FIB 30: Acceptance of stay cable systems using prestressing steels

86 Pages·2005·3.03 MB·English

Acceptance of stay cable
systems using
prestressing steels

Recommendation prepared by
Task Group 9.2

January 2005
Subject to priorities defined by the Steering Committee and the Presidium, the results of fib’s work in
Commissions and Task Groups are published in a continuously numbered series of technical publications
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Any publication not having met the above requirements will be clearly identified as preliminary draft.
This Bulletin N° 30 was approved as an fib recommendation in April 2004 by the fib Council.

This report was drafted by fib Task Group 9.2, Stay cable systems:
Dieter Jungwirth (Convenor)
György L. Balázs (Budapest University of Technology and Economics, Hungary), Pierre Boitel
(Freyssinet International, France), Yves Bournand (VSL Technical Centre Europe, France), Pietro Brenni
(BBL Systems Ltd., Switzerland), Alain Chabert (Laboratoire Central des Ponts et Chaussées, France),
Gordon Clark (Gifford and Partners Ltd., United Kingdom), André Demonté (Trefileurope Fontainunion,
Belgium), Hans Rudolf Ganz (VSL International, Switzerland), Christian Gläser (Technical University
München, Germany), Philippe Jacquet (Bouygues Travaux Publics, France), Jean-Francois Klein
(Tremblet SA, Switzerland), Jacob Koster (Ballast Neerdam, The Netherlands), Benoit Lecinq (SETRA,
France), Manfred Miehlbradt (EPF Lausanne, Switzerland), Theodore L. Neff (Post Tensioning
Institute, USA), Toshihiko Niki (Sumitomo Electric Industries, Japan), Oswald Nützel (DSI Int. GmbH,
Germany), Amar Rahman (BBR Systems, Switzerland), Reiner Saul (Leonhardt, Andrä und Partner,
Germany), S. Sengupta (Span Consultants Pvt. Ltd., India), Khaled Shawwaf (DSI, USA), J.H.A. Van
Beurden (Nedri-Spanstaal B.V., The Netherlands), Yash Paul Virmani (Federal Highway Administration,
USA)

Full address details of Task Group members may be found in the fib Directory or through the online services on
fib's website, www.fib-international.org .

Cover pictures: Sunshine Skyway Bridge (Florida, USA), Olympic Tent (Munich, Germany), Rosario-Victoria
Bridge (Argentina), Millau Bridge (France), Ibi Bridge (Japan), Yiling Yangtze River Bridge (People’s Republic
of China)

© fédération internationale du béton (fib), 2005

Although the International Federation for Structural Concrete fib - féderation internationale du béton - created
from CEB and FIP, does its best to ensure that any information given is accurate, no liability or responsibility of
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otherwise, without prior written permission.

First published in 2005 by the International Federation for Structural Concrete (fib)
Post address: Case Postale 88, CH-1015 Lausanne, Switzerland
Street address: Federal Institute of Technology Lausanne - EPFL, Section Génie Civil
Tel. [phone]; Fax [phone]; [email protected]; www.fib-international.org

ISSN 1562-3610
ISBN 2-88394-070-3

Printed by Sprint-Digital-Druck Stuttgart
Foreword
Cable-stayed structures have become increasingly popular over the last 10 to 20 years.
Many long span stay cable bridges have been built for highway traffic with spans up to and
now even beyond 1000 m main span. A significant number of cable-stayed railway bridges
has also been constructed. More recently many very elegant pedestrian cable-stayed structures
have been built and have become landmark structures. But also cable-supported roofs and
other building structures have found increasing interest.
Surprisingly, there have been only a very limited number of specifications for the stay
cable systems which form a key element of these structures. The best known are the
recommendations published by the Post-Tensioning Institute in the USA, and more recently,
the recommendations published by the French Highway Administration, SETRA.
These recommendations are the first specifications published by fib for stay cable
systems. They introduce a significant number of new developments and specifications which
have not been available in previous documents:
 Corrosion protection philosophy with a multi-barrier approach for the prestressing
steel used for the stay cables and a rational design approach for structural steel
components. A leak tightness test is also specified to verify the connection details
between the free length and the anchorage zone of the stay cable
 Design and testing of stay cables for the inevitable flexural effects which occur close
to the anchorages and other deviation points of the stay cables. These recommendations
specify testing that covers flexural effects up to a certain degree. Designers will not
need to consider these flexural effects anymore in the design for stay cable systems
tested in accordance with these recommendations
 Selected information on stay cable vibrations and special damping devices to control
such vibrations
 Suitable details for lightning protection of cable-stayed structures
 Design considerations and testing procedures for stay cable saddles which are
increasingly popular for cable-stayed structures with very slender pylons
 State-of-the-art specifications for the main materials and components for stay cable
systems including quality control procedures
 Specific requirements for the common installation methods of stay cables are provided
including the strand by strand installation and stressing methods
 A comprehensive list of references, relevant standards, and extended literature.
I express my sincere thanks to Professor Jungwirth, the convenor of Task Group TG 9.2,
and the members of TG 9.2. Professor Jungwirth has taken up the work with great initiative
and has been able to motivate the Task Group members to produce a comprehensive and most
valuable document, which will become a standard reference for stay cable systems
specifications. I also express my thanks to the several experts who have dedicated significant
time to review and improve these recommendations, in particular Michel Virlogeux and
David Goodyear. I also extend my thanks to Gordon Clark for his editing of the report for
English grammar.
Hans Rudolf GANZ
Chairman of Commission 9
Reinforcing and Prestressing Materials and Systems
fib Bulletin 30: Acceptance of stay cable systems using prestressing steels iii
Contents
Introduction 1
1 Scope 1
2 Definitions and symbols
2.1 Definitions 2
2.2 Symbols 4
3 Design and detailing
3.1 General 5
(3.1.1 Redundancy of cable-stayed structures – 3.1.2 Fire, impact, vandalism –
3.1.3 Replaceability of stay cables – 3.1.4 Transverse loads applied from stay cables
to the structure – 3.1.5 Bending stresses in stay cables
3.2 Design / sizing of stay cables 8
(3.2.1 Service conditions (SLS) – 3.2.2 Fatigue limit state (FLS) – 3.2.3 Ultimate
limit state (ULS) – 3.2.4 Earthquakes – 3.2.5 Construction and cable replacement
3.3 Detailing and lightning protection 12
(3.3.1 Detailing – 3.3.2 Lightning protection)
3.4 Saddles 17
(3.4.1 General – 3.4.2 Transfer of differential stay cable forces – 3.4.3 Minimum
radius of curvature of saddle pipe)
3.5 Execution aspects 18
(3.5.1 Stage-by-stage analysis – 3.5.2 Length adjustment capability of stay cables –
3.5.3 Construction tolerances)
3.6 Cable vibrations 19
(3.6.1 General – 3.6.2 Special damping devices – 3.6.3 Cross ties)
3.7 Inspection and maintenance 21
4 Functional requirements for stay cables
4.1 Evolution of stay cable technology 22
4.2 General requirements 22
(4.2.1 General – 4.2.2 Durability design, corrosion protection)
4.3 Requirements for the free length 24
(4.3.1 Corrosion protection philosophy for tensile elements – 4.3.2 Protection
philosophy for other materials – 4.3.3 Reference system for corrosion protection –
4.3.4 Equivalent systems for corrosion protection – 4.3.5 Systems with lower
corrosion protection – 4.3.6 Additional requirements)
4.4 Requirements for the transition zones 28
(4.4.1 Corrosion protection – 4.4.2 Stay pipe dilation – 4.4.3 Guide deviators –
4.4.4 Damping of stay cables – 4.4.5 Anti-vandalism pipes)
4.5 Requirements for anchorages 32
(4.5.1 Types of stay cable anchorages – 4.5.2 Corrosion protection philosophy for
mild steel anchorage components – 4.5.3 Additional requirements)
4.6 Requirements for saddles 35
(4.6.1 General – 4.6.2 Corrosion protection – 4.6.3 Saddle performance)
iv fib Bulletin 30: Acceptance of stay cable systems using prestressing steels
5 Materials: properties, requirements, testing
5.1 General 36
5.2 High tensile steel for tensile elements (prestressing steel) 37
(5.2.1 General – 5.2.2 Hot dipped metallically coated prestressing steel)
5.3 Structural steel for anchorages, saddles, guide deviators and pipes 39
5.4 Stainless steel 39
5.5 Sheathing for prestressing strands 39
5.6 Filling materials 41
(5.6.1 Soft filling materials – 5.6.2 Hardening filling materials)
5.7 Stay pipes and other pipes 43
(5.7.1 General – 5.7.2 Thermoplastic stay pipes – 5.7.3 Steel stay pipes –
5.7.4 Other pipes)
5.8 Guide deviators 46
5.9 Damping devices 46
6 Testing of stay cable systems
6.1 General 46
6.2 Initial approval testing (qualification testing) 46
(6.2.1 Anchorage fatigue and tensile testing – 6.2.2 Saddle fatigue and tensile testing
– 6.2.3 Leak tightness testing)
6.3 Suitability testing 55
6.4 Quality control testing 56
7 Installation
7.1 General 58
(7.1.1 Quality management system – 7.1.2 Qualification of personnel –
7.1.3 Execution documents)
7.2 Shipment and storage of components 59
7.3 Assembly and installation 59
7.4 Stressing and adjustment 61
7.5 Corrosion protection 63
8 Inspection and monitoring
8.1 General 64
8.2 Initial inspection 64
8.3 Routine inspection 64
8.4 Detailed inspection 65
8.5 Exceptional inspection 66
8.6 Monitoring 66
9 Maintenance, repair, replacement and strengthening 66
10 References and literature
10.1 References 67
10.2 Standards 68
10.3 Extended literature 71
fibBulletin 30: Acceptance of stay cable systems using prestressing steels v

Introduction
Cable-stayed bridges are structurally optimised systems employing light stiffening beams,
continuously supported by the stays, for large span cantilevers with an efficient transfer of
forces to the pylons. Spans of up to 500 m with concrete decks and up to 1000 m with steel
stiffening beams (either composite or pure steel decks) are economically practicable.
The most important elements in these aesthetic structures are the stay cables. More than
20 years ago stay cables consisted of spiral strands and fully locked cables, as originally used
in steel construction. Today special quality tensile elements similar to those used in
prestressed concrete construction are setting new standards in these fields of application. Stay
cables can be manufactured with prestressing steels within HDPE pipes or steel pipes with
fillers for corrosion protection or with individually protected strands, which are either
prefabricated or fabricated on site. Modular concept of the systems allows design using very
large stays, the largest today with up to 205 strands (ultimate strength of 54 MN) per cable.
While most of these stay cables are used for bridge construction, similar cables are also
widely used in extradosed structures and building construction.
Over the past years some national Stay Cable Recommendations have been issued, e.g.
by PTI (USA), [1], and SETRA/CIP (France), [2]. Also a European specification is in
preparation, see [S1]. These recommendations and specifications typically cover locally
available materials and construction practices.
These fib recommendations have been formulated by an international working group
comprising more than 20 experts from administrative authorities, universities, laboratories,
owners, structural designers, suppliers of prestressing steels and stay cable suppliers. This
text has been written to cover best construction practices around the world, and to provide
material specifications which are considered to be the most advanced available at the time of
preparing this text. For ease of use (for client, designer and cable supplier), the complex
content has been arranged thematically according to the system components into chapters
focusing on performance characteristics, requirements and acceptance criteria.
References are provided with a separate section on standards. An extensive list of
literature on the subject of stay cables and cable-stayed structures is also provided.
1 Scope
These recommendations are intended to give technical guidelines regarding design,
testing, acceptance, installation, qualification, inspection and maintenance of stay cable
systems using prestressing steels (strands, wires or bars) as tensile elements which can be
applied internationally. These recommendations are meant to be applicable for cable-stayed
bridges and other suspended structures such as roofs. They may also be used for hangers in
arch structures and as suspension cables, as appropriate.
Requirements and comments have been specified for all parties involved in design and
construction in order to aim for a uniform and high quality and durability. The interfaces to
the structural Designer are highlighted. The essential subjects are:
• Design and detailing of stay cables including saddles and damping devices
• Durability requirements and corrosion protection systems
• Requirements for the materials
• Testing requirements for the stay cables
• Installation, tolerances, qualification of companies and personnel
• Inspection, maintenance and repair.
fibBulletin 30: Acceptance of stay cable systems using prestressing steels 1
The main subject of these recommendations are stay cables with tensile elements
consisting of prestressing steel. Generally, these are strands and wires. Bars may be of
practical use for short, single bar stays and are normally not used for typical highway bridge
stays. In particular for architectural applications, stainless steel bars have been used.
However, this type of bar is not specifically considered in these recommendations although
the general philosophy given applies.
These recommendations do not cover the technology of stay cables whose tensile
elements are ropes, locked-coil cables, etc. or which consist of composite materials.
Nevertheless, in many cases the specified performance criteria may also be applicable to these
systems, although numerical values given for the acceptance criteria may need to be adjusted.
For these systems it has been difficult to provide multiple protective layers similar to those
specified for stay cables made from prestressing steel and therefore, the quality of corrosion
protection may not be equivalent.
While extradosed cables have similarities with stay cables, generally agreed design and
system acceptance criteria are not yet available and therefore, this type of cable is not covered
here.
2 Definitions and symbols
2.1 Definitions (see Fig. 2.1)
Accessories
Auxiliary components such as anchorage caps, anti-vandalism pipe, sleeves, boots, etc.
Anchorage
A mechanical device, usually comprising several components (anchor head or wedge
plate, bearing plate, socket, ring nut, etc.), designed to retain the load in the stressed stay cable
and to transmit the load to the cable-stayed structure. Anchorages can be as follows:
Adjustable anchorage: Anchorage with a threaded nut or with shims, allowing an
-
adjustment of the stay cable length without moving the prestressing steel relative to the
anchorage
Fixed anchorage: Anchorage which does not allow adjustment of the stay cable length.
-
Anchorages may be further divided into:
Stressing end anchorages which permit stressing of the stay cable
-
Dead end anchorages which are not provided for stressing of the stay cable.
-
Barrier / Corrosion barrier
Envelopment of the tensile element of the stay cable protecting the element or cable from
environmental influences and their consequences, in particular corrosion. Barriers can be of
two types:
External barrier: A barrier which is exposed to the outside environment
-
Internal barrier: A barrier which is directly applied to the tensile element.
-
Bearing
See guide deviator.
2 2 Definitions and symbols
Centralizer / Spacer
A non-load bearing device between or around the tensile elements to fix the position of
the stay pipe relative to the tensile elements.
Cross tie
Element connecting the stay cables between each other and/or to the structure (bridge
deck) to modify the period of vibration of the stay cable.
Damping device
A device to control cable vibrations.
Designer (consulting engineer)
The engineer responsible for the design of the cable-stayed structure. His exact scope of
works and role varies with local customs.
Fatigue load
Variable loads on the cable-stayed structure, in accordance with relevant standards for
fatigue loading.
Filler / Filling material
An interface, filler, blocking agent or coating preventing the penetration of external
contaminants to, or migration along, the tensile element.
Free length
The length of a stay cable beyond the cable anchorage or saddle and transition zones.
Guide deviator
A device (sometimes called elastic bearings) located at the end of the stay cable free
length which provides two functions:
(1) laterally guiding the stay cable to protect the anchorage from transverse forces and
bending stresses (Guide), and
(2) deviating the tensile elements to form a compact bundle of parallel elements in the free
length (Deviator).
These two functions may be combined into one single element or may be provided with two
separate elements.
Guide pipe
A pipe used as recess former in a cable-stayed structure (deck and/or pylon) for the
installation and possible removal of the stay cable anchorage zone. The guide pipe is
sometimes called formwork tube or recess pipe.
Inspection
A primarily visual examination, often at close range, of a structure or its components with
the objective of gathering information about their form, current condition, service
environment and general circumstances. National requirements are often specified.
Lifetime / Service life / Design working life
The planned period of use of the structure, or parts of it, for its intended purpose with the
anticipated maintenance but without major repair. It must be specified by the owner.
fibBulletin 30: Acceptance of stay cable systems using prestressing steels 3