Seminar Presentation by Prof. Michel Virlogeux _ translated and support by Mr Viet at MOT Serminar 2007

1. Some aspects of the design of stay cables
By Michel VIRLOGEUX
Honorary President FIP and fib

2. Summary
1.Introduction
2.Drag forces on stay cables
3.Stay cable quality
4.Installation, tension and maintenance
5.Cable vibrations
6.Fire and lightnings

3. 1. Introduction
1.1 Historical survey
1.2 Parallel wire systems
1.3 Parallel strand systems

10. 2. Drag forces on stay cables
2.1 Drag coefficient
2.2 Importance of drag forces. Experience of
the Normandy Bridge
2.3 Conclusion on the importance of drag
forces

11. 6
3
10.15
/23,1
²
2
1
−
=
=
=
=
v
v
UD
R
mkg
DCUF
e
dd
ρ
ρ

12. A duct of the Higashi-Kobr Bridge

13. The drag coefficients of the different ducts tested in 1991 for the Normandie Bridge by the CSTB

14. A recent pipe for a Freyssinet stay cable,
with the two imbricated helical filets
Drag coefficients of three HDPE pipes;
a typical cylinder, a cylinder equiped with
one helical filet and the last with two.

15. Drag coefficients measured on profiles with dimples (Kwork and Wong 2004)

16. Experience of the Normandy Bridge

17. Drag forces on the deck : proportional to the span
and depending of shapes.
Drag forces on the stay cables: proportional to
the square of the span.
Drag forces on the stay cables : proportional to
the diameter.
Capacity of the stay cables : proportional to the
square of the diameter.

19. 3 – Stay cable quality
3.1 Corrosion protection.
3.2 Strenght and fatigue resistance.
3.3 Prefabrication against constitution in situ.

20. Corrosion protection.
Two complementary nested barriers
SETRA – fib – PTI
example : galvanisation
+ oil wax
+ HDP extrusion
No role for the external duct (or pipe)

21. Strength and fatigue resistance
Tests on wires and strands.
Tests on anchorage bending effects.
Anchorage by Wedges

22. Prefabrication against construction in situ

23. 4. Installation, tension and maintenance
4.1 Prefabricated stay cables.
A large coil transported an a truck

24. Two examples of heavy cranes used for lifting
the coil and installing the stay cable.

25. The installation of a long
stay cable at the lower
anchorage of the Tatara
Bridge

26. Stay cables constitued in situ

27. The example of the Normandie Bridge

29. Maintenance

30. Conclusion

31. 5. Cable vibrations
5.1 Statics of stay cables
5.1 Dynamics of stay cables
5.3 Internal and aerodynamic damping
5.4 Different types of cable vibrations
5.5 Countermeasures.

32. F
mgL
f
8
²
=

33. F
m
k
L
Tk
2
=

34. • Internal damping (ratio to critical)
Injection with cement grout : 0.01 %
Lock-coil cable : 0.1 %
Parallel individually protected strands : 0.1 to
0.15%
Parallel strands injected with oil wax : 0.15 %
Damping of stay cables
• Aerodynamic damping
transverse vibrations
vertical vibrations
m
TUDC
m
TUDC
kd
k
kd
k
π
ρ
π
ρ
ξ
ξ
8
4
=
=

35. Differents types of cable vibrations

36. Vortex shedding
D
US
Nc =
k
c
T
D
U
18,0
=

37. Wake effects

38. Buffeting
Torsional instability
t
c
T
D
U
2
=

39. Aerodynamic stability
•Shape
•Lock oil cables
•Ice and snow
D
US
Nc
3
=
U
UC
dU
dC dd )(2
−≤
•Oblique winds
•Drag crisis

40. Rain and Wind induced vibrations

42. Parametric excitation
)(
²
²2
ω
πω
ω
H
k
AA
k
k =

43. Cable/structure interaction

56. Countermeasures
Dampers

57. A damper on the Iroise Bridge over the River Elorm

58. A damper on the Erasmus Bridge

59. A damper Vasco de Gama Bridge

60. Countermeasures
Duct Shaping
The Longitudinal channels of the ducts
for the Higashi-Kobe Bridge
A ducts of the Higashi-Kobe Bridge

61. A duct of the Beaucaire Bridge
with the helical filets
Countermeasures
Duct Shaping

62. The dimples on the ducts for the
Tatara Bridge
Countermeasures
Duct Shaping

63. Counter measures
Cross Cables

64. Counter measures
Cross Cables

65. Counter measures
Cross Cables

66. Counter measures
Cross Cables

67. Counter measures
Cross Cables

69. 6. Fire and lightnings
6.1 Fire
6.2 Lightnings

72. 7. Codes and recommendations
SETRA fib PTI