bridge axis of the viaduct has a value corresponding to the designed excitation acceleration. We designed the viaduct undercarriage so that the earthquake corresponding to the designed acceleration
Rolling of the viaduct can be suppressed, and traveling safety of a vehicle traveling on the viaduct can be ensured.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0052

[Correction method] Change

[Correction contents]

Further, according to the method for designing a railway viaduct understructure according to claim 3 and the railway viaduct understructure according to claim 4, a lateral vibration of the viaduct is prevented with respect to an earthquake corresponding to the designed acceleration. It is possible to suppress the shaking and reliably ensure the traveling safety of the vehicle traveling thereon.

Continued on the front page (72) Inventor Kazu Wakui 2-8-38 Hikaricho, Kokubunji-shi, Tokyo Inside the Railway Technical Research Institute (72) Inventor Nobuyuki Matsumoto 2-8-38 Hikaricho, Kokubunji-shi, Tokyo Railway Within the Research Institute of Technology (72) Inventor Masamichi Sogabe 2-8-38 Hikaricho, Kokubunji, Tokyo Metropolitan Institute of Technology (72) Inventor Hiroyuki Arita 2-8-38 Hikaricho, Kokubunji, Tokyo Railway Technical Research Institute

Claims (3)

[Claims] The present invention comprises a ramen structure arranged in a direction orthogonal to a bridge axis, and a brace material arranged in an in-plane space of the ramen structure, and the brace material is connected to the brace material via a predetermined energy absorbing member. The lower structure of a railway viaduct that is connected to a ramen structure. 2. The lower structure of a railway viaduct according to claim 1, wherein a natural frequency of the railway viaduct in a direction orthogonal to the bridge axis is 2 Hz or more. 3. A run that separates a safety area and a derailment area related to run safety into a group of curves obtained by determining the relationship between the vibration frequency and the lateral displacement amplitude of the track at the track laying position of the viaduct for each vibration acceleration. A graph in which the safety limit curves are superimposed is created, and the excitation frequency of the traveling safety limit curve corresponding to the design excitation acceleration is determined using the graph, and the natural frequency of the viaduct in a direction orthogonal to the bridge axis is obtained. And a brace material arranged in the plane orthogonal to the bridge axis and connected to the ramen structure via a predetermined energy absorbing member so as to be equal to or higher than the excitation frequency. A method for designing a railway viaduct undercarriage, comprising designing a railway viaduct undercarriage comprising: