ANALYTICAL AND EXPERIMENTAL STUDY

OF SLEEPER SAT S 312

IN SLAB TRACK SATEBA SYSTEM

C. Guigou-Carter

M. VillotC.S.T.B.

Center for Building Science and Technology

38400 St Martin d’Hères, France

B. Guillerme

C. PetitSATEBA

71100 Chalon/Saône, France

75088 Paris La Défense, France

Introduction

• Work carried out for SATEBA within framework of the new Eurostar

train track construction below London city.

• Simple prediction tool based on 2D model to predict the performance

of track-work

• Determination of sleeper pads dynamic stiffness corresponding to

specific mitigation levels

• Development of experimental rig on a full width section of track to

measure the dynamic stiffness of sleeper pads

Track-Work Prediction Model

Rail

Concrete Slab

Rail Pad

Ground

Unsprung Mass

Applied Force

z

x

Sleeper

Sleeper Pad

Insertion Gain per 1/3 octave band

calculated from velocity level at ground/slab interface

Reference track : without sleepers and sleeper pads

2D Model

Track-Work Characteristics

• Three types of trains :

Eurostar with maximum 2150 kg/axle

Domestic passenger stock with maximum 1309 kg/axle

freight stock with maximum 3750 kg/axle

• Rail pads with stiffness of 720 MN/m2 and loss factor of 20%

• Sleepers spaced every 0.6 m correspond to 350 kg/m

Sleeper pads of different stiffness and loss factor 16%

Track-Work Prediction Results

Effect of Train Type - Sleeper Pads Dynamic Stiffness 60 MN/m2

-40

-30

-20

-10

0

10

20

5.0

6.3

8.0

10.0

12.5

16.0

20.0

25.0

31.5

40.0

50.0

63.0

80.0

100.0

125.0

160.0

200.0

250.0

Frequency (Hz)

Ins

ert

ion

Ga

in (

dB

)

Eurostar

Domestic Passenger Stock

Freight Stock

Track-Work Prediction Results

Effect of Sleeper Pads Dynamic Stiffness - Eurostar Train Type

-40

-30

-20

-10

0

10

20

5.0

6.3

8.0

10.0

12.5

16.0

20.0

25.0

31.5

40.0

50.0

63.0

80.0

100.0

125.0

160.0

200.0

250.0

Frequency (Hz)

Ins

ert

ion

Ga

in (

dB

)

Sleeper Pad 35 MN/m2

Sleeper Pad 60 MN/m2

Sleeper Pad 106 MN/m2

Experimental Test Rig - Measurement Principle

Excitation

mass m1

Blocking

mass m2

Vibration ExciterStatic pre-load rams

Tested

system

Displacement

transducer u1

Displacement

transducer u2

Force transducers Fblocking

Vibration insulators

NF EN ISO 10846-2

Transfer dynamic stiffness

K2,1 (Fblocking/u1)

Measurement of Sleeper Pads Dynamic Stiffness

Experimental Test Rig - General View

Vertical static load

Dynamic vibration exciter

Blocking mass m2

Force transducer

U-shaped support

Excitation mass m1

(8-shaped support)

Vibration insulator

Rail track

Sleeper block

Sleeper block boot

Horizontal static jack

Front

Rear

Experimental Test Rig - Accelerometers Mounting

Accelerometer on

blocking mass m2

Accelerometer

on rail

Experimental Test Rig - Shaker Mounting

Vertical static load

Dynamic vibration exciter

U-shaped support

Excitation mass m1

(8-shaped support)Vibration insulator

Spring suspension

Stinger

Experimental Test Rig - Blocking Force Measurement

• Blocking force measured with 3

force transducersFblocking = F1 + F2 + F3

• Total blocking force corrected by

the inertial forceFtotal blocking = Fblocking + Finertial

= Fblocking + m2 (2f)2 u2

Experimental Test Rig - Lateral Load Application

Experimental Test Rig - Stiffness Characterization

• Requirements :

Decoupling 20 log10(u1 /u2 ) 15 dB

Inertial force correction < 10%

Displacement difference between rails head < 15%

• Dynamic stiffness calculation of sleeper pads

Krear = Ftotal blocking / u1 rear rail

Kfront = Ftotal blocking / u1 front rail

Kpads = (Krear + Kfront ) / 2 and Kpad = Kpads / 2

Limitations of Experimental Test Rig

• Vibration levels on laboratory floor were negligible

• Horizontal velocity of both rails and both sleeper blocks found negligible

• Static and dynamic force distribution between rear and front was good

• Blocking mass m2 presented modal behavior around 100, 125 and

156 Hz.

• Inertial force correction ≈ 20 % at 63 Hz : above requirements

Measurements valid at 8, 16 and 31.5 Hz

Measurement Results at 8 Hz

Static Load Vertical 40 kN Vertical 40 kN

Horizontal 10 kN

Vertical 64 kN Vertical 64 kN

Horizontal 5 kN

Rear/Front Displacement Difference (%) 5.8 10.4 1.9 12.0

Front decoupling (dB) 21.3 19.0 19.5 16.2

Rear decoupling (dB) 22.6 24.1 20.7 21.4

Blocking force Fblocking (N) 125.10 126.68 111.29 111.51

Total Blocking force Fblocking total (N) 126.04 127.60 112.17 112.45

Blocking force error (%) 0.7 0.7 0.8 0.8

Pad dynamic stiffness (MN/m)

With inertial force correction12.9 14.4 15.2 16.9

Dynamic stiffness increases

with applied vertical static load

with applied horizontal static load

and with excitation frequency

Concluding Comments

• Simple prediction tool was presented and used to define sleeper pads

dynamic stiffness corresponding to specific mitigation levels

• Experimental rig to characterize sleeper pads dynamic stiffness was

described and its limitations discussed

• Measurements were performed for different sleeper pads under

different vertical and horizontal static loads