Dimensions

Colours

Introduction Freyssinet has designed a special duct for housing stay cables, performing the following functions:

• Protecting strands from ultraviolet radiation (UV),

• Ensuring impermeability to runoff water,

• Providing aerodynamic stability for the stay cable.

The sheath is made from high density polyethylene (HDPE). The Freyssinet duct is provided with a helical fillet and offers two vital additional advantages:

• Excellent durability,

• Prevention of aerodynamic instability under the combined effect of rain and wind.

DescriptionTo guarantee satisfactory mechanical properties and a high level of resistance to physical and chemical attacks, the Freyssinet stay cable duct is coextruded in two connected layers:

• The 1.5 mm outer layer is coloured with mineral colorants and treated against ultraviolet radiation and chemical and salt attacks using state-of-the-art stabilising additives;

• The inner layer is made from black HDPE; with a minimum thickness of 4.5 mm, it provides the mechanical strength of the sheath.

In order to ensure the aerodynamic stability of the stay cable, a double helical rib the same colour as the duct is incorporated during production.

A range of compact and super compact stay cables with smaller diameters is available to reduce stay cable drag.

Serebriany Bor, Russia

Technical data sheet reference no.: FT En C I 1 7

The table below gives the dimensions of sheaths for standard, compact and super compact stay cables:

Standard stay cable Compact stay cableSuper compact

stay cable*

Anchor unit

Max. no. of strands

Outer diameter

(mm)

Total thickness

(mm)

Outer diameter

(mm)

Total thickness

(mm)

Outer diameter

(mm)

Total thickness

(mm)

12 12 125 6 110 6 100 6

1913 105 6

19 140 6 125 6 120 6

2721 125 6

27 160 6 140 6 130 6

31 31 160 6 150 6 140 6

37 37 180 6 160 6 150 6

4842 160 6

48 200 6.4 180 6 170 6

55 55 200 6.4 190 6 180 6

61 61 225 7.1 200 6.4 190 6

75

69 200 6.4

73 205 6.5

75 250 7.9 225 7.1 210 6.7

9185 225 7.1

91 280 8.9 240 7.6 230 7.3

109102 245 7.8

109 315 10 260 8.2 250 7.9

127121 265 8.4

127 315 10 280 8.9 270 8.5

169151 290 9.2

169 355 11.2 320 10.1 310 9.8

* Super compact stay cables require the use of compact strands.The Standard Dimension Ratio (SDR) D/e<32 is optimised for ungrouted stay cables.

Ducts are available as standard in the following colours, the stability over time of which has been tested (colour chart not contractually binding):

Stay cable ducts

Freyssinet stay cable sheath

WhiteRAL 9003

YellowRAL 1016

Pale greyRAL 7035

Red RAL 3020

Pastel blueRAL 5024

GreenRAL 6021

Mediterranean blueRAL 5018

Metallic grey (brushed stainless

steel effect)

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• High levels of UV resistance• Low drag• Great aerodynamic stability• Wide range of colours

Proven durability

References and Figures

Aerodynamic stability

All rights reserved by FREYSSINET. Product names are trademarks of FREYSSINET. The information in this document is subject to change. Whilst it is as accurate as possible, it is not in any way binding on FREYSSINET.

Freyssinet • 1 bis, rue du Petit Clamart - Bât C - 78140 Vélizy-Villacoublay - France • Ph.:+33 1 46 01 84 84 - Fax:+33 1 46 01 85 85 • www.freyssinet.com

DurabilityHDPE is a material that can withstand most chemical and physical attacks. The main ageing mechanisms of HDPE are photo-oxidation of the polymer chains and environmental stress cracking (ESC).

In order to prevent photo-oxidation, the Freyssinet sheath was formulated with anti-oxidant additives. It was then successfully tested in a SEPAP 12-24 chamber for over 8,000 hours, corresponding to a service life of around 100 years in temperate regions.

To prevent ESC, the Freyssinet sheath has a telescopic section that enables the main sheath to slide without load, which prevents the development of thermal stress cycles.

Nga Tu So, Vietnam

InstallationThe tubes are delivered to site in 12 metre lengths. They are protected by plastic film so that they don't get dirty during installation.

The tubes are mirror welded in accordance with the applicable standards. Particular care is taken to align the helical ribs at the ends of two sections of sheath before they are welded together.

Stay cable ducts

One of the main causes of stay cable vibration is excitation in light rain combined with a moderate wind.

Two streams of water then run down the sheath, one stable on the lower fibre and the other unstable on the upper fibre, changing the aerodynamic profile of the sheath.The double helical ribs on the Freyssinet stay cable sheath divert the streams of water and prevent excitation while providing a low drag coefficient (thus reducing the transverse loads on the structure).

The shape of the ribs and the pitch of the helix that they form around the sheath result from a long-term research programme undertaken with the Centre Scientifique et Technique du Bâtiment (CSTB) for the Pont de Normandie bridge.

The curve below, produced during wind tunnel tests, shows the efficiency of the helical rib:

The drag coefficient of the Freyssinet sheath was tested in a wind tunnel, revealing a coefficient of less than 0.6 in wind speeds of up to 50m.s-1.

The use of compact and super compact stay cables instead of standard ones decreases the wind resistance of the stay cables by 15 to 20% respectively, whilst reducing the drag and Reynolds number accordingly.

Total installed length: 270,000 mNumber of colours available: 19Diameters available (min./max.): 90 mm/400 mm

Dynamic efficiency of sheath

Vibr

atio

n am

plitu

de 7 m/s 15 m/s

Wind speed

M0, HungaryBai Chay, Vietnam

Rion Antirion, Greece

Without rib

With rib

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