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Article / Book Information
Title

EFFECTS OF THERMAL CHANGE AND TRACK CONDITIONS ON
THE DEFLECTION OF RC SLAB GIRDER RAILWAY BRIDGES

Authors

Namimatsu S, Yoshida K, Kato S, Tanabe A

Citation

The 3rd ACF Symposium 2019, , ,Pub. date

2019, 9Powered by T2R2 (Tokyo Institute Research Repository)

The 3rd ACF Symposium 201910-11 September 2019
Assessment and Intervention of Existing Structures
Sapporo, Japan___________________________________________________________________________EFFECTS OF THERMAL CHANGE AND TRACK CONDITIONS ON
THE DEFLECTION OF RC SLAB GIRDER RAILWAY BRIDGES
Namimatsu S1*,Yoshida K2 , Kato S3 and Tanabe A4
1, 2

Technology Research and Development Department (Komaki), CENTRAL JAPAN RAILWAYCOMPANY, Aichi, Japan
E-mail: saki.namimatsu@jr-central.co.jp, k-yoshida@jr-central.co.jp
3
Research Division, JR CENTRAL CONSULTANTS COMPANY, Aichi, Japan
E-mail: s-ootake@jrcc.co.jp
4
Infrastructure Div., NIKKEN SEKKEI CIVIL ENGINEERING LTD, Osaka, Japan
E-mail: tanabe.atsushi@nikken.jp

ABSTRACTThis paper mention about the application of deflection monitoring for maintenance method of RC slab
girder bridges in the Tokaido Shinkansen.
Firstly, it is described that the background of the importance of continuous monitoring regarding
railway bridges. The dynamic responses of RC bridges affect to the running safety and the ride quality.
The deflection is widely used as the evaluation index of them. Therefore, it is necessary to check thedeflection of the bridges. Additionally, measuring large amount of data is useful to grasp bridge
characteristics.
Conventionally, deflection is measured from the part underneath a bridge .However, it is difficult tomeasure large amount of data because this way is limited to several conditions, such as, under-passing
roads and rivers. From this kind of condition, our department developed a deflection monitoring
device, which can capture the small signal caused by fluctuation of deflection. By using this device,large amount of data could be obtained. The measurement results by the device are described in thesecond part of this paper. Continuous monitoring of several bridges were conducted to obtain large
amount of data. The maximum period was six months.
The third part describes the effects of thermal effects and track conditions on the fluctuation of thedeflection and natural frequency. After the track maintenance, the defection tends to be small. This
tend might be caused by the reduction of the rolling stock oscillation due to track maintenance.
Furthermore, the deflection tends to be small as the temperature went up. This tend might be causedby following mechanism: 1) Thermal expansion may cause contacting girder ends to parapets ofabutments, 2) The contact constrains rotation of girder and change boundary conditions, 3) it results
increasing natural frequency and reducing deflection.
Keywords: Continuous monitoring, Deflection, Natural frequency, RC slab girder bridges, High speed
rail.

1. INTRODUCTION
In Japan, many of infrastructures wereconstructed in 1950s, and they will be aged innear future. Therefore, it is important to inspect
and retrofit them appropriately. However, thereis the problem of the shortage of inspectors andbudgets. Thus, efficient maintenance andmanagement are required. Furthermore,
technological development of monitoring andinspection utilizing sensors and robots arepromoted.
Railway bridges deflect due to train passage.
Deflection limits have been given by the span
length and train speed because large deflection
decrease running safety and ride quality. Table
1 and 2 show the limits for running safety andthe ride quality [1]. The maintenance andmanagement of railway bridges are performed
quantitatively based on deflection and its limit.
Thus, the soundness of railway bridges in theTokaido Shinkansen can be evaluated bycomparing deflection and its limit. However,large gap exists between actual deflection andlimit value [2, 3]. Thus, it is necessary to
determine evaluation index for the maintenanceof RC slab girder bridges based on current
situations.
Current design code requires same deflection
limit for same span despite of various structuraldetails (RC, PC, Extradosed, etc.). However, thedynamic characteristics of concrete bridges may
be affected by beside span, such as condition offoundation, piers, abutments, skew, location, etc.
Therefore, it is necessary to grasp the dynamic
characteristics of the actual bridges when the
new evaluation index is considered.
Ring-type displacement meters and lasertype displacement meters [4] have being
commonly used to measure deflection at the
span center of the railway bridges. Howeverthese methods may be difficult to measure if an
obstacle, such as a river, a road, another railway
etc., exists under the bridge. In addition, thesemethods have to be operated by workers at thesite, therefore it was difficult to acquire large
amount of data. If large amount data could beacquired and analyzed, it will make possible tograsp the features of the structures and to catchthe sign of troubles. Then, the fact lead us to
new efficient accurate reliable maintenancesystem instead of traditional maintenancesystem relied on inspector’s experience andknow-hows.
From these backgrounds, this study is aiming
to grasp the factors which may affect the
dynamic characteristics of the RC slab girder
bridges. In this study, influence by track
maintenance and temperature effects on the
dynamic characteristics of RC girder bridges
were discussed by using long-term measured
data obtained by a newly developed “Deflection
Monitoring Device”, which enables theacquisition of a large amount of data
continuously and unattended, regardless of theunder the bridge condition.

Table 2 Limits for ride quality(Shinkansen)
Maximum
Span
speed
(m)
(km/h)
260
L/2000300
L/2800360
L/3500Design deflection
ration
0.455
0.357
0.286

2. CONTINUOUS MEASUREMENT
2.1

Measuring Device

An author’s department developed a new
deflection monitoring device [5]. Table 3 andFigure 1 shows the outline of this device. The
body of this device is made of polycarbonate
resin. In order to avoid power consuming, thisdevice records with intervals and it sleep afterrecording train passage. Recording is triggeredby train’s vibration, and measured acceleration
data is stored to SD memory card.
This device includes MEMS acceleration
sensor. To convert with high accuracy, it isnecessary to have high resolution and low noise.
The EPSON M-A351AU10 was selected to use
this device by comparing multiple sensors.
Measured acceleration response data isconverted to displacement data via velocity byintegration twice.
Table 3 Outline of deflection monitoring device
Manufacture's type

DEICY
BCMX01

Measurement range±50cm/s²

Resolution

0.6μm/s²

Frequency band

10Hz

Sampling frequency

500Hz

Pre-trigger time

1s

Table 1 Limits for running safety(Shinkansen)

Trigger acceleration

0，0.2，0.5，1.0m/s²

Recording time

maximum 9s

Maximum
speed(km/h)

Span(m)

Design deflection ration

Power source

size C battery × 3

Weight

1.5kg

260

L/700

1.429

300

L/900

1.111

360

L/11000.91(H)100mm
Size(W)123mm(D)123mm

Power switch

SD Memory card holder

deflection range (see Figure 4).

DIP switch

DeviceL

Acceleration sensor

L/2

Circuit board
Battery

DeviceDown line

Up lineAttaching bolt

DeviceDeviceRailway track

Inspection aisle

Inspection aisle

Measuring condition

It was carried out by using the device that
continuous measurement of deflection of RC
girder bridges in the Tokaido Shinkansen.
So far, we have measured on 16 bridges [6].
The measurement period is at least one weekand up to six months.
As shown in Figure 2, the devices were
installed at span center on the up and down line
sidewalks. Data were acquired about 16 data aday, measured from 7 o’clock to 22 o’clockwith an hour intervals. Sampling ratio is 500 Hz.
Triggering rates, which is made the automatic
measurement which begins to measure, was set
to 0.2m/s².
Figure 3 shows an example of acceleration
waveform and displacement waveform. The
acquired acceleration data were processed to
calculate a displacement data (deflection).
Specifically, for the purpose of baseline
correction, the acceleration data was preparedwith by 1 Hz high-pass filter before converting
into displacement data.

2.3

Deflection Range

In this paper, the displacement range is used
to evaluation. It is calculated from the deflection
wave with the peak-to-peak amplitude being
one displacement range, and the eighth largest
value of the deflection range is defined as thedisplacement（mm）

2.22（a）acceleration waveform

1

0
-1
-2
0

2

time（s） 6

4

8

10

8

10

（b）displacement waveform（1HPF）

2
1
0
-1
-2
0

4 time（s） 62

Figure 3 Acceleration waveform anddisplacement waveform

displacement（mm）

Figure 1 Deflection monitoring device

acceleration（mm/s²）

Figure 2 Installation method21maximum

1

2

3

4

5

6

7

8

9

10 11 12 13 14 15 16

0

deflection-1

minimum

-2
0

1

2

median of 16 amplitudes → deflection
3
4
5
6
7
time（s）

8

9

Figure 4 Calculation method of deflection range

2.4

Target Bridges

From the results of continuous measurement ofseveral bridges, we confirmed these bridges thatchange in deflection range and natural
frequency under the influence of track
maintenance and temperature effect.
This paper presents these two measurement
results shown in Table 4. Table 4 shows thedetails of each bridge. The influence of track
maintenance was confirmed in “A bridge”. The
influence of temperature effect was confirmed
in “B bridge”.

10

A bridge

B bridge

Span

10m

12.5m

Angle

left 65onothing

straight
sectionpile
foundation

relaxation
curve
pile
foundation

285km/h

285km/hLinerFoundation
form
Maximum
train speed
Meteorologicalobservation
point
Measurement
periodThe number ofdata

Shizuoka

Ebina−0.51. Thus, correlations were not strong. From
this result, it was found that this bridge might
not affected by temperature change.
On the other hand, the variation of thedeflection range decreased in some period.
These periods overlapped with events such as
track maintenance. For example, the result ofaround Oct. 5 was overlapped with track
maintenance.
1098

Deflection(mm)Table 4 Details of each bridgefrom Sept. 5,
from Sept.
2017 to Feb.
26, 2018 to1, 2018
Oct. 23, 2018
3805

7

6
5
4
3
2

1
0
Sep. 1

1880

Sep. 26

Oct. 21

Nov. 15
Day

Dec. 10Jan. 4Jan. 29

Figure 5 Transition of deflection

3. RESULT OF A BRIDGE

10
9

Measurement result
Deflection(mm)Figure 5 shows the transition of deflection range.
During the measurement period, the deflection
range was distributed in the range of 2 to 6 mm,
and the average value was 3.79 mm. However,
the average value of deflection range for various
train speeds does not make much sense because
deflection range is affected by trains speed.
Therefore it is included only as a reference.
The deflection range peaked at around 235
km/h from the relationship between train speed
and deflection range shown in the figure 6. It
was confirmed that resonance occurred at thetrain speed. Such resonance might enlarge thedaily variation of deflection range.
The transition of natural frequency during
the measurement period is shown in Figure 7.
Natural frequency was distributed in the rangeof 8 to 9 Hz except for the data which deviatedgreatly. The median value of the natural
frequency was 8.30 Hz.
Figure 8 shows the daily transition ofdeflection range, natural frequency and averagetemperature near this bridge. The averagetemperature fluctuated in the range from 0 to
30oC during the 150-day measurement period.
Furthermore, the correlation coefficient ofdeflection range and average temperature was−0.20. The correlation coefficient of the natural
frequency and the average temperature were

8
7
6

5
4
3
2
1
0
200

220

240
260
Speed(km/h)

280

300

Figure 6 Relationship between deflection range
and train speed (A bridge)

109Frequency(Hz)

3.1

8

7

6
Sep. 1

Sep. 26

Oct. 21

Nov. 15
Day

Dec. 10Jan. 4Jan. 29

Figure 7 Transition of natural frequency (Abridge)

10

30

X

Y

average 3.97mm

average 3.52mm

9

9
25

7

20

6
5

15

4

10

3

1

0
Sep. 1

7
6
5

4
3
2

deflection(average)
frequency(median)
average tempurature

2

8

Deflection(mm)8Temperature(℃)

Deflection(mm) or Frequency(Hz)

10

5

0
Oct. 1 Oct. 2 Oct. 3 Oct. 4 Oct. 5 Oct. 6 Oct. 7 Oct. 8 Oct. 9 Oct. 10Day

0Sep. 26

Oct. 21

Nov. 15
Day

Dec. 10Jan. 4

Track maintenance work

1

Jan. 29

Figure 9 Result of around Oct. 5

Figure 8 Transition of daily deflection, natural
frequency and average temperature in A bridge
7

X

Influence of track work

Figure 9 indicates that deflection ranges on Oct.
5 were smaller than deflection ranges on otherdays. In addition, the overall variation was also
smaller. A tamping work with a multiple tie
tamper was carried out at night on Oct. 4. We
named period from Oct. 1 to Oct. 4 as X, andnamed period from Oct. 5 to Oct. 10 as Y. X is
before the tamping work. Y is after. The
average value of deflection range was 3.97 mm
in period X and 3.52 mm in period Y. It
decreased 0.45 mm by the tamping work.
Figure 10 shows the relationship between
train speed and deflections in the period X andthe period Y. Deflection range between 220km/h and 285 km/h decreased.
Figure 11 shows the special distribution oflevel deviation of left rail. Black line indicatesin the period X and red break line indicates in
the period Y. This figure showed thatfluctuation at the entrance of the bridge havebeen removed. According to Japanese designcode for train structures, the dynamic response
acting on the structures can be expressed asfollowing equations [1].
The impact coefficient i is product ofcoefficients of speed effect i and vehicle
oscillation effects ic.
i = (1+i )(1+ic )-1(1)

It is thought that the ic was reduced byeliminating the high and low deviations, and the
reduction of the deflection value was affected.

Y

5

4Shift down

3

2

220

230

240

250
260
Speed(km/h)

270

280

290

Figure 10 Relationship between train speed anddeflection of A bridge
5
Train direction

Orbital high and low（mm）

3.2

Deflection(mm)6bridge4：Before3：After

2
1
0

-1
-2
-3

-4
-5
600

610

620

distance（m）

630

640

650

Figure 11 Spatial distribution of level deviationof A bridge (left rail)

4. RESULT OF B BRIDGE
4.1

Measurement Results

The transition of deflection range is shown in
Figure 12. During the measurement period, thedeflection range was distributed in 2 to 4 mm.
The average deflection range was 2.88 mm.
From the relationship between the train
speed and the deflection range is shown in
Figure 13. The deflection range increased bytrain speed. Thus, resonance did not occur inthis speed band.
The transition of natural frequency is shownin Figure 14. During the measurement period,

Deflection(mm)

10

10
9

Frequency(Hz)

8
7
6
5
4
Sep. 22

Sep. 27

Oct. 2

Oct. 7

Oct. 12Day

Oct. 17

Oct. 22

Oct. 27

Figure14 transition of natural frequency (Bbridge)1030
deflection(average)
frequency(median)
average temperature

9
8

25

7

20

Temperature (℃)

Deflection(mm) or Frequency (Hz)the natural frequency was distributed in therange of 8 to 9 Hz except for the data which
deviated greatly. Median was 8.30 Hz.
Figure 15 shows the transition of daily
deflection range, natural frequency and theaverage temperature around this bridge. The
average temperature fluctuated in the range of
15 to 30oC. Average temperatures on Oct. 1 andOct. 7 were over 25oC. They were warmer thanother days. It seems to be that higher air
temperature increased natural frequency anddecreased deflection range.
Moreover, correlation coefficient of thedeflection range and the average temperature
was 0.79. It means that they have strong
positive correlation. On the other hand,correlation coefficient between the natural
frequency and the average temperature was 0.79, strong negative correlation. Thus dynamic
behaviour of this bridge might be influenced by
the temperature change.

6
5

15

4

10

3

2

9

1

8

0
Sep. 22

7

5

Sep. 27

Oct. 2

Oct. 7

Oct. 12Day

Oct. 17

Oct. 220Oct. 27

6

Figure15 Transition of deflection range, natural
frequency and average temperature (B bridge)

5
4
3
2
1
0
Sep. 22

Sep. 27

Oct. 2

Oct. 7

Oct. 12Day

Oct. 17

Oct. 22

Oct. 27

Figure12 Transition of deflection range (Bbridge)10
9Deflection(mm)

8
7
6
5

4
3
2
1
0
200

220

240
260
Speed(km/h)

280

300

Figure13 Relationship between speed anddeflection (B bridge)

4.2

Influence of temperature effectFigure 16 shows the restraint condition of the
support of concrete girder. If the outside airtemperature is not so high, there is a gap
between girder ends and parapets of abutments.
This condition may be considered as simple
support condition. On the other hand, when theoutside air temperature is high, expanded girder
causes contacting girder ends to parapets, andfixing rotations at the both ends of girders. It
was inferred that the natural frequency
increased and the deflection decreased in theory,
because boundary condition of the girder isshifted from simple support condition to semifixed support condition. It was estimated thatthe natural frequency was changed by this kindof mechanism which is observed in the up lineof the A bridge.
In order to verify this hypothesis, it isdesirable to directly confirm the condition ofgirder ends in the field. However doublereinforcement slab girders cannot be visuallyinspected in proximity because structural accessto girder ends is impossible.
Therefore, the influence of changes in theOther than high temperature
Gap
GirderAbutment

High temperature
Contact
Expansion
GirderAbutment

L

L

Simple support

Fix at both ends

Deflection under distributed load q

5qL⁴
δ= 384EI

qL⁴
δ=384EI

Figure 16 Constraint condition at supports

GirderLower joint
Abatment
Normal condition
GirderLower joint

Mortarplacement
Abatment

Reproduce girder end concrete

Figure 17 Girder end condition

Experiment

Measurement

15
Frequency(Hz)fixed conditions at both ends on the natural
frequency and the deflection was examined by
an experiment.
The experiment was carried out by using a
10 m span real scale RC slab girder model.
Total length is 10.7 m. Details of the specimen
are given in the reference [7]. The girder issimply supported in normal condition as shownin Figure 17. There are gaps between girder
ends and parapets. Horizontal movement of thegirder is not restricted at movable bearing. In
order to simulate the semi-fixed condition(girder ends contact state) of actual structures,
girder ends and parapets were integrated bypouring mortar into the gap between them.
Horizontal movement of the movable bearing
was restrained, too.
Natural frequency was calculated byprocessing the acceleration data obtained bydropping weight vibration tests. Verticalacceleration at the center of girder bottom wasmeasured about 20 second when a 40 kg weightwas dropped from 30 cm above sidewalk.
Measurements were performed 10 times foreach condition. Fourier spectra were obtainedby FFT, and they were averaged. Natural
frequency was determined as a frequency at the
maximum peak in the range from 1 to 15 Hz of
the averaged spectrum, because we focus on thefirst-order natural frequency．
Figure 18 shows comparison of experimental
and measured results. In the case of experiment,
natural frequencies were 8.38 Hz for normal
condition, and 10.24 Hz for the contact
condition. Contacting between girder ends andparapet resulted that the natural frequency
increased about 22% by condition change.
In the case of actual measured result, natural
frequencies of the B bridge became higher whenhigh temperature days: Oct. 1 (max. 32.2oC) andOct. 7 (max. 33.4oC). Natural frequency on Oct.
1 was about 4% higher than other days, and it
on Oct. 7 was about 16% higher than others. In
addition, increase rate of the natural frequency
was larger than one on Oct. 7 where the averagetemperature was approximately 1oC higher than
one of Oct. 1. Comparing with the Oct. 7 result
indicates that the measured value showed asmaller increase rate, but the natural frequency
increased about 4 to 16% by temperature.
We can say from above findings that thenatural frequency was effected by the change of
constraint condition at the girder ends due totemperature change.

10.24

10

Day estimated to be girder
ends contact state

8.38
6.90

7.20

Other

Oct. 18.00

50NormalContact

Oct.7

Figure 18 Comparison of experimentand measurement

5. CONCLUSIONSREFERENCES

In this study, effects of track maintenance andtemperature on the dynamic characteristics ofRC slab girder bridges were evaluated by using
continuous measurement data obtained by the
newly developed deflection monitoring devices.
The following findings were obtained from thisstudy.
1) The development of the deflection
monitoring device has enabled continuous
measurement.
2) By continuous monitoring, it was
confirmed that the tendency of deflection
value changes due to the influence of train
speed and the influence of track
maintenance, during snow damage
operation regulation.
3) The analysis of the level deviation
waveforms before and after the track
consolidation operation showed that theelimination of the level deviations affected
the reduction of the deflection value.
4) In a bridge affected by temperature effects,
the deflection value tends to decrease as thenatural frequency increases, and there is apositive correlation between temperatureand natural frequency, and a negative
correlation between temperature anddeflection value.
5) The expansion of the girder due totemperature effects is considered to be thecause of the change of the natural
frequency due to the change of theconstraint condition of the supporting point.
6) As a result of carrying out an experiment
simulating the condition where girder ends
and parapets of abutments were in contact,
the natural frequency was 8.38Hz at normal
and 10.24Hz at the time of girder end
contact.
7) As a result of contact between girder ends
and parapets of abutments, the natural
frequency is increased by about 22%compared to normal. In the experiment also,
the natural frequency changes because theconstraint condition of the girder ends
changes.
8) In the measurement, the natural frequency
increases by about 4 to 16% when theconstraint condition of the girder end
changes.
Continuous measurement will be continued,
and investigations will be conducted on factorsthat affect girder deflection.

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Design Standards for Railway Structures
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Feb. 2006.
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2011.
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