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New train regulation method based on wind direction and velocity of natural wind against strong winds
Journal of Wind Engineering and Industrial Aerodynamics 90 (2002) 1601–1610
New train regulation method based on wind direction and velocity of natural wind against strong winds Toshiaki Imaia,*, Toshishige Fujiia, Katsuji Tanemotob, Taisuke Shimamuraa, Tatsuo Maedab, Hiroaki Ishidac, Yu Hibinod a
Disaster Prevention Technical Division, Railway Technical Research Institute, Tokyo 185-8540, Japan b Environmental Engineering Division, Railway Technical Research Institute, Tokyo 185-8540, Japan c Railway Dynamics Division, Railway Technical Research Institute, Tokyo 185-8540, Japan d Vehicle Structure Technology Division, Railway Technical Research Institute, Tokyo 185-8540, Japan
Abstract Since there have been some railway accidents caused by strong winds in recent years in Japan, it is necessary to establish effective measures to prevent wind-induced accidents and ensure safety of train operation under strong winds. On February 22, 1994, a derailment accident was caused by strong winds on the Nemuro line of Hokkaido Railway Company. Railway Technical Research Institute carried out researches on investigation of the accident and measures at this section. As countermeasures, wind barriers were installed and a new train regulation method based on not only a natural wind velocity but also a natural wind direction was applied to the section. As a result, the railway company has had much less chances of slowdown and suspending of train operation than before and never experienced cancellation of train operation. r 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction On February 22, 1994, a derailment accident was caused by strong winds on the Nemuro line of Hokkaido Railway Company (JRH). The first and the second of seven vehicles overturned and the third vehicle derailed on an embankment of a curved section. JRH decided to take measures at the curved section and the *Corresponding author. 0167-6105/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 1 6 7 - 6 1 0 5 ( 0 2 ) 0 0 2 7 3 - 8
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T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
neighboring section after the accident. Railway Technical Research Institute (RTRI) carried out researches on investigation of the accident and measures at this section. We made wind tunnel tests on the effect of wind fences on embankments and bridges at the section. We also observed strong winds to investigate their characteristics of this section. Effective measures should be established by a combination of hardware and software measures. As a result, wind barriers were installed and a new train operation regulation method based on not only a natural wind velocity but also a natural wind direction was applied to the section.
2. Basic policy about measures against strong winds Effective measures should be established by a combination of hardware; vehicles to withstand strong winds, wind barriers and others and software; slowdown of the train speed and suspending and release of train operation. The criteria for suspending and release of train operation depend on a critical natural wind velocity of overturning of the vehicle, characteristics of strong winds and the time of train passing through the windy section as shown in Fig. 1. Here the critical natural wind velocity of overturning of the vehicle is defined as the natural wind velocity when the load of the windward wheels of the vehicle vanishes due to strong winds. The following are practical measures to reduce the risk of overturning of vehicles. 2.1. Measures on vehicles There are many kinds of vehicles and infrastructures; bridges, viaducts and embankments in Japan. Aerodynamic forces exerted on vehicles running on infrastructures depend on not only configuration of vehicles but also that of infrastructures [1]. Accordingly each kind of vehicle on each kind of infrastructure has each critical wind velocity of overturning. The smallest critical wind velocity at the section should be taken into consideration for designing the criteria to suspend the train operation at the section [2].
Design of suspension and release criteria
Evaluate wind velocities of overturning Configuration of vehicles Speed of vehicles Configurations of embankments, bridges and viaducts Specifications of vehicles (mass, center of gravity, etc.) Specification of structures (cant) Specification of wind barriers (noise barrier)
Characteristics of natural winds Rising rate of wind velocity Gust factor Fluctuation of wind direction Conditions for train operation Passing time of windy section Duration time for suspension
Fig. 1. Conditions determining suspension and release criteria.
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
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Increasing the weight of the vehicle raises the critical wind velocity of overturning, however, it will not be practical because lighter vehicles are more advantageous to track maintenance. On manufacture of a new light vehicle, it should be designed aerodynamically in order that aerodynamic forces exerted on it become small. 2.2. Wind barriers (fences and walls) A wind fence is the most effective of hardware measures for already existing railways. The effect of the wind fence depends on its height, porosity and its position distant from the center of a track. We have clarified the effect of the wind fence on aerodynamic forces (a side force, a lift force and a rolling moment) exerted on a vehicle by wind tunnel tests. The side force exerts more an influence on the overturning of the vehicle than the lift force and the rolling moment. Fig. 2 shows the effects of wind fences. The vertical axis denotes the side force coefficient CS of the vehicle on a bridge, where the side force coefficient CS is expressed by the following formula: CS ¼ FS =12 rU 2 bl;
ð1Þ
where FS (N) is the side force exerted perpendicularly on the vehicle, r ðkg=m3 Þ the density of air, Uðm=sÞ the wind velocity relative to the vehicle, b (m) the height of car and l (m) is the length of car body. The horizontal axis denotes the wind direction b relative to the vehicle. Fig. 3 shows the relation among the wind velocity U and the wind direction b relative to the vehicle, the train speed V and the natural wind velocity W and the natural wind direction a: 2.3. Slowdown of train speed As shown in Fig. 3, the critical natural wind velocity depends on the natural wind direction a and the train speed V : It can be calculated using the aerodynamic
Side force coefficient
2
Without fences
1.5
h=3m,porosity40% h=2m,porosity10%
1
h=3m,porosity20% h=3m,porosity10%
0.5
0
30
50
70
90
110
Wind direction relative to vehicle Fig. 2. Effects of wind fences on side force coefficients.
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T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
U : Wind velocity relative to vehicle V : Train speed W : Natural wind velocity
-V U
β
α : Natural wind direction W β : Wind direction relative to vehicle
α
V
Wind velocity of overturning (m/s)
Fig. 3. Natural wind velocity and wind velocity relative to vehicle.
60
V= 45 (km/h) V=110 (km/h)
50
40
30 40
50
60 70 80 Natural wind direction α
90
Fig. 4. Slowdown effect on wind velocity of overturning.
coefficients of the side force, the lift force and the rolling moment as a function of the wind direction b relative to the vehicle, the train speed and specifications of the vehicle and infrastructure. Fig. 4 shows an example of the relation among the critical natural wind velocity, the natural wind direction a and the train speed V : In this case, the mass of the car body is 3:58 104 kg; the height of the car body is 2:61 m; the height of the car body center from the rail level is 2:32 m; and the gauge is 1:067 m: Fig. 5 shows the results of wind tunnel tests on the side force coefficient CS of the leading vehicle running on an embankment, which are used for calculation in Fig. 4. From Fig. 4, it is clear that the slowdown of the train speed increases the critical natural wind velocity of overturning. Especially, its effect becomes remarkable from 701 to 1001 of the natural wind direction. 2.4. Suspending of train operation The vehicle will instantaneously overturn as soon as the natural wind velocity exceeds the critical natural wind velocity of overturning. Accordingly, we should
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
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Side force coefficient
2.0 1.5 1.0 0.5 0.0
Leading vehicle Middle vehicle 0 10 30 50 70 90 Wind direction relative to vehicle
Fig. 5. Side force coefficient obtained through the wind tunnel tests.
evaluate the wind velocity of suspending of train operation by not a mean wind velocity but an instantaneous wind velocity. In Japan, when the instantaneous natural wind velocity measured by an anemometer at the section exceeds the wind velocity of suspending of train operation, the train is stopped at a safe place such as a station or a yard for a fixed duration. The wind velocity of suspending operation for conventional railways is 30 m=s in ordinary sections and 25 m=s in windy sections such as bridges. The wind velocity of suspending operation should be lower than the critical wind velocity of overturning of the vehicle. The margin d between the wind velocity of suspending operation and the critical wind velocity of overturning of the vehicle should be evaluated by the time of the train passing through the section and the rising rate of wind velocity at the section.
3. Regulation of train operation based on wind velocity and wind direction The usual regulation method is based on only the wind velocity, however, that based on not only the wind velocity but also the wind direction will be possible if the natural wind has a tendency to blow to the particular direction at the section and the fluctuation of wind direction is small. As mentioned in Fig. 4, the critical natural wind velocity of overturning at the train speed can be calculated as a function of the natural wind direction a: Fig. 6 shows the procedure to determine the wind velocity of suspending of train operation. The curve of the wind velocity of suspending (the dotted curve) can be derived from the curve of the critical wind velocity of overturning (the solid curve) by shifting downward with the margin d mentioned in Section 2.4 and horizontally with a margin f: We determine the margin d by the maximum value of the increase of the wind velocity and the margin f by the maximum value of the fluctuation of wind direction during the time of the train passing through the section. To do so, we need data of a long time on the natural
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
Wind velocity (m/s)
1606
Wind velocity of overturning
δ Margin δ Margin φ *
40
φδ
δ
δ
φ
Wind velocity to suspend the operation 50 60 70 80 Natural wind direction α
φ Allowable for operation * 90
Fig. 6. Concept of regulation of operation based on wind direction and wind velocity.
wind velocity and direction measured by an anemometer at the section. From the necessity of the actual regulation method, the curve of the wind velocity of suspending is simplified to two levels of the wind velocity of suspending according to the wind direction (the solid line in Fig. 6). This new regulation method was applied to the section where the wind-induced accident happened on the Nemuro line of JRH on February 22 in 1994. We go into details in the next section.
4. Measures by wind fences and new regulation method in JRH JRH decided to take measures at this section after the accident. RTRI carried out researches on investigation of the accident and measures at this section. We made wind tunnel tests on the effect of wind fences on embankments and bridges at the section. We also observed strong winds to investigate their characteristics of this section. 4.1. Overview of section The section where the accident occurred in 1994 is located near the center part of Hokkaido in Japan. This area is the eastern foot of the Hidaka mountains. The length of the section is about 1:8 km; the length of embankments is 1390 m and that of bridges is 340 m: The radius of the curved section is 500 m with a 105 mm cant and gradient of 12/1000. Maximum height of embankments is 14:7 m: Vehicles change the direction by 1401 during running through this curved section (Fig. 7).
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
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Fig. 7. Layout of infrastructure and barriers at the section.
Table 1 Specification of wind fence
Porosity Height from rail level Distance from track center Route length
Embankment
Bridge
40% 2:0 m 3:5 m 1390 m
20% 3:0 m 3:5 m 340 m
4.2. Wind tunnel tests We made wind tunnel tests on the effect of wind fences on the embankment and the bridge at the section. The specifications of wind fences were determined in order that the critical natural wind velocity of overturning became 40 m=s or over on the embankment and the bridge (Table 1). The critical natural wind velocity 40 m=s has
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T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
an enough margin d to the wind velocity of suspending of train operation, which will be described in Section 4.4. 4.3. Characteristics of strong winds at section We observed strong winds at this section for 7 months. This area lies leeward of the mountain for a cold air coming from the Continent of Asia. Regarding the wind direction, two important characteristics are as follows: (1) Most of strong winds at an instantaneous wind velocity of 20 m=s or over blow from west because strong winds blow down from the mountains. (2) The angles between the mean wind direction of the past 10 min and the instantaneous wind direction are less than 301 when winds are strong enough to overturn vehicles (Fig. 8). In this case, the margin f in the Section 3 is required to be 301: 4.4. Details of measures and their effects on regulation of train operation Considering the results of the observation of natural winds, JRH installed wind fences only on the western side of the embankment and the bridge because most of strong winds blow from west. The measures should be effective for all wind direction. When the strong winds blow from the direction where the wind fences are effective, the wind velocity of suspending was determined to be 30 m=s; which is the same as used in ordinary section of JRH. When the strong winds blow from the direction where the wind fences are not effective, the wind velocity of suspending was determined to be 25 m=s and the wind velocity of slowdown of the train speed to 45 km=h is determined to be 20 m=s: In this case, the same margin d as where the fences are effective was ensured. The former range of the wind direction is from 2401 to 3001 and the latter range is the rest. These angles were determined in consideration of the margin f; the direction of the train running through the curved section and the train speed. Fig. 9 shows the new regulation scheme regarding the wind direction and the wind velocity.
Fig. 8. Relation between fluctuation of wind direction and instantaneous wind velocity.
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
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N (0 deg.) 30m/s 300 deg.
25m/s 20m/s
W (270 deg.)
E (90 deg.)
Regular Slow-down at 45km/h
240 deg.
Suspension S
(180 deg.)
Fig. 9. New regulation scheme regarding wind direction and wind velocity.
600
Frequency of trains behind schedule Frequency of canceled trains Frequency of suspended operations
503
478
500 400
276
Under new regulation
300
185 134
200
240 26
64
50
94 28
100 0
1994
1995
1996
25
1997
0
93
0
1998
Fig. 10. Effect of regulation of operation based on wind velocity and wind direction.
For about 2 years after the introduction of this new regulation method, about 90% of strong wind higher than 20 m=s blew from the direction where the wind fences were effective. As a result, JRH has had much less chances of slowdown and suspending of train operation than before and never experienced cancellation of train operation (Fig. 10).
5. Conclusions On February 22, 1994, a derailment accident was caused by strong winds on the Nemuro line of JRH. RTRI carried out researches on investigation of the accident
1610
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
and measures at this section. We made wind tunnel tests on the effect of wind fences on embankments and bridges at the section. We also observed strong winds to investigate their characteristics of this section. As countermeasures, wind barriers were installed and a new train operation regulation method based on not only a natural wind velocity but also a natural wind direction was applied to the section. As a result, JRH has had much less chances of slowdown and suspending of train operation than before and never experienced cancellation of train operation.
References [1] T. Maeda, Wind-induced accidents of train/vehicles and their countermeasures, ASCE, August 1996, p. 2. [2] T. Fujii, et al., Wind-induced accidents of train/vehicles and their measures in japan, Q. Rep. Railw. Tech. Res. Inst. 40 (1) (1999).
New train regulation method based on wind direction and velocity of natural wind against strong winds Toshiaki Imaia,*, Toshishige Fujiia, Katsuji Tanemotob, Taisuke Shimamuraa, Tatsuo Maedab, Hiroaki Ishidac, Yu Hibinod a
Disaster Prevention Technical Division, Railway Technical Research Institute, Tokyo 185-8540, Japan b Environmental Engineering Division, Railway Technical Research Institute, Tokyo 185-8540, Japan c Railway Dynamics Division, Railway Technical Research Institute, Tokyo 185-8540, Japan d Vehicle Structure Technology Division, Railway Technical Research Institute, Tokyo 185-8540, Japan
Abstract Since there have been some railway accidents caused by strong winds in recent years in Japan, it is necessary to establish effective measures to prevent wind-induced accidents and ensure safety of train operation under strong winds. On February 22, 1994, a derailment accident was caused by strong winds on the Nemuro line of Hokkaido Railway Company. Railway Technical Research Institute carried out researches on investigation of the accident and measures at this section. As countermeasures, wind barriers were installed and a new train regulation method based on not only a natural wind velocity but also a natural wind direction was applied to the section. As a result, the railway company has had much less chances of slowdown and suspending of train operation than before and never experienced cancellation of train operation. r 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction On February 22, 1994, a derailment accident was caused by strong winds on the Nemuro line of Hokkaido Railway Company (JRH). The first and the second of seven vehicles overturned and the third vehicle derailed on an embankment of a curved section. JRH decided to take measures at the curved section and the *Corresponding author. 0167-6105/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 1 6 7 - 6 1 0 5 ( 0 2 ) 0 0 2 7 3 - 8
1602
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
neighboring section after the accident. Railway Technical Research Institute (RTRI) carried out researches on investigation of the accident and measures at this section. We made wind tunnel tests on the effect of wind fences on embankments and bridges at the section. We also observed strong winds to investigate their characteristics of this section. Effective measures should be established by a combination of hardware and software measures. As a result, wind barriers were installed and a new train operation regulation method based on not only a natural wind velocity but also a natural wind direction was applied to the section.
2. Basic policy about measures against strong winds Effective measures should be established by a combination of hardware; vehicles to withstand strong winds, wind barriers and others and software; slowdown of the train speed and suspending and release of train operation. The criteria for suspending and release of train operation depend on a critical natural wind velocity of overturning of the vehicle, characteristics of strong winds and the time of train passing through the windy section as shown in Fig. 1. Here the critical natural wind velocity of overturning of the vehicle is defined as the natural wind velocity when the load of the windward wheels of the vehicle vanishes due to strong winds. The following are practical measures to reduce the risk of overturning of vehicles. 2.1. Measures on vehicles There are many kinds of vehicles and infrastructures; bridges, viaducts and embankments in Japan. Aerodynamic forces exerted on vehicles running on infrastructures depend on not only configuration of vehicles but also that of infrastructures [1]. Accordingly each kind of vehicle on each kind of infrastructure has each critical wind velocity of overturning. The smallest critical wind velocity at the section should be taken into consideration for designing the criteria to suspend the train operation at the section [2].
Design of suspension and release criteria
Evaluate wind velocities of overturning Configuration of vehicles Speed of vehicles Configurations of embankments, bridges and viaducts Specifications of vehicles (mass, center of gravity, etc.) Specification of structures (cant) Specification of wind barriers (noise barrier)
Characteristics of natural winds Rising rate of wind velocity Gust factor Fluctuation of wind direction Conditions for train operation Passing time of windy section Duration time for suspension
Fig. 1. Conditions determining suspension and release criteria.
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
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Increasing the weight of the vehicle raises the critical wind velocity of overturning, however, it will not be practical because lighter vehicles are more advantageous to track maintenance. On manufacture of a new light vehicle, it should be designed aerodynamically in order that aerodynamic forces exerted on it become small. 2.2. Wind barriers (fences and walls) A wind fence is the most effective of hardware measures for already existing railways. The effect of the wind fence depends on its height, porosity and its position distant from the center of a track. We have clarified the effect of the wind fence on aerodynamic forces (a side force, a lift force and a rolling moment) exerted on a vehicle by wind tunnel tests. The side force exerts more an influence on the overturning of the vehicle than the lift force and the rolling moment. Fig. 2 shows the effects of wind fences. The vertical axis denotes the side force coefficient CS of the vehicle on a bridge, where the side force coefficient CS is expressed by the following formula: CS ¼ FS =12 rU 2 bl;
ð1Þ
where FS (N) is the side force exerted perpendicularly on the vehicle, r ðkg=m3 Þ the density of air, Uðm=sÞ the wind velocity relative to the vehicle, b (m) the height of car and l (m) is the length of car body. The horizontal axis denotes the wind direction b relative to the vehicle. Fig. 3 shows the relation among the wind velocity U and the wind direction b relative to the vehicle, the train speed V and the natural wind velocity W and the natural wind direction a: 2.3. Slowdown of train speed As shown in Fig. 3, the critical natural wind velocity depends on the natural wind direction a and the train speed V : It can be calculated using the aerodynamic
Side force coefficient
2
Without fences
1.5
h=3m,porosity40% h=2m,porosity10%
1
h=3m,porosity20% h=3m,porosity10%
0.5
0
30
50
70
90
110
Wind direction relative to vehicle Fig. 2. Effects of wind fences on side force coefficients.
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T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
U : Wind velocity relative to vehicle V : Train speed W : Natural wind velocity
-V U
β
α : Natural wind direction W β : Wind direction relative to vehicle
α
V
Wind velocity of overturning (m/s)
Fig. 3. Natural wind velocity and wind velocity relative to vehicle.
60
V= 45 (km/h) V=110 (km/h)
50
40
30 40
50
60 70 80 Natural wind direction α
90
Fig. 4. Slowdown effect on wind velocity of overturning.
coefficients of the side force, the lift force and the rolling moment as a function of the wind direction b relative to the vehicle, the train speed and specifications of the vehicle and infrastructure. Fig. 4 shows an example of the relation among the critical natural wind velocity, the natural wind direction a and the train speed V : In this case, the mass of the car body is 3:58 104 kg; the height of the car body is 2:61 m; the height of the car body center from the rail level is 2:32 m; and the gauge is 1:067 m: Fig. 5 shows the results of wind tunnel tests on the side force coefficient CS of the leading vehicle running on an embankment, which are used for calculation in Fig. 4. From Fig. 4, it is clear that the slowdown of the train speed increases the critical natural wind velocity of overturning. Especially, its effect becomes remarkable from 701 to 1001 of the natural wind direction. 2.4. Suspending of train operation The vehicle will instantaneously overturn as soon as the natural wind velocity exceeds the critical natural wind velocity of overturning. Accordingly, we should
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
1605
Side force coefficient
2.0 1.5 1.0 0.5 0.0
Leading vehicle Middle vehicle 0 10 30 50 70 90 Wind direction relative to vehicle
Fig. 5. Side force coefficient obtained through the wind tunnel tests.
evaluate the wind velocity of suspending of train operation by not a mean wind velocity but an instantaneous wind velocity. In Japan, when the instantaneous natural wind velocity measured by an anemometer at the section exceeds the wind velocity of suspending of train operation, the train is stopped at a safe place such as a station or a yard for a fixed duration. The wind velocity of suspending operation for conventional railways is 30 m=s in ordinary sections and 25 m=s in windy sections such as bridges. The wind velocity of suspending operation should be lower than the critical wind velocity of overturning of the vehicle. The margin d between the wind velocity of suspending operation and the critical wind velocity of overturning of the vehicle should be evaluated by the time of the train passing through the section and the rising rate of wind velocity at the section.
3. Regulation of train operation based on wind velocity and wind direction The usual regulation method is based on only the wind velocity, however, that based on not only the wind velocity but also the wind direction will be possible if the natural wind has a tendency to blow to the particular direction at the section and the fluctuation of wind direction is small. As mentioned in Fig. 4, the critical natural wind velocity of overturning at the train speed can be calculated as a function of the natural wind direction a: Fig. 6 shows the procedure to determine the wind velocity of suspending of train operation. The curve of the wind velocity of suspending (the dotted curve) can be derived from the curve of the critical wind velocity of overturning (the solid curve) by shifting downward with the margin d mentioned in Section 2.4 and horizontally with a margin f: We determine the margin d by the maximum value of the increase of the wind velocity and the margin f by the maximum value of the fluctuation of wind direction during the time of the train passing through the section. To do so, we need data of a long time on the natural
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
Wind velocity (m/s)
1606
Wind velocity of overturning
δ Margin δ Margin φ *
40
φδ
δ
δ
φ
Wind velocity to suspend the operation 50 60 70 80 Natural wind direction α
φ Allowable for operation * 90
Fig. 6. Concept of regulation of operation based on wind direction and wind velocity.
wind velocity and direction measured by an anemometer at the section. From the necessity of the actual regulation method, the curve of the wind velocity of suspending is simplified to two levels of the wind velocity of suspending according to the wind direction (the solid line in Fig. 6). This new regulation method was applied to the section where the wind-induced accident happened on the Nemuro line of JRH on February 22 in 1994. We go into details in the next section.
4. Measures by wind fences and new regulation method in JRH JRH decided to take measures at this section after the accident. RTRI carried out researches on investigation of the accident and measures at this section. We made wind tunnel tests on the effect of wind fences on embankments and bridges at the section. We also observed strong winds to investigate their characteristics of this section. 4.1. Overview of section The section where the accident occurred in 1994 is located near the center part of Hokkaido in Japan. This area is the eastern foot of the Hidaka mountains. The length of the section is about 1:8 km; the length of embankments is 1390 m and that of bridges is 340 m: The radius of the curved section is 500 m with a 105 mm cant and gradient of 12/1000. Maximum height of embankments is 14:7 m: Vehicles change the direction by 1401 during running through this curved section (Fig. 7).
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
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Fig. 7. Layout of infrastructure and barriers at the section.
Table 1 Specification of wind fence
Porosity Height from rail level Distance from track center Route length
Embankment
Bridge
40% 2:0 m 3:5 m 1390 m
20% 3:0 m 3:5 m 340 m
4.2. Wind tunnel tests We made wind tunnel tests on the effect of wind fences on the embankment and the bridge at the section. The specifications of wind fences were determined in order that the critical natural wind velocity of overturning became 40 m=s or over on the embankment and the bridge (Table 1). The critical natural wind velocity 40 m=s has
1608
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
an enough margin d to the wind velocity of suspending of train operation, which will be described in Section 4.4. 4.3. Characteristics of strong winds at section We observed strong winds at this section for 7 months. This area lies leeward of the mountain for a cold air coming from the Continent of Asia. Regarding the wind direction, two important characteristics are as follows: (1) Most of strong winds at an instantaneous wind velocity of 20 m=s or over blow from west because strong winds blow down from the mountains. (2) The angles between the mean wind direction of the past 10 min and the instantaneous wind direction are less than 301 when winds are strong enough to overturn vehicles (Fig. 8). In this case, the margin f in the Section 3 is required to be 301: 4.4. Details of measures and their effects on regulation of train operation Considering the results of the observation of natural winds, JRH installed wind fences only on the western side of the embankment and the bridge because most of strong winds blow from west. The measures should be effective for all wind direction. When the strong winds blow from the direction where the wind fences are effective, the wind velocity of suspending was determined to be 30 m=s; which is the same as used in ordinary section of JRH. When the strong winds blow from the direction where the wind fences are not effective, the wind velocity of suspending was determined to be 25 m=s and the wind velocity of slowdown of the train speed to 45 km=h is determined to be 20 m=s: In this case, the same margin d as where the fences are effective was ensured. The former range of the wind direction is from 2401 to 3001 and the latter range is the rest. These angles were determined in consideration of the margin f; the direction of the train running through the curved section and the train speed. Fig. 9 shows the new regulation scheme regarding the wind direction and the wind velocity.
Fig. 8. Relation between fluctuation of wind direction and instantaneous wind velocity.
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
1609
N (0 deg.) 30m/s 300 deg.
25m/s 20m/s
W (270 deg.)
E (90 deg.)
Regular Slow-down at 45km/h
240 deg.
Suspension S
(180 deg.)
Fig. 9. New regulation scheme regarding wind direction and wind velocity.
600
Frequency of trains behind schedule Frequency of canceled trains Frequency of suspended operations
503
478
500 400
276
Under new regulation
300
185 134
200
240 26
64
50
94 28
100 0
1994
1995
1996
25
1997
0
93
0
1998
Fig. 10. Effect of regulation of operation based on wind velocity and wind direction.
For about 2 years after the introduction of this new regulation method, about 90% of strong wind higher than 20 m=s blew from the direction where the wind fences were effective. As a result, JRH has had much less chances of slowdown and suspending of train operation than before and never experienced cancellation of train operation (Fig. 10).
5. Conclusions On February 22, 1994, a derailment accident was caused by strong winds on the Nemuro line of JRH. RTRI carried out researches on investigation of the accident
1610
T. Imai et al. / J. Wind Eng. Ind. Aerodyn. 90 (2002) 1601–1610
and measures at this section. We made wind tunnel tests on the effect of wind fences on embankments and bridges at the section. We also observed strong winds to investigate their characteristics of this section. As countermeasures, wind barriers were installed and a new train operation regulation method based on not only a natural wind velocity but also a natural wind direction was applied to the section. As a result, JRH has had much less chances of slowdown and suspending of train operation than before and never experienced cancellation of train operation.
References [1] T. Maeda, Wind-induced accidents of train/vehicles and their countermeasures, ASCE, August 1996, p. 2. [2] T. Fujii, et al., Wind-induced accidents of train/vehicles and their measures in japan, Q. Rep. Railw. Tech. Res. Inst. 40 (1) (1999).